JP2011118167A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent, at a low cost and with a simple configuration, a photoreceptor drum, intermediate transfer belt, or the like, from becoming out of control when feedback control and feed forward control are executed. <P>SOLUTION: The torque detecting section 160 of an image forming apparatus 100A calculates the load torque of a drum motor 181 based on a PWM command value from a feedback control section 14 and a speed command value from a control section 10. A threshold determining section 162 refers to a control table 163 from the load torque and the rotating speed of the drum motor 181 when determining that the load torque of the drum motor 181, supplied from the torque detecting section 160, is outside a predetermined threshold range. Then, the threshold determining section 162 obtains the optimal control value (the altered linear velocity of the drum motor 181) in which the load torque of the drum motor 181 is within a normal range. The feedback control section 14 generates a PWM command value, based on the control value of the drum motor 181 or the like, to supply the PWM command value to a motor drive section 180. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet. Specifically, the detected load torque of the first drive unit is compared with a preset threshold range indicating the appropriate load range of the first drive unit, and the load torque of the first drive unit is determined based on the comparison result. Is determined not to be within the threshold range, the first drive unit and the first drive unit are controlled by controlling the drive of at least one of the first and second drive units to adjust the speed difference between the photosensitive drum and the belt. The load torque of the first drive unit is adjusted to an appropriate load by moving the load torque between the two drive units.

  2. Description of the Related Art In recent years, image forming apparatuses such as digital multifunction peripherals having a copying function, a scanner function, a printer function, and a facsimile function have been widely used. In a tandem type color image forming apparatus, a predetermined color image is formed on a recording sheet by superimposing single color images (toner images) formed on a photosensitive drum constituting a plurality of single color image forming units on an intermediate transfer belt. Transcription. At this time, the image carrier (photosensitive drum) constituting each single-color image forming unit is required to obtain a good color image at the same speed and without speed fluctuation. Therefore, as the speed control of the photosensitive drum, the rotational speed control using both the feedback control and the feedforward control is performed by using the angular speed detection means by the encoder.

  However, in the conventional speed control method, load fluctuations occur on the photosensitive drum and the intermediate transfer belt due to the temperature of the photosensitive drum and the intermediate transfer belt, the wear of the rotating member of the driving device, the adhesion of the toner image, and the like. There is a problem that the occurrence of drive abnormality increases due to deviation from the forward control range. For example, the adhesion of the toner image to the photosensitive drum may reduce the load on the photosensitive drum and the belt, and may deviate from the feedforward control range due to fluctuations in driving characteristics.

  In order to prevent the drive abnormality due to the load fluctuation, when the speed fluctuation occurs, the brake value for the brake device is controlled via the brake control circuit to suppress the fluctuation of the rotational speed of the photosensitive body. A control device has been proposed (see Patent Document 1). According to this drive control device, the rotation fluctuation of the photosensitive drum can be suppressed, and control breakage can be avoided.

JP-A-6-332277

  However, the drive control device described in Patent Document 1 has the following problems. That is, since the bias brake used as the brake device of the drive control device is very expensive, there is a problem that the price of the image forming apparatus on which the bias brake is mounted is also expensive. In addition, when the bias brake is employed, the load for the bias brake is always excessively greater than the normal load, so that it is necessary to increase the output of the drive motor. As a result, there is a problem in that an arrangement space for the drive motor must be secured more than before, and power consumption increases.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to control a photosensitive drum, an intermediate transfer belt, and the like when feedback control and feedforward control are executed with a low-cost and simple configuration. It is to avoid breaking.

  In order to solve the above-described problems, an image forming apparatus according to the present invention includes a photosensitive drum on which a toner image is latent, a belt on which the toner image latent on the photosensitive drum is transferred, and a photosensitive drum. A first driving unit that drives, a second driving unit that drives the belt to have a predetermined speed difference from the photosensitive drum, and a load torque of the first driving unit is detected, and the detected first driving is detected. A control unit that performs feedforward control based on the load torque of the unit and performs feedback control based on the control target value obtained by the feedforward control so that the load torque of the first drive unit falls within an appropriate range; The control unit compares the load torque of the first drive unit with a threshold range indicating a preset appropriate load range of the first drive unit, and the load of the first drive unit is determined based on the comparison result. Torque is in the threshold range If it is determined that there is not, the load torque of the first drive unit is adjusted appropriately by controlling the drive of at least one of the first and second drive units to adjust the speed difference between the photosensitive drum and the belt. It is characterized by adjusting to the load.

  In the present invention, when feedforward control and feedback control are performed, the threshold value indicating the range of the load torque of the first drive unit obtained by detection and the appropriate load of the first drive unit set in advance. The range is compared by the control unit. If it is determined from the comparison result that the load torque of the first driving unit is not within the threshold range, the driving of at least one of the first and second driving units is controlled, and the speed between the photosensitive drum and the belt is controlled. The difference is adjusted. Thus, the load torque can be moved from the first drive unit to the second drive unit or from the second drive unit to the first drive unit between the first drive unit and the second drive unit. Therefore, the load torque of the first drive unit can be returned (changed) to an appropriate load according to the adjustment of the speed difference.

  According to the first aspect of the present invention, the first load based on the comparison result between the detected load torque of the first drive unit and a threshold range indicating the range of the appropriate load of the first drive unit set in advance. Since the load torque of the drive unit is adjusted to an appropriate load, control breakage of the photosensitive drum and the intermediate transfer belt when the feedback control and the feedforward control are executed can be avoided with a low-cost and simple configuration.

  According to the second aspect of the present invention, the load torque of the first drive unit can be adjusted to an appropriate load by using a table, so that feedback control and feedforward control are executed with a low cost and simple configuration. In this case, the speed of the photosensitive drum, the intermediate transfer belt, etc. can be controlled.

  According to the third aspect of the present invention, the speed of the first drive unit is accelerated when it is smaller than the first threshold, and the first when the load torque of the first drive unit is larger than the second threshold. Since the load torque of the first drive unit can be adjusted to an appropriate load by performing speed change control that reduces the speed of the drive unit, feedback control and feedforward control can be performed with a low-cost and simple configuration. When executed, speed control of the photosensitive drum, the intermediate transfer belt, and the like can be performed.

  According to the fourth aspect of the invention, the load torque of the first drive unit can be adjusted to the optimum load by changing and controlling the speed of the second drive unit that drives the belt, which is low cost and simple. With this configuration, speed control of the photosensitive drum, the intermediate transfer belt, and the like can be performed when feedback control and feedforward control are executed.

  According to the fifth aspect of the present invention, the load torque of the first drive unit can be adjusted to the optimum load by changing the speed of the second drive unit that drives the belt, and the cost is low and simple. With this configuration, speed control of the photosensitive drum, the intermediate transfer belt, and the like can be performed when feedback control and feedforward control are executed.

  According to the sixth aspect of the invention, since the speed change control of the first and second drive units is performed with an accuracy of 0.1% with respect to the speed of the first and second drive units, the unit of speed adjustment Can be prevented, and the speed control of the first and second drive units can be performed with high accuracy and efficiency.

1 is a diagram illustrating an example of a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a diagram illustrating an example of a block configuration of an image forming apparatus. It is a figure which shows an example of a structure of a control table. It is a figure which shows an example of the relationship between the load torque and linear velocity of a drum motor, and the load torque and linear velocity of a belt motor. 6 is a flowchart illustrating an example of an operation of the image forming apparatus. It is a figure which shows an example of a structure of the image forming apparatus which concerns on the 2nd Embodiment of this invention. 6 is a flowchart illustrating an example of an operation of the image forming apparatus. 10 is a flowchart illustrating an example of an operation of the image forming apparatus according to the third exemplary embodiment of the present invention.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
<1. First Embodiment>
[Configuration example of image forming apparatus]
The image forming apparatus 100 </ b> A according to the present invention compares the load torque of the drum motor 181 detected by the torque detection unit 160 with a preset threshold range indicating the range of the appropriate load of the drum motor 181, and the comparison result When it is determined that the load torque of the drum motor 181 is not within the threshold range, the load torque of the drum motor 181 is controlled by controlling the drive of the drum motor 181 and adjusting the speed difference between the photosensitive drum 20 and the intermediate transfer belt 90. Is adjusted to an appropriate load.

  As illustrated in FIG. 1, the image forming apparatus 100 </ b> A includes a paper feeding unit 70, a transport unit 80, an image forming unit 18, and a fixing unit 40. The paper feed unit 70 has a plurality of paper feed trays 71 and paper feed rollers 72. Each of the plurality of paper feed trays 71 stores sheets of A4 size, B5 size, etc., and a predetermined paper carried out of the paper feed tray 71 is transported to the transport unit 80 via the paper feed roller 72.

  The conveyance unit 80 includes a conveyance roller 81, a registration roller 82, and a detection sensor 83. The conveyance roller 81 abuts the sheet conveyed from the sheet feeding unit 70 against the registration roller 82. The registration roller 82 corrects the conveyance direction of the sheet conveyed from the sheet feeding unit 70 and conveys the corrected sheet to the secondary transfer unit 92. The detection sensor 83 detects the leading edge of the paper conveyed from the paper supply unit 70.

  The image forming unit 18 includes a Y color image forming unit 30Y, an M color image forming unit 30M, a C color image forming unit 30C, a K color image forming unit 30K, an intermediate transfer belt 90, and a secondary transfer unit 92. . The Y color image forming unit 30Y includes a charging unit 22Y, an exposure unit 24Y, a developing unit 26Y, a photosensitive drum 20Y as an image carrier, and a sensor 28Y. The charging unit 22Y uniformly charges the surface of the photosensitive drum 20Y before writing an image. The exposure unit 24Y forms an electrostatic latent image on the photosensitive drum 20Y by irradiating the photosensitive drum 20Y with a uniformly charged surface with laser light. The developing unit 26Y develops the electrostatic latent image formed on the photosensitive drum 20Y by the exposure unit 24Y with a toner member. The sensor 28Y detects a patch or the like formed in the non-transfer area.

  The other configurations of the M color image forming unit 30M, the C color image forming unit 30C, and the K color image forming unit 30K are the same as those of the above-described Y color image forming unit 30Y, and thus the description thereof is omitted.

  The toner images formed on the surfaces of the photosensitive drums 20Y, 20M, 20C, and 20K for the respective colors are superimposed on the intermediate transfer belt 90, and the superimposed toner images are formed on the sheet surface in the secondary transfer unit 92. Transcribed. The sheet on which the toner image is transferred is conveyed to the fixing unit 40. The fixing unit 40 heats and pressurizes the paper on which the toner image has been transferred, thereby pressing the toner image onto the paper to make the toner image stable on the paper. The sheet on which the toner image is pressure-bonded is carried out to a paper discharge tray (not shown). The intermediate transfer belt 90 is an example of a belt.

[Block Configuration Example of Image Forming Apparatus]
Next, an example of a block configuration of the image forming apparatus 100A according to the present invention will be described. As shown in FIG. 2, the image forming apparatus 100 </ b> A includes a control unit 10, a motor control unit 60, and an image forming unit 18. The control unit 10 and the motor control unit 60 constitute an example of a control unit.

  The control unit 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and is based on a program such as an OS and firmware installed in the ROM. The image forming apparatus 100A is comprehensively controlled by controlling each part of 100A. Further, the control unit 10 supplies a speed command value for instructing the rotation speed of the drum motor 181 that drives the photosensitive drum 20 to each of the feedback control unit 14 and the feedforward control unit 16. The speed command value can be arbitrarily set by the user, for example, on a speed setting screen displayed on the display unit, or an optimum speed can be set in advance in the ROM or the like. Further, the control unit 10 generates a mode command for switching to at least one of feedback control and feedforward control, and supplies the mode command to the mode control unit 12 described later.

  The motor control unit 60 includes a mode control unit 12, a feedback control unit 14, and a feedforward control unit 16. The mode control unit 12 controls the driving state of the motor. Based on the mode command supplied from the control unit 10, the mode control unit 12 controls the feedback control unit 14 and the feedforward control unit 16 to perform feedback control and feedforward. At least one of the controls is executed.

  The feedforward control unit 16 includes a torque detection unit 160, a threshold setting unit 161, a threshold determination unit 162, and a control table 163. The torque detection unit 160 acquires the PWM command value output from the feedback control unit 14 and the speed command value from the control unit 10, and supplies the electric power and drum supplied to the drum motor 181 from the acquired PWM command value and speed command value. The rotational speed (number of rotations) of the motor 181 is calculated. The torque detection unit 160 calculates the load torque (load current) of the drum motor 181 by dividing the calculated power by the rotation speed, and supplies the calculated rotation speed and load torque of the drum motor 181 to the threshold determination unit 162. To do. It should be noted that a table in which the PWM command value and the load torque at each speed are associated with each other is prepared in advance, and the load torque of the drum motor 181 is acquired by referring to the table according to the PWM command value from the feedback control unit 14. Anyway.

  The threshold setting unit 161 is connected to an operation unit (not shown), and acquires threshold information input by, for example, a user operation on the operation unit. Here, the threshold value is a value indicating a reference as to whether or not the load torque of the drum motor 181 detected by the torque detector 160 is within a normal range in which drive abnormality does not occur. The threshold setting unit 161 sets the threshold information acquired from the operation unit as a threshold used when determining whether or not the load torque of the drum motor 181 is appropriate.

  The threshold determination unit 162 determines whether or not the load torque of the drum motor 181 supplied from the torque detection unit 160 is within a preset threshold range. When the threshold determination unit 162 determines that the load torque of the drum motor 181 is outside the preset threshold range, the threshold determination unit 162 determines from the load torque and rotation speed (linear speed) of the drum motor 181 supplied from the torque detection unit 160. Reference is made to the control table 163. Then, an optimum parameter (optimum speed) at which the load torque of the drum motor 181 is within a normal range is acquired from the control table 163 and supplied to the feedback control unit 14.

  The control table 163 stores parameters (control values) for changing the load torque of the drum motor 181 to a normal range when a load change occurs in the drum motor 181. In the control table 163, as shown in FIG. 3, the linear speed (rotational speed) of the drum motor 181 that is actually set by the user in the column direction is arranged in a predetermined step, and the torque detection unit 160 actually performs the row direction. The detected load torque (load current) of the drum motor 181 is arranged in a predetermined step. An optimum linear velocity value (control value) of the drum motor 181 for adjusting the load torque of the drum motor 181 to the optimum value is arranged at a position overlapping in the column direction and the row direction. The acceleration / deceleration step of the control table 163 is set in units of 0.1%, for example. This is because if the step unit is set roughly, the load torque of the drum motor 181 whose speed has been changed may exceed the normal range.

  Further, as shown in FIG. 3, the control table 163 is provided for each speed of the drum motor 181 whose speed is changed. For example, a control table for controlling the load torque of the drum motor 181 to 300 mA, a control table for controlling the load torque to 305 mA, a control table for controlling the load torque to 310 mA, and the like are included.

  For example, when the load torque of the drum motor 181 is controlled to 300 mA, as shown in FIG. 3, the linear speed of the drum motor 181 during image formation is 299 mm / s, and the load current detected by the torque detector 160 is When the current is 330 mA, 298.5 mm / s is obtained as a change value of the linear speed of the drum motor 181 by referring to the control table 163 (see the hatched portion).

  Returning to FIG. 2, the feedback control unit 14 determines the speed command value supplied from the control unit 10, the control value (optimum parameter) of the drum motor 181 supplied from the threshold value determination unit 162 of the feedforward control unit 16, and the drum motor 181. The PWM command value for rotating the drum motor 181 in an appropriate (normal) range is generated based on the motor rotation speed fed back from the motor and supplied to the motor driving unit 180 of the image forming unit 18.

  The image forming unit 18 includes a drum unit 18A for driving the photosensitive drum 20, and a belt unit 18B for driving the intermediate transfer belt 90. The drum unit 18 </ b> A includes a motor driving unit 180, a drum motor 181, a drum driving mechanism unit 182, and the photosensitive drum 20. Based on the PWM command value supplied from the feedback control unit 14, the motor driving unit 180 generates a PWM signal having a frequency and a duty ratio corresponding to the PWM command value and supplies the PWM signal to the drum motor 181.

  The drum motor 181 rotates at a predetermined number of rotations (rotation speed) based on the PWM signal supplied from the motor drive unit 180, and the rotation speed of the drum motor 181 is set to each of the feedback control unit 14 and the mode control unit 12. To supply. The drum motor 181 constitutes an example of a first drive unit. The drum drive mechanism 182 receives the rotation of the drum motor 181 and rotates the photosensitive drum 20 at a predetermined rotational speed via various transmission mechanisms (for example, gears) and various clutches.

  The belt portion 18B includes a motor driving portion 183, a belt motor 184, a belt driving mechanism portion 185, and an intermediate transfer belt 90. Based on the PWM command value supplied from the control unit 10, the motor drive unit 183 generates a PWM signal having a frequency and duty ratio corresponding to the PWM command value and supplies the PWM signal to the belt motor 184.

  The belt motor 184 rotates at a predetermined rotation speed (rotational speed) based on the PWM signal supplied from the motor drive unit 183. The belt motor 184 constitutes an example of a second drive unit. The belt drive mechanism 185 receives the rotation of the belt motor 184 and rotates the intermediate transfer belt 90 at a predetermined rotation speed so as to have a speed difference from the drum motor 181 via various speed change mechanisms (for example, gears) and various clutches. Let Note that the intermediate transfer belt 90 may also perform feedback control and feedforward control in the same manner as the photoconductive drum 20.

[Relationship between drum motor and belt motor]
Next, the relationship between the linear speed difference between the drum motor 181 and the belt motor 184 and the load torque (drive current) will be described. In the image forming apparatus 100A according to the present invention, the drum motor 181 and the belt motor 184 are rotationally driven by a predetermined linear velocity difference. For example, the rotational speed of the belt motor 184 is set to be faster than the rotational speed of the drum motor 181. When there is a linear speed difference between the drum motor 181 and the belt motor 184, the belt motor 184 having a high rotational speed is in a state of assisting (pulling) the drum motor 181 having a low rotational speed.

  In this state, as shown in FIG. 4, when the linear speed of the drum motor 181 is increased, the assist amount of the belt motor 184 is reduced, so that the load current of the belt motor 184 decreases with a predetermined inclination. On the other hand, the load current of the drum motor 181 increases because the assist amount decreases and the burden increases. Therefore, when the load torque of the drum motor 181 is out of the proper range, a part of the load torque of the belt motor 194 is moved to the load torque of the drum motor 181 by changing and adjusting the linear speed of the drum motor 181. The load torque of the drum motor 181 can be controlled to an appropriate load.

[Operation example of image forming apparatus]
Next, an example of the operation of the above-described image forming apparatus 100A will be described. In this example, a case where the speed fluctuation control of the drum motor 181 is performed between sheets during the image forming operation will be described. As shown in FIG. 5, in step S <b> 10, the motor control unit 60 executes both feedback control by the feedback control unit 14 and feedforward control by the feedforward control unit 16 during image formation. At the time of image formation, since the load torque of the drum motor 181 has already been acquired by density stabilization processing before image formation, the drum motor 181 is combined with feedback control and feedforward control at the stage of normal image formation. Rotation control can be performed.

  In step S20, when the control unit 10 determines that the rotation speeds of the drum motors 181 of all colors are stable in a state where the feedback control and the feedforward control are used together, the image is formed so as to perform image formation based on the image data. Each part of the forming apparatus 100A is controlled.

  In step S <b> 30, the feedforward control unit 16 acquires, for example, a PWM command value for one rotation of the photosensitive drum 20 output from the feedback control unit 14 and a speed command value supplied from the control unit 10. The load torque of the drum motor 181 is calculated based on the PWM command value and the speed command value.

  In step S40, the control unit 10 determines whether or not the processing operation is between sheets during the image forming operation. If the control unit 10 determines that the processing operation of the image forming apparatus 100A is between sheets, the control unit 10 proceeds to step S50. On the other hand, if it is determined that the processing operation is not between sheets, the timing returns to step S10 because it is not the timing to perform load torque change control of the drum motor 181.

  In step S50, the threshold determination unit 162 of the feedforward control unit 16 determines whether or not the load torque of the motor driving unit 180 detected by the torque detection unit 160 is within a preset threshold range. When the threshold determination unit 162 determines that the load torque of the drum motor 181 detected by the torque detection unit 160 is within a preset threshold range, the detected load torque is determined to be within a normal range. Then, the load torque change control process is terminated and the process proceeds to a normal image forming process. On the other hand, if it is determined that the load torque of the drum motor 181 detected by the torque detector 160 is not within the preset threshold range, the detected load torque is not within the normal range, and the process proceeds to step S60.

  In step S60, the threshold value determination unit 162 of the feedforward control unit 16 refers to the control table 163 from the load torque and linear velocity of the drum motor 181 detected by the torque detection unit 160, and the load torque of the drum motor 181 is targeted. A proper parameter (control value) that is a value is acquired. For example, when the target load torque of the drum motor 181 is set to 300 mA, the control table 163 for the load torque 300 mA is referred to as shown in FIG. When the actual linear velocity of the drum motor 181 at the time of image formation is 299 mm / s and the load current detected by the torque detector 160 is 330 mA, the optimum value of the linear velocity of the drum motor 181 is 298. .5 mm / s (control value) is read from the control table 163 and acquired.

  In step S <b> 70, the feedback control unit 14 generates a PWM command value that optimizes the load torque of the drum motor 181 based on the control value supplied from the feedforward control unit 16 and supplies the PWM command value to the motor driving unit 180. For example, as described above, when the linear velocity of the drum motor 181 acquired from the control table 163 is 298.5 mm / s, the feedback control unit 14 changes the linear velocity of the drum motor 181 from 299 mm / s to 298.5 mm / s. Control to slow down. As a result, as shown in FIG. 4, the load of the drum motor 181 moves to the belt motor 184, so that the load torque of the drum motor 181 is controlled to an appropriate value of 330 mA.

  As described above, according to the first embodiment, the load is applied between the drum motor 181 and the belt motor 184 in accordance with the change in the linear speed of the drum motor 181 and the photosensitive drum. 20 can be moved. Thereby, the load torque of the drum motor 181 can be adjusted to an appropriate range by setting the linear velocity of the drum motor 181 to an optimum value. Therefore, since the load torque can be adjusted without requiring an expensive brake device as in the prior art, the photosensitive drum 20 when the feedback control and the feedforward control are executed with a low cost and simple configuration. Controlled breakage of the intermediate transfer belt 90 can be prevented. As a result, unnecessary cost increase, useless power consumption, and enlargement of the drive unit can be avoided. In the first embodiment, the speed change control is performed at a timing other than the image forming process such as a sheet interval, so that the feedforward control is prevented from being broken while preventing the productivity from being lowered due to the interruption of the job. can do.

<2. Second Embodiment>
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that speed change control is performed based on the result of threshold determination without using the control table 163. Since the configuration of the other image forming apparatus 100A is the same as that of the first embodiment described above, common components are assigned the same reference numerals and detailed description thereof is omitted.

[Configuration example of image forming apparatus]
As illustrated in FIG. 6, the feedforward control unit 16 of the image forming apparatus 100 </ b> B includes a torque detection unit 160, a threshold setting unit 161, and a threshold determination unit 162. The torque detection unit 160 acquires the PWM command value output from the feedback control unit 14 and the speed command value from the control unit 10, and calculates the load torque of the drum motor 181 from the acquired PWM command value and speed command value. To the threshold value determination unit 162.

  The threshold setting unit 161 sets a first threshold Th1 and a second threshold Th2 used when determining whether or not the load torque of the drum motor 181 is appropriate based on the threshold input by the operation unit. Here, the first threshold value Th1 is a value at which the drum motor 181 cannot rotate if the load torque is smaller than this value, and the second threshold value Th2 is an overload state if the load torque is larger than this value. It is a value that becomes.

  The threshold determination unit 162 determines whether the load torque of the drum motor 181 supplied from the torque detection unit 160 is smaller than a preset first threshold Th1 or larger than a second threshold Th2. When the threshold value determination unit 162 determines that the load torque of the drum motor 181 is outside the preset threshold value range, the control value for accelerating or decelerating the rotation speed (linear speed) of the drum motor 181 by a predetermined unit. Is supplied to the feedback control unit 14.

  The feedback control unit 14 determines the load torque of the motor drive unit 180 based on the control value supplied from the threshold determination unit 162, the speed command value supplied from the control unit 10, and the motor rotation speed fed back from the drum motor 181. A PWM command value for driving in an appropriate range is generated and supplied to the motor drive unit 180.

[Operation example of image forming apparatus]
Next, an example of the operation of the image forming apparatus 100A according to the second embodiment will be described. Since the processing from step S100 to S130 shown in FIG. 7 is the same as the processing from step S10 to S40 shown in FIG. 5 described in the first embodiment, the description is simplified. In step S <b> 100, the motor control unit 60 executes both feedback control by the feedback control unit 14 and feedforward control by the feedforward control unit 16 during image formation.

  In step S110, when the control unit 10 determines that the rotation speeds of the drum motors 181 for all colors are stable in a state where both feedback control and feedforward control are used, the image is formed so as to perform image formation based on the image data. Each part of the forming apparatus 100A is controlled. Subsequently, in step S120, the feedforward control unit 16 obtains, for example, a PWM command value for one rotation of the photosensitive drum 20 output from the feedback control unit 14, and determines the drum motor 181 from the average value of the PWM command values. Calculate the load torque.

  In step S130, the control unit 10 determines whether or not the processing operation of the image forming apparatus 100A is between sheets during the image forming operation. If the control unit 10 determines that the processing operation of the image forming apparatus 100A is between sheets, the control unit 10 proceeds to step S140. On the other hand, when it is determined that the processing operation of the image forming apparatus 100A is not between sheets, the timing returns to step S100 because it is not the timing for performing the load torque change control.

  In step S140, the threshold determination unit 162 of the feedforward control unit 16 determines whether or not the load torque of the drum motor 181 detected by the torque detection unit 160 is smaller than a preset first threshold Th1. If the threshold determination unit 162 determines that the load torque of the drum motor 181 detected by the torque detection unit 160 is smaller than the first threshold Th1, the threshold determination unit 162 determines that the detected load torque is abnormal and proceeds to step S150. On the other hand, if it is determined that the load torque of the drum motor 181 detected by the torque detector 160 is not smaller than the first threshold value Th1, the process further proceeds to step S160.

  In step S150, the feedback control unit 14 generates a control value that accelerates the rotational speed of the drum motor 181 by 0.1% with respect to the linear speed of the drum motor 181 that is currently driven, and sends the control value to the feedback control unit 14. Supply. The reason why the linear velocity acceleration change unit is set to 0.1% is that the resolution is not roughened. Therefore, even if it is not 0.1%, it can be selected as long as the resolution does not become rough. Further, the rotational speed change control of the drum motor 181 is performed so that the linear velocity difference between the drum motor 181 and the belt motor 184 is ± 1% or less. This is because if the linear velocity difference between the drum motor 181 and the belt motor 184 exceeds ± 1%, the image formation is affected.

  When the speed change is completed, the process returns to step S130 again to determine again whether or not the processing operation of the image forming apparatus 100A is between sheets. If it is determined that there is a gap between sheets, it is determined again whether or not the load torque of the drum motor 181 subjected to acceleration control in step S150 is smaller than the first threshold Th1. Such change control processing in units of 0.1% is repeated until the load torque of the drum motor 181 becomes larger than the first threshold value Th1.

  On the other hand, in step S160, the threshold determination unit 162 of the feedforward control unit 16 determines whether or not the load torque of the drum motor 181 detected by the torque detection unit 160 is greater than a preset second threshold Th2. If the threshold determination unit 162 determines that the load torque of the drum motor 181 detected by the torque detection unit 160 is greater than the second threshold Th2, the threshold determination unit 162 determines that the detected load torque is abnormal and proceeds to step S170. On the other hand, when it is determined that the load torque of the drum motor 181 detected by the torque detector 160 is smaller than the second threshold Th2, the image forming process is continued assuming that the load torque is within the optimum value range.

  In step S <b> 170, the feedback control unit 14 generates a control value that decelerates the rotational speed of the drum motor 181 by 0.1% with respect to the linear speed of the drum motor 181 that is currently driven to generate the feedback control unit 14. To supply. The reason why the linear velocity deceleration amount is set to 0.1% is to prevent the resolution from becoming rough. When the speed change is completed, the process returns to step S130 again to determine again whether or not the processing operation of the image forming apparatus 100A is between sheets. If it is determined that there is a gap between sheets, it is determined again whether or not the load torque of the drum motor 181 controlled to be decelerated in step S170 is greater than the second threshold Th2. Such change control processing in units of 0.1% is repeated until the load torque of the drum motor 181 becomes smaller than the second threshold Th2.

  As described above, the same effects as those of the first embodiment described above can also be obtained by the second embodiment. That is, the load can be moved between the drum motor 181 and the belt motor 184 via the intermediate transfer belt 90 and the photosensitive drum 20 in accordance with the change in the linear speed of the drum motor 181. Thereby, the load torque of the drum motor 181 can be adjusted to an appropriate range by setting the linear velocity of the drum motor 181 to an optimum value. Therefore, since the load torque can be adjusted without requiring an expensive brake device as in the prior art, the photosensitive drum 20 when the feedback control and the feedforward control are executed with a low cost and simple configuration. Controlled breakage of the intermediate transfer belt 90 can be prevented. In addition, since no table or the like is used, the memory capacity can be reduced.

<3. Third Embodiment>
Next, a third embodiment will be described. The third embodiment is different from the first and second embodiments that control the rotational speed (linear speed) on the drum motor 181 side in that the rotational speed (linear speed) on the belt motor 184 side is changed and controlled. Is different. The configuration of the other image forming apparatus 100B is the same as that of the image forming apparatus 100A described in the first and second embodiments described above. Description is omitted.

[Operation Example of Image Forming Apparatus (Speed Change Control by Threshold Determination)]
Next, an example of the operation of the image forming apparatus 100B according to the third embodiment will be described. In this example, a case where the speed change control of the belt motor 184 is performed between sheets during an image forming operation will be described. As shown in FIG. 8, first, in step S200, the motor control unit 60 executes the feedback control by the feedback control unit 14 and the feedforward control by the feedforward control unit 16 in combination during image formation.

  In step S210, when the control unit 10 determines that the rotation speeds of the drum motors 181 of all colors are stable in a state where the feedback control and the feedforward control are being performed, the control unit 10 performs image formation based on the image data. Each part of the image forming apparatus 100B is controlled. Subsequently, in step S220, the feedforward control unit 16 obtains, for example, a PWM command value for one rotation of the photosensitive drum 20 output from the feedback control unit 14, and calculates the load torque of the drum motor 181.

  In step S230, the control unit 10 determines whether or not the processing operation of the image forming apparatus 100B is between sheets during the image forming operation. If the control unit 10 determines that the processing operation of the image forming apparatus 100B is between sheets, the control unit 10 proceeds to step S240. On the other hand, if it is determined that the processing operation of the image forming apparatus 100B is not between sheets, it is not the timing for performing the load torque change control of the drum motor 181, so the process returns to step S200 and the normal control is continued.

  In step S240, the threshold determination unit 162 of the feedforward control unit 16 determines whether or not the load torque of the drum motor 181 detected by the torque detection unit 160 is smaller than a preset third threshold Th3. If the threshold determination unit 162 determines that the load torque of the drum motor 181 detected by the torque detection unit 160 is smaller than the third threshold Th3, the threshold determination unit 162 determines that the detected load torque of the drum motor 181 is abnormal. Proceed to S250. On the other hand, if it is determined that the load torque of the drum motor 181 detected by the torque detector 160 is not smaller than the third threshold Th3, the process proceeds to step S260.

  In step S250, the feedback control unit 14 generates a control value that decelerates the rotational speed of the belt motor 184 by 0.1% with respect to the linear speed of the belt motor 184 that is currently being driven, and thereby generates the feedback control unit 14. Is supplied to the control unit 10. Here, the reason why the deceleration unit of the rotational speed of the belt motor 184 is set to 0.1% is to perform speed change control efficiently and with high accuracy. Further, the rotational speed of the belt motor 184 is controlled so that the linear velocity difference between the belt motor 184 and the drum motor 181 is ± 0.3% or less. This is because when the difference in linear velocity between the belt motor 184 and the drum motor 181 exceeds ± 0.3%, the image formation is affected. In particular, since the belt motor 184 drives the intermediate transfer belt 90 to rotate and has a great influence on image formation, the linear speed difference is made smaller than when the speed change control of the drum motor 181 is performed. To do.

  When the speed change is completed, the process returns to step S230 again to determine again whether or not the processing operation of the image forming apparatus 100B is between sheets. If it is determined that there is a gap between sheets, it is determined again whether or not the load torque of the drum motor 181 subjected to the deceleration control in step S250 is smaller than the third threshold Th3. Such speed change control in units of 0.1% is repeated until the load torque of the drum motor 181 becomes larger than the third threshold Th3.

  The control unit 10 supplies the PWM command value supplied from the feedback control unit 14 to the motor drive unit 183 of the belt unit 18B. Based on the PWM signal supplied from the motor drive unit 183, the belt motor 184 rotates by decelerating the current linear speed by 0.1%. As a result, the load of the belt motor 184 moves to the drum motor 181 via the intermediate transfer belt 90 and the photosensitive drum 20, so that the load torque of the drum motor 181 can be adjusted to an appropriate range.

  On the other hand, in step S260, the threshold determination unit 162 of the feedforward control unit 16 determines whether or not the load torque of the drum motor 181 detected by the torque detection unit 160 is larger than a preset fourth threshold Th4. If the threshold determination unit 162 determines that the load torque of the drum motor 181 detected by the torque detection unit 160 is larger than the fourth threshold Th4, the threshold determination unit 162 determines that the detected load torque is abnormal and proceeds to step S270. On the other hand, when it is determined that the load torque of the drum motor 181 detected by the torque detector 160 is not larger than the fourth threshold Th4, image formation is performed assuming that the load torque of the drum motor 181 is within the optimum value range. continue processing.

  In step S <b> 270, the feedback control unit 14 generates a control value that accelerates the rotational speed of the belt motor 184 by 0.1% with respect to the linear speed of the belt motor 184 that is currently driven to generate the feedback control unit 14. Is supplied to the control unit 10. Here, the reason why the acceleration unit of the rotational speed of the belt motor 184 is 0.1% and the reason why the linear speed difference between the belt motor 184 and the drum motor 181 is 0.3% or less are as described above. Since it is the same, it abbreviate | omits. When the speed change is completed, the process returns to step S230 again to determine again whether or not the processing operation of the image forming apparatus 100B is between sheets. When it is determined that there is a gap between sheets, it is determined again whether or not the load torque of the drum motor 181 subjected to acceleration control in step S270 is larger than the fourth threshold Th4. The speed change control is repeatedly performed until the load torque of the drum motor 181 becomes smaller than the fourth threshold Th4.

  The control unit 10 supplies the PWM command value supplied from the feedback control unit 14 to the motor drive unit 183 of the belt unit 18B. The belt motor 184 rotates by accelerating by 0.1% with respect to the current linear velocity based on the PWM signal supplied from the motor driving unit 183. As a result, the load of the belt motor 184 moves to the drum motor 181 via the intermediate transfer belt 90 and the photosensitive drum 20, so that the load torque of the drum motor 181 can be adjusted to an appropriate range.

[Operation example of image forming apparatus (speed change control by control table)]
Next, speed change control using a control table will be described. The difference between the control table used in the second embodiment and the control table 163 described in the first embodiment is that the change linear velocity of the drum motor 181 is not at the overlapping position in the column direction and the row direction. The change linear velocity of the belt motor 184 is arranged. In the present embodiment, the load torque of the drum motor 181 is adjusted to an appropriate range by controlling the change to the changed linear speed of the belt motor 184.

  When speed change control is performed using the control table of this example, for example, the linear speed (rotational speed) of the drum motor 181 set by the user is acquired from the control unit 10 and detected by the torque detection unit 160. The load torque (load current) of the drum motor 181 is acquired. Subsequently, the control table is referred to from the acquired linear speed of the drum motor 181 and the load torque, and the changed linear speed of the belt motor 184 at which the drum motor 181 becomes an appropriate load is read and acquired. The feedforward control unit 16 supplies a control value based on the changed linear speed of the belt motor 184 to the feedback control unit 14. In the control unit 10, the PWM command value supplied from the feedback control unit 14 is supplied to the motor driving unit 183 of the belt unit 18B. The belt motor 184 rotates by changing the rotation speed based on the PWM signal supplied from the motor driving unit 183. As a result, the load of the belt motor 184 moves to the drum motor 181 via the intermediate transfer belt 90 and the photosensitive drum 20, so that the load torque of the drum motor 181 can be adjusted to an appropriate range.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. In the above embodiment, the load torque change control is performed between papers, but the present invention is not limited to this. It can be applied at any time without interrupting the job. In the above embodiment, the speed change control is performed on either the drum motor 181 side or the belt motor 184 side. However, both the drum motor 181 and the belt motor 184 can be controlled simultaneously. .

DESCRIPTION OF SYMBOLS 10 ... Control part, 12 ... Mode control part, 14 ... Feedback control part, 16 ... Feed forward control part, 18 ... Image formation part, 20 ... Photosensitive drum, 60. ..Motor control unit, 90 ... intermediate transfer belt, 160 ... torque detection unit, 161 ... threshold setting unit, 162 ... threshold determination unit, 163 ... control table, 181 ... drum Motor, 184 ... belt motor, 100A, 100B ... image forming apparatus, Th1 ... first threshold, Th2 ... second threshold, Th3 ... third threshold, Th4 ... 4th threshold

Claims (6)

A photosensitive drum on which a toner image is latent,
A belt onto which a toner image latent image is transferred to the photosensitive drum;
A first drive unit for driving the photosensitive drum;
A second drive unit that drives the belt to have a predetermined speed difference from the photosensitive drum;
The load torque of the first drive unit is detected, feedforward control is performed based on the detected load torque of the first drive unit, and the first target is obtained based on the control target value obtained by the feedforward control. A control unit that performs feedback control so that the load torque of the driving unit is within an appropriate range,
The controller is
The load torque of the first drive unit is compared with a preset threshold range indicating an appropriate load range of the first drive unit, and the load torque of the first drive unit is determined based on the comparison result. Is determined not to be within the threshold range, the first and second driving units are controlled to adjust the speed difference between the photosensitive drum and the belt by controlling the driving of the first driving unit. An image forming apparatus, wherein the load torque of the drive unit is adjusted to an appropriate load. The controller is
A table in which the speed and load torque of the first drive unit obtained by detection and the appropriate speed of the first drive unit for returning the load torque of the first drive unit to the proper load torque are associated with each other. Have
When it is determined that the load torque of the first drive unit obtained by detection is not within the preset threshold range, the table is referred to from the detected speed and load torque of the first drive unit. The image forming apparatus according to claim 1, wherein the appropriate speed of the first drive unit is acquired, and the first drive unit is drive-controlled so as to obtain the acquired appropriate speed. The controller is
When the lower limit of the threshold range is a first threshold and the upper limit of the threshold range is a second threshold,
When it is determined that the load torque of the first drive unit obtained by detection is smaller than the first threshold value set in advance, the speed of the first drive unit is accelerated by a predetermined unit,
When it is determined that the load torque of the first driving unit obtained by the detection is larger than the second threshold value set in advance, the speed of the first driving unit is reduced by a predetermined unit. The image forming apparatus according to claim 1. The controller is
A table in which the speed and load torque of the first drive unit and the appropriate speed of the second drive unit for returning the load torque of the first drive unit to an appropriate load torque are associated with each other;
When it is determined that the load torque of the first driving unit obtained by the detection is not within the preset threshold range, the speed and the load torque of the first driving unit are referred to the table. The said 2nd drive part is acquired and the said 2nd drive part is drive-controlled so that it may become the acquired said appropriate speed. The said 2nd drive part is obtained. Image forming apparatus. The controller is
When the lower limit of the threshold range is the third threshold and the upper limit of the threshold range is the fourth threshold,
When it is determined that the load torque of the first driving unit obtained by the detection is smaller than the preset third threshold, the speed of the second driving unit is reduced by a predetermined unit,
When it is determined that the load torque of the first driving unit obtained by the detection is larger than the preset fourth threshold, the speed of the second driving unit is accelerated by a predetermined unit. The image forming apparatus according to any one of claims 1 to 3. The speed change control of the first and second drive units is performed with an accuracy of 0.1% with respect to the speed of the first and second drive units. The image forming apparatus according to any one of the above.

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