JP2010276777A - Image forming apparatus and control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent failure of a feedforward control when performing the control of the feedback and feedforward of a motor for driving photoreceptor drums or the like. <P>SOLUTION: An image forming apparatus includes: a control unit which performs the speed feedback control and speed feedforward control of the drive motor; a load detecting unit which detects the drive load torque of the drive motor; and a load torque generation unit which generates a predetermined drive load in addition to a normal drive load with respect to the drive motor. The control unit has a threshold set within a load torque range in which the speed feedforward control is executable, and when the load torque detected by the load detecting unit is equal to or less than the threshold, the control unit performs the control and operation of the load torque generation unit, and increases the drive load with respect to the drive motor, and the failure of the speed feedforward control is avoided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms a toner image on an image carrier such as a photosensitive drum that rotates by an electrophotographic method, and a control unit that is provided in the image forming apparatus. The present invention relates to rotational drive control that performs control to keep the rotational speed of the motor uniform.

In an electrophotographic image forming apparatus, a toner image is formed on an image carrier such as a rotating photosensitive drum or photosensitive belt, and the formed toner image is directly or indirectly transferred onto a recording paper and further fixed. An image is formed.
In this image formation, if the speed of the image carrier that rotates at a uniform rotational speed is changed in forming a latent image for image exposure by the exposure means, distortion in the sub-scanning direction occurs in the formed image.
In a tandem color image forming apparatus, a single color image formed by a plurality of single color image forming units is superimposed to form a color image on a recording sheet. The image carrier in each single color image forming unit is the same. It is an indispensable condition for obtaining a high-quality color image that is high speed and has no unevenness in speed. For this reason, if the speed of the image carrier of each color image forming unit is different, color misregistration occurs.
For speed control of the photoconductor, various control methods using speed detecting means have been proposed. However, if the angular speed of the photoconductor is to be controlled at a constant speed in real time, the rotational speed control is performed using the angular speed detecting means by the encoder. Rotational speed control method is used.
For this type of rotational speed control, the following Patent Document 1 and Patent Document 2 propose proposals for efficient processing.

In Japanese Patent Laid-Open No. 2004-228561, a profile of the rotation unevenness of the photosensitive drum at a certain time is measured using feedback control or feedforward control with respect to the angular velocity control of the photosensitive drum, and the profile is measured until the next determined sampling timing. It has been proposed to perform angular velocity control using data.
Further, in Patent Document 2, when the angular velocity control of the photosensitive drum is controlled using feedback control and feedforward control, the current drum position before one rotation is updated while constantly updating the angular velocity deviation profile in the memory. It is proposed that the angular velocity unevenness is rapidly converged by performing drive control with reference to the angular velocity deviation value at.

  Incidentally, a cleaning blade is pressed against the surface of the photosensitive drum to remove the toner on the surface of the photosensitive drum. At this time, the frictional load between the surface of the photosensitive drum and the cleaning blade largely fluctuates due to environmental conditions, image formation history, changes in the characteristics of the cleaning blade over time, and the like. Feedback control is performed so that the photosensitive drum is rotated at a constant rotational speed even when such a change in friction load occurs.

  Further, as a technique for eliminating the adverse effects caused by the rotation of the rotating body not being performed smoothly, a technique for adjusting meandering and shifting generated in the belt has been proposed in Patent Document 3. In this technique, a torque generating mechanism that generates an arbitrary torque in a rotating body other than the driving rotating body that supports the belt is provided, and the above meandering and shifting are prevented by adjusting the torque of the torque generating mechanism.

  Further, in order to cope with a change with time with respect to the cleaning blade, in order from the upstream in the rotation direction of the image carrier, a first cleaning blade and a second cleaning blade that contains an abrasive and can be contacted and detached are provided periodically. An apparatus for bringing the second cleaning blade into contact with the image carrier has been proposed (Patent Document 4). With this apparatus, even when foreign matter that is difficult to remove with the first cleaning blade adheres to the surface of the image carrier, foreign matter can be removed with the second cleaning blade, and image quality can be maintained over a long period of time. Yes.

  Similarly, in order to cope with a change with time with respect to the cleaning blade, in Patent Document 5, a change in the frictional force between the image carrier and the cleaning blade is detected, and the cleaning blade and the image carrier in the vicinity of the contact portion of the cleaning blade are detected. An image forming apparatus that can change the angle formed by the body has been proposed.

JP-A-6-327278 JP 2003-186368 A JP 2008-181071 A JP 2006-293286 A JP 2003-21995 A

  Incidentally, PLL-controlled brushless motors that are generally constructed by hardware have constant settings that can maintain a wide and stable rotation. On the other hand, in order to ensure a wide and stable operation, the suppressing power against fluctuation is small. Therefore, the control method of a motor that needs to suppress fluctuations such as a drum motor and a belt motor is insufficient, and feed is performed in addition to the PLL control (feedback control) in order to suppress fluctuations. Forward control is applied to suppress low-frequency fluctuations (such as one-turn unevenness).

However, as shown in Patent Documents 1 and 2, as the speed control of the drive motor, in a device that performs speed feedback control and speed feedforward control, the load on the photosensitive drum and the like is reduced and the drive characteristics change. When deviating from the feedforward control range, the possibility of occurrence of a drive abnormality increases. This is because when the feedforward control is applied, the control range in which the rotation can be stably performed becomes narrow, and it is impossible to achieve both suppression of fluctuation and a wide stable rotation region. In other words, when feed-forward control is applied, the range in which stable rotation is possible due to fluctuations in the rotation speed and load is narrower than when performing normal PLL control, and control failure occurs due to load fluctuations. To do.
In order to avoid this, it is conceivable to avoid a control failure by setting a bias brake to the photosensitive drum so as to be overloaded from the beginning. However, in this method, since the load for the bias brake is always excessively greater than the normal load, it is necessary to increase the output of the drive motor, which is necessary in terms of motor size (space), cost, and power. There is also a problem that there are many useless parts.

Further, in the proposed technique disclosed in Patent Document 3, the belt shift position detected by the belt shift position detection unit in the belt drive is compared with the target belt shift position, and a torque generation mechanism according to the calculated position deviation. Although the torque generation mechanism is variable, the motor is not controlled based on load information, and is difficult to apply to the feedback control and feedforward control. The purpose of avoiding the control failure in can not be achieved.
Further, the proposed techniques disclosed in Patent Documents 4 and 5 are not related to the speed control of the drive motor, and of course cannot achieve the purpose of avoiding the failure of the feedforward control.

  The present invention has been made against the background of the above circumstances, and provides an image forming apparatus and a control unit capable of preventing generation of useless energy as much as possible and avoiding control failure of feedforward control. Objective.

  That is, in the image forming apparatus of the present invention, a drive motor that performs speed feedback control and speed feedforward control, a control unit that performs the speed feedback control and the speed feedforward control on the drive motor, and the drive A load detection unit that detects a drive load torque of the motor; and a load torque generation unit that can generate a predetermined drive load in addition to a normal drive load for the drive motor, and the control unit includes: And a threshold value set within a load torque range in which the speed feedforward control can be performed, and when the load torque detected by the load detector is less than or equal to the threshold, the load torque generator is controlled. , By increasing the driving load on the drive motor, it is possible to avoid failure of the speed feedforward control And wherein the door.

  The control unit of the present invention is a control unit that performs speed feedback control and speed feedforward control on the drive motor, and is a threshold value set within a load torque range in which the speed feedforward control can be performed. When the drive load torque of the drive motor is less than or equal to the threshold value, the load torque generation unit that generates a predetermined drive load in addition to the normal drive load for the drive motor is controlled to drive the drive motor. It is possible to avoid failure of the speed feedforward control by increasing the load.

  According to the present invention, when the load torque of the drive motor falls below a preset threshold value, the load on the drive motor is increased by the load torque generation unit under the control of the control unit, and control failure in the feedforward control can be avoided. If the load torque of the drive motor shows an appropriate high load torque without falling below the above threshold, the drive mode can be operated with a normal load without increasing the load on the drive motor, and wasteful energy Control breakdown in feedforward control can be avoided without causing consumption.

  The control unit includes a CPU and a program that operates the CPU, a ROM that stores the program, a RAM that temporarily stores data and functions as a work area, a storage unit that includes a nonvolatile memory that stores setting data, process parameters, and the like. Composed.

  As the drive motor, a motor for driving an image carrier such as a photosensitive drum or a photosensitive belt is typically shown. In the image carrier, as described above, since slight rotation unevenness adversely affects image quality, rotation control with high accuracy (for example, several μm order) is required. However, the present invention is not limited to a specific drive target in the drive motor.

The load detection unit that detects the load torque of the drive motor can detect the drive load torque from the PWM command value of the drive motor. The PWM command value is generated by the control unit, and the load torque of the drive motor can be easily calculated from the command value and the speed of the drive motor. For example, for one rotation of the image carrier, the average value of the load torque can be calculated from the average value of the PWM command value and the rotation speed of the drive motor. Here, the PWM command value means a PWM duty command value for controlling the PWM duty.
When the load torque is calculated by the control unit using the PWM command value, the control unit functions as a load detection unit.

  When speed feedforward control is performed on the drive motor, a control value can be determined based on a speed fluctuation profile to be driven by the drive motor and a parameter for speed feedforward control. The control unit generates a reverse phase instruction value for canceling the periodic speed fluctuation of the image carrier with respect to the profile, based on the speed feedforward control parameter. The control unit performs control such as P control, PI control, PD control, and PID control by adding a control value related to feedback control to the reverse phase instruction value. The parameter for speed feedforward control is set in advance according to the load torque in order to cancel the speed fluctuation of the rotating body, and is prepared as a control table.

  The threshold value is set within a load torque range in which the speed feedforward control can be performed, for example, within a load torque range in which a speed feedforward control parameter can be used. The threshold value is set so that the feedforward control may fail when the threshold value is lower than the threshold value, and the feedforward control is prevented from failing when the threshold value is exceeded. Therefore, the threshold value can be appropriately set in consideration of the safety level. The threshold value is stored in a storage unit included in the control unit, and can be used for rotation control by appropriately referring to the control unit.

  In the present invention, a load torque generating unit that can generate a predetermined driving load in addition to the normal driving load is used for the driving motor. As the load torque generating unit, various types can be used. For example, the load torque generating unit can be configured by an electromagnetic brake capable of changing a brake torque by an input current or an input voltage. Examples of the electromagnetic brake include a bias type and a powder type. Incorporating this electromagnetic brake into the drive motor, or adding brake torque to the drive object or drive force transmission mechanism, generates a predetermined drive load in addition to the normal drive load for the drive motor Is possible.

  As the load torque generating unit, a mechanism included in the image forming apparatus can be used. For example, a second cleaning blade that can be pressed / released with respect to the image carrier is installed downstream of the first cleaning blade used for cleaning the image carrier, and can be used as a load torque generator.

  The second cleaning blade has a function of cleaning the image carrier in addition to a function as a load torque generating unit. Therefore, by properly using the first cleaning blade and the second cleaning blade, it is possible to reduce the difference in deterioration over time of both and to lengthen the replacement cycle. For example, normal cleaning performance can be realized by any one of the cleaning blades, and the control unit stores the pressure bonding time of each of the cleaning blades and alternates at a predetermined cycle by control of the control unit. In addition, when the load torque of the drive motor detected by the load detector becomes equal to or less than the threshold value, both the cleaning blades are pressure-bonded and used to avoid failure of the feedforward control. The predetermined period is also set in advance and stored in the control unit, and the cleaning blades are alternately used while being compared with the elapsed time of pressure bonding of the cleaning blades. The predetermined period can be set as appropriate, and an appropriate time can be set so that the difference in deterioration between the two cleaning blades is reduced. For example, the cycle can be set to thousands of image forming sheets.

In the control unit, as described above, the threshold value related to the load torque is set and used for control. However, a second threshold value having a value larger than the threshold value can be set and used for control. . The second threshold value is the load torque applied by the load torque generator when the load torque for the drive motor is increased by the load torque generator when the load torque exceeds the second threshold. Can be used to unlock or reduce. The second threshold value has a value larger than the first threshold value. If a load torque is generated more than this, the first threshold value is canceled even if the load increase by the load torque generating unit is canceled. The load increase is canceled on the assumption that a state of a load torque exceeding the above is obtained. Thereby, it is possible to avoid wasteful energy consumption when there is no risk of failure of the feedforward control. In addition, when the load torque that can be generated in the load torque generation unit can be adjusted, if the load torque is equal to or greater than the second threshold value, control is performed so as to reduce the amount of load torque that is increased in the load torque generation unit. You can also. The second threshold value is set so that the load torque when the load torque amount increased by the load torque generating unit is canceled and the load torque is canceled exceeds the first threshold value.
Further, a third threshold value is set between the first threshold value and the second threshold value, and when the load torque is equal to or greater than the third threshold value, the load torque amount increased by the load torque generating unit is reduced, It is also possible to perform control so as to cancel the increase in load torque above the third threshold.

As described above, in the image forming apparatus of the present invention, the drive motor that performs speed feedback control and speed feedforward control, and the control unit that performs the speed feedback control and the speed feedforward control on the drive motor. A load detection unit that detects a drive load torque of the drive motor, and a load torque generation unit that can generate a predetermined drive load in addition to the normal drive load for the drive motor, The control unit has a threshold set within a load torque range in which the speed feedforward control can be performed, and when the load torque detected by the load detection unit is equal to or less than the threshold, the load torque generation unit To control the speed feed forward control by increasing the driving load on the drive motor. Possible and,
The control unit of the present invention is a control unit that performs speed feedback control and speed feedforward control on the drive motor, and has a threshold set within a load torque range in which the speed feedforward control can be performed. When the drive load torque of the drive motor is less than or equal to the threshold value, the load torque generation unit that generates a predetermined drive load in addition to the normal drive load for the drive motor is controlled to operate the drive load for the drive motor. Since it is possible to avoid failure of the speed feedforward control by increasing,
It is possible to increase the driving load only when necessary by the torque generating means, and it is possible to avoid failure of the feedforward control without using unnecessary energy with a motor having a minimum required size.
In addition, when the load torque generator that generates load torque is realized with a cleaning blade, it is not necessary to use an expensive bias brake, and it is possible to avoid failure of feedforward control with an inexpensive machine configuration. It becomes. Further, by controlling the use of the two cleaning blades, the cleaning blade replacement cycle can be further extended.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. Similarly, it is a control block diagram. Similarly, it is a figure which shows the fluctuation profile and the cancellation result by feedforward control. Similarly, it is a flowchart showing a procedure of load control at the time of initial operation. Similarly, it is a flowchart showing a load control procedure during execution of JOB. Similarly, it is the flowchart which shows the procedure of load control between JOB. Similarly, it is a flowchart showing a procedure of load control during an initial operation using a second threshold. Similarly, it is a flowchart showing a procedure of load control during execution of JOB using the second threshold. Similarly, it is a flowchart showing a procedure of load control between JOBs using the second threshold. Similarly, it is a flowchart showing a procedure of load control between JOBs when the first and second cleaning blades are alternately used.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration block diagram of an image forming apparatus of the present invention.
The engine control unit 2 controls a motor that performs a mechanical operation in the image forming apparatus 1, and includes a CPU, a program that operates the CPU, a storage unit that includes a ROM, a RAM, a nonvolatile memory, and the like. Has been.
The engine control unit 2 is connected to a motor control unit 3 that controls driving of a motor 4 that rotationally drives a photosensitive drum, which is an image carrier, by serial connection or bus connection so that they can communicate with each other. The engine control unit 2 instructs the motor control unit 3 to perform feedback control and feedforward control.

The motor control unit 3 includes a CPU, a program for operating the CPU, a storage unit including a ROM, a RAM, a nonvolatile memory, and the like. The motor control unit 3 transmits a PWM command value for controlling the speed of the motor 4 corresponding to feedback control and feedforward control to the motor 4 as a PWM signal. Further, in the motor 4, rotation is detected and fed back to the motor control unit 3 as an FG signal.
The engine control unit 2 and the motor control unit 3 function as a control unit of the present invention by cooperating. In the case where the image forming apparatus 1 is a color image forming apparatus capable of forming a color image, the motor control unit 3 is configured to correspond to each color (for example, four colors of YMCK). Therefore, the motor 4 and the photosensitive drum are also configured to correspond to each color (for example, four colors of YMCK).

  Further, the output of the encoder 5 that detects the rotation of the drum shaft of the photosensitive drum is transmitted to the motor control unit 3. In the figure, two encoders are shown, but in an image forming apparatus having a color image forming unit, a photosensitive drum is prepared for each color, and an encoder for detecting the rotation of each photosensitive drum is prepared. The detection results are individually transmitted to the motor control unit 3.

  Further, the image forming apparatus 1 includes a motor load variable unit 6 that variably generates a load torque for the motor 4 to increase the load torque in the motor 4. The motor load varying means 6 corresponds to a load torque generating unit of the present invention. The motor load varying means 6 is subjected to load generation control by being given a control signal by either the engine control unit 2 or the motor control unit 3.

  The motor load varying means 6 can be constituted by a variable bias brake provided in the rotational drive system of the photosensitive drum or a second cleaning blade positioned downstream of the first cleaning blade for cleaning the photosensitive drum. In a color image forming apparatus including a plurality of photosensitive drums, a motor load unit 6 is provided for each photosensitive drum.

FIG. 2 is a diagram illustrating a control block in which the rotation control of the motor 4 is performed by the control unit.
The motor control unit 3 performs only the feedback control as the drum drive control during the stabilization operation excluding the registration adjustment operation in the initial operation (adjustment operation such as image stabilization) after the image forming apparatus is turned on. I do.
That is, the FG signal is fed back from the motor 4, and in the rotating drum driven by the motor 4, the rotation of the drum shaft is detected by the encoder 5, and the detected value is fed back. The motor control unit 3 outputs a PWM command value so that the target value is obtained by these feedback signals, and controls the motor 4. The frequency of the PWM command value is usually about 20 kHz. In the feedback control, methods such as P control, I control, PI control, and PID control can be appropriately used. Further, the motor control unit 3 measures the control output (PWM command value = drive torque) to the motor 4 of each color at that time.

In the normal operation after the initial operation, the motor control unit 3 generates a speed fluctuation profile for the past one round of rotation of the rotating drum of each color from the detection result by the encoder 5. An example of the speed variation profile is shown in FIG. The broken line in the figure is the target value, that is, the command speed, and the speed fluctuation profile varies with respect to the command speed.
The motor control unit 3 can average the PWM command value for one rotation of each color photosensitive drum, and calculate the drive torque based on the electric power and the rotation speed supplied to the motor 4 of each color. Further, the driving torque may be obtained as an average value for one rotation of each color photosensitive drum. The calculation method of the driving torque can be performed by a conventional method. Therefore, the motor control unit 3 functions as a load detection unit that detects the driving load torque of the motor 4 of each color.

  In the motor control unit 3, a parameter for canceling the speed variation according to the drive torque is stored in advance in the storage unit, and a necessary parameter is selected from the calculated drive torque. The parameter may be set for each color. The motor control unit 3 generates a reverse phase component for each color that cancels out the speed fluctuation from the parameter and the speed fluctuation profile as shown in FIG. In addition to the above PI control, feedforward control is performed. As shown in FIG. 3 (c), the feedforward control to which the reverse phase component is added cancels the speed fluctuation, thereby obtaining a stable rotational drive state.

Further, the motor control unit 3 assumes a driving torque range in which the above parameters can be used, and a threshold value is set as a value having a safety level with respect to the lower limit within the torque range. That is, the threshold value is set so that the feed forward control does not fail when the threshold value is exceeded, and the control failure does not occur immediately below the threshold value. The threshold value is stored in a storage unit included in the motor control unit 3 and is referred to as appropriate. The threshold value may be set for each color, or a value common to each color may be set. The motor control unit 3 compares the load torque and the threshold value obtained above for each color, controls the motor load variable means 6 according to the magnitude, and performs load switching for the motor 4 of each color.
Below, the procedure is demonstrated based on the flowchart of FIGS. In the following description, each flowchart is described, but the same procedure is performed for each color. Therefore, the procedure may differ depending on each color according to each determination content.

First, the control procedure by the control unit during the initial operation will be described with reference to FIG.
As described above, the image forming apparatus 1 is stabilized (step s1), the feedforward control is turned off, the rotation control of the motor 4 is performed only by the feedback control, and the load torque of the motor 4 is measured. (Step s2). The load torque is obtained by the calculation method using the PWM command value described above. After the stabilization operation is completed (step s3), it is determined whether or not the motor load variable means 6 is turned on (step s4). If the motor load variable means 6 is turned on (step s4, YES (ON)), the initial operation is completed without performing the following control procedure. On the other hand, when the motor load varying means 6 is OFF (step s4, NO (OFF)), it is determined whether or not the load torque measured above is equal to or less than a set torque threshold (step s5). ). If the load torque exceeds the threshold value (step s5, NO), the load switching control is not necessary, and thus the initial operation is completed.

  On the other hand, if the load torque is equal to or less than the threshold value (step s5, YES), the control may fail when the feedforward control is performed, so the load control for the drive motor is performed (step s6). That is, the motor load variable means 6 is controlled to operate, and the drive load is increased by adding a predetermined drive load generated by the motor load variable means 6 in addition to the normal drive load to the drive motor. As a result, the drive load on the motor exceeds the threshold value, and failure control when feedforward control is performed is avoided. Note that the amount of driving load that is increased by the motor load varying means 6 is assumed in advance, and it is desirable that the amount of load be such that control failure can be reliably avoided and wasteful energy consumption is minimized.

Next, a control procedure for executing load switching during JOB execution will be described with reference to FIG.
When JOB is started (step s10), the control for the motor is also normal control, and the drive control of the motor 4 is performed by using the feedback control and the feedforward control together, and the load torque of the motor 4 is measured. Is performed (step s11). The load torque is obtained by the calculation method using the PWM command value as described above. During execution of JOB, it is determined whether or not the motor load variable means is ON (step s12). If the motor load variable means is ON (step s12, YES (ON)), it is determined that there is no need to switch the motor load, and the procedure proceeds to a job completion determination procedure (to step 17).

  On the other hand, when the motor load variable means is OFF (step 12, NO (OFF)), whether or not load control is necessary depending on whether or not the load torque measured above is equal to or less than a set torque threshold value. A determination is made (step s13). If the load torque exceeds the threshold value (step s13, NO), the load switching control is not necessary, and the procedure shifts to the job completion determination procedure (to step 17). On the other hand, if the load torque is less than or equal to the threshold value (step s13, YES), the feedforward control may fail, so the copy operation related to the JOB is temporarily stopped (step s14), and the load control is performed (step). s15). In other words, the motor load variable means 6 is controlled to operate, and the drive load is increased by adding a predetermined drive load generated by the motor load variable means 6 to the motor 4 in addition to the normal drive load. As a result, the drive load on the motor 4 exceeds the threshold value, and failure control when feedforward control is performed is avoided.

  After executing the load control, the copying operation is resumed (step s16), and the above procedure is repeated until the job is completed (step s17). Note that the copying operation is resumed in a state where the rotation of the photosensitive drum is stable.

Furthermore, a control procedure for performing load switching between JOBs will be described below based on the flowchart of FIG.
When JOB is started (step s20), the control for the motor becomes normal control, and the drive control of the motor is performed by using the feedback control and the feedforward control together, and the load torque of the motor 4 is the same as described above. Is measured (step s21). The above control is performed until the job is completed (step s22, NO). When the job is completed (step s22, YES), the operation is stopped (motor stop) (step s23), and then the motor load variable means is turned on. It is determined whether or not (step s24). If the motor load variable means is ON (step s24, YES (ON)), the motor load switching is not necessary and the normal operation is completed.

  On the other hand, when the motor load variable means is OFF (step 24, NO (OFF)), it is determined whether or not load control is necessary depending on whether or not the load torque measured above is equal to or less than the torque threshold value. (Step s25). If the load torque exceeds the threshold value (step s25, NO), the load switching control is not necessary and the normal operation is completed. On the other hand, when the load torque is equal to or less than the threshold value (step s25, YES), the feedforward control may fail, so the load control is performed (step s26). That is, the motor load variable means 6 is controlled to operate, and the drive load is increased by adding a predetermined drive load generated by the motor load variable means 6 in addition to the normal drive load to the drive motor. As a result, the driving load on the motor exceeds the threshold value, and failure control when feedforward control is performed after the next JOB is avoided. After performing the load control, the normal operation is completed.

  In the above control procedure, the load switching control is performed by setting one threshold value, but the control unit has two threshold values (first threshold value, second threshold value, first threshold value <second threshold value). ) Can be set to perform load switching control. The first threshold value and the second threshold value are stored in the storage unit of the motor control unit 3 and referred to as appropriate, similarly to the above threshold value. The control procedure will be described below based on the flowcharts of FIGS.

First, the control procedure by the control unit during the initial operation will be described with reference to FIG.
As described above, the image forming apparatus 1 is stabilized (step s30), the feedforward control is turned off, the rotation control of the motor 4 is performed only by the feedback control, and the load torque of the motor 4 is measured. (Step s31). After the stabilization operation is completed (step s32), it is determined whether or not the motor load varying means 6 is in an operation ON state (step s33). If the motor load variable means 6 is ON (step s33, YES (ON)), it is determined whether or not the measured load torque is equal to or greater than a second threshold (step s36). If the load torque is below the second threshold value (NO in step s36), the current load torque may be maintained, and thus the initial operation is completed without switching the load. On the other hand, if the load torque is equal to or greater than the second threshold (step s36, YES), the motor load variable means 6 is controlled to OFF because the load torque is not such that feedforward control fails even when the load is released. Therefore, the second threshold value is set so that the load torque of the motor exceeds the first threshold value even when the increased load is released in consideration of the load torque amount generated by the motor load variable means. A threshold of 2 is set. After the OFF control, the initial operation is completed.

On the other hand, if the motor load varying means 6 is OFF in the determination (step s33) (step s33, NO (OFF)), it is determined whether or not the measured load torque is equal to or less than the first threshold value (step s33). Step s34). If the load torque exceeds the first threshold value (step s34, NO), the load switching control is not necessary, and thus the initial operation is completed.
On the other hand, when the load torque is less than or equal to the first threshold (step s34, YES), there is a possibility that the control will fail when the feedforward control is performed. On the other hand, in addition to the normal driving load, a predetermined driving load generated by the motor load varying means 6 is added (step s35).
If there is a possibility that the feedforward control may fail due to the above procedure, increase the driving load on the motor.If the feedforward is not likely to fail even if the increased driving load is released, increase the driving load. By canceling, it is possible to reliably avoid control failure and to prevent wasteful energy consumption.

Next, a control procedure for performing load switching using the first and second threshold values during execution of JOB will be described with reference to FIG.
When JOB is started (step s40), the control for the motor becomes normal control, and the drive control of the motor is performed by using the feedback control and the feedforward control together, and the load torque of the motor 4 is measured ( Step s41). During the operation, it is determined whether or not the motor load variable means is ON (step s42). If the motor load variable means is ON (step s42, YES (ON)), the measured load torque is the second. It is determined whether or not the threshold is equal to or greater than (step s48). If the load torque is lower than the second threshold (step s48, NO), the current load torque may be maintained, and the procedure proceeds to a procedure for determining completion of JOB (to step s47).
On the other hand, if the load torque is equal to or greater than the second threshold (step s48, YES), the procedure for performing OFF control on the motor load variable means 6 is performed because the feedforward control does not fail even when the load increase is canceled. . That is, the copying operation related to the JOB is temporarily stopped (step s49), and the motor load varying means 6 is controlled to be OFF (step s50). Next, the copying operation is started (step s51), and the process proceeds to a procedure for determining completion of JOB (to step s47).

  On the other hand, when the motor load variable means 6 is OFF in the determination (step s42) (step 42, NO (OFF)), it is determined whether or not the load torque is equal to or less than the first threshold value (step s43). If the load torque exceeds the first threshold value (step s43, NO), the load switching control is not necessary, and the procedure shifts to a job completion determination procedure (to step s47). On the other hand, if the load torque is less than or equal to the first threshold (step s43, YES), the feed-forward control may fail, so the copy operation related to the job is temporarily stopped (step s44), and the motor load variable means 6 is turned on (step s45). Thereafter, the copying operation is resumed (step s46), and the above procedure is repeated until the job is completed (step s47).

Further, a control procedure for performing load switching between the JOBs using the first and second threshold values will be described based on the flowchart of FIG.
When JOB is started (step s60), the control for the motor becomes normal control, and the drive control of the motor is performed by using the feedback control and the feedforward control together, and the load torque of the motor 4 is measured ( Step s61). Control is performed until the job is completed (step s62, NO). When the job is completed (step s62, YES), the operation is stopped (motor stop) (step s63), and then the motor load variable means 6 is turned on. It is determined whether or not (step s64). If the motor load variable means 6 is ON (step s64, YES (ON)), it is determined whether or not the measured load torque is greater than or equal to the second threshold (step s67). If the load torque is below the second threshold value (step s67, NO), the current load torque may be maintained, and the normal operation is completed.
On the other hand, if the load torque is greater than or equal to the second threshold (step s67, YES), the load load torque is not broken even when the load is released. Step s68), the normal operation is completed.

On the other hand, if the motor load varying means is OFF in the determination (step s64) (step 64, NO (OFF)), it is determined whether or not the load torque measured above is equal to or less than the first threshold value. Is performed (step s65). If the load torque exceeds the first threshold (step s65, NO), the load switching control is not necessary and the normal operation is completed. On the other hand, if the load torque is less than or equal to the first threshold (step s65, YES), the feedforward control may fail, so the motor load variable means is ON-controlled (step s66), and the normal operation is completed.
In the control procedures shown in FIGS. 7 to 9, the motor load variable means 6 is controlled to be OFF when the motor load variable means 6 is ON and the load torque is equal to or greater than the second threshold. If the variable means 6 can adjust the load torque amount, it is also possible to perform control to reduce the load torque amount instead of the OFF control.

In the above embodiment, the load is switched by the ON / OFF control of the motor load varying means. An example in which the second cleaning blade is used as the motor load varying means will be described below.
The second cleaning blade is installed on the downstream side of the first cleaning blade installed for cleaning the photosensitive drum, and each of them is pressed against the photosensitive drum by the engine control unit 2 or the motor control unit 3. / Release control is performed. In the following description, it is assumed that the cleaning blade is controlled by the engine control unit 2. The first and second cleaning blades can realize the necessary cleaning performance by themselves.

  The first and second cleaning blades are each managed by the engine control unit 2 for the pressure bonding time. For example, the first and second cleaning blades are managed by the number of sheets on which image formation has been performed. The crimping time is stored in the storage unit of the engine control unit 2 and is updated as the image is formed. In the engine control unit 2, the first cleaning blade and the second cleaning blade are set to be alternately used at a predetermined cycle, and the pressure bonding time of 5000 sheets, for example, is set as the cycle. The cycle is stored in the storage unit of the engine control unit 2 and is referred to as appropriate.

  Hereinafter, a load switching control procedure of the apparatus including the second cleaning blade as a motor load varying unit will be described with reference to FIG. In this control procedure, an example of performing load switching between JOBs will be described.

  When JOB is started (step s70), the pressure bonding time of the cleaning blade on the side being used for image formation is measured and added (step s71). Further, the control for the motor is normal control, and the drive control of the motor is performed by using the feedback control and the feedforward control together, and the load torque of the motor 4 is measured (step s72). Control is performed until JOB is completed (step s73, NO), and when JOB is completed (step s73, YES), operation stop (motor stop) is performed (step s74). Thereafter, the pressure bonding time is compared with the set cycle to determine whether or not the pressure bonding time of the cleaning blade being used has reached a predetermined cycle (step s75). If the predetermined period has not been reached (step s75, NO), the cleaning blade being used is continuously used as it is (step s76). On the other hand, when the cleaning blade has reached the predetermined period (step s75, YES), the pressure bonding of the cleaning blade in use is released, and the other cleaning blade is pressure bonded to the photosensitive drum. At this time, the object whose pressure bonding time is measured is switched to the cleaning blade whose use has been switched (step s76).

  Next, it is determined whether or not the motor load varying means 6 is ON (step s77). If the motor load varying means is ON (step s77, YES (ON)), the first and second cleaning blades are both pressed against the photosensitive drum, and the respective pressing times are measured. Has been. In this state, it is determined whether or not the measured load torque is greater than or equal to the second threshold value (step s80). If the load torque is lower than the second threshold value (step s80, NO), the current load torque may be maintained, so that the normal operation is completed with both the cleaning blades being pressed.

  On the other hand, when the load torque is equal to or greater than the second threshold value (step s80, YES), it is not a load torque that causes the feedforward control to fail even when the load is released. Is released (step s81), and the normal operation is completed. In this selection of press-bonding / release, it is desirable that the one having a shorter pressing time of the cleaning blade is kept pressed and the one having a longer pressing time is released. Thereby, it can be made the tendency for the difference of both use time to become small.

    On the other hand, if the motor load variable means is OFF in the determination (step s77) (step 77, NO (OFF)), it is determined whether or not the load torque measured above is not more than the first threshold value. Is performed (step s78). If the load torque exceeds the first threshold (step s78, NO), the load switching control is not necessary, and the normal operation is completed. On the other hand, when the load torque is less than or equal to the first threshold (step s78, YES), there is a possibility that the feedforward control may fail. Both the cleaning blades are pressed against the photosensitive drum to increase the load torque of the motor (step s79). Thereafter, normal operation is completed. In the following JOB and later, if both cleaning blades are pressure-bonded, both of the pressure-bonding times of the used cleaning blades are measured.

  As described above, it is possible to lengthen the replacement cycle by reducing the difference in deterioration with time of the first and second cleaning blades, and to reliably avoid failure of the feedforward control. In the above description, the load torque is switched by pressing / releasing the first and second cleaning blades. However, the pressure applied to the first and second cleaning blades can be changed when pressing. The load torque may be switched by changing the applied pressure.

  The present invention has been described based on the above embodiment, but the present invention is not limited to the content of the above embodiment, and can be appropriately changed without departing from the scope of the present invention. is there.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Engine control part 3 Motor control part 4 Motor 5 Encoder 6 Motor load variable means

Claims (17)

A drive motor that performs speed feedback control and speed feedforward control, a control unit that performs the speed feedback control and speed feedforward control on the drive motor, and load detection that detects a drive load torque of the drive motor And a load torque generating unit capable of generating a predetermined driving load in addition to the normal driving load for the driving motor,
The control unit has a threshold set within a load torque range in which the speed feedforward control can be performed, and when the load torque detected by the load detection unit is equal to or less than the threshold, the load torque generation unit The image forming apparatus is characterized in that the speed feedforward control can be prevented from being broken by increasing the driving load on the driving motor.   The speed feedback control is performed based on a parameter for speed feedforward control, and the threshold is set within a load torque range in which the parameter for speed feedforward control can be used. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the load detection unit detects the drive load torque from a PWM command value of the drive motor.   The image forming apparatus according to claim 1, wherein the drive motor is configured to rotationally drive an image carrier that performs image formation.   The image forming apparatus according to claim 4, wherein the control unit determines a feedforward control value based on a past speed fluctuation profile for one rotation of the image carrier.   The image forming apparatus according to claim 1, wherein the load torque generating unit is an electromagnetic brake capable of changing a brake torque according to an input current or an input voltage.   The image forming apparatus according to claim 6, wherein the electromagnetic brake is a bias type or a powder type.   The load torque generating means is a second cleaning blade which is installed downstream of a first cleaning blade used for cleaning the image carrier and can be pressed / released to / from the image carrier. 5. The image forming apparatus according to 3 or 4.   The second cleaning blade can change the pressure of the pressure bonding, and the controller can control the change of the pressure according to the load torque of the drive motor detected by the load detector. The image forming apparatus according to claim 8, wherein the image forming apparatus is provided.   Both the first cleaning blade and the second cleaning blade can be pressure-bonded / released to the image carrier, and the cleaning performance can be realized by any one of the cleaning blades, and the control unit The control unit controls the pressure bonding / release of both the first cleaning blade and the second cleaning blade, stores the pressure bonding time of each of the cleaning blades, and alternately uses them in a predetermined cycle, and is detected by the load detection unit. 10. When the load torque of the drive motor is equal to or less than the threshold value, both the cleaning blades are press-bonded to prevent failure of the feedforward control. Image forming apparatus.   The control unit has the threshold value as a first threshold value, is set within a load torque range in which the speed feedforward control can be executed, and has a second threshold value that is larger than the first threshold value. When the load torque generating unit is operating to increase the driving load on the drive motor, the load torque is generated when the load torque detected by the load detecting unit is equal to or greater than the second threshold. The image forming apparatus according to claim 1, wherein the image forming apparatus controls the operation of the image forming apparatus to cancel or reduce an increase in driving load on the driving motor. A control unit that performs speed feedback control and speed feedforward on the drive motor,
If the drive torque of the drive motor has a threshold set within a load torque range in which the speed feedforward control can be performed and the drive load torque of the drive motor is equal to or less than the threshold, a predetermined drive is added to the normal drive load for the drive motor. A control unit that controls a load torque generation unit that generates a load to increase a drive load on the drive motor, thereby preventing failure of the speed feedforward control.   The speed feedback control is performed based on a parameter for speed feedforward control, and the threshold is set within a load torque range in which the parameter for speed feedforward control can be used. Control part.   13. The drive motor according to claim 12, wherein the drive motor rotationally drives an image carrier that forms an image, and the drive load torque is calculated by averaging PWM command values for one rotation of the image carrier. 13. The control unit according to 13.   The control unit according to any one of claims 12 to 14, wherein the load torque generated by the load torque generation unit can be changed and controlled according to a drive load torque for the drive motor.   The first cleaning blade used for cleaning the image carrier and the second cleaning blade disposed downstream of the first cleaning blade and constituting the load torque generating means are controlled to be pressed / released. When the load torque of the drive motor that drives the image carrier is equal to or less than the threshold value, both the cleaning blades are pressure-bonded to control the feedforward control. The control unit according to any one of claims 12 to 15, wherein the bankruptcy can be avoided.   The threshold value is set as a first threshold value, and is set within a load torque range in which the speed feedforward control can be executed, and has a second threshold value that is larger than the first threshold value. When the load torque generating unit is operating to increase the drive load on the drive motor, if the load torque is greater than or equal to the second threshold value, the load torque generating unit is controlled to operate and the drive load on the drive motor is The control unit according to any one of claims 12 to 16, wherein an increase in the number is canceled or reduced.

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