JP2016139132A - Rotor driving device, image forming apparatus, and control method of rotor driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor driving device that can suppress an instantaneous change in speed.SOLUTION: A rotor driving device comprises: driving means that drives to rotate a rotor; paper feed detection means that detects the state of the rotor to feed a sheet-like medium; and speed setting means that sets the speed of rotation of the rotor on the basis of a value related to driving torque of the driving means. The speed setting means sets the speed of rotation of a third rotor with a value related to driving torque of the third rotor during a non-paper feed period as a reference value so that the value related to driving torque during a paper feed period becomes a value of driving torque smaller than the reference value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a rotating body driving device, an image forming apparatus, and a method for controlling the rotating body driving device.

  2. Description of the Related Art Conventionally, an image forming apparatus is known that separately controls a plurality of mounted rotating bodies (intermediate transfer roller, secondary transfer roller, registration roller). In this case, there is a problem in that interference torque is generated between the rotating bodies due to the component tolerance, paper type, contact / separation or speed difference generated by contact pressure change, and shock jitter is generated in the recording medium.

  In view of the above-mentioned problems, the interference torque generated between the rotating bodies is changed by changing the rotation speed of the registration roller based on the sum of the control elements (drive current or drive torque) of the intermediate transfer roller and the secondary transfer roller. A configuration for reducing the speed difference by reducing the speed difference is disclosed (for example, see Patent Document 1).

  Although the above conventional technology can reduce the interference torque generated between the three rotating bodies, it cannot suppress the shock jitter that occurs when the recording medium passes through the registration roller.

  The reason for this is that instantaneous speed fluctuations that occur when the recording medium passes through the registration rollers cannot be suppressed to the extent that there is little interference between the rotating bodies.

  An object of one embodiment of the present invention is to provide a rotating body drive device capable of suppressing instantaneous speed fluctuations.

In view of the above problems, in one embodiment of the rotating body drive device of the present invention,
The first rotating body, the second rotating body, and the third rotating body are provided, and the sheet-like medium is conveyed by at least one of the first rotating body to the third rotating body. A rotating body drive device,
Drive means for rotationally driving at least the third rotating body;
A paper passing detection means for detecting a paper passing state of the sheet-like medium of the rotating body;
Speed setting means for setting a rotation speed of the third rotating body based on a value relating to a driving torque of the driving means;
The speed setting means includes
The third rotation is performed so that the value related to the driving torque when the third rotating body is not passing is set as a reference value, and the value related to the driving torque when passing the paper is a value that is smaller than the reference value. Set the body rotation speed.

  According to one embodiment of the present invention, it is possible to provide a rotating body drive device capable of suppressing instantaneous speed fluctuations.

1 is a configuration diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. 1 is a diagram illustrating a schematic configuration of a rotating body driving device that constitutes an image forming apparatus according to a first embodiment; It is explanatory drawing which shows the outline | summary of the interference torque which arises between a secondary transfer part and a resist part. FIG. 2 is a diagram illustrating a hardware configuration of a motor control unit that configures the image forming apparatus according to the first embodiment. It is a figure which shows the functional block diagram of the drive control part of 1st Embodiment. It is explanatory drawing explaining the principle of the process which a speed setting part performs. It is a figure explaining the rotational speed setting process of the rotary body drive device in 1st Embodiment. It is a figure explaining the procedure of the analysis process shown in FIG. It is a figure explaining the alternative signal of interference torque (change of a drive torque).

  Hereinafter, a control method for a rotating body driving device, an image forming apparatus, and a rotating body driving device according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples described below. In the following description, the same or corresponding members or parts described in all the attached drawings are denoted by the same or corresponding reference numerals, and redundant description is omitted. Also, the drawings are not intended to show the relative ratio between members or parts. Accordingly, specific dimensions can be determined by one skilled in the art in light of the following non-limiting embodiments.

  In the following embodiments, a case where the rotating body driving device according to the present invention is mounted on an image forming apparatus will be described as an example. In particular, a configuration and method for appropriately driving and controlling the registration roller in the relationship between the intermediate transfer roller and the registration roller will be described. Of course, the same can be applied to drive control of other rotating bodies. Further, the “sheet medium” described in the claims is hereinafter referred to as “recording medium”.

  In short, the rotating body driving device according to the present embodiment uses a driving torque (an example of “value related to driving torque”) when the registration roller is not passing as a torque reference value (an example of “reference value”), The rotational speed of the registration roller is set so that the driving torque during paper feeding is a torque fluctuation amount smaller than the torque reference value (an example of a “value that becomes a small driving torque”). In other words, when the recording medium passes through the registration roller, the instantaneous speed fluctuation generated in the intermediate transfer belt or the like is suppressed to prevent shock jitter. Hereinafter, this point will be described with reference to the drawings.

(overall structure)
First, the overall configuration of the image forming apparatus 100 according to the present embodiment will be described. FIG. 1 shows the overall configuration of the image forming apparatus 100 according to the first embodiment.
An image forming apparatus 100 shown in FIG. 1 is an electrophotographic system, is preferably a digital multi-function peripheral, and preferably has a copying function, a printer function, a facsimile function, and the like. However, the image forming apparatus 100 may be an ink jet method, a sublimation thermal transfer method, or a dot impact method that forms an image by ejecting ink droplets.

  The image forming apparatus 100 according to this embodiment includes an image reading unit 1, an image writing unit 2, a photoconductor unit 3, a photoconductor drum 4, a developing unit 5, an intermediate transfer unit 6, an intermediate transfer belt 7, a secondary transfer unit 8, It has a resist unit 9, a tray 10, a transport unit 11, and a fixing unit 12.

  The image reading unit 1 scans the original while irradiating the original with a light source, and reads an image of reflected light from the original with a 3-line CCD (Charge Coupled Device) sensor. The read image is subjected to image processing such as scanner γ correction, color conversion, image separation, and gradation correction processing by the image processing unit, and then sent to the image writing unit 2. The image writing unit 2 modulates the driving of an LD (Laser Diode) according to the image data. In the photosensitive unit 3, an electrostatic latent image is written by a laser beam from the LD on a uniformly charged rotating photosensitive drum 4, and toner is attached by the developing unit 5 to be visualized.

  The image formed on the photosensitive drum is transferred onto the intermediate transfer belt 7 of the intermediate transfer unit of the intermediate transfer unit 6. When full-color copying is executed in the image forming apparatus 100, toner images of four colors (black, cyan, magenta, yellow) are sequentially superimposed on the intermediate transfer belt 7. When image formation and transfer of all colors are completed, the registration unit 9 supplies the recording medium from the tray 10 in synchronization with the intermediate transfer belt 7, and the secondary transfer unit 8 transfers the recording medium from the intermediate transfer belt 7 to the recording medium. The toner image is secondarily transferred. The recording medium to which the toner image has been transferred is sent to the fixing unit 12 through the conveying unit 11, and is discharged after the toner image is fixed on the recording medium by the fixing roller and the pressure roller.

  FIG. 2 is a schematic diagram illustrating the configuration of the rotating body driving device that constitutes the image forming apparatus according to the first embodiment. In the image forming apparatus 100 of this embodiment, the intermediate transfer belt is rotated by the rotating body driving device shown in FIG. 2 to convey the recording medium. 2A shows a schematic overall view of the above-described rotating body driving device, FIG. 2B shows the peripheral configuration of the secondary transfer unit 8, and FIG. 2C shows the periphery of the resist unit 9. The configuration was shown.

  The intermediate transfer belt 7 is endlessly moved by the rotation of the intermediate transfer roller 60 and the secondary transfer counter roller 61, which are one of the stretching rollers, while being stretched by a plurality of stretching rollers disposed in the belt loop. Thus, an intermediate transfer portion 6 for transferring the toner image to the recording medium is formed.

  The intermediate transfer roller 60 is driven by an intermediate transfer motor 64. The intermediate transfer motor 64 is preferably a brushed DC motor or a brushless DC motor. A gear reduction mechanism is provided between the intermediate transfer motor 64 and the intermediate transfer roller 60, and the driving force of the intermediate transfer motor 64 is reduced by the amount corresponding to the gear ratio of the intermediate transfer roller 60. Is transmitted to. This reduction mechanism has a configuration in which a small-diameter gear on the rotation shaft of the intermediate transfer motor 64 and a large-diameter gear on the rotation shaft of the intermediate transfer roller 60 are meshed with each other. Further, the intermediate transfer roller 60 may have a roller encoder 65.

  The rotating body driving device has speed detection means (corresponding to the conveyance speed detection means) for detecting the conveyance speed of the intermediate transfer belt 7. As the speed detecting means, it is preferable to adopt a belt encoder system. That is, an encoder pattern 70 is engraved on the front surface or the back surface of the intermediate transfer belt 7, and the belt surface speed is detected by reading the encoder pattern 70 with the encoder sensor 71. In FIG. 2A, the encoder sensor 71 is installed at a substantially central position between the driven roller 62 and the intermediate transfer roller 60. However, in order to correctly measure the belt surface speed, the encoder sensor 71 may be a flat portion in another place.

  For example, if the encoder sensor 71 is laid out on a rotating shaft that is not flat, the influence of the curvature of the shaft will appear, and the spacing between the encoder patterns 70 will change due to variations in the thickness of the belt and environmental variations. End up. Then, the correct belt surface speed cannot be obtained. Here, the encoder sensor 71 is assumed to be a reflective optical sensor having slits at equal intervals, but any sensor that can accurately detect the belt surface position from the encoder pattern 70 may be used. For example, a CCD camera or the like may be used to detect the surface position by image processing. In addition, the encoder pattern 70 can be eliminated by using a Doppler method or a sensor method that can detect the surface position by image processing from irregularities on the belt surface.

  Moreover, a rotary encoder system can be adopted as another speed detection means. That is, a rotary encoder is provided on the rotation shaft of the driven roller 62. Since the driven roller 62 is a roller that rotates following the endless movement of the intermediate transfer belt 7, the conveyance speed of the intermediate transfer belt 7 can be detected.

  As described later, the speed detecting means of the intermediate transfer belt 7 detects the amount of speed fluctuation of the intermediate transfer belt 7 when the recording medium passes through the registration roller 90, and the optimum rotation speed of the registration roller 90 is obtained. Can be confirmed (determined).

Next, the peripheral configuration of the secondary transfer unit 8 will be described with reference to FIG. 2B.
The secondary transfer unit 8 has a secondary transfer roller 80. The secondary transfer roller 80 is disposed outside the belt loop of the secondary transfer facing roller 61 at a position that contacts the surface of the intermediate transfer belt 7 at a position facing the secondary transfer facing roller 61. A portion 800 is formed (see FIG. 2A). By applying electric charges to the surfaces of the secondary transfer roller 80 and the intermediate transfer belt 7, the recording medium can be adsorbed on the surfaces.

  The secondary transfer roller 80 is driven by a secondary transfer motor 83. A reduction mechanism is provided between the secondary transfer roller 80 and the secondary transfer motor 83. The secondary transfer motor 83 preferably employs the same brushed DC motor or brushless DC motor as the intermediate transfer motor 64. The secondary transfer roller 80 may have a roller encoder 82, and the secondary transfer motor 83 may have a motor encoder 84.

Next, the peripheral configuration of the resist portion 9 will be described with reference to FIG. 2C.
The registration unit 9 has a registration roller 90. The registration roller 90 is a roller disposed immediately before the pressure contact portion 800 (on the downstream side of the secondary transfer roller 80) in the recording medium conveyance path, and is driven by a registration motor 93. A speed reduction mechanism is provided between the registration roller 90 and the registration motor 93. The registration roller 90 may include a roller encoder 92, and the registration motor 93 may include a motor encoder 94. The recording medium is conveyed to the pressure contact portion 800 between the secondary transfer roller 80 and the secondary transfer opposing roller 61 by the rotation in the conveyance direction of the registration roller 90 and the counter roller 91 disposed at a position facing the registration roller 90. Then, the toner image is transferred from the intermediate transfer belt 7 to the recording medium at the press contact portion 800. Thereafter, when the recording medium is removed from the registration roller 90, there is a problem that an instantaneous speed fluctuation occurs in the intermediate transfer belt 7 and the like, resulting in shock jitter. Hereinafter, the interference torque generated between the secondary transfer portion 8 and the resist portion 9 will be described, and the principle of the shock jitter will be described.
Incidentally, in this embodiment, the intermediate transfer roller 60 is a first rotating body, the secondary transfer roller 80 is a second rotating body, and the registration roller 90 is a third rotating body.

<Description of interference torque by recording medium>
The interference torque generated between the secondary transfer portion 8 and the resist portion 9 will be described with reference to FIG.
FIG. 3 is a diagram for explaining the influence caused by the interference torque when the registration roller 90 conveys the recording medium K to the intermediate transfer belt 7 and the secondary transfer roller 80.
3A shows a case where the linear velocity (or rotational speed) of the registration roller 90 is higher than that of the secondary transfer portion 8, and FIG. 3B shows a case where the linear velocity of the registration roller 90 is slower than that of the secondary transfer portion 8. It is. Both show the state where the recording medium K straddles both the secondary transfer roller 80 and the registration roller 90.

  In short, the drive torque change, that is, the interference torque is caused by the following reasons. That is, when the recording medium K is removed from the registration roller 90 during conveyance of the recording medium, a sudden torque change occurs, so that a speed fluctuation occurs in the intermediate transfer belt 7, but the surface speed of the intermediate transfer belt 7 is feedback controlled. Again, the speed is constant. Shock jitter occurs depending on the magnitude of the speed fluctuation at this time.

  Further, when the linear speeds of the registration roller 90 and the intermediate transfer belt 7 are different, the drive torque changes as a result of the change in the recording medium conveying force, that is, an interference torque is generated. The interference torque described here is generated when the intermediate transfer motor 64 is affected by pushing or pulling from the registration roller 90 with the recording medium K as a medium during conveyance of the recording medium. In order to measure this interference torque, the state in which the recording medium K straddles the secondary transfer portion 8 and the registration portion 9 and the amount of change in the driving torque (conveyance torque) of the registration roller 90 during non-sheet passing may be observed. .

  As shown in FIG. 3A, when the linear velocity of the registration roller 90 is high, the registration roller 90 enters a state where the recording medium K is pushed. Then, the conveyance speed of the recording medium K is increased, and interference torque is generated between the recording medium K and the surface of the intermediate transfer belt 7. Since the intermediate transfer belt 7 is controlled at a constant linear velocity, the conveyance torque decreases in order to keep the surface linear velocity constant. Since the recording medium K is transported in such a controlled state, when the recording medium K is removed from the registration roller 90, the transport speed of the intermediate transfer belt 7 varies greatly instantaneously.

  As shown in FIG. 3B, when the linear velocity of the registration roller 90 is low, the registration roller 90 is in a state of pulling the recording medium K. Then, the conveyance speed is slowed down, and interference torque is generated between the recording medium K and the surface of the intermediate transfer belt 7. Since the intermediate transfer belt 7 is controlled at a constant linear velocity, the conveyance torque increases in order to keep the surface linear velocity constant. Since the recording medium K is transported in such a controlled state, when the recording medium K is removed from the registration roller 90, the transport torque changes and a large speed fluctuation occurs instantaneously. In addition, since the secondary transfer unit 8 controls not only the intermediate transfer belt 7 but also the secondary transfer roller 80, it is considered that interference torque is generated.

  In the present embodiment, in the secondary transfer unit 8 and the registration unit 9, instantaneous speed fluctuations of the intermediate transfer belt 7 (secondary transfer unit 8) when the recording medium K is removed from the registration roller 90 are suppressed. Is the main purpose.

(Hardware configuration of image forming apparatus)
The motor control unit 20 included in the image forming apparatus 100 according to the present embodiment will be described below with reference to FIG. FIG. 4 is a diagram illustrating the motor control unit 20 according to the first embodiment.
The motor control unit 20 has a function of controlling the driving of a plurality of rotating bodies (intermediate transfer roller, secondary transfer roller, registration roller) shown in FIG. It is included in “Driver”. In the present embodiment, in particular, the rotational drive of the registration roller 90 is controlled to control the instantaneous speed fluctuation that occurs when the recording medium leaves the registration roller 90.

  In the image forming apparatus 100 of the present embodiment, the motor control unit 20 is connected to a main control unit 110 that controls the entire image forming apparatus 100, and the rotational speed of the intermediate transfer motor 64, the secondary transfer motor 83, and the resist are registered. The rotational speed of the roller 90 is controlled.

  When an image data output instruction or the like is operated from the operation unit 120 of the image forming apparatus 100, the main control unit 110 instructs the motor control unit 20 to drive each motor. Specifically, when receiving an image data output instruction or the like, the main control unit 110 instructs the motor control unit 20 on a command value to each motor, a start / stop instruction, a target speed, a rotation direction, and the like. Upon receiving this instruction, the motor control unit 20 controls the driving of each motor. The main control unit 110 exchanges information with the motor control unit 20 such as motor information (rotational speed, etc.), PWM value (corresponding to the pulse width modulation signal in the claims), drive current, encoder value, etc. And a memory 130 for storing information. The memory 130 further has information on the maximum value (O) and the minimum value of the rotation speed used when determining the rotation speed of the registration roller 90. As the minimum value, a threshold (setting allowable minimum value) corresponding to the recording medium is set and stored. It also has a torque conversion table showing the relationship between the torque multiplier and speed used when calculating the drive torque from the drive current.

  The motor control unit 20 of this embodiment includes a drive control unit 21, pre-drivers 221, 222, and 223, and FETs 231, 232, and 233.

  As will be described in detail later, the drive control unit 21 sets the rotation speed of the registration roller 90 so that the driving torque when the registration roller 90 is not passing is set as a torque reference value and the torque fluctuation amount is smaller than the torque reference value. It has a function to do.

  The pre-driver 221 and the FET 231 have a function of supplying a constant drive current to the intermediate transfer motor 64. The pre-driver 222 and the FET 232 have a function of supplying a constant drive current to the secondary transfer motor 83. The pre-driver 223 and the FET 233 have a function of supplying an appropriate driving current to the registration motor 93.

  The drive control unit 21 acquires rotational speed information from the roller encoder 65 and the encoder sensor 71 of the intermediate transfer roller 60. Further, the rotational speed from the motor encoder 84 of the secondary transfer motor 83 and the roller encoder 82 of the secondary transfer roller 80 is acquired. Further, the rotational speeds from the motor encoder 94 of the registration motor 93 and the roller encoder 92 of the registration roller 90 are collected.

  The drive control unit 21 collects drive currents of the intermediate transfer motor 64, the secondary transfer motor 83, and the registration motor 93, calculates a control output to each motor, and outputs a PWM instruction value (pulse width) to each pre-driver. Modulated signal). The drive control unit 21 calculates drive torque from the acquired drive current. Specifically, the rotational torque and driving current of each motor 64, 83, 93 (or each roller 60, 80, 90) are acquired, and the driving torque using a torque conversion table or the like showing the relationship between the torque multiplier and the speed. It can be calculated by converting to. The rotation speed can be detected by a pulse signal (including a pseudo pulse converted from the Hall element signal) from each motor (or each roller). The drive current may be calculated by obtaining a PWM instruction value. The calculated drive torque is stored in the memory 130.

  The drive control unit 21 can calculate the drive current of each motor based on the PWM instruction value. However, there is a possibility that an error may occur due to the influence of the fluctuation or response of the motor drive circuit including the pre-driver. Therefore, in order to grasp the driving current of the motor with higher accuracy, the driving current may be grasped by measuring the current of the FET. That is, the drive current can be grasped from the combined current value flowing through the shunt resistor connected to the FETs 231 to 233.

  In the pre-drivers (221, 222, 223), as an example, the rotation angle of each motor (64, 83, 93) is recognized by the Hall element signal, the PWM signal is converted into a motor three-phase output signal, and the FET (231) 232, 233) to drive each motor. Thus, the rotational speeds of the intermediate transfer motor 64, the secondary transfer motor 83, and the registration motor 93 can be controlled based on the target speed signal that is an instruction value of each motor.

  Furthermore, the drive control unit 21 stores collected data and calculation data in the memory 130 as needed, and notifies the main control unit 110 of information such as an abnormality notification. Incidentally, the memory 130 may be configured to be included in the drive control unit 21 as well.

  Thus, in the present embodiment, the drive control unit 21 functions as a part of a rotating body drive control device that controls the driving of the three rotating bodies.

(Function block of drive control unit)
Next, the drive control unit 21 will be specifically described. FIG. 5 shows functional blocks of the drive control unit 21.

  The drive control unit 21 includes a position / speed detection unit 301, a motor drive control unit 302, a drive current detection unit 303, a drive torque calculation unit 304, a paper passing detection unit 305, a speed setting unit 306, and a determination unit 307. .

  The position / velocity detection unit 301 is a pulse signal (including a pseudo pulse converted from a Hall element signal) output from each encoder added to each motor 64, 83, 93 (or each roller 60, 80, 90). From the above, the rotational position and rotational speed of each motor 64, 83, 93 (or each roller 60, 80, 90) are detected. In addition, information from a speed detection unit that detects the conveyance speed of the intermediate transfer belt 7 is also acquired.

  The motor drive control unit 302 controls the rotation speeds of the motors 64, 83, and 93 based on the control signal output from the speed setting unit 306. In this embodiment, the rotational speed of the registration roller 90 is appropriately controlled by controlling the registration motor 93.

  The drive current detector 303 detects the drive current of each motor 64, 83, 93. As described above, the drive current can be grasped from the combined current value flowing through the shunt resistors connected to the FETs 231 to 233. Further, it can be implemented by detecting a PWM instruction value or the like.

  The drive torque calculation unit 304 (corresponding to the drive torque calculation unit) is configured to detect the rotation speed of each motor (or each roller) detected by the position / speed detection unit 301 and the drive current (or PWM instruction) detected by the drive current detection unit 303. Value) to calculate the driving torque. The drive torque can be calculated using the torque conversion table described above. In this embodiment, when a “value corresponding to the driving torque” other than the driving torque is used, the driving torque calculating unit 304 can be omitted. The “value corresponding to the drive torque” is, for example, a drive current command value. Further, the “value relating to the driving torque” in the claims refers to the driving torque and the “value corresponding to the driving torque” described above.

The sheet passing detection unit 305 (corresponding to a sheet passing detecting unit) has a function of detecting whether or not the recording medium has passed (passed) through the secondary transfer roller 80. The following three detection methods are conceivable.
(1) a method of monitoring the drive torque detected by each of the encoders 82 and 84 installed in the secondary transfer roller 80 or the secondary transfer motor 83;
(2) a method of detecting that the registration roller 90 has started conveying the recording medium,
(3) A method of monitoring the drive current flowing through the FET (231, 232, 233),
and so on.

  The method (1) will be specifically described. The driving torque that acts on the secondary transfer roller 80 is larger during conveyance of the recording medium than when it is not conveyed. After receiving the drive command from the main control unit 110, the sheet passing detection unit 305 waits for the passage of time during which the rotation speed of the secondary transfer roller 80 is stabilized, and monitors the drive torque. For example, when the change speed (gradient) of the drive torque becomes equal to or greater than the threshold value, the sheet passing detection unit 305 determines that the recording medium has entered the secondary transfer roller 80.

  The method (2) will be specifically described. The registration roller 90 has a function of adjusting the timing so that the toner image on the intermediate transfer belt 7 is printed on the recording medium and restarting the conveyance. Since the main control unit 110 detects that the registration roller 90 has started to be transported, the sheet passing detection unit 305 receives a notification from the main control unit 110 that the registration roller 90 has started transporting.

  Since the distance from the registration roller 90 to the secondary transfer roller 80 and the conveyance speed are known, the sheet passing detection unit 305 determines that the recording medium has entered the secondary transfer roller 80 after a predetermined time has elapsed after receiving the notification. be able to. In addition, detection of the passage of a recording medium detected by a sensor installed near the secondary transfer roller 80 may be used.

  The method (3) will be described. The drive current flowing through the FETs (231, 232, 233) increases as the addition of the secondary transfer roller 80 increases. Therefore, when the recording medium enters the secondary transfer roller 80, the drive current flowing through the FETs (231, 232, 233) increases. Therefore, for example, the sheet passing detection unit 305 determines that the recording medium has entered the secondary transfer roller 80 when the change speed (gradient) of the drive current becomes a predetermined value or more.

  A speed setting unit 306 (corresponding to a speed setting unit) uses the driving torque when the registration roller 90 is not passing as a torque reference value, and the rotation speed of the registration roller 90 so that the torque fluctuation amount is smaller than the torque reference value. Has the function of setting. Incidentally, the set rotation speed is set so that the torque fluctuation amount with respect to the torque reference value is 0 or less.

  When setting the rotation speed of the registration roller 90, the speed setting unit 306 first determines the driving torque when the registration roller 90 is not passing as a torque reference value. Then, the first torque fluctuation amount is calculated from the torque reference value and the driving torque when the registration roller 90 passes. When the first torque fluctuation amount is positive, the rotation speed of the registration roller 90 is changed slowly. When the first torque fluctuation amount is negative, the rotation speed of the registration roller 90 is changed faster.

  Next, in the registration roller 90 after the rotation speed is changed based on the first torque fluctuation amount, the second torque fluctuation amount is calculated from the torque reference value when the paper is not passed and the driving torque when the paper is passed. To do. Then, a linear expression is calculated from the first torque fluctuation amount and the second torque fluctuation amount, and based on the primary expression, the rotational speed of the registration roller 90 is set so that the torque fluctuation amount with respect to the torque reference value is 0 or less. Set. This point will be described later.

  The determination unit 307 calculates the amount of variation from the speed information of the intermediate transfer belt 7 when the recording medium passes through the registration roller 90, and determines the validity of the rotation speed of the registration roller 90 set by the speed setting unit 306. It has a function. The speed information of the intermediate transfer belt 7 is acquired from the speed detecting means described above. That is, it can be acquired from a speed detection means that employs a belt encoder system in which the encoder pattern 70 is read by the encoder sensor 71 or a rotary encoder system in which a rotary encoder is provided on the rotation shaft of the driven roller 62.

  If the obtained speed fluctuation amount of the intermediate transfer belt 7 is within a threshold value (or a target value), it is determined that the rotation speed of the registration roller 90 is optimum.

  Therefore, each process of the speed setting unit 306 and the determination unit 307 can prevent a shock jitter by suppressing an instantaneous speed fluctuation generated in the intermediate transfer belt 7 when the recording medium passes through the registration roller 90. Become.

<Control principle>
Next, the principle of setting the rotation speed of the registration roller 90 performed by the speed setting unit 306 and the determination unit 307 will be described with reference to FIG.
FIG. 6A shows the relationship between the registration roller linear velocity and the torque fluctuation amount. The horizontal axis indicates the linear speed (or rotational speed) of the registration roller. The vertical axis shows the torque fluctuation amount of the driving torque of the registration motor 93 in the paper passing state with the driving torque of the registration motor 93 when not passing the paper as a torque reference value. This is an estimated torque value of the registration roller 90 (or the registration motor 93) in a state where the recording medium straddles the secondary transfer roller 80 and the registration roller 90. The estimated torque value is a load torque value calculated based on a current value of the registration roller 90 or a PWM instruction value to the registration motor 93 and an actual rotation speed value. In a state where each motor is accurately controlled at a constant speed or a predetermined speed, the drive torque can be calculated from only the current value and the PWM instruction value.

  Each of the intermediate transfer roller 60 and the secondary transfer roller 80 is driven by feedback control at a constant speed, and the linear speed of the registration roller 90 is gradually increased. Then, the drive torque varies in a state where the recording medium straddles the secondary transfer roller 80 (pressure contact portion 800) and the registration roller 90 (hereinafter referred to as section a). It can be seen that the driving torque fluctuation amount at this time tends to increase linearly as shown in FIG. 6A. From this, if there are two values (two points) of the torque fluctuation amount when the registration roller 90 passes, a linear expression (rotational speed) of the registration roller 90 and a linear expression of the torque fluctuation amount can be calculated.

  When the driving torque of the registration roller 90 when the registration roller 90 does not pass is used as a torque reference value and the driving torque of the registration roller 90 increases in the section a, the registration roller 90 pushes the recording medium into the secondary transfer unit 8. (State of FIG. 3A). On the other hand, when the resist driving torque in the section a decreases, the registration roller 90 is pulled by the secondary transfer roller 80 (pressure contact portion 800) using the recording medium as a medium (state shown in FIG. 3B). .

  FIG. 6B shows the relationship between the registration roller linear velocity and the intermediate transfer belt velocity fluctuation. The horizontal axis indicates the linear velocity of the registration roller. The vertical axis represents the instantaneous speed fluctuation of the intermediate transfer belt 7 when the recording medium comes out of the registration roller 90. It is known that the speed fluctuation of the intermediate transfer belt 7 in the pressure contact portion 800 when the recording medium is removed from the registration roller 90 during conveyance of the recording medium has a correlation with shock jitter.

  Here, FIG. 6B and FIG. 6A are compared. In the state where the torque fluctuation amount of FIG. 6A is small and the speed fluctuation amount of the intermediate transfer belt 7 is small in the state where the registration roller 90 is pulled by the secondary transfer portion using the recording medium as a medium (below the torque reference value). It can be seen that J exists (FIG. 6B). It is clear from experimental results that the region J where the speed fluctuation amount is small is a region where measurement variation is small.

  The fact that there is little measurement variation means that the optimum speed setting value of the registration roller 90 can be accurately determined.

  Therefore, by setting the rotation speed of the registration roller 90 so as to fall within this region J, it is possible to set and determine the optimum speed setting value of the registration roller 90. In this way, instantaneous speed fluctuations of the intermediate transfer belt 7 can be suppressed.

That is, the optimum rotation speed of the registration roller 90 can be determined by the following method.
1. The amount of torque fluctuation of the registration roller 90 during conveyance of the recording medium is small and negative (0 or less).
2. After calculating the rotational speed of the registration roller 90 that falls within the region J, the effect of suppressing the instantaneous speed fluctuation of the intermediate transfer belt 7 is determined.

  By the rotation speed setting process by this determination method, the optimum rotation speed of the registration roller 90 with respect to the intermediate transfer roller 60 and the secondary transfer roller 80 can be determined, and the intermediate transfer belt 7 generated when the recording medium passes through the registration roller 90. The instantaneous speed fluctuation can be suppressed.

(Rotation speed setting process)
A procedure for setting the optimum rotation speed of the registration roller 90 will be described with reference to the flowchart shown in FIG.

  This rotational speed setting process is performed when the torque fluctuation of the registration roller 90 (or registration motor 93) of the image forming apparatus 100 exceeds a predetermined range. Further, it can be continuously performed during the image output operation. In short, this rotational speed setting process is a process flow in which the graph shown in FIG. 6A is first created, the rotational speed that falls within the area J of the graph shown in FIG. 6B is calculated, and the effect is confirmed by determination. . Hereinafter, a description will be given with reference to FIG.

  In ST <b> 1, the drive control unit 21 performs a first analysis on the drive torque of the registration roller 90 (hereinafter, also including the registration motor 93). This first analysis determines the torque reference value (horizontal axis) in FIG. 6A and the first torque fluctuation amount P1 with respect to the torque reference value. Specific processing of the processing steps of the first analysis will be described with reference to FIG.

  In FIG. 8, first, in ST20, the motor control unit 20 causes the drive torque calculation unit 304 to calculate the drive torque of the registration roller 90 when the recording medium is not passed. The drive torque calculation unit 304 calculates the drive torque from the encoder information or pulse signal (including the pseudo pulse) of the registration roller 90 acquired from the position / speed detection unit 301 and the drive current acquired from the drive current detection unit 303.

  The driving torque of the registration roller 90 at the time of non-sheet passing calculated in ST20 is set to the torque reference value (horizontal axis) shown in FIG. 6A.

  Next, in ST21, the motor control unit 20 causes the driving torque calculation unit 304 to calculate the driving torque of the registration roller 90 when the recording medium is fed. Then, in ST22, the amount of change with respect to the torque reference value of the driving torque (during paper feeding) is calculated. If the step of ST22 is demonstrated in FIG. 6, it means calculating the 1st torque fluctuation amount P1, for example. When the above ST20 to ST22 are performed, the first analysis is completed. The speed setting of the registration roller 90 is a reference value obtained from design information.

  Returning to the flowchart of FIG. 7, in ST2, the drive control unit 21 determines that the torque fluctuation amount of the driving torque during paper feeding calculated by the first analysis (first torque fluctuation amount P1) is positive with respect to the torque reference value. It is determined whether it is (plus). In the illustrated example, a positive case is shown.

  If the torque fluctuation amount is positive in ST2 (YES), the rotational speed is adjusted so that the torque fluctuation amount of the registration roller 90 becomes negative (minus) (ST3).

  When the torque fluctuation amount is negative (minus) in ST2 (NO), the rotational speed is adjusted so that the torque fluctuation amount of the registration roller 90 becomes positive (plus) (ST4).

  The processing of ST2 to ST4 is to calculate a first equation by calculating a second torque fluctuation amount P2 that passes through the first torque fluctuation amount P1 in FIG. 6A. This is because, as described with reference to FIG. 6A, when the linear velocity of the registration roller 90 is gradually increased, the amount of torque fluctuation in the state where the recording medium straddles the secondary transfer roller 80 (pressure contact portion 800) and the registration roller 90. However, it has a tendency to rise linearly. Further, the second torque fluctuation amount P2 can be approximated to the region J (0) by the processing of ST2 to ST4. As will be described later, since the rotational speed of the registration roller 90 is within the region J where the torque fluctuation amount is small and becomes 0 or less as shown in FIGS. 6A and 6B, the second torque fluctuation amount P2 is approximated to zero. Therefore, it is possible to contribute to the determination and setting of the rotation speed with high accuracy.

  Next, in ST5, the drive control unit 21 performs a second analysis regarding the drive torque of the registration roller 90. This is because, after the rotation speed is changed based on the first torque fluctuation amount P1, the second torque fluctuation amount is calculated from the torque reference value when the paper is not passed and the driving torque when the paper is passed. (P2) is calculated. The second analysis also has the same processing steps as described with reference to FIG.

  Then, in ST6 of FIG. 7, from the first torque fluctuation amount (P1) calculated by the first analysis (ST2) and the second analysis (ST5) and the second torque fluctuation amount (P2), a linear expression is obtained. calculate. This means that in FIG. 6A, a linear P passing through the first torque fluctuation amount P1 and the second torque fluctuation amount P2 is calculated. By calculating this linear P, the optimum region J for setting and determining the rotational speed of the registration roller 90 can be determined. In the region J, as described above, the maximum value is a value at which the torque fluctuation amount with respect to the torque reference value is 0, and the minimum value is a minus value with a torque fluctuation amount with respect to the torque reference value of 0 or less, depending on the recording medium. Is a preset allowable minimum value. The setting allowable minimum value is a preset threshold value and is stored in the memory 130.

  In ST6, the drive control unit 21 causes the speed setting unit 306 to set (temporarily) the rotation speed of the registration roller 90 that falls within the region J. At this time, the speed setting unit 306 first sets the rotation speed to be the center position of the region J shown in FIGS. 6A and 6B.

  In ST7, the drive control unit 21 rotates the registration roller 90 at the rotation speed set by the speed setting unit 306. In this state, the determination unit 307 is caused to check the speed fluctuation of the intermediate transfer belt 7 immediately after the recording medium passes through the registration roller 90. This calculates the amount of fluctuation from the speed information of the intermediate transfer belt 7 when the recording medium passes through the registration roller 90, and determines the validity of the rotation speed of the registration roller 90 set by the speed setting unit 306. . The speed information of the intermediate transfer belt 7 is acquired from the speed detecting means described above. That is, it can be acquired from a speed detection means that employs a belt encoder system in which the encoder pattern 70 is read by the encoder sensor 71 or a rotary encoder system in which a rotary encoder is provided on the rotation shaft of the driven roller 62.

  In ST8, when the determination unit 307 determines that the acquired speed fluctuation amount of the intermediate transfer belt 7 is within the threshold value and is the optimum rotation speed (YES), the determination unit 307 sets the rotation speed of the registration roller 90. In the claims, it is described as “determining the effectiveness of the rotation speed of the third rotating body”. The determination of effectiveness is determination of whether the speed fluctuation amount is within a threshold value. If it is within the threshold value, instantaneous speed fluctuation does not occur, so it can be said that the rotation speed is effective (optimal). “Within threshold” means within the range J.

  If the determination unit 307 determines in ST8 that the rotation speed is not optimal (NO), in ST9, the speed setting unit 306 temporarily determines the rotation speed of the registration roller 90 again in the region J, and proceeds to ST7. Repeat the fine adjustment until it is determined that the rotation speed is optimal. The optimum rotation speed setting process of the registration roller 90 is completed by the above steps.

  As described above, the rotating body drive device according to the first embodiment uses the driving torque when the registration rollers are not passing as a torque reference value, and the torque fluctuation amount when the driving torque during passing is smaller than the torque reference value. Thus, the rotation speed of the registration roller is set.

  More specifically, in the registration roller 90, the first torque fluctuation amount is calculated from the torque reference value when not passing paper and the drive torque when passing paper. When the first torque fluctuation amount is positive, the rotation speed of the registration roller 90 is changed slowly. When the first torque fluctuation amount is negative, the rotation speed of the registration roller 90 is changed faster.

  Next, in the registration roller 90 after the rotation speed is changed based on the first torque fluctuation amount, the second torque fluctuation amount is calculated from the torque reference value when the paper is not passed and the driving torque when the paper is passed. To do. Then, a linear expression is calculated from the first torque fluctuation amount and the second torque fluctuation amount, and based on the primary expression, a registration is performed so that the torque fluctuation amount with respect to the torque reference value is 0 or less (in the region J). The rotation speed of the roller 90 is set.

Therefore, by setting the rotation speed of the registration roller 90 so as to fall within the area J, the amount of fluctuation in the speed of the intermediate transfer belt can be suppressed as shown in FIG. The optimum speed setting value of the roller 90 can be accurately determined.
Thus, the optimum speed setting value of the registration roller 90 can be set and judged, and instantaneous speed fluctuations occurring in the intermediate transfer belt 7 can be reliably suppressed to prevent shock jitter.

  In this embodiment, when the first torque fluctuation amount P1 is positive, the rotation speed of the registration roller 90 is changed to be slow, and when the first torque fluctuation amount P1 is negative, the registration roller 90 The process includes changing the rotational speed faster to obtain the second torque fluctuation amount P2.

  Therefore, the second torque fluctuation amount P2 can be approximated to the region J (0). Since the rotational speed of the registration roller 90 is in the region J where the torque fluctuation amount is small and becomes 0 or less, the second torque fluctuation amount P2 is approximated to 0, so that the rotational speed can be determined and set with high accuracy. Can contribute.

(Modification)
3 and 6, the interference torque caused by the surface speed difference between the intermediate transfer belt 7, the secondary transfer roller 80, and the registration roller 90 has been described. At this time, in order to measure the interference torque, the recording medium K is calculated from the state where the recording medium K straddles the secondary transfer unit 8 and the registration unit 9 and the amount of change in the driving torque (conveying torque) of the registration roller 90 when the sheet is not passed. Was. The interference torque is used as an adjustment index.

  However, in addition to the interference torque (load torque) information, a signal useful as an adjustment index can be used. This point will be described with reference to FIG. FIG. 9 is a diagram illustrating a signal that can be used as a substitute signal for the interference torque (change in drive torque) of the present embodiment.

  The interference torque is the roller or belt surface conveying force, and the torque estimation unit 600 uses the drive current signal of each motor (64, 83, 93) output from the unit U, the PWM signal of the motor, and the actual rotation speed information. Any of the estimated torque values calculated based on the load torque (interference torque) (FIG. 9A).

  FIG. 9B shows a schematic diagram of a signal flow under feedback control.

  A target speed is input to the controller 601. The controller 601 outputs a motor command value to the motor 602 (64, 83, 93). The motor 602 outputs the measured value (drive current value, PWM value) of the motor 602 to the unit U2. The unit U2 outputs (torque estimated value, torque measured value (estimated value)).

  In FIG. 9B, in a state where each motor (64, 83, 93) is accurately controlled to a constant speed or a predetermined speed, information on the drive current value, the PWM value, and the motor command value is represented by the load torque ( It can be used as an adjustment index in the same manner as the estimated torque value and the actually measured torque value (measured value). The reason is that the fluctuation of the interference torque due to the surface speed difference between the intermediate transfer belt 7, the secondary transfer roller 80 and the registration roller 90 is a fluctuation in a frequency band included in the control band in the feedback control. Therefore, driving speed information (measurement speed) is reflected in the controller 601 by performing feedback control. That is, since the interference torque information is reflected in each signal upstream of the signal, it can be applied as an adjustment index.

  Accordingly, the “value relating to the driving torque” in the claims applicable as the conveying force includes the motor current command value, the motor current actual measurement value, the motor PWM command value, the motor PWM actual measurement value, the motor torque actual measurement value, and the motor torque estimation. Value, measured value of roller torque, estimated value of roller torque, and the like. Each of the above values corresponds to the “value corresponding to the driving torque” described above.

  As described above, the preferred embodiment of the present invention has been described, but the present invention is not limited to the above-described embodiment. The present invention can be variously modified or changed in light of the appended claims. For example, the present invention can be similarly applied to all drive devices having a plurality of rotating bodies.

DESCRIPTION OF SYMBOLS 1 Image reading part 2 Image writing unit 3 Photosensitive unit 4 Photosensitive drum 5 Developing unit 6 Intermediate transfer part 7 Intermediate transfer belt 8 Secondary transfer part 9 Registration part 10 Tray 11 Conveying part 12 Fixing part 60 Intermediate transfer roller 61 Secondary Rolling opposite roller 62 Follower roller 64 Intermediate transfer motor 70 Encoder pattern 71 Encoder sensor 80 Secondary transfer roller 83 Secondary transfer motor 90 Registration roller 91 Counter roller 93 Registration motor (drive means)
20 Motor control unit 21 Drive control units 221 to 223 Pre-drivers 231 to 233 FET
100 Image forming apparatus 110 Main control unit 120 Operation unit 130 Memory 301 Position / velocity detection unit
302 Motor drive control unit 303 Drive current detection unit
304 drive torque calculation unit (drive torque calculation means)
305 Paper passing detection unit (paper passing detecting means)
306 Speed setting section (Speed setting means)
307 determination unit (determination means)
K recording medium P linear P1 first torque fluctuation amount P2 second torque fluctuation amount

JP 2013-29807 A

Claims (9)

The first rotating body, the second rotating body, and the third rotating body are provided, and the sheet-like medium is conveyed by at least one of the first rotating body to the third rotating body. A rotating body drive device,
Drive means for rotationally driving at least the third rotating body;
A paper passing detection means for detecting a paper passing state of the sheet-like medium of the rotating body;
Speed setting means for setting a rotation speed of the third rotating body based on a value relating to a driving torque of the driving means;
The speed setting means includes
The third rotation is performed so that the value related to the driving torque when the third rotating body is not passing is set as a reference value, and the value related to the driving torque when passing the paper is a value that is smaller than the reference value. A rotating body driving device characterized by setting a rotational speed of the body. A conveyor belt stretched between the first rotating body and the second rotating body;
A transport speed detecting means for detecting a transport speed of the transport belt;
Determination means for determining the effectiveness of the rotational speed of the third rotating body set by the speed setting means from the speed fluctuation amount acquired from the transport speed detecting means;
The rotating body drive device according to claim 1, further comprising: The speed setting means includes
In the third rotating body, a first torque fluctuation amount is calculated from the reference value when the paper is not passed and a value related to the driving torque when the paper is passed,
When the first torque fluctuation amount is positive, the rotational speed of the third rotating body is changed slowly,
2. The rotating body drive device according to claim 1, wherein when the first torque fluctuation amount is negative, the rotation speed of the third rotating body is changed faster. The speed setting means includes
In the third rotating body after the rotation speed has been changed based on the first torque fluctuation amount, the second torque is calculated from the reference value at the time of non-sheet passing and the value relating to the driving torque at the time of sheet passing. Calculate the amount of fluctuation,
A linear expression is calculated from the first torque fluctuation amount and the second torque fluctuation amount,
The rotating body drive device according to claim 3, wherein the rotation speed of the third rotating body is set based on the primary expression. The maximum value of the rotation speed of the third rotating body set by the speed setting means is
A torque fluctuation amount with respect to the reference value is zero,
The minimum value of the rotational speed set by the speed setting means is a set allowable value that the sheet-like medium has a torque fluctuation amount with respect to the reference value of less than 0. The rotating body drive device as described in any one of Claims. Drive torque calculation means for calculating the drive torque of the drive means;
The drive torque calculating means includes
2. The rotating body driving device according to claim 1, wherein the driving torque is calculated using a pulse width modulation signal of the driving means and rotation speed information. Drive torque calculation means for calculating the drive torque of the drive means;
The drive torque calculating means includes
2. The rotating body driving apparatus according to claim 1, wherein the driving torque is calculated using a driving current of the driving unit and rotation speed information.   An image forming apparatus comprising the rotating body driving device according to claim 1. A first rotating body, a second rotating body, and a third rotating body are provided, and the sheet-like medium is conveyed by at least one of the first rotating body to the third rotating body. A method of controlling a rotating body drive device to be performed,
A driving step of rotating at least the third rotating body;
A paper passing detection step of detecting a paper passing state of the sheet-like medium of the rotating body;
A speed setting step of setting a rotation speed of the third rotating body based on a value relating to a driving torque of the driving step;
The speed setting step includes:
The third rotation is performed so that the value related to the driving torque when the third rotating body is not passing is set as a reference value, and the value related to the driving torque when passing the paper is a value that is smaller than the reference value. A method for controlling a rotating body drive device, comprising: setting a rotational speed of a body.

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