JP2007267536A - Drive unit used for image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit for driving a device coupled to an output shaft at a required speed and performing a normal feedback control. <P>SOLUTION: The drive unit 1 includes a power transmission unit, a fixing member 10 and a control unit 21. The power transmission unit is equipped with a plurality of planetary rollers 4 pressed to the outer peripheral surface of a motor rotary shaft 3 and comprising an elastic body, a ring 6 contacting to the plurality of planetary rollers 4 on its inner peripheral surface and having a projection part 6a projecting out of the outer peripheral surface, a fixed body 9 covering the ring 6 and wherein an opening 9a having a width allowing the projecting part 6a to move a specified distance is opened, a carrier roller 7 rotating in conjunction with the rotation of the planetary rollers 4, and the output shaft 8 outputting the rotation of the carrier roller to the outside. The fixing member 10 can take a fixed state wherein the projecting part 6a immovably fixes the ring 6 in the opening and also a released state releasing the fixation of the ring 6. The control unit 21 controls the fixing member 10 so that the fixing member 10 can take the fixed state from the start till the end of an image forming process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a driving device used in an image forming apparatus.

  A color image forming apparatus such as a color printer or a color copying machine has a driving device for rotating and driving devices such as a photosensitive drum and a transfer belt for each color component. Some drive devices include a motor and a planetary reduction device that reduces the rotation of the motor.

  In recent years, with the cost reduction of color image forming apparatuses, planetary rollers in planetary reduction devices are being formed at least partially using an elastic body such as rubber, as shown in Patent Document 1. Since the planetary roller, which is an elastic body, is pressed against an output shaft that transmits the rotation of the motor to the outside, elastic deformation occurs. Elastic deformation generated in the elastic body of the planetary roller causes fluctuations in the rotational speed of the output shaft of the speed reducer. Further, an image generated while the rotational speed of the output shaft of the speed reducer fluctuates, color misregistration, color unevenness, and the like appear.

Patent Document 2 discloses a rotation drive device that makes the rotation speed of the output shaft uniform by directly controlling the rotation speed of the motor when an elastic body is used for the planetary roller. Specifically, the rotation drive device of Patent Document 2 includes a stepping motor, a reduction device, and feedback control means. The speed reduction device includes a torque transmission unit that transmits torque by frictional contact with an elastic body and does not include a torque transmission unit using gears, and decelerates the rotation of the motor and outputs it to the photosensitive drum. The feedback control means detects the output rotation speed of the speed reducer, obtains a difference value from the target speed, gives a speed command signal to the motor based on the difference value, and directly controls the rotation speed of the motor.
JP 2002-115751 A Japanese Patent Application Laid-Open No. 2002-171779

  However, Patent Document 2 has the following problems.

  The elastic deformation generated in the planetary roller of the elastic body until the motor stops rotating and restarts causes unevenness in the rotational speed of the output shaft of the reduction gear for a while after the restarting. When the motor is stopped, the period in which the rotational speed of the output shaft of the speed reducer caused by the elastic deformation generated in the planetary roller is not uniform is much longer than the response time when the apparatus of Patent Document 2 performs feedback control. Therefore, if the rotation speed of the output shaft of the reduction gear caused by the elastic deformation generated in the planetary roller is detected by the feedback control according to the device of Patent Document 2 to control the rotation speed of the motor, It will occur.

  Therefore, the present inventor has invented and has filed an application for a drive device that prevents unevenness in the rotational speed of the output shaft of the speed reducer caused by the elastic deformation of the planetary roller from affecting the image (Japanese Patent Application No. 2005-). 368480). This driving device is in contact with a plurality of planetary rollers of an elastic body on the inner peripheral surface, and has a ring having a protruding portion protruding on the outer peripheral surface, and covers the ring at a position corresponding to the protruding portion of the ring. This is a device that includes a planetary reduction device having a fixed body with an opening formed therein, and drives the motor so that the protruding portion reciprocates within the opening when no image forming operation is performed.

  However, when the motor is started in response to an instruction to start an image forming operation, if the ring protrusion is in a position where it can move within the opening of the fixed body, the ring protrusion moves within the opening of the fixed body due to the rotation of the motor. It moves by the movable distance. During this period, the drive device cannot output rotation for rotating the photosensitive drum at a target speed, and thus cannot perform normal feedback control.

  In particular, when the motor is started, if the rotation speed of the transfer belt driven while contacting the photosensitive drum is faster than the rotation speed of the photosensitive drum, the photosensitive drum is rotated along with the rotation of the transfer belt, so that the ring Rotating in the opposite direction, the ring protrusion moves away from the inner wall of the opening and moves in the opening. As a result, the drive device cannot perform feedback control.

  Therefore, the present invention can drive a device such as a photosensitive drum or a transfer belt connected to an output shaft at a desired speed from the time when the motor is started upon receiving an instruction to start an image forming operation, and is normal. Provided is a drive device capable of performing accurate feedback control.

  In order to solve the above-mentioned problems, the invention 1 provides a drive device including a planetary roller power transmission unit, a fixing means, and a control means. The planetary roller type power transmission unit is in pressure contact with the outer peripheral surface of the rotating shaft of the motor, and is in contact with a plurality of planetary rollers at least partially made of an elastic body and the plurality of planetary rollers on the inner peripheral surface, A ring having a protrusion protruding on the surface; and a ring that is positioned so as to cover the ring, and has a width that allows the protrusion to move a predetermined distance to a position corresponding to the protrusion of the ring A fixed body having an opening, a carrier roller that rotates in conjunction with the rotation of the planetary roller, and an output shaft that outputs the rotation of the carrier roller to the outside. The fixing means fixes the ring so that the protruding portion of the ring cannot move within the opening of the fixed body and the ring is fixed so that the protruding portion of the ring can move within the opening of the fixing body. The fixed release state to be released can be taken. The control unit controls the fixing unit so that the fixing unit is in the fixed state between the start of the image forming process and the end of the image forming process.

  According to this drive device, since the ring is fixed from the start to the end of the image forming process, the power transmission unit has a rotational speed of the motor regardless of the position of the protrusion of the ring within the opening of the fixed body. Is transmitted from the start of the motor. Therefore, the drive device can drive the image carrier connected to the output shaft at a desired speed from the time of starting the motor, and can perform normal feedback control.

  According to a second aspect of the present invention, in the first aspect of the present invention, the fixing unit is in the fixed release state after the control unit has received an instruction to end the image forming process and has received an instruction to start the next image forming process. And a driving device that controls the rotation of the motor so that the protruding portion of the ring reciprocates within the opening of the fixed body.

  This apparatus releases the ring from the end of the image forming process until it receives the next image forming process start instruction. For example, the protruding part of the ring reciprocates in the opening of the fixed body. The motor can be rotated at a very low speed. When the motor rotates at a slow speed, the planetary roller also rotates at a slow speed. Thereby, it can prevent that an elastic deformation | transformation arises in the elastic body of the planetary roller which contact | connects the outer peripheral surface of a motor rotating shaft.

  A third aspect of the present invention provides the driving device according to the first or second aspect, wherein the fixing means is an electromagnet that can be energized with current, and the control means controls current energization and deenergization to the electromagnet. To do.

  Thereby, the drive device can more securely fix and release the ring.

  According to the present invention, when the motor is started in response to an instruction to start an image forming operation, the driving device can drive a device such as a photosensitive drum or a transfer belt connected to the output shaft at a desired speed. Normal feedback control can be performed.

<Embodiment>
FIG. 1 is a diagram showing a cross-sectional configuration of a driving device 1 according to the present embodiment and connection with peripheral devices. 1 is connected to an image forming apparatus 31, and is used as an apparatus for driving a photosensitive drum 32 provided in the image forming apparatus 31 as shown in FIG.

  The image forming apparatus 31 is a color image forming apparatus used for, for example, a color printer or a color copying machine. In this embodiment, the image forming apparatus 31 is a so-called tandem full-color image forming apparatus in which four unfixed visible images are transferred onto a recording sheet and then fixed, as shown in FIG. Take an example. The image forming apparatus 31 has an image forming section for each color (Y, M, C, B) including a photosensitive drum 32 and the like arranged along the sheet conveyance path. The driving device 1 is provided corresponding to each photoconductive drum 32 so that each photoconductive drum 32 can be driven.

(1) Configuration of Drive Device Hereinafter, the configuration of the drive device 1 will be described with reference to FIGS. 1, 3, and 4.

  The drive device 1 includes a motor 2 as a rotational drive source, a motor rotation shaft 3, a plurality of planetary rollers 4, a ring 6, a carrier roller 7, an output shaft 8, a fixed body 9, a fixed member 10, and a control unit 21.

  The motor rotation shaft 3 outputs the rotation of the motor 2 to the outside. The plurality of planetary rollers 4 are positioned in a state of being pressed between the outer peripheral surface of the motor rotating shaft 3 and the inner peripheral surface of the ring 6. In this embodiment, the case where there are three planetary rollers 4 is taken as an example. The edge of each planetary roller 4 is formed of an elastic body 4a such as rubber or resin. The ring 6 is formed of a metal such as Fe, is positioned so as to surround the three planetary rollers 4, and is in contact with each planetary roller 4 on the inner peripheral surface. Further, the ring 6 has a protruding portion 6a protruding on the outer peripheral surface. The carrier roller 7 is located on the opposite side of the motor 2 when viewed from the planetary roller 4, and is connected to the planetary roller 4 by the rotation shaft 4 b of the planetary roller 4. The carrier roller 7 is connected to the output shaft 8 via a bearing 8 a located at a part of the fixed body 9. The output shaft 8 outputs the rotation of the carrier roller 7 to the outside on the same axis as the motor rotation shaft 3. The fixed body 9 is located outside the motor 2 and surrounds the motor rotating shaft 3, the three planetary rollers 4, the ring 6 and the carrier roller 7. The fixed body 9 is formed with an opening 9 a having a width that allows the protrusion 6 a to move a predetermined distance at a position corresponding to the protrusion 6 a of the ring 6. Hereinafter, the planetary roller 4, the ring 6, the carrier roller 7, the output shaft 8, and the fixed body 9 are collectively referred to as a “planetary roller power transmission unit”.

  The fixing member 10 is positioned so as to face the ring 6 with the fixing body 9 interposed therebetween, and includes an electromagnet 10a and a current-carrying portion 10b for flowing a current through the electromagnet 10a as shown in FIG. The fixing member 10 is in a fixed state in which the energizing portion 10b applies a current to the electromagnet 10a and the electromagnet 10a is turned on, so that the protruding portion 6a of the ring 6 fixes the ring 6 so that it cannot move within the opening 9a of the fixing body 9. Become. The fixing member 10 also fixes the ring 7 so that the projecting portion 7a of the ring 6 can move within the opening 9a of the fixed body 9 when the energizing portion 10b stops energizing the electromagnet 10a and the electromagnet 10a is turned off. The fixed release state is released.

  The control unit 21 is located outside the motor 2 and the fixed body 9, and is connected to the motor 2, the fixed member 10, and the image forming apparatus 31 as shown in FIGS. 1 and 4. The configuration of the control unit 21 will be described later.

(2) Operations of Planetary Roller Type Power Transmission Unit and Motor Rotating Shaft Here, operations of the planetary roller type power transmission unit and the motor rotating shaft 3 will be described with reference to FIG.

  First, the case where the ring 6 is fixed by the fixing member 10 will be described. When the motor rotation shaft 3 rotates in the rotation direction of the motor 2, the three planetary rollers 4 revolve in the same direction as the rotation direction of the motor rotation shaft 3 along the inner peripheral surface of the ring 6 around the motor rotation shaft 3. To do. Further, each planetary roller 4 rotates in the direction opposite to the rotation direction of the motor rotation shaft 3 around the rotation shaft 4 b of each planetary roller 4. The carrier roller 7 rotates in conjunction with the revolution of the planetary roller 4. That is, the carrier roller 7 rotates in the same direction as the rotation direction of the motor rotation shaft 3. At this time, the carrier roller 7 rotates at a speed at which the rotation of the motor rotating shaft 3 is decelerated by the rotation of the planetary roller 4.

  When the ring 6 is not fixed by the fixing member 10, in addition to the above-described operation, the ring 6 rotates in conjunction with the revolution of the planetary roller 4. That is, the ring 6 rotates about the motor rotation shaft 3 in the same direction as the revolution direction of the planetary roller 4, but has the protrusion 6 a, so that the protrusion 6 a passes through the opening 9 a of the fixed body 9. Rotate as much as you can move. For example, when the motor rotating shaft 3 and the ring 6 rotate clockwise and the protrusion 6a of the ring 6 contacts the inner wall of the opening 9a of the fixed body 9, the ring 6 stops rotating. In this state, when the motor rotating shaft 3 starts to rotate in the reverse direction, the protruding portion 6a of the ring 6 is separated from the inner wall of the opening 9a in contact, and the ring 6 rotates in the same direction as the motor rotating shaft 3. And if the protrusion part 6a contact | connects the inner wall on the opposite side to the opening part 9a of the fixing body 9, the ring 6 will stop rotation. That is, by changing the rotation direction of the motor rotating shaft 3, the protruding portion 6 a of the ring 6 reciprocates within the opening 9 a of the fixed body 9.

(3) Configuration of Control Unit As shown in FIG. 4, the control unit 21 includes a timer 22, a motor drive control unit 23, a motor rotation direction control unit 24, a motor rotation speed control unit 25, and a fixed member control unit 26. Each function will be specifically described below.

(3-1) Timer The timer 22 outputs time information. The time information of the timer 22 is used when the motor drive control unit 23, the motor rotation direction control unit 24, the motor rotation speed control unit 25, and the fixed member control unit 26 generate signals.

(3-2) Motor Drive Control Unit The motor drive control unit 23 performs drive control of the motor 2. Specifically, the motor drive control unit 23 generates a motor drive control signal MOT_DR for controlling on / off of the drive of the motor 2 based on the time information from the timer 22 and outputs the motor drive control signal MOT_DR to the motor 2.

(3-3) Motor Rotation Direction Control Unit The motor rotation direction control unit 24 generates a motor rotation direction control signal MOT_DIR for instructing the rotation direction of the motor based on the time information from the timer 22 and outputs it to the motor 2. To do.

  Specifically, the motor rotation direction control unit 24 performs the ringing from when the image forming apparatus 31 ends the image forming process to when the signal indicating the start of the next image forming process is received from the image processing apparatus 31, for example. The rotation direction of the motor 2 is controlled so that the protruding portion 6a reciprocates in the opening 9a of the fixed body 9. Further, the motor rotation direction control unit 24 receives the signal indicating the start of the image forming process and acquires the signal indicating the end of the image forming process so that the motor 2 rotates in the forward direction. The rotation direction of the motor 2 is controlled.

(3-4) Motor Rotation Speed Control Unit The motor rotation speed control unit 25 generates a motor rotation speed control signal MOT_FCLK for instructing the rotation speed of the motor 2 with reference to time information from the timer 22, and Output.

  Specifically, the motor rotation speed control unit 25 performs the ringing from when the image forming apparatus 31 ends the image forming process to when the signal indicating the start of the next image forming process is received from the image processing apparatus 31, for example. The rotational speed of the motor 2 is controlled so that the six protrusions 6a move at a very low speed in the opening 9a of the fixed body 9. Further, after receiving a signal indicating the start of the image forming process, the motor rotation speed control unit 25 generates a motor rotation speed control signal MOT_FCLK for the motor 2 to perform steady rotation, and outputs the motor rotation speed control signal MOT_FCLK to the motor 2.

(3-5) Fixing member control unit The fixing member control unit 26 uses the ring lock control signal R_LOCK for controlling whether or not the energization unit 10b of the fixing member 10 supplies current to the electromagnet 10a as time information from the timer 22. As a reference and output to the energization unit 10b.

  Specifically, the fixing member control unit 26 receives a signal indicating the start of the image forming process and then receives a signal indicating the end of the image forming process from, for example, the image forming apparatus 31. The ring lock control signal R_LOCK for energizing is output to the energizing unit 10b. The fixing member control unit 26 is a ring for stopping energization of the energization unit 10b after receiving a signal indicating the end of the image forming process until receiving a signal indicating the start of the next image forming process. The lock control signal R_LOCK is output to the energization unit 10b.

(4) Operation of Each Function in Control Unit FIG. 5 is a timing chart for explaining the operation of the control unit 21. The image formation processing signal in FIG. 5 is a signal for indicating that an image forming operation is being performed by the image forming apparatus 31 and represents a period during which the image forming operation is being performed as “1”. The image formation instruction signal is a signal for instructing the start and end of image formation processing. The motor drive control signal MOT_DR represents “0” for motor stop and “1” for drive. The motor rotation direction control signal MOT_DIR represents “1” as the clockwise direction of the motor rotation shaft 3 and “0” as the counterclockwise direction of the motor rotation shaft 3 in FIG. The ring lock control signal R_LOCK indicates that the energization of the energization unit 10b is “1” and the energization stop is “0”.

  First, when the control unit 21 receives an image formation instruction signal indicating an end instruction for image formation processing from the outside of the image forming apparatus 31 or the like, the motor drive control unit 23 of the control unit 21 temporarily resets the motor drive control signal MOT_DR. Then, the motor drive control signal MOT_DR “1” is output to the motor 2. The motor rotation direction control unit 24 generates a motor rotation direction control signal MOT_DIR for periodically changing the rotation direction of the motor 2 so that the protrusion 6a of the ring 6 reciprocates within the opening 9a of the fixed body 9. And output to the motor 2. Specifically, the motor rotation direction control unit 24 continues to output pulses having a predetermined cycle and a predetermined high period. The motor rotation speed control unit 25 outputs to the motor 2 a motor rotation speed control signal MOT_FCLK for allowing the protrusion 6 a of the ring 6 to move at a very low speed in the opening 9 a of the fixed body 9. In FIG. 5, the motor rotation speed control signal MOT_FCLK is synchronized with the motor rotation direction control signal MOT_DIR. And the fixing member control part 26 outputs the ring lock control signal R_LOCK "0" for stopping the electricity supply to the electromagnet 10a of the electricity supply part 10b to the electricity supply part 10b.

  Thereby, the electricity supply part 10b stops electricity supply, and the ring 6 is released from being fixed. The motor 2 rotates at a slight speed in the clockwise direction or the counterclockwise direction based on the signals sent from the motor drive control unit 23, the motor rotation direction control unit 24, and the motor rotation speed control unit 25. Then, the protrusion 6 a of the ring 6 reciprocates in the opening 9 a of the fixed body 9, and the planetary roller 4 reciprocates a predetermined width on the outer peripheral surface of the motor rotating shaft 3. As a result, no pressure is applied to a fixed portion of the elastic body 4a of the planetary roller 4 in contact with the outer peripheral surface of the motor rotating shaft 3.

  Next, when the control unit 21 receives an image formation instruction signal indicating an instruction to start image formation processing from the outside of the image forming apparatus 31 or the like, the motor drive control unit 23 of the control unit 21 resets the motor drive control signal MOT_DR once. Then, the motor drive control signal MOT_DR “1” is output to the motor 2 again. The motor rotation direction control unit 24 and the motor rotation speed control unit 25 rotate the motor 2 in one direction at a steady speed that is faster than when waiting for reception of a signal to start image forming processing. A control signal MOT_FCLK and a motor rotation direction control signal MOT_DIR are output to the motor 2. The fixing member control unit 26 outputs a ring lock control signal R_LOCK “1” for energizing the electromagnet 10a to the energization unit 10b.

  As a result, the energization unit 10b starts energization, and a magnetic force is generated in the electromagnet 10a. The ring 6 formed of a metal such as Fe is fixed by the magnetic force of the electromagnet 10a. The motor 2 rotates at a rotation direction and speed based on the motor rotation direction control signal MOT_DIR and the motor rotation speed control signal MOT_FCLK, and eventually reaches a steady rotation state. When the rotation of the motor 2 reaches the steady rotation state, the image forming process is executed by the image forming apparatus 31 (image forming process signal “1”).

(5) Effect The driving device 1 fixes the ring 6 by the fixing member 10 after receiving an instruction to start the image forming process until receiving an instruction to end the image forming process. As a result, regardless of the position of the protrusion 6a of the ring 6 in the opening 9a of the fixed body 9, the planetary roller power transmission unit has a rotational speed obtained by reducing the rotational speed of the motor 2 at a desired ratio. It is transmitted from time. Therefore, the driving device 1 can drive the photosensitive drum 32 at a desired speed from the time of starting the motor 2 and can perform normal feedback control.

  Then, the drive device 1 releases the fixing of the ring 6 by the fixing member 10 until the driving device 1 receives the instruction to end the next image forming process after receiving the instruction to end the image forming process. The motor 2 is rotated at a very low speed so as to reciprocate within the opening 9a of the fixed body 9. As a result, the planetary roller 4 also rotates at a slow speed. Therefore, it is possible to prevent pressure from being applied to a fixed portion of the elastic body 4a of the planetary roller 4 that is in contact with the outer peripheral surface of the motor rotating shaft 3, so that elastic deformation of the elastic body 4a of the planetary roller 4 can be prevented.

<Other embodiments>
In the above embodiment, the case where the fixing member has a configuration using an electromagnet has been described. However, the fixing member may be anything as long as the ring can be fixed and released.

  The drive device of the present invention can be used as a drive device for a photosensitive drum in a color image forming apparatus such as a color printer or a color copying machine.

The figure which showed the cross-sectional structure of the drive device which concerns on this embodiment, and the connection with the peripheral device. 1 is a schematic diagram of an image forming apparatus in which a driving device of the present embodiment is used. III-III sectional view taken on the line of a drive device. The function block diagram of a control part. The timing chart for demonstrating operation | movement of a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive device 2 Motor 3 Motor rotating shaft 4 Planetary roller 4a Elastic body 6 Ring 6a Projection part 7 Carrier roller 8 Output shaft 9 Fixing body 9a Opening part 10 Fixing member

Claims (3)

A plurality of planetary rollers, which are in pressure contact with the outer peripheral surface of the rotating shaft of the motor, and at least partly made of an elastic body, are in contact with the plurality of planetary rollers on the inner peripheral surface, and projecting portions protruding on the outer peripheral surface A fixed body having a ring that has a width that allows the protrusion to move a predetermined distance at a position corresponding to the protrusion of the ring. A planetary roller power transmission unit comprising: a carrier roller that rotates in conjunction with the rotation of the planetary roller; and an output shaft that outputs the rotation of the carrier roller to the outside.
A fixed state in which the protruding portion of the ring fixes the ring so that it cannot move within the opening of the fixed body, and an unlocking that releases the fixing of the ring so that the protruding portion of the ring can move within the opening of the fixed body. A fixing means capable of taking a state, and
Control means for controlling the fixing means so that the fixing means is in the fixing state after an instruction for starting image forming processing is given until an instruction for ending the image forming processing is given;
Including a driving device.   The control unit controls the fixing unit so that the fixing unit is in the fixed release state after an instruction to end the image forming process and before an instruction to start the next image forming process is issued. The drive device according to claim 1, wherein the rotation of the motor is controlled such that the protruding portion of the ring reciprocates within the opening of the fixed body. The fixing means is an electromagnet that can be energized with current,
The drive unit according to claim 1, wherein the control unit controls energization and deenergization of the current to the electromagnet.

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