JP2016090952A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably execute in a short time an operation of changing the rotation speed of a fixation member and a pressure member when the speed is, for example, switched between the fixation operation time and the standby time when the fixation operation is not performed, in a fixation device which fixes a toner image on a recording medium between the fixation member and the pressure member.SOLUTION: A fixation device 30 that fixes a toner image t on a recording medium S between a fixation member 31 and a pressure member 32 is provided with a first rotation transmission mechanism 41 and a second rotation transmission mechanism 42 for transmitting the rotation of a rotation drive device 40 to the fixation member and the pressure member and having different speed reduction ratios; and pressure changing means 35 for changing the pressure force between the fixation member and the pressure member. When the first rotation transmission mechanism and the second rotation transmission mechanism for transmitting the rotation to the fixation member and the pressure member are switched from one to the other by a control device 50, the pressure force between the fixation member and the pressure member is adjusted by the pressure changing means.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device for fixing an unfixed toner image on a recording medium and an image forming apparatus using such a fixing device. In particular, a fixing member, a heating device that heats the fixing member, a pressure member that pressurizes a recording medium on which an unfixed toner image is formed, and the fixing member. A rotation transmission mechanism for transmitting the rotation of the rotation driving device to the pressure member, and heating and pressurizing the recording medium between the fixing member and the pressure member to form an unfixed toner image. In a fixing device for fixing on a recording medium, rotation of a fixing member or a pressure member that is rotated by a rotation driving device, for example, when switching between a fixing operation for fixing a toner image on a recording medium and a standby time when no fixing operation is performed In changing the speed, it is characterized in that such an operation can be performed stably in a short time.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a composite machine thereof, generally, a recording medium on which a toner image is transferred from an image carrier such as a photoreceptor is guided to a fixing device and transferred to the recording medium. The fixed unfixed toner image is fixed on a recording medium in this fixing device.

  Here, in such a fixing device, in general, the fixing member and the pressure member are rotated by the rotation driving device in a state where the pressure member is pressed against the fixing member heated by the heating device. A recording medium on which a toner image is formed is guided between the fixing member and the pressure member, and the recording medium is heated and pressurized between the fixing member and the pressure member to thereby form unfixed toner. The image is fixed on the recording medium.

  In recent years, in order to shorten the first copy time in the image forming apparatus, an IH (induction heating) apparatus is used as a heating apparatus so that the fixing member is heated quickly, and a standby operation without performing a fixing operation is performed. In this case, the fixing member and the pressure member are continuously rotated to maintain the fixing member in a heated state.

  However, in recent years, as the image forming speed is increased, the speed of rotating the fixing member and the pressure member has been increased, and the fixing member and the pressure member have a high speed even during standby without performing the fixing operation. In other words, noise is generated due to rotation, and a load applied to the fixing member, the pressure member, the rotation driving device, and the like is increased, and the life of the fixing device is reduced.

  For this reason, in the fixing device as described above, the rotation speed at which the fixing member and the pressure member are rotated by the rotation driving device is slowed down during the standby time when the fixing operation is not performed as compared with the fixing operation, and noise is generated. Suppression is being studied.

  Conventionally, as shown in Patent Document 1, in a fixing device or the like, when a rotating body is rotated by a rotation driving device, a reduction ratio is used as a rotation transmission mechanism that transmits the rotation of the rotation driving device to the rotating body. A rotation transmission mechanism provided with a different first rotation transmission mechanism and a second rotation transmission mechanism and switching the rotation direction of the rotation drive device according to the use mode to transmit the rotation of the rotation drive device to the rotating body, It has been proposed to switch between a first rotation transmission mechanism and a second rotation transmission mechanism and to change the rotation speed of the rotating body by the rotation driving device according to the use mode.

  However, when switching the rotation direction in the rotation drive device as described above and switching the rotation transmission mechanism that transmits the rotation in the rotation drive device to the rotating body between the first rotation transmission mechanism and the second rotation transmission mechanism, After stopping the rotation of the rotating body by the rotation driving device, it is necessary to switch the rotation direction in the rotation driving device, and it takes a lot of time to stop the rotation of the rotating body by the rotation driving device. There was a problem that variations occurred in the time until the rotation stopped.

  For this reason, even if the fixing device described in Patent Document 1 is used, the operation of changing the rotation speed of the fixing member or the pressure member rotated by the rotation driving device is stabilized in a short time. It was difficult to do.

JP 2005-54861 A

  In the present invention, in a state where the fixing member heated by the heating device is pressed against the pressure member, the fixing member and the pressure member are rotated by a rotation driving device, and a recording in which an unfixed toner image is formed is provided. A fixing device that guides a medium between the fixing member and a pressure member, and heats and presses the recording medium between the fixing member and the pressure member to fix an unfixed toner image on the recording medium. When changing the rotation speed of the fixing member and the pressure member rotated by the rotation driving device in the case of switching between the fixing operation for fixing the toner image on the recording medium and the standby time without performing the fixing operation, etc. It is an object of the present invention to enable such operations to be performed stably in a short time.

  In the fixing device according to the present invention, in order to solve the above-described problem, a recording in which an unfixed toner image is formed between the fixing member, a heating device for heating the fixing member, and the fixing member. A pressure member that pressurizes the medium; and a rotation transmission mechanism that transmits the rotation of the rotation driving device to the fixing member and the pressure member, and the recording between the fixing member and the pressure member. In a fixing device that heats and pressurizes a medium to fix an unfixed toner image on a recording medium, the rotation transmission mechanism transmits the rotation in the rotation driving device to the fixing member and the pressure member. A first rotation transmission mechanism and a second rotation transmission mechanism that have different reduction ratios, a control device that controls switching between the first rotation transmission mechanism and the second rotation transmission mechanism, and the fixing member and With pressure member Pressure changing means for changing the pressing force of the fixing member, and when the control device switches between the first rotation transmission mechanism and the second rotation transmission mechanism, the pressure changing means causes the fixing member and the pressure member to be changed. The pressing force between them was adjusted.

  In this fixing device, when the control device switches between the first rotation transmission mechanism and the second rotation transmission mechanism as described above, for example, the rotation direction of the rotation driving device is changed by the control device. Then, switching between the first rotation transmission mechanism and the second rotation transmission mechanism is performed, or an electromagnetic clutch is provided in each of the first rotation transmission mechanism and the second rotation transmission mechanism, and by the control device, The electromagnetic clutch to be operated can be switched to switch between the first rotation transmission mechanism and the second rotation transmission mechanism. As described above, when the control device changes the rotation direction of the rotation drive device and switches between the first rotation transmission mechanism and the second rotation transmission mechanism, the rotation direction change by the rotation drive device is quickly performed. When the switching between the first rotation transmission mechanism and the second rotation transmission mechanism is performed, the pressure change means increases the pressing force between the fixing member and the pressure member, It is preferable to quickly stop the rotation of the fixing member and the pressure member by the rotation driving device.

  Further, in this fixing device, when the control device switches the first rotation transmission mechanism and the second rotation transmission mechanism as described above, the second rotation transmission mechanism is more effective than the reduction ratio in the first rotation transmission mechanism. In the fixing operation in which the reduction ratio is increased and the toner image is fixed on the recording medium, the rotation in the rotation driving device is transmitted to the fixing member and the pressure member by the first rotation transmission mechanism, while the fixing operation is performed. At the time of standby not to be performed, the rotation of the rotation driving device can be transmitted to the fixing member and the pressure member by the second rotation transmission mechanism. As described above, when the fixing operation is not performed, the second rotation transmission mechanism having a larger reduction ratio than that of the first rotation transmission mechanism is switched, and the rotation of the rotation driving device is pressurized with the fixing member by the second rotation transmission mechanism. When transmitting to the member, the rotation speed of the fixing member and the pressure member is slower in the standby time than in the fixing operation.

  In addition, when the control device switches the first rotation transmission mechanism and the second rotation transmission mechanism between the fixing operation and the standby state in this way, the pressure changing means causes the fixing member and the pressure member to It is preferable that the pressing force is stronger than the pressing force during standby.

  In the image forming apparatus according to the present invention, the fixing device as described above is used to fix the toner image on the recording medium.

  Further, the image forming apparatus includes a third rotation transmission mechanism that transmits the rotation of the rotation driving device in the fixing device to another driving member. During the fixing operation, the third rotation transmission mechanism is used. The rotation of the rotation drive device is transmitted to the other drive member, while the control device controls the rotation drive device so that the rotation of the rotation drive device is not transmitted to the other drive member during the standby time when the fixing operation is not performed. Can be.

  In the fixing device of the present invention, the first rotation transmission mechanism and the second rotation transmission mechanism having different reduction ratios are used as the rotation transmission mechanism for transmitting the rotation of the rotation driving device to the fixing member and the pressure member as described above. When the first rotation transmission mechanism and the second rotation transmission mechanism are switched by the control device and the rotation speed of the fixing member and the pressure member is changed, the pressure changing means pressurizes the fixing member and the pressure member. Since the pressing force between the members is adjusted, the rotation of the fixing member and the pressure member can be quickly controlled.

  In the fixing device of the present invention, when the first rotation transmission mechanism and the second rotation transmission mechanism are switched by the control device as described above, the control device changes the rotation direction of the rotation drive device to change the first rotation transmission mechanism and the second rotation transmission mechanism. When switching between the one rotation transmission mechanism and the second rotation transmission mechanism, if the pressing force between the fixing member and the pressure member is increased by the pressure changing means, the rotating fixing member and the pressure member are rotated. Can be quickly stopped at the time of switching to the rotation transmission mechanism, and variation in time until the rotation of the fixing member and the pressure member is stopped is reduced. Therefore, as described above, the control device changes the rotation direction of the rotation drive device, switches between the first rotation transmission mechanism and the second rotation transmission mechanism, and changes the rotation speed for rotating the fixing member and the pressure member. The operation to be performed can be performed stably in a short time.

  In the fixing device of the present invention, the first rotation transmission mechanism and the second rotation transmission mechanism are switched between the fixing operation for fixing the toner image on the recording medium as described above and the standby time when the fixing operation is not performed. When the rotation speed of the fixing member and the pressure member rotated by the rotation driving device is reduced in the standby time as compared with that in the fixing operation, generation of noise during the standby time is suppressed and the heating device is heated. The amount of heat radiated from the fixing member can be reduced.

  Further, at the time of switching between the fixing operation and the standby time when the fixing operation is not performed, the rotation direction of the rotation driving device is changed by the control device as described above, and the first rotation transmission mechanism and the second rotation transmission mechanism are changed. When the pressure is changed and the pressing force between the fixing member and the pressure member is increased by the pressure changing means, the fixing member and the pressure member rotating at the time of switching can be stopped quickly, and the fixing member The variation in time until the rotation of the pressure member stops is reduced, the time for switching between the fixing operation and the standby time can be shortened, and efficient image formation can be performed. .

1 is a schematic explanatory view showing an example of an image forming apparatus using a fixing device according to an embodiment of the present invention. 1 is a schematic explanatory diagram illustrating a fixing device according to an embodiment of the present invention. In the fixing device according to the above-described embodiment, a first example of a rotation transmission mechanism that transmits the rotation in the rotation driving device to the pressure roller and the paper discharge roller is shown. During the fixing operation, the rotation in the rotation driving device is the first rotation. It is the schematic explanatory drawing which showed the state transmitted by a transmission mechanism. In the rotation transmission mechanism shown in FIG. 3, it is the schematic explanatory drawing which showed the state which transmits the rotation in a rotation drive device by a 2nd rotation transmission mechanism at the time of standby. In the fixing device according to the above-described embodiment, a second example of a rotation transmission mechanism that transmits the rotation in the rotation driving device to the pressure roller is shown. During the fixing operation, the rotation in the rotation driving device is transmitted by the first rotation transmission mechanism. It is the schematic explanatory drawing which showed the state made to do. FIG. 6 is a schematic explanatory view showing a state in which the rotation in the rotation driving device is transmitted by the second rotation transmission mechanism during standby in the rotation transmission mechanism shown in FIG. 5.

  A fixing device according to an embodiment of the present invention and an image forming apparatus using the fixing device will be specifically described with reference to the drawings. The fixing device and the image forming apparatus according to the present invention are not limited to those shown in the following embodiments, and can be appropriately modified and implemented without departing from the scope of the invention.

  In the image forming apparatus 1 using the fixing device 30 according to the embodiment of the present invention, as shown in FIG. 1, four imaging cartridges 10A to 10D are mounted therein.

  In each of the imaging cartridges 10A to 10D, the photosensitive member 11, the charging device 12 for charging the surface of the photosensitive member 11, and the surface of the charged photosensitive member 11 are exposed according to image information. An exposure device 13 that forms an electrostatic latent image on the surface of the photoconductor 11, a developing device 14 that supplies toner to the electrostatic latent image formed on the surface of the photoconductor 11 to form a toner image, and the photoconductor 11. A cleaning device 15 is provided for removing the toner remaining on the surface of the photosensitive member 11 after the toner image formed on the surface of the photosensitive member 11 is transferred to the intermediate transfer belt 21.

  Here, in each developing device 14 in each of the imaging cartridges 10A to 10D, the color of the toner to be accommodated is different, and black, yellow, magenta, and cyan toners are accommodated.

  In this image forming apparatus 1, in each of the imaging cartridges 10A to 10D, the surface of the photoconductor 11 is charged by the charging device 12, and the surface of each photoconductor 11 thus charged is exposed to the exposure device. 13, exposure is performed according to image information, an electrostatic latent image corresponding to the image information is formed on the surface of each photoconductor 11, and the electrostatic latent image formed on the surface of each photoconductor 11 is applied to the electrostatic latent image described above. The respective color toners are supplied from the respective developing devices 14 to form toner images of the respective colors on the surface of the respective photoreceptors 11.

  Next, the toner images of each color formed on the surface of each photoconductor 11 in each of the imaging cartridges 10 </ b> A to 10 </ b> D are sequentially transferred to the intermediate transfer belt 21 and synthesized on the intermediate transfer belt 21. The formed toner image is formed, and the toner remaining on the surface of each photoconductor 11 after transfer is removed from the surface of each photoconductor 11 by the cleaning device 15.

  On the other hand, the recording medium S accommodated in the image forming apparatus 1 is fed by a paper feed roller 22 and guided to a timing roller 23, and the recording medium S is fed to the intermediate transfer belt 21 at an appropriate timing by the timing roller 23. And the transfer roller 24, the toner image formed on the intermediate transfer belt 21 is transferred to the recording medium S. The toner remaining on the intermediate transfer belt 21 without being transferred to the recording medium S is removed from the intermediate transfer belt 21 by the second cleaning device 25.

  In addition, the recording medium S on which the toner image is transferred as described above is guided to the fixing device 30, and the fixing device 30 fixes the unfixed toner image on the recording medium S, and then the toner image is fixed. The recording medium S is discharged by the discharge roller 27.

  Next, the fixing device 30 according to the embodiment of the present invention will be specifically described.

  Here, in the fixing device 30 according to this embodiment, as shown in FIG. 2, a fixing roller 31 is used as a fixing member, and an IH heating device 32 is provided on the outer peripheral side of the fixing roller 31. The outer peripheral surface side of the fixing roller 31 is heated by 32.

  Further, a pressure roller 33 is used as a pressure member for pressing the recording medium S on which the toner image t is formed with the fixing roller 31, and the pressure roller 33 is pressed by a biasing means 34 such as a spring. The pressing roller 33 is urged to be pressed by the fixing roller 31, and the pressing force for pressing the pressing roller 33 against the fixing roller 31 by the urging unit 34 is adjusted by the pressure changing unit 35.

  In the fixing device 30 of this embodiment, the outer peripheral surface side of the fixing roller 31 is heated by the heating device 32, and the fixing roller 31 and the pressure roller 33 are rotated by the rotation driving device 40. In the fixing operation in which the unfixed toner image t is fixed to the recording medium S, the recording medium S is heated and pressed between the fixing roller 31 and the pressure roller 33 so as to be unfixed. The toner image t is fixed on the recording medium S. On the other hand, at the standby time when the fixing operation is not performed, the rotational speed at which the rotation roller 40 rotates the fixing roller 31 and the pressure roller 33 is set to be slower than that during the fixing operation.

  Here, in the fixing device 30 of this embodiment, when the fixing roller 31 and the pressure roller 33 are rotated by the rotation driving device 40, the rotation of the rotation driving device 40 is applied by the rotation transmission mechanisms 41 and 42. The pressure roller 33 is transmitted to rotate the pressure roller 33, and the fixing roller 31 is driven to rotate as the pressure roller 33 rotates.

  Further, as the rotation transmission mechanisms 41 and 42, the first rotation transmission mechanism 41 and the second rotation transmission mechanism 42 having different reduction ratios are provided, and the rotation transmission for transmitting the rotation in the rotation driving device 40 to the pressure roller 33. The mechanisms 41 and 42 are switched between the first rotation transmission mechanism 41 and the second rotation transmission mechanism 42 by the control device 50. In this embodiment, the reduction ratio in the second rotation transmission mechanism 42 is made larger than the reduction ratio in the first rotation transmission mechanism 41.

  In the fixing device 30 of this embodiment, during the fixing operation for fixing the unfixed toner image t to the recording medium S, the rotation of the rotation driving device 40 is caused to rotate the pressure roller 33 by the first rotation transmission mechanism 41 having a small reduction ratio. The rotation speed of the pressure roller 33 and the fixing roller 31 is increased, and the speed at which the unfixed toner image t is fixed on the recording medium S is increased.

  On the other hand, during the standby time when the fixing operation is not performed, the rotation of the rotation driving device 40 is transmitted to the pressure roller 33 by the second rotation transmission mechanism 42 having a large reduction ratio, and the rotation between the pressure roller 33 and the fixing roller 31 is performed. The speed is reduced to suppress the generation of noise during standby, and the heat from the fixing roller 31 heated by the heating device 32 is suppressed from being wasted.

  Further, in the fixing device 30 of this embodiment, when the control device 50 switches between the first rotation transmission mechanism 41 and the second rotation transmission mechanism 42 during the fixing operation and the standby time as described above. The pressing force for pressing the pressure roller 33 against the fixing roller 31 by the biasing means 34 is adjusted by the pressure changing means 35.

  Furthermore, in this embodiment, the third rotation transmission mechanism 43 that transmits the rotation in the rotation driving device 40 to the paper discharge roller 27 is provided, and the rotation in the rotation driving device 40 is performed by the first rotation transmission mechanism 41 as described above. In the fixing operation for transmitting the pressure to the pressure roller 33, the rotation of the rotation driving device 40 is transmitted to the paper discharge roller 27 by the third rotation transmission mechanism 43 to rotate the paper discharge roller 27. On the other hand, in the standby state in which the rotation of the rotation driving device 40 is transmitted to the pressure roller 33 by the second rotation transmission mechanism 42, the rotation of the rotation driving device 40 is transferred to the discharge roller 27 by the third rotation transmission mechanism 43. The third rotation transmission mechanism is controlled by the control device 50 so as not to transmit and to prevent the discharge roller 27 from rotating. So as to control the transmission of rotation by 3.

  Next, in the fixing device 30 in this embodiment, the rotation transmission mechanisms 41 and 42 that transmit the rotation of the rotation driving device 40 to the pressure roller 33 are reduced by the control device 50 between the fixing operation and the standby time. Is switched between the first rotation transmission mechanism 41 and the second rotation transmission mechanism 42 having different values, and the third rotation transmission mechanism 43 controls the transmission of the rotation of the rotation driving device 40 to the paper discharge roller 27 by the third rotation transmission mechanism 43. An example will be described.

  Here, in the first example of the fixing device 30 shown in FIGS. 3 and 4, when the rotation transmission mechanisms 41 and 42 that transmit the rotation in the rotation driving device 40 to the pressure roller 33 are provided, The fixing operation speed reduction gear 404 having a large diameter gear portion 404a and a small diameter gear portion 404b is larger than the first transmission gear 403 provided to mesh with the rotation gear 402 attached to the rotation shaft 401 and rotate. The first transmission gear 403 and the fixing operation are fixed so that the large-diameter gear portion 405a of the standby reduction gear 405 having the radial gear portion 404a, the large-diameter gear portion 405a, and the small-diameter gear portion 405b are engaged with each other. The reduction gear 404 and the standby reduction gear 405 are integrated, and the fixing operation reduction gear is centered on the rotation shaft 403a of the first transmission gear 403. 04 that to allow the reduction gear 405 each other via the swing standby. Further, a standby auxiliary gear 406 meshed with the small-diameter gear portion 405b of the standby deceleration gear 405 is provided so as to mesh with a driving gear 407 for transmitting the rotation to the pressure roller 33. ing.

  Here, in the standby reduction gear 405 and the fixing operation reduction gear 404, the gear ratio of the small-diameter gear portion 405b to the large-diameter gear portion 405a in the standby reduction gear 405 is set as the fixing operation reduction gear 404. Is smaller than the gear ratio of the small-diameter gear portion 404b to the large-diameter gear portion 404a. In this way, when the rotation of the rotary gear 402 in the rotary drive device 40 is transmitted to the drive gear 407, the drive gear 407 is transferred from the standby reduction gear 405 via the standby auxiliary gear 406. The number of rotations transmitted to the driving gear 407 is smaller than the number of rotations transmitted from the fixing operation reduction gear 404 to the driving gear 407.

  When the pressure roller 33 is rotated by the driving gear 407, the rotation of the driving gear 407 is transmitted to the pressure roller 33 via another transmission gear (not shown). ing.

  Further, when the third rotation transmission mechanism 43 for transmitting the rotation of the rotation driving device 40 to the paper discharge roller 27 is provided, it is engaged with the rotation gear 402 attached to the rotation shaft 401 of the rotation driving device 40 so as to engage with the one-way type. A transmission gear 408 is provided, and a paper discharge roller driving gear 409 is provided so as to mesh with the one-way transmission gear 408, and the rotation of the paper discharge roller driving gear 409 is transmitted to the paper discharge roller 27 for paper discharge. The roller 27 is rotated.

  Here, in performing the fixing operation in the fixing device 30, as shown in FIG. 3, the fixing operation is performed by the control device 50 around the rotation shaft 403 a of the first transmission gear 403. While the reduction gear 404 for standby and the reduction gear 405 for standby are rotated in a predetermined direction (clockwise), the small-diameter gear portion 404b of the reduction gear 404 for fixing operation is meshed with the driving gear 407. The standby reduction gear 405 is separated from the standby auxiliary gear 406 so that the small-diameter gear portion 405 b of the standby reduction gear 405 does not mesh with the standby auxiliary gear 406.

  In this state, the control device 50 rotates the rotary gear 402 in the rotational drive device 40 in the forward direction (counterclockwise in the example shown in the figure), and the rotation of the rotary gear 402 is The first rotation transmission mechanism 41 composed of the first transmission gear 403 and the fixing operation reduction gear 404 is transmitted to the driving gear 407 and rotated, and the rotation of the driving gear 407 causes the pressurization. The roller 33 and the driven fixing roller 31 are rotated, and the unfixed toner image t is fixed on the recording medium S between the fixing roller 31 heated by the heating device 32 and the pressure roller 33 as described above. I will let you.

  In addition, the one-way transmission gear 408 is rotated in accordance with the rotation of the rotary gear 402 that rotates in the forward direction as described above, and the discharge roller driving gear 409 is rotated, whereby the discharge sheet is discharged. The roller 27 is rotated so that the recording medium S on which the toner image t is fixed is discharged.

  Then, after the fixing operation is performed, in order to shift to the standby state, the fixing roller 31 and the pressure roller 33 that are rotating as described above are stopped. Thus, the rotation of the rotation driving device 40 is stopped, and the pressure roller 33 is strongly pressed against the fixing roller 31 by the pressure changing means 35. Here, when the pressure roller 33 is strongly pressed against the fixing roller 31 in this way, the rotating fixing roller 31 and the pressure roller 33 are quickly stopped, and the rotation is stopped. Variations in time to completion are also reduced.

  Then, in a standby state where the unfixed toner image t is not fixed on the recording medium S between the fixing roller 31 and the pressure roller 33, the rotation of the fixing roller 31 and the pressure roller 33 is stopped as described above. Then, as shown in FIG. 4, the control device 50 causes the fixing operation reduction gear 404 and the standby reduction gear 405 to center around the rotation shaft 403 a of the first transmission gear 403. Is rotated in the opposite direction (counterclockwise) to the fixing operation so that the small-diameter gear portion 405b of the standby reduction gear 405 is engaged with the standby auxiliary gear 406 engaged with the drive gear 407. On the other hand, the fixing operation speed reduction gear 404 is connected to the driving gear 407 so that the small-diameter gear portion 404b of the fixing operation speed reduction gear 404 does not mesh with the driving gear 407. It is moved away from 07.

  In this state, the control device 50 rotates the rotating gear 402 in the rotation driving device 40 in the reverse direction (clockwise in the example shown in the figure) during the fixing operation. The rotation of 402 is transmitted to the drive gear 407 by the second rotation transmission mechanism 42 constituted by the first transmission gear 403, the standby reduction gear 405, and the standby auxiliary gear 406. The gear 407 is rotated so that the pressure roller 33 and the fixing roller 31 are rotated.

  When the pressure roller 33 and the fixing roller 31 are rotated in this manner, the number of rotations transmitted from the standby reduction gear 405 to the drive gear 407 via the standby auxiliary gear 406 as described above. However, the rotational speed is less than the rotational speed transmitted from the fixing operation speed reduction gear 404 to the driving gear 407, and the rotational speeds of the pressure roller 33 and the fixing roller 31 rotated by the driving gear 407 are the same as those in the fixing operation. In this case, the noise is delayed during standby, noise generated during standby is suppressed, and excessive heat is prevented from being radiated from the fixing roller 31 heated by the heating device 32.

  Further, in the second example of the fixing device 30 shown in FIGS. 5 and 6, the rotation of the rotation driving device 40 is provided when the rotation transmission mechanisms 41 and 42 for transmitting the rotation of the rotation driving device 40 to the pressure roller 33 are provided. A fixing operation speed reduction gear 404 provided with an electromagnetic clutch 404c for turning on / off rotation transmission with respect to a first transmission gear 403 provided to rotate in mesh with a rotation gear 402 attached to a shaft 401; And a standby reduction gear 405 provided with an electromagnetic clutch 405c for turning on / off the rotation, and a driving gear 407 for transmitting the rotation to the pressure roller 33. The gear 404 and the standby reduction gear 405 are provided so as to mesh with each other.

  Here, in the standby reduction gear 405 and the fixing operation reduction gear 404, the diameter of the standby reduction gear 405 is made larger than the diameter of the fixing operation reduction gear 404, and the rotation driving device 40 is configured as described above. When the rotation of the rotation gear 402 is transmitted to the drive gear 407, the rotation speed transmitted from the standby reduction gear 405 to the drive gear 407 is changed from the fixing operation reduction gear 404 to the drive gear 407. The number of revolutions to be transmitted is reduced.

  In performing the fixing operation in the fixing device 30, as shown in FIG. 5, the control device 50 turns on the electromagnetic clutch 404 c provided in the fixing operation reduction gear 404, while In this state, the electromagnetic clutch 405c provided in the standby reduction gear 405 is turned off, and in this state, the rotary gear 402 in the rotary drive device 40 is rotated in a predetermined direction (counterclockwise in the example shown in the figure). Then, the rotation of the rotation gear 402 is transmitted to the drive gear 407 by the first rotation transmission mechanism 41 including the first transmission gear 403 and the fixing operation reduction gear 404, thereby driving the drive gear. 407 is rotated. Then, the rotation of the driving gear 407 rotates the pressure roller 33 and the driven fixing roller 31, and the fixing roller 31 and the pressure roller 33 heated by the heating device 32 as described above. In the meantime, the unfixed toner image t is fixed on the recording medium S.

  In addition, in the case of shifting to the standby state after performing the fixing operation, as in the case described above, the control device 50 stops the rotation of the rotation drive device 40 and the above-described operation. The pressure changing means 35 strongly presses the pressure roller 33 against the fixing roller 31 so that the fixing roller 31 and the pressure roller 33 are quickly stopped, and variations in time until these rotations are stopped are varied. Reduce.

  Then, in a standby state where the unfixed toner image t is not fixed on the recording medium S between the fixing roller 31 and the pressure roller 33, the rotation of the fixing roller 31 and the pressure roller 33 is stopped as described above. Then, as shown in FIG. 6, the control device 50 turns on the electromagnetic clutch 405 c provided in the standby reduction gear 405, while being provided in the fixing operation reduction gear 404. The electromagnetic clutch 404c is turned off. In this state, the rotation gear 402 in the rotation driving device 40 is rotated in the same direction as that during the fixing operation, and the rotation of the rotation gear 402 is caused by the first transmission gear 403 and the standby reduction gear 405. Is transmitted to the driving gear 407 by the second rotation transmission mechanism 42 configured by the following, and the driving gear 407 is rotated to rotate the pressure roller 33 and the fixing roller 31.

  Even when the pressure roller 33 and the fixing roller 31 are rotated in this manner, the rotational speed transmitted from the standby reduction gear 405 to the driving gear 407 is fixed as in the case described above. The rotational speed transmitted from the operating speed reduction gear 404 to the driving gear 407 is less, and the rotation speed of the pressure roller 33 and the fixing roller 31 rotated by the driving gear 407 is higher than that during the fixing operation. In this case, noise generated during standby is suppressed, and excessive heat release from the fixing roller 31 heated by the heating device 32 is prevented.

1: Image forming apparatuses 10A, 10B, 10C, 10D: Imaging cartridge 11: Photoconductor 12: Charging device 13: Exposure device 14: Developing device 15: Cleaning device 21: Intermediate transfer belt 22: Paper feed roller 23: Timing roller 24 : Transfer roller 25: second cleaning device 27: paper discharge roller 30: fixing device 31: fixing roller (fixing member)
32: Heating device 33: Pressure roller (pressure member)
34: urging means 35: pressure changing means 40: rotation drive device 41: first rotation transmission mechanism 42: second rotation transmission mechanism 43: third rotation transmission mechanism 50: control device 401: rotation shaft 402: rotation gear 403: First transmission gear, 403a: Rotating shaft 404: Reduction gear for fixing operation, 404a: Large-diameter gear portion, 404b: Small-diameter gear portion, 404c: Electromagnetic clutch 405: Reduction gear for standby, 405a: Large-diameter gear portion, 405b : Small-diameter gear section, 405c: Electromagnetic clutch 406: Standby auxiliary gear 407: Driving gear 408: One-way transmission gear 409: Paper discharge roller driving gear S: Recording medium t: Toner image

Claims (7)

  A fixing member; a heating device that heats the fixing member; a pressure member that pressurizes a recording medium on which an unfixed toner image is formed between the fixing member; A rotation transmission mechanism for transmitting the rotation of the rotation driving device to the member, and heating and pressurizing the recording medium between the fixing member and the pressure member to record an unfixed toner image. The first rotation transmission mechanism and the second rotation transmission mechanism having different reduction ratios for transmitting the rotation of the rotation driving device to the fixing member and the pressure member are used as the rotation transmission mechanism. And a control device for controlling switching between the first rotation transmission mechanism and the second rotation transmission mechanism, and a pressure changing means for changing the pressing force between the fixing member and the pressure member. , Said control device Than when switching the first rotation transmission mechanism and the second rotation transmission mechanism, by the pressure changing means, a fixing device, characterized in that adjusting the pressing force between the fixing member and the pressure member.   The fixing device according to claim 1, wherein the control device changes a rotation direction in the rotation driving device to switch between the first rotation transmission mechanism and the second rotation transmission mechanism. A fixing device.   2. The fixing device according to claim 1, wherein an electromagnetic clutch is provided for each of the first rotation transmission mechanism and the second rotation transmission mechanism, and the electromagnetic clutch to be operated is switched by the control device, whereby the first rotation transmission mechanism is provided. And a second rotation transmission mechanism are switched.   4. The fixing device according to claim 1, wherein a reduction ratio in the second rotation transmission mechanism is made larger than a reduction ratio in the first rotation transmission mechanism to record a toner image. During the fixing operation for fixing to the medium, the rotation of the rotation driving device is transmitted to the fixing member and the pressure member by the first rotation transmission mechanism, while the second rotation transmission mechanism is used for the standby time when the fixing operation is not performed. A fixing device that transmits rotation in a rotation driving device to a fixing member and a pressure member.   5. The fixing device according to claim 4, wherein, at the time of switching between the fixing operation and the standby time, the pressure changing unit causes the pressing force between the fixing member and the pressing member to be greater than the pressing force during the standby time. An image forming apparatus characterized by strengthening.   An image forming apparatus using the fixing device according to claim 1 as a fixing device for fixing an unfixed toner image on a recording medium.   The image forming apparatus according to claim 6, further comprising a third rotation transmission mechanism that transmits the rotation of the rotation driving device in the fixing device to another driving member, and the third rotation transmission mechanism during a fixing operation. Thus, while the rotation of the rotation drive device is transmitted to the other drive member, the control device controls the rotation drive device so that the rotation of the rotation drive device is not transmitted to the other drive member during the standby time when the fixing operation is not performed. An image forming apparatus.

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