JP2016143016A - Fixation unit and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the phase of a pressure release cam 55 from being deviated by mistake in the state where a fixation unit 17 is detached from an apparatus body 101.SOLUTION: An image formation apparatus is turned into the transmission state where a boss 59b rotates together with an input side gear 59a rotating with a rotation drive force from a drive source and a planetary gear 57 rotates while revolving so as to rotate an output side gear 55a in the state where a fixation unit 17 is attached to an apparatus body 101 and rotation of a fixed gear 58 is restricted by a notch groove 60, and is turned into the cut-off state where the output side gear 55a does not rotate but the planetary gear 57 rotates while revolving in the case where rotation of a pressure release cam 55 is restricted with a frictional force acting between a pressure plate 52 and the pressure release cam and a rotational load is applied to a carrier 59 in the state where the fixation unit 17 is detached from the apparatus body 101.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing unit and an image forming apparatus that is detachably provided with a fixing unit.

  2. Description of the Related Art Conventionally, as a fixing unit that can be attached to and detached from an apparatus main body of an image forming apparatus, a configuration that transmits a driving force from a driving source of the apparatus main body to a fixing unit using a gear train is known. For example, a configuration is known in which driving force is transmitted via a gear train to a fixing film provided in a fixing unit, which is in pressure contact with each other, and a pressure release cam that releases a pressure contact state between pressure rollers. As a configuration of the gear train, a configuration has been proposed in which play is provided in the rotation direction of the gear on the fixing unit side. For example, the fixing unit disclosed in Patent Document 1 employs a configuration in which play is provided in the rotation direction of the pressure roller gear and biasing force is applied by biasing means in a direction in which the play increases.

Japanese Patent Laying-Open No. 2005-258039

  The configuration of the conventional example has the following problems. When the pressure release cam (pressing member) is urged by the pressure plate to perform the preceding rotation, it is impossible to avoid a collision sound due to clogging of the rotational play existing in the gear train. As the number of gears interposed from the drive motor of the apparatus main body to the pressure release cam increases, the amount of play in the rotational direction accumulated in the gear train increases, and the collision noise also increases.

  In addition, when the gear train that drives the pressure release cam is used to provide play in the rotation direction of the gear, the user accidentally enters the gear on the input side with the fixing unit removed from the device body, such as when the device is shipped. There is a risk that the pressure releasing cam will be out of phase.

  In view of the above problems, an object of the present invention is to suppress erroneously shifting the phase of a pressing member in a state where the fixing unit is detached from the apparatus main body.

In order to achieve the above object, the fixing unit according to the present invention includes:
The image forming apparatus is detachable from a main body of the image forming apparatus, and includes a fixing member and a pressure member that presses the fixing member to form a fixing nip portion. The recording material is sandwiched and conveyed by the fixing nip portion. In the fixing unit for fixing the unfixed toner image on the recording material,
A biasing member that biases one of the fixing member and the pressure member against the other to press the fixing member and the pressure member against each other;
An urging force provided from the urging member to either the fixing member or the pressure member by changing the pressing state against the urging member by being provided so as to be able to press the urging member and rotating. And a pressing member capable of changing a pressure contact force acting between the fixing member and the pressure member,
A drive transmission mechanism capable of rotating the pressing member by transmitting a rotational driving force from a driving source to the pressing member;
With
The drive transmission mechanism is
With planetary gear,
An input side gear member comprising: a gear portion that is rotated by a rotational driving force from the drive source; and a support portion that rotatably supports the planetary gear and rotates integrally with the gear portion;
An output side gear that meshes with the planetary gear and rotates with the pressing member;
A regulated gear that meshes with the planetary gear and whose rotation is regulated by a regulating unit provided in the apparatus body in a state where the fixing unit is attached to the apparatus body;
Have
In a state where the fixing unit is attached to the apparatus body and the rotation of the regulated gear is regulated by the regulating unit, the support unit rotates together with the gear unit that is rotated by a rotational driving force from the driving source, It becomes a transmission state in which the planetary gear rotates while revolving so that the output side gear rotates,
In a state where the fixing unit is removed from the apparatus main body, rotation of the pressing member is restricted by a frictional force acting between the pressing member and the input side gear member is subjected to a rotational load. A side gear is not rotated, and the planetary gear is in a shut-off state in which it rotates while revolving.

  In order to achieve the above object, an image forming apparatus of the present invention is characterized in that the fixing unit is detachable and has the apparatus main body provided with the restricting portion.

  According to the present invention, it is possible to suppress erroneously shifting the phase of the pressing member in a state where the fixing unit is detached from the apparatus main body.

1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is an external perspective view illustrating a configuration of a fixing unit according to the first exemplary embodiment. 1 is an exploded perspective view showing a mysterious planetary gear mechanism of Embodiment 1. FIG. Explanatory drawing explaining the pressure release structure in Example 1. The figure explaining the force which acts on the mysterious planetary gear mechanism of Example 1. The figure which shows in order the attachment operation | movement of the fixing unit in Example 1. FIG. 6 is an external perspective view showing a fixing unit according to a second embodiment. The perspective view which shows the worm gear mechanism and the wonder planetary gear mechanism of Example 2. Exploded perspective view of the wonder planetary gear mechanism of the second embodiment Operation explanatory diagram of Embodiment 2

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
<Overall configuration of image forming apparatus>
With reference to FIG. 1, an overall configuration of a color electrophotographic image forming apparatus (hereinafter simply referred to as an image forming apparatus) according to a first embodiment will be described. FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of the image forming apparatus according to the first embodiment. In the first embodiment, a laser color printer is used as an example of the image forming apparatus. However, other configurations may be used as long as the fixing unit can be attached to and detached from the apparatus main body.

  The image forming apparatus according to the first embodiment includes process cartridges 5Y, 5M, 5C, and 5K that are detachable from the apparatus main body 101. Here, the apparatus main body 101 is a part of the image forming apparatus excluding the process cartridge 5 and the fixing unit 17 that are detachable from the apparatus main body 101. The process cartridges 5Y, 5M, 5C, and 5K have substantially the same configuration except that the colors for image formation are different. Hereinafter, the subscripts Y, M, C, and K for representing an element provided for one of the colors will be omitted if they are not particularly distinguished.

  The process cartridge 5 includes a photosensitive drum 1, a developing device 23, and a cleaning device 24. The developing device 23 includes a developing roller 3 that develops the electrostatic latent image formed on the photosensitive drum 1 with toner as a developer, a supply roller 12 that supplies toner to the developing roller 3, and a toner that is accommodated in the developing device 23. It has the stirring member 34 which stirs.

  In the apparatus main body 101, a laser unit 7 is disposed below the process cartridge 5. The laser unit 7 performs exposure on the photosensitive drum 1 based on the image signal. The photosensitive drum 1 is charged to a predetermined negative potential by the charging roller 2 and then exposed by the laser unit 7 to form an electrostatic latent image. The electrostatic latent image is reversely developed by the developing roller 3 and negative toner is adhered to form toner images of yellow Y, magenta M, cyan C, and black K, respectively.

  Further, the apparatus main body 101 is provided with an intermediate transfer belt unit. The intermediate transfer belt unit includes an intermediate transfer belt 8, a driving roller 9, and a secondary transfer counter roller 10. Further, primary transfer rollers 6Y, 6M, 6C, and 6K are disposed on the inner peripheral surface side of the intermediate transfer belt 8 so as to face the photosensitive drums 1Y, 1M, 1C, and 1K, and bias application (not shown) is applied. The transfer bias is applied by the means.

  Each photosensitive drum rotates in the direction of arrow B, and the intermediate transfer belt 8 rotates in the direction of arrow A. The toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially intermediated from the toner images on the photosensitive drum 1Y by applying a positive bias to the primary transfer rollers 6Y, 6M, 6C, and 6K. Primary transfer is performed on the transfer belt 8. Then, the four color toner images are conveyed to the secondary transfer roller 11 in an overlapping state.

  Further, a feeding / conveying device is provided at the lower part of the apparatus main body 101. The feeding / conveying device includes a paper feeding cassette 13 that stores recording material P such as paper, a paper feed roller 14 that feeds the recording material P stored in the paper feeding cassette 13, and a transport that transports the fed recording material P. A roller pair 15 is provided. The recording material P conveyed from the feeding / conveying device is conveyed to the secondary transfer roller 11 by the registration roller pair 16.

  Then, a four-color toner image formed on the intermediate transfer belt 8 is secondarily transferred to the recording material P by applying a positive bias to the secondary transfer roller 11. The recording material P onto which the toner image has been secondarily transferred is conveyed to a fixing unit (fixing device) 17 where it is heated and pressed by a fixing film 18 and a pressure roller 19 to fix the toner image. The recording material P on which the toner image is fixed is discharged to the outside of the apparatus main body 101 by the discharge roller pair 20.

<Configuration of fixing unit>
Next, the configuration of the fixing unit according to the first exemplary embodiment will be described with reference to FIG. FIG. 2 is an external perspective view illustrating a configuration of the fixing unit according to the first exemplary embodiment. The fixing unit 17 includes a fixing film 18 as a fixing member, and a pressure roller 19 as a pressure member that forms a fixing nip portion in pressure contact with the fixing film 18. The fixing unit 17 sandwiches and conveys the recording material P at the fixing nip portion, and transfers the untransferred toner image that has been secondarily transferred onto the recording material P (on the recording material).
To settle.

  As shown in FIG. 2, the fixing unit 17 includes a fixing frame 50, a film holder 51, a pressure plate (plate member) 52, a pressure spring (spring member) 53, a pressure release shaft 54, and pressure release as a pressing member. A cam 55 and a strange planetary gear mechanism 56 are provided. The pressure plate 52 and the pressure spring 53 correspond to the urging member of the present invention. In the first embodiment, the configuration in which the urging force from the pressure spring 53 is applied to the fixing film 18 via the pressure plate 52 is adopted. However, the configuration is not limited to this, and the pressure spring as the urging member is used. Alternatively, the biasing force may be directly applied to the fixing film 18.

  The pressure roller 19 is rotatably supported by the fixing frame 50. Inside the fixing film 18, a support holder (not shown) that holds the fixing film 18 in a cylindrical shape is provided. The support holder is provided with a heater (not shown) as a heating element for heating the fixing nip portion via the fixing film 18. The film holders 51 are provided at both ends of the fixing film 18 so as to rotatably hold the fixing film 18. The film holder 51 is supported so as to be movable along the cutout groove 50a of the fixing frame 50 (see FIG. 4).

  The pressure plate 52 is rotatably supported at the tip (the lower end in FIG. 2) with the hole 50b of the fixing frame 50 as a rotation fulcrum. The rear end of the pressure plate 52 (the upper end in FIG. 2) is urged by a pressure spring 53 held by the fixing frame 50. The pressing plate 52 moves the film holder 51 along the notch groove 50 a with the hole 50 b as a rotation fulcrum by the urging force of the pressing spring 53, and presses the fixing film 18 against the pressing roller 19. In this way, a fixing nip portion is formed between the fixing film 18 and the pressure roller 19. The recording material P on which the unfixed toner image is transferred passes through the fixing nip portion, and is heated and pressed to fix the toner image.

<Fixing pressure release configuration>
Next, with reference to FIGS. 2 to 4, the fixing pressure releasing configuration in the first embodiment will be described. FIG. 3 is an exploded perspective view showing the mysterious planetary gear mechanism of the first embodiment. FIG. 4 is an explanatory diagram illustrating a pressure release configuration according to the first embodiment.

  If the pressure roller 19 and the fixing film 18 are left in pressure contact with each other, there is a problem that the elastic layers on the surfaces of the fixing film 18 and the pressure roller 19 are permanently deformed. Further, when the user performs jam processing with the recording material P remaining in the fixing nip portion, the pressure roller 19 and the fixing film 18 are in pressure contact with each other, whereby the recording material P is torn and the torn recording material P There is a problem that a piece remains in the machine. In order to avoid these problems, the first embodiment is configured such that the pressure contact state between the pressure roller 19 and the fixing film 18 is released when the main body is shipped, when a jam occurs, or after a designated job.

  As shown in FIG. 4, in order to release the pressure contact state between the pressure roller 19 and the fixing film 18, the pressure release cam 55 has a pressure point V of the film holder 51 on the pressure plate 52 and a pressure spring 53. Between the energizing points W. A rotational driving force from a driving source of the apparatus main body 101 is transmitted to the pressure release cam 55 via the mysterious planetary gear mechanism 56.

As shown in FIG. 3, the mysterious planetary gear mechanism 56 includes an output side gear 55a that rotates together with the pressure release cam 55, a planetary gear 57, a fixed gear 58 as a regulated gear, and a carrier 59 as an input side gear member. The The output side gear 55a of the first embodiment is a sun gear in which the teeth on the outer peripheral side mesh with the planetary gear. Further, as shown in FIG. 2, the pressure release shaft 54 is rotatably supported with respect to the fixing frame 50. The pressure release cam 55 is fixed with a parallel pin or the like so that it can rotate in synchronism with the pressure release shaft 54.

  The fixed gear 58 and the carrier 59 are supported so as to be freely rotatable with respect to the pressure release shaft 54. The carrier 59 has an input side gear 59a as a gear portion that meshes with the drive train on the apparatus main body 101 side, and a boss 59b that supports the planetary gear 57 so as to be able to rotate. The fixed gear 58 has a regulated portion 58 a that regulates the rotation of the fixed gear 58 when the fixing unit 17 is attached to the apparatus main body 101.

  In the state where the fixing unit 17 is attached to the apparatus main body 101, the rotation of the fixed gear 58 is restricted. In this state, when the input side gear 59a rotates by the rotational driving force from the drive source of the apparatus main body 101, the planetary gear 57 rotates while revolving. Then, due to the rotation of the planetary gear 57, the output side gear 55a meshing with the planetary gear 57 rotates, and the pressure release cam 55 rotates.

  When the fixing unit 17 is detached from the apparatus main body 101, the rotation of the fixed gear 58 is not restricted and can be freely rotated. On the other hand, the pressure release cam 55 presses the pressure plate 52 against the urging force from the pressure spring 53 shown in FIG. 4C when the fixing unit 17 is detached from the apparatus main body 101. In position. At this time, the pressure release cam 55 receives a frictional force so that the rotation is restricted by the urging force of the pressure spring 53. For this reason, even when the rotation unit is applied to the carrier 59 (input side) with the fixing unit 17 removed from the apparatus main body 101 and the planetary gear 57 rotates while revolving, the fixed gear 57 only rotates idle. The output side gear 55a (output side) does not rotate. That is, it will be in the interruption | blocking state which the pressure release cam 55 does not rotate. As described above, the mysterious planetary gear mechanism 56 of the first embodiment has a clutch function capable of switching between transmission and interruption of the rotational driving force.

  Further, the planetary gear 57 is rotatably provided on a boss 59b on the carrier 59 so as to mesh with both the output side gear 55a and the fixed gear 58. The output side gear 55 a and the fixed gear 58 have different numbers of teeth and are appropriately shifted so that they can mesh simultaneously with the planetary gear 57. Accordingly, the carrier 59 (input side) cannot be rotated from the output side gear 55a (output side) (self-locking function). As described above, the mysterious planetary gear mechanism 56 of the first embodiment has a self-locking function in addition to the clutch function.

<Fixing pressure release operation>
Next, with reference to FIGS. 4 and 5, the fixing pressure releasing operation in the first embodiment will be described. 4A shows a pressure contact state where the pressure release cam 55 is in a non-pressing position where the pressure release cam 55 is not pressing the pressure plate 52, and FIG. 4B shows that the pressure release cam 55 is in the middle of rotation and the pressure plate. The state which has pressed 52 is shown. 4 (c) shows a pressure release state where the pressure release cam 55 is stationary and presses the pressure plate 52, and FIG. 4 (d) shows that the pressure release cam 55 rotates. It is a figure which shows the state in the middle of returning from the press position of FIG.4 (c) to the non-pressing position of FIG.4 (d). FIG. 5 is a diagram for explaining the force acting on the mysterious planetary gear mechanism. 4 and 5, the rotational driving force from the driving source is transmitted from the apparatus main body 101 to the pressure release cam 55, that is, the fixing unit 17 is attached to the apparatus main body 101.

  The pressure release cam 55 according to the first embodiment is provided so as to be able to press the pressure plate 52, and changes the urging force applied to the fixing film 18 from the pressure plate 52 by changing the pressing state against the pressure plate 52 by rotating. . With such a configuration, it is possible to change the pressing force acting between the fixing film 18 and the pressure roller 19.

First, the operation when shifting from the pressure contact state to the pressure release state will be described. The carrier 59 rotates by the rotational driving force from the drive source of the apparatus main body 101, the boss 59b provided on the carrier 59 rotates in the direction of arrow E in FIG. 5A, and the planetary gear 57 revolves in the direction of arrow E. . As a result, the planetary gear 57 contacts the output side gear 55a while rotating in the direction of arrow F with the fixed gear 58 as a fulcrum. Further, as the planetary gear 57 revolves and rotates, the output side gear 55a rotates in the direction of arrow D, and the pressure release cam 55 rotates in the direction of arrow C.

  As shown in FIG. 4B, the pressure release cam 55 starts to rotate in the direction of arrow C, presses the pressure plate 52, and performs a pressure release operation (separation operation) for separating the fixing film 18 from the pressure roller 19. Start. When the pressure release cam 55 reaches the pressing position, that is, when the pressure release cam 55 reaches a position where the surface radius of the pressure release cam 55 is in contact with the pressure plate 52, the pressure release operation is completed. The state at this time is shown in FIG.

  Since the urging force f urged from the pressure plate 52 to the pressure release cam 55 in the pressure release state is directed toward the center of the pressure release shaft 54, no rotational torque is generated in the pressure release cam 55, and the pressure release is performed. The cam 55 is stationary in a stable state.

  Next, the operation when returning from the pressure release state to the pressure contact state will be described. Similar to the above operation, the rotational driving force from the drive source of the apparatus main body 101 is transmitted to the pressure release cam 55 via the mysterious planetary gear mechanism 56, and the pressure release cam 55 starts to rotate in the direction of arrow C. As shown in FIG. 4D, the pressure release cam 55 starts to rotate in the direction of arrow C, presses down the pressure plate 52 in the direction of arrow p, and starts a pressure contact operation. At this time, the force f biased from the pressure plate 52 to the pressure release cam 55 works downward from the rotation center of the pressure release cam 55. Therefore, rotational torque is generated in the same direction (arrow C direction) as the rotational direction of the pressure release cam 55. As a result, the pressure release cam 55 rotates so-called in advance. As a result, the drive transmission is reversed and the drive transmission is performed from the output side to the input side.

  Due to the preceding rotation of the pressure release cam 55 (by applying a rotational load), the output side gear 55a collides with the planetary gear 57 in the direction of arrow D in FIG. 5, and the driving force f acts on the planetary gear 57. On the other hand, the planetary gear 57 receives a reaction force g from the fixed gear 58. Since the driving force f and the reaction force g work in opposite directions and cancel each other, the planetary gear 57 does not rotate.

  Thereafter, when the pressure release cam 55 reaches the state shown in FIG. 4A, the operation of returning from the pressure release state to the pressure contact state is completed. By adopting the configuration as described above, in the first embodiment, the play of the drive train on the input side due to the rotation of the planetary gear 57 that may occur due to the reverse of the drive transmission in the process from the pressure release state to the pressure contact state. It is possible to greatly reduce the impact sound due to clogging. Note that the number of the bosses 59b and the planetary gears 57 may be any number, but a configuration in which a plurality of bosses 59b and planetary gears 57 are provided is preferable in order to transmit stable driving force. For example, even in a configuration in which three or more planetary gears 57 are provided, if the driving force f and the reaction force g cancel each other, impact noise due to play clogging does not increase.

<Fixing unit mounting operation>
Further, with reference to FIG. 6, the mounting operation of the fixing unit in the first embodiment will be described. FIGS. 6A and 6B are diagrams sequentially illustrating a fixing unit mounting operation according to the first exemplary embodiment. In FIG. 6, in order to show the configuration of the pendulum gear 61, a part of the configuration of the main body frame 62 is omitted.

  First, the configuration of the main body frame 62 included in the apparatus main body 101 will be described. The main body frame 62 holds the fixing unit 17 and has a shape that can be positioned. Further, the main body frame 62 transmits a notch 60 as a restricting portion (notch) for restricting the rotation of the fixed gear 58 as the regulated gear, and the rotational driving force from the drive source to the fixing unit 17. A pendulum gear 61 is provided.

  The pendulum gear 61 includes a pendulum gear 61a, a pendulum gear 61b, and a holding portion 61c. The pendulum gear 61 b meshes with an input side gear 59 a provided on the carrier 59 of the fixing unit 17. The pendulum gear 61a receives driving from the upstream drive train and transmits the rotational driving force to the pendulum gear 61b. The pendulum gear 61b operates to be swingable by the holding portion 61c with respect to the rotation center 61d.

  Next, an operation for mounting the fixing unit 17 to the apparatus main body 101 will be described. First, the fixing unit 17 is placed on a holding portion (not shown) on the main body frame 62. In this state, as shown in FIG. 6A, the fixing unit 17 is roughly positioned in the vertical direction in the figure, and the regulated portion 58 a of the fixed gear 58 is separated from the main body notch portion 60.

  Therefore, the rotation of the fixed gear 58 is not constrained and idles, and the input side gear 59a of the carrier 59 is not subjected to a rotational load. Since the fixed gear 58 is idling, it is not known where the phase of the regulated portion 58a is. In FIG. 6A, the phase of the regulated portion 58a is shifted by 90 degrees with respect to the positioning direction.

  Next, as shown in FIG. 6B, when the fixing unit 17 is pushed in the body attachment direction (arrow H direction), the regulated portion 58 a of the fixed gear 58 is moved to the phase matching portion of the body notch portion 60. Contact 60a. When pushed further in the arrow H direction as it is, the regulated portion 58a rotates in the arrow K direction in FIG. 6B, and the phase of the regulated portion 58a is adjusted to the positioning direction.

  As shown in FIG. 6C, when the fixing unit 17 is further pushed in the direction of the arrow H, the restricted portion 58 a of the fixed gear passes through the straight portion 60 b near the center of the main body notch portion 60. In this process, the input side gear 59a of the carrier 59 meshes with the pendulum gear 61b on the apparatus main body 101 side, and the pendulum gear 61b rotates in the direction of arrow L in the figure. At this time, even if the tooth tips of the input side gear 59a and the pendulum gear 61b come into contact with each other, the restricted portion 58a of the fixed gear 58 does not quarrel with the straight portion 60b. A clearance is provided in the straight portion 60b.

  As shown in FIG. 6D, when the fixing unit 17 is further pushed in the direction of the arrow H, the regulated portion 58a of the fixed gear 58 reaches the positioning portion 60c along the slope of the main body notch portion 60. . In this state, since the fixed gear 58 is restrained with respect to the rotation direction, the fixed gear 58 cannot rotate. Thus, the fixing unit 17 is attached to the apparatus main body 101, and the rotational driving force from the drive source of the apparatus main body 101 is transmitted to the carrier 59 through the pendulum gear 61 to transmit the pressure release cam 55. It becomes a state.

  As described above, in the first embodiment, the wonder planetary gear mechanism 56 having a clutch function is used so that the pressure release cam 55a does not rotate in a state where the fixing unit 17 is detached from the apparatus main body 101. Therefore, it is possible to suppress the occurrence of a human error in which the user accidentally touches and moves the carrier 59 and changes the phase of the pressure release cam 55 with the fixing unit 17 removed from the apparatus main body 101. Further, when the pressure release cam 55 on the output side rotates in advance when the pressure release state is changed to the pressure contact state, the planetary gear 57 is configured not to rotate, so that it is possible to reduce an impact sound due to play blockage of the gear train. .

(Example 2)
Next, Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 7 is an external perspective view showing the fixing unit of the second embodiment. FIG. 8 is a perspective view showing the worm gear mechanism and the wonder planetary gear mechanism of the second embodiment. FIG. 9 is an exploded perspective view of the mysterious planetary gear mechanism of the second embodiment. FIG. 10 is an operation explanatory diagram of the second embodiment. In FIG. 10, in order to show the configuration of the planetary gear 57 and the sun gear 71, a part of the configuration of the carrier 59 is omitted.

  In the first embodiment, the configuration in which the mysterious planetary gear mechanism having both the clutch function and the self-locking function is employed in the drive transmission mechanism that transmits the drive to the pressure release cam has been described. On the other hand, in the second embodiment, a configuration in which a mysterious planetary gear mechanism having a clutch function and a worm gear mechanism having a self-locking function are employed as a drive transmission mechanism will be described. Note that the same reference numerals are used for the same configurations as those of the image forming apparatus and the fixing unit described in the first embodiment, and description thereof is omitted.

<Fixing pressure release configuration>
First, the mysterious planetary gear mechanism having the clutch mechanism of the second embodiment will be described. As shown in FIGS. 8 and 9, the mysterious planetary gear mechanism 70 includes a sun gear 71 as an output side gear, a carrier 59 as an input side gear member, a planetary gear 57, and a fixed gear 79 as a regulated gear. ing. The sun gear 71, the carrier 59, and the fixed gear 79 are supported so as to be freely rotatable with respect to a shaft 78 that is rotatably supported by the main body frame 62.

  The sun gear 71 is configured integrally with a worm wheel 74 that meshes with the worm gear 73. The carrier 59 has an input side gear 59a as a gear portion that meshes with a gear train on the apparatus main body 101 side, and a boss 59b as a support portion that supports the planetary gear 57 in a rotatable manner. The planetary gear 57 is disposed so as to mesh with both the sun gear 71 as the output side gear and the fixed gear 79 as the regulated gear. The fixed gear 79 is an internal gear provided with teeth on the inner peripheral surface side, and is arranged so as to mesh with the planetary gear 57. Further, the fixed gear 79 is provided with a regulated portion 79 a that restricts the rotation of the fixed gear 79 when the fixing unit 17 is attached to the apparatus main body 101.

  As in the first embodiment, in a state where the rotation of the fixed gear 79 is not restrained, even if the carrier 59 (input) is rotated, the fixed gear 79 idles and the rotational driving force from the drive source is not transmitted to the sun gear 71. . That is, the mysterious planetary gear mechanism 70 has a clutch function.

  Next, a worm gear mechanism having a self-locking function will be described. The worm gear mechanism of the second embodiment includes a worm gear 73, a worm shaft 77, and a worm gear 75. As shown in FIG. 8, the worm wheel 74 is disposed so as to mesh with the worm gear 73. The worm gear 73 and the worm gear 75 are fixed with a parallel pin or the like so as to be able to rotate in synchronization with the worm shaft 77. The worm shaft 77 is supported by the fixing frame 50 so that both ends can be freely rotated.

  The worm wheel 76 is disposed so as to mesh with the worm gear 75. The worm wheel 76 and the pressure release cam 55 are fixed with a parallel pin or the like so that the worm wheel 76 and the pressure release cam 55 can rotate in synchronization with the pressure release shaft 54. The pressure release shaft 54 is rotatably supported with respect to the fixing frame 50.

In the above configuration, there are two meshing portions of the worm gear. The worm gear 73 and the worm wheel 74, which are the first meshes, transmit the drive from the worm wheel 74 to the worm gear 73. Therefore, it is necessary to reversibly design the drive conditions of the worm gear. In other words, the worm gear is designed so that the lead angle> the friction angle. The worm gear 75 and the worm wheel 76 which are the second mesh are transmitted from the worm gear 75 to the worm wheel 76. In order to provide a self-locking function that does not transmit the driving force from the output side to the input, it is necessary to irreversibly design the driving conditions of the worm gear. In other words, the worm gear is designed so that the lead angle of the worm gear is smaller than the friction angle. Thereby, a self-locking function can be realized.

  As described above, in the second embodiment, the worm gear mechanism realizes the self-locking function that prevents the driving force from being transmitted from the output side to the input side, and transmits and blocks the drive transmission from the input side to the output side. The switching clutch function is realized by the mysterious planetary gear mechanism 70.

<Fixing pressure release operation>
Next, with reference to FIG. 10, the fixing pressure releasing operation in the second embodiment will be described. First, the operation when shifting from the pressure contact state to the pressure release state will be described. Although the rotation direction of the pressure release cam 55 is opposite to that of the first embodiment, other fixing pressure release configurations and operations are the same as those described in FIG. 4 of the first embodiment.

  The carrier 59 rotates in the direction of arrow M by the rotational driving force from the drive source of the apparatus main body 101, and the boss 59b on the carrier 59 rotates in the direction of arrow N in FIG. As a result, the planetary gear 57 rotates in the arrow P direction and the sun gear 71 rotates in the arrow Q direction with the fixed gear 79 as a fulcrum. As the sun gear 71 rotates, the worm wheel 74 rotates in the arrow Q direction. Thereby, the worm gear 73 rotates in the arrow S direction, and the worm shaft 77 and the worm gear 75 also rotate in the arrow S direction. Further, as the worm gear 75 rotates, the worm wheel 76 rotates in the arrow T direction. As a result, the pressure release cam 55 starts to rotate in the direction of the arrow U, presses the pressure plate 52, and starts a pressure release operation (separation operation).

  When the maximum cam surface radius portion of the pressure release cam 55 reaches the pressure release position, the pressure release operation (separation operation) is completed. In this state, the urging force f applied from the pressure plate 52 to the pressure release cam 55 is directed toward the center of the pressure release shaft 54, and therefore no rotational torque is generated in the pressure release cam 55, and the stationary state is stable. To do. At this time, since the urging force f from the pressure plate 52 is not transmitted to the film holder 51, the fixing pressure is released.

  Next, the operation when returning from the pressure release state to the pressure contact state will be described. Similar to the above operation, the rotational driving force from the drive source of the apparatus main body 101 is transmitted to the pressure release cam 55 via the mysterious planetary gear mechanism 70 and the worm gear mechanism, and the pressure release cam 55 starts to rotate. The pressure release cam 55 starts to rotate in the direction of the arrow U, presses down the pressure plate 52, and starts a pressure contact operation. At this time, the force f biased from the pressure plate 52 to the pressure release cam 55 works downward from the rotation center of the pressure release cam 55. Therefore, a rotational torque in the same direction as the rotational direction of the pressure release cam 55 is generated. As a result, the pressure release cam 55 rotates so-called in advance. As a result, the drive transmission is reversed and the drive transmission is performed from the output side to the input side.

  The rotational torque due to the preceding rotation of the pressure release cam 55 is transmitted to the worm wheel 76 via the pressure release shaft 54. However, as described above, since the driving conditions of the worm gear in this portion are designed to be irreversible, the driving force is not transmitted from the worm wheel 76 to the worm gear 75. Therefore, the carrier 59 (input side) does not rotate (self-lock function).

  Since the mounting operation of the fixing unit 17 to the apparatus main body 101 is the same as that of the first embodiment, the description thereof is omitted. In the second embodiment, the mysterious planetary gear mechanism 70 functions as a clutch, and in a state where the fixing unit 17 is detached from the apparatus main body 101, the fixed gear 79 is idled even if the carrier 59 (input) is rotated. Is not transmitted to the pressure release cam 55 (output). Therefore, it is possible to avoid a human error that the user erroneously moves the carrier 59 and changes the phase of the pressure release cam 55 with the fixing unit 17 removed. In addition, when the pressure release cam 55 on the output side rotates in advance when the pressure release state is changed to the pressure contact state, the planetary gear 57 does not rotate, so the play of the gear train of the mysterious planetary gear mechanism (input side) is adopted. Impact noise caused by clogging can be reduced.

  In Examples 1 and 2, the fixing film as the fixing member is urged by the pressure plate against the pressure roller as the pressure member. However, in the present invention, the fixing member and the pressure member are used. Any configuration may be used as long as one of the two is biased with respect to the other. In other words, the pressure member and the fixing member may be pressed against each other by urging the pressure member against the fixing member with a pressure plate.

DESCRIPTION OF SYMBOLS 17 ... Fixing unit, 18 ... Fixing film (fixing member), 19 ... Pressure roller (pressure member), 55 ... Pressure release cam (pressing member), 55a ... Output side gear, 56 ... Mysterious planetary gear mechanism (drive transmission) Mechanism), 57 ... planetary gear, 58 ... fixed gear (regulated gear), 59 ... carrier (input side member)

Claims (10)

The image forming apparatus is detachable from a main body of the image forming apparatus, and includes a fixing member and a pressure member that presses the fixing member to form a fixing nip portion. The recording material is sandwiched and conveyed by the fixing nip portion. In the fixing unit for fixing the unfixed toner image on the recording material,
A biasing member that biases one of the fixing member and the pressure member against the other to press the fixing member and the pressure member against each other;
An urging force provided from the urging member to either the fixing member or the pressure member by changing the pressing state against the urging member by being provided so as to be able to press the urging member and rotating. And a pressing member capable of changing a pressure contact force acting between the fixing member and the pressure member,
A drive transmission mechanism capable of rotating the pressing member by transmitting a rotational driving force from a driving source to the pressing member;
With
The drive transmission mechanism is
With planetary gear,
An input side gear member comprising: a gear portion that is rotated by a rotational driving force from the drive source; and a support portion that rotatably supports the planetary gear and rotates integrally with the gear portion;
An output gear that meshes with the planetary gear and rotates with the pressing member;
A regulated gear that meshes with the planetary gear and whose rotation is regulated by a regulating unit provided in the apparatus body in a state where the fixing unit is attached to the apparatus body;
Have
In a state where the fixing unit is attached to the apparatus body and the rotation of the regulated gear is regulated by the regulating unit, the support unit rotates together with the gear unit that is rotated by a rotational driving force from the driving source, It becomes a transmission state in which the planetary gear rotates while revolving so that the output side gear rotates,
In a state where the fixing unit is removed from the apparatus main body, rotation of the pressing member is restricted by a frictional force acting between the pressing member and the input side gear member is subjected to a rotational load. The fixing unit is in a shut-off state in which the planetary gear rotates while revolving without rotating the side gear.   The pressing member rotates so as to take a pressing position for pressing the biasing member to release the pressure contact state between the fixing member and the pressing member, and a non-pressing position spaced from the biasing member, The fixing unit according to claim 1, wherein the fixing unit is in the pressing position in a state where the fixing unit is detached from the apparatus main body.   The fixing unit according to claim 1, wherein the number of teeth of the regulated gear is different from the number of teeth of the output side gear.   4. The structure according to claim 1, wherein the gear portion is configured not to rotate when a rotational load is applied to the output side gear in a state where the fixing unit is attached to the apparatus main body. The fixing unit according to Item.   The worm wheel that rotates together with the pressing member, and a worm gear that meshes with the worm wheel and transmits a rotational driving force from the driving source to the pressing member via the worm wheel. Fixing unit.   The fixing unit according to claim 1, wherein the output side gear is a sun gear in which a tooth portion provided on an outer peripheral side meshes with the planetary gear.   The fixing unit according to any one of claims 1 to 6, wherein a plurality of the support portions and a plurality of the planetary gears supported by the support portions so as to be capable of rotating are provided.   The urging member includes a plate member pressed by the pressing member, and a spring member that urges one of the fixing member and the pressure member to the other via the plate member. The fixing unit according to claim 1, wherein the fixing unit is a unit.   An image forming apparatus, comprising: the apparatus main body including the restriction unit, the fixing unit being detachable from the fixing unit according to claim 1. The restricting portion is a notch formed in a main body frame included in the apparatus main body,
The image forming apparatus according to claim 9, wherein the regulated gear includes a regulated portion that fits into the notch and regulates rotation of the regulated gear.

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