JP6561653B2 - Fixing device, image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In the image forming apparatus described in Patent Document 1, when the pressure roll is set at a position separated from the fixing belt, the pair of fixing belt driving rolls rotationally drive the fixing belt. The pair of fixing belt driving rolls are disposed so as to contact the axial end portions of the outer peripheral surface of the fixing belt.

JP 2009-109673 A

  When the rotational force is transmitted to the fixing belt from the axial end portion on the outer peripheral surface of the fixing belt (endless member) to rotate the fixing belt, the fixing belt is twisted at the central portion side of the fixing belt, The fixing belt may be damaged.

  An object of the present invention is to suppress the endless member from being damaged as compared with the case where the rotational force is transmitted to the outer peripheral surface of the endless member from the axial end portions of the endless member.

The fixing device according to the first aspect of the present invention is an endless, rotating endless member that heats or receives a part of the circumferential direction, a separation position that is separated from the endless member, and a contact position that contacts the endless member. And the pressure member that presses the recording medium against the endless member, and the rotation direction of the endless member when the pressure member is disposed at the separated position. And a transmission member that contacts a central portion of the endless member and transmits a rotational force to the endless member.

A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect , wherein the transmission member includes a shaft member and a cylindrical foam body through which the shaft member passes, the foam body being And contacting with the endless member.

The fixing device according to a third aspect of the present invention is the fixing device according to the first aspect or the second aspect , wherein the pressure member rotates and the pressure member is disposed at the contact position. A moving member that transmits a rotational force to the endless member, and moves the transmitting member to a first position where the transmitting member contacts the endless member and a second position where the transmitting member separates from the endless member; A control unit that controls the moving member so that the transmitting member is disposed at the second position when the pressing member transmits a rotational force to the endless member. .

An image forming apparatus according to a fourth aspect of the present invention includes an image forming unit that forms an image on a recording medium, and any one of the first to third aspects that fixes the image formed on the recording medium to the recording medium. And a fixing device as described above.

According to the fixing device of the first aspect of the present invention, the endless member is damaged as compared with the case where the rotational force is transmitted to the outer peripheral surface of the endless member from the end portions of the endless member in the axial direction. Can be suppressed.

According to the fixing device of the second aspect of the present invention, the amount of heat taken away from the endless member can be reduced as compared with the case where the solid member is in contact with the endless member.

According to the fixing device of the third aspect of the present invention, when the pressure member is disposed at the contact position and transmits the rotational force to the endless member, the rotation member is disposed at the first position. Thus, the amount of heat taken away from the endless member can be reduced.

According to the image forming apparatus of the fourth aspect of the present invention, the deterioration of the quality of the output image is suppressed as compared with the case where the fixing device described in any one of the first to third aspects is not provided. can do.

FIG. 3 is a front view showing a heating unit of the fixing device according to the embodiment of the present invention. 1 is a side view showing a fixing device according to an embodiment of the present invention. 1 is a side view showing a fixing device according to an embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a relationship between a magnetic permeability and a temperature of a temperature-sensitive magnetic member used in a heating unit of the fixing device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of a fixing belt used in a heating unit of a fixing device according to an embodiment of the present invention. 1 is a configuration diagram illustrating an image forming unit used in an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is the front view which showed the heating part of the fixing device which concerns on the comparison form of this invention.

  An example of a fixing device and an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. In the drawing, an arrow H indicates the vertical direction of the apparatus (vertical direction), an arrow W indicates the apparatus width direction (horizontal direction), and an arrow D indicates the depth direction of the apparatus (horizontal direction).

(overall structure)
As shown in FIG. 7, in the image forming apparatus 10 according to the present embodiment, a storage unit that stores a sheet member P as a recording medium from the lower side to the upper side in the vertical direction (arrow H direction). 14, a conveying unit 16 that conveys the sheet member P accommodated in the accommodating unit 14, and an image forming unit 20 that performs image formation on the sheet member P conveyed by the conveying unit 16 from the accommodating unit 14 in this order. Is provided.

[Container]
The accommodating portion 14 includes an accommodating member 26 that can be pulled out from the apparatus main body 10 </ b> A of the image forming apparatus 10 to the near side in the apparatus depth direction, and the sheet member P is stacked on the accommodating member 26. Further, the accommodating portion 14 is provided with a delivery roll 30 that sends out the sheet member P stacked on the accommodating member 26 to a conveying path 28 that constitutes the conveying portion 16.

[Transport section]
The transport unit 16 includes a plurality of transport rolls 32 that transport the sheet member P along the transport path 28.

(Image forming part)
The image forming unit 20 includes four image forming units 18Y, 18M, 18C, and 18K of yellow (Y), magenta (M), cyan (C), and black (K). In the following description, Y, M, C, and K may be omitted when there is no need to distinguish between Y, M, C, and K.

  As shown in FIG. 6, each color image forming unit 18 is irradiated with an image carrier 36, a charging roll 38 for charging the surface of the image carrier 36, and exposure light of each color to the charged image carrier 36. And an exposure device 42 for performing the above operation. Further, the image forming unit 20 is provided with a developing device 40 that develops the electrostatic latent image that is exposed by the exposure device 42 described above and formed on the image carrier 36 and visualizes it as a toner image.

  Further, as shown in FIG. 7, the image forming unit 20 transfers the toner images formed by the image forming units 18 of the respective colors to the endless transfer belt 22 and the transfer belt 22. And a transfer roll 24 for transferring the toner image to the sheet member P.

  Further, the image forming unit 20 is provided with a fixing device 80 that heats and pressurizes the toner image on the sheet member P and fixes the toner image on the sheet member P.

  Details of the fixing device 80 will be described later.

(Operation of image forming apparatus)
In the image forming apparatus 10, an image is formed as follows.

  First, the charging rolls 38 for each color to which a voltage is applied come into contact with the surface of the image carrier 36 for each color and uniformly charge the surface of the image carrier 36 at a predetermined potential. Subsequently, based on data input from the outside, the exposure device 42 irradiates the surface of the charged image carrier 36 with exposure light to form an electrostatic latent image.

  As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the image carrier 36 of each color. Further, each color developing device 40 develops the electrostatic latent image and visualizes it as a toner image. Further, the toner image formed on the surface of the image holding member 36 for each color is transferred to the transfer belt 22.

  Therefore, the sheet member P sent out from the accommodating member 26 to the transport path 28 by the sending roll 30 is sent out to the transfer position T where the transfer belt 22 and the transfer roll 24 come into contact. At the transfer position T, the sheet member P is nipped and conveyed between the transfer belt 22 and the transfer roll 24, so that the transfer roll 24 transfers the toner image on the surface of the transfer belt 22 to the sheet member P.

  The toner image transferred to the sheet member P is fixed to the sheet member P by the fixing device 80. Then, the sheet member P on which the toner image is fixed is discharged to the outside of the apparatus main body 10A by the transport roll 32.

(Configuration of fixing device)
Next, the fixing device 80 will be described.

  As shown in FIG. 3, the fixing device 80 includes a heating unit 82 that heats the toner image formed on the sheet member P, and a pressure member as an example of a pressure member that pressurizes the sheet member P toward the heating unit 82. And a roll 84.

[Heating section]
The heating unit 82 includes a fixing belt 102 as an example of an endless (tubular) endless member. As shown in FIG. 1, support members 46 that support the inner peripheral surface of the fixing belt 102 are disposed on both ends of the fixing belt 102. Specifically, the support member 46 has a circular portion 46 </ b> A having a circular cross section, and the outer peripheral surface of the circular portion 46 </ b> A is in contact with both ends of the inner peripheral surface of the fixing belt 102. Thereby, the support member 46 supports the inner peripheral surface of the rotating fixing belt 102.

[Bobbin]
As shown in FIG. 2, the bobbin 108 has an arc shape that follows the outer peripheral surface of the fixing belt 102 when viewed from the rotation axis direction of the fixing belt 102 (the same direction as the apparatus depth direction). Further, in the bobbin 108, a convex portion 108 </ b> A is formed on the center side in the circumferential direction of the surface opposite to the fixing belt 102.

  An excitation coil 110 as an example of a magnetic field generating member that generates a magnetic field H by energization is wound around the bobbin 108 a plurality of times around the convex portion 108A. A magnetic core 112 formed in an arc shape following the arc shape of the bobbin 108 is disposed at a position facing the excitation coil 110, and the magnetic core 112 is supported by the bobbin 108.

[Fixing belt]
As shown in FIG. 5, the fixing belt 102 includes a base layer 124, a heat generating layer 126, an elastic layer 128, and a release layer 130 arranged from the inside to the outside, and these are laminated. It is united. The fixing belt 102 has a diameter of 30 [mm] and a length in the depth direction of 370 [mm].

  The base layer 124 has a strength to support the heat generating layer 126, has heat resistance, and is made of a member that penetrates the magnetic flux of the magnetic field H and hardly generates heat due to the action of the magnetic field. In the present embodiment, a nonmagnetic stainless steel having a thickness of 35 [μm] is used as the base layer 124.

  The heat generating layer 126 is composed of a member that generates heat by electromagnetic induction. Further, the heat generating layer 126 is made thinner than the skin depth, which is the thickness at which the magnetic field H can penetrate, in order to penetrate the magnetic flux of the magnetic field H. In the present embodiment, copper having a thickness of 10 [μm] is used as the heat generating layer 126.

  The elastic layer 128 is composed of a member having elasticity and heat resistance. In the present embodiment, silicon rubber having a thickness of 200 [μm] is used as the elastic layer 128.

  The release layer 130 is composed of a member that facilitates peeling of the sheet member P from the fixing belt 102. In the present embodiment, as the release layer 130, a 30 μm thick tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin is used.

  Further, lubricating oil (for example, silicon oil) is applied to the inner peripheral surface of the fixing belt 102 in order to reduce frictional resistance with a temperature-sensitive magnetic plate 114 described later.

  Further, as shown in FIG. 2, fixing is performed on the inner side of the fixing belt 102, in a region that does not face the exciting coil 110 in the radial direction, and on the discharge side region (upper region in the drawing) of the sheet member P. A temperature detection sensor 134 that detects the temperature of the belt 102 is disposed.

  Further, a rotating device 138 that rotates the fixing belt 102 is disposed above the fixing belt 102. Further, inside the fixing belt 102, a contact member 152 that contacts the inner peripheral surface of a portion of the fixing belt 102 facing the exciting coil 110 along the circumferential direction of the fixing belt 102 is provided.

[Rotating device]
The rotating device 138 includes a rotating roll 140 as an example of a transmission member that contacts the outer peripheral surface of the fixing belt 102 and rotates the fixing belt 102.

  Details of the rotating device 138 will be described later.

[Contact member]
The contact member 152 includes a temperature-sensitive magnetic plate 114 formed of a temperature-sensitive magnetic member, and a substrate 154 that is stacked on the opposite side of the fixing belt 102 with respect to the temperature-sensitive magnetic plate 114.

  The temperature-sensitive magnetic plate 114 has an arc shape when viewed from the depth direction of the apparatus, and is in contact with the inner peripheral surface of the fixing belt 102 that is opposed to the exciting coil 110 in the radial direction.

  The temperature-sensitive magnetic plate 114 has temperature-sensitive characteristics as shown in FIG. A temperature-sensing characteristic in which the magnetic permeability starts to decrease continuously as the temperature rises from the magnetic permeability change start temperature in a temperature range that is equal to or higher than the fixing (heating) setting temperature of the fixing belt 102 and lower than the heat resistance temperature of the fixing belt 102. It is comprised with the member which has. As a result, when the temperature of the temperature-sensitive magnetic plate 114 rises and the magnetic permeability decreases above the permeability change start temperature, the magnetic flux penetrating the fixing belt 102 is reduced, and the heat generation of the fixing belt 102 is suppressed. It has become. In this embodiment, an iron-nickel alloy (Fe—Ni) having a thickness of 300 μm is used as the temperature-sensitive magnetic plate 114.

  The magnetic permeability change start temperature is a temperature at which the magnetic permeability (measured in accordance with JIS C2531) starts to decrease, and refers to a temperature at which the amount of magnetic flux penetrating starts to change.

  As shown in FIG. 2, the substrate 154 has an arc shape when viewed from the depth direction of the apparatus, and is in contact with the temperature-sensitive magnetic plate 114 so as to overlap the fixing belt 102. The substrate 154 and the temperature-sensitive magnetic plate 114 are fixed by a fixing means (not shown) (for example, welding).

  The substrate 154 is a member that conducts heat generated by the temperature-sensitive magnetic plate 114 in the depth direction of the apparatus. As a result, the temperature distribution in the apparatus depth direction of the temperature-sensitive magnetic plate 114 becomes the same, and local (partial) temperature rise is suppressed. In the present embodiment, aluminum having a thickness of 400 [μm] is used as the substrate 154.

  Further, a temperature detection sensor 135 for detecting the temperature of the temperature-sensitive magnetic plate 114 is disposed inside the fixing belt 102 and in the region on the entry side of the sheet member P (the region on the lower side in the figure).

  A support member 118 that supports the contact member 152 is disposed inside the contact member 152 (on the left side in the drawing).

[Support member]
As shown in FIG. 2, the support member 118 extends in the apparatus depth direction, is formed by bending an aluminum plate, and is disposed so as to straddle the upper end portion of the contact member 152 and the lower end portion of the contact member 152. Has been. The upper end portion of the support member 118 supports the upper end portion of the contact member 152, and the lower end portion of the support member 118 supports the lower end portion of the contact member 152.

  The support member 118 has a thickness equal to or greater than the above-described skin depth, and is configured so that the magnetic flux of the magnetic field H does not penetrate.

[flame]
The frame 158 is disposed on the opposite side of the contact member 152 with the support member 118 interposed therebetween. The frame 158 includes a main body member 160 extending in the apparatus depth direction, an upper support member 162 that supports an upper portion of the support member 118, and a lower support member 164 that supports a lower portion of the support member 118. It is equipped with. Further, the frame 158 includes a clamping unit 156 that sandwiches the fixing belt 102 with a rotary roll 140 described later.

  The main body member 160 has a pentagonal outer shape when viewed from the apparatus depth direction, and extends in the apparatus depth direction. Further, both ends of the body member 160 in the apparatus depth direction are fixed to a frame (not shown). Further, the main body member 160 is in contact with the support member 118 and supports the support member 118.

  The sandwiching portion 156 has a proximal end portion attached to the main body member 160, an extension portion 156A extending upward, and attached to a distal end portion of the extension portion 156A, and is formed along the inner peripheral surface of the fixing belt 102. And an arcuate arc portion 156B.

  On the other hand, on the side opposite to the side on which the support member 118 is disposed in the main body member 160, a pressing pad 132 that fixes the fixing belt 102 between the pressing roll 84 is fixed. In the present embodiment, a liquid crystal polymer is used as a material constituting the pressing pad 132.

  The pressing pad 132 is in contact with the inner peripheral surface of the fixing belt 102 even when the pressing roll 84 moves to a separation position described later.

[Pressure roll]
The pressure roll 84 includes a cored bar 84A made of a metal such as aluminum, and a sponge elastic layer 84B of foamed silicon rubber having a thickness of 5 [mm] coated on the cored bar 84A. Further, the pressure roll 84 has a release layer (not shown) made of carbon tetrafluoride / perfluoroalkoxyethylene copolymer (PFA) containing carbon having a thickness of 50 [μm] outside the sponge elastic layer 84B. ).

  Further, the cored bar 84A of the pressure roll 84 is moved by a retract mechanism (not shown) so as to move in the apparatus width direction. The retraction mechanism causes the pressure roll 84 to contact the fixing belt 102 to press the fixing belt 102 (see FIG. 3) and to a separation position (see FIG. 2) away from the fixing belt 102. It is supposed to move.

  Further, a rotational force from a motor (not shown) is transmitted to the core metal 84A of the pressure roll 84, and the pressure roll 84 rotates in the direction of arrow F shown in FIG.

(Main part configuration)
Next, the rotating device 138 will be described.

  As illustrated in FIG. 1, the rotating device 138 is disposed above the fixing belt 102, and includes a rotating roll 140 that transmits a rotational force to the fixing belt 102, and an actuator as an example of a moving member that moves the rotating roll 140. 142. Further, the rotating device 138 includes a motor 144 that rotates the rotating roll 140, and a controller 146 that controls the actuator 142 and the motor 144. The configuration of the control unit 146 will be described together with the operation of the main configuration described later.

[Rotating roll]
The rotary roll 140 supports a shaft member 140A extending in the apparatus depth direction, a roll portion 140B as an example of a cylindrical foam through which the shaft member 140A passes, and portions on both ends of the shaft member 140A in the apparatus depth direction. And a bearing 140C.

  The shaft member 140A is formed using a metal material and has an outer diameter of 5 [mm]. Two bearings 140C are provided and are molded using a resin material to form a so-called sliding bearing.

  The roll part 140B is molded using a foamed rubber member, and has an outer diameter of 15 [mm] and an axial length of 100 [mm]. The rotating roll 140 is disposed such that the center line C1 of the roll unit 140B in the apparatus depth direction overlaps the center line C2 of the fixing belt 102 in the apparatus depth direction. The outer peripheral surface of the roll 140B is in contact with the central portion in the rotation axis direction on the outer peripheral surface of the fixing belt 102.

  Regarding the roll unit 140B, the viewpoint of transmitting the rotational force to the fixing belt 102, the viewpoint of suppressing the twist of the rotating fixing belt 102, and the amount of heat taken from the fixing belt 102 by the roll unit 140B are reduced. The following dimensions are preferable from the viewpoint.

  The length (length L1 in FIG. 1) is preferably 100 [mm] or more and 210 [mm] or less. Moreover, it is preferable that an outer diameter (outer diameter D1 of FIG. 1) is 10 [mm] or more and 15 [mm] or less.

[Actuator]
The actuators 142 are respectively arranged on the opposite sides of the fixing belt 102 with the bearing 140C interposed therebetween. The actuator 142 includes a first position (see FIG. 2) where the rotating roll 140 (roll unit 140B) contacts the fixing belt 102 and a second position (see FIG. 3) where the rotating roll 140 is separated from the fixing belt 102. In addition, the rotary roll 140 is moved.

〔motor〕
The rotational force of the motor 144 is transmitted to the rotary roll 140. Specifically, the pulley 150A is attached to one side (right side in the drawing) of the shaft member 140A, and the pulley 150B is attached to the rotating shaft 144A of the motor 144. A belt 150C is wound around the pulley 150A and the pulley 150B. The rotational force of the motor 144 is transmitted to the rotary roll 140 via the belt 150C.

(Effects of main components)
Next, the operation of the fixing device 80 will be described in comparison with the fixing device 200 according to the comparative embodiment.

  First, the configuration of the fixing device 200 will be described mainly with respect to differences from the fixing device 80 according to the present embodiment.

  As shown in FIG. 8, two rotation devices 202 that rotate the fixing belt 102 are provided, and are respectively arranged on the upper side with respect to both end portions of the fixing belt 102 in the apparatus depth direction.

  Each rotating device 202 includes a rotating roll 210, a motor 230, and a control unit 240 that controls the motor 230.

  Each rotary roll 210 includes a shaft member 210A, a cylindrical roll portion 210B through which the shaft member 210A passes, and a bearing 210C that supports portions on both ends of the shaft member 210A in the apparatus depth direction. Each of the roll portions 210 </ b> B comes into contact with both end portions in the depth direction of the apparatus on the outer peripheral surface of the fixing belt 102. In this way, the roll unit 210B is always in contact with the outer peripheral surface of the fixing belt 102.

  The motor 230 applies rotational force to a rotating roll 210 via a belt 232C wound around a pulley 232A attached to one side of the shaft member 210A and a pulley 232B attached to the rotating shaft 230A of the motor 230. To communicate.

  Further, inside the fixing belt 102, sandwiching portions 236 that sandwich the fixing belt 102 with the rotary roll 210 are respectively disposed. Furthermore, each rotating device 202 includes a common control unit 240 that controls the motor 230.

  Hereinafter, the operation of the fixing device 80 and the fixing device 200 will be described.

  In the non-operating state of the fixing devices 80 and 200, as shown in FIG. The rotating roll 140 (roll unit 140B) is disposed at a first position (see FIG. 1) that contacts the fixing belt 102 when the control unit 146 controls the actuator 142.

  When a job is instructed by the user and the image forming apparatus 10 is operated, in the fixing device 200 according to the comparative example, the control unit 240 controls the respective motors 230, and the motors 230 are respectively rotated via the belts 232 </ b> C. Rotate. As each rotating roll 210 rotates, the fixing belt 102 rotates following the rotating roll 210 (see FIG. 8).

  Further, an alternating current is supplied to the exciting coil 110, and the magnetic field H as a magnetic circuit is repeatedly generated and extinguished around the exciting coil 110 (see FIG. 2). When the magnetic field H crosses the heat generating layer 126 (see FIG. 5) of the fixing belt 102, an eddy current is generated in the heat generating layer 126 so that a magnetic field that prevents the magnetic field H from changing is generated. As a result, the fixing belt 102 generates heat.

  In the fixing device 200, as shown in FIG. 8, the respective roll portions 210 </ b> B are in contact with both end portions in the device depth direction on the outer peripheral surface of the fixing belt 102. Therefore, a force for rotating the fixing belt 102 acts on both ends of the fixing belt 102.

  In contrast, the pressing pad 132 is in contact with the inner peripheral surface of the fixing belt 102 in the depth direction of the apparatus (see FIG. 2). A frictional force is generated between the pressing pad 132 and the rotating fixing belt 102 in the depth direction of the apparatus. For this reason, a force in the direction opposite to the rotation direction of the fixing belt 102 acts on the fixing belt 102 in the depth direction of the apparatus.

  Due to the force acting on the fixing belt 102 by the rotary roll 210 and the force acting on the fixing belt 102 by the pressing pad 132, the fixing belt 102 is fixed at the central portion in the apparatus depth direction (portion H1 in FIG. 8). A twisting force acts on the belt 102.

  On the other hand, in the fixing device 80 according to the embodiment, the control unit 146 controls the motor 144, and the motor 144 rotates the rotary roll 140 via the belt 150C. As the rotating roll 140 rotates, the fixing belt 102 follows the rotating roll 140 and rotates in the direction of arrow E in FIG. 2 (see FIGS. 1 and 2).

  Further, an alternating current is supplied to the exciting coil 110, and the magnetic field H as a magnetic circuit is repeatedly generated and extinguished around the exciting coil 110. When the magnetic field H crosses the heat generating layer 126 (see FIG. 5) of the fixing belt 102, an eddy current is generated in the heat generating layer 126 so that a magnetic field that prevents the magnetic field H from changing is generated. As a result, the fixing belt 102 generates heat.

  In the fixing device 80, as shown in FIG. 1, the roll portion 140B is in contact with a central portion in the depth direction of the device on the outer peripheral surface of the fixing belt. For this reason, a force for rotating the fixing belt 102 acts on the central portion of the fixing belt 102.

  In contrast, the pressing pad 132 is in contact with the inner peripheral surface of the fixing belt 102 in the depth direction of the apparatus (see FIG. 2). A frictional force is generated between the pressing pad 132 and the rotating fixing belt 102 in the depth direction of the apparatus. For this reason, a force in the direction opposite to the rotation direction of the fixing belt 102 acts on the fixing belt 102 in the depth direction of the apparatus.

  By the force acting on the fixing belt 102 by the rotating roll 140 and the force acting on the fixing belt 102 by the pressing pad 132, the fixing belt 102 is fixed at both end portions in the apparatus depth direction (portion H2 in FIG. 1). A twisting force acts on the belt 102.

  Then, after the fixing belt 102 of the fixing devices 80 and 200 has reached the fixing set temperature, the pressure roll 84 rotates in the direction of arrow F in response to a rotational force from a motor (not shown) as shown in FIG. To do. Further, the retract mechanism is operated, and the pressure roll 84 is moved from the separated position to the contact position as shown in FIG.

  When the pressure roll 84 moves to the contact position, the rotation roll 140 (roll unit 140B) of the fixing device 80 is moved from the first position and separated from the fixing belt 102 by the control unit 146 controlling the actuator 142. It arrange | positions in a 2nd position (refer FIG. 3). Note that the rotating roll 210 of the fixing device 200 is kept in contact with the fixing belt 102.

  Further, the control units 146 and 240 control the motors 144 and 230, and the rotations of the motors 144 and 230 are stopped. Further, the rotational force transmitted to the fixing belt 102 is released, and the fixing belt 102 rotates following the rotating pressure roll 84.

  Then, the sheet member P to which the toner image is transferred is conveyed toward the fixing devices 80 and 200. Further, the sheet member P conveyed toward the fixing devices 80 and 200 is heated and pressed by the fixing belt 102 and the pressure roll 84, and the toner image is fixed on the sheet member P.

  Furthermore, when all the jobs are completed, the pressure roll 84 moves from the contact position to the separation position, and the rotation of the pressure roll 84 stops. Further, the supply of alternating current to the exciting coil 110 is stopped.

  Further, when the pressure roll 84 is disposed at the separated position, the rotating roll 140 (roll unit 140B) of the fixing device 80 is moved from the second position by the control unit 146 controlling the actuator 142, so that the fixing belt. It arrange | positions in the 1st position (refer FIG. 1) which contacts 102. FIG.

(Summary)
As described above, when the rotating roll 210 of the fixing device 200 according to the comparative example rotates the fixing belt 102, the fixing belt 102 is the central portion (portion H1 in FIG. 8) of the fixing belt 102 in the apparatus depth direction. A twisting force acts on 102. Thus, in the case of the fixing device 200, a twisting force acts on the fixing belt 102 at a portion between the one rotating roll 210 and the other rotating roll 210 in the fixing belt 102. That is, both sides of the fixing belt 102 where the twist is generated are restrained.

  On the other hand, when the rotary roll 140 of the fixing device 80 according to the embodiment rotates the fixing belt 102, the fixing belt 102 is located at both ends of the fixing belt 102 in the apparatus depth direction (portion H2 in FIG. 1). A twisting force is applied. As described above, in the case of the fixing device 80, a twisting force acts on the fixing belt 102 at a portion of the fixing belt 102 between the rotary roll 140 and both ends of the fixing belt 102. That is, one side of the portion where the fixing belt 102 is twisted is not restrained.

  In this way, by using the fixing device 80, one side of the portion where the fixing belt 102 is twisted is not restrained. Accordingly, as compared with the case of using the fixing device 200 in which both sides of the fixing belt 102 where the twist is generated are used, the force causing the twist is released to the unconstrained side. Damage to the belt 102 is suppressed.

  Further, the roll part 140 </ b> B of the rotary roll 140 is in contact with the fixing belt 102. Here, the roll part 140B is a foam. For this reason, the amount of heat taken away from the fixing belt 102 by the rotary roll 140 is smaller than when the roll portion is solid.

  Further, when the pressure roll 84 is disposed at the contact position and transmits the rotational force to the fixing belt 102, the rotation roll 140 is disposed at the second position. Accordingly, when the pressure roll 84 transmits the rotational force to the fixing belt 102, the rotary roll 140 is deprived of the fixing belt 102 as compared with the case where the rotary roll 140 is disposed at the first position. The amount of heat is reduced.

  In the image forming apparatus 10, the fixing belt 102 is prevented from being damaged, so that deterioration of the fixing quality of the toner image on the sheet member P is suppressed. Thereby, the quality degradation of an output image is suppressed.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments can be taken within the scope of the present invention. This will be apparent to those skilled in the art. For example, in the above-described embodiment, the temperature of the fixing belt 102 is increased by the heat generation of the fixing belt 102. However, the fixing belt receives heat from a heating member (receives heat) from a part in the circumferential direction. The temperature of 102 may be increased.

  Moreover, in the said embodiment, although the foam was used as the roll part 140B, you may use a solid member as a roll part. In this case, the effect produced by using the foam does not occur.

  Further, in the above-described embodiment, when the pressure roll 84 transmits the rotational force to the fixing belt 102, the rotary roll 140 is disposed at the second position. However, even if the rotary roll is disposed at the first position. Good. In this case, when the pressure roll 84 transmits the rotational force to the fixing belt 102, the effect exerted by arranging the rotary roll 140 at the second position does not occur.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Image forming part 80 Fixing apparatus 84 Pressure roll (an example of a pressure member)
102 fixing belt (an example of an endless member)
140 Rotating roll (an example of a transmission member)
140A Shaft member 140B Roll part (an example of a foam)
142 Actuator (Example of moving member)
146 Control unit

Claims (4)

An endless member that is endless, rotates, and part of the circumferential direction generates heat or receives heat;
A pressurizing member that pressurizes a recording medium to the endless member when moved to a separation position that is separated from the endless member and a contact position that contacts the endless member;
When the pressurizing member is disposed at a separated position, only the central side portion of the endless member in the rotation axis direction of the endless member and the outer peripheral surface side of the endless member are in contact with each other, and are rotationally driven to rotate. A transmission member that transmits the endless member to the endless member;
An arc portion disposed on the opposite side of the transmission member across the endless member and formed in an arc shape along the inner peripheral surface of the endless member;
The fixing device , wherein a contact length between the transmission member and the endless member is 100 or more and 210 or less in the rotation axis direction when a length of the endless member in the rotation axis direction is 370 . The transmission member includes a shaft member and a foam that is cylindrical and penetrates the shaft member;
The fixing device according to claim 1, wherein the foam is in contact with the endless member. The pressure member rotates, and when the pressure member is disposed at the contact position, a rotational force is transmitted to the endless member,
A moving member that moves the transmission member to a first position where the transmission member contacts the endless member and a second position where the transmission member separates from the endless member;
A control unit that controls the moving member to arrange the transmitting member at the second position when the pressing member transmits a rotational force to the endless member;
The fixing device according to claim 1, further comprising: An image forming unit for forming an image on a recording medium;
The fixing device according to any one of claims 1 to 3, wherein an image formed on the recording medium is fixed to the recording medium.
An image forming apparatus comprising: