JP2014211556A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to reduce thermal effect of a fixing belt due to a heating member when rotation of the fixing belt is stopped without enlarging the device, and to reduce the risk of heat deformation or burn out, and an image forming apparatus.SOLUTION: A fixing apparatus includes: a fixing member for fixing developer to a printing medium with a developer image formed thereon; a heating member which generates heat by means of a heat generating body and moves close to or away from the fixing member; a pressure member which is brought into press-contact with the fixing member to convey the printing medium with the fixing member; and separation/contact means which brings the fixing member and the heating member into contact with each other as the fixing member is driven and separates the fixing member from the heating member as the driving of the fixing member is stopped. An image forming apparatus is also provided.

Description

  The present invention relates to a fixing device that fixes a developer image on a print medium and an image forming apparatus including the fixing device.

  Among fixing devices included in a conventional electrophotographic image forming apparatus, there is a fixing device that fixes a developer image on a printing medium using a heated fixing belt. Such a fixing device has a heating member having a heating element, a heating surface that generates heat by the heating element, a curved surface portion, and a heating member facing portion formed on the opposite side of the curved surface portion. A heat transfer member is provided, the heat generating surface is pressed against the heating member facing portion, the curved surface portion is in contact with the fixing belt, and has a configuration in which the fixing belt is stretched (for example, a patent) Reference 1).

JP2011-257455A

  However, in the conventional fixing device having the above-described configuration, the curved surface portion of the heating member is always in contact with the fixing belt regardless of the rotation of the fixing belt. As described above, even when the rotation of the fixing belt is stopped, if the curved surface portion of the heating member and the fixing belt are always in contact with each other, for example, a control error, a jam due to a conveyance failure of the print medium, a follower, etc. Due to various causes such as the occurrence of slip due to the malfunction of the member, the contact region of the fixing belt that contacts the curved surface portion of the heating member is excessively heated, which may cause thermal deformation or burning of the fixing belt. Further, once the thermal deformation or burnout of the fixing belt occurs due to such a cause, there is a possibility that the printing quality itself may be adversely affected and the printing operation itself may be disabled.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the thermal effect of the fixing belt by the heating member when the fixing belt stops rotating without increasing the size of the apparatus. Another object of the present invention is to provide a fixing device and an image forming apparatus capable of reducing the risk of thermal deformation and burning.

  In order to solve the above-described problems, a fixing device according to the present invention includes a fixing member that fixes a developer on a printing medium on which a developer image is formed, and heat generated by a heating element so as to be separated from and contacting the fixing member. A heating member, a pressure member that is provided in pressure contact with the fixing member and conveys the print medium between the fixing member, and the fixing member and the heating member are brought into contact with each other as the fixing member is driven. And a contact / separation means for separating the fixing member and the heating member when driving of the fixing member is stopped.

  The image forming apparatus according to the present invention includes an image forming unit that forms a developer image on a print medium, a fixing member that fixes the developer on the print medium on which the developer image is formed, and a heat generator. A heating member that is separated from and in contact with the fixing member, a pressure member that is pressed against the fixing member and that conveys the print medium between the fixing member, and the driving member drives the fixing member. The fixing member and the heating member are brought into contact with each other, and separation / contact means for separating the fixing member and the heating member when the driving of the fixing member is stopped is provided.

  According to the present invention, the fixing member and the heating member are brought into contact with each other when the fixing member is driven, and the fixing member and the heating member are separated when the driving of the fixing member is stopped. When the rotation of the belt is stopped, the heat influence of the fixing belt by the heating member can be reduced, and the risk of thermal deformation and burnout can be reduced.

1 is a configuration diagram illustrating an outline of a printer according to a first embodiment. FIG. 2 is a side view of the fixing device according to the first embodiment drawn with main members. FIG. 2 is a perspective view of the fixing device according to the first embodiment drawn with main members and members necessary for disposing the main members. FIG. 4 is an exploded perspective view in which a fixing belt as a fixing member, a spring as an elastic member, and a spring are removed from the members shown in FIG. 3. It is a perspective view explaining the structure of the heater which concerns on 1st Embodiment. It is a perspective view explaining the composition of the heat diffusion member concerning a 1st embodiment. It is a perspective view of the heater and heat diffusion member concerning a 1st embodiment. It is a side view which makes the direction of the arrow of plane S1 of Drawing 7 a viewpoint. It is a side view which makes the direction of the arrow of plane S2 of Drawing 7 a viewpoint. FIG. 6 is a side view for explaining the operation of the fixing device before the start of the printing operation according to the first embodiment. It is the elements on larger scale which expanded the area | region D1 of FIG. FIG. 6 is a side view for explaining the operation of the fixing device after starting the printing operation according to the first embodiment. It is the elements on larger scale which expanded the area | region D2 of FIG. FIG. 10 is a side view for explaining the operation of the fixing device before starting the printing operation according to the second embodiment. It is the elements on larger scale which expanded the area | region D3 of FIG. FIG. 10 is a side view for explaining the operation of the fixing device after the start of the printing operation according to the second embodiment. It is the elements on larger scale which expanded the area | region D4 of FIG. FIG. 9 is a side view illustrating a fixing device according to a modified example with main members, (a) is a side view illustrating the operation of the fixing device before the start of the printing operation, and (b) is the fixing after the start of the printing operation. It is a side view explaining operation | movement of an apparatus. It is a perspective view explaining the structure of the heater as a heating member which concerns on a modification. 10 is a flowchart for explaining the operation of the fixing device after the start of a printing operation according to a modified example. It is a figure explaining the separation operation | movement of the fixing member with respect to a heating member, (a) is a state of separation, (b) is a figure explaining the state of contact | abutting.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

[First Embodiment]
FIG. 1 is a configuration diagram illustrating an outline of a printer 10 as an image forming apparatus including a fixing device 100 according to the present embodiment. The printer 10 is, for example, a printer that can print an image by an electrophotographic method on the print medium 1.

  The printer 10 has a print medium conveyance path S formed in a substantially S-shape starting from a print medium cassette 2 containing the print medium 1 before printing and starting from a stacker 7 on which the print medium 1 after printing is stacked. Prepare. The print medium cassette 2 stores the print medium 1 in a stacked state, and is detachably attached to the lower part of the printer 10. The stacker 7 is formed by using an outer casing of the apparatus, and stacks the printed print media 1 discharged outside the apparatus.

  In the print medium transport path S having the print medium cassette 2 side as the upstream side and the stacker 7 side as the downstream side, the print medium transport unit 3a including a pair of transport rollers for transporting the print medium 1 from the upstream side to the downstream side. 3b, 3c, 3d are arranged in order. The print medium transport unit 3a transports the print medium 1 transported from the print medium cassette 2 or the print medium reversing unit 6 described later to the print medium transport unit 3b. The print medium transport unit 3 b corrects the skew of the print medium 1 transported by the print medium transport unit 3 a and transports the print medium 1 to the developer image forming unit 4. The print medium transport unit 3c transports the print medium 1 transported from the fixing device 100 to the print medium transport unit 3d. The print medium transport unit 3d discharges the print medium 1 transported by the print medium transport unit 3c to the stacker 7 or drives the print medium 1 in the direction opposite to the direction of discharge to the stacker 7, thereby It is conveyed to the reversing unit 6.

  The developer image forming unit 4 as an image forming unit is provided between the print medium transport unit 3b and the print medium transport unit 3c. The developer image forming unit 4 includes at least a photosensitive drum (not shown), a charging device for uniformly and uniformly charging the surface of the photosensitive drum, and a static light formed based on light emitted from an LED (Light Emitting Diode) element. A developer supply means for supplying a developer to the electrostatic latent image is provided. The developer image forming unit 4 develops the developer image 1t by supplying developer (for example, toner) to the electrostatic latent image formed based on the light emitted from the LED head 5 provided on the upper side. This is a device for transferring this to the print medium 1.

  The LED head 5 is a printing light exposure apparatus having an LED element and a lens array so that the light emitted from the LED element forms a position on the surface of a photosensitive drum (not shown) based on image information. It is arranged.

  By the way, the fixing device 100 disposed downstream of the developer image forming unit 4 in the print medium transport path S fixes the developer image 1t transferred onto the print medium 1 by heating and pressing. , An apparatus for transporting the print medium 1 to the print medium transport section 3c further downstream. Here, in the case of single-sided printing in which printing is performed only on one side of the print medium 1, the print medium 1 is conveyed as it is to the print medium conveyance unit 3 d and discharged to the stacker 7. On the other hand, in the case of duplex printing in which printing is performed on both sides of the print medium 1, the print medium 1 is once transported to the print medium transport unit 3d. Then, by the reverse rotation of the conveyance roller pair provided in the print medium conveyance unit 3d, the print medium 1 is disposed under the developer image forming unit 4 with the developer image 1t formation surface as an upper surface. It is conveyed to the reversing unit 6. The print medium reversing unit 6 transports the print medium 1 to the print medium transport unit 3a. At this time, the developer image 1t formation surface of the print medium 1 is turned upside down, and the print medium 1 is conveyed to the print medium conveyance unit 3b with the developer image 1t formation surface as a lower surface. After the developer image 1 t is formed again in the developer image forming unit 4, the print medium 1 is transported to the print medium transport unit 3 d and discharged to the stacker 7. Internal mechanisms involved in printing operations such as single-sided printing and double-sided printing are controlled by a print control unit (not shown) provided in the printer 10.

  FIG. 2 is a side view of the fixing device 100 according to the present embodiment drawn with main members. 3 is a perspective view depicting the fixing device 100 with main members and members necessary for disposing the main members. FIG. 4 shows a fixing belt 105 as a fixing member from the members shown in FIG. It is the disassembled perspective view which removed the spring 103 and the spring 112 which are elastic members.

  First, the configuration of the main members of the fixing device 100 that controls the fixing operation will be described. The fixing device 100 includes a fixing belt 105 as a fixing member, a fixing roller 106 and a pressure roller 107 as pressure members. The fixing roller 106 and the pressure roller 107 form a nip N via the fixing belt 105. The fixing device 100 causes the printing medium 1 to pass through from the direction B in the figure, and heats and presses the nip N to fix the developer image 1t. Inside the fixing belt 105, that is, the space formed by the tension of the fixing belt 105, the fixing roller 106, the heater 101 as a heating element, and the transfer of heat generated from the heater 101 to the fixing belt 105, A metal member (hereinafter referred to as a heat diffusing member 102) that serves as a tension member and a guide and serves as a heating member and a contact / separation means, and a tension member 104 that serves as a tension member and a guide for the fixing belt 105. It is configured. The spring 103, which is an elastic member for the purpose of applying pressure or tension, is arranged so that one end side is fixed to the frame and the other end side presses the heat diffusing member 102 with the pressure indicated by F1 in FIG. Has been.

  As shown in FIGS. 2, 3, and 4, the fixing roller 106 includes a cored bar portion 106a and an elastic layer 106b. The fixing roller 106 according to the present embodiment can be formed, for example, in a roller shape in which the elastic layer 106b is made of a silicone sponge having a thickness of 2 mm and the outer diameter is φ34 mm. Each of the end portion 106a1 and the end portion 106a2 of the cored bar portion 106a is supported by the hole 1103L of the side plate 110L and the hole 1103R of the side frame 110R via the rotation bearing 113L and the rotation bearing 113R shown in FIG. A fixing gear 109 is attached to one end 106a2 of the cored bar 106a through a hole 1103R of the side frame 110R, and the fixing roller 106 is driven by a driving force transmitted from a driving system (not shown). It can be rotated in the direction of arrow A1 in FIG.

  The fixing belt 105 is an endless belt member that is stretched by the heat diffusing member 102, the stretching member 104, and the fixing roller 106, and can be driven in the direction of arrow A2 in FIG. It is comprised so that. The fixing belt 105 is driven while being heated by the heater 101 via the contacting heat diffusion member 102. Such a fixing belt 105 is, for example, a polyimide base material having an inner diameter of 45 mm and an inner surface thickness of 0.1 mm. (Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube).

  As shown in FIGS. 2, 3, and 4, the pressure roller 107 includes a cored bar portion 107a and an elastic layer 107b. The pressure roller 107 according to the present embodiment can be configured, for example, as a roller shape in which the elastic layer 107b is made of a silicone sponge having a thickness of 2 mm and the outer layer is covered with a PFA tube and the outer diameter is φ34 mm. Each of the end portion 107a1 and the end portion 107a2 of the cored bar portion 107a has a hole 1104L in the side plate 110L through the rotation bearing 114L and the rotation bearing 114R, the pressure bearing support member 111L, and the pressure bearing support member 111R shown in FIG. And it is attached to the hole 1104R of the side frame 110R. As shown in FIG. 3, a pressure of 20 kgf is applied to each of the pressure bearing support member 111L and the pressure bearing support member 111R by the spring 112L and the spring 112R in the + Y-axis direction in the drawing. Due to the pressure applied by the springs 112L and 112R, the pressure roller 107 can be displaced in the Y-axis direction in the drawing, and presses the elastic layer 106b of the fixing roller 106 via the fixing belt 105. As a result, a crushing deformation region between the elastic layer 107 b of the pressure roller 107 and the elastic layer 106 b of the fixing roller 106 is formed as the nip N. The pressure roller 107 can be rotated in the direction of an arrow A3 in FIG. 2 with the nip N formed with the fixing roller 106 following the rotation of the fixing roller 106.

  The heater 101 is a heating member provided with a heating element for heating the fixing belt 105, and generates heat while being in contact with the heat diffusion member 102 by screwing (not shown) or pressing force of an elastic body (not shown). The detailed configuration of the heater 101 will be described later.

  As described above, the heat diffusing member 102 is a metal member that also serves as a transmission of heat generated from the heater 101, a tension and guide of the fixing belt 105, and a separating means. The rotation fulcrum 102c1 and the rotation fulcrum 102c2 at both ends of the heat diffusion member 102 are respectively supported by the hole 1102L of the side plate 110L and the hole 1102R of the side frame 110R via the bearing 115L and the bearing 115R shown in FIG. A rotational displacement is possible. Further, the heat diffusion member 102 includes flat portions 102d1 and 102d2 to which pressure is applied by the spring 103L and the spring 103R, in addition to the rotation fulcrum 102c1 and the rotation fulcrum 102c2. Each of the flat surface portion 102d1 and the flat surface portion 102d2 is pressurized by the spring 103L and the spring 103R in a state of being inserted into the hole 1101L of the side frame 110L and the hole 1101R of the side frame 1101R, and the applied pressure of the springs 103L and 103R Thus, the heat diffusion member 102 can be displaced in the Y-axis direction in FIG. A detailed configuration of the heat diffusion member 102 will be described later.

  The stretching member 104 is a member for the purpose of stretching and guiding the fixing belt 105. The tension member 104 is a rod-like member having a length in the short direction (the length in the + Z direction in FIG. 3 or 4) of the fixing belt 105 as a length in the longitudinal direction, and both ends thereof are provided with holes 1105L and holes 1105L in the side frame 110L. The holes are supported in the holes 1105R of the side frames 1101R.

  FIG. 5 is a perspective view illustrating the configuration of the heater 101. The heater 101 is provided with a resistance wire 101b on a plate-like base material 101a having a flat portion (planar shape portion) formed in a flat shape, and generates heat when a current flows through the resistance wire 101b. A power source and a control circuit are connected to the resistance wire 101b via a connector (not shown), and can be energized at an arbitrary timing. For example, the heater 101 illustrated in FIG. 5 has a structure in which a resistance wire 101b is laminated on a stainless steel (SUS) substrate 101a having a longitudinal length of 350 mm, a short length (width) of 10 mm, and a thickness of 1 mm. The output of the resistance line 101b is 1000W.

  FIG. 6 is a perspective view illustrating the configuration of the heat diffusing member 102. The heat diffusion member 102 includes a curved surface portion 102a as a heating member formed with a convex curved surface that comes into contact with the fixing belt 105, and a heater 101 formed on the opposite (back) side of the surface on which the curved surface portion 102a is formed. A heater-facing portion 102b having a planar shape that comes into contact with the resistance wire 101b is provided. The curved surface portion 102 a is abutted and covered by the fixing belt 105, but the flat surface portion 102 d 1 and the flat surface portion 102 d 2 are formed at both ends that are not covered by the fixing belt 105. For example, the heat diffusion member 102 shown in FIG. 6 can be formed as a part of a cylindrical shape having a thickness of about 1 mm using A6063 which is an extruded aluminum material, and the curvature radius of the curved surface portion 102a is about 50 mm. The

  Next, heat transfer due to the contact of the heat diffusion member 102 with the heater 101 and the function of each portion of the heat diffusion member 102 will be described. 7 is a perspective view of the heater 101 and the heat diffusing member 102, FIG. 7-S1 is a side view with the arrow direction of the plane S1 in FIG. 7 as a viewpoint, and FIG. 7-S2 is FIG. It is sectional drawing which makes an arrow direction of plane S2 a viewpoint. In FIG. 7, FIG. 7-S1, and FIG. 7-S2, the plane portion 102d1 and the plane portion 102d2, the rotation fulcrum 102c1 and the rotation fulcrum 102c2 of the heat diffusion member 102 are symbols for identifying both ends. Are described as a plane portion 102d and a rotation fulcrum 102c.

  As shown in FIGS. 7-S1 and 7-S2, the heat generated by the resistance wire 101b on the substrate 101a constituting the heater 101 causes the resistance wire 101b to contact the heater facing portion 102b of the heat diffusion member 102. Is transmitted. The transmitted heat further reaches the curved surface portion 102 a while diffusing in the heat diffusing member 102 and reaches the fixing belt 105. In this case, between the heater facing portion 102b and the resistance wire 101b, a semi-solid grease or the like having high heat resistance and high heat conductivity and being arbitrarily deformable is applied, whereby the heater facing portion 102b and the resistance wire 101b are coated. The heat generated in the resistance wire 101b may be efficiently transmitted to the heat diffusing member 102 via the heater facing portion 102b.

  As described above, the flat portions 102 d are formed at both ends of the heat diffusion member 102 in parallel with the heater facing portion 102 b and at positions where the heater 101 is pressed. Further, the rotation fulcrum 102c is closer to the downstream side in the moving direction of the fixing belt 105 that moves while being in contact with the curved surface portion 102a of the heat diffusing member 102 (in the direction of the X axis in FIGS. Is provided. The rotation fulcrum 102c is formed at a position that bisects the curved surface portion 102a. In other words, the curved surface portion 102 a has a heat transfer curved surface 102 a-1 serving as a moving mechanism whose main function is to transfer heat to the fixing belt 105 by bringing the fixing belt 105 and the heater 101 into contact with each other, and the fixing belt 105. It can be divided into a posture control surface 102 a-2 as a detection mechanism that detects the movement of the fixing belt 105 by controlling the posture of the heat diffusing member 102 as a main function. According to the heat diffusing member 102 having such a configuration, the fixing belt 105 and the heater 101 as the heating member are brought into contact with the driving of the fixing belt 105 in conjunction with the movement of the fixing belt 105 as the fixing member. As the fixing belt 105 stops driving, the fixing belt 105 and the heater 101 can be separated from each other. 3 to 6, the heater 101, the heat diffusion member 102, the fixing roller 105, and the pressure roller 107 extend in the Z-axis direction in FIG. 4 orthogonal to the driving direction of the fixing belt 105. The printing medium 1 to which the developer image 1t is transferred is conveyed in the + X-axis direction in FIG.

  Next, a printing operation of the printer 10 having the above configuration will be described with reference to FIG. First, when a print control unit (not shown) of the printer 10 receives a print command including image information from a host device (not shown), it starts a printing operation based on the received image information.

  A print control unit (not shown) takes out the print media 1 stored in the print media cassette 2 one by one from the uppermost portion and feeds them to the print medium transport path S.

  The print medium 1 fed out to the print medium conveyance path S is nipped and conveyed to the print medium conveyance unit 3b by a conveyance roller pair provided in the print medium conveyance unit 3a. The print medium transport unit 3b corrects the skew of the print medium 1 transported by the print medium transport unit 3a and transports the print medium 1 to the developer image forming unit 4.

  In parallel with this, a printing control unit (not shown) controls a high-voltage power supply (not shown), and a predetermined voltage is applied to a photosensitive drum, a charging device, a developer supply unit, etc. (not shown) provided in the developer image forming unit 4. Is applied. Next, a print control unit (not shown) controls the LED head 5 to irradiate the surface of the photosensitive drum uniformly and uniformly with light corresponding to the image information, thereby forming an electrostatic latent image.

  Then, the developer supplying means supplies the developer to the electrostatic latent image formed on the surface of the photosensitive drum to perform reversal development, thereby forming a developer image 1t. The developed developer image 1t is transferred onto the print medium 1 in accordance with the timing of passage of the print medium 1 through the developer image forming unit 4.

  The printing medium 1 to which the developer image 1t has been transferred is applied with heat and pressure when passing through the nip N of the fixing device 100 maintained at a predetermined temperature, and the developer is melted to melt the developer image 1t. Is established.

  In the fixing device 100, the printing medium 1 on which the developer image 1t is fixed is conveyed to the printing medium conveying unit 3c. Here, in the case of single-sided printing in which printing is performed only on one side of the print medium 1, the print medium 1 is conveyed as it is to the print medium conveyance unit 3 d and discharged to the stacker 7. On the other hand, in the case of duplex printing in which printing is performed on both sides of the print medium 1, the print medium 1 is once transported to the print medium transport unit 3d. Then, by the reverse rotation of the conveyance roller pair provided in the print medium conveyance unit 3d, the print medium 1 is disposed under the developer image forming unit 4 with the developer image 1t formation surface as an upper surface. It is conveyed to the reversing unit 6. The print medium reversing unit 6 transports the print medium 1 to the print medium transport unit 3a. At this time, the developer image 1t formation surface of the print medium 1 is turned upside down, and the print medium 1 is conveyed to the print medium conveyance unit 3b with the developer image 1t formation surface as a lower surface. After the developer image 1t is formed again in the developer image forming section 4, the print medium 1 is transported to the print medium transport section 3d, discharged to the stacker 7, and a series of printing operations is completed.

  Next, the fixing operation by the fixing device 100 in the printing operation will be described with reference to FIGS. 7-S2, FIG. 8, and FIG. 8-D1. FIG. 8 is a side view for explaining the operation of the fixing device 100 before the start of the printing operation, and FIG. 8-D1 is a partially enlarged view in which a region D1 in FIG. 8 is enlarged.

  Before the start of the printing operation, the fixing roller 106 serving as a driving force supply source is stopped. Therefore, the fixing belt 105 and the pressure roller 107 that are driven by the driving of the fixing roller 106 are stopped. In this state, the flat surface portion 102d of the heat diffusing member 102 is pushed down by the pressure F1 of the spring 103 shown in FIG. 8-D1, and the heat transfer curved surface 102a-1 has the rotation fulcrum 102c as the rotation center. It moves in the −Y-axis direction indicated by D1, and is separated from the fixing belt 105. At this time, the fixing belt 105 is stretched by the bridging member 104 and the posture control surface 102a-2 shown in FIG. 7-S2, and the heat transfer curved surface 102a-1 and the fixing belt 105 are shown in FIG. 8-D1. In this state, the separation distance L shown in FIG.

  Note that the heat transfer curved surface 102a-1 and the fixing belt 105 are separated from each other when the fixing roller 106 is normally stopped when the printing operation is completed, the fixing roller 106 is stopped due to the jam of the printing medium 1, and the fixing roller 106 is rotated. The same operation is performed when slipping between the fixing roller 106 and the fixing belt 105 occurs.

  FIG. 9 is a side view for explaining the operation of the fixing device 100 after the start of the printing operation, and FIG. 9-D2 is a partially enlarged view in which a region D2 in FIG. 9 is enlarged. When the printing operation is started and the fixing roller 106 rotates in the direction A1 in FIG. 9, the fixing belt 105 is driven in the direction of arrow A2 in FIG. 9, and the pressure roller 107 is driven in FIG. It rotates following the direction of the middle arrow A3. At this time, the posture control surface 102a-2 shown in FIG. 7-S2 is driven by the fixing belt 105, and the tensile force (tension) in the −Y-axis direction shown in FIG. It will be pulled by F3. As a result, the moment F <b> 2 works and the heat transfer curved surface 102 a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other, and a sliding state is established. That is, the moment F2 at the rotation fulcrum 102c in FIG. 9-D2 is generated by the tension F3 accompanying the driving of the fixing belt 105. When the pressure F1 of the spring 103 is exceeded, the heat transfer curved surface 102a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other.

  When the heat transfer curved surface 102a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other and are in a sliding state, a printing control unit (not shown) starts energizing the resistance wire 101b of the heater 101 to generate heat. . Since the resistance wire 101b is in contact with the heater facing portion 102b of the heat diffusion member 102, the heat diffusion member 102 is heated. Further, the curved surface portion 102a of the heat diffusing member 102 heats the inner surface of the fixing belt 105 that is in contact, and the fixing belt 105 is in a heated state.

  The surface temperature of the fixing belt 105 is detected by a temperature detection unit (not shown) disposed near the surface and notified to a print control unit (not shown). Upon receiving the notification, the print control unit (not shown) controls the amount of power supplied to the heater 101, and the surface temperature of the fixing belt 105 is maintained at an appropriate fixing temperature. When the surface temperature of the fixing belt 105 is an appropriate fixing temperature, the print medium 1 reaches the nip N from the direction of arrow B in FIG. The developer image 1t transferred onto the printing medium 1 passes through the nip N formed by the fixing roller 106 and the pressure belt 107 via the fixing belt 105, and is thus applied with heat and pressure. Fixed on. When the print medium 1 that has passed through the nip N is discharged from the fixing device 100, the fixing operation ends.

  As described above, according to the first embodiment, the thermal diffusion member and the fixing belt are separated from each other on the condition that the rotation of the fixing belt is stopped, thereby reducing or avoiding the problem of thermal deformation and burning of the fixing belt. can do. Since the influence of heat on the fixing belt is reduced, the life of the fixing belt is expected to be extended. In the first embodiment, since the rotation of the fixing gear and the fixing roller is not a separation condition, it is possible to reliably reduce the thermal influence on the fixing belt. In other words, even if the fixing gear and the fixing roller are rotating, the fixing belt may not be driven due to the occurrence of slip or the like. Rather, it is more reliable in reducing the thermal effect on the fuser belt.

[Second Embodiment]
The configurations of the printer and the fixing device according to the second embodiment are substantially the same as those of the printer 10 and the fixing device 100 described in the first embodiment. Therefore, in the description of the present embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 10 is a side view for explaining the operation of the fixing device 100 ′ before the start of the printing operation according to the present embodiment, and FIG. 10-D3 is a partially enlarged view in which a region D3 in FIG. 10 is enlarged.

  The fixing device 100 ′ according to the present embodiment includes a heat radiating member 116 in addition to the configuration of the fixing device 100 according to the first embodiment. The heat radiating member 116 is disposed at a position away from the heater 101 when the fixing belt 105 rotates.

  Such a heat radiating member 116 can be configured as a long plate member made of a material such as aluminum or copper. The heat dissipating member 116 according to this embodiment is configured as a member having a planar surface 116a close to the base material 101a of the heater 101, having a longitudinal length of 350 mm, a short direction length of 10 mm, and a thickness of 1 mm or more. Although the facing surface 116b facing the surface 116a close to the base material 101a of the heater 101 is depicted as a planar shape in the drawing, the shape is not limited to this, and may be a shape such as a radiating fin. Further, heat radiating silicone or the like having excellent heat resistance may be attached to the surface 116a of the heater 101 close to the base material 101a. Although not shown, the heat dissipating member 116 is fixed to the side frame 110L and the side frame 110R shown in FIG. 3 or 4 by screwing or the like.

  Before the start of the printing operation, the fixing roller 106 serving as a driving force supply source is stopped as in the first embodiment. Therefore, the fixing belt 105 and the pressure roller 107 that are driven by the driving of the fixing roller 106 are stopped. In this state, the flat surface portion 102d of the heat diffusing member 102 shown in FIG. 8-D1 is pressed by the pressure F1 of the spring 103 shown in FIG. 10-D3, and the heat transfer curved surface 102a- shown in FIG. 1 moves in the −Y-axis direction shown in FIG. 10-D3 with the rotation fulcrum 102c as the rotation center, and is separated from the fixing belt 105.

  At this time, the base material 101a of the heater 101 and the surface 116a of the heat radiating member 116 come into contact with each other. When there is heat storage in the heater 101 and the heat diffusion member 112, the heat storage is released by the heat radiating member 116, and the heat transfer of the fixing belt 105 in contact with the attitude control surface 102a-2 shown in FIG. Heat can be suppressed. The fixing belt 105 is stretched by the bridging member 104 and the attitude control surface 102a-2, and the heat transfer curved surface 102a-1 and the fixing belt 105 maintain a separation distance L shown in FIG. 10-D3. It becomes a state.

  Note that the heat transfer curved surface 102a-1 and the fixing belt 105 are separated from each other when the fixing roller 106 is normally stopped when the printing operation is completed, the fixing roller 106 is stopped due to the jam of the printing medium 1, and the fixing roller 106 is rotated. The same operation is performed when slipping between the fixing roller 106 and the fixing belt 105 occurs.

  FIG. 11 is a side view for explaining the operation of the fixing device 100 ′ after the start of the printing operation, and FIG. 11-D4 is a partially enlarged view in which a region D4 in FIG. 11 is enlarged. When the printing operation is started and the fixing roller 106 rotates in the direction A1 in FIG. 11, the fixing belt 105 is driven in the direction of the arrow A2 in FIG. 11, and the pressure roller 107 is driven in FIG. It rotates following the direction of the middle arrow A3. At this time, the posture control surface 102a-2 shown in FIG. 7-S2 is driven by the fixing belt 105, and pulling force (tension) in the -Y-axis direction shown in FIG. It will be pulled by F3. As a result, the moment F <b> 2 works and the heat transfer curved surface 102 a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other, and a sliding state is established. That is, the moment F2 at the rotation fulcrum 102c in FIG. 11-D4 is generated by the tension F3 accompanying the driving of the fixing belt 105, and the acting force F4 at the rotation action point based on the lever principle is used as a turning point. When the pressure F1 of the spring 103 is exceeded, the heat transfer curved surface 102a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other.

  When the heat transfer curved surface 102a-1 of the heat diffusing member 102 and the inner surface of the fixing belt 105 come into contact with each other and are in a sliding state, a printing control unit (not shown) starts energizing the resistance wire 101b of the heater 101 to generate heat. . Since the resistance wire 101b is in contact with the heater facing portion 102b of the heat diffusion member 102, the heat diffusion member 102 is heated. Further, the curved surface portion 102a of the heat diffusing member 102 heats the inner surface of the fixing belt 105 that is in contact, and the fixing belt 105 is in a heated state.

  The surface temperature of the fixing belt 105 is detected by a temperature detection unit (not shown) disposed near the surface and notified to a print control unit (not shown). Upon receiving the notification, the print control unit (not shown) controls the amount of power supplied to the heater 101, and the surface temperature of the fixing belt 105 is maintained at an appropriate fixing temperature. When the surface temperature of the fixing belt 105 is an appropriate fixing temperature, the print medium 1 reaches the nip N from the direction of arrow B in FIG. The developer image 1t transferred onto the printing medium 1 passes through the nip N formed by the fixing roller 106 and the pressure belt 107 via the fixing belt 105, and is thus applied with heat and pressure. Fixed on. When the print medium 1 that has passed through the nip N is discharged from the fixing device 100, the fixing operation ends.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, the heater and the heat diffusing member come into direct contact with the heat radiating member, thereby efficiently releasing the heat storage of the heater and the heat diffusing member. be able to. Therefore, as compared with the first embodiment, it is possible to more effectively reduce and avoid the problem of thermal deformation and burnout of the fixing belt, and further increase the life of the fixing belt can be expected.

[Modification]
In 1st Embodiment and 2nd Embodiment, the form using the thermal-diffusion member provided with the detection mechanism and the moving mechanism as a separation / contact means was demonstrated. The modification described here includes a sensor as a detection mechanism that detects driving of the fixing belt 105, a solenoid (push-type solenoid) as a moving mechanism, and a control unit that controls the sensor and the solenoid. A mode in which the heater 101 ′, which is a heating body, is in contact with the fixing belt 105 while the heater 101 is driven and the heater 101 ′ is separated from the fixing belt 105 when the driving of the fixing belt 105 is stopped will be described.

  FIG. 12 is a side view illustrating the fixing device 200 according to the modified example with main members, and FIG. 12A is a side view illustrating the operation of the fixing device 200 before the start of the printing operation. FIG. 6B is a side view illustrating the operation of the fixing device 200 after the start of the printing operation. FIG. 13 is a perspective view illustrating the configuration of a heater 101 ′ as a heating member according to this modification. Also in the description of this modification, the same portions as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 12A and 12B, the fixing belt 105 of the fixing device 200 according to this modification is replaced with the heat diffusion member 120 described in the first embodiment and the second embodiment. The tension member 104 and the tension member 104 ′ are stretched by the fixing roller 106. Here, the tension member 104 ′ is a member for the purpose of tensioning and guiding the fixing belt 105, similarly to the tension member 104. Further, the fixing device 200 is a sensor 210 serving as a detection mechanism for detecting the driving and stopping of the fixing belt 105 provided in the vicinity of the surface of the fixing belt 105, and a movement that controls the contact and separation of the heater 101 ′ with respect to the fixing belt 105. A solenoid 230 as a mechanism and a control unit 220 that controls driving of the solenoid 230 based on an input signal from the sensor 210 are provided.

  Here, the configuration of the heater 101 ′ according to this modification will be described with reference to FIG. The heater 101 ′ according to this modification example has a planar portion formed in a planar shape and a resistor (not shown) that generates heat when a current flows, like the heaters 101 according to the first and second embodiments. Lines are provided. The heater 101 ′ according to the present modification is configured to be able to directly contact the fixing belt 105 by driving the solenoid 230, and the flat surface portion 101 to which the pressing force from the spring 103 is applied at both ends thereof. 'd1 and plane portion 101'd2 are formed. Most of the flat portion of the heater 101 ′ is covered with the fixing belt 105 by abutting with the fixing belt 105, but the flat portion 101 ′ d 1 and the flat portion 101 ′ d 2 are at both ends not covered with the fixing belt 105. Is formed.

  Next, the operation of the fixing device 200 before and after the start of the printing operation will be described using the flowcharts of FIGS. 12 (a), 12 (b), and 14. FIG. FIG. 14 is a flowchart for explaining the operation of the fixing device 200 after the start of the printing operation.

  First, as shown in FIG. 12A, when the fixing belt 105 is not driven, the heater 101 ′ is located at a position away from the fixing belt 105 by a pressing force F 1 ′ of the spring 103.

  In step S300 in FIG. 14, when the printing operation is started and the fixing belt 105 is driven (Yes in step S300), the sensor 210 detects this and sends a signal to the control unit 220 that the driving of the fixing belt 105 has started. Output.

  Based on the signal input from sensor 210, control unit 220 drives solenoid 230 (step S310). When the solenoid 230 starts driving, the heater 101 ′ is brought into contact with the fixing belt 105 with a pressure F5 larger than the pressure F1 ′ of the spring 103 (step S320 and FIG. 12B).

  When the printing operation is finished and the driving of the fixing belt 105 is stopped (Yes in step S330), the sensor 210 detects this and outputs a signal indicating that the driving of the fixing belt 105 is stopped to the control unit 220.

  Based on the signal input from the sensor 210, the control unit 220 stops driving the solenoid 230. When the drive of the solenoid 230 is stopped (step S340), the heater 101 ′ is separated from the fixing belt 105 by the pressure F1 ′ of the spring 103, and returns to the state shown in FIG.

  As described above, according to the present modification, as in the first and second embodiments, the driving of the fixing belt does not directly act on a heating member such as a heater, but the contact with the fixing belt, It is also possible to control the separation operation with an external force such as a solenoid.

  In the description of the first embodiment, the second embodiment, and the modified examples, the mode in which the heater as the heating member makes contact with the fixing belt as the fixing member has been described. As shown in FIGS. 15A and 15B, the fixing belt 500 is separated from or brought into contact with the heater 400 serving as a heating member (FIG. 15A). Of course, the form (FIG. 15B) is also possible.

  In the description of the present embodiment and the modifications, an electrophotographic printer has been described as an example of a suitable image forming apparatus of the present invention. However, the present invention is not limited to this, and for example, a facsimile, a copier, and a multifunction machine Etc. can also be used.

DESCRIPTION OF SYMBOLS 1 Print medium 2 Print medium cassette 3a, 3b, 3c, 3d Print medium conveyance part 4 Developer image formation part 5 LED head 6 Print medium inversion unit 7 Stacker 10 Printer 100, 100 ', 200 Fixing apparatus 101, 101', 400 Heater 101a Base material 101b Resistance wire 102 Heat diffusion member 102a Curved surface portion 102a-1 Heat transfer curved surface 102a-2 Attitude control surface 102b Heater facing portion 102c1, 102c2 Rotating fulcrum 102d1, 102d2 Plane portion 103L, 103R Spring 104, 104 ′ Tension Mounting member 105,500 Fixing belt 106 Fixing roller 106a Core metal part 106a1, 106a2 End part 106b Elastic layer 107 Pressure roller 107a Core metal part 107b Elastic layer 109 Fixing gear 110L, 110R Side frame 1101L, 1101R Hole 1102L 1102R hole 1103L, 1103R hole 1104L, 1104R hole 1105L, 1105R hole 111L, 111R pressure bearing member 112L, 112R spring 113L, 113R rotating bearing 114L, 114R rotating bearing 115L, 115R bearing 116 heat radiating member 116a surface 116b facing surface 210 sensor 220 Control unit 230 Solenoid

Claims (9)

A fixing member for fixing the developer to the printing medium on which the developer image is formed;
A heating member that generates heat by the heating element and is in contact with the fixing member;
A pressure member that is provided in pressure contact with the fixing member and conveys the print medium to and from the fixing member;
The fixing member and the heating member are brought into contact with each other when the fixing member is driven, and separation means for separating the fixing member and the heating member when the driving of the fixing member is stopped is provided. Fixing device.   The fixing device according to claim 1, wherein the separation / contact means includes a detection mechanism for detecting a movement of the fixing member, and a moving mechanism for bringing the fixing member and the heating member into contact with each other according to the detection by the detection mechanism. apparatus.   The detection mechanism and the moving mechanism are integrally formed, the detection mechanism includes a turning point that receives turning force by the movement of the fixing member, and the moving mechanism has a rotation fulcrum that supports the movement of the fixing member; The fixing device according to claim 2, further comprising a rotating action point that moves the heating member by movement of the turning point.   The fixing device according to claim 3, wherein the rotation fulcrum is disposed between the turning point and the rotation action point.   The said detection mechanism is comprised with the sensor which detects the motion of the said fixing member, and the said moving mechanism contacts the said fixing member and the said heating member based on the output of the said sensor. Fixing device.   The fixing device according to claim 2, wherein the heating member and the moving mechanism are integrally formed.   The fixing device according to claim 6, wherein the heating member is in contact with the fixing member via the moving mechanism. A heat dissipating member provided at a position capable of contacting the heating member;
8. The fixing device according to claim 6, wherein when the heating member is separated from the fixing member, the heating member comes into contact with the heat radiating member.   An image forming apparatus comprising the fixing device according to claim 1.