JP2013015631A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage to an image heating member due to toner and the like adhering to a rubbing member when the rubbing member is brought into contact with the image heating member.SOLUTION: The image heating device includes means for performing an operation such that while power supply control means controls heating mean, the rubbing member is kept in contact with image heating means, which rotates at a first speed, for a preset time, and then the rubbing member is brought into contact with the image heating means, which rotates at a second speed higher than the first speed.

Description

  The present invention relates to an image heating apparatus that heats an image formed on a recording material used in an image forming apparatus that forms an image on the recording material by an electrophotographic method such as a multifunction machine, a copying machine, a printer, or a fax machine. .

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system or the like, an image heating apparatus that heats an image formed on a recording material with toner at a nip portion formed by an image heating member and a pressure member is used. The image heating member that comes into contact with the toner image is provided with a release layer formed of a tube or coating made of a material excellent in release properties such as a fluororesin on the surface layer. Since the release layer is in contact with the toner image, the influence on the image is large, and a configuration that can maintain the surface property of the release layer is desirable.

  As disclosed in Patent Document 1 and Patent Document 2, the surface roughness of the release layer of the image heating member can be obtained by bringing the rubbing member into contact with the release layer of the image heating member. A technique for maintaining the above has been proposed. As this rubbing member, as disclosed in Patent Document 3, a rotatable rubbing member having a surface layer bonded with alumina abrasive grains is brought into contact with the surface layer of the image heating member to form a rubbing nip, A system for rotationally driving the rubbing member has also been put into practical use. Further, by allowing the rubbing member to be able to contact and separate from the image heating member, the image heating member can be prevented from being excessively worn by the rubbing member.

JP 2005-266785 A JP2007-34068 JP2008-040363A

  When the rubbing member can be brought into and out of contact with the image heating member, the temperature of the rubbing member when the rubbing member is separated from the image heating member is when the rubbing member is in contact with the image heating member. Low compared to the temperature of As a result, when the rubbing member is brought into contact with the image heating member, the toner or the like adhering to the rubbing member adheres to the rubbing member in a solid state. If the rubbing member is brought into contact with the image heating member in a state where the toner or the like is fixed, there is a possibility that hard deposits may adversely affect the image heating member. Therefore, before the rubbing operation to the image heating member by the rubbing member, the rubbing member is brought into contact with the image heating member to melt the toner and the like adhering to the rubbing member while reducing the influence on the image heating member. A configuration is desired.

  Accordingly, the present invention provides an image heating means for heating a toner image formed on a recording material, a heating means for heating the image heating means, and heating so that the temperature of the image heating means becomes a preset temperature. An energization control unit that controls energization of the unit, a rubbing member that abuts the image heating member and rubs the surface of the image heating member, and the rubbing member is brought into contact with and separated from the image heating member In an image heating apparatus having an approach / separation mechanism and a speed switching mechanism that switches a rotation speed of the image heating unit, the rubbing member rotates at a first speed while the energization control unit controls the heating unit. Execution means for performing an operation of abutting the image heating means rotating at a second speed higher than the first speed after the abutting for a predetermined time on the image heating means. It is characterized by having.

  An object of the present invention is to melt the toner or the like adhering to the rubbing member by bringing the rubbing member into contact with the image heating member while reducing the influence on the image heating member.

Sectional drawing which shows the fixing device of an Example. 1 is a cross-sectional view illustrating an image forming apparatus according to an embodiment. FIG. 2 is an external view illustrating a fixing device according to an embodiment. The side view which shows the fixing device of an Example. The side view which shows the fixing device of an Example. FIG. 3 is a flowchart and a block diagram for explaining a fixing nip forming operation in the embodiment. The partial perspective view explaining the roughening mechanism of an Example, and a fragmentary sectional view. The flowchart and block diagram explaining the roughening nip formation operation | movement of an Example. 6 is a flowchart for explaining details of the fixing member surface property recovery operation according to the embodiment.

(Example)
FIG. 2 (image forming apparatus main body diagram) is a cross-sectional view of a color electrophotographic printer which is an example of the image forming apparatus of this embodiment.

  The image forming apparatus shown in FIG. 2 uses an image forming unit 510Y using yellow Y toner, an image forming unit 510M using magenta M toner, an image forming unit 510C using cyan C toner, and a black BK toner. An image forming unit 510 including the used image forming unit 510BK is provided.

  In this embodiment, the image forming units 510Y, 510M, 510C, and 510BK have the same configuration except for the color of the toner, and therefore the image forming unit 510Y will be described as a representative.

  A photosensitive drum 511 as an image carrier is charged by a charging roller 512 as a charging member so as to have a predetermined potential set in advance. Thereafter, an electrostatic latent image is formed on the photosensitive drum 511 by a laser scanner 513 which is an image exposure apparatus. The electrostatic latent image is developed by the developing device 514, and a toner image is formed on the photosensitive drum 511. The toner image on the photosensitive drum 511 is transferred to an intermediate transfer belt 531 which is a belt member.

In the image forming units 510M, 510C, and 510BK, toner images are formed on the respective photosensitive drums as described above, and transferred to the intermediate transfer belt 531 so that the toner images overlap each other. In this way, a color toner image is formed on the intermediate transfer belt 531.
On the other hand, the recording material S is sent out one by one from the cassette 520 that accommodates the recording material, and is sent to the registration roller pair 523. The registration roller pair 523 conveys the recording material between the intermediate transfer belt 531 and the secondary transfer roller 535 at a timing when the toner image formed on the intermediate transfer belt 531 is transferred to the recording material. The color toner image on the intermediate transfer belt is transferred to the recording material S by the secondary transfer roller 535 by electrostatic force. Thereafter, the toner image of the recording material is fixed on the recording material by being heated and pressed in the fixing device 100. Thereafter, the recording material S on which the toner image is fixed is conveyed and discharged by a discharge roller pair 540 to a discharge tray 565 in the upper part of the apparatus.

Next, the fixing device 100 as an image heating device will be described.
FIG. 1 is a cross-sectional view of the fixing device 100, and FIG. 3 is a perspective view of the fixing device 100. FIG. 1 is a diagram illustrating a state where the fixing belt and the pressure belt are separated from each other, and FIG. 4 is a diagram illustrating a state where the fixing belt and the pressure belt are in contact with each other. FIG. 5 is a diagram illustrating a belt tension mechanism in the fixing device 100.

  The fixing device in this embodiment has a configuration using an induction heating method. Note that the present invention is not limited to an induction heating type image heating apparatus, and the same effect can be obtained by using the present invention even in a configuration using a heating element such as a halogen heater.

  This will be described with reference to FIG. A coil unit 170 which is a magnetic flux generation unit as a heating means is composed of a coil, a magnetic core, and a holder for holding them, and is provided near the upper surface layer of the fixing belt 105. The coil generates a magnetic flux by an alternating current, and the magnetic flux is guided to the core magnetic body to generate an eddy current in the conductive layer of the fixing belt 105 as an image heating member. The eddy current generates Joule heat due to the specific resistance of the fixing belt 105. Based on the temperature information from the thermistor 220 for detecting the surface temperature of the fixing belt 105, the energization control unit (CPU) energizes the coil so that the temperature of the fixing belt 105 becomes 150 ° C. which is the image heating temperature. Control.

  The pressure belt 120, which is a pressure member, is looped around two support rolls, that is, a pressure roll 121 and a tension roll 122 having a function of applying belt tension, and can be circulated and rotated with a predetermined tension (for example, 200 N). Has been passed. In this embodiment, the pressure belt 120 is a nickel metal layer having a thickness of 50 μm, a width of 380 mm, and a circumferential length of 200 mm, for example, coated with silicon rubber having a thickness of 300 μm and a PFA tube on the surface layer. .

  The fixing belt 105 is looped around two support rolls, that is, a drive roll 131 and a tension roll 132 having a function of applying belt tension, and can be circulated and rotated with a predetermined tension (for example, 200 N). In this embodiment, as the fixing belt 105, a magnetic metal layer such as a nickel metal layer or a stainless steel layer, which is a conductive layer having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm, is coated with silicon rubber having a thickness of 300 μm. Are coated with a PFA tube.

  As shown in FIG. 4, the fixing belt 105 and the pressure belt 120 are pressed to form a fixing nip portion U for nipping and conveying the recording material and fixing the toner image on the recording material by heat and pressure. .

  On the inner side of the pressure belt 120 corresponding to the recording material conveyance side (the inlet side of the fixing nip portion) of the fixing nip portion U where the pressure belt 120 and the fixing belt 105 are pressed and the recording material is nipped and conveyed, A pressure pad 125 formed of silicon rubber is in contact with the pressure belt 120.

  The pressure roll 121 is a roll for suspending a pressure belt 120 having an outer diameter of φ20 made of solid stainless steel, for example, and the recording material is discharged from a fixing nip portion U formed by the pressure belt 120 and the fixing belt 105. On the exit side of the fixing nip.

  The tension roll 122 is a hollow roll formed of stainless steel, for example, with an outer diameter of about 20 mm and an inner diameter of about 18 and stretches the belt. Both end portions of the tension roll 122 are supported by bearings 126, and a tension spring 127 applies a 20 kgf tension to the belt.

  A pad stay 137 made of, for example, stainless steel (SUS material) is in contact with the fixing belt 105 inside the fixing belt 105 corresponding to the inlet side of the fixing nip portion U. The pad stay 137 presses the pressure pad 125 via the fixing belt 105 and the pressure belt 120 to form a part of the fixing nip portion U.

  The drive roll 131 is formed by integrally forming a heat-resistant silicon rubber elastic layer on a core metal surface layer having an outer diameter of φ18 made of solid stainless steel. The driving roll 131 is disposed on the exit side of the fixing nip portion, and the elastic layer is elastically distorted by a predetermined amount by the pressure contact of the pressure roll 121.

  The tension roll 132 is a hollow roll formed of stainless steel with an outer diameter of about 20 mm and an inner diameter of about 18 and stretches the fixing belt 105.

  Driving is input to the driving roll 131 from the outside by the driving motor 301 shown in FIG. 3, and the fixing belt 105 is conveyed by the rotation of the driving input gear 120 and the driving roll 131. In the fixing device in this embodiment, the rotational speed of the drive motor 301 is two speeds. One is a first speed Va for fixing the toner image formed on the recording material S to the recording material S during image formation. On the other hand, when the image forming apparatus is started up, that is, when the temperature of the fixing belt 105 of the fixing apparatus is lower than the target temperature of 150 ° C. or when the temperature reaches the target temperature, the image forming apparatus waits for image formation. Two speed Vb. This is rotated in order to make the temperature of the fixing belt 105 uniform. The rotational speed of the drive motor 301 in this embodiment is 3000 rpm for Va and 300 rpm for Vb. As described above, this embodiment includes a speed switching mechanism that switches the rotation speed of the fixing belt 105 by changing the rotation speed of the drive motor 301.

  The upper frame 305 is configured by an upper plate 140 that rotatably supports the drive roll 131 and holds the end of the pad stay 137. The lower frame 306 is configured by a lower plate 303 that rotatably supports the pressure roll 121 and holds the end of the pressure pad 125. The lower frame 306 is rotatably supported by a hinge shaft 304 provided on the lower plate 303.

  With the hinge shaft 304 as the center, the pad stay 137 and the pressure pad 125 are pressed on the upstream side, and the drive roll 131 and the pressure roll 121 are pressed on the downstream side via the fixing belt 105 and the pressure belt 120, respectively. Each pressing is performed by applying a predetermined pressure (for example, 400 N) from the pressure spring 305, thereby forming a fixing nip N. The lower frame is configured to be movable between a pressure position shown in FIG. 4 and a separation position shown in FIG. 1 by rotation of the pressure cam 308 provided at both ends of the pressure cam shaft 307. The pressure cam shaft 307 is rotated when the pressure motor 302 shown in FIG. 3 is driven and the pressure gear 309 operates.

  The operation of forming the fixing nip U by the movement of the pressure roll 121 and the pressure pad 125 will be described with reference to the flowchart shown in FIG. 6A and the block diagram of FIG. 6B.

First, the block diagram of FIG. 6b will be described.
In this embodiment, the CPU 10 which is a control unit that controls the image forming apparatus sends a signal to the motor driver 11 to control the operation of the pressure motor 302.

  Next, a flowchart of the fixing nip U forming operation will be described with reference to FIG. When the CPU 10 issues a pressurization command (S6-1, S6-2), the motor driver 11 causes the rotation shaft of the pressurization motor 302 to rotate in the CW direction (clockwise direction when viewed from the rotation direction load side) at a predetermined rotation speed. A certain N rotations are made (S6-2). As a result, the pressure cam shaft 307 is rotated by the pressure gear 309 to move the pressure pad 125 and the pressure roll 121 supported by the lower frame 306 to the pressure position. When the pressure pad 125 and the pressure roll 121 are moved to the pressure position (S6-4), the fixing belt 105 and the pressure belt 120 are brought into pressure contact to form a fixing nip U (S6-5). Similarly, when a separation command is issued from the CPU 10 (S6-6), the pressure motor 309 rotates R in the CCW direction (counterclockwise direction when viewed from the rotation direction load side) (S6-7). Then, the pressure pad 125 and the pressure roll 121 supported by the lower frame 306 move to the separation position (S6-8), and the fixing nip U is released (S6-9).

  Next, the configuration of the roughening roller 400, which is a sliding member that recovers the surface property of the fixing belt 105, will be described with reference to FIG.

  First, the configuration of the roughening roller 400 will be described with reference to FIG. The roughing roller 400 is rotatably supported via a bearing by an RF support arm 141 rotatably supported by a fixed shaft 142 on the side plate 140. The roughing roller 400 is driven by an RF drive gear 401 fixed to the end of the driving roll and an RF gear 403 fixed to the end of the roughing roller, and rotates in a direction opposite to the moving direction of the fixing belt 105.

  When the fixing belt 105 is pressed against the roughing roller 400 via the RF pressure member 404, the roughing roller 400 is urged by the RF pressure spring 404 and pressed against the fixing belt 105 with a force of 15 kgf. At the same time that the roughing roller 400 comes into pressure contact, the roughing roller driving gear A 412 (FIG. 7c) disposed on the driving roll 131 and the roughing roller driving gear B413 (FIG. 7c) disposed on the roughing roller 400 mesh with each other. The roller 400 rotates. The roughing roller 400 having a polishing layer on the surface rotates with a predetermined peripheral speed difference with respect to the fixing belt 105, thereby uniformly and uniformly leveling the surface of the fixing belt 105. Demonstrate. On the other hand, when the peripheral speed difference is small, the surface roughness is small with respect to the desired roughness. In this embodiment, the rough roller driving gears A and B are set to a ratio of 1.3: 1, and the peripheral speed difference is 90 mm / s when the rotational speed of the driving motor is 3000 rpm.

  The roughing roller 400 has abrasive grains closely bonded to the surface of a stainless steel core bar having a diameter of 12 mm via an adhesive layer. The average particle diameter of the abrasive grains 93b is about 3 μm to about 16 μm. The abrasive is an alumina-based material. This material has higher hardness in each step than the surface of the fixing belt 105 and has excellent abrasiveness because the particles have an acute angle shape. By roughening the fixing belt 105 and roughening the roller 400 under the above conditions, the surface layer of the fixing belt 105 can be set to about Rz 0.5 to 1.0. An image fixed with roughness can be an image having appropriate gloss.

  Next, a contact / separation mechanism for performing the contact / separation operation of the roughening roller 400 with the fixing belt will be described with reference to FIG. The RF support arm 141 that supports the roughing roller 400 holds an RF separation spring 405 having the other end held by the RF separation shaft 406, and is pressed against the RF cam 407 by the RF separation spring 405. The RF cam 407 is fixed to the RF cam shaft 408. An RF detachable gear 409 is fixed to the RF pressure shaft 408, and the RF cam shaft 408 is rotated via the RF motor gear 411 by the rotation of the RF pressure motor 410. As a result, the RF support arm 141 operates according to the profile of the RF cam 407 to move the roughing roller 400 to the pressurization position and the separation position where the rough nip R is formed.

  The pressing operation of the pressing mechanism of the roughing roller 400 used in this embodiment will be described with reference to the flowchart shown in FIG. 8A and the block diagram shown in FIG. 8B.

First, the block diagram of FIG. 8b will be described.
In this embodiment, the CPU 10 which is a control unit that controls the image forming apparatus sends a signal to the motor driver 12 to control the operation of the RF pressure motor 410.

  Next, the flowchart about the pressurization operation | movement of the pressurization mechanism of the roughening roller 400 is demonstrated using FIG. 8a.

  When a pressure command is issued by the CPU 10 (S8-1, S8-2), the motor driver 12 causes the RF pressure motor 410 to rotate at a predetermined number of rotations in the CW direction (clockwise as viewed from the rotation direction load side). Make a certain M rotation (S8-3). As a result, the RF camshaft is rotated by the RF detachable gear 409, thereby moving the roughing roller 400 supported by the RF support arm 141 to the pressing position (S8-4). The fixing belt and the roughening roller 400 are pressed against each other to form a nip R (S8-5) Similarly, when a separation command is issued (S8-6), the RF pressure motor is It rotates M in the CCW direction (counterclockwise direction as viewed from the load side in the rotational direction) (S8-7) By this rotation, the roughing roller 400 supported by the RF support arm 141 moves to the separation position (S8-). 8) The rough nip R is released (S8-9).

  Next, the operation of the fixing device will be described. When the image forming signal is input, the fixing belt rotates at the second speed of 300 rpm in a state where the energization control unit controls the energization of the coil so that the temperature of the fixing belt becomes 150 ° C. Then, when a signal for starting the passing of the recording material is output, the energization control unit controls the energization of the coil so that the temperature of the fixing belt becomes 150 ° C., and the fixing belt has a first speed of 3000 rpm. Rotate with. Thereafter, in order to form the fixing nip portion U, a pressurizing operation for pressing the pressure belt toward the fixing belt is performed. The recording material on which the toner image is formed is conveyed to the fixing nip portion U formed by this operation, whereby the toner image is fixed on the recording material. When the operation of fixing the toner on the recording material is completed, the fixing nip portion U is released, and a transition is made to a standby state where the input of an image forming signal is waited.

In the present embodiment, the surface property recovery operation is executed in the following cases.
(Case 1) When the number of continuous image formations reaches a predetermined number (100 in this embodiment) during the image forming job (Case 2) After rotation after the end of the image forming job (Case 3) Operating the image forming apparatus Input of surface recovery operation signal from operation unit

  The surface property recovery operation of the fixing belt 120 by the roughening member is performed when the toner image on the recording material is not heated, that is, when the fixing operation is not performed. Therefore, when the surface property recovery operation is performed during the execution of the image forming job as in (Case 1), the image forming operation is interrupted and the surface property recovery operation is performed. Then, after the surface property recovery operation is completed, the image forming operation is resumed. In (Case 2) and (Case 3), since the process of heating the toner image on the recording material is not performed, the surface property recovery operation is performed according to the surface property recovery operation described later. Of course, the surface property recovery operation may be executed when the toner image on the recording material other than the case described above is not heated.

Next, details of the surface property recovery operation will be described with reference to FIG.
In the present embodiment, when the above-mentioned case occurs, the surface property recovery operation is started (S13-1).
When the surface property recovery operation is started, the fixing device shifts to a surface property recovery operation enabled state. The conditions for the possible state are that the temperature of the fixing belt 105 is 150 ° C., which is a preset temperature, and that the rotational speed of the drive motor 301 is a low speed of 300 rpm (S13-2). When this condition is reached, the roughing roller is moved to the pressure position, and the state shown in FIG. 7b is reached, and the roughening nip R is formed (S13-3). Next, the roughening nip R formation state is continued for a predetermined time (10 seconds in this embodiment) (S13-4). The operation to be continued for a predetermined time is a roughing roll heating operation in order to sufficiently melt and soften the toner adhered on the roughening roller 400 and the wax contained in the toner. Further, by performing this operation under the condition that the peripheral speed difference between the fixing belt 105 and the roughening roller 400 is small, it is possible to reduce the influence of the toner and wax adhering to the roughening roller 400 on the surface layer of the fixing belt 105. it can. The peripheral speed difference in this embodiment is 9 mm / s. By this roughening roll heating operation, the surface temperature of the roughening roller 400 can be increased to 100 ° C or more from the minimum surface temperature of 60 ° C during standby. The toner used in the image forming apparatus of this embodiment has a glass transition point of 90 ° C., and the wax has a glass transition point of 80 ° C. By setting the roughening roller to a temperature higher than these glass transition points, it is possible to sufficiently melt the toner and wax. After the roughing roller heating operation (after 10 seconds), the drive motor 301 is accelerated from the low speed of 300 rpm to the high speed of 3000 rpm (S13-5), and the peripheral speed difference between the fixing belt 105 and the roughing roller 400 is set to 90 mm / s. The roughing operation for rotating for a predetermined time is performed (S13-6). In this embodiment, the roughing operation is performed for 15 seconds. After the roughing operation, the roughening nip R is released by the RF pressure motor 410 (S13-7). Finally, the rotation of the drive motor 301 is decelerated to 300 rpm (S13-8), and the fixing belt surface property recovery operation is completed. By this series of operations, the surface roughened to about Rz 2.0 with a paper having a basis weight of about 220 gsm could be recovered to about Rz 0.5 to 1.0.

  In this embodiment, the circumferential speed difference between the fixing belt 105 and the roughing roller 400 in the roughing roller heating operation for melting toner and wax and the main roughing operation is performed by changing the rotation speed of the drive motor 301. . In addition, for example, the fixing belt 105 and the roughing roller 400 each have a drive motor, and the same effect can be obtained even if the peripheral speed difference is changed by changing the rotation speed of the roughing roller 400. . Further, a one-way clutch may be provided between the roughing roller 400 and the roughing roller drive gear B. In this case, the roughing roller heating operation is the same even if the circumferential speed difference is changed by rotating the driving motor 301 in the reverse direction, driving the roughening roller 400 to the fixing belt 105, and performing normal rotation in this roughening operation. An effect can be obtained.

  In this embodiment, before the operation of roughening the surface layer of the fixing belt 105 to the desired roughness by the roller 400, the surface temperature of the roughening roller 400 is set to a temperature equal to or higher than the melting point of the toner or wax to be adhered. . Accordingly, it is possible to reduce the occurrence of scratches and defects on the surface layer of the fixing belt 105 due to the adhered toner or wax by melting and roughing the adhered toner or wax. As a means for achieving this, it is realized by performing a roughing roller heating operation in which both members are pressed and then rotated for a predetermined time at a peripheral speed difference smaller than the peripheral speed difference between both members in the roughing operation.

  In addition to this configuration, the same effect can be obtained by providing a heating means such as a heater to increase the temperature of the roughing roller 400.

Further, the fixing device and the pressure member are described as the fixing device, but the same effect can be obtained even if the fixing member and the pressure member are applied to a fixing device in which both are rollers or one is a belt.
As described above, according to the present invention, the toner or the like attached to the rubbing member by bringing the rubbing member into contact with the image heating member can be melted while reducing the influence on the image heating member.

DESCRIPTION OF SYMBOLS 100 Fixing device 105 Fixing belt 120 Pressure belt 141 RF support arm 400 Roughening roller
406 RF separation shaft 405 RF separation spring 407 RF cam 408 RF cam shaft 409 RF detachable gear 410 RF pressure motor 411 RF motor gear 412 Roughing roller drive gear A
413 Roughening roller drive gear B

Claims (3)

An image heating unit for heating the toner image formed on the recording material, a heating unit for heating the image heating unit, and control of energization to the heating unit so that the temperature of the image heating unit becomes a preset temperature. An energization control unit that performs contact, a rubbing member that abuts the image heating member and rubs the surface of the image heating member, a contact / separation mechanism that contacts and separates the rubbing member from the image heating member, In an image heating apparatus having a speed switching mechanism for switching the rotation speed of the image heating means,
After the energization control means controls the heating means, the rubbing member makes contact with the image heating means rotating at the first speed for a preset time, and then the rubbing member is moved from the first speed. An image heating apparatus comprising: execution means for executing a contact operation with the image heating means rotating at a fast second speed.   The difference in peripheral speed between the rubbing member and the image heating means when the rubbing member is in contact with the image heating means rotating at the first speed is that the rubbing member is rotating at the second speed. The image heating apparatus according to claim 1, wherein a difference in peripheral speed between the rubbing member and the image heating unit when contacting the image heating unit is smaller.   The said execution means performs the said operation, when the operation | movement which the said image heating means heats the toner image formed on the recording material to the recording material is not performed. The image heating apparatus according to any one of the above.

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