JP2011028097A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing the damage of a separation claw and a first rotating body and preventing the occurrence of image defects caused by the fact that a large amount of toner is accumulated on the separation claw, and to provide an image forming apparatus having the fixing device. <P>SOLUTION: The fixing device includes the first rotating body 9a; a heater 91 which heats the first rotating body 9a from inside; a second rotating body 9b, which forms a fixing nip N9 between the second rotating body 9b and the first rotating body 9a and holds and conveys a material to be transferred T between the second rotating body 9b and the first rotating body 9a; the separation claw 92 which is arranged on the downstream side of the fixing nip N9, in the conveying direction of the material to be transferred T and can change a contact position R1 and a separation position R2; a counting part 941, which counts the number of conveyed materials to be transferred T; a count determination part 942, which determines whether a predetermined plurality of conveyed materials to be transferred is counted; and a separation claw control part 944, which makes the position of the separation claw 92 change from the contact position R1 to the separation position R2, when it is determined that the predetermined plurality of conveyed materials to be transferred is counted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device that fuses toner constituting a toner image and fixes it on a transfer material such as paper. About.

  Conventionally, in an image forming apparatus using an electrophotographic method, a charging process for charging the surface of a photosensitive drum, and exposure for forming an electrostatic latent image on the surface of the photosensitive drum by irradiating the charged photosensitive drum with laser light. A developing process in which toner is attached to an electrostatic latent image formed on the surface of the photosensitive drum and developing the toner image formed on the surface of the photosensitive drum on a sheet as a transfer material An image is formed on the paper by sequentially performing a transfer process for transferring and a fixing process for fixing the toner image transferred onto the paper to the paper.

Among the above steps, in the fixing step, a first rotating body, a second rotating body that forms a fixing nip by sandwiching a sheet on which a toner image is transferred between the first rotating body, and a first rotating body, A fixing device is used that includes a heater that heats the fixing nip from the inside of the rotator, and a separation claw that is disposed on the downstream side of the fixing nip and has a leading end abutting the surface of the first rotator.
In the fixing device described above, first, the sheet on which the toner image has been transferred in the transfer process is conveyed to a fixing nip formed between the first rotating body and the second rotating body. Next, in the fixing nip, the toner component constituting the toner image transferred to the paper is heated and melted by the heater, and the toner image is fixed on the paper. The sheet on which the toner image is fixed in the fixing nip is conveyed to the downstream side of the fixing nip by the rotation of the first rotating body and the second rotating body. At this time, the sheet on which the toner image is fixed is conveyed in a state of being attached to the first rotating body by the adhesive force of the melted toner component. The paper attached to the surface of the first rotating body is peeled off from the surface of the first rotating body by the separation claw.

By the way, in the fixing device, a small amount of toner component remains on the surface of the first rotating body when the sheet is held in the fixing nip and the toner image is fixed on the sheet. The toner component remaining on the surface of the first rotating body is scraped off by a separation claw that comes into contact with the surface of the first rotating body, and gradually accumulates on the tip side of the separation claw. Therefore, in the fixing device in which the separation claw is always in contact with the surface of the first rotating body, a large amount of toner component is accumulated on the front end side of the separation claw. When a large amount of toner component deposited on the leading end of the separation claw is peeled off from the separation claw and adhered to the surface of the first rotating body, the sheet conveyed to the fixing nip is clamped and adhered to the first rotating body. There has been a problem that a large amount of the toner component thus fixed is fixed on the paper and an image defect occurs. Further, in the fixing device in which the separation claw is always in contact with the surface of the first rotating body, there is a problem that the contact portion of the separation claw and the separation claw in the first rotating body is worn.
In view of this, there has been proposed a fixing device that separates the separation claw from the first rotating body every time a sheet is conveyed (see, for example, Patent Documents 1 to 3).

JP-A-1-288886 JP-A-4-291384 JP 2001-100584 A

  However, in the fixing devices disclosed in Patent Documents 1 to 3, the separation claw is separated from the first rotating body and the first time every time one sheet of paper is conveyed between the first rotating body and the second rotating body. The separation claw is brought into contact with one rotating body. Therefore, the separation claw and the first rotating body may be damaged due to repeated contact between the separation claw and the first rotating body.

  Accordingly, the present invention provides a fixing device that can prevent the separation claw and the first rotating body from being damaged, and can prevent the occurrence of image defects due to the accumulation of a large amount of toner on the separation claw, and the image forming apparatus having the fixing device. The purpose is to provide.

  The present invention relates to a fixing device that melts toner constituting a toner image transferred to a sheet-like transfer material and fixes the toner image on the transfer material, and includes a first rotating body that is rotatable in a predetermined direction, A fixing nip is formed between the heater disposed inside the first rotating body and heating the first rotating body from the inside, and the first rotating body disposed opposite the first rotating body, A rotatable second rotating body that sandwiches and conveys the material to be transferred with the first rotating body, and a downstream side of the fixing nip in the conveying direction of the material to be transferred, and a leading end side of the first rotating body is the first rotating body. A separation claw capable of changing a contact position that is in contact with the surface of the first rotating body and a spaced position in which the tip side is separated from the surface of the first rotating body; the first rotating body and the second rotating body; A counting unit that counts the number of the transfer materials conveyed through A count determination unit that determines whether a predetermined plurality of sheets have been counted in the counting unit; and when the count determination unit determines that a predetermined plurality of sheets have been counted, the position of the separation claw is determined from the contact position. The present invention relates to a fixing device including a separation claw control unit that changes the separation position.

  The fixing device further includes a transfer material determination unit that determines whether or not the transfer material is disposed in the fixing nip, and the separation claw control unit moves the transfer material determination unit into the fixing nip. When it is determined that the transfer material is not disposed, it is preferable that the position of the separation claw is changed from the contact position to the separation position.

  According to another aspect of the present invention, there is provided a fixing device for fusing toner constituting a toner image transferred to a sheet-like transfer material and fixing the toner image on the transfer material, and a first rotating body rotatable in a predetermined direction; A fixing nip is formed between the heater disposed inside the first rotating body and for heating the first rotating body from the inside and the first rotating body disposed opposite the first rotating body. And a rotatable second rotator that sandwiches and conveys the transfer material with the first rotator, and is disposed downstream of the fixing nip in the transfer direction of the transfer material. Separation claw capable of changing a contact position contacting the surface of the first rotating body and a separating position where the tip side is separated from the surface of the first rotating body, and printing of a toner image on the transfer material A printing rate measuring unit for measuring the printing rate, and a mark measured by the printing rate measuring unit. A printing rate integration unit that integrates the rate, an integration value determination unit that determines whether the integration value integrated by the printing rate integration unit has reached a predetermined value, and the integration value determination unit that determines whether the integration value is a predetermined value. The present invention relates to a fixing device including a separation claw control unit that changes the position of the separation claw from a contact position to a separation position when it is determined that the value has been reached.

  The fixing device further includes a transfer material determination unit that determines whether or not the transfer material is disposed in the fixing nip, and the separation claw control unit moves the transfer material determination unit into the fixing nip. When it is determined that the transfer material is not disposed, it is preferable that the position of the separation claw is changed from the contact position to the separation position.

  The printing rate measurement unit measures a printing rate for each transfer material, and the printing rate integration unit adds the printing rate measured by the printing rate measurement unit in the conveyance direction of the transfer material. It is preferable to calculate a value obtained by multiplying a predetermined coefficient corresponding to the length and integrate the calculated values.

  The printing rate measuring unit measures a printing rate in one of a plurality of regions formed by dividing the transfer material in a direction intersecting the transport direction, and the printing rate integrating unit It is preferable to integrate the printing rate in the one area measured by the printing rate measuring unit.

  Moreover, it is preferable that the printing rate measurement unit measures the printing rate of the transfer material in a region of the plurality of regions that is sandwiched by a portion of the first rotating body that contacts the separation claw.

  The present invention also provides an image carrier on which an electrostatic latent image is formed on a surface, a developing unit for developing a toner image on the electrostatic latent image formed on the image carrier, and the image carrier. The present invention relates to an image forming apparatus including a transfer unit that transfers a toner image to a sheet-like transfer material and the fixing device described above.

  According to the present invention, there is provided a fixing device capable of preventing the separation claw and the first rotating body from being damaged, and preventing the occurrence of image defects due to the accumulation of a large amount of toner on the separation claw, and the image forming apparatus having the fixing device. Can be provided.

FIG. 3 is a diagram for explaining an arrangement of each component of a printer as an image forming apparatus of the present invention. It is a figure which shows the structure and function of the fixing device of 1st Embodiment, and is a figure which shows the fixing device of the state in which the separation nail | claw was located in the contact position. FIG. 3 is a diagram illustrating a state where a separation claw in the fixing device of the first embodiment is located at a separation position. FIG. 6 is a flowchart showing the operation of the fixing device of the first embodiment. FIG. 10 is a functional block diagram illustrating functions of a fixing device according to a second embodiment. FIG. 10 is a flowchart showing the operation of the fixing device of the second embodiment.

The best mode for carrying out the present invention will be described below with reference to the drawings.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus in the present embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component of the printer 1.

As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a sheet T as a sheet-like transfer material based on predetermined image information. And a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing device 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8, and a fixing device 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transport path L for paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8, in order from the upstream side to the downstream side with respect to the surface of the photosensitive drum 2. Static elimination by the static eliminator 12, cleaning by the drum cleaning unit 11, and fixing by the fixing device 9 are performed.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of the arrow shown in FIG. 1 around an axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

  The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information output from an external device such as a PC (personal computer). By scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 that can be disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner contained in the toner cartridge 5 to the developing device 16. The toner supply unit 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a transfer bias applying unit (not shown).

  The transfer roller 8 is brought into contact with or separated from the photosensitive drum 2. Specifically, the transfer roller 8 is configured to be movable between a contact position where the transfer roller 8 is in contact with the photosensitive drum 2 and a spaced position where the transfer roller 8 is separated from the photosensitive drum 2. Specifically, the transfer roller 8 is moved to the contact position when the toner image developed on the photosensitive drum 2 is transferred to the paper T, and is moved to the separation position in other cases.

  A sheet T conveyed on the conveyance path L is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The static eliminator 12 is disposed to face the surface of the photosensitive drum 2. The static eliminator 12 irradiates the surface of the photosensitive drum 2 with light, thereby neutralizing the surface of the photosensitive drum 2 after the transfer is performed (removing the electric charge).

  The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning unit 11 removes toner and deposits remaining on the surface of the photosensitive drum 2, and transports the removed toner and the like to a predetermined recovery mechanism for recovery.

The fixing device 9 melts the toner constituting the toner image transferred onto the paper T and fixes it on the paper T. The fixing device 9 includes a heating roller 9a as a first rotating body heated by a heater 91 (described later), a pressure roller 9b as a second rotating body pressed against the heating roller 9a, and a separation claw 92 (described later). And comprising. The heating roller 9a and the pressure roller 9b convey the paper T onto which the toner image has been transferred so as to sandwich the paper T. When the paper T is conveyed so as to be sandwiched between the heating roller 9a and the pressure roller 9b, the toner transferred onto the paper T is melted and fixed on the paper T.
Details of the configuration of the fixing device 9 will be described later.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. The paper feed cassette 52 is configured to be drawable in the horizontal direction from the front side (right side in FIG. 1) of the apparatus main body M. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 arranged at the paper feed side end of the paper feed cassette 52 (the right end in FIG. 1). The cassette paper feed unit 51 includes a double feed prevention mechanism including a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T to the transport path L one by one. Prepare.

  A manual paper feed unit 64 is provided on the right side surface (right side in FIG. 1) of the apparatus main body M. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The manual paper feed unit 64 feeds the paper T placed on the open manual feed tray 65 to the manual feed path La.

  The conveyance path L for conveying the paper T is a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer nip N, a second conveyance path L2 from the transfer nip N to the fixing device 9, and a discharge from the fixing device 9. A third conveyance path L3 to the section 50, a manual conveyance path La that joins the paper supplied from the manual sheet feeding unit 64 to the first conveyance path L1, and a third conveyance path L3 from the upstream side to the downstream side. And a return transport path Lb that reverses the paper and returns it to the first transport path L1.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the return transport path Lb branches from the third transport path L3, and includes a first roller pair 54a and a second roller pair 54b. One roller of the first roller pair 54a and one roller of the second roller pair 54b are combined.

  A sensor (not shown) for detecting the paper T and a skew (oblique feeding) of the paper T are provided in the middle of the first transport path L1 (specifically, between the second junction P2 and the transfer roller 8). A pair of registration rollers 80 for adjusting the timing of the (paper) correction and the toner image is arranged. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the paper T (upstream in the transport direction). The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

  A sheet detection sensor S is also arranged in the middle of the second transport path L2. This sensor S is arranged immediately before the fixing device 9 in the transport direction of the paper T (upstream side in the transport direction).

The return conveyance path Lb is a conveyance path that is provided so that the opposite surface (non-printing surface) to the surface that has already been printed faces the photosensitive drum 2 when performing duplex printing on the paper T.
According to the return conveyance path Lb, the sheet T conveyed from the first branching section Q1 to the paper discharge section 50 side by the first roller pair 54a is reversed and returned to the first conveyance path L1 by the second roller pair 54b. , And can be conveyed to the upstream side of the registration roller pair 80 disposed on the upstream side of the transfer roller 8. A predetermined toner image is transferred onto the non-printing surface by the photosensitive drum 2 on the paper T that has been turned upside down by the return conveyance path Lb.

  A paper discharge unit 50 is formed at the end of the third transport path L3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side surface of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The paper discharge unit 50 discharges the paper T conveyed through the conveyance path L3 to the outside of the apparatus main body M by the third roller pair 53.

  On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T formed with a predetermined toner image and discharged from the paper discharge unit 50 are stacked and stacked.

Next, details of the fixing device 9 of the present embodiment will be described with reference to FIGS.
FIG. 2 is a diagram illustrating the configuration and functions of the fixing device 9 according to the first embodiment, and is a view of the fixing device 9 with the separation claw 92 positioned at the contact position R1 as viewed from the axial direction of the heating roller 9a. is there. FIG. 3 is a diagram illustrating the fixing device 9 in a state where the separation claw 92 is located at the separation position R2.

  As shown in FIGS. 2 and 3, the fixing device 9 of this embodiment includes a heating roller 9 a as a first rotating body, a pressure roller 9 b as a second rotating body, a heater 91, and a separation claw 92. The separation claw driving unit 93 and the control unit 94 are provided.

  The heating roller 9a is configured to be rotatable about a rotation axis extending in a direction orthogonal to the conveyance direction D1 of the paper T. For example, the heating roller 9a is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polyethylene) having a thickness of about 30 μm on the outer peripheral surface of a metal roller such as Al (aluminum) having a thickness of about 1 mm. It is configured by providing a release layer made of a heat-resistant film made of a fluororesin such as (tetrafluoroethylene).

  As shown in FIGS. 2 and 3, the pressure roller 9b is disposed such that its outer peripheral surface comes into contact with the outer peripheral surface of the heating roller 9a. The pressure roller 9b is configured to be rotatable about a rotation axis parallel to the axis of the heating roller 9a. More specifically, the pressure roller 9b is provided with an elastic layer made of silicon rubber or the like having a thickness of about 5.5 mm on the outer peripheral surface of a core metal such as aluminum or iron having a diameter of about 14 mm. Is provided with a release layer made of a fluororesin such as PFA or PTFE having a thickness of about 50 μm.

  As shown in FIGS. 2 and 3, a roller shaft 901 that serves as a rotation shaft protrudes from both ends of the pressure roller 9 b in the axial direction. The roller shaft 901 is rotatably supported by a case of the apparatus main body M in the printer 1 and other members (not shown).

  An electric motor (not shown) that rotates the heating roller 9a is connected to the heating roller 9a. The heating roller 9a is rotationally driven by an electric motor at a predetermined speed, and the pressure roller 9b contacting the outer peripheral surface of the heating roller 9a is rotated following the rotation of the heating roller 9a. Thus, a fixing nip N9 is formed between the heating roller 9a and the pressure roller 9b to sandwich the paper T on which the toner image is transferred.

  As shown in FIGS. 2 and 3, the heater 91 heats the fixing nip N9 that is a contact portion between the heating roller 9a and the pressure roller 9b. Specifically, the heater 91 heats the inner peripheral surface of the heating roller 9a, the heat is transferred to the outer peripheral surface of the heating roller 9a, and the heat is further transferred to the fixing nip N9. The heater 91 is composed of, for example, a halogen heater or a ceramic heater. The heater 91 is disposed substantially at the center of rotation of the heating roller 9a.

  In this way, the heater 91 applies heat to the paper T that is nipped and conveyed between the heating roller 9a and the pressure roller 9b via the heating roller 9a. As a result, the paper T on which the toner image has been transferred is conveyed to the fixing nip N9 and passed therethrough, whereby the toner on the paper T is melted and fixed on the paper T.

  As shown in FIGS. 2 and 3, the separation claw 92 is disposed on the downstream side of the fixing nip N9 in the transport direction D1 of the paper T. The separation claw 92 is configured to be able to change a contact position R1 where the tip side is in contact with the surface of the heating roller 9a and a separation position R2 where the tip side is separated from the surface of the heating roller 9a. A plurality of the separation claws 92 are arranged at predetermined intervals in the axial direction of the heating roller 9a. Specifically, a pair of separation claws 92 are arranged at positions corresponding to the vicinity of both ends in the width direction (direction orthogonal to the conveyance direction D1) of each of the plurality of sizes of paper T to be conveyed. That is, in the image forming apparatus 1 corresponding to three types of paper having different widths, three pairs (six) of the separation claws 92 are provided.

The separation claw 92 has a shape in which the thickness gradually decreases from the proximal end side toward the distal end side. The base end side of the separation claw 92 is connected to a housing (not shown) that accommodates the heating roller 9a and the pressure roller 9b via a shaft member 902 that extends along the axial direction of the heating roller 9a.
The separation claw drive unit 93 is connected to the shaft member 902. The separation claw drive unit 93 is configured by, for example, an electric motor.
The separation claw 92 can change the contact position R <b> 1 and the separation position R <b> 2 when the shaft member 902 is rotated by the separation claw driving unit 93.

As shown in FIG. 2, the control unit 94 includes a count unit 941, a count determination unit 942, a paper determination unit 943 as a transfer material determination unit, and a separation claw control unit 944.
The counting unit 941 pressurizes with the heating roller 9a based on the detection result of the sensor S for detecting paper (for example, the sensor S arranged on the upstream side of the heating roller 9a and the pressure roller 9b in the second conveyance path L2). The number of sheets T conveyed between the rollers 9b is counted.

  The count determination unit 942 determines whether a predetermined plurality of sheets have been counted by the count unit 941. For example, the count determination unit 942 determines whether the number of sheets conveyed by the count unit 941 has reached 100.

  The paper determination unit 943 determines whether or not the paper T is arranged in the fixing nip N9. Specifically, the sheet determination unit 943 determines that the sheet T is not disposed in the fixing nip N9 when the sheet T is not detected by the sensor S.

The separation claw control unit 944 is a case where the count determination unit 942 determines that the predetermined number of sheets has been counted, and the paper determination unit 943 determines that the paper T is not disposed in the fixing nip N9. Then, the separation claw driving unit 93 is driven to change the position of the separation claw 92 from the contact position R1 to the separation position R2 (see FIG. 3).
Further, the separation claw control unit 944 returns the separation claw 92 to the contact position R1 again after a predetermined time has elapsed (for example, one second) after the separation claw 92 is positioned at the separation position R2.

Next, the operation of the fixing device 9 of the first embodiment will be described with reference to FIGS.
In the printer 1 of the first embodiment, when the power of the printer 1 is turned on, the charging unit 10, the laser scanner unit 4, the developing device 16, the transfer roller 8, the printer control unit (not shown), and the fixing unit from the power source unit. Electric power is supplied to each of the devices 9, and the charging unit 10, the laser scanner unit 4, the developing device 16, the transfer roller 8, and the fixing device 9 are controlled by a control signal from the printer control unit. Then, the charging process, the exposure process, the development process, the transfer process, and the fixing process are sequentially performed.

  Specifically, in the printer 1 of the present embodiment, the paper T sent out from the registration roller pair 80 passes through the first conveyance path L1 to the transfer nip N between the photosensitive drum 2 and the transfer roller 8. Be transported. When the paper T is conveyed toward the photosensitive drum 2 as described above, first, the charging unit 10 charges the entire surface of the photosensitive drum 2 in the charging process, and the laser scanner unit 4 performs laser irradiation in the exposure process. Laser light is irradiated from a light source (not shown) toward the photosensitive drum 2 to form an electrostatic latent image on the surface of the photosensitive drum 2 irradiated with the laser light.

  Next, the developing device 16 supplies the toner charged in the developing process to the photosensitive drum 2 by the developing roller 17, thereby attaching the toner to the electrostatic latent image formed on the surface of the photosensitive drum 2, Develop the toner image. Subsequently, the transfer roller 8 transfers the toner image attached to the surface of the photoconductive drum 2 onto the paper T that passes between the photoconductive drum 2 and the transfer roller 8 in the transfer process.

  Then, the paper T on which the toner image is transferred in the transfer step is conveyed toward the fixing device 9 through the second conveying path L2, and the fixing nip between the heating roller 9a and the pressure roller 9b in the fixing device 9 is transferred. It is conveyed to N9.

  Also, by turning on the control signal output from the printer control unit to the heater 91, the supply of electric power from the power source unit to the heater 91 is started, the heater 91 generates heat, and the heating roller 9a is heated by the heater 91. Heating is started. At the same time, by turning on a control signal output from the printer control unit to an electric motor (not shown) that drives the heating roller 9a, supply of electric power from the power supply unit to the electric motor is started, and the heating roller 9a is started. Is rotated, and the pressure roller 9b is driven and rotated in accordance with the rotation of the heating roller 9a.

  As a result, the fixing nip N9 and the outer peripheral surface of the pressure roller 9b are also heated as described above. Then, the fixing device 9 applies the toner attached to the paper T passing through the fixing nip N9 between the heating roller 9a and the pressure roller 9b in the fixing process from the heater 91 to the toner through the heating roller 9a. The toner image is fixed on the paper T by being melted by heat and applying pressure to the paper T by the pressure roller 9b.

  The paper T on which the toner image has been fixed by passing through the fixing nip N9 is conveyed in a state of being attached to the heating roller 9a by the adhesive force of the melted toner (see FIG. 2). Here, when the separation claw 92 is positioned at the contact position R <b> 1, the leading end side of the paper T conveyed while attached to the heating roller 9 a comes into contact with the leading end side of the separation claw 92 and is peeled off. Thus, the paper T is transported along the third transport path L3 (see FIG. 1).

  In the state where the separation claw 92 is positioned at the contact position R1, the fixing nip is located on the distal end side of the separation claw 92 (more specifically, on the downstream side in the rotation direction of the heating roller 9a on the distal end side of the separation claw 92). During the fixing in N9, the toner component TN remaining on the surface of the heating roller 9a is accumulated (see FIG. 2). Here, when the position of the separation claw 92 is moved from the contact position R <b> 1 to the separation position R <b> 2, the toner component TN accumulated on the leading end side of the separation claw 92 is separated from the separation claw 92. The toner component TN separated from the separation claw 92 is conveyed along with the rotation of the heating roller 9a while adhering to the surface of the heating roller 9a (see FIG. 3), and is fixed on the paper T at the fixing nip N9. Here, when the amount of the deposited toner component TN is small, an image defect is not noticeable even when the deposited toner component TN is fixed on the paper T. However, when a large amount of toner component TN is accumulated, An image defect occurs on the paper T on which a large amount of the toner component TN is fixed.

Next, a specific operation of the fixing device 9 according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the fixing device 9 of the first embodiment.
In step S1, printing by the printer 1 is started. In this state, the separation claw 92 is located at the contact position R1.

  In step S2, the control unit 94 determines whether or not a plurality of sheets T are continuously printed. If the control unit 94 determines that a plurality of sheets T are to be printed continuously, the process proceeds to step S3. If the controller 94 determines that the plurality of sheets T are not printed continuously, the process returns to step S1.

  In step S3, the counting unit 941 counts the number of sheets T conveyed between the heating roller 9a and the pressure roller 9b, and proceeds to step S4.

  In step S4, the count determination unit 942 determines whether a predetermined plurality of sheets (for example, 100 sheets) have been counted by the counting unit 941. If it is determined by the counting unit 941 that a predetermined number of sheets have been counted, the process proceeds to step S5. If the counting unit 941 determines that a predetermined number of sheets has not been counted, the process returns to step S3.

  In step S5, the paper determination unit 943 determines whether or not the paper T is disposed in the fixing nip N9. If the paper determination unit 943 determines that the paper T is not disposed in the fixing nip N9, the process proceeds to step S6. If the paper determination unit 943 determines that the paper T is disposed in the fixing nip N9, step S5 is repeated.

  In step S6, the separation claw control unit 944 drives the separation claw driving unit 93 to change the position of the separation claw 92 from the contact position R1 to the separation position R2. Further, the separation claw controller 944 returns the separation claw 92 to the contact position R1 again after a predetermined time has elapsed (for example, one second) after the separation claw 92 is positioned at the separation position R2, and the process proceeds to step S7. move on.

  In step S7, the control unit 94 resets the count of the count unit 941 and returns to step S2.

The fixing device 9 according to the first embodiment described above has the following effects.
As described above, when printing a plurality of sheets T with the separation claw 92 positioned at the contact position R1, the leading end of the separation claw 92 is heated when the toner image is fixed in the fixing nip N9. The toner component TN remaining on the surface of the roller 9a gradually accumulates. The amount of the toner component TN deposited on the leading end side of the separation claw 92 increases as the number of sheets T on which the toner image is fixed in the fixing nip N9 increases. When a large amount of toner component TN deposited on the front end side of the separation claw 92 is separated from the separation claw 92, this large amount of toner component TN adheres to the surface of the heating roller 9a and rotates with the heating roller 9a. It is conveyed and fixed on the paper T at the fixing nip N9. As a result, an image defect occurs on the paper T on which a large amount of the toner component TN is fixed.
Therefore, when the predetermined number of sheets is counted by the count determination unit 942, the separation claw control unit 944 changes the position of the separation claw 92 from the contact position R1 to the separation position R2. Accordingly, the toner component deposited on the tip side of the separation claw 92 is changed by changing the separation claw 92 from the contact position R1 to the separation position R2 before the toner component TN deposited on the tip side of the separation claw 92 becomes large. TN can be separated from the separation claw 92. Therefore, even if the toner component TN separated from the separation claw 92 is fixed on the paper T, image defects are unlikely to occur.
Further, the position of the separation claw 92 is not changed every time one sheet T is conveyed, and the position of the separation claw 92 is changed when a predetermined number of sheets of paper T are conveyed. Thereby, the contact frequency of the separation claw 92 and the surface of the heating roller 9a resulting from the change of the position of the separation claw 92 from the separation position R2 to the contact position R1 can be reduced. Therefore, the separation claw 92 and the heating roller 9a are not easily damaged.

  In addition, when the paper determination unit 943 determines that the paper T is not disposed in the fixing nip N9, the separation claw control unit 944 changes the position of the separation claw 92 from the contact position R1 to the separation position R2. Thereby, the position of the separation claw 92 is changed from the contact position R1 to the separation position R2 in a state where the paper T is not conveyed by the heating roller 9a and the pressure roller 9b. Therefore, it is possible to prevent the paper T from being caught in the heating roller 9a due to the separation claw 92 being located at the separation position R2.

  Next, a fixing device 9A according to a second embodiment of the present invention will be described with reference to FIGS. In the following description of the embodiments, the same constituent elements are denoted by the same reference numerals, and the description thereof is omitted or simplified. FIG. 5 is a functional block diagram illustrating functions of the fixing device 9A according to the second embodiment.

  The fixing device 9A of the second embodiment is different from the first embodiment in the configuration of the control unit 94A. The control unit 94A of the second embodiment includes a paper determination unit 943, a printing rate measurement unit 945, a printing rate integration unit 946, an integration value determination unit 947, and a separation claw control unit 944A.

The printing rate measuring unit 945 measures the printing rate for each sheet T based on the toner image data obtained from the printer control unit 100. For example, the printing rate measuring unit 945 measures the printing rate of one sheet from the area of the entire region of one sheet T and the area of the toner image printed on the sheet T.
Further, the printing rate measuring unit 945 may measure the printing rate in one of a plurality of regions formed by dividing the paper T in a direction intersecting the transport direction D1.
In this case, it is preferable that the printing rate measurement unit 945 measures the printing rate of the region of the paper T that is sandwiched by the portion of the heating roller 9a that contacts the separation claw 92 among the plurality of regions.

The printing rate integration unit 946 integrates the printing rate measured by the printing rate measurement unit 945.
In the second embodiment, the printing rate integration unit 946 multiplies the printing rate of each sheet measured by the printing rate measurement unit 945 by a predetermined coefficient corresponding to the length of the sheet T in the transport direction D1. And the calculated values are integrated.
Here, for example, when the coefficient when the A4 size paper T is conveyed with the width direction as the conveyance direction D1 is 1, for example, the coefficient when the A3 size paper T is conveyed with the longitudinal direction as the conveyance direction D1. Becomes 2. For this reason, when the A3 size paper T is transported next after the A4 size paper T has been transported and the print rate of each sheet is 5%, the print rate integration unit 946 performs integration. The value to be obtained is 5 (%) × 1 + 5 (%) × 2 = 15. As described above, when a sheet T having a different size is transported by calculating and integrating a value obtained by multiplying the printing rate of one sheet by a predetermined coefficient corresponding to the length of the sheet T in the transport direction D1. Even in the case, the accurate printing rate can be accumulated.
Note that the printing rate integration unit 946, when the printing rate measurement unit 945 measures the printing rate of one area among a plurality of areas formed by dividing the paper T, the printing rate of this one area. Is accumulated.

The integrated value determination unit 947 determines whether the integrated value integrated by the printing rate integration unit 946 has reached a predetermined value.
The paper determination unit 943 determines whether or not the paper T is arranged in the fixing nip N9. Specifically, the sheet determination unit 943 determines that the sheet T is not disposed in the fixing nip N9 when the sheet T is not detected by the sensor S.

The separation claw control unit 944A is a case where it is determined that the integrated value integrated by the integrated value determination unit 947 has reached a predetermined value, and the paper T is disposed in the fixing nip N9 by the paper determination unit 943. If it is determined that it is not, the separation claw driving unit 93 is driven to change the position of the separation claw 92 from the contact position R1 to the separation position R2.
Further, the separation claw control unit 944 returns the separation claw 92 to the contact position R1 again after a predetermined time has elapsed (for example, one second) after the separation claw 92 is positioned at the separation position R2.

Next, a specific operation of the fixing device 9A according to the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the fixing device 9A of the second embodiment.
In step S11, printing by the printer 1 is started. In this state, the separation claw 92 is located at the contact position R1.

  In step S12, the control unit 94A determines whether or not a plurality of sheets T are continuously printed. If it is determined by the control unit 94A that a plurality of sheets T are continuously printed, the process proceeds to step S13. If the controller 94A determines that the plurality of sheets T are not printed continuously, the process returns to step S11.

  In step S13, the printing rate measuring unit 945 measures the printing rate for each sheet T based on the toner image data obtained from the printer control unit 100, and proceeds to step S14. Specifically, the print rate measuring unit 945 measures the print rate in one of a plurality of regions formed by partitioning the paper T in a direction intersecting the transport direction D1. Here, the printing rate measuring unit 945 measures the printing rate of the region of the paper T that is sandwiched by the portion of the heating roller 9a that contacts the separation claw 92 among the plurality of regions.

  In step S14, the printing rate integration unit 946 integrates the printing rate measured by the printing rate measurement unit 945 and proceeds to step S15. Specifically, the printing rate integration unit 946 multiplies the printing rate for each sheet measured by the printing rate measurement unit 945 by a predetermined coefficient corresponding to the length in the transport direction D1 of the sheet T. Calculate and integrate the calculated values.

  In step S15, the integrated value determining unit 947 determines whether the integrated value integrated by the printing rate integrating unit 946 has reached a predetermined value. If the integrated value determining unit 947 determines that the integrated value integrated by the printing rate integrating unit 946 has reached a predetermined value, the process proceeds to step S16. If the integrated value determining unit 947 determines that the integrated value integrated by the printing rate integrating unit 946 has not reached the predetermined value, the process returns to step S13.

  In step S <b> 16, the paper determination unit 943 determines whether or not the paper T is arranged in the fixing nip N <b> 9. If the paper determination unit 943 determines that the paper T is not disposed in the fixing nip N9, the process proceeds to step S17. If the paper determination unit 943 determines that the paper T is disposed in the fixing nip N9, step S16 is repeated.

  In step S17, the separation claw control unit 944A drives the separation claw driving unit 93 to change the position of the separation claw 92 from the contact position R1 to the separation position R2. Further, the separation claw control unit 944A returns the separation claw 92 to the contact position R1 again after a predetermined time (for example, one second) after the separation claw 92 is positioned at the separation position R2, and the process returns to step S18. move on.

  In step S18, the control unit 94A resets the count of the printing rate integration unit 946 and returns to step S12.

According to the fixing device 9A of the second embodiment described above, the following effects are obtained.
In the fixing device 9A, the amount of the toner component TN adhering to the surface of the heating roller 9a increases as the printing rate increases. When the amount of the toner component TN adhering to the surface of the heating roller 9a increases, the amount of the toner component TN deposited on the front end side of the separation claw 92 also increases.
Therefore, when the integrated value determination unit 947 determines that the integrated value integrated by the printing rate integration unit 946 has reached a predetermined value, the separation claw control unit 944 moves the position of the separation claw 92 from the contact position R1. It was changed to the separation position R2. Accordingly, the toner component deposited on the tip side of the separation claw 92 is changed by changing the separation claw 92 from the contact position R1 to the separation position R2 before the toner component TN deposited on the tip side of the separation claw 92 becomes large. TN can be separated from the separation claw 92. Therefore, even if the toner component TN separated from the separation claw 92 is fixed on the paper T, image defects are unlikely to occur.
Further, the position of the separation claw 92 is not changed every time one sheet T is conveyed, and the position of the separation claw 92 is changed when a predetermined number of sheets of paper T are conveyed. Thereby, the contact frequency of the separation claw 92 and the surface of the heating roller 9a resulting from the change of the position of the separation claw 92 from the separation position R2 to the contact position R1 can be reduced. Therefore, the separation claw 92 and the heating roller 9a are not easily damaged.

  In addition, when the paper determination unit 943 determines that the paper T is not disposed in the fixing nip N9, the separation claw control unit 944 changes the position of the separation claw 92 from the contact position R1 to the separation position R2. Thereby, the position of the separation claw 92 is changed from the contact position R1 to the separation position R2 in a state where the paper T is not conveyed by the heating roller 9a and the pressure roller 9b. Therefore, it is possible to prevent the paper T from being caught in the heating roller 9a due to the separation claw 92 being located at the separation position R2.

  Further, the printing rate integration unit 946 calculates a value obtained by multiplying the printing rate for each sheet by a predetermined coefficient corresponding to the length in the transport direction D1 of the sheet T, and integrates the calculated value. I let you. As a result, even when sheets T of different sizes have been conveyed, accurate printing rate accumulation can be performed. Therefore, since the amount of the toner component TN deposited on the front end side of the separation claw 92 can be accurately predicted, the effect of preventing image defects can be improved.

  Further, the printing rate measuring unit 945 was caused to measure the printing rate in one of a plurality of regions formed by dividing the paper T in the direction intersecting the transport direction D1. Thereby, the printing rate can be measured more efficiently.

  On the leading end side of the separation claw 92, the toner component TN attached to the portion of the surface of the heating roller 9a that contacts the separation claw 92 is scraped off and accumulated by the separation claw 92. Therefore, among the plurality of areas formed by dividing the sheet T in the direction intersecting the transport direction D1 in the printing rate measuring unit 945, the area of the sheet T that is sandwiched by the portion where the separation claw 92 contacts the heating roller 9a. The printing rate was measured. As a result, the amount of the toner component TN that accumulates on the leading end side of the separation claw 92 can be predicted more accurately, so that the effect of preventing image defects can be further improved.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the second embodiment, the printing rate measuring unit 945 is caused to measure the printing rate for each sheet of paper T, but the present invention is not limited to this. In other words, the printing rate measuring unit may continuously measure the printing rate of the paper in a region divided by a predetermined length (for example, 1 cm) in the transport direction. In this case, the printing rate integration unit integrates the printing rate continuously measured by the printing rate measurement unit. Even with this method, it is possible to accurately calculate the print rate regardless of the size of the conveyed paper.

In the first embodiment and the second embodiment, the heating roller 9a (first rotating body) is driven to rotate and the pressure roller 9b (second rotating body) is driven to rotate. Instead, the second rotating body may be driven to rotate, and the first rotating body may be driven to rotate.
Further, although the heating roller 9a is used as the first rotating body, a heating rotating body made of a flexible belt formed in an endless manner can be used instead. Similarly, although the pressure roller 9b is used as the second rotating body, a pressure rotating body formed of an endless flexible belt can be used instead.
The fixing device 1 of the present invention may be unitized and configured to be detachable from the apparatus main body of the image forming apparatus, or may be configured integrally with the apparatus main body of the image forming apparatus.

The type of the image forming apparatus according to the present invention is not particularly limited, and may be a copier, a printer, a facsimile, or a complex machine of these.
The sheet-shaped transfer material is not limited to paper, and may be a film sheet, for example.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum (image carrier), 16 ... Developing device, 9 ... Fixing device, 9a ... Heating roller (first rotating body), 9b ... Addition Pressure roller (second rotator), 91... Heater, 92... Separation claw, 941... Count unit, 942.

Claims (8)

A fixing device that melts toner constituting a toner image transferred to a sheet-like transfer material and fixes the toner image on the transfer material,
A first rotating body rotatable in a predetermined direction;
A heater that is disposed inside the first rotating body and that heats the first rotating body from the inside;
A fixing nip is formed between the first rotating body and the first rotating body, and a rotatable second transporting medium that sandwiches and conveys the material to be transferred with the first rotating body. Two rotating bodies,
A contact position where the front end side is in contact with the surface of the first rotating body and the front end side is separated from the surface of the first rotating body. Position and changeable separation nails,
A counting unit that counts the number of transfer materials conveyed between the first rotating body and the second rotating body;
A count determination unit that determines whether a predetermined plurality of sheets have been counted in the counting unit;
A separation claw control unit configured to change the position of the separation claw from a contact position to a separation position when it is determined that the predetermined plurality of sheets have been counted in the count determination unit; A transfer material determination unit for determining whether the transfer material is arranged in the fixing nip;
The separation claw control unit changes the position of the separation claw from a contact position to a separation position when the transfer material determination unit determines that the transfer material is not disposed in the fixing nip. The fixing device according to 1. A fixing device that melts toner constituting a toner image transferred to a sheet-like transfer material and fixes the toner image on the transfer material,
A first rotating body rotatable in a predetermined direction;
A heater that is disposed inside the first rotating body and that heats the first rotating body from the inside;
A fixing nip is formed between the first rotating body and the first rotating body, and a rotatable second transporting medium that sandwiches and conveys the material to be transferred with the first rotating body. Two rotating bodies,
A contact position where the front end side is in contact with the surface of the first rotating body and the front end side is separated from the surface of the first rotating body. Position and changeable separation nails,
A printing rate measuring unit for measuring a printing rate of a toner image on the transfer material;
A printing rate integration unit that integrates the printing rate measured by the printing rate measurement unit;
An integrated value determination unit that determines whether the integrated value integrated by the printing rate integration unit has reached a predetermined value by the printing rate integration unit;
A separation claw control unit configured to change the position of the separation claw from a contact position to a separation position when it is determined that the integration value integrated by the integration value determination unit has reached a predetermined value. A transfer material determination unit for determining whether the transfer material is arranged in the fixing nip;
The separation claw control unit changes the position of the separation claw from a contact position to a separation position when the transfer material determination unit determines that the transfer material is not disposed in the fixing nip. The fixing device according to 3. The printing rate measuring unit measures a printing rate for each piece of the transfer material,
The printing rate integration unit calculates a value obtained by multiplying the printing rate measured by the printing rate measurement unit by a predetermined coefficient corresponding to the length of the transfer material in the transport direction and integrates the calculated value. The fixing device according to claim 3 or 4. The printing rate measuring unit measures a printing rate in one of a plurality of regions formed by dividing the transfer material in a direction intersecting the transport direction;
The fixing device according to claim 3, wherein the printing rate integration unit integrates the printing rate in the one area measured by the printing rate measurement unit.   The fixing according to claim 6, wherein the printing rate measuring unit measures a printing rate of the transfer material in a region sandwiched by a portion of the first rotating body that is in contact with the separation claw among the plurality of regions. apparatus. An image carrier on which an electrostatic latent image is formed on the surface;
A developing device for developing a toner image on the electrostatic latent image formed on the image carrier;
A transfer unit for transferring the toner image formed on the image carrier to a sheet-like transfer material;
An image forming apparatus comprising: the fixing device according to claim 1.

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