JP6098753B1 - Fixing apparatus and image forming apparatus - Google Patents

Abstract

A fixing device that enables movement of a shielding member in conjunction with a rotation / stop operation of a heating belt is provided as compared with a case where a driving source for moving the shielding member is separately provided. An endless heating belt that is rotated by being heated by a heating source, a pressure member that is in pressure contact with the heating belt, and a frictional force that acts between the heating belt when the heating belt is rotated. A shielding member that moves to a retracted position that enables heating by the heating source or a shielding position that shields heating from the heating source. [Selection] Figure 3

Description

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

  2. Description of the Related Art Conventionally, there is a fixing device configured to perform a fixing process by heating an endless belt with a heating source and heating a recording medium on which a toner image is transferred by the heated endless belt. In such a fixing device, for example, Patent Document 1 and Patent can be used as a technique that can solve the problems associated with the unintentional heating of the same portion of the endless belt by a heating source when the endless belt stops rotating. The one disclosed in Document 2 has already been proposed.

  Patent Document 1 is a fixing device that fixes a toner image on a recording material. The fixing belt is formed in a cylindrical shape extending in a predetermined axial direction and is rotatably supported. A fixing nip is formed between the fixing belt and the fixing belt, and a pressure roller that is rotationally driven in this state, and a pressure applied to the pressure roller. Receiving from the inner peripheral side of the fixing belt and supporting the fixing belt, a heating source provided in the fixing belt for heating the fixing belt from the inner peripheral side, and the shaft in the fixing belt And a shield that shields the support from the heating source and is insulated from the support, and the shield has a cross-sectional shape orthogonal to the axial direction of the fixing belt. Is convex on the heating source side Are those formed.

  Japanese Patent Application Laid-Open No. H11-228688 has a fixing device that includes two rotating bodies that are in contact with each other and a heating source that heats one of the rotating bodies, and the rotating body that is heated by the heating source includes an endless thin belt. The rotating body heating area by the heating source is made variable according to the change in operation of the rotating body.

JP 2010-20248 A JP 2014-56146 A

  The object of the present invention is to enable the movement of the shielding member in conjunction with the rotation / stopping operation of the heating belt as compared with a case where a drive source for moving the shielding member is separately provided.

The invention described in claim 1 is an endless heating belt that is heated and rotated by a heating source;
A pressure member pressed against the heating belt;
A shielding member that moves to a retracted position that enables heating by the heating source or a shielding position that shields heating by the heating source by a frictional force acting between the heating belt and the heating belt;
Is a fixing device.

  The invention described in claim 2 is the fixing device according to claim 1, wherein the shielding member is supported so as to be movable along a moving direction of the heating belt.

According to a third aspect of the present invention, the heating source is disposed so as to heat the heating belt through an opening, and the shielding member opens and closes the opening. It is a fixing device.
According to a fourth aspect of the present invention, the shielding member moves to the retracted position when the heating belt rotates forward, and moves to the shielding position by an urging member when the heating belt stops. The fixing device according to any one of the above.
The invention described in claim 5 is an endless heating belt that is heated and rotated by a heating source;
A pressure member pressed against the heating belt;
When the heating belt is rotated forward, the frictional force acting between the heating belt moves to a retreat position that enables heating by the heating source, and during reverse rotation that is introduced before the heating belt is stopped. A shielding member that moves to a shielding position that shields heating by the heating source by a frictional force acting between the heating belt and the heating belt;
Is a fixing device.
The invention described in claim 6 is the fixing device according to any one of claims 1 to 5, wherein the shielding member is provided in a pressure contact portion where the heating belt and the pressure member are in pressure contact.
A seventh aspect of the present invention is the invention according to any one of the first to sixth aspects, wherein the shielding member has a high friction coefficient sheet having a higher friction coefficient than a material of the shielding member on a surface in contact with the heating belt. It is a fixing device.

The invention described in claim 8 is an image forming unit that forms an image on a recording medium;
Fixing means for fixing an image formed on the recording medium by the image forming unit;
With
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

  According to the first aspect of the present invention, it is possible to move the shielding member in conjunction with the rotation / stopping operation of the heating belt, as compared with a case where a driving source for moving the shielding member is separately provided.

  According to the second aspect of the present invention, the shielding member is supported so as to be movable along the moving direction of the heating belt, and is attached so as to move to the shielding position where the heating by the heating source is shielded by the urging member. Compared with the case where it is not energized, it is possible to suppress the heating belt from being damaged by the heat from the heating source with a simple configuration.

According to the invention described in claim 3, the shielding member reliably suppresses the heating belt from being damaged by the heat from the heating source, as compared with the case where the shielding member is not configured to open and close the opening. can do.
According to the invention described in claim 4, when the heating belt is stopped, the shielding member can be reliably moved to the retracted position by the urging force of the urging member.
According to the fifth aspect of the present invention, the shielding member can be moved to the shielding position without using the urging member.
According to the invention described in claim 6, since the shielding member plays a role of the press contact portion forming member during the forward rotation of the heating belt, it becomes possible to improve the fixing property when the fixing member is conveyed. .
According to the seventh aspect of the present invention, it is possible to move the shielding member to the retracted position more reliably when the heating belt rotates.

  According to the eighth aspect of the present invention, the heating belt can be prevented from being damaged by the heat from the heating source, and the life of the fixing device can be extended.

1 is a schematic configuration diagram showing an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied. 1 is a configuration diagram illustrating an image forming unit of an image forming apparatus according to Embodiment 1 of the present invention; 1 is a cross-sectional configuration diagram illustrating a fixing device according to a first embodiment of the present invention. 1 is a perspective configuration diagram illustrating a fixing device according to Embodiment 1 of the present invention. FIG. 1 is a cross-sectional configuration diagram illustrating a main part of a fixing device according to Embodiment 1 of the present invention; FIG. 3 is a cross-sectional configuration diagram illustrating an operation of the fixing device according to the first embodiment of the present invention. FIG. 3 is a perspective configuration diagram illustrating an operation of the fixing device according to the first embodiment of the present invention. It is a cross-sectional block diagram which shows the fixing device based on Embodiment 2 of this invention. It is a cross-sectional block diagram which shows the fixing device based on Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus to which the fixing device according to the first embodiment is applied. FIG. 1 shows an outline of the entire image forming apparatus, and FIG. 2 shows an enlarged main part (image forming apparatus, etc.) in the image forming apparatus.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color printer, for example. The image forming apparatus 1 includes a plurality of image forming apparatuses 10 as an example of an image forming unit that forms a toner image developed with toner constituting the developer 4, and toner images formed by the image forming apparatuses 10. An intermediate transfer device 20 that respectively holds and finally transports it to a secondary transfer position for secondary transfer onto a recording sheet 5 as an example of a recording medium, and a required recording to be supplied to the secondary transfer position of the intermediate transfer device 20 A paper feeding device 50 that accommodates and conveys the paper 5 and a fixing device 40 that fixes the toner image on the recording paper 5 that has been secondarily transferred by the intermediate transfer device 20 are provided. In the figure, reference numeral 1a denotes a main body of the image forming apparatus 1, and the main body 1a is formed of a support structure member, an exterior cover, and the like.

  The image forming device 10 includes four image forming devices 10Y, 10M, 10C, and 10K that respectively form four color toner images exclusively for yellow (Y), magenta (M), cyan (C), and black (K). It is configured. These four image forming devices 10 (Y, M, C, K) are arranged so as to be arranged in a line in an inclined state in the internal space of the main body 1a. The four image forming devices 10 (Y, M, C, and K) are relatively high because the yellow (Y) image forming device 10Y is positioned above the vertical direction, and the black (K) image forming device. 10K exists at a relatively low position.

  The yellow (Y), magenta (M), cyan (C), and black (K) image forming devices 10 (Y, M, C, and K) each include an electrostatic latent image as shown in FIGS. A rotating photosensitive drum 11 is provided as an example of an image holding member for holding an image, and the following devices as examples of toner image forming means are mainly disposed around the photosensitive drum 11. ing. The main devices are a charging device 12 that charges a peripheral surface (image holding surface) on the photosensitive drum 11 on which an image can be formed to a required potential, and image information (on the charged peripheral surface of the photosensitive drum 11). The exposure device 13 as an example of an electrostatic latent image forming unit that irradiates light based on a signal to form an electrostatic latent image (for each color) having a potential difference, and the corresponding color (Y , M, C, K) developing device 14 (Y, M, C, K) which develops with toner of developer 4 to form a toner image, and primary transfer means for transferring each toner image to intermediate transfer device 20 Primary transfer device 15 (Y, M, C, K) as an example, and drum cleaning device that removes adhering matter such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer and cleans it. 16 (Y, M, C, K).

  The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar base material to be grounded. The photosensitive drum 11 is supported so as to rotate in a direction indicated by an arrow A when power is transmitted from a rotation driving device (not shown).

  The charging device 12 includes a contact-type charging roll that is disposed in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. As the charging voltage, when the developing device 14 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied. As the charging device 12, a non-contact type charging device such as a scorotron disposed in a non-contact state on the surface of the photosensitive drum 11 may be used.

  The exposure device 13 forms an electrostatic latent image by irradiating the circumferential surface of the charged photosensitive drum 11 with light configured according to image information input to the image forming apparatus 1. Is. When the latent image is formed, image information (signal) input to the image forming apparatus 1 by any means is transmitted to the exposure apparatus 13.

  The exposure device 13 irradiates the photosensitive drum 11 with light corresponding to image information by LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photosensitive drum 11 to electrostatic latent images. The LED print head that forms As the exposure device 13, a device that deflects and scans laser light configured according to image information along the axial direction of the photosensitive drum 11 may be used.

  As shown in FIG. 2, each of the developing devices 14 (Y, M, C, K) has an interior of a device housing 140 as an example of a developer storage container in which an opening and a storage chamber for the developer 4 are formed. In addition, a developing roller 141 that holds the developer 4 and conveys it to the developing region facing the photosensitive drum 11, and a stirring and conveying member such as two screw augers that convey the developer 4 while passing the developing roller 141 while stirring the developer 4. 142, 143, and a layer thickness regulating member 144 that regulates the amount (layer thickness) of the developer held on the developing roll 141 are arranged. A developing voltage is supplied to the developing device 14 from a power supply device (not shown) between the developing roll 141 and the photosensitive drum 11. Further, the developing roll 141 and the agitating / conveying members 142 and 143 are rotated in a required direction by receiving power from a rotation driving device (not shown). Further, as the four-color developer 4 (Y, M, C, K), a two-component developer containing a nonmagnetic toner and a magnetic carrier is used.

  The primary transfer device 15 (Y, M, C, K) is in contact with the periphery of the photosensitive drum 11 via an intermediate transfer belt 21 and rotates, and a contact type provided with a primary transfer roll to which a primary transfer voltage is supplied. This is a transfer device. As the primary transfer voltage, a DC voltage having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

  As shown in FIG. 2, the drum cleaning device 16 is disposed so as to be in contact with the peripheral surface of the photosensitive drum 11 after the primary transfer with a container-shaped main body 160 that is partially opened at a required pressure. A cleaning plate 161 that removes and removes deposits such as toner, and a sending member 162 such as a screw auger that collects and removes deposits such as toner removed by the cleaning plate 161 and sends them to a collection system (not shown). ing. As the cleaning plate 161, a plate-like member (for example, a blade) made of a material such as rubber is used.

  As shown in FIG. 1, the intermediate transfer device 20 is disposed so as to exist at a position above each image forming device 10 (Y, M, C, K). The intermediate transfer device 20 includes an intermediate transfer belt 21 that rotates in a direction indicated by an arrow B while passing a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), and an intermediate transfer belt 21. Are arranged on the outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support rolls 25 and a plurality of belt support rolls 22 to 26 that hold the toner in a desired state from the inner surface thereof. The secondary transfer device 30 as an example of a secondary transfer member for secondary transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5, and the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30 And a belt cleaning device 27 that removes and adheres toner, paper dust, and other adhering matter.

  As the intermediate transfer belt 21, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. Further, the belt support roll 22 is configured as a drive roll that is rotationally driven by a driving device (not shown), the belt support roll 23 is configured as a surface roll that holds the traveling position of the intermediate transfer belt 21, and the belt support roll 24 is The intermediate transfer belt 21 is configured as a tension applying roll that applies tension, the belt support roll 25 is configured as a secondary transfer backup roll, and the belt support roll 26 is disposed on the back side of the intermediate transfer belt 21 with which the belt cleaning device 27 contacts. It is comprised as a support roll which supports from.

  As shown in FIG. 1, the secondary transfer device 30 is configured to move the intermediate transfer belt 21 at a secondary transfer position that is an outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. The contact type transfer device includes a secondary transfer roll 31 that rotates in contact with a peripheral surface and is supplied with a secondary transfer voltage. The secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20 is supplied with a DC voltage having a polarity opposite or the same as the charging polarity of the toner as a secondary transfer voltage.

  The belt cleaning device 27 is disposed so as to come into contact with the peripheral surface of the intermediate transfer belt 21 after the secondary transfer and the container-like main body 270 partially opened to remove adhered matters such as residual toner. The cleaning plate 271 is cleaned, and the adhering material such as toner removed by the cleaning plate 271 is collected and sent to a collecting system (not shown) and sent out such as a screw auger. As the cleaning plate 271, a plate-like member (for example, a blade) made of a material such as rubber is used.

  The fixing device 40 includes a belt-shaped heating rotator 41 that is heated by a heating source so that the surface temperature is maintained at a required temperature, and a predetermined pressure in a state substantially along the axial direction of the heating rotator 41. A belt-type or drum-type pressurizing rotator 42 rotating in contact with each other is arranged. In the fixing device 40, a contact portion where the heating rotator 41 and the pressing rotator 42 come into contact becomes a fixing processing portion (nip portion) that performs a required fixing process (heating and pressing). The fixing device will be described in detail later.

  The sheet feeding device 50 is disposed so as to be present at a position below the yellow (Y), magenta (M), cyan (C), and black (K) image forming devices 10 (Y, M, C, K). Is done. The paper feeding device 50 is a single (or plural) paper container 51 that accommodates recording papers 5 of a desired size and type, and sends out the recording paper 5 from the paper container 51 one by one. It is mainly composed of devices 52 and 53. The paper container 51 is attached, for example, so that it can be pulled out to the front side (side surface on which the user faces during operation) of the main body 1a, that is, the left side surface in the illustrated example.

  Examples of the recording paper 5 include plain paper, thin paper, and OHP sheet used in electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, the surface of the recording medium 5 is preferably as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. So-called cardboard having a relatively large basis weight can be used.

  Between the paper feeding device 50 and the secondary transfer device 30, a single (or plural) paper conveyance roll pair 54, a conveyance guide 55, and the like that convey the recording paper 5 delivered from the paper supply device 50 to the secondary transfer position. Is provided. The pair of paper transport rolls 54 is configured as, for example, a roll (registration roll) that adjusts the transport timing of the recording paper 5. Further, a conveyance guide for conveying the recording sheet 5 after the secondary transfer fed from the secondary transfer roll 31 of the secondary transfer device 30 to the fixing device 40 between the secondary transfer device 30 and the fixing device 40. 57, 58, etc. are provided. Further, in the portion near the paper discharge port formed in the main body 1 a, the recording paper 5 after fixing sent out from the fixing device 40 is fed to a paper discharge portion 60 provided on the upper portion of the main body 1 a via the conveyance guide 59. A paper discharge roll pair 61 for discharging is disposed.

  Between the fixing device 40 and the paper discharge roll pair 61, a switching gate 62 for switching the paper transport path is provided. The rotation direction of the paper discharge roll pair 61 can be switched between a normal rotation direction (discharge direction) and a reverse rotation direction. When images are formed on both sides of the recording paper 5, after the rear end of the recording paper 5 having an image formed on one side passes through the switching gate 62, the rotation direction of the paper discharge roll pair 61 is set to the normal rotation direction (discharge). Direction) to reverse direction. The recording paper 5 transported in the reverse direction by the paper discharge roll pair 61 is transported to the double-sided transport path 63 formed so as to be substantially along the vertical direction by switching the transport path by the switching gate 62. The duplex conveyance path 63 includes a sheet conveyance roll pair 64 that conveys the recording sheet 5 to the sheet conveyance roll pair 54 with the front and back sides reversed, and conveyance guides 65 to 68.

  In FIG. 1, reference numeral 70 indicates a manual feed tray that is openably and closably provided on the front surface (left side surface in the figure) of the main body 1 a of the image forming apparatus 1. Is provided with a feeding device 71 for feeding the recording sheets 5 stored in the manual feed tray 70 one by one, and a manual feed conveyance path 76 including a plurality of sheet conveyance roll pairs 72 to 74, a conveyance guide 75, and the like. Yes.

  Further, reference numeral 145 (Y, M, C, K) in FIG. 1 is arranged in a plurality along the direction perpendicular to the paper surface, and at least the toner supplied to the corresponding developing device 14 (Y, M, C, K). Each of the toner cartridges containing the developer is shown.

  Further, reference numeral 100 in FIG. 1 indicates a control device that comprehensively controls the operation of the image forming apparatus 1. The control device 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a bus connecting these CPU and ROM, a communication interface, and the like (not shown).

<Operation of Image Forming Apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Here, using the four image forming devices 10 (Y, M, C, K), an operation of forming a full-color image configured by combining toner images of four colors (Y, M, C, K). Will be described.

  When the image forming apparatus 1 receives command information for requesting an image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 30, and the fixing apparatus. 40 etc. starts.

  In each image forming device 10 (Y, M, C, K), each photoconductor drum 11 is first rotated in the direction indicated by an arrow A, and each charging device 12 makes a required surface of each photoconductor drum 11 on the surface. Each is charged to a polarity (negative polarity in the first embodiment) and a potential. Subsequently, the exposure apparatus 13 converts the image information input to the image forming apparatus 1 into each color component (Y, M, C, K) with respect to the surface of the photosensitive drum 11 after charging. The light emitted on the basis of the signal is irradiated to form an electrostatic latent image of each color component composed of a required potential difference on the surface.

  Subsequently, each image forming device 10 (Y, M, C, K) corresponds to the electrostatic latent image of each color component formed on the photosensitive drum 11 charged to a required polarity (minus polarity). Color (Y, M, C, K) toner is supplied from the developing roll 141 and electrostatically attached to perform development. By this development, the electrostatic latent images of the respective color components formed on the respective photosensitive drums 11 are visualized as toner images of four colors (Y, M, C, K) respectively developed with the corresponding color toners. It becomes.

  Subsequently, when each color toner image formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 (Y, M, C, K) are primarily transferred in such a manner that the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 21 that rotates in the direction indicated by the arrow B of the intermediate transfer device 20.

  Further, in each image forming apparatus 10 for which the primary transfer has been completed, the drum cleaning device 16 cleans the surface of the photosensitive drum 11 by removing the adhered material so as to scrape off. Thereby, each image forming apparatus 10 is brought into a state in which the next image forming operation can be performed.

  Subsequently, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and conveyed to the secondary transfer position. On the other hand, the paper feeding device 50 sends out the required recording paper 5 to the paper feeding conveyance path 56 in accordance with the image forming operation. In the paper feed transport path 56, a pair of paper transport rolls 54 as registration rolls feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

  At the secondary transfer position, the secondary transfer roll 31 of the secondary transfer device 30 collectively transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5. Further, in the intermediate transfer device 20 after the secondary transfer is completed, the belt cleaning device 27 removes adhered matters such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer, and cleans it.

  Subsequently, the recording paper 5 on which the toner image has been secondarily transferred is peeled from the intermediate transfer belt 21 and the secondary transfer roll 31 and then conveyed to the fixing device 40 via the conveyance guides 57 and 58. In the fixing device 40, the necessary fixing process (heating and heating) is performed by introducing and passing the recording sheet 5 after the secondary transfer through the contact portion between the rotating rotating body 41 for heating and the rotating body 42 for pressing. Pressure) to fix the unfixed toner image on the recording paper 5. Finally, the recording paper 5 after the fixing is completed is, for example, a paper set on the upper portion of the main body 1a by the paper discharge roll pair 61 in the image forming operation only for forming an image on one side. It is discharged to the discharge unit 60.

  When forming images on both sides of the recording paper 5, the recording paper discharge roller pair 61 does not discharge all of the recording paper 5 having an image formed on one side to the paper discharge unit 60 by the paper discharge roll pair 61. While the trailing edge of the recording paper 5 is held, the rotation direction of the paper discharge roll pair 61 is switched to the reverse direction. The recording paper 5 conveyed in the reverse direction by the paper discharge roll pair 61 passes through the upper part of the switching gate 62, and then passes through the double-sided conveyance path 63 including the paper conveyance roll pair 64, the conveyance guides 65 to 68, and the like. The paper is transported to the pair of paper transport rollers 54 with the front and back sides reversed. The pair of paper transporting rolls 54 feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing, forms an image on the back surface of the recording paper 5, and is installed on the upper portion of the main body 1a by the paper discharge roll pair 61. The paper is discharged to the paper discharge unit 60.

  Through the above operation, the recording paper 5 on which a full color image formed by combining four color toner images is output.

<Configuration of fixing device>
3 and 4 respectively show the fixing device according to the first embodiment. FIG. 3 shows the entire fixing device, and FIG. 4 shows the main part of the fixing device.

  3 and 4, the fixing device 40 includes an endless belt-like heating belt 41, which is an example of a heating rotating body, as a pair of rotating bodies that are pressed against each other to form a nip portion N. An endless belt-like pressure belt 42 which is an example of a pressure rotating body is provided.

  As the heating belt 41, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin as necessary is used. The heating belt 41 is stretched in a state where a required tension is applied between a driving roll 43 that is rotationally driven by a driving device (not shown) and a holding member 44 that is formed in a substantially cylindrical shape. The heating belt 41 is rotationally driven at a fixing speed (for example, 100 m / sec) determined in advance by the drive roll 43 during fixing.

  The drive roll 43 is rotatably supported by a lower frame 46 constituting the casing 45 of the fixing device 40 via a bearing member (not shown). The holding member 44 is attached in a state of being fixed to the lower frame 46 of the housing 45.

  The holding member 44 is formed in a substantially cylindrical shape in cross section by bending a sheet metal or the like. A cylindrical heater 47 is disposed inside the holding member 44 as an example of a heat source. As the heater 47, in order to improve the heating efficiency by the holding member 44, a heater using radiant heat such as a halogen lamp or a nichrome wire heater is desirable. The holding member 44 covers substantially one third of the outer peripheral surface of the heater 47 from the upper end of the heater 47 in a cylindrical shape, and slidably contacts the inner peripheral surface of the heating belt 41 to rotatably support the heating belt 41. A cylindrical portion 441, a flat plate portion 442 extending upward from the side of the heater 47 (right side in the figure), and the upper end of the flat plate portion 442 are bent toward the side (right side in the drawing). And a support plate portion 443 that supports a back surface (lower surface) of a shutter member, which will be described later. Further, the holding member 44 has a slit-like opening 444 for heating the heating belt 41 from the inner surface side by the radiant heat radiated from the heater 47 between the upper end portion of the cylindrical portion 441 and the support plate portion 443. I have. Note that the inner peripheral surface of the cylindrical portion 441 of the holding member 44 is desirably finished in a mirror state in order to improve the heating efficiency by the heater 47. Further, the outer peripheral surface of the cylindrical portion 441 of the holding member 44 is preferably coated with a release agent or the like in order to reduce sliding resistance with the heating belt 41.

  Similar to the heating belt 41, the pressure belt 42 is an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin as necessary. used. The pressure belt 42 is rotatably mounted on the outer periphery of a pressure member 48 for pressing the pressure belt 42 against the heating belt 41.

  The pressure member 48 is formed in a substantially polygonal cross section with a metal, a heat-resistant synthetic resin, or the like. The pressure member 48 is attached in a state of being fixed to the upper frame 500 constituting the casing 45 of the fixing device 40 via an attachment member 49 having a substantially L-shaped cross section. The upper frame 500 of the housing 45 is attached to the lower frame 46 so as to be rotatable about a fulcrum 501. The upper frame 500 of the housing 45 is attached in a direction in which it is pressed against the lower frame 46 by coil springing 502 as an example of an urging member attached between the front end portion of the housing 45 and the front end portion of the lower frame 46. It is energized. Therefore, the pressure belt 42 is pressed against the heating belt 41 stretched between the drive roll 43 and the holding member 44 by the pressure member 48 with a required pressing force.

  Furthermore, in this embodiment, as shown in FIGS. 3 and 4, a shutter member 503 is provided as an example of a shielding member that opens and closes the opening 444 of the holding member 44 and shields the heating by the heater 47. The shutter member 503 is formed wider than the opening width of the opening 444 of the holding member 44 by metal, heat-resistant synthetic resin, or the like, and is longer than the length along the direction intersecting the moving direction of the heating belt 41. It is formed in a flat plate shape. Also, the shutter member 503 has both end portions 531 bent upward along the direction intersecting the moving direction of the pressure belt 42, and the heating belt 41 is moved to the upper frame 500 via the both end portions 531. It is mounted so as to be movable along the direction. Further, the back surface of the shutter member 503 is supported by the support plate portion 443 of the holding member 44. The back surface of the shutter member 503 is supported by the support plate portion 443 of the holding member 44, so that the shutter member 503 is pressed against the back surface of the heating belt 41 with a required pressing force. A frictional force (dynamic frictional force) corresponding to a required pressing force acts between the shutter member 503 and the heating belt 41 when the heating belt 41 rotates. The shutter member 503 is provided in a nip portion (pressure contact portion) where the heating belt 41 and the pressure belt 42 are in pressure contact. Therefore, when the heating belt 41 is rotated forward, the shutter member 503 is supported by the support plate portion 443 of the holding member 44 to form a nip portion where the heating belt 41 and the pressure belt 42 are in pressure contact with each other, as shown in FIG. Since it plays the role of a nip portion forming member, the fixability during conveyance of the recording paper 5 as the member to be fixed is improved. Note that the surface of the shutter member 503 is coated with a material having a high coefficient of friction or a friction material such as silicon, urethane, or felt to increase the friction force generated between the shutter member 503 and the heating belt 41 as necessary. You may comprise so that the member which increases force may be affixed.

  The shutter member 503 has an opening 444 of the holding member 44 by a coil spring 505 as an example of an urging member whose base end is held by a spring holding member 504 provided on the upper frame 500 of the housing 45. It is biased in the closing direction. The shutter member 503 closes the opening 444 of the holding member 44 by the biasing force of the coil spring 505 when the heating belt 41 is stopped. The biasing force of the coil spring 505 is set to be smaller than the frictional force that acts between the shutter member 503 and the heating belt 41 when the heating belt 41 rotates.

<Operation of fixing device>
In the fixing device 40 according to this embodiment, an unfixed toner image is fixed on the recording paper 5 as follows.

  As described above, when the image forming apparatus 1 receives command information for requesting a monochrome image forming operation (printing) from a user interface (not shown), a printer driver, or the like, the image forming apparatus 10, the transfer apparatus 20, the fixing apparatus 40, and the like. Starts.

  As shown in FIGS. 6 and 7, when the fixing device 40 receives command information for requesting an image forming operation (printing), the driving roll 43 is rotationally driven along the direction of the arrow by a driving device (not shown). Energization of the heater 47 is started, and the heating belt 41 is heated by the heater 47.

  At this time, in the fixing device 40, when the heating belt 41 is rotationally driven by the driving roll 43, the shutter member 503 is moved in the same direction as the moving direction of the heating belt 41 due to the frictional force acting between the heating belt 41 and the shutter member 503. The shutter member 503 moves to the retracted position where the opening 444 of the holding member 44 is opened. Therefore, the heating belt 41 can be heated by the heater 47. Note that when the shutter member 503 moves to the retracted position due to the frictional force acting between the shutter member 503 and the heating belt 41, a slip occurs between the shutter member 503 and the retracted position is maintained.

  Thereafter, in the fixing device 40, when the heating belt 41 is heated by the heater 47 to a temperature higher than the required fixing temperature, the recording paper 5 fed from the paper feeding device 50 and having the toner image transferred thereon by the intermediate transfer device 20 is transferred. Then, the unfixed toner image transferred onto the recording paper 5 is subjected to a fixing process by passing through the nip portion N where the heating belt 41 and the pressure belt 42 are in pressure contact.

  Further, in the fixing device 40, when the fixing process for the required recording paper 5 is completed, the energization to the heater 47 is cut off, the heating of the heating belt 41 is stopped, and the temperature of the heating belt 41 falls below the required stoppable temperature. Then, the rotation of the drive roll 43 is finished and the heating belt 41 is stopped.

  By the way, in such a fixing device 40, before the temperature of the heating belt 41 falls below the required stoppable temperature, the drive roll 43 stops due to an unexpected situation such as a power failure, and the rotation of the heating belt 41 stops. There is a case to do. At this time, if the opening 444 of the holding member 44 remains open, the same part of the heating belt 41 stopped by the radiant heat accompanying the remaining heat of the heater 47 may be continuously heated. . In this case, depending on the temperature rise of the heating belt 41, the heating belt 41 may be thermally damaged. Even when the shutter member 503 is configured to be operated by a driving source such as a motor, the driving source does not operate normally in an unexpected situation such as a power failure, and the same problem occurs.

  On the other hand, in the fixing device 40 according to the present embodiment, when the rotation of the heating belt 41 stops, the frictional force accompanying the rotation of the heating belt 41 does not act on the shutter member 503. Therefore, as shown in FIGS. 3 and 4, the shutter member 503 uses any driving source to a closed position where the shutter member 503 is biased by the biasing force of the coil spring 505 to close the opening 444 of the holding member 44. Move without The shutter member 503 closes the opening 444 of the holding member 44 and stops in contact with the end of the cylindrical portion 441 of the holding member 44.

  Therefore, even when the driving roll 43 stops due to an unexpected situation such as a power failure, the opening 444 of the holding member 44 is closed by the shutter member 503 simultaneously with the stop of the rotation of the heating belt 41. Therefore, the situation where the same part of the heating belt 41 is heated by the radiant heat accompanying the residual heat of the heater 47 is avoided, and the heating belt 41 is avoided or suppressed from being thermally damaged.

[Embodiment 2]
FIG. 8 shows a fixing device according to the second embodiment.

  In the fixing device according to the second embodiment, as shown in FIG. 8, the shutter member 503 does not move linearly but is attached to be rotatable along the inner peripheral surface of the holding member 44. The holding member 44 is provided with an opening 444 on the upstream side in the moving direction of the heating belt 41 from the nip portion where the heating belt 41 and the pressure belt 42 are in pressure contact with each other. The holding member 44 is urged so as to close the opening 444 of the holding member 44 by a coil spring (not shown) attached to the rotating shaft or the like.

  In the fixing device according to the second embodiment, the wide opening 444 can be set on the upstream side in the moving direction of the heating belt 41 from the nip portion where the pressure belt 42 presses the heating region of the heating belt 41. The heating belt 41 can be efficiently heated. In the second embodiment, it is not necessary to provide an opening in the upper part of the holding member 44, and a wide nip portion can be stably secured.

[Embodiment 3]
FIG. 9 shows a fixing device according to the third embodiment.

  As shown in FIG. 9, the fixing device according to the third embodiment has a high friction coefficient sheet 503 a having a higher friction coefficient than the material of the shutter member 503 on the surface where the shutter member 503 contacts the heating belt 41. ing. The high friction coefficient sheet 503a is provided on the surface of the shutter member 503 by means such as sticking. As the high friction coefficient sheet 503a, for example, a sheet made of a material having a higher coefficient of friction than the metal or heat resistant resin constituting the shutter member 503 such as silicon or urethane is used.

  As described above, by providing the high friction coefficient sheet 503 a having a higher friction coefficient than the material of the shutter member 503 on the surface where the shutter member 503 contacts the heating belt 41, the shutter member 503 is more surely rotated when the heating belt 41 rotates. It is possible to move to the retracted position.

  In the third embodiment, when the heating belt 41 is stopped, the shutter member 503 is urged by the urging force of the coil spring 505 and moves to the closed position. Therefore, the biasing force of the coil spring 505 is set to a value larger than the frictional force acting between the high friction coefficient sheet 503a of the shutter member 503 and the heating belt 41.

[Embodiment 4]
The fixing device according to the fourth embodiment is configured to move the shutter member 503 to the retracted position by driving the heating belt 41 and to move the shutter member 503 to the shielding position.

  That is, in the fourth embodiment, when the fixing device 40 is stopped, an operation for moving the heating belt 41 by a predetermined distance in the direction opposite to the normal rotation direction is inserted. The shutter member 503 stops after moving to the shielding position during the reverse rotation of the heating belt 41. In the fourth embodiment, the shutter member 503 can be moved to the shielding position without using a biasing member such as the coil spring 505.

  In the above-described embodiment, the full-color image forming apparatus that forms four color toner images of yellow (Y), magenta (M), cyan (C), and black (K) has been described as the image forming apparatus. Of course, the present invention can be similarly applied to the image forming apparatus.

  In the above-described embodiment, the case where a pressure belt is used as the pressure rotator has been described. However, as a pressure rotator, a roll member may be used as a matter of course. In addition, when what consists of a roll-shaped member is used as a rotary body for pressurization, a roll-shaped member functions as a pressurization member.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 1a ... Image forming apparatus main body 11 ... Photosensitive drum 40 ... Fixing device 41 ... Heating belt 42 ... Pressure belt 47 ... Heating source 503 ... Shutter member 505 ... Coil spring

Claims (8)

An endless heating belt heated and rotated by a heating source;
A pressure member pressed against the heating belt;
A shielding member that moves to a retracted position that enables heating by the heating source or a shielding position that shields heating by the heating source by a frictional force acting between the heating belt and the heating belt;
A fixing device provided with   The fixing device according to claim 1, wherein the shielding member is supported so as to be movable along a moving direction of the heating belt.   The fixing device according to claim 1, wherein the heating source is disposed so as to heat the heating belt through an opening, and the shielding member opens and closes the opening.   4. The fixing device according to claim 1, wherein the shielding member is moved to the retracted position when the heating belt is rotated forward, and is moved to the shielding position by an urging member when the heating belt is stopped. 5. An endless heating belt heated and rotated by a heating source;
A pressure member pressed against the heating belt;
When the heating belt is rotated forward, the frictional force acting between the heating belt moves to a retreat position that enables heating by the heating source, and during reverse rotation that is introduced before the heating belt is stopped. A shielding member that moves to a shielding position that shields heating by the heating source by a frictional force acting between the heating belt and the heating belt;
A fixing device provided with   The fixing device according to claim 1, wherein the shielding member is provided in a pressure contact portion where the heating belt and the pressure member are in pressure contact.   The fixing device according to claim 1, wherein the shielding member has a high friction coefficient sheet having a higher friction coefficient than a material of the shielding member on a surface contacting the heating belt. An image forming unit for forming an image on a recording medium;
Fixing means for fixing an image formed on the recording medium by the image forming unit;
With
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

Images