JP2009216800A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of improving the fixability. <P>SOLUTION: A guide section 120 as a guide means for guiding a belt member 72 to a heating roll 70 is disposed at on the upstream side of a block 112 in the running direction of the belt. The guide section 120 is integrally formed with the block 112 and projects toward the heating roll 70. The guide section 120, formed on the block 112, guides the belt member 72 toward the heating roll at the upstream in the running direction of the belt, and is guided to the heating roll side 70, into contact with the heating roll 70, in front of a nip N. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device having a heating roll, and an image forming apparatus such as a printer, a facsimile, and a copying machine having the fixing device.

For example, in Patent Document 1, a pressing member that is disposed on the back surface side of a fixing belt and presses the fixing belt against the fixing roll and forms a contact nip area between the fixing belt and the fixing roll; A pressure member that supports the pressure member so that the downstream pressure has a higher pressure distribution than other parts, and adjusts the pressure distribution and the contact nip width so that the contact nip width becomes narrower as the downstream pressure in the contact nip area increases. A fixing device including a variable mechanism is disclosed.
Further, for example, Patent Document 2 discloses a heat fixing device having a heating unit and a pressing unit including a heat storage member for storing heat from the heating unit.
Further, for example, Patent Document 3 discloses a fixing belt that heats an image on a recording material at a nip portion, a fixing roller that drives the fixing belt, and a fixing belt disposed inside the fixing belt to form a nip portion. A fixing device is disclosed that includes a fixing pad, and a fixing roller is provided with a high friction layer in a contact area with the fixing belt and a low friction layer in a contact area with the fixing pad.

JP 2007-163692 A JP 2002-278333 A JP 2007-003968 A

  The present invention has been made from the above-described background, and an object thereof is to provide a fixing device capable of improving the fixing property.

  In order to achieve the above object, a fixing device according to the present invention includes a rotatable heating roll, a belt member that travels following the rotation of the heating roll, and the opposite side of the heating roll with respect to the belt member. A pressing member that presses the heating roll through the belt member, a support member that supports the pressing member to press the heating roll toward the heating roll, and an upstream side of the pressing member in the belt traveling direction. And guiding means for guiding the belt member closer to the heating roll side.

  Preferably, the belt member is in contact with the heating roll on the upstream side in the belt traveling direction from a position where the pressing member presses the heating roll via the belt member.

  Suitably, the said guide means is comprised from the guide part formed integrally with the said supporting member.

  Suitably, the said guide means is comprised from the guide part formed so that it might protrude in the said heating roll side.

  Suitably, the said guide means is comprised from the guide part formed so that it might not contact | abut on the said heating roll through the said belt member.

  The present invention includes an image forming apparatus having the above-described fixing device.

  According to the present invention, it is possible to provide a fixing device capable of improving the fixability.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 10 according to an embodiment of the present invention.
The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 is provided on the upper portion of the image forming apparatus main body 12. For example, two-stage sheet feeding units 18 and 18 can be arranged below the image forming apparatus main body 12.

Each paper feed unit 18 includes a paper feed unit main body 20 and a paper feed cassette 22 in which a recording medium such as a sheet is stored. The paper feed cassette 22 is slidably attached to the paper feed unit main body 20 and is pulled out in the front direction (right direction in FIG. 1).
In addition, a pickup roll 24 is disposed in the upper part near the rear end of the paper feed cassette 22, and a retard roll 26 and a feed roll 28 are disposed behind the pickup roll 24.

The conveyance path 32 is a recording medium path from the pickup roll 24 to the discharge port 34 of the lowermost sheet feeding unit 18, and this conveyance path 32 is near the back surface (left side surface in FIG. 1) of the image forming apparatus main body 12. In addition, it has a portion formed substantially vertically from the pickup roll 24 of the lowermost sheet feeding unit 18 to the fixing device 36 described later.
A transfer device 42 and an image carrier 44 described later are disposed on the upstream side of the fixing device 36 in the conveyance path 32, and a resist roll 38 is disposed on the upstream side of the transfer device 42 and the image carrier 44.
Further, a discharge roll 40 is disposed in the vicinity of the discharge port 34 of the conveyance path 32.
Accordingly, the recording medium fed from the paper feed cassette 22 of the paper feed unit 18 by the pickup roll 24 is fed by the retard roll 26 and the feed roll 28 and guided to the transport path 32, and is temporarily stopped by the registration roll 38, The developer image is transferred between a transfer device 42 and an image carrier 44 described later, and the transferred developer image is fixed by the fixing device 36 and discharged from the discharge port 34 by the discharge roll 40. It is discharged to the part 16.

However, in the case of duplex printing, it is returned to the reverse path.
That is, the front side of the discharge roll 40 in the conveyance path 32 is divided into two forks, and a switching claw 46 is provided at the divided portion, and a reverse path 48 is formed from the divided portion to the registration roll 38.
The reversing path 48 is provided with transport rolls 50a to 50c. In the case of double-sided printing, the switching claw 46 is switched to the side that opens the reversing path 48, and the discharge roll 40 is in front of the rear end of the recording medium. At this time, the discharge roll 40 is reversed, the recording medium is guided to the reverse path 48, and is discharged from the discharge port 34 to the discharge unit 16 through the registration roll 38, the transfer device 42, the image carrier 44 and the fixing device 36. It is.

The image forming unit 14 is of an electrophotographic type, and is charged by the image carrier 44 made of a photosensitive member, a charging device 56 made of, for example, a charging roll for uniformly charging the image carrier 44, and the charging device 56. An optical writing device 58 for writing a latent image on the image carrier 44 with light, a developing device 60 having a developing roll so as to visualize the latent image of the image carrier 44 formed by the optical writing device 58 with toner, A transfer device 42 composed of, for example, a transfer roll for transferring a toner image by the developing device 60 to a recording medium, a cleaning device 62 for cleaning the toner remaining on the image carrier 44, and a toner on the recording medium transferred by the transfer device 42 The image forming apparatus includes a fixing device 36 that fixes an image on a recording medium.
The optical writing device 58 includes, for example, a scanning type laser exposure device, and forms a latent image on the image carrier 44 across a process cartridge 64 described later.
The optical writing device 58 may use an LED, a surface emitting laser, or the like as another embodiment.

In the process cartridge 64, the image carrier 44, the charging device 56, the developing device 60, and the cleaning device 62 are integrated, and these can be replaced as a unit.
The process cartridge 64 can be removed from the image forming apparatus main body 12 by opening the discharge unit 16.

FIG. 2 shows details of the fixing device 36.
The fixing device 36 includes a heating roll 70, a belt member 72 formed in an endless belt shape, a guide member 74 that rotatably guides the belt member 72, and a belt member 72 that is disposed inside the belt member 72. A pressing unit 76 that presses against the belt 70;
The guide member 74 is disposed at both ends of the belt member 72 and the pressing unit 76, and the pressing unit 76 is supported by the guide member 74.
A sliding sheet (not shown) for reducing friction between the belt member 72 and the pressing unit 76 may be provided between the belt member 72 and the pressing unit 76.

The heating roll 70 includes a cylindrical roll portion 84 and a heater 86 disposed in the roll portion 84.
The roll part 84 is supported by a bearing for heating rolls (not shown) so as to be rotatable, and rotates in the arrow A direction.
The roll portion 84 includes a core 88 made of, for example, iron or aluminum, and a release layer 90 coated or applied to the core 88. The core 88 has an outer shape of, for example, 30 mm and a thickness of, for example, 0.7 mm. It is.
The release layer 90 is made of an insulating material having excellent release properties, such as PFA, and has a film thickness of, for example, 20 μm.

A plurality of (for example, five) peeling claws 92 are in contact with the roll portion 84.
The heater 86 is composed of, for example, two lamps.
A thermostat 94 is provided on the opposite side of the heating roll 70 from the belt member 72 so as to face the heating roll 70.

An inlet chute 96 is provided on the upstream side of the nip N. A sheet S that is a recording medium conveyed in the direction of arrow B is guided to the inlet chute 96, and the leading end of the sheet S is guided to the nip N.
An outlet chute 98 is provided on the downstream side of the nip N.

The belt member 72 is provided between the heating roll 70 and the pressing unit 76, and a nip N is formed when the heating roll 70 and the belt member 72 are pressed and contacted by the pressing unit 76. Thus, the sheet S is conveyed.
The belt member 72 travels in the direction of arrow C following the rotation of the heating roll 70 by being in pressure contact with the heating roll 70.
The belt member 72 is formed of, for example, a synthetic resin such as polyimide in an endless belt shape having a thickness of 75 μm, for example, and a release layer made of PFA or the like is provided on the surface.

The pressing unit 76 includes a pressing pad 110 that is a pressing member that presses the heating roll 70 via the belt member 72, a block 112 that supports the pressing pad 110, and a housing 114 that supports the block 112 and the belt member 72. And a frame 116 that supports the housing 114.
That is, the block 112 which is each component of the pressing unit 76, the housing 114, and the frame 116 cooperate to support the pressing pad 110 so as to press it.
The pressing pad 110 is formed of an elastic body such as LSR (liquid silicone rubber), for example, and the pressing pad 110 presses the heating roll 70 via the belt member 72 (hereinafter, referred to as “when pressed”). It is designed to be elastically deformed.
The block 112 has a substantially U-shaped cross section made of, for example, LCP (liquid crystal polymer) having high heat resistance.
The block 112 presses the pressing pad 110 toward the heating roll 70 side.

The housing 114 is made of a synthetic resin such as PBT (polybutylene terephthalate), for example, and supports the block 112 and presses it toward the heating roll 70 and supports the belt member 72.
The frame 116 has a substantially U-shaped cross section made of metal such as iron or aluminum, and supports the housing 114 and presses it toward the heating roll 70.
Both ends of the frame 116 are supported by the guide member 74.
The guide member 74 is urged toward the heating roll 70 by an urging means (not shown).

3 to 5, a block 112 according to the present embodiment is shown.
On the upstream side of the block 112 in the belt running direction (left side in FIG. 3), a guide portion 120 is provided as a guide means for guiding the belt member 72 closer to the heating roll 70 side (lower side in FIG. 3).
The guide part 120 is formed integrally with the block 112 and is formed so as to protrude to the heating roll 70 side.
Further, the shape of the leading end of the guide portion 120 is formed in a smooth curved surface so that the belt member 72 can slide smoothly.

6 to 8 show a state in which the pressing pad 110 presses the heating roll 70 via the belt member 72.
A nip N having a width W1 (shown in FIG. 6) is formed by the heating roll 70 and the belt member 72.
In FIG. 6, the sheet S is conveyed in the direction of arrow B from the upstream side in the belt traveling direction (left side in FIG. 6) and enters the nip N, the heating roll 70 rotates in the direction of arrow A, and the belt member 72 is heated by the heating roll 70. Is traveling in the direction of arrow C.

As shown in FIGS. 6 to 8, the belt member 72 is guided to the heating roll 70 side on the upstream side in the belt traveling direction by the guide portion 120 formed in the block 112, and contacts the heating roll 70 before the nip N. Thus, a contact surface having a width W2 (shown in FIG. 6) is formed.
Further, the guide part 120 does not hit the heating roll 70 via the belt member 72.

By bringing the belt member 72 into contact with the heating roll 70 in front of the nip N, the conveyance path of the sheet S can be brought closer to the heating roll 70 side, so that before the sheet S enters the nip N, the sheet S Can be heated.
Further, since the sheet S can be heated before entering the nip N, the fixing efficiency of the toner image can be improved.
Further, since the contact area between the belt member 72 and the heating roll 70 is increased by an area corresponding to the width W2, the followability of the belt member 72 with respect to the heating roll 70 can be improved.
Moreover, since the guide part 120 as a guide means is formed integrally with the block 112, the number of parts can be reduced as compared with the case where, for example, a roll member is installed.
Further, since the guide unit 120 does not hit the heating roll 70 via the belt member 72, the sheet S can be smoothly conveyed to the nip N.

Further, by bringing the belt member 72 into contact with the heating roll 70 before the nip N, the conveyance path of the sheet S can be brought closer to the heating roll 70 side without bringing the inlet chute 96 closer to the heating roll 70, and accordingly The inlet chute 96 can be suppressed from being heated by the heating roll 70.
In the case of double-sided printing, the printed surface (front surface) of the sheet S on which an image has already been formed contacts the inlet chute 96 at the time of reverse side printing, but when the inlet chute 96 is heated, the sheet S The toner is released from the printing surface and adheres to the inlet chute 96, and the surface of the inlet chute 96 is soiled.
In the present embodiment, since heating of the inlet chute 96 can be suppressed, it is possible to suppress the surface of the inlet chute 96 from being stained with toner even in the case of double-sided printing.
Furthermore, it is possible to eliminate the need for a coating process for preventing toner adhesion on the surface of the inlet chute 96.

In the above-described embodiment, an example in which the guide unit is formed in the block 112 is shown. However, the guide unit may be formed on the upstream side of the housing 114 in the belt traveling direction.
In the above-described embodiment, an example in which the belt member 72 contacts the heating roll 70 before the nip N is shown. However, the belt member 72 is brought close to the heating roll 70 before the nip N. Also good.

1 is a side view showing an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. It is a side view showing a block concerning an embodiment of the present invention. It is a perspective view which shows the block which concerns on embodiment of this invention. It is a perspective view which shows the block which concerns on embodiment of this invention. It is a side view which shows the state which the press pad is pressing the heating roll via a belt member. It is a perspective view which shows the state which the press pad is pressing the heating roll via a belt member. It is a perspective view which shows the state which the press pad is pressing the heating roll via a belt member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 36 Fixing apparatus 70 Heating roll 72 Belt member 74 Guide member 76 Press unit 78 Impregnation pad 110 Press pad 112 Block 114 Housing 116 Frame 120 Guide part

Claims (6)

A rotatable heating roll;
A belt member that travels following the rotation of the heating roll;
A pressing member disposed on the opposite side of the heating roll with respect to the belt member, and pressing the heating roll via the belt member;
A support member that supports the pressing member so as to press it toward the heating roll;
A fixing device provided on the upstream side of the pressing member in the belt traveling direction and guiding the belt member to approach the heating roll. The fixing device according to claim 1, wherein the belt member is in contact with the heating roll on the upstream side in a belt traveling direction from a position where the pressing member presses the heating roll via the belt member. The fixing device according to claim 1, wherein the guide unit includes a guide portion formed integrally with the support member. The fixing device according to claim 1, wherein the guide unit includes a guide portion formed so as to protrude toward the heating roll. The fixing device according to claim 1, wherein the guide unit includes a guide portion that is formed so as not to hit the heating roll via the belt member.   An image forming apparatus comprising the fixing device according to claim 1.

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