JP2000029346A - Fixing device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the separating performance of paper and to prevent an elastic roller from being damaged because a separation pawl bites at the elastic roller. SOLUTION: This device is a fixing device to fix a toner image on paper while carrying the paper, and is provided with a pair of fixing rollers consisting of a heat roller 54 and a pressure roller 55 whose surface is formed of an elastic member and which is arranged so as to freely approach and recede to/from the heat roller 54, the separation pawl 153 that is provided on the downstream side of the pressure roller 55 in the carrying direction of the paper and whose top end abuts on the peripheral surface of the pressure roller 55 and that is movable with the pressure roller 55, a pawl supporting plate 152 supporting the separation pawl 153 and a spring 156 pressing the separation pawl 153 so that the top end abuts on the peripheral surface of the pressure roller 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fixing device for an image forming apparatus, and more particularly to a fixing device for fixing a toner image on a sheet while conveying the sheet.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine, a printer, and a facsimile machine includes an image forming section for forming a toner image on a sheet, a sheet feeding section for supplying the sheet to the image forming section, and a toner image on the sheet. And a fixing unit for fixing the image.
The fixing unit includes a pressure roller and a heat roller that are in pressure contact with each other, and a heater is provided inside the heat roller.
In this fixing device, a sheet of paper is supplied and passed between the rollers, so that the toner image on the sheet is heated and melted, and the toner image is fixed on the sheet.

On the downstream side of the roller pair of the fixing device in the sheet transport direction, a separation claw is arranged supported by a claw support plate. The separation claw is urged toward the roller by a spring, and the tip of the separation claw contacts the peripheral surface of the roller. This prevents the paper from being entangled in the rollers.

[0004]

One of the two rollers of the fixing device is fixed, while the other is arranged so as to be able to approach and separate from the fixed roller. As a result, the distance between the two rollers changes according to the thickness of the sheet, and the pressing force between the two rollers is appropriately adjusted. Normally, the heat roller is fixed, and the pressure roller is arranged so as to approach and separate from the heat roller.

However, when the position of the pressure roller changes according to the thickness of the sheet, the claw support plate for supporting the separation claw is fixed inside the side surface of the image forming apparatus main body. , The paper separation performance deteriorates. Further, when a paper jam occurs on the downstream side in the transport direction of the roller pair during the transport of the paper, the separation claw may be pushed to the pressure roller side by the paper that has become bellows due to the paper jam. Then, there is a problem that the tip of the separation claw that has contacted the pressure roller bites into the pressure roller, and the pressure roller whose surface is formed of an elastic member is damaged. SUMMARY OF THE INVENTION An object of the present invention is to prevent the separation performance of a sheet from deteriorating and to prevent the elastic roller from being damaged by the separation claw biting into the elastic roller.

[0006]

According to a first aspect of the present invention, there is provided a fixing device for fixing a toner image on a sheet while conveying the sheet, wherein the fixing roller pair includes a separation claw. , A claw support and a biasing member. The fixing roller pair includes a first roller and a second roller having a surface formed of an elastic member and arranged so as to be able to approach and separate from the first roller. The separation claw is provided on the downstream side of the second roller in the sheet conveying direction, and the leading end abuts on the peripheral surface of the second roller, and is movable with the second roller. The claw support plate supports the separation claw. The urging member urges the separation claw such that its tip comes into contact with the peripheral surface of the second roller.

In this device, when the second roller moves according to the thickness of the sheet, the separation claw moves following the second roller. Here, since the separation claw and the second roller move in the same manner, there is no gap between the two to maintain good separation performance, and the separation claw does not bite into the peripheral surface of the second roller. The rollers are not damaged.

According to a second aspect of the present invention, there is provided a fixing device for an image forming apparatus, wherein the claw support plate is rotatably mounted on the axis of the second roller. In this device, the pawl support plate can rotate concentrically with the second roller, and moves together with the second roller. Here, the second
It is possible to maintain the relative positional relationship between the separation claw and the second roller with respect to any change in the position of the roller, prevent the separation performance of the sheet from deteriorating, and prevent the second roller from being damaged. it can.

According to a third aspect of the present invention, in the fixing device of the image forming apparatus according to the first aspect, the second roller is rotatably supported by a support arm that is rotatable about a rotation axis, and rotates together with the support arm. And approaches and separates from the first roller. The separation claw is mounted on the support arm. In this device, the second roller is supported by the support arm, and the support arm turns according to the thickness of the sheet, and the positional relationship with the first roller is adjusted. Since the separation claw is mounted on the support arm, the separation claw moves with the movement of the second roller.

Therefore, the positional relationship between the separation claw and the second roller is always maintained in the same positional relationship.
It is possible to prevent the sheet separating performance from being deteriorated due to the movement of the roller, and to prevent the second roller from being damaged. According to a fourth aspect of the present invention, in the fixing device of the image forming apparatus according to any one of the first to third aspects, the image forming apparatus further includes a guide member that guides the sheet passing through the fixing roller pair to a downstream side, and the guide member is provided together with the separation claw. It is movable.

In this apparatus, the fixing process is performed, and the sheet separated from the second roller by the separation claw is guided by a guide member and further conveyed downstream. At this time, when the separation claw moves with the movement of the second roller, the guide member also moves together with the separation claw. Regarding the separation of the sheet from the second roller, the positional relationship between the separation claw and the guide member is important. For example, if the guide member is fixed so as not to be movable, and the separation claw moves together with the second roller, the positional relationship between the separation claw and the guide member changes, and the sheet is separated by the guide member before the paper is separated by the separation claw. A guided situation occurs.

Therefore, here, the guide member is moved together with the separation claw so that the positional relationship between the separation claw and the guide member does not change. The fixing device of the image forming apparatus according to claim 5 is the fixing device according to claim 1 or 2,
The nail support plate also serves as a guide. Here, the configuration is simplified. 7. A fixing device for an image forming apparatus according to claim 6, wherein the first roller is a heat roller having a heater therein, and the second roller is pressed against the heat roller. And

Normally, since the surface of the pressure roller is formed of an elastic member, the separation claw that is in contact with the pressure roller can be moved together with the pressure roller, thereby preventing biting into the elastic surface.

[0014]

FIG. 1 is a longitudinal sectional view of a copying machine to which an embodiment of the present invention is applied. The copying machine 1 has a main body 10 and a document holder 11 mounted on the upper part of the main body 10 so as to be openable and closable. An original platen 15 on which an original is placed is disposed on the main body 10 at an upper portion thereof. Inside the main body 10, an image forming unit 16 is provided at the left end as viewed from the front and substantially at the center in the vertical direction.
Further, a paper supply unit 17 for supplying paper to the image forming unit 16 is provided at a lower portion.

The paper supply section 17 includes paper supply cassettes 18 and 19 which are detachably attached to the main body 10 and store papers, and a stack bypass 20 provided above the paper supply cassettes. An optical system 21 for reading image information of a document placed on the document table 15 is provided below the document table 15. The optical system 21 includes a light source 22 for irradiating light to the surface of the document placed on the document table 15, mirrors 23, 24, and 25 for deflecting light reflected from the surface of the document.
A lens 26 for converging light from the mirror 25,
An image sensor 27 such as a CCD sensor that receives light converged by the lens 26 and generates an image data signal corresponding to an original image.

The image forming section 16 has a photosensitive drum 30 on the surface of which an electrostatic latent image is formed.
0, a main charging device 31, a developing device 32,
It has a transfer roller 33 and a cleaning device 34. The main charging device 31 is a device for charging the surface of the photoconductor drum 30, and is disposed diagonally above and to the right of the photoconductor drum 30. At a predetermined distance from the main charging device 31, the photosensitive drum 3
A developing device 32 for forming a toner image on the image sensor 0 is disposed. The developing device 32 stores toner inside, and visualizes the electrostatic latent image formed on the photosensitive drum 30 by the toner. The transfer roller 33 is a device for transferring the toner image on the photosensitive drum 30 to a sheet, and is disposed on the left side of the photosensitive drum 30. The cleaning device 34 is arranged above the photosensitive drum 30.

On the right side of the photosensitive drum 30, a laser unit 35 for forming an electrostatic latent image on the peripheral surface of the photosensitive drum 30 is provided. The laser unit 35 forms an electrostatic latent image on the peripheral surface of the photosensitive drum 30 based on an image data signal obtained from the image sensor 27. Paper feed unit 17
Includes a vertical transport path 41 for transporting the paper from each of the paper cassettes 18 and 19 toward the image forming unit 16 and a bypass transport path 42 for transporting the paper from the stack bypass 20 to the image forming unit 16. I have. Each paper cassette 18,
Pickup rollers 43 and 44 for taking out the stored paper are provided in the stack 19 and the stack bypass 20.
45 and a pair of paper feed rollers 46, 47, and 48 for feeding the sheets one by one to the transport path. In the vertical transport path 41, transport roller pairs 49 and 50 are provided.
The bypass conveyance path 42 is provided with a conveyance roller pair 51. The vertical transport path 41 and the bypass transport path 42 join below the transfer position where the photosensitive drum 30 and the transfer roller 33 face each other. A registration roller 5 for holding the conveyed paper at a predetermined position is located at the confluence.
2 are provided.

Above the photosensitive drum 30 and the transfer roller 33, a fixing device 53 for fusing and fixing the toner transferred onto the paper is provided. The fixing device 53 has a heat roller 54 having a built-in heater and a pressure roller 55 pressed against the heat roller 54. The fixing device 53 transfers a toner image formed on the surface of a sheet that conveys the sheet by holding the sheet between the rollers. It fixes by heating.

Further above the fixing device 53, a branch 5
6 are provided. On the right side of the branch portion 56, a discharge tray 57 for discharging sheets via a discharge roller pair 60 is provided.
And a discharge roller pair 6 disposed above the discharge tray 57.
1 and a sub-eject tray 58 from which sheets are ejected. A switchback unit 59 for reversing the sheet at the time of double-sided copying is provided at the lower left of the branch unit 56.
Is arranged. The branching section 56 is provided with a branching claw 62 for switching the sheet conveying direction between the direction of the discharge tray 57 and the direction of the switchback section 59. Branch claw 62
Two branch claws 63 and 64 are provided on the left side of. Below the two branch claws 63 and 64, a switchback transport path 65 for guiding a sheet to a switchback section 59 is provided.
A sub-tray conveyance path 66 for guiding the sheet to the sub-discharge tray 58 is provided above. A sheet is fed to a finisher such as a sorter or a stable sorter (not shown) between the two branch claws 63 and 64. A finisher transport path 67 for transport is provided. Branch claws 63, 64
Switches the transported paper to the switchback transport path 65,
It is possible to switch so as to guide to either the sub-tray conveyance path 66 or the finisher conveyance path 67.

Next, the fixing device 53 will be described in detail. As shown in FIG. 2, the fixing device 53 includes a heat roller 54 having heaters 121 and 122 therein, and a heat roller 54.
And a pressure roller 55 that comes into pressure contact with the roller. Pressure roller 55
Is composed of a cylindrical roller base made of synthetic resin, metal and other materials, and a coated tube made of a fluororesin material, urethane rubber and other elastic materials covering the peripheral surface of the roller base. It is configured to rotate around 123.

The position of the pressure roller 55 with respect to the heat roller 54 can be moved by the position variable mechanism 124, whereby the pressure contact force between the rollers 54 and 55 can be changed. The position variable mechanism 124 includes a pair of support arms 128 (only one support arm is supported in the figure) whose lower ends are rotatably supported by a fixing housing 126 via a pivot shaft 125, and a pair of support arms 128. A spring 127 for urging the upper end of each support arm 128 toward the heat roller 54.

A semicircular notch 129 is formed at an intermediate portion of the support arm 128 on the heat roller 54 side in the vertical direction.
a is formed, and the pressure roller 55
Both ends of the rotary shaft 123 are rotatably supported via bearings 130, respectively. One end of the spring 127 is locked near the end surface of the upper end of the support arm 128 on the side of the heat roller 54, and the other end is locked to the fixing housing 126. As described above, the support arm 128 is Clockwise (toward the heat roller 54).

Next, the sheet separating mechanism 1 of the fixing device 53
50 will be described in detail. The paper separating mechanism 150 shown in FIG. 3 is provided inside the apparatus of the position variable mechanism 124 shown in FIG. That is, the pressure roller 55 is provided so as to be sandwiched between a pair of support arms 128 provided at both ends in the width direction of the pressure roller 55. This paper separating mechanism 150
Are a plurality of separation claws 153 provided in the vicinity of the pressure roller 55 on the downstream side in the transport direction, a claw support plate 152 for supporting a support portion 154 formed on the separation claw 153, and a separation claw 15.
A spring 156 for urging the front end of the pressure roller 3 toward the peripheral surface of the pressure roller 55
And a separation claw 151 disposed downstream of the heat roller 54.

The claw support plate 152 has a base end rotatably attached to the rotating shaft 123 of the pressure roller 55, and an upper end extending along the sheet transport direction. The end surface 152a on the heat roller 54 side is
5 is a guide section for guiding a sheet passing through the sheet 5 to the downstream side. The upper end of the claw support plate 152 is urged toward the heat roller 54 by a spring 157. The spring 157 is disposed in a compressed state between the inside of the side surface of the main body 10 and the end surface of the claw support plate 152 opposite to the heat roller 54 at the upper end. In addition, a stopper 160 is provided near the upper end of the claw support plate 152, and regulates the clockwise rotation of the claw support plate 152. For this reason, the claw support plate 152
3 can be turned counterclockwise concentrically with the rotating shaft 123 of the pressure roller 55 against the urging force of the spring 157 from the state shown in FIG.

Each of the separation claws 151 and 153 is formed of a synthetic resin material which is less thermally deformed, and has a sharp tip. The separation claw 153 is rotatably supported at a substantially middle position of the claw support plate 152 in the vertical direction.
The spring 156 is connected to the upper end of the separation claw 153 and the claw support plate 1.
52 and a portion thereof in a compressed state.
The tip of the separation claw 153 is always in contact with the peripheral surface of the pressure roller 55.

Next, the operation of the copying machine will be briefly described. When a document is placed on the document table 15 and the copy start button is pressed, the image information of the document on the document table 15 is read by the optical system 21 and the photosensitive drum 3 is correspondingly read.
0, an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 32 to form a toner image.

On the other hand, a sheet according to the size of the document is fed from the sheet feeding unit 17. Then, this sheet is stored in the image forming section
6 and the toner image on the photosensitive drum 30 is transferred onto a sheet. The sheet is further transported upward and sent to the fixing device 53, where it is discharged onto a tray 57 on the sheet. The sheet on which the fixing process has been completed is discharged onto the discharge tray 57 via the branch claw 62.

In the fixing device 53, the position variable mechanism 1
24 by the urging force of the spring 127 constituting the pressure roller 5
5 and the heat roller 54 are pressed against each other. When a thick sheet of paper such as an envelope passes between the rollers, the support arm 128 pivots counterclockwise in FIG. 2 around the pivot shaft 125, whereby the pressure roller 55
Move away from. At the same time, the nail support plate 1
Reference numeral 52 rotates clockwise around the rotation shaft 123 of the pressure roller 55. The upper end of the claw support plate 152 is
7 and is in contact with the stopper 160.
Since the separation claw 153 is attached to the claw support plate 152, the separation claw 153 also turns with the claw support plate 152 and moves with the pressure roller 55. The separation claw 153 has a distal end thereof formed by a spring 156.
Therefore, even if the position of the pressure roller 55 moves, the tip of the separation claw 153 can always be kept in contact with the peripheral surface of the pressure roller 55. Therefore, no gap is formed between the separation claw 153 and the pressure roller 55, and the paper is not wrapped around the roller.

If a paper jam occurs when the paper is conveyed between the heat roller 54 and the pressure roller 55, the separation claw 153 and the claw support plate 152 are formed by the bellows-shaped paper.
Of the heat roller 54 is pushed toward the pressure roller 55. Then, the claw support plate 152 turns counterclockwise against the urging force of the spring 157, and at the same time, the separation claw 15
3 also turns, so that it is possible to avoid being pushed from the accordion-shaped paper. That is, it is possible to suppress the tip of the separation claw 153 from biting into the peripheral surface of the pressure roller 55.

In this embodiment, since the claw support plate 152 and the separation claw 153 are attached to the pressure roller 55, when the pressure roller 55 is removed, the claw support plate 152 and the separation claw 153 are simultaneously removed as one unit. And good maintainability. [Another Embodiment] The fixing device of the image forming apparatus according to the present invention can further adopt the following embodiments. Here, the description will focus on the separation mechanism 150 in particular.

As shown in FIG. 4, the paper separating mechanism 165 has a plurality of separating claws 167 mounted on a support arm 128 via a rod 166. The support arm 128 is different from the above-described embodiment in that the support arm 128 has a protruding portion 128a protruding toward the heat roller 54 on the upper part, but the other points are the same as the above-described embodiment. And
The rod 166 is connected to the protrusion 12 of the pair of support arms 128.
8a, it is provided extending in the front-rear direction of the device. The plurality of separation claws 167 are provided rotatably at predetermined intervals in the axial direction with respect to the rod 166. Therefore, the separation claw 167 is located downstream of the pressure roller 55 in the sheet conveyance direction. Note that a compression spring 168 is provided above the separation claw 167, so that the tip of the separation claw 167 is in contact with the peripheral surface of the pressure roller 55.

The heat roller 5 of the pair of protrusions 128a
A guide member 169 is provided between the four end portions in the front-rear direction of the apparatus. This guide member 169 is
The sheet that has passed between the heat roller 54 and the pressure roller 55 is guided downstream. In such a fixing device, when a thick sheet passes between the rollers 54 and 55, the pressure roller 55 receives a force in a direction away from the heat roller 54, thereby causing the support arm 128 to rotate counterclockwise about the pivot 125. Rotate around. Accordingly, the separation claw 167 and the guide member 1
68 also moves in the same direction. Therefore, the positional relationship between the pressure roller 55 and the separation claw 167 is maintained. Further, the positional relationship between the separation claw 167 and the guide member 168 is also maintained.

Therefore, even if the pressure roller 55 moves, the sheet separation performance does not deteriorate, and the jamming of the separation claw 167 into the pressure roller 55 due to a jam can be prevented. Further, in this embodiment, since the separation claw is supported by using the support arm, the configuration is simplified as compared with the above embodiment.

[0034]

According to the present invention, since the fixing device has the separation claw that can move together with the elastic roller, the positional relationship between the separation claw and the elastic roller does not greatly change. Can be prevented from being entangled, and the sheet separating performance is not impaired. Further, it is possible to prevent the separation claw from biting into the elastic roller when a paper jam occurs, thereby preventing the roller from being damaged.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a copier employing an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a fixing device of the copying machine.

FIG. 3 is a longitudinal sectional view showing a sheet separating mechanism of the fixing device of the copying machine.

FIG. 4 is a longitudinal sectional view showing a sheet separating mechanism of a fixing device of a copying machine employing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 53 Fixing device 54 Heat roller 55 Pressure roller 123 Rotating shaft 152 Claw support plate 153, 167 Separation claw 156 Spring

Claims (6)

[Claims] 1. A fixing device for fixing a toner image on a sheet while conveying the sheet, comprising: a first roller, a surface formed of an elastic member, and moving toward and away from the first roller. Second freely arranged
A fixing roller pair including a roller, a separation claw provided downstream of the second roller in the sheet conveyance direction and having a leading end abutting on the second roller peripheral surface and movable with the second roller; and supporting the separation claw. A fixing device for an image forming apparatus, comprising: a claw support plate that performs the operation; and an urging member that urges the separation claw such that a tip of the separation claw contacts the peripheral surface of the second roller. 2. A fixing device for an image forming apparatus according to claim 1, wherein said claw support plate is rotatably attached to an axis of said second roller. 3. The second roller is rotatably supported by a support arm that is rotatable about a rotation axis, and rotates together with the support arm to approach and separate from the first roller. The fixing device of the image forming apparatus according to claim 1, wherein the separation claw is mounted on the support arm. 4. The apparatus according to claim 1, further comprising a guide member for guiding a sheet passing through the pair of fixing rollers to a downstream side, wherein the guide member is movable together with the separation claw. Fixing device of the image forming apparatus. 5. The nail support plate also serves as the guide.
A fixing device for an image forming apparatus according to claim 1. 6. The image forming apparatus according to claim 1, wherein said first roller is a heat roller having a heater therein, and said second roller is a pressure roller pressed against said heat roller. Device fixing device.