JP2000352890A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming device that are superior in their reliability at having a jammed sheet recovered without imparting any damage to a device. SOLUTION: In this device, when paper P is discriminated to be jammed within a fixing device 109, rotation of the fixing roller 1 is reversed (the paper P is carried in a reverse direction as the direction when it is carried to a carrying path 57), the jammed paper P can be processed without having a top and bottom separating claw 54 pressed against the fixing roller 1 or the press roller 50 by having the jammed paper that is detected by a sensor carried to an upstream side of a nip part of a fixing roller 1 and a press roller 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which is applied to an image forming apparatus or the like and heats and presses a sheet.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a fixing device in an image forming apparatus includes a fixing roller 1 and a pressure roller 50 which is in contact with the fixing roller 1. The sheet (hereinafter, paper P) enters the contact portion (hereinafter, nip portion) to fix the toner image on the paper P. When the paper P stops near the downstream side of the fixing roller 1 in the normal transport direction of the paper P (the direction in which the paper P is discharged to the outside of the image forming apparatus), the lower flag B61 indicates the arrow in FIG. Rotate in the direction D to turn off the sensor (not shown).

When the sensor is turned off, the control circuit determines that the paper P has been delayed or stayed, and the fixing roller 1 is moved to the position shown in FIG.
Is stopped in the direction indicated by the arrow C (rotation direction in which the sheet P is normally conveyed), and a jam is displayed on the operation unit (not shown).

In response to the jam error display, the user manually rotates the handle 11 protruding from the side shown in FIG. 3 to rotate the fixing roller 1 via the input gear 10 and the roller gear 6, Jammed paper P
Has been conveyed to either the upstream or downstream side of the fixing roller 1 to remove the jammed paper P.

[0005]

However, in the above conventional example, the user determines the error condition of the paper P, and rotates the handle 11 to convey the paper P to either the upstream or downstream of the fixing roller 1 and to feed the paper P Since P was removed,
Depending on the stopped state of the jammed paper P, the upper and lower separation claws 54 and 55 are pressed against the fixing roller 1 or the pressure roller 50, and in the worst case, there is a problem that the fixing roller 1 or the pressure roller 50 is damaged. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a highly reliable fixing device and an image forming apparatus for recovering a jam sheet without damaging the apparatus. An object of the present invention is to provide a forming apparatus.

[0007]

According to the present invention, in order to achieve the above object, a rotating body for heating and pressing a sheet while rotating the sheet forward and conveying the sheet downstream is provided. A fixing unit having a separating unit that separates the sheet stuck to the rotating body on the side, and a jam detecting unit that detects a sheet jam of the fixing unit.
When the jam detecting means detects a sheet jam, the rotating body is rotated in the reverse direction to return the sheet to the upstream side of the fixing unit.

Therefore, since the jam sheet is returned to the upstream side of the fixing section, the separating means is not pressed against the rotating body when the jam sheet is collected, and the jam sheet can be collected without damaging the apparatus. it can.

It is preferable that the jam detecting means detects a sheet jam when the conveyed sheet does not reach a predetermined position within a predetermined time and is delayed, or when the sheet stays at a predetermined position.

[0010] The jam detecting means is disposed downstream of the separating means, and is rotated by being pressed by a jam sheet stopped at the downstream side of the rotating body by being caught by the separating means and detecting a sheet jam. It is preferred that

It is preferable that when the jam detecting means detects a sheet jam, the rotating body performs reverse rotation for a time equal to or more than (size in the sheet conveying direction ÷ sheet conveying speed).

It is preferable that a drive source for driving the rotating body is provided independently.

In the image forming apparatus of the present invention, the fixing device described above, an image forming unit for forming an image on a sheet,
It is characterized by having.

It is preferable that the image forming apparatus further includes a conveying unit for conveying the sheet from the image forming unit to the fixing device, and the conveying unit is commonly driven by a driving source for driving the rotating body.

[0015]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

This embodiment will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the image forming apparatus. In FIG.
Reference numeral 102 denotes an optical unit for projecting image information of the document 101 onto the photosensitive drum 103.

In the vicinity of the photosensitive drum 103, a developing device 104 for supplying toner to the photosensitive drum 103 for visualizing the electrostatic latent image on the photosensitive drum 103, and transfers the toner image to a sheet P as a sheet. At the same time, a transfer / separation charger 105 having a separation unit for removing the sheet P electrostatically attracted to the photosensitive drum 103, and removes the residual toner (not transferred to the sheet P) on the photosensitive drum 103. And a blank unit (not shown) for regulating an electrostatic latent image area are arranged to form an image forming unit. .

At the downstream side of the photosensitive drum 103 in the paper P transport direction, a transport device 108 as transport means for transporting the paper P on which the toner image has been transferred to the fixing device 109 is arranged.

The paper P coming out of the fixing device 109 is discharged to a paper discharge tray 111 outside the apparatus by a paper discharge roller 112, or the photosensitive drum 1 is used when making double-sided and multiple copies.
03 is provided with a paper discharge reversing device 110 for controlling whether to convey the paper P to a paper re-feeding device 113 for re-feeding the paper P again. Reference numeral 114 denotes a paper feed cassette for stacking and stocking the paper P.

Next, the operation of the above configuration will be described step by step.

When the user presses a copy start button (not shown), the sheets P stacked in the sheet cassette 114 are conveyed one by one to the vertical path conveying unit 116 from the sheet cassette 114 by the sheet feeding device 115. , Registration roller 1
It is sent to 17.

Next, the optical unit 102 starts scanning to project the image information of the document 101 onto the photosensitive drum 103, and the registration roller 117 starts to convey the paper P in synchronization with the scanning. At this time, the photosensitive drum 103
The electrostatic latent image of the image information of the original 101 formed thereon becomes a toner image by the developing device 104, transfers the toner image to the paper P conveyed by the transfer / separation device 105, and fixes the fixing device by the conveyance device 108. The fixing device 109 conveys the toner image to the sheet P.

Thereafter, in the case of a single-sided copy, the sheet P is conveyed to the sheet ejection rollers 112 by the sheet ejection reversing device 110 and ejected to the sheet ejection tray 111 outside the apparatus.

In the case of double-sided or multiple copies,
The sheet P on which the toner image has been fixed by the fixing device 109 is conveyed to the sheet re-feeding device 113 by the sheet discharging reversing device 110 and sent to the registration roller 117.

Then, the toner image is transferred again to the photosensitive drum 103 and transferred to the photosensitive drum 103.
9. The sheet is discharged onto a sheet discharge tray 111 outside the apparatus via a sheet discharge reversing device 110 and a sheet discharge roller 112.

During the above-described series of operations, a plurality of sensors (not shown) provided on the transport path of the paper P
Is detected after the paper is fed and arrives at a predetermined position after a lapse of a predetermined time (delay), or when the paper is not passed through after a lapse of a certain time after arrival at the predetermined position (residence).

When a delay or stay (jam) is detected by a sensor (not shown), a warning indicating that the paper P has jammed is displayed on the operation unit (not shown), and the conveyance of the paper P is performed by the entire apparatus or one of the devices. It is controlled by a control circuit (not shown) so as to be stopped at a portion.

Next, the mechanism of the fixing device 109 will be described with reference to FIGS.

FIG. 3 is a top view of the driving mechanism of the fixing device 109 as viewed from above. 1 is a fixing roller as a rotating body,
Reference numerals 2 and 3 denote front and rear side plates for holding the fixing roller 1 and the like.
Reference numerals 4 and 5 denote holding members for rotatably holding the fixing roller 1 on the front and rear side plates 2 and 3, reference numeral 6 denotes a roller gear which is integrally formed with the fixing roller 1 and rotates the fixing roller 1,
Reference numeral 7 denotes a motor, and reference numeral 8 denotes an idler gear for transmitting the driving force of the motor 7 to the roller gear 6.

Reference numeral 10 denotes an input gear connected to the roller gear 6. The input gear 10 is turned by turning a handle 11.
The fixing roller 1 can be rotated.

FIG. 4 is a front sectional view of the fixing device 109. The fixing device 109 is disposed below the fixing roller 1 in contact with the fixing roller 1, the pressing roller 50 serving as a rotating body, and disposed above the fixing roller 1 to clean dirt on the fixing roller 1. The fixing device includes a web device 51, a fixing upper cover 52, a pre-fixing guide 53 for guiding the sheet P to a contact portion (hereinafter referred to as a nip portion) between the fixing roller 1 and the pressing roller 50, a fixing roller 1, a pressing roller, An upper separating claw 54 and a lower separating claw 55 are provided as separating means provided for separating the sheet P when the sheet P is stuck to the sheet 50. The fixing unit is provided by these configurations.

The fixing device 109 includes a transport roller 5.
6, a conveyance path 57, and flags A60 and B61 as jam detecting means for detecting a jam of the paper P.

Next, with reference to FIGS. 1, 5 and 6, the state of conveyance of the sheet P will be described.

In FIG. 5, the sheet P is conveyed to the conveying path 57 in the direction of arrow B by the rotation of the fixing roller 1 in the direction of arrow C,
The flag A60 is rotated in the direction of arrow A, and the sensor (not shown) is turned off.

At this time, it is determined by the control circuit (not shown) whether or not the paper P has jammed in the flag A60. If the jam has not occurred, the paper P is conveyed as it is.

However, when the paper P is caught by the upper and lower separation claws 54 and 55 and stopped at the downstream side of the fixing roller 1 as shown in FIG. 6, the flag B61 rotates in the direction of arrow D, and the sensor shown in FIG. Is turned off.

At this time, it is determined by the control circuit (not shown) that the paper P has jammed on the downstream side of the fixing roller 1, and
As shown in FIG. 1, the fixing roller 1 is rotated in the reverse direction and rotated for a certain period of time t (t ≧ (the conveying direction size of the sheet P being conveyed / the conveying speed of the sheet P)) in the direction of the arrow E, and the sheet P is rotated. The sheet is reversely conveyed to the pre-fixing guide 53 side, that is, upstream of the fixing roller 1.

Here, the fixed time t is set as a time during which the paper P can be always conveyed backward to the upstream side of the fixing roller 1, and is not limited to this.

As described above, in the present embodiment, the transport path 5
Rotation of the flag B61 on the surface following 7 in the direction of arrow D
When the FF sensor is turned off, the paper P
Is determined to have jammed in the fixing device 109.

Then, the rotation of the fixing roller 1 is reversed (conveyed in a direction opposite to the direction in which the sheet P is conveyed to the conveying path 57), and the jammed sheet P detected by the sensor is transferred to the fixing roller 1 and the pressure roller. The upper and lower separation claws 54 and 55 are conveyed to the upstream side of the nip of the fixing roller 1.
The jammed paper P can be processed without being pressed against the pressure roller 50.

Therefore, in order to recover the paper P that has forcibly jammed as in the prior art, the fixing roller 1 and the pressure roller 50 are pressed by the pressed upper and lower separation claws 54 and 55.
Will not be damaged.

The determination of a jam in the fixing unit may be performed not only by the flag B61 but also by the flag A60. Flags A, B60, 6
The jam in the fixing unit may be determined by using a method other than the method of detecting the jam according to the first embodiment.

It is also preferable that the driving source of the fixing roller 1 is provided independently and independently of the other devices so that the fixing roller 1 can quickly reversely rotate when a jam is detected. At this time, it is more preferable that the conveying device 108 upstream of the fixing device 109 also conveys the sheet to the upstream side in common with the fixing roller 1, since no contradictory conveying force acts on the sheet P. .

[0044]

As described above, according to the present invention, when a sheet jam is detected in the fixing unit, the rotation of the rotating body is reversed and the jam sheet is conveyed to the upstream side, so that the jam sheet can be easily collected. The separation means is not pressed against the rotating body and the rotating body is damaged, as in the prior art.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating reverse driving of a fixing device according to an embodiment during a jam.

FIG. 2 is a front sectional view of the image forming apparatus.

FIG. 3 is a top view illustrating the fixing device.

FIG. 4 is a front sectional view of the fixing device.

FIG. 5 is an explanatory diagram illustrating a state in which the fixing device is transported.

FIG. 6 is an explanatory diagram illustrating a jam of the fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 7 Motor 50 Pressure roller 54 Upper separation claw 55 Lower separation claw 56 Transport roller 57 Transport path 60 Flag A 61 Flag B

Claims (7)

[Claims] 1. A rotating body for heating and pressing a sheet while rotating the sheet forward and conveying the sheet downstream, and separating means for separating a sheet attached to the rotating body downstream of the rotating body. A fixing unit having the fixing unit, a jam detecting unit for detecting a sheet jam of the fixing unit,
The fixing device according to claim 1, wherein when the jam detecting unit detects a sheet jam, the rotating body is rotated in the reverse direction to return the sheet to an upstream side of the fixing unit. 2. The apparatus according to claim 1, wherein said jam detecting means detects a sheet jam when the conveyed sheet does not reach a predetermined position within a predetermined time and is delayed, or when the sheet stays at a predetermined position. The fixing device according to claim 1. 3. The jam detecting means is disposed downstream of the separating means, is pressed by a jam sheet stopped on the downstream side of the rotating body by being caught by the separating means, and rotates to detect a sheet jam. The fixing device according to claim 1, wherein the fixing device is a flag. 4. When the jam detecting means detects a sheet jam, the rotating body performs reverse rotation for a time equal to or more than (size in the sheet conveying direction （sheet conveying speed). Item 4. The fixing device according to item 1, 2 or 3. 5. The fixing device according to claim 1, wherein a driving source for driving the rotating body is independently provided. 6. An image forming apparatus comprising: the fixing device according to claim 1; and image forming means for forming an image on a sheet. 7. A fixing device according to claim 1, further comprising a conveying unit for conveying the sheet from the image forming unit to the fixing device, wherein the conveying unit is similarly driven by a driving source for driving the rotating body. Item 7. An image forming apparatus according to Item 6.