JP2001013813A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the separableness of a recording paper from a fixing roller after fixing process. SOLUTION: This fixing device 10 has a fixing roller 11 with a heating element therein, and separation pawls 15a-15d for separating recording paper by abutting on the fixing roller 11. In this case, a means for recognizing a recording-paper size and the separation pawls 15a and 15d on both sides among the separation pawls 15a-15d are made movable in the longitudinal direction of the fixing roller 11, the inside separation pawls 15b and 15c are fixed, and the separation pawls 15a-15d are disposed so that the recording paper is separated from the vicinity of its end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus such as a copying machine or a printer employing an electrophotographic system.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of a conventional electrophotographic copying machine.
FIG. 6 is a sectional view of a conventional fixing device.

In the electrophotographic copying machine shown in FIG. 1, reference numeral 1 denotes a copying machine main body, 2 denotes a scanner section for reading a document placed on a document table, and the scanner section 2 includes a document illumination lamp 2a and a plurality of mirrors. 2b and a lens 2c. Reference numeral 3 denotes a photosensitive drum such as OPC or amorphous silicon. The photosensitive drum 3 forms a latent image of a document sent from the scanner unit 2.

Next, an electrophotographic process will be described.

First, the photosensitive drum 3 is uniformly charged by a charging roller 4 and then a light image sent from the scanner unit 2 is irradiated onto the photosensitive drum 3 to form an electrostatic latent image corresponding to the original. It is formed on the photosensitive drum 3.

Next, the toner from a developing unit 5 containing a toner made of magnetic powder or the like is caused to fly on the photosensitive drum 3 with a predetermined developing bias to develop an electrostatic latent image, and this is visualized as a toner image. Become Subsequently, by applying a predetermined transfer bias to the transfer roller 6, the photosensitive drum 3
The developed toner image is transferred onto the recording paper P which is sequentially conveyed from the cassette 20 to the conveyance guide pair 22, the registration roller 23, and the transfer guide 24. The residual toner on the photosensitive drum 3 after the completion of the transfer process is collected as waste toner by a rubber blade 7a provided on the cleaner 7. Thereafter, the photosensitive drum 3 is electrostatically discharged by the erase lamp 8 to prepare for the next copying process.

On the other hand, the recording paper P on which the toner image has been transferred
Is conveyed to the fixing device 10 through the transport unit 9 and is held by the fixing roller 11 and the pressure roller 12 as a heat roller pair, and is heated to receive the toner image. And
The recording paper P on which the toner image has been fixed is delivered to a discharge roller pair 25.
And the paper is stacked on the paper discharge tray 26, and a series of copying processes is completed.

Next, the configuration of the fixing device 10 will be described with reference to FIG.

In FIG. 6, reference numeral 11 denotes a fixing roller having a built-in heating means such as a halogen heater, and reference numeral 12 denotes a pressing roller. The pressing roller 12 is constituted by an elastic roller which rotates following the fixing roller 11. . The fixing roller 11
Is controlled to a predetermined temperature by temperature detecting means including a leaf spring 13a and a thermistor 13b.

The recording paper P on which the toner image has been transferred through the transfer process is guided by a fixing entrance guide 14 to a pressure contact portion between the fixing roller 11 and the pressure roller 12 (hereinafter, referred to as a fixing nip portion). While being conveyed by the fixing roller 11 and the pressure roller 12, the toner is fixed by heat and pressure. Then, the recording paper P on which the toner image has been fixed is guided to the paper discharge unit by the guide pair 19.

After fixing, the surface of the fixing roller 11 is cleaned by a felt roller 18 impregnated with silicon oil or the like.

Next, the functions of the upper separating claw 15 and the lower separating claw 16 will be described.

As the material used for the separation claws 15, 16, a heat-resistant resin such as polyimide is often used.
The tip portions of 5, 16 are formed sharply.

There are various types of recording papers P. Among them, thin papers, OHP film-like papers, etc., pass through a fixing nip portion after the fixing roller 11 and the pressure roller 1 have passed.
2 easily (wrap around the side with the toner image).

The upper separating claw 15 and the lower separating claw 16 prevent the jam by preventing the jammed recording paper P from being forcibly separated from the fixing roller 11 or the pressure roller 12. The contact position of the claw 15 and the lower separation claw 16 with the fixing roller 11 and the pressure roller 12 is several mm to several tens mm from the end of each size of the recording paper P used in the longitudinal direction.
It is set to the position of the degree. In the circumferential direction of the fixing roller 11 and the pressure roller 12, the upper separating claw 15 is located at a position several mm from the exit of the fixing nip portion, and the lower separating claw 16 is set at 10 mm.
It is arranged in the position of the degree. Incidentally, the contact positions of the upper separating claw 15 and the lower separating claw 16 in the circumferential direction of the fixing roller 11 and the pressing roller 12 are generally set on the same generatrix.

When the upper separating claw 15 and the lower separating claw 16 are brought into contact with the same position of the fixing roller 11 and the pressing roller 12 in the longitudinal direction for a long time, the contact position of the upper separating claw 15 and the lower separating claw 16 is changed. Of the fixing claw 11 and the pressure roller 12 to cause scratches and the like, which may cause an image defect.
mm reciprocation is also performed.

In many fixing apparatuses, a hard roller is used for the fixing roller 11 and an elastic roller is used for the pressure roller 12, so that the recording paper P is easily curled toward the fixing roller 11, and usually, many copies are made. The object is a one-sided image, and the recording paper P is also easily wrapped around the fixing roller 11 due to the binding force between the toner and the roller.

Furthermore, since the offset toner that has not been completely fixed on the recording paper P adheres to the fixing roller 11 on the printing surface side, the upper separation claw 15 tends to be easily stained by this toner. For this reason, the upper separating claw 15 is
Generally narrower than that. On the other hand, the pressure roller 1
2 has a large number of elastic rollers and is easily damaged. For this reason, a wide separation claw 16 is often used.

[0019]

However, in the case of the conventional fixing device, the type and state of the recording paper, when the image density is high, when the margin at the leading end of the image is small, and further, usually, the fixing is performed periodically. If the maintenance is neglected, the tip of the separation claw becomes dirty with toner, paper dust, etc., and the recording paper is caught on the dirt, so that the recording paper cannot be normally separated and a jam is rarely caused. . Such a problem is particularly likely to occur in the upper separating claw that contacts the fixing roller.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of improving the separability of a fixed recording sheet from a fixing roller.

[0021]

According to one aspect of the present invention, there is provided a fixing roller having a heating element therein, and a plurality of separating claws for contacting the fixing roller to separate recording paper. And a mechanism for fixing the separation claw or moving the separation claw at least in the longitudinal direction or the circumferential direction of the fixing roller so as to separate the recording paper from the vicinity of its end. And a separating claw is provided on the main body.

According to a second aspect of the present invention, in the first aspect of the present invention, the separation claw for separating the recording paper first is disposed at the left and right margins of the recording paper.

According to a third aspect of the present invention, in the first aspect of the present invention, of the plurality of separating claws, two separating claws at both ends first simultaneously separate the recording paper, and then separate the recording paper at both ends. A separation claw is provided so that the recording paper is separated by a separation claw other than the claw.

According to a fourth aspect of the present invention, in the first aspect of the invention, the recording paper is first separated from one of the separation claws at both ends of the plurality of separation claws, and the following is separated first. A separation claw is provided so as to sequentially separate the recording paper from the separation claw side.

[0025]

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

<Embodiment 1> FIG. 1 is a view of a fixing device 10 according to Embodiment 1 of the present invention as viewed from a sheet discharging side. In this figure, the same elements as those shown in FIG. , And a description thereof will be omitted below.

In the fixing device 10 according to the present embodiment, 4
The upper separating claws 15a, 15b, 15c, 15d are provided,
The two outer upper separation claws 15a and 15d
Are configured to be capable of reciprocating in the longitudinal direction.

The fixing roller 11 and the pressure roller 12 are pressed against each other with a predetermined pressure, and the fixing roller 11 is rotated by receiving a driving force from a driving source (not shown) external thereto. Rotates following the fixing roller 11.
Further, a felt roller 18 is brought into contact with the fixing roller 11 to clean the surface of the fixing roller 11.

Next, how the upper separating claws 15a to 15d contact the fixing roller 11 will be described.

The upper separating claw 15a,
15b, 15c and 15d are arranged in this order, the upper separating claws 15a and 15d on both sides can be reciprocated in the longitudinal direction as described above, and the inner upper separating claws 15b and 15c are fixed.

The upper separating claw 15 in the circumferential direction of the fixing roller 11
Looking at the positions a to 15d, the upper separating claws 15a and 1
5d is in contact with a position closer to the fixing nip portion than the inner upper separation claws 15b and 15c. This is because the edge of the recording paper has a relatively weak binding force to the fixing roller 11 as compared to the center, and therefore, it is easier to separate the edge of the recording paper before the edge of the recording paper is separated from the center. .

When looking at the contact positions of the upper separating claws 15a to 15d in the longitudinal direction, the upper separating claws 15a and 15d on both sides are located at the left and right margins at both ends of the recording paper, depending on the size of the recording paper. Move to the abutment point.

Incidentally, the detection of the size of the recording paper is automatically performed only by the user setting the document on the reader section. That is, the size of recording paper to be copied is automatically determined according to the transfer mode (magnification, double-sided, etc.), or the paper to be copied is manually selected from a plurality of paper cassettes by an "automatic paper selection function". Determines the size of the recording paper to be copied.

The upper separating claws 15a and 15d on both sides are thus provided.
The recording paper is moved so as to be positioned in the margins on both sides of the recording paper by driving the separation claw moving means (not shown) based on the determined copy size information of the recording paper. Here, the upper separation claws 15a and 15d are located at the minimum size and the maximum size of the recording paper in the range of the left and right paper edges (15a to 15a ',
(Range 15d to 15d ').

On the other hand, the inner upper separation claws 15b and 15c are fixed so as to be located inside the minimum size of the recording paper.

The four lower separating claws 16a, 16b, 16
Reference numerals c and 16d are arranged at appropriate intervals in the longitudinal direction of the pressure roller 12, and they are in contact with the surface of the pressure roller 12 at an appropriate pressure.

As described above, in the present embodiment,
Of the four upper separating claws 15a to 15d, only the two upper separating claws 15a and 15d on both sides are moved in the longitudinal direction according to the size of the recording paper, so that the recording paper is reliably separated by a simple mechanism. Can be done.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a view of the fixing device 10 according to the present embodiment as viewed from the sheet discharge side. In this figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals. Is omitted.

In the first embodiment, the standard for passing recording paper is the center, whereas in the present embodiment, the standard for passing recording paper is one side.

As shown in FIG. 2, the fixing device 10 according to the present embodiment is also provided with four upper separation claws 15e, 15f, 15g, and 15h as in the first embodiment. In the copying machine according to the present embodiment, the right side (the front side of the copying machine body) in FIG. 2 is a paper passing reference, and the front end of the recording paper is constant regardless of the size.

In this embodiment, attention is paid to the above point, and in this embodiment, the upper separation claw 15h on the paper passing reference side is fixed. The contact position of the upper separation claw 15h is determined by the other three separation claw 15h.
e, 15f, 15g, closest to the fixing nip area,
In addition, it is disposed so as to be located in a margin on the front side of the recording paper.

On the other hand, the other three upper separation claws 15g, 15
f and 15e are configured to be movable in the longitudinal direction, and the four upper separating claws 15e to 15e to 15e, depending on the size of the recording paper.
At least two (including 15h) out of 15h are configured to contact the fixing roller 11.

As shown in FIG. 2, when the recording paper to be passed is the maximum size, the four separation claws 15e to 15e
h is used, and in the case of the minimum size, the fixed upper separation claw 1
5h and two upper separation claws 15f ', 1 moved in the longitudinal direction
5g 'is used. If the size of the recording paper is intermediate, the three upper separating claws 15e ',
The recording paper is separated using 15f 'and 15g'.

In the circumferential direction of the fixing roller 11, the upper separation claw 15h starts separation of the recording paper earliest.
These separation claws 15g ', 1 are arranged such that the upper separation claws 15g' → 15f '→ 15e' start separating the recording paper in this order.
5f 'and 15e' are sequentially arranged from upstream to downstream in the rotational direction.

In the first embodiment, the upper separation claws 15a and 15d located at the left and right margins are arranged so as to separate the recording paper at the same time. However, as in the present embodiment, the recording paper is divided into one margin. And sufficient separation performance can be ensured even when the upper separation claws 15e, 15f, and 15g are separated.
The advantage is that the mechanism can be simplified because the moving directions of the two can be the same.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a cross-sectional view of the fixing device according to the present embodiment, and FIG. 4 is a view of the identification attaching device as viewed from the sheet discharging side. FIGS. 1, 2 and 6 show these drawings. The same reference numerals are given to the same elements as those described above, and description thereof will be omitted below.

In this embodiment, four upper separation claws 15
h, 15i, 15j, and 15k, two upper separating claws 15h and 15k on both sides can be moved in the circumferential direction and the longitudinal direction of the fixing roller 11 by the driving means 32 (see FIG. 4). The upper separating claws 15i and 15j are fixed. The circumferential movement of the upper separating claws 15h and 15k on both sides is performed along the arc rail 31 via the positioning pins 30 as shown in FIG.

In this embodiment, a case where ordinary paper is copied is usually used, and a case where recording paper having a poor separability after fixing (hereinafter referred to as special paper) is copied. And the contact positions of the upper separating claws 15h and 15k are changed between the two.

Therefore, according to the present embodiment, most of the commonly used recording papers have no problem in the separability, and the four upper separating claws 15h to 15k are fixed at the circumferentially fixed positions (in the figure,
It is only necessary to make contact with the horizontal line A).

However, since it is known that recording paper such as thin recording paper or OHP film does not have a very good separation property before passing the paper, the user can use a special paper mode function provided in the copying machine in advance. By selecting, the upper separating claws 15h, 15k on both sides of the upper separating claws 15h to 15k are selected.
At position 1 near the fixing nip at both ends of the special paper size
5h ', 15k' (horizontal line B in the figure) so as to make contact with them. In the present embodiment, as shown in FIG. 4, a case of special paper having a small size is shown.

According to the present embodiment, the recording paper having a poor separability is registered as a known special paper, and only when the user selects the special paper mode function, the upper separation pawls on both sides are registered. Since the configuration for moving 15h and 15k is adopted, even special paper can be reliably separated.

[0053]

As is apparent from the above description, according to the present invention, a fixing device having a fixing roller having a heating element therein and a plurality of separation claws for contacting the fixing roller to separate recording paper. Means for recognizing the size of the recording paper,
A mechanism for fixing or moving the separation claw at least in the longitudinal direction or the circumferential direction of the fixing roller is provided, and the separation claw is disposed so as to separate the recording paper from the vicinity of the end thereof.
The effect is obtained that the separability of the fixed recording paper from the fixing roller can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram of a fixing device according to a first embodiment of the present invention as viewed from a sheet discharging side.

FIG. 2 is a view of a fixing device according to a second embodiment of the present invention as viewed from a sheet discharging side.

FIG. 3 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a fixing device according to a third embodiment of the present invention as viewed from a sheet discharging side.

FIG. 5 is a sectional view of a conventional electrophotographic copying machine.

FIG. 6 is a sectional view of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing apparatus 11 Fixing roller 12 Pressure roller 15a-15k Upper separation claw 16a-16d Lower separation claw 31 Arc rail 32 Drive means P Recording paper

Claims (4)

[Claims] 1. A fixing device comprising: a fixing roller having a heating element therein; and a plurality of separation claws for contacting the fixing roller to separate recording paper; means for recognizing a size of the recording paper; A fixing mechanism for fixing the recording paper in at least a longitudinal direction or a circumferential direction of the fixing roller, and a separating claw disposed to separate the recording paper from the vicinity of the end thereof. 2. The fixing device according to claim 1, wherein a separation claw for separating the recording paper first is disposed in a left and right margin of the recording paper. 3. The separation pawls at both ends of the plurality of separation pawls simultaneously separate recording paper first, and then separate the recording paper by separation pawls other than the separation pawls at both end parts. 2. The fixing device according to claim 1, further comprising a claw. 4. A recording paper is first separated from one of the separation claws at both ends of the plurality of separation claws, and the recording paper is separated so as to sequentially separate the recording paper from the side of the separation claw to be separated first. 2. The fixing device according to claim 1, further comprising a claw.