JPH02226280A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To satisfactorily transfer a toner image on the whole surface of a transfer paper and to miniaturize a device by setting an angle theta that is formed by the tangent line of a toner transfer position and the extension line of the advancing angle of the transfer paper held by a toner fixing means at 180 deg. or below to the tangent line. CONSTITUTION:A paper guide member 13 with a projecting part on its upper part is provided on the transfer paper carrying path between a toner transfer means including a corona discharge wire 4 for transfer and a toner fixing device including fixing rollers 20 and 21. The trailing edge of the transfer paper 26 passes through a photosensitive body 1 and the toner transfer means and the transfer paper 26 is held by the toner fixing means 20 and 21 and is carried in the paper ejecting direction. At this time, the angle theta is made by the tangent line 102 of the toner transfer position and the extension line 105 of advancing angle of the transfer paper 26 held by the fixing rollers 20 and 21. The angle thetais downward set 180 deg. or below. Consequently, even when width between the upper projecting part of the paper guide member 13 and the fixing means is 160mm or below, that is, the device is miniaturized, the transfer paper 26 still maintains sufficient elasticity. Thereby, imperfect transfer is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic device, and more particularly, to an improvement in an electrophotographic device that can transfer a good toner image over the entire surface of transfer paper. .

[Conventional technology]

Conventionally, a paper conveyance path from a toner transfer section to a fixing section of an electrophotographic apparatus often has a configuration as shown in FIG.

In FIG. 2, the toner transfer portion of the photoreceptor 1 includes a toner transfer corona discharge wire 4 for transferring the toner image 15 formed as a visible image on the photoreceptor 1 onto a transfer paper 26, and A charge-removing corona discharge wire 16 is provided to remove charge from the transfer paper 26 that is charged by the toner transfer corona discharge wire 4 and is attracted to the photoreceptor 1 by electrostatic force. The corona discharge wire 4 for toner transfer and the corona discharge wire 16 for static elimination are housed in a corona discharger case 2, and the corona discharger case 2 is connected to the photoreceptor 1.
It is open only in the direction. However, a paper intrusion prevention bridge 13 for preventing the transfer paper 26 from intruding into the corona discharger case 2 is partially fitted above the opening direction of the charge eliminating corona discharge wire 16. A pair of upper and lower toner fixing rollers 20 and 21 are arranged in front of the corona discharger case 2 (in the paper conveyance direction). I will guide you to.

Here, to summarize the above description, in FIG. 2, the transfer paper 26 is conveyed from a paper cassette (not shown) by paper conveyance rollers 5, 6, and paper guides 7.8.
to the toner transfer portion of the photoconductor 1, and the corona discharge of the toner transfer corona discharge wire 4 causes the photoconductor 1 to
It is charged to a potential opposite to that of the toner image 15 above, and the toner image 15 on the photoreceptor 1 is transferred by Coulomb force.

Thereafter, the transfer paper 26 is neutralized by the corona discharge of the static elimination corona discharge wire 16, and after being separated from the photoconductor 1, the transfer paper 26 is moved to the toner fixing roller 2 by the paper conveyance belt 25.
The toner image 15 transferred onto the transfer paper 26 is fixed.

By the way, when the toner image 15 on the photoreceptor 1 is transferred onto the transfer paper 26, if the toner image 15 on the photoreceptor 1 and the transfer paper 26 are not in close contact, the toner transfer efficiency will be reduced. , so-called transfer defects occur. That is, in order to successfully transfer the toner image 15 onto the entire surface of the transfer paper 26, it is necessary to bring the transfer paper 26 and the photoreceptor 1 into close contact over the entire surface of the transfer paper 26.

Then, in the 1-ner transfer section of the electrophotographic device, the transfer paper 2
When transferring toner from the front edge of 6 to the center, paper guide 7.8
Since the transfer paper 26 can be sandwiched and guided from above and below to the front of the toner transfer portion, it is easy to bring the photoreceptor 1 and the transfer paper 26 into close contact with each other. However, when transferring the trailing edge of the paper where the transfer paper 26 separates from the paper guide 7.8, the force that brings the transfer paper 26 into close contact with the photoreceptor 1 is due to the electrostatic attraction that acts between the transfer paper 26 and the photoreceptor 1. In the case of a transfer paper with strong rigidity, a gap is easily created between the photoreceptor 1 and the transfer paper 26 due to the flap of the transfer paper, resulting in a transfer failure.

A conventional technique for preventing such transfer defects is described in, for example, Japanese Patent Application Laid-Open No. 60-79375.
To explain using FIG. 2, when the front end of the transfer paper 26 completes the transfer, separates from the photoreceptor 1, and falls onto the paper conveyance belt 25, as shown by the two-dot chain line 104, the paper is prevented from entering. Since the front end of the transfer paper 26 hangs downward due to its own weight with the convex portion of the upper surface of the bridge 13 as a fulcrum, the transfer paper 26
On the rear end side, the reaction force generates a force that urges the upper side of the photoreceptor, and it is possible to prevent poor adhesion due to flapping of the transfer paper 26.

[Problem to be solved by the invention]

As described above, according to the electrophotographic apparatus described in Japanese Patent Application Laid-Open No. 60-79375, the toner transfer/fixing operation is in progress.

When the transfer paper 26 that has passed through the paper intrusion prevention bridge 13 heads toward the toner fixing rollers 20 and 21 diagonally downward, a reaction force using the protrusion on the paper intrusion prevention bridge 13 as a fulcrum is generated due to the fall of the transfer paper 26 due to its own weight. The rear end side of the transfer paper 26 is urged toward the photoreceptor 1 side to prevent poor adhesion due to the transfer paper 26 flapping.

However, according to experiments, when paper with a basis weight of 93 g/rri used for general office work is held on both sides with one end fixed, the distance between the supporting points Ω and the deflection δ at that time are as shown in Figure 3. When the relationship was measured, it was found that when Q is approximately 160 rm1 or more, δ is largely deflected, but when Ω is approximately 160 III11 or less, it is hardly deflected. That is, as shown by the two-dot chain line 104 in FIG.
6, it is necessary to provide a distance of at least 160 m between the convex portion of the upper surface of the paper intrusion prevention bridge 13, which serves as a fulcrum, and the toner fixing rollers 20 and 21 (toner fixing point).

However, products that use conventional electrophotographic methods are
Most of them are copying machines, and in addition to being equipped with a document reading section for reading originals of the same size as the transfer paper, the equipment itself is usually at least A4 in size.
Since the length in the paper feeding direction exceeds 297 nwn, which is the longitudinal direction of the size (A4 size, which is the most frequently used size), the problem of poor fixing as described above does not occur.

In addition, electrophotographic printers such as laser printers, which have become significantly smaller in recent years, are still mainly used as text printers due to the processing speed of the personal computers connected to them, and There is little need for printing up to this point, and in most cases, the trailing edge of the transfer paper is outside the guaranteed printing range.

However, recently, like optical filing systems,
Devices that can read and print the entire surface of a document are beginning to be placed in general office environments, and electrophotographic devices such as laser printers, which are used as output devices, are small and have the ability to print on the entire surface of the transfer paper. There is a growing demand for performance that can be printed on.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved electrophotographic device that is capable of keeping the trailing edge of a transfer sheet in close contact with a photoreceptor in a stable manner and transferring a toner image well over the entire surface of the transfer sheet even when the device is miniaturized. It's about doing.

[Means to solve the problem]

The purpose is to provide a means for conveying a transfer paper to a toner transfer position, a means for transferring a toner image formed on a photoconductor onto the transfer paper at the transfer position, and a means for fixing the transferred toner image on the transfer paper. An electrophotographic apparatus comprising:
A paper guide member having an upward protrusion is provided in the paper transport path between the toner transfer means and the toner fixing means, and
When the trailing edge of the transfer paper passes between the photoreceptor and the toner transfer means, the toner fixing means grips the transfer paper on which toner has already been transferred and forcibly transports it in the paper ejection direction. This is achieved by setting the angle θ between the tangent to the transfer position and the extended line of the approach angle of the transfer paper held by the toner fixing means downward to θ≦180° with respect to the tangent to the toner transfer position. .

[Effect]

However, as mentioned earlier, Japanese Patent Application Laid-Open No. 60-79375
According to the electrophotographic device (Fig. 2) described in the publication, the third
From the experimental results shown in the figure, if the convex part on the upper surface of the paper intrusion prevention bridge 13 and the toner fixing rollers 20 and 21 (toner fixing point) are separated by 160 mm or more, the paper intrusion prevention bridge Transfer paper 26 that has passed through 13
When the transfer paper 26 moves diagonally downward toward the toner fixing rollers 20 and 21, based on the falling weight of the transfer paper 26, a reaction force using the protrusion on the paper intrusion prevention bridge 13 as a fulcrum causes the rear end side of the transfer paper 26 to be attached to the photoreceptor. 1 side, it is possible to prevent poor adhesion due to flapping of the transfer paper 26. In this case,
The positions of the toner fixing rollers 20 and 21 viewed from the tangential direction of the transfer position on the photoreceptor 1.

No matter what position or angle the transfer paper 26 enters, it does not affect the transfer paper 26 at the transfer position.

However, if the distance between the toner transfer point of the photoreceptor 1 and the toner fixing rollers 20 and 21 (toner fixing point) is to be narrowed, in other words, if the electrophotographic apparatus is to be downsized, then the reference numeral 13 in FIG. Even if the paper intrusion prevention bridge shown in FIG. 3 is provided, the experimental results shown in FIG. The paper 26 is
Due to the rigidity of the transfer paper 26 itself, it reaches the toner fixing side without bending, and as a result, when transferring the toner image 15 to the rear end of the transfer paper 26, the transfer paper 26
The rear end of 6 will flap and transfer defects will occur.

On the other hand, as shown in FIG. 7, the tangent line 10 of the toner transfer position
2 and the approach angle extension line 105 of the transfer paper 26 held between the toner fixing rollers 20 and 21, when the angle θ is set downward with respect to the tangent 102 of the toner transfer position to 0>180°, Since the front part of the transfer paper 26 is lifted around a point shifted toward the toner fixing roller 20.21 from the toner transfer position on the photoreceptor 1, the front part of the transfer paper 26 is lifted up, so that the transfer paper 26 is placed on the photoreceptor 1 side at the toner transfer position. A force f' urging in the opposite direction is generated.

The approach angle of the transfer paper held between the toner fixing rollers 20 and 21 is as shown in FIG. It represents the angle that the paper 26 makes with the toner fixing rollers 20 and 21, and the extension line 105 of the approach angle of the transfer paper 26 is:
The toner fixing rollers 20 and 21 are uniformly determined by the diameter and hardness of each of the rollers 20 and 21 that make up the toner fixing rollers 20 and 21, and the insertion of the transfer paper 26 into the 1 henna fixing rollers 20 and 21 is as follows. , it is desirable that the transfer material 26 be conveyed from the direction of the extension line 105 of the approach angle.

In contrast, in the present invention, a paper guide member having an upward protrusion is provided in the paper transport path between the toner transfer means and the toner fixing means, and as shown in FIG. When the trailing edge of the paper 26 passes between the photoreceptor 1 and the toner transfer means 20.21, the toner fixing means 20.21 grips the transfer paper 26 on which toner has already been transferred and forcibly moves it in the paper ejection direction. The tangent line 102 of the toner transfer position and the toner fixing means 20° 21 when the toner is being conveyed to
From the experimental results shown in FIG. 3, by setting the angle 0 formed by the approach angle extension line 105 of the transfer paper 26 held between the two sides to be O≦18° below the tangent line 102 of the toner transfer position. Even if the distance between the convex portion of the upper surface of the paper guide member 13 and the toner fixing means 20.21 (toner fixing point) is set to 160 mm or less, that is, even if the electrophotographic apparatus is to be miniaturized, the distance shown in FIG. According to the structure, unless the transfer paper is extremely weak in rigidity, the transfer paper 26 still has sufficient elasticity in the length between the upper surface convex part of the paper guide member 13 and the toner fixing means 20.21. . That is, the toner fixing means 20.21 grips the transfer paper 26 on which toner has already been transferred and forcibly conveys it in the paper ejection direction, thereby moving the front end of the transfer paper 26 to the toner transfer position below the photoreceptor 1. Push down (2
The transfer paper 26 can be urged toward the photoreceptor 1 at the toner transfer position on the photoreceptor 1 by the reaction force using the convex portion on the upper surface of the paper guide member 13 as a fulcrum (dotted chain line 103). In addition,
In the case of transfer paper with extremely low rigidity, the transfer paper adheres closely to the photoreceptor 1 due to the electrostatic attraction force of the photoreceptor 1.
The problem of poor transfer across the entire area of the transfer paper does not occur. Furthermore, in the configuration shown in FIG. 6, at least the force f' shown in FIG. 7 (that is, the force f' that urges the transfer paper 26 in the direction opposite to the photoreceptor 1 side) is not generated, and the toner image is Transfer defects can be prevented.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings. FIG. 1 is an explanatory diagram of the overall structure of a transfer fixation section showing an embodiment of an electrophotographic apparatus according to the present invention.

In FIG. 1, reference numerals 5 and 6 indicate a pair of upper and lower transfer paper transport rollers that start transporting the transfer paper 26 in synchronization with the development process of the photoreceptor 1; 4 is a toner transfer corona discharge wire for transferring the toner image 15 formed as a visible image on the photoreceptor 1 onto a transfer paper 26; 16 is an electrostatic force applied to the photoreceptor 1; 2 is a corona discharge wire that covers the toner transfer corona discharge wire 4 and the transfer paper weight removal corona discharge wire 16; The paper intrusion prevention bridge whose overall shape is clearly shown in FIG. , the upper surface convex portion of the paper intrusion prevention bridge 13 is
The tangent line of the toner transfer position on the photoreceptor 1 (dotted chain line 1
o2) located above. 20 and 21 are a pair of upper and lower toner fixing rollers that fix the toner image 15 transferred onto the transfer paper 26; 14, the toner fixing roller 2 fixes the transfer paper 26;
0 and 21, the toner pre-fixing guide 14 is shown. Therefore, in the embodiment of FIG. 1, the transfer paper 26
When the trailing edge passes the toner transfer position on the photoreceptor 1, the toner fixing rollers 20 and 21 are gripping the transfer paper 26 on which toner has already been transferred and forcibly conveying it in the paper ejection direction. The angle θ between the tangent 102 of the toner transfer position and the extension line 105 of the approach angle of the transfer paper 26 held between the toner fixing rollers 20 and 21 is set to 175° downward with respect to the tangent 102 of the toner transfer position. It is. Further, the distance between the convex portion on the upper surface of the paper intrusion prevention bridge 13 and the toner fixing rollers 2C1 and 21 is set to 125 mm.

Further, the distance between the toner transfer position on the photoreceptor 1 and the toner fixing rollers 20 and 21 is set to 140 pixels.

In addition, in FIG. 1, the transfer paper 26 is attached to a pair of upper and lower paper guides 7.
8 shows a state where the transfer paper 26 is about to be guided to the transfer section on the photoreceptor 1, and after this, the transfer paper 26 is charged by the corona discharge of the toner transfer corona discharge wire 4.
The toner image 15 on the photoreceptor 1 is transferred onto the transfer paper 26 . At this time, the toner image 1 is placed on the front edge of the transfer paper 26.
5, the transfer paper 26 can be urged toward the photoreceptor 1 by a pair of upper and lower paper guides 7.8 located in front of the transfer section surface. In addition, when transferring the toner image 15 to the center part of the transfer paper 26, the paper guide 8 located before and after the transfer part and the convex upper surface of the paper intrusion prevention bridge 13 allow the toner image 15 to be Place the paper 26 on the photoreceptor 1
It can be biased to the side.

In addition, when transferring the toner image 15 to the rear edge of the transfer paper 26, in the present invention, when the rear edge of the transfer paper 26 passes the toner transfer position on the photoreceptor 1, the toner fixing roller 20 and 21 are sandwiching the transfer paper 26 on which toner has already been transferred and forcibly conveying it in the paper discharge direction, and the tangent 102 of the toner transfer position, and the transfer paper 26 sandwiched between the toner fixing rollers 20 and 21. Approach angle extension line 1
05 is the tangent line 102 of the toner transfer position.
By setting the angle downward to 0≦180° (175° in the case of the embodiment shown in FIG. 1), from the experimental results shown in FIG. ; Between 21 (toner fixing point) and 160
mn or less, that is, even when downsizing the electrophotographic apparatus, the length between the upper surface convex part of the paper intrusion prevention bridge 13 and the toner fixing roller 20.21 is Now, the transfer paper 26 still has sufficient elasticity. That is, the toner fixing roller 2
0 and 21 grip the transfer paper 26 on which toner has already been transferred and forcibly convey it in the paper ejection direction.
6 downward from the tangent to the toner transfer position on the photoreceptor 1 (double-dotted line 102) (double-dotted line 102).
03), the transfer paper 26 can be urged toward the photoreceptor 1 at the toner transfer position on the photoreceptor 1 by the reaction force using the convex portion on the upper surface of the paper intrusion prevention bridge 13 as a fulcrum. In addition, in the case of transfer paper with extremely low rigidity, the transfer paper is
Because the electrostatic attraction force causes the photoreceptor to adhere closely along the photoconductor, there is no problem of poor transfer across the entire area of the transfer paper.

In the illustrated embodiment, the tangent line between the transfer paper holding position of the pair of upper and lower toner fixing rollers 20 and 21 and the toner transfer position on the photoreceptor 1 (dotted chain line 102 in FIG.
) direction is less than the radius of the upper roller 20 (in the case of the embodiment shown in FIG. 1, five books), but according to this configuration,
The transfer paper 26 conveyed from the photoreceptor 1 side can always be smoothly fed between the toner fixing rollers 20 and 21. In other words, if the toner fixing rollers 20 and 21 are arranged extremely low, if the rigidity of the transfer paper 26 is large,
Despite the rotation of the toner fixing rollers 20 and 21, the transfer paper 26 rides above the toner fixing roller 20, but as described above, the transfer paper holding position of the pair of upper and lower toner fixing rollers 20 and 21 If the distance between and the tangent line of the toner transfer position on the photoreceptor (dotted chain line 1o2 in FIG. 1) is less than the radius of the upper roller 20 (5 mm in the embodiment shown in FIG. 1), the photoreceptor Even if the transfer paper 26 conveyed from the body 1 side has high rigidity, the transfer paper 26 is always guided along the rotational direction of the toner fixing roller 20 so that the transfer paper 26 is always attached to the toner fixing roller 2.
It can be fed smoothly between 0 and 21.

By the way, Japanese Patent Publication No. 54-125039 and 54-12
No. 5040, No. 59-22060, No. 62-1862
No. 77, No. 62-229262, No. 62-22926
No. 3, No. 63-88569, etc., show diagrams in which the toner fixing device is located below the toner transfer point between the photoreceptor and the transfer paper, but none of them. Also, the paper guide member located in the paper transport path between the toner transfer point and the toner fixing device and having an upwardly protruding protrusion is not provided. When the transfer paper moves diagonally downward toward the toner fixing device, no force is generated that urges the rear end of the transfer paper toward the photoconductor due to the force that uses the protrusion of the guide member as a fulcrum.

Although this is not a main effect of the present invention, but a secondary effect, the transfer paper 26 has a projection on the paper guide member (in the case of the illustrated embodiment, the upper surface of the paper intrusion prevention bridge 13) in the vicinity of the toner transfer position. As shown in FIG. 8, even if an impact force is applied from the conveying direction of the transfer paper 26 during toner transfer, the front end side of the transfer paper 26 It has also been found that the more the transfer position is pushed down from the tangential direction of the transfer position, the more effective it is to absorb transfer deviation in the paper transport direction due to impact.

Furthermore, based on the experimental results shown in FIG.
Although the effect is remarkable when the distance between the upper surface convex portion and the toner fixing roller 20.21 (toner fixing point) is 160 m or less, the present invention can be applied to an electrophotographic apparatus where the distance is 160 m or more. There is no problem.

〔Effect of the invention〕

The present invention is as described above, and as is clear from the description of the illustrated embodiments, according to the present invention, even if the distance between the toner transfer point of the photoreceptor and the toner fixing means is narrowed -19= As a result, even though electrophotographic devices are becoming smaller, the trailing edge of the transfer paper can always be stably brought into close contact with the photoreceptor, and the toner image can be transferred satisfactorily over the entire surface of the transfer paper.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the overall configuration of a toner transfer and fixing section showing an embodiment of an electrophotographic apparatus according to the present invention, FIG. 2 is an explanatory diagram of the entire configuration of a toner transfer and fixing section in a conventional electrophotographic apparatus, and FIG. The figure is a characteristic diagram showing the relationship between the distance between supporting points and the amount of deflection when the paper is deflected by its own weight. Partial cutaway perspective views, FIGS. 5 to 7 are shown with reference numbers 20 and 21 in FIG.
Figure 8 is an explanatory diagram of the behavior of the transfer paper 26 when the nip position of the pair of upper and lower toner fixing rollers is changed. See Figure 5 to see if there is any misalignment.
FIG. 9 is a conceptual diagram illustrating the approach angle of the transfer paper 26 to the toner fixing rollers 20 and 21. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 4...Corona discharge wire for toner transfer, 7 and 8...Paper guide, 13...Paper intrusion prevention bridge, 15.Toner image, 20 and 21.1-Fixing roller , 26... Transfer paper.

Claims (1)

[Scope of Claims] 1. Means for conveying a transfer paper to a toner transfer position, means for transferring a toner image formed on a photoconductor to the transfer paper at the transfer position, and a toner image on the transferred transfer paper. In an electrophotographic apparatus, a paper guide member having an upward protrusion is provided in a paper conveying path between the toner transfer means and the toner fixing means, and a trailing edge of the transfer paper is arranged on the photoreceptor. When passing between the toner transfer means and the toner transfer means, the toner transfer position is tangent to the toner fixing means when the toner fixing means grips the transfer paper on which toner has already been transferred and forcibly conveys it in the paper ejection direction. An electrophotographic apparatus characterized in that an angle θ formed by an extension line of an approach angle of the transfer paper held between the two is set downward to a tangent to the toner transfer position so that θ≦180°. 2. In the invention described in claim 1, the distance between the protrusion of the paper guide member and the paper holding position of the toner fixing means is 160 mm in the tangential direction of the toner transfer position on the photoreceptor.
An electrophotographic device having a size of 1 mm or less. 3. In the invention as set forth in claim 1 or 2, the toner fixing means is composed of a pair of upper and lower rollers, and the toner fixing rollers of the pair have a transfer paper holding position and a toner transfer position on the photoreceptor. An electrophotographic apparatus in which the distance from the tangential direction of the upper fixing roller is less than the radius of the upper fixing roller.