JPH063974A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce such defective transferring as scattering at the time of transferring by specifying the positions of a transfer charging member and a transferring guide. CONSTITUTION:A tangent L1 on a point IS is included, the leading edge E of a transferring lower guide 6B is positioned on the upper part of the tangent L1, and an angle formed by the transferring material carrying surface of the transferring guide 6 and a horizontal direction is set smaller than the angle formed by the tangent L1 of the point IS and the horizontal direction. That is, the end part of the transferring guide 6 on a most downstream side guiding the transferring material is positioned on the upper part including the tangent L1 of an image carrier 1 on the point on a most upstream side in a transferring material moving direction among contacting parts between the image carrier 1 and the transferring roller 2, and the angle formed by the transferring material guiding surface of the transferring guide 6 and the horizontal direction is set smaller than the angle formed by the tangent L1 and the horizontal direction. Thus, the spring, blur, and defective carrying of the transferring material at the time of entering a transferring nip part can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer which utilizes an image forming process such as electrophotography and electrostatic recording, and more particularly to transferring an image on an image carrier to a transfer material. Further, the present invention relates to an image forming apparatus having a transfer charging member such as a transfer roller that comes into contact with an image carrier.

2. Description of the Related Art Conventionally, a transfer roller is brought into contact with a photosensitive member which is an image carrier, a transfer material is fed between them, and a toner image on the photosensitive member is transferred by applying a bias voltage to the transfer roller. In the case of an electrophotographic apparatus or the like in which the image is transferred to a fixing device by a photoconductor and a transfer roller,
As shown in FIG. 3, the transfer material was made to smoothly enter the contact portion 1S between the photoconductor 1 and the transfer roller 2, and was sent out from the contact portion in a direction substantially along the outer periphery of the transfer roller 2.

[0003]

In the above-mentioned conventional example, because of the conveying path in the vicinity of the contact portion between the photoconductor 1 and the transfer roller 2, the force that causes tension on the transfer material when the transfer material passes through the transfer portion. Is applied, the resultant transfer material exerts a force in the direction of separating the transfer roller from the photoconductor.

Further, the transfer roller 2 is pressed against and brought into contact with the photosensitive member 1 by a supporting member (not shown) using an elastic body such as a spring. Therefore, the transfer material exerts a force on the transfer roller 2 in a direction in which it is separated from the photoconductor, and displaces the transfer roller from the regular position, thereby changing the distance and contact area between the photoconductor and the transfer roller.

On the contrary, in order to prevent the displacement of the transfer roller 2, when the transfer roller is pressed against the photoconductor with a sufficient force, the transfer material P reaches the photoconductor 1S,
When sandwiched between the transfer nip portion, the transfer roller is an elastic body and the photosensitive member is a rigid body in the transfer nip portion. Therefore, as shown in FIG. 5, the transfer roller is dented and the transfer material is deformed along it. Attempt to jump in the tangential direction at 1S. At this time, the transfer material P contacts the transfer guide 8A and its deformation is restricted, and the impact thereof disturbs the transferred image. Similarly, when the transfer material P is conveyed while being driven by the transfer nip portion and the registration roller, the transfer material P is transferred when the trailing end of the transfer material passes through the registration roller or when it passes through the transfer guides 8A and 8B. The trailing edge of P jumps up and disturbs the transferred image at that time.

Furthermore, since a transfer bias voltage is applied to the transfer roller 2, the transfer material P is smoothly inserted into the transfer nip as shown in the figure.
A strong electric field is formed in the slight gap a between the photoconductor 1 and the transfer roller 2 near the S, and the photoconductor 1 is applied to the transfer material P.
There is a defect that a toner image failure, that is, so-called pre-transfer occurs due to the upper toner image flying in the air gap A and transferring.

Further, as is generally known, in transfer using a transfer roller, a slight speed difference, that is, a peripheral speed difference, exists between the rotational movement speed of the photoconductor 1 and the rotational movement speed of the transfer roller. Since the transfer material P forms a loop in the upstream of the transfer nip, that is, between the registration roller and the transfer roller, the transfer material P exhibits a complicated behavior, and thus a defect of the transferred image is likely to occur. Also had.

(Object of the Invention) An object of the present invention is to provide an image forming apparatus which prevents image defects and forms good images.

Another object of the present invention is to provide an image forming apparatus having improved transfer material transportability in the vicinity of the transfer portion.

(Constitution of the Invention) A transfer charging member that contacts the image carrier to electrostatically transfer the toner image on the image carrier to the transfer medium, and a guide member that guides the transfer medium to the transfer position.
In the image forming apparatus having the image forming apparatus, the most downstream end of the guide member for guiding the transfer material is an image at a point on the most upstream side in the transfer material moving direction in the contact portion between the image carrier and the transfer charging member. It is characterized in that it is positioned above and including the tangent line L _{1 of the} carrier, and the angle formed between the transfer material guide surface of the guide member and the horizontal direction is smaller than the angle formed between L ₁ and the horizontal direction. is there.

[0011]

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

1 and 2 are schematic side views of the vicinity of the transfer position and the apparatus main body of the image forming apparatus of the present invention, respectively, with reference to which the operation of the apparatus will be described.

As shown in FIG. 2, O is a document to be copied, 104 is a scanning optical system as an exposing means for irradiating the document with light to expose the photoconductor 1 as a light image, and 102 is the photoconductor 1. A charging roller as a charging means for uniformly charging the
Reference numeral 101 is a developing device that is a developing unit for developing an electrostatic latent image on the photoconductor 1 with a toner image, 103 is a cleaner that removes and cleans residual toner on the photoconductor 1, and 105 is a transfer sheet. A fixing device as a means for fixing the transferred toner image, 106 is a discharging needle as a discharging means for discharging the transfer material, 3 is a pair of registration rollers for feeding and conveying the transfer material P, and 6 is a transfer material P. Transfer guide pair to be introduced into the section,
Reference numeral 4 denotes a conveyor belt which is a means for conveying the transfer material on which toner has been transferred to the fixing device 105.

The scanning optical system 104 irradiates the original O with light and exposes the reflected light to the photoconductor 1. Since the surface of the photoconductor 1 is cleaned by the cleaner 103 in advance and then uniformly charged by the charging roller 102, an electrostatic latent image is formed by imagewise exposure by the scanning optical system 104. It This latent image is on the photoreceptor 1.
It is driven to rotate in the direction of arrow A, and is developed by the developing device 101 as a toner image corresponding to the latent image. The developed toner image on the photoconductor 1 is, together with the transfer material P conveyed by the registration roller pair 3 by the driven paper feeding system (not shown), in synchronization with the rotation of the photosensitive drum.
It is transferred onto the transfer material P by the transfer action of the transfer roller 2. After that, the photoconductor 1 is again subjected to the cleaning action and the charging action in the same manner to be used for the next image formation. On the other hand, the transfer material P on which the toner image has been transferred is discharged from the photoconductor 1 by removing the transfer charge by the charge removing action of the charge removing needle 106, and is sent to the conveyance belt 4. The transfer material P is transferred to the fixing device 105 by the conveyor belt 4 and is transferred to the fixing device 105.
The toner image is fixed on the transfer material P under the action of heating and pressurizing, and one cycle of image formation is completed.

The most characteristic constitution of the present invention will be described below with reference to FIG. 1. A drum-shaped photosensitive member 1 having a grounded aluminum as a base material and an induction photosensitive layer applied thereon is a rigid body. It has an outer diameter of 30 mm and is in the direction of arrow A.
It is rotationally driven at ₁ = 197.2 mm / sec. Two
Is a transfer roller, which is formed by dispersing a conductive material such as carbon in urethane, EPDM (a terpolymer of ethylene propylene diene), etc. on a cored bar made of a conductive rigid material such as metal. , Volume resistance is 10 ⁵ to 10
^The hardness is adjusted to about 20 Ωcm by Asker C to about ¹⁰ Ωcm and is faster than the peripheral speed of the photoconductor 1 in the direction of arrow B ν ₀ = 2
It is rotationally driven at 00 mm / sec. The transfer roller 2 is arranged so as to start contact with the point 1S on the photoconductor 1 and move away from the point 1e. The transfer roller 2 biases its core with a spring at a total pressure of about 550 gr at two positions on the front side and the back side of the non-image area in the longitudinal direction (direction perpendicular to the paper surface of FIG. 1). Has been pressed. A transfer bias of about 1 to 10 kv is applied to the core metal. 3A is a resist upper roller, which is made of a conductive rigid body material such as SUS, and has an outer diameter of 13 mm and is rotationally driven in the direction of the arrow at the same peripheral speed of the photoreceptor 1 as ν ₀ = 200 mm / sec. There is. Further, 3B is a lower resist roller, which is SUS
A core metal such as is coated with a rubber material, and has an outer diameter of 16 mm, in the direction of the arrow, the same as the peripheral speed of the registration upper roller ν ₀ =
It is rotationally driven at 200 mm / sec.

Transfer guide pairs 6A and 6B are made of a conductive rigid material such as SUS having a thickness of about 1 mm, and are grounded via a varistor. The transfer material conveyed by the registration roller pair 3 is guided to an appropriate position in the transfer area, and the behavior of the transfer material is regulated. Reference numeral 4 denotes a conveyor belt. After the toner-transferred transfer material is separated from the photoconductor 1, the transfer material reaches the belt and is sent to the fixing device in the arrow direction at ν ₀ = 200 mm / sec.

Here, what is important is the positional relationship between the transfer nip formed by the photosensitive member 1 and the transfer roller 2, the transfer guide pair 6, and the conveyor belt 4. The front end of the transfer material is conveyed by being sandwiched between the upper registration roller 3A and the lower registration roller 3B, and goes toward the transfer nip along the transfer guide 6A or 6B. In this configuration, the upper resist roller 3A has a smaller outer diameter and a higher hardness than the lower resist roller 3B. Therefore, in the nip portion of the registration roller pair 3, the transfer material is below the registration lower roller 3B.
Since the leading edge of the transfer material being conveyed is dented and pinched here, it tends to rise upward (convex downward) in the figure, so that the transfer material is conveyed along the upper transfer guide 6A.
After passing through the transfer guide 6A, it goes straight on and reaches a point 1A on the photoconductor 1 (intersection of the extension line of the transfer upper guide and the photoconductor), and the point 1S is kept in close contact with the photoconductor 1.
Head to. Here, the position of the point 1A is below the point 1S, that is, on the transfer roller 2 rather than on the photoconductor, or due to the transfer bias applied to the transfer roller 2, the electric field is very strong. 1A must be above the area because pre-transfer occurs in the area a formed near 1S. On the other hand, depending on the type and state of the transfer material, it may not follow the upper transfer guide 6A but may follow the lower transfer guide 6B. Therefore, on the photoconductor 1 on the extension of the tip E of the transport surface of the lower transfer guide 6B. Similarly for point 1B
The conditions must be the same as point 1A above. However, if the points 1A and 1B are too far away from the pre-transfer area a, that is, if the positions of the transfer guide positions 6A and 6B are too high, if thick paper or a strong transfer material is used, the point 1A After reaching 1B or 1B, the photoconductor 1 is separated again to cause poor adhesion, and pre-transfer occurs or 1Aor
The angle surrounding 1B (1S-1A (or 1B) -transfer guide tip) becomes smaller than 180 °, and the transfer material is conveyed while being bent, so that the conveyance resistance increases and a paper passing defect easily occurs.

Here, the inventors of the present invention have conducted various experiments,
I found out the following. That is, the transfer material is not bent as much as possible and in the pre-transfer area a, the photosensitive member 1
In order to pass through the transfer nip while the transfer material is in close contact,
Positions the lower transfer guide tips E above the tangential line L ₁ comprises a tangent L ₁ at the point 1S, and the angle between the transfer material conveying surface and horizontal transfer guide 6 (installing equipment in the normal use state) Is set smaller than the angle formed by the tangent line L ₁ of the point 1S and the horizontal direction. That is, the most downstream end of the transfer guide that guides the transfer material is located on the tangent line L ₁ of the image carrier at the most upstream side point in the transfer material moving direction of the contact portion between the image carrier and the transfer roller. Since the angle between the transfer guide surface of the transfer guide and the horizontal direction is smaller than the angle between the tangent line L ₁ and the horizontal direction, the transfer material splashes when entering the transfer nip. The points 1A and 1B can be set above the pre-transfer area within the range of use of the transfer bias described above while preventing blurring and conveyance failure. Specifically, regarding the position of the tip of the transfer guide, the point E is (12, -12.5) in the coordinates with the center of the photoconductor 1 as (0, 0).

Further, the shock when the transfer material comes out of the registration roller pair 3 causes a gap C between the transfer guide 6A and the lower transfer guide 6B at the most downstream side in the transfer material moving direction.
The problem could be solved by setting it to 1.0 to 2.0 mm.
Further, the transfer material is fed by the registration roller pair 3 at a speed of ν ₀ , and in the transfer nip portion, the transfer material upper side is at the speed ν ₁ of the photoconductor 1 and the lower side is at the speed ν of the transfer roller 2.
Since the paper is about to be fed at ₀ (ν ₀ > ν ₁ ), slippage may occur and an attempt may be made to form a loop between the registration roller pair 3 and the transfer nip.
By changing the angle of the transfer material conveying surface of the lower transfer guide 6B,
As shown in FIG. 1, the distance between the transfer guides is C <D (D
Can be absorbed by setting the distance between the upper guide and the lower guide on the most upstream side in the transfer material moving direction. The above-mentioned slip has an effect on the toner dropout of the transfer material.

On the other hand, the transfer material passing through the rear end 1e of the transfer nip comes along the tangent line L ₂ at the point 1e.
By locating the transfer material landing point F of the conveyor belt on the extension line of L ₂ and immediately below, the transfer material on which the unfixed transfer toner is placed is smoothly moved from the point 1e to the conveyor belt 4.
It was found that image distortion did not occur.

Further, the tip E of the upper transfer guide 6A has a tangent line L.
Than _1, even 1mm about upwardly, the sheet passing failure or the like is not generated,
A stable image was obtained.

Next, FIG. 3 shows a second embodiment of the image forming apparatus of the present invention.

The second embodiment also has the same basic structure as the image forming apparatus shown in FIG. 2 except for the vicinity of the transfer portion, and therefore the description of the basic image forming process will be omitted.

FIG. 3 shows a case where a transfer brush is used instead of the transfer roller as the transfer bias applying means. In the transfer brush 2, from the transfer high-voltage power supply 20,
Bias voltage is applied, 1S downstream of transfer nip
The tip E of the lower transfer guide 6B is positioned on the extension of the tangent line at, the transfer material conveying surface of the lower transfer guide 6B is made horizontal, and the angle formed between the transfer material conveying surface of the upper transfer guide 6A and the horizontal direction is It is set smaller than the angle between the tangent line L _{1 of} 1S and the horizontal direction, and the opening C of the transfer guide is 1.0 to 2.0 mm.
When set to, a good image without transfer disturbance was obtained. As the transfer brush used in the present embodiment, a fiber obtained by dyeing acrylic fine fibers with copper sulfide and conductive treatment was used, but as the conductive fibers, those obtained by kneading conductive fine powder with resin fibers, A compounded material, or a semiconductive material such as carbon fiber obtained by carbonizing resin fiber or the like to give conductivity can be used. A volume resistance of 10 ¹⁰ Ωcm or less can be used, and is preferably about 10 ⁸ Ωcm.

Next, a third embodiment of the image forming apparatus of the present invention is shown in FIG.

The third embodiment also has the same basic configuration as the image forming apparatus shown in FIG. 2 except for the vicinity of the transfer portion, and therefore the description of the basic image forming process and other operations and operations will be omitted.

In FIG. 4, a transfer blade is used instead of the transfer roller as the transfer bias applying means. A bias voltage is applied to the transfer blade 22 from the high-voltage power supply 20 for transfer, and the tip E of the transfer guide 6B is positioned about 1 mm above the extension of the tangent line L ₁ of 1S downstream of the transfer nip. Other conditions are Example 1,
It is equivalent to 2.

When the image is displayed with the above settings,
Similar to the first and second embodiments described above, there was no transfer disorder and a good image was obtained.

The blade material used was the roller material of the first embodiment formed into a blade shape.

[0030]

As described above, according to the present invention, by properly setting the positions of the transfer charging member and the transfer guide, it is possible to reduce transfer defects such as blurring and scattering during transfer.

Further, it is possible to prevent peculiar hollowing-out and conveyance failure in the pressure contact transfer, improve the image quality, and reduce jams.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a first embodiment near a transfer section of an image forming apparatus of the present invention.

FIG. 2 is a side view of the image forming apparatus of the present invention.

FIG. 3 is a schematic side view showing a second embodiment in the vicinity of a transfer portion of the image forming apparatus of the present invention.

FIG. 4 is a schematic side view showing a third embodiment in the vicinity of a transfer portion of the image forming apparatus of the present invention.

FIG. 5 is a schematic side view in the vicinity of a conventional transfer portion.

[Explanation of symbols]

 1 photoconductor 2 transfer roller 3 registration roller 4 conveyor belt 6 transfer guide

Claims (5)

[Claims] 1. An image forming apparatus comprising: a transfer charging member that comes into contact with an image carrier to electrostatically transfer a toner image on the image carrier to the transfer material; and a guide member that guides the transfer material to a transfer position. In the apparatus, the most downstream end of the guide member for guiding the transfer material is
Of the contact portion between the image carrier and the transfer charging member, it is located above and including the tangent line L ₁ of the image carrier at a point on the most upstream side in the transfer material moving direction, and the transfer material guide surface of the guide member. And an angle formed by the horizontal direction is smaller than an angle formed by L ₁ and the horizontal direction. 2. The guide member has upper and lower guide members, and the distance between the upper guide member and the lower guide member is 1.0 to
The image forming apparatus according to claim 1, wherein the image forming apparatus has a length of 2.0 mm. 3. The image forming apparatus according to claim 1, wherein the transfer charging member has a roller shape. 4. The image forming apparatus according to claim 1, wherein the transfer charging member has an elastic layer. 5. The image forming apparatus according to claim 1, wherein the transfer charging member has a brush shape.