JPH0792829A - Transfer device - Google Patents

Abstract

PURPOSE:To restrain the scattering of developer, to prevent the blurring of an image and to obtain more sharp image by forming the contact surface of a transfer electrode with recording paper as a curved surface having specified curvature. CONSTITUTION:The recording paper is supplied to a photoreceptor 14 from a resist roller 44 through a paper guide 46, and a toner image formed on the outer surface of the photoreceptor 14 is transferred. At the time of transferring, transfer voltage having a polarity(positive) reverse to the electrostatic charging polarity(negative) of insulating non-magnetic toner 36 is applied to the transfer electrode 50 of a transfer device 10 from a transfer power source 51, so that transfer electric field is formed. Toner 36 is preferentially transferred on the recording paper by the transfer electric field. In such a case, the contact surface of the transfer electrode 50 is formed as the curved surface having the specified curvature, so that the width of the transfer electric field is made narrower than in the conventional manner, and transfer time is shortened. Thus, the scattering of the developer 40 caused by the reciprocation of conductive magnetic toner 38 is restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device, and more particularly to a transfer device for transferring a toner image formed on a photoconductor to a recording sheet by forming a transfer electric field with a transfer electrode.

[0002]

2. Description of the Related Art Conventionally, a toner image 4 formed on a photoconductor 3 is transferred onto a recording paper 5 by forming a transfer electric field 2 using a transfer roller 1 as shown in FIG. It was

[0003]

In the prior art in which the transfer electric field is formed by using the transfer roller 1, the transfer electric field 2 has a wide width, so that the transfer time becomes long. Therefore,
When a mixture of a conductive magnetic toner 6 (having a characteristic of reciprocating in an electric field) and an insulating non-magnetic toner 7 is used as a developer, the conductive magnetic toner 6 is transferred by the transfer electric field 2. Since the reciprocating time becomes long, the developer is likely to be scattered and the image after transfer is blurred.

Therefore, a main object of the present invention is to provide a transfer device capable of obtaining a clearer image.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a toner image developed with a developer in which a conductive magnetic toner and an insulating non-magnetic toner are mixed is transferred. In a transfer device including a transfer electrode arranged and transferring a toner image formed on the surface of the photoconductor to the recording paper by forming a transfer electric field at the transfer electrode, the contact of the transfer electrode with the recording paper The transfer device is characterized in that the surface is formed into a curved surface having a predetermined curvature so as to prevent the conductive magnetic toner from scattering.

[0006]

By forming the contact surface of the transfer electrode that contacts the recording paper into a curved surface having a predetermined curvature, the width of the transfer electric field can be narrowed and the transfer time can be shortened. Therefore, it is possible to suppress the scattering of the developer due to the reciprocating motion of the conductive magnetic toner.

[0007]

According to the present invention, since scattering of the developer can be suppressed, blurring of the image can be prevented and a clearer image can be obtained. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0008]

EXAMPLE Referring to FIG. 1, a transfer device 10 of this example.
The image forming apparatus 12 to which is applied is an optical printer, a copying machine,
It is applied to a facsimile or the like and includes the photoconductor 14. As is clear from FIG. 2, the photoconductor 14 includes a cylindrical light-transmissive conductor 16, and a transparent electrode layer 18 and a photoconductor layer 20 having a predetermined thickness are provided on the outer peripheral surface of the light-transmissive conductor 16. Is formed. However, as the photosensitive member 14, a photosensitive belt or the like may be used instead of the photosensitive drum as in the embodiment. The LED array head 22 is arranged inside the photoconductor 14, and the LED array head 2
2 is used to expose the photoreceptor 14. Since the translucent conductor 16 is grounded, when the photoconductor 14 is exposed, the surface potential of the exposed portion becomes 0V.

On the other hand, a developing device 24 is arranged outside the photoconductor 14 as shown in FIG. The developing device 24 is
It includes a toner box 28 having an opening 26 formed in a lower portion thereof. A magnetic roller 30 having S poles and N poles alternately formed on the outer peripheral surface thereof is disposed in the opening 26.
The outer peripheral surface of 0 is covered with a developing sleeve 32 so as to be rotatable. A bias voltage (negative in this embodiment) is applied to the developing sleeve 32 by a bias power source 34. Then, inside the toner box 28, a developer 40 in which an insulating non-magnetic toner 36 and a conductive magnetic toner 38 are mixed at a predetermined ratio is stored.

Below the photoconductor 14, the photoconductor 1
Registration roller 4 for supplying recording paper 42 (FIG. 5) to recording paper 4
4. A paper guide 46 for guiding the recording paper 42 and the transfer device 10 are arranged at predetermined positions. With reference to FIGS. 3 to 5, the transfer device 10 includes a main body 48 that is arranged so as to face the outer surface of the photoconductor 14 and extend in the axial direction of the photoconductor 14, and the tip portion of the main body 48. The recording paper 42
A transfer electrode 50 whose contact surface with a curved surface having a predetermined curvature is provided, and the transfer electrode 50 has a transfer power source 51.
(FIGS. 1 and 5) are connected. Supports 52 are attached to both ends in the length direction of the main body 48, and the support 52 is provided with a hole 56 through which the shaft 54 passes and a roller 58 that abuts on the photoconductor 14. The shaft 56 fixed to the frame 61 is attached to the hole 56 of the support 52 and the spring 60 arranged below the support 52.
4 is inserted. Since the roller 58 is brought into contact with the photoconductor 14 by the spring 60, the distance between the transfer electrode 50 and the outer surface of the photoconductor 14 can always be kept constant even when the photoconductor 14 is eccentric.

In operation, when the developing sleeve 32 in the developing device 24 (FIG. 1) is rotated, as shown in FIG.
The conductive magnetic toner 38 magnetically attracted to the S pole and the N pole of the magnetic roller 30 and the insulating non-magnetic toner 36 coupled to the conductive magnetic toner 38 by the Coulomb force serve as the magnetic brush 62 on the surface of the photoconductor 14. It is pulled out to the opposite position. A conductive path is formed on the magnetic brush 62 by the conductive magnetic toner 38. When the magnetic brush 62 comes into contact with the surface of the photoconductor 14,
Charges are injected into the surface of. As a result, the photoconductor 14
Surface and developing sleeve 32 have the same potential and polarity,
The Coulomb force acting on the insulating non-magnetic toner 36 becomes 0,
There is no electric force to attach the insulating non-magnetic toner 36 to the surface of the photoconductor drum 14.

Under such a charged state of the photoconductor 14, when the photoconductor 14 is exposed from the inner surface side of the photoconductor 14 by the LED array head 22, a well type potential as shown in FIG. 6 is formed only in the exposed portion. To be done. Therefore, the Coulomb force on the insulating non-magnetic toner 36 is zero.
Relationship is broken, and a weak Coulomb force acts on the insulating non-magnetic toner 36 around the closest portion of the photosensitive non-magnetic toner 36 to the photoconductor 14, so that the non-magnetic insulating image is formed on the electrostatic latent image formed on the outer surface of the photoconductor 14. The toner 36 is moved. Along with this, the conductive non-magnetic toner 36 and the conductive magnetic toner 38 combined by the local Coulomb force are also moved. In this way, the electrostatic latent image formed on the outer surface of the photosensitive drum 14 is developed by the developer 40 (insulating nonmagnetic toner 36 and conductive magnetic toner 38).

A recording paper 42 (FIG. 5) is supplied to the photoconductor 14 from a registration roller 44 through a paper guide 46, and the toner image formed on the outer surface of the photoconductor 14 is transferred to the recording paper 42. At the time of transfer, as shown in FIG. 5, a transfer voltage having a polarity (positive) opposite to the charging polarity (negative) of the insulating non-magnetic toner 36 is applied to the transfer electrode 50 of the transfer device 10 by the transfer power source 51, whereby the transfer voltage is applied. , Transfer electric field 6
4 is formed. Due to this transfer electric field 64, the insulating non-magnetic toner 36 is preferentially transferred onto the recording paper 42.
Then, the recording paper 42 on which the toner image is transferred is discharged to the outside through a fixing device or the like (not shown).

According to this embodiment, since the contact surface of the transfer electrode 50 is formed into a curved surface having a predetermined curvature, the width of the transfer electric field 64 (FIG. 5) can be made narrower than before.
The transfer time can be shortened. Therefore, the scattering of the developer 40 due to the reciprocating motion of the conductive magnetic toner 38 can be suppressed, and a clearer image can be obtained. Table 1 shows
In this embodiment, the image density evaluation, the resolution evaluation and the comprehensive evaluation when the contact surface radius R (FIG. 5) is changed are summarized.

[0015]

[Table 1]

From Table 1, the contact surface radius R of the transfer electrode 50 is shown.
Is preferably 5.0 mm or less, and the best result can be obtained at 0.5 mm. When the high resistance toner is used, the transfer time is shortened, which causes a problem that the transfer efficiency is deteriorated. However, as can be seen from the graph of FIG. 7, this problem is caused by using the low resistance toner. It can be resolved.

[Brief description of drawings]

FIG. 1 is an illustrative view showing an image forming apparatus to which an embodiment of the present invention is applied.

FIG. 2 is an illustrative view showing a developing operation in the image forming apparatus of FIG.

FIG. 3 is an illustrative view showing one embodiment of the present invention.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a partially enlarged view showing an embodiment of the present invention.

FIG. 6 is an illustrative view showing a well-type potential on the surface of the photoconductor.

FIG. 7 is a graph showing the relationship between the transfer time and the transfer efficiency of low resistance toner and high resistance toner.

FIG. 8 is an illustrative view showing a conventional technique.

[Explanation of symbols]

 10 ... Transfer device 12 ... Image forming device 14 ... Photosensitive member 48 ... Main body 50 ... Transfer electrode 51 ... Transfer power source

Claims (1)

[Claims] 1. A toner image transferred by a developer containing a mixture of a conductive magnetic toner and an insulating non-magnetic toner, the transfer comprising: a transfer electrode disposed facing the surface of a photoconductor. In a transfer device configured to transfer the toner image formed on the surface of the photoconductor to a recording paper by forming a transfer electric field with the transfer electrode, a contact surface of the transfer electrode that contacts the recording paper is A transfer device, wherein the transfer device is formed on a curved surface having a predetermined curvature so as to prevent scattering of the conductive magnetic toner.