JP3327509B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for conveying a sheet onto which a toner image has been transferred in an image forming apparatus or the like.
In particular, the present invention relates to a transport mechanism capable of holding a charged paper after transfer at an appropriate potential.

For example, in an electrophotographic apparatus, if a toner image transferred to a sheet is moved or scattered before being fixed, a print shift or blur occurs, resulting in poor print quality. In addition, since the paper transport path and the fixing unit are soiled and the maintenance cycle such as cleaning becomes short and troublesome, improvement thereof is strongly demanded.

[0003]

2. Description of the Related Art In an image forming apparatus, for example, an electrophotographic apparatus shown in FIG. 7, an image carrier (photosensitive drum) 1 is charged by a pre-charging section 2 to form an electrostatic latent image by an optical system unit 3 and then developed. In the section 4, the electrostatic latent image is developed with the charged toner to form a toner image. This toner image is transferred to the paper 10 charged to the opposite polarity to the toner by the corona wire 6 of the transfer unit 5.

In order to guide the paper sheet 10 after the transfer of the toner image, a metal paper transport guide 7 as a paper transport path is fixed to the apparatus frame 8 (which is an earth ground). The paper 10 is appropriately tensioned by means (not shown), and is brought into non-contact with the metal
Transported horizontally until The toner image transferred to the paper 10 is heat-fixed by a flash lamp 9 a of the fixing unit 9.

[0005] During that time, cleaning and maintenance are performed on the metal paper transport guide 7 and the protective glass cover 9b of the fixing unit 9 contaminated with the scattered toner at a predetermined cycle or as needed.

[0006]

In order to transfer a toner image to paper, for example, about -2 by corona discharge at a transfer portion.
It is necessary to apply a potential of KV. For this reason, the sheet, which is a medium resistance member, has a potential of -2 KV, and the sheet vibrates in an attempt to discharge the electric charge, and the vibration causes the sheet to come into contact with a peripheral member or the toner to be scattered. . If the charge is excessively attenuated, the toner cannot be held on the sheet, and the unfixed toner moves and scatters.

[0007] Alternatively, when the sheet is conveyed while the conveyance direction is bent and the back surface (opposite surface of the image forming surface) of the sheet comes into contact with the metal sheet conveyance guide, the contact discharge abruptly attenuates the toner and the toner is conveyed. Toner cannot move and scatter. For this reason, there has been a problem in that print quality is deteriorated due to print misregistration or print fading, and not only the paper but also the paper transport path and the fixing unit are soiled.

In view of the above problems, it is an object of the present invention to provide an image forming apparatus capable of conveying toner transferred onto a charged sheet to a fixing unit without moving or scattering.

[0009]

In order to achieve the above object, in an image forming apparatus according to the present invention , a metal sheet conveying guide from a transfer section to a fixing section is provided between a transfer section and a fixing section.
The metal paper transport guide is provided after the transfer of the toner image.
At a position facing the toner transfer side of the paper without contact.
In addition, it is configured to be connected to the device frame via a resistor.

With this configuration, the resistance value of the resistor is selected to be, for example, a medium resistance value of about several MΩ, so that the potential of the sheet after the transfer of the toner image is gradually reduced to the frame ground through the resistor. And discharge can be held at a potential within a certain range, so that the movement and scattering of the toner due to the vibration of the sheet due to the high potential discharge and the excessive attenuation of the potential can be suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described below in detail with reference to the embodiments shown in the drawings. Note that the same reference numerals are used for the parts described in the conventional drawings, and description thereof is omitted.

As shown in the schematic diagram of one embodiment of the present invention in FIG. 1, the image forming apparatus of the present invention has a structure in which a space between a transfer section 5 and a fixing section 9 is provided on both sides of a sheet 10 after toner transfer. A metal paper transport guide 12 which is located at a position facing and close to the contact, is electrically insulated by an insulating spacing member 11 such as phenol resin (bakelite) and is fixed to the apparatus frame 8 (used as an earth ground FG); And a resistor 13, for example, a fixed resistor 13 a or a variable resistor 13 b, which is interposed and connected between each metal sheet transport guide 12 and the apparatus frame 8.

The paper 10 is conveyed horizontally with an appropriate tension applied by means not shown, as in the prior art. The metal paper transport guide 12 is a stainless plate.
Next, FIG. 2 shows the use of the paper transport mechanism configured as described above to weigh 55 kg of paper, and to remove high quality paper having a moisture content of 3% of paper of -2K.
Charged to V and transported in a non-contact manner to the metal paper transport guide,
FIG. 9 is a diagram illustrating a relationship between a resistance value of a variable resistor as a result of measuring a sheet potential after conveyance and a sheet potential after conveyance.

As shown in the figure, in the case of the conventional structure, since the metal paper conveyance guide is directly attached to the apparatus frame and the resistance value is approximately 0Ω with respect to FG, the paper potential after conveyance is -0.2 KV. It has become.

However, the paper potential immediately after the transfer is the paper weight /
It depends on the type and paper moisture content. FIG. 3 is a diagram showing the relationship between the paper weighing / type and the paper potential as a result of transporting the paper charged at −2 KV in a non-contact manner and measuring the paper potential after the transport. The resistance value of the fixed resistor connected to the metal paper conveyance guide is 5 MΩ.

As shown, the potential of the charged paper depends on the paper weight / type. Since the sheet potential in the conventional structure indicated by the mark “○” has a resistance value of approximately 0Ω, the potential is reduced to the range of −0.2 KV to −0.1 KV depending on the paper weight / type. It can be seen that the sheet potential in the above can be suppressed to the range of -2.0 KV to -1.2 KV because the resistance value of the metal sheet conveyance guide to the FG is 5 MΩ, and the attenuation of the sheet potential can be suppressed.

FIG. 4 is a diagram showing the relationship between the paper moisture content and the paper potential. The resistance value in this case is 3.5 MΩ
It is. The resistance of the metal paper transport guide is negligible. As shown in the figure, the potential of the charged paper depends on the moisture content of the paper, but the potential of the paper in the conventional structure shown by a circle is attenuated to -0.5 to -0.1 KV, but is shown by a cross. The sheet potential in the structure of this embodiment is -2.0 to -1.0.
It can be seen that it can be suppressed to KV.

Since the potential of the charged paper depends on the paper weight / type and the paper moisture content, if a variable resistor is connected instead of the fixed resistor, the potential of the paper is greatly increased according to the potential of the charged paper. The resistance value can be adjusted appropriately so as not to be attenuated.

As described above, the metal paper transport guide is FG
By electrically selecting the resistance value of the resistor interposed between the ground support and the metal paper conveyance guide with respect to the earth ground, for example, by selecting a medium resistance value of about several MΩ. Since the potential of the paper after the transfer of the toner image can be properly discharged and maintained at a potential within a certain range up to the fixing device, the vibration of the paper due to the high potential discharge and the movement and scattering of the toner due to excessive attenuation of the potential can be suppressed. Can be.

FIG. 5 is a diagram showing the relationship between the number of prints and the light transmittance of the protective glass cover. The light transmittance of the conventional structure indicated by a circle and the light transmittance of the structure of the present embodiment indicated by a cross are indicated by the print. Although it decreases as the number increases,
According to the structure of the present embodiment, the decrease in light transmittance is small, and it can be seen that the contamination of the protective glass cover by the toner can be reduced. Of course, it is needless to say that the metal sheet conveyance guide, which is the sheet conveyance path between the transfer section and the fixing section, and the peripheral portion thereof are also less contaminated by toner.

In the description of the above embodiment, the metal paper transport guide is electrically insulated by the insulating spacing member and fixed to the apparatus frame, and the metal paper transport guide and the apparatus frame (FG) are connected to each other. The resistor 13 has a medium resistance of several MΩ in place of the resistor, for example, a black zinc-plated insulating resistor layer as shown in the schematic diagram of another embodiment of FIG. 13c or an acrylic resin insulation resistive film 13d is adhered to the metal paper transport guide 12 (in the case of a plating layer, a plateable material) and directly fixed to the apparatus frame 8 and passed through the resistor 13c or 13d. The discharge may be gradual. In this case, the same operation and effect as described above can be obtained. The same operation and effect can be obtained by disposing the metal sheet transport guide on only one side of the sheet or by contacting the back side of the sheet.

[0022]

As described in detail above, according to the present invention,
Since the movement and scattering of toner can be suppressed by optimally maintaining the potential of the charged paper in the paper transport path, it is possible to improve the printing quality such as printing deviation and blurred printing, and to reduce the frequency of cleaning and maintenance. It exerts a very useful effect.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electrophotographic apparatus showing an embodiment according to the present invention.

FIG. 2 is a diagram showing a relationship between a resistance value of a sheet conveyance path and a sheet potential after conveyance according to an embodiment of the present invention;

FIG. 3 is a diagram showing the relationship between paper weighing / type and paper potential according to an embodiment of the present invention;

FIG. 4 is a diagram showing a relationship between paper moisture content and paper potential according to the structure of the embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the number of prints and the light transmittance of the protective glass cover according to the embodiment of the present invention.

FIG. 6 is a schematic view of an electrophotographic apparatus showing another embodiment according to the present invention.

FIG. 7 is a schematic view of a conventional electrophotographic apparatus.

[Explanation of symbols]

 5: transfer unit 9: fixing unit 10: paper 12: metal paper conveyance guide 13: resistor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-112082 (JP, A) JP-A-4-212186 (JP, A) JP-A-2-75665 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 510

Claims (1)

(57) [Claims] An image bearing member includes a charging unit and an optical system unit.
Forms a more electrostatic latent image, and the developing unit
The latent image is developed to form a toner image.
Transfers the image to paper and fixes the transferred toner image in the fixing unit
In the image forming apparatus, the metal from the transfer section to the fixing section is provided between the transfer section and the fixing section.
Paper transport guide, and the metal paper transport guide
Non-contact with the toner transfer side of the paper after the transfer of the toner image.
An image forming apparatus which is connected to an apparatus frame via a resistor at a predetermined position .