JPH03194576A - Transfer belt device - Google Patents

Abstract

PURPOSE:To execute uniform transfer without irregularity at a transfer part by making a conductive member where a prescribed voltage is impressed by interposing a belt abut on a holding roller positioned on the upstream side of the transfer part. CONSTITUTION:When a paper supply roller 53 is rotated, a transfer belt 71 abuts on a photosensitive drum 10 and a bias voltage for electrostatic charging is impressed on an elastic brush 65 which abuts on the belt 71 from a power source 66. The leading edge part of a recording paper P is sent between the brush 65 and the belt 71 by the roller 53. Here, electric charge is injected to the paper P by the bristle tip of the brush 65. Then, the paper P is uniformly electrostatically charged, attracted by the belt 71 and carried to the transfer part 160. Since the paper P is uniformly electrostatically charged before transfer by the brush 65 and attracted and carried by the belt 71 in such a manner, the uniform transfer is executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a transfer material for an image forming apparatus such as an electrophotographic copying machine,
The present invention relates to a transfer belt device that electrostatically supports and transports a toner image on an image carrier to transfer it onto the transfer material by physical means, and then transports the toner image to a fixing means.

[Conventional technology]

FIG. 3 is a cross-sectional configuration diagram showing an embodiment of a conventional electrophotographic copying machine. In the figure, IO is a photosensitive drum that is a drum-shaped image carrier, 20 is a charger that charges the circumferential surface of the photosensitive drum 10, 30 is an exposure device, 13 is an image exposure section, 40 is a developing device, and 50 is a transfer device. material supply device, 53 is a paper feed roller, P
16 is a transfer paper which is a transfer material, 16 is a transfer device which is a charger for transfer, 17 is a separator which is a static eliminator for separation, 80 is a fixing device, 90 is a cleaning device, and 56 is a conveying means for the recording paper P. This is a conveyor belt.

To explain the operation of the copying machine, after the charger 20 uniformly charges the circumferential surface of the photoreceptor drum 10, the photoreceptor drum 1
The exposure device 30 performs exposure in the image exposure section 13 on the zero peripheral surface to form an electrostatic latent image. Thereafter, the latent image is developed and visualized by the developing device 40 to become a toner image. This toner image is transferred to the transfer material supply device 50 at the same time.
The image is transferred onto the recording paper P fed by the paper feed roller 53 . This transfer is performed by charging the recording paper P with a polarity opposite to that of the toner by a transfer device 16 from behind. After the transfer, a high alternating voltage is applied by the separator I7 to eliminate static electricity, and the recording paper P is separated from the photoreceptor drum 10. The separated recording paper P is conveyed to the fixing device 80 by the conveyance belt 56, and the toner image thereof is fixed and discharged from the apparatus.

On the other hand, the photoreceptor drum 10 to which the toner image has been transferred is cleaned of residual toner by a cleaning device 90 and is ready for the next copy.

However, in the above configuration, in order to ensure the transferability and separation of the toner image, the transfer device 16 and the separator 1 are
However, the discharge efficiency must be adjusted to find the point that functions best, and this discharge efficiency is greatly affected by the environment, resulting in a problem that the tolerance range for reliability is narrow. The transferability is influenced by the electric charge of the recording paper P, the mechanical properties of the recording paper P (stiffness 2 surface smoothness,
These conditions vary greatly depending on the storage conditions of the recording paper P and the environment at the time of transfer (temperature, humidity), etc.
It is difficult to maintain it in good condition all the time.

Furthermore, when the drum diameter of the photosensitive drum 10 is large, when the recording paper P is transferred to the conveyor belt 56, the force to return to the original flat state is smaller than when the drum diameter is small, so that the toner image is After the transfer, the recording paper P adheres to the photoreceptor drum 10 and tends to cause paper jams, which leads to a decrease in the paper passing performance of the machine, resulting in deterioration of reliability.

As a technique for improving the above-mentioned drawbacks, a belt-shaped transfer/conveying device shown in FIG. 4 is disclosed in US Pat. No. 3,357,325 and the like.

In FIG. 4, 10 is a photosensitive drum which is a drum-shaped image bearing member, 70a is a transfer belt device which is a belt-shaped transfer/conveyance device, 71 is a transfer belt which holds charge and attracts a transfer material, 72. 73 is a holding roller for supporting, stretching and rotating the transfer belt 71; 60 is a pre-transfer paper charger that performs corona discharge to attract the recording paper P to the transfer belt 1-71 by electrostatic force; 16 is a toner image charging device; A transfer unit 160, which is a transfer charger for transferring the image from the photosensitive drum 10 to the recording paper P, is a transfer unit. With such a configuration,
The recording paper P fed by the paper feed roller 53 can be conveyed while being attached to the transfer belt 71, and excellent transfer efficiency and separation efficiency can be obtained in the transfer section.

The transfer belt device 70a is a preferred device in a color image forming apparatus in which toner images are formed on the photoreceptor drum 10 in a superimposed manner and transferred to the recording paper P at one time.

In the color image forming apparatus, the photosensitive drum 10
In order to superimpose toner images on top of each other, a plurality of developing devices are provided at the peripheral edge of the photoreceptor drum 10, which increases the diameter of the drum, and since sufficient separation performance cannot be obtained with the conventional electrostatic transfer separation method, more reliable separation performance is required. The transfer belt device needs to have a large amount of transfer charge because the toner image stacking method requires a large amount of toner adhesion, so it needs to have a large transfer charge retention ability. This is because it is excellent.

[Problem to be solved by the invention]

In the transfer belt device 70a shown in FIG. 4, the recording paper P is charged before transfer by a pre-transfer paper charger 60, and is attracted and conveyed by a moving transfer belt 71. As the pre-transfer paper charger 60, a charger using corona discharge is conventionally used.

However, in a corona discharge type charger, if the recording paper does not come into close contact with the transfer belt 71 and enters under the discharge electrode 62 in a suspended state, the paper will not be sufficiently charged and the separation from the photoreceptor drum 10 will be poor. When the recording paper P becomes full, the leading edge of the recording paper P curls and advances toward the discharge electrode 62 of the transfer paper charger 60, causing the discharge electrode 62 to become disconnected.

There was a problem that short circuits and the like could occur.

Also, JP-A-1-121878 and JP-A-1-121879
Even in the technique disclosed in the above publication, the above problem has not been solved because the recording paper is charged by corona discharge. In order to solve this problem, there is a method of providing a plate member upstream of the lead member 61 to guide the recording paper P so that it enters normally, but this method has the disadvantage that charging becomes uneven. It wasn't satisfying.

Further, the discharge electrode 62 made of a thin wire is easily soiled during use, and when the discharge electrode 62 is soiled, discharge unevenness occurs, and charge application to the recording paper P becomes uneven. If transfer is performed in this state, there is a problem in that transfer unevenness corresponding to uneven discharge of the pre-transfer paper charger 60 occurs.

In image forming apparatuses using reversal development, which are often used these days (
-) is often charged, but when (=) is charged, the above-mentioned charging unevenness is likely to occur and is particularly problematic.

The present invention solves the above-mentioned problems, and the recording paper P enters onto the transfer belt 71 correctly, the pre-transfer paper is charged uniformly, the recording paper P is attracted to the transfer belt 71 in a good condition, and the transfer unevenness is prevented. An object of the present invention is to provide a transfer belt device that does not generate ozone and generates little ozone.

[Means to solve the problem]

The purpose is to provide a transfer belt device in which a rotating belt stretched between holding rollers is brought into contact with an image carrier via a transfer material, and a toner image on the image carrier is transferred to and conveyed to the transfer material. A conductive member made of an elastic plan, to which a predetermined voltage is applied, is brought into contact with a holding roller located upstream of the transfer section, sandwiching the belt, and the transfer is performed between the belt and the conductive member. This is achieved by a transfer belt device that is characterized by holding and conveying the material.

〔Example〕

FIG. 1 is a cross-sectional view of the structure of an embodiment of the transfer belt device of the present invention, and FIG. 2 is a cross-sectional view of the structure of the transfer belt device of FIG. 1 showing an operating state.

In the figure, the same parts as those of the conventional image forming apparatus and transfer belt device 70a shown in FIGS. 3 and 4 are denoted by the same reference numerals, and since their operations are almost the same, detailed explanation of the overlapping parts will be omitted.

54 is a guide plate provided between the paper feed roller 53 and the holding roller 72, 70 is a transfer belt device, and 65 is a conductive fiber material fixedly installed at the upstream side of the transfer section 160 of the main body of the device. An elastic brush 66, which is a conductive member that charges the paper before transfer, is a power source for applying a bias voltage to the elastic brush 65.

In case there is no elastic brush 6 between the elastic brush 65 and the power source 66,
A protective resistor may be inserted in series to prevent a large current from flowing when 5 contacts a grounding part or the like.

The holding rollers 72 and 73 are rollers made of a conductive metal material, and the holding roller 72 on the upstream side is grounded or at a predetermined potential close to the grounded state. Reference numeral 74 indicated by a chain double-dashed line is a roller support member, one end of which has a fixed shaft centered around the axis of the holding roller 73, and the other end connected to the movable shaft of the holding roller 72. As shown in FIG. 1, the holding roller 72 is biased downward,
It is spaced apart from the circumferential surface of the photosensitive drum 10. At this time, the bristles 65a of the elastic brush 65 are the transfer bell! -71, either completely away from it or just barely touching it. Therefore, the elastic brush 65 does not lose its elasticity or become bent over a long period of time, and the transfer belt is completely charged without any dust or dirt adhering to it. It can be made longer.

During transfer, the roller support member 74 is rotated counterclockwise against the force of the elastic member by, for example, a solenoid or a motor operated under the control of the apparatus main body control section, and the second
As shown in the figure, the transfer belt 71 comes into contact with the photosensitive drum 10 and the bristles 65a of the elastic brush 65.

Note that the elastic brush 65 is not fixed to the main body of the apparatus, but is attached to the roller holding member 74 via a member so as to be rotatable about its base 65b, and its bristles 65a are separated from the transfer belt 71 when not transferring. At the time of transfer, a solenoid or the like is actuated under the control of a control section so that the bristles 65a of the elastic brush 65 touch the transfer belt 7.
1 may be rotated so as to come into contact with a predetermined pressure.

Although stainless steel wire can also be used for the conductive fibers of the elastic brush 65, in this embodiment good results have been obtained by using carbon-containing rayon having a volume resistivity of 10' to 10' Ω·cm.

The structure of the transfer belt 71 is, for example, two layers, and the main body is made of an endless high-resistance sheet of silicone rubber, polyurethane rubber, butyl rubber, etc., having a volume resistivity of about 10"Ω·cm and having a thickness of about 0.5 to 1 mm. The upper layer of this sheet is spray-coated with, for example, fluorine thread resin to lower the frictional resistance and prevent dirt from adhering to it.

Next, the operation of the transfer belt device 7o will be explained.

At the same time as the paper feed roller 53 starts rotating, the transfer belt 7), which has already been rotated at the same time as the start of the copying operation, comes into contact with the photosensitive drum IO and the elastic brush 65 that is in contact with the transfer belt 71 is brought into contact with the power supply 66. A charging bias voltage is applied. The leading end of the recording paper P is fed between the elastic brush 65 and the transfer belt 71 by the paper feed roller 53. Here, the recording paper P is the bristles 65a of the elastic brush 65.
Electric charge is injected into the sheet to uniformly charge it, and the sheet is attracted to the transfer belt 71 and conveyed to the transfer section 160. When the leading edge of the recording paper P passes the transfer section 160 by a certain length (for example, 5 mm), the transfer power of the transfer device 16 (not shown) is turned on to start transferring the toner image.

In this manner, the recording paper P is uniformly charged by the elastic brush 65 before being transferred, and is attracted and conveyed to the transfer belt 71, so that it can be transferred uniformly.

In addition, this charging requires only a lower applied voltage than corona discharge, which reduces the cost of the power source 66, eliminates the generation of ozone, and reduces the deterioration of the life of the transfer belt and the negative effects on the human body. It also has the advantage of being able to

In the transfer belt device of this embodiment, the elastic plan 65 is provided at a position facing the holding roller 72 that is on or near the ground, so that the recording paper P fed from the transfer material supply device 50 can be more efficiently In addition to performing charging well and reliably, the distance to the transfer unit 160 is configured to be short, so there is less reduction in charge due to leakage during conveyance, and the transfer bell 1-71 firmly attracts and holds the recording paper P while conveying it. It becomes possible to do so.

Furthermore, since a bias voltage having the same polarity as the charging of the toner in the developer is applied to the elastic brush 65, the toner on the photoreceptor drum IO is attracted to the recording paper P until the recording paper P reaches the transfer section 160. never be done.

Therefore, clear copy image quality can be obtained.

This bias voltage is applied at a linear velocity of movement of the circumferential surface of the photoreceptor drum 10 of 140 mm/sec and an image width of 300 to 350 mm.
mm.

When the paper thickness is 65 g/m'', constant voltage control is performed so that the voltage is 0.5-2.0 KV (same polarity as the toner).

Further, a high voltage having a polarity opposite to that of toner charging is applied to the transfer device 16 under constant current control to transfer the toner image. This constant current control is performed by switching control such that, for example, the current is 300 pA in the case of high humidity and 200 μA in the case of low humidity, and charging is performed. Therefore, the charging current changes according to changes in humidity, which is the most susceptible, and in combination with the above-mentioned charging of the paper before transfer, the adsorption force and transfer efficiency are always maintained within a certain range, so they are always constant regardless of the environment. Reliable adsorption/
Conveying power and high transfer efficiency can be obtained.

〔Effect of the invention〕

According to the present invention, with the configuration described above, the recording paper correctly enters onto the transfer belt, the paper is charged in various ways before transfer, the recording paper is attracted and conveyed to the transfer belt, and the recording paper is transferred. It has now become possible to provide an excellent transfer belt device that performs uniform transfer without unevenness and generates less ozone, which is harmful to the life of the transfer belt and the human body.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a cross-sectional view showing the operating state of the transfer belt in FIG. 1, and FIG. 3 is a cross-sectional view of a conventional electrophotographic copier. FIG. 4 is a cross-sectional configuration diagram showing the configuration, and FIG. 4 is a schematic configuration diagram showing an embodiment of a conventional transfer belt device. IO...Photosensitive drum 50...Transfer material supply device 53...Paper feed roller 65...Elastic brush 66
...Power source 70...Transfer belt device 71
...Transfer belt 72, 73...Holding roller 74...
・Roller support member 160...Transfer part P...Recording paper

Claims (2)

[Claims] (1) A transfer belt device in which a rotating belt stretched between holding rollers is brought into contact with an image carrier via a transfer material, and a toner image on the image carrier is transferred to and conveyed to the transfer material, A conductive member to which a predetermined voltage is applied is brought into contact with a holding roller located on the upstream side of the transfer section, with the belt sandwiched therebetween,
A transfer belt device, characterized in that the transfer material is held and conveyed between the belt and the conductive member. (2) The transfer belt device according to claim 1, wherein the conductive member is an elastic brush.