JPH03231274A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a good transferring and separating performance by controlling the amount of current of a means which feeds the transferring charge to a transfer belt according to the amount of current flowing in plural supporting rollers on which the transfer belt is hung, and controlling the amount of current flowing in an image carrier side to an appropriate value regardless of any change in the environment. CONSTITUTION:The amount of current fed to a controller 12 through supporting rollers 111 to 113 is measured, the current IT output from a power source 13 is increased by just the increased amount of this amount of current, and a separation failure such as the transfer material being wrapped to a photosensitive body drum 1 is not generat ed. On the other hand, under low temperature, low humidity, although the transfer belt 2 becomes dry and its volume resistivity is increased, an appropriate amount of current fed to the photosensitive body drum 1 side is secured, and transfer failure due to deficient amount of current is not generated. Furthermore, when a transfer material on which it is difficult to carry out transferring is passed through, since the amount of current fed to the photosensitive body drum 1 side is secured to be an appropriate value, transfer failure and separation failure is not generated. Thus, transferring and separation can be carried out well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic method or an electrostatic recording method that uses a transfer process, and particularly relates to an image forming apparatus such as a copying machine or a printer that uses a transfer process. The present invention relates to an improvement in a transfer device that transfers a developed image formed on an image carrier to a transfer material.

A transfer belt is provided that runs in synchronization with the differential speed J and in contact with or in close proximity to the surface of the supporting image carrier to form a transfer site, and a transfer material such as paper is adsorbed onto this transfer belt. In an image forming apparatus configured to convey toner images on the image carrier side to a transfer site and transfer the toner image on the image carrier side to the transfer material at this transfer site, a charge is supplied from a charge supplying means to the transfer belt to form a toner image on the image carrier. A transfer device equipped with a type of transfer device that transfers a developed image onto a transfer material has already been proposed and is well known in this technical field.

FIG. 4 shows an example of a conventional electrophotographic image forming apparatus equipped with such a type of transfer device, in which the transfer belt 2 is suspended between a plurality of support rollers and
A cylindrical image bearing member, in this example, a photoreceptor drum 1, rotates in the direction of arrow B, and travels in the direction of arrow B in the figure, and comes into contact with the surface of the photoreceptor drum 1 to form a transfer site. It is located.

The surface of the photosensitive drum 1 is uniformly charged by a primary charger 5, and image information 6 such as an image-modulated laser beam or reflected light from a document is applied to this charged surface to form an electrostatic latent image. Ru. Toner is supplied from the developing device 7 to this electrostatic latent image to form a toner image.
When this toner image arrives at the transfer site as the toner image rotates, a transfer bias is applied by the charge supply means 1, in this example, the transfer electrode 3, and the toner image on the photoreceptor drum l is conveyed by the transfer belt 2. transferred to the transferred transfer material P. After the transfer, the transfer material P carrying the toner image leaves the transfer site and is conveyed by the transfer belt 2, then separated from the transfer belt 2 and sent to the fixing device 9, where the toner image is fixed and fixed on the transfer material P. and discharged to the outside.

When the transfer material P is separated from the transfer belt 2, a charger 4 is installed near the separation part in order to prevent the toner from scattering due to peeling discharge and forming water droplets on the image.
is arranged to eliminate static electricity from the transfer material P and the transfer belt 2. Further, some toner that has not been transferred to the transfer material P during transfer is removed by passing through the cleaner 10, and the photosensitive drum 1 enters the next image forming process.

In the conventional image forming apparatus as described above, the transfer belt 2 has a volume resistivity of 1.0XIO'Ω-cm as measured at normal temperature and normal humidity (23°C, 60%), and a dielectric material. rate is 6.0
A conductive elastic body is brought into contact with the transfer belt 2 as a transfer electrode 3 from the opposite side of the photoreceptor drum 1 at the transfer site, and a voltage of -3,000V is applied. ing. With this configuration, good transfer and separation performance can be obtained in the above-mentioned room temperature environment, but at high temperatures, the transfer paper may wrap around the photoreceptor drum (such as separation failure may occur), or conversely, under low temperature , transfer defects may occur in low humidity environments.The cause of these defects is that the volume resistivity of the transfer belt changes depending on the environment, and the amount of current flowing from the transfer electrode differs.This defect has been removed. In order to do this, the power source for applying a predetermined voltage to the transfer electrode was controlled by constant current so that the amount of current flowing from the transfer electrode was made constant, but the above problem was not solved.

Therefore, an object of the present invention is to provide an image forming apparatus that can control the amount of current flowing to the carrier side to an appropriate value regardless of changes in the environment, and thus has good transfer and separation performance. .

A specific object of the present invention is to detect the amount of current flowing into at least one of a plurality of support rollers suspending a transfer belt,
The current amount of the means for supplying charge for transfer to the transfer belt is controlled according to the detected current amount, and the amount of current flowing toward the image carrier at the transfer site can be controlled to an appropriate value regardless of changes in the environment. An object of the present invention is to provide an image forming apparatus.

Section 1 for solving the problem The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention includes a traveling image carrier, and an endless type that is suspended between a plurality of support rollers, forms a transfer site in contact with or in close proximity to the image carrier, and travels in synchronization with the image carrier. In an image forming apparatus including a transfer belt and a charge supply means for supplying charges to a surface of the transfer belt opposite to the image carrier, the amount of current flowing into at least one of the plurality of support rollers is The image forming apparatus includes a control means for detecting the current amount and controlling the amount of current of the charge supply means according to the detected amount of current.

According to a preferred embodiment of the present invention, the amount of current flowing into at least one of the plurality of support rollers is measured by the control means when the image forming operation is stopped before the image forming operation.

According to a preferred embodiment of the present invention, the amount of current flowing into at least one of the plurality of support rollers is measured by the control means during rotation before the image forming operation.

According to a preferred embodiment of the present invention, based on the measured current amount, the self-control means controls the charge supply means at a constant current when the transfer material is not conveyed, and when the transfer material is conveyed, the electric charge supply means is controlled at a constant current. The charge supply means is controlled at a constant voltage using a fixed voltage.

According to a preferred embodiment of the present invention, the charge co-feeding means for supplying charges to a surface of the transfer belt opposite to the image bearing member supplies charges by bringing an electrode into contact with the transfer belt.

According to a preferred embodiment of the present invention, the self-charge supply means for supplying charges to the surface of the transfer belt opposite to the image carrier supplies charges by a corona charger that is not in contact with the transfer belt. .

According to a preferred embodiment of the present invention, the volume resistivity of the transfer belt is between 10 and 10'' Ω-cm.

According to a preferred embodiment of the present invention, the transfer belt has a volume resistivity of 1010 to 1013 Ω-cm.

For example, in order to perform good transfer and separation, it is necessary to control the amount of current flowing toward the image carrier at the transfer site to an appropriate value. If the amount of current flowing to the image carrier side is too small, the above-mentioned transfer defect will occur, and if it is too large, a separation defect will occur in which the transfer material adheres to the image carrier. On the other hand, even if the amount of current flowing from the transfer electrode is controlled to be constant as described above, the amount of current flowing to the support roller that suspends the transfer belt changes depending on the environment, so the amount of current flowing to the image carrier side is not constant. ,
For this reason, in the conventional apparatus, transfer defects and separation defects occurred.

The present invention has been made with attention to the above points, and embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 1 shows a first example in which the present invention is applied to an electrophotographic copying machine.
4 is a schematic cross-sectional view of main parts showing an embodiment of the image forming apparatus, and since it has the same configuration as the image forming apparatus shown in FIG. Explanation of these elements will be omitted.

In this embodiment as well, the transfer belt 2 has a volume resistivity of 1.0 x 10'' at room temperature, as in the conventional device.
The belt 2 is made of a resin having a diameter of Ω-cm, a dielectric constant of 6.0, and a thickness of 400 μm, and a transfer electrode 3 serving as a charge supply means is brought into contact with the back surface of the belt 2 at the transfer site. A plurality of (three in this example) support rollers 11, . 11. ．． 11. are each controller 12
connected to ground through. This controller 12
is the current r flowing into the controller through each support roller
The value of c ('I!1 flow rate) is measured, and the current I7 output from the power source 13 is controlled so that the air Ie becomes a certain constant value. That is, when the current Ic flowing into the controller 12 fluctuates (for example, increases), the current IT output from the power supply 13 also fluctuates and increases by the same amount), and the current difference between the two is controlled so that it is always constant. . In this embodiment, the air IC is controlled to be 3 μA.

Next, the operation of the image forming apparatus of the present invention having the above configuration will be explained.

For example, under high temperature and high humidity conditions, the transfer belt 2 absorbs moisture and its volume resistivity decreases, so in the conventional configuration shown in FIG. However, according to the configuration of the present invention, the amount of current flowing into the controller 12 through the support rollers 11+ to 113 is measured, and only the increase in this amount of current is outputted from the power source 13. In other words, since IT Ic is controlled to be constant, the amount of current flowing to the photoreceptor drum side is approximately constant, and the current does not flow too much to the photoreceptor drum side. Therefore, separation defects such as the transfer material being wrapped around the photoreceptor drum did not occur.On the other hand, at low temperatures and low humidity, the transfer belt 2 dries and its volume resistivity increases. Since IT-I is controlled to be constant, the amount of current flowing to the photosensitive drum side is almost constant.
An appropriate amount of current flowing to the photoreceptor drum side is ensured. Therefore, transfer defects due to insufficient amount of current did not occur. Furthermore, it can be used for transferring OHP paper and cardboard (
Even when a thin transfer material was passed through the paper, the amount of current flowing to the photoreceptor drum was maintained at an appropriate value, so no transfer or separation defects occurred, and good transfer and separation could be performed.

In this embodiment, the above-mentioned currents are always controlled, but the currents Ic and I are controlled only when stopped before the copy operation or during idle rotation.
t is measured, and the corresponding current IT (
Even when outputting IT-1 (=constant), stable transfer and separation performance similar to that of the above example was obtained.

In addition, when passing transfer materials of various sizes, the current I and the current are applied only when stopped or during forward rotation. Measure the current air (IT-Ic=
Even when the voltage was set to 8 at a constant voltage to output a constant voltage, the same stable transfer and separation performance as in the above example was obtained.

The above performance is based on the transfer belt's volume resistivity of 10'' to 101.
It has been confirmed in the range of 6Ω-cm, especially in the range of 1010 to 1
The effect was remarkable in the range of 0.013 Ω-cm. Similar effects were also observed when a two-layer transfer belt was used. Furthermore, it goes without saying that the same effects as in the above embodiment can be obtained in devices such as full-color copying machines that use a transfer belt and a plurality of photoreceptors, or in devices that perform multiple transfers. be.

FIG. 2 is a schematic sectional view showing a second embodiment of the image forming apparatus according to the present invention. In this embodiment, there are a plurality of support rollers 11+ to 11. which suspend the transfer belt 2. Among them, only the support roller lla located at the transfer material-belt separation section is connected to ground through the controller 12, and the remaining support rollers are directly grounded. Therefore, in this embodiment, the controller 12 measures only the value (amount of current) of the current IC flowing into the controller through the support roller 112, and transmits the current IT output from the power source 13 to the air. It will be controlled so that it becomes a certain constant value. For this purpose, another directly grounded support roller 11. ．． 11m is measured in advance, and the ratio of the amount of current flowing to the support roller 11□ to the amount of current flowing to all the support rollers, that is, the amount of current flowing to the support roller 11g measured by the controller 12 is determined as the ratio of the amount of current flowing to the support roller 11□ to the amount of current flowing to all the support rollers 11. ~113 no 1! Measure in advance what percentage of the flow rate this will be. Then, the current air output from the controller 12 is controlled based on this measured value.

−■. so that it remains constant regardless of changes in the environment.

As described above, since the air Ic is controlled to be constant in this embodiment as well, the amount of current flowing to the photoreceptor drum side is approximately constant, and an appropriate amount of current flowing to the photoreceptor drum side is ensured. Therefore, even under high temperature and high humidity conditions, the transfer material does not wrap around the photoreceptor and ram (separation failures), and even under low temperature and low humidity conditions, transfer failures due to insufficient current do not occur. Furthermore, even when a transfer material that is difficult to transfer, such as OHP paper or cardboard, is passed through, the amount of current flowing to the photoreceptor drum side is maintained at an appropriate value, so there will be no transfer or separation defects. Good transfer and separation were achieved.Furthermore, in this example, the amount of current flowing into all the support rollers can be calculated by simply measuring the amount of current flowing into one support roller, which is simpler than in the first example above. There is also the advantage that the same effects as in the first embodiment can be obtained with the configuration.

FIG. 3 is a schematic sectional view showing a third embodiment of the image forming apparatus according to the present invention. This third embodiment uses a corona charger 14 as a charge supply means in place of the transfer electrode 3 of the second embodiment, and has the same structure as the second embodiment except for this. Also in this example, It
Since Ie is controlled to be constant, the amount of current flowing to the photoreceptor drum side is approximately constant, and an appropriate amount of current flowing to the photoreceptor drum side is ensured. Therefore, even under high temperature and high humidity conditions, the transfer material will not wrap around the photoreceptor drum (separation defects) will not occur, and even under low temperatures and low temperatures, transfer defects due to insufficient current will not occur, etc. Needless to say, the same effects as in the first and second embodiments can be obtained, but in this embodiment, a corona charger 14 that does not contact the transfer belt 2 is used, so that
This has the advantage that the transfer belt can be driven with small torque.

It should be noted that the above embodiments are merely illustrative of the present invention, and therefore, it goes without saying that various modifications and changes can be made as necessary. For example, the number of support rollers that suspend the transfer belt may be two or more, and the number of support rollers that measure the amount of current is not limited to one or all of them. Further, the present invention can be applied to an image forming apparatus in which the transfer belt does not come into contact with the image carrier but runs close to it in synchronization. Furthermore, the present invention can also be applied to image forming apparatuses other than electrophotographic copying machines, printers, etc. The invention is applicable.

K1J and Eiri As explained above, the image forming apparatus according to the present invention detects the amount of current flowing into at least one of the plurality of support rollers suspending the transfer belt, and controls the transfer belt according to the detected amount of current. By controlling the amount of current in the means for supplying charge for transfer, the amount of current flowing to the image carrier side can be controlled to an appropriate value regardless of changes in the environment, so that the transfer material adheres to the image carrier. This method has a remarkable effect in that neither separation defects nor transfer defects due to insufficient current occur, and stable and good transfer and separation performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of essential parts showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic sectional view of a main part of a second embodiment of an image forming apparatus according to the present invention. FIG. 3 is a schematic cross-sectional view of main parts showing a third embodiment of an image forming apparatus according to the present invention. FIG. 4 is a schematic cross-sectional view of essential parts of an example of a conventional image forming apparatus. 1; Photosensitive drum 2: Transfer belt 3: Transfer electrodes 11+ to 113: Support roller controller 13: Power source corona charger No changes to the engraving of the drawings. Figure 2 Figure 3 Figure 4 Procedure amendment ( method) % formula %

Claims (1)

[Scope of Claims] 1) A traveling image carrier, and an endless shape that is suspended between a plurality of support rollers, forms a transfer site in contact with or in close proximity to the image carrier, and travels in synchronization with the image carrier. a transfer belt,
an image forming apparatus comprising a charge supplying means for supplying charges to a surface of the transfer belt opposite to the image carrier, detecting an amount of current flowing into at least one of the plurality of support rollers; An image forming apparatus comprising: a control means for controlling the amount of current of the charge supply means according to the amount of current supplied to the charge supply means.