JPH0876617A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device with an inexpensive simple constitution, capable of preventing staining on the rear surface of a transfer paper due to the sticking of toner to a transfer member, without providing a special cleaning device on the transfer member. CONSTITUTION: In the image forming device which is provided with an image carrier 1 and the transfer member 7 coming into press-contact therewith, passes the transfer paper between the image carrier 1 and the transfer member 7 and transfers a toner image formed on the surface of the image carrier 1 to the transfer paper, when the device is stopped in the emergency and then, restarted, at least a part of untransferred toner remaining on the image carrier 1 is transferred to the side of the transfer member 7 and the toner thereon is transferred to a region where the untransferred toner on the image carrier 1 is not stuck again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus used in copying machines, facsimiles, etc.,
In particular, it relates to removal of toner stains on the transfer member.

[0002]

2. Description of the Related Art In recent years, a contact type transfer device has been widely used in place of the conventional charger type transfer system for the purpose of preventing ozone generation and improving transportability. This contact type transfer device (transfer member)
While having the above advantages, when the toner on the photoconductor drum adheres to the transfer member because it is in contact with the photoconductor drum that is the image carrier, and causes problems such as smearing on the back of the transfer paper. There is. This is because a large amount of the regular developing toner on the photosensitive drum comes into contact with the transfer member, and most of the toner image is transferred to the transfer member by the transfer bias voltage applied at the same time.

In order to solve such a problem, Japanese Unexamined Patent Application Publication No. Sho 5
As disclosed in JP-A-4-104836, when the abnormal operation occurs, the polarity of the voltage applied to the transfer member (transfer roller) is switched to prevent the toner on the photosensitive drum from adhering to the transfer member. A method has been proposed. As shown in FIG. 7, this image forming apparatus has a configuration in which a transfer member 7 is in contact with the photosensitive drum 1 and a power source 8 for supplying a bias voltage is connected to the transfer member 7. In this configuration, as shown in FIG. 8, after an emergency stop due to a jam or the like during operation, t ₁ at the time of start
The positive bias voltage applied by the
This is to prevent the developing toner from being attached to the transfer member 7 side so much and to return the adhered toner to the photosensitive drum 1 side again. Further, the negative bias voltage applied at t ₂ thereafter is included in the developing toner, or the polarity is reversed due to charge injection or the like during the application of the positive bias voltage. It is for returning the toner to the photosensitive drum 1 side. The cleaning of the transfer member 7 ends at t ₃ , and then the bias control enters the standby state.

With such a structure and operation, it is possible to prevent the transfer member 7 from being contaminated with toner, but a large amount of the developed toner can be applied to the photosensitive drum 1 at a time.
However, if the toner amount exceeds the permissible cleaning amount, cleaning failure occurs, and a contact type charging member (not shown) located on the downstream side in the rotation direction of the photoconductor drum 1 (not shown). ) Is contaminated with toner, causing problems such as poor charging. This problem is particularly noticeable in the color copying machine as shown in FIG. 4 when the toners of the respective colors are transferred to the intermediate transfer body 11 and transferred to the transfer paper 6 at once. As a countermeasure against this, as disclosed in Japanese Patent Laid-Open No. 55-76368, a method has been proposed in which the toner on the photosensitive drum is attached to a transfer member and the toner is removed by a cleaning device provided on the transfer member. There is.

[0005]

However, in the above-mentioned conventional image forming apparatus, it is necessary to provide the transfer member with a mechanism for cleaning, which causes a problem that the apparatus itself becomes large. . Further, when a mechanical cleaning method using a blade or the like is adopted for a transfer member of a foamable elastic roller type, problems such as an increase in rotation torque and poor cleaning are caused. There is a problem in that the structure is complicated and the cost is increased because the material is required to be covered and coating is required. Therefore, according to the present invention, it is possible to solve the above-described problems of the related art and prevent toner from adhering to the transfer member and causing back stain on the transfer paper without providing a separate cleaning device for the transfer member. An object is to provide an image forming apparatus having a low cost and a simple structure.

[0006]

According to a first aspect of the present invention, there is provided an image carrier and a transfer member that is in pressure contact with the image carrier, and the transfer paper is sandwiched between the two. In addition, in an image forming apparatus that applies a transfer bias voltage to the transfer member to transfer the toner image formed on the surface of the image carrier to the transfer paper, when the apparatus is restarted after an emergency stop, At least a part of the untransferred toner remaining on the image carrier is transferred to the transfer member side, and the toner on the transfer member is transferred again to the area on the image carrier where the untransferred toner is not attached. To do it again,
In claim 2, the image carrier carries toner images of a plurality of colors, and the toner images of the plurality of colors are transferred onto the transfer paper at one time. In claim 3, the image carrier comprises: Being equipped with a blade type cleaning device,
According to a fourth aspect of the present invention, the bias voltage applied to the transfer member when the untransferred toner remaining on the image carrier is transferred to the transfer member is different from the bias voltage during normal transfer. Then, the bias voltage control for retransferring the toner transferred onto the transfer member to the image carrier side is different from the control used during normal cleaning of the transfer member.

[0007]

Therefore, according to the first and second aspects, at the time of restarting after the emergency stop of the image forming apparatus, at least a part of the untransferred toner left on the image carrier is transferred to the transfer member side, Then, the toner on the transfer member is transferred again to the area of the image carrier on which the untransferred toner is not adhered, so that the toner on the image carrier can be conveyed to the cleaning device at once. In addition, the burden of cleaning is lightened, and it is possible to prevent defective cleaning from occurring.

According to the third aspect of the invention, since the image bearing member has a lighter load on the cleaning device, the cleaning device can be a simple structure and a low-cost blade system. According to claim 4, the bias voltage applied to the transfer member when the untransferred toner remaining on the image carrier is transferred to the transfer member is different from the bias voltage at the time of regular transfer. The toner transferred to the transfer member does not increase more than necessary, and the cleaning of the transfer member becomes easy. According to the fifth aspect, the bias voltage control when retransferring the toner transferred onto the transfer member to the image carrier side is different from the control used during normal cleaning of the transfer member. By using the toner, the toner on the transfer member is not returned to the image carrier at one time, and the load on the cleaning device for the image carrier is reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, contact around the photosensitive drum 1,
Alternatively, the contact type charging member 2, a developing device 4 for visualizing the latent image formed on the photosensitive drum 1 to form a toner image in close proximity, and a photosensitive device for easily transferring the toner image to the transfer paper 6 A pre-transfer exposure device 5 for changing the surface potential of the body drum 1, a contact type transfer member 7 for transferring a toner image onto a transfer paper 6, and a bias optimal for transfer and cleaning is applied to the transfer member 7. Power source 8 for cleaning, a blade type cleaning device 9 for removing the untransferred toner from the photoconductor drum 1, a static elimination exposure member 10 for uniformizing a non-uniform charging potential on the photoconductor drum 1, and the like. Are arranged. Reference numeral 3 denotes exposure light for forming a latent image on the photosensitive drum 1, and the transfer member 7 is connected to a power source 8 for applying a transfer bias voltage.

In this structure, when the transfer paper 6 is jammed before it reaches the contact portion between the photoconductor drum 1 and the transfer member 7 and an emergency stop occurs, the toner already developed on the photoconductor drum 1 is developed. It exists between the device 4 and the contact portion between the photosensitive drum 1 and the transfer member 7. Here, when the transfer paper having the jam is removed and the apparatus starts to operate, the photosensitive drum 1 is driven and
When a bias voltage is applied to the transfer member 7 from the power source 8 as shown in FIG. ₃ , a negative bias voltage is applied at the first time t ₁ so that the positive toner image developed on the photosensitive drum 1 is A part is transferred onto the surface of the transfer member 7. This bias voltage application is different from the bias voltage application during normal transfer, and the amount of toner that moves at this time changes depending on the strength of the applied bias.

After the developed toner area on the photosensitive drum 1 has passed through the contact portion with the transfer member 7, cleaning of the transfer member 7 is started at t ₂ and the bias voltage is switched to a positive value. As a result, the positive polarity toner moved to the surface of the transfer member 7 is again transferred to the photosensitive drum 1.
I'll put it back to you. By this bias voltage application, most of the toner on the transfer member 7 returns to the photosensitive drum 1 side,
A part of the toner charged to the opposite polarity still remains on the transfer member 7. Therefore, by applying the negative bias voltage again at t ₃ , the toner of the opposite polarity can be moved to the photosensitive drum 1 side, and t
_{At 4} , the cleaning section A of the transfer member 7 is completed. The bias control after t ₄ enters the standby state.

By this control, it is possible to prevent the developing toner on the photosensitive drum 1 from being carried to the cleaning device 9 at one time and burdening the cleaning device 9 at the time of jamming or the like. As described above, the bias voltage control for cleaning the transfer member 7 at the time of the emergency stop of the apparatus is different from the bias voltage control for the normal cleaning of the transfer member 7. Although a roller is used as the transfer member 7 in this embodiment, the transfer member is not limited to this and may be a transfer belt 7'as shown in FIG. In the figure, 12 is a bias roller. Further, the present invention is
It can also be applied to a color image forming apparatus as shown in FIG. In the figure, the same members as those in FIG. 1 are denoted by the same reference numerals, 2'is a charging charger, 4'is a developing device, and 11 is an intermediate transfer belt.

Next, another embodiment of the transfer bias voltage control will be described with reference to FIG. This embodiment is substantially similar to the embodiment shown in FIG. 2 and the same reference numerals are used, but the toner transferred from the photosensitive drum 1 to the transfer member 7 at t ₁ is returned to the photosensitive drum 1 again. At t ₂
The bias voltage applied thereafter is gradually increased. By this control, a large amount of toner on the surface of the transfer member 7 does not return to the photosensitive drum 1 side within one rotation of the transfer member 7, and the cleaning device 9 for the photosensitive drum 1 (see FIG. 1). Don't put a heavy burden on. In addition to the control shown in FIG. 6, in the control shown in FIG. 6, the bias voltage applied at the time of transferring toner from the photosensitive drum 1 to the transfer member 7 at t ₁ is the bias voltage applied at the time of normal transfer (broken line). ) Is weaker than. As a result, the untransferred toner remaining on the photosensitive drum 1 is not transferred to the transfer member 7 more than necessary, and the transfer member 7 can be easily cleaned thereafter.

[0014]

As described above, according to the first and second aspects, at least one of the untransferred toner left on the image carrier is restarted after the emergency stop of the image forming apparatus. Part is transferred to the transfer member side, and the toner on the transfer member is transferred again to the area of the image carrier on which the untransferred toner is not attached, so that the toner on the image carrier is transferred to the cleaning device at once. Since it is not transported, the load on the cleaning device for the image carrier can be reduced,
It is possible to prevent poor cleaning.
Further, it is not necessary to separately provide a mechanism for cleaning the transfer member, so that the apparatus can be made compact and the cost can be reduced.

According to the third aspect of the present invention, since the image bearing member has a lighter load on the cleaning device, the image bearing member is provided with the blade type cleaning device, so that the cost can be reduced. According to claim 4,
Since the bias voltage applied to the transfer member when transferring the untransferred toner left on the image carrier to the transfer member is different from the bias voltage at the time of regular transfer, the toner transferred to the transfer member is more than necessary. Cleaning of the transfer member can be facilitated without increasing the amount, and contamination of the transfer member can be minimized. Further, according to claim 5, the bias voltage control when the toner transferred onto the transfer member is retransferred to the image carrier side is different from the control used during normal cleaning of the transfer member. The load on the body cleaning device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a time chart showing transfer bias voltage control.

FIG. 3 is a schematic configuration diagram showing an image forming apparatus using a transfer belt.

FIG. 4 is a schematic configuration diagram showing a color image forming apparatus for four colors.

FIG. 5 is a time chart showing another embodiment of transfer bias voltage control.

FIG. 6 is a time chart showing still another embodiment of transfer bias voltage control.

FIG. 7 is a schematic configuration diagram showing a conventional image forming apparatus.

FIG. 8 is a time chart showing conventional transfer bias voltage control.

[Explanation of symbols]

 1 image carrier 7 transfer member 9 cleaning device

Claims (5)

[Claims] 1. An image carrier, and a transfer member that is in pressure contact with the image carrier. The transfer paper is passed between the transfer member and the transfer member, and a transfer bias voltage is applied to the transfer member. In an image forming apparatus that transfers the toner image formed on the surface of the image carrier to the transfer paper, at least when the apparatus is restarted after an emergency stop, at least untransferred toner left on the image carrier is An image forming apparatus, wherein a part of the toner is transferred to the transfer member side, and the toner on the transfer member is transferred again to an area on the image carrier where the untransferred toner is not attached. 2. The image forming apparatus according to claim 1, wherein the image carrier carries toner images of a plurality of colors and transfers the toner images of the plurality of colors onto the transfer paper at one time. 3. The image carrier according to claim 1, further comprising a blade type cleaning device.
The image forming apparatus described. 4. The bias voltage applied to the transfer member when the untransferred toner remaining on the image carrier is transferred to the transfer member is different from the bias voltage during normal transfer. 1. The image forming apparatus according to 1. 5. The bias voltage control for retransferring the toner transferred onto the transfer member to the image carrier side is different from the control used during normal cleaning of the transfer member. The image forming apparatus described.