JPH0695530A - Image forming device - Google Patents

Abstract

PURPOSE:To provide stable images by imparting a desired pressing force for enhancing the sticking property of a transfer material to a toner image holder even after an image forming device is used for a long period of time and when the device is used at low temperatures. CONSTITUTION:A pressing member 18 disposed upstream of a transfer corotron is brought into elastic contact with the back face of a transfer material holder and presses a transfer material against a toner image holder, thus functioning to enhance the sticking property of the transfer material to the toner image holder and also to restrict the discharging area of the transfer corotron in an area where the transer material is stuck to the toner image holder. Because the pressing member is charged by the transfer corotron, a low resistance member 18a made by a metallic plate spring of high resiliency is covered with a high resistance member 18b and is supported by a holder 19. A stable pressing force is therefore available without being deteriorated with the lapse of time and at low temperatures, and the of the pressing member being settled when used for a long or at low temperatures is reduced and the rate of deterioration of the restoring force of the member is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an image by transferring a toner image on an image carrier formed by an electrophotographic method or the like onto a transfer material carried on a transfer material carrier by applying a transfer electric field. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus for fixing a color other than black toner on a transfer (sheet) material, for example, a color image forming apparatus, is provided with developing devices for four colors of black, yellow, magenta and cyan. A method is known in which a toner image carried on a toner image carrier is sequentially transferred to a transfer material on a transfer material carrier to form a color image.
A typical color image forming apparatus will be described with reference to FIG.
Around the toner image carrier 5, developing devices 1, 2, 3, 4 for four colors of black, yellow, magenta and cyan are arranged. The exposure device 9 writes data on the toner image carrier 5 uniformly charged by the charger 8 based on the color image information color-separated by the image reading device (not shown),
The toner image bearing member 5 is sequentially developed by each developing device.

On the other hand, the transfer material 7 is fed by a paper feeding device 10, aligned by a transfer material aligning device (registry roll) 20, and then guided to a paper guide device 21 disposed adjacent to the suction device 11. Then, the transfer material carrier 6 is wound around the transfer material carrier 6 by the suction corotron 17 and the suction device 11 and held by electrostatic attraction. On the transfer material 7 on the transfer material carrier 6, the toner images of the respective colors successively developed by the transfer corotron 12 are transferred to form an image in which four colors are overlapped. After that, the transfer material 7 is guided to the fixing device 14 by the peeling claw 13 and fixed to form a color image, which is discharged from the main body of the device.

The untransferred toner remaining on the toner image carrier 5 is cleaned by the cleaning device 15 each time. On the other hand, the toner and carrier also adhere to the transfer material carrier 6. If the transfer material is wrapped around the transfer material carrier in that state, the image on the transfer material is disturbed during image transfer. Therefore, the cleaning is performed by the transfer material carrier cleaner 16 before image formation, after image formation, or both.

In this method, the transfer material carrier 6 and the transfer material 7 are
When the toner is adsorbed and conveyed to the transfer position, the transfer material comes into close contact with the transfer position and the toner image is transferred. The toner image on the toner image carrier 6 flies from before the close contact. At this time, it suffices if the toner image flies straight to the target position on the transfer material, but if it flies off that position, the transferred toner image swells and is disturbed, and a clear image cannot be obtained. As a countermeasure,
A transfer assist baffle 18 is provided to regulate the discharge area of the transfer corotron and to suppress the gap between the photoconductor and the transfer material during transfer, thereby maintaining stable transfer performance.

Further, as one method for maintaining good transferability, it is necessary to increase the degree of adhesion between the transfer material and the toner image carrier, and therefore the transfer material is transferred from the inner surface of the transfer material carrier to the toner image carrier. A pressing member made of an elastic material that presses is provided. A technique for restricting the discharge area of the transfer corotron and improving transferability has been proposed in, for example, JP-A-3-4270. The content disclosed therein is a pressing member formed by covering the periphery of a member having a volume resistivity of 10 ⁵ Ωcm or less with a member having a volume resistivity of 10 ¹⁰ Ωcm or more, which is pressed by a transfer material and a transfer material carrier. This is a technique for obtaining good image quality by bringing the image carrier closer to the image carrier and suppressing uneven charging due to a charging device or the like that applies a transfer electric field.

[0007]

However, the member having a volume resistivity of 10 ¹⁰ Ωcm or more, which constitutes the pressing member, is made of a synthetic resin such as RET, and the elastic force of the member when used for a long time or at a low temperature. However, there is a problem in that the transfer image may be missing. On the other hand, for the transfer assisting baffle, a material having high electrical insulation is required as a selectable material, and a Mylar film is generally used. Mylar film is required to have thermal properties, chemical properties, mechanical properties, etc. in addition to electrical properties. Among the mechanical characteristics among them, there is a problem that the change in spring force is “settling”. Especially in a copying machine such as a color machine having a transfer material holding member, the stop position is set to prevent the transfer material holding member from being deformed. In the method of retracting to the back side of the tie bar and so on.

In this system, the "sagging" phenomenon of the transfer assisting baffle is accelerated and the long-term maintainability is increased, or the spring force required for contraction of the transfer material holding member is increased at low temperature or the baffle itself at low temperature. There is a problem such as a decrease in resilience. An object of the present invention is to provide a desired pressing force for increasing the degree of adhesion of a transfer material to a toner image bearing member even after long-term use and low-temperature use, and to form a stable image. To provide a device.

[0009]

To achieve the above object, the present invention has a pressing member for pressing a transfer material and a transfer material carrying member against a toner image carrying member, and holding the transfer material and the transfer material carrying member on the transfer material carrying member. In the image forming apparatus for transferring the toner image formed on the toner image carrying member to the transferred transfer material, the pressing member has a structure in which a low resistance member having elasticity is covered with a high resistance member. Another invention is the above invention,
It is characterized by the following configuration. That is, (1) the low resistance member is a metal leaf spring. (2) The leaf spring is in an insulated structure. (3) The pressing member is provided on the upstream side in the vicinity of the transfer corotron so as to regulate the discharge area of the transfer corotron.

[0010]

By using a pressing member in which a low-resistance member having elasticity is covered with a high-resistance member, there is little "sagging" during long-term use or at low temperature, and reduction in restoring force is suppressed, and a toner image carrier is provided. A high degree of adhesion of the transfer material to is maintained, and an image without omission can be obtained. Further, when the pressing member is provided on the upstream side close to the transfer corotron, the discharge area of the transfer corotron is regulated, and an image without disturbance can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main configuration of an image forming apparatus of the present invention.
The pressing member 18 is elastically contacted with the back surface of the transfer material carrier 7, presses the transfer material 7 against the toner image carrier 5 to enhance the adhesion of the transfer material to the toner image carrier, and upstream of the transfer corotron 12. The transfer region of the transfer corotron 12 is also provided on the side, and also has a function of restricting the transfer region to a region where the transfer material is in close contact with the toner image carrier. As shown in FIG.
The pressing member 18 has a structure in which a low resistance member 18a is covered with a high resistance member 18b in order to obtain charging by the transfer corotron 12, and in particular, the low resistance member 18a is made of a metal leaf spring having high elasticity. Is used. 1
Reference numeral 9 is a holder for the pressing member 18.

According to the present embodiment, since the metal leaf spring is used as the low resistance member, a stable pressing force can be obtained without deterioration over time and low temperature. In this embodiment, 2
The low resistance member 18a is sandwiched between the high resistance members 18b of the members to cover it, but as shown in FIG.
The high resistance member 18b formed of a member is a low resistance member 18a.
May be configured so as to cover the entire surface.

[0019]

As described above, according to the present invention, since the pressing member in which the elastic low resistance member is covered with the high resistance member is used, a stable pressing force can be obtained even in a long-term and low temperature environment. It can be applied to the transfer material and the toner image carrier, and an image without missing or disturbed images can be stably obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an image forming apparatus of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of a pressing member.

FIG. 3 is a diagram showing a cross-sectional structure of another embodiment of the pressing member.

FIG. 4 is a schematic diagram showing a schematic configuration of an image forming apparatus to which the present invention is applied.

[Explanation of symbols]

5 toner image carrier, 6 sheet material holding device, 7 sheet material, 11 adsorption device, 17 adsorption corotron, 18
Pressing member, 18a High resistance member, 18b Elastic low resistance member, 19 Holder, 20 Sheet material aligning device (register roll), 21 Sheet material guide part

Claims (4)

[Claims] 1. A transfer material held on the transfer material carrying member, comprising a pressing member for pressing the transfer material and the transfer material carrying member against the toner image carrying member. An image forming apparatus for transferring a toner image, wherein the pressing member is formed by covering a low resistance member having elasticity with a high resistance member. 2. The image forming apparatus according to claim 1, wherein the low resistance member is a metal leaf spring. 3. The image forming apparatus according to claim 2, wherein the leaf spring is insulated. 4. The image forming apparatus according to claim 1, wherein a pressing member is provided on the upstream side close to the transfer corotron, and the discharge area of the transfer corotron is regulated.