JPS62134675A - Transfer device - Google Patents

Abstract

PURPOSE:To surely prevent the leakage of a transfer current independently of circumstances to transfer images of good quality by connecting electrically a shield case of a transfer charger and a guide part which guides and carries a transfer material. CONSTITUTION:A transfer charger 1 is arranged near a photosensitive body 10, which has a photosensitive layer on the surface and is formed cylindrically and is rotated in a prescribed direction, in a copying machine. The transfer material is carried from a transfer material guide path 2 to the transfer position of an electrifier 1 and is brought into contact with the electrifier, and an image is transferred there. An upper member 1a of the shield case is arranged at the upstream side of the electrifier 1 in the running direction of the transfer material, and a lower insulated member 1b is arranged at the downstream side of it, and a discharging wire 1c is provided in the electrifier 1. The member 1a and the guide path 2 are connected electrically and are insulated from a copying machine body earth part 4 by an insulating material 3. The shield case of the electrifier 1 and the guide path 2 are earthed through a constant voltage element 5 to prevent the leakage of the transfer current independently of circumstances.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to image forming apparatuses that utilize an electrostatic transfer process, such as electrostatic copying machines and printers, and particularly to transfer mounting thereof. be.

(Prior art and problems to be solved) A transferable toner image is formed using charged toner on the surface of an image carrier, and a sheet-like transfer material mainly made of paper is brought into contact with the toner image. 2. Description of the Related Art Image forming apparatuses configured to transfer a toner image onto a transfer material by imparting a charge with a polarity opposite to that of the toner have been widely used in the past.

As a transfer means in such an image forming apparatus, a discharge wire is arranged in a conductive shield case that is open to the image carrier side, and a discharge current (transfer wire) is disposed in the direction of the image carrier. A commonly used transfer charger is configured to apply an electric charge of opposite polarity to the toner to the transfer material using a transfer charger that allows a current (current) to flow therethrough.

With this type of transfer means, it goes without saying that transfer will not occur unless the electrostatic adsorption force between the transfer material and the toner is greater than that between the image carrier and the toner. In order to obtain an image, it is necessary to maintain a sufficient transfer current at all times.

However, in this type of device, paper is often used as the transfer material, whose characteristics change greatly depending on changes in the environment, so if the resistance of the transfer material becomes low, especially in a high humidity environment, the transfer current will be reduced by the transfer material. This has the disadvantage that leakage occurs to the ground portion of the device, particularly to the guide path portion through which the transfer material is conveyed, making it impossible to obtain a sufficient transfer current and resulting in deterioration of image quality.

In order to avoid such drawbacks, attempts have been made to insulate the guide path or ground it via a constant voltage element, but it has not yet been possible to reliably prevent transfer current leakage. Ta.

The present invention has been made in view of the current situation, and provides a transfer device that can reliably prevent transfer current leakage as described in 1rj and contribute to obtaining high-quality images, regardless of the environment. The purpose is to provide

(2) Structure of the invention (technical means for solving the problem) In order to achieve the above object, the present invention provides electrical connection between the shield case of the transfer charger and the guide section that guides and conveys the transfer material. The present invention is characterized in that it is configured so that leakage of transfer current does not occur through this connection even when the resistance of the transfer material becomes low.

With this configuration, leakage of transfer current in directions other than the intended direction is minimized under any environment, and sufficient current necessary for transfer can always be obtained.

(Description of Embodiments) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic side view of the main parts showing the case where the present invention is applied to a copying machine equipped with a rotating cylindrical photosensitive member having a photosensitive layer on its surface, and is rotated in the direction of the arrow. A transfer charger l is disposed close to the photoreceptor 10, and the toner image formed on the surface of the photoreceptor is synchronized with the transfer material (not shown) conveyed by the transfer material guide path 2. The transfer material reaches the transfer site where the transfer charger exists and comes into contact with it, and at this position, the transfer material is given a charge with the opposite polarity to the toner and transfer is performed, and then the transfer material advances and separates 'fa'M.
It is assumed that the toner reaches the position of the container 11 and is separated from the photoreceptor by this action, and further advances to reach a fixing site (not shown) by the conveying device 12.

As is well known, the area around the photoreceptor is mainly 1′
It goes without saying that components necessary for image formation, such as electrical appliances, image signal writing means, a developing device, and a cleaner for removing residual toner, are provided, but these are not directly related to the present invention, so they will not be described here. The explanation for this will be omitted.

In such an apparatus, as shown in the figure, a transfer charger 1 and a transfer material conveyance guide path 2 are electrically connected.

Fig. 2 shows only the transfer charger and the guide path, and the charger l has its shield case connected to the member 1a on the upstream side as seen in the traveling direction of the transfer material, and the member 1a on the downstream side insulated from this. A discharge wire lc is provided in the case, and a transfer current is directed toward the photoreceptor from the upper opening of the charger as shown in the figure, and imparts a predetermined polarity to the transfer material (not shown) passing between the two. This will give a charge of .

In such a case, the upstream member 1 of the shield case
A and the guide path 2 are electrically connected by a conductive wire as shown in the figure, and are insulated from the image forming apparatus.

Therefore, even if the transfer material has a low resistance, the transfer current does not leak through the transfer material, and a predetermined electric field strength can be maintained.

FIG. 3, like FIG. 2, is a diagram showing only the area near the transfer charger of the copying machine (the same applies to the parts described later).
, corresponding parts are indicated by the same reference numerals.

In this case, each member 1a, l of the shield case is
b is in contact with the copying machine body ground portion 4 via the insulating member 3, and the member 1a is not grounded and connected to the guide path, so the transfer current cannot flow into the member 1a and the guide path 2. do not have.

In FIG. 4, the upstream member 1a is insulated from the downstream member 1b and the main body of the apparatus, and the upstream member is grounded via a constant voltage element 5. If part of the transfer current continues to be supplied to the upstream member 1a from the discharge wire, there is a risk that the potential of the member will gradually increase. It is designed to obtain electric current.

FIG. 5 shows the above-mentioned device in which a discharge region suppressing portion 1d is formed on the upstream member 1a of the charger 1.

By providing the discharge area suppressing portion in this manner, it is possible to prevent the transfer material traveling from the right side in the drawing from being prematurely subjected to a discharge electric field, but on the other hand, there is a risk that the potential of the upstream member 1a may rise too much. In this case, the above drawbacks can be avoided by grounding the member 1a via a constant voltage element as shown.

Figure 6 shows a device in which insulating materials 3a and 3b are arranged on the inner surfaces of members 1a and lb on both the upper and lower sides of the charger, respectively, so that the transfer current flows more effectively in the direction of the photoreceptor. In this device, the guide section 2 that guides and conveys the transfer material guides both sides of the registration roller 2C, the upstream side section 2a, and the downstream side section 2b, together with the upstream side member La of the charger, via the constant voltage element 5. It is grounded. This configuration is effective even in the case of a large transfer material whose leading end has reached the transfer site but whose rear end is on the upstream side of the registration rollers.

Furthermore, in this embodiment, as shown in the timing chart of FIG. 7, the sequence controller 6 connects the switch 7 to the terminal 7a except during image formation.
The member 1a and the guide portion 2 are grounded, and during image formation, the terminal 7b is switched to the terminal 7b and grounded via the constant voltage element 5.

FIG. 8 shows a structure in which an elastic member 8 attached to the guide path is in contact with the upper member 1a between the guide path 2 and the charger 1.

With this configuration, the charger 1 can be configured independently from other members, so that the charger can be easily configured to be detachable from the image forming apparatus main body for maintenance and repair. .

Furthermore, by forming the elastic member 8 from a suitable material and changing its resistance value, it is possible to maintain a higher potential than that of the guide path portion and the upper member 1a of the shield case. Furthermore, by forming the elastic member with a moisture-sensitive member whose resistance value changes depending on humidity, it becomes possible to maintain the potential of the upper member at an optimum value depending on the surrounding environment.

FIG. 9 shows the upstream member 1a of the charger 1 in the above system.
This shows a configuration in which the voltages of the constant voltage elements of the guide path 2 are set to different values, and a constant voltage element or a resistance element 9 is arranged between the guide path and the elastic member. The maximum voltage (varistor voltage) between the constant voltage elements applied to the upper member 1a is vl, the varistor voltage of the guide path is v2, and when Vl>V2, the constant voltage element 5 is placed at the position indicated by the solid line in the figure, and Vl <V2
At this time, the member 1a is grounded via the constant voltage element (5) as shown by the dotted line.

With this configuration, the resistive element 9 is made into a variable resistor and can be adjusted to the optimum varistor voltage depending on the characteristics of the transfer material, the toner, and the environment in which the apparatus is used, so that high-quality images can always be obtained.

In Figure %10, only the discharge area suppressing part 1d of the charger is insulated from other parts of the shield case and connected to the guide path 2 to prevent leakage of discharge current, and the transfer material is stored. A humidifier 14 is disposed near the cassette 6, and the constant voltage value of the constant voltage element 5 is changed via the determination device 13 according to the output thereof, so as to reduce the potential of the suppressor. There is.

Figure 12 shows the lower limit (C) that does not cause white spots on the image and the upper limit (D) that does not cause screen smearing due to leakage of the suppressor 1d of the charger or rise in potential, both of which correspond to humidity. It is assumed that the judgment device 13 is activated during the /\latching period between.

(3) Effects of the invention Since the present invention has the configuration described above,
Even if the transfer material absorbs moisture and becomes low in resistance due to high humidity, it can reliably prevent the transfer current from leaking to other parts and provide sufficient transfer current to the designated transfer area. can do.

Figure 12 is a graph showing this, with the solid line (
In the normal case as shown in A), the transfer potential rapidly decreases as the water content of the transfer material increases, but according to the present invention, the water content of the transfer material decreases as shown by the dashed line. It can be seen that the change in the transfer potential due to the difference in the transfer potential is extremely small, and a substantially uniform transfer effect can be obtained at all times.

[Brief explanation of drawings]

FIG. 1 is a side view of the main parts showing an embodiment in which the present invention is applied to a copying machine, FIG. 2 is a side view showing the configuration of the same transfer section, and FIGS. 3 to 6 are side views similarly showing the transfer section. , FIG. 7 is a diagram showing a timing chart of the transfer device shown in FIG. 6, FIGS. 8 to 10 are side views of main parts showing other embodiments of the present invention, and FIG. 11 is a diagram showing a transfer device according to the present invention. FIG. 12 is a graph illustrating the operating range of the device shown in FIG. 10. 1...φ transfer charger, 2...-guide path, No. 3...insulating material, 5...constant voltage element, 7...changeover switch, 8...
ψ elastic member, 9 - constant voltage element or high resistance element,
lae... Upper part of the shield case, 10...
Photoreceptor. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1. A transfer material is brought into contact with a transferable toner image formed with charged toner on the surface of an image carrier, and a charge of a predetermined polarity is applied to the transfer material by a transfer charger to form the toner image. An image forming apparatus configured to transfer images onto a transfer material, wherein a part of the transfer charger is electrically connected to a guide path that brings the transfer material to a position of the charger. 2. The transfer device according to claim 1, wherein the charger and the guide path are grounded via a constant voltage element. 3. The transfer device according to claim 1 or 2, wherein the charger and the guide path are connected to each other by an elastic member so as to be able to move toward and away from each other.