JPS62247384A - Transfer agent separating device for image forming device - Google Patents

Abstract

PURPOSE:To obtain good transfer and separation at all times irrespective of environment and characteristic of transfer agent by providing a hygroscopic member that becomes high resistance by moisture absorption in electrically suspended state in the vicinity of a position where a separation electrode is adjacent to the transfer agent. CONSTITUTION:A hygroscopic member 6 such as paper, etc., that changes resistance value according to humidity is provided in an insulating member in the vicinity of a separation electrode 5. In ambience of low humidity, the resistance value of the hygroscopic member 6 is high, and made to insulating state. Accordingly, even when high voltage is applied to the separation electrode, the rising of potential of the member 6 due to electrostatic induction is slow, and after the termination of transfer, until transfer paper passes a separating device 4, the distribution of electric lines of force due to the separation electrode 5 is concentrated and static is removed sufficiently and separating action is also ensured. On the other hand, in the ambience of high humidity, the hygroscopic member 6 is charged by electrostatic induction and potential is raised, and corona discharge between the transfer agent and separation electrode 5 is dispersed and suppressed and the leak of charge of the transfer agent is checked. Thus, the omission of transfer can be prevented.

Description

Detailed Description of the Invention (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine or a printer, and particularly to a transfer material separation device thereof. It is something.

(Prior art and issues to be solved) A transferable image formed by charged toner on the surface of an image carrier,
Image forming apparatuses that include a process of bringing a transfer material, mainly paper, into contact with each other and transferring a toner image onto the transfer material by the action of a transfer charger, and then separating this transfer material from an image carrier have been well known. It is.

In this type of device, in order to transfer the toner image to the transfer material, a transfer charger applies a charge of opposite polarity to the toner to transfer the image electrostatically, so that the image is transferred after the transfer. The material tends to stick to the image carrier, and therefore, it is necessary to actively separate the transfer material from the image carrier at a position after transfer.

Conventional separation means for this purpose include those that use mechanical means such as separation claws and separation belts, those that use air flow, and those that use a transfer charger to neutralize the electric charge applied to the transfer material during transfer. , or a curvature separation method in which the transfer material is given a large curvature near the transfer site and then separated using the elasticity and weight of the transfer material itself.
A number of proposals have been made, and although each has its advantages and disadvantages, they have achieved some degree of effectiveness.

On the other hand, in recent years, image forming apparatuses of this type have become increasingly smaller and more compact, and from this point of view, the above-mentioned curvature separation means is preferable because it does not require any special additional mechanism. However, on the other hand, this method has the disadvantage that it tends to cause poor separation when the transfer material is thin and is not easily strained.

Therefore, in order to avoid such drawbacks, an extremely small separation electrode formed in the shape of a needle or plate is arranged downstream of the transfer charger when viewed in the direction of transfer of the transfer material. A structure has been proposed in which the charge on the transfer material is removed by applying a bias voltage lower than the voltage at which self-discharge starts depending on the polarity.

With such a configuration, a small and compact separation device can be obtained without damaging the photoreceptor or disturbing the toner image as in the above-mentioned separation charger.

However, even with such separation devices, the characteristics of paper, which is most commonly used as a transfer material, change significantly depending on the environment, especially humidity, so it may not be possible to obtain suitable results in all cases. do not have.

In other words, in a low-humidity environment, paper has a high resistance and retains charge well, so it has a strong adsorption force to the image carrier after transfer. In order to separate this, the bias voltage applied to the separation electrode must be increased. On the other hand, in a high-humidity environment, the resistance of the transfer paper becomes lower and the charge moves more easily. Therefore, the charge applied to the transfer charger leaks to the separation electrode through the transfer material, causing a problem with the transfer. There is a risk that sufficient electric field strength cannot be obtained for this purpose, resulting in transfer defects such as transfer omissions, and in order to prevent this, it is necessary to keep the bias voltage of the separation electrodes low.

In order to avoid such inconveniences, it is immediately conceivable that the configuration could be configured to detect the environmental humidity and the resistance value of the transfer paper and adjust the applied voltage for separation accordingly. It is easy to understand that this method is impractical because it requires additional mechanisms such as sensors and control circuits, which increases the complexity and size of the device.

The present invention has been made in order to cope with such a situation, and it is an object of the present invention to provide a transfer material separation device that can always obtain good transfer and separation effects regardless of the environment or the characteristics of the transfer material. This is the purpose.

(2) Structure of the invention (technical means for solving the problem, its operation) In order to achieve the above objects, 1. In the present invention, a transferable toner image formed on the surface of an image carrier is transferred to a transfer material such as paper. At this position, a transfer charger applies a charge of a predetermined polarity to the transfer material, thereby transferring the toner image on the image carrier side to the transfer material, and then applies a charge of the opposite polarity to the transfer material. In an image forming apparatus that separates the transfer material from the image carrier by eliminating the charge during transfer as much as possible by applying a charge of opposite polarity to It is characterized in that members whose values change are arranged in an electrically floating state.

With this configuration, a stable separation effect can be obtained at all times by promoting or suppressing the discharge of the separation electrodes in accordance with changes in environmental humidity and characteristics of the transfer material.

(Explanation of Examples) (Technical Means for Solving the Problems and Their Effects) Fig. 1 shows a copying machine using a cylindrical image carrier (hereinafter referred to as photoreceptor) l that rotates in the direction of arrow A. FIG. 3 is a side view showing the main part of the applied example, in which a transfer charger 3 is shown near the surface of the main part;
is arranged.

As the photoreceptor rotates, the toner image formed on the surface of the photoreceptor reaches the transfer site where the transfer charger 3 is located, and at this position, a transfer paper (not shown) is transported by the transport path 2 in the direction of arrow B. ), and the transfer is performed by the action of the transfer charger.

A separation device M4 is disposed adjacent to the transfer charger 3 on the downstream side when viewed in the traveling direction of the transfer material.

Ru.

This separation device consists of a pair of insulating members 4a and 4b closely arranged on the side wall portion of the transfer charger, a metal plate member sandwiched between these members and having a sawtooth shape on the side facing the photoreceptor, and a large number of insulating members 4a and 4b. It is formed by a separate electrode 5 having a configuration in which needle-like members are arranged in a row, and is connected to a high voltage power source 7.

Further, in the vicinity of the separation electrode 5, a moisture absorbing member 6, such as paper, whose resistance value changes depending on the humidity is disposed on the insulating member.

The transfer material that has completed the transfer process then reaches the position of the separation device, where the charge during transfer is removed by a corona discharge of opposite polarity to that during transfer applied by the separation electrode, and thereafter due to the elasticity and weight of the transfer paper itself. It is assumed that it is separated from the photoreceptor and transported to the next process.

In this case, in a low humidity environment, the moisture absorption member 6 has a high resistance value and is in an insulating state, so even if a high voltage is applied to the one-separation electrode 5, the potential of this member due to electrostatic induction increases slowly, and after the transfer is completed, Until the transfer paper passes through the separation device, the distribution of electric lines of force due to the separation electrodes is not concentrated and disturbed as shown in Figure 2, and sufficient static electricity is removed.
A separating action is also ensured.

On the other hand, in a high-humidity environment, the resistance of the moisture absorbing member decreases, and for this reason, when a high voltage bias is applied to the separation electrode 5, the moisture absorbing member is rapidly charged by electrostatic induction in a short period of time, and its potential increases. As shown in FIG. 3, the dispersion of corona discharge between the transfer material and the separation electrode is suppressed, and the leakage of electric charge from the transfer material is prevented, thereby preventing transfer failure.

Next, experimental examples of the present invention will be explained.

In a copying machine, a cylindrical photoconductor with a diameter of 30 mm was used, and as a separation electrode, the part facing the photoconductor was formed in a sawtooth shape with a tooth height of 3II11 and a pitch of 11 m.
A stainless steel plate with a thickness of 1 layer was used, and this was placed at a position 25 mm downstream from the shield wall of the transfer charger, and an 11 layer wide paper was used as a moisture absorption member, 1 to 2 inches thick from the tip of the separation electrode. It was pasted and placed in position.

Such a separation device is installed, and the transfer voltage is -5.3KV,
Bias on separation electrode +3.5 KV, process speed 50
When operated at am/sec, a stable separation effect was obtained over a wide humidity range from thin paper to cardboard to OHP paper without deterioration in image quality.

Although not shown, as the separation electrode, as mentioned above,
It may be constructed by using needle-like electrodes or by expanding thin wires.

As the moisture-absorbing member, various materials other than paper such as synthetic fibers and ceramics can be used, and an appropriate moisture-absorbing substance may be applied to the tips of the separation electrodes.

(3) Effects of the Invention Since the present invention has the configuration described above, regardless of the environment in which the image forming apparatus is used, stable transfer and separation effects can be obtained at all times without deterioration of image quality. be able to.

[Brief explanation of drawings]

FIG. 1 is a side view of the main part of an embodiment in which the present invention is applied to a copying machine, and FIGS. 2 and 3 are enlarged side views of the main part showing the operation of the separating device according to the present invention. DESCRIPTION OF SYMBOLS 1... Φ photoreceptor, 2... Transport path, 3... Transfer charger, 4... Bone separation device, 5... Separation electrode, 6... Moisture absorbing member.

Claims (1)

[Scope of Claims] An image forming apparatus including a transfer charger disposed close to an image carrier, and a separation electrode disposed downstream of the transfer charger as viewed in the traveling direction of the transfer material, comprising: a position where the separation electrode is close to the transfer material; A transfer material separation device in which a moisture absorbing member that lowers resistance by absorbing moisture is placed in an electrically floating state in the vicinity of the transfer material separating device.