JPH0467183A - Transferring and separating device for picture forming device - Google Patents

Abstract

PURPOSE:To obtain pictures of a good picture quality by applying pulsative voltages as a transferring and separating biases and applying the separating bias only while application of the transferring bias is stopped. CONSTITUTION:Pulsative voltages are used as a transferring and separating biases and a voltage having a square pulse waveform is used as the negative bias voltage to be applied across a transferring electrifier 2. The positive separating bias is applied across a conductor belt 4 from a power source 40 during a stopping period t2. The separating bias is not applied during a period t1 during which the transferring bias is applied. By shifting the applying periods of the transferring and separating biases from each other in such a manner, mutual interference with each other between a transferring and separating means can be eliminated and occurrence of such a picture defect as a drop in picture density, void, etc., can be prevented and high-quality pictures can be obtained.

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 separation device thereof. It is something.

(Prior Art and Problems to be Solved) In a well-known image forming apparatus that includes a step of further transferring a transferable toner image electrostatically formed on the surface of an image carrier to a transfer material such as paper, there is a problem in the transfer process. Due to the electric charge imparted to the transfer material, the transfer material tends to attract the image carrier.
At the post-transfer position, it is necessary to neutralize and eliminate the charge acquired during transfer by electrifying the transfer material with a polarity opposite to that during transfer.

For this purpose, for example, after the transfer, the charge on the leading edge of the transfer material is neutralized by an AC corona, and then the transfer material is forcibly separated from the image carrier using a separating claw, or the transfer material is grounded after the transfer. A number of methods have been proposed, such as applying a voltage to the conductor after separating the leading edge of the transfer material by bringing the conductor into contact (conductor separation method). The image near the tip of the material may be distorted or the image carrier may be damaged by the nails.
In the latter case, there still remains the problem of a decrease in image density at the leading edge of the transfer material and the occurrence of white spots.

In order to avoid the above-mentioned drawbacks of the conductor separation method, measures such as adding a pre-transfer charger or using a scorotron as the transfer charger have been proposed (Japanese Patent Application Laid-Open No. 1983-1999)
No. 185465), both of which are undesirable as they tend to complicate the device and increase costs.

Generally, in this type of device, a separation means such as a separation charger is disposed downstream of the transfer charger (as viewed in the traveling direction of the transfer material); Since they are very close to each other and apply vias of different polarity to each other, it is difficult for each to maintain the desired effect by interfering with each other.

The operating mode described in 2 will be briefly described with reference to FIG. 6. This figure schematically shows the vicinity of the transfer separation site of the image forming apparatus. It is assumed that the surface of the toner image T is uniformly negatively charged, and a toner image T is formed by applying positively charged toner to an electrostatic latent image formed by imagewise exposure.

When this toner image arrives at the transfer site where the image carrier 1 and the transfer charger 2 face each other, a transfer material P is supplied to the transfer site from the right side in the figure, and along with this, a negative transfer bias is applied to the transfer charger 2. is applied, and the toner image adhering to the image carrier side is transferred to the transfer material.

The transfer material tends to be attracted to the image carrier 1 due to the transfer bias applied during the transfer, but after the transfer, the negatively charged transfer material approaches the conductor belt 5 which is positively biased by the power source 4. The image carrier 1 is separated from the image carrier 1 by an even stronger attraction force, and is conveyed to a fixing site (not shown) while being attracted to the belt 5.

In such a device, since the transfer site and the separation conveyance site are close to each other and have different charging polarities, a portion of the transfer current flows in the direction of the conductor belt 5 and actually contributes to the transfer. Insufficient transfer current causes image defects such as a decrease in image density and white spots.

The present invention was made to deal with this situation, and by using pulsed currents for transfer and separation and controlling the timing of flowing both types of currents, the above-mentioned image defects can be avoided. It is an object of the present invention to provide a transfer separation device that can prevent the occurrence of such problems and obtain high-quality images.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an image carrier on which a toner image is electrostatically formed in a transfer separation device of an image forming apparatus. A transfer material is supplied to a transfer site formed by a transfer means disposed close to the transfer material, and a transfer bias is applied to the transfer means to transfer the toner image onto the transfer material, and then a separation bias is applied to the separation means. The transfer material is separated from the image carrier after transfer, and the transfer bias and the separation bias are both pulsed voltages, and the separation bias is applied only when the transfer bias is at rest. It is characterized by the fact that

With this configuration, interference between the transfer means and the separation means can be eliminated, image defects such as a decrease in image density and white spots can be prevented, and good images can always be obtained.

(Description of Embodiment) Section 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention. It is indicated by the symbol .

The negative bias voltage applied to the transfer charger 2 is the second
The pulse waveform is rectangular as shown in Figure A, and a positive separation bias as shown in Section 2B is applied to the conductor belt 5 by the power source 40 at the rest period, time t2 shown in the figure, and this separation As shown in the figure, the bias is stopped at the time tl shown in the figure during the application of the transfer bias.

In this way, by temporally shifting the application timing of the transfer bias and the separation bias, interference between the transfer means and the separation means as described above can be eliminated, and image defects such as a decrease in image density and white spots can be avoided. It is possible to prevent the occurrence of , and the transfer bias voltage can be low, so it is possible to reduce the output of the power supply, which is advantageous in terms of cost.

At this time, the traveling speed of the transfer material is set to v9, and the transfer charger 2 is set to
The opening width is dl, the distance between the charging wire and the image carrier 1 is d2,
The peak voltage of the transfer bias is ■ and the frequency is f?
When [=17 (t + + t 2 )],
Generally speaking, the larger 2 is, or d,
The smaller d2 is, the thicker fT or vT (the better the transfer will be), and the amount of transfer current when bias is applied as shown in Figure 2A can be adjusted by changing tl and ■7; Since it is also related to the frequency and voltage waveform, it is advantageous to use the adjustment in (1).

Furthermore, by adjusting the peak voltage (5) of the pulse voltage waveform applied to the conductor belt 5, the attraction force can be changed depending on the environment and the copy mode, and constant current control is also possible.

Although the case where the transfer bias is a rectangular wave pulse has been described above, the pulse voltage manually applied to the transfer charger is not limited to this, and various waveforms such as those shown in Section 3 (a) to d) can be used. However, in these cases, if there is a component with a polarity opposite to that of the transfer component, or if there are slopes at the rise and fall of the voltage, the pulse waveform of the separation bias will be similar to the discharge starting voltage during transfer. It is necessary to take this into consideration and pause during discharge.

FIG. 4 shows another embodiment of the present invention, in which the frequency of the transfer bias pulse and the frequency of the separation pulse are set to be different from each other in the apparatus shown in FIG. The width t1 and the separation pulse width t match,
No voltage is applied to the conductive belt 5 when the transfer bias is applied, and a separation bias is applied to the belt 5 at t2 when the transfer bias is stopped.

It is easy to understand that even with such means, interference between the transfer means and the separation means does not occur, and high-quality transfer can be performed.

FIG. 5 shows still another embodiment, in which the transfer pulse width tT and the separation pulse width t are
It is set so that t r < t-.

In this case as well, the same effect as in the above embodiment can be achieved by causing both pulses to be generated in relation to each other as shown in FIG.

In this case, t8 can be expanded to t/f, r jT (t'y is the frequency of the transfer bias), so
It becomes possible to lower the peak value (1) of the separation bias.

Although some combinations of the transfer bias pulse waveform and the separation bias waveform have been described above, the combinations of pulse waveforms are not limited to these. What?
It will be readily understood that various combinations are possible.

(3) As described in detail, according to the present invention, in an image forming apparatus using an electrostatic transfer process, the transfer bias applied to the transfer means and the separation bias applied to the separation means are mutually controlled. Since there is no interference, it is possible to perform good transfer and separation, which has a remarkable effect on obtaining high-quality images.Furthermore, it is possible to lower the output of the bias power supply, make it more compact, and prevent the occurrence of leaks. It is also effective in preventing and reducing ozone generation.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing the main parts of an image forming apparatus suitable for applying the present invention, FIGS. 2A and 2B are waveform diagrams of transfer and separation biases applied to the same apparatus, and FIG. FIGS. 4 and 5 are diagrams showing waveforms of transfer and separation biases showing embodiments of the present invention; FIGS. 4 and 5 are waveform diagrams of further transfer and separation biases showing embodiments of the present invention; FIG. 6 is a diagram showing known image forming methods. FIG. 2 is a schematic side view for explaining transfer and separation operations of the device. DESCRIPTION OF SYMBOLS 1... Image carrier, 2... Transfer charger, 5... Conductor belt, 30.40... Bias type cylinder diagram Figure 3 Figure 4 Figure 5 ) % formula % 1, Indication of the case Patent application No. 179685/1999 2, Name of the invention Transfer separation device for an image forming device 3, Address of the person making the amendment 6, Subject of the amendment 1-9 Nishi-Shinbashi, Minato-ku, Tokyo Detailed description of the invention and brief description of the drawings in Specification No. 11, all section 7 of the drawings, contents of amendments (1) Page 4, line 1 of the specification: ``Change Figure 6 to ``Figure 7.'' correct. (2) ``Figure 2A'' on page 7, line 3 of the same book, ``Figure 2B'' on line 5 of the same book.
"Fig. 2" and "Fig. 3" respectively. (3) In the fourth line from the bottom of page 8 of the same book, "Figure 3" is corrected to "Figure 4." (4) Change “Figure 4” to “District 5” in line 5, page 9 of the same book, page 1 of the same book.
In line 6, "Figure 5" is corrected to "Figure 6." (5) In the second line of page 10 of the same book, "District 5" is corrected to "Figure 6." (6) The "Brief Description of Drawings" column of the specification shall be corrected as follows. ``Figure 1 is a schematic side view showing the main parts of an image forming apparatus suitable for applying the present invention, Section 2 is a waveform diagram of the transfer bias applied to the same apparatus, and Figure 3 is a separation diagram applied to the same apparatus. Bias waveform diagram, 4th
The figure is a waveform diagram of transfer and separation bias showing an embodiment of the present invention. Figures 5 and 6 are waveform diagrams of further transfer and separation bias showing an embodiment of the present invention. Figure 7 is a known image. FIG. 3 is a schematic side view for explaining the transfer and separation operations of the forming device. 1... Image carrier, 2... Transfer charger, 5... Conductor belt, 30.40... Bias power supply. (7) Correct the drawing as shown in the attached sheet (no change in content). Figure 4 Figure 5 i 1 Hee publication Figure 6 T r

Claims (1)

[Claims] A transfer material is supplied to a transfer site formed by an image carrier on which a toner image is electrostatically formed and a transfer means disposed close to the image carrier, and a transfer bias is applied to the transfer means. In an image forming apparatus configured to transfer a toner image onto a transfer material and then apply a separation bias to a separating means to separate the transferred transfer material from an image carrier, both the transfer bias and the separation bias are pulses. 1. A transfer separation device for an image forming apparatus, wherein a separation bias is applied only when the transfer bias is at rest.