JPH04172474A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To obtain good images by providing a charging means for charging a holding means with electricity before a transfer material is held by the holding means according to identification of a monocolor code by an identifying means. CONSTITUTION:When e.g. the monocolor setting key 2 of a control panel 22 is controlled the key 2 is lighted by an LSD and a monocolor mode signal is given to a CPU 3. The CPU 3 drives a transfer charger 5 by means of a current controlling circuit 4 in response to the mode signal given and precharging for a transfer drum 13 is carried out and then paper is fed to the drum 13 and transfer is carried out whereby a good image can be obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a method for holding the transfer material with a holding means such as a transfer drum when transferring a toner image formed on a photoreceptor drum to a transfer material. Regarding the image forming mode.

<Prior Art> Full-color image forming apparatuses having a transfer drum have been known so far (see, for example, Japanese Patent Laid-Open No. 113481/1981). In this type of full-color image forming apparatus, plain paper, OHP sheet, etc. are used as transfer materials on the circumference of the transfer drum.
Label paper, postcards, etc. are wrapped around and held, and the holding means is charged (at the same time, the holding means is brought into contact with the photoreceptor drum and rotated synchronously, and the toner image formed on the photoreceptor drum is transferred to the transfer material). A transfer step of transferring the toner image and a separation step of separating the transfer material onto which the toner image has been transferred from the transfer drum are performed.

A common method for holding the transfer material by the holding means is to use electrostatic adsorption.

For example, Japanese Patent Application Laid-open No. 1-1093.81 discloses a method of electrostatically charging (1) a transfer material to be electrostatically attracted to a transfer drum before performing a transfer process.

On the other hand, many image forming apparatuses that have holding means such as transfer drums can form color images in which multiple colors are layered.
Such devices are usually switchable between a monochrome mode for producing a single color image or a multicolor mode for producing a color image.

The above-mentioned monocolor mode performs the transfer process once or twice to obtain a single-color image, and multicolor mode means that the transfer process is performed three or four times for each color, including cyan, magenta, yellow, and sometimes black. A color image is obtained by performing multiple transfer steps and overlapping multiple colors.

<Problems to be Solved by the Invention> By the way, when the method described in JP-A-1-109381 is adopted in the multicolor mode, the potential of the transfer drum increases due to electrostatic charge before the start of the transfer process, and then This method has drawbacks such as a reduction in transfer efficiency due to multiple transfer charges performed during the transfer process, making it difficult to obtain good images.

In particular, there was a drawback that the more the number of transfer charges overlapped, such as the third and fourth times, the worse the transfer efficiency became.

The present invention has been made to solve the above problems, and is capable of reliably holding a transfer material in a holding means, and also capable of obtaining a good image even when used in multicolor mode. The purpose of the present invention is to provide an image forming apparatus.

Means for Solving the Problems> An image forming apparatus according to the present invention for solving the above problems includes a determining means and a determining means for determining whether the image forming mode is a monochrome mode or a multicolor mode. The present invention is characterized in that it includes a charging means for charging the holding means before the transfer material is held by the holding means based on the fact that the transfer material is determined to be a monochrome mode.

Function> In the image forming apparatus according to the present invention, the determining means determines whether the image forming mode is a monochrome mode or a multicolor mode. When the determining means determines that the image forming mode is a monochrome mode, the holding means is charged in advance by the charging means based on the output of the determination. Therefore, the transfer material subsequently supplied to the holding means is well electrostatically attracted to the holding means.

In the multi-color mode, the holding means is not charged in advance, but transfer is performed multiple times, and by the -th transfer, the transfer material is held well by the holding means, and the second and subsequent transfers prevent color misalignment, etc. It never happens.

<Example> Next, an example of the present invention will be described below with reference to the drawings.

[FIG. 3 is a schematic cross-sectional view showing the schematic configuration of a full-color copying machine A according to an embodiment of the present invention.

The full-color copying machine A is equipped with a document placement plate 6 for placing an original, and a reading sensor 7 for reading the contents of the document placed on the document placement plate 6. The reading sensor 7 has a built-in lamp 71 for illuminating the original. Further, a moving device (not shown) for moving the reading sensor 7 in the direction of arrow X, a laser scanning unit 8 that outputs a laser beam based on a signal given from the reading sensor 7, and a laser provided from the laser scanning unit 8 A photoreceptor drum 9 on which an electrostatic latent image is formed by exposure to light, and four developing devices 91 of magenta, cyan, yellow, and black provided to develop the electrostatic latent image on the photoreceptor drum 9. .92.93,9
4. A developing unit 11 in which the four developing devices 91 to 94 are attached and can be shifted up and down by an elevator mechanism 12 to bring a selected developing device into contact with the photoreceptor drum 9; A transfer drum 13 that is rotatable in the Y direction and serves as a holding means for holding paper; a paper feed cassette 14 that stores the paper to be supplied;
Manual paper feed port 15 for feeding paper from outside copying machine A
, a paper transport path 16 for supplying paper to the transfer drum;
The paper on which the toner image has been transferred is separated from the transfer drum 13.

a transfer drum cleaner 1 for removing foreign matter on the surface of the transfer drum 10;
9. A transport bell for transporting the paper separated from the transfer tram 13) 20 (CF) A fixing bag W21 for fixing the toner image on the paper is provided.

Further, a transfer charger 5 is arranged within the transfer drum 13 at a position facing the photosensitive drum 9 .

FIG. 2 is a block diagram of the control circuit of the full-color copying machine A according to this embodiment, and only the parts related to the present invention are shown.

The operation panel 22 is provided, for example, on the outer surface of the upper part of the full-color copying machine A, and the panel 22 is provided with two mode switching keys, a multicolor setting key 1 and a monochrome setting key 2, which can be selectively operated. It is being

When the multicolor setting key 1 is operated, for example, the key 1 is lit by a built-in LED, and a multicolor mode signal is given to the CPU 3.

Furthermore, when the monochrome setting key 2 is operated, the key 2 is lit by a built-in LSD, and a monocolor mode signal is given to the CPU 3.

The CPU 3 causes the current control circuit 4 to drive the transfer charger 5 based on the applied mode signal.

FIG. 1 shows the transfer charger 1 in the CPU 3 in FIG.
3 is a flowchart showing an example of a control operation.

When the image forming operation is started, the image forming mode is determined (step 1). This determination is performed based on the mode signal described above.

When the image forming mode is determined to be monochrome mode, C
A control signal is given from the PU 3 to the current control circuit 4, and the current control circuit 4 drives the transfer charger 5 to perform precharging to charge the transfer drum 13 (step 2). After the precharge is completed, the paper is supplied to the transfer drum 13, and the transfer process (step 3) begins.

When it is determined that it is image forming mode or multicolor mode,
The paper is immediately supplied to the transfer drum 13, and the transfer process (
Enter step 3).

When the transfer process (step 3) begins, the transfer charger 5 is driven by the current control circuit 4 at a specific timing a required number of times.

As described above, in the full color copying machine A, the CPU 3
If the image forming mode is determined to be monochrome,
Before the paper is supplied to the transfer drum 13, the transfer drum 1
3 is precharged and charged, the paper P is well electrostatically attracted to the transfer drum 13.

Moreover, if the image forming mode is determined by the CPU 3 to be the multicolor mode, precharging is not performed, so that the potential of the transfer drum 13 is not increased unnecessarily before the start of the transfer process. In this case, the transfer drum 13 is charged by driving the transfer charger 1 for the first transfer in the transfer process, and the paper is transferred to the transfer drum 13.
Since it is electrostatically attracted to the paper, there is no risk of paper misalignment during the second and subsequent transfers, and multi-color overlapping can be performed without color misregistration.

<Effects of the Invention> As described above, according to the image forming apparatus of the present invention, when performing image formation in monochrome mode, the holding means is charged in advance by the charging means, so that the transfer material is securely attached to the holding means. It is possible to obtain a good image without causing any positional shift.

Furthermore, when forming an image in multi-color mode, the holding means is not charged in advance, so there is no reduction in transfer efficiency due to an increase in the potential of the holding means, and a good image can be obtained. In particular, the third and fourth images are transferred more efficiently than before.

[Brief explanation of drawings]

FIG. 1 shows a CPU of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of a control circuit of an image forming apparatus according to an embodiment of the present invention, and FIG. FIG. 2 is a schematic cross-sectional view. 1...Transfer charger, 3...CPU. 10... Transfer drum, A... Image forming device, P...
Paper. Patent applicant: Sanda Kogyo Co., Ltd. Representative: Patent attorney: Kosaku Inaoka (two idiots) Figure 1

Claims (1)

[Scope of Claims] 1. A monochrome mode that has a holding means for holding a transfer material and performs one transfer step of transferring a toner image onto the transfer material held by the holding means, or a monochrome mode in which the above-mentioned transfer steps are performed multiple times. an image forming apparatus that can be used in a multi-color mode, wherein the image forming mode is determined to be a mono-color mode by a determining means for determining whether the image forming mode is a mono-color mode or a multi-color mode; An image forming apparatus based on the above, comprising a charging means for charging the holding means before the transfer material is held by the holding means.