JPH06208307A - Transfer controller for image forming device - Google Patents

Abstract

PURPOSE:To prevent the track of the trailing edge of a transfer material and faulty transfer from occurring with environmental change. CONSTITUTION:This image forming device is provided with an image carrier, an electrostatic latent image forming means and a transfer material carrying device having a dielectric film for carrying the transfer material and a transfer corotron 17 for transferring a toner image formed on the image carrier on the transfer material; and it is provided with a temperature detecting means 31 and a humidity detecting means 32 which are disposed in the device, a transfer material type detecting means 33 disposed in a transfer material carrying path, and means 35 and 37 for controlling transfer off-timing according to temperature, humidity and the type of the transfer material. It is good to control transfer off-timing according to the resistance value of the transfer material and the type of the transfer material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, etc., which uses an electrophotographic method, and uses a dielectric film as a transfer material carrier to form a toner image formed on the image carrier. The present invention relates to a transfer control device that transfers images onto a transfer material.

[0002]

2. Description of the Related Art Conventionally, in a system in which an organic photoconductor is used as an image carrier, the image is visualized by a reversal phenomenon method and is transferred to a transfer material by electrostatic transfer, it is applied to the transfer material carrier by a transfer means. It is known that the polarity of the charge does not have the photosensitivity of the photoconductor, so that a history remains on the photoconductor due to the transfer of the transfer charge to the photoconductor side in the transfer process. For example, when a latent image is formed on an image carrier having a negative charging characteristic and the toner is negatively charged to reversely develop the latent image, the polarity of the transfer corotron is set to positive, and , The positive charge from the transfer corotron is injected into the transfer material through the dielectric film, the positive charge is accumulated in the surface area of the rear end of the transfer material, and the rear end of the transfer material separates from the image carrier. At that time, peeling discharge occurs, and the positive charge moves onto the image carrier having the negative charge, so that a streak-like history (hereinafter, referred to as a trailing edge of the sheet) appears on the copy in the next cycle. .

For example, in Japanese Unexamined Patent Publication No. 2-73278, high humidity conditions and low resistance transfer materials are cited as factors that tend to cause the trailing edge of the paper. A method of making the material electrically conductive has been proposed, and Japanese Patent Laid-Open No. 64-15778 proposes a method of discharging the trailing edge of the transfer material by the discharging means on the downstream side of the transferring means. In addition, a method has also been proposed in which charge application to the transfer material is turned off at the trailing edge of the paper.

[0004]

However, as a measure against the above-mentioned conventional trailing edge of the sheet, in the method of turning off the charge application to the transfer material at the trailing edge of the sheet or the method of controlling the discharging output to the photoconductor. Means that the measures against the trailing edge of the paper are not sufficient, and particularly when the film for overhead projector (OHP film) is used, the above-mentioned countermeasures are insufficient under high humidity conditions, and the trailing edge of the paper is generated. I have a problem.

Under the high humidity condition, the electric field due to the electric charges applied to the transfer carrier has a spread due to the decrease of the surface resistance of the transfer material. Therefore, the transfer off timing set under the low humidity condition causes the transfer under the high humidity condition. An electric field is generated up to the trailing edge of the material, and trailing edge traces are generated due to the transfer of electric charges. There was a problem that would occur.

An object of the present invention is to solve the above problems and to provide a transfer control device capable of preventing the trailing edge trace of a transfer material and the occurrence of transfer failure due to environmental changes.

[0007]

Therefore, a transfer control device in an image forming apparatus of the present invention is a transfer material having an image carrier, an electrostatic latent image forming means, and a dielectric film for carrying the transfer material. In an image forming apparatus including a conveying device and a transfer corotron for transferring a toner image formed on an image carrier onto a transfer material, a temperature detecting unit and a humidity detecting unit disposed in the device, The present invention is characterized by including a transfer material type detecting means arranged in the transfer material conveying path, and means for controlling transfer off timing according to temperature, humidity and transfer material type. The transfer off timing may be controlled according to the resistance value of the transfer material and the type of the transfer material.

[0008]

In the present invention, the transfer off timing is controlled by the temperature, the humidity or the resistance value of the transfer material and the type of the transfer material, and the transfer off timing is accelerated when the high temperature and high humidity or the transfer material has the low resistance value. To control.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing an example in which the transfer control device according to the present invention is applied to a color electrophotographic copying machine. The present invention is not limited to such a color electrophotographic copying machine, but can be applied to an image forming apparatus using a dielectric film as a transfer material carrier.

The color electrophotographic copying machine includes an automatic document feeder 1, an image input unit 2, an image output unit 3, and a transfer material feeding unit 4.
Consists of. The color original document is placed on the platen glass 5 by the automatic original document feeder 1. The image input unit 2 includes an imaging unit 6, a wire 7 for driving the unit, a drive pulley 9, etc., and uses a CCD line sensor and a color filter in the imaging unit 6,
In the case of four-color full color, a color original is read for each of the primary colors of light B (blue), G (green), and R (red), and after being converted into a digital image signal, this signal is the primary color of toner. Y (yellow), C (cyan), M (magenta), K
In order to improve the reproducibility of color, gradation, definition, etc., the color gradation toner signal is converted into an ON / OFF binary signal in order to improve the reproducibility of color, gradation, definition, etc. Output to the image output unit 3.

The image output unit 3 has a scanner 10 and a drum-shaped image carrier 11 made of an organic photoconductor, and a charge for uniformly charging the image carrier 11 around the image carrier 11. A device 12, a developing device unit 13 for developing the electrostatic latent image into a toner image, a transfer device 14 for transferring the toner image onto a transfer material, and a cleaner 16 for collecting the untransferred residual toner are arranged. The image carrier 11 is rotationally driven by an electric motor as shown by an arrow.

In the laser output section 10a of the scanner 10, for example, a yellow image signal from the image input section 2 is converted into an optical signal, and the image carrier is passed through the polygon mirror 10b, the f / θ lens 10c and the reflection mirror 10d. A latent image corresponding to the original image is formed on 11. If this yellow latent image is transferred to a transfer material through development, the image carrier 1
In No. 1, after the residual toner is removed by the cleaner 16, it is charged again by the charger 12, and the laser output unit 10a is
Outputs a cyan image signal. Hereinafter, latent images of magenta and black image signals are sequentially formed.

The developing unit 13 includes a yellow developing unit 13Y, a cyan developing unit 13C, and a magenta developing unit 13.
M and black developing devices 13K are provided, and each developing device is arranged around the rotating shaft. Then, for example, when a yellow toner image is formed, development is performed by the yellow developing device 13Y at the position shown in the figure, and when a cyan toner image is formed, the developing device unit 13 is rotated to rotate the image carrier 1
The cyan developing device 13C is disposed at a position in contact with 1.
The magenta and black developments are similarly operated.

A transfer material carrier made of a dielectric film is stretched around the outer periphery of the transfer drum 15 which constitutes the transfer device 14. The transfer drum 15 is formed by a dedicated electric motor or the image carrier 11 and a gear. They are connected and driven to rotate as shown by the arrow. A transfer corotron 17, a separation corotron 18, and a separation corotron 18 are provided inside and outside the transfer drum 15.
A toner charge control corotron 19, a peeling claw 20, a charge eliminating corotron 21, a cleaner 22, a pressing roll 23, and an adsorption corotron 25 are arranged. A temperature sensor 31 and a humidity sensor 32 are arranged near the transfer drum 15.

The paper feed tray 4a of the transfer material supply unit 4
The transfer material that is conveyed and fed from the sheet conveying roller 26, the paper feed guide 27, and the registration roller 28 from 4d is attracted to the transfer material carrier by the corona discharge of the attraction corotron 25. The transfer drum 15 rotates in synchronism with the image carrier 11, and, for example, a toner image developed by yellow is transferred onto a transfer material by a transfer corotron 17, and the transfer drum 15 rotates so that other colors are sequentially transferred. Transcribed.

When the transfer drum is rotated four times and the transfer of four colors is completed, AC charge is removed by the separating corotron 18 provided inside and outside the transfer drum 15, the transfer material is separated by the peeling claw 20, and the conveying path 29 is provided. After that, the toner image is sent to the fixing device 30 and is fused and fixed, and the copy cycle ends.

FIG. 1 is a block diagram showing an embodiment of the transfer control device of the present invention. The transfer control device 35 includes a temperature detection unit 31, a humidity detection unit 32, and a transfer material type detection unit 33.
And the rear end signal of the transfer material are input, and the transfer control device 35
Determines the transfer-off timing based on these signals and the information stored in the transfer-off-timing storage means 37, and outputs it to the transfer power supply 36 to control the transfer corotron 17 to be turned off. Here, the transfer material type detection means 33
Is an OHP film detecting means, and an optical detecting device is provided in the middle of the transfer material carrying path to automatically determine the type of the transfer material. The transfer on timing is controlled by the transfer material front end signal.

FIG. 2 shows the experimental results according to the present invention,
In a color multiplex transfer device using a transfer drum having an outer diameter of 168 mm using PVdF (polyvinylidene fluoride) as a transfer material carrier and an organic photosensitive member having an outer diameter of 84 mm as a photosensitive member, the discharge off timing of the transfer colontron is normally set. When the same transfer was performed at the time of transferring the paper and the transfer of the OHP film, trailing edge marks were generated in the A4 size longitudinal copy of the OHP film under high humidity conditions. OHP here
As the film, a PET film having a surface coated with a surfactant and a resin layer in order to improve toner transferability and fixing property was used. Then, a humidity-sensitive polymer humidity sensor and an IC temperature sensor are installed in the apparatus, and the output from this is A / D converted and input to the CPU so that the discharge off timing can be changed by the temperature and humidity. Due to the value of the discharge-off timing, a transfer failure in the image area or a trailing edge mark was generated, and the allowable range was as shown in FIG. FIG. 2 shows the result when the image is not placed up to 3 mm from the rear end of the transfer material S. As is apparent from the above, it is necessary to turn off the transfer off point L early under high humidity conditions.

Therefore, as shown in FIG. 3, the transfer off timing is controlled. FIG. 3 shows the information stored in the transfer-off-timing storage means 37 of FIG. 1. Based on the temperature and humidity data, the transfer-off timing is shown in FIG. ) Has a memory that can be changed as a table. That is, in the case of high temperature and high humidity, the transfer off point is controlled to be increased. Here, this transfer-off timing was applied only to the OHP film.
In case of plain paper and OHP film, 28 ℃ 85%
Figure 3 shows the results of the occurrence of transfer dropouts and trailing edges in the environment.
It shows in (C). With plain paper, neither transfer omission nor trailing edge trace was generated even at off timing under low humidity conditions, and by controlling the off timing of only the OHP film, it was possible to obtain a copy with neither trailing edge trace nor transfer failure.

In the above embodiment, the control of the transfer off timing is divided into the regions as shown in FIG. 3, but the transfer off timing may be controlled as a function of temperature and humidity.

FIG. 5 shows another embodiment of the image forming apparatus to which the present invention is applied. In the present embodiment, the transfer material conveying belt 51 constituting the transfer device 14 is made of an endless belt-shaped dielectric film, wound around a driving roll 52 and a driven roll 53, and rotated in the direction of arrow A. Four sets of image forming units K, Y, M, and C for black, yellow, magenta, and cyan are arranged facing the transfer material transport belt 51.
By rotation, four color toner images are transferred in multiple. In this case as well, it could be improved by changing the transfer off timing. At this time, the transfer off timing was controlled by using the above sensor and calculating the absolute humidity from the temperature / humidity data and controlling in the region shown in FIG. Under high humidity conditions, it was necessary to cut the transfer before the trailing edge of the image area. This is because the resistance of the transfer material decreases and the charge spreads.

In the above embodiment, the transfer off timing is controlled based on the temperature and humidity data, but in short, the environmental change of the resistance of the transfer material and the transfer carrier is predicted and controlled. Therefore, the same result can be obtained by directly measuring the resistance value of the transfer material. 7 and 8 show an example of detecting the resistance of the transfer material. The same components as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 7 shows an example in which a resistance detection means 55 for detecting a current flowing between rollers by applying a voltage to one of the rollers 26 is provided. FIG. 8 shows the suction roll 23.
The resistance value of the transfer material and the transfer carrier is detected by using the resistance detection means 56 for detecting the current flowing through the transfer material. The same result can be obtained by controlling the transfer-off timing based on the output result.

[0024]

As is apparent from the above description, according to the present invention, the transfer is turned off when the high temperature and high humidity or the transfer material has a low resistance value according to the transfer material type, temperature and humidity conditions or the transfer material resistance value. By controlling the timing to be fast, it is possible to prevent the trailing edge of the transfer material and the occurrence of transfer failure due to environmental changes.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a transfer control device of the present invention.

FIG. 2 is a diagram showing an experimental result according to the present invention.

FIG. 3 is a diagram for explaining information stored in a transfer-off timing storage unit of FIG.

FIG. 4 is a configuration diagram showing an example in which the transfer control device according to the present invention is applied to a color electrophotographic copying machine.

FIG. 5 is a diagram showing another embodiment of an image forming apparatus to which the present invention is applied.

FIG. 6 is a diagram showing another example of controlling transfer-off timing.

FIG. 7 is a diagram showing an example of detecting the resistance of a transfer material.

FIG. 8 is a diagram showing an example of detecting the resistance of a transfer material.

[Explanation of symbols]

15, 51 ... Transfer material conveying device, 17 ... Transfer corotron,
31 ... Temperature detecting means 32 ... Humidity detecting means, 33 ... Transfer material type detecting means, 34
Transfer signal rear end signal 35 Transfer control device 36 Transfer power 37 Transfer off timing storage means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 1/29 Z 9186-5C

Claims (2)

[Claims] 1. A transfer material conveying device having an image bearing member, an electrostatic latent image forming means, a dielectric film for holding the transfer material, and a toner image formed on the image bearing member on the transfer material. In an image forming apparatus including a transfer corotron for transferring to a sheet, a temperature detecting unit and a humidity detecting unit arranged in the apparatus, a transfer material type detecting unit arranged in a transfer material conveying path, a temperature, A transfer control device comprising means for controlling transfer off timing according to humidity and the type of transfer material. 2. An image carrier, an electrostatic latent image forming means, a transfer material conveying device having a dielectric film for carrying the transfer material, and a toner image formed on the image carrier on the transfer material. In an image forming apparatus including a transfer corotron for transferring to a sheet, a resistance value detection unit that detects a resistance value of a transfer material,
1. A transfer control device, comprising: a transfer material type detecting means disposed on a transfer material conveying path; and means for controlling transfer off timing according to a resistance value of the transfer material and a transfer material type.