JPH0619334A - Image forming device - Google Patents

Abstract

PURPOSE:To perform transfer operation with optimum transfer current in accordance with the thickness of a sheet in spite of the fluctuation of humidity in an image forming device where the transfer current of a transfer device for transferring a toner image on an image carrier is controlled according to the thickness of the sheet. CONSTITUTION:This image forming device forming an electrostatic latent image on the image carrier (photosensitive drum) 10 by latent image forming parts 11 and 12, developing the electrostatic latent image to a toner image by a developing device 13, transferring toner image on the image carrier 10 to the sheet by the transfer device 14, and controlling the transfer current of the transfer device 14 by the resistance value output of a paper thickness measuring means 22 measuring the resistance of the sheet is provided with a humidity detection means 23 detecting the humidity and a control part 24 controlling the transfer current of the transfer device 14 based on the resistance value output from the means 22 and the output from the means 12.

Description

Detailed Description of the Invention

(Table of Contents) Industrial Application Field of the Prior Art (FIG. 5) Problem to be Solved by the Invention Means for Solving the Problem (FIG. 1) Action Example (a) Description of One Example (FIG. 2) To FIG. 4) (b) Description of another embodiment Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for controlling a transfer current for transferring a toner image on an image carrier of a transfer device by controlling a sheet thickness.

In an image forming apparatus such as a copying machine, a printer or a facsimile machine, a latent image forming type recording apparatus such as an electrophotographic apparatus is used in order to record plain paper. In such an image forming apparatus, an electrostatic latent image is formed, developed, and a toner image is transferred to a sheet to obtain a toner image on the sheet. Therefore, the transfer operation is performed well regardless of the thickness of the sheet. ,
Stable operation is required.

[0004]

2. Description of the Related Art FIG. 5 is an explanatory diagram of a conventional technique. For example, in an electrophotographic apparatus, as shown in FIG. 5, a photosensitive drum 10 is charged by a charger 11, an optical image is exposed by a laser optical system 12, and an electrostatic latent image corresponding to the image is formed and developed. Bowl 1
3 toner development is performed, and this toner image is transferred to the paper cassette 20.
The transfer charging device 14 transfers the transferred toner to a sheet conveyed by the abutting roller 21 and the conveying roller conveys it to the fixing device. The cleaner 15 removes residual toner from the photosensitive drum 10.

A transfer method using such a transfer charger is
The transfer charging device 14 is driven by the transfer current of the transfer power supply 16 to transfer and charge the back surface of the paper, the attraction force between the photosensitive drum 10 and the toner is reduced, and the toner is attracted from the photosensitive drum 10 to the paper.

By the way, various types of paper are used in the apparatus, such as high-quality paper and recycled paper, and with a uniform transfer current, toner cannot be satisfactorily transferred on all papers of these thicknesses. .

Therefore, the paper thickness is measured, the transfer power source 16 is controlled, the transfer current is increased for thick paper to prevent transfer omission, and the thin paper is used for thin paper. , The transfer current has been set low.

As a method for measuring the paper thickness, there are an optical measuring method and a physical measuring method, but a method of measuring the paper thickness from a resistance value by applying a voltage between the front and back sides of the paper for simplicity of measurement. Has been adopted.

That is, a power source E and a resistor R are connected to the abutting roller 21, a current is passed between the abutting rollers 21, and the change in the current due to the resistance value of the paper between the abutting rollers 21 is changed by the voltage of the resistor R. Then, the transfer power source 16 is controlled by detecting the thickness of the sheet from the resistance value of the sheet.

[0010]

However, the prior art has the following problems. The resistance value of the paper is easily influenced by humidity, and the resistance value changes due to the influence of humidity. Therefore, the optimum value of the transfer current cannot be derived only by measuring the paper thickness, and the resistance value depends on the paper thickness. Optimal transfer control becomes difficult.

Even if the paper thickness is the same, the optimum transfer current changes depending on the humidity, and the optimum transfer current cannot be obtained only by measuring the paper thickness. Therefore, it is an object of the present invention to provide an image forming apparatus capable of performing a transfer operation with an optimum transfer current according to the thickness of a sheet, regardless of fluctuations in humidity.

It is another object of the present invention to provide an image forming apparatus capable of easily and continuously determining an optimum transfer current from measured values.

[0013]

FIG. 1 shows the principle of the present invention. According to a first aspect of the present invention, an electrostatic latent image is formed on the image carrier 10 by the latent image forming units 11 and 12, and the electrostatic latent image is developed into a toner image by the developing device 13. The toner image is transferred to the sheet by the transfer device 14, and the humidity is detected in the image forming apparatus that controls the transfer current of the transfer device 14 by the resistance value output of the paper thickness measuring unit 22 that measures the resistance of the sheet. The humidity detecting means 23, the resistance value output of the paper thickness measuring means 22, and the control section 24 for controlling the transfer current of the transfer device 14 based on the output of the humidity detecting means 23 are provided. .

According to claim 2 of the present invention, in claim 1,
The control unit 24 determines the transfer current by fuzzy control from the resistance value output and the humidity detection output.

A third aspect of the present invention is characterized in that, in the first or second aspect, the humidity detecting means 23 is provided in the sheet storage portion 20 for storing a sheet.

[0016]

According to the first aspect of the present invention, since the resistance value of the sheet and the optimum transfer current are affected by the humidity, the humidity detecting means 23 is provided, and the measured value of the paper thickness measuring means 22 and the detection of the humidity detecting means 23 are provided. Determine the exact thickness of the sheet from the humidity,
By controlling the transfer current corresponding to the determined thickness, the transfer operation can be performed with an accurate transfer current according to the thickness of the sheet.

In the second aspect of the present invention, fuzzy control is suitable for obtaining a graph relationship in which the relationship between the resistance measurement value and the paper thickness and the relationship between the paper thickness and the transfer current continuously change depending on the humidity. Therefore, the transfer current is determined by fuzzy control, and fine control is possible although there is ambiguity.

In claim 3 of the present invention, the humidity detecting means 23
Is provided in the sheet storage unit 20, it is possible to accurately measure the humidity of the sheet and control the transfer.

[0019]

【Example】

(a) Description of one embodiment FIG. 2 is a configuration diagram of one embodiment of the present invention, FIG. 3 is an illustration diagram of one embodiment of the present invention (No. 1), and FIG. 4 is an illustration diagram of one embodiment of the present invention (No. 2). ).

In FIG. 2, the same components as those shown in FIGS. 1 and 5 are designated by the same symbols, 20 is a paper cassette, which accommodates paper, and 21 is an abutting roller. A sheet thickness detecting section for conveying the sheet taken out by the sheet cassette 20 after abutting the sheet,
A current is supplied from the power source E to the pair of abutting rollers 21 via the resistance R, and the resistance change between the abutting rollers 21 is detected from the current between the abutting rollers 21 to detect the resistance value of the sheet.

Reference numeral 23 denotes a humidity detector, which is the paper cassette 2
The humidity of 0 is detected, which is provided in the vicinity of the paper cassette 20, and 24 is a fuzzy control unit, which measures the thickness of the paper from the measured resistance value of the paper thickness detection unit 22 and the humidity detected by the humidity detector 23. The optimum transfer voltage is determined and the transfer current of the transfer power supply 16 is controlled.

The relationship between paper thickness and paper resistance is shown in FIG.
As shown in (A), the resistance value (ohm / cm) increases almost in proportion to the paper thickness (micron), but the room temperature is 26 °.
In C, there is a difference between the humidity of 60% and the humidity of 80% as shown in the figure.

The relationship between the paper thickness and the optimum transfer current is shown in FIG.
As shown in (B), the optimum transfer current (micro A) increases almost in proportion to the paper thickness (micron), but at room temperature 2
At 6 ° C, there is a difference between the humidity of 60% and the humidity of 80% as shown in the figure.

Therefore, from the relationship shown in FIGS. 3A and 3B, the characteristics of the measured resistance value and the optimum transfer current value shown in FIG. 4 are created according to the humidity and stored in the fuzzy controller 24. I'll do it.

The fuzzy control unit 24 stores the characteristics of the measured resistance value and the optimum transfer current discretely according to the characteristics of the fuzzy control, but also stores the characteristics with a large humidity interval. However, the optimum transfer current for the measured resistance value at that humidity can be calculated by calculation.

For example, as shown in FIG. 4, even if the measured resistance value and the optimum transfer current value are stored at room temperature of 26 ° C. and humidity of 60% and humidity of 80%, the optimum values of different humidity are stored. The transfer current can be calculated by fuzzy inference calculation, and the optimum transfer current of the measured values between the measured values at the time of setting the characteristics can be easily calculated by fuzzy inference calculation.

As described above, the paper thickness can be accurately measured with respect to the humidity change, and further, the transfer operation can be performed by setting the ideal transfer condition according to the paper thickness, and good printing can be performed. (b) Description of Other Embodiments In addition to the above embodiments, the present invention can be modified as follows.

Although the image forming apparatus has been described as an electrophotographic mechanism in the above-described embodiments, it may be used as a printing mechanism (for example, an electrostatic recording mechanism) for transferring a toner image. The sheet PP is not limited to paper, and other medium can be used.

Although the image forming apparatus has been described as a printer,
It may be another image forming apparatus such as a copying machine or a facsimile. Although the control unit has been described as the fuzzy control unit, it may be configured by another control unit.

Although the transfer device has been described as the transfer charger,
A transfer charging roller may be used. Although the present invention has been described with reference to the embodiments, various modifications are possible within the scope of the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

[0031]

As described above, according to the present invention,
It has the following effects. Since the transfer current is set by measuring the paper thickness based on the resistance value and detecting the humidity, the paper thickness of the sheet can be accurately detected regardless of the humidity change, and the optimum transfer current can be set.

Since the transfer current is determined according to the humidity,
An optimum transfer current can be set for humidity, and good transfer is possible.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram (Part 1) of the embodiment of the present invention.

FIG. 4 is an explanatory view (No. 2) of the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 10 Photosensitive Drum (Image Bearing Body) 11 Charging Device 12 Optical Unit 13 Developing Device 14 Transfer Device 15 Cleaner 16 Transfer Power Supply 20 Paper Cassette 21 Abutting Roller 22 Paper Thickness Detection Unit 23 Humidity Detector 24 Fuzzy Control Unit

Claims (3)

[Claims] 1. A latent image forming section (11,
12) forms an electrostatic latent image, a developing device (13) develops the electrostatic latent image into a toner image, and the toner image of the image carrier (10) is transferred to a sheet by a transfer device (14). At the same time, in the image forming apparatus for controlling the transfer current of the transfer device (14) by the resistance value output of the paper thickness measuring means (22) for measuring the resistance of the sheet, a humidity detecting means (23) for detecting humidity is provided. And a control unit (24) for controlling the transfer current of the transfer unit (14) based on the resistance value output of the paper thickness measuring unit (22) and the output of the humidity detecting unit (23). Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the controller (24) determines the transfer current by fuzzy control based on the resistance value output and the humidity detection output. 3. The image forming apparatus according to claim 1, wherein the humidity detecting means (23) is provided in a sheet containing section (20) for containing a sheet.