JPH03116062A - Image forming device - Google Patents

Abstract

PURPOSE:To form a stable image excellent in printing quality regardless of the surface state of a transfer paper different by the sort of paper by feedback- controlling an image forming condition in accordance with the smooth state of the surface of the transfer paper. CONSTITUTION:The transfer paper 2 stocked in a paper feeding cassette is fed to the transfer part of a photosensitive body, etc., at a constant speed by a paper feeding roller 1. An output obtained by detecting the smoothness of the surface of the transfer paper 2 by the use of a detection means 3 is compared 4A with a threshold and the image forming condition such as a developing bias value, an electrostatic charging quantity, an exposing light quantity and a transfer charging quantity, in an electrophotographic process is controlled in accordance with the obtained output. Thus, a printed result which is different by the state of the smoothness of the surface of the transfer paper 2 is evaded and the stable image is always formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus in an electrophotographic process that controls image forming conditions when using various types of transfer paper.

(Prior art) When recording an image on transfer paper using an image forming apparatus using an electrophotographic process method, setting conditions and setting values for each process are generally determined based on the smoothness of the surface of the standard transfer paper. . Further, feedback control was not performed as a factor in image forming conditions depending on the state of smoothness of the surface of the transfer paper.

In this way, in the past, transfer paper was a vague category of plain paper, but even though it is simply plain paper, the surface of the transfer paper may be rough depending on the manufacturer and the purpose of use.
There are many different types, from smooth to smooth.

(Problems to be Solved by the Invention) By the way, when recording is performed by transferring a toner image formed on a photoreceptor to a transfer paper using an electrophotographic process method,
The degree of adhesion to the photoreceptor varies depending on the smoothness of the transfer paper, resulting in a difference in the amount of toner transferred.

That is, if a transfer paper with a rough surface is used, the degree of adhesion with the photoreceptor is poor, and the amount of toner transferred is small, resulting in poor transfer efficiency and printing with low recording density. Furthermore, if a transfer paper with a smooth surface is used, the adhesion to the photoreceptor is good, resulting in good toner transfer efficiency and printing with good recording density.

Although the toner transfer efficiency is affected by the degree of smoothness of the surface of the transfer paper, conventionally the setting conditions for each process are set based on the smoothness of the standard QPF paper passing as the central value.
Because the setting value was determined.

For transfer paper that deviates significantly from the central value, it was either not possible to use it, or the print quality could not be guaranteed.

(Objective of the Invention) An object of the present invention is to provide an image forming apparatus which is always stable and which ensures that there is no difference in printing results depending on the smoothness of the surface of the transfer paper described above.

(Structure and operation) In order to achieve the above object, the present invention includes a means for detecting the smooth state of the surface of a transfer paper, and an output obtained by the detecting means to detect the developing bias value, the amount of charge, The present invention is characterized in that it includes means for controlling image forming conditions such as photo-sensitivity and transfer charge amount.

The present invention transports transfer paper at a constant speed, uses a reflective photosensor to compare the output obtained depending on the smoothness of the transfer paper surface with a threshold value, and controls image forming conditions based on the obtained output. .

(Embodiment) FIG. 1 shows an embodiment of the transfer paper surface sensor used in the present invention, and FIG. 2 is an explanatory diagram of an example of the operation of the transfer paper surface sensor of FIG. 1.

In FIG. 1, a paper feed roller 1 feeds transfer paper 2 stocked in a paper feed cassette to a transfer unit such as a photoreceptor, and conveys the transfer paper at a constant speed. 3 is a reflective photosensor, which is a light emitting diode 3A.

It consists of a light receiving phototransistor 3B. 4 is a comparator circuit, and one terminal (-) of the comparator 4A has a variable resistor VR.
, and the reference voltage E l1ar which is the threshold input by the voltage division of the resistor R1, and the output voltage E detected by the phototransistor 3B is connected to the other terminal (+) of the variable resistor VR.
, and are input by the voltage division of resistor R2. Reference numeral 5 denotes a frequency-voltage (FV) conversion circuit, which obtains an output (m pressure EO) corresponding to the comparator output (it pressure EC) of the comparator circuit 4. Hereinafter, the circuit for detecting the smooth state of the transfer paper surface shown in FIG. 1 will be referred to as a transfer paper surface sensor.

Let me explain the operation of this transfer paper surface sensor.

A paper feed roller 1 transports a transfer paper 2 at a constant speed in the direction of arrow (A). At this time, light is irradiated onto the surface of the transfer paper from the light emitting diode 3A of the reflective photosensor 3 arranged at a predetermined distance from the transfer paper, and if there are irregularities on the surface of the transfer paper, the light is scattered there and is transmitted to the light receiving phototransistor 5. 3B, the amount of received light corresponding to the degree of scattering is input. Since the amount of light received by the light-receiving phototransistor changes depending on the unevenness, it has an alternating current component, and the amplitude of this alternating current component is used to detect the depth of the four parts.

By the way, the surface condition of transfer paper depends on the paper type as shown in Figure 2 (1).
As schematically shown in Figure 2, there are three types of transfer paper: relatively smooth transfer paper (a), transfer paper with moderate unevenness (b), and transfer paper with even roughness (c). can do.

Therefore, the reference voltage E of the comparator 4A of the Humbalate circuit 4
□, (threshold value) is set to the level shown by the broken line in FIG. 2 (2), and the more uneven the surface of the transfer paper 2 is, the more frequently the threshold value will be crossed. Therefore, this comparator 4A
output EC (Fig. 2 (3)).

In addition to the FV conversion circuit 5, it is possible to obtain an output voltage EO ((4) in FIG. 2) depending on the smoothness of the surface of the transfer paper.

FIG. 3 shows an embodiment of a developing bias control device for a laser printer based on an electrophotographic process using the transfer paper surface sensor.

In the figure, 6 is the transfer paper surface sensor of FIG. 1, and the output voltage E0 of the FV conversion circuit 5 is input to the developing bias control line 7. Reference numeral 8 denotes an existing bias control input section for the developing bias control circuit 7, into which the bias human power El is input. 9 is a photosensitive drum constituting a transfer section, and 10 is a developing roller in a developing device.

To explain the control operation of the developing bias, which is one of the image forming conditions, the smooth state of the transfer paper is detected by the transfer paper surface sensor 6, and the result is used as the output voltage EO (Fig. 2 (4)) to develop the image. Input to bias control circuit 7. In this case, if the transfer paper has a rough surface as shown in (b) or (,) of FIG. The developing bias value V is set so that the film adheres. Also, Figure 2 (1
If the transfer paper is smooth as shown in (a) of ), the developing bias value V is set to suppress the toner adhering to the photoreceptor drum. This set bias value is applied to the developing roller 10.

Figure 4 is a graph showing the relationship between the developing bias value V (horizontal axis) and the toner-attached Ff t T (vertical axis) on the photoreceptor drum.As shown in Figure 1, the developing bias value V is Set the upper and lower bias limits based on the smooth transfer paper on the right and the rough transfer paper on the left, centering on the broken line).
The toner adhesion IT is adjusted within the bias adjustment range. If the bias upper limit is exceeded, a toner adhesion failure region occurs, and if the bias lower limit is exceeded, a background smudge occurs, so the developing bias value V is adjusted within the bias adjustment range.

In this way, by controlling the amount of toner adhesion according to the smoothness of the surface of the transfer paper, when using rough transfer paper with poor transfer efficiency, the absolute amount of toner adhering to the photoreceptor drum can be reduced. Since there is a large amount of toner, the amount of toner on the transfer paper does not decrease and a good printing result can be obtained.

On the other hand, if you use smooth transfer paper with good transfer efficiency, the amount of toner on the photoreceptor drum will be suppressed, resulting in more toner being transferred than necessary.

There are no problems such as crushed characters or smearing, in other words,
It is possible to obtain consistently good printing results regardless of the condition of the surface of the transfer paper.

FIG. 3 above shows the case where the development bias control circuit feedback-controls the amount of toner adhering to the photoreceptor drum based on the smoothness of the surface of the transfer paper, but this means controls the amount of charge on the photoreceptor drum.

Feedback control of image forming conditions such as exposure light and transfer charge can be performed to ensure good printing results.

(Effect of the invention) As explained above, the present invention uses image forming conditions.

Since feedback control is performed based on the smoothness of the surface of the transfer paper, it is possible to provide an image forming apparatus with stable print quality regardless of the surface state of the paper type of the transfer paper.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the transfer paper surface sensor used in the present invention, Fig. 2 is an explanatory diagram of an example of the operation of the transfer paper surface sensor of Fig. 1, and Fig. 3 is an illustration of an example of the operation of the transfer paper surface sensor used in the present invention. FIG. 4, which is an embodiment of the developing bias control device, is a graph showing the relationship between the developing bias value and the amount of toner adhering to the photosensitive drum. ]-...Paper feed roller, 2...Transfer paper, 3...
Reflective photosensor, 4... Comparator circuit, 4A... Comparator, 5... FV conversion circuit,
6... Transfer paper surface sensor 7... Development bias control circuit, 8... Bias control input section, 9
...Photosensitive drum, 10...Developing roller

Claims (1)

[Claims] A means for detecting a smooth state of a surface of a transfer paper, and a means for controlling image forming conditions such as a developing bias value, an amount of charge, an amount of exposure light, an amount of transfer charge, etc. in an electrophotographic process using the output obtained by the detection means. An image forming apparatus comprising: