JPH03157681A - Transferring device for image forming device - Google Patents

Abstract

PURPOSE:To carry out stable transferring by controlling a transfer means to be a constant current at least twice at the time when no paper is passed and controlling to the constant voltage by setting a controlled voltage of the transfer means at the time when paper is passed according to a factor decided from electrical current and a voltage value. CONSTITUTION:In a low temperature low humidity environment L/L and a high temperature high humidity environment H/H, a resistance value is greatly varied by environmental change when inverse developing is carried out by negative toner utilizing a transfer roll 2, etc., and an OPC photosensitive body. Then the fixed current value of ATVC at the time of the rotation of the roll 2 are set at I1 and I2, each generating voltage of V1 and V2 are retained, by deriving slant alpha=(V2-V1)/I2-I1, the environment is detected, and by varying the factor K which is multiplied to the generating voltage according to the change in the environment and an appropriate bias can always be impressed. With this constitution, there is no transfer failure or toner scattering in the L/L environment, deterioration of image can be prevented even in the H/H environment, and in a normal temperature normal pressure N/N environment none of above as a matter of course.

Description

Detailed Description of the Invention (1) Object of the Invention (Field of Industrial Application) This invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer, and to a transfer apparatus thereof. It is something.

(Prior art and problems to be solved) An image bearing member and a contact type transfer means such as a transfer roller that comes into contact with the image carrier are provided, and the abutment area between the two is used as a transfer site.
An image forming apparatus has already been proposed which includes a step of guiding a transfer material to the region and transferring the transferable l/toner image formed on the surface of the image carrier up to this point to the transfer material.

In such a device, the bias applied to the transfer means during transfer is controlled by constant voltage or constant current (5), but the transfer means such as the transfer roller uses an OPC43 optical body and uses negative toner. In the case of a device that performs reversal development, the resistance is usually in the semiconductive range of 108 to 1010 Ω.
It is not easy to adjust the resistance value because it uses a
Furthermore, even if it can be adjusted, the resistance value will increase (change) due to environmental changes, and in a low temperature and low humidity environment (15℃, 1O%RH1
(referred to as L/i-) and a high temperature and high humidity environment (32℃, 85%
At RH1+ (referred to as /H), the resistance value may vary by more than one order of magnitude, making it virtually impossible to deal with all situations with a single current or voltage.

In order to cope with such a situation, the present applicant has already used the above-mentioned J: Uni OPC photoreceptor in order to cope with changes in the resistance of the transfer means and transfer material due to environmental changes, and differences in the size of the transfer material. When using a transfer roller as a transfer means in an apparatus that performs reversal development using negative toner, when the transfer roller is rotating in contact with the photoreceptor, the primary charged portion of the photoreceptor is used to stabilize the transfer roller. We proposed a control means (called ATVC) that controls the current, holds the voltage generated at that time, and when the transfer material arrives at the transfer site, performs transfer by controlling the voltage at a constant voltage. It has been made possible to achieve a certain effect in response to the

However, the above-mentioned ATVC has a problem in that positive memory is generated in the photoreceptor when performing constant current control when paper is not passing, and when this occurs, it appears as fog in subsequent images.

In order to avoid this, the constant current value of ATVC may be reduced, but this will lower the generated voltage and cause transfer defects.

Therefore, by reducing the constant current value of ATVC as much as possible to avoid the occurrence of memory, and by setting the transfer bias by multiplying the generated voltage by an appropriate coefficient, it is possible to prevent transfer defects, especially in low temperature and low humidity environments. This made it possible to prevent the outbreak.

However, in such a method, in a high-temperature environment where the desired transferability can be obtained with a low voltage, the charge may become excessive and penetrate the transfer material, resulting in transfer defects or transfer omissions due to leakage.

The present invention has been made in order to cope with such a current situation, and the above-described constant current control or constant voltage control by ATVC is performed with at least two or more constant current values or constant voltage values, and two or more generated constant current values or constant voltage values are The environment is detected by comparing the voltage or current value of The object of the present invention is to provide a transfer device that can obtain a low bias value and perform stable and good transfer at all times regardless of the environment.

(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 a transfer device for an image forming apparatus, which includes an image carrier and a contact type transfer device that is in pressure contact with the image carrier. In an image forming apparatus, the transfer means is provided with a transfer means, and a transfer material is inserted through a transfer site that is a pressure contact portion between the two, and the transfer means is controlled with a constant current at least twice when paper is not passing, and each current value and The present invention is characterized in that the control voltage of the transfer means is set at the time of sheet passing using a coefficient determined from the voltage value generated in each case, thereby performing constant voltage control.

With this configuration, stable transferability can be obtained at all times regardless of the environment.

(Description of Embodiments) FIG. 1 is a schematic side view of an image forming apparatus showing an embodiment of the present invention, in which a cylindrical photoreceptor 1 having an axis perpendicular to the plane of the paper and rotating in the direction of the arrow shown in the figure. The OPC photosensitive layer on the surface of is uniformly negatively charged by a charging roller 3 connected to a power source 4a, and when the charged surface is irradiated with an image-modulated laser beam 5, the potential of that portion is attenuated. An electrostatic latent image is formed.

When the latent image arrives at a development site where the photoreceptor 1 and the developing device 6 face each other, negatively charged toner is supplied from the developing device to the latent image, and a toner image is formed by reversal development.

On the downstream side of the development area when viewed in the traveling direction of the photoreceptor 1, there is a transfer area formed as a pressure nip between the photoreceptor 1 and the transfer roller 2 that is in pressure contact with the photoreceptor 1, and when the toner image reaches the transfer area, At the same time, transport path 7
The transfer material P is supplied to the transfer site, and at the same time, a transfer bias is applied to the transfer roller 2 by the high voltage power supply 4b controlled via the AD converter 10a%DA converter lOb and the CPU 9. The toner image is transferred to the transfer material.

Thereafter, the transfer material carrying the toner image is separated from the photoconductor and conveyed to a fixing site (not shown), and some of the toner remaining on the photoconductor is removed by a cleaner 8, and the next image forming process begins. It turns out.

The apparatus used in the experiment will be explained in more detail.

The diameter of the photoreceptor is 30ψ, and the process speed is 30ffiI.
II/sec, the maximum paper passing speed was 2161, and the diameter of the transfer roller was 18φ.

The transfer roller has a core metal with a diameter of 6φ and is made of foamed EPDM and Zn.
By dispersing fillers such as O, SnOx, the resistance can be increased to 10
The hardness was adjusted to about s to 1010 Ω, and the hardness was in the range of 20 to 40 degrees in terms of Asker-C hardness.

The resistance value was determined by pressing the roller and the conductive plate together so that a nip of 4 mra was formed under a load of 500 gr, and taking the resistance value when IKV was applied.

Using the above roller, with the surface of the photoreceptor charged at 1600V, the generated voltage characteristics (IV characteristics) corresponding to the constant current value by ATVC are determined by L/L, N/N (23℃
, 60%RH1 normal temperature and normal pressure).

Figure 2 shows the results measured in each H/H environment.

The IV characteristic at N/N will be further explained.

The constant current value of ATVC during pre-rotation is 1μA and I2μ.
A, the voltage is applied to the photoreceptor, and each generated voltage is set to V1.
Hold as V*.

If the difference between the constant current values I+ and I= is small, the knee characteristic curve in the vicinity can be considered to be almost linear, so the slope a of the I-V characteristic curve in this part is approximately as follows: a= It can be expressed as (Vi Vl)/(I--I,).

The inclination a shows different values depending on the environment. When using a transfer roller with a resistance value of 1.5×10'Ω measured by the measurement method described above, the value ax of the inclination a in an N/N environment is aH= (v* −v+l/ (I.

-L)=(1470-920)/(2-1)Xl
0-' = 5.5x 10' tt6°Similarly, H/
The slope at H is aH = 4.3 x l O', and the slope at L/L is aL = 8.0 x lol'.

According to experiments, the resistance value of the transfer roller is 10"~10I0
When changing within the range of Ω, L/L under EM environment, at, ≧7X10”N/
Under the N environment, the following values were obtained: 5X 10''<aN<7X10' H/ Under the Htii environment, the values as≦5X10' were obtained.

In other words, the environment can be detected by performing ATVC with two current values and finding the slope a from these, and by changing the coefficient according to changes in the bi boundary, it is possible to always apply the optimum bias. Become.

The table below shows the experimental results for setting the coefficients using the transfer roller described above.

(Left below) From the experimental results for L and above, the coefficient is set to 1 for L/L.
2~1,4, 1.0~ in N/N], 2.11/
It can be seen that good results can be obtained by setting H in the range of 0.8 to 1.0.

FIG. 3 is an algorithm showing the above process.

When we applied the above results to the apparatus shown in Fig. 1 and conducted a paper passing test, we found that not only L/L in the N/Nff1 mound.
Even in high-resistance transfer materials such as transfer paper and OHP paper that have been left to dry under the E environment, good transfer performance is obtained without transfer defects or toner scattering, and even in the H/H environment. It was also confirmed that it is possible to prevent deterioration of image quality due to penetration or leakage of the transfer material due to excessive charge.

Next, an embodiment will be described in which the transfer means is controlled with a constant voltage twice to detect the environment when paper is not passing, such as during pre-rotation, and the transfer bias is set based on this.

The image forming apparatus itself is the one shown in Figure 1, and the process speed is 60 mm/sec, and negative toner is used for reversal development.The transfer roller has a resistance value of 5XIO' to 10XIO. A material made of foamed EPDM adjusted to 'Ω was used.

Figure 4 shows a transfer roller of 5 x 10'Ω (at IKV), a photoreceptor charged to 1600 Ω in an N/N environment, a constant voltage control of the transfer roller, and a current value flowing into the photoreceptor. This figure shows the VI characteristics when measured over the circumference of the transfer roller and averaged.

By taking the average value in this way, even if there is unevenness in the resistance value in the circumferential direction of the transfer roller, the generated current will not fluctuate greatly.

The constant voltage V and %V were set to o, 5KV, and 1.0, respectively, and the generated current was 1. ．． Hold 11.

If the distance between V, , and V is small, the characteristics between them can be considered to change linearly, so the slope a of the curve is a
It can be approximately expressed as = (It - I+) / (Va - Vl).

Since the slope a differs depending on each environment, if these values are found in the same way as in the previous case, the slope aN in an N/N environment is a-= (I - I + ) / (Va - ■ + )
= (2,2-0,9)xlO-'/ (1-0,5)
XIO-" = 2.6X10-', similarly, aH=
4.2X10-9, aL=1.4xtO-'' is obtained.

According to experiments, the resistance value of the transfer roller is 5X, 10'~5
If it swings within the range of X10'Ω, for L/L, aL≦2, for OX I O-'N/N,
2, OXIO-9<aN<3.5X10-
At 9 H/H, a value of aH≧3.5×10−” was obtained.

Therefore, in this case as well, the environment can be detected by performing constant voltage control using two arbitrary voltages when paper is not passing, measuring the generated currents corresponding to these voltages, and determining the slope a.

After detecting the environment, ATVC is performed, and a coefficient by which the generated voltage is multiplied can be set for each environment. In this case, a constant current control of 5 μA was performed when using non-standard paper, and when the coefficient for making the generated voltage the optimum transfer bias in each environment was determined, the value was almost the same as that in the above embodiment, and L/L 1.2-1.4 for N/N, 1.0-1 for N/N
．． 2, H/H was 0.8 to 1.0.

When the above-described embodiment was applied to the apparatus shown in Figure 1 and paper was fed, high-quality images without transfer defects could be obtained in each environment.

Note that, although the same applies to the above-mentioned embodiment, when the above method is applied to a device with different process speeds, the V-I characteristics of the contact transfer means such as the transfer roller are measured and newly calculated. Of course, by setting the coefficients, the same effects as in the above case can be achieved.

FIG. 5 shows the algorithm of the above embodiment.

Next, a description will be given of means for continuously changing the coefficients for setting the transfer bias described above.

The same device as shown in FIG. 1 was used,
A case will be described in which reversal development is performed using negative toner at a process speed of 30 mm/sec.

As the transfer means, a transfer roller having a resistance value of 1.5×10”Ω was used.

FIG. 6 shows the upper and lower limits when measuring the I-■ characteristic at the L/L and H/Hi boundaries, and therefore the shaded area shows the variation range of the characteristic curve due to environmental changes.

Since the characteristic curve changes continuously in this way, the slope a also changes continuously, and its range is defined as (Vi□-V-J / (I z -I r )≦a≦
(V, LV, L) / (L - I, ).

In order to continuously change the coefficient K that multiplies the generated voltage as a linear function of change in the slope a, the slope a and the coefficient are created based on the values obtained in the first embodiment described above. The relationship between is shown in Figure 7.

According to this, when a≦5X10', K=1.4,
5X10''< a <7X10', K= 3x1
0-"a+2.9, when a≧7X10", K=0.
It is set at 8.

Using a transfer roller having the above-mentioned resistance value, a paper passing experiment was conducted with the coefficient K set according to the environment as described above, and it was confirmed that high quality images could be obtained regardless of environmental changes. FIG. 8 schematically shows the algorithm for the above case.

If the resistance values of the transfer rollers are different, 1
It goes without saying that the same effect can be obtained by finding the -V curve and setting the coefficients.

(3) Effects of R Bright As explained in 1., in an image forming apparatus equipped with a transfer means that contacts a photoreceptor, two or more currents are generated by the transfer means during paper feeding such as pre-rotation. Alternatively, the voltage or current generated by applying a voltage value is detected, and the coefficient by which the voltage generated by ATVC is multiplied is changed depending on the environment, so the optimum transfer bias suitable for the environment can be determined. This eliminates transfer failures such as skipping of tozu in low-temperature, low-humidity environments, and deterioration of image quality due to excessive charge in high-temperature, high-speed environments such as punch-through & J, nok, etc. Regardless of the conditions, stable transfer performance can be obtained at all times, and this has a remarkable effect on obtaining high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of the main parts of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a graph showing the I-V characteristics of the above transfer roller, FIG. 3 is the same algorithm as above, and FIG. 4 is Transfer roller I-
FIG. 5 is a graph showing the V characteristic; FIG. 5 is a graph showing the same algorithm as above; FIG.
-Graph showing v characteristics. FIG. 7 is a graph showing the relationship between the slope a and the coefficient. FIG. 8 is a diagram showing the same algorithm as above. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 2...Transfer roller, 3...Charging roller, 4...Power source, 5...Image signal, (3...Developer, 8...Cleaner, 9...・・CI:) IJ, 1
0...Converter. Fig. 2 ATVC foot voltage stagnation value 1 (uA) Fig. Transfer low-7 mark g3 voltage □, (kv) Fig. Fig. 6 Fig. Type 91 Fig.

Claims (3)

[Claims] (1) In an image forming apparatus comprising an image bearing member and a contact type transfer means that is in pressure contact with the image carrier, and in which a transfer material is inserted through a transfer portion that is a pressure contact portion between the two, the transfer means is inserted when the paper is not passing. The present invention is characterized in that constant current control is performed at least twice, and the control voltage of the transfer means is set at the time of sheet feeding by a coefficient determined from each current value and the voltage value generated in each case, thereby performing constant voltage control. Transfer device. (2) In an image forming apparatus that includes an image carrier and a contact type transfer means that is in pressure contact with the image carrier, and in which a transfer material is inserted through the transfer portion that is the pressure contact portion between the two, at least the transfer means is moved when paper is not passing. A transfer device that performs constant voltage control twice and sets the control voltage of the transfer means when paper is passed using a coefficient determined from each voltage value and the current value generated in each case. (3) The transfer device according to any one of claims 1 and 2, wherein the coefficient determined from the current and voltage values controlled when paper is not passing continuously changes depending on the environment.