JPH03144473A - Image forming device - Google Patents

Abstract

PURPOSE:To stably perform satisfactory multiple transfer by adjusting the supply of power to a transfer, electrification means according to the result of a detecting means during a break of consecutive transfer. CONSTITUTION:During a break of consecutive transfer, the supply of power to the transfer, electrification means 5b is adjusted according to the result detected by the detecting means 16 detecting at least either the ambient temperature or humidity of a transfer material. The value of an inter-color transfer current supplied to a transfer electrifier 6 is controlled with an appropriate inter-color transfer current determined according to an area specified based on temperature/humidity detecting signals output from the temperature/humidity sensors 16 as a target value. Thus, a satisfactory image can be stably formed.

Description

Detailed Description of the Invention [Industrial Application Fields] The present invention carries a transfer material on an endlessly moving transfer material carrying sheet, and applies a transfer electric field to this transfer material to transfer an image onto a photosensitive drum, an insulating drum, etc. The present invention relates to an image forming apparatus having a multi-transfer device that can be applied to a color copying machine, a color printer, etc., in which toner images formed on a carrier are sequentially transferred onto a transfer material in an overlapping manner.

[Prior Art] FIG. 14 is an explanatory diagram of a conventional electrophotographic color copying machine for forming full-color copy images. In the figure, a photosensitive drum 1 is surrounded by a corona charger 2, an N-end optical system 3.
Developing device 4. Transfer drum5. A cleaning device 6 is placed. The optical system 3 includes a document scanning section 3a and a color separation filter 3b.
Consists of. The developing device 4 has four color developing devices around the central axis 4b, 4Y in the figure is a yellow developing device, 4M is a magenta developing device, 4C is a cyan developing device, and 4 is a black developing device. It is arranged as a vessel. Further, the entire developing device rotates to sequentially develop each of the four colors. Further, the transfer drum 5 includes a cylinder 5a and a transfer charger 5b.

Transfer material gripper 5c, inner charger 5d, outer charger 5
A transfer material carrying sheet is provided in an opening area formed by cutting out a part of the drum 5, and the transfer material is supported on the sheet.

To form a full-color image, first, a green color-separated electrostatic latent image is formed on the photosensitive drum 1, and developed by the magenta developer 4M. On the other hand, the transfer material is transferred from the transfer material cassette 7 via a conveyance system and gripped by a gripper 50 of the transfer drum. As the rotation of the transfer drum 5 progresses, the toner image on the photosensitive drum 1 is transferred onto the transfer material by the transfer charger 5b, and at the same time, the transfer material is attracted to the transfer material carrying sheet. This operation is repeated three more times for cyan, yellow, and black in the same manner as in the known full-color image method. When the transfer of the four-color toner image is completed, it is separated from the transfer drum 5 and transferred via the heat roller fixing device 9. and is discharged onto tray IO.

However, in the image forming apparatus configured as described above, when a transfer material of large size paper (A3, B4, leisure, etc.) is loaded on the transfer drum 5, the distance 11 ( Since the distance between the leading edge and the trailing edge (hereinafter referred to as the distance between the leading edge and the trailing edge) is shorter than that of small-sized paper (A4, 85, etc.), the developing device of the rotary movable developing device 4 can reduce the distance between the leading edge and the trailing edge within the time that the transfer drum 5 rotates. There is a problem of not being able to move in time.

This problem has been avoided in conventional devices by having two main operation sequences: (1) a sequence for small size, and (2) a sequence for large size. In other words, ■ is as shown in the operation overview of the conventional device mentioned above,
This is a mode in which a four-color toner image is transferred by four rotations of the transfer drum (four-rotation mode). Regarding (3), in order to solve the problem related to the developing device, C during the transfer of each color toner image is
This is a 7-rotation mode in which the transfer drum is rotated for a total of 7 rotations, including one idle rotation of the transfer drum (hereinafter referred to as intercolor rotation).

FIG. 15 shows a table summarizing the sequences of (1) and (2) with a focus on the number of rotations of the photosensitive drum and the transfer drum. ■ indicates A4 size, and ■ indicates A3 size.

Here, the transfer charger 5b is turned on not only during transfer of the four-color toner image but also during inter-color rotation, but this is to prevent re-transfer (offset) of toner on the transfer material during inter-color rotation. Usually, a smaller amount of high pressure is applied than when transferring four-color toner images.

[Problems to be Solved by the Invention] Incidentally, in the conventional color image forming apparatus having the above-mentioned configuration, the transfer charger 5b during intercolor rotation does not change, regardless of changes in the environment in which the color image forming apparatus is installed.
The high voltage applied to the toner is controlled to always be at a constant value, and retransfer of the toner image is prevented at this constant value.

However, when the color image forming apparatus is placed in a high-temperature environment, the value of the volume resistivity of the transfer material P used is lower than the value of the volume resistivity of the transfer material P used when the color image forming apparatus is placed in a room-temperature environment (for example, an air temperature of 23° C. and a humidity of 60%). When the transfer material P is paper, the amount decreases by about two orders of magnitude compared to when the transfer material P is placed on paper. Also, regarding the transfer material carrying sheet, the surface resistance value of the transfer material carrying sheet decreases because moisture is adsorbed on the surface thereof.

Therefore, the voltage applied to the transfer charger 5b was too low to sufficiently hold the transferred toner image, and a small amount of toner was retransferred onto the photosensitive drum during intercolor rotation. The graph shown in FIG. 16 quantitatively captures this development by measuring the toner density on the transfer material every rotation of the transfer drum 5. Here, the horizontal axis is the rotation speed of the transfer drum, and the vertical axis is the reflection density. It can be seen that the reflection density of colors that have undergone a lot of intercolor rotation is reduced. In this case, for example, when copying a black original, the resulting copy becomes a greenish black with no magenta.

On the other hand, when the color image forming apparatus is placed in a low temperature and low humidity environment, the value of the volume resistivity of the transfer material P used is
compared to when the transfer material P is placed under
increases by about two orders of magnitude for paper. Further, regarding the transfer material carrying sheet, the surface resistance value of the transfer material carrying sheet increases because the amount of moisture adsorbed on the surface thereof decreases.

Therefore, the voltage applied to the transfer charger 5b is too high, and although it is possible to obtain sufficient toner retention force to prevent retransfer, toner adheres to the back surface of the transfer material carrying sheet and the surface of the transfer material, respectively. Since the charge is conveyed to the transfer position without attenuation, the transfer of the second and subsequent colors could not be performed satisfactorily due to the so-called chi-Y-shrink phenomenon. The graph shown in FIG. 17 quantitatively captures this phenomenon by measuring the toner density on the transfer material every rotation of the transfer drum 5. Although there is no retransfer due to intercolor rotation as shown in FIG. 16, the density at the time of toner image transfer decreases as the sequence progresses. In this case, for example, when copying a black original, the resulting copy will be black with a blue tint, without the black and yellow.

Therefore, when such a multicolor electrophotographic copying machine is placed in a normal temperature environment (temperature 23°C, humidity 60%), the two phenomena of retransfer and charge-up are maintained in balance. Due to this design, good multiple transfer is performed and an appropriate image can be obtained, but these conditions cannot be maintained in the above-mentioned high-temperature environment or low-temperature and low-humidity environment, resulting in a decrease in image quality.

An object of the present invention is to provide an image forming apparatus that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an image bearing member, a transfer material holding means for holding a transfer material, and a method for transferring a visible image formed on the image bearing member to the transfer material. a transfer charging device that operates to cause transfer; a detection device that detects at least one of temperature and humidity in the vicinity of at least the transfer material supplied to the transfer material carrying device; means for adjusting the amount of power supplied to the transfer charging means, and when the visible image repeatedly formed on the image carrier is repeatedly transferred to the transfer material carried by the transfer material carrying means, the adjusting means adjusts the amount of power supplied to the transfer charging means. During the period between transfers, the amount of power supplied to the transfer charging means is adjusted according to the detection result of the detection means.

Further, the present invention includes an image carrier, a transfer material carrier for holding a transfer material, a transfer charging device that operates to transfer a visible image formed on the image carrier to the transfer material, and at least a transfer material carrier for holding the transfer material. a first detection means for detecting at least one of temperature and humidity near the transfer material supplied to the means; a second detection means for detecting whether the transfer material is a special sheet; the first detection means and the second detection means; and means for adjusting the amount of power supplied to the transfer charging means based on the detection results obtained by the detection means.

[Function] According to the present invention, by providing the above configuration, the detection results of the installation environment of the apparatus and the type of transfer material are introduced into the control of the transfer charging means, thereby stably forming a good image. do.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. The overall configuration of FIG. 1 is the same as that of the image forming apparatus shown in FIG. 14, and its outline will be explained as follows.

That is, the image forming apparatus shown in FIG. 1 is of a type that is equipped with a transfer material carrying means, that is, a transfer drum, and has an image carrying member, that is, a photosensitive drum 1, and a peripheral portion of the photosensitive drum 1. The provided cleaner 6,-
Charger 2. Developing device 4. Transfer charging means, that is, a transfer charger 5b, etc., an inner neutralizing charger 5d, and an outer neutralizing charger 5e.

Transfer sheet 5f loaded on transfer drum cylinder 5a
is the main component.

The above configuration will be described in more detail as follows. The gap defined by the negative charger 2 and the developing device 4 is irradiated with image exposure light from the image exposure means 3. In this embodiment, the transfer f-electric device 5b has an opening width of 22+++a+, and the distance between the discharge wire in the charger and the transfer sheet 5f is 11
+ss. The transfer sheet 5
A PVDF (polyvinylidene fluoride) sheet with a thickness of 150 μm is used for f, and the
It rotates at a speed of ec.

Furthermore, according to this embodiment, a temperature/humidity detection means, that is, a temperature/humidity sensor 16 is provided to detect the temperature and humidity of the atmosphere inside the color image forming apparatus. The temperature/humidity sensor (2) is disposed near the transfer drum 5 at a position where it does not inhibit the movement of the transfer material. The temperature and humidity sensor 16
is configured to output a voltage signal in accordance with the temperature/humidity detected inside the device. Regarding the image forming operation in the color image forming apparatus configured as described above,
Since this has already been explained with reference to FIG. 14, the explanation thereof will be omitted.

FIG. 2 shows a control system included in the image forming apparatus according to the first embodiment of the present invention. In FIG. 2, the temperature and humidity sensor 16 is.

A temperature detection signal (hereinafter referred to as "T signal") and a temperature detection signal (hereinafter referred to as "H signal") are output, and the ^/D converter 50
6 converts the T signal from analog to digital and converts it to I10.
A/D converter 515 converts the H signal into analog/digital and outputs it to the r10 port 507, respectively. The variable adjustment means, or CPO 510, adjusts the I10 ports 507 and 508 prior to a series of image forming operations by the image forming apparatus.
Read each signal input to the memory 511 and refer to table 1 (shown in FIG. 3) built in the memory 511 to determine the area in which each signal is set in table 1.
Specify the area to which environment of ~■ it belongs to. Along with this, the CPU 510
1, the intercolor transfer current value data corresponding to the T signal and H signal is read from the table 2, and the read intercolor transfer current is D/D value data via I10 boat 512
^Output to converter 513. The D/^ converter 513 performs digital/analog conversion on the intercolor transfer current value data output from the CPU 510 via the I10 port 512, and then outputs it to the high voltage power supply device 514. A transfer current is supplied to the transfer charger 6 based on the intercolor transfer current value data. Note that, as is already well known, the series of processing operations by cpusto described above are executed prior to the copying operation, that is, the image forming operation.

FIG. 3 shows the contents of table 1 stored in the memory 511 shown in FIG. In Table 1, regions ■ to ■ are appropriately divided and defined by multiple equal moisture content curves determined by temperature and humidity, respectively. The charging characteristics of the material P and the moisture absorption and charging characteristics of the transfer material carrying sheet such as the transfer material conveying belt are approximately equal;
It is thought that the environment is similar. The data shown in FIG. 4 is stored in table 2 stored in memory 511.
This shows the details of the content. The table 2 shows the most appropriate intercolor transfer current value at the representative point of each region when the environment such as temperature and humidity in which the image forming apparatus is installed is divided into regions ■ to ■. are set corresponding to each of the areas. The aforementioned representative point is represented by the point X shown in FIG. 3. Appropriate intercolor transfer current values for each of the regions (1) to (2) shown in FIG. 4 are obtained through the following process.

First, representative points (indicated by X in FIG. 3) in each environment shown by regions (1) to (2) in FIG. 3 are set, and appropriate intercolor current values at each of these representative points are determined.

Here, as an example, a method for determining the appropriate intercolor current value for the region (■) will be shown. First, the relationship between the intercolor transfer current (1) for the first color, magenta and the second color, cyan, and the reflection density of the magenta toner image on the transfer material after the intercolor rotation was investigated. The result is the fifth
As shown in the graph in the figure. Because the aforementioned retransfer (offset) occurs in the region where the current is small,
There is a large drop in concentration. Also, even if the current rMe≧200 (μA) is too large, the concentration will drop. This is also due to offset, but the development is slightly different.

That is, the polarity of the toner (- in this case) is reversed (+) due to the electric field caused by the large intercolor transfer current, and the toner is pulled toward the photosensitive drum 1 side.

From this result, it can be said that the appropriate IMC is 100≦T&lc≦200 (μ^), but if a large intercolor transfer current is set, the transfer sheet 5f will be charged up, resulting in failure in the second and subsequent color transfers. A problem arises in which Therefore, the shoulder portion of the curve in FIG. 5 is defined as the optimum intercolor transfer current.

Between the second color cyan and the third color yellow, add 3 more
The distance between the color yellow and the fourth color black is determined in a similar manner, but in the experiment in this example, it was determined that rMc = Icy - IvK100 (μA).

Further, the optimum intercolor transfer current for each area is as shown in FIG.

As explained above, according to the first embodiment according to the present invention, the area illustrated in FIG. , ``Since the value of the intercolor transfer current supplied to the transfer charger 6 is controlled using the appropriate intercolor transfer current value determined according to the specified area as the target value, the moisture absorption state of the transfer material P is controlled. It is now possible to supply the transfer electric current 6 with an intercolor transfer current having a magnitude corresponding to a change in the volume resistance value of the transfer material P due to a change in the transfer material P or a change in the surface resistance value of the transfer material carrying sheet.

(Second Embodiment) In the first embodiment, each environment area is considered to be the same environment, so near the boundary, it is a discontinuous function with respect to the appropriate color-to-color transfer current. Therefore, when using a material that exhibits sensitive changes to the environment, which will be described later, it may not be possible to perform appropriate control. Being sensitive to the environment means that the volume resistivity of transfer materials changes significantly; for example, lightweight coatings used for flyers, etc., even if they are uncoated paper or coated paper. Paper etc. Furthermore, in the case of toner, its electric charge changes greatly, such as those whose binder is made of polyester resin.

In such a case, more accurate control can be performed according to the second embodiment described below.

FIG. 6 shows a control system included in the image forming apparatus according to the second embodiment. Further, the main body of the image forming apparatus is the same as the main body used in the first embodiment shown in FIG.

The control system shown in FIG. 6 will be explained below, but the explanation of parts that overlap with those in FIG. 2 of the first embodiment will be omitted.

The T signal and H signal that came into CPIJ51 Q are calculated and replaced with another value, the amount of moisture W in the air. The amount of moisture in the air is the weight (g) of moisture contained in 1 kg of air, and is an absolute value. This is determined according to the following formula.

H= p/p, x 100 (%)
...(1) P: Water vapor partial pressure (mmHg) P,: Saturated water vapor pressure (mmh) π: Total pressure (usually 760 questions) 1g) The procedure is as follows: First, P is determined using equation (1). PS is called by referring to the T signal using table 4 in memory 511. The detailed contents of Table 4 are shown in FIG. Next, P calculated by equation (1) is (
2) Substitute into the equation to find I and W. For example, when T = 30°C and H = 80%, w = 21.6 (g/kg).

Next, by referencing the obtained W with Table 3, an appropriate intercolor transfer current is determined. The contents of Table 3 are as shown in FIG.

FIG. 9 shows the appropriate intercolor transfer current for the amount of moisture in the air, and the method for determining this is almost the same as the method for determining the table in the first embodiment. First, a plurality of environments as shown in FIG. 9 are set, and the appropriate intercolor current for each environment is determined using the same method as in the first embodiment. Plot against water content (X mark in Figure 8). Furthermore, interpolation is performed using a straight line between each environment.

(Third Embodiment) The transfer material is usually paper, but in special cases, a transparent sheet for projection (hereinafter referred to as transparent sheet) is used. A typical transparent sheet is made of polyethylene, and its volume resistance is 10"
(Ω・cm) and large. Therefore, it is necessary to set an intercolor transfer current for transparent sheets separately from paper.

The configuration diagram of the image forming apparatus used in the third embodiment is shown in the first
Shown in Figure 0. The equipment used in the first embodiment is
However, a transmission type optical sensor 17 for detecting a transparent sheet is provided in the paper feeding section.

When paper is fed, this sensor 17 determines whether it is paper or a transparent sheet.

FIG. 11 shows a control system included in the image forming apparatus according to the third embodiment. Regarding the control method, see Example 2
Since there is a difference between the two, the details will be omitted and a brief explanation will be added.

The sensor 17 determines whether it is paper or a transparent sheet. If it is paper, table 3 is referred to, if it is a transparent sheet, table 3 is referred to, and if it is a transparent sheet, table 5 is referred to.

The contents of table 5 are shown in FIG.
μm), as a result of conducting the experiment shown in the first example using a sheet made of polyethylene terephthalate, such a value was obtained.

Furthermore, in creating the table shown in FIG. 12, a plurality of environments were set, and the appropriate intercolor transfer current at that time was determined through experiments, and the results are shown in FIG.

By using this embodiment, it is possible to supply an appropriate intercolor transfer current for each type of transfer material.

Among the three embodiments of the present invention, for convenience of explanation, the transfer charger 5b
The current supplied to the device is controlled by constant current, but
Constant voltage control may be used instead of constant current control. Further, although the explanation is given as IHC"ICY-IYK, it is not contrary to the spirit of the present invention to create a table with different values C for each in order to perform proper multiple transfer.

Further, in the first embodiment, there is no problem in increasing or decreasing the areas (1) to (2) as needed.

[Effects of the Invention] As explained above, according to the present invention, problems such as poor transfer can always be prevented regardless of the environment in which the image forming apparatus is installed and regardless of the type of transfer material. It is possible to provide an image forming apparatus without any

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is a schematic diagram showing a control system included in the image forming apparatus according to the first embodiment of the present invention. Block diagram: FIG. 3 is a diagram showing the contents of table 1 stored in the memory 511 shown in FIG. 2, and FIG. 4 is a diagram showing the contents of the table 1 stored in the memory 511 shown in FIG. FIG. 5 is a diagram showing the contents of Table 2 stored in the table 2, and FIG. 6 is a block diagram showing a control system included in the image forming apparatus according to the second embodiment of the present invention, and FIG. 7 is a block diagram showing the control system included in the image forming apparatus according to the second embodiment of the present invention. FIG. 8 shows the contents of the table stored in the memory 511 shown in FIG. 6. 9 shows a table summarizing the experimental data used to create the table 3 stored in the memory 511 shown in FIG. 6, and FIG. 1O shows the present invention. FIG. 11 is a block diagram showing a control system included in the image forming apparatus according to the third embodiment of the present invention; FIG. 12 is a schematic diagram showing an image forming apparatus according to the third embodiment of the present invention; , a diagram showing the contents of the table 5 stored in the memory 511 shown in FIG. 11C, and FIG. 13 shows the contents of the table 5 stored in the memory 511 shown in FIG. Figure 14 is a schematic diagram showing the configuration of an image forming apparatus according to the prior art; Figure 15 is a transfer charger of an image forming apparatus according to the prior art. FIG. 16 is a diagram showing data showing image defects in an image forming apparatus according to the prior art under high temperature and high humidity conditions. FIG. It is a figure which shows the data showing the state of image defect in the lower part. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 5... Transfer drum, 5b... Transfer charger, 5f... Transfer material carrying sheet, 16... Temperature/humidity sensor, 510... cpu. 17...Transparent sheet detection sensor. 0 0 0 0 Temperature T ('C) Figure 3 Figure 9 Figure 13 for transparent sheet

Claims (1)

[Claims] 1) an image carrier, a transfer material holding means for holding a transfer material,
a transfer charging device that operates to transfer a visible image formed on the image carrier to a transfer material; and a detection device that detects at least one of temperature and humidity near the transfer material supplied to the transfer material carrying device. and means for adjusting the amount of power supplied to the transfer charging means based on the detection result obtained by the detection means, and the visible image repeatedly formed on the image carrier is carried by the transfer material carrying means. The image forming apparatus is characterized in that when repeatedly transferring images onto a transfer material, the adjusting means adjusts the amount of power supplied to the transfer charging means in accordance with the detection result of the detecting means during a period between transfers. 2) an image carrier, a transfer material holding means for holding a transfer material;
a transfer charging device that operates to transfer a visible image formed on the image carrier to a transfer material; and a first device that detects at least one of temperature and humidity in the vicinity of at least the transfer material supplied to the transfer material carrying device. a detection means, a second detection means for detecting whether the transfer material is a special sheet, and the first detection means;
An image forming apparatus comprising: a means for adjusting an amount of power supplied to the transfer charging means based on the detection results respectively obtained by the detection means and the second detection means.