JP2003122068A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of an abnormal image due to insufficient transferring or excessive transferring in an electrophotographic method image forming apparatus. SOLUTION: In forming an image, the transfer condition is adjusted according to the state of variation of electrified amount of toner. Grasping of the state of variation of the electrified amount can be carried out, for example, by a mechanical counter or an electronic counter integrated to a device main body or a counter for passed number of pages of an image forming unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming method.

[0002]

2. Description of the Related Art As is generally known, an electrophotographic image forming method forms a latent image on a photosensitive member by charging and exposure, and electrically charges the charged toner to the latent image in a developing section. This process is visualized by adhering the image, the visible image is mainly electrically transferred to a sheet in the transfer section, and the transferred image is fixed by heat and pressure in the fixing section. Further, the developing method in such an image forming method includes one-component development in which only toner is directly charged and two in which toner and carrier are stirred and charged.
There is component development.

By the way, the charge amount of the toner does not depend on the state of the image forming apparatus (hereinafter sometimes abbreviated as apparatus),
It is desirable that the toner charge amount is always constant, but in reality, as shown in FIG. 1, the toner charge amount often changes depending on the characteristics of the toner and the developer, the structure of the apparatus, and the operation speed. Further, even when it is known in advance that the charging characteristics of the toner will change, there are problems that side effects occur due to the change in the characteristics of the toner, and that costs are increased by using another material.

When the charge amount of the toner changes, the amount of charge required to attract the toner attached to the photosensitive member in the same amount to the paper (transfer paper) also changes, so that the transfer condition remains fixed. It has been confirmed that the transfer state may not be maintained in some cases.

In the technique of Japanese Patent No. 3031070, which aims to eliminate such a problem, a device for reading the line width of a reference image prepared in advance is provided on the photoconductor, and development is performed according to the read line width. The process conditions such as charging are changed. This image forming method is effective for grasping the state of the apparatus, but as described above, it is necessary to provide an apparatus for detecting the line width of the reference image, and although it has high performance, the apparatus installation space and From a cost perspective, it is not always satisfactory.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to set a transfer condition in accordance with a change in characteristics of toner so as to prevent insufficient transfer or excessive transfer without complicating the structure of the image forming apparatus. An object of the present invention is to provide an image forming method capable of preventing the occurrence of abnormal images such as missing images.

[0007]

The invention according to claim 1 is
This is an image forming method characterized in that, when an image is formed by an electrophotographic image forming apparatus, a transfer condition is adjusted according to a change situation of a charge amount of toner. Even if the charge amount of the toner changes with time, by correcting to an appropriate transfer condition, it becomes difficult to cause an abnormality such as insufficient transfer or excessive transfer.

The invention according to claim 2 is the image forming method according to claim 1, wherein the change state of the charge amount is grasped by a mechanical counter or an electronic counter built in the apparatus main body. In the present invention, the change over time of the toner charge amount is grasped by the alternative evaluation value, so that the occurrence of an abnormal image can be prevented even with a simple device structure.

The invention according to claim 3 is the image forming method according to claim 1, characterized in that the change state of the charge amount is grasped by a sheet passing number counter of the image forming unit. According to the present invention, in the image forming method according to the first aspect, it is possible to more accurately grasp the change with time of the toner charge amount, and the abnormal image generation preventing function is enhanced.

The invention according to claim 4 is the image forming method according to claim 1, wherein the transfer condition is adjusted by adjusting at least one of a transfer current and a transfer pressure. In the present invention, the occurrence of abnormal images can be prevented more effectively by narrowing down the targets for changing the transfer conditions.

According to a fifth aspect of the present invention, the transfer condition is changed according to an increase in the number of counts of the mechanical counter, the electronic counter, or the sheet passing number counter.
The image forming method according to any one of 1 to 4. In the present invention, the abnormal image can be prevented more effectively by adjusting the transfer condition according to the counting result of the predetermined counter.

The invention according to claim 6 is the image forming method according to claim 5, wherein an upper limit and a lower limit are set for the adjustment value of the transfer condition. In the present invention, the transfer condition is adjusted within an appropriate range, so that the abnormal image can be prevented more effectively.

[0013]

[Test Example] A test example according to the present invention will be described below. Test Example 1 FIG. 1 is a graph showing changes in the toner charge amount (specific charge amount: Q / M) due to changes in ambient temperature and humidity in a general electrophotographic image forming apparatus. It is desirable that the toner charge amount is always constant (the "ideal state" in FIG. 1), but it generally changes due to environmental changes, load due to device operation, and the like.

Test Example 2 FIG. 2 is a graph showing the changing state of the transfer rate when the toner charge amount changes. This is a 30mm diameter photoreceptor,
These are the results when an image was formed under the conditions of two-component development, a ferrite carrier having a particle size of 50 μm, a toner average particle size of 7.5 μm, a transfer roller outer diameter of 16 mm, contact transfer, and constant current control. From FIG. 2, it can be seen that the transfer rate also changes according to the change in Q / M. Thus, the transfer rate is Q / M of the toner.
Therefore, adjusting transfer conditions according to changes in Q / M is effective in preventing abnormal images.

Test Example 3 FIG. 3 is a graph showing the relationship between the number of copies counted by the apparatus main body counter and the toner Q / M, and it can be seen that Q / M rises as the “counter number increases”.

Test Example 4 FIG. 4 shows the number of copies and toner Q when the image forming unit portion (image forming unit counter) is replaced during use of the apparatus.
It is a graph which shows the relationship of / M. In the case of an image forming apparatus, which has become popular in recent years, such that the image forming unit can be replaced before the life of the apparatus main body is exhausted, as shown in FIG. The change situation cannot be grasped accurately. Therefore, as shown in FIG. 4, by measuring the number of copies by the image forming unit counter as a substitute characteristic, it becomes possible to set a transfer condition more suited to the changing situation of the toner charging characteristic.

Test Example 5 There are mainly two characteristics that determine the transfer conditions, a transfer current and a transfer voltage, and an abnormal image can be prevented by adjusting either of these characteristics according to the changing state of the toner Q / M. be able to. In this test example, the transfer current was used as a characteristic value for setting transfer conditions, and this condition was made variable.

Test Example 6 FIG. 5 is a graph showing the results of a test example in which the transfer current is changed according to the counter value (the number of copies). In this test example, toner Q increases as the number of copies increases.
Based on the finding that / M increases, the transfer current is increased according to the counter value. Since the initial transfer condition and how to change the transfer condition according to the counter vary depending on the device and toner used, it is desirable to accurately grasp each tendency and set appropriately.

Test Example 7 FIG. 6 is a graph showing the results of a test example in which the transfer current is changed according to the counter value and the transfer current has upper and lower limits. The toner Q / M does not continue to rise indefinitely, but is generally maintained at this level after rising (falling) to a certain level as shown in FIG.
Therefore, the upper limit (lower limit) of the transfer current is adjusted according to this level.
By setting, it is possible to maintain the transfer condition most suitable for the change in the toner Q / M.

[0020]

As is apparent from the above description, in the present invention, in the electrophotographic image forming apparatus, it is generally easy to set the transfer condition suitable for the toner characteristics in which it is difficult to always maintain the same charge amount. By optimizing the configuration, it is possible to accurately prevent the occurrence of an abnormal image.

[Brief description of drawings]

FIG. 1 is a graph showing a change state of a toner charge amount (specific charge amount: Q / M) due to a change in ambient temperature and humidity in a general electrophotographic image forming apparatus.

FIG. 2 is a graph showing how the transfer rate changes when the toner charge amount changes.

FIG. 3 is a graph showing the relationship between the number of copies by the counter of the apparatus main body and toner Q / M.

FIG. 4 is a graph showing a relationship between the number of copies and toner Q / M in a test example in which an image forming unit portion (image forming unit counter) is exchanged during use of the apparatus.

FIG. 5 is a graph showing a result of a test example in which a transfer current is changed according to a counter value (the number of copies).

FIG. 6 is a graph showing the results of a test example in which the transfer current is changed according to the counter value and the transfer current has upper and lower limits.

Claims (6)

[Claims] 1. An image forming method, characterized in that, when an image is formed by an electrophotographic image forming apparatus, a transfer condition is adjusted according to a change state of a charge amount of toner. 2. The image forming method according to claim 1, wherein the change status of the charge amount is grasped by a mechanical counter or an electronic counter built in the apparatus main body. 3. The image forming method according to claim 1, wherein a change state of the charge amount is grasped by a sheet passing number counter of the image forming unit. 4. The image forming method according to claim 1, wherein the transfer condition is adjusted by adjusting at least one of a transfer current and a transfer pressure. 5. The image forming method according to claim 1, wherein the transfer condition is changed in accordance with an increase in the count number of a mechanical counter, an electronic counter or a sheet passing number counter. 6. The image forming method according to claim 5, wherein an upper limit and a lower limit are set for the adjustment value of the transfer condition.