JPS63214776A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an invariably stable image by providing a resistance element for correcting the impedance of a primary electrostatic charger in a process cartridge. CONSTITUTION:The output voltage V0 of a high-voltage power source 15 is V0=IR0, where I is a constant current flowing through the electrostatic charging line 2A of the primary electrostatic charger, R0 is the impedance of the primary charger 2, and the resistance value of a variable resistance element 16 is 0OMEGA. When it is assumed that the process cartridge 12 has this impedance and the output voltage V0 is the optimum value (V1+V2)/2 of a transfer voltage, the impedance is R1 (R1<R0) when the distance between the electrostatic charging line 2A and a photosensitive drum 1 is narrowed down for potential correction, and then the transfer voltage V1 becomes V1=IR1<V0 and deviates from the best condition V0. For the purpose, the resistance value R1' of the variable resistance element 16 is set to a value satisfying (R1'+R1)I=V0, i.e. R1'=R0-R1, thereby obtaining the optimum transfer voltage.

Description

Detailed Description of the Invention A. Object of the Invention [Field of Industrial Application] The present invention relates to an image forming apparatus using an electrophotographic method, an electrostatic recording method, etc.
The present invention relates to an image forming apparatus in which a process cartridge assembled in one housing is configured to be detachable and replaceable from the main body of the image forming apparatus, and uses a common high voltage power source for primary charging and transfer charging.

[Conventional technology]

In an image forming apparatus, a high-voltage power supply supplies voltage to a primary charger for charging an image carrier such as a photosensitive drum, and a voltage is supplied to a transfer charger to transfer a developed image on the image carrier to a transfer material such as paper. In order to reduce costs, the high-voltage power supply is used in common.

In addition, the process cartridge, in which at least a charger and an image carrier are assembled in one housing, is made removable and replaceable with respect to the main body housing of the image forming apparatus, and when the number of transferred sheets reaches a preset number, the process cartridge is replaced with a new one. There are image forming apparatuses of this type.

In some of the above-mentioned cartridge replacement systems, each cartridge contains a developer of a different color so that the color of the image can be changed by replacing the cartridges.

In the case of the above-mentioned one color correspondence method, the materials of the developer are different between black and each color other than that, and the developing conditions are also somewhat different.

In this case, if development is performed under the same conditions, "fogging" or other abnormalities in image quality may occur, so it is necessary to change the charging setting of the image carrier depending on the color of the developer in the process cartridge.

In addition, the potential of the process cartridge may vary due to the charging sensitivity of the image carrier, variations in the shape of the primary charger, etc. In order to correct this potential, the charging settings of each process cartridge may be changed. It needs to change.

As means for changing the above-mentioned charging settings, generally the shape of the shield of the primary charger is changed or the distance between the charging line and the image carrier is adjusted.

By the way, when the charging current is a constant current in an image forming apparatus that supplies high voltage to the primary charger and the transfer charger from a common power source, the high output voltage is determined according to the impedance of the primary charger. In other words, the voltage supplied to the transfer charger changes depending on the impedance of the single band in the process cartridge 7.

As shown below, you can change the shape of the shield of the primary charger,
When the distance between the charging line and the image carrier changes, the impedance of the primary charger changes and at the same time, the transfer voltage changes as well.

Although it is possible to study the effects of fluctuations in transfer voltage on both transferability and separability, the transferability and separability relative to transfer voltage when separation conditions are constant in an electrostatic separation type image forming apparatus are generally shown in Figure 5. As shown, they have contradictory tendencies, and the range of transfer voltage is determined in a region where both characteristics are satisfied.

In view of the above points, when changing the charging setting of the process cartridge, the shape of the shield of the primary charger and the distance between the charging line and the image carrier should be changed so that the impedance of the primary charger does not change. is possible.

[Problem that the invention seeks to solve]

However, since the above-described apparatus is configured to change the shape of the shield of the primary charger depending on the type of process cartridge, the flow of air around the charger changes, resulting in the following drawbacks.

That is, discharge products such as ozone may stagnate in the charger, or the discharge products may flow in a direction that adversely affects an image bearing member such as a photosensitive drum. Furthermore, there is a possibility that this may be disadvantageous with respect to the rise in temperature E around the image carrier.

The above device simultaneously changes the shape of the shield of the primary charger and the distance between the charging line and the image carrier when changing charging settings due to variations in potential between process cartridges or differences in developer color. Moreover, since the impedance of the primary charger must be designed so that it does not change, the design is difficult and it is virtually impossible to completely correct variations in potential of each process cartridge and charging settings.

The present invention aims to solve the above-mentioned problems in image forming apparatuses.

Summary: Structure of the Invention [Means for Solving Problems] In order to achieve the above object, the present invention uses a common power source for primary charging and transfer charging, and connects at least the charger and the image carrier to one unit. In an image forming apparatus configured such that the process cartridge incorporated in the housing can be attached to and replaced with respect to the main body liquid of the image forming apparatus, and the distance between the charging line of the primary charger and the image carrier can be adjusted, The present invention is characterized in that it includes a resistance element for impedance correction of the primary charger.

[For production]

By adjusting the distance between the charging line of the primary charger and the image carrier for each process cartridge or type of process cartridge, the required charging settings can be set to obtain appropriate transfer and separation properties. At this time, changes in the impedance of the primary charger that occur due to adjustment of the distance between the charging line and the image carrier are corrected using a resistive element.

〔Example〕

FIG. 1 is a longitudinal sectional front view of a transfer type electrophotographic copying apparatus embodying the present invention, and FIGS. 2 and 3 are electrical circuit diagrams of each embodiment of the apparatus of the present invention.

The image forming apparatus of this embodiment includes a rotating photosensitive drum 1 as an image carrier. A primary charger 2 that charges the photosensitive drum 1 positively or negatively. Reciprocating document placement table 3. an exposure optical system comprising a document illumination light source 4, a short-focus imaging element array 5, etc.; a developing device comprising a developing sleeve 6 and a toner storage chamber 7;
Transfer charger 8, transfer material feeding mechanism 9, cleaning device l
This is a transfer type electrophotographic copying apparatus in which necessary image forming process equipment such as an O1 fixing device 11 is built into the apparatus housing.

The image forming process equipment includes a photosensitive drum primary charger 2, a developing sleeve 6, a toner storage chamber 7 and a cleaning device! Reference numeral 110 is made into a cartridge, and the process cartridge 12 is moved horizontally (
It is constructed so that it can be inserted and removed in the direction perpendicular to the paper surface.

In the figure, 14A-14B are rails that guide the insertion and removal.
Reference numeral 15 denotes a high-voltage power supply common to the primary charger 2 and the transfer charger 8. Although omitted in the figure, the primary charger 2 is equipped with a distance adjustment mechanism between its charging line 2A and the image carrier 1. ing. Its adjustment mechanism is the same as the conventional one. Also, the primary charger 2
Although it is equipped with a shield, this is also omitted from the figure because it is the same as the conventional one.

Next, to explain the configuration and operation of the embodiment shown in FIG.
．． Assuming that the impedance of the primary charger 2 is Ro and the resistance value of the variable resistance element 16 is 0Ω, the output voltage v0 of the high voltage power supply 15 is . =IR0. The variable resistance element 16 is connected to the charging line 2A side of the primary charger 2.

It is assumed that the process cartridge 12 has the impedance shown below, and the output voltage vo is shown in Figure 5 above.

Assume that the process cartridge 12 is equipped with a photosensitive drum 1 having a low charging ability due to manufacturing variations.

When the distance between the charging line 2A and the photosensitive drum 1 is narrowed for potential correction, the impedance becomes R (R, <R), and the transfer voltage v1 is v1=llIR, <V. Therefore, it deviates from the optimal condition vo.

Therefore, the resistance value R/1 of the variable resistance element 16 is set as (R'1+R
1) The optimum transfer voltage can be obtained by setting a value that satisfies I=Vo, that is, R,=Ro−R.

In the above embodiment, when R1>R, the variable resistance element 16 is connected to the charging line 8A of the transfer charger 8 as shown in FIG.
It should be connected to the side of the

A fixed resistance element may be used in place of the variable resistance element 16, and this may be replaced with one having a desired resistance value.

The present invention can be implemented not only to correct the transfer voltage but also to correct the separation voltage. In an electrostatic separation type device, the charge removal voltage φ current may be corrected by a resistance element provided in the process cartridge 12. Can be done.

FIG. 4 shows an embodiment in which the above-mentioned separation voltage is corrected in a device that uses a static eliminating needle 17 to separate transfer paper, and the impedance correction resistance element 16 is connected in the circuit of the static eliminating needle 17. ing.

C5 Effects of the Invention As described above, according to the apparatus of the present invention, the primary charger provided in the process cartridge can The impedance correction resistance element of the secondary charger allows the necessary charging settings to be made for each process cartridge or the type of process cartridge, so the air flow around the primary charger hardly changes, and the discharge product There is no difference between process cartridges with respect to adverse effects on the image carrier or temperature rise around the image carrier, and stable images can always be obtained.

Further, there is no need to bother with designing the shape of the shield of the primary charger, and a simple shape and configuration is sufficient, which has the effect of allowing the charging settings of each process cartridge to be changed with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of an image forming apparatus implementing the present invention;
FIGS. 2, 3, and 4 are electrical circuit diagrams of each embodiment of the apparatus of the present invention, and FIG. 5 is a diagram showing characteristics of transferability and separability related to transfer voltage. 1 is an image carrier (photosensitive drum), 2 is a primary charger, 3 is a document mounting table, 4 is a light source for illuminating the document, 5 is a short focus imaging element array, 6 is a developing sleeve, 7 is a toner storage chamber, 8 is transfer charger, 10 is cleaning? 11 is a fixing device;
12 is a process cartridge, 13 is a housing, 15 is a high-voltage power supply, and 16 is a resistance element for impedance correction.

Claims (2)

[Claims] (1) A common power source is used for primary charging and transfer charging, and a process cartridge that incorporates at least a charger and an image carrier in one housing is removable and replaceable with respect to the image forming apparatus main body housing, and the primary charging 1. An image forming apparatus configured to be able to adjust the distance between a charging line of a charger and an image carrier, characterized in that a resistive element for impedance correction of a primary charger is provided in a process cartridge. (2) The image forming apparatus according to claim 1, wherein the impedance correction resistance element of the primary charger is a resistance element such as a variable resistance or a fixed resistance for changing the separation current or separation voltage.