JPH03249669A - Image forming device - Google Patents

Abstract

PURPOSE:To appropriately electrify an image carrier by varying a diameter of an edge part which is not related to image formation of the image carrier responding to the type of a processing cartridge, and by moving an electrifying wire, etc., for just the varied amount of the diameter of the image carrier in the radial direction of the image carrier, and thereby moving the electrifying wire, etc., just for the amount of variation in diameter of the image carrier in the radial direction of the image carrier. CONSTITUTION:In a corona electrifying device 14, an electrifying wire 30 is installed in parallel to a photosensitive body drum 1 in its central part, and wire supporting members 32 and 32 are provided freely slidable in the direction of the diameter of the photosensitive body drum 11 against a shield 31 in both the edge parts of the shield 31. While abutting and supporting rollers 32a and 32b supported in a lower part of this wire supporting member to a non image range in the edge part of the photosensitive drum 11, the electrifying wire 30 is positioned and supported by V notche parts 32b and 32b in an upper part of the wire supporting member. Therefore, the distance between the electrifying wire 30 of a corona electrifying device 14 and the photosensitive drum 11 can be varied according to the type of the processing cartridge. Thus, regardless of the type of the processing cartridge, the image carrier inside the processing cartridge can be appropriately electrified by the corona electrifying device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus employing an electrophotographic method, such as a copying machine or a laser beam printer.

(Prior Art) In a copier, etc., a photosensitive drum (image carrier), a corona charger, a developing device, a cleaning device, etc. are integrally assembled.
Process cartridges in which these devices can be integrally attached to and detached from the main body of the apparatus are widely used.

This process cartridge is designed to facilitate maintenance of the equipment by replacing the entire process cartridge when the internal equipment reaches the end of its service life. In addition, the color of the toner used in the developer in the process cartridge is black.

Since the color can be changed to red, blue, etc., it is possible to change the color of the image by replacing the process cartridge.

On the other hand, when several types of process cartridges are used in the same apparatus main body, the following problems arise due to differences in charging characteristics depending on the type of toner and differences in developing methods.

For example, if a black cartridge (a process cartridge using black toner) and a red cartridge (a process cartridge using red toner) are used in a copying machine, under the same latent image conditions, If the output value of the developing bias to the developing device in the process cartridge is the same, different images will occur between the black cartridge and the red cartridge due to the difference in the charging characteristics of black toner and red toner. When a proper image is formed (its bias output value) and the cartridge is replaced with a red cartridge, an image is formed.
There may be slight fogging in the image.

This development is particularly noticeable when the black cartridge and red cartridge use different development methods. For example, the black cartridge uses a single-component developer containing only toner, while the red cartridge uses a two-component developer consisting of toner and carrier. When using a black cartridge, a better image will be formed by increasing the potential difference (latent image contrast) between the dark potential (VO) and the light potential (Vt, ) of the photosensitive drum, whereas a red cartridge will form a better image. In a cartridge, if the latent image contrast is too high, carrier adhesion occurs in the dark area (image area), resulting in loss of image color and deterioration of image fixability.

In order to prevent the above-mentioned disadvantages, it is necessary to change the latent image conditions, and for this reason, process cartridges using different corona chargers have been put into practical use depending on the type of toner, etc.

(Problem to be Solved by the Invention) However, since the process cartridge is considered a consumable item, considering the low cost and simple configuration of the process cartridge itself, a corona charger with a long life is not available outside the process cartridge. It is preferable to arrange it on the side of the main body of the device.

Therefore, when a configuration is adopted in which a corona charger is provided on the apparatus main body side, it is necessary to change the latent image conditions of the photosensitive drum depending on the type of process cartridge, so by detecting the type of process cartridge from the apparatus main body, There were problems in that complex controls were required, such as changing the voltage conditions applied to the corona charger on the apparatus main body side and changing the amount of light from the exposure device to the photosensitive drum.

The present invention has been made in view of the above-mentioned problems, and its purpose is to prevent the use of various types of process cartridges even when a corona charger is installed in the main body of the apparatus. An object of the present invention is to provide an image forming apparatus that does not require complicated control.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a process cartridge that is detachably installed in an apparatus main body, and a process cartridge that is installed on the apparatus main body side outside the process cartridge. In an image forming apparatus having a corona charger that charges an image carrier therein, the diameter of the end of the image carrier that is not involved in image formation is changed depending on the type of process cartridge, and the charging wire of the corona charger is Alternatively, a support member for supporting the grid is configured to be movable in the radial direction of the image carrier with respect to the shield, and this support member is supported in contact with the diameter changing portion of the image carrier.

(Function) When the process cartridge is installed in the apparatus main body, the diameter changing portion at the end of the image carrier engages with a support member such as a charging wire of a corona charger on the apparatus main body side, and the support member is attached to the image carrier. The charging wire or the like is moved in the radial direction of the image carrier by the amount of change in diameter. Therefore, the charging wire and the like move accordingly, and the charging conditions for the image carrier can be changed.

Therefore, by selecting the diameter of the diameter changing portion of the image carrier according to the type of developer in the process cartridge, the image carrier in the process cartridge can be properly charged using the corona charger on the apparatus main body side. I can do something.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

First, an outline of an image forming operation performed by an image forming apparatus equipped with a process cartridge will be explained with reference to FIG.

In the figure, reference numeral 10 denotes a process cartridge that is detachably installed in the apparatus main body l, and this cartridge container 10
Inside a, there is a photosensitive tram 11 that is an image carrier that rotates in a fixed direction, a developing device 12 that supplies toner that is a developer to the photosensitive tram 11, and a developer that collects residual toner from the photosensitive tram 11 after transfer. A cleaning device 13 for cleaning the photosensitive tram 11 is also integrally assembled.

When any of the above-mentioned devices in the process cartridge 1O reaches the end of its lifespan, maintenance is facilitated by replacing the entire process cartridge 10. In addition, near the photosensitive drum 11 on the side of the main body l of the apparatus, -
A corona charger 14 that uniformly charges the photosensitive drum 11 is provided as a secondary charger.

That is, when the photosensitive tram 11 is uniformly charged by the corona charger 14 and then exposed to only image light by a scanner unit (not shown), an image area (
A potential voltage is generated between the dark area) and the non-image area (light area),
An electrostatic latent image is formed. The electrostatic latent image is directed toward the developing device 12 as the photosensitive tram 11 rotates, and the developing device 12
The toner is supplied by the developing sleeve 20, which is a developer carrier, and is converted into a toner image. The toner image is transferred onto a transfer paper via a transfer charger (not shown), and the transfer paper is conveyed to a fixing device (not shown).

The toner image is fixed as a permanent image. Further, the photosensitive tram 11 after the transfer is cleaned by a cleaning device 13 and prepared for the next image formation.

Now, in order to meet the demand for color images, some of the developing devices 12 in the process cartridge 10 have color toners other than black, such as red and blue.By replacing this process cartridge 10, It is possible to form images in a variety of colors.

Here, black toner and, for example, red toner generally have different constituent components, so black cartridge 10A (referring to process cartridge 10 that uses black toner) and red cartridge 10B (referring to process cartridge 10 that uses red toner) However, unless the charging potential of the photosensitive tram 11 is slightly changed, good images may not be obtained with black toner and red toner.

A case will be described below in which the dark potential of the latent image of the red cartridge IOB is made lower than that of the black cartridge IOA.

That is, if it is necessary to change the charging potential of the photosensitive drum 11 by the corona charger 14 depending on the type of the process cartridge IO, the charging wire 30 of the corona charger 14 and the photosensitive drum 11 may be changed depending on the type of the process cartridge 10. The distance between them can be changed. This will be explained below with reference to FIGS. 1 and 2. Furthermore, figure M41 (
a) shows the case of red cartridge IOB, and Fig. 1(b) shows the case of red cartridge IOB.
) shows the case of black cartridge IOA.

The corona charger 14 is configured such that a charging wire 30 is disposed in parallel with the photosensitive tram 11 in the center thereof, and the charging wire 30 is surrounded by a shield 31, or the shield 31 is placed at both ends of the shield 31. A wire support member 32 that is slidable in the radial direction of the photosensitive tram 11
．． 32 (only one side is shown in both Figures 1 and 2)
The rollers 32a, 32a pivotally supported at the lower part of the wire support member 32, 32 are supported in contact with the non-image area at the end of the photosensitive tram 11, and the V-notch portions 32b, 32b at the upper part of the wire support member are supported. The charging wire 30 is positioned and supported. It is assumed that the wire support members 32, 32 are biased toward the photosensitive drum 11 by the tension of the charging wire 30 or by a spring member (not shown).

In addition, as shown in FIG. 1(a), the red cartridge I
A belt member 33.33 is wound around the contact portions 11a, lla of the wire support member 32.32 of the OH photosensitive drum 11 with the rollers 32a, 32a, and the contact portions 11a, I
The wire support member 3 of the black cartridge IOA is responsible for la.
The diameter of the contact portions 11a and lla of 2.32 was made larger.

Therefore, as shown in FIG. 1(b), in the case of the black cartridge IOA, the distance between the photosensitive drum 11 and the charging wire 30 is h2, whereas in the case of the red cartridge IOA, the distance between the photosensitive drum 11 and the charging wire 30 is h2. Distance between charging wires 30,
becomes larger by the thickness t of the belt member 33. That is, h
, =h, +t. Since the belt member 33 requires a certain degree of rigidity and wear resistance, for example, polyethylene terephthalate, polyacetal resin, or the like is used as the material for the belt member 33.

When the red cartridge IOA is installed in the apparatus main body 1, compared to the black cartridge IOH, the wire support members 32 and 32 of the corona charger 14 extend the charging wire 30 by the thickness t of the belt member 33 and the photosensitive drum. Therefore, even if the same voltage is applied to the charging wire 30 of the corona charger 14 as in the case of the black cartridge IOA, the photosensitive tram 11 of the red cartridge IOB
The charging voltage of the photosensitive drum 1 in the red cartridge IOA can be lowered compared to that of the black cartridge IOA.
A good red toner image can be formed on the surface of the toner.

Further, as shown in FIG. 4, in the corona charger 14 having a crit 34, the charging wire 30 is fixed, the grid 34 is biased toward the photosensitive tram 11, and the corona charger 14 is provided at both ends of the crit 34 in the width direction. Abutting member 35.・
. . may be brought into contact with both end contact portions 11a and lla of the photosensitive tram 11.

By doing this, when the red cartridge IOA is installed in the apparatus main body 1, the distance between the crit 34 of the corona charger 14 and the photosensitive tram 11 is shorter than when the black cartridge 10B is installed in the apparatus main body 1. Since the member 33 is separated by the thickness t, even if the same voltage as in the case of the black cartridge IOB is applied to the charging wire 30, the charging voltage of the photosensitive tram 11 of the red cartridge 10 can be lowered compared to that of the black cartridge IOH. It is possible to obtain the same effect as when moving the charging wire 30 described above.

As described above, even when the corona charger 14 is disposed outside the process cartridge 10, each process cartridge 10
With respect to O, both ends of the optical tram 11 abut m1la, lla
By simply changing the diameter of the corona charger 1,
The positions of the four charging wires 30 or grids 34 can be changed, thereby making it possible to obtain a desired dark potential on the photosensitive drum 11 in each process cartridge 10.

Incidentally, a similar effect can be achieved by having the gear 7 lunge at the end of the photosensitive tram 11 for rotating the photosensitive drum 11 overlap the functions of the belt members 33 and 33 described above.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. Components having the same functions as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted.

In this embodiment, a one-component developer (toner only) is used for the black cartridge IOB, or a two-component developer (a mixture of toner and carrier) is used for the red cartridge IOA, which uses red toner. Let me explain the case.

The developing sleeve 20 in the developing device 12 has an abutting roller 21
, 21 to the photosensitive tram 11 and a certain gap K (hereinafter S
The developing sleeve 720 is arranged so as to have a gap (referred to as D gap), rotates while holding toner on the outer circumference of the developing sleeve 720 by the action of magnetic force, etc., and supplies the toner toward the photosensitive drum 11, or is a two-component developing sleeve 720. In the case of the development method, it is necessary to hold carriers that do not contribute to the development work around the development sleeve 20, so the layer of toner and carrier held around the development sleeve 20 becomes thick. Therefore, in the red cartridge IOA of the two-component development method, it is necessary to make the SD gap K between the developing sleeve 20 and the photosensitive drum 11 larger than in the black cartridge IOB of the -component development method.

Therefore, in this embodiment, the corona chargers 14 provided at both ends of the photosensitive tram 11 of the red cartridge 10A are
The abutment rollers 21, 21 of the developing sleeve 20 are brought into contact with the belt members 33, 33 of the contact parts 11a, lla, and the size d2 of the SD gap of the red cartridge IOA is adjusted to the size d2 of the SD gap of the black cartridge 10B. dI plus the thickness t of the belt member 33.

Therefore, when using a two-component developer of red toner and carrier in the red cartridge IOA, first, the belt members 33 and 33 are wound around the abutting portions 11a and lla of the photosensitive tram 11 for the corona charger 14. The diameter of this is expanded, the distance between the charging wire 30 or grid 34 of the corona charger 14 and the photosensitive drum 11 is made slightly longer than that of the black cartridge IOB, and the same voltage as that of the black cartridge IOB is applied to the corona charger 14. Even when a voltage is applied to the charging wire 30, the red cartridge IOA is configured to form a good image.

Next, the abutting roller 2 of the developing sleeve 20 of the developing device 12 is
1.21 as the belt member 33.33 of the photosensitive tram 11
The contact portion 11a is wrapped around the contact portion 11a.

11a and insert the SD gap K into the black cartridge I.
The thickness is t larger than that of OH.

As a result, even when a two-component developer is used in the red cartridge IOA, the SD gap K between the developing sleeve 20 and the photosensitive drum 11 can be properly maintained, and the developing device 12 can maintain an appropriate SD gap K for the photosensitive drum 11. This will result in a good development. That is, red cartridge I
In OA, compared to the black cartridge IOB, the potential difference between dark potential and light potential (latent image contrast) can be made smaller, and there is no carrier adhesion in the dark area (image area), resulting in a clear image with good fixing properties. This means that it can be formed.

In the above first and second embodiments, the case where the toner color is different or the case where a -component developer or a two-component developer is used has been explained, but the present invention is not limited to this, and the developer Of course, the present invention can be applied to obtain a desired dark potential even if the latent image conditions of the photosensitive tram 11 need to be changed.

Further, in the first and second embodiments described above, the contact portions 11a and 11 of the photosensitive tram 11 with the corona charger 14 on the red cartridge IOA side are based on the black cartridge IOB.
It is of course possible to increase the diameter of la, or conversely to reduce the diameter of the contact portions 11a and lla of the black cartridge IOB that contact the corona charger 14 of the photosensitive tram 11 with reference to the red cartridge IOA. .

(Effects of the Invention) As is clear from the above description, according to the present invention, when the corona charger is disposed outside the process cartridge on the apparatus main body side, the corona charger can be easily controlled without complicated control on the apparatus main body side. Regardless of the type of process cartridge, the image carrier in the process cartridge can be appropriately charged by the corona charger.

Therefore, it is possible to provide a process cartridge that is inexpensive and has a simple structure, and it is also possible to form good images using a wide variety of developers and the like.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the positional relationship between the photosensitive drum and the corona charger of the image forming apparatus according to the first embodiment, and FIG.
The figure is a perspective view showing a contact state between the photosensitive drum and the corona charger of the same image forming apparatus, FIG. 3 is a cross-sectional view around the process cartridge of the same image forming apparatus, and FIG. 4 is a photosensitive drum according to a modified embodiment. FIG. 5 is a longitudinal sectional view showing the positional relationship between the photosensitive drum and the developing sleeve of the image forming apparatus according to the second embodiment, and FIG. FIG. 2 is a side sectional view showing the positional relationship between the photosensitive drum and the developing sleeve of the image forming apparatus. 1... device main body, 10. IOA, IOB...process cartridge, 11...photosensitive tram (image carrier),
11a--Contact part (diameter changing part), 14--Corona charger, 30--Charging wire, 31--Shield,
32... Wire support member (support member) 34... Grid, 35... Abutment member (support member)

Claims (2)

[Claims] (1) Image formation having a process cartridge that is detachably installed in the apparatus main body, and a corona charger that is installed outside the process cartridge on the apparatus main body side and charges the image carrier in the process cartridge. In the device,
The diameter of the end of the image carrier that is not involved in image formation is changed depending on the type of process cartridge, and the support member that supports the charging wire or grid of the corona charger is placed in the radial direction of the image carrier with respect to the shield. An image forming apparatus characterized in that it is configured to be movable, and the support member is supported in contact with the diameter changing portion of an image carrier. (2) The image forming apparatus according to claim 1, wherein the diameter changing portion of the image carrier comes into contact with an end of a developer carrier of a developing device in a process cartridge.