JPS63187268A - Process cartridge for forming image - Google Patents

Abstract

PURPOSE:To set the impedances of primary electrifiers between various cartridges to the same, and to obviate the difference of transfer conditions, by varying the form of a shield member of the primary electrifier in accordance with the kind and the purpose of the cartridge. CONSTITUTION:The impedances of primary electrifiers between various cartridges used by the same body are set to the same, and in order to eliminate the difference of transfer conditions generated between each cartridge, for instance, in case of the primary electrifier of a black cartridge and the primary electrifier of a red cartridge, the right side shield lower part of a primary shield 11 of the red cartridge, or the right side shield upper part, or the left side shield upper part is bent so as to bring it close to a primary wire 10, and the impedance of each red cartridge is set so as to go to the same as the impedance of the black cartridge.

Description

Detailed Description of the Invention [Industrial Application Field of the Invention] The present invention relates to an image forming apparatus that obtains an image using an electrostatic latent image. This relates to a cartridge that is more removable.

[Prior art]

BACKGROUND ART Conventionally, in image forming apparatuses, particularly copying machines, laser beam printers, etc., an image forming section has been integrated into a cartridge that is detachable from the main body and has been put into practical use.

The first advantage of this cartridge is that it is maintenance-free, and the second is that it is easy to change colors (for example, change the color from black to red).

However, when several types of cartridges are used in the same main body, various problems arise. For example, let us take a black cartridge (cartridge using black toner) and a red cartridge (cartridge using red toner) as examples. When black toner and red toner are developed under the same development conditions and latent image conditions, the V-D curves are different due to differences in charging characteristics of the toners, and different images are produced for black and red at the same aperture value. For example, if a black cartridge produces a proper image with no fog (its aperture value), and the image is taken with a red cartridge, there is a risk that the image will be slightly fogged. Further, a particular problem arises when the developing methods are different between the black cartridge and the red cartridge. - As an example, consider the case where the black cartridge is used for one-component development and the red cartridge is used for two-component development. For black cartridges, it is better to have a large latent image contrast in order to widen the fog latitude, and for red cartridges, if the contrast is too large, carrier adhesion will occur in the dark areas, damaging the color and reducing fixation. or cause inconvenience. Therefore, in order to select appropriate latent image conditions and development conditions for each cartridge, when each cartridge is inserted into the main body, a signal corresponding to each cartridge is output, and the output of the high voltage transformer on the main body side is changed. It is desirable to deal with the following.

However, providing such a control mechanism in the main body is very disadvantageous in terms of cost, and is practically impossible.

Therefore, in order to change the latent image conditions, there is one that has actually been put into practical use, in which the height of the wire from the drum surface of the primary charger of each color cartridge is changed. In other words, the wire height of the red cartridge is made higher than the wire height of the black cartridge, and the dark potential of the red cartridge is kept lower than that of the black cartridge. This solves the above-mentioned problems such as carrier adhesion in the dark areas, and also reduces costs by changing only the height of the primary wire of the cartridge without the need for any control mechanism for latent image conditions on the main body side. was also very advantageous.

However, this method also has some disadvantages (for example, when the high-voltage transformer on the main body side has the following specifications. The principle of this high-voltage transformer is shown in FIG. 2).

FIG. 2 is a schematic cross-sectional view of the image forming section as a cartridge. The photosensitive drum 1 rotates as shown by the arrow in FIG. The photosensitive drum 1 is uniformly charged by the primary charger 2 and then moved to the image exposure section 8 . In the image exposure section 8, when the image is irradiated with light corresponding to an image, an electrostatic latent image is formed. Thereafter, the electrostatic latent image formed on the photosensitive drum 1 is developed by the developing device 3 to become a visible image. This visible image is transferred onto transfer paper (not shown) by a corona caused by the transfer charger 4.

After the transfer, the surface of the photosensitive drum 1 is cleaned by a cleaning device 5. The voltage applied to the primary charger 2 and the transfer charger 4 is supplied from a high voltage transformer 6.

Here, the high voltage transformer 6 will be explained in more detail.

The output of the high voltage transformer branches into two paths, a primary charger 2 and a transfer charger 4, on the way. After branching to the primary charger 2, it is connected to the wire of the primary charger via a primary side resistor R. On the other hand, the transfer charger 4 is directly connected to the transfer wire. By the way, high voltage transformer 6
is a constant current transformer that detects the shield current Is and controls the primary total current 1p to be kept constant. Here, it is assumed that both the primary charger and the transfer charger generate negative corona.

If the impedance of the primary charger is Zp, then Vp=I
pZp・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・(1) Formula (Zp: 1
(Determined by the shape of the secondary charger, etc.) Here, if the impedance Zp of the primary charger is constant, the total primary current 1p =
const, so the primary voltage Vp is determined.

By the way, the transfer voltage Vt is as follows: Vt = Vp - IpR...
・・・・・・・・・・・・・・・(2) Formula % Formula %) Since it is obtained, Vt is also determined. If the impedance of the transfer charger is 21, the total transfer current It is It=Vt/Zt・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(3) Equation (21
: Determined by the shape of the transfer charger, etc.) Therefore, once the primary charger and transfer charger are determined, the primary voltage vp, primary total current 1p, transfer voltage Vt, transfer total current It
is determined. (1), (2).

From formula (3), vp=f, (Zp)=IpZp Vt=Fz (Zp)=Ip (Zp-R)・I
t = f 3 (Z I) ) = I p/Z
It can be said that t (Z p −R). Therefore, if the wire height of the primary charger of the black cartridge and the red cartridge is changed, the impedance Zp of the primary charger will be different in these two cartridges, the primary layer pressure Vp, the transfer voltage vt1, the total transfer current It will have different values when these two cartridges are used.

In other words, there arises an inconvenience that the transfer conditions are different between the black cartridge and the red cartridge. A specific example is shown in Figure 3. This uses a certain constant current transformer to set the dark potential of the red cartridge 1oov lower than the dark potential of the black cartridge, so when the wire height of the primary charger is changed (however, the shield shape is the same) No. 1
The following are the transfer conditions.

As is clear from Fig. 3, the red cartridge has stronger transfer than the black cartridge, and the image tends to jump.
In addition, when only the black cartridge is used, the current capacity of the high voltage transformer 6 is Ip + It = 405 + 420 = 825 μA, but when considering the red cartridge, the current capacity of the high voltage transformer 6 is Ip +
It can be seen that a current capacity of It=405+492=897 μA is required.

As described above, the transfer conditions differ depending on the cartridge, and the current capacity of the high voltage transformer 6 needs to be increased, resulting in an increase in the size of the transformer and the cost.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to eliminate the difference in transfer conditions that occurs between each cartridge by making the impedance of the primary charger the same between various cartridges used in the same main body. It is possible to eliminate this, and it is also possible to reduce the size and cost of the high voltage transformer.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. For convenience of explanation, the black cartridge and red cartridge will be explained as described above. In other words, assume that the dark potential of the latent image of the red cartridge is lower than that of the black cartridge. In FIG. 1, (a) is the primary charger for the black cartridge, and (b), (c), and (d) are the primary chargers for the red cartridge according to the embodiment of the present invention.

According to the conventional example shown in FIG. 3, if the height of the drum wire is changed with the same shield shape, the distance between the wire and the shield changes, and the impedance changes. Therefore, if the distance between the wire and the shield is moved by the same amount as the distance between the photosensitive drum and the wire, a primary charger with the same impedance can be made. Figures (b), (c), and (d) show changes in the shield shape. (b) shows the lower part of the right shield, (c) shows the upper part of the right shield, and (d) shows the upper part of the left shield by 1. Next wire 10
The impedances are set to be the same as the impedance of (a).

Next, another embodiment is shown in FIG. In FIG. 4, the primary charger for the black cartridge is shown as (a), and the primary charger for the red cartridge is shown as (b). In FIG. 4, the shape of the primary shield 11 is the same in both (a) and (b). In (a), an insulating sheet 12 is applied uniformly to the right side of the primary shield 11 in the longitudinal direction of the charger. As a result, the impedance of the primary charger in (b) is substantially matched with that in (a). In this case, although the current capacity of the high-voltage transformer remains the same, there is an advantage in that shield members of the same shape can be used. This insulating sheet is preferably made of a material such as polyethylene terephthalate.

Yet another embodiment is shown in FIG. In FIG. 5, the primary charger for the black cartridge is shown in (a), and the primary charger for the red cartridge is shown in (b). In this case, (a) (
Both of b) have the same shield shape.

In order to match the impedance of (a) with that of (b), the primary wire of (b) is not only moved away from the surface of the photosensitive drum but also moved closer to the right shield plate. Another way of interpreting this is to say that the entire shield has moved, with the shield shape unchanged, relative to the same wire position.

As described above, by making some changes to the members of the primary shield plate, it is possible to realize a primary charger having the same impedance. The above explanation has only been about two-color cartridges, black and red, but there is no need to be particular about the colors; for example, a cartridge specifically for photocopying (
Needless to say, it can be applied to cartridges for special purposes such as cartridges with a different V-D curve.

〔Effect of the invention〕

As explained above, even if the latent image conditions between each cartridge are changed by changing the shield member of the primary charger, the impedance of the primary charger of each cartridge does not change, so the image is transferred between each cartridge. Since there is no need to create a difference in conditions or provide the high voltage transformer with unnecessary current capacity, the high voltage transformer can be made smaller and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a primary charger showing an embodiment of the present invention, FIG. Fig. 2 is an explanatory diagram of a conventional example showing the primary and transfer conditions between various cartridges when using the high-pressure unit shown in Fig. 2; Fig. 4 is a sectional view of another embodiment of the present invention; FIG. 5 is a sectional view of another embodiment of the present invention.

Claims (1)

[Claims] (1) In an image forming process cartridge that is detachable from the image forming apparatus, at least one
For image forming, including a secondary charger, wherein the form of the shield member of the primary charger is changed depending on the type and use of the cartridge, and the discharge impedance of the primary charger of each cartridge is the same. process cartridge.