JPH04350890A - Cleaning device for image forming device - Google Patents

Abstract

PURPOSE:To adjust the press-contact force of a cleaning blade in accordance with the amount of residual toner, to always keep the minimum press-contact force and to improve the durability of the blade and an image carrier by providing a means for detecting the quantity of the residual toner on the image carrier and a means for imparting the press-contact force in accordance with the detected quantity to the blade. CONSTITUTION:The density of the residual toner at a position after transferring is measured by a density sensor including a light source and a photodetector. In the case that density difference is present on an original, output from the density sensor is integrated over the entire length of the original in the rotating direction of the image carrier 1. According to the integrated value, a solenoid 7 is energized/ disenergized by a control circuit 6 so that the press-contact force of the cleaning blade 3 to the image carrier 1 may be varied. Namely, when the quantity of the toner on the image carrier 1 is measured and the obtained quantity is large, the blade 3 is turned in a direction shown by an arrow B to make the press-contact force of the blade 3 to the image carrier 1 stronger, and when the obtained quantity of toner is small, the blade 3 is turned in a direction C to make the press-contact force of the blade 3 to the image carrier 1 weak.

Description

[Detailed description of the invention]

0001

[Purpose of the invention]

[Industrial Application Field] This invention relates to image forming apparatuses that utilize an electrostatic transfer process, such as electrostatic copying machines and printers.
In particular, it relates to the cleaning device.

0002

[Prior Art and Problems to be Solved] In a well-known image forming apparatus that includes a step of transferring a toner image electrostatically formed on the surface of an image carrier onto a transfer material such as paper, the toner image is transferred to the transfer material during transfer. It is necessary to sufficiently remove a portion of the toner that does not transfer and remains on the image carrier each time.

Various proposals have been made for cleaning the residual toner for this purpose, but one method involves pressing a sharp edge formed on a cleaning blade made of an elastic material such as urethane rubber against the surface of the image carrier to remove the residual toner. It is well known that devices configured to scrape off toner have been widely used since they are simple, compact, and cost-effective.

[0004] Such a cleaning blade usually has its blade edge in contact with the moving image carrier in a direction opposite to the running direction (counter direction).
For this reason, a large frictional force inevitably acts between the surface of the image carrier and the blade edge.

In reality, a portion of the scraped toner is interposed between the blade edge and the surface of the image carrier and acts as a lubricant, so that in most cases a good cleaning effect is maintained. When copying a large number of images with low image density and low toner usage, the amount of lubricating toner is insufficient and friction increases, causing phenomena such as chattering at the tip of the blade and curling of the blade. There is a risk of

[0006] In order to avoid such problems, coatings are applied to reduce the friction on the surface of the image carrier.
Various measures have been taken, such as improving the arrangement of the blades and the pressing force. However, these methods affect the development and transfer functions, resulting in deterioration of image quality, and in the case of high-density images, toner slippage occurs, so that satisfactory results have not yet been obtained.

[0007] The present invention has been made to deal with such a situation, and includes a cleaning device that uses a cleaning blade, in which the pressing force of the blade against the image carrier is adjusted in accordance with the amount of residual toner. By this,
An object of the present invention is to provide a cleaning device that can constantly press a blade against an image carrier with the minimum necessary pressure, thereby obtaining a good cleaning function at all times, and increasing the durability of the image carrier and the cleaning blade. That is.

[0008]

[Structure of the invention]

[Technical Means for Solving the Problems and Their Effects] In order to achieve the above object, the present invention provides a cleaning device for an image forming apparatus equipped with a cleaning blade for removing residual toner from the surface of a moving image bearing member. The present invention is characterized by comprising an amount detecting means and a means for changing the contact pressure of the cleaning blade against the image carrier depending on the detected amount of toner.

With this configuration, the cleaning blade can be pressed against the image carrier at all times with the minimum necessary contact pressure, which prevents damage to the image carrier and the cleaning blade, and prevents chattering of the blade, curling of the blade, etc. It is possible to prevent this and perform good cleaning.

0010

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a side view of a cleaning device showing an embodiment of the present invention. 2 are placed close together.

The cleaning device 2 is provided with a cleaning blade 3.
One edge of the toner comes into pressure contact with the surface of the image carrier to scrape off and remove toner generated at a transfer site (not shown) and arriving at a cleaning site.

The scraped off toner is guided by the scooping sheet 4 to reach a toner storage section in the cleaning device, and is then discharged to the outside by the conveying screw 5.

[0013] Around the image carrier 1, a primary charger,
Although members necessary for image formation such as an image signal applying means, a developing device, and a transfer means are provided, they are omitted because they are not directly related to the present invention.

[0014] In the cleaning device as described above,
In the illustrated case, a support member 3' that supports the cleaning blade 3 is swingably attached at a pivot position D, and the support member 3' is connected to a solenoid 7 that is energized and deenergized by a control circuit 6. It has been done.

Then, the amount of toner on the image carrier is measured in the manner described later, and if the amount is large, the cleaning blade 3 is rotated in the direction of arrow B in the figure to press the blade against the image carrier. If the amount of toner is small, the force is increased, and if the amount of toner is small, it is rotated in the direction C in the figure to weaken the pressing force of the image carrier fart.

By doing this, in the case of a high-density image that uses a large amount of toner, the cleaning blade is strongly pressed against the image carrier to prevent the toner from slipping through, and in the case of a low-density image, the blade pressure is reduced. By weakening the blade pressure, it is possible to prevent the occurrence of blade curling, etc., and to make it possible to contact the image carrier with the lowest possible blade pressure within the required range,
It is possible to increase the durability of the image carrier and the cleaning blade.

To explain the means for measuring the amount of residual toner on the surface of the image carrier, as shown in FIG. do.

For example, if there is a density difference in the document as shown in "FIG. 3", the density sensor output is integrated over the entire length of the document in the rotational direction of the image carrier ("FIG. 4").
, the solenoid 7 is energized and deenergized by the control circuit 6 so as to change the pressing force p of the cleaning blade against the image carrier as shown in FIG. 5 according to this integral value k.

By the way, in the above case, if there is a large density difference on the same document and a large amount of residual toner is present on the surface of the image carrier, cleaning failure may occur.

[0020] Therefore, in order to deal with such a situation,
As shown in "Fig. 6", the output of the concentration sensor is integrated at predetermined time intervals, and the blade pressure P is changed over time as shown in "Fig. 7" and "Fig. 8" according to the integrated value data. do it like this.

By means of such a means, cleaning can be effectively performed even when there is a large density difference in the rotational direction of the image carrier.

Furthermore, by arranging a plurality of sensors in the axial direction of the image carrier and changing the blade pressure according to the maximum value of the integrated output value of each sensor, the axial direction of the image carrier can be adjusted. It is also possible to correspond to the difference in concentration.

In particular, in a digital image forming apparatus, in order to measure the amount of residual toner on the surface of an image carrier, it is also possible to estimate the amount of toner from image data of an electrostatic latent image formed on the surface. be.

"FIG. 9" shows an embodiment in such a case, where the input from the reader 20 is an image signal, for example.
A/D conversion is performed to an 8-bit digital image signal, and the output level of the image signal for each pixel is integrated by a video counting means, and this is set as a video count value D. Depending on the magnitude of this value D, the CPU 22 controls the drive circuit 23 to change the pressing force of the cleaning blade against the image carrier, as shown in FIG.

That is, when the video count value D, which is the amount of image data, is large in terms of the amount of image data corresponding to the latent image, it is assumed that there is a large amount of residual toner, and the blade pressure is increased, and when the video count value D is small, the blade pressure is increased. Assuming that there is little residual toner, the blade pressure is reduced.

[0026] With this configuration, there is no need to dispose a density sensor near the image carrier, and the configuration can be simplified.

[0027]

As explained above, according to the present invention, when a cleaning blade is used to remove residual toner on an image bearing member, the cleaning blade is applied to the image bearing member according to the amount of residual toner. Since the contact pressure between the two can be changed, sufficient cleaning function can be maintained even if the friction between the two is minimized, preventing damage to the image carrier and cleaning blade and extending their service life. It is possible to effectively prevent chatter and curling of the cleaning blade, and to perform stable and good cleaning at all times.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a cleaning device showing an embodiment of the present invention.

[Fig. 2] An explanatory diagram showing a means for measuring the amount of residual toner

[Figure 3] Diagram showing the density distribution of the original

FIG. 4 is a graph showing the relationship between the integral data of the output value of the density sensor and the rotation time of the image carrier;

[Fig. 5] A graph showing the relationship between the integral data of the concentration sensor output and the blade pressure,

FIG. 6 is a graph showing the relationship between the integrated data of the density sensor output and the rotation time of the image carrier for each time period;

[Figure 7]
A graph showing the relationship between the integrated data of the concentration sensor output and the blade pressure,

FIG. 8 is a graph showing blade pressure versus rotation time of the image carrier;

FIG. 9 is a flowchart showing the driving of the cleaning blade by the video counting means;

FIG. 10 is a graph showing changes in blade pressure according to video count values;

[Explanation of symbols]

Claims (3)

[Claims] 1. A cleaning device for an image forming apparatus comprising a cleaning blade for removing residual toner on the surface of a moving image carrier, comprising: a residual toner amount detecting means; A cleaning device equipped with means for changing the contact pressure of the [Claim 2] The residual toner amount detection means is a means for detecting the residual toner concentration on the surface of the image bearing member [Claim 1]
Cleaning device as described. 3. The cleaning device according to claim 1, wherein the residual toner amount detection means is means for integrating image data of an electrostatic latent image formed on the image carrier.