JPS61240267A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent blade rolling-up, cleaning failures, filming, etc., and to form an image of good quality by changing the projecting length of a cleaning member, and making an abutting pressure of direction of an abutting surface on a carrier different in position. CONSTITUTION:A part corresponding to non-developed image corresponding areas (a), (a) of blade holders 67A, 67B is notched and made shorter than the middle part. In a developed area (x) of a photosensitive drum 20, toner is formed already by a copy cycle until the previous time and it serves as a lubricant, and the frictional resistance of an abutting surface of this area and a cleaning blade 66 is low. Also, as for the non-developed image corresponding areas (a), (a) of the cleaning blade 66, the contact pressure is low since a projecting length L from a holder 67 is longer than that of the middle part, and the frictional resistance of the abutting surface of the drum 20 also becomes low. In this way, rolling-up of the blade 66, damage of the surface of the photosensitive drum 20, drum filming, cleaning failures generated by triboelectrification existing between the blade and the photosensitive drum 20, etc. can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus equipped with a cleaning device.

[Technical background of the invention and its problems] Generally, in an image forming apparatus such as an electronic copying machine, a cleaning blade (cleaning member) is used to remove untransferred toner (developer) remaining on a photoreceptor drum serving as an image bearing member. It is designed to be scraped off.

By the way, if a large frictional force exists between the photoreceptor drum and the cleaning blade, the photoreceptor drum surface may be damaged, toner may be filmed on the drum, and the blade may not be able to maintain its original contact form due to stress. As a result of investigation, it has been found that due to curling and the electrostatic influence caused by friction, for example, a uniform surface potential cannot be obtained during the charging process, resulting in image unevenness and fogging. Further, in order to reduce the frictional force, the pressure of the cleaning blade may be reduced, but in this case, the original function of cleaning cannot be achieved, resulting in poor cleaning and filming.

Therefore, in the past, as a measure to reduce the frictional force between the blade and the photoreceptor, wax or other additives were added to the developer.
Attempts are being made to include 81 drugs. however,
In this case, there are disadvantages in that the lubricant such as wax in the toner used may impair the toner's fixing properties and cause so-called filming, which is the formation of a thin toner film on the photoreceptor, resulting in poor image quality. This makes it highly unstable and prevents its practical application.

In addition, it has been known to apply a lubricant such as wax to the surface of the photoreceptor, but the film thickness of the ff1lft agent on the photoreceptor must be set to a thickness that does not impede the electrostatic properties of the photoreceptor, that is, a few There was no way to maintain the thickness below about 100 angstroms for a long period of time. Attempts have also been made to improve the blades by using materials with a lower coefficient of friction, but the problem still remains that additives reduce other properties, especially mechanical strength.

In addition, conventionally, in a copying machine using a blade cleaning method, the hardness of the photoreceptor is Fe, Aj! Because it is much smaller than other materials (e.g., Se-based photoreceptor, Vickers hardness is around 501o/mm2), if a blade or the like is in contact with a stationary drum, the photoreceptor may deform under pressure over time. This often occurs and significantly reduces image quality and reliability.

For this reason, conventional means have been practically used to release the contact between the blade and the drum when the drum is stationary.

However, the method in which the blades are brought into contact and released has a drawback in that the blades themselves become stained with toner, resulting in poor images.

Further, when the cleaning blade is located above the photoreceptor, there is a drawback that when the blade is released, the toner that cannot be cleaned often stains the inside of the machine. Furthermore, as a result of imparting such movement to the blade, there is a problem in that the accuracy of contact with the photoreceptor is likely to be disturbed.

Additionally, during the initial installation of the photoreceptor drum, operators and service personnel generally spray a lubricating powder such as polyvinylidene fluoride (polyvinylidene fluoride) with a thickness of about 5 μm on the drum to reduce the friction between the drum and the blade. There is, but
The work is done manually, which is cumbersome, and there are problems with reliability as the drum is touched during the work.

Other attempts have been made to form a single layer of toner on the photoreceptor during initial setting. As shown in FIG. 6, first the drum is rotated, and at the same time the developing bias is reversed to form a single layer of toner on the photoreceptor during period A, and then during period B during the second rotation of the drum. By bringing the blade into contact with the blade, the toner layer is used as a lubricant. However, in the contact area between the photoreceptor and the blade, where a single layer of toner is not formed, the frictional resistance is still large, and there is a problem in that the blade turns over and damages the photoreceptor.

[Object of the Invention] The present invention has been made in view of the above circumstances, and has the object thereof. However, although it has a relatively simple configuration,
An object of the present invention is to provide an image forming apparatus equipped with a cleaning device capable of solving the above-mentioned problems.

[Summary of the Invention] In order to achieve the above object, the present invention provides an image forming apparatus having a cleaning device that performs cleaning by bringing a cleaning member held by a holding means into contact with an image carrier, in which the cleaning member protrudes. It is characterized in that by changing the length, the contact pressure in the direction on the contact surface to the image carrier is varied depending on the position.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 3 show the external appearance of an electronic copying machine to which the image forming apparatus of the present invention is applied. In the figures, 1 is a copying machine body with a built-in copying mechanism, and 2 is attached to the right side of the copying machine body 1. A paper feed cassette 3 is a paper discharge tray mounted on the left side of the main body 1 of the copying machine. Further, on the top surface of the copying machine main body 1, there is provided a document table 4 that can freely reciprocate in the left-right direction (in the direction of arrow a'). ..., exposure setting key 7a,
7b, there is provided an operation panel 10 on which input keys including a print key 8 are arranged.

The document table 4 includes a document placement plate (glass plate) 12 on which a document 11 is placed, and a document cover 13 that covers the top surface of the document placement plate (glass plate) 12 .

Further, the cassette cover 14 of the paper feed cassette 2 has a third
As shown in the figure, there is provided a manual paper feed tray 15 for manually feeding paper P' as appropriate. In addition, 16 shown in Figure 3
is the power switch.

Next, the internal mechanism of the electronic copying machine will be explained with reference to FIG. In the figure, reference numeral 20 denotes a drum-shaped photoreceptor (photoreceptor drum) disposed approximately in the center of the copying machine main body 1. The photoreceptor drum 20 is synchronized with the document table 4 in the direction of arrow b' by a drive mechanism (not shown). It is driven by First, a document image uniformly charged by a charger 21 and uniformly irradiated by an exposure lamp 22 is imaged on a photoreceptor drum 20 by a focusing light transmitter (trade name: Self-Oak Lens Array) 23, and then statically illuminated. It is designed to form an electric latent image.

The formed electrostatic latent image is turned into a toner image and sent to the transfer charger 25 side by a developing device 24 including a developing roller 24A.

Automatically or manually fed paper P or P- is fed by a paper feeding device 26, and a toner image previously formed on the photosensitive drum 20 is transferred onto the paper P or P' by a transfer charger 25. Furthermore, the toner image is peeled off from the photoreceptor drum 20 by a peeling charger 27 using AC corona discharge, passes through a conveyance path 28, is melted and fixed onto the paper P (P'') by a fixing device [29, and is detachably attached by a discharge roller 30. Paper is ejected to tray 3. On the other hand, paper P (
After the toner image is transferred onto the photoreceptor drum 20, the residual toner remaining on the photoreceptor drum 20 is removed by a cleaning device f (cleaning device) 3.
1, and the potential on the photosensitive drum 20 is lowered to a certain level or less by bypass slit light 32, which is obtained by branching the light from the exposure lamp 22, and the photosensitive drum 20 is made ready for the next copying operation.

Further, 33 is a fan as a cooling device, which exhausts heat generated from the heat generating part exposure lamp 22 and the fixed food equipment w129 inside the machine.

Inside the copying machine main body 1, an upper frame and a lower frame (not shown) are pivotally supported at one end via a support shaft 37, and the other ends of both frames are configured to be opened at a desired angle, for example, 25 degrees. ing. The upper frame is provided with a charger 21, a focusing light transmitter 23, an exposure lamp 22, a developing device 24, etc. around the photoreceptor drum 20. Each device such as a cleaning device 31 and a static elimination lamp 32 is attached by appropriate means, and a fan 33 as a cooling device, a paper feed roller 38 of a paper feed device 26, and a document table 4 are also attached to the frame and the upper unit. It constitutes 1A. Further, each mechanism such as the paper feed cassette 2, transfer charger 25, peeling charger 27, conveyance path 28, forming guide plate 39, fixing device @ 29, discharge roller pair 30, tray 3, etc. is attached by appropriate means to the lower unit. It constitutes 1B. After rotating and removing the front cover 18 of the copying machine main body 1, the structure is such that it can be opened and closed almost along the transport path 28 of the paper P (PM) via a housing opening/closing device (not shown). Even when paper P (P') becomes jammed on the conveyance path 28, it can be easily taken out.

In addition, 50.50 in FIG. 3 corrects the inclination of the leading edge of automatically fed paper P or manually fed paper P- in the paper feed cassette 2, and forms a toner image on the photoreceptor drum 20. Paper P or P according to the timing of the movement.
' is a pair of registration rollers that supplies the paper to the transfer charger 25, and 51 is a paper detection switch disposed immediately before the pair of registration rollers 50 and 50.

52 is a paper feed switch, 53 is a total counter, 54 is a vapor empty switch that detects when the paper P in the paper feed cassette 2 is empty, and 55 is a developing device 24.
56 is a toner cartridge, 58 is a toner, -! The detector 59 is an upper cover of the developer, and unless this is closed, the document table 4 will not move. Further, through this opening, the toner cartridge 56 can be replaced and the developing device 24 can be replaced 9 and removed.

Further, 60 is a high voltage transformer, and a shield case for the transfer charger 25 and the peeling charger 27 is formed integrally with the casing thereof. Reference numeral 61 designates a static elimination brush 62 as a handle formed for opening and closing the upper unit 1A, 63 a reflector surrounding the back of the exposure lamp 22, and 64 an auxiliary reflector.

Further, 65 is a weight for bringing a cleaning blade 66, which is a cleaning member of the cleaning device, into contact with the photoreceptor drum 20 at a constant pressure, and a solenoid (not shown) causes the blade to move toward and away from the photosensitive drum 20.

Note that 67 is a blade holder (holding means) that holds the cleaning blade.

Note that the reflector 63, the auxiliary reflector 64, and the convergent light transmission body 23 are assembled as one unit.

Next, referring to FIGS. 4 and 5, the cleaning device 31, the photosensitive drum 20, and the developing roller' 2
The relationship between 4A and its surroundings will be explained.

In FIG. 4, a cleaning device @31 is arranged on the left side of the photosensitive drum in the drawing, a developing roller 24A is arranged on the right side in the drawing, and an exposure lamp 22. An optical system including a convergent light transmission body 23 and the like is arranged. Furthermore, 2
1 is a charging charger, 25 is a transfer charger, and 27 is a peeling charger.

The cleaning device 31 mainly includes a cleaning blade 66 held by a blade holder 67 and a weight 65 attached to one end of the blade holder 67.

The photosensitive drum 20. The relationship between the cleaning blade 66 and the developing roller 24A is as shown in FIG. 5, which is a plan view thereof. This is an area (non-image area) that does not contribute to image formation. The y area of the developing roller 24A is an area where the developer is conveyed, and the length 1 of the cleaning blade 66 is usually longer than the length of the developing area x in the areas X and y. Here, a portion of the blade holder 67 and the cleaning blade 66 held therein in the longitudinal direction corresponding to the image development region X is defined as a development region, and the remaining both side portions a and a are defined as non-development region. Define.

Next, details of the configuration of the cleaning device, which is a feature of the present invention, will be explained.

In the present invention, as shown in FIG. 7(a), a plate-shaped cleaning blade (the material is (for example, polyurethane) 66, and the blade holder 67A.

The portions corresponding to the non-image corresponding areas a and a in 67B are cut out to be shorter than the middle portion. That is, the non-image corresponding area a of the cleaning blade 66
, a portion is made to protrude largely from the blade holder 67. Note that 66a is the edge portion of the blade.

FIG. 7(b) shows another embodiment, in which only the areas a and a portion of the blade holder 67 are formed with a taper that widens from the outside toward the middle, similar to the case of (a) above. We are trying to provide this functionality.

FIG. 7(C) shows yet another embodiment, in which the blade holder 67 is used in contrast to the above (a) and (b).
The shape is made to be long in the region a and short in other regions. That is, the above (a), (b)
) is applicable when the hardness of the cleaning blade 66 is not very high, whereas the case shown in FIG.
) is applied when the hardness is large.

Next, the operation of the device will be explained.

The photosensitive drum 20 is moved in the direction of arrow b' by a drive mechanism (not shown).
direction in synchronization with the document table 4.

Then, the charger 21 uniformly charges the original image, and the exposure lamp 22 uniformly irradiates the document image onto the photoreceptor drum 20 using the focusing light transmitter 23 to form an electrostatic latent image. let The formed static alim image is sent to the transfer charger 25 side as a toner image by a developing device 24 including a developing roller 24A.

A sheet P or P' that is automatically or manually fed is fed by a sheet feeding device 26, and a toner image previously formed on the photosensitive drum 20 is transferred onto the sheet P or P' by a transfer charger 25. Furthermore, the toner image is peeled off from the photoreceptor drum 20 by a peeling charger 27 using AC corona discharge, passes through a conveyance path 28, and is melted and fixed onto the paper P (P') by a fixing device 29, and is then moved to a tray that can be attached or removed by an ejection roller 30. It is discharged at 3.

On the other hand, after transferring the toner image onto the paper P (PM), the photoreceptor 2
The residual toner remaining on the photoreceptor drum 20 is cleaned by a cleaning device (cleaning device) 31, and the bypass slit light 32, which is obtained by branching the light from the exposure lamp 22, is used to clean the residual toner on the photoreceptor drum 20.
The upper potential is lowered to a certain level or less to enable the next copy operation.

Here, the operation of the cleaning device will be described.

As mentioned above, this cleaning device
(This is for cleaning untransferred toner remaining on the photoreceptor drum 20 without being transferred to the PM,
The above function is achieved by the tip of the cleaning blade 66 held by the blade holder 67 protruding in a direction opposite to the rotational direction b' of the photoreceptor drum 20 and coming into contact with it. Next, with reference to FIG. 8, the relationship between the length of the cleaning blade protruding from the holder and the contact pressure W will be explained. As shown in the figure, when the blade 66 held by the holder 67 is held at the holding angle Φ and only the protrusion length is protruding, the pressure W and the edge angle θ of the contact surface X are calculated by the following formula [11i2] is required. Let M be the amount of bite of the contact surface X, and let t be the thickness of the blade.

W-MEt 3 /4 L3 [gr/am] - (11
θ-'s -3M/2LcosΦ[rad]-(2 Here, as E is greater than Young's modulus, the contact pressure largely depends on the protrusion length L of the blade in the direction of the contact surface, and as L becomes longer, the pressure decreases. As it weakens and becomes shorter, the pressure will become stronger.

Based on the above, the operation of the cleaning device will be explained. Since toner has been formed in the developing area X of the photosensitive drum 20 by the previous copy cycle, this acts as a lubricant, and the frictional resistance between this area and the contact surface of the cleaning blade 66 is low. and the non-image corresponding area a of the cleaning blade 66;
Since the protruding length of the portion a from the holder 67 is longer than that of the intermediate portion, the contact pressure is low, and therefore the frictional resistance at the contact surface with the photoreceptor drum 20 is also low. As a result, the blade 66 curls up, the surface of the photoreceptor drum 20 is damaged, drum filming occurs, and the friction between the blade and the photoreceptor drum 20 occurs due to the large frictional stress between the blade 66 and the photoreceptor drum 20 as in the conventional case. Image defects caused by frictional charging that exists between the blade and the drum, as well as defects such as poor cleaning and drum filming caused by reducing the blade pressure as much as possible in order to reduce the frictional stress between the blade and the drum. All problems can be solved, and the original function of the cleaning device can be fully demonstrated.

The above explanation is for the case where the cleaning blade 66 has a general hardness (for example, 60 degrees to 80 degrees), and the shape of the holder 67 is configured as shown in FIGS. 7(a) and 7(b). Regarding the case, cleaning blade 6
When the hardness of the blade 6 is high (for example, 100 degrees or more), the shape of the holder 67 is made longer at both ends, as shown in FIG. This is particularly effective in preventing the blade from turning over at both ends (area a) of the blade 66.

Next, a case will be described in which the above-mentioned initial setting method is used. For example, using a photoreceptor drum first,
Considering the case where the photoreceptor drum is replaced, there is a problem that the lubricant is not formed on the developing area, so the II friction resistance increases, so as mentioned above, during the first rotation, the developing lit area However, toner is not formed in the non-development area. However, according to the present invention, since the contact pressure of the blade in the non-image corresponding area a is made different from that in the image corresponding area, the frictional stress can be reduced and the problem can be solved.

[Effects of the Invention] According to the present invention described in detail above, it is possible to provide an apparatus that has a simple configuration, can solve problems such as blade curling, poor cleaning, and filming, and can form high-quality images. .

[Brief explanation of drawings]

Fig. 1 is an external view of an apparatus according to an embodiment of the present invention, and Fig. 2 (a
) is a view of one mode of the operation part, and the same figure (b) is the same figure (a
), FIG. 3 is a schematic sectional view of the device, FIG. 4 is a sectional view of the cleaning device and its surroundings, FIG. 5 is a plan view showing the relationship among the photosensitive drum, cleaning blade, and developing roller, and FIG. 6 is a time chart of the initial setting method, FIGS. 7(a) to 7(C) are enlarged perspective views of the cleaning blade portion, and FIG. 8 is a diagram explaining the reason for achieving the object of the present invention. 20... Image carrier, 24A... Developing roller, 31...
...Cleaning device, 66...Cleaning member, 67...
-Cleaning member holding means.

Claims (3)

[Claims] (1) In an image forming apparatus having a cleaning device that performs cleaning by bringing a cleaning member held by a holding means into contact with an image carrier, the protrusion length of the cleaning member is changed so that the surface of the cleaning member that comes into contact with the image carrier is An image forming apparatus characterized in that the contact pressure in the direction is varied depending on the position. (2) The image forming apparatus according to claim 1, wherein the positional contact pressure of the cleaning member is changed by changing the shape of the cleaning member holding portion of the holding means. (3) The image forming apparatus according to claim 2, wherein the holding means has a different shape in a range corresponding to an area other than an area contributing to image formation on the image carrier.