JPH11119620A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing toner from sticking to a photoreceptor while suppressing the wear of a cleaning means and the photoreceptor. SOLUTION: The device is provided with the photoreceptor drum (photoreceptor) 1 for forming an electrostatic latent image, a developing device for developing the electrostatic latent image and forming a toner image, a transfer device for transferring the toner image, and a cleaning device 9 equipped with a cleaning blade (cleaning means) 9-2 which is brought into contact with the photoreceptor drum 1 so as to clean the toner remaining on the photoreceptor drum 1 after the toner image is transferred. In this case, the value of viscoelasticity tan δ when the cleaning blade 9-2 of the cleaning device 9 is in use is set to be 0.18 to 0.38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer employing an electrophotographic system.

[0002]

2. Description of the Related Art In a conventional image forming apparatus having a cleaning device, there are problems of toner adhesion (including fusing) and cleaning failure.

[0003] Here, the adhesion of the toner means that the toner adheres to the surface of the photoreceptor due to electrostatic or surface tension, and this includes a generally-used fusion of the toner. This phenomenon of toner adhesion hinders the formation of images (including electrostatic latent images) formed on the photoreceptor surface,
An image defect or the like is generated on an image finally formed.

Therefore, conventionally, a cleaning blade has been brought into strong contact with the surface of the photoreceptor to remove the toner adhering to the surface of the photoreceptor drum as if it were half-removed.

[0005]

However, in the above-mentioned conventional cleaning method, the durability stability of the photosensitive member and the cleaning blade is impaired, and the reliability cannot be ensured for a long time. For example, when the cleaning blade is strongly applied to the surface of the photoconductor, the frictional force generated between the surface of the photoconductor and the cleaning blade also increases, and if the cleaning blade is not firmly supported, the cleaning blade is turned.

[0006] Even if the cleaning blade can be firmly supported, a great hindrance to the driving of the photosensitive member will occur, which will adversely affect the image formation itself.

Even if a high-performance drive system and a strong support can be secured, the cleaning blade and the photoreceptor eventually become severely worn, making it impossible to use them for a long time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of preventing toner from adhering to a photoreceptor while suppressing abrasion of a cleaning unit and a photoreceptor. To provide.

[0009]

In order to achieve the above-mentioned object, according to the present invention, there is provided a photosensitive member for forming an electrostatic latent image, and a developing device for developing the electrostatic latent image to form a visible image as a toner image. An image forming apparatus comprising: a developing device for developing a toner image; a transfer device for transferring a toner image; and a cleaning device including a cleaning unit for cleaning toner remaining on the photoconductor after transferring the toner image by contacting the photoconductor. Viscoelasticity tan δ when the cleaning means of the cleaning device is used
Is set to 0.18 to 0.38.

According to a second aspect of the present invention, in the first aspect of the present invention, the photoconductor or the cleaning unit is so arranged that the value of the viscoelastic coefficient tan δ of the cleaning unit during image formation is 0.18 to 0.38. The temperature is adjusted.

According to a third aspect of the present invention, in the first or second aspect of the invention, the temperature of the photosensitive member or the cleaning means is adjusted to a substantially constant temperature during image formation.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the cleaning means is brought into contact with the photosensitive member by an elastic body other than the cleaning means.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the elastic body is constituted by a spring for pressing a member supporting the cleaning means.

According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the elastic body is constituted by a leaf spring interposed between the cleaning means and a member supporting the cleaning means. .

According to a seventh aspect of the present invention, in the first to fifth or sixth aspects of the present invention, a mechanism for supplying toner to the surface of the photoconductor is provided upstream of the cleaning means in the rotation direction of the photoconductor. And

According to an eighth aspect of the present invention, in the first to sixth or seventh aspects, the cleaning means is pressed against the photosensitive member by an equalizing mechanism.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a main part of an electrophotographic copying machine according to the present invention, and FIG. 2 is a sectional view of a cleaning device of the electrophotographic copying machine.

In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image bearing member. As is well known, the photosensitive drum 1 is placed on or around a conductive support such as an aluminum drum provided on the inner peripheral side. Constituted by forming a conductive layer,
It rotates in the direction of the arrow in FIG.

Around the photosensitive drum 1, a charging device 2, a developing device 3, a transfer guide 6, a transfer separating device 7, a cleaning device 9, and the like are arranged.

The charging device 2 is, in the illustrated example, a scorotron charger, which primarily charges the photosensitive drum 1. A known exposure unit (not shown) is provided downstream of the charging device 2 in the drum rotation direction, and an exposure L from the exposure unit forms an electrostatic latent image on the photosensitive drum 1. The electrostatic latent image is developed by the developing device 3. That is, the developing device 3 is provided with a developing roller 4 having a magnetic field generating means inside, and the developing roller 4 frictionally charges the toner 5 stored inside and develops an electrostatic charge on the surface of the photosensitive drum 1. Toner 5 for latent image
And the electrostatic latent image is developed to be visualized as a toner image.

The toner 5 is a one-component magnetic toner (styrene-acrylic toner) having a volume resistance of 10%.
⁶ to 10 ¹² Ωcm, critical surface tension is about 35 dyn / cm
It is. The critical surface tension of the surface of the photosensitive drum 1 is 40
４５45 dyn / cm.

On the other hand, the transfer paper 8 is guided by the transfer guide 6 and supplied between the transfer / separation device 7 and the photosensitive drum 1. The transfer paper 8 is transferred onto the photosensitive drum 1 by the action of the transfer / separation device 7. Is transferred. The transfer separation device 7 uses a corona discharge to assist the transfer of the toner image from the photosensitive drum 1 to the transfer paper 8 and the separation of the transfer paper 8 after the transfer of the toner image from the photosensitive drum 1. Here, the polarity of the corona discharge used for the transfer is opposite to that of the toner 5, and the polarity of the corona discharge used for the separation is the same as that of the toner 5.

The cleaning device 9 collects the transfer residual toner remaining on the photosensitive drum 1 after the transfer of the toner image.
And a cleaning blade 9-2. The cleaning blade 9-2 comes into contact with the surface of the photosensitive drum 1 to peel off the transfer residual toner on the surface of the photosensitive drum 1, and the peeled transfer residual toner is provided in the cleaning container 9-1 in FIG. The toner is conveyed to a waste toner box (not shown) provided in the image forming apparatus by the toner conveying screw 9-4 shown and collected.

The cleaning blade 9-2
Has a characteristic that changes with temperature as shown in FIG.

In the electrophotographic copying machine according to the present embodiment, a drum heater 1-1 used for another purpose is provided inside the photosensitive drum 1, and the photosensitive drum 1 is used for the photosensitive drum. The surface temperature of the drum 1 is approximately 4
It is kept at 2 ° C. Due to this effect, the operating environment temperature of the cleaning blade 9-2 also becomes approximately 42 ° C.

The cleaning blade 9-2 has a thickness of 3 m.
m plate-like urethane rubber and supporting plate 9-5
-6 and fixed with a free length of 3 m
m. The set angle of the cleaning blade 9-2 at the fixed position is set to 28 degrees with respect to the tangential direction of the drum. It has been confirmed that similar results are obtained for this set angle from 24 degrees to 32 degrees.

The viscoelasticity of the cleaning blade 9-2 used in the present embodiment is higher than that of a conventionally used cleaning blade in tan δ.
It is considered that the ability to follow the surface of the photosensitive drum 1 is slightly reduced.

Therefore, in the present embodiment, in order to suppress the deterioration of the ability of the cleaning blade 9-2 to follow the surface of the photosensitive drum 1, the contact of the cleaning blade 9-2 with the photosensitive drum 1 is set. The cleaning blade 9-2 was pressed against the surface of the photosensitive drum 1 by a spring pressing system using a pressure spring 9-3. The spring pressing force of the cleaning blade 9-2 is 20 g / cm. As a result of pressing the cleaning blade 9-2 against the surface of the photosensitive drum 1 by the pressing spring 9-3, the photosensitive drum 1 and the cleaning blade 9-2 are stable. A desired nip can be formed to perform the desired cleaning function. A system that only fixes the cleaning blade in addition to the spring pressure can be considered, but in this system, the pressure acting on the tip of the cleaning blade is determined by the elastic force generated at a part other than the tip of the cleaning blade that is not fixed. Will be covered. It seems that it is possible to cover with the elastic force of the cleaning blade itself depending on the setting, but it is difficult to use the cleaning blade with high tan δ,
Also, adverse effects are expected in terms of reliability.

Cleaning blade 9 by spring pressure system
-2, the pressure of the cleaning blade 9 is substantially constant.
-2 follows the photosensitive drum 1, and the viscoelastic properties of the cleaning blade 9-2 can provide an effect of removing toner adhesion.

If the viscoelasticity is too high, poor cleaning due to the curling of the cleaning blade occurs. A low value of the elasticity term means that the frequency of the stick-slip event, if it occurs, is low, which means that poor cleaning may occur.

In the present embodiment, a recoating mechanism for the toner 5 is provided inside the cleaning device 9. With this configuration, a certain area in the nip between the cleaning blade 9-2 and the photosensitive drum 1 is used as a lubricant. Is supplied as the toner 5. With this mechanism, the coefficient of friction between the cleaning blade 9-2 and the photosensitive drum 1 via the toner 5 becomes about 0.1, the frictional force is stabilized at a low value, and basically no stick-slip or the like occurs.

However, at the longitudinal end of the cleaning blade 9-2, the toner 5 may not be sufficiently re-coated in some cases. In that case, the friction coefficient between the cleaning blade 9-2 and the nip portion of the surface of the photosensitive drum 1 reaches 0.5, and the probability of occurrence of stick-slip increases in that portion. If the ratio of the elasticity term of the cleaning blade 9-2 is high, the cleaning blade 9-2
The frequency of the vibration generated is high, and even if a stick-slip occurs, its influence does not extend to poor cleaning. On the other hand, if a cleaning blade having a higher viscosity is used, stick-slip results in poor cleaning.

Therefore, in the present embodiment, the value of tan δ of the cleaning blade 9-2 is set to 0.18-0.
38 was set.

[Confirmation Experiment] Ta of Cleaning Blade
The effect depending on nδ was confirmed.

The upper limit was based on the occurrence of cleaning failure of the cleaning blade, and the lower limit was an effect of preventing the occurrence of fusion.

In setting the upper and lower limits, the temperature of the photosensitive drum surface was set to 42 ° C. as described in the present embodiment. Then, while keeping other physical properties of the cleaning blade unchanged, the value of tan δ was varied in steps of 0.02.

In setting the upper limit of tan δ, about 500,000 sheets of image forming durability were performed using a document having a printing ratio of 6%, which is said to have the average image output. In the endurance process, it was examined whether or not cleaning failure occurs due to chattering of the cleaning blade or "dropout". As a result, when the value of tan δ was 0.40 in the use environment, a cleaning failure occurred at the time of forming an image having about 400,000 durable sheets.

In determining the lower limit of tan δ, the ability to remove the adhered toner is ascertained, and the amount of toner adhered to the surface of the photosensitive drum using the photosensitive drum on which toner has been adhered using a cleaning blade conventionally used is determined. Confirmed the cancellation ability.

After replacing each cleaning blade with the same value of tan δ as above for the photosensitive drum on which toner adhesion has occurred, if the number of durable sheets is 1000 and the toner adhesion is in the direction of eliminating toner, the toner adhesion elimination ability Confirm that there is. The cleaning blade (tan δ = 0.18 and tan δ = 0.28) which has been recognized to have the toner adhesion elimination ability is used for long-term durability (1
(Million sheets), no decrease in toner adhesion was observed during long-term durability. For this reason, it can be determined that there is an effect of preventing toner adhesion.

When a durability test was performed using a cleaning blade with tan δ = 0.16, it was confirmed that toner adhered to the photosensitive drum surface on the image on about 300,000 sheets. Therefore, the lower limit of tan δ is 0.
It was set to 18.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional view of the cleaning device of the electrophotographic copying machine according to the present embodiment. In this figure, the same elements as those shown in FIG. 2 are denoted by the same reference numerals.

In the first embodiment, the pressure of the cleaning blade 9-2 is applied to the photosensitive drum 1 using the pressing spring 9-3. In the present embodiment, the support for fixing the cleaning blade 9-2 is provided. A SUS leaf spring 9-7 was provided between the sheet metal 9-5 and the cleaning blade 9-2 itself. The leaf spring plate 9-7 includes a cleaning blade 9-2.
Make up for the lack of elasticity in the part other than the ridge line part of. At the edge of the cleaning blade 9-2, the effect of directly removing the toner adhered on the photosensitive drum 1 is maintained, and the edge of the cleaning blade 9-2 reliably contacts the surface of the photosensitive drum 1. The pressing ability of the cleaning blade 9-2 by the leaf spring 9-7 is secured in a part other than the part.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a sectional view of a cleaning device of the electrophotographic copying machine according to the present embodiment, and FIG. 6 is a perspective view of a pressing mechanism of the cleaning device. In these drawings, the same elements as those shown in FIG. Are denoted by the same reference numerals.

In the first embodiment, the cleaning blade 9-2 was used with the spring pressure reduced to 15 g / mm.

In this embodiment, the cleaning blade 9
-2 Reduces the amount of wear on the ridgeline and reduces the durable life by about 2
It is doubled.

By reducing the spring pressure, the nip amount between the cleaning blade 9-2 and the surface of the photosensitive drum 1 was 20 μm on average, but 12 μm in the present embodiment.
m. This allows the cleaning blade 9
If the same configuration as that of the first embodiment is adopted by lowering only the pressure of -2, the toner may slip off between the cleaning blade 9-2 and the photosensitive drum 1.

In this embodiment, a configuration is shown in which the same cleaning blade 9-2 can be used for a longer period of time than in Embodiment 1 while preventing toner from adhering.

That is, in this embodiment, an equalizing mechanism is added to the supporting mechanism of the cleaning blade 9-2.
Here, the equalizing mechanism opens a shaft hole 9-5a at the center of the cleaning blade supporting metal plate 9-5, and opens the shaft hole 9-5a.
This is a mechanism for holding the supporting metal plate 9-5 and the cleaning blade 9-2 so as to be rotatable in the direction of the arrow in FIG. 6 by the pressing shaft 9-8 passed through -5a. By this equalizing mechanism, the cleaning blade 9-2 is subjected to substantially uniform pressurization on the near side and the back side in the longitudinal direction, so that a stable nip can be formed in the longitudinal direction of the cleaning blade 9-2.

The supporting metal plate 9-5 is rotatable in a vertical plane with respect to the pressing shaft 9-8. The positions of the back side and the front side of the cleaning blade 9-2 follow the surface of the photosensitive drum 1, and The pressure balance in the longitudinal direction of the cleaning blade 9-2 becomes substantially equal. Therefore, stability against cleaning failure can be ensured, and the value of tan δ of the viscoelastic characteristic is 0.18 to 0.1 even when the pressure of the cleaning blade 9-2 is reduced by the secured stability.
38 cleaning blades 9-2 can be realized.

[0051]

As is apparent from the above description, according to the present invention, a photosensitive member for forming an electrostatic latent image and a developing device for developing the electrostatic latent image and visualizing the electrostatic latent image as a toner image. An image forming apparatus comprising: a transfer device that transfers a toner image; and a cleaning device that includes a cleaning unit that abuts on the photoconductor and cleans toner remaining on the photoconductor after the transfer of the toner image. The value of the viscoelastic modulus tanδ when the cleaning means is used is 0.18 to
Since it is set to 0.38, it is possible to obtain an effect that it is possible to prevent the toner from adhering to the photoconductor while suppressing the wear of the cleaning unit and the photoconductor.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electrophotographic copying machine according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view of the cleaning device of the electrophotographic copying machine according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing viscoelastic characteristics of the cleaning blade used in the first embodiment of the present invention.

FIG. 4 is a sectional view of a cleaning device of an electrophotographic copying machine according to Embodiment 2 of the present invention.

FIG. 5 is a sectional view of a cleaning device of an electrophotographic copying machine according to Embodiment 3 of the present invention.

FIG. 6 is a perspective view of a pressure mechanism of a cleaning device of an electrophotographic copying machine according to Embodiment 3 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum (photoreceptor) 3 developing device 5 toner 7 transfer / separation charger (transfer device) 9 cleaning device 9-1 cleaning container 9-2 cleaning blade 9-3 pressure spring (elastic body) 9-4 toner transport screw 9-5 Cleaning blade support sheet metal 9-6 Pressing plate 9-7 Leaf spring (elastic body) 9-8 Pressure shaft

Claims (8)

[Claims] 1. A photoreceptor for forming an electrostatic latent image, a developing device for developing the electrostatic latent image and visualizing the electrostatic latent image as a toner image, a transfer device for transferring a toner image, and A cleaning device having a cleaning unit for cleaning the toner remaining on the photoreceptor after the transfer of the toner image, wherein the value of the viscoelastic coefficient tanδ when the cleaning unit of the cleaning device is used is set to 0. An image forming apparatus characterized in that the setting is made in the range of 18 to 0.38. 2. The method according to claim 1, wherein the temperature of the photoconductor or the cleaning unit is adjusted so that the value of the viscoelastic coefficient tan δ of the cleaning unit during image formation is 0.18 to 0.38. Image forming apparatus. 3. An image forming apparatus according to claim 1, wherein said photosensitive member or said cleaning means is adjusted to a substantially constant temperature during image formation. 4. An image forming apparatus according to claim 1, wherein said cleaning means is brought into contact with said photosensitive member by an elastic body other than said cleaning means. 5. The image forming apparatus according to claim 4, wherein the elastic body is configured by a spring that presses a member that supports the cleaning unit. 6. The image forming apparatus according to claim 4, wherein said elastic body is constituted by a leaf spring interposed between said cleaning means and a member supporting said cleaning means. 7. The image forming apparatus according to claim 1, further comprising a mechanism for supplying toner to the surface of the photoconductor upstream of the cleaning unit in the rotation direction of the photoconductor. 8. An image forming apparatus according to claim 1, wherein said cleaning means is pressed against said photosensitive member by an equalizing mechanism.