JP3236442B2 - Image forming device - Google Patents

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, a facsimile or a printer for forming an image by an electrophotographic system. More specifically, the present invention relates to a digital or analog image forming apparatus having features in a cleaning portion and a developing portion.

[0002]

2. Description of the Related Art Conventionally, in such an image forming apparatus, a cleaning blade or a rotating fur brush is directly applied to an electrostatic image carrier to collect excess toner remaining on the electrostatic image carrier after transfer. Due to the contact, the surface of the electrostatic image carrier is damaged, and there is a disadvantage that cleaning failure is likely to occur due to damage, turning over, chattering, breakage and the like of the cleaning blade.

[0003] As a conventional technique for preventing such a problem, Japanese Patent Application Laid-Open No. 57-111576 discloses a method of improving the cleaning performance by adding a cleaning aid such as a fatty acid metal salt such as zinc stearate as an external additive of a toner. It is disclosed.

Japanese Patent Laid-Open Publication No. 1-2229281 discloses a method of reducing the coefficient of friction between a cleaning blade and a photoreceptor by adhering a small amount of toner to a background portion in order to prevent the cleaning blade from being turned upside down. By
It is disclosed that the cleaning property is improved.

[0005] In addition, it has been proposed that the blade end is formed of a material having a small coefficient of friction to prevent the blade from being turned up or chattered, thereby preventing the occurrence of cleaning failure (for example, Japanese Patent Application Laid-Open No. Hei 2 (1990) -1990). 106780 and 3-269478).

[0006]

However, Japanese Patent Application Laid-Open No.
As disclosed in JP-A-7-111576, when a fatty acid is added to a toner to reduce the friction coefficient between a blade and a photoconductor,
Since the coefficient of friction is small, the toner is liable to slip, which causes image deterioration such as blurring and white spots due to rubbing in the developing section.

Further, if the friction coefficient between the blade and the toner is reduced by adhering the toner to the background of the photoreceptor as disclosed in Japanese Patent Application Laid-Open No. 1-229281, the consumption of the toner is increased with respect to the number of copies. In such a case, if the idle rotation is performed without performing the copy, the toner will run out.

In general, regarding the cleaning performance of an electrophotographic image forming apparatus, recently, as the toner particle diameter has been reduced and the toner particle has become more spherical, the cleaning failure due to blade cleaning tends to be more problematic. is there.

Further, in the case of fur brush cleaning, as described above, the surface of the electrostatic image carrier may be damaged.
In addition, it is difficult to reduce the size of the apparatus, which hinders downsizing of the machine body.

As a cleaning method for solving such a problem, the present applicant provides a cleaning member at a distance from the surface of the electrostatic image carrier, applies a bias voltage to the cleaning member, and applies a bias voltage on the electrostatic image carrier. A method for removing residual toner by electrostatically attracting and transferring residual toner has been proposed, and a patent application has already been filed (Japanese Patent Application No. 5-3).
29968).

However, in this method, only one cleaning member is used, and a bias voltage is applied to only one cleaning member. Therefore, depending on the adhesion state between the electrostatic image carrier after transfer and the residual toner, the residual toner can be sufficiently removed. Could not be removed.

It is an object of the present invention to improve this point and to make it possible to reliably remove residual toner by a plurality of cleaning members that are not in contact with the electrostatic image carrier. Another object of the present invention is to make it possible to remove the residual toner even if some of the residual toner on the electrostatic image carrier after transfer has the same polarity as the bias voltage. It is in.

[0013]

An image forming apparatus according to the present invention includes a plurality of cleaning members 20A and 2 for electrostatically sucking residual toner, as shown in the following embodiments.
OB are spaced apart from the surface of the electrostatic image carrier 10 and bias voltages having different polarities are applied to the cleaning members 20A and 20B.

Then, the cleaning members 20A
-A partition member 27 is arranged between 20B and the partition member 2
7 is a conductor, and the distance between the conductor and the electrostatic image carrier 10 is a distance that does not cause dielectric breakdown.

[0015]

According to the present invention, the residual toner on the electrostatic image carrier after the transfer is reliably removed by the plurality of cleaning members in a non-contact state with the electrostatic image carrier. Further, by selecting the polarity of the bias voltage applied to the cleaning member, the efficiency of removing the residual toner is improved. Further, in the present invention, by applying a bias voltage to the cleaning member, the residual toner on the electrostatic image carrier is transferred to the cleaning member by suction without contact with the electrostatic image carrier. Even if a small spherical toner or minute toner is used, the cleaning performance does not decrease. Therefore, such a toner can be used without any problem, so that the image quality can be improved.
There are also various side effects.

[0016]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a recording unit of an image forming apparatus according to an embodiment of the present invention.

The illustrated image forming apparatus includes a drum-shaped photosensitive member 10 serving as an electrostatic image bearing member substantially at the center of the main body. Around the photoreceptor 10, a charging device 11, a developing device 12, a transfer / separation device 13, and a cleaning device 15 are disposed in this order in the driving direction indicated by the arrow. Although not shown, an optical writing device is provided above the photoconductor 10.

At the time of recording, the sheet is sent out from a sheet cassette (not shown), and is conveyed to the lower side of the photoreceptor 10 at a timing by a registration roller 16. Photoconductor 10
Is driven in the clockwise direction indicated by the arrow, and at this time, the charging device 11
To form a latent image on the photoreceptor 10 by irradiating the surface with laser light L from an optical writing device,
Subsequently, when passing through the position of the developing device 12, the electrostatic latent image is sequentially visualized with toner. This visible image (toner image) is transferred by the transfer / separation device 13 onto the upper surface of the sheet P conveyed to the lower side of the photoreceptor 10 to separate the sheet P. Then, the sheet P is conveyed to a fixing device (not shown), where the visible image is fixed and then discharged outside. On the other hand, after image transfer,
The residual toner adhered to the surface of the photoconductor 10 is removed by the cleaning device 15 for cleaning.

As shown in FIG. 2, the cleaning device 15 includes a box-shaped cleaning case 19 that is long in the axial direction of the photoconductor 10, and includes first and second roller-shaped cleaning cases 19 in the cleaning case 19. Cleaning member 2
0A and 20B are arranged in parallel in the direction of rotation of the photoconductor 10. The cleaning case 19 is provided with a long window 19a on the photoconductor 10 side, the cleaning members 20A and 20B are opposed to the surface of the photoconductor 10 through the long window 19a, and gaps G1 and G2 (for example, G1 = G2) = 105 μm),
These cleaning members 20A and 20B are individually rotatably supported. Further, elongated blade-shaped cleaning blades 21A and 21B are fixed in the cleaning case 19, and one side of each of the cleaning blades 21A and 21B is
B is pressed against the outer periphery. Further, bias applying devices 25A and 25A for applying DC bias voltages having different polarities to the cleaning members 20A and 20B, respectively.
B is electrically connected.

In such a configuration, after image transfer,
When cleaning the photosensitive member 10, the two cleaning members 20A and 20B are rotated in the same direction by a drive motor (not shown) in the same direction as indicated by an arrow, and the bias applying devices 25A and 20B are applied to the cleaning members 20A and 20B. From 25, DC bias voltages VDC1 and VDC2 having different polarities are applied. Then, for example, a negative potential difference (for example, −500 V to −1500 V) is generated between the first cleaning member 20 </ b> A and the photoconductor 10, and a positive polarity potential difference is generated between the second cleaning member 20 </ b> B and the photoconductor 10. Potential difference (for example, +500 V to +150
0V), and the residual toner of the positive polarity on the photoconductor 10 is
The residual toner of negative polarity is electrostatically attracted and transferred to the outer periphery of the first cleaning member 20A and to the outer periphery of the second cleaning member 20B. Then, the transferred residual toner is mechanically removed from the cleaning members 20A and 20B by the cleaning blades 21A and 21B. Therefore, the cleaning members 20 </ b> A and 20 </ b> B always suck the residual toner with the clean surface facing the photoconductor 10.
The waste toner removed from the cleaning members 20A and 20B is collected in a waste toner collection tank (not shown).

In this case, the gaps G1 and G2 may be set in accordance with the characteristics of the image forming apparatus, and need not always be the same. The polarity of the bias voltage applied to the two cleaning members 20A and 20B may be opposite to the above. Further, the voltage value is set in accordance with the characteristics of the residual toner and the characteristics of the image forming apparatus.

In the above embodiment, a DC bias voltage is applied to the first and second cleaning members 20A and 20B. However, as shown in FIG. 3, for example, an AC / DC bias is applied to these cleaning members 20A and 20B. The devices 26A and 26B may be connected to each other, and mutually different voltages VAC / DC1 and VAC / DC2 in which AC and DC are superimposed may be applied.

In this case, the voltage value of the DC component may be the median of the voltage values of the AC component. The frequency of the AC component is 10
0 Hz to 3000 Hz. When only the DC bias voltage is applied, all the residual toner may not be able to be suction-transferred and may be left out due to the conditions at the time of image formation and the characteristics of the toner.However, when a voltage in which AC and DC are superimposed is applied,
The residual toner can be more effectively suctioned, so that there is almost no residual toner. Even when a voltage in which AC and DC are superimposed is applied, the voltage value and the order of the applied polarities are set in accordance with the characteristics of the residual toner and the characteristics of the image forming apparatus.

As described above, the distribution of the charge amount of the toner after transfer may differ depending on the characteristics of the toner and the characteristics of the image forming apparatus. According to experiments, a combination of a certain toner and a certain image forming apparatus (referred to as combination A)
When the image was formed by the above, the residual toner after the transfer was
The charge amount distribution as shown in FIG. Next, when an image was formed using a combination of another toner and an image forming apparatus (referred to as combination B), the residual toner after transfer showed a charge amount distribution as shown in FIG.

It can be seen that the residual toner of the combination A shown in FIG. 4 is composed of both the positive toner and the negative toner. On the other hand, it can be seen that the residual toner of the combination B shown in FIG. 5 consists only of the toner having the negative polarity.

Therefore, as shown in FIG. 4, the first and second residual toners having both polarities are mixed.
By applying bias voltages of opposite polarities to the cleaning members 20A and 20B, residual toner of both polarities can be removed.

The residual toner having only one polarity as shown in FIG. 5 can be suctioned by using a single cleaning member to which a bias voltage having a different polarity is applied. In the case where the transfer efficiency of the toner image to the transfer paper is reduced, a large amount of residual toner must be removed in the cleaning process, and a single cleaning member may not be able to cope with the problem. In such a case, by applying a bias voltage having the same polarity to both of the two cleaning members 20A and 20B, that is, a polarity different from that of the residual toner, it is possible to cope with a large amount of residual toner. This is effective even when the transfer paper has a paper jam. In addition, two cleaning members 20A and 2
Even when a bias voltage having the same polarity is applied to both of 0B and 0B, the voltage value may be set in accordance with the characteristics of the residual toner and the characteristics of the image forming apparatus. However, the voltage value is
It is not necessary for the two cleaning members 20A and 20B to be the same.

In the above-described embodiment, after the residual toner is sucked toward the first cleaning member 20A, before the recovery of the toner from the first cleaning member 20A is completed, a bias having a polarity opposite to that of the bias is applied. When the second cleaning member 20B to which the voltage is applied approaches, the residual toner heading for the first cleaning member 20A is sucked by the second cleaning member 20B, and further, the photosensitive member is transferred from the second cleaning member 20B. 10
There is a risk of being sucked again and returning.

Therefore, in the embodiment shown in FIG. 6, a partition member 27 is provided between the first cleaning member 20A and the second cleaning member 20B in addition to the above-described structure. Due to the partition member 27, residual toner sucked from the photoconductor 10 toward the first cleaning member 20A is removed from the second cleaning member 20B.
Further, the residual toner sucked from the photoconductor 10 toward the second cleaning member 20B is not attracted to the first cleaning member 20A. Therefore, the residual toner once absorbed by the cleaning members 20A and 20B is not sucked back to the photoconductor 10 and returned.

FIG. 7 shows a modification of the partition member 27. One end 27a of the partition member 27 is extended downward while curving in accordance with the outer periphery of the first cleaning member 20A. With this configuration, even if the residual toner collected by the second cleaning member 20B is scraped off from the second cleaning member 20B and falls, it does not adhere to the first cleaning member 20A again. It becomes an effective partition member. Even when the shape of the cleaning member is not a roller, the same effect can be expected by adjusting the partition member to that shape.
It is more effective if the shape is adjusted to the shape of 5 itself.

The provision of the partition member 27 has such an advantage. However, if the residual toner remains adhered to the partition member 27, the cleaning property may be deteriorated, or the photoreceptor 10 may be damaged due to insulation breakdown. May cause damage. Therefore, when the partition member 27 is made of a dielectric material having a volume resistance of 10 ⁷ Ωcm or more, even if the photosensitive member 10 is deflected in the rotational direction and the partition member 27 and the photosensitive member 10 are close to each other, the dielectric breakdown is not caused. Good image quality was obtained for a long time without producing.

However, it has been found that when such a partition member 27 made of a dielectric material is used, the residual toner is easily scattered from the cleaning members 20A and 20B depending on the type of toner and the characteristics of the image forming apparatus. Therefore,
When a conductive material was used for the partition member 27, an electric field was generated between the conductive member and the cleaning members 20A and 20B, so that scattering of the toner did not occur. However, if the gap between the partition member 27 and the photoreceptor 10 is narrow, insulation breakdown occurs between the two, damaging the photoreceptor 10 and the like. Therefore, when the gap is set to 1 mm, the photoreceptor 10 shakes. In some cases, dielectric breakdown did not occur, and good image quality was obtained over a long period of time. However, this value is a value specific to the device used in the experiment, and the partition member 2 in each device was used.
7 and the material of the photoconductor 10.

FIG. 8 shows a cleaning case 19 of the cleaning device 15 in which a fur brush 30 is further provided. The fur brush 30 is located closer to the image transfer position than the cleaning position by the first cleaning member 20A, that is, located on the upstream side (lower side in the drawing) in the rotation direction of the photoconductor 10, and rotates while contacting the photoconductor 10. It has become. In this case, the fur brush 30
Is not for collecting the residual toner on the photoconductor 10 but for weakening the electric / mechanical coupling force between the residual toner and the photoconductor 10 and electrostatically sucking the residual toner by the cleaning members 20A and 20B. This is to make it easier.
For this reason, the fur brush 30 has a light contact with the photoreceptor 10 and has a diameter of about 10 to 30 mm.

Further, instead of weakening the mechanical adhesion of the residual toner, a static eliminator may be provided to weaken the electrostatic adhesion. In that case,
For example, as shown in FIG. 9, a pre-cleaning charger 35 is arranged near the image transfer position of the cleaning position so as to face the surface of the photoconductor 10. Then, a negative voltage is applied to the photoconductor 10 by the pre-cleaning charger 35 to reduce the charge amount. Thereby, the electrostatic adhesion of the residual toner is weakened and the residual toner is
0 can be easily separated from the surface.

The pre-cleaning charger 35
Instead, as shown in FIG. 10, for example, as shown in FIG.
A configuration may be adopted in which the static elimination lamp 40 is arranged to face the surface of the zero. Then, the photosensitive member 1 is moved by the discharging lamp 40.
By irradiating light to 0 to reduce the amount of charge on the surface, as in the case of FIG. 9, the electrostatic adhesion of the residual toner is weakened and the residual toner is easily separated from the surface of the photoconductor 10. it can.

The fur brush 30 and a neutralizing device such as a neutralizing lamp 40 are used in combination to weaken the adhesion of the residual toner both mechanically and electrostatically, so that the surface of the photosensitive member 10 Can be made easier. Also,
As the charge removing device, a configuration including both the pre-cleaning charger 35 and the charge removing lamp 40 may be employed.

In the illustrated embodiment described above, the cleaning members 20A and 20B are rotated by transmitting the driving torque of the drive motor.
It is preferable that the linear velocity on the outer periphery of A / 20B is higher than the linear velocity on the surface of photoconductor 10. By doing so, the moving area of the cleaning members 20A and 20B per unit area on the photoconductor 10 is increased by the amount by which the linear speed of the cleaning members 20A and 20B is faster than the linear speed of the photoconductor 10, so that cleaning is performed. It is possible to make more residual toner adhere to the members 20A and 20B and collect them. According to the experiment, when the linear velocity of the cleaning members 20A and 20B was 1.5 to 3 times the linear velocity of the photoconductor 10, the toner recovery rate was good. However, the linear velocity of the cleaning members 20A and 20B may be set according to the toner used and the characteristics of the image forming apparatus. Further, it is not necessary to make the linear speeds of the cleaning members 20A and 20B the same.

As in the illustrated embodiment, the present invention applies a bias voltage to the cleaning members 20A and 20B to remove the residual toner on the photosensitive member 10 without contact with the photosensitive member 10. -Since suction transfer is performed to 20B, the use of a spherical toner, a small toner, or a polymerized toner produced by a polymerization method having a small particle size does not cause a decrease in cleaning performance as in the related art.

That is, the spherical toner generally provided conventionally has a small particle size of 10 μm or less and, of course, has a substantially spherical shape and poor catching ability. In the cleaning device, the bad conditions are overlapped, and the cleaning performance is reduced. However, according to the present invention, since suction is performed in a non-contact state, the conventional problem does not occur. In the experiment, the average particle size obtained by heat treatment of the pulverized toner was 8 μm.
, A good cleaning property was shown. It can easily be presumed that there is no particular problem even if the particle size is less than this, and in the apparatus according to the present invention, the average particle size
When the following spherical toner is used, both cleaning performance and high image quality can be achieved.

Further, since the fine toner conventionally provided generally has a small particle size of 7 μm or less, a conventional cleaning device in which a cleaning blade is slidably contacted with a photoreceptor is used.
Excess toner passed between the photosensitive member surface and the blade, resulting in poor cleaning performance. However, according to the present invention, since there is no such penetration of the toner, a fine toner having an average particle diameter of 7 μm or less can be used without any problem. An experiment was conducted using a fine toner having an average particle size of 4 μm.
Good cleaning properties were shown.

Further, the conventional polymerized toner obtained by the polymerization method generally has a small particle size of 10 μm or less, and has a spherical shape and poor catching property. For a conventional cleaning device that is in sliding contact with a photoreceptor, bad conditions are overlapped, and cleaning performance is reduced. But,
According to the present invention, such a polymerized toner having an average particle diameter of 10 μm or less can be used without any problem. As polymerized toner,
When an experiment was conducted using a dispersion-polymerized toner having the formulation described in JP-A-4-137372, good cleaning properties were exhibited.

Further, a toner containing a lubricant may be used. As the lubricant, a lubricant having a low friction coefficient such as, for example, 0.5 wt% zinc stearate powder (average particle size: 1 μm) is preferable. Instead of zinc stearate powder, 0.5
wt% -1.0wt% silica (average particle size 0.1μm)
Alternatively, 0.5 wt% to 1.0 wt% of alumina (average particle size: 0.5 μm) or fatty acid metal salt may be added. Further, such a lubricant may be directly applied to the surface of the photoconductor 10.

When the toner internally or externally added with the lubricant is used, or when the lubricant is directly applied to the photoreceptor 10, the residual toner is easily separated from the surface of the photoreceptor 10, so that the cleaning member 20A. The transfer of the residual toner by electrostatic attraction by 20B is facilitated, and the cleaning property is improved.

On the other hand, when the toner to which the lubricant is added is used, the development of the photosensitive member 1 is repeated by repeating the development.
In the case where the friction coefficient of the surface of No. 0 gradually decreases, and when a lubricant is applied, the friction coefficient of the photosensitive member surface is positively reduced, so that the toner itself becomes slippery.

In order to compensate for this, Japanese Patent Laid-Open No.
By adopting a non-contact developing method using a non-magnetic one-component toner described in Japanese Patent No. 127177, it is possible to achieve both high cleaning performance and high image quality development. The non-contact developing method disclosed in this publication is a method proposed by the present applicant, and is an earlier method, in which the toner is carried in a single layer on the developing roller, and the linear velocity ratio of the developing roller is changed to the electrostatic image. By improving the linear velocity of the carrier from 2 to 4 times, the toner layer on the developing roller is multi-layered and developed at almost the same speed, so that the uniformity and high speed of the solid image are improved. I have.
According to the experiment, OPC was used as the electrostatic image carrier, and the latent image potential was -50 to -150 V, and the developing bias was 0 to-
Good images were obtained with a pulse bias of 1000 V and a frequency of 1.5 to 2.0 KHz. Therefore, by using a lubricant and developing by a non-contact developing method, it is possible to provide a high-quality image forming apparatus with no image deterioration in which both cleaning and developing characteristics are matched.

In the above embodiment, an image forming apparatus using a so-called one-component developing method has been described. However, the present invention is applicable to an image forming apparatus using a two-component developing method in which the same operation and effect can be obtained. Thus, the present invention can be widely applied to a general electrophotographic imaging system. In the embodiment, the rotation direction of the cleaning member has been described in the forward direction, but the same applies to the reverse direction. Further, the number of cleaning members is not limited to two, but may be three or more. Furthermore,
In the above embodiment, a so-called negative-positive method has been described, but the present invention can be applied to a positive-positive method. Further, the numerical values shown in the above embodiments are values specific to the used apparatus, and it is needless to say that the values should be set in consideration of the difference in the structure of the apparatus and the like.

[0047]

The effect according to the present invention, according to the present invention is as elevation gel and the next.

According to the present invention, the residual toner on the electrostatic image carrier after the transfer can be electrostatically attracted and transferred by the plurality of cleaning members in a non-contact state with the electrostatic image carrier. The residual toner on the image carrier can be reliably removed.
Further, since bias voltages having different polarities are applied to the plurality of cleaning members, even if a part of the residual toner on the electrostatic image carrier after transfer has the same polarity as the bias voltage, The residual toner can also be removed.

[0049] By disposing the partition member between the cleaning member, the residual toner is sucked from the electrostatic image bearing member, such a situation that returns to the electrostatic image bearing member and transferred between the cleaning member beforehand Can be prevented.

[0050]

[0051] Further, the partition member as a conductor therewith by a distance that does not cause dielectric breakdown distance between the electrostatic image bearing member, and at the same time attained easily prevent breakdown of the partition member, the cleaning member attained even prevent residual toner scattering.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a recording unit of an image forming apparatus illustrating the present invention.

FIG. 2 is a schematic configuration diagram in which a cleaning device side in FIG. 1 is enlarged.

FIG. 3 is a schematic configuration diagram showing a case where an AC voltage and a DC voltage are superimposed and applied to a cleaning member.

FIG. 4 is a graph showing an example of a charge distribution of residual toner on a photoconductor after a transfer / separation step.

FIG. 5 is a graph showing another example of the charge distribution of the residual toner on the photosensitive member after the transfer / separation step.

FIG. 6 shows a partition member interposed between the two cleaning members.
It is a schematic block diagram showing a case .

FIG. 7 is a schematic configuration diagram showing a case where a partition member is deformed from the case of FIG. 6;

FIG. 8 is a schematic configuration diagram showing another example including a fur brush.

9 is a schematic structural view of a recording portion of the images forming apparatus including a precleaning charger.

10 is a schematic structural view of a recording portion of the images forming apparatus provided with a discharge brush.

[Explanation of symbols]

 Reference Signs List 10 photoconductor (electrostatic image carrier) 13 transfer / separation device 20A / 20B cleaning member 21A / 21B cleaning blade 25A / 25B bias applying device 26A / 26B AC / DC bias applying device 27 partition member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 21/10-21/12

Claims (1)

(57) [Claims] 1. An image forming apparatus for removing residual toner on an electrostatic image carrier with a cleaning member after image transfer, wherein the plurality of cleaning members for electrostatically attracting the residual toner are provided on the surface of the electrostatic image carrier. Juxtaposed away from
While applying bias voltages having different polarities to the cleaning members,
Place a partition member between them, and make the partition member a conductor,
The distance between this and the electrostatic image carrier does not cause dielectric breakdown.
An image forming apparatus with a long distance .