JP4065474B2 - Development device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device used to visualize an electrostatic latent image formed on an image carrier in an image forming apparatus such as an electrophotographic system.
[0002]
[Prior art]
In an image forming apparatus using electrophotography, a developing device using a one-component developer has a slightly different configuration depending on the type of toner (one-component toner) used as the developer. In particular, the force for carrying the toner on the surface of the developing roller (developer carrier) varies depending on whether the toner itself is magnetic.
[0003]
In the case of magnetic toner, by providing a magnet in the developing roller, the toner can be carried on the surface of the developing roller mainly by magnetic force and conveyed.
[0004]
On the other hand, in the case of non-magnetic toner, since magnetic force cannot be used, the mirroring force on the surface of the developing roller generated by the charge amount of the toner itself is used, and the toner is carried on the developing roller by this mirroring force. Thus, it can be conveyed. Therefore, when non-magnetic toner is used, a means for supplying toner to the developing roller and applying a charge amount that causes a mirroring force to the toner is required instead of using a magnet. As this means, a toner supply roller disposed in contact with the developing roller is generally used.
[0005]
The toner supply roller supplies toner to the developing roller, and in the contact nip region between the developing roller and the toner supply roller, the toner is frictionally charged by friction generated between the toner and the toner and is carried on the developing roller. The toner is imparted with a charge amount that produces a sufficient mirror power.
[0006]
Since the non-magnetic toner is non-magnetic, it can be easily colored. Currently, the toner mainly used in the developing device of the color image forming apparatus is a non-magnetic toner.
[0007]
However, it has been found that the conventional developing device using this non-magnetic toner has a problem to be solved. A typical example of a one-component contact developing device using nonmagnetic toner will be described below with reference to FIG.
[0008]
  The developing device 101 carries an insulative non-magnetic one-component toner T contained therein and rotates in the Y direction in the figure, and develops in contact with the photosensitive drum 100 which is an image carrier that rotates in the X direction in the figure. A roller 102, a toner supply roller 104 that supplies the developing roller 102 with nonmagnetic one-component toner T rotated in the direction of arrow Z in the figure, and a toner regulation that regulates the amount of toner T applied and the amount of charge on the developing roller 102 Development as a meansblade103, a stirring member 105 that stirs the toner T and supplies the toner T to the toner supply roller 104, and the like.
[0009]
The photosensitive drum 100 with which the developing roller 102 comes into contact is preferably made of a rigid body, and the developing roller 102 preferably has elasticity. The developing blade 103 made of metal is preferably used for charging the nonmagnetic toner.
[0010]
The toner T regulated by the developing blade 103 is conveyed to a developing area where the photosensitive drum 100 and the developing roller 102 are in contact with the rotation of the developing roller 102, and a direct current developing bias is applied to the developing roller 102 from a power source (not shown). Is applied to the electrostatic latent image formed on the surface of the photosensitive drum 100 from the developing roller 102 carried by the mirror force, and is attached and developed to visualize the latent image as a toner image.
[0011]
The toner that does not contribute to the development and remains on the surface of the developing roller 102 is returned to the developing device 101 as the developing roller 102 rotates, and is collected via the toner supply roller 104.
[0012]
As described above, the developing device 101 basically uses an insulating non-magnetic one-component toner as the toner T, and the toner T supplied from the toner supply roller 104 is carried on the developing roller 102. This is performed by the mirroring force generated by frictional charging of the toner T in the contact area between the toner supply roller 104 and the developing roller 102. The amount of toner T carried on the developing roller 102 (the coating amount) is adjusted by the difference in peripheral speed between the developing roller 102 and the toner supply roller 104.
[0013]
[Problems to be solved by the invention]
As described above, in the nonmagnetic one-component developing device 101, the coating of the toner T supplied from the toner supply roller 104 onto the developing roller 102 is frictionally charged with the toner T in the contact area between the toner supply roller 104 and the developing roller 102. Therefore, the coating amount of the toner T on the developing roller 102 not only depends on the material of the toner and the material of the developing roller 102 and the toner supply roller 104 but also depends on the rubbing force. It was highly dependent.
[0014]
As a result, even if the material of the toner and the material of the developing roller 102 and the toner supply roller 104 are optimized, if the frictional force between the developing roller 102 and the toner supply roller 104 is reduced, the triboelectric charge amount of the toner is reduced. There is a problem in that the amount of toner carried on the developing roller 102 decreases, and the density of an output image obtained by transferring and fixing the image onto a transfer material after development decreases.
[0015]
According to the study by the present inventors, the developed toner image on the photosensitive drum 100 is generally about 0.6 mg / cm per unit area in order to obtain a sufficient density on the output image.²The amount of toner is required. In order to secure this toner amount, at least about 0.33 mg / cm on the surface of the developing roller 102 under the condition that the peripheral speed of the developing roller 102 is 180% higher than the peripheral speed of the photosensitive drum 100.²The amount of toner is required.
[0016]
Even if the amount of toner carried on the developing roller 102 is small, if the increase in the developing roller peripheral speed relative to the photosensitive drum peripheral speed is increased, the necessary toner amount on the photosensitive drum can be secured. This is undesirable because it increases the driving torque of the developing roller, leading to an increase in cost. Therefore, practically, the upper limit of the increase in the peripheral speed of the developing roller is 180%, and when the peripheral speed is 180% or less, at least about 0.33 mg / cm on the surface of the developing roller.²If the above toner amount cannot be secured, the density of the output image will be reduced. Further, at a peripheral speed of 180% or less, if a larger amount of toner cannot be secured, 0.6 mg / cm is applied on the photosensitive drum.²The amount of toner cannot be secured, resulting in a decrease in the output image.
[0017]
The rubbing force between the developing roller 102 and the toner supply roller 104 will be described. This rubbing force is the contact force between the developing roller 102 and the toner supply roller 104 and the circumference between the developing roller and the toner supply roller. It is determined and determined by the speed difference and the friction coefficient of the surfaces of the developing roller and the toner supply roller. If the rubbing force is large, the frictional charging of the toner supplied between the developing roller 102 and the toner supply roller 104 is promoted, and as a result, the toner having a charge amount that generates a mirroring force that can be carried on the developing roller. The number increases, and the amount of toner carried on the surface of the developing roller increases.
[0018]
That is, the rubbing force between the developing roller 102 and the toner supply roller 104 is closely related to the amount of toner carried on the surface of the developing roller, and the amount of toner carried on the surface of the developing roller increases the rubbing force. If the rubbing force is decreased, it decreases. Therefore, conventionally, in order to carry a necessary amount of toner on the surface of the developing roller, the developing roller 102 is set so that the rubbing force between the developing roller and the toner supply roller is set in accordance with the necessary amount of toner. The contact force between the toner and the toner supply roller 104 is increased, and the peripheral speed difference between them is increased.
[0019]
However, the above-mentioned rubbing force is one factor that determines the life of the developing device. Increasing the rubbing force leads to acceleration of toner deterioration, and the toner fusion to the developing roller and the developing blade. Causing image deterioration such as increase in fog and the like, leading to shortening of the life of the developing device.
[0020]
On the other hand, in Japanese Patent Application Laid-Open No. 63-180983, the unevenness on the surface of the developing roller 102 is increased, and the amount of toner on the developing roller is increased by a mechanical conveying force regardless of the above-mentioned rubbing force. A method is disclosed. However, as described in the publication, the unevenness on the surface of the developing roller affects the image quality, and there is a limit to increasing the unevenness.
[0021]
According to the study by the present inventors, in order not to impair the image quality, the unevenness on the surface of the developing roller 102 needs to be 15 μm or less in the surface roughness Rmax. In this surface roughness region, the mechanical conveying force Thus, it is difficult to sufficiently increase the amount of toner on the developing roller. Furthermore, in such a mechanical conveyance, the toner carrying amount on the developing roller does not depend much on the charge amount of the toner, so that the toner charge amount distribution on the developing roller becomes wide, and the charge having the opposite polarity to the charge polarity of the toner. As a result, the amount of reversal toner increases and so-called “image fog” (reversal fog) in which toner adheres to non-image areas during development increases.
[0022]
Japanese Patent Laid-Open No. 63-180983 also discloses a method different from the above method as a method for increasing the amount of toner on the developing roller. This another method forms an electric field such that the toner is supplied from the toner supply roller 104 toward the developing roller 102, and charges the toner by this electric field to apply the charge. This is to increase the amount of coating, and all of the above problems have been solved.
[0023]
However, this method reduces the resistance of the developing roller to 10 as disclosed in the publication.⁸-10¹³Must be Ωcm. The resistance region material is likely to change in resistance value due to environmental changes, and it is difficult to manufacture a developing roller stably in large quantities.
[0024]
In addition, it is said that the toner coating amount is increased by applying electric charge to the toner by an electric field. However, according to the study by the present inventors, when the electric field is applied, the toner that has been charged to some extent around the developing roller is originally charged to the developing roller. Since it is biased to the vicinity, it is considered that the amount of toner supplied to the developing roller increases and the amount of coating increases. Therefore, in order to increase the toner coating amount on the developing roller, it is not necessary to take measures to increase the frictional charging between the toner supply roller and the developing roller. It means that the width can be expanded.
[0025]
However, increasing the toner supply amount to the developing roller without increasing the frictional charging leads to a large variation in the charging amount of the toner coated on the developing roller. The toner charge amount distribution of the toner coat layer on the developing roller becomes wider as in the case of an increase in the toner coat amount due to the mechanical conveying force. As a result, similarly, there arises a problem that image fogging during development increases.
[0026]
In summary, in the conventional developing device, the toner is supplied to the surface of the developing roller 102 and the coating is performed by the rubbing force between the developing roller 102 and the toner supplying roller 104. This rubbing force determines the life of the developing device. One reason is that an increase in the rubbing force leads to accelerated toner deterioration, causing image deterioration such as toner fusion to the developing roller and developing blade 106 and increased fogging of the image. Was inviting. In order to solve these problems, when the toner amount on the developing roller is increased by a mechanical method or the like, there is a problem that image fogging occurs and image quality is deteriorated.
[0027]
An object of the present invention is to always secure a necessary amount of toner on the developing roller in a developing device using non-magnetic one-component toner even if the rubbing force between the developing roller and the toner supply roller is reduced. Another object of the present invention is to provide a developing device that can perform good development without causing toner deterioration and image fogging and obtain a high-quality output image.
[0028]
[Means for Solving the Problems]
  The above object is achieved by the developing device according to the present invention. In summary, the present invention relates to a rotating developer carrying member in contact with or close to an image carrier on which an electrostatic latent image is formed, and a one-component developer for developing the electrostatic latent image. A developer supply member made of a rotating elastic body that is in contact with the developer carrier and is arranged to contact the developer carrier.A developer supply member having a foam layer on the surfaceAnd a developer amount regulating member disposed on the downstream side of the developer carrying member in the rotational direction of the developer carrying member, which regulates the amount of developer carried on the developer carrying member, A partition wall that partitions a developer carrying member, a developer supply member, a developer amount regulating member provided with the developer amount regulating member, and a toner hopper that supplies the developer to the developer portion, and an opening through which the developer passes A developing device including a partition wall,
  A developer circulation control member is installed in contact with the upper portion of the developer supply member, and the developer circulates above the developer supply member by the rotation of the developer carrier and the developer supply member. The developer carrying member, the developer supply member, and the developer circulation control member are partitioned.Developer circulationForming a region,
  Developer is supplied to the developer circulation area from above the developer circulation control member from the toner hopper through the opening.
  The opening is formed to a position below a contact position between the developer supply member and the developer circulation control member, and the developer circulation control memberContact with the foam layerByDeveloper is discharged from the foam layer,In the developing device, the developer removed from the developer supply member can pass through the opening and be collected from the developing unit to the toner hopper.
[0029]
According to the present invention, preferably, the developer circulation control member is arranged in such a manner that it intersects a horizontal tangent passing through the upper surface of the developer supply member from the lower side and protrudes to a region above the tangent. To do. The center of the developer supply member is positioned below a horizontal line passing through the center of the developer carrier. The cross-sectional shape at the tip of the developer circulation control member on the developer supply member side can be a rectangle. The cross-sectional shape at the tip of the developer circulation control member on the developer supply member side can be a curved surface. The developer circulation control member may have a circular cross-sectional shape. The developer supply member may be a foamed sponge roller.
[0030]
  In addition, the developer supply member as a first developer supply member, a second developer supply member that rotates to supply the developer to the first developer supply member,The second developer supply member is provided in the toner hopper;The developer circulation control member can be positioned in the developer flow formed by supplying the developer to the first developer supply member by the second developer supply member.The
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described in more detail with reference to the drawings.
[0032]
Example 1
FIG. 1 is a schematic configuration diagram showing an embodiment of the developing device of the present invention.
[0033]
In this embodiment, a developing device of a contact developing system in which the developing roller is disposed in contact with the photosensitive drum will be described as an example. However, the present invention is applied to a developing device of a non-contact developing system in which the developing roller is disposed in non-contact with the photosensitive drum. Can also be applied.
[0034]
In FIG. 1, reference numeral 100 denotes a negative photosensitive drum which is an image carrier. In this embodiment, an OPC photosensitive member having an outer diameter of 30 mm is used. The photosensitive drum 100 is rotationally driven in the X direction in the drawing at a predetermined rotational speed.
[0035]
The developing device 1 of this embodiment is roughly divided into a toner hopper portion 1a and a developing portion 1b. The toner hopper portion 1a and the developing portion 1b are partitioned by a partition wall 1c having an opening 1d serving as a toner passage at the center. A developing roller 2 as a developer carrying member is disposed in an opening of the developing unit 1b facing the photosensitive drum 100. The developing roller 2 is in contact with the photosensitive drum 100 and is rotated at a predetermined rotational speed in the Y direction in the drawing. Driven by rotation. In this embodiment, the developing roller 2 having an outer diameter of 16 mm was used.
[0036]
In the developing roller 2, an elastic layer is formed on a metal core such as aluminum or stainless steel, and a charge imparting layer is further formed thereon. For the elastic layer, in order to reduce the hardness of the developing roller 2, a low hardness LTV silicone solid rubber, or a foamed sponge such as a silicone resin, a urethane resin, or EPDM can be used.
[0037]
When foamed sponge is used for the elastic layer, it is preferable to provide a solid layer having a thickness of about several mm or less on the sponge layer surface. This is because the charge imparting layer provided thereon is a thin layer having a thickness of about several μm. Therefore, if the solid layer is not provided on the surface of the sponge layer, the uneven shape of the surface of the lower sponge layer appears on the surface of the developing roller 2. This is because the surface roughness Rmax (JIS B0601) of the developing roller 2 becomes too large. In the present invention, a surface roughness tester SE-30H manufactured by Kosaka Laboratory was used for measuring the surface roughness Rmax.
[0038]
According to the study by the present inventors, the surface roughness Rmax of the developing roller 2 generally needs to be 15 μm or less, and when this value is exceeded, as described above, the charge amount distribution of the carried toner becomes broad. Therefore, so-called inversion fog occurs. In particular, when a charge imparting layer or the like is applied directly on the sponge layer, the coating liquid becomes uneven in the sponge, that is, walls and pores, so that a very large uneven shape appears. As a result, irregularities on the surface of the sponge layer appear on the toner image developed on the photosensitive drum and the output image, resulting in a very cluttered image.
[0039]
In order to prevent this, when an elastic layer made of a sponge layer is used, a solid layer may be provided on the surface of the sponge layer. Even if a solid layer is provided on the surface, it is possible to obtain a low developing roller hardness for the developing roller 2 by setting the thickness to several mm or less and the low hardness of the sponge layer.
[0040]
The charge imparting layer of the developing roller 2 needs to reduce the dynamic friction coefficient of the surface in order to reduce the high charge imparting property to the toner and the rubbing force with the photosensitive drum 100. For this reason, a charge imparting layer was formed from a material in which release particles such as a fluorine resin resin and polyamide resin particles were dispersed in a resin having high charge imparting property such as a polyamide resin or an acrylic-modified silicone resin.
[0041]
Both the elastic layer and the charge imparting layer are electrically conductive, and conductive materials such as carbon powder and metal are dispersed and mixed in these materials. The electric resistance value of the elastic layer and the charge imparting layer is 10 in volume resistivity.^Three-10⁹It is adjusted to Ωcm. Resistance value is 10^ThreeBelow Ωcm, when there is a pinhole in the photosensitive drum 100, during development, current concentrates in the pinhole, and the development voltage drops to make development impossible. On the other hand, the resistance value is 10⁹If it exceeds Ωcm, the toner carried on the developing roller 2 is likely to be charged up, so that the coating state of the toner on the developing roller 2 becomes unstable and the coating amount is insufficient. Further, the developability is lowered and the image density is also lowered.
[0042]
In this embodiment, a conductive polyamide in which a low hardness and conductive LTV layer is formed as an elastic layer on a stainless steel core, and carbon and polyamide resin particles are dispersed in polyamide resin as a charge imparting layer on the surface. The developing roller 2 was configured by forming a resin coat layer.
[0043]
The hardness of the developing roller 2 was about 40 ° in Asker C, the surface roughness was about 10 μm in Rmax, and about 7 μm in Rz (JIS B0601).
[0044]
As shown in FIG. 1, intrusion amount regulating rollers 3 are attached to the shafts at both ends of the core of the developing roller 2. In this embodiment, the outer diameter of the rollers 3 is set to 15.5 mm. The penetration amount of the developing roller 2 into the photosensitive drum 100 was set to about 250 μm.
[0045]
A toner supply roller 4 is installed on the opposite side of the developing roller 2 from the photosensitive drum 100. The toner supply roller 4 is disposed in contact with the developing roller 2 and is driven to rotate at a predetermined rotational speed in the Z direction in the figure. In the present embodiment, as will be described later, a spherical low-melting-point polymerization toner is used as the non-magnetic toner T, and the toner supply roller 4 has an outer diameter in order to supply the toner to the surface of the developing roller 2. An insulating urethane sponge roller with a hardness of 16 mm and a hardness of 10 degrees (Asker C) was used, and this was placed in contact with the developing roller 2 with an intrusion amount of about 100 μm.
[0046]
The toner hopper unit 1a of the developing device 1 is provided with a toner agitation unit 5. The agitation unit 5 rotates in the direction of arrow W in the drawing to convey the nonmagnetic toner T in the hopper unit 1a while agitating. The toner is supplied to the developing unit 1b through the opening 1d of the partition wall 1c.
[0047]
Above the developing roller 2 of the developing device 1, a developing blade 6 is installed as a developer amount regulating member, and this developing blade 6 has a predetermined contact pressure at a position downstream of the toner supply roller 4 in the rotational direction. In contact with the counter. The developing blade 6 regulates the non-magnetic toner T carried on the developing roller 2 to form a predetermined amount of toner layer, and gives a predetermined amount of frictional charge by frictional charging.
[0048]
As the developing blade 6, a phosphor bronze thin plate provided with an elastic body having a charging characteristic opposite to that of the toner T such as urethane rubber or LTV at a contact portion with the developing roller 2, and the surface of the elastic body is a toner. A material coated with a resin such as a polyamide resin having a high charge-imparting property with respect to T, or a stainless steel thin plate having a distal end bent into an L shape as shown in FIG. 1 can be used. This developing blade made of a thin stainless steel plate is used with the bent portion at the tip thereof in contact with the surface of the developing roller 2.
[0049]
In this embodiment, in order to reduce the rubbing force between the developing roller 2 and the developing blade 6 as much as possible while increasing the charge imparting property to the toner T by the developing blade 6, The stainless steel plate which bent the front-end | tip part of was used. The thickness was 100 μm, and the contact pressure of the bent portion to the developing roller 2 was about 15 g / cm as linear pressure.
[0050]
The characteristic feature of the present invention is that the toner circulation control means 7 is provided in the vicinity of the upper side of the toner supply roller 4 as shown in FIG. In this embodiment, the toner circulation control means 7 is formed of a plate-like body having a rectangular cross section and extending in the longitudinal direction of the toner supply roller 4, and is disposed in non-contact with the toner supply roller 4. The toner circulation control means 7 is a member for controlling the toner circulation. As shown in FIG. 2, the toner circulation control means 7 is located above the toner supply roller 4 between the developing roller 2 and the toner circulation control means 7. A is formed. In this embodiment, the toner circulation control means 7 is formed of a resin made of the same material as the casing of the developing device 1 (in this embodiment, an ABS resin containing glass fiber). The material may be anything and may be a metal member such as stainless steel.
[0051]
In FIG. 2, the center of the developing roller 2 (center of the core) is taken as the origin O, and the x-axis is drawn in the horizontal direction and the y-axis is drawn in the vertical direction to consider the xy coordinates. If the center of the toner supply roller 4 (center of the core) is Q, the center Q of the toner supply roller 4 needs to be positioned at least in the first quadrant, the fourth quadrant, and preferably the fourth quadrant of the xy coordinates. It is. This is because if the toner supply roller center Q exists in this area, the toner can be held in the toner circulation area A by the gravity of the toner itself.
[0052]
The location of the toner circulation control means 7 will be described with reference to FIG. As shown in FIG. 2, considering the upper horizontal tangent line α on the circumferential direction of the toner supply roller 4, the toner circulation control means 7 crosses the tangent line α from the lower side to the upper area of the tangent line α. It is preferable to arrange in a protruding manner. Thereby, the toner circulation area A can be formed between the developing roller 2 and the toner circulation control means 7 on the upper side of the toner supply roller 4 as described above.
[0053]
When the toner circulation control means 7 is arranged in a region below the tangent α that does not intersect the tangent α, that is, in a range below the height of the toner supply roller 4 from the bottom surface 1e of the developing portion 1b shown in FIG. The toner circulation area is limited to a narrow area A ′ below the height position (tangent line α) of the toner supply roller 4 between the developing roller 2 and the toner supply roller 4 as in the conventional developing device. The effect of the invention is reduced. On the other hand, when the entire toner circulation control means 7 is positioned above the tangent line α, if the distance from the toner supply roller 4 at the tip of the toner circulation control means 7 is about 5 mm or more, the toner is likely to fall out from the gap. Therefore, it is difficult to maintain the toner circulation area A.
[0054]
Therefore, even if the toner circulation control means 7 is located on the upper side crossing the tangent line α, or on the upper side without intersecting, the tip of the toner circulation control means 7 may be within a distance of about 5 mm from the toner supply roller 4. preferable.
[0055]
The developing device 1 can be suitably used for a general reversal developing type image forming apparatus (for example, a page printer such as an LBP or LED). In this embodiment, an image is formed under image output conditions in which the charging potential of the photosensitive drum 100 is −650 V, the potential of the exposed portion on the photosensitive drum 100 is −100 V, and the developing voltage applied to the developing roller 2 is DC-350 V. Image evaluation was performed. This will be described later.
[0056]
Next, the nonmagnetic one-component toner T used in the present invention will be described. In this example, a polymerized toner having a low melting point, a spherical shape, and excellent transferability and fixability was used. The degree of sphericalness of the toner can be indicated by using toner shape factors SF-1 and SF-2.
[0057]
In the present invention, the shape factors SF-1 and SF-2 are FE-SEM (S-800) manufactured by Hitachi, Ltd., and 100 toner particle images are randomly sampled, and the image information is obtained via the interface. Then, it was introduced into an image analysis apparatus (Luxex 3) manufactured by Nicole and analyzed, and defined as a value obtained from the following equation.
[0058]
SF-1 = {(MXLNG)²/ AREA} × (π / 4) × 100
SF-2 = {(PERI)²/ AREA} × (π / 4) × 100
Where MXLNG: absolute maximum length, AREA: toner projected area,
PERI: Circumference length
The toner shape factor SF-1 indicates the degree of sphericity of the toner, and when it is larger than 140, the shape gradually changes from spherical to irregular. SF-2 indicates the degree of unevenness on the toner surface. If this is larger than 120, the unevenness on the toner surface becomes remarkable.
[0059]
The nonmagnetic toner T used in the present invention preferably has a weight average particle diameter of 3 to 10 μm, a shape factor SF-1 of 100 to 140, and SF-2 of 100 to 120. In this example, a negative non-magnetic toner having a weight average particle diameter of 7 μm, SF-1 of 130, and SF-2 of 120 was used.
[0060]
The weight average particle diameter of the toner can be measured by various methods. In the present invention, a multisizer manufactured by Cole Counter Co. was used for the measurement.
[0061]
Next, the operation principle and effect of the developing device of this embodiment will be described with reference to FIGS. 3 and 4 are explanatory views showing the flow of toner in the vicinity of the toner supply roller. FIG. 3 shows the case of the developing device of this embodiment, and FIG. 4 shows the case of the conventional developing device.
[0062]
In the conventional developing device, the frictional force between the developing roller 2 and the toner supply roller 4 is reduced by reducing the outer diameter of the toner supply roller 4 or reducing the amount of the toner supply roller 4 entering the developing roller 2. 4 is reduced, the triboelectric charge amount of the toner T decreases in the sliding area between the developing roller 2 and the toner supply roller 4 indicated by B in FIG. Therefore, the triboelectric charge amount of the toner T in the toner circulation D generated from the rubbing region B is reduced by the rotation operation of the developing roller 2 and the regulating operation of the toner on the surface of the developing roller 2 by the developing blade 6. In addition to this, in the conventional apparatus, as indicated by an arrow C in FIG. 4, the circulation of new toner T supplied from the toner hopper 1a by the stirring means 5 occurs, and the developing roller 2 and the toner supply roller The average charge amount of the toner T in the vicinity of the rubbing region B with the toner 4 is further reduced, and the average charge amount of the toner having a charge amount that can be carried on the surface of the developing roller 2 by the mirror force is further reduced. .
[0063]
As a result, as described in the conventional example, a necessary amount of sufficiently charged toner cannot be ensured on the developing roller 2, and the density of the output image is lowered to obtain a high-quality output image. difficult.
[0064]
This tendency can be seen in the conventionally used pulverized toner, but is particularly remarkable when a spherical toner such as the above-described polymerized toner is used. This is because the spherical toner is superior in slidability of the toner itself as compared with the pulverized toner, and the reduction amount of the frictional charge amount is considered to be large.
[0065]
In contrast, in the present embodiment, as shown in FIG. 3, since the toner circulation control means 7 is provided, the new toner T supplied from the toner hopper 1a to the developing unit 1b by the stirring means 5 As indicated by E1, since the toner circulation control means 7 temporarily blocks the flow, a large amount of new toner T is prevented from flowing into the toner circulation area A and becomes a small amount of flow E2 into the toner circulation area A. Inflow.
[0066]
In this toner circulation area A, toner circulation F is generated by the toner supply roller 4, the developing roller 2 and the developing blade 6. However, since a small amount of new toner T flows, the toner circulation area A is smaller than the conventional one. The rate at which uncharged toner is mixed in the toner circulation F in FIG. Further, since the toner circulation F can be prevented from diffusing into the toner hopper 1a by the toner circulation control means 7, it is possible to always ensure the toner circulation F in the toner circulation area A.
[0067]
As described above, in this embodiment, the toner T can be circulated many times by being put on the flow of the toner circulation F. Therefore, the chance of individual friction in the toner circulation F is increased, and the friction region B is increased. Even if the rubbing force on the toner is reduced, the triboelectric charge amount of each toner can be increased, and the average charge amount of the toner is also increased.
[0068]
As a result, the ratio of uncharged toner in the toner circulation area A can be reduced, and the ratio of the toner T having a charge amount that can be carried on the surface of the developing roller 2 by the mirror force is increased. Accordingly, the amount of toner carried on the surface of the developing roller 2 increases, and the toner coat amount (M / S) per unit area on the surface of the developing roller increases.
[0069]
An experiment was conducted to confirm the effect of this example. As described above, an image is formed under image output conditions in which the charging potential of the photosensitive drum 100 is −650 V, the potential of the exposed portion on the photosensitive drum 100 is −100 V, and the developing voltage applied to the developing roller 2 is DC-350 V. Image evaluation was performed. The peripheral speed of the developing roller 2 was increased by 180% of the peripheral speed of the photosensitive drum 100.
[0070]
The number of images formed is 6000, and the test environment is 26 ° C. and 60% Rh. The evaluation items are changes with respect to the toner coat amount M / S on the developing roller 2, the output image density of the solid black image, and the number of image fogged images formed in the non-image area on the photosensitive drum 100. These measurement methods or evaluation methods are as follows.
[0071]
The toner coat amount M / S on the developing roller was measured as follows. During the passing of the paper, the toner coat layer on the surface of the developing roller 2 is sucked and collected by the vacuum cleaner every about 500 sheets, and the weight of the collected toner is measured, and this is defined as M (mg). Next, the area of the suction area of the toner coat layer on the surface of the developing roller 2 is measured, and this is calculated as S (cm²). By dividing M by S, the toner amount M / S per unit area on the developing roller 2 was obtained. The results are shown graphically in FIG.
[0072]
The output image density was measured as follows. A solid black image was output every 250 sheets during the sheet passing, the image density was measured at 9 points in the image, and the average value of these was obtained to obtain the image density. A Macbeth densitometer was used for the measurement. The results are shown graphically in FIG.
[0073]
Evaluation of image fogging in the non-image area on the photosensitive drum was performed as follows. A solid white image is output every approximately 500 sheets while the paper is passing, the operation of the image forming apparatus is stopped, and the Mylar tape is pressed against the developed surface of the photosensitive drum 100, so that the fog toner on the surface adheres to the Mylar tape. The tape with the fog toner attached thereto was pasted on a white paper, and the reflectance H1 was measured using a densitometer TC-6DS manufactured by Tokyo Denshoku Co., Ltd. Further, the same mylar tape that was not used as a reference tape was pasted on a white paper, and the reflectance H0 was measured. Then, the amount of fog toner on the photosensitive drum was obtained by calculation of H1−H0. The measurement was performed 6 times, and the average value was defined as the fog toner amount on the photosensitive drum. The results are shown graphically in FIG.
[0074]
5 to 7 also show the results of the conventional example in addition to the first embodiment. This conventional example is a result when the developing device of FIG. 1 is used in a state in which the toner circulation control means 7 is removed, and is the same as described above.
[0075]
As is apparent from FIG. 5, in this embodiment, the toner coat amount M / S on the surface of the developing roller 2 tends to be slightly reduced at the initial stage of image formation, but significantly from the initial stage of image formation as compared with the conventional example. A sufficient developing amount is obtained from the initial stage under the condition that the circumferential speed difference of the developing roller 2 used in this embodiment is 180% with respect to the photosensitive drum 100.
[0076]
In this embodiment, the toner amount of the solid black image on the photosensitive drum 100 is about 0.63 mg / cm which is sufficient even as described in the conventional example.²Degree can be obtained. Accordingly, as shown in FIG. 6, the output image can be greatly improved as compared with the conventional example. Even if the sliding force between the developing roller and the toner supply roller is reduced, the image fog increases and the toner is increased. A high-quality image could be output without accelerating degradation and reducing image density.
[0077]
As shown in FIG. 7, in this embodiment, there was no tendency for the amount of reversal fog on the photosensitive drum 100 to increase as compared with the conventional example. In the present invention, since the toner is supplied to the surface of the developing roller 2 with the mirror power generated by the charge amount of the toner itself, the charge amount distribution of the toner coated on the surface of the developing roller 2 becomes sharp. As a result, no increase in reversal fog due to an increase in reversal toner (positively charged toner) appears to be observed.
[0078]
Although the effect of the present embodiment has been described above, this effect was also recognized when the pulverized toner was used. Therefore, the present invention is effective not only for the pulverized toner having excellent charging characteristics due to the high frictional force of the toner itself, but also for the spherical toner which is difficult to obtain the charge amount due to the high sliding property of the toner itself. It has been confirmed that
[0079]
In this embodiment, since it is possible to reduce the rubbing force between the developing roller 2 and the toner supply roller 4, it is possible to improve the durability by preventing the deterioration of the toner itself, and the core / shell structure. Since the polymerized toner can be used under a low rubbing force, fixing at a low temperature is possible, and energy saving can be further promoted.
[0080]
As described above, according to this embodiment, when developing using a non-magnetic one-component toner, even if the rubbing force between the developing roller and the toner supply roller is reduced, the developing roller is always on the developing roller. The required amount of toner can be secured, and development can be performed satisfactorily without causing toner deterioration or image fogging, and a high-quality output image can be stably obtained.
[0081]
Example 2
FIG. 8 is a sectional view showing another embodiment of the developing device of the present invention. In the first embodiment shown in FIG. 1, the toner circulation control means 7 of the developing device 1 is arranged in non-contact with the toner supply roller 4. However, in this embodiment, as shown in FIG. The toner circulation control means 8 is used in contact with the toner supply roller 4. The other configuration of the present embodiment is basically the same as that of the first embodiment, and the same reference numerals as those in FIG. 1 in FIG. 8 denote the same members.
[0082]
According to the present embodiment, the following new effects are produced in addition to the effects of the first embodiment. When the toner circulation control unit 8 is disposed in contact with the toner supply roller 4, the toner remaining after the toner supply roller 4 peels off from the surface of the developing roller 2 and is attached to the toner supply roller 4 is removed from the toner supply roller 4 by the toner circulation control unit 8. Can do.
[0083]
At this time, as shown in FIG. 9, if the opening 1d of the partition wall 1c of the developing device is opened to a position below the contact position of the toner circulation control means 8 with the toner supply roller 4, the toner supply The undeveloped toner removed from the roller 4 can be circulated from the developing unit 1b to the toner hopper 1a through the paths indicated by arrows F1 and F2 in FIG. 9 and collected in the toner hopper 1a.
[0084]
For this reason, on the upstream side of the rubbing region B between the developing roller 2 and the toner supply roller 4, it is possible to cool in the toner hopper 1a the toner remaining after development that has received frictional heat during peeling. As a result, compared to Example 1, it is possible to prevent heat accumulation of undeveloped toner and to prevent toner deterioration due to heat accumulation. Therefore, in this embodiment, the life of the developing device 1 can be extended with respect to toner deterioration.
[0085]
It has also been found that the following effects are obtained by the contact arrangement of the toner circulation control means 8.
[0086]
As shown in the first exemplary embodiment, the toner supply roller 4 contacts the developing roller 2 with a predetermined contact nip, and has a low hardness in order to reduce the contact pressure as much as possible. Required. Therefore, in general, the toner supply roller 4 is formed of a foamed sponge, and the surface thereof is also in a sponge state in order to improve both the toner removal performance on the surface of the developing roller 2 and the toner transportability to the developing roller 2. Is used.
[0087]
For this reason, a part of the toner on the toner supply roller 4 enters the sponge on the surface of the toner supply roller 4 in the contact nip with the developing roller 2, and thereafter, the toner remains on the toner supply roller 4. A situation occurs where it is held in a sponge near the surface. As a result, the same toner passes through the contact nip between the developing roller 2 and the toner supply roller 4 many times, and the deterioration of the toner proceeds by receiving a rubbing force each time.
[0088]
Although this deteriorated toner has permeated into the sponge on the surface of the toner supply roller 4, it slightly exudes due to the contact pressure in the contact nip between the developing roller 2 and the toner supply roller 4, and reaches the developing roller 2. May be supplied. According to the study by the present inventors, if the deteriorated toner is present on the developing roller 2, toner fusion is caused on the contact surface of the developing blade 6 with the developing roller 2, and therefore it is preferable to prevent the generation of the deteriorated toner as much as possible. .
[0089]
In contrast, in this embodiment, since the toner circulation control means 8 is brought into contact with the surface of the toner supply roller 4, the toner entering the sponge on the surface of the toner supply roller 4 is hit by the toner circulation control means 8. The toner that has been struck out is circulated to the toner hopper 1a and collected in the same manner as described above, and the toner is rubbed many times in the sponge on the surface of the toner supply roller 4. Deterioration due to can be prevented.
[0090]
According to the present embodiment, as in the first embodiment, when developing using a non-magnetic one-component toner, even if the rubbing force between the developing roller and the toner supply roller is reduced, it is always on the developing roller. A necessary amount of toner can be ensured and development can be performed satisfactorily without causing image fogging, and a high-quality output image can be stably obtained. Furthermore, toner deterioration can be prevented, toner fusion to the developing blade can be prevented, and the durability of the developing device can be further improved.
[0091]
Example 3
The toner circulation control means 7 and 8 of the first and second embodiments are rectangular in cross section and have a plate shape extending in the longitudinal direction of the toner supply roller 4, but in this embodiment, as shown in FIG. The toner circulation control means 9 having a curved cross-sectional shape was used. In this embodiment, in order to increase the effect of the toner circulation control means 9, the toner circulation control means 9 is brought into contact with the toner supply roller 4 as in the second embodiment.
[0092]
When contacting the toner supply roller 4 with the curved surface at the tip of the toner circulation control means 9, the contact nip with the toner supply roller 4 can be widened while maintaining a low pressure. It is possible to enhance the discharge effect of the toner that has entered inside without increasing the pressure. As a result, this example can achieve an effect that exceeds that of Example 2.
[0093]
In the above, the toner circulation control means 9 has a curved end surface as a whole, but it is sufficient that the side facing the toner supply roller 4 is curved. In addition, the entire toner circulation control means may be a round bar extending in the longitudinal direction of the toner supply roller 4.
[0094]
【The invention's effect】
As described above, according to the present invention, in a developing device using non-magnetic one-component toner, it is always necessary on the surface of the developing roller even if the rubbing force between the developing roller and the toner supply roller is reduced. By securing a sufficient amount of toner, good development can be performed without causing toner deterioration and image fogging, and a high-quality image can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a developing device of the present invention.
FIG. 2 is an explanatory diagram showing an installation position of toner circulation control means installed on the toner supply roller of the developing device of FIG. 1;
FIG. 3 is an explanatory diagram showing a toner flow in the vicinity of a toner supply roller of the developing device of FIG. 1;
FIG. 4 is an explanatory diagram showing a toner flow in the vicinity of a toner supply roller of a conventional developing device.
FIG. 5 is a graph showing a change in toner coat amount M / S on a developing roller with respect to the number of formed images in the developing device of FIG. 1 and a conventional developing device.
FIG. 6 is a graph showing a change in image density with respect to the number of formed images by development in the developing device of FIG. 1 and a conventional developing device.
7 is a graph showing a change in the amount of fog on the photosensitive drum with respect to the number of images formed by development in the developing device of FIG. 1 and a conventional developing device.
FIG. 8 is a cross-sectional view showing another embodiment of the developing device of the present invention.
FIG. 9 is an explanatory diagram showing a toner flow in the vicinity of the toner supply roller of the developing device of FIG.
FIG. 10 is a cross-sectional view showing still another embodiment of the developing device of the present invention.
FIG. 11 is a cross-sectional view showing a conventional developing device.
[Explanation of symbols]
1 Developer
1a Toner Hopper
1b Development section
2 Development roller
4 Toner supply roller
6 Development blade
7, 8, 9 Toner circulation control means
100 photosensitive drum

Claims (8)

A rotating developer carrier disposed in contact with or close to an image carrier on which an electrostatic latent image is formed, and a one-component developer for developing the electrostatic latent image is supplied to the developer carrier. A developer supply member made of a rotating elastic body placed in contact with the developer carrier, the developer supply member having a foam layer on the surface, and the developer carried on the developer carrier. A developer amount regulating member disposed downstream of the developer carrying member in the rotation direction of the developer carrying member, the developer carrying member, the developer supplying member, and the developer amount; In a developing device comprising: a partition wall that partitions a developing section provided with a regulating member and a toner hopper section that supplies developer to the developing section, the partition wall having an opening through which the developer passes;
A developer circulation control member is installed in contact with the upper portion of the developer supply member, and the developer circulates above the developer supply member by the rotation of the developer carrier and the developer supply member. Forming a developer circulation region partitioned by the developer carrier, a developer supply member and a developer circulation control member;
Developer is supplied to the developer circulation area from above the developer circulation control member from the toner hopper through the opening.
The opening is formed to a position below a contact position between the developer supply member and the developer circulation control member, and development is performed from within the foam layer by the contact of the developer circulation control member with the foam layer. The developing device , wherein the developer discharged and the developer removed from the developer supply member passes through the opening and can be collected from the developing portion to the toner hopper portion.   2. The developing device according to claim 1, wherein the developer circulation control member is arranged in such a manner that it intersects a horizontal tangent line passing through an upper surface of the developer supply member from the lower side and protrudes into a region above the tangent line.   The developing device according to claim 1, wherein a center of the developer supply member is positioned below a horizontal line passing through a center of the developer carrying member.   The developing device according to claim 1, wherein a cross-sectional shape at a tip of the developer circulation control member on the developer supply member side is a rectangle.   The developing device according to claim 1, wherein a cross-sectional shape at a tip of the developer circulation control member on the developer supply member side is a curved surface.   The developing device according to claim 1, wherein the developer circulation control member has a circular cross-sectional shape.   The developing device according to claim 1, wherein the developer supply member is a foamed sponge roller.   The developer supply member is used as a first developer supply member, and a second developer supply member that rotates to supply the developer to the developer supply member is provided. The second developer supply member includes the toner hopper portion. The developer circulation control member is located in a developer flow formed by supplying the developer to the first developer supply member by the second developer supply member. The developing device according to any one of items 7 to 7.

Images