JP2016109922A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress creep of a supply roller and stabilize supply of toner from the supply roller to a developing roller to prevent the occurrence of unevenly printed defective images.SOLUTION: A developing case 15 of a vertical type developing device stores a non-magnetic one-component developer including a toner having a particle diameter of 8 μm or less and circularity of 0.97 or more. The developing case 15 has an arcuate inner surface 15a formed along an outer peripheral shape of a supply roller 17. The arcuate inner surface 15a and supply roller 17 has a gap with a predetermined size formed therebetween. The supply roller 17 has a leveling member 26 in contact with its surface.SELECTED DRAWING: Figure 2

Description

The present invention relates to a developing device mounted on an image forming apparatus such as a copying machine, a facsimile, or a printer, and an image forming apparatus including the developing device.

A developing device mounted on an electrophotographic image forming apparatus has a developing roller as a developer carrier and a supply roller for supplying non-magnetic one-component toner (negative polarity) to the developing roller. In addition, the developing device includes a stirring member that conveys toner in the container in the vicinity of the supply roller, a developing blade as a developer regulating member that regulates the amount of toner on the developing roller, and the like. Since the developing roller contacts the photosensitive drum, it is formed of an elastic body.

The supply roller serves to supply toner to the developing roller and to remove the toner on the developing roller after development, and is also referred to as a “strip-off supply roller”. The roller portion of the supply roller is made of an elastically deformable sponge, and the toner on the developing roller is scraped off by the bubble structure on the surface of the sponge, and the toner conveyed in the bubble structure is electrically and mechanically developed. Rub to supply.

Since the supply roller has a bubble structure, toner tends to aggregate in the bubble structure. When toner aggregates in the bubble structure, circulation of the toner in the supply roller is hindered. If the apparatus is operated as it is in this state, a decrease in fluidity due to toner deterioration or an increase in adhesion between toners occurs, and the cohesive force prevents toner supply. As a result, there is a problem that toner supply cannot catch up with an image having a high density, and an image that gradually fades in the latter half of the solid image is generated.

In recent years, demands for higher image quality, lower environmental impact, etc. have become stronger, and the use of polymerized toner is increasing from the viewpoint of toner diameter reduction, shape control, and low-temperature fixing. Since the polymer toner has a spherical shape and a small diameter, it has high fluidity and is more likely to enter the bubbles of the supply roller. In addition, the polymerized toner can exist in a high density due to its small diameter, and the toner tends to aggregate into a bubble structure.

For this reason, for example, in the development of a non-magnetic one-component polymerized toner, the toner deteriorates with the passage of time, and the fluidity and charging performance decrease. At this time, in a state where the toner is clogged in the supply roller and the toner is pushed from above in the vertical development, the fluidity of the toner in the supply roller is lowered. For this reason, the toner aggregates around the supply roller, or the aggregated toner is solidified and packed as it is.

As a result, the amount of toner supplied from the supply roller to the developing roller is insufficient, and for example, density unevenness of the image occurs during solid printing. As described above, the increase in fluidity and aggregation due to the spheroidization and reduction in the diameter of the toner, and the resulting poor supply of toner, reduction in toner concentration, and generation of blurred images are major issues.

In order to prevent the blurred image, for example, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-5487, the supply roller 64 is prevented from being clogged by the diaphragm member 75, and the toner supply to the developing roller 45 is stabilized. The reduction of the image density is suppressed by the conversion (FIG. 2). Further, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-163789), the toner held by the stripping supply roller 11 is removed by the removing member 14 so as to suppress a decrease in image density by stabilizing the toner supply. (Fig. 1).

However, if the “squeezing member 75” or the “removing member 14” is provided, these members bite into the supply roller, and thus the supply roller may be creeped. In particular, as in the devices of Patent Documents 1 and 2, if the amount of biting of the “throttle member 75” or “removing member 14” into the supply roller is larger than the amount of biting of the developing roller relative to the supply roller, the deformation of the supply roller The amount becomes excessive and creep tends to occur. The amount of biting is described in claim 3 of patent document 1 and claim 5 of patent document 2.

Furthermore, if the devices of Patent Documents 1 and 2 are left in a high-temperature environment such as summer, the supply roller creeps and deforms with the "drawing member 75" or "removing member 14", even if the amount of biting is not excessive. A habit is generated on the supply roller. Then, only the part with the habit is not supplied with toner and reset (peeling off the toner from the developing roller) to the developing roller. This causes not only a blurred image but also a new defect factor such that the image falls out in a straight line in the horizontal direction (sub-scanning direction). This makes it difficult to store the developing device or process unit in a warehouse or the like.

Accordingly, an object of the present invention is to level the toner layer on the surface of the supply roller while suppressing creep of the supply roller, thereby stabilizing the toner supply from the supply roller to the developing roller, and generating uneven defective images. Is to prevent.

In order to solve the above problems, an image forming apparatus according to the present invention includes:
A non-magnetic one-component developer is accommodated in a case, the non-magnetic one-component developer contains toner having a particle size of 8 μm or less and a circularity of 0.97 or more, and a toner storage chamber storing the toner is an upper portion of the case A vertical developing device,
In the case,
A rotatable developing roller that forms a toner layer on the surface and makes contact with an image carrier on which an electrostatic latent image is formed to attach the toner of the toner layer to the image carrier and visualize the electrostatic latent image When,
A supply roller that has an elastic layer in contact with the developing roller on a surface thereof and supplies the toner to the developing roller by rotating, and collects the toner remaining on the developing roller on the elastic layer;
A leveling member that contacts the peripheral surface of the elastic layer of the supply roller and smoothes the toner layer attached to the peripheral surface;
The developing device is characterized in that the case has an arc-shaped inner surface along the outer peripheral shape of the supply roller, and the arc-shaped inner surface is separated from the peripheral surface of the supply roller by a predetermined distance.

  According to the present invention, since the arc-shaped inner surface along the outer peripheral shape of the supply roller is formed on the inner surface of the case at a predetermined distance from the peripheral surface of the supply roller, the toner does not stay near the lower portion of the supply roller. The toner scraped off by the supply roller can be carried along the supply roller. The toner is leveled by bringing the leveling member into contact with the toner adhering to the peripheral surface of the supply roller including the scraped toner, and the toner having a uniform toner layer thickness is uniformly supplied to the developing roller. Thus, the uneven solid image can be eliminated.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a process unit attached to the image forming apparatus of FIG. 1. 1 is a schematic diagram showing a comparison between a developing device of Example 1-3 of the first embodiment of the present invention and a conventional developing device. It is an enlarged photograph which shows the surface of a supply roller, (a) is a new supply roller, (b) is a supply roller used over time without a leveling member, (c) is a supply roller used over time with a leveling member It is an enlarged photograph which shows each surface of. It is a figure which shows the difference of the image formed with the case where a smoothing member exists and the case where it does not exist. FIG. 9 is a partial cross-sectional view of a process unit in which a leveling member is divided and arranged in a circumferential direction and an axial direction with respect to a supply roller according to a second embodiment of the present invention. It is a side view of the supply roller which shows the state which divided and arranged the leveling member in two rows. FIG. 6 is a lower cross-sectional view of a process unit showing a third embodiment of the present invention, where (a) is a cross-sectional view before mounting on the image forming apparatus main body, and (b) is a cross-sectional view when mounted on the image forming apparatus main body. It is.

Hereinafter, first to third embodiments of the present invention will be described with reference to the drawings. Note that members, components, and the like having the same function or shape in each drawing are denoted by the same reference numerals as much as possible and will not be described after being described once.

(Schematic configuration of image forming apparatus)
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus including a process unit including a developing device according to first to third embodiments of the present invention. The overall configuration and operation of the image forming apparatus will be described with reference to FIG.

An image forming apparatus 1 shown in FIG. 1 includes a photoreceptor 2 as an image carrier that carries an image on the surface, and a charging unit 3 that is disposed around the photoreceptor 2 and charges the surface of the photoreceptor 2. The image forming apparatus 1 also includes an exposure unit 4 that exposes the surface of the photoreceptor 2 and a developing device 5 that visualizes the electrostatic latent image on the photoreceptor 2. The image forming apparatus 1 is also transferred with a transfer unit 6 that transfers a visible image (toner image) on the photoconductor 2 to a sheet S as a transfer sheet, and a cleaning unit 7 that cleans the surface of the photoconductor 2. Fixing means 8 for fixing the image on the paper S is provided.

The transfer means 6 includes an intermediate transfer belt 9, a primary transfer roller 10 that presses the intermediate transfer belt 9 against the photosensitive member 2, a secondary transfer roller 11, and a motor (not shown) that rotationally drives the intermediate transfer belt 9 in a predetermined direction. And have. In the present embodiment, among these, the photosensitive member 2, the charging unit 3, the developing device 5, and the cleaning unit 7 constitute a process unit 12 (see FIG. 2), and each process unit 12 is attached to the main body of the image forming apparatus 1. On the other hand, it is detachable.

The process unit 12 facilitates maintenance and replacement of the photoreceptor 2 and the developing device 5 and the like. Further, by applying the developing device of the present invention to the process unit 12, it is possible to easily realize and maintain good image quality without density unevenness. Further, the developing device of the present invention may be applied to the form of a developing unit or a toner unit.

A plurality of process units 12 having the above-described configuration are installed corresponding to, for example, yellow, cyan, magenta, and black colors. In the present embodiment, four process units 12 of each color are arranged in parallel along the moving direction (longitudinal direction) of the intermediate transfer belt 9.

Next, an image forming operation of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. When the image forming operation is started, the photosensitive member 2 is rotationally driven, and the surface of the photosensitive member 2 is uniformly charged by the charging unit 3 so as to have a predetermined polarity. Then, based on image information sent from a reading means (not shown) or print data sent from a PC (personal computer) electrically connected to the image forming apparatus 1, the surface (charged surface) of the photoreceptor 2. ) To form an electrostatic latent image. The electrostatic latent image is formed by exposure from the exposure unit 4.

The developing device 5 supplies toner to the electrostatic latent image formed on the photoreceptor 2 in this way. By supplying the toner, the electrostatic latent image is visualized (visualized) as a toner image. The toner images on the respective photoreceptors 2 are sequentially transferred to the transfer unit 6 (intermediate transfer belt 9), whereby a visible image is formed on the intermediate transfer belt 9.

Specifically, a visible voltage visualized on the surface of each photoconductor 2 by applying a predetermined voltage (primary transfer bias) from a high voltage power source (not shown) between the primary transfer roller 10 and the photoconductor 2. The image is primarily transferred onto the surface of the intermediate transfer belt 9. In this way, a visible image of each color is transferred in sequence on the surface of the intermediate transfer belt 9, thereby forming a full-color image.

The full-color image transferred and formed on the intermediate transfer belt 9 is subjected to secondary transfer onto the paper S by applying a predetermined voltage (secondary transfer bias) between the secondary transfer roller 11 and the intermediate transfer belt 9. Is done. Thereafter, the sheet S on which the toner image is secondarily transferred is conveyed to the fixing unit 8 and is heated and pressed to fix the toner image on the sheet S. The sheet S on which the image is fixed is conveyed further downstream of the fixing unit 8 and discharged (output) out of the image forming apparatus 1.

The above description is the image forming operation when a four-color full-color image is formed on the paper S. However, the present invention can be applied to devices other than the four-color full-color image forming apparatus. That is, a single-color image is formed using any one of the four process units 12, or a two-color or three-color image is formed using two or three process units 12. It is also possible. Of course, an image including five or more process units 12 can form a single color image to five or more colors by the same image forming operation as described above.

(Configuration of developing device)
Hereinafter, the configuration of the developing device 5 according to the first to third embodiments of the present invention will be described. As will be described later, the first to third embodiments are different in the arrangement form of the leveling member and the presence or absence of the separation function with respect to the supply roller.
<First Embodiment>
FIG. 2 shows the configuration of the developing device 5 according to the first embodiment of the present invention. The developing device 5 has a developing case 15. The developing case 15 is connected to the main body of the image forming apparatus 1 through an additional supply container that can be attached and detached via a toner supply path. When the amount of toner in the developing device decreases, a replenishment container filled with toner is installed and toner is replenished in a timely manner so that printing can be continued without interruption.

The toner replenishment timing can be supplied in a timely manner by providing a detection means for detecting that the toner in the replenishing container is exhausted or detecting that the toner in the developing device is low. Alternatively, the toner replenishment timing can be provided in a timely manner assuming consumption by providing a printing dot counter instead of the detection means. As a replenishment method, there are a method of replenishing a predetermined amount of toner a plurality of times at a predetermined timing, and a method of replenishing almost all toner in a replenishment container at once.

Inside the developing case 15, a toner storage chamber 13 that stores toner as a nonmagnetic one-component developer and a toner supply chamber 14 below the toner storage chamber 13 are disposed adjacent to each other in the vertical direction. A partition wall 22 of the developing case 15 is defined between the upper toner storage chamber 13 and the lower toner supply chamber 14. In the partition wall 22, a toner supply port 23 that connects the toner storage chamber 13 and the toner supply chamber 14 is formed.

The toner supply port 23 may be always open, but a replenishment amount adjusting member such as a shutter or a replenishing roll may be provided in the toner supply port 23. The supply amount adjusting member can be operated in a timely and appropriate amount by a signal from a level sensor 18 that detects the toner amount in the toner supply chamber 14, for example.

An agitator 24 is disposed in the toner storage chamber 13. The toner supplied to the toner storage chamber 13 is agitated and loosened by the agitator 24. On the other hand, in the toner supply chamber 14, a stirring auxiliary member 21, a developing roller 16, a supply roller 17, an end seal, a regulation blade 19, an inlet seal 20, a leveling member 26, and a stirring member 29 are disposed.

The agitating member 29 is disposed immediately below the toner supply port 23 and agitates the toner in the toner supply chamber 14. The agitation assisting member 21 is for assisting the agitation of the toner, and the agitation assisting member 21 is pressed against the back of the front end of the regulating blade 19. The front surface of the front end of the regulating blade 19 is in contact with the peripheral surface of the developing roller 16. The front end of the regulation blade 19 is pressed against the developing roller 16 by the contact pressure of the stirring assisting member 21.

The developing roller 16 is disposed such that a part of its peripheral surface is exposed from the developing case 15. The exposed peripheral surface of the developing roller 16 is in contact with the photoreceptor 2. The supply roller 17 is in contact with the developing roller 16 and is configured to convey the toner supplied from the toner supply chamber 14 to the developing roller 16. The end seal is configured to be in sliding contact with the axial end portion of the developing roller 16 and prevent toner leakage from the axial end portion.

The regulating blade 19 is in sliding contact with the peripheral surface of the developing roller 16 and regulates the amount of toner attached to the developing roller 16. The inlet seal 20 prevents toner leakage between the developing roller 16 and the developing case 15. The inlet seal 20 is disposed in the developing case 15 at a position located downstream of the portion where the developing roller 16 contacts the photoreceptor 2 in the rotational direction.

The surface of the supply roller 17 is formed of a material having an opening on the surface, such as a continuous foam (open cell) urethane. Thus, the toner conveyed into the toner supply chamber 14 is efficiently attached to the roller surface layer portion and taken in, and the attached toner can be stably supplied to the surface of the developing roller 16. Further, by using a continuous foam, it becomes easy to bite the leveling member 26 described later. In addition, the electrical resistance value of the supply roller 17 (surface layer portion thereof) is set to, for example, the third power to the fourth power Ω.

A voltage that is offset to the same polarity as the toner charging polarity with respect to the potential of the developing roller 16 is applied to the supply roller 17 as a supply bias. This supply bias acts in such a direction that the toner preliminarily charged at the contact portion with the developing roller 16 is pressed against the developing roller 16. Of course, the polarity of the voltage applied to the supply roller 17 is not limited to the above type. Depending on the type of toner, the voltage applied to the supply roller 17 can have the same potential as the developing roller 16 or the opposite polarity.

The developing roller 16 has a surface layer 25 having predetermined elasticity covered on the outer periphery. On the surface of the surface layer portion 25, a film (not shown) made of a material that is easily charged to a polarity opposite to that of the toner is formed. Here, in order to keep the contact state with the photoreceptor 2 as uniform as possible, the surface layer portion 25 is formed of, for example, a material (for example, rubber) having a JIS-A hardness standard of 50 degrees or less and has a developing bias. In order to act, the electric resistance value is set to the third power to the tenth power.

The surface roughness of the surface of the developing roller 16 (that is, the outer peripheral surface of the surface layer portion 25 of the developing roller 16) is set to, for example, Ra, 0.2 μm or more and 2.0 μm or less. Due to the surface roughness, a required amount of toner can be held on the outer peripheral surface of the surface layer portion 25 of the developing roller 16.

The regulating blade 19 is formed of a metal plate spring material such as SUS304CSP, SUS301USP, or phosphor bronze, for example, and a free end thereof is brought into contact with the peripheral surface of the developing roller 16. In this way, the regulating blade 19 is brought into contact with the peripheral surface of the developing roller 16 so that the toner layer adhering to the peripheral surface of the developing roller 16 is leveled to a predetermined thickness. At the same time, the toner is charged by friction charging between the developing roller 16 and the regulating blade 19.

The pressing force of the regulating blade 19 on the developing roller 16 is adjusted to a range of 10 N / m or more and 100 N / m or less in consideration of, for example, the pressure applied by the stirring assisting member 21. In order to assist frictional charging, a voltage that is offset to the same polarity as the charging polarity of the toner with respect to the potential applied to the developing roller 16 is applied to the regulating blade 19 as a regulating bias.

As the toner stored (filled) in the toner storage chamber 13 of the developing device 5, for example, a toner manufactured by a pulverization method or a polymerization method is used. Further, the toner manufactured by the above-described method can be used as an external additive having silica fine particles impregnated with silicon oil adhered thereto. By using the toner to which the silica fine particles are attached, even a small-diameter / spherical toner contributes to improvement in cleaning performance and transfer efficiency, and in turn, prolonging the life of the developing device 5 (the process unit 12 including the developing device 5).

The toner used has a circularity of 0.97 or more. In this embodiment, the circularity of the toner is defined as a circularity a by a value obtained from the following equation (1). The circularity a is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is perfectly spherical, and the circularity a becomes smaller as the surface shape becomes more complicated.
Circularity a = L ₀ / L (1)
(L ₀ : circumference of a circle having the same projected area as the particle image, L: circumference of the projected image of the particle)

The bottom wall of the developing case 15 located below the supply roller 17 is formed to have an arcuate inner surface 15 a along the peripheral surface of the supply roller 17. A gap of 1 to 3 mm is formed between the arcuate inner surface 15 a and the peripheral surface of the supply roller 17.

The leveling member 26 is fixed to the inner surface of the lower vertical wall of the developing case 15 near the supply roller 17. The specific form of the leveling member 26 can be, for example, a sheet-like object as shown in FIG. 3B or a triangular object as shown in FIG. Here, as will be described later, the leveling member 26 in the form of a sheet will be described as a first example, and the leveling member 26 in the form of a triangle will be described as a second and third example. Of course, the leveling member 26 can take a form other than the sheet-like object or the triangular object.

The leveling member 26 can be formed of various materials. For example, when the leveling member 26 is made of PET, the supply of toner to the developing roller 16 can be promoted. This is because PET is in a positive charge series with respect to polyester or styrene acrylic toner, and the toner can be charged by friction.

(Development operation)
Next, the developing operation of the developing device 5 according to the first embodiment of the present embodiment will be described with reference to FIG. In the developing device 5, the supply roller 17 is rotated in a predetermined direction, and the toner adhered to the surface thereof is conveyed to a contact portion with the developing roller 16, whereby the conveyed toner is supplied to the surface of the developing roller 16. To do. Then, by rotating the developing roller 16 in the same direction as the supply roller 17, the toner held on the surface passes through the nip portion with the regulating blade 19 and is conveyed to a position facing the photoreceptor 2.

As a result, the toner thinned to a predetermined thickness is supplied to the position facing the photoreceptor 2 by the rotation of the developing roller 16. Then, the photosensitive member 2 is rotated in the opposite direction to the developing roller 16, and the surface of the developing roller 16 is moved in the same direction as the surface of the photosensitive member 2 at a position facing the photosensitive member 2. As a result, the toner held in a thin layer on the surface of the developing roller 16 is changed into a developing bias applied to the developing roller 16 and a latent image electric field formed by the electrostatic latent image on the photoreceptor 2. In response, it moves to the surface of the photoreceptor 2 and the electrostatic latent image is developed.

In the embodiment of the present invention, as described above, the arc-shaped inner surface 15 a is formed on the bottom wall of the developing case 15 below the supply roller 17 with a gap of 1 to 3 mm from the supply roller 17. Further, a leveling member 26 that contacts the peripheral surface of the supply roller 17 is disposed on the downstream side of the arcuate inner surface 15a. Therefore, the toner scraped from the developing roller 16 by the rotation of the supply roller 17 can be carried along the arcuate gap of 1 to 3 mm. For this reason, the toner does not stay in the gap below the supply roller 17.

Further, the toner scraped off in this way and the toner originally attached to the surface layer of the supply roller 17 are brought into contact with the leveling member 26 by the rotation of the supply roller 17 so that the toner layer thickness is made uniform. . The toner layer having the uniform thickness is supplied to the developing roller 16 by the subsequent rotation of the supply roller 17. Therefore, there is no unevenness in toner replenishment to the developing roller 16, and the uneven solid image, which has been a problem in the past, is solved.

(Effect verification of 1st Embodiment and comparative example, and experimental conditions)
Table 1 shows results of verifying the effects of Example 1 of the first embodiment and the comparative example. The apparatus conditions and experimental conditions for the effect verification are as follows.
<Device conditions>
・ Experimental equipment: SPC730 (A3 color printer) vertical development
(Except for leveling member and toner, Example 1 and Comparative Example are common)
-Leveling member: 0.1 mm thick sheet-like material made of PET is installed with a biting amount of 0.9 mm (see FIG. 3B)
Toner: Comparative example is pulverized toner (particle size 8 μm, circularity 0.92)
Example 1 is a polymerized toner (particle size 6 μm, circularity 0.97, particle size 8 μm, circularity 0.97)
・ Development: Urethane-based elastic developing roller φ16 (shaft diameter φ8)
Urethane sponge supply roller φ14 (shaft diameter φ6)
Deviation amount of developing roller with respect to supply roller: 0.9 mm
・ Photoconductor: CT layer film thickness: 25 μm ・ Cleaning blade: Urethane rubber blade, counter contact / inlet seal: 100 μm thick urethane rubber sheet <Experimental conditions>
・ Temperature 27 ° C, humidity 80%, printing chart 2%, 1PJls paper feed, and 10,000 sheets printed, two A3 solid images were output and the second image evaluated. The presence or absence of toner spills was evaluated by the amount of toner accumulated in the inlet seal.
<Judgment criteria>
・ Solid density unevenness ... No solid second sheet unevenness ⇒ ○, other ⇒ ×
-Toner spillage: When toner is spilled by vibrating the developing device ⇒ ×, no spill ⇒ ○
Table 1 shows the improvement of the blur image according to the amount of biting of the leveling member 26 (0.9 mm).

From Table 1, it can be seen that even when polymerized toner (particle size 6 μm, circularity 0.97) is used, the solid density unevenness and toner spillage can be prevented under the conditions of Example 1 where the case gap is 3 mm or less. It was.

(Effect verification and experimental conditions of Example 2 and comparative example of the first embodiment)
Table 2 shows the results of effect verification of Example 2 and the comparative example of the first embodiment. The apparatus conditions and experimental conditions for the effect verification are as follows.
<Device conditions>
Experimental apparatus: SPC730 (A3 color printer) vertical development (same as Example 1)
-Leveling member: A PET-like triangular object with a leading edge having a tip angle R different from that of the sheet-like material of Example 1 is installed with a biting amount of 0.9 mm (see FIG. 3 (c)).
<Experimental conditions and criteria>
Solid density unevenness: The same creep as in Example 1. A new unit was left at a temperature of 40 ° C. and a humidity of 90% for 1 week, and then a 2 × 2 image was output to check whether horizontal streaks were generated. If streaks are generated, it is marked as x.

From Table 2, when polymerized toner (particle size 6 μm, circularity 0.97) is used and the case gap is 3 mm, creep occurs under the condition of the comparative example in which the leveling member 26 bites into 1.1 mm. To do. However, it was found that creeping can be prevented by setting the biting amount of the leveling member 26 to be equal to or less than the biting amount (0.9 mm) of the developing roller as in the two examples.

Further, when the leveling member 26 is triangular, solid density unevenness occurs even without creep under the conditions of the comparative example in which the contact width is 2 mm. However, it has been found that if the contact width is 3 mm or more, desirably 4 mm or more, a contact pressure reduction and a sufficient leveling effect can be obtained, so that creep and solid density unevenness can be prevented under the same conditions.

(Effect verification and experimental conditions of Example 3 and Comparative Example of the first embodiment)
Table 3 shows the results of the effect verification of Example 3 of the first embodiment and the comparative example. The apparatus conditions and experimental conditions for the effect verification are as follows.

<Device conditions>
Experimental apparatus: SPC730 (A3 color printer) vertical development (same as Example 1)
-Leveling member: Experiment by changing the level of roughness of the triangular resin material made of polyester resin with a tip angle R different from the sheet-like material of Example 1 (see FIG. 3 (c)). )
(Surface roughness is measured with KEYENCE Vk9500 50x lens, surface roughness)

<Experimental conditions and criteria>
・ Supply roller peeling: The developing unit was rotated for 5 hours in the environment of 30 ° C. and humidity 80% with the apparatus of Example 1, and the presence or absence of peeling or tearing of the supply roller was confirmed. When trouble occurs, it is marked as x.
-Torque: Rotate the development unit with the apparatus of Example 1 to measure the torque (If there is a torque 1.2 times greater than that without the leveling member, it is marked as x)

Others: A better effect was obtained when a PET (polyethylene terephthalate) sheet was used than when the leveling member was PTFE (polytetrafluoroethylene) or PVDF (polyvinylidene fluoride). This is considered to be because the polarity is positive with respect to the toner component and the toner is charged.

According to Table 3, in the comparative example in which the tip R shape of the leveling member 26 is 1 mmR, the supply roller 17 is bald due to the acute-angled shape of the R, but in the second rounder example of 3 mmR, the supply roller It was found that no baldness occurred because the stress of 17 was reduced. As for the surface roughness, there is no problem with the baldness and torque of the supply roller 17 from Ra1 μm to Ra5 μm, but the friction and load of the supply roller 17 increase at Ra10 μm, and it has been found that there is a problem with baldness and torque. .

(Surface condition of the supply roller after endurance)
Next, the surface state of the supply roller 17 will be described. FIG. 4A shows the surface state of a new supply roller 17. Compared to this surface state, the surface state of the supply roller 17 after endurance becomes a mottled state with aggregated toner or the like as shown in FIG. 4B when the leveling member 26 is not provided, as shown in FIG. The sponge surface is not seen at all.

However, when the leveling member 26 was installed, it was confirmed that a uniform toner layer was formed as shown in FIG. 4C, and that the sponge surface, which is the base of the toner layer, could be seen. From this, it can be seen that toner aggregation in the developing roller 16 is eliminated.

Further, according to the experiment of the third embodiment described later separately from the experiment (see Table 6), if the biting amount is less than 0.4 mm, the leveling effect is insufficient and a defective image (scratch occurs in the solid image). That is, the effect of improving the toner aggregation on the surface of the supply roller 17 is small, and an image A like the left half of FIG. 5 is obtained. On the other hand, when the bite of 0.4 mm or more was secured, an image B with improved blurring as shown in the right half of FIG. 5 was output.

However, if the leveling member 26 is bitten deeper than the amount of the developing roller 16 biting into the supply roller 17 (0.9 mm), the sponge of the supply roller 17 is scraped off by the corner of the tip of the leveling member 26. There has occurred. For this reason, the biting amount of the leveling member 26 in this embodiment is preferably 0.4 mm or more and less than the biting amount of the developing roller 16.

Second Embodiment
6A and 6B show a second embodiment in which leveling members are arranged in a distributed manner to prevent creep under a high temperature / high humidity environment. In this second embodiment, the leveling member 26 is divided into a plurality of parts in the axial direction as shown in FIGS. 6A and 6B, and divided into two rows in the circumferential direction. In FIG. 6B, the leveling members 26 are arranged in two rows of an upstream leveling member 26a and a downstream leveling member 26b. The upstream leveling member 26a is divided into nine sections, and the downstream leveling member 26b is divided into eight sections. doing. The leveling member 26 is configured in a so-called zigzag arrangement in which the downstream leveling member 26b is located on the downstream side between the upstream leveling members 26a. The division form is not limited to 8 divisions and 9 divisions in the two columns. It is also possible to have an arbitrary number of divisions of two columns or more.

As shown in FIG. 6A, the upstream leveling member 26 a is shorter than the downstream leveling member 26 b and bites into the supply roller 17 in a trailing contact. On the other hand, the downstream leveling member 26b is longer than the upstream leveling member 26a and bites into the supply roller 17 in a counter contact manner. The axial length A of the leveling members 26a and 26b is 5 mm or more, and the circumferential contact width B is 3 mm. Further, the gap C between rows of the leveling members 26a and 26b on the upstream side and the downstream side is 4 mm or more, and the gap D in the axial direction of the leveling member 26 is 2 mm or more and 5 mm or less.

(Effect verification and experimental conditions of Example 1 and comparative example of 2nd Embodiment)
Table 4 shows the results of effect verification of Example 1 of the second embodiment and the comparative example. The apparatus conditions and experimental conditions for the effect verification are as follows.

<Device conditions>
Experimental apparatus: SPC730 (A3 color printer) vertical development (same as Example 1 of the first embodiment)
・ Toner: Polymerized toner particle size 6 μm, circularity 0.98, particle size 8 μm, circularity 0.98
・ External additive: Uses small diameter, medium diameter, large diameter silica ・ Development: Urethane elastic developing roller φ16, urethane sponge supply roller φ14,
Biting amount 0.9mm
・ Cleaning blade: Urethane rubber blade, counter contact / photosensitive body: CT layer film thickness: 25 μm Photosensitive body, inlet seal: 100 μm urethane rubber sheet used

<Creep experiment conditions>
・ After leaving the cartridge in a packaged state at a temperature of 40 ° C. and a humidity of 90% for 1 week, 2 × 2 images and all solid images are taken.
・ 2% printing rate After printing 10,000 sheets with 1 sheet intermittent operation, 2 solid images are taken. ◎: All 2 solid images are OK. ○: The first of all solid images is OK.

From Table 4, from the comparative example of Example 1 with the same bite amount (0.9 mm) and contact width (3 mm), and the integrated comparative example (length: 310 mm), even if there is no problem in solid density unevenness, Although creep occurs, it has been found that by arranging the leveling member 26 at a length of 5 mm or more and at intervals of 2 mm to 5 mm, both solid density unevenness and creep due to high temperature standing can be prevented.

From the two comparative examples, it was found from the two comparative examples that if the leveling member 26 is 4 mm in length while the interval 3 mm remains the same, even if the contact width is 2 mm or 3 mm, there is no problem in creep even if there is no problem with creep. In addition, when the interval is 1 mm, creep occurs even if there is no problem with the solid density unevenness. Therefore, it was found that the interval is required to be at least 2 mm. However, since the solid density unevenness occurs when the interval is 6 mm, it has been found that the interval needs to be 5 mm or less.

(Effect verification of 2nd Embodiment and comparative example, and experimental conditions)
Table 5 shows the results of effect verification of Example 2 of the second embodiment and the comparative example. The apparatus conditions and experimental conditions for the effect verification are as follows.

<Device conditions>
Experimental apparatus: SPC730 (A3 color printer) vertical development (same as Example 1 of the first embodiment)
・ Toner: Polymerized toner particle size 6 μm, circularity 0.98, particle size 8 μm, circularity 0.98
・ External additive: Uses small diameter, medium diameter, large diameter silica ・ Development: Urethane elastic developing roller φ16, urethane sponge supply roller φ14, biting amount 0.9 mm
・ Cleaning blade: Urethane rubber blade, counter contact / photosensitive body: CT layer film thickness: 25 μm Photosensitive body, inlet seal: 100 μm urethane rubber sheet used

<Creep experiment conditions>
・ After leaving the cartridge in a packaged state at a temperature of 40 ° C. and a humidity of 90% for 1 week, 2 × 2 images and all solid images were taken.
・ 2% printing rate After printing 10,000 sheets with 1 sheet intermittent operation, 2 solid images are taken. ◎: All 2 solid images are OK. ○: The first of all solid images is OK.

From Table 5, it was found that creep was generated in the integrated type even though it was advantageous for preventing solid density unevenness. It was found that solid density unevenness and creep can be prevented when this is divided (length 5 mm, interval 3 mm). However, when the row spacing is set to 0, creep occurs, and thus it has been found that the row spacing needs to be at least 4 mm, preferably 5 mm or more, to prevent creep.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the leveling member 26 is configured to be separable from the supply roller 17 as a countermeasure against creep of the supply roller 17. Specifically, as shown in FIG. 7, a rivet-shaped leveling member push-up member 27 is disposed on the lower side wall of the developing case 15 near the supply roller 17 of the process unit 12.

Although at least one leveling member push-up member 27 is disposed, a plurality of leveling member push-up members 27 may be disposed at equal or unequal intervals according to the length of the leveling member 26 in the width direction. The leveling member push-up member 27 is inserted so as to be movable back and forth with respect to a through hole formed in the lower side wall.

A leveling member 26 is disposed on the inner surface of the lower side wall of the developing case 15. As this leveling member 26, for example, a polyester resin plate having a thickness of 0.3 mm can be used. The upper end of the leveling member 26 is fixed to the lower side wall, and the lower end is opposed to the peripheral surface of the supply roller 17. Then, the tip of the leveling member push-up member 27 is brought into contact with the back surface of the leveling member 26. The round head of the leveling member push-up member 27 protrudes outside the lower side wall.

On the other hand, as shown in FIG. 7B, a pressing portion 28 made of a plate member is disposed at the process unit 12 mounting position of the image forming apparatus 1 main body. The pressing portion 28 is disposed horizontally in the main body of the image forming apparatus 1, and both left and right end portions of the pressing portion 28 are fixedly supported by a pair of left and right side plates constituting the main body of the image forming apparatus 1.

When the process unit 12 is not attached to the main body of the image forming apparatus 1, the leveling member 26 is separated from the supply roller 17 as shown in FIG. The leveling member 26 may have an appropriate thickness so that the leveling member 26 is naturally separated by its own elasticity. Alternatively, an elastic member such as a spring may be separately provided on the inner surface of the lower side wall, and the leveling member 26 may be urged away from the supply roller 17 by the elastic member.

If the leveling member 26 is separated from the supply roller 17 as described above, even if the apparatus is exposed to a high temperature environment when the apparatus is stored in a warehouse or the like before the image forming apparatus 1 is shipped, the supply roller 17 There is no habit (creep) on the peripheral sponge.

On the other hand, when the process unit 12 is attached to the main body of the image forming apparatus 1, the pressing portion 28 on the main body side presses the round head of the smoothing member push-up member 27, so that the smoothing member push-up member 27 is placed inside the process unit 12. Push in the direction. As a result, the back surface of the leveling member 26 is pressed by the front end portion of the leveling member push-up member 27, and the front end portion of the leveling member 26 bites into the peripheral surface of the supply roller 17 at a predetermined depth.

Therefore, similarly to the first embodiment and the second embodiment described above, toner aggregation in the supply roller 17 can be eliminated. Note that such a separation function of the leveling member 26 can be realized by a configuration other than the attachment / detachment of the process unit 12, such as a configuration in which the leveling member 26 is directly and manually separated.

(Effect verification and experimental conditions of the example and comparative example of the third embodiment)
Table 6 shows results of effect verification of the example of the third embodiment and the comparative example. The apparatus conditions and experimental conditions for the effect verification are as follows.

<Device conditions>
Experimental apparatus: SPC730 (A3 color printer) vertical development (same as Example 1 of the first embodiment)
・ Developing roller: It is made of conductive urethane having a diameter of φ6 mm and a diameter of φ12 mm, and uses a slightly high-resistance elastic body having a volume resistance of 5 × 10 ⁶ Ω · cm or more.
Supply roller: Use a foamed urethane foam material made conductive by carbon having a diameter of 10 mm on a core metal having a diameter of 5 mm.
・ Leveling member: Polyester resin 0.3 mm thick plate (Mitsubishi Resin Corporation Dialermy)

<Experimental conditions>
-The developing cartridge is filled with 100% toner, and an image is printed after 1000 sheets of 1% intermittent printing on A4 paper in an environment of room temperature 23 ° C. and humidity 50%.
・ Development roller feed roller biting amount: 0.9 mm
-Feeding roller biting amount of leveling member: 0.1 mm, 0.3 mm, 0.5 mm, 0.8 mm, 0.9 mm

<Decision criteria for blurred images>
○: No change in density on the entire surface of the solid image △: Smudge can be confirmed slightly at the rear end of the solid image ×: Scratch can be clearly confirmed on the solid image

From the above conditions, as shown in FIG. 5 and Table 6, the effect of improving toner aggregation on the surface of the supply roller 17 is small when the biting amount is 0.3 mm or less, and an image A as shown in the left half of FIG. End up. On the other hand, when the bite of 0.4 mm or more was secured, an image B with improved blurring as shown in the right half of FIG. 5 was output. However, if the leveling member 26 is bitten deeper than the amount of the developing roller 16 biting into the supply roller 17 (0.9 mm), the sponge of the supply roller 17 is scraped off by the corner of the tip of the leveling member 26. Will occur. Therefore, the biting amount of the leveling member 26 in this embodiment is preferably 0.4 mm or more and less than the biting amount of the developing roller 16.

  Although the present invention has been specifically described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims. Needless to say.

1: Image forming apparatus 2: Photoconductor 3: Charging means 4: Exposure means 5: Developing apparatus 6: Transfer means 7: Cleaning means 8: Fixing means 9: Intermediate transfer belt 10: Primary transfer roller 11: Secondary transfer roller 12 : Process unit 13: Toner storage chamber 14: Toner supply chamber 15: Development case 16: Development roller 17: Supply roller 18: Level sensor 19: Regulator blade 20: Entrance seal 21: Agitation auxiliary member 22: Partition wall 23: Toner supply Mouth 24: Agitator 25: Surface layer portion 26: Leveling member 27: Leveling member push-up member 28: Pressing portion 29: Stirring member

JP 2003-5487 A JP 2004-163789 A

Claims (10)

A non-magnetic one-component developer is accommodated in a case, the non-magnetic one-component developer contains toner having a particle size of 8 μm or less and a circularity of 0.97 or more, and a toner storage chamber storing the toner is an upper portion of the case Is a vertical developing device disposed in the case,
A rotatable developing roller that forms a toner layer on the surface and makes contact with an image carrier on which an electrostatic latent image is formed to attach the toner of the toner layer to the image carrier and visualize the electrostatic latent image When,
A supply roller that has an elastic layer in contact with the developing roller on a surface thereof and supplies the toner to the developing roller by rotating, and collects the toner remaining on the developing roller on the elastic layer;
A leveling member that contacts the peripheral surface of the elastic layer of the supply roller and smoothes the toner layer attached to the peripheral surface;
The developing device according to claim 1, wherein the case has an arc-shaped inner surface along the outer peripheral shape of the supply roller, and the arc-shaped inner surface is separated from the peripheral surface of the supply roller by a predetermined distance.   2. The developing device according to claim 1, wherein a gap of 1 to 3 mm is formed between an arcuate inner surface of the case and a peripheral surface of the supply roller.   The developing device according to claim 1, wherein the leveling member is disposed so as to be able to contact and separate from the supply roller.   The developing device according to claim 1, wherein a circumferential length of a contact portion of the leveling member with respect to the supply roller is 3 mm or more.   The amount of biting of the leveling member with respect to the supply roller is less than or equal to the amount of biting of the developing roller with respect to the supply roller, and the contact width in the circumferential direction between the supply roller and the leveling member is 4 mm or more. 4. The developing device according to claim 1, wherein   The developing device according to claim 1, wherein the leveling member is divided and installed.   Each of the divided plurality of leveling members has a contact width in the circumferential direction of 3 mm or more, a length in the longitudinal direction of 5 mm or more with respect to the supply roller, and a biting amount with respect to the supply roller with respect to the supply roller. The developing device according to claim 6, wherein the developing device is less than a biting amount of the developing roller. The developing device according to claim 1, wherein a surface roughness Ra of a contact portion of the leveling member with respect to the supply roller is 5 μm or less.   9. The developing device according to claim 1, wherein the elastic layer of the supply roller is a conductive foamed urethane foam material.   An image forming apparatus comprising: a process unit having at least an image carrier supported by the case of the developing device according to claim 1 and detachable from the main body of the image forming apparatus.