JP6186925B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to a charging mechanism for a one-component developer.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.

One of the developers used for development is a one-component developer using a nonmagnetic toner.
The following systems are known as charging and layer forming systems for non-magnetic one-component developers.
First, an elastic body, a rigid body, or a layer thickness regulating blade that combines them is pressed against the developing roller, and the developer that passes through the contact portion is frictionally charged (charged). Second, the layer thickness regulating blade There is charge injection charging to apply a voltage between the developing roller and the developing roller. In addition to this, there is also known a method in which a developer is charged by direct irradiation with electrons / ions.

In the above-described method, since a very narrow range of the contact position between the layer thickness regulating blade and the developing roller is used as a region used for the frictional charging of the developer, a charge amount of a certain amount or more is given to the developer. May be difficult.
Therefore, an area where the supply roller is pressed against the developing roller may be used as the developer triboelectric charging area, in addition to the position described above.
FIG. 14 is a diagram showing a configuration in the case where the above-described pressure contact position between the developing roller and the supply roller is used as a frictional charging region.
In FIG. 14, a developing roller B pressed against the layer thickness regulating blade A and a supply roller C capable of frictionally charging the developer by contacting the developing roller B are provided in the developing tank.
In this configuration, the one-component developer frictionally charged at the contact position N with the supply roller C is pumped up to the developing roller B, and a layer is formed in a spiked state by a chain of toner frictionally charged by the layer thickness regulating blade A. Is done.
However, in this configuration, if the one-component developer before reaching the layer thickness regulating blade A is not charged to a certain amount or more, a chain between the developers cannot be obtained, and the layer formation by the layer thickness regulating blade is normal. Not done.

In order to solve such a problem, the developer moving toward the layer thickness regulating blade is frictionally charged at a position (contact nip portion) N where the developing roller B and the supply roller C are in contact with each other. Yes.
However, the length of the contact nip portion N between the rollers is influenced by the outer diameter size of each roller, and may be insufficient to hold the developer with a charge amount of a certain amount or more. .
For example, when the outer diameter of the developing roller B using the rubber layer material is 20 mm and the outer diameter of the supply roller C using the elastic foam member is 13 mm, the amount of biting at the contact nip portion is 2 mm. A contact nip width in the circumferential direction of only about 7.5 mm can be obtained.
In addition, when the counter rotation method is used, the moving direction of both rollers is reversed in the contact nip portion, so that it is easy to prevent the developer from entering.
For this reason, among the developers that have passed through the length of the contact nip portion N, the developer that does not have a predetermined charge amount or more is rebounded by the layer thickness regulating blade A, and no layer is formed. It stays in front of the layer thickness regulating blade indicated by symbol L1.

If the developer not having a certain amount of charge or more stays in front of the layer thickness regulating blade A, the charge amount of the developer moving on the developing sleeve B may be lowered. As a result, the charge amount of the developer moving on the developing roller B decreases, and the carrying amount necessary for development is obtained without the layer thickness of the developer passing through the layer thickness regulating blade A reaching the predetermined thickness. No state.
In addition, the developer is a material that deteriorates with time. Specifically, the external additive particles such as silica adhering to the toner base are peeled off and the toner contact medium is reduced, so that the charging property is reduced. descend. As a result, just using the contact nip width results in the same result as when the contact nip width is further reduced due to the fact that a satisfactory charge amount cannot be imparted to the developer.

The effect of such a decrease in the charge amount due to deterioration over time becomes prominent when a solid image with a large amount of developer consumption is formed.
FIG. 14B is a diagram showing a relationship between the charge amount of the developer layer on the developing roller B before passing through the layer thickness regulating blade A and the number of solid image printable sheets (solid follow-up sheet number). The amount of charge on the roller was measured with an electrometer as the amount of charge flowing into the roller during toner suction.
As is apparent from FIG. 14B, the charge amount in the toner layer is about −15 to −20 μC / g when new. With this charge amount, the solid follow-up number of sheets can be maintained at 30 to 50 sheets.
However, since the charge amount of the toner layer after passing through the contact nip after a long period of operation falls to about −3 to −4 μC / g, it becomes impossible to continuously print solid images.

Therefore, as a configuration for promoting frictional charging, a configuration has been proposed in which a contact member D that contacts the supply roller is provided at a position different from the contact nip portion of the supply roller, as shown in FIG. (For example, Patent Document 1).
However, in this configuration, since the contact member only bites into a part of the supply roller, the effect of expanding the frictional charging region is small. Moreover, as indicated by the arrows in FIG. 14D, the presence of the contact member hinders the movement of the developer that moves as the supply roller C rotates, and the toner that is the staying developer is fixed due to soft aggregation. Cause.

  In order to solve such a problem that the charge amount of the developer is insufficient, charged particles and toner are mixed in a hollow roller having a toner inlet / outlet formed on the peripheral wall, and the toner is mixed by stirring and mixing. A configuration for performing frictional charging has been proposed (for example, Patent Document 2).

  In addition, as a configuration using a hollow roller as a roller facing the developing roller, there is a hollow roller that can be deformed into a concave shape following the peripheral surface shape when contacting the peripheral surface of the developing roller (for example, Patent Document 3).

The configuration disclosed in the above patent document has the following problems.
The configuration disclosed in Patent Document 2 can eliminate the problems of the configuration disclosed in Patent Document 1, but requires a combination with charged particles during friction charging. That is, the configuration disclosed in Patent Document 2 stirs and mixes the toner used as the developer and the charged particles. In other words, the toner is charged after the same frictional charge as in the case of using a two-component developer. It is the composition which discharges. Therefore, there is a possibility that the charge using the developer itself cannot be obtained and the charge amount of the toner cannot be held above a certain amount depending on the mixing ratio of the charged particles and the toner.

Further, in the configuration disclosed in Patent Document 2, since the charging efficiency of the toner depends on the rotation speed of the hollow roller, the control becomes complicated due to the balance with the mixing ratio described above.
Further, the charged particles mixed with the toner may be discharged from the toner inlet / outlet when the outer shape changes due to deterioration with time, which hinders layer formation in the developing sleeve.
On the other hand, in the configuration disclosed in Patent Document 3, the length of the contact nip portion is increased by pressing the supply roller formed of a hollow roller against the developing roller. However, since the charge state is in accordance with the length of the contact nip portion, it is necessary to increase the length of the contact nip portion in order to increase the charge amount. For this reason, if the pressure contact force between both rollers is increased and the length of the contact nip portion is increased, the mechanical strength between the rollers will be affected. May be needed.

  An object of the present invention is to provide a configuration capable of reducing the image quality by ensuring a certain amount of triboelectric charge amount without adding a special component in view of the problem when charging a one-component developer. Another object of the present invention is to provide a developing device and an image forming apparatus.

In order to achieve this object, the present invention provides a developing roller that supplies a developer to an electrostatic latent image on a latent image carrier to process a visible image, and is pressed against the developing roller. A developing device that uses a one-component developer and includes a layer thickness regulating member that regulates the layer thickness of the developer that is carried, a supply roller that is capable of supplying the developer in pressure contact with the developing roller, The supply roller is a double-structured roller including an outer cylindrical member and an inner cylindrical member, and an elastic layer capable of capturing the developer is provided on at least an outer peripheral surface of the inner cylindrical member, and the outer cylindrical member Is provided with an opening made of a through-hole on the outer peripheral surface, and the outer cylindrical member and the inner cylindrical member can rotate with a linear velocity difference in the same direction or in the opposite direction, and the elastic layer includes the supply roller Uses material that can expand and contract in the radial direction Is, until reaching the opening moves while abutting the inner surface of the outer cylindrical member, there to be expanded and deformed to a developing device according to feature when facing the front Symbol opening.

  According to the present invention, it is possible to secure a frictional charging region along the circumferential surface of the roller by the developer entering between the dual-structure rollers. In particular, since there is a speed difference between the rollers, the developer trapped in the elastic layer located between the rollers can be increased in triboelectric charging opportunity and increased in charge amount.

It is a schematic diagram showing a process cartridge using a developing device according to an embodiment of the present invention. It is a schematic diagram for demonstrating the structure of the developing device which concerns on embodiment of this invention. FIG. 3 is a table showing specifications of an embodiment relating to the size and numerical aperture of an opening in a supply roller used in the developing device shown in FIG. 2. FIG. 4 is a diagram for explaining the relationship between the number of running sheets and the toner charge amount on the developing roller in the embodiment based on the specifications shown in FIG. 3. FIG. 3 is a diagram for explaining a configuration of a supply roller used in the developing device shown in FIG. 2. It is a figure for demonstrating the deformation | transformation state of the coating | coated member used for the supply roller shown in FIG. FIG. 7 is an enlarged view of a main part for explaining a moving state of the developer according to a deformed state of the covering member illustrated in FIG. 6. It is a figure for demonstrating the movement state of the developer with the supply roller using the coating | coated member shown in FIG. It is a figure which shows the principal part modification of the outer side cylindrical member used for the image development apparatus shown in FIG. It is a figure which shows the modification of the supply roller shown in FIG. It is a figure which shows another modification of the supply roller shown in FIG. It is a figure which shows the principal part modification of the supply roller shown in FIG. FIG. 2 is a schematic diagram for explaining the configuration of an image forming apparatus that uses the process cartridge shown in FIG. 1. It is a figure which shows the time-dependent change of the toner charge amount by the conventional structure of a developing device and this structure.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the embodiments shown in the drawings.
FIG. 1 is a diagram showing a process cartridge including a developing device according to an embodiment of the present invention.
In the figure, a process cartridge 100 accommodates a drum-shaped photosensitive member 2 as a latent image carrier and an apparatus used for image forming processing around the photosensitive member 2. As devices used for the image forming process, a charging device 3, a developing device 4, and a cleaning device 5 are provided.

The developing device 4 includes a developer tank that includes a developer storage chamber 101 and a developer supply chamber 102 that can store a one-component developer.
In the developer supply chamber 102, a developing roller 103, a layer thickness regulating member 104, and a supply roller 105 are arranged.
The developing roller 103 is a member that is used to supply a developer to the electrostatic latent image on the photoreceptor 2 to perform visible image processing.
The layer thickness regulating member 104 is a member used to regulate the layer thickness of the developer that is pressed against the developing roller 103 and carried on the developing roller 103.
The supply roller 105 is used as a member that can be pressed against the developing roller 103 and can supply the developer.

In the developer supply chamber 102, when the developer is introduced from the developer storage chamber 101, the developer is agitated by the rotatable agitator 106 to prevent aggregation and is supplied to the supply roller 105.
A partition wall 112 is provided between the developer storage chamber 101 and the developer supply chamber 102, and a supply port 114 is formed in the partition wall 112 for communicating the developer through both spaces. Yes.

The detail of each member mentioned above is demonstrated below.
A developing bias having a predetermined polarity is applied to the developing roller 103 from a power source (not shown).
An offset voltage having the same polarity as the developer charging potential is applied as a supply bias to the supply roller 105 with respect to the potential of the developing roller 103, and the pre-charged developer at the contact position with the developing roller 103 is applied. It is pressed against the developing roller 103.
However, the polarity of the voltage applied to the supply roller 105 is not limited to the same polarity as described above, and the same potential or polarity as the developing roller 103 can be reversed depending on the type of developer.

As the developing roller 103, a roller coated with an elastic rubber layer is used, and a surface coat layer made of a material that is easily charged to a polarity opposite to that of the developer is provided on the surface.
The elastic rubber layer is set to a hardness of 50 degrees or less according to JIS-A in order to keep the contact state with the photoreceptor 2 uniform, and further has an electric resistance value of 10 ³ to 10 ¹⁰ Ω in order to act a developing bias. Set to Further, the surface roughness of the elastic rubber layer is set to 0.2 to 2.0 μm in Ra so that a necessary amount of developer can be held on the surface.
The developing roller 103 can rotate counterclockwise and can convey the developer held on the surface to a position facing the layer thickness regulating member 104 and the photoreceptor 2.

  The layer thickness regulating member 104 is a cantilever member using a metal leaf spring material such as SUS304CSP, SUS301CSP, or phosphor bronze, and is in contact with the surface of the developing roller 103 with a pressure of 10 to 100 N / m. . The layer thickness regulating member 104 can be brought into contact with the developing roller 103 by the pressure described above, and can apply a charge due to frictional charging along with the thinning of the developer. Further, a voltage offset to the same polarity as the charging polarity of the developer with respect to the potential applied to the developing roller 103 is applied to the layer thickness regulating member 104 as a regulating bias in order to assist frictional charging.

The photosensitive member 2 is rotationally driven in a clockwise direction, and the surface of the developing roller 103 moves in the same direction as the traveling direction of the photosensitive member 2 at a position facing the photosensitive member 2.
The developer thinned on the developing roller 103 is conveyed to a position facing the photoconductor 2 by the rotation of the developing roller 103. The conveyed developer moves to the surface of the photoconductor 2 in accordance with the developing bias applied to the developing roller 103 and the latent image electric field formed by the electrostatic latent image on the photoconductor 2, and the electrostatic latent image can be formed. Visual processing.
A seal seal 115 is provided in contact with the developing roller 103 at a portion where the developer remaining on the developing roller 103 without being developed on the photosensitive drum 2 returns to the developer supply chamber 102 again. The developer is sealed so as not to leak out of the developing device.

  The process cartridge 100 is filled with toner manufactured by a pulverization method or a polymerization method. The toner can also use silica containing silicon oil as an external additive. The effects of using silicon oil-containing silica as an external additive include extending the life of the process cartridge, improving cleaning properties, and improving transfer efficiency.

FIG. 2 is a diagram showing the main parts of the photosensitive member 2 and the developing device 4 in the process cartridge 100.
In the figure, the supply roller 105 provided in the developing device 4 is a double-structured roller having an outer cylindrical member 105a and an inner cylindrical member 105b. The outer cylindrical member 105a has a through hole on the outer peripheral surface. An opening 105c is formed.

The number and size of the openings 105c can be selected in accordance with the amount of toner supplied. In this embodiment, the types shown in FIG. 3 can be selected.
In FIG. 3, the number of openings 105c and the type of size are shown as Examples 1-4.

  A bias is applied between the outer cylindrical member 105a and the inner cylindrical member 105b in the supply roller 105 to smoothly move toner used as a developer from the inner cylindrical member 105b toward the outer cylindrical member 105a. Specifically, there is a bias relationship in which the potential of the inner cylindrical member 105b is lower than the potential of the outer cylindrical member 105a.

  Since the present embodiment is configured as described above, the developer in the developer supply chamber 102 is placed in the gap between the opening 105c formed in the outer cylindrical member 105a of the supply roller 105 and the inner cylindrical member 105b. I can get in. As a result, the developer is frictionally charged by circulating in the circumferential region between the outer and inner cylindrical members 105a and 105b obtained by the double structure.

In this embodiment, the region necessary for the triboelectric charging of the developer becomes a space along the circumferential direction with a gap between the rollers having a double structure, and therefore, the developing roller 103 and the supply roller 105 shown in FIG. The friction charging opportunity is increased by enlarging the friction charging area in the contact nip portion that abuts.
Therefore, unlike charging friction at the contact nip portion, it becomes possible to increase the charge amount of the developer and to charge more than a certain amount without requiring a bias mechanism necessary for charging. . In addition, in this embodiment, it is not necessary to provide a contact member or the like for promoting the frictional charging of the developer to the supply roller 105 as shown in FIG. Therefore, the triboelectric charging property during movement can be improved.

FIG. 4 shows the experimental results comparing the developer charge amount based on the type of the opening 105c shown in FIG. 2 with the configuration shown in FIG.
As is clear from the figure, the charge amount of the developer on the developing roller 103 before the layer thickness is regulated by the layer thickness regulating member 104 is substantially constant even when the number of running sheets is increased to −15 μC / The result which maintained g or more was obtained. This appears as a significant difference from the configuration shown in FIG.
It is also possible to apply a bias between the two cylindrical members and perform bias charging in the preliminary charging.
In this case, the effect of frictional charging is further increased, and even when the external additive particles are peeled off from the toner base due to deterioration over time, a sufficient opportunity for frictional charging can be provided, so that −15 μC / g even after toner deterioration The above can be maintained.

Next, a configuration for improving the triboelectric charging efficiency of the developer using the supply roller 105 will be described with reference to FIG.
In FIG. 5, the supply roller 105 having a double structure is provided with an elastic layer capable of capturing the developer on at least the outer peripheral surface of the inner cylindrical member 105b, and when operating, both cylindrical members are either in the same direction or in the opposite direction. It is rotated with a speed difference.
FIG. 5A is an external view of the supply roller 105, and FIG. 5B is a cross-sectional view of the supply roller 105.
In FIG. 5A, an opening 105c made of a through hole is formed on the outer peripheral surface of the outer cylindrical member 105a, and the outer peripheral surface of the inner cylindrical member 105b is covered with a covering member as shown in FIG. 5B. 105 g is provided. Note that FIG. 5B shows a case where four openings 105c shown in FIG. 5A are provided at equal positions in the circumferential direction.

As shown by reference numeral 105g, the covering member is provided not only on the inner cylindrical member 105b side but also on the outer cylindrical member 105a side, and the outer surfaces of both cylindrical members 105a and 105b are covered with the covering members 105f and 105g. Yes.
The covering member 105g that covers the outer surface of the inner cylindrical member 105b is an elastic layer made of a material that can expand and contract in the radial direction of the supply roller 105 (for the sake of convenience, the same reference numeral 105g as the covering member is used).

As the cylindrical members 105a and 105b, metal processed products or resin molded products are used. Further, as the covering members 105f and 105g constituting the elastic layer, a member capable of capturing the toner of the one-component developer and capable of frictionally charging the captured toner between the developing roller 103 and the inner wall of the outer cylindrical member 105a is used. It is done.
Specifically, an elastic layer capable of capturing a developer is formed by using a foamed elastic member having a cell system of about 100 to 200 μm that can expand and contract in the radial direction of the supply roller 105, a so-called foamed member. doing. As a result, when the developer in the developer supply chamber 102 enters from the opening 105c formed in the outer cylindrical member 105a of the supply roller 105, it is captured in the open bubbles of the covering member 105g.
The covering member may be an elastic member capable of capturing and transporting toner used for the developer, for example, a sheet material such as a brush or felt in which a plurality of fibers are arranged in the circumferential direction, or a hairy member or Mylar. Can be used.
Further, the inner cylindrical member 105b and the outer cylindrical member 105a themselves may be made of an elastic body. In FIG. 5, reference numeral 105e indicates a rotation axis.

On the other hand, with respect to the speed difference between the cylindrical members, the following conditions are assigned as an example.
When the developing roller 103 has a speed of 200 mm / s, when the linear velocity of the outer cylindrical member 105 a is 200 mm / s in the same direction as the developing roller 103, the linear velocity of the inner cylindrical member 105 b is 100 mm in the same direction as the developing roller 103. The determined speed difference is assigned to / s.
The higher the speed of the outer cylindrical member 105a, the higher the supply capability. However, if the speed is too high, the toner falling speed cannot catch up and the supply roller 105 is idled. The inner cylindrical member 105b may be driven. As the linear velocity difference between the outer cylindrical member 105a and the inner cylindrical member 105b increases, the effect of increasing the frictional charging efficiency can be obtained.
That is, the developer trapped in the covering member 105g is rubbed in the open cell using the difference in speed generated between the outer cylindrical member 105a and the inner cylindrical member 105b and is frictionally charged.

FIG. 6 is a diagram for explaining the operation based on the specifications given to the outer cylindrical member 105a and the inner cylindrical member 105b described above.
In this figure, when the outer cylindrical member 105a and the inner cylindrical member 105b rotate and move with a certain speed difference, the inner cylindrical member 105b moves in the direction indicated by the arrow in the drawing and is positioned on the outer surface of the inner cylindrical member 105b. The covering member 105g, which is an elastic layer, also moves.
The covering member 105g, which is an elastic layer, contracts and deforms when moving on the inner surface of the outer cylindrical member 105a, and expands and deforms along the radial direction of the supply roller 105 when reaching the opening 105c of the outer cylindrical member 105a. Projecting outward from the opening 105c.
At this time, the covering member 105g expands and deforms due to the shape restoring force from the contraction deformation on the upstream side of the peripheral edge of the opening 105c in the moving direction, and the toner captured in accordance with this operation is blown out to the outside to blow out the outer cylinder. It can discharge | release toward the outer side of the member 105a. The covering member 105g contracts and deforms toward the inner surface of the outer cylindrical member 105a on the downstream side of the periphery of the opening 105c in the moving direction, and interlocks with the movement of the inner cylindrical member 105b. In FIG. 6, an arrow F1 indicates a direction in which the covering member 105g expands and deforms, and an arrow F2 indicates a direction in which the covering member 105g contracts and deforms.

FIG. 7 is a diagram illustrating a moving state of the developer according to the deformation of the covering member illustrated in FIG.
In the figure, in the non-opening portion of the outer cylindrical member 105a, the inner covering member 105g is compressed to the thickness D2 by the inner cylindrical member 105b and the outer cylindrical member 105a, and is restored to the thickness D1 in the opening 105c. For example, D1 is 2.5 mm and D2 is 0.5 mm.
The thickness D4 of the outer cylindrical member 105a is, for example, 1.5 mm, and the edge of the peripheral edge of the opening is rounded, for example, inside the cylinder so that it can slide smoothly with the covering member 105g located on the inner cylindrical member 105b side. Processing such as shape is given. As the shape of the end portion, a configuration in which the inner side of the cylinder is cut off at an acute angle so as to be a surface cut off obliquely may be used. In this case, a relationship is used in which the inner opening width of the surface facing the covering member 105g on the inner cylindrical member 105b side is larger than the outer opening width.
In FIG. 7, the toner moves inside the inner cylindrical member 105b and the outer cylindrical member 105a while being captured by the covering member 105g located on the inner cylindrical member 105b side, and follows the path shown by the arrow F3 in the opening 102c. Can move outside.

FIG. 8 is a diagram showing a developer moving state on the supply roller 105 using the deformation of the covering member 105g shown in FIG.
In the figure, the toner as the developer is taken into the supply roller 105 from the upstream side in the moving direction with respect to the opening 105c, and the coating member on the inner cylindrical member 105b side is utilized by utilizing the speed difference between both cylindrical members. It is rubbed in 105 g of open bubbles and triboelectrically charged. On the downstream side in the direction of movement of the developer with respect to the opening 105c, the coating member 105g expands and projects from the opening 105c, and the developer is pushed out and captured by the coating member 105f on the outer cylindrical member 105a side. When conveyed, the toner is supplied to the developing roller 103. The arrows shown in FIG. 8 indicate the moving direction of the developer.

FIG. 9 is a view showing a modification regarding the configuration of the outer cylindrical member 105a.
In the same figure, on the inner surface of the outer cylindrical member 105b, for example, convex ribs 105h having a height of 100 μm are formed obliquely at intervals of 200 μm to form a large number of uneven portions. The structure of the unevenness is set at an acute angle with respect to the rotation direction.
The direction of the groove is different in every 2 mm square, and the slanted convex rib 105h slides with the inner cylindrical member 105b, so that the toner that has entered the inner side of the outer cylindrical member 105a is even in the axial direction. To be stirred. The rib 105h may be concave, and the width of the groove may be a size that allows the toner between the grooves to be scraped off. Further, in order to uniformly agitate and triboelectrically charge the toner, a configuration in which the surface roughness of the inner peripheral surface becomes rough may be used.
Such a structure can be obtained by processing a flat plate surface and then deforming it into a cylindrical shape. In addition, it may be cast and drawn while rotating the central mold or may be cut. However, when pulling out the mold, if an oblique rib shape is created, the spiral shape is applied to the entire surface of the shaft, and the charged toner is not biased to either side of the axial direction. It is desirable to select the configuration.

Next, a modification of the main part relating to the supply roller 105 will be described.
FIG. 10 shows a cross-sectional shape of the outer cylindrical member 105a having an opening 105c at a corresponding position in the circumferential direction, and the inner cylindrical member (indicated by reference numeral 105b ′ for convenience) having the same center of rotation as the outer cylindrical member 105a. Shows an example of an elliptical shape.
In this configuration, when the toner that is the developer introduced from the outer cylindrical member 105a moves, a powder pressure difference can be generated due to a gap difference with the inner surface of the outer cylindrical member 105a. Therefore, the density of the moving toner Change can be used to improve fluidity. That is, the toner that moves due to the above-described gap difference has a coarse and dense portion, which improves the fluidity and stabilizes the supply performance unlike the case where the toner moves in a uniformly aggregated state.
When the movement state of the toner changes, when the opening 105c of the outer cylindrical member 105a faces and contacts the developing roller 103, a rotation phase in which the large diameter portion of the inner cylindrical member 105b faces the opening 105c is obtained. If the rotation speed is adjusted, toner supply performance can be secured.

FIG. 11 is a diagram illustrating another modification example of the main part of the supply roller 105.
In the same figure, the outer cylindrical member 105a has an opening 105c formed at one place in the circumferential direction as in the configuration shown in FIG. 5A, and the inner cylindrical member (indicated by reference numeral 105b1 for convenience) is an outer cylindrical member. The center of rotation is decentered with respect to the center of rotation of 105a.
In this configuration as well, as in the configuration shown in FIG. 10, a toner powder pressure difference is likely to occur due to a gap difference between the outer cylindrical member 105a and the inner cylindrical member 105b1. Thereby, the fluidity | liquidity of a toner can be improved and the stable supply property can be ensured.
Even in this configuration, when the opening 105c of the outer cylindrical member 105a faces the developing roller 103, a rotation phase in which the circumferential surface having the maximum outer diameter of the inner cylindrical member 195b1 faces the opening 105c is obtained. By adjusting the rotation speed, it is possible to ensure toner supply.

Next, a modified example regarding the configuration of the supply roller 105 will be described.
The modification shown in FIG. 12 is different from the other examples in that at least one opening 105c ′ is also provided in the inner cylindrical member 105b in addition to the opening 105c provided in the outer cylindrical member. This is characterized in that the developer can go in and out of the inner cylindrical member 105b through the opening 105c ′ on the inner cylindrical member 105b side.
In FIG. 12, the outer cylindrical member 105a and the inner cylindrical member 105b used for the supply roller 105 are both constituted by hollow rollers, and each of the rollers has openings 105c and 105c ′ at positions facing each other in the circumferential direction. Is formed.
In the above configuration, the developer can enter and leave the inside of the inner cylindrical member 105b in addition to the space between the outer cylindrical member 105a and the inner cylindrical member 105b. Therefore, in addition to the outer surfaces of the outer cylindrical member 105a and the inner cylindrical member 105b, the covering member shown in FIG. 5 is provided on the inner surface. This facilitates the circulation of the developer in the gap between the rollers.
When the openings 105c and 105c ′ formed in the outer cylindrical member 105a and the inner cylindrical member 105b coincide with each other in the circumferential direction, a developer flow path is formed as indicated by an arrow in FIG. Thereby, it becomes easy to take in and discharge the toner as the developer into the roller.
In this configuration, as described above, when the openings 105c and 105c ′ of the cylindrical members coincide with each other, a developer flow path is formed, and the developer flows through each opening.
For this reason, the rotation phases of the openings of the respective cylindrical members do not coincide so that the developer can be pushed out from the opening 105c of the outer cylindrical member 105a while avoiding the state where the openings coincide with the developing roller 103. It is necessary to be in a state.
Therefore, when the non-opening portion of the outer cylindrical portion 105a faces the developing roller 103, the rotation speed at which the rotational phase in which the non-opening portion of the inner cylindrical portion 105b faces the opening portion of the outer cylindrical portion 105a is adjusted. desirable.

Next, the configuration of the image forming apparatus 1 in which the process cartridge including the developing device according to the above-described embodiment is used will be described with reference to FIG.
An image forming apparatus 1 shown in FIG. 13 is a color printer including image forming stations capable of forming images of a plurality of colors, and the process cartridge 100 shown in FIG. 1 is arranged in each image forming station. .
The photoreceptors 2 provided in the process cartridge 100 are arranged along the extended surface of the intermediate transfer belt 7 used in the primary transfer device. The toner images formed on the photoreceptors 2 of the respective image forming stations are sequentially transferred to the intermediate transfer belt 7 via the primary transfer roller 8 with respect to the intermediate transfer belt 7 for each color.
The intermediate transfer belt 7 is a member that is wound around the driving roller 7A and the driven roller 7B and is movable in the direction of the arrow in the drawing. A secondary transfer roller 11 is disposed across the intermediate transfer belt 7 at a position facing the driven roller 7B located on one end side of the intermediate transfer belt 7 in the extending direction. The superimposed image is batch-transferred onto the sheet 10 conveyed from 13.
The sheet 10 on which the superimposed image is transferred is conveyed to the fixing device 12 and the toner is fixed by heat and pressure by melting and permeating action.
The paper feeding device 13 includes a paper feeding cartridge 13A capable of stacking paper and a feeding roller 13B.
In the paper feeding device 13, the uppermost paper among the stacked papers is fed out, and the fed paper is set to the registration timing by the registration rollers 14 arranged in the transport path, and then the secondary paper. Feeded to the transfer position.
The intermediate transfer belt 7 that has passed the secondary transfer position is prepared for the next image transfer after the untransferred toner is removed by the cleaning device 15. In FIG. 13, reference numeral 6 denotes a writing device.

According to the embodiment described above, the developer charging amount can be increased since the friction charging area of the developer can be secured to the length of the contact nip portion N formed by the developing roller 103 and the supply roller 105. It becomes possible. In addition, the developer trapped in the elastic layer can be moved while being rubbed by giving a speed difference between the rollers having a double structure, so that the triboelectric charge amount can also be increased.
Further, the expansion / contraction deformation of the elastic layer using the covering member allows the developer to be blown out at the time of expansion deformation in addition to the above-mentioned rubbing action, so there is not necessarily provided a bias mechanism or the like for discharging to the outside. Can ensure a stable supply. As a result, it is possible to prevent the image quality from deteriorating by maintaining the charge amount of a certain amount or more in the developer regardless of changes with time.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photoconductor 4 Developing apparatus 100 Process cartridge 103 Developing roller 104 Layer thickness control member
105 Supply roller 105a Outer cylindrical member 105b, 105b ', 105b1 Inner cylindrical member 105c Opening portion 105f, 105g Cover member 105h Rib

JP-A-10-213963 JP 2008-090100 A JP-A-11-249410

Claims (14)

A developing roller that supplies a developer to the electrostatic latent image on the latent image carrier to process a visible image, and the layer thickness of the developer that is pressed against the developing roller and carried on the developing roller is regulated. A developing device that uses a one-component developer and includes a supply roller capable of supplying the developer in pressure contact with the developing roller,
The supply roller is a double-structured roller having an outer cylindrical member and an inner cylindrical member,
At least an outer peripheral surface of the inner cylindrical member is provided with an elastic layer capable of capturing the developer,
The outer cylindrical member is provided with an opening made of a through hole on the outer peripheral surface,
The outer cylindrical member and the inner cylindrical member can rotate with a linear velocity difference in the same direction or in the opposite direction,
Said elastic layer, said collapsible material is used in the radial direction of the supply roller, until reaching the opening, moves while abutting the inner surface of the outer cylindrical member, opposed to the front Symbol opening a developing device for a feature to be expanded and deformed upon. The developing device according to claim 1, wherein a bias unit that moves the developer from the inner cylindrical member toward the outer cylindrical member is provided between the outer cylindrical member and the inner cylindrical member. .   The developing device according to claim 1, wherein the elastic layer is a foamed member having open cells.   The developing device according to claim 1, wherein the elastic layer uses a brush in which a plurality of fibers are arranged in a circumferential direction.   The developing device according to claim 1, wherein a peripheral edge of the opening is formed in a round shape on the inner surface of the outer cylindrical member.   3. The developing device according to claim 1, wherein a surface obtained by obliquely cutting an inner side of a surface facing the elastic layer is used as a peripheral edge of the opening on the inner surface of the outer cylindrical member.   The developing device according to claim 1, wherein a large number of concave and convex portions having acute angles with respect to a circumferential direction are formed on an inner surface of the outer cylindrical member.   The developing device according to claim 1, wherein the inner cylindrical member has an elliptical cross-sectional shape having the same rotational center as the outer cylindrical member.   The developing device according to claim 1, wherein the inner cylindrical member has a rotation center that is eccentric with respect to a rotation center of the outer cylindrical member. The opening, said have been eclipsed least one set to separate from the inner cylindrical member and the outer cylindrical member, the developer inside and outside of the inner cylindrical member can be out through the opening of the inner cylindrical member side The developing device according to claim 1, wherein The elastic layer is moved at a timing at which when the opening of the outer cylindrical member faces the developing roller, a rotational phase that expands and deforms from the opening and protrudes from the opening is obtained. An apparatus according to any one of claims 1 to 1 0.   The developing device according to claim 1, wherein a toner using oil-containing silica as a post-processing agent is used as the developer. The elastic layer moves while abutting against the inner surface of the outer cylindrical member and moves the developer while dragging until reaching the opening, and expands and deforms when facing the opening, thereby causing the developer to expand. developing equipment according to any one of claims 1 to 12, characterized in that it is possible to flick.   An image forming apparatus using the developing device according to claim 1.

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