JP2006091530A - Development apparatus and image forming apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development apparatus in which a developer charging amount and a developer amount on a developer carrier are stabilized, and an image forming apparatus using it. <P>SOLUTION: The development apparatus comprises a freely turnable developer carrier 1 carrying the developer on the surface and a charging regulation member 2 coming into contact with the developer carrier 1 freely turnably for regulating the charging of the developer on the developer carrier 1 by applied charging bias 5. The surface of at least one of the developer carrier 1 and the charging regulation member 2 is provided with a surface resin layer 3 containing only an ion conductive substance 4 as a conductant agent, in which volume resistivity is ≥1×10<SP>9</SP>Ωcm and an insulation resistance value per axial direction length 8 cm at the time of applying DC 500V is ≥4.9×10<SP>9</SP>Ω. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing device using a one-component developer and an image forming apparatus using the same.

  As a developing device used in a conventional image forming apparatus such as an electrophotographic method, a one-component developing method using a one-component developer consisting only of toner and a two-component developing method using a two-component developer consisting of toner and a carrier. Is known. Among them, the one-component development type developing device does not require mixing with the carrier, stirring, and toner concentration control, so that the device can be reduced in size and cost, and further, the developer can be replaced. Since it is unnecessary, it is increasingly used mainly in printers that require maintenance-free operation.

Further, in such a one-component developing type developing device, as a method for regulating the charging of the toner on the developing roll (developer carrying member), a layer thickness regulating member such as a blade is once brought into pressure contact with the developing roll. After regulating the layer thickness (toner amount), a method of regulating the toner charge amount is known by placing a charge regulating member such as a charging roll in contact with or spaced from the developing roll (for example, Patent Documents 1 to 3). 3).
In such a system, the toner is usually mechanically rubbed at the contact portion between the developing roll and an elastic toner supply roll that is disposed upstream of the developing roll and supplies toner. It adheres on the developing roll while being charged. Thereafter, the toner whose layer thickness is regulated by the layer thickness regulating member is further charged by the charge regulating member. Therefore, there is a problem that the toner melts and adheres due to sliding between the toner supply roll and the developing roll or pressure contact of the layer thickness regulating member. Further, it is difficult to say that the combined use of the layer thickness regulating member and the charge regulating member is preferable for reducing the cost of the apparatus.

Furthermore, Patent Document 2 describes a mode in which a charger such as a scorotron is used as a charge regulating member. However, since a complicated corona charger is used, the structure of the charge regulating member itself becomes complicated. Lowering the price becomes even more difficult. In Patent Document 3, the charge regulating member is separated from the developing roll and a high-voltage AC electric field is applied between them. The electrode of the charger serving as the charge regulating member includes conductive fine particles and It is also described that the volume resistivity containing ion conductive fine particles and the like is preferably 10 ⁷ to 10 ⁸ Ω · cm.
However, in these systems described above, the specific aspect of the charge regulating member in contact with the developing roll is not clarified. Furthermore, as disclosed in Patent Document 3, although an embodiment including conductive fine particles, ion conductive fine particles, and the like as an electrode of a charger is shown, there is no description or suggestion about evaluation of these additives in particular. The current situation is that nothing has been done.

JP 2003-57949 A (Embodiment of the Invention, FIG. 2) JP 2002-108099 A (first embodiment, FIG. 1) JP 10-232550 A (Embodiment of the Invention, FIG. 1) JP 2002-244430 A (Embodiment of the Invention, FIG. 1) JP-A-4-249270 (Example, FIG. 2) JP 2002-268332 A (Embodiment 1, FIG. 1) Japanese Patent No. 2586502 (Example, FIG. 1) JP 2002-304043 A (Example, FIG. 4)

For this reason, a method has been proposed in which the contact pressure of the layer thickness regulating member to the developing roll is reduced to reduce toner adhesion (see, for example, Patent Documents 4 to 8).
Patent Document 4 describes an aspect in which a layer thickness regulating member made of an elastic body that is in contact with the developing roll at a predetermined low pressure is used in order to reduce stress when the toner on the developing roll is uniformly thinned. Has been. However, even if such a layer thickness regulating member is used over a long period of time, there is a concern that a problem of toner fixation may occur.

In Patent Document 5, a flexible film having a volume resistivity of 10 ³ to 10 ⁸ Ω · cm is used as a charging member of a photosensitive member by mixing and dispersing metal powder or carbon black in a resin, and one end portion thereof. And a method of charging the photosensitive member by bringing the other free end side into contact with the photosensitive member. However, in this system, the same portion of the free end of the flexible film that contacts the photoconductor always comes into contact with each other, and the film is likely to deteriorate. In addition, paper dust and toner are likely to adhere to the contact portion. When such a configuration is applied to the developing roll, the amount of toner present at the contact portion is increased compared to charging on the photosensitive member. It becomes easy to invite.

Patent Document 6 describes a mode in which conductive particles such as carbon black are mixed and dispersed to have a volume resistivity of 10 ³ to 10 ¹⁰ Ω · cm as a film-like charging member that charges a photoreceptor. Further, in this patent document, by providing uniform unevenness on the film, it is possible to prevent fine deposits on the photosensitive member from adhering to the charging member side and to stabilize the charging characteristics over a long period of time. Further, this document proposes a method in which a developing tube is covered with a flexible tube having a diameter larger than this diameter, and only the flexible tube is in contact with the photosensitive member in the developing region with the photosensitive member. . Examples of the flexible tube include a sheet obtained by adding carbon or metal fine powder to a soft resin sheet made of a resin such as polycarbonate, nylon, and fluorine resin, a metal thin film such as nickel, stainless steel, and aluminum, and the resin sheet. It is noted that a laminated sheet with a metal thin film is used.
However, when conductive particles such as carbon black are used as the conductive agent in this way, it is difficult to maintain a uniform electric field in the nip area during charging, and the variation in the toner charge amount in the nip area becomes large. .

Patent Document 8 proposes a charging device using a metal hollow pipe such as stainless steel as a charging roll. In this charging roll, an elastic roll is provided outside the hollow pipe, and the surface of the elastic roll is covered with a tube (cylindrical electrode). The elastic roll is made by mixing and dispersing an ion conductive material or an electron conductive material in a foamable resin such as urethane, acrylic or nylon, or a synthetic rubber such as EPDM, silicone, NBR, ECH, or SBR. Examples of the conductive material include perchlorates (for example, lithium perchlorate, sodium perchlorate, ammonium perchlorate, etc.) and quaternary ammonium salts. Examples of the electron conductive material include carbon black, graphite, and conductive materials. Examples thereof include powders of conductive metals (for example, aluminum and stainless steel) and powders of conductive metal oxides (tin oxide, indium oxide, titanium oxide, etc.). Furthermore, the tube is obtained by mixing and dispersing the above-described ion conductive material and electron conductive material in a resin such as urethane, acrylic, nylon, and polyvinylidene fluoride.
However, in this configuration, since the inside of the tube is filled with an elastic roll, the contact pressure at the charge regulating portion is not necessarily weak, and the tube shown in the examples is made of polyamide resin. (Nylon) is a structure in which carbon black is mixed and dispersed, and no attention is paid to the difference between the ion conductive material and the electron conductive material.

  The present invention has been made to solve the above technical problems, and provides a developing device in which the developer charge amount and developer amount on the developer carrier are stable, and an image forming apparatus using the same. To do.

That is, in the present invention, as shown in FIG. 1, a developer carrying body 1 that is rotatable and carries a developer on the surface thereof, and is in contact with and applied to the developer carrying body 1 in a freely rotatable manner. A developing device including a charge regulating member 2 that regulates charging of the developer on the developer carrying member 1 with a charging bias 5, wherein at least one of the developer carrying member 1 and the charge regulating member 2 One surface contains only the ion conductive material 4 as a conductive agent, the volume resistivity is 1 × 10 ⁹ Ω · cm or more, and the insulation resistance value per axial length of 8 cm when DC 500 V is applied is 4.9 × 10 ^A surface resin layer 3 having a resistance of 9Ω or more is provided.

In such technical means, the developing device according to the present application uses a one-component developer, and the developer may be either magnetic or non-magnetic.
The developer carrier 1 may be either a roll or a belt as long as it can carry the developer. From the viewpoint of effective development, the developer carrier 1 faces the developer carrier 1. The mode of being arranged in contact with the image carrier on which the electrostatic latent image is carried is preferable from the viewpoint of effective development, but may be in a non-contact manner with the image carrier.

The charging regulating member 2 in the present invention may be either a roll or a belt as long as it is rotatable. However, a predetermined amount of biting is ensured from the viewpoint of effectively regulating charging on the developer carrier 1. Therefore, in the aspect in which the developer carrier 1 is a rigid body, the charging restriction member 2 is preferably an elastic body or a flexible tube. In the embodiment in which the developer carrier 1 is an elastic body (including a flexible tube), the charge regulating member 2 may be a rigid body.
Further, it is possible to simultaneously regulate the developer layer thickness on the developer carrier 1 by the charge regulating member 2, and in this case, on the developer carrier 1 upstream of the charge regulating member 2. The developer amount may already be regulated in layer thickness, or may not be regulated in particular.

In the present invention, in particular, at least one surface of the developer carrier 1 or the charge regulating member 2 has a volume resistivity of 1 × 10 ⁹ Ω · cm or more including only the ion conductive material 4 as a conductive agent. In addition, the surface resin layer 3 having an insulation resistance value of 4.9 × 10 ⁹ Ω or more per axial length of 8 cm when DC 500 V is applied is characterized. Thus, when only the ion conductive material 4 is included as a conductive agent in the surface resin layer 3, the ion conductive material is easily dispersed uniformly because of its good dispersibility in the resin, and the resistance distribution of the surface resin layer 3 is For example, as compared with the case where an electron conductive material is used as the conductive agent, it becomes more uniform, and uniform charging regulation to the developer becomes possible.

2A and 2B are schematic views showing a cross section of the surface resin layer 3. FIG. 2A is a state in which the ion conductive substance 4 is mixed and dispersed in the resin 5, and FIG. The state in which the electron conductive material 6 such as carbon black is mixed and dispersed is shown.
Unlike the electron conductive material 6, the ion conductive material 4 is excellent in dispersibility with respect to the resin (basically, it is dispersed at the molecular level), and thus is easily dispersed uniformly in the resin 5. When an electric field is applied, the current path in the resin 5 is uniform, and there is no particularly weak point, and a uniform current flows over the entire surface resin layer 3.

On the other hand, when the electron conductive material 6 is dispersed in the resin 5, the particle size of the electron conductive material 6 is also large, and cluster-like lumps are formed at various places. For this reason, when an electric field is applied to the surface resin layer 3, a portion having weak electric resistance characteristics (for example, a portion indicated by an arrow in the figure) is formed, and a uniform current is allowed to flow over the entire surface resin layer 3. I can't. Further, when the electron conductive material is used, for example, when the carbon black is used and when the metal fine particles are used, the change direction of the resistance value differs depending on the material used. That is, for example, since carbon black has semiconducting properties, a heat generation phenomenon occurs due to current when an electric field is applied, and the resistance tends to decrease, and there is a concern that it is difficult to perform stable charge control.
Therefore, when the surface resin layer 3 is used for electric field control (current control), the surface resin layer 3 in which the ion conductive material 4 is dispersed in the resin 5 can maintain more stable conditions.

In the present invention, at least one of the developer carrier 1 and the charge regulating member 2 is constituted by a flexible tube provided with the surface resin layer 3, and at least both of them are included in the flexible tube. If the back surface side of the flexible tube other than the charge regulation region in contact with the member is contact-supported by the support member, the stress applied to the developer in the charge regulation region is made use of the flexibility of the surface resin layer 3. Is reduced, and it becomes possible to further prevent the developer from sticking.
Further, a conductive layer is laminated on the back surface side of the front surface resin layer 3 so that a charging bias 5 for applying charging to the developer can be applied between the charge regulating member 2 and the developer carrier 1. In this case, the charging bias 5 can be more uniformly applied to the developer in the charge regulation region. The lamination with the conductive layer may be performed by, for example, a lamination configuration of a thin metal sleeve and the surface resin layer 3 or a method of forming a conductive layer on the back surface of the surface resin layer 3 by means such as physical plating.
Furthermore, in the vicinity of the charge regulation region on the back surface side of the front surface resin layer 3, if a conductive member to which a charging bias 5 for applying charge to the developer can be applied is provided, for example, the front surface resin layer 3 becomes a conductive layer. Even in the non-stacked mode, the charging bias 5 can be effectively applied to the developer.

Further, the charging bias 5 between the developer carrier 1 and the charge regulating member 2 preferably includes a direct current controlled by a constant current, so that the resistance of the surface resin layer 3 or the like is reduced due to environmental fluctuations or the like. Even if it changes, it becomes possible to provide a stable charging bias 5 to the developer.
Furthermore, if an alternating electric field is superimposed on the charging bias 5, the amount of charge on the developer can be further increased. The charge amount of the developer can be controlled by changing the peak-to-peak voltage of the AC electric field.

  In the present invention, in the above-described developing device, in a mode in which the developer carrying member 1 includes the surface resin layer 3, the charge regulating member 2 performs layer thickness regulation together with developer charge regulation. In this case, the charge regulating member 2 can be effectively bited into the developer carrier 1 and the layer thickness regulation can be effectively functioned. In this case as well, by applying a constant current-controlled DC electric field as the charging bias 5 and further superimposing the AC electric field, it is possible to increase the charge amount as in the above-described effect.

  Furthermore, the second embodiment of the developing device in the present invention may be as follows. In other words, the developer carrying body 1 that is rotatable and carries the developer on the surface thereof, and the developer carrying body 1 that is in contact with the developer carrying body 1 is rotatable and the charging of the developer on the developer carrying body 1 is regulated. A charge control member, and a charge control unit that variably controls a charge bias condition applied to the charge control member according to an environmental change, and at least one of the developer carrier 1 and the charge control member 2 The surface is composed of a surface resin layer 3 containing only the ion conductive material 4 as a conductive agent.

As described above, by changing the charging bias condition according to the environmental change, for example, the charging condition suitable for the temperature and humidity in the environmental atmosphere can be brought about, and the development characteristics can be further stabilized.
At this time, as the surface resin layer 3, the volume resistivity including only the ion conductive material 4 is 1 × 10 ⁹ Ω · cm or more, and the insulation resistance value per axial length of 8 cm when DC 500 V is applied is 4. By setting it to 9 × 10 ⁹ Ω or more, it becomes possible to maintain uniform charging conditions in the charge regulation region.
The present invention is also directed to an image forming apparatus including the developing device described above.

According to the present invention, since at least one of the developer carrying member and the charge regulating member is provided with the surface resin layer containing the ion conductive material as the conducting agent, the developer carried out between the developer carrying member and the charge regulating member When charging is regulated, it is possible to provide a developing device that can apply a uniform electric field to the whole and can regulate the amount of charge stably to the developer.
Further, at least one of the developer carrying member and the charge regulating member is provided with a surface resin layer using an ion conductive material as a conductive agent, and the charging bias is changed according to the environmental change of the charge regulating member. In the charging regulation of the developer performed between the developer carrying member and the charging regulating member, an electric field suitable for the environmental conditions can be uniformly applied to the whole, and the stable charging amount regulation to the developer can be performed. A possible developing device can be provided.
Further, by using these developing devices, it is possible to provide an image forming apparatus having stable developing characteristics.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 3 shows an image forming apparatus according to the first embodiment to which the present invention is applied.
In the figure, reference numeral 21 denotes a photoconductor that carries an electrostatic latent image made of an organic photoconductor that rotates in the direction of the arrow. The photoconductor 21 is charged by a charging device 22 such as a scorotron, and a laser writing device or the like. An electrostatic latent image is written by the exposure device 23 having an LED array. The written electrostatic latent image is formed as a potential image based on contrast with a high potential portion not exposed to light because the surface potential of the photosensitive member 21 exposed to light decreases.

In the developing device 30 according to the present embodiment, a toner that is a non-magnetic one-component developer is accommodated in a developing housing 31, and the toner is carried on a developing roll 32 as a developer carrying member. By applying a developing bias from 33, the developing roll 32 is held at an intermediate potential between the high potential portion and the low potential portion of the electrostatic latent image, and the image portion of the electrostatic latent image is developed with charged toner. It is what you do.
A toner supply roll 34 that supplies toner to the developing roll 32 is disposed behind the developing roll 32 at a position separated from the developing roll 32.

Further, the transfer device 26 is constituted by, for example, a transfer roll disposed in contact with the photoconductor 21, and applies a transfer bias in a direction in which a toner image on the photoconductor 21 is attracted by a bias power source 27, thereby causing the photoconductor 21 to be attracted. The upper toner image is transferred to the recording material 28.
The toner remaining on the photoreceptor 21 is removed by, for example, a doctor blade type cleaning device 29.
In this embodiment, the recording material 28 to which the toner image on the photosensitive member 21 is transferred is conveyed to the fixing device 50, and the toner image is fixed to the recording material 28 by the fixing device 50. The fixing device 50 has, for example, a heat roll method, and includes a heating roll 51 and a pressure roll 52. By passing the recording material 28 between the heating roll 51 and the pressure roll 52, the toner image is recorded. 28 is fixed.

  Here, the developing device 30 of the present invention will be described in detail with reference to FIG. In the drawing, a developing device 30 is disposed behind a developing roll 32 that rotates in contact with a photosensitive member 21 made of a metal such as stainless steel and is spaced from the developing roll 32 and supplies toner to the developing roll 32. A toner supply roll 34 made of a metal roll such as stainless steel is provided, and the developing roll 32 and the toner supply roll 34 are configured to rotate in the same direction (with direction) at the opposing portions thereof. The toner supply roll 34 is not limited as long as it can supply toner to the developing roll 32, and not only a metal roll but also an elastic foam can be used.

  Further, a toner hopper 35 for containing toner is provided behind the toner supply roll 34, and the toner is agitated by the agitator 36. The agitator 36 is provided with a resin shaft such as a PET (polyester) sheet on a resin shaft, and rotates in the toner hopper 35 so as to stir the toner and supply the toner to the toner supply roll 34 side. It has become.

Further, in the present embodiment, the toner charge amount on the developing roll 32 and the charge that regulates the toner amount are disposed downstream of the facing area between the developing roll 32 and the toner supply roll 34 at a position facing the developing roll 32. A roll 37 is provided in pressure contact with the developing roll 32. On the other hand, a scraping member 38 that scrapes off the residual toner on the developing roll 32 is provided upstream of a region where the developing roll 32 and the toner supply roll 34 face each other.
The developing roll 32 in the present embodiment is composed of a semiconductive resin in which an ion conductive material is mixed and dispersed as a conductive agent in a fluorine resin or a polyamide resin, and the volume resistivity is 10 ¹⁰ Ω · cm. A seamless tube 321 that can be rotated, and a conductive member 322 that is fixedly disposed therein, supports the seamless tube 321, and is connected to the bias power source 33. In addition, at the portion where the seamless tube 321 of the developing roll 32 is in contact with the charging roll 37 and the photosensitive member 21, the conductive member 322 is provided with a concave portion (A portion, B portion) so that the pressure contact with the seamless tube 321 is sufficiently performed. ing.
In the present embodiment, bias power sources 41 and 42 are connected to the charging roll 37 and the toner supply roll 34, respectively, and a predetermined bias is applied between the charging roll 37 and the developing roll 32 and between the toner supply roll 34 and the developing roll 32. It is to be applied. Reference numeral 39 denotes a cleaning blade for cleaning the toner adhering to the charging roll 37.

FIG. 5 is a partially enlarged view showing a pressure contact state between the developing roll 32 and the charging roll 37. The developing roll 32 in the present embodiment is in a state where the seamless tube 321 is fixed to a ring-shaped support member 323 made of metal or the like at both ends. The conductive member 322 described above is provided inside the support member 323, and one end of the conductive member 322 extends to the outside through a hole opened in the support member 323. Therefore, the conductive member 322 is connected to the bias power source 33 (see FIG. 4).
On the other hand, the charging roll 37 is composed of a metal roll 371 such as stainless steel, and a rubber roll 373 made of urethane resin fixed to the rotating shaft 372 of the metal roll 371 is provided at both ends of the metal roll 371. Yes. Since the rubber roll 373 is in a position facing the support member 323 of the seamless tube 321, the seamless tube 321 of the developing roll 32 rotates together with the support member 323 by the rotation of the charging roll 37. Further, since the seamless tube 321 and the charging roll 37 are maintained in pressure contact with each other with a predetermined biting amount d, the developing roll 32 is driven to rotate stably as the charging roll 37 rotates. Yes.

Next, the operation of the developing device 30 according to the present embodiment will be described with reference to FIG.
In the drawing, the toner stirred by the agitator 36 in the toner hopper 35 is supplied to the toner supply roll 34 side by the rotation of the blades of the agitator 36. The toner carried on the toner supply roll 34 is conveyed along with the rotation of the toner supply roll 34 and reaches a portion facing the developing roll 32. At this time, the toner on the toner supply roll 34 is developed by an electric field effect due to a supply bias (formed by the bias power supply 33 and the bias power supply 42) between the developing roll 32 and the toner supply roll 34 at the facing portion. A toner layer that is supplied to the roll 32 side and whose toner amount is substantially regulated is formed on the developing roll 32.

The toner supplied to the developing roll 32 reaches the nip area with the charging roll 37. At this time, the toner is charged by the constant current electric field by the bias power supply 41. Further, the toner leveling effect in the nip area also helps, and on the downstream side of the nip area between the developing roll 32 and the charging roll 37, a toner thin film having a predetermined toner charge amount and a predetermined toner amount is formed on the developing roll 32. A layer is formed.
Then, this thin toner layer is conveyed to a developing area in the nip area between the developing roll 32 and the photosensitive member 21, and in the developing area, development is performed by the developing bias from the bias power source 33, and the electrostatic latent image on the photosensitive member 21 is discharged. The image is visualized. Further, on the downstream side of the developing area, the residual toner that remains without being developed on the developing roll 32 is scraped off from the developing roll 32 by the scraping member 38. In the present embodiment, in the development area, the photosensitive member 21 and the developing roller 32 are in contact with each other with an appropriate contact pressure, which is useful for improving the image quality of the toner image on the developed photosensitive member 21.

Thus, in the present embodiment, the toner on the developing roll 32 can be made into a uniform thin layer, and the toner charge amount can also be controlled uniformly throughout. Further, the contact pressure between the developing roll 32 and the charging roll 37 is also reduced by using the seamless tube, and the stress applied to the toner is greatly reduced as compared with the case where an elastic body is used for the developing roll, for example. .
Therefore, the toner is hardly fixed, and a stable development performance can be maintained even when used for a long time.

FIG. 6 shows a charging roll 61 used in a developing device as a modification of the embodiment to which the present invention is applied. In this figure, as a mode of using the charging roll 61, unlike the above-described embodiment, the developing roll is a rigid body, and the charging roll 61 includes a seamless tube 611 as a surface resin layer. .
Therefore, the developing roll rotates, and the charging roll 61 that is in pressure contact with the developing roll is driven to rotate. Note that the photoconductor and the developing roll are spaced apart.
The charging roll 61 in this example has a configuration in which circular support portions 613a are provided at both ends of a metal shaft 613 such as stainless steel and a seamless tube is covered on the surface.
And this seamless tube has the surface resin layer 611 which uses an ion conductive substance as a electrically conductive agent in the surface layer, and is comprised by what laminated | stacked the conductive layer 612 on the back surface. Therefore, in this example, it is not necessary to provide a conductive member for supporting the surface resin layer 611 and energizing the surface resin layer 611 inside the seamless tube.

As described above, there is no difference in the effective charge amount control for the toner, even if the configuration in which the seamless tube is covered as the charging roll is compared with the configuration in which the seamless tube is covered on the developing roll described above. The characteristics can be stabilized. In order to bring the charging roll 61 into contact with the developing roll and maintain a stable nip, the surface resin layer 611 of the charging roll 61 needs to be bent by the pressure contact of the developing roll. Therefore, it is necessary to dispose the developing roll on the flexible portion of the charging roll 61 (the portion excluding the circular support portion 613a).
By doing so, the pressure contact state between the developing roll and the charging roll 61 is stabilized, and stable charging control is possible.

  In the present embodiment, the development roll is covered with a seamless tube and the charging roll is a metal rigid body. However, the present invention is not limited to this, and an elastic body, for example, can be used as the charging roll. Furthermore, it is possible to cover the charging roll with a seamless tube and to make the developing roll side an elastic body.

Embodiment 2
FIG. 7 shows a flowchart of charging control of the developing device according to Embodiment 2 of the image forming apparatus to which the present invention is applied. Although the present embodiment is configured in substantially the same manner as the developing device 30 (see FIG. 4) in the first embodiment, an environmental sensor (temperature / humidity sensor) is provided in the vicinity of the charging roll 37 as environmental detection means. This is different from the first embodiment. Since the configuration of the developing device 30 is the same as that of the first embodiment, it is omitted here.

In the present embodiment, the applied current control routine of the bias power supply 41 (see FIG. 4) connected to the charging roll 37 is as shown in FIG.
First, when the image forming apparatus warms up, it is determined by a built-in CPU or the like based on a signal from the environment sensor whether there has been a change from the immediately preceding environment stored in the apparatus (step S1).
If it is determined that there is an environmental change, the constant current value of the bias power supply 41 is changed by an amount corresponding to the change amount, and the applied current value to the charging roll 37 is increased or decreased (step S2).
If it is determined that there is no environmental change, the constant current value of the bias power supply 41 is maintained as it is, and the applied current value to the charging roll 37 is not changed (step S3).

In this way, by regulating the charging of the toner with a current value suitable for the environment, for example, an optimum toner charge amount can be imparted even in a high-temperature, high-humidity environment and a low-temperature, low-humidity environment, and development characteristics can be stabilized. An image forming apparatus with good image quality can be realized.
Further, if the signal input from the environment sensor is not only performed when the image forming apparatus is warmed up but is appropriately performed, the development characteristics can be further stabilized.

Example 1
This example was performed with an experimental machine having the same configuration as that of the first embodiment and the length of the charging roll in the axial direction being 8 cm, and contained an ion conductive material as a seamless tube of the developing roll. This is an evaluation of the relationship between the value of the current flowing to the charging roll and the toner charge amount when polyvinylidene fluoride (PVdF) is used.
In this example, the seamless tube is PVdF with a thickness of 100 μm and has a volume resistivity of the following four types: 1 × 10 ⁹ , 1 × 10 ¹⁰ , 1 × 10 ¹¹ , 1 × 10 ¹² Ω · cm. The current value was -5 to -40 [mu] A.
FIG. 8 shows the evaluation results, and it has been found that the amount of charge increases proportionally as the applied current is increased. Further, no clear result was obtained regarding the relationship with the volume resistivity of PVdF, but it was found that, for example, when the applied current was set to −20 μA or more, a charge amount of −20 μC / g or more was obtained. did.

Example 2
In this example, as in Example 1, the relationship between the applied current and the charge amount was evaluated. However, the seamless tube used was different from Example 1. In this example, a PVdF seamless tube containing carbon black having a thickness of 100 μm and a volume resistivity of 1 × 10 ⁸ Ω · cm, and a carbon having a thickness of 144 μm and a volume resistivity of 1 × 10 ⁷ Ω · cm. A seamless tube of polyamide (PA) resin containing black was used.
FIG. 9 shows the evaluation results. In all cases, the charge amount was very low, and the charge amount did not change even when the applied current was increased.

Example 3
In this example, the seamless tube evaluated in Example 1 and Example 2 described above was used, and the VI characteristics (voltage-current characteristics) between the charging roll and the developing roll were measured using an experimental machine. It is. As shown in FIG. 10, in the case of PA of 10 ⁷ Ω · cm and PVdF of 10 ⁸ Ω · cm, as shown in FIG. 10, when the applied voltage is increased, the current suddenly rises, and when the applied voltage is -500V, Since a large current flows, it was judged that it cannot be used for charging control.
When the insulation resistance value is converted from each current value when the applied voltage is −500 V, PA of 10 ⁷ Ω · cm is 3.5 × 10 ⁶ Ω, and PVdF of 10 ⁸ Ω · cm is 1.4 × 10. ⁷ Ω, 10 ⁹ Ω · cm PVdF is 4.9 × 10 ⁹ Ω, 10 ¹⁰ Ω · cm PVdF is 1.7 × 10 ¹¹ Ω, 10 ¹¹ Ω · cm PVdF is 1.5 × 10 ¹² Ω The PVdF of 10 ¹² Ω · cm was 4.5 × 10 ¹² Ω.
From this result, even if the volume resistivity is too high, it is necessary to increase the applied voltage for current control, and a range of about 10 ⁹ to 10 ¹⁰ Ω · cm is assumed to be a practical range of volume resistivity.

As described above, from the results of Examples 1 to 3, the volume resistivity is 1 × 10 ⁹ Ω · cm or more and the insulation resistance value per axial length of 8 cm when DC 500 V is applied is 4.9 × 10 ⁹ Ω. It is understood that charging control can be stabilized by using the seamless tube (corresponding to the surface resin layer) as described above.

Example 4
In this example, a PVdF seamless tube having a thickness of 100 μm and a volume resistivity of 10 ¹⁰ Ω · cm is used, and a constant current applied to the charging roll in a state where the biting amount is set to 60 to 70 μm. The change in the charge amount when the AC component is superimposed is evaluated.
The results are shown in FIG. 11 for the case of only the DC component, and in FIG. 12 for the case where the AC component is superimposed.
With only the direct current component, it was found that the charge amount was constant at about −58 μC / g at an applied current of −30 μA or more, and the charge amount could not be varied even when the current was changed beyond this.
On the other hand, as shown in FIG. 12, when the AC component is superimposed (the DC component is fixed at −150 μA and the AC of f = 2 kHz is superimposed), the charge amount changes depending on the AC voltage (peak-to-peak voltage V _pp ). Turned out to be.
Therefore, if the charge amount is controlled to, for example, −60 to −90 μC / g, a DC power source of −150 μA is used as a bias power source applied to the charging roll, and a peak-to-peak voltage is set to 500 to 1000 V at a frequency of 2 kHz. It is understood that alternating current may be superimposed, and it is understood that by controlling the peak-to-peak voltage, it becomes possible to control to a predetermined charge amount.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. (A) (b) is explanatory drawing which shows the effect | action which concerns on this invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. FIG. 2 is an explanatory diagram illustrating a developing device according to the first embodiment. FIG. 3 is an explanatory diagram showing a main part of the first embodiment. FIG. 6 is an explanatory view showing a charging roll as a modification of the first embodiment. FIG. 10 is an explanatory diagram showing current control of the developing device according to the second embodiment. It is explanatory drawing which shows the result of Example 1. FIG. FIG. 6 is an explanatory diagram showing the results of Example 2. It is explanatory drawing which shows the result of Example 3. FIG. It is description which shows the case of only a direct-current component among the results of Example 4. FIG. It is explanatory drawing which shows the case where an alternating current component is superimposed among the results of Example 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developer carrier, 2 ... Charge control member, 3 ... Surface resin layer, 4 ... Ion conductive substance, 5 ... Charging bias

Claims (11)

A developer carrying member that is rotatable and carries a developer on its surface;
A developing device provided with a charge regulating member that rotatably contacts the developer carrying member and that regulates the charging of the developer on the developer carrying member with an applied charging bias;
At least one surface of the developer carrying member or the charge regulating member contains only an ion conductive material as a conductive agent, has a volume resistivity of 1 × 10 ⁹ Ω · cm or more, and an axial length when DC 500 V is applied. A developing device comprising a surface resin layer having an insulation resistance value of 4.9 × 10 ⁹ Ω or more per 8 cm. The developing device according to claim 1,
At least one of the developer carrying member and the charge regulating member is composed of a flexible tube having a surface resin layer,
A developing device characterized in that, in the flexible tube, at least the back side of the flexible tube other than the charge regulation region where both members are in contact is supported and supported by a support member. The developing device according to claim 1 or 2,
A developing device, wherein a conductive layer capable of applying a charging bias for applying charge to the developer is laminated on a back surface side of the surface resin layer. The developing device according to claim 1 or 2,
A developing device, characterized in that a conductive member to which a charging bias for applying charging to a developer can be applied is provided in the vicinity of a charge regulation region where the developer is regulated to charge on the back surface side of the surface resin layer. The developing device according to claim 3 or 4,
The developing device according to claim 1, wherein the charging bias between the developer carrying member and the charge regulating member includes a DC electric field controlled at a constant current. The developing device according to claim 3 or 4,
The developing device according to claim 1, wherein the charging bias is one in which an alternating electric field is superimposed. The developing device according to claim 6.
A developing device that controls the charge amount of a developer by changing a peak-to-peak voltage of the AC electric field. In the developing device according to claim 2, the developer carrying member includes a surface resin layer.
The developing device according to claim 1, wherein the charge regulating member regulates the charge of the developer on the developer carrying member and also regulates the layer thickness of the developer. A developer carrying member that is rotatable and carries a developer on its surface;
A charge regulating member that is rotatable in contact with the developer carrying member and regulates the charging of the developer on the developer carrying member;
Charging control means for variably controlling the charging bias condition applied to the charging regulating member according to environmental changes,
A developing device, wherein the surface of at least one of the developer carrying member and the charge regulating member is composed of a surface resin layer containing only an ion conductive material as a conductive agent. The developing device according to claim 9, wherein
The surface resin layer has a volume resistivity of only 1 × 10 ⁹ Ω · cm or more containing only an ion conductive material as a conductive agent, and an insulation resistance value per axial length of 8 cm when DC 500 V is applied. developing apparatus is characterized in that at ⁹ Omega more.   An image forming apparatus comprising the developing device according to claim 1.

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