JP4649966B2 - Developing device and image forming apparatus using the same - Google Patents

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.

In an image forming process using such a one-component development system, in order to obtain an optimal image, a sensor for measuring environmental changes, a sensor for detecting the surface potential of a photoconductor, etc. are usually provided in the image forming apparatus. Based on information from these sensors, the surface potential and exposure amount of the photoconductor, the developing bias of the developing device, the transfer current of the transfer device, and the like are controlled to maintain an appropriate image (for example, Patent Document 1). , 2).
In Patent Document 1, a pattern image for comparison is formed on a photoconductor to detect a change in the line width in order to keep the line width of the image constant and provide optimum image quality even when the environment and image forming conditions change. The scheme is shown as follows. In other words, the line width of the comparison pattern image is detected by the reflection type photosensor, and the voltage of the developer carrying member or the thinning regulating member is controlled so that the difference from the preset reference line width is eliminated. ing. In this patent document, a method of detecting the surface potential of the developer carrying member and adjusting the line width of the comparative pattern image together with information on the surface potential is also shown.
In Patent Document 2, density reading means for detecting the density of the toner image developed on the photoconductor is provided, and the transfer bias is determined based on the toner density obtained from the density reading means and the development bias value. A scheme that provides optimal image quality is shown. In particular, the potential characteristics of the photoconductor and the charging characteristics of the toner are greatly influenced by the temperature and humidity, so that the above-described method can prevent the influence of the temperature and humidity.

Japanese Patent Laid-Open No. 5-11596 (Example, FIG. 1) Japanese Patent Laying-Open No. 2003-15371 (Embodiment 1, FIG. 5)

However, in the above-described method, in order to obtain an optimum image quality, an environmental change is detected, a surface potential on the photosensitive member, a line width of a pattern image or a toner density is detected, and a developer is carried. Since it is intended to optimize various image process conditions by detecting the surface potential of the body, it is necessary to provide temperature / humidity detection means, density detection means, line width detection means, etc. There is a problem that impairs downsizing and downsizing.
Further, it is not intended to control the charging condition by paying attention to the energized state when the charge on the developer carrying member is regulated.

  The present invention has been made to solve the above technical problem, and is a developing device capable of reducing the cost at a low cost with a stable developer charge amount on the developer carrying member, and an image using the same. A forming apparatus is provided.

That is, as shown in FIG. 1, the basic configuration of the present invention includes a rotatable tubular thin film member and a tubular thin film member fixedly enclosed in the tubular thin film member so as to support the tubular thin film member. A developer member 1 carrying a developer on the surface of the tubular thin film member, and developing at a portion corresponding to the recess of the conductive member. A charge regulating member 2 which is disposed in contact with the cylindrical thin film member of the agent carrier 1 and regulates the charge of the developer on the developer carrier 1, and the charge regulating member 2 and the developer carrier 1 A charging bias supplying unit 3 for supplying a charging bias for charging the developer in between, a detecting unit 5 capable of detecting an energization state of the charging regulating member corresponding to an environmental change at the time of supplying the charging bias, and a detecting unit 5 the reference value charge amount of the developer based on a detection result by I am characterized in comprising a charging control unit 4 for controlling the charging bias as One.

In such technical means, the developing device according to the present invention 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. However, an embodiment in which the electrostatic latent image is carried in contact with the image carrier is preferable, but an embodiment in which the electrostatic latent image is not in contact with the image carrier may be used.

  The charge regulating member 2 in the present invention may be in contact or non-contact with the developer carrier 1 as long as the developer on the developer carrier 1 can be charged. From the viewpoint of effectively performing charge control of the developer on the developer carrier 1, it is preferable to secure a predetermined amount of biting between the developer carrier 1 and the rotating member as the charge regulating member 2. preferable. Further, in the aspect in which the developer carrying body 1 is a rigid body, the charging regulating member 2 is preferably in the form of an elastic body or a flexible tube, and the developer carrying body 1 is provided with a surface resin layer. In the aspect of including a body (including a flexible tube), the charge regulating member 2 may be a rigid body.

The charging bias supply means 3 is applied between the charge regulating member 2 and the developer carrier 1 and charges the developer. As a typical aspect, a constant current application or a constant voltage application is performed. An embodiment is mentioned. Furthermore, if the charging bias supply means 3 supplies a constant DC current, the charging control can be controlled at a constant current, a stable charge amount can be imparted to the developer, and the charge amount can be easily controlled. become.
Furthermore, the charging control means 4 only needs to be able to control at least the charging bias supply means 3, and may be a mode in which other control (for example, development bias) is performed simultaneously. The charging control unit 4 is provided with the detecting means 5 for detecting an energization state during charging bias supply, Thus, control is more effectively in the charge control unit 4 based on the information from the detection means 5 Will be made.

The detection means 5 may be any detection method as long as it can detect a change in the energization state. For example, a change in voltage applied to the charge regulating member 2 during energization, a current change during energization, A method for detecting the surface potential of the member and the like can be mentioned. If the charging state is known by detecting the voltage and current in this way, an appropriate developer charge amount can be obtained even if there is an environmental change or the like.
Further, as the detection means 5, it is preferable to detect a voltage change of the developer carrier 1 or the charge regulating member 2, and in this case, constant current control is performed between the developer carrier 1 and the charge regulating member 2. Effective.

In the present invention, it is preferable that a semiconductive resin layer is provided on the opposite surface of at least one of the developer carrier 1 or the charge regulating member 2, and thereby the developer is uniformly applied during charging. A current distribution is obtained, and a uniform charge amount can be imparted to the developer.
The semiconductive resin layer preferably has a volume resistivity in the range of 10 ⁸ to 10 ¹¹ Ω · cm. If the volume resistivity is smaller than 10 ⁸ Ω · cm, a sufficient discharge current can be obtained at the time of charging regulation. Does not flow, and sufficient charging to the developer is not performed. On the other hand, if the volume resistivity is larger than 10 ¹¹ Ω · cm, the discharge during the charge regulation is difficult to occur, and the charge imparting action itself to the developer does not function.

  Furthermore, the semiconductive resin layer preferably contains an ion conductive substance as a conductive agent. By using the ion conductive substance as a conductive agent in this way, the dispersibility in the resin is improved, and the semiconductive resin layer is improved. The uniformity of the resistance distribution of the conductive resin layer is improved, the charging current supplied to the developer at the time of charging regulation is made uniform over the entire developer, and a more uniform charge amount can be obtained. If the conductive agent contains an electron conductive material such as carbon black, the dispersibility in the resin is poor, the cohesive force between the particles is strong, and the particles are coarsened. The uniformity of the resistance distribution is inferior, the charging current is not uniform throughout the developer, it tends to flow partially, or abnormal discharge tends to occur, and a non-uniform charge amount is imparted to the developer. Will be.

Further, in the present invention, since embodiments the developer carrying member 1 carries convey the developer on the surface of and the cylindrical thin member having a rotatable cylindrical membrane member, the driving force of the charging regulation member 2 It is preferable to provide a driving force transmitting means for transmitting to the developer carrier 1, thereby simplifying the drive mechanism of the developer carrier 1 and suppressing stress applied to the developer. Therefore, it is possible to provide a developing device capable of maintaining stable performance at low cost. Examples of the cylindrical thin film member include a resin tube obtained by applying a conductive agent to a resin such as a polyamide resin or a fluorine-based resin, a metal thin plate tube such as SUS, aluminum, or a nickel electroformed product. By using such a cylindrical thin film member, the pressure contact force with the contact member can be reduced, and the stress on the developer can be reduced.

And as a typical aspect of the driving force transmitting means, a driving pressing member that is positioned at both ends of the cylindrical thin film member with the rotation shaft of the charging regulating member 2 as a core material and pressed against the cylindrical thin film member, and the cylindrical thin film member And a support member that sandwiches the cylindrical thin film member together with the drive pressing member. At this time, the support member may be fixedly arranged or may be rotated. In the aspect in which the support member is fixedly disposed, the support member is preferably excellent in slidability with the cylindrical thin film member.
The present invention is also directed to an image forming apparatus including the developing device described above.

According to the present invention, an energization state when supplying a charging bias for charging the developer between the developer carrying member and the charge regulating member is detected, and the charge amount of the developer is determined based on the detection result. The charging bias is controlled so as to maintain the reference value, so that the developer on the developer carrier can be charged appropriately even if there is an environmental change, etc., and the image quality is stable during development. Can be maintained. Further, since a means such as an environmental sensor is not required, a developing device that can be reduced in cost and size can be provided.
And in this invention, the cylindrical thin film member which can be freely rotated, and the cylindrical thin film member was fixedly included in the cylindrical thin film member so as to support the cylindrical thin film member, and a recess was formed in at least a part of the peripheral surface. A developer carrying body that carries a developer on the surface of the cylindrical thin film member, and the cylindrical thin film member of the developer carrying body at a portion corresponding to the concave portion of the conductive member. Since the charge regulating member that is arranged in contact and regulates the charging of the developer on the developer carrying member is used, stress applied to the developer can be suppressed.
Furthermore, if the charging bias is controlled at a constant current, a more stable electric field during charging can be supplied, and the charge amount of the developer can be further stabilized.
By using these developing devices, it is possible to provide an image forming apparatus with stable development characteristics.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 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 photoreceptor having a photosensitive layer such as an organic photoreceptor on the surface rotating in the direction of the arrow and carrying an electrostatic latent image. The photoreceptor 21 is a charging device 22 such as a charging roll. The electrostatic latent image is written by the exposure device 23 having a laser writing device or 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 a transfer bias in a direction in which the toner image on the photoconductor 21 is attracted by a bias power source 27 is applied, thereby the photoconductor. The toner image on 21 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 52 and a pressure roll 51, and a recording material 28 is passed between the heating roll 52 and the pressure roll 51 so that a toner image is obtained. It is fixed on the recording material 28.

  Here, the developing device 30 of the present invention will be described in detail with reference to FIG. In FIG. 1, a developing device 30 is disposed behind a developing roll 32 that rotates in pressure contact with a photosensitive member 21 having a photosensitive layer provided on a surface of a metal substrate such as stainless steel. A toner supply roll 34 made of a metal roll such as stainless steel for supplying toner is disposed, and the developing roll 32 and the toner supply roll 34 are configured to rotate in the same direction (with direction) at the opposite portions thereof. Yes. The toner supply roll 34 is not limited as long as it can supply toner to the developing roll 32. For example, an elastic member or the like can be used in addition to the metal roll. A bias power source 42 is connected to the toner supply roll 34 in the present embodiment, and the toner on the toner supply roll 34 is supplied to the developing roll 32.

  Further, a toner hopper 35 for storing toner is provided behind the toner supply roll 34, and the toner stored in the toner hopper 35 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 that the toner is stirred and supplied 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 charging roll that regulates the toner amount are disposed at a position facing the developing roll 32 on the downstream side of the facing portion between the developing roll 32 and the toner supply roll 34. 37 is provided in pressure contact with the developing roll 32. On the other hand, a scraping member 38 that scrapes the residual toner on the developing roll 32 is provided upstream of the facing portion between the developing roll 32 and the toner supply roll 34.

The developing roll 32 in the present embodiment is a semiconductive resin layer 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. The pivotable seamless tube 321 is configured, and a conductive member 322 fixedly disposed therein and connected to the bias power source 33 so as to support the seamless tube 321. Examples of the ion conductive substance used in this embodiment include perchlorate (for example, lithium perchlorate, sodium perchlorate, ammonium perchlorate, etc.), quaternary ammonium salt, and the like.

  Further, a conductive member 322 made of a conductive material having a small sliding friction when the seamless tube 321 rotates is fixedly disposed inside the seamless tube 321 of the developing roll 32. The conductive member 322 is provided with recesses (A part and B part) in which the seamless tube 321 can be deformed at a position facing the photoreceptor 21 and the charging roll 37, and seamlessly connected to the photoreceptor 21 and the charging roll 37. A sufficient nip region can be formed at a low pressure with the tube 321.

The charging roll 37 in the present embodiment is obtained by coating the SUS roll surface with a tube similar to the seamless tube 321 of the developing roll 32, and the tube has a volume resistivity of 10 ¹⁰ Ω · cm containing an ion conductive substance. The semiconductive resin layer is used.
In particular, a bias power source 41 is connected to the charging roll 37 of the present embodiment so that a charging current under constant current control can flow between the charging roll 37 and the developing roll 32. Further, the charging roll 37 is connected to the control device 44 via a detection unit 43 as voltage detection means, and voltage information of the charging roll 37 detected by the detection unit 43 is transmitted to the control device 44. ing. Further, the control device 44 controls the bias power supply 41 based on the voltage information from the detection unit 43 so that an appropriate charging current can flow. Reference numeral 39 denotes a cleaning blade for cleaning the toner adhering to the charging roll 37.

  The control device 44 in the present embodiment controls the bias power supply 41 and at the same time controls the bias power supply 33 and the bias power supply 27 (see FIG. 2) to supply the optimum developing bias and the optimum transfer bias. , So that the stability of image quality can be maintained.

FIG. 4 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 has a configuration in which a 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 (see FIG. 3) described above is provided inside the support member 323, and one end of the conductive member 322 extends 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. 3).
On the other hand, the charging roll 37 has a structure in which a SUS metal roll is covered with a tube, and a urethane resin rubber roll 372 fixed to shafts 371 at both ends of the SUS metal roll is disposed. The rubber roll 372 is in a position facing the support member 323 of the seamless tube 321, and the seamless tube 321 of the developing roll 32 rotates together with the support member 323 by the rotation of the charging roll 37, so that the seamless tube 321 rotates. . In addition, since the seamless tube 321 and the charging roll 37 are maintained in pressure contact with each other with a predetermined bite amount d, the developing roll 32 (seamless tube 321) is driven by the rotation of the charging roll 37 to perform stable rotation. To do.

Here, as shown in FIG. 5, the control device 44 in the present embodiment is configured by, for example, a microcomputer system (CPU 61, ROM 62, RAM 63, input / output interfaces 64, 65). Voltage information processing program (for example, charging current control, development bias control, transfer bias control), appropriate charging current reference value according to environmental conditions and its allowable range (specifically voltage information), and previous charging current Information such as a value (specifically, voltage information from the detection unit 43) is stored in advance.
And in this control apparatus 44, after the voltage information from the detection part 43 is taken in into CPU61 via the input interface 64, CPU61 reads the change of voltage information and appropriate charging conditions are set so that it may be set. The bias power supply 41 is controlled via the output interface 65, and the charging current is changed when necessary. At this time, the bias power sources 33 and 27 are also controlled to optimize the developing bias and the transfer bias.

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 where the charging roll 37 bites into the developing roll 32 by a predetermined biting amount. In this nip area, the toner is charged by a constant current electric field by the bias power source 41, particularly by discharge around the nip area. At the same time, the toner leveling effect in the nip area is also helped, 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 electrostatic latent image on the photosensitive member 21 is developed. The image is developed with toner. Further, on the downstream side of the developing region, the residual toner that remains without being developed on the developing roll 32 is scraped off by the scraping member 38. In the present embodiment, the photosensitive member 21 and the developing roller 32 in the developing region are in contact with each other with an appropriate contact pressure (small contact pressure), which is useful for improving the image quality of the toner image on the developed photosensitive member 21. ing.

In the operation of such a developing device, an operation for an environmental change in the present embodiment will be described.
Generally, when the humidity increases during charging, the discharge start voltage increases and the flowing current decreases. However, when the charging current is controlled at a constant current, the voltage that flows in to compensate for the decreased current increases. To do. On the other hand, when the humidity decreases, the discharge start voltage decreases and the voltage that flows in decreases. On the other hand, when the temperature rises, the discharge start voltage decreases and the flowing current increases, but the voltage flowing in for constant current control decreases. On the other hand, when the temperature is lowered, the discharge start voltage is increased and the flowing voltage is increased. For this reason, if a constant current continues to flow during charging, the charge amount of the toner charged varies depending on the environmental conditions, and the charge amount (charge amount outside the reference value) cannot be formed satisfactorily.
In addition, it is necessary to consider the influence of the material itself used for the developing roll 32 and the charging roll 37 for the environmental change.
If the charge amount of the toner becomes too large, the amount of development decreases and image defects such as a decrease in image density occur. On the other hand, if the charge amount of the toner becomes too small, the toner adhesion to the developing roll 32 (mainly adhering by the mirror image force) becomes small, and a cloud is generated or the toner is scattered to a part other than the development. It is easy to cause and effects such as in-flight contamination occur.
Therefore, by detecting how the voltage at which the charging current flows is changed and resetting it to a current value suitable for the environment, an appropriate charging condition can be maintained. In addition, by detecting the environmental change in this way, it is possible to change to development conditions and transfer conditions suitable for the conditions, leading to stabilization of the image quality as a whole.

FIG. 6 shows the flow of the environment change detection routine in the present embodiment. This flow will be described below with reference to FIG.
When the voltage information from the detection unit 43 is taken into the control device 44, the control device 44 first compares whether or not the voltage of the charging roll 37 has changed with a reference value (including an allowable range) (step S1). Note that the reference value is a value determined by the range of the charging current value in which appropriate image formation can be performed within the environmental conditions permitted by the image forming apparatus.
If there is no change in the voltage, it is determined that the environment has not changed, and the current applied to the charging roll 37, the development bias, and the transfer bias are set to the set values (the set values as they are) (step S2). By ending the routine, the proper charge amount is maintained and proper image formation continues.

If there is a change in the voltage, it is determined that there has been a change in the environment, and it is determined whether or not the voltage has increased compared to the reference value (step S3). If so, the current applied to the charging roll 37 is controlled to decrease by a predetermined amount, and at the same time, the developing bias and the transfer bias are changed to predetermined values (step S4). Here, the voltage and current are shown in absolute values, and the fact that the voltage increases means that the voltage detected by the detection unit 43 increases as the current increases. .
Further, at this time, if the voltage is lowered, the current applied to the charging roll 37 is controlled to be increased by a predetermined amount, and at the same time, the developing bias and the transfer bias are changed (step S5).
That is, when the charging current is set to a constant current value when the voltage increases or decreases due to environmental changes, the toner charge amount increases or decreases, and an appropriate image cannot be formed. Therefore, it is possible to optimize the toner charge amount by supplying an appropriate charging current.
Furthermore, as described above, when the value of the current passed through the charging roll 37 is changed, the voltage at the detection unit 43 is measured again, and it is determined whether or not this voltage is within the reference value. If the result of this determination is that the voltage is within the reference value, the routine is terminated; otherwise, the routine returns to step S1 (step S6).

  In the present embodiment, since the semiconductive resin layer used for the developing roll 32 and the charging roll 37 contains an ion conductive material as a conductive agent, for example, an electron conductive material such as carbon black. Compared to those including the above, stable and uniform charging conditions (stable and uniform discharge between the developing roll 32 and the charging roll 37 are maintained) are maintained.

As described above, in the present embodiment, the environmental change can be easily detected by the voltage change obtained from the detection unit 43, and the charging condition suitable for the environment can be obtained. At the same time, the development bias and the transfer bias can be adjusted to the environmental conditions. Therefore, the charge amount of the toner on the developing roll 32 can always be maintained at an appropriate value, and an optimum image quality can be obtained. Furthermore, a temperature sensor, a humidity sensor, a surface potential meter, etc. are not required, and the cost and size of the apparatus can be reduced.
Further, in the present embodiment, the contact pressure between the developing roll 32 and the charging roll 37 is also reduced by using the seamless tube 321, and the stress applied to the toner is also the case where an elastic body is used for the developing roll 32, for example. Compared to, it is greatly reduced. Therefore, the toner is hardly fixed, and a stable development performance can be maintained even when used for a long time.
Further, since the developing roll 32 is rotated by the driving force of the charging roll 37, the driving conditions of the developing roll 32 and the toner supply roll 34 can be arbitrarily set to conditions suitable for toner supply. In addition, since a separate drive system such as a gear is not required, the apparatus can be simplified and the cost can be reduced.

In the present embodiment, a method of performing constant current control as a charging bias is shown. However, if a constant voltage electric field is applied between the developing roll 32 and the charging roll 37 and a current change caused by an environmental change is used, the constant current control is performed. The same effect as when current control is performed can be obtained.
For example, if a surface potential meter is used to detect the surface potential on the charging roll 37 in the vicinity of the charging nip region, it is possible to detect a change substantially similar to the voltage change in the nip region. Since the sensor, the humidity sensor, etc. are not required, the apparatus cost can be reduced.

FIG. 7 shows a charging roll 71 as a modification of the charging roll 37 (see FIG. 3) used in the present embodiment. Hereinafter, the charging roll 71 will be described with reference to FIG. As a mode of using this charging roll 71, unlike the present embodiment, the developing roll 32 is a rigid body, and the charging roll 71 includes a seamless tube 73 as a semiconductive resin layer.
Such a charging roll 71 has a configuration in which circular support portions 72a are provided at both ends of a metal shaft 72 such as stainless steel and a seamless tube 73 is covered on the surface.
And this seamless tube 73 has the surface resin layer 73a 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 73b on the back surface. Therefore, in this example, it is not necessary to provide a conductive member (conductive member as shown in FIG. 3) for supporting the surface resin layer 73a and energizing the surface resin layer 73a inside the seamless tube 73. .

As described above, even when the configuration in which the seamless tube 73 is covered as the charging roll 71 is adopted, the toner is effective as compared with the configuration in which the developing roll 32 is covered with the seamless tube (the embodiment of the present embodiment). There is no difference in charge amount control, and the development characteristics can be stabilized. In order to bring the charging roll 71 into contact with the developing roll 32 and maintain a stable nip, it is necessary that the surface resin layer 73a of the charging roll 71 bend by the pressure contact with the developing roll 32. Therefore, it is necessary to arrange the developing roll 32 so as to face the flexible portion of the charging roll 71 (the portion excluding the region of the circular support portion 72a).
By doing so, the pressure contact state between the developing roll 32 and the charging roll 71 becomes stable, and stable charging control becomes possible.

  In this embodiment, control is performed to detect voltage fluctuations caused by environmental changes and reset the charging conditions (charging current values) appropriately. For example, changes with time of the developing roll 32 and the charging roll 37 are performed. (E.g., the number of prints, etc.) in advance, an appropriate charging current at that time is obtained, and if this data is stored as a table in the control device 44, an optimum reference value when a change with time is assumed. Needless to say, it is possible to always set the value and to enable more effective charge amount control.

  Further, in the present embodiment, the developing roll 32 and the charging roll 37 are both covered with a seamless tube as a semiconductive resin layer. However, the present invention is not limited to this, and the charging roll 37 may be, for example, a metal or an elastic body. Can also be used. Further, the charging roll 37 can be a seamless tube, and the developing roll 32 side can be an elastic body.

Embodiment 2
FIG. 8 shows a developing device 30 according to the second embodiment to which the present invention is applied. In this figure, the present embodiment is configured in substantially the same manner as the developing device 30 of the first embodiment, but the charging bias supply method is different from the first embodiment, and the constant current control is performed in the first embodiment. On the other hand, constant voltage control is performed in the present embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and the detailed description is abbreviate | omitted.

In FIG. 8, the bias power supply 41 in the present embodiment is configured by a constant voltage power supply, and a stable voltage is always applied between the charging roll 37 and the developing roll 32. In the present embodiment, a detection unit 45 is provided between the charging roll 37 and the bias power supply 41, and information from the detection unit 45 is transmitted to the control device 44.
The detection unit 45 in the present embodiment is configured by, for example, a resistor and detects a current value that is energized during charging, and the control device 44 receives information on the voltage drop of the resistor. Communicated.
Therefore, for example, when the charging state changes due to an environmental change, the energization current changes, and the change in the energization current is detected by the detection unit 45 so that the constant voltage value of the bias power supply 41 is changed from the control device 44. As a result, the charged state is stabilized.

FIG. 9 shows a flow of the charge amount control routine in the present embodiment, and this operation will be described with reference to FIG.
When the current information (voltage drop) from the detection unit 45 is taken into the control device 44, the control device 44 first compares whether or not there is a change in the current of the charging roll 37 with a reference value (including an allowable range) ( Step S11). Note that the reference value is a value determined by the range of the charging voltage value in which appropriate image formation can be performed within the environmental conditions permitted by the image forming apparatus.
If there is no change in the current, it is determined that there has been no environmental change, the voltage applied to the charging roll 37 is kept at the set value (the set value as it is) (step S12), and the routine is terminated. The proper charge amount is maintained, and proper image formation is continued.

If there is a change in the current, it is determined that there has been a change in the environment, and it is determined whether the current has increased compared to the reference value (step S13). If it has increased, control is performed so that the voltage applied to the charging roll 37 is decreased by a predetermined amount (step S14).
Further, at this time, if the current is reduced, the voltage applied to the charging roll 37 is controlled to be increased by a predetermined amount (step S15).
In other words, when the current increases or decreases due to environmental changes, if the charging voltage is set to a constant voltage value that is set, the toner charge amount increases or decreases, and an appropriate image cannot be formed. Therefore, the toner charge amount can be optimized by applying an appropriate charging voltage.
Furthermore, as described above, when the voltage value applied to the charging roll 37 is changed, the voltage drop at the detection unit 45 is measured again, and it is determined whether or not the current value is within the reference value. Do. If the result of this determination is that the current is within the reference value, the routine is terminated; otherwise, the routine returns to step S11 (step S16).

As described above, the same effect as in the first embodiment can be obtained by detecting a change in current when the charging roller 37 and the developing roller 32 are energized.
Furthermore, although only the charge amount control is shown in the present embodiment, it is also possible to control the developing bias and the transfer bias at the same time as in the first embodiment.

Example 1
In this example, both the developing roll and the charging roll have a seamless tube, and a constant current control was performed as in Embodiment 1 using an experimental machine in which the axial length of the charging roll was about 8 cm. This is an evaluation of the relationship between the value of the current passed through the charging roll and the toner charge amount.
As a seamless tube of the developing roll, polyvinylidene fluoride (PVDF) containing an ion conductive material having a thickness of 100 μm and having a volume resistivity of the following four types, that is, 1 × 10 ⁸ , 1 × 10 ⁹ , were from ^{1 × 10 10, 1 × 10} 11 Ω · cm.
As the seamless tube for the charging roll, PVDF containing an ion conductive material having a thickness of 100 μm and having a volume resistivity of 1 × 10 ¹⁰ Ω · cm was used.
Then, when the current applied as the charging current was −10 to −40 μA, the charge amount of the toner thin layer formed on the developing roll was measured.
As a result, as shown in FIG. 10, in the case of the volume resistivity of the four types of seamless tubes of the developing roll, the charge amount changes almost in proportion to the applied current, and the applied current is changed. Thus, it was confirmed that the charge amount could be controlled.
In particular, when the volume resistivity of the seamless tube of the developing roll was 1 × 10 ⁸ Ω · cm, the charge amount changed to −15 to −60 μC / g when the applied current was changed to −10 to −40 μA. .

From the above, as in this embodiment, a seamless tube is used for the developing roll and the charging roll, the volume resistivity of the seamless tube of the charging roll is 1 × 10 ¹⁰ Ω · cm, and the volume of the seamless tube of the developing roll. It was confirmed that the charge amount can be sufficiently controlled even when the resistivity is set to 1 × 10 ⁸ to 1 × 10 ¹¹ Ω · cm. This indicates that the control of the charge amount can be performed by changing the applied current to some extent, so that specific control can be easily performed.
In this embodiment, since negatively charged toner is used as the toner, the applied current flowing from the bias power source to the charging roll is negative (flowing from the charging roll toward the bias power source). However, when positively charged toner is used, it is applied. The current becomes positive.

In this example, as a result of further detailed evaluation, if at least one of the developing roll and the charging roll has a volume resistivity in the range of 1 × 10 ⁸ to 1 × 10 ¹¹ Ω · cm, It was confirmed that the toner charge amount can be controlled by changing the current applied to the roll.

Example 2
In this example, instead of Example 1 in which a constant current is supplied to the charging roll, the relationship between the applied voltage and the toner charge amount when constant voltage control is performed is confirmed as in the second embodiment. .
The charging roll and the developing roll had the same configuration as in Example 1, and the toner charge amount was measured by changing the volume resistivity of the seamless tube of the developing roll.
As a result, as shown in FIG. 11, even when the seamless tube of the developing roll was changed, the relationship between the applied voltage and the charge amount changed linearly. Therefore, similarly to the case where the constant current control is performed as in the first embodiment, the charge amount control with respect to the environmental change becomes possible.
As can be seen from FIG. 11, in the constant voltage control, the slope of the straight line indicating the relationship between the applied voltage and the charge amount is steep, so that it is difficult to control the charge amount by changing the applied voltage. Accompanied by. That is, there is a concern that it is difficult to control the fine charge amount because a large change in the charge amount is brought about by slightly changing the applied voltage.
Therefore, it was confirmed that the charge amount control in the present invention is more practical when the constant current control is performed as in the first embodiment, and the control over the details of the charge amount is possible.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning 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. 2 is an explanatory diagram illustrating a control device according to Embodiment 1. FIG. FIG. 3 is an explanatory diagram showing a flow of the first embodiment. It is explanatory drawing which shows the image development roll as a modification of embodiment. FIG. 10 is an explanatory diagram illustrating a developing device according to a second embodiment. 10 is an explanatory diagram showing a flow of Embodiment 2. FIG. It is explanatory drawing which shows the result of Example 1. FIG. FIG. 6 is an explanatory diagram showing the results of Example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developer carrier, 2 ... Charge control member, 3 ... Charging bias supply means, 4 ... Charge control means, 5 ... Detection means

Claims (10)

A rotatable cylindrical thin film member, and a conductive member fixedly encased in the cylindrical thin film member so as to support the cylindrical thin film member and having a recess formed in a part of the peripheral surface thereof, A developer carrying member carrying a developer on the surface of the cylindrical thin film member ;
A charge regulating member disposed in contact with the cylindrical thin film member of the developer carrying member at a portion corresponding to the concave portion of the conductive member and performing charge regulation of the developer on the developer carrying member;
A charging bias supply means for supplying a constant current controlled charging bias for charging the developer between the charge regulating member and the developer carrying member;
A detecting means capable of detecting an energization state of the charging regulating member corresponding to an environmental change at the time of charging bias supply ;
And a charging control means for controlling the constant current value of the charging bias so as to keep the reference value charge amount of the developer on the basis of the detection result of the detecting means,
The charging control unit obtains a change amount from a difference between a detection result by the detecting unit and a set value corresponding to an energization state of the charging regulating member under a predetermined environmental condition, and a constant current value of the charging bias is obtained. developing apparatus is characterized that you control the charging bias supplying means so that the current value corresponding to the environmental conditions corresponding to the change amount. A rotatable cylindrical thin film member, and a conductive member fixedly encased in the cylindrical thin film member so as to support the cylindrical thin film member and having a recess formed in a part of the peripheral surface thereof, A developer carrying member carrying a developer on the surface of the cylindrical thin film member ;
A charge regulating member disposed in contact with the cylindrical thin film member of the developer carrying member at a portion corresponding to the concave portion of the conductive member and performing charge regulation of the developer on the developer carrying member;
A charging bias supplying means for supplying a constant voltage controlled charging bias for charging the developer between the charge regulating member and the developer carrying member;
A detecting means capable of detecting an energization state of the charging regulating member corresponding to an environmental change at the time of charging bias supply ;
And a charging control means for controlling the constant current value of the charging bias so as to keep the reference value charge amount of the developer on the basis of the detection result of the detecting means,
The charging control unit obtains a change amount from a difference between a detection result by the detecting unit and a set value corresponding to an energization state of the charging regulating member under a predetermined environmental condition, and a constant voltage value of the charging bias is obtained. developing apparatus is characterized that you control the charging bias supplying means so that the voltage value corresponding to the environmental conditions corresponding to the change amount. The developing device according to claim 1,
The developing device characterized in that the charging bias supply means supplies a constant DC current. The developing device according to claim 1 ,
A developing device characterized in that the detecting means detects a voltage change of the developer carrying member or the charge regulating member. The developing device according to claim 1 or 2 ,
A developing device, wherein a semiconductive resin layer is provided on an opposing surface of at least one of a developer carrying member and a charge regulating member. The developing device according to claim 5, wherein
The developing device characterized in that the semiconductive resin layer has a volume resistivity of 10 ⁸ Ω · cm or more and 10 ¹¹ Ω · cm or less. The developing device according to claim 5, wherein
The developing device, wherein the semiconductive resin layer contains an ion conductive material as a conductive agent. The developing device according to claim 1 or 2 ,
And a driving force transmitting means for transmitting the driving force of the charge regulating member to the developer carrying member. The developing device according to claim 8, wherein
The driving force transmitting means is located at both ends of the cylindrical thin film member with the rotation axis of the charge regulating member as a core material and is pressed against the cylindrical thin film member;
A developing device comprising: a support member provided on an inner peripheral surface side of the cylindrical thin film member and sandwiching the cylindrical thin film member together with the drive pressing member. An image carrier for carrying an electrostatic latent image;
An image forming apparatus comprising: the developing device according to claim 1 for developing an electrostatic latent image on the image carrier.

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