JP2007017866A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, capable of appropriately adjusting the charging characteristics of toner as a developing device where deteriorated toner and new toner are mixed, and to provide an image forming apparatus that uses the same. <P>SOLUTION: The developing device 24 develops a latent image on a photoreceptor 21 with a single-component toner, and is equipped with a toner containing part 33 containing the toner served for development; a toner hopper 39 storing the toner supplied to the toner containing part 33; a developing roller 31 carrying the contained toner on its surface and supplying it to the photoreceptor 21; a charge member 35 adjusting the charge of the toner, by applying electric field to the carried toner farther upstream position than the developing position on the developing roller 31; and a control part 44 applying voltage between the charge member 35 and the developing roller 31 and making the absolute value of the voltage larger within a prescribed time, after supplying the toner to the toner containing part 33 from the toner hopper 39 than in other time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device used in an electrophotographic image forming apparatus and an image forming apparatus using the same. More specifically, the present invention relates to a developing device using one-component toner and an image forming apparatus using the developing device.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a developing device that develops an electrostatic latent image formed on an image carrier with toner is used. A developing device using a one-component toner that does not use a carrier generally has a toner container and a developer carrier that supplies toner to an image carrier. In addition, the developer carrying member is pressed with a toner supplying member for forming an appropriate toner layer, a layer thickness regulating member, a discharging member for discharging the residual toner, and the like under predetermined conditions. It has been. For this reason, the toner on the developer carrying member is applied with a force due to a predetermined pressure or electric field at these press contact points.

  In the one-component toner, a plurality of kinds of external additives having a small particle diameter are generally attached to the surface of a base material composed of a resin and a color material. When a force due to pressure or an electric field is applied to such a toner, the charging characteristics of the toner change due to detachment of the external additive, embedding in the base material, cracking of the base material, and the like. The deteriorated toner thus formed may cause problems such as image noise such as background fogging and toner scattering in the apparatus. Therefore, for example, in the image forming apparatus described in Patent Document 1, a contact member that contacts the developer carrying member is provided, and an alternating voltage is applied to the contact member to adjust the charging characteristics of the toner.

In recent years, there has been a demand for further downsizing and longer life of image forming apparatuses. One of the means for reducing the size is to reduce the size of the imaging unit. For example, there is a type in which a developing unit including a toner container is miniaturized as much as possible by separately arranging a toner hopper for storing new toner and a supply mechanism. In such an image forming apparatus, when the amount of toner in the toner storage portion falls below a predetermined amount, the replenishment mechanism is driven to supply new toner from the toner hopper to the toner storage portion.
JP 2000-98739 A

  However, in the developing device having the replenishment mechanism as described above, new toner is mixed with toner deteriorated by replenishment. In such a situation, the toner charging characteristics are greatly changed, and there is a possibility that the charging characteristics cannot be adjusted by a charging member such as a contact member of the image forming apparatus described in Patent Document 1. In particular, when the developer drive time and bias application time other than during image formation are long, or when the number of times of printing at a low printing ratio is large, the toner deterioration is large, or the volume of the toner container is small, so When the ratio to the toner existing in the toner container increases, there is a problem that the change in the toner charging characteristics is large and the adjustment of the toner charging characteristics becomes difficult.

  Further, in a developing device with a long life specification setting, the toner tends to adhere to the developer carrying member and the charging member with durability. If the toner adheres to the developer carrying member, it may cause image noise, and if the toner adheres to the charging member, the charging function may be deteriorated. In particular, when the potential difference between the charging member and the developer carrying member is increased in order to strongly adjust the charge amount of the deteriorated toner, there is a problem that the toner is easily fixed.

  The present invention has been made to solve the problems of the conventional developing device and the image forming apparatus using the same. That is, the problem is that a developing device capable of appropriately adjusting the charging characteristics of the toner and an image forming apparatus using the same even if the developing device has a developing device in which deteriorated toner and new toner are mixed. Is to provide.

  The developing device of the present invention, which has been made for the purpose of solving this problem, is a one-component developing device, and includes a toner container for storing toner to be developed, a toner hopper for storing toner to be supplied to the toner container, and a container. A developing roller for carrying the toner on the surface and supplying the toner to the image carrier, and a charging member for adjusting the charge of the toner by applying an electric field to the toner carried at a position upstream of the developing position on the developing roller And a voltage adjusting unit that applies a voltage between the charging member and the developing roller and makes the absolute value of the voltage larger than the other time within a predetermined time after replenishing the toner from the toner hopper to the toner storage unit. Is.

  According to the developing device of the present invention, the toner is stored in the toner hopper and replenished to the toner container. The toner in the toner container is carried on the surface of the developing roller and supplied to the image carrier. The toner on the developing roller is charged by a charging member before development. Here, since the voltage applied between the charging member and the developing roller is increased within a predetermined time after replenishing the toner from the toner hopper to the toner container, the new toner is mixed with the deteriorated toner for a while. Is actively charged. On the other hand, since this voltage is not increased at other times, problems such as toner sticking are avoided. Therefore, even if the developing device has a developing device in which deteriorated toner and new toner are mixed, the developing device can appropriately adjust the charging characteristics of the toner.

Furthermore, in the present invention, it is desirable to have a pressing member that presses the charging member against the developing roller.
By doing so, the charge adjusting force for the toner on the developing roller by the charging member becomes large while being pressed by the pressing member. Therefore, the charge can be adjusted more effectively.

Furthermore, in the present invention, it is desirable that the charging member is movable between a state where it contacts the developing roller and a state where it does not contact the developing roller.
In this way, the charge adjustment force for the toner on the developing roller by the charging member is large while the developing roller is in contact with the developing roller. Therefore, the charge can be adjusted more effectively.

Furthermore, in the present invention, it is desirable that the charging member has a charging member driving unit that is brought into contact with the developing roller only within a predetermined time after toner replenishment from the toner hopper to the toner storage unit, and separated from the developing roller at other times.
In this way, the charge adjusting force by the charging member is increased only within a predetermined time after the replenishment of toner from the toner hopper to the toner container. Therefore, the charge can be adjusted more effectively.

  The present invention also includes an image carrier and a developing device that develops a latent image of the image carrier with a one-component toner (hereinafter simply referred to as “toner”), and a toner image formed on the image carrier. An image forming apparatus for forming an image by transferring a toner to a medium, comprising: a toner containing portion that contains toner to be developed; a toner hopper that stores toner to be replenished to the toner containing portion; A developing roller that is carried and supplied to the image carrier, a charging member that adjusts the charge of the toner by applying an electric field to the toner carried at a position upstream of the developing position on the developing roller, and the charging member and the developing roller And an image forming apparatus having a voltage adjusting unit that applies a voltage between the toner hopper and the toner hopper so that the absolute value of the voltage becomes larger than the other time within a predetermined time after replenishing the toner from the toner hopper to the toner storage unit.

  According to the developing device of the present invention and the image forming apparatus using the same, it is possible to appropriately adjust the charging characteristics of the toner even if the developing device has a developing device in which deteriorated toner and new toner are mixed. ing.

"First form"
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a so-called tandem color printer.

  In the color printer 1 of this embodiment, as shown in FIG. 1, the image forming units 10Y, 10M, 10C, and 10K for each color are arranged along the intermediate transfer belt 11, and a toner image of each color is formed by these. Are superimposed on the intermediate transfer belt 11. The superimposed toner images are transferred onto a recording sheet by the secondary transfer device 12 and fixed by the fixing device 13 to form a color image. The image forming units 10Y, 10M, 10C, and 10K for the respective colors are the same devices, and the YMCK subscript is omitted in the following description.

  As shown in FIG. 1, the image forming unit 10 includes a photoconductor 21 and a charging device 22, an exposure device 23, a developing device 24, a primary transfer device 25, and a cleaning device 26 disposed around the photoconductor 21. The photosensitive member 21 is rotationally driven as indicated by an arrow in the figure, and is uniformly charged by a charging device 22 such as a charging roller. The charged photoconductor 21 is exposed by an exposure device 23 such as a laser or LED to form an electrostatic latent image. The formed electrostatic latent image is developed with toner of each color in the developing device 24 and transferred to the intermediate transfer belt 11 by the primary transfer device 25. The toner remaining on the photoreceptor 21 after the transfer is scraped off and collected by a cleaning device 26 such as a cleaning blade.

  Here, as shown in FIGS. 1 and 2, the developing device 24 according to the present embodiment includes a developing roller 31 and a supply roller 32, and supplies the toner stored in the toner storage portion 33 to the photosensitive member 21. Is. Further, a regulating member 34, a charging member 35, and a charge eliminating member 36 are in contact with the developing roller 31, respectively. The regulating member 34 regulates the toner layer on the developing roller 31 to have a predetermined thickness. The charging member 35 adjusts the charge by applying an electric field to the toner on the developing roller 31. The neutralizing member 36 neutralizes residual toner remaining on the developing roller 31 even after development.

  Further, as shown in FIG. 2, the toner containing portion 33 is provided with an optical toner remaining amount detecting means 37, and a signal is transmitted when the toner remaining amount becomes a predetermined amount or less. In addition, a toner hopper 39 is connected to the toner container 33 via a toner conveyance path 38. In the toner conveyance path 38, a conveyance screw 48 that conveys the toner in the toner hopper 39 to the toner storage unit 33 is provided. Further, a replenishment motor 49 is connected to the conveying screw 48, and the replenishment motor 49 is driven in response to the output of the toner remaining amount detecting means 37. As a result, new toner is added to the toner container 33 as necessary.

  Further, a high voltage power supply 41 is connected to the developing roller 31 and a developing voltage is applied. The high voltage power supply 41 is controlled by the control unit 42. The charging member 35 is connected to a high voltage power supply 43 and applied with a voltage. The high voltage power supply 43 is controlled by the control unit 44. The charging member 35 is a conductive sheet having a surface resistance value of 10E + 4 to 10E + 8 (Ω), and is pressed against the developing roller 31 by a flat spring 45 with a uniform force in the axial direction.

  Here, in this embodiment, a voltage is not always applied to the charging member 35. The potential difference between the charging member 35 and the developing roller 31 is controlled as shown in FIG. That is, when the replenishing motor is driven in response to the signal from the toner remaining amount detecting means 37, the control unit 44 controls the high voltage power source 43 to apply a voltage of about + 200V to the voltage of the developing roller 31 for 300 seconds. To do. Alternatively, the voltage is applied in the same manner even after printing with a printing ratio of 5% or less has been performed exceeding the specified number. Alternatively, the voltage is applied in the same manner even when the driving time of the developing device 24 and the bias application time are long except during image formation.

  Here, the voltage applied by the high voltage power supplies 41 and 43 is not limited to a DC voltage, but may be an AC voltage. In the case of an AC voltage, the applied voltage value may be changed so that the effective value of the potential difference is expanded for a certain time after toner replenishment. Furthermore, the method of pressing the charging member 35 against the developing roller 31 is not limited to the leaf spring, and an elastic material such as a foamed urethane material or rubber may be used, or pressing with a metal rod may be used. Furthermore, the integral charging member 35 may be formed by coating a conductive sheet on a metal leaf spring. Further, the time during which the voltage is applied is not limited to 300 seconds, and may be changed according to the amount of toner supply.

  In this way, when the toner is replenished by the signal from the toner remaining amount detecting means 37, a voltage is applied to the charging member 35 by the high voltage power supply 43 by the control unit 44. Therefore, when the new toner is mixed with the deteriorated toner, the charge of the toner is positively adjusted by the charging member 35, so that a large change in toner charging characteristics can be suppressed. On the other hand, since the voltage is not always applied to the charging member 35, the toner does not adhere to the charging member 35.

  As described above in detail, according to the color printer 1 of the first embodiment, the voltage is applied to the charging member 35 only when new toner is replenished, so that the deteriorated toner and the new toner are mixed. Even with a developing device, it is possible to appropriately adjust the charging characteristics of the toner.

"Second form"
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is the same as the first embodiment except for the charging member of the developing device, and the same members are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 4, the charging member 51 of the developing device 50 according to the present embodiment is formed integrally with only a conductive sheet and does not have a leaf spring. For example, a sheet having a surface resistance of 10E + 4 to 10E + 8 (Ω), a thickness of 60 to 80 (μm), and a Young's modulus of 0.04 to 0.3 × E + 10 (Pa) may be selected as the conductive sheet. Further, the charging member 51 is held slightly apart from the developing roller 31 as indicated by the solid line in the figure when no voltage is applied.

  The charging member 51 of this embodiment is also connected to the high-voltage power supply 43 as in the first embodiment, and a voltage is applied at the same timing as in FIG. When a voltage is applied to the charging member 51, an electric field is formed between the developing roller 31 and the charging member 51 is attracted to the developing roller 31 as indicated by a broken line in the drawing. Therefore, the toner charge is positively adjusted at the same timing as in the first embodiment.

  When the voltage applied to the charging member 51 is stopped, the charging member 51 returns to the original position indicated by the solid line in the drawing by the elastic force of the charging member 51 itself. Alternatively, a weak spring or the like may be provided on the charging member 51 so that the charging member 51 returns to the solid line position with its urging force.

  As described in detail above, according to the image forming apparatus of the second embodiment, as in the first embodiment, even if it has a developing device that mixes deteriorated toner and new toner, The charging characteristics of the toner can be adjusted.

"Third form"
Hereinafter, a third embodiment of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is the same as the first embodiment except for the charging member of the developing device, and the same members are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 5, the charging member 61 of the developing device 60 of this embodiment is a charging member 61 made of a conductive sheet similar to the charging member 35 of the first embodiment, and is attached to a leaf spring 62 or the like. The leaf spring 62 is connected to a solenoid 63 and holds the charging member 61 so as to be able to contact and separate from the developing roller 31. Further, a high voltage power supply 43 is connected to the charging member 61. Here, the high voltage power supply 43 is not particularly controlled, and a voltage is constantly applied so that the charging member 61 is about +200 V with respect to the developing roller 31.

  On the other hand, a controller 64 is connected to the solenoid 63 and is driven at the same timing as in FIG. That is, when the replenishing motor is driven in response to the signal from the toner remaining amount detecting means 37, the control unit 64 controls the solenoid 63 to press the charging member 61 against the developing roller 31 as indicated by a broken line in the drawing. . Alternatively, the charging member 61 is similarly pressed against the developing roller 31 even after printing with a printing ratio of 5% or less has been performed exceeding the specified number. Therefore, the toner charge is positively adjusted at the same timing as in the first embodiment.

  As described in detail above, according to the image forming apparatus of the third embodiment, similarly to the first embodiment, even if it has a developing device that mixes deteriorated toner and new toner, The charging characteristics of the toner can be adjusted.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, each component of the image forming apparatus 1 is not limited to the above, but may be any function as long as each function can be implemented. For example, the photoconductor 21 is not limited to a roller but may be a belt-like photoconductor. The charging device 22 is not limited to the roller charging method, and may be a corona discharge charging charger, blade, brush, proximity charging member, or the like. The cleaning device 26 may be a cleaning brush, a cleaning roller, or the like. Alternatively, a cleanerless system without the cleaning device 26 may be used. In addition to the fixing roller system, the fixing device 13 may be a fixing belt system, a non-contact type fixing system, or the like. Further, the transfer method is not limited to the two-step transfer method, and a direct transfer method in which the toner image is transferred from the photosensitive member to the recording material may be used.

It is sectional drawing which shows schematic structure of the color printer which concerns on a 1st form. It is sectional drawing which shows schematic structure of the developing device which concerns on a 1st form. It is a time chart which shows the example of the voltage applied to a charging member. It is sectional drawing which shows schematic structure of the developing device which concerns on a 2nd form. It is sectional drawing which shows schematic structure of the developing device which concerns on a 3rd form.

Explanation of symbols

1 Color printer (image forming device)
24, 50, 60 Developing device 31 Developing roller 33 Toner storage unit 35, 51, 61 Charging member 39 Toner hopper 44 Control unit (voltage adjustment unit)
45 Leaf spring (pressing member)
63 Solenoid (Charging member drive)

Claims (5)

In a one-component developing device,
A toner container for storing toner to be developed;
A toner hopper for storing toner to be replenished to the toner container;
A developing roller for carrying the toner stored on the surface and supplying the toner to the image carrier;
A charging member for adjusting the charge of the toner by applying an electric field to the toner carried at a position upstream of the developing position on the developing roller;
A voltage adjusting unit that applies a voltage between the charging member and the developing roller, and makes the absolute value of the voltage larger than the other time within a predetermined time after replenishing the toner from the toner hopper to the toner containing unit. A developing device comprising: The developing device according to claim 1,
A developing device comprising: a pressing member that presses the charging member against the developing roller. The developing device according to claim 1,
The developing device, wherein the charging member is movable between a state in contact with the developing roller and a state not in contact with the developing roller. The developing device according to claim 3,
A developing device comprising: a charging member driving portion that contacts the developing roller only within a predetermined time after toner replenishment from the toner hopper to the toner containing portion, and is separated from the developing roller at other times. apparatus. An image carrier and a developing device that develops the latent image of the image carrier with a one-component toner (hereinafter simply referred to as “toner”), and transfers the toner image formed on the image carrier to a medium; In an image forming apparatus for forming an image,
A toner container for storing toner to be developed;
A toner hopper for storing toner to be replenished to the toner container;
A developing roller for carrying the toner stored on the surface and supplying the toner to the image carrier;
A charging member for adjusting the charge of the toner by applying an electric field to the toner carried at a position upstream of the developing position on the developing roller;
A voltage adjusting unit that applies a voltage between the charging member and the developing roller, and makes the absolute value of the voltage larger than the other time within a predetermined time after replenishing the toner from the toner hopper to the toner containing unit. An image forming apparatus comprising:

Images