JP3285728B2 - Developing device and image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile, a printer, and the like.
More particularly, the present invention relates to a developing device provided with a developing device for pre-driving a developer carrier and an image forming device using the developing device .

[0002]

2. Description of the Related Art Conventionally, as a developing device of this type, a one-component developer is supplied to a non-magnetic developer carrier, and a developer amount regulating member disposed in close proximity to the developer carrier. In a developing device in which the developer is pressed into a thin and uniform layer as a thin and uniform layer, the developer is sent to a holder holding an electrostatic latent image on the surface, and the developer is attached to the electrostatic latent image, the developer amount regulating member is ,
A developing device comprising an electrode layer made of a conductive material to which an alternating voltage is applied, and an insulating layer laminated on the electrode layer so as to be disposed on the developer carrier side is known. (See, for example, JP-A-59-17486).
No. 1). In this developing device, the developer amount regulating member is vibrated in synchronization with the frequency of the alternating voltage by applying the alternating voltage, so that the developer carrying amount is maintained even when the pressing force of the developer amount regulating member against the developer is reduced. A thin and uniform layer of the developer can be stably formed on the body.

[0003]

By the way, in this type of developing device, if the surface portion of the developer carrier passes through the developing device once and is regulated only by the supply of the developer and the amount of the developer,
It is difficult to supply a sufficient amount of the developer to the developer carrying member to meet a relatively large amount of developer consumption such as the amount of developer consumed by developing a solid image latent image. For this reason, for example, when developing a solid image latent image over one or more rounds of the developer carrier, the amount of developer on the developer carrier gradually decreases during this development. Therefore, if the next latent image is developed in a state where the amount of the developer on the developer carrier is excessively reduced, the development density becomes insufficient. In addition, as a result of developing a latent image having a relatively large amount of developer consumption, such as a solid image latent image, the next latent image remains in a state where such an excessive decrease in the developer is partially generated. Is developed,
This results in uneven development density. Such a defect,
This is particularly likely to occur in a full-color image forming apparatus in which a solid image is frequently formed. Such a problem is that the amount of developer carried on the developer carrier at the time of the start of development is, for example, such that when the solid image latent image is developed as described above, excessive density shortage does not occur on the image. It can be prevented by setting the amount to have a margin. For this reason, even if any latent image has been developed in the past, the development is started so that the amount of the developer on the developer carrier at the start of the development becomes a sufficient amount of the developer as described above. Prior to this, preliminary driving of the developer carrier may be performed, in which the developer carrier is driven to supply the developer to the developer carrier. In the preliminary driving of the developer carrier, the developer is transported on the developer carrier, and the developer may be scattered. Therefore, the preliminary driving of the developer carrier is as short as possible. It is desirable to be able to finish in time.

[0004]

[0005] The present invention has been made in view of the above background, the purpose of that is thin and formed by applying an alternating electric field to the developer amount regulating member for regulating the amount of developer on the developer carrying member and Good development can be performed with a uniform layer of the developer, and the developer can be quickly loaded by pre-driving the developer to reduce the shortage of the developer on the developer due to the preceding development. An object of the present invention is to provide a developing device capable of restoring the amount of developer on a body .

[0006]

To achieve the above Symbol purpose SUMMARY OF THE INVENTION, The invention according to claim 1, in a region facing the image bearing member a latent image is formed on the surface, and carries the developer conveying A developer carrying member, a developer amount regulating member that regulates an amount of the developer carried on the developer carrying member, and a bias voltage applying unit that applies a bias voltage to the developer amount regulating member. After the developer carrier is pre-driven during non-development to carry the developer on the developer carrier surface, the developer is used to develop the latent image formed on the image carrier. In a developing device provided with a developing device, a bias voltage applied to the developer amount regulating member by the bias voltage applying unit is:
During development, a bias voltage consisting of a DC component and an alternating component is used, and at the time of preliminary driving, a bias voltage consisting of only a DC component is used.

According to a second aspect of the present invention, in the developing device according to the first aspect, a plurality of the developing units are provided, and the plurality of developing units are moved to position an arbitrary developing unit at a developing position opposed to the image carrier. The pre-driving is performed on a developer carrier of a developing device to be used for the next development.

According to a third aspect of the present invention, in the developing device according to the second aspect, a bias receiving member for receiving the bias voltage to the developer amount regulating member provided in each of the plurality of developing units, and a developing position. A developing bias voltage applying member provided on the developing device main body side facing the bias voltage receiving member of a developing device; and a developing device in a standby position where the developing device used for the next development is located. The bias voltage applying means is constituted by a bias voltage applying member during pre-driving provided on the developing device main body side facing the bias voltage receiving member.

[0009] 請 Motomeko 4 invention, an image bearing member, a latent image on the surface
In the area facing the image carrier on which
A developing device that carries and transports the developer with the body and develops the latent image
And an image forming apparatus having the developing device.
Wherein the developing device according to claim 1, 2 or 3 is used.
It is assumed that .

[0010]

According to the first to fourth aspects of the present invention, the developing device, in which the bias voltage applying means applies a DC bias voltage to the developer amount regulating member at the time of pre-driving, supplies the developer amount regulating member with a DC component and a DC component. The developer adheres more quickly to the surface of the developer carrying member than in the case where the pre-driving is performed by applying a bias voltage including an AC component. Further, the amount of the developer adhered to the surface of the developer carrier is regulated by the developer amount regulating member. Further, at the time of development, a developing device in which a bias voltage composed of a DC component and an AC component is applied to the developer amount regulating member by a bias voltage applying means, the developer charged to the opposite polarity or the low-charged developer carries the developer. The normally charged developer removed from the body surface adheres to the surface of the developer carrier.

In particular, in the second aspect of the present invention, the developing is performed by moving the plurality of developing units and positioning an arbitrary developing unit at a developing position opposed to the image carrier. Further, in the developing device to be used for the next development, preliminary driving is performed on the developer carrier, and the amount of the developer on the surface of the developer carrier is regulated. Therefore, the developing device in which the amount of the developer on the surface of the developer carrier is regulated is moved to the developing position and used for the next development.

According to a third aspect of the present invention, in the developer amount regulating member of the developing device at the developing position, the bias receiving member faces the bias receiving member at the developing position. During the development, a bias is applied in contact with the bias voltage applying member disposed on the side. The developer amount regulating member of the developing device at the standby position where the developing device to be used for the next development is located is located at the standby position, and the bias voltage receiving member faces the bias voltage receiving member. The bias voltage is applied by contacting the bias voltage applying member disposed during the pre-driving operation.

[0013]

[0014]

【Example】

Embodiment 1 Hereinafter, a first embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine (hereinafter, referred to as a copying machine) which is an image forming apparatus will be described. In the following description, it is assumed that, for example, a non-magnetic one-component toner (hereinafter, referred to as toner), which is charged to a negative polarity by friction, is used as the developer. FIG. 1 is a sectional view showing a schematic configuration of the developing device according to the present embodiment. The developing device according to the present embodiment has the configuration shown in FIG.
As shown in FIG. 1, one developing unit 21 is provided, and a belt-shaped photosensitive member (hereinafter, referred to as a photosensitive member) as an image carrier that moves in the direction of arrow a in the figure is provided on the upper part of a casing 22 of the developing unit 21. An opening 22a is formed in a portion facing the belt 1). Here, the photoconductor is not limited to a belt shape. The opening 2 is provided in the casing 22.
2a, a developing roller 23 as a developer carrying member disposed so as to face the photoreceptor belt 1 and disposed below the developing roller 23 so that the surface thereof rubs against the developing roller 23. A supply roller 24 as a developer supply member and a thin layer blade 25 as a developer amount regulating member for regulating the amount of toner on the developing roller 23 are provided.

The developing roller 23 has a predetermined peripheral speed ratio with respect to the photoreceptor belt 1 and has a surface area opposite to the photoreceptor belt 1 as shown by an arrow b in FIG. It is configured to rotate in the same direction as the movement direction. An electric field is applied to the developing roller 23 by the bias power supply 23 a so that the toner frictionally charged to a negative polarity receives an electrostatic force from the developing roller 23 toward the photosensitive belt 1. Is applied. In addition,
It is desirable that the developing bias voltage is set so that the potential difference between the developing roller 23 and the photoreceptor belt 1 becomes about 200V.

The supply roller 24 has a volume resistance of 10 ⁶ to 10 ⁸ Ω ·
cm of an elastic body such as polyurethane foam, and has a predetermined peripheral speed ratio with respect to the developing roller 23, and the surface of the developing roller 23 at the rubbing portion A with the developing roller 23 as shown by an arrow c in the figure. It is configured to rotate in the same direction as the movement direction. In addition, the rubbing portion A is the supply roller 2
4 is a toner supply position to the developing roller 23. Also,
An electric field is applied to the supply roller 24 such that the toner frictionally charged to a negative polarity receives an electrostatic force from the supply roller 24 toward the developing roller 23 by the bias power supply 24a.
A DC supply bias voltage such as that formed between the developing roller 23 and the developing roller 23 is applied. Note that this supply bias voltage is
The potential difference between the developing roller 23 and the supply roller 24 is about 15
It is desirable to set it to be 0 to 200V.

The thin-layer blade 25 is provided on the downstream side of the rubbing portion A in the moving direction of the surface of the developing roller 23 and near the opening 22a so that its end is in contact with the developing roller 23. And is made of a conductive elastic body such as a metal plate having a thickness of 0.1 mm, for example. In this embodiment, a blade bias voltage to be described later is applied to the thin blade 25.

On the left side of the rubbing portion A between the developing roller 23 and the supply roller 24, a well-known first screw-shaped toner conveying member (hereinafter, referred to as a first conveying member) for conveying the toner from the near side to the far side of the drawing. 26).
A well-known screw-shaped second toner conveying member (hereinafter, referred to as a second toner conveying screw) 27 for conveying the toner from the back side to the front side of the paper is provided below the supply roller 24. I have.

At the longitudinal end of the developing unit 21, a toner hopper is provided as a hopper (not shown). Here, the first toner conveying screw 26 is disposed in parallel with the developing roller 23 and the supply roller 24 from the toner hopper to the other end in the longitudinal direction of the developing device 21. Developing roller 23 and supply roller 24 so as to transport toner toward
And at a predetermined peripheral speed ratio. The casing 22 is formed so that a part thereof is in contact with the supply roller 24 as shown in FIG. 1, and the developing roller 23, the supply roller 24 and the casing 22 surround the first toner conveying screw 26. A toner transport space 26a is formed.

In the above configuration, the first toner conveying screw 26 conveys the toner from the toner hopper into the toner conveying space 26 a by rotating in a predetermined direction, and supplies the toner onto the supply roller 24. The toner supplied on the supply roller 24 is rubbed by the supply roller 24 and the developing roller 23 in the rubbing portion A, and is charged to a negative polarity. Then, the toner charged to the negative polarity receives an electrostatic force from the supply roller 24 side to the development roller 23 side by an electric field formed between the development roller 23 and the supply roller 24, and It is supplied and carried on the surface of the roller 23. The toner carried on the surface of the developing roller 23 is conveyed to a region where the thin layer blade 25 contacts the surface. In this area, the toner on the developing roller 23 is transported to the developing area G after the toner is thinned by the thin layer blade 25, and the electrostatic latent image formed on the surface of the photoreceptor belt 1 in the developing area G is removed. Develop by contact development.

Here, the toner not used in the developing step is transported by the first toner transport screw 26 to the end of the developing device opposite to the toner hopper. A toner circulating portion (not shown) is provided outside the effective diameter portion in the axial direction of the developing roller 23 and the supply roller 24 at the end of the developing device opposite to the toner hopper. The toner transported to the toner circulating portion by the first toner transport screw 26 falls to the lower part of the developing device 21 by gravity.

Below the developing unit 21, the second toner conveying screw 27 is provided with the developing roller 23 and the supply roller 24.
And the first toner conveying screw 26 are disposed in parallel with each other,
It is rotated so as to convey the toner in a direction opposite to the first toner conveying screw 26, and conveys the toner not used in the developing step to the toner hopper. (Hereinafter, margin)

In the developing area G, the toner is used for developing the electrostatic latent image on the photoreceptor belt 1, and after passing through the developing area G, the amount of toner adhering on the surface of the developing roller 23 becomes less than a specified amount. Therefore, it is necessary to restore the toner adhesion amount on the surface portion to a specified amount before the surface portion is used for the next development. As a result of intensive studies, the present inventors have found that a blade bias voltage composed of a DC component and an AC component (hereinafter referred to as a DC superimposed AC blade bias voltage) is used as a blade bias voltage applied to the thin blade 25. When the toner is used and when a blade bias voltage obtained by removing an AC component from the DC superimposed AC bias voltage, that is, when a DC blade bias voltage (hereinafter, referred to as a DC blade bias voltage) is used, toner adhesion on the surface of the developing roller 23 is performed. It was found that the time required to restore the amount to the specified amount was different.
This will be described with reference to FIG.

FIG. 2 is a graph showing the relationship between the number of rotations of the developing roller and the amount of toner adhering on the developing roller. Note that the amount of toner adhering on the developing roller when a DC blade bias voltage is used as the blade bias voltage is indicated by a triangle in the figure, and the toner adhering amount on the developing roller when a DC superimposed AC blade bias voltage is used. The amounts are indicated by □ in the figure. Further, the rotation speed of the developing roller is the same speed when the DC blade bias voltage is used and when the DC superimposed AC blade bias voltage is used.

From the results shown in FIG. 2, the toner adhesion amount on the surface of the developing roller 23 is smaller when the DC blade bias voltage is used as the blade bias voltage than when the DC superimposed AC blade bias voltage is used. It was found that the developing roller 23 recovered from 0 to the specified amount with a small number of rotations. That is, the recovery of the toner layer on the developing roller 23 is quickly performed.

When a DC blade bias voltage is used as the blade bias voltage, the developing roller 2
The toner on 3 is formed by an electrostatic force received from an electric field formed between the developing roller 23 and the thin layer blade 25 and a contact pressure of the thin layer blade 25 against the developing roller 23.
Pressed onto the surface of the developing roller 23, the developing roller 2
3 adheres.

When a DC bias AC blade bias voltage is used as the blade bias voltage, the toner on the developing roller 23 vibrates on the surface of the developing roller 23 where the thin layer blade 25 contacts. 25, the toner is separated into a normally charged toner, a reversely charged toner and a lowly charged toner, and only the normally charged toner adheres to the developing roller 23, and the reversely charged toner and the lowly charged toner are developed. Tend to be returned to the vessel 21. In this case, the reversely charged toner or the lowly charged toner is removed from the developing roller 23, and the reversely charged toner or the lowly charged toner does not scatter on the photosensitive belt 1 in the developing area G. Of the photoreceptor belt 1 to prevent contamination of the background.

Therefore, in this embodiment, the bias power supply 25
As a blade bias voltage applied to the thin layer blade 25 by a, during non-development, as shown in FIG. 3A, a direction in which the toner triboelectrically charged to a negative polarity is pressed onto the developing roller 23 by the bias power supply 25a. The developing roller 23 is preliminarily rotated using a DC blade bias voltage generated between the developing roller 23 and an electric field which receives the electrostatic force of the developing roller 23. The DC blade bias voltage at this time is desirably set so that the potential difference between the developing roller 23 and the thin layer blade 25 is 150 to 200V. Further, at the time of development, development is performed using a DC superimposed AC blade bias voltage as shown in FIG. 3B as the blade bias voltage.

As described above, by using the DC blade bias voltage during the pre-rotation, the pre-rotation of the developing roller 23 can be performed quickly on the surface of the developing roller 23 as compared with the case where the DC superimposed AC blade bias voltage is used during the pre-rotation. Can be recovered. In addition, by using the DC superimposed AC blade bias voltage during the development, the above-described effect of suppressing the background portion of the photoreceptor belt can suppress the contamination of the background portion of the photoreceptor belt 1 and perform favorable development. In addition, since the developing roller is pre-rotated at the time of non-development and development is performed after forming a uniform toner layer on the surface of the developing roller, it is possible to use the uniform toner layer on the surface of the developing roller from the start of development to obtain a good image. Development can be performed.

Embodiment 2 FIG. 4 is a sectional view showing a developing device according to a second embodiment. The developing device is disposed near the photoreceptor belt 1 and accommodates a yellow developing device 21Y, a magenta developing device 21M, a cyan developing device 21C, and a black developing device 21B in a casing 31. It is configured. Hereinafter, this developing device is referred to as a revolver developing unit. Revolver developing unit 3 of FIG.
Numeral 0 is provided so as to be rotatable about a rotation center axis, and is rotated in the casing 31 in a direction indicated by an arrow d by a drive mechanism (not shown). By this rotation, each developing unit 21Y, 2Y
Any of the developing devices 1M, 21C and 21B can be moved to a developing position facing the photoreceptor belt 1.

FIG. 4 shows a state in which the yellow developing unit 21Y is arranged at the developing position. In addition, each of the developing devices 21Y, 21M, 21C, 21 in the second embodiment.
B has the same configuration and operation as the developing device 21 in the first embodiment, and therefore detailed description is omitted. Further, each of the developing devices 21Y, 21M, 21C, 21B
The same members that correspond to the developing device 21 in the first embodiment are shown by changing only the English characters at the end of the reference numerals in FIG.

The developing units 21Y, 21M, 21C, 2 in FIG.
Reference numeral 1B denotes a developing device using a non-magnetic one-component developer, which stores yellow, magenta, cyan, and black toners, respectively, and supplies the toners to an electrostatic latent image formed on the photoreceptor belt 1. The electrostatic latent image is visualized. Each of the developing devices 21Y, 21M, 21C, and 21B has a cylindrical developing roller 23Y, 23M as a developer carrier.
23C, 23B, and thin layer blades 25Y, 25M, 25C, 25B as a developer regulating amount regulating member are provided, respectively. Further, each of the developing rollers 23Y, 2Y
3M, 23C and 23B are the developing units 21Y, 21M, 2
The openings 21a provided in 1C and 21B are arranged so that a part thereof is exposed to the outside.

The revolver developing unit 30 having the above configuration
Are synchronized with the color information, and the developing units 21Y, 21M, 21
C, 21B are rotated about a rotation center axis so as to be selectively disposed at the developing position, and the developing devices 21Y, 21M, 21
C and 21B are the developing rollers 23Y and 2
By rotating 3M, 23C, 23B in the direction of arrow b in the figure,
The corresponding electrostatic latent images formed on the photosensitive belt 1 are sequentially developed. Then, the developed images are superimposed on a transfer paper (not shown) to form a full-color image.

In this embodiment, before the developing device used for the next development (hereinafter, this developing device is referred to as a standby unit) is moved to the developing position, the developing roller of the developing device is pre-rotated. . During the preliminary rotation, a DC blade bias voltage is applied to the thin layer blade of the developing device. During development, a DC superimposed AC blade bias voltage is applied to a thin layer blade of a developing device (hereinafter, this developing device is referred to as a current unit) arranged at a developing position.

To switch the blade bias voltage to be applied to the thin layer blade, energization of the thin layer blade is performed by, for example, contacting a contact provided on the thin layer blade with a bias provided by a revolver developing unit 30 shown in FIG. It can be performed by mechanically disconnecting by applying or disconnecting to the application electrode, or by electrically disconnecting by using a sensor. Here, an example in which the blade bias voltage applied to the thin layer blade is switched by electrically disconnecting the energization of the thin layer blade using a sensor will be described with reference to FIG.

FIG. 5 is a flowchart showing an example of the process control for switching each blade bias. Since the switching process control of each blade bias of each developing device is the same, the description will be made by taking the magenta developing device 21M located at the standby position in the drawing as an example. In the example of FIG. 5, a gate 13 that can be electrically opened and closed by a DC blade bias voltage 13 and a DC superimposed AC blade bias voltage 12 respectively.
a, 12a are connected to a developing device at a standby position, for example, a thin layer blade 25M of a magenta developing device 21M, and respective gates 13a, 12a are located in the revolver developing unit 30 of the magenta developing device 21M. Is connected to the position detection sensor 11 that detects Further, the position detection sensor 11 opens and closes a gate 13a connected to the DC blade bias voltage 13 and a gate 12a connected to the DC superimposed AC blade bias voltage 12 according to the position of the magenta developing device 21M in the revolver developing unit 30. It has the function of switching.

In the example of FIG. 5, the position detecting sensor 11
Detects that the magenta developing device 21M is located at the standby position, for example, opens the gate 13a connected to the DC blade bias voltage 13 and closes the gate 12a connected to the DC superimposed AC blade bias voltage 12.
Thereby, the thin layer blade 25M of the magenta developing device 21
, A DC blade bias voltage 13 is applied. When the position detection sensor 11 detects that the magenta developing device 21M is located at the developing position, for example, it closes the gate 13a connected to the DC blade bias voltage 13 and opens the gate 12a connected to the DC superimposed AC blade bias voltage 12. . Thereby, the magenta developing device 21
Is applied to the thin blade 25M. Thus, each gate 13a,
By electrically opening and closing 12a, it is possible to switch the blade bias voltage applied to the thin layer blade.

FIG. 6 is a flowchart showing an example of drive control of the standby unit and the current unit. In the example of FIG. 6, the driving force of a driving unit such as a motor (not shown) is transmitted to the developing device located at the standby position via the clutch 43, that is, to the developing roller of the standby unit, and is also transmitted via the clutch 44. Is transmitted to the developing device located at the developing position, that is, the developing roller of the current unit. When transmitting this driving force, each clutch 43,
The operation of 44 is controlled by the action of the solenoid 42 driven by the solenoid driving means 41. And
For example, at the time of development, the solenoid 42 connects the clutch 44, so that the driving force of a driving unit (not shown)
It is transmitted to the developing roller of the current unit. At the time of preliminary rotation, by connecting the clutch 43 while the solenoid 42 remains connected to the clutch 44,
The driving force of the driving means is transmitted to the developing roller of the standby unit.

Here, in this embodiment, as described later,
The developing device that has been preliminarily rotated is moved to a developing position by driving a revolver rotation motor. In the example of FIG. 6, a case where the developing rollers of each unit are driven by using a plurality of motors by driving the developing rollers of the standby unit and the current unit using a single motor as a driving unit, for example. In comparison with the above, it is possible to reduce the difference in control timing between the driving of the revolver rotation motor and the driving of the developing roller of each unit.

FIG. 7 is a timing chart for driving the photoreceptor belt motor, applying the DC blade bias voltage to the standby unit, driving the revolver rotation motor, and applying the DC superimposed AC blade bias voltage to the current unit. ing. Note that the timing of the development roller preliminary rotation drive in the standby unit and the application of the DC blade bias voltage to the standby unit coincide with each other, and the drive of the current unit and the application of the DC superimposed AC blade bias voltage to the current unit. Are the same.

The revolver developing unit 3 of this embodiment
Reference numeral 0 denotes a current unit, that is, a magenta developing device 21M located upstream of the yellow developing device 21Y in the rotation direction of the revolver developing unit 30 in FIG. In the magenta developing device 21M located at the standby position, the DC blade bias voltage applied to the thin layer blade 25M is turned on as shown in FIG.
Starts preliminary rotation. By this preliminary rotation, the toner starts to adhere to the surface of the developing roller 23M, and the toner on the surface becomes a toner layer having a uniform thickness by the thin layer blade 25M.

Here, the developing device disposed at the standby position, that is, the magenta developing device 21M in FIG.
M surface contacts the surface of the photoreceptor belt 1 and the roller 23M
A part of the upper toner layer is removed from the surface of the roller 23M. For this reason, there is a possibility that image formation at the start of development may be adversely affected.

Therefore, in the present embodiment, taking into account the amount of toner removed from the developing roller surface of the developing device at the standby position, the amount of toner adhering to the developing roller surface by the preliminary rotation is smaller than the amount required for development. The length of the preliminary rotation of the roller is set so as to increase.

The DC blade bias voltage applied to the thin layer blade of the developing device at the standby position, that is, the thin layer blade 25M of the magenta developing device 21M in FIG.
F, the pre-rotation of the developing roller 23M is completed, and at the same time, the revolver rotation motor is turned on to start the operation as shown in FIG. By the operation of the revolver rotation motor, the magenta developing device 21M at the standby position is arranged at the developing position and becomes a current unit. At this time, the developing unit disposed on the upstream side in the rotation direction of the revolver developing unit 30 from the developing unit at the standby position, that is, the cyan developing unit 21C in FIG. 4 is the standby unit.

In the developing device at the developing position, the DC superimposed AC blade bias voltage applied to the thin blade is ON.
At the same time, the developing roller is driven to rotate to develop the latent image on the photosensitive belt 1. The developing device at the standby position, that is, the cyan developing device 21C in FIG.
Starts preliminary rotation.

Then, at the same time when the DC superimposed AC blade bias voltage is turned off, the pre-rotation of the developing roller of the developing device in the standby position is completed, the revolver rotation motor is turned on, and the developing device is turned on. It is moved from the position to the developing position to become a current unit. Then, the developing device at the standby position, that is, the cyan developing device 21C in FIG.
Develops the latent image on the photoreceptor belt 1 at the developing position in the same manner as the magenta developing device 21M. Hereinafter, each of the developing devices arranged on the upstream side in the rotation direction of the revolver developing unit 30, that is, the black developing device 21B and the yellow developing device 2 in FIG.
1Y becomes a standby unit in order. And each developing unit is
After each developing roller is pre-rotated and a toner layer is formed on the surface of the developing roller, it moves to a developing position and becomes a current unit in order to develop a latent image on the photosensitive belt 1.

As described above, according to the present embodiment, a DC blade bias voltage, that is, a DC blade bias is applied to the developing roller of the developing device during the pre-rotation, so that the pre-rotation is performed similarly to the first embodiment. The toner layer on the surface can be quickly recovered. In addition, since DC bias AC blade bias voltage is applied during development,
As in the case of the first embodiment, the soiling of the background portion of the photoreceptor belt 1 can be suppressed by the action of suppressing the background portion of the photoreceptor belt 1 to perform favorable development.

Further, since the developing roller of the developing device used for the next development is pre-rotated to form a uniform toner layer on the surface of the developing roller, the developing device is arranged at the developing position to perform the development. Good development can be performed using a uniform toner layer on the surface of the developing roller from the start of development.

Further, considering the amount of toner removed from the surface of the developing roller by contact with the photoreceptor belt 1, the amount of toner adhering to the surface of the developing roller becomes larger than the amount necessary for development. Since the roller is preliminarily rotated, it is possible to reduce adverse effects on image formation at the start of development due to toner being removed from the roller surface.

In a specific pre-rotation test of the developing roller, a negatively charged toner was used, and the developing bias voltage was -200.
V, when the reversal development is performed by setting the supply bias voltage to the supply roller made of urethane sponge with a volume resistance of 10 ⁶ to 10 ⁸ Ωcm to -400 V and the DC blade bias voltage to 150 to 200 V. Good results were obtained. During development, a DC component of 150 to 200 V and a peak-to-peak value of 2
Good results were obtained when a blade bias voltage consisting of an AC component of 50-1000 V and a frequency of 1-2 kHz was used. (Hereinafter, margin)

The above embodiment is an example in which the switching of the blade bias voltage applied to the thin layer blade is performed by electrically connecting and disconnecting the thin layer blade using a sensor. Instead of supplying power to the thin layer blade, the developing devices 21Y and 21Y in the revolver developing unit 30
Switching can also be performed by mechanically making and breaking the connection with the rotational movement of 21M, 21C and 21B. Hereinafter, the configuration of a first modified example of the revolver developing unit 30 that switches the blade bias voltage applied to the thin layer blade with the rotational movement of each developing device will be described with reference to FIG. The points that are not particularly described are the same as those of the revolver developing unit 30 in FIG.

FIG. 8 is a sectional view showing the structure of a first modified example of the revolver developing unit 30. As shown in FIG. In this example, the casing 31 has a hollow portion in the center, and a non-rotating portion for supporting a bias voltage applying electrode during development and a bias voltage applying electrode during preliminary driving described later in this hollow portion. The electrode support member 32 is inserted. Each developing unit 21Y,
21M, 21C and 21B are the respective thin layer blades 2
5Y, 25M, 25C, and 25B have bias receiving terminals 28Y, 28M, 28C, and 28B as bias receiving members for receiving a blade bias voltage.

The electrode support member 32 is provided with a DC bias as a bias voltage applying member during development on the developing device at the developing position, that is, on the peripheral side surface of the yellow developing device 21Y facing the bias voltage receiving terminal 28Y in the drawing. An AC blade bias applying electrode 33 is arranged, and a developing device at a standby position where a developing device to be used for the next development is located, that is, in the figure, on a peripheral side surface facing the bias voltage receiving terminal 28M of the magenta developing device 21M. A DC blade bias applying electrode 3 as a bias voltage applying member during pre-driving
4 are arranged. The bias receiving terminal, the DC superimposed AC blade bias applying electrode, and the DC blade bias applying electrode constitute the bias voltage applying means.

In the example of FIG. 8, the thin layer blade 25Y of the yellow developing unit 21Y at the developing position has the bias receiving terminal 28Y disposed opposite the terminal 28Y by the electrode support member 32 at the developing position. In contact with the applied DC bias AC blade bias applying electrode 33, a DC bias AC blade bias voltage is applied. Then, the thin layer blade 25 of the magenta developing device 21M at the standby position
M is a bias voltage receiving terminal 2 in the standby position.
8M comes into contact with the DC blade bias applying electrode 34 disposed opposite the terminal 28M by the electrode support member 32, and a DC blade bias voltage is applied.

Each of the developing units 21Y, 21M, 21C,
When the magenta developing device 21M is arranged at the developing position by rotating the magenta developing device 21B, the thin-layer blade 25M of the magenta developing device 21M makes the bias voltage receiving terminal 28M contact the DC superimposed AC blade bias applying electrode 33. Then, a DC superimposed AC blade bias voltage is applied. At this time, the contact between the bias receiving terminal 28Y and the DC superimposed AC blade bias applying electrode 33 is disconnected and the application of the blade bias to the thin layer blade 25Y is finished, and the yellow developing device 21M
Developing device 21 located on the upstream side in the rotational movement direction
C is arranged at the standby position, and the thin-layer blade 25C of the cyan developing device 21C is contacted with the bias receiving terminal 28C and the DC blade bias application electrode 34, and is applied with the DC blade bias.

Thus, each of the developing units 21Y, 21M, 2M
A predetermined blade bias is reliably applied by disconnection between the bias receiving terminal and each application electrode due to the rotational movement of 1C and 21B.

FIGS. 9A and 9B are cross-sectional views showing the configuration of a second modified example of the revolver developing unit 30. FIG. Note that components which are not particularly described are configured similarly to the revolver developing device of FIG. The revolver developing unit 10 in the example of FIGS. 9A and 9B has a developing device that is detachable from the main body of the revolver developing unit 30, and a thin-layer blade of the developing device when starting up the newly mounted developing device. A blade bias applying means 35 for applying a blade bias to the DC blade bias applying electrode 34 is connected to the DC blade bias applying electrode 34 via a switch 35a.

In the apparatus in which each of the developing units can be detachably attached to the main body of the revolver developing unit 10, the attaching and detaching of the developing units is permitted for the current developing unit at an arbitrary rotation position of the revolver developing unit 10. Structure,
A structure that allows only the developing device at a specific position, for example, the standby position, may be adopted. As the latter structure,
It is conceivable to provide a cover provided with a detachable window corresponding to the developing device at the standby position on the front side in the detaching direction of the revolver developing unit. In the following description, with such a structure, the detachment of the developing device is permitted only for the developing device at the standby position, and when detaching the developing device at the other revolver developing unit rotation position,
For example, it is assumed that an operator operates a knob or the like (not shown) of the revolver developing unit to rotate the unit, and moves the desired developing device to the standby position, and detaches the developing device. Also in this example, as shown in FIG. 9B, for example, the magenta developing device 2 is in the standby position.
Only for 1M, the bias receiving terminal 28M provided on the thin layer blade 25 is connected to the DC blade bias applying electrode 34 similarly to the revolver developing unit 30 of FIG.
Shall be in contact with In this example, a switch 35a for switching ON / OFF the application of the DC blade bias is provided between the DC blade bias application electrode 34 and the power supply.

First, after removing the developing device from the main body of the revolver developing unit 10 at the standby position, the developing device is started up every time one developing device is mounted in the mounting space at the standby position of the main body of the revolver developing unit 10. The case of performing the operation will be described. In this case, the revolver developing unit 3
The main unit 0 is provided with a developing device presence / absence detection sensor for detecting whether or not the developing device is present at the standby position. When it is detected that the developing device is mounted in the mounting space 36 at the standby position, the switch 35a is turned on as shown in FIG. 9B, and the DC blade bias applying electrode 34 and the start-up By connecting to the DC blade bias applying means 35, the thin layer blade 25 of the developing device at the standby position is provided.
A DC blade bias voltage is applied to M, and the developing roller of the developing device is preliminarily rotated in this state, whereby a toner layer is quickly formed on the surface of the developing roller 23M. Thus, the newly mounted developing device can be quickly started.

Next, the user operates the revolver developing unit 1
While rotating 0, taking out the developing device at the standby position, and mounting the developing device in the mounting space after taking out the plurality of developing devices, for a plurality of newly mounted developing devices, A case will be described in which the robot is sequentially moved to the standby position one by one and preliminarily rotated. In this case, of the revolver developing unit 10, a sensor that detects the developing device that has been removed and mounted, and which of the developing devices has been removed and mounted based on the output of the sensor. Storage means for storing information. The control means controls the rotation of the revolver rotation motor so as to sequentially move the newly mounted developing device to the standby position based on the stored contents of the storage means, and further controls the newly mounted developing device. When the developer reaches the standby position, the switch 35a is turned on, and the developing roller of the developing device is set in the standby state while a DC blade bias voltage is applied to the thin layer blade 25M of the developing device in the standby position. Rotate. The time for performing the pre-rotation of the developing roller in the bias application state is determined in advance for each newly installed developing device, and when this time elapses, switching to the next developing device is performed, and The developing roller is preliminarily rotated with the bias applied thereto. This makes it possible to quickly form a toner layer on the surface of the developing roller for all newly mounted developing devices, and to quickly start up the developing devices.

In the above example, it is not determined whether the developing device mounted on the main body of the developing unit 10 is new. However, even if the mounted developing device is not a new one, the developing device can be started up as described above. For example, it is possible to start up the developing device in which the charge amount on the developing roller is reduced while being removed from the main body of the developing unit 10 as described above. Therefore, by starting up a developing device having a reduced charge amount on the developing roller, it becomes possible to form a good image using the developing device.

Further, in a specific developing roller start-up test of this modification, a negatively charged toner was used, a developing bias voltage was -200 V, and a urethane sponge having a volume resistance of 10 ⁶ to 10 ⁸ Ω · cm was supplied. Supply bias voltage to the roller is -400
When the blade bias voltage of V and DC was set to 150 to 200 V, the developing roller could be started up in about 30 seconds.

[0063]

According to the first to fourth aspects of the present invention, at the time of pre-driving, the developing device in which a DC bias voltage is applied to the developer amount regulating member is applied with a bias voltage composed of a DC component and an AC component. In this case, the amount of the developer on the developer carrying member can be quickly recovered by preliminary driving because the developer is more quickly attached to the surface of the developer carrying member. In addition, since the developer carrier whose amount of the developer attached to the surface is regulated is used from the start of development, a good image can be formed from the start of development. Further, when the developing device is constituted by one developing device, the time required for the preliminary driving can be set relatively short, and the image forming speed can be improved. In addition, during development, a bias voltage composed of a DC component and an AC component is applied to the developer amount regulating member to cause the normally charged developer to adhere to the surface of the developer carrying member. The developer can be more excellently developed, and the developer charged to the opposite polarity or the low-charged developer is removed from the developer carrier, so that the developer can be transferred from the developer carrier to the background of the image carrier during development. There is no scattering of the developer charged to the opposite polarity or the low-charged developer, so that the background of the image carrier can be prevented from being stained.

In particular, according to the second aspect of the present invention, development can be performed by moving a plurality of developing units and positioning an arbitrary developing unit at a developing position facing the image carrier. Further, a developing device in which the amount of the developer on the surface of the developer carrier is regulated can be used for the next development.

According to the third aspect of the present invention, in the developer amount regulating member of the developing device, the bias voltage receiving member comes into contact with the bias voltage applying member during the preliminary driving at the standby position. Since a desired bias voltage is applied at each position by contacting the bias voltage applying member during development at the developing position, the bias receiving member and the bias voltage applying member are moved between the bias receiving member and the bias voltage applying member by moving the developing device. By the disconnection, a predetermined bias voltage can be reliably applied to the developer amount regulating member.

[0066]

Japanese Unexamined Patent Publication Nos. 61-254960 and 62-151875 disclose a developing device having a plurality of developing devices and selectively using any one of the developing devices. A voltage obtained by superimposing an alternating voltage on a DC voltage is applied to the carrier of the developing device, and a DC voltage is also applied to the carrier of the developing device that is not in use in order to prevent the developer from being scattered. Things are disclosed. Comparing the configuration of this known developing device with, for example, the configuration of the developing device of claim 1, it is common in that the voltage applied to the members in the developing device is switched between during development and during non-development. The target to which the voltage to be switched is applied is different.
Further, there is no description suggesting the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a developing device according to a first embodiment.

FIG. 2 is a graph showing the relationship between the number of rotations of a developing roller and the amount of toner adhering to the roller.

FIG. 3A is an explanatory diagram of a blade bias voltage applied to a thin layer blade during non-development. (B) is an explanatory diagram of a blade bias voltage applied to a thin layer blade during development.

FIG. 4 is a cross-sectional view illustrating a schematic configuration of a developing device according to a second embodiment.

FIG. 5 is a flowchart illustrating an example of blade bias switching process control.

FIG. 6 is a flowchart illustrating an example of drive control of a standby unit and a current unit.

FIG. 7 is a timing chart of driving of a photoreceptor belt motor, application of a DC blade bias to a standby unit, driving of a revolver rotation motor, and application of a DC superimposed AC bias to a current unit.

FIG. 8 is a cross-sectional view illustrating a configuration of a first modified example of the revolver developing unit.

FIGS. 9A and 9B show a second example of the revolver developing unit.
Sectional drawing which shows the structure of the modification of FIG.

[Explanation of symbols]

 Reference Signs List 1 photoreceptor belt 21 developing device 21Y yellow developing device 21M magenta developing device 21C cyan developing device 21B black developing device 23 developing roller 25 thin blade 25a blade bias applying means 25Y thin blade 25M thin blade 25C thin blade 25B thin layer Blade 28Y Bias receiving terminal 28M Bias receiving terminal 28C Bias receiving terminal 28B Bias receiving terminal 30 Revolver developing unit 32 Electrode support member 33 DC superimposed AC blade bias applying electrode 34 DC blade bias applying electrode

──────────────────────────────────────────────────続 き Continued on the front page (72) Noriyuki Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Utsugi Fujishiro 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Chiyako Kobayashi Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-3-155577 (JP, A) JP-A-55 -11226 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/06 101 G03G 15/08

Claims (4)

(57) [Claims] A developer carrying member for carrying and transporting the developer in a region facing the image carrying member having a latent image formed on a surface thereof;
A developer amount regulating member that regulates an amount of the developer carried on the developer carrying member; and a bias voltage applying unit that applies a bias voltage to the developer amount regulating member. A developing device for developing a latent image formed on an image carrier using the developer after preliminarily driving the developer carrier to carry the developer on the surface of the developer carrier; In the apparatus, as a bias voltage applied to the developer amount regulating member by the bias voltage applying unit, a bias voltage including a DC component and an alternating component is used during development, and a bias voltage including only a DC component is used during pre-driving. A developing device, characterized in that: 2. The image forming apparatus according to claim 1, wherein said developing device includes a plurality of developing devices, and the developing device is moved to move an arbitrary developing device to a developing position facing the image carrier to perform development. 2. The developing device according to claim 1, wherein the driving is performed on a developer carrier of a developing device used for the next development. 3. A bias receiving member for receiving the bias voltage in the developer amount regulating member provided in each of the plurality of developing devices, and a bias voltage receiving member of the developing device at a developing position opposed to the bias voltage receiving member. A developing device for applying a bias voltage during development provided on the side of the developing device main body, and a bias voltage receiving member of the developing device at a standby position where the developing device used for the next development is located. 3. The developing device according to claim 2, wherein said bias voltage applying means is constituted by a pre-driving bias voltage applying member provided on a main body side. 4. An image carrier and an image having a latent image formed on a surface thereof.
The developer is carried by the developer carrier in the area facing the carrier
And a developing device for transporting and developing the latent image
In the forming apparatus, the developing device according to claim 1, 2 or 3 is used as the developing device.
An image forming apparatus characterized by being used.