JPH10207223A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overelectrification caused by electric charge remaining on a developer carrier by grounding the developer carrier, when a developing device is placed in a nondeveloping position. SOLUTION: Electrostatic latent images of three colors formed on a light shielding belt 1 are developed in such a manner that developing units of yellow, magenta and cyan, Y, M and C are moved to a developing position facing the photoreceptor belt 1 one after another by a rotary motion at each angle of 120 deg. on a circumference, synchronized with the development timing of color corresponding to a color developing unit 6, to form single-color images of each color. At this time, a developing device for black 7 is controlled to retreat from the developing position facing the photoreceptor belt 1 to the nondeveloping position by the rotation of a cam 25. Further, the electrostatic latent image corresponding to a black image on the belt 1 is developed by the developing device for black 7 moved to the developing position, to form the single-color image of black. Further, a grounding means for grounding each developing roller of the color developing unit 6 or the developing device for black 7, at the nondeveloping position is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.
A developer carrier that carries a developer to be supplied to the latent image carrier on the surface, a developer supply member that supplies the developer to the developer carrier, and a layer thickness of the developer on the developer carrier. The present invention relates to an image forming apparatus for moving a developing device having a regulating member for regulating a developer between a developing position for performing a developing operation and a non-developing position retracted from the developing position.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, various methods have been proposed for stably supplying a developing bias voltage to the developer carrier in a developing device (for example, Japanese Patent Application Laid-Open No. No. 43973, JP-A-7-248664
Reference).

[0003]

However, even after taking measures to stably supply the developing bias voltage to the developer carrying member, the electric charge accumulated in the developer carrying member is removed after the end of the developing operation. Time is required (when the time constant is large) or when the resistance value of the developer carrier is high (even when the overall resistance value is within a predetermined range, the developer carrier has a two-layer structure and its surface layer (Including the case where the resistance value is high), the residual charge is easily generated in the developer carrying member, and in the next step, the toner may be overcharged and an image defect may occur.

The present invention has been made in view of the above background, and an object of the present invention is to provide an image forming apparatus capable of preventing toner from being overcharged due to charges remaining on a developer carrier. It is to be.

[0005]

In order to achieve the above object, the present invention is directed to a developer carrying member for carrying a developer to be supplied to a latent image carrying member on a surface thereof, and the developer carrying member. A developing device having a developer supply member for supplying a developer to the developing device, and a developer regulating member for regulating a layer thickness of the developer on the developer carrying member; An image forming apparatus that moves between a non-development position and a non-development position, wherein a grounding means is provided for grounding the developer carrier when the development device is located at the non-development position. .

According to the first aspect of the present invention, the developing device is moved between a developing position for performing a developing operation and a non-developing position retracted from the developing position. When the developing device is located at the developing position, the developer on the developer carrier supplied by the developer supply member is formed on the latent image carrier after its layer thickness is regulated by the developer regulating member. The electrostatic latent image is visualized. On the other hand, when the developing device is located at the non-development position, the developer carrier is grounded by grounding means, and the charge is removed so that the toner remaining in the developer carrier is not overcharged in the next step. I do.
As a result, after the development operation is completed, it takes time to remove the charges accumulated in the developer carrier (when the time constant is large), or when the resistance value of the developer carrier is high (total resistance value). Is within the predetermined range, the developer carrier is 2
(Including the case where the surface layer has a high resistance value in the layer structure), no residual charge is generated in the developer carrier in the next step.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, when the developing device is located at the non-developing position, the developing device is disposed so as to contact the developer carrier. A grounding means for grounding the developer supply member and the developer regulating member is provided.

In the image forming apparatus according to the second aspect, when the developing device is located at the non-developing position, the grounding means allows
The developer supply member and the developer regulating member disposed so as to be in contact with the developer carrier are grounded. As a result, the electric charge accumulated in the developer carrier is also removed from the contact portion between the developer supply member and the developer regulating member.

[0009] The invention of claim 3 is based on claim 1 or 2.
In the image forming apparatus, the grounding means is a leaf spring member, and when the developing device is located at the non-developing position, the leaf spring member is connected to the conductor portion of the developer carrier or the developer carrier. The present invention is characterized in that it is configured to be in contact with conductors of the body, the developer supply member and the developer regulating member.

In the image forming apparatus of the present invention, when the developing device is located at the non-developing position, the leaf spring member is connected to the conductor of the developer carrier, or the developer carrier, the developer supply member and the developing device. The agent regulating member is brought into contact with the conductor of each member and grounded. When the developing device is rotated in one direction to move between the developing position and the non-developing position, the free end of the leaf spring member is located downstream of the fixed end in the rotating direction of the developing device. It is desirable to arrange so that rotation of the developing device is not easily hindered.

Further, the invention of claim 4 is the invention of claim 1 or 2
In the image forming apparatus, the grounding means is a static elimination brush, and the static elimination brush, when the developing device is located at the non-development position, the conductor portion of the developer carrier, or the developer carrier, The developer supply member and the developer regulating member are configured to be in contact with respective conductors.

In the image forming apparatus according to the present invention, when the developing device is located at the non-developing position, the discharging brush is connected to the conductor of the developer carrier or the developer carrier, the developer supply member and the developing device. The agent regulating member is brought into contact with the conductor of each member and grounded.

[0013] The invention of claim 5 is the invention of claim 3 or 4.
In the above image forming apparatus, a cleaning means for cleaning the conductor portion is provided immediately before grounding by the grounding means.

In the image forming apparatus according to the fifth aspect, the conductor is cleaned by the cleaning means immediately before grounding by the grounding means, and the adhered matter or the like adhered to the conductor is removed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device used in a color printer (hereinafter, referred to as a printer) as an image forming apparatus will be described. FIG. 1 is a front view showing a schematic configuration inside the printer according to the present embodiment. In FIG. 1, a belt-shaped photoconductor (hereinafter, referred to as a photoconductor belt) 1 as a latent image carrier is provided between rotating rollers 2 and 3 and rotates in the direction of arrow A. Around the photoreceptor belt 1, a charging device 4, a laser beam 5
A laser writing unit 5 for irradiating G, a rotary color developing unit (hereinafter, referred to as a color developing unit) 6 as a rotary developing device for supporting a plurality of developing units in a switchable manner, and a black containing a black developer. A developing device 7, an intermediate transfer belt 10, a cleaning device 15 for a photoconductor, a static elimination lamp L, and the like are provided.

The printer according to the present embodiment is similar to the printer shown in FIG.
As shown in (1), the photoreceptor belt 1, the charging device 4, the intermediate transfer belt 10, the cleaning unit 16, the transport guide 21 for forming the transport path of the transfer paper, and the like are unitized as a process cartridge so that they can be replaced when the life is reached. Is configured. Further, in order to improve the operability of replacement when the life of the color developing unit 6 and the black developing device 7 reaches the end of the life or improvement of the processing when a jam occurs, the front frame 8 of a part of the main body is centered on the support shaft 9A. It is configured to be rotatable and openable.

FIG. 3 is an enlarged view of the vicinity of the color developing unit 6 and the black developing device 7, and FIG. 4 is a perspective view of the color developing unit 6. As shown in FIG. 3, the color developing unit 6 is provided with an inner casing 29 that is a rotating body and is rotatable about a rotation center O. The inner casing 29 can be rotated clockwise in the figure by driving a drive mechanism (not shown). Further, the inner casing 29 integrally holds the developing units Y, M, and C respectively containing yellow, magenta, and cyan color developers.

Since the three color developing units Y, M, and C have the same form and are configured to perform the same operation, the following description will be made by taking the yellow developing unit Y located at the developing position as an example. The structure will be described. For the other developing devices, corresponding members will be denoted by reference numerals with subscripts of M and C in order to distinguish magenta and cyan developing devices, and description thereof will be omitted.

The yellow developing unit Y includes a casing 2
9a, a developing roller 30Y as the developer carrier
A supply roller 31Y as the developer supply member,
The image forming apparatus includes a blade 32Y as the developer regulating member, and first and second screw-shaped toner conveying members 33Y and 34Y.

The supply roller 31Y is made of an elastic material such as polyurethane foam, and is configured to rub against the developing roller 30Y and rotate in the same direction as the developing roller 30Y at a predetermined linear velocity ratio.

The blade 32Y is made of a spring-like thin plate made of stainless steel or the like.
Y, the developing roller 30Y and the supply roller 31
It is arranged downstream of the rubbing portion with Y in the supply roller rotation direction.

The first toner conveying member 33Y is the same as that shown in FIG.
The toner container 35 provided at one end side (the front side in FIG. 4) of the color developing unit 6 shown in FIG.
Y, a developing roller 30Y and a supply roller 31
It is arranged in parallel with Y, and is configured to convey toner from the front of the drawing toward the back. The first toner conveying member 33Y includes a developing roller 30Y and a supply roller 3Y.
1Y and rotates at a predetermined linear velocity ratio with them. Further, the toner transport space surrounding the first toner transport member 33Y is provided in the casing 29 of each developing device.
a, a supply roller 31Y, a developing roller 30Y, and the like, which are disposed so as to be in contact with a part of the casing portion 29a.

The second toner conveying member 34Y is connected to the developing roller 30 similarly to the first toner conveying member 33Y.
Y, which is disposed in parallel with the supply roller 31Y, rotates so as to convey the toner in a direction opposite to the first toner conveying member 33Y, and conveys the toner not used in the developing process to the toner storage section 35Y. I do.

The color developing unit 6 includes:
As shown in FIG. 4, when the yellow developing device Y is located at the developing position on the inner side of the drawing with respect to the toner storage unit 35 </ b> Y and on the front side of the developing roller 30 </ b> Y with the developing roller 30 </ b> Y. , The supply roller 31Y and the blade 32Y are provided with developing electrodes 40Y, 41Y and 42Y as conductors for supplying a predetermined developing bias voltage supplied from the power pack 39 via the main body electrode 38 shown in FIG. I have.

The toner cartridge 45 shown in FIG.
Is detachably attached to the toner container 35 and can be replaced when toner is supplied.

The first and second toner conveying members 33, 3
By appropriately setting the toner conveyance amount by the toner supply unit 4, the toner can be supplied onto the supply roller 31 without performing the toner amount detection in the developing device and complicated toner supply amount control. Therefore, the color developing unit 6 according to the present embodiment is a small-sized apparatus having a large degree of freedom in layout and a small sectional occupation ratio with respect to the photosensitive belt 1.

The above-mentioned black developing device 7 is a developing device of a type in which black toner is contained in a developing container. The developing device is formed integrally as a so-called developing cartridge in which the life of the developing device is replaced when the toner runs out. It is. This black developing device 7
In the same manner as the developing units of the color developing unit 6, the photosensitive belt 1 is rotated such that the developing roller 30 rotates with the photosensitive belt 1 in the same direction as the moving direction of the photosensitive belt 1 at a predetermined linear velocity ratio. Are disposed opposite to each other. The developing roller 3 on the opposite side to the developing position facing the photoreceptor belt 1
Behind 0, a supply roller 31 made of an elastic material such as foamed polyurethane is provided so as to rub against the developing roller 30 in the rubbing portion and to rotate in the same direction as the developing roller 30 at a predetermined linear velocity ratio. Further, a blade 32 made of a thin plate having a spring property such as stainless steel is provided so that one end thereof is in contact with the developing roller 30. In the casing, a paddle 36 and an agitator 37 for conveying and stirring the toner toward the supply roller 31 and the developing roller 30 are provided.
Is provided.

The black developing device 7 is movable in the horizontal direction with respect to the photoreceptor belt 1, is separated from the photoreceptor belt 1 during non-development, and the developing roller 30 approaches or approaches the photoreceptor belt 1 during development. The separating operation is performed so as to move to the developing position in contact with the developing position. In the black developing device 7,
Similarly to the respective developing units of the color developing unit 6, a developing electrode (not shown) for supplying a predetermined developing bias voltage to each of the developing roller 30, the supply roller 31, and the blade 32 when located at the developing position is provided. ing.

In this case, the developing cartridge is of the type containing toner. However, a developing device of a type that replaces the toner cartridge and replenishes toner, such as the color developing unit 6, may be used.

A fan 23 is provided above the electrical equipment / control device 22 housed on the left side of the color developing unit 6 and the black developing device 7, and the air is exhausted so that the temperature inside the device does not rise too much. doing. In addition, the paper cassette 1
7 and a relatively small-sized paper feeding device 24.

The image forming process by the above-described printer is performed as follows. First, the formation of a multicolor image is performed according to the imaging system described below. The laser writing unit 5 based on a color image signal sent from an external image reading device, a host computer, or the like.
Is driven, a light beam (laser beam) generated by a semiconductor laser (not shown) is scanned by a polygon mirror 5B rotated by a drive motor 5A, and an optical path is bent by a mirror 5D via an f-θ lens 5C. Then, the light is emitted from the optical window member 5F to the outside of the unit case 5E, and is exposed on the outer peripheral surface of the photosensitive belt 1 uniformly charged in advance by the charging charger 4 to form an electrostatic latent image. here,
The image pattern to be exposed is a single-color image pattern when a desired full-color image is separated into yellow, magenta, cyan, and black.

The electrostatic latent images of the three colors formed on the photoreceptor belt 1 are rotated in yellow at 120 degrees around the circumference in synchronization with the development timing of the corresponding color of the color developing unit 6. , Magenta and cyan developing units Y,
M and C are sequentially moved to a developing position facing the photoreceptor belt 1 and developed, so that a single-color image of each color is formed. At this time, the black developing device 7 is controlled to retreat from the developing position facing the photosensitive belt 1 to the non-developing position by the rotation of the cam 25. Further, the electrostatic latent image corresponding to the black image on the photoreceptor belt 1 is transferred to the black developing device 7 moved to the developing position.
To form a black monochrome image.

The first single-color image on the photosensitive belt 1 is transferred to the intermediate transfer belt 1 by a bias brush 13 as a primary transfer member provided inside the intermediate transfer belt 10.
0 (primary transfer). By repeating the same process, the second monochrome image, the third monochrome image, and the fourth monochrome image are transferred to the intermediate transfer belt 1.
The image is transferred so as not to be misaligned by being superimposed on each of the zeros. The surface of the photoreceptor belt 1 is cleaned by the cleaning blade 15A each time a single-color image is formed and transferred onto the intermediate transfer belt 10. In the present embodiment, the waste toner scraped by the cleaning blade 15A is stored in the collection container 15B, and the collection container 15B is appropriately replaced.

From the paper feed cassette 17 to the paper feed roller 1
8. Transfer transferred to the nip portion between the intermediate transfer belt 10 and the transfer roller 14 via the conveying roller pair 19 and the registration roller pair 20 at a timing such that the positions of the transfer material and the image become normal. The yellow, magenta, cyan, and black images superimposed on the intermediate transfer belt 10 are collectively transferred onto a transfer material such as paper or plastic (secondary transfer). After the transfer, the transfer paper is fixed by the fixing device 26 to complete a full-color image. Then, the transfer material after the fixing is discharged by a discharge roller pair 27 to a discharge stack portion 28 above the main body frame 9.

The surface of the intermediate transfer belt 10 after the secondary transfer is cleaned by a cleaning unit 16 for the intermediate transfer belt. This cleaning unit 16
Cleaning blade 16A, toner transport auger 16
B is provided. The cleaning blade 16A is kept at a position separated from the surface of the intermediate transfer belt 10 at the time of the secondary transfer via the separation arm 16C, and only during the cleaning after the secondary transfer as shown in the drawing.
Is pressed against the surface of Further, the auger 16B transports the waste toner scraped by the cleaning blade 16A to the collection container 15B by a transport unit (not shown).

Here, the features of this embodiment will be described. As described above, when it takes time to remove the electric charge accumulated on the developing roller after the developing operation is completed, or when the resistance value of the developing roller is high (the developing resistance is high even if the overall resistance value is within a predetermined range). (Including the case where the roller has a two-layer structure and the surface layer has a high resistance value), the developing roller tends to generate residual charges, and in the next step, the toner is overcharged, resulting in image defects, specifically, horizontal band-like unevenness. There was a risk of doing.
Therefore, the printer according to the present embodiment includes a grounding unit that grounds the respective developing rollers of the color developing unit 6 or the black developing device 7 at the non-developing position in order to prevent toner overcharging in the next process. .

According to the study by the present inventor, even if the overall resistance value of the developing roller is in the range of 105 to 108Ω, the developing roller has a two-layer structure and the surface layer has a resistance value of 1013Ω or more. In this case, it was found that a residual charge was generated. The developing roller of the present embodiment has an overall resistance value of 1
It has a characteristic of 0.5 to 108 Ω and a capacitance of several hundred pF.

Further, since the grounding means in the color developing unit 6 and the black developing device 7 are configured to perform the same operation, the grounding means will be described by taking the color developing unit 6 as an example, The description of the device 7 is omitted.

FIG. 5 is an enlarged view of the vicinity of the color developing unit 6 provided with the grounding means, and FIG. 6A is a perspective view of a leaf spring member 43 as the grounding means. The leaf spring member 43 is configured to contact each of the three developing electrodes provided in each of the developing devices Y, M, and C at the non-developing position of the color developing device unit 6. As a result, the electric charge accumulated in the developing rollers 30Y, 30M, 30C is removed, so that there is no residual electric charge generated in the developing roller in the next step.

In this embodiment, the leaf spring member 43 is used.
To the developing electrodes 40Y, M, C of the developing rollers 30Y, M, C.
C, and supply rollers 31Y, M, C and blades 32Y, which are arranged to contact the developing roller.
M and C development electrodes 41Y, M, C, 42Y,
M and C are also in contact with each other so that the developing roller 30
The electric charges accumulated in Y, M, and C are easily released.

In this embodiment, as shown in FIG. 6A, the free end 43a of the leaf spring member 43 is
The leaf spring member 4 is disposed so as to be located on the downstream side in the rotation direction of the color developing unit 6 as shown by the arrow D from the side b.
3 prevents the rotation of the color developing unit 6 from being hindered. Instead of this leaf spring member, a static elimination brush shown in FIG. 3B which is hard to hinder the rotation of the color developing unit 6 may be used.

In this embodiment, the cleaning device is located downstream of the position of the main body electrode 38 in the direction of rotation of the color developing unit 6 and upstream of the grounding position of the leaf spring member 43. 44 is provided so that the three developing electrodes of the developing device after the completion of the developing operation are cleaned just before the grounding, and the deposits and the like adhering to the developing electrodes are removed.

As described above, in the present embodiment, when the color developing unit 6 or the black developing device 7 is located at the non-developing position, the leaf spring member 43 as the grounding means is supplied to the developing roller of each developing device. The charge accumulated on the developing roller is removed by a simple method of bringing the roller and the blade into contact with the respective developing electrodes. As a result, even if it takes time to remove the charges accumulated on the developing roller, or if the resistance value of the surface layer of the developing roller is high, residual charges are generated on the developing roller in the next step. Nothing. Accordingly, it is possible to prevent the toner from being overcharged due to the charge remaining on the developing roller, and to obtain a good image.

In this embodiment, the leaf spring member 43 as a grounding means is disposed such that its free end 43a is located downstream of the fixed end 43b in the rotation direction of the color developing unit 6. I have. Therefore, it is difficult to prevent the rotation of the color developing unit 6.

In this embodiment, the cleaning device 4
In step 4, the developing electrode is cleaned immediately before grounding to remove the deposits and the like adhering to the developing electrode. Therefore,
Poor contact between the leaf spring member 43 and the developing electrode can be prevented.

[0046]

According to the first to fifth aspects of the present invention, it may take time to remove the charges accumulated in the developer carrier after the end of the developing operation, or the resistance value of the developer carrier may be reduced. Even when the charge is high, no residual charge is generated on the developer carrier in the next step. Therefore, there is an excellent effect that the toner can be prevented from being overcharged due to the charge remaining on the developer carrier, and a good image can be obtained.

In particular, according to the second aspect of the present invention, the electric charge accumulated in the developer carrier is also removed from the contact portion between the developer supply member and the developer regulating member, so that the electric charge is easily released. There is an excellent effect.

In particular, according to the third aspect of the present invention, the leaf spring member is brought into contact with the conductor of the developer carrier or the conductors of the developer carrier, the developer supply member and the developer regulating member. There is an excellent effect that the grounding means can be configured by such a simple method.

In particular, according to the fourth aspect of the invention, when the developing device is located at the non-development position, the discharging brush is connected to the conductor of the developer carrier or the developer carrier, the developer supply member and There is an excellent effect that the grounding means can be constituted by a simple method of contacting the conductor portion of each developer regulating member.

In particular, according to the fifth aspect of the present invention, just before the grounding by the grounding means, the conductor portion is cleaned to remove the deposits and the like adhering to the conductor portion. There is an excellent effect that poor contact with the conductor can be prevented.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a schematic configuration of a printer according to an embodiment.

FIG. 2 is a front view of the printer with a front frame opened.

FIG. 3 is an enlarged view of the vicinity of a color developing unit and a black developing device of the printer.

FIG. 4 is a perspective view of the color developing unit.

FIG. 5 is an enlarged view of the vicinity of a color developing unit having a grounding means.

FIG. 6A is a perspective view of a leaf spring member. (B) is a perspective view of a static elimination brush as a modification of the grounding means.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoreceptor belt 2, 3 rotating roller 4 charging device 5 optical writing unit 6 color developing unit 7 black developing device 8 front frame 9 main body frame 10 intermediate transfer belt 11, 12 rotating roller 13 bias brush 14 transfer roller 15 photosensitive Cleaning unit for body belt 16 Cleaning unit for intermediate transfer belt 17 Paper feed cassette 18 Paper feed roller 19 Transport roller pair 20 Registration roller pair 21 Transport guide 22 Electrical equipment / control device 23 Fan 24 Paper feed device 25 Cam 26 Fixing device 27 Discharge Roller pair 28 Discharge stack unit 29 Inner casing 30, 30Y, M, C Developing rollers 31, 31Y, M, C Supply rollers 32, 32Y, M, C Blades 33Y, M, C First toner conveying member 34Y, M , C Second toner transport member 35Y, M , C Toner storage section 36 Paddle 37 Agitator 38 Main body electrode 39 Power pack 40, 41, 42 Developing electrode 43 Leaf spring member 44 Cleaning device 45 Toner cartridge

Claims (5)

[Claims] 1. A developer carrying member for carrying a developer to be supplied to a latent image carrier on a surface thereof, a developer supplying member for supplying a developer to the developer carrying member, and a developing device on the developer carrying member. An image forming apparatus that moves a developing device having a developer regulating member that regulates a layer thickness of the developer between a developing position for performing a developing operation and a non-developing position retracted from the developing position; An image forming apparatus provided with a grounding means for grounding the developer carrying member when is located at a non-development position. 2. An image forming apparatus according to claim 1, wherein said developer supply member and said developer are arranged to be in contact with said developer carrier when said developing device is located at a non-developing position. An image forming apparatus comprising a grounding means for grounding a regulating member. 3. The image forming apparatus according to claim 1, wherein said grounding means is a leaf spring member, and said developer carrier is provided when said developing device is located at a non-development position. An image forming apparatus configured to be in contact with each of the conductor portions of the developer carrier, the developer carrying member, the developer supply member, and the developer regulating member. 4. The image forming apparatus according to claim 1, wherein said grounding means is a discharging brush, and said discharging brush is connected to a conductor of said developer carrier when said developing device is located at a non-development position. An image forming apparatus configured to be in contact with a conductor of each of the developer carrier, the developer supply member, and the developer regulating member. 5. An image forming apparatus according to claim 3, wherein a cleaning means for cleaning said conductor is provided immediately before grounding by said grounding means.