JPH10111603A - Developing device and image forming device adopting same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the developer feeding capacity corresponding to the developer carrier larger than that of a conventional one by providing an auxiliary developer feeding member on a developing device feeding the developer contained in a developing vessel to the developer carrier by the developer feeding member. SOLUTION: In the developing device developing a latent image on the image carrier by the developer on the developer carrier by feeding the developer contained in the developing vessel to the developer carrier 35 by the developer feeding member 36, plural auxiliary developer feeding members 39a and 39b feeding the developer contained in the developing vessel corresponding to the developer feeding member 36 is severally provided opposite to the developer feeding member 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus such as a copying machine, a facsimile, a printer, and the like, and to an image forming apparatus using the same. The present invention relates to a developing device that supplies a developer to a developer carrier by a developer supply member and develops a latent image on an image carrier with a developer on the developer carrier, and an image forming apparatus using the device.

[0002]

2. Description of the Related Art Conventionally, dry developing apparatuses used for electrophotography, electrostatic recording and the like include a two-component developer containing a toner and a carrier and a one-component developer containing no carrier. Some are used. In the former case, good images can be obtained relatively stably, but on the other hand, deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier are apt to occur. There is. On the other hand, the latter device contains a magnetic substance in the toner and moves the toner by using a magnetic force, and the other apparatus does not contain a magnetic substance in the toner and moves the toner using a force other than the magnetic force. There are things. Since the magnetic material contained in the toner is opaque, a device using a non-magnetic developer is suitable for color development. In this case, the developer is stably applied to a developing roller, for example, without using a magnetic force. Need to be supplied to Therefore, Japanese Patent Application Laid-Open No. 61-426
No. 72 discloses a developing device using a non-magnetic one-component developer, which is provided with a developer supply roller for supplying the developer to the developing roller by rotating while contacting the developing roller. Have been. According to this technique, a sufficient amount of charge is applied to the toner, and a thin toner layer suitable for uniform thinning can be stably formed on the developing roller.

Further, in an image forming apparatus capable of forming an image of two colors, for example, black and red, based on an image signal, the amount of red development is smaller than that of black, and the red developer is caused by idling of a red developer. Deterioration and scattering easily occur. So, for example,
JP-A-5-134530, JP-A-6-20827
Japanese Patent Application Laid-Open No. 7-107421 discloses an apparatus that controls the driving timing of a developing device based on the presence or absence of an image signal to reduce the idling time of the developing device.

[0004]

However, in the developing device provided with the developer supply roller, when the amount of toner to be adhered in the image to be formed (hereinafter, referred to as toner adhering amount) is large, There is a problem that the toner on the developing roller runs short and the image density is reduced.
Such a problem can also occur when a developing device provided with the developer supply roller is used as a developing device that controls the drive timing of the developing device based on the presence or absence of the image signal. That is, in the apparatus disclosed in JP-A-5-134530 and JP-A-6-208277, even if the presence of an image signal is detected and the developing device is driven, the developer is supplied onto the developing roller by the developer supply roller. If the toner amount is too small for the toner adhering portion amount, the image density will be reduced. To prevent this, if the drive timing of the developing device is set to a sufficiently early timing, idling of the developing device, which is the original purpose of this control, occurs, and toner deterioration and scattering occur.

[0005] The applicant of the present invention has previously disclosed a developing device which carries a developer and a developing device capable of preventing toner scattering and the like without fluctuation of image density. A developer supply member for supplying the developer, wherein the developing device develops a latent image formed on the image carrier based on an image signal, and applies a supply bias voltage to the developer supply member. There has been proposed a developing device comprising a supply bias voltage applying means and a control means for controlling the supply bias voltage applying means according to the image signal (Japanese Patent Application No. 148160/1996). Also in this developing device, when, for example, one rotating roller is used as the developer supply member, there is a possibility that the supply amount of the developer to, for example, the developing roller as the developer carrier is insufficient and the image density is reduced. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to supply a developer contained in a developing device to a developer carrier by a developer supply member. A developing device for developing a latent image on an image carrier with a developer on a carrier, the developing device having a greater developer supply capacity to the developer carrier than before, and an image forming apparatus using the same It is to provide.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a developer contained in a developing device is supplied to a developer carrying member by a developer supplying member, and the developer carrying member is supplied with the developer. In a developing device that develops a latent image on an image carrier with a developer on a body, a plurality of developer auxiliary supply members that supply the developer contained in the developing device to the developer supply member, It is characterized in that it is provided so as to face the developer supply member.

According to a second aspect of the present invention, in the developing device of the first aspect, the developer supply member is driven such that the surface moves in a predetermined direction, and the plurality of auxiliary developer supply members are provided on the surface. A rotating body that rotates in contact with each other is used, and the rotating direction of the rotating body is set so as to move in a direction opposite to the surface at a contact portion with the surface. .

According to a third aspect of the present invention, in the developing device of the first or second aspect, between the developer carrying member and the developer supply member, and between the developer supply member and at least one of the developer auxiliary members. Between at least one of the supply member and
It is characterized in that a predetermined bias voltage is applied.

According to a fourth aspect of the present invention, there is provided the developing device for developing a latent image formed on an image carrier based on an image signal, wherein the bias voltage is controlled in accordance with the image signal. Control means for performing the control.

According to a fifth aspect of the present invention, there is provided an image forming apparatus in which a latent image formed on an image carrier is developed by a developing device based on an image signal to form an image. A third or fourth developing device is used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) as an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. This example of a copying machine is an example of a two-color digital copying machine, and includes a document reading unit, an image processing unit, and a printer unit. An ADF or a sorter can be used in combination.

Below the photosensitive drum 11 as an image carrier, there is provided a paper transport path 15 from a paper feed device composed of a paper feed cassette 12 and a paper feed roller 13 to a paper discharge receiver 14. A registration roller 16, a transfer device 17, a separator 18, and a fixing device 19 are provided in the middle of the paper transport path 15.

Around the photosensitive drum 11, a first image forming unit 20 for forming a specific color, for example, a black image, on the photosensitive drum 11, and a chromatic, for example, red image, on the photosensitive drum 11 A second image forming unit 21 for forming thereon, a cleaning device 22, and a static eliminator 23
And are arranged. The first image forming unit 20 includes a first charger 24 for uniformly charging the photosensitive drum 11,
It comprises a first exposure device 25 and a first developing device 26. The second image forming unit 21 includes a second charger 27,
A self-scanning second exposure device 28 and a second developing device 29 are assembled on a support 30.

In the document reading section, color image information of the document 1 placed on the document table is read by the CCD 3 via the optical system 2 and the output signal is read by the image processing section (IPU) 4. The image is divided into a color portion (hereinafter, referred to as a second color) of a toner and a portion of another color and converted into an electric image signal. Then, the image signal of the color portion of the second color toner is sent to the second exposure device 28 and the second development control portion 5 of the printer unit, and the image signals of the other color (hereinafter, referred to as the first color) portion are It is sent to the first exposure unit 25 of the printer unit.

In the printer section, the photosensitive drum 11 is driven to rotate clockwise by the main motor and is uniformly charged to, for example, -800 V by the first charger 24. An electrostatic latent image of an image of a color is formed. In this case, the first exposure unit 25 modulates and drives a laser light source (not shown) with an image signal of the first color from the image processing unit by a driving circuit, deflects the light from this laser light source by the polygon mirror 31,
Irradiation is performed on the photosensitive drum 11 while scanning in the main scanning direction (the axial direction of the photosensitive drum 11) via the photosensitive drum 11. The polygon mirror 31 is driven to rotate by a polygon motor 33. The electrostatic latent image of the first color image on the photosensitive drum 11 is supplied by a first developing device 26 with a developer of the first color by a developing roller 34 to which a developing bias voltage is applied from a developing bias power supply. The first color toner is then developed into a visible image of the first color.

Next, the photosensitive drum 11 is connected to the second charger 27.
, So that it is almost uniformly charged. Then, the photosensitive drum 11
The second exposure unit 28 receives an exposure according to the image signal of the second color from the image processing unit by the LED array of the second exposure unit 28 to form an electrostatic latent image of the image of the second color. Then, in the second developing device 29, the electrostatic latent image of the second color image is developed with the developing agent of the second color by the developing roller 35 to which the developing bias voltage is applied from the developing bias power source. Is a visible image. The developing bias voltage applied to the developing roller 35 may be any one of a DC voltage, an AC voltage, and a pulse voltage.

On the other hand, the transfer paper is fed from a paper feed cassette 12 to a registration roller 16 by a paper feed roller 13, and the registration roller 16 sends the transfer paper in synchronization with the visible image on the photosensitive drum 11. The transfer paper is a photosensitive drum 11
The upper visible image is transferred by the transfer device 17 and separated from the photosensitive drum 11 by the separator 18, the visible image is fixed by the fixing device 19, and is discharged to the paper receiving tray 14 as a copy. After the transfer paper is separated from the photosensitive drum 11, the residual toner is removed by the cleaning device 22, and the charge is removed from the charge removing device 2.
3 erases the residual charge.

Next, the second developing unit 29 will be described with reference to FIG. The second developing device 29 includes the photosensitive drum 11
A casing provided with an opening facing the surface, a developing roller 35 as a developer carrier that is partially exposed from the opening and is driven to rotate at a predetermined linear speed in a counterclockwise direction by an arrow; It is housed in a developer supply roller 36 as a developer supply member that is driven to rotate clockwise in the direction of an arrow while being pressed against the right side portion, and is housed in a hopper portion as a developer storage means formed on the right side portion in the casing. Agitators 37 and 38 for supplying the non-magnetic one-component developer (hereinafter, referred to as toner) to the surface of the developer supply roller 36 and stirring the toner in the hopper portion; And a blade 39 as a developer regulating member for regulating the thickness of the toner layer on the developing roller 35 conveyed to the developing area, which is the opposite portion of the developing roller 35, so as to equalize the thickness. Further, the roller 40 is provided coaxially with the developing roller 35, and the roller 40 is brought into contact with the non-image forming area of the photosensitive drum 11 so as to maintain a small gap between the developing roller 35 and the photosensitive member 11. Is configured.

In the present embodiment, in order to improve the ability to supply toner to the developing roller 35, the developing roller 35 comes into contact with the developer supply roller 36, and the contact portion is opposite to the surface of the developer supply roller 36. The auxiliary developer supply rollers 39a and 39b, which are rotationally driven to move in the directions of
Book is provided.

In the present embodiment, the developing roller 3
5, the dielectric portion and the conductive portion are regularly or irregularly distributed over a small area on the surface portion, and the toner is carried by a minute closed electric field formed between the dielectric portion and the conductive portion. Is used. FIG. 3A is a perspective view of the developing roller 35, and FIG. 3B is an enlarged view of the surface of the developing roller 35. The developing roller 35 is formed by forming a groove having a depth of about 100 μm in an aluminum core 35a by iris knurling, and then coating and cutting an epoxy-modified silicone resin to form a surface of the dielectric portion 35b and a conductive portion 35c. Are configured to be exposed alternately. Then, as shown in FIG. 3C, the dielectric portion 35b
Further, a large number of minute closed electric fields E are formed on the surface of the developing roller 35 by holding a triboelectric charge having a positive polarity opposite to the negative polarity which is the charging polarity of the toner. The minute closed electric field E causes the non-magnetic toner of negative polarity to adhere to the dielectric portion 35b. This dielectric portion 35b
Is performed by frictional charging between the developer supply roller 36 and the toner. For this reason, as shown in FIG.
In the triboelectric series, as the material of the dielectric portion 35a, a material located on the plus side of the material of the toner or developer supply roller 36 is used. Further, since the conductive portion 35c also comes into contact with the toner, the conductive portion 35c is made of a material located on the plus side of the toner in the frictional charging series so as not to charge the toner in a direction opposite to a desired charging polarity. Further, the auxiliary developer supply roller 3
9 is made of the same material as the developer supply roller 36 because the toner also frictions with the developer supply roller 36.

The developing roller 35 and the agitator 37,
Reference numeral 38 denotes a second developing unit 29 which is driven to rotate by a main motor.
The toner inside is agitated by agitators 37 and 38 and is supplied to auxiliary developer supply rollers 39a and 39b, and is supplied to the developer supply roller 36 by the auxiliary developer supply rollers 39a and 39b. Auxiliary developer supply rollers 39a, 3
9b, as shown in FIG.
1, a voltage is generated between the developer supply roller 36 and the electric field such that the frictionally charged toner receives an electrostatic force from the auxiliary developer supply rollers 39a and 39b toward the developer supply roller 36. Is applied to the developer supply roller 36 by the bias power supply 41. An electric field is applied to the developer supply roller 36 such that the frictionally charged toner receives an electrostatic force from the developer supply roller 36 side toward the development roller 35 side. And a supply bias voltage such as that formed between them. Therefore, the supply roller bias power supply 41 has output terminals for the auxiliary developer supply rollers 39a and 39b and for the developer supply roller 36, respectively. The toner supplied to the developer supply roller 36 is
Further, the developer supply roller 36 is supplied to the developing roller 35 with the rotation, and the blade 39
After being regulated to a certain amount by the above, the toner is supplied to the photosensitive drum 11.

FIG. 3 is a control block diagram showing a part of the control in this embodiment. As described above, the document reading unit having the charge coupled device (CCD) 3 reads the document 1 and outputs an image signal to the image processing unit (IPU) 4. Then, the image processing unit (IPU) 4 processes the image signal and
The image signal of the second color and the image signal of the second color are output to the first exposure device 26 and the second exposure device 28 of the printer unit, and the image signal of the second color is transmitted to the second development control unit 5. Output.

In this embodiment, based on the image signal of the second color output from the image processing section, a supply bias voltage corresponding to the area ratio of the image is supplied to the auxiliary developer supply roller 3.
9a, 39b and the developer supply roller 36,
The second development control unit 5 controls the supply roller bias power supply 41.

That is, there is a proportional relationship between the area ratio of an image and the consumption amount of toner as a developer for forming the image, and the consumption amount of toner increases as the area ratio of the image increases. . Therefore, the amount of toner consumption and the auxiliary developer supply rollers 39a and 39b and the developer supply roller 36
The supply bias voltage is controlled in order to balance the amount of developer supplied to the developing roller 35 with the above. Specifically, the larger the potential difference between the auxiliary developer supply rollers 39a and 39b and the developer supply roller 36 and the larger the potential difference between the developer supply roller 36 and the development roller bias (so-called development bias), the larger the development roller 35. The developer supply amount for is increased. Therefore, the area ratio of the image is large,
The supply bias voltage is changed so that the larger the toner consumption is, the larger the potential difference becomes. This balances the amount of toner consumed and the amount of developer on the developing roller 35, and reduces the image density because the amount of toner supplied to the developing roller is smaller than the amount of toner required for image formation. Or because the amount of toner supplied to the developing roller is larger than the amount of toner consumed by image formation, the toner scatters through the opening of the developing device, or stays on the developing roller many times. It prevents deterioration due to idling.

As described above, in the second development control unit 5,
Instead of or in addition to changing the supply bias voltage according to the area ratio of the image, the peripheral speed of the developer supply roller 36 is changed to control the amount of developer supply to the development roller 35. Is also good. Specifically, when the image area ratio is large and the amount of toner consumption is large, the peripheral speed of the auxiliary developer supply rollers 39a and 39b and the developer supply roller 36 is increased to increase the developer supply capacity. When the area ratio of the image is small and the amount of toner consumption is small, the developer supply roller 36 is driven so that the peripheral speed of the rollers 39a, 39b and 36 is reduced to reduce the developer supply capability. Supply roller motor 42
Is controlled, and the peripheral speed of the developer supply roller 36 is changed in accordance with the area ratio of the image, so that the balance between the amount of toner consumption and the amount of the developer on the developing roller 35 can be balanced. (Hereinafter, margin)

A second development control unit 5 as control means
Accordingly, the moving speed of the developer supply roller 36 as the developer supply member, that is, the peripheral speed is changed according to the information on the area ratio of the image obtained by the image signal, and the agitator as the developer stirring means is changed. 37,
The conveying speed of the agitators 37 and 38 may be controlled in accordance with the area ratio of the image by changing the peripheral speed of the peripheral 38.

The above-described embodiment describes the present invention as follows.
Although the present invention is applied to a color digital copying machine, the present invention is applicable to a developing device having another structure and using a non-magnetic one-component developing device and an image forming apparatus using the developing device. The effect of can be obtained.

According to the first to fifth aspects of the present invention, a plurality of developer supply members, each of which is opposed to the developer supply member, supplies the developer contained in the developing device to the developer carrier. Since the developer contained in the developing device is supplied by the developer auxiliary supply member, the developer supply capability to the developer carrier is increased as compared with the case where the developer supply member is not provided. Can be. Therefore, even when an image having a large toner adhesion portion is formed, a decrease in image density due to a shortage of the developer on the developer carrying member can be prevented.

In particular, according to the invention of claim 2, claim 1
In the developing device, with respect to the developer supply member whose surface moves in a predetermined direction, the rotating bodies as the plurality of developer auxiliary supply members transfer the developer while their surfaces move in opposite directions at the contact portions. Since the developer is supplied, the total surface area of the developer auxiliary supply members opposing each other with the area and speed difference of the developer supply member at the contact portion becomes larger than when the surfaces move in the same direction at the contact portion. . Therefore, the developer supply capacity can be relatively large. In particular, since the rubbing at the contact portion can be improved, the developer supply capacity can be increased, and the charging of the developer can be further improved.

According to the third aspect of the present invention, between the developer carrier and the developer supply member, and between the developer supply member and at least one of the auxiliary developer supply members, A predetermined bias voltage is applied to at least one of the two, and an electric field for moving the developer charged to the polarity from the developer supply member to the developer carrier, or from the developer auxiliary supply member to the developer supply member. As a result, the ability to supply the developer to the developer carrier can be increased by this electric field.

Further, according to the invention of claim 4, according to claim 3,
The bias voltage is controlled in accordance with the image signal, and when an image having a large amount of toner adhesion is developed, the bias is conversely adjusted so that the ability of supplying the developer onto the developer carrier is further increased. In the case of developing an image with a small amount of toner adhesion, the bias can be made so that the ability to supply the developer onto the developer carrier becomes small. It is possible to prevent a decrease in image density due to an insufficient amount of the developer on the carrier and to prevent toner deterioration and toner scattering when developing an image with a small amount of toner adhering portion.

Instead of controlling the bias in accordance with the image signal as in the fourth aspect of the invention, or in addition to this, the bias of the developer supply member or the developer auxiliary supply member may be controlled in accordance with the image signal. The surface moving speed may be controlled to control the ability of the developer to supply the developer to the developer carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine according to an embodiment.

FIG. 2 is an enlarged view of a second developing device 29 of the copying machine.

3A is a perspective view of a developing roller 35 of the second developing device 29. FIG. (B) is an enlarged view of the surface of the developing roller 35. (C)
3 is a cross-sectional view of a surface portion of the developing roller 35. (D) is an explanatory view of each component material of the second developing device.

FIG. 4 is a control block diagram showing a part of control of the copying machine.

[Explanation of symbols]

 Reference Signs List 11 photoconductor drum 29 second developing device 35 developing roller 36 developer supply roller 39a, 39b auxiliary developer supply roller 39a auxiliary developer supply roller 5 second development controller 41 supply roller bias power supply

Claims (5)

[Claims] A developing device for supplying a developer contained in a developing device to a developer carrier by a developer supply member and developing the latent image on the image carrier with the developer on the developer carrier; A plurality of developer auxiliary supply members for supplying the developer contained in the developing device to the developer supply member,
A developing device, wherein the developing device is provided so as to face the developer supply member. 2. The developing device according to claim 1, wherein said developer supply member is driven so that the surface moves in a predetermined direction, and is rotated in contact with said surface as said plurality of developer auxiliary supply members. A rotating body that rotates, and the direction of rotation of the rotating body is set so as to move in a direction opposite to the surface at a contact portion with the surface. 3. A developing device according to claim 1, wherein said developer carrier and said developer supply member are located between said developer supply member and at least one of said developer auxiliary supply members. A predetermined bias voltage is applied to at least one of the developing device and the developing device. 4. A developing device for developing a latent image formed on an image carrier based on an image signal according to claim 3, further comprising control means for controlling said bias voltage in accordance with said image signal. A developing device. 5. An image forming apparatus for forming an image by developing a latent image formed on an image carrier based on an image signal by a developing device, wherein the developing device is used as the developing device.
An image forming apparatus using the developing device.