JPH06180527A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the gradation and resolution of a monochrome image by developing an electrostatic latent image, formed on an image carrier, by the use of two-component developer composed of toner and carrier and a noncontact method, and adjusting a bias voltage and an alternating electric field at the time of image formation, especially at the time of electrostatic latent image formation on the image carrier. CONSTITUTION:In an image forming device which develops an electrostatic latent image, formed on the image carrier 30, with the two-component developer containing toner and carrier, without the contact of the electrostatic latent image with a development sleeve 371, development is carried out by the use of the toner under the application of an AC bias between the image carrier 30 and the development sleeve 371, the frequency of an AC alternating electric field is set to a value of between 2 and 5 kHz in the AC bias when image formation is carried out on the image carrier 30, and it is set to a value of between 5 and 10 kHz when image formation is not carried out on the image carrier 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrostatic latent image formed on an image bearing member by a non-contact method using a two-component developer composed of toner and carrier to form the electrostatic latent image on the image bearing member. The present invention relates to a means for adjusting the bias voltage and the alternating electric field at the time of forming an image, especially at the time of forming an image to improve the gradation and resolution of a black image.

[0002]

2. Description of the Related Art As described above, a two-component developer composed of a non-magnetic toner and an insulating magnetic carrier is ejected from a developing sleeve toward an electrostatic latent image formed on an image carrier to eject only the non-magnetic toner. Then, there is a method of performing non-contact development. In the case of the present developing method, an AC bias and a DC bias are applied between the image carrier side that forms an electrostatic latent image and the developing rotary sleeve, and only the non-magnetic toner is ejected from the developing rotary sleeve to form the electrostatic latent image. On the other hand, a toner image is formed.

[0003]

SUMMARY OF THE INVENTION According to the present invention, only a toner of a two-component developer comprising the above-mentioned non-magnetic toner and an insulating magnetic carrier (hereinafter referred to as carrier) is developed on an electrostatic latent image in a non-contact manner. In the developing method, AC and DC bias voltages are applied between the image carrier and the developing sleeve that conveys the two-component developer to the developing portion as described above. At that time, the resolution is improved by lowering the frequency of the AC bias. Also, the resolution is improved by increasing the AC voltage. Although the image quality is improved by increasing the frequency and voltage of the AC bias in this way, when the AC bias voltage of a certain value or more and the frequency are lowered, color mixture occurs when full color development with four colors is performed. In this case, for example, when it is desired to form a yellow color, other colors are mixed. Further, since the most frequently used character image is formed, there is a drawback that the character image becomes unclear even when developing with black toner.

The present invention has been specifically devised in order to remedy the above-mentioned drawbacks. That is, the frequency of the alternating electric field and the AC bias voltage are set to optimum values during full-color development with the above four colors and when a character image is formed using black toner, and color mixing and image blurring are prevented.

[0005]

In order to achieve the above object, the present invention uses a two-component developer containing a toner and a carrier for the electrostatic latent image formed on the image carrier in claim 1. In an image forming apparatus for developing a developing sleeve on the electrostatic latent image by a non-contact method, a developing means for developing with toner by applying an AC bias between the image carrier and the developing sleeve. the image forming time in image bearing member is set to any value between 2～5KH _Z the frequency of the AC alternating electric field in said AC bias, when the image bearing member above a non-image state, the Frequency 5
It is characterized in that set to any value between 10KH _Z.

In the second aspect, a two-component developer containing toner and carrier is used for the electrostatic latent image formed on the image carrier, and a developing sleeve is developed for the electrostatic latent image by a non-contact method. In the image forming apparatus, a developing means for applying an AC bias between the image bearing member and the developing sleeve to develop with toner, wherein the AC bias peak and It is characterized in that the peak value voltage is set to any value between 1.4 and 2.5 KV, and set to any value between 0.5 and 1.4 KV during non-image formation on the image carrier.

In the third aspect, a two-component developer containing toner and carrier is used for the electrostatic latent image formed on the image carrier, and the developing sleeve is developed for the electrostatic latent image by a non-contact method. In the image forming apparatus, a developing means for applying an AC bias between the image carrier and the developing sleeve to develop with toner, the AC alternating electric field at the AC bias when the image is not formed on the image carrier. Frequency is 5 to 10 KHz, peak-to-peak voltage is 0.5 to 1.4 KV, and the frequency of the AC alternating electric field is 2 in the AC bias during full color in image formation.
.About.5 KHz, the peak-to-peak voltage is 1.4 to 2.5 KV, and in the monochrome mode, the frequency is lower or higher than that in the full color.

[0008]

FIG. 1 shows an embodiment in which a plurality of developing devices used in the present invention are provided in the peripheral portion of a photosensitive drum. FIG. 1 shows the main configuration of a multicolor image forming apparatus as an embodiment. A is an image reading system, B is a laser writing system unit, C is an image forming unit, and D is a paper feeding unit. A color image is formed by the following process.

In the reading system A, 11 is a document table, and the document stored in the document table 11 is illuminated by a halogen lamp 13 attached to a carriage 12 that slides in the horizontal direction. Movable mirror unit 15 has mirrors 16 and 17
Is attached, also slide horizontally,
In combination with the mirror 14 attached to the carriage 12, the optical image of the original is led to the lens reading unit 20.

The carriage 12 and the movable mirror unit 15 are driven via wires (not shown) connected to a stepping motor, and are slid in the same direction at speeds of V and 1/2 V, respectively. .

The lens reading section 20 comprises a lens 21, a prism 22, a reading substrate 24, and a plurality of CCDs 25.

The light image of the original transmitted by the mirrors 14, 16 and 17 is focused by the lens 21 and
Each image is separated by 22 and formed on a plurality of CCDs 25 provided on a substrate 24.

The image signal output from the CCD 25 is
Signal processing is performed in the signal processing unit. The signal processing unit outputs color signals that are color-separated according to the toner color,
It is inputted to the laser writing system unit B which is an exposing means.

In the laser writing system unit B, a laser beam generated by a semiconductor laser (not shown) is rotationally scanned by a polygon mirror 32 rotated by a drive motor 31, and an optical path is bent by a mirror 34 via an Fθ lens 33. Then, dots are formed by being projected onto the peripheral surface of the photoconductor drum 30 to which electric charges have been applied by the charger 35 which is a charging means in advance.

On the other hand, when the scanning is started, the beam is detected by the index sensor, the modulation of the beam by the first color signal is started, and the modulated beam scans the peripheral surface of the photosensitive drum 30. . Therefore, a latent image corresponding to the first color, for example, yellow, is formed on the peripheral surface of the photoconductor drum 30 by the main scanning by the laser beam and the sub-scanning by the rotation of the photoconductor drum 30. This latent image is developed by a developing device 36 in which yellow toner (visual medium) is loaded in the developing means, and a toner image is formed on the surface of the photosensitive drum 30. The obtained toner image passes through the cleaning device 51, which is a cleaning unit separated from the peripheral surface of the photosensitive drum 30, while being held on the drum surface, and enters the next copy cycle.

That is, the photoconductor drum 30 is recharged by the charger 35, and then the second color signal output from the signal processing unit is input to the writing system unit B and the above-mentioned first color signal is output. Writing is performed on the surface of the photosensitive drum 30 to form a latent image in the same manner as in the above case. The latent image is developed as a second color by the developing device 37 loaded with, for example, magenta toner.

This magenta toner image is formed in the presence of the previously formed yellow toner image.

Reference numeral 38 denotes a developing device having cyan toner, which is a photosensitive drum based on a control signal generated by a signal processing section.
30 A cyan toner image is formed on the surface. A developing device 39 having black toner forms a black toner image on the surface of the photoconductor drum 30 based on a control signal generated by the signal processing unit. AC and DC biases are applied to the sleeves of the developing devices 36, 37, 38, 39, jumping development is performed by a two-component developer, and the photoconductor drum is grounded.
No. 30 is contactlessly developed.

The color image thus formed on the peripheral surface of the photosensitive drum 30 is sent from the paper feeding section D by the paper feeding belt 41 and the second feeding roller 42 in the transfer pole 40 provided as a transfer means. It is transferred to a recording paper which is a recording medium. The recording paper on which the toner image has been transferred is separated from the drum surface by a separation electrode 43, and is fixed via a conveyor belt 44.
It is transported to 45 and the image is fixed.

On the other hand, the blade of the cleaning device 51 is attached to the photosensitive drum 30 separated from the peripheral surface of the recording paper.
51A contacts and removes the residual toner. After the completion of the removal, the toner is separated from the peripheral surface of the drum again, and a new color image forming process is started.

The layout of each of the above-mentioned main components will now be described. As shown in FIG. 1, the image reading system A is housed in an independent dedicated case 1 and is mounted and mounted on an upper portion of a main body 2 which will be described later. Has been.

The main body 2 incorporates an image recording system including the writing system B, the image forming section C, the sheet feeding section D, etc., and the image is transferred via a flexible cable group connected to the housing 1. The color signal from the reading system A is received.

In the main body 2, the photoconductor drum 30 is located substantially in the center and faces the right peripheral surface of the photoconductor drum 30.
6, 37, 38 and 39 are arranged horizontally, while the charger 35 and the cleaning device 51 are arranged on the left peripheral surface.

The photosensitive drum 30, the developing devices 36, 37,
38, 39 and the cleaning device 51 are not directly attached to the pair of front and rear substrates fixed to the main body 2, but are mounted on the support member 3 which is removably incorporated into the main body 2 so as to support the bearing or be detachably attached. There is.

When the image forming process is carried out by the above-mentioned superposition method, the photosensitive drum 30 has a peripheral surface having a length of one page of B4 or A3 which is the maximum recording body with a slight margin. The length is required, and the outer diameter dimension is required to be at least about 130 mm to 150 mm, and in this embodiment, a 150 mm photosensitive drum is rotated at a peripheral speed of 140 mm per second.

On the other hand, regarding the developing devices 36, 37, 38 and 39, as will be described later in detail, the outer diameter of the developing sleeve can be reduced to 20 mm without reducing the image performance, and the thickness (height) of each developing device can be reduced. ) Can be sufficiently suppressed to about 40 mm or less, and as a result, four developing devices corresponding to full color, that is, developing devices 36, 37, 38, 39 in this embodiment, are attached to the outer diameter of the photosensitive drum 30. It is possible to further stack and arrange them in a horizontal state in the space corresponding to the range.

Therefore, the support member 3 influences the layout of the members such as the upper laser writing system B, the lower transfer electrode 40 and the separation electrode 43, which are members directly attached to and fixed to the main body 2, and the transport system members. Even if the upper and lower heights thereof are limited to the minimum size sufficient to cover the photoconductor drum 30 so as not to give the above-mentioned problem, it goes without saying that the cleaning device 51 is not limited to the plurality of developing devices 36, 37, 38, 39. It is possible to install and store all of the above, and it is possible to configure the recording paper transport path in a substantially straight line, which is effective in preventing jams, and even if jams occur, Processing is easy.

Each of the developing devices 36, 37, 38 and 39 has the following structure.

In this embodiment, the developing devices 36, 37, 38, 39 are all of the same structure. The developing device used in the present invention will be described with reference to the sectional view of the developing device 37 shown in FIG.

370 is a housing, 371 is a developing sleeve, 37
2 is a magnetic roll, 373 is a developer layer thickness regulating member, 373A is a fixing member for the layer thickness regulating plate 373, 376A and 376B are first and second stirring members, 374 is a supply roller, 375 is a scraper, and 377 is stirring. It is a partition plate.

The toner replenished in the apparatus is sufficiently agitated and mixed with the carrier by the first agitating member 376A rotating in the direction of the arrow and the second agitating member 376B rotating so as to overlap each other in the opposite direction. Supply roller as developer
It is sent to the developing sleeve 371 via 374.

The first agitating member 376A and the second agitating member 376B are screw-shaped members having a left-handed helix angle that rotate in mutually opposite arrow directions, and are pushed backward by the thrust of the second agitating member 376B. The toner and the conveyed carrier are agitating partition plates whose upper edges are inclined downward toward the back side.
After passing 377 in sequence, it moved to the side of the first stirring member 376A, was conveyed to the front side by its thrust force, and became a homogeneous developer that was frictionally charged by the mixing action of the toner and the carrier in the meantime, and rotated in the direction of the arrow in a sponge form The supply roller 378 adheres in layers to the peripheral surface of the developing sleeve 371 that rotates in the time direction.

A housing 3 is provided on the surface of the developing sleeve 371.
A layer thickness regulating member 373 held by a fixing member 373A extending from 70 is pressed against the surface near the end to regulate the layer thickness of the conveyed developer, and is in the range of 100 μm to 500 μm, preferably 150 μm to 400 μm. The thin developing layer is used to form a thin developing layer.

A fixed magnetic roll 372 and a thin developer layer formed on the outer surface of the developing sleeve 371 which rotates in the direction of the arrow on the outer side of the magnetic roller 372 is a photosensitive drum which rotates in the direction of the arrow in the developing area E. The latent image on 30 is spaced apart and the developing layer is transported in a range of 7 to 10 mg / cm ² .
Non-contact development is performed to form a toner image.

An AC bias 379, in which a DC bias 380 is superposed during non-contact development, is added to the developing device 37 as described above.
It is applied to the developing sleeve 371. Further, the AC bias 379 is variable in the voltage converter 3711 and variable in the frequency converter 3712. An output device 3713 is connected to the CPU 3714 and is connected to the voltage conversion device 3711 to operate the voltage conversion device 3711 via the output device 3713 when a voltage conversion signal is received by the CPU 3714. 3715 is a power supply for the voltage converter 3711. The frequency converter 3712 connected to the AC bias 379 is also connected to the CPU 3714 via the output device 3716.

The present invention is configured as described above,
Now, the photoconductor drum 30 is charged by the charger 35, and the laser writing system unit B starts exposure as described above. At this time, depending on the image forming state, the frequency of the alternating electric field in the AC bias applied when starting the image formation by the toner on the developing sleeve 371 is output from the CPU 3714 and a conversion signal is sent to the frequency conversion device 3712 via the device 3716. during non-image formation sets the frequency to any value between 5~10KH _Z, the frequency converter at the time of image formation 37
12 issues a switching signal from the CPU3714 set to any value between 2~5KH _Z. Also, the voltage of the AC bias 379 is output from the CPU 3714 at the peak and peak value.
A conversion signal is sent to the voltage conversion device 3711 via the 3713 and set to any value between 0.5 and 1.4 KV during non-image formation,
At the time of image formation, the voltage converter 3711 is set to any value between 1.4 and 25 KV. By thus setting the frequency and voltage of the alternating field in the AC bias, the reproducibility of black characters used as character images is improved.

Even when full-color development is performed by the developing devices 36, 37, 38, and 39, in copying by general image formation, copying with black toner is an important factor, and only by developing device 39 is black toner developing. and further improve the set black character reproduced 2KH _Z the frequency of the alternating electric field in the AC bias. In order to prevent the occurrence of color mixture, the developing device 39 first develops in the developing order. Furthermore, L. Since D transmission is also required, in this case, yellow, magenta, and cyan are changed to black toner.

[0038] Since being biased further in a non-image state to set the frequency of the alternating electric field for preventing color mixing in 10KH _Z, the peak-and-peak voltage value of the voltage is fixed. If the alternating electric field is fixed, set the peak-to-peak voltage value between 2.2KV and 1.4KV.

In the non-image state, the frequency of the AC alternating electric field is 5 to 10 KHz, peak and
The peak voltage is 0.5 to 1.4 KV, the frequency of the AC alternating electric field is 2 to 5 KHz, and the peak-to-peak voltage is 1.4 at the AC bias during full color in image formation.
The voltage may be set to ~ 2.5 KV, and in the monochrome mode, it may be set as a lower frequency or a higher voltage than that in the full color.

[0040]

According to the present invention, yellow, magenta, cyan,
A full-color image forming apparatus having a black four-color developing device, in particular, to prevent a single color from being mixed with another color by being developed, and in general, black development used for the most frequently used character image Can be reproduced well.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an image forming apparatus including a developing device of the present invention.

FIG. 2 is a vertical sectional view showing a developing device of the present invention.

[Explanation of symbols]

 2 Main body 3 Support member 30 Photosensitive drum 36, 37, 38, 39 Developing device 371 Developing sleeve 379 AC bias 380 DC bias 3711 Voltage converter 3712 Frequency converter 3714 CPU

Claims (3)

[Claims] 1. An image in which a two-component developer containing a toner and a carrier is used to develop an electrostatic latent image formed on an image carrier by a developing sleeve in a non-contact method with respect to the electrostatic latent image. In the forming apparatus, a developing means for developing with toner by applying an AC bias between the image carrier and the developing sleeve, wherein the frequency of the AC alternating electric field at the AC bias when forming an image on the image carrier. 2 to
Set to any value between 5KH _Z, when the image bearing member above a non-image state, the image forming apparatus characterized by setting the frequency to any value between 5～10KH _Z . 2. An image in which a two-component developer containing a toner and a carrier is used to develop an electrostatic latent image formed on an image bearing member by a developing sleeve in a non-contact method with respect to the electrostatic latent image. In the forming apparatus, a developing unit that applies an AC bias between the image carrier and the developing sleeve to develop with toner, and a peak and peak of the AC bias during image formation on the image carrier. Value voltage 1.
An image forming apparatus characterized in that it is set to any value between 4 and 2.5 KV, and is set to any value between 0.5 and 1.4 KV during non-image formation on an image carrier. 3. An image in which a two-component developer containing toner and a carrier is used to develop an electrostatic latent image formed on an image bearing member by a developing sleeve in a non-contact method with respect to the electrostatic latent image. In the forming apparatus, a developing unit that develops with toner by applying an AC bias between the image carrier and the developing sleeve, wherein the frequency of the AC alternating electric field at the AC bias when the image carrier is not imaged. 5
~ 10KHz, peak-to-peak voltage 0.5-1.4KV, full-color during image formation, AC alternating electric field frequency 2-5KHz, peak-and-peak voltage 1.4-2.5KV in the above-mentioned AC bias. In the monochrome mode, the image forming apparatus has a lower frequency or a higher voltage than that in the full color mode.