JPH11194608A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of stably obtaining an excellent image having no defect such as void at a boundary part between a halftone part and a solid part by uniformly forming electric field for regulating developing electric field in a developing area and excellently regulating the developing electric field by preventing the vibration of a wire electrode for regulating developing electric field provided on an upstream side in the moving direction of a developer carrier in the developing area. SOLUTION: As for the wire electrode 11 for regulating the developing electric field, which is installed on an upstream side in the rotating direction of a developing sleeve in the developing area being a part where a photoreceptor drum and the developing sleeve are opposed, and whose both ends in a longitudinal direction are fixed; its vibration is detected by a detection element 15 at the time of developing, vibration data for causing the vibration whose phase is reverse to that of the vibration of the electrode 11 are calculated based on the vibration data detected by a vibration signal processing/generating means 16, and the electrode 11 is vibrated in the reverse phase by a vibration element 17 so as to negate the vibration of the electrode 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, an electrostatic latent image is formed on an image carrier, developed and visualized as a toner image, and the toner image is formed on a transfer material. The image is obtained by transferring.

In general, the above-mentioned developing methods include a one-component developing method using a one-component developer consisting of toner alone and a two-component developing method using a two-component developer consisting of magnetic particles (magnetic carrier) and toner. However, the one-component developing method has advantages such as a simpler configuration of the developing device and easy maintenance, and various one-component developing devices based on the one-component developing method have been proposed. Has been put to practical use.

As an example, FIG. 4 does not show an image forming apparatus provided with a one-component developing device. The developing device installed in the image forming apparatus of FIG. 4 has a cylindrical non-magnetic developing sleeve as a toner carrier installed in a developing container 5 containing a magnetic toner T of a one-component magnetic developer, and fixed inside the developing container. The magnetic force of the placed magnet roller 4 causes the magnetic toner T
Is held on the developing sleeve 3, and by rotating the developing sleeve 3 in the direction of the arrow b in the figure, the held magnetic toner T is transported toward the developing section facing the photosensitive drum 1 as an image carrier. During the transportation, the magnetic toner T is transferred to the magnetic blade 6.
The toner is regulated by the concentrated magnetic field formed by the magnetic pole N1 of the magnet roller 4 and is applied on the developing sleeve 3 in a thin layer.

[0005] The developing sleeve 3 and the photosensitive drum 1 are
They are arranged with a gap of 500 μm. An electric field is formed between the developing sleeve 3 and the photosensitive drum 1 by applying a developing bias in which a DC voltage is superimposed on an AC voltage by a bias power supply 7, and a thin layer applied to the developing unit is applied. The magnetic toner T develops the latent image by a so-called jumping development method in which the magnetic toner T flies and adheres to the electrostatic latent image formed on the photosensitive drum 1 by the action of the electric field.

The above-described developing device is used for a black-and-white image forming apparatus. In recent years, there is a developing device used for an image forming apparatus for developing a color image by using a color non-magnetic toner as a developer. Has been put to practical use.

However, in the above-described developing device, since the developing is performed while the developing sleeve 3 is not in contact with the photosensitive drum 1, the electric field spreads in the developing space, which often causes a problem. For example, when images having different contrasts are adjacent to each other, that is, when the halftone portion H and the solid portion D are adjacent to each other as shown in FIG. .

The white spot phenomenon is largely caused by the edge effect of the boundary portion to be emphasized and the stagnation of the toner on the upstream side of the developing nip, and contacts the solid portion D at the boundary G as shown in FIG. This occurs when the toner to be developed at the boundary on the halftone H side is drawn into the solid portion D having a large contrast.

In order to see these details in detail, FIG.
3 shows a distribution of an electric field vector and a potential in a development nip. The condition is that the latent image potential of the halftone portion H on the photosensitive drum 1 is -530 V, and the latent image potential of the solid portion D is -2V.
At 50 V, the potential of the developing sleeve 3 opposed to it is -580 V
It is time. The outer diameters of the photosensitive drum 1 and the developing sleeve 3 are 30 μm and 20 μm, respectively, and the rotation direction is the forward direction in which the facing portion moves in the same direction.

Referring to FIG. 7, looking at the direction of the electric field vector generated from the developing sleeve 3, the direction of the electric field is directed to the solid portion D avoiding the boundary on the halftone portion H side.
Further, it can be seen that the electric field wraps around the halftone portion H from the halftone portion H to the solid portion D in the region W at the boundary portion. That is, the boundary G approaches the developing sleeve 3,
When the development at the boundary portion starts, the toner that has left the developing sleeve 3 flies and adheres to the boundary portion on the solid portion D side according to the direction of the electric field without going to the boundary portion on the halftone H side. Further, even if the toner flies and adheres to the boundary portion on the halftone H side, the toner adhered from the photosensitive drum 1 is peeled off in the region of W, and the toner is directed to the solid portion D direction. As a result, a few m is set at the boundary on the halftone portion H side.
m occurs in white, which is a phenomenon that appears remarkably when performing non-contact development.

Therefore, in order to prevent this, as shown in FIG. 8, a wire-shaped auxiliary electrode 11 is provided upstream of the space of the developing section (developing space), and a bias is applied to the wire electrode 11 to apply a bias. A method has been proposed in which the direction of the electric field formed in the developing space on the upstream side of the developing unit is controlled to reduce the stagnation of toner and the edge effect.

According to this method, when the boundary G approaches the developing sleeve 3 and the development of the boundary starts, an electric field acts on the toner to press the toner on the developing sleeve 3. Is prevented from falling into the image area on the solid portion D side, and the toner is prevented from flying from the halftone portion H to the solid portion D.

[0013]

However, when the wire electrode 11 is arranged in the developing space, the wire electrode 11 generates an AC electric field formed by a developing bias, a developing potential and a voltage applied to the electrode 11 itself. Oscillates due to the included electric field. Since the wire electrode 11 is disposed in the developing space with both longitudinal ends fixed, the vibration width becomes large at the center of the wire electrode 11, and the effect as an auxiliary electrode is formed between the longitudinal end and the center of the electrode 11. Had different results.

When the wire electrode 11 vibrates, an appropriately set developing electric field changes, so that the developing state changes between the longitudinal end and the center of the end of the developing section.

Further, the wire electrode 11 at the center is
When the vibration width of the photosensitive drum 1 is large,
Alternatively, it may come into contact with the developing sleeve 3 and electrical leakage may occur.

If a leak occurs, the wire electrode 11 breaks, preventing white spots from being prevented. In addition, the broken wire electrode 11 comes into contact with the photosensitive drum 1 and the developing sleeve 3 to form a large flaw. In some cases, normal image formation becomes impossible.

Another object of the present invention is to prevent the vibration of a wire electrode for regulating the developing electric field, which is provided on the upstream side in the moving direction of the developer carrying member in the developing region, so that the electric field for regulating the developing electric field is formed in the developing region. Can be uniformly formed, the developing electric field can be well regulated, and it is possible to stably obtain a good image having no defects such as white spots at the boundary between the solid portion and the halftone portion. It is another object of the present invention to provide an image forming apparatus capable of preventing a danger of a leak due to a vibration of a wire electrode and a damage of an image carrier and a developer carrier due to disconnection of the wire electrode.

[0018]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier and a developer carried on a developer carrier,
The electrostatic latent image formed on the image carrier is developed by the developer while being conveyed to a development area facing the developer carrier and forming a developing electric field between the image carrier and the developer carrier. An image forming apparatus, comprising: a developing unit that performs the developing operation; and a wire electrode fixed at both ends to which a voltage that regulates the developing electric field is applied, the wire electrode being disposed on the upstream side of the developing area in the direction of movement of the developer carrier. Vibration detection means for detecting the vibration of, the calculated vibration data of the phase opposite to the detected vibration of the wire electrode, a vibration signal processing / generator to output, based on the output vibration data of the opposite phase, An image forming apparatus further comprising: a vibration generator for applying the opposite-phase vibration to the wire electrode.

In another aspect of the present invention, instead of the vibration detecting means for detecting the vibration of the wire electrode, a vibration waveform forming circuit for predicting and calculating the vibration of the wire electrode according to the image data is provided. A generator calculates and outputs vibration data of the opposite phase to the predicted calculated vibration of the wire electrode, and outputs the vibration of the opposite phase based on the vibration data of the opposite phase output by the vibration generator. Is applied.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of the image forming apparatus of the present invention.

In this image forming apparatus, as shown in FIG. 1, a charging roller 8 for uniformly charging the surface of the photosensitive drum 1 is provided around the photosensitive drum 1 rotating in the direction of arrow a as an image carrier. A laser driver 12 used to form an electrostatic latent image on the surface of the photosensitive drum 1 by image exposure based on image data, a developing device 2 for developing the latent image to visualize it as a toner image, and transferring the obtained toner image A transfer roller 9 for transferring to the material P and a cleaner 10 for removing the toner remaining on the photosensitive drum 1 after the transfer are installed, and the transferred toner image is fixed to the transfer material P on the extension of the transfer material P in the moving direction. A fixing device 13 is provided.

The developing device 2 has a developing container 5 containing a magnetic toner T of a one-component magnetic developer, and an opening of the developing container 5 which faces the photosensitive drum 1.
A cylindrical non-magnetic developing sleeve 3 that is arranged at an interval of μm and rotates in a direction indicated by an arrow b in the forward direction of the rotation direction of the photosensitive drum 1, and is non-rotatably fixed inside the developing sleeve 3. The image forming apparatus includes a magnet roller 4 and a magnetic blade 6 disposed on the top of the developing sleeve 3 at a distance of 100 to 300 μm. A developing power source 17 for applying a developing bias is connected to the developing sleeve 3, and a developing electric field is formed in a developing area where the photosensitive drum 1 and the developing sleeve 3 face each other by applying the developing bias.

According to the present embodiment, the photosensitive drum 1 is located at a position upstream of the photosensitive drum 1 in the rotational direction of the developing sleeve 1 in the space of the developing area (also upstream of the photosensitive drum 1 in the rotational direction).
A wire electrode 11 as an auxiliary electrode for regulating the developing electric field is arranged at a position separated by μm, and both ends in the longitudinal direction of the wire electrode 11 are fixed by fixing members 20 as shown in FIG. A power supply 14 for applying a bias for electric field regulation is connected to the wire electrode 11.

Further, a vibration preventing means is provided for the wire electrode 11. That is, a detection element 15 for detecting the vibration of the wire electrode 11 is connected, and the vibration detection element 15 calculates the vibration data for generating the opposite-phase vibration based on the vibration data obtained by detecting the vibration of the wire electrode 11. A vibration signal processing / generating means 16 for outputting the vibration signal is connected to the vibration signal processing / generating means 16. The vibration element generates vibration based on the output vibration data of the anti-phase vibration and vibrates the wire electrode 11. 17 are connected. The vibration element 17 is connected to the wire electrode 11.

An image forming operation in the present image forming apparatus will be described.

In this embodiment, a laser is used as a light source for image exposure, and the photosensitive drum 1 is provided with a photosensitive layer 1b on a conductive drum 1a serving as a base, and the photosensitive layer 1b is made of amorphous silicon. It is formed by depositing or applying a material in which a resin is dispersed and mixed with a metal optical semiconductor such as zinc oxide, selenium, and cadmium sulfide, or an organic optical semiconductor such as phthalocyanine and polyvinyl carbazole.

The photosensitive drum 1 is rotated in the direction of arrow a, and the surface of the photosensitive drum 1 is uniformly charged to -700 V by a charging roller 8 as a primary charging means. Image exposure is performed by 12 to form an electrostatic latent image on the surface of the photosensitive drum 1. The surface potential of the latent image portion of the photosensitive drum 1 is determined by the sensitivity of the photosensitive layer 1b to light and the amount of image exposure. In this embodiment, the solid portion is -250V, and the halftone portion is -250V.
The exposure was controlled so as to be 530V.

The latent image formed on the photosensitive drum 1 in this manner is conveyed to a portion facing the developing device 2 as the photosensitive drum 1 rotates. In the developing device 2, the magnetic toner T is held on the developing sleeve 3 by the magnetic force of the magnet roller 4 fixed and arranged inside the developing sleeve 3,
The rotation of the developing sleeve 3 in the direction of the arrow b in the drawing conveys the held magnetic toner T toward the developing area facing the photosensitive drum 1. During the conveyance, the magnetic toner T is regulated by a concentrated magnetic field formed by the magnetic blade 6 and the magnetic pole N1 of the magnet roller 4, and is applied on the developing sleeve 3 in a thin layer.

A bias power supply 7 supplies a peak-to-peak voltage 2 between the developing sleeve 3 and the photosensitive drum 1.
By applying a developing bias in which a DC voltage of -580 V is superimposed on an AC voltage having a frequency of 2 kHz and a frequency of 2 kHz, a developing electric field is formed, and the magnetic toner T applied in a thin layer and conveyed to the developing area is The latent image is developed by the so-called jumping development method, which flies and adheres to the electrostatic latent image on the photosensitive drum 1 by the action of (1).

In this embodiment, a DC voltage of -700 V is applied from the power supply 14 to the wire electrode 11 disposed on the upstream side of the development area in order to regulate the development electric field during the development.

Normally, in the space of the development area, as described with reference to FIG. 7, the electric field generated from the development sleeve 3 goes to the solid part D avoiding the boundary on the halftone part H side of the image. In the region of W at the boundary of the halftone portion H, since the electric field wraps around from the halftone portion H to the solid portion D, a white spot of several mm occurs at the boundary portion on the halftone portion H side.

When a voltage is applied to the wire electrode 11 disposed on the upstream side of the developing area, the electric field near the developing sleeve 3 is generated on the upstream side of the developing area as described with reference to FIG. Acting in the direction, and can suppress the electric field wrapping around from the halftone portion to the solid portion, so that the toner to be developed at the boundary portion on the halftone portion H side is prevented from falling into the image area on the solid portion D side, In addition, the toner is prevented from flying from the halftone portion H to the solid portion D.

However, the wire electrode 11 arranged in the developing area is provided with a developing bias, a latent image potential and an electrode 11.
Vibrates due to an electric field including an AC electric field formed by a voltage applied to itself. Since the wire electrode 11 is fixed at both ends in the longitudinal direction, the amplitude particularly at the central portion becomes very large, and in some cases, the wire electrode 11 comes into contact with the photosensitive drum 1 or the developing sleeve 3 to cause an electric leak. The electrode 11 is disconnected and comes into contact with the photosensitive drum 1 and the developing sleeve 3 to damage them.

Therefore, in the present embodiment, at the time of development, the vibration of the wire electrode 11 is detected by the detecting element 15 and the detected vibration data is sent to the vibration signal processing / generating means 16. Then, based on the vibration data, the vibration data for causing the vibration in the opposite phase to the vibration of the wire electrode 11 is calculated. And vibration signal processing / generating means 1
6 outputs the vibration data of the opposite phase to the vibrating element 17, causes the vibrating element 17 to vibrate in the opposite phase, transmits the vibration of the opposite phase from the vibrating element 17 to the wire electrode 11, Vibration to the phase cancels the vibration of the wire electrode 11 due to the electric field including the AC electric field.

A series of steps from the detection of the vibration of the wire electrode 11 to the cancellation of the vibration of the wire electrode 11 due to the opposite-phase vibration is repeated until the vibration of the wire electrode 11 becomes substantially zero. Electrode 11
Continue to not always vibrate.

As described above, according to the present embodiment, the wire electrode 11 does not vibrate in response to the electric field which is constantly changed in the developing area along with the fluctuation of the latent image potential. An electric field can be formed uniformly in the longitudinal direction of the wire electrode 11.

That is, by forming a favorable electric field for regulating the developing electric field, as shown in FIG. 8, the electric field in the vicinity of the developing sleeve 3 acts toward the center of the developing sleeve as shown in FIG. The electric field wrapping around the portion can be suppressed, and thereby the halftone portion H
It is possible to prevent the toner to be developed at the side boundary portion from dropping into the image area on the solid portion D side, and prevent the toner from flying from the halftone portion H to the solid portion D. Therefore,
A good image having no white spots in the halftone portion at the boundary portion with the solid portion can be obtained.

The toner image formed on the photosensitive drum 1 is
Thereafter, the toner image is transferred to the transfer material P by the transfer roller 9, and then the toner image is fixed to the transfer material P by the fixing device 13.
Further, the transfer residual toner remaining on the photosensitive drum 1 is cleaned by a cleaner 19 such as a fur brush, and is prepared for the next image formation.

Embodiment 2 FIG. 3 shows a vibration preventing means according to another embodiment of the present invention.

The present embodiment is characterized in that the means for preventing vibration of the wire electrode 11 comprises a vibration signal processing / generator 16, a vibration element 17, and a vibration waveform forming circuit 18.

The vibration waveform forming circuit 18 is provided with a table of vibration data of the wire electrodes 11 obtained by performing calibration in advance according to arbitrary image data. By comparing the image data output from the generator with the vibration data in the table, the vibration of the wire electrode 11 in the development area is predicted and calculated.

Then, the obtained predicted vibration data of the wire electrode 11 is sent to the vibration signal processing / generating means 16, and the vibration signal processing / generating means 16 has a phase opposite to the vibration of the wire electrode 11 based on the predicted vibration data. Vibration data for causing vibration is calculated, vibration data of the opposite phase is output to the vibration element 17, and the vibration element 17 is vibrated in the opposite phase, so that the wire electrode 11 is vibrated by the vibration of the opposite phase, The vibration of the wire electrode 11 due to the electric field including the AC electric field is canceled.

Therefore, according to the present embodiment, the electric field for regulating the developing electric field can be formed well in the developing area by eliminating the vibration of the wire electrode 11 during the developing operation.
A good image having no white spots in the halftone portion at the boundary portion with the solid portion can be obtained.

[0045]

As described above, according to the present invention,
For the wire electrode that forms an electric field for regulating the development electric field provided on the upstream side in the movement direction of the developer carrier in the development area, at the time of development, the vibration is detected or the vibration is predicted and calculated from the image data. The vibration data of the opposite phase is calculated, and the wire electrode is caused to vibrate in the opposite phase by the vibration data of the opposite phase, so that the vibration of the wire electrode can be canceled out. The electric field can be formed uniformly, and the developing electric field can be well regulated, and a good image can be stably obtained without any white spots in the halftone portion at the boundary with the solid portion. It is also possible to prevent the danger of leakage accompanying the damage and the damage of the image carrier and the developer carrier due to the disconnection of the wire electrode.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a block diagram illustrating a vibration preventing unit provided for a wire electrode for regulating a developing electric field provided in the image forming apparatus of FIG. 1;

FIG. 3 is a block diagram showing a vibration preventing means according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating a conventional image forming apparatus with a part thereof omitted;

FIG. 5 is an explanatory diagram illustrating white spots in an image generated by the image forming apparatus of FIG. 4;

FIG. 6 is a potential diagram showing the white spots in FIG. 5 in terms of potential.

7 is an explanatory diagram illustrating an electric field vector and a potential distribution in a development region of the image forming apparatus in FIG.

8 is an explanatory diagram showing an electric field vector and a potential distribution in the developing region when an electric field for regulating a developing electric field is generated by a wire electrode provided upstream of the developing region in the rotation direction of the developing sleeve in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing sleeve 2 developing device 3 developing sleeve 7 developing bias power supply 11 wire electrode 14 wire bias power supply 15 vibration sensing element 16 vibration signal processing / generation circuit 17 vibration element 18 vibration waveform forming circuit

Claims (2)

[Claims] An image carrier, a developer carried on the developer carrier, and transported to a development area opposed to the developer carrier;
Developing means for developing an electrostatic latent image formed on the image carrier with a developer while forming a developing electric field between the image carrier and the developer carrier; and a developer carrier in the developing area. In an image forming apparatus provided with a wire electrode fixed at both ends to which a voltage regulating the development electric field is applied, which is disposed on the upstream side in the movement direction, a vibration detecting means for detecting vibration of the wire electrode; A vibration signal processing / generator for calculating and outputting vibration data of the opposite phase to the vibration of the wire electrode, and a vibration generator for applying the opposite phase vibration to the wire electrode based on the outputted vibration data of the opposite phase. An image forming apparatus further comprising a container. 2. An image carrier and a developer carried on the developer carrier, and transported to a development area opposed to the developer carrier,
Developing means for developing an electrostatic latent image formed on the image carrier with a developer while forming a developing electric field between the image carrier and the developer carrier; and a developer carrier in the developing area. In an image forming apparatus comprising: a wire electrode fixed at both ends to which a voltage regulating the developing electric field is applied, which is disposed on an upstream side in a moving direction, a vibration waveform for predicting and calculating a vibration of the wire electrode in accordance with image data. A forming circuit, a vibration signal processing / generator for calculating and outputting vibration data having a phase opposite to the predicted calculated vibration of the wire electrode, and a vibration having the opposite phase based on the output vibration data having the opposite phase. And a vibration generator for applying a force to the wire electrode.