JPH06258924A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device preventing the generation of leak when a developing means comes into contact with an image carrier and the generation of contact fault as well. CONSTITUTION:A developing device is stopped at a developing position, and only DC bias voltage (-550V) is applied on a developing roller. After the voltage rises, the developing device is pressed from the back side and moved, then the developing roller is moved to be near a or to abut to the photosensitive drum. At this time, since only DC bias is applied on the developing roller, leak is prevented. Also, since the DC bias, which is enough effective to prevent fogging, has beam already applied when the developing device is moved near the photosensitive drum, reverse fogging is not generated. Thereafter, AC bias (1600Vpp) is applied on the developing device and the developing of latent image is started. At the time of completion of developing, AC bias is turned off at first and the developing device is separated from the photosensitive drum at a state that only the DC bias is applied. Next, the DC bias is turned off.

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 or a printer such as an electrophotographic system or an electrostatic recording system,
In particular, having a plurality of developing devices that can be brought into contact with and separated from the image carrier,
Further, when developing an electrostatic latent image, it is useful when applied to an image forming apparatus that applies at least an alternating electric field to a developing device.

[0002]

2. Description of the Related Art Conventionally, developers (toners) of different colors
A plurality of developing devices for accommodating each of them are formed, and a visible image (toner image) is formed on a photosensitive drum as an image carrier by each process of charging, exposing, and developing by using an electrophotographic method, and the toner image is formed. By repeating the process of transferring the toner images onto the recording material a plurality of times, the toner images of a plurality of colors are superimposed and transferred onto the recording material, and the superimposed images are fused and fixed by a fixing unit to form a full-color or multicolor multicolor image. Obtained color image forming apparatuses are widely used. An image forming apparatus of this type has been put into practical use with the configuration described in German Patent No. 2607727, Japanese Patent Laid-Open No. 50-50935, and the like.

In the electrophotographic color image forming apparatus previously proposed by the applicant, a transfer drum is provided,
FIG. 15 shows a schematic configuration example of a color image forming apparatus that forms a multicolor image by a plurality of recording cycles.

In FIG. 15, a photoconductor drum 1 as an image carrier rotates steadily in the direction of an arrow shown in the figure, and a contact type charging device (in this example, a uniform charging) is applied to the photoconductor drum 1 along the rotation direction. Roller charger 3), a so-called rotary developing device provided with a plurality of developing devices 4a, 4b, 4c and 4d for separately storing developers (color toners) of different colors for developing electrostatic latent images after exposure. The device 4, the recording material (paper) to which the developed visible image is transferred is held by the recording material holding means, and the transfer drum 10 as a recording material carrying member to be conveyed and the residual toner on the photosensitive drum 1 are removed. Each cleaning device 26 is provided.

The developing device 4 is a so-called rotary developing device in which one of a plurality of (four in this example) developing devices 4a to 4d supported by a support 9 is set in advance at a developing position by rotating the support 9. As shown in a magnified view of FIG. 16, the developing opening surfaces 5a, 5 of the developing devices 4a, 4b, 4c and 4d are arranged on the same cylinder centered on the support body rotation shaft 9a.
b, 5c and 5d are set.

Further, each developing device 4a, 4b, 4c, and 4
In d, a yellow toner (Y), a magenta toner (M), a cyan toner (C), and a black toner (BK) are contained, respectively, and the coating roller 6a,
6b, 6c and 6d, and toner regulating members 7a and 7
b, 7c and 7d are provided, and the developing roller 8a,
Along with the rotation of 8b, 8c, and 8d, the toner on the toner applying rollers 6a to 6d is applied to the developing rollers 8a to 8d, and the toner regulating members 7a to 7d provide necessary tribo to the toner.

The material of the regulating members 7a to 7d is preferably nylon or the like when the toner has a negative polarity and silicon rubber or the like when the toner is positively charged. In short, the polarity is opposite to the polarity of the toner. A material that is electrostatically charged is preferable. Further, it is preferable to select the peripheral speed in the range of 1.0 to 2.0 times the peripheral speed of the photosensitive drum 1.

Further, each of the developing devices 4a, 4b, 4c and 4d mounted on the support 9 has an opening surface 5 for development thereof.
The a, 5b, 5c and 5d are driven so as to always face the surface of the photosensitive drum 1. One means of this driving method is described in detail, for example, in Japanese Patent Laid-Open No. 50-93437.

The transfer drum 10 is rotatably supported at the center thereof in the direction of the arrow shown in the drawing, and faces the photosensitive drum 1 in a state of being in contact with the surface of the photosensitive drum 1 or being slightly separated therefrom. is doing. This transfer drum 10
Conductive drum housing 10a without a notch (diameter 1 in this example)
The elastic layer 10b (in this example, urethane foam made of Inoac having a thickness of 2 mm) is wound on a 56 mm metal cylinder).
Furthermore, a dielectric sheet 10c (thickness 1 in this example)
This is a so-called solid-state transfer drum having a structure in which a polyvinylidene fluoride (PVdF) sheet of 00 μm is wound. Further, a gripper 22 that holds the leading end of the fed recording material is provided.

Around the transfer drum 10, the recording material fed from the recording material cassette 17 by the pickup roller 18 is arranged along the rotation direction of the transfer drum 10.
Adsorption roller 23 as means for electrostatically adsorbing to the dielectric layer 10c, corona charger 2 for separation for separating the recording material electrostatically adsorbed on the transfer drum 10 after the transfer process, assisting separation, and after separation Separation pawl 24 for guiding the recording material to the fixing device 25, a transfer drum cleaning device 27 for removing the toner and the like adhering to the surface of the transfer drum 10 after the recording material separation, and an initial potential of the transfer drum 10 surface. A static elimination roller charger 28 for eliminating static electricity is provided.

The photosensitive drum 1 has a diameter of 40 in this example.
mm organic cylinder (OPC) on the outer surface of aluminum cylinder
Is applied to rotate the photoconductor in the direction of the arrow in the figure at a peripheral speed of 100 mm / sec. As the photoconductor, A-Si,
CdS, Se or the like may be applied.

The roller charger 3 has -700V.
A bias voltage obtained by superimposing an AC voltage having a peak-peak voltage (Vpp) of 1500 V at a frequency of 700 Hz is applied to the DC voltage of, and the photosensitive drum 1 is uniformly charged to approximately -700 V.

On the other hand, a laser diode 11, which constitutes an exposure device, a rotary polygon mirror 13 which is driven to rotate by a high-speed motor 12, a lens 14 and a folding mirror 15 are arranged above the main body of the apparatus. When an image signal according to the first color image pattern of yellow is input, the optical signal emitted from the laser diode 11 irradiates the photoconductor drum 1 through the optical path 16, and the first color image is radiated on the photoconductor drum 1. Electrostatic latent image of is formed. In this case, the light-irradiated spot on the photosensitive drum 1 is almost −
It becomes 100V.

The developing device 4 is a developing device corresponding to the electrostatic latent image of the first color formed on the photosensitive drum 1 by the optical signal, and in this case, a yellow latent image is formed, so yellow toner is applied. The contained developing device 4a is placed at a developing position facing the photoconductor drum 1, and when the latent image advances to the developing position as the photoconductor drum 1 rotates, toner is electrostatically adhered to the latent image to form a latent image. Development is performed to form a yellow visible image (toner image).

When the electrostatic latent image of the first color is developed and visualized by the yellow developing device 4a, the transfer drum 10 is fed from the recording material cassette 17 by the pickup roller 18 in parallel with this process. The front end of the recorded recording material is held by the gripper 22, and the recording material is wound around the surface by the rotational movement of the transfer drum 10. At this time, the recording material is sandwiched between the suction roller 23 that can be brought into contact with and separated from the transfer drum 10 and the dielectric sheet 10c that forms the surface of the transfer drum, and at the same time, an electric charge is applied by the suction roller 23 to which a voltage is applied, thereby transferring Electrostatically attracted to the drum surface.

The recording material held on the transfer drum 10 is conveyed by the rotation of the transfer drum 10 to an image transfer portion at a position facing the photoconductor drum 1, and a yellow toner image formed on the photoconductor drum 1 is conveyed. Is transferred onto the recording material held on the transfer drum 10 by a transfer bias voltage applied to the transfer drum 10 from a power source (not shown).

After that, the photosensitive drum 1 is cleaned by a cleaning device 26 such as a known fur brush, blade means, etc., that remains on the surface of the photosensitive drum 1 and is uniformly charged again by the roller charger 3. After that, an electrostatic latent image based on the image signal of the second color, for example, magenta, is formed on the photosensitive drum 1 by the exposure device. The electrostatic latent image of the second color is developed by the magenta developing device 4b corresponding to the image signal of the second color and becomes a magenta toner image. The magenta toner image of the second color is superposed and transferred onto the recording material held and conveyed by the transfer drum 10 at the transfer position. As a result, the second-color magenta toner image is superimposed on the first-color yellow toner image that was previously transferred.

The above-mentioned steps of charging, exposing, developing and transferring are repeated for the third color cyan (C) and fourth color black (BK) image formation. When the color toner images are transferred in an overlapping manner, the separation corona charger 2 is operated, and the recording material conveyed by the transfer drum 10 and the dielectric sheet 10 of the transfer drum 10 are transferred.
The electrostatic attraction between c is removed. Further, the gripper 22 is opened, and at the same time, the separation claw 24 is operated to separate the recording material from the transfer drum 10 to separate the known heating and pressure fixing device 25.
Send to. The toner images that have been multi-transferred by the fixing device 25 are fused and fixed on the recording material to form a desired color print.

The transfer drum 10 after the recording material is separated is
If necessary, the transfer drum cleaning device 27 such as a fur brush or a web removes the toner or the like adhering to the surface of the device, and then the destaticizing roller charger 28 is actuated to destaticize the electrically initial state. Preferably.

By the way, in the conventional image forming apparatus, a developing device as shown in FIG. 17 is also used. In the developing device 400, a non-magnetic toner is stored in a developer hopper 401, and the toner is supplied to the toner feeding member 40.
2 to the developing chamber 403, and the toner applying roller 4
04 onto the developing sleeve 405.

The toner applying roller 404 and the developing sleeve 405 are rotated in the directions of the arrows shown in the figure. The toner coated on the developing sleeve 405 is elastic blade 406.
Then, the developing sleeve 405 is uniformly coated with a thin layer, and is used for developing the electrostatic latent image formed on the photosensitive drum (not shown). A leak prevention sheet 407 for preventing toner from leaking is provided at the opening of the developing chamber 403 on the downstream side in the rotation direction of the developing sleeve 405.

In general, not all toner applied on the developing sleeve is used for development, and toner with high tribo remains on the developing sleeve. If the high tribo toner accumulates on the developing sleeve, it prevents new toner from coming into contact with the developing sleeve, and sufficient tribo is not imparted to this toner. As a result, toner that does not have enough tribo and toner that has been charged up coexist on the developing sleeve to form a broad tribo distribution, and fog and density decrease due to low tribo toner, blotch due to high tribo toner, etc. It causes the trouble of. The coating roller scrapes off the residual toner after development from the developing sleeve to stably supply the toner, thereby suppressing the above-mentioned problems.

By using the coating roller in this way, it is possible to always obtain a stable image in which the density does not change.

[0024]

The development will be described in detail. As described above, since the rotary developing system has a high space efficiency, the apparatus can be downsized and the four developing devices can have the same shape. Therefore, there is an advantage that the productivity is good.

At the time of development, a clear image can be obtained by applying an alternating voltage (hereinafter abbreviated as AC bias) on which a DC voltage (DC bias) is superimposed.

Next, a specific example will be described.

The latent image potential is a dark part potential (hereinafter, Vd
Will be abbreviated) = − 700V, and the light portion potential (hereinafter abbreviated as Vl) = − 100V. As a developing method, a reversal developing method is used, which has a lot of advantages such as sharpness, and is developed in the Vl portion, which has been generalized in recent laser printers and the like. Therefore, as the developing bias, AC bias (Vac) = 1600 Vpp, DC bias (Vdc)
= -550V. Further, the gap between the photosensitive drum 1 and the developing rollers 8a to 8d of the developing devices 4a to 4d (hereinafter, referred to as S
The distance between −D) is 300 μm, and the toner is a negatively charged toner.

Under the above conditions, the inventors of the present invention have made extensive studies and as a result, the following problems have occurred.

As described above, each of the developing devices 4a to 4d separates from the photosensitive drum 1 when the printing of the first color is completed, and quickly rotates, so that the developing device of the next color faces the photosensitive drum 1. Next, the photosensitive drum 1 is pressed against the photosensitive drum 1, abuts against a predetermined positioning unit (not shown), and stops at an appropriate position for development (a position where the SD distance is 300 μm). During this operation, as the developing bias, an appropriate bias without fogging (a bias obtained by superimposing a DC bias on the above-mentioned AC bias at the time of development) was applied during the moving operation of the developing device.

In such a developing system, when the developing device comes into contact with the developing roller, the developing roller is deflected by the momentum of the contact, and the photosensitive drum and the developing roller are temporarily brought close to or in contact with each other.
A phenomenon that leakage occurs at the peak value of C has occurred. Further, although the developing bias is applied during the moving operation, the contact for bias application slides with the moving operation. At this time, since a high voltage of 1600 Vpp is applied, when repeated operations are repeated for a long period of time, the contact is gradually carbonized, causing a problem of contact failure.

In order to avoid this phenomenon, it is naturally conceivable that the developing bias is not applied during the moving operation of the developing device and the developing bias is applied after the moving operation is completed. However, when this is executed, the developing device is located at a position suitable for development with respect to the photosensitive drum, that is, SD.
In the state where the gap is 300 μm, there is a state where the developing bias is 0V. At this time, since the potential of the photosensitive drum is Vd and −700V, the potential contrast with the developing roller is −700V.

Since negatively charged toner is used here,
Ideally, toner is not developed, but in reality, all toner does not have the same tribo and the same polarity. There is toner that you do not have.
Therefore, the contrast of -700V is too high,
Not only the toner is wastefully consumed, but also the toner is scattered inside the apparatus. Particularly, in the case of the above-described color image forming apparatus, the transfer drum is soiled, which is a serious problem.

On the other hand, the developing device 400 as shown in FIG.
In the above, the developing sleeve 405 and the coating roller 404 are always in contact with each other with a nip width. Generally, the developing sleeve is made of a rigid body such as aluminum or stainless steel, and the coating roller is made of an elastic material such as urethane. Therefore, if abutting at the same position for a long time without being used, the abutting surface on the coating roller side is permanently deformed, and periodic image unevenness as shown in FIG. 18 occurs. was there.

Therefore, an object of the present invention is to apply an alternating electric field only when the developing means is in contact with the image carrier and when the developing device is moving for contacting and separating operations. It is an object of the present invention to provide a good image forming apparatus that prevents the occurrence of leaks by applying only a DC voltage, does not cause contact failure, and does not cause fog.

Another object of the present invention is to prevent permanent deformation of the developer applying means used for applying the developer to the developer carrying member of the developing means and always obtain a stable image without image unevenness. It is to provide an image forming apparatus capable of performing the above.

[0036]

The above object is achieved by the image forming apparatus according to the present invention. In summary, in the first aspect of the present invention, in the first aspect, an image carrier and a latent image formed on the image carrier are developed and made into a visible image. A plurality of possible developing means, and at the time of developing the latent image, in an image forming apparatus that applies an alternating electric field to the developing means, at the time of the contacting and separating operation of the developing means with respect to the image carrier, a direct current is applied. The image forming apparatus is characterized in that only a voltage is applied.

In a second aspect, the present invention provides
An image carrier, and a plurality of developing means that develops a latent image formed on the image carrier to make it a visible image and can be brought into contact with and separated from the image carrier. At the time of developing, in an image forming apparatus that applies at least an alternating electric field to the developing means, the contacting operation is performed with respect to the image carrier while applying only the DC voltage to the developing means. The image forming apparatus is characterized in that an alternating electric field is applied to the developing means in contact therewith.

Further, in the third aspect, the present invention provides
An image carrier, and a plurality of developing means that develops a latent image formed on the image carrier to make it a visible image and can be brought into contact with and separated from the image carrier. At the time of development, in an image forming apparatus that applies at least an alternating electric field to the developing means, application of the alternating electric field to the developing means is terminated while the developing means is in contact with the image carrier, and a DC voltage is applied. The image forming apparatus is characterized in that only the developing means in the contact state is applied and then the developing means is separated from the image carrier.

Further, in a fourth aspect, the present invention comprises an image carrier and a developing means for developing the latent image formed on the image carrier to make it a visible image. Means
A developer storage chamber for storing the developer, and a development chamber provided adjacent to the developer storage chamber and provided with at least a developer carrier and a developer applying unit for applying the developer to the developer carrier. In the image forming apparatus, which is configured to be detachably provided in the main body of the image forming apparatus, the developer applying unit is brought into contact with and separated from the developer carrier. The image forming apparatus is characterized in that it can be switched.

[0040]

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

FIG. 1 is a timing chart for explaining the operation mode of the essential parts of the first embodiment in which the present invention is applied to an electrophotographic color image forming apparatus, and FIG. 2 is a latent image in this embodiment. FIG. 6 is a timing chart showing the relationship between the potential and the developing bias. The entire structure of the color image forming apparatus of this embodiment is the same as that of the electrophotographic color image forming apparatus shown in FIGS. 15 and 16, and therefore it is not shown in the drawings. Hereinafter, referring to these drawings. explain.

As shown in FIG. 2, in the present embodiment,
The latent image potential is Vd = -700V, Vl = -100V, and the developing bias is DC bias Vdc = -550.
V, AC bias Vpp = 1600V, frequency f = 12
It is 00 Hz.

Next, the operation will be described.

When the developing device corresponding to the latent image of the first color formed on the photosensitive drum 1 is brought into contact with the photosensitive drum 1, the developing device 4 is first rotated to form the latent image of the first color. The corresponding developing device, for example, the yellow developing device 4a is stopped at the developing position facing the precharged photosensitive drum 1. At this time, the photosensitive drum 1 and the developing roller 8a of the developing device 4a are sufficiently separated from each other (about 5 mm), and there is no fear of fogging.

Next, Vdc (-550) is applied to the developing roller 8a.
V) only is applied. After the voltage rises, the developing device 4a is pressed from the rear side, and the developing device 4a is moved to a position where the SD distance is 300 μm. At this time, since only Vdc is applied to the developing roller 8a, even if the developing roller 8a slightly bends due to the momentum of movement, no leak occurs. Further, the developing device 4 is placed at a position where the distance between S and D is 300 μm.
When “a” moves, Vdc, which is sufficiently effective for removing fog, has already been applied, so that reversal fog does not occur.

After that, AC bias (1600 Vpp)
Then, the bias shown in FIG. 2 is applied to the developing device 4a to start developing the latent image of the first color.

When the development is completed, the AC bias is first turned off this time, and the developing device 4a is separated from the photosensitive drum 1 with only the DC bias applied. Then DC
The bias is also turned off, the developing bias is completely turned off, and then the developing device 4 is rotated so that the developing device corresponding to the latent image of the second color, for example, the magenta developing device 4b, faces the precharged photosensitive drum 1. Put on. The subsequent process is the same as that of the yellow developing device 4a.

According to this structure, since the AC bias is not applied during the moving operation of the developing device, there is no leak when the developing device is in contact with the developing device, and contact failure such as carbonization of the contact occurs even when the developing device is operated for a long time. Further, since the DC bias is applied during the moving operation of the developing device, fog does not occur and toner does not scatter, and therefore, an image forming apparatus having excellent durability can be provided. it can.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a timing chart for explaining the operation mode of the essential parts of the second embodiment in which the present invention is applied to an electrophotographic color image forming apparatus, and FIG. 4 is a latent image in this embodiment. FIG. 6 is a timing chart showing the relationship between the potential and the developing bias. The overall structure of the color image forming apparatus of this embodiment is also the same as that of the electrophotographic color image forming apparatus shown in FIGS. 15 and 16, and therefore not shown in the drawings. Hereinafter, referring to these drawings. explain.

As shown in FIG. 4, in this embodiment,
The latent image potential is Vd = -700 as in the first embodiment.
V and Vl = -100V. On the other hand, regarding the developing bias, as shown in the figure, the peak voltage Vma on the developing promoting side is obtained.
x = -1500V, voltage Vmin = 0V on the stripping side, and an AC bias with an application time ratio (hereinafter, abbreviated as duty ratio) of 1: 4 on the accelerating side and the stripping side is 1: 4.
The frequency f was 1200 Hz.

When such a developing bias is used, the image becomes sharp and the printing quality is greatly improved. However,
In the case of such a bias, the integrated average value of the AC bias is −300V. That is, Vpp = 1500
-300V for AC bias with V and duty ratio of 1: 4
The bias is a superposition of the DC bias of.

In the first embodiment described above, the developing device was brought into contact with and separated from the developing device while being converged to the superimposed DC bias (-550V), and a sufficient effect was obtained. However, in the present embodiment, the superimposed DC bias is obtained. Since the bias becomes -300V as described above, the defoaming effect cannot be said to be sufficient,
Since the reverse contrast (Vd-Vdc) is too large, reverse fog occurs.

Therefore, when the bias having the above-mentioned duty ratio is used, the DC applied when the developing device is contacted and separated.
The bias is desired to be an appropriate value of −550V. Therefore, in the present embodiment, the AC bias is turned on / off while the DC bias is applied as in the first embodiment.
Instead of controlling the bias by turning off, as shown in FIG. 4, a bias having an appropriate duty ratio is applied at the time of development, and a DC bias, which is an integrated average value, is applied at the time of contact and separation of the developing device, which is suitable for fogging removal. The DC bias is applied.

According to this structure, even when an AC bias having a duty ratio such that the integrated average value does not become an appropriate DC bias for fogging removal is used, the AC bias is not applied during the moving operation of the developing device, so that development is performed. There is no leakage at the time of contact with the developing device, and there is no contact failure such as carbonization of the contact even if it is operated for a long period of time. Furthermore, during the moving operation of the developing device, an appropriate DC bias is applied for fogging removal. Therefore, fog does not occur and toner does not scatter,
Therefore, it is possible to provide an image forming apparatus having excellent durability.

Next, a third embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a timing chart showing the relationship between the latent image potential and the developing bias in the third embodiment in which the present invention is applied to the electrophotographic color image forming apparatus. Note that the overall configuration of the color image forming apparatus according to the present embodiment is also shown in FIG.
Since it is the same as the electrophotographic color image forming apparatus shown in FIG. 16 and is not shown, it will be described below with reference to these drawings.

The color image forming apparatus uses a plurality of color toners, specifically, yellow toners, magenta toners, cyan toners, and black toners, but the characteristics (mainly developability) of the respective toners are not always the same. It doesn't. Therefore, when such toners of a plurality of colors are used, it is desirable to apply a developing bias suitable for each of them and perform optimal development.

There are various means for achieving this proper bias. For example, Vpp of AC bias, frequency,
Peak voltage Vmax on the development promoting side, voltage V on the stripping side
This is a method of changing min etc. In this embodiment, the voltage Vmin on the stripping side is changed according to the toner.

In the case of the toner used in the image forming apparatus of this embodiment, the optimum Vmin of the yellow toner is +
The optimum Vmin of magenta toner and cyan toner is 0V, and the optimum Vm of black toner is 50V.
in was −50V. Therefore, the proper AC bias is applied at the time of developing with each toner, but as the DC bias for removing the fog at the time of contact and separation of the developing device, even if the characteristics of the toner are slightly different, as long as the toner of the same polarity is used. , The appropriate value is almost unchanged.

From this fact, the image quality is a very important factor. Therefore, in this embodiment, as shown in FIG. 5, an appropriate AC bias is applied according to the toner at the time of development, but the contact of the developing device is applied. When separated, the same (-550V
(No.) Only a DC bias for removing fog is applied. The latent image potentials are Vd = -700V and Vl = -100V, as in the second embodiment.

According to this structure, while the high image quality is achieved, it is possible to reduce the cost during the moving operation of the developing device at the minimum cost.
Since no C-bias is applied, there is no leak when the developing device contacts, there is no contact failure such as carbonization of the contact even if it is operated for a long period of time, and further, fogging is removed during the moving operation of the developing device. Since an appropriate DC bias is applied, fog does not occur, and toner does not scatter, so that an image forming apparatus having excellent durability can be provided.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
~ It demonstrates with reference to FIG.

FIG. 6 is a schematic sectional view showing the internal structure of the developing device 400 used in the fourth embodiment of the electrophotographic color image forming apparatus to which the present invention is applied. In addition,
Members, parts, elements and the like corresponding to those of the developing device shown in FIG. 17 are designated by the same reference numerals and the description thereof will be omitted unless necessary.

In the developing device 400 of this embodiment, the developing chamber 403 and the developer hopper 401 are partitioned by a partition plate 408 which is a partition wall, and the toner is supplied to the developing chamber 403 provided in the partition plate 408. The opening 409 for the toner is sealed by the toner seal 410, and the toner in the developer hopper 401 leaks to the developing chamber 403 during the transportation of the developing device 400, and this leaks to the outside from the gap of the developing chamber 403. Are prevented.

Partition plate 408 of the toner seal 410
FIG. 7 shows an enlarged state of attachment to the. The toner seal 410 is a two-leaf sheet portion 410 that is folded in two such that one sheet portion 410a that seals the opening 409 of the partition plate 408 is longer than the other sheet portion 410b.
One of the sheet portions 410a is made up of a and 410b, and is adhered to a portion around the opening portion 409 of the partition plate 408, which is shown by hatching in FIG. The free end of the other sheet portion 410b is a slit 411 formed in the side wall of the developing device 400.
The toner seal 410 and the partition plate 408 are detached from each other by pulling the end portion outward, and the toner seal 410 can be removed.

When the toner seal 410 is removed,
The toner in the developer hopper 401 is transferred to the toner feeding member 40.
2 to the inside of the developing chamber 403 through the opening 409.

Further, in this embodiment, the coating roller 404 is used.
Is movable, and its moving mechanism is shown in FIG.
FIG. 9 shows the coating roller 4 in the developing chamber 403 of the developing device 400.
FIG. 4 is a schematic plan view showing the arrangement relationship of 04, the toner seal 410 and the like together with the developing sleeve 405. The coating roller 40 protruding outward from both side walls (side walls of the developing chamber 403, the developer hopper 401, etc.) 413 of the developing device 400.
4, a spring member 415 is attached between each of the side walls 413 and the protrusions 414 provided on the side of the developing sleeve.
It is biased to the 05 side.

Further, the toner seal 410 is provided with two sheet-shaped supporting members 412 at positions facing both ends of the cored bar 404a, respectively.
12 supports the cored bar 404a at both ends thereof,
The coating roller 404 is held in a state of being separated from the developing sleeve 405. These support members 412 are shown in FIG.
As shown in 0, a part of the ring-shaped portion that supports the core metal 404a is cut off, and it can be removed from the core metal 404a by pulling it by applying a force. That is, when the toner seal 410 is pulled out, the supporting members 412 are removed from the core metal 404a and are pulled out together with the toner seal 410. Various elastomers such as PET, polyethylene, and polyimide having a thickness of about 100 μm are suitable for the toner seal 410 and the supporting member 412.

Here, both side walls 413 of the developing device 400.
Is provided with a guide hole (not shown) through which the core metal 404a of the coating roller 404 can move.
When the support member 412 is removed, the support member 412 can be moved along the guide holes from the position separated from the developing sleeve 405 shown in the drawing to the coating position. The slit 41 for the guide hole and the toner seal 410
Reference numeral 1 is sealed to the toner in the developing chamber 403 by an elastic material such as urethane.

In this way, the application roller 404 separated from the developing sleeve 405 is replaced with the toner seal 410.
When the support member 412 is disengaged from the core metal 404a, the spring member 415 moves it to the coating position where it abuts the developing sleeve 405.
By removing the toner seal 410, the application roller 404 can apply the toner sent from the developer hopper 401 to the developing chamber 403 to the developing sleeve 405.

Generally, the application roller and the developing sleeve are in contact with each other at the same position for the longest time before the developing device is attached to the image forming apparatus such as when the developing device is stored in a warehouse or the like. it is conceivable that.

Therefore, as described above, if the application roller and the developing sleeve are separated from each other in the state where the toner seal is provided, the application roller is permanently deformed before being mounted in the image forming apparatus. Can be prevented.

Although the present invention is applied to the developing device using the non-magnetic toner in the above embodiment, the present invention is not limited to this, and the magnetic toner or the non-magnetic toner and the magnetic particles are mixed. The present invention can be applied to a developing device using the above-mentioned one.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
1 and FIG. 12 will be described. The members, parts, elements and the like corresponding to those of the developing device shown in FIG. 17 are designated by the same reference numerals and the description thereof will be omitted unless necessary.

FIG. 11 is a schematic sectional view showing one end side of the coating roller 404 of the developing device 400 used in the fifth embodiment of the electrophotographic color image forming apparatus to which the present invention is applied, and FIG. 4 is a schematic plan view showing the arrangement relationship of a coating roller 404, a developing sleeve 405 and the like in a developing chamber 403 of the container 400. FIG. Also in this embodiment, the coating roller 404 is movable. Both side walls of the developing device 400 (side walls of the developing chamber 403, the developer hopper 401, etc.) 41
The core metal 404a of the coating roller 404 protruding outward from each of 3 is supported by a supporting member 416, and these supporting members 416 are swingably provided with a shaft shown by A in FIG. 11 as a fulcrum. .

Further, spring members 415 are mounted between the supporting members 416 and the projections 417 provided on the side walls 413 on the developer hopper 401 side.
4 is always urged toward the developer hopper 401 side.

On the other hand, a drive gear 418 is attached to one end of the core metal 404a of the coating roller 404, and this drive gear 418 drives the coating roller 404 on the main body side.
9 and 9 and is stopped at a position separated from the developing sleeve 405. FIG. 11a shows this state. In this state, the gear 419 on the main body side rotates in the direction of the arrow in the figure, and the drive gear 418 of the coating roller 404 is driven by this to rotate in the direction of the arrow in the figure.
Since the support member 416 of No. 4 is swingably provided,
As shown in FIG. 11B, the coating roller 404 moves toward the developing sleeve 405 and contacts the developing sleeve 405.
At this time, the driving force applied to the coating roller 404 must be stronger than the tension of the spring member 415.

From the gear 419 on the main body side to the coating roller 418
When the drive to the end is completed, the application roller 404 is separated from the developing sleeve 405 again by the tension of the spring member 415, and stops at the separated position shown in FIG. 11a. At this time, the distance for separating the coating roller 404 from the developing sleeve 405 is preferably about 1 mm to 3 mm.

As described above, in this embodiment, since the coating roller 404 is separated from the developing sleeve 405 when the developing device is not in operation, the coating roller 404 is used.
It is considered that the contact time of the developing roller 405 with the developing sleeve 405 is the longest, for example, when the developing device is stored in a warehouse or the like, that is, before the application roller 404 is attached to the image forming apparatus. Not only can permanent deformation be prevented, but even after being mounted on the image forming apparatus, when not in use, the coating roller 404 and the developing sleeve 40 are not used.
Since 5 are separated, there is an advantage that the deformation of the coating roller 404 can be prevented more effectively.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
3 and FIG. 14 will be described. The members, parts, elements and the like corresponding to those of the developing device shown in FIG. 17 are designated by the same reference numerals and the description thereof will be omitted unless necessary.

In this embodiment, the present invention is applied to a rotary developing device of an electrophotographic color image forming apparatus having a structure as shown in FIG. Therefore, the entire structure of the color image forming apparatus of this embodiment is the same as that of the electrophotographic color image forming apparatus shown in FIG. 15 except for the rotary developing device, and therefore the description thereof is omitted here.

In this embodiment, when the coating roller of the developing device which is in operation is interlocked with the rotational movement of the rotary developing device and is automatically placed at the developing position facing the photosensitive drum. The application roller is automatically brought into contact with the developing sleeve. That is, only the application roller of the developing device that performs the developing operation is automatically brought into contact with the developing sleeve.

The moving mechanism of each of the developing devices 4a to 4d of the rotary developing device 4 will be described below with reference to FIGS. Since the developing devices 4a to 4d have the same configuration, FIG. 13 shows one developing device 4a as a representative example.

Also in this embodiment, the coating roller 404 is movable. Both side walls of the developing device 4a (developing chamber 4
03, the side wall of the developer hopper 401 and the like), and the cored bar 404a of the coating roller 404 protruding outward from the side walls of the developing chamber 403 and the developer hopper 401, respectively. Spring members 415 are attached to the protrusions 417, respectively, and the springs 415 always bias the application roller 404 obliquely downward. Therefore, the coating roller 404 is always separated from the developing sleeve 405.

Further, guide holes 420 through which the core metal 404a of the coating roller 404 can be moved are provided on both side walls of the developing device 4a, and the coating roller 404 extends along these guide holes 420 as shown by arrows in the figure. From the separated position pulled by the spring member 415,
It can be moved to a coating position where it abuts the developing sleeve 405 against the tension of 15. The guide holes 420 are made of an elastic material such as urethane and are used in the developing chamber 40.
The toner inside 3 is sealed.

As shown in FIG. 14, the developing devices 4a to 4d are rotated in the directions of the arrows shown in the drawing, and are sequentially arranged at the developing position to perform the developing operation. Each developing device is at the position of B in FIG.
That is, when the developing device is approached to the developing position B, it is engaged with the cored bar 404a at both ends of the applying roller 404, and at the developing position B, the developing roller is stopped when the developing position is reached. Core metal 404a of coating roller 404
A pair of substantially elliptical application roller pushing-up members (cam members) 421 shown in the drawing are arranged in a fixed state so as to move to the developing sleeve 405 side.

With this structure, each of the developing devices 4a to 4a
When the developing position B approaches the developing position B, cores 404a on both ends of the applying roller 404 engage with the applying roller pushing-up member 421 respectively, and as the developing position approaches the developing position B, the applying roller 404 moves on the cam surface of the applying roller pushing-up member 421. As a result, the spring member 415 is pushed obliquely upward along the guide hole 420 against the tension of the spring member 415 and abuts on the developing sleeve 405 at the developing position B with a predetermined nip width. When the development is completed and the developing device 4 starts to rotate again, the coating roller pushing-up member 421 and the core metal 404 of the coating roller 404.
Since the engagement with a is released, the application roller 404 is separated from the developing sleeve 405 again by the tension of the spring member 415, and stops at the separated position shown in FIG.

As described above, also in this embodiment, since the coating roller 404 is separated from the developing sleeve 405 when the developing device is not in the operating state, the coating roller 404.
It is considered that the contact time of the developing roller 405 with the developing sleeve 405 is the longest, for example, when the developing device is stored in a warehouse or the like, that is, before the application roller 404 is attached to the image forming apparatus. Not only can permanent deformation be prevented, but even after being mounted on the image forming apparatus, when not in use, the coating roller 404 and the developing sleeve 40 are not used.
Since 5 are separated, there is an advantage that the deformation of the coating roller 404 can be prevented more effectively.

In each of the above-described embodiments, the case where the present invention is applied to the electrophotographic color image forming apparatus has been described. However, the present invention is applicable to images of printers, copiers, etc. having various other electrophotographic methods. The invention is equally applicable to the image forming apparatus such as the image forming apparatus or the printers and copying machines having various configurations other than the electrophotographic method. Further, it goes without saying that the configurations, shapes, operation modes, etc. of members, parts, elements and the like including the developing device can be variously modified and changed as necessary.

[0091]

As described above, in the image forming apparatus according to the present invention, only the DC voltage is applied and the alternating electric field is not applied when the developing means is moving. There are no leaks when abutting, no contact failure such as carbonization of contacts even after long-term operation, no fog, and no toner scattering. There is.

Further, in the image forming apparatus according to the present invention, the developer applying means is separated from the developer carrying body when the developing means is not in operation, so that the developer applying means and the developer carrying body are in the same position. It is possible to prevent permanent deformation of the developer applying unit that occurs when the roller is in contact for a long period of time, and thus to suppress periodic image unevenness.

[Brief description of drawings]

FIG. 1 is a timing chart for explaining an operation mode of a main part of a first embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 2 is a timing chart showing the relationship between the latent image potential and the developing bias in the first embodiment of the invention.

FIG. 3 is a timing chart for explaining an operation mode of a main part of a second embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 4 is a timing chart showing the relationship between the latent image potential and the developing bias in the second embodiment of the present invention.

FIG. 5 is a timing chart showing a relationship between a latent image potential and a developing bias in a third embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

FIG. 6 is a schematic cross-sectional view showing an internal configuration of a developing device used in a fourth embodiment in which the present invention is applied to an electrophotographic color image forming apparatus.

7 is a schematic perspective view showing in an enlarged manner a mounting state of a toner seal used in the developing device of FIG. 6 on a partition plate.

FIG. 8 is a front view of a partition plate for indicating a sticking position of a toner seal.

9 is a schematic plan view showing an arrangement relationship of a coating roller, a toner seal and the like in a developing chamber of the developing device of FIG. 6 together with a developing sleeve.

FIG. 10 is a plan view showing a support member that supports a cored bar of the application roller of the developing device of FIG.

FIG. 11 is a schematic cross-sectional view showing one end side of a coating roller of a developing device used in a fifth embodiment of an electrophotographic color image forming apparatus to which the present invention is applied.

FIG. 12 is a coating roller in the developing chamber of the developing device of FIG.
FIG. 3 is a schematic plan view showing a positional relationship of developing sleeves and the like.

FIG. 13 is a schematic sectional view showing an internal configuration of a developing device used in a sixth embodiment of an electrophotographic color image forming apparatus to which the present invention is applied.

14 is a schematic cross-sectional view showing the internal structure of a rotary developing device incorporating the developing device of FIG.

FIG. 15 is a schematic cross-sectional view showing an overall configuration of an example of an electrophotographic color image forming apparatus to which the present invention can be applied.

16 is a schematic sectional view showing a rotary developing device used in the color image forming apparatus of FIG.

FIG. 17 is a schematic sectional view showing an internal configuration of a conventional developing device.

FIG. 18 is a diagram illustrating an example of a state where periodic image unevenness occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 4 Developing device 4a-4d Developing device 5a-5d Development opening surface 6a-6d Coating roller 7a-7d Toner regulating member 8a-8d Developing roller 9 Support 10 Transfer drum 400 Developer 401 Developer developer hopper 402 Toner Feeding member 403 Developing chamber 404 Coating roller 404a Coating roller core metal 405 Development sleeve 406 Elastic blade 407 Leak prevention sheet 408 Partition plate 410 Toner seal 411 Slit 412 Support member 413 Developer side wall 414, 417 Projection 415 Spring member 416 Support Member 418 Drive gear 419 Main body side gear 420 Guide hole 421 Application roller pushing member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuya Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Tetsuya Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. An image carrier, comprising: a plurality of developing means for developing a latent image formed on the image carrier to visualize the latent image; In the image forming apparatus, which applies at least an alternating electric field to the developing means when developing the latent image, only a DC voltage is applied during the contacting / separating operation of the developing means with respect to the image carrier. Image forming apparatus. 2. An image carrier, and a plurality of developing means capable of developing and visualizing a latent image formed on the image carrier to make the latent image visible and contactable with the image carrier. At the time of developing the latent image, in an image forming apparatus that applies at least an alternating electric field to the developing means, a contact operation is performed with respect to the image carrier while applying only a DC voltage to the developing means. An image forming apparatus characterized in that an alternating electric field is applied to the developing means in contact after the contact operation. 3. An image carrier, and a plurality of developing means capable of developing a latent image formed on the image carrier to visualize the latent image and contacting and separating the image carrier. , At the time of developing the latent image, in an image forming apparatus that applies at least an alternating electric field to the developing means, applying an alternating electric field to the developing means while the developing means is in contact with the image carrier. The image forming apparatus is characterized in that only the direct current voltage is applied to the developing means in the contact state and then the developing means is separated from the image carrier. 4. An image carrier, and a developing means for developing the latent image formed on the image carrier to visualize the latent image. The developing means stores a developer. A chamber, and is provided adjacent to the developer storage chamber, at least a developer carrier,
An image forming apparatus having a developing chamber provided with a developer applying unit for applying a developer to the developer carrier, and being configured to be detachably arranged in the main body of the image forming apparatus, An image forming apparatus capable of switching contact and separation of the developer applying unit with respect to the developer carrier. 5. A developer seal provided between the developer storage chamber and the developing chamber is removed, so that the developer applying unit is brought into contact with the developer carrying member from a separated position to a contact position. The image forming apparatus according to claim 4, wherein the image forming apparatus is moved to the position. 6. The developer applying means is provided so as to be swingable, and when a driving force is transmitted from the image forming apparatus main body to the developer applying means, the developer applying means comes into contact with the developer carrying member to drive the developer. The image forming apparatus according to claim 4, wherein when the toner is not transmitted, the toner is separated from the developer carrying member. 7. A plurality of the developing means containing different color developers are supported by a movable developing means support, and when each developing means is placed at a developing position, the developer is 5. The image forming apparatus according to claim 4, wherein when the coating unit comes into contact with the developer carrier and the developing unit moves away from the developing position, the developer coating unit separates from the developer carrier.