JP2745320B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention includes a developing roller that forms an electrostatic latent image on the surface of a latent image carrier and rotates while carrying a developer in a color copy mode. The electrostatic latent image is visualized with a color toner by a color developing device, and in a black-and-white copy mode, the electrostatic latent image is blackened by a black developing device having a developing roller that rotates while carrying a developer. After the visible image is transferred to the transfer material, the toner remaining on the surface of the latent image carrier is cleaned by a cleaning device, and when the copy mode is switched, the developing device that has been used up to that time is used. The present invention relates to an image forming method for executing a developer removing operation of rotating the developing roller to remove the developer when the developer exists between the developing roller and the latent image carrier.

[Conventional technology]

The above-described image forming method capable of selectively obtaining a color visible image and a black-and-white visible image is widely used in an electronic copying machine, a printer, a facsimile, and the like. As the developer, a two-component developer composed of a carrier and a toner or a one-component developer composed of only a toner is used.

The purpose of executing the developer removing operation is to change the copy mode while maintaining the developer between the developing roller of the developing device and the latent image carrier, which has been used before, while the copy mode is switched. This is because, when the image forming operation in the mode is performed, the remaining toner of the developer adheres to the surface of the latent image carrier, causing a problem such as disturbing the visible image.

Conventionally, when the above-described developer removing operation is performed, the developing roller is rotated, but the latent image carrier is stopped. This is because this operation does not form a visible image on the latent image carrier, and it has been considered that there is no point in rotating the latent image carrier.

[Problems to be solved by the invention]

By the way, since the developing roller rotates during the developer removing operation, it is inevitable that the developer carried on the developing roller, more precisely, the toner, adheres to the surface of the latent image carrier. At this time, if the latent image carrier is stopped as described above, the developer on the developing roller passes through the same portion of the carrier, so that a large amount of toner adheres to this portion.

When the image forming operation of the newly selected copy mode is performed after the developer removing operation, the surface of the latent image carrier is cleaned by the cleaning device, so that the toner adhered to the latent image carrier is also cleaned as described above. However, since the amount of toner adhered to the toner is large as described above, it is difficult to remove all of the toner by a single cleaning operation.

For this reason, the image forming operation of the newly selected copy mode is performed while the toner remains on the surface of the latent image carrier, but in this case, the visible image formed by this image forming operation is formed. Is inevitable that the image quality of the image is significantly reduced.

The present invention has been made based on the above-described novel recognition, and an object of the present invention is to provide an image forming method in which the above-described conventional disadvantages are eliminated by a simple configuration.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an image forming method of the type described at the beginning, in which a latent image carrier is also rotated when a developer removing operation is performed, and toner adhered to the carrier is cleaned by a cleaning device. Suggest a configuration.

It is particularly advantageous to start the rotation of the latent image carrier before starting the rotation of the developing roller when performing the developer removing operation.

[Action]

At the time of the developer removing operation, the toner adheres to the surface of the latent image carrier. At this time, since the latent image carrier is rotating, the toner is dispersed and adheres to the surface of the latent image carrier, and the toner adheres to the surface of the latent image carrier. A large amount of toner does not adhere to only a part.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings, and the above-mentioned conventional disadvantages will be more specifically clarified with reference to the drawings.

FIG. 1 shows an example of a color copier for carrying out the method according to the present invention. First, the overall configuration will be described.
Illumination scanning is performed on the original (not shown) placed on the contact glass 10 by moving the illumination device 11 to the right in the figure together with the first mirror 12. The scanning light image at this time enters the lens 15 via the second mirror 13 and the third mirror 14 moving in the same direction, and is thereafter reflected by the fourth mirror 16 to form a plurality of color separation filters 17.
R, 17G, 17B and a filter device 17 having an ND filter 17N, and a drum-shaped photosensitive member 18 which is a configuration example of a latent image carrier.
Is projected. Each of the filter devices 17
R, 17G, 17B, 17N are arranged radially, they rotate together, and any one filter is brought into the optical path. The photoconductor 18 rotates clockwise in FIG.
Prior to the above-mentioned image projection, the surface of 18 is uniformly charged to a predetermined polarity by a charger 19. Therefore, an electrostatic latent image is formed on the surface of the photoreceptor 18 by the above-described image projection.

Around the photoreceptor 18, color developing units such as a yellow developing unit 21Y, a magenta developing unit 21M, and a cyan developing unit 21C are provided, and a black developing unit 21B is provided.

When the color copy mode is selected by pressing a copy mode switching key (not shown) of the operation unit attached to the copying machine main body, the light image passing through the lens 15 as described above is filtered by the filter device 17. Of color separation filter in
One, for example, passes through the red filter 17R, the light image of the red component is extracted, thereby, as described above,
An electrostatic latent image is formed on the photoreceptor surface. This latent image is visualized with cyan toner by a cyan developing unit 21C, which is one of the color developing units.

A transfer paper, which is an example of a transfer material sent from a paper supply unit 23, is wound around a transfer drum 22 that is opposed to the photoreceptor 18 and rotates counterclockwise.
The visible image is transferred by 20. The toner remaining on the photoreceptor 18 after the transfer of the visible image is cleaned by the cleaning device 27 and is discharged by the discharging device 33.

Next, the same document is again scanned by illumination. The light image from the document at this time passes through a green filter 17G provided in the optical path, and a light image of a green component is extracted. This light image is exactly the same as described above,
The electrostatic latent image obtained by image formation and projection on the photoreceptor 18 is visualized with magenta toner of the magenta developing unit 21M. This visible image is also transferred to the transfer paper wound around the transfer drum 22 so as to be superimposed on the previous cyan visible image. After the transfer of the visible image, the photosensitive member 18 is cleaned of residual toner by a cleaning device 27, and is discharged.

Similarly, a light image of a blue component is taken out by a blue filter 17B, and this light image is formed and projected on a photoreceptor 18, and an electrostatic latent image thus obtained is a yellow color image of a yellow developing unit 21Y. The visible image is superimposed on the previous visible image and transferred onto the transfer paper on the transfer drum 22, and the photoconductor 18 after the visible image transfer is cleaned by the cleaning device 27. It is cleaned and then neutralized.

After the last transfer is completed, the transfer paper is separated
The sheet is separated from the transfer drum 22 by 24 and a separation claw 25, and then is discharged outside the apparatus as a full-color copy paper through a fixing device 26.

Next, when the black and white copy mode is selected, the light image reflected by the original and passed through the lens 15 is filtered by the filter device 17.
ND filter (neutral density filter) 17N, and an electrostatic latent image is formed on the photoreceptor 18 in the same manner as in the color copy mode. The ND filter is a filter that basically transmits all light of the blue component, the red component, and the green component. The latent image thus formed is visualized by black toner of the black developing device 21B. This visible image is also transferred to the transfer paper on the transfer drum 22,
After the transfer, the transfer paper is detached from the transfer drum 22 and, when passing through the fixing device 26, the transferred visible image is fixed on the transfer paper. In this way, the transfer paper is discharged outside the machine as a black-and-white visible image copy paper. Also in this case, the surface of the photoreceptor after the transfer of the visible image is cleaned by the cleaning device 27, and then the charge is removed.

In the copying machine shown in FIG. 1, a cleaning agent 32 composed of a toner and a carrier is carried on a cleaning sleeve 32 which is driven to rotate by the magnetic force of a magnet 31 inside the cleaning sleeve 32, and is conveyed. Although the magnetic brush cleaning device 27 that cleans the upper remaining toner is employed, a cleaning device using a cleaning blade or a fur brush may be employed.

In the black-and-white copy mode, a light image from a document may be formed and projected on the photosensitive member 18 without passing through a filter at all, that is, without passing through the ND filter 17N.

Further, in consideration of the fact that the black-and-white copy mode is used more frequently than the color copy mode, the illustrated copying machine is configured to automatically select the black-and-white copy mode when the copy mode selection key is not pressed. Have been.

Next, the details of the color developing devices 21Y, 21M, 21C will be described with reference to FIG. These developing devices are provided with casings 3Y, 3M, 3C containing the developer, developing rollers 4Y, 4M, 4C made of a non-magnetic material arranged in close proximity to the photoreceptor 18, and opposed to these rollers. It has developer agitating and pumping members 7Y, 7M, 7C. In this example, a two-component developer composed of a magnetic carrier and a toner is used as the developer. As can be understood from the above description, the yellow toner is used in the yellow developing device 21Y, and the magenta toner is used in the magenta developing device 21M. Toner and cyan toner are used in the cyan developing unit 21C. It is well known that additives are added to toner as needed.

Inside each of the developing rollers 4Y, 4M, 4C, a magnet group 5 is provided in an arrangement as shown, and these are held in a non-rotating state. On the other hand, each developing roller 4Y, 4Y
M and 4C are driven to rotate in the direction of the solid arrow during the developing operation. Hereinafter, the case of rotating in this direction is referred to as “forward rotation”.

Here, as shown in FIG. 3, assuming that the cyan developing device 21C is picked up, the magnet group 5 provided inside the developing roller 4C includes magnets 5a, 5b, 5c and 5d, and the magnetic poles on the side facing the developing roller 4C are arranged as indicated by S and N in the figure. No magnet is provided between the magnets 5b and 5c, and the magnetic short-circuit plate 6 made of a soft magnetic member is bridged between these magnetic poles to form a magnetic field intensity reduction region 113. The configuration shown in FIG. 3 is exactly the same in the other color developing units 21M and 21Y.

When the color copy mode is selected as described above, first, the cyan developing device 21C performs a developing operation. At this time, the developing roller 4C rotates forward in the direction of the solid line arrow, and the developer stirring and pumping member described above. 7C rotates counterclockwise, and pumps the developer present at the bottom of casing 3C to developing roller 4C. The developer supplied to the developing roller 4C in this manner is carried on the developing roller 4C by the magnetic force of the magnet group 5, and is conveyed in the rotation direction by the rotation of the developing roller 4C. Is scraped off, and the amount of developer is regulated. In this way, the developer carried on the developing roller 4C that rotates forward is carried to the area where the developing roller 4C and the photoreceptor 18 face each other, where it is developed into an electrostatic latent image formed on the photoreceptor. The toner in the agent migrates electrostatically,
This electrostatic latent image is visualized as described above. The developer used for the development is further transported to the area where the magnetic field intensity is reduced.
At 113, since the magnetic field in this area is weak, the developer on the developing roller 4C falls down by its own weight and is stirred by the developer stirring and pumping member 7C.

Next, similarly, the magenta developing unit 21M visualizes the electrostatic latent image with magenta toner, and subsequently, the yellow developing unit 21Y visualizes the electrostatic latent image with yellow toner.

Here, when the developing is performed by one of the developing units 21M, 21C, or 21Y and the developing agent is present between the developing roller of another developing unit and the photoconductor 18, the developing that is being performed is performed. The toner of the developing device that has not been developed adheres to the electrostatic latent image to be developed by the developing device or the visible image that has already been developed, and deteriorates the image quality of the visible image.

Therefore, when one developing unit has completed the developing operation, a developer removing operation for removing the developer existing between the developing roller of the developing unit and the photoconductor 18 is executed. In the present embodiment, the developer is conveyed while forming ears by the magnetic force of the magnet group during the developing operation. On the other hand, if the developer is removed, the developer is cut off. Will be referred to as an ear breaking operation.

Here, as an example, the cutting operation of the cyan developing device 21C will be described. When the developing operation by the developing device 21C is completed, the developing roller 4C is rotationally driven in the direction of the dashed arrow opposite to the rotating direction. Is done. At the time of this rotation, the magnetic field intensity reduction region 113 is located with respect to the region where the developer is to be pumped, so that the developer was not pumped up by the developing roller 4C, and was carried on the developing roller 4C until then. The developer is conveyed in the same direction as the rotation direction by the reverse rotation of the developing roller 4C, and drops downward from the developing roller 4C by its own weight. Thus, the cutting of the developing roller 4C is performed, and then the developing roller 4C stops.

Subsequently, the magenta developing device 21M performs the developing operation. After the operation is completed, the cutting operation is performed in the same manner as described above, and the developing roller 4M stops. Next, also in the yellow developing device 21Y for performing the developing operation, after the operation is completed, the cutting operation is performed, and then the developing roller 4Y stops.

The color developing devices 4C, 4M, and 4Y in this example execute the ear breaking operation while the photoconductor 18 is rotating.

Next, the black developing device 21B will be described with reference to FIG. 4. This developing device 21B also contains a two-component developer composed of a black toner and a magnetic carrier to which additives are added as necessary. A casing 3B, a developing roller 4B made of a non-magnetic material opposed to the photoreceptor 18, and a developer stirring and pumping member 7B.
And Inside the developing roller 4B, symbols P1 to
A magnet group 5B composed of magnets with P5 is fixedly arranged.

When the black and white copy mode is selected and the developing operation is performed, the developing roller 4B and the developer stirring and pumping member 7B are driven to rotate counterclockwise in FIG. 4, respectively, and the developer is supplied onto the developing roller 4B. You. The supplied developer is carried on the developing roller 4B by the action of the magnetic force of the magnet group 5B,
Due to the rotation of the roller 4B, the developer is conveyed in the same direction as the rotation direction, and the amount of the developer is regulated by the doctor unit 12B.
The toner is carried between the developing roller 4 and the developing roller 4B, where the black toner in the developer is transferred to an electrostatic latent image, and the latent image is visualized. At this time, the soft magnetic member 3 is covered so as to cover the portion between the magnets P2 and P3.
The strength of the magnetic field on the surface portion of the developing roller opposed to the position including the position indicated by the solid line 7 is weakened. Therefore, when the developer used for development reaches this area, the developer separates from the developing roller 4B by its own weight and falls downward.

When the developing operation is completed, the developing roller 4B stops rotating, but when the black-and-white copy mode is still selected after that, even after the developing operation is completed, the cutting operation as performed by the color developing device, that is, The operation of removing the developer existing between the developing roller 4B and the photoconductor 18 is not executed. That is, as long as the mode cannot be switched to the color copy mode, the developer is always carried on the developing roller 4B. This is because, in the black-and-white copy mode, a visible image is formed only by one black developing unit 21B, so that the color developing units 21M, 21Y, 21C
This is because there is no risk that the visible image will be disturbed even if the black developing device does not cut the ears.

However, when the operator switches the copy mode from the monochrome copy mode to the color copy mode by pressing the copy mode switching key after the black developing device 21B performs the developing operation as described above, the black developing device 21B In this case, if the ear breaking operation is not performed, the visible image is disturbed at the time of the next image formation in the color copy mode, and the image quality is deteriorated.

Therefore, when the mode is switched from the black-and-white copy mode to the color copy mode after the black-and-white visible image forming operation is completed, the above-described soft magnetic member 37 is moved to the position shown in FIG. 4 before executing the color copy mode image forming operation. From the position shown by the solid line, it is rotated and displaced in the counterclockwise direction in the figure, and is placed at the position of the virtual line that shields the magnetic field of the developer pumping magnets P3 and P4. As a result, the developer does not adhere to the developing roller 4B. In this state, if the developing roller 4B is rotated clockwise an appropriate number of times, the developer remaining on the developing roller 4B is separated from the developing roller 4B. Then, it is collected in the lower region of the casing 3B. In this way, the developing roller 4B and the photosensitive member 18
In the region between and there is no ear in which the developer does not exist,
After the cutting operation, the developing roller 4B is stopped.
When the image forming operation in the color copy mode is started after this, the toner of the black developing device 21B is charged during the operation.
Thus, it is possible to prevent color mixing and disturbance of the visible image without adhering to the image.

As described above, when the developer is present between the developing roller 4B of the developing device 21B and the photoconductor 18 at the time of switching the copy mode, the developing roller 4B is rotated to A developer removing operation for removing the developer, that is, an ear breaking operation is executed. At that time, in the conventional copying machine, the photoreceptor 18 is stopped during the ear breaking operation as described above. This is because the ear breaking operation is not an operation for forming a visible image on the photoconductor, and it has been considered that rotating the photoconductor 18 has no meaning at all. However, in this case, the developing roller 4B carrying the developer rotates during the cutting operation, so that the same portion of the stopped photosensitive member 18 is rubbed by the developer. For this reason, the toner in the developer migrates to the photosensitive member,
Here, a large amount of toner adheres. When the image forming operation in the color copy mode is started in this state, the large amount of the adhered toner is subjected to a cleaning action by the cleaning device 27. However, since the amount is large, the adhered toner is removed in one cleaning operation. All of them could not be removed, and there was a risk that this toner would be mixed into the color visible image.

Therefore, in the present invention, as described above, the black developing device 21 is used.
When the cutting operation is performed at B, not only the developing roller 4B but also the photoreceptor 18 is rotated clockwise in FIG. 1, and the surface thereof is cleaned by the cleaning device 27. In this way, even if the toner in the developer adheres to the photoconductor 18 with the rotation of the developing roller 4B, the toner does not adhere only to the same portion of the photoconductor 18.
That is, when the toner sequentially adheres to the photoconductor 18, the photoconductor 18
Since 18 is rotating, the toner adheres to the surface in a dispersed state. Therefore, the toner adhered to the photoreceptor 18 can be easily cleaned by the cleaning device 27. The amount of rotation of the photoreceptor 18 at that time can be set as appropriate. However, if the adhering toner is cleaned while rotating the photoreceptor 18 several times, the adhering toner on the photoreceptor 18 can be particularly reliably cleaned. Further, when the photoconductor 18 is rotated, it is advantageous that the surface of the photoconductor 18 is neutralized by the static eliminator 33 to initialize the surface of the photoconductor 18.

By cleaning the photoreceptor 18 as described above so that the black toner is not adhered thereto, and pressing the print key to execute the image forming operation in the color copy mode, a high-quality full-color image can be obtained. it can.

At the time of the above-described ear breaking operation, the photoconductor 18 may be started to rotate at the same time as the rotation of the developing roller 4B.
If the photoreceptor 18 is rotated before the rotation of the photoconductor 18 is started, the toner attached to the photoconductor 18 can be more effectively dispersed.

FIG. 5 (a) shows the amount of toner adhering to the photosensitive member 18 when the developing roller 4B is rotated during the cutting operation, when the photosensitive member 18 is stopped, that is, when the conventional method is adopted. It is explanatory drawing which shows typically. Similarly, FIG. 5B shows the state of toner adhesion when the developing roller 4B and the photoconductor 18 are simultaneously rotated, and FIG. 5C shows that the photoconductor 18 is rotated before the developing roller 4B. , Respectively, shows the state of toner adhesion when the toner is turned on. When the rotation start timings of the developing roller 4B and the photosensitive member 18 are simultaneously set as shown in FIG. 5B, the amount of the adhered toner is smaller than when the photosensitive member 18 is stopped as shown in FIG. 5A. Although it can be dispersed, T1 still remains on a part of the photoconductor at the start of rotation of the photoconductor.
A relatively large amount of toner adheres as indicated by. However, as shown in FIG. 5 (c), if the photoconductor 18 starts rotating before the developing roller 4B, the adhered toner can be positively dispersed from the start of the rotation of the developing roller 4B. Are largely dispersed and adhered to the wide surface of the photoreceptor 18.

In the copying machine shown in FIG. 1, the cutting operation in each of the color developing units 21Y, 21M, and 21C is performed while the photoconductor 18 is rotating, and the developing unit 21Y that is operated last is operated.
When the copy mode is switched from the color copy mode to the black-and-white copy mode because the cutting operation is performed in the developing device 21Y regardless of whether the copy mode is switched to the black-and-white copy mode when the development mode is completed. ,
The developer does not already exist on each of the developing rollers 4C, 4M, and 4Y.
Therefore, it is not necessary to perform the cutting operation according to the present invention as performed in the developing device 21B, but it may be necessary to perform the cutting operation depending on the configuration of the color developing device.

For example, as shown in FIG.
R (or each of the color developing units 21Y, 21M, 21C shown in FIG. 2) and the black developing unit 21B
In a copier that obtains a monochrome color visible image or a black-and-white visible image, when the single color copy mode using the color developing unit 21R is selected, the developer is always carried on the developing roller 4R of the developing unit 21R. It can be configured as follows. Even when the developing device 21R is not performing the developing operation, the developer is carried on the developing roller 4R. At this time, when the mode is switched from the single color copy mode to a copy mode for obtaining a visible image of another color, for example, a monochrome copy mode, the color developing device
In 21R, it is necessary to perform the cutting operation. this is,
In the above embodiment, when the black-and-white copy mode is selected, the developer may be always carried on the developing roller 4B of the black developing device 21B. This is for the same reason that the ear breaking operation must be performed in 21B. As described above, even when the cutting operation is performed in the color developing device 21R, the developer on the roller 4R is removed while rotating the developing roller 4R, and at this time, the photosensitive member 18 is also rotated, and only a part of the surface thereof is rotated. A large amount of toner can be prevented from adhering, and the toner adhering in a dispersed state on the photoreceptor can be effectively removed by the cleaning device (FIG. 1).

What has been described above is that the individual developing units of the color developing units 21Y, 21M and 21C shown in FIGS. 1 and 2 are used to copy from a single color copy mode for obtaining a monochromatic color visible image to another copy mode. When the mode is switched,
It can be applied in exactly the same way.

As described above, the present invention cannot be applied only when switching from the black-and-white copy mode to another copy mode.

The present invention can be applied to a case where a one-component developer containing no carrier is used or a case where a non-magnetic developer is used in each developing device.

〔The invention's effect〕

According to the configuration of the first aspect, it is possible to easily and effectively clean the toner adhered to the latent image carrier during the developer removing operation performed when the copy mode is switched.

According to the configuration of the second aspect, the toner adhered to the latent image carrier can be dispersed over a wider surface, and the adhered toner can be more reliably cleaned.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a color copying machine for carrying out the method according to the present invention, FIG. 2 is an enlarged view of the color developing device shown in FIG. 1, FIG. FIG. 4 is an enlarged view of the black developing device, FIGS. 5 (a), (b) and (c) are explanatory diagrams showing the amount of toner adhering to the photoconductor in comparison with the conventional example, and FIG. FIG. 11 is a configuration diagram showing still another embodiment. 4Y, 4M, 4C, 4B, 4R: developing roller 21Y, 21M, 21C, 21R: color developing device 21B: black developing device 27: cleaning device

Claims (2)

(57) [Claims] An electrostatic latent image is formed on a surface of a latent image carrier, and in a color copy mode, the electrostatic latent image is formed into a color image by a color developing device having a developing roller which rotates while carrying a developer. In the black-and-white copy mode, the electrostatic latent image is visualized with black toner by a black developing device having a developing roller that rotates while carrying a developer, and the visible image is converted to a visible image with the black toner. The toner remaining on the surface of the latent image carrier after being transferred to the transfer material is cleaned by a cleaning device, and when the copy mode is switched, the developing is performed between the developing roller of the developing device and the latent image carrier that have been used so far. In the image forming method for performing a developer removing operation of removing the developer by rotating the developing roller when the developer is present, the latent image carrier is also rotated when the developer removing operation is performed. Adheres to the body Image forming method characterized by cleaning and the toner by the cleaning device. 2. When the developer removing operation is performed, the rotation of the latent image carrier is started before the rotation of the developing roller is started.
The image forming method as described in the above.