JP3359175B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus of a color electrophotographic recording system such as a facsimile, and more particularly, to an image forming apparatus having a rotary developing device for developing a photoreceptor.

[0002]

2. Description of the Related Art A rotating body is provided opposite to a photoreceptor and a developing device using a plurality of toners of different colors is provided. The developing device is supported on a predetermined position by a plurality of developing devices. Various rotary developing devices have been proposed in which a latent image on a photoreceptor is developed with each color toner by sequentially rotating and transporting a developing device to a developing position. Some inventions of a rotary developing device having a toner container at one end in the longitudinal direction of the developing device and replenishing toner from the toner cartridge to the toner container with the rotation of the developing device have already been proposed. .

[0003]

Conventionally, for example, in an image forming apparatus described in Japanese Patent Application Laid-Open No. Sho 60-254063, rotation of a developing device is performed in accordance with a color selection mode of a color image to be developed. Alternatively, control is performed to select the moving direction and to minimize the moving distance of the developing device to a predetermined developing position. However, after the development, the developing device was stopped at the developing position where the developing device of the last developed color was opposed to the photoconductor, so that when the next image forming process was performed, the developing device of any color was changed to the developing position. I did not know if it was in. Therefore, the time required for the developing unit of the required color to move to the developing position varies, and the color of the developing unit is detected by having a memory for storing which developing unit is in the developing position. It was necessary to have a sensor, which increased costs.

In an image forming apparatus having a rotary developing device described in Japanese Patent Application Laid-Open No. S61-151564, the rotary developing device is rotated to a reference position serving as a reference for driving a rotating body before the operation is started. Was so controlled. However, if the rotary developing device is simply rotated to the reference position, the rotation angle to the reference position is 90 degrees.
In this case, the developing roller of at least one developing device passes through the developing position facing the photoconductor, and at this time, a part of the toner properly held on the developing roller is transferred to the photoconductor. As a result, there is a problem that a portion having a small amount of toner is generated in a horizontal band shape in the toner layer on the developing roller. At this time, when an image is output, a portion having a low density is generated in a horizontal band shape.

Further, if the rotary developing device is simply rotated to the reference position, if the developing device of the last color which has been developed is within 180 degrees from the reference position, the developing device is moved after the end of the image forming process. In order to rotate to the reference position, it is rotated by 180 degrees or more. Due to this, when it takes more time than necessary, and when two or more developing devices pass a developing position facing the photoconductor, the toner transferred from the developing roller of the first developing device to the photoconductor is
The toner adheres to the developing roller of the second developing device, and this causes toner of another color to be mixed into the developing roller of the second developing device. There is also a problem that the toner is discolored by the color mixture and a visible image of a predetermined color cannot be obtained.

On the other hand, Japanese Utility Model Application Laid-open No. 63-153258.
As shown in the figure, a toner storage section in which a predetermined amount of toner is retained by a rotation operation of the developing device is provided in the vicinity of a developing roller in each of the developing devices, in a vicinity of a developing roller. In the rotary developing device having the configuration provided, since a large amount of toner is stored in advance in each developing device,
There is a disadvantage that the entire developing device becomes large.

In view of the above, a toner container for storing toner to be supplied to each developing device is provided integrally, for example, at an end portion of each developing device. The toner cartridge is supplied so that the insides thereof communicate with each other. The toner is supplied from the toner cartridge to the toner container by the rotation of the developing device, and the toner is supplied from the toner container to the developing device and the toner is supplied from the developing device. Recently, there has been provided a rotary developing device configured to collect excess toner in a storage unit using a conveying member such as a screw.

In the rotary developing device having this configuration, toner can be supplied from the toner cartridge to the toner container without using any mechanical toner transport mechanism. Further, the toner used in the developing device is housed in the toner container and the toner cartridge, and is not directly housed in the developing device. It is possible to prevent the whole from becoming large.

However, in this configuration, since the toner is replenished from the toner cartridge to the toner accommodating portion by one rotation of the developing device, for example, the control is such that the rotation of the developing device repeats the normal rotation and the reverse rotation at a small angle. Is performed, the toner on the toner storage section and the developing roller runs short, and a problem occurs that satisfactory development is not performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to form a high-quality image in an image forming apparatus having a rotary developing device that performs development by being opposed to a photosensitive member. And

[0011]

According to the present invention, in order to achieve the above object, a plurality of developing devices accommodating a developer are arranged around a rotating shaft, and an arbitrary developing device is arranged around the rotating shaft. In a rotary image forming apparatus that rotates to a developing position opposed to a latent image carrier and performs development and toner replenishment, the distance for moving any developing device to a predetermined reference position after development is minimized. There is provided a selecting means for selecting whether the rotating body rotates or the rotating body rotates only in one direction. Also, the selection of this selection means
The selection may be made by performing a predetermined image forming operation.

[0012]

According to the image forming apparatus of the present invention, when the rotating body is rotated so as to minimize the distance for moving an arbitrary developing device to a predetermined reference position, the moving body is not wasted. Also, there is no unnecessary color mixing of the toner in the developing device. Further, if the rotation of the rotating body is selected in only one direction, the toner can be reliably supplied from the toner cartridge to the toner container.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a diagram illustrating an example of a full-color printer including a developing device in the image forming apparatus of the present invention. In the printer shown in FIG. 1, a belt-shaped photoreceptor 1 as a latent image carrier is uniformly charged by a charging roller 2 and then scanned and exposed based on image information by a laser optical device 3 to form an electrostatic image on the surface. A latent image is formed. Here, the image information to be exposed is monochromatic image information obtained by decomposing a desired full-color image into yellow, magenta, cyan, and black color information. The formed electrostatic latent image is developed with predetermined yellow, magenta, cyan, and black toners by a rotary developing device 4 described later, and an image of each color is formed on the photoconductor 1.

A photoreceptor belt 1 which rotates in the direction of arrow A in FIG.
The respective color images formed thereon are sequentially transferred onto the intermediate transfer belt 5 rotating in the direction of arrow B in the drawing in synchronization with the photoreceptor belt 1 for each of the single colors of yellow, magenta, cyan, and black. The yellow, magenta, cyan, and black images superimposed on the intermediate transfer belt 5 are collectively transferred by the transfer roller 6 onto the transfer paper conveyed from the paper supply cassette 8 to the transfer section via the paper supply roller 9 and the registration roller 10. Transcribed. After the transfer is completed, the transfer paper is fixed by the fixing device 7 to complete a full-color image.

FIG. 2 shows an embodiment of the developing device in the image forming apparatus of the present invention. Photoreceptor belt 1 described above
, A rotary type (also referred to as a revolver type or rotary type) developing device 4 as a developing device according to the present invention is disposed. In the rotary developing device 4, a casing 20 forming a rotating body is provided rotatably about a rotation center O, and the casing 20 is rotated in the direction of arrow C by a drive mechanism (not shown). The casing 20 has a shape that divides the developing device into four parts, thereby forming the respective color developing units 22-Y, M, C, and K.

FIG. 2 shows a state in which one developing unit 22-Y is at the developing position. Each developing unit 22-
Y, M, C, and K are provided with cylindrical developing rollers 23-Y, M, C, and K as developer transport members. Each of the developing rollers 23-Y, M, C, and K is arranged so that a part thereof is exposed to the outside from an opening 22a provided in the casing 20, and is synchronized with color information by an arrow C in the figure.
To develop the corresponding electrostatic latent image.

The developing unit of this embodiment is a developing device using a non-magnetic one-component developer. Each unit contains yellow, magenta, cyan, and black toners, and selectively includes a rotation center O. Is rotated to the developing position to sequentially develop the electrostatic latent images formed on the photoreceptor belt 1, and the developed images are superimposed on the intermediate transfer belt 5 and the transfer paper as described above, thereby forming a full-color image. To form

Hereinafter, an embodiment of a developing device in the image forming apparatus of the present invention will be described with reference to FIG. Since the color developing units 22-Y, M, C, and K take the same form and the same operation, the developing unit 22 for one color (yellow) is used here.
Only -Y will be described. In FIG. 3, the developing unit 22-Y is disposed below the photoreceptor belt 1 as a latent image carrier, and forms an electrostatic latent image formed on the photoreceptor belt 1 located above the developing unit 22-Y. A toner as a non-magnetic one-component developer is supplied.

In FIG. 3, reference numeral 22 denotes a developing unit, and an opening 22a is formed above the developing unit 22 at a developing position. In the opening 22a, a developing roller 23 as a developer carrier rotates in the same direction as the photosensitive member moving direction (arrow D in the figure) at a predetermined peripheral speed ratio with the photosensitive member so as to face the photosensitive member. It is arranged as follows. Below the developing roller 23, a supply roller 31 as a toner supply member made of an elastic material such as foamed polyurethane rubs against the developing roller 23, and rubs against the developing roller 23 at a predetermined peripheral speed ratio. At the contact portion with the developing roller 23 in the same direction (arrow E in the drawing).

On the downstream side of the supply roller 31 in the moving direction of the developing roller 23, near the opening 22a, a thickness of 0.1 m is provided.
A thin layer blade 32 made of an elastic material such as a stainless steel thin plate or urethane rubber having a length of about m is provided so that the vicinity of one end thereof is in contact with the developing roller 23. In the drawing, reference numeral 33 denotes a screw-shaped first toner conveying member to be described later, which conveys the toner from the near side to the far side in the drawing.

In front of the developing unit 22, FIG.
Is provided. The toner conveying member 33 is a screw-shaped first toner conveying member. The toner conveying member 33 is disposed in parallel with the developing roller 23 and the supply roller 31 from the toner storing section 15 to the other side plate of the developing device 4. It is rotated at a predetermined peripheral speed ratio in conjunction with the developing roller 23 and the supply roller 31 so as to convey the toner from the side to the back side. Casing 20
The developing roller 23, the supply roller 31, and the casing 20 form a toner conveying space 34 surrounding the toner conveying member 33.

Screw-shaped first toner conveying member 33
Is rotated at a predetermined peripheral speed ratio in conjunction with the developing roller 23 and the supply roller 31 so as to convey the toner from the near side to the far side of the drawing. By this rotation, the first toner conveying member 33 conveys the toner from the toner storage section 15 into the toner conveying space, and supplies the toner onto the supply roller 31. The toner supplied onto the supply roller 31 is supplied while being charged to the surface of the developing roller 23 by the supply roller 31, and is carried on the surface of the developing roller 23.
The toner carried on the surface of the developing roller 23 is
2, the electrostatic latent image formed on the surface of the photoreceptor belt 1 is formed into a uniform and thin toner layer having a predetermined thickness, and is developed by contact development.

By the way, the toner not used in the developing step is transported by the first toner transporting member 33 to the end of the developing device opposite to the toner container 15. A space for toner circulation is provided outside the effective diameter portion of the developing roller 23 and the supply roller 31 in the axial direction. The toner conveyed to the end of the developing device by the first toner conveying member 33 falls to the lower part of the developing unit 22 by gravity.

Below the developing unit 22, a second toner conveying member 35, also in the form of a screw, is provided with the developing roller 2.
3, is arranged in parallel with the supply roller 31, and the first toner conveying member 33, and is rotated so as to convey the toner in a direction opposite to the first toner conveying member 33, and is not used in the developing process. The conveyed toner is transported to the toner storage unit 15. By appropriately setting the transport amounts of the first toner transport member 33 and the second toner transport member 35, the supply roller 31 can be detected without detecting the toner amount in the developing unit 22 or performing complicated supply amount control. It is possible to provide a small developing device which can be supplied on the top, has a large degree of freedom in layout, and has a small cross-sectional occupation ratio with respect to the photosensitive belt. A toner cartridge is detachably mounted in the toner storage unit 15. The toner cartridge is mounted and replaced when the developing device 4 is newly mounted or when the toner is exhausted, and a necessary amount of toner is always stored in the toner storage unit 15.

Next, the reference position of the developing device in the image forming apparatus of the present invention will be described with reference to FIG. At times other than the image forming operation, that is, before and after the image forming operation, the developing device 4 waits and stops at the reference position of the developing device as shown in FIG. In this embodiment, the developing roller 23-Y of the yellow developing device 22-Y and the developing roller 2 of the black developing device 22-K are used.
A position at which the rollers 23-Y and 23-K do not contact the photoreceptor belt 1 at a substantially middle point of 3-K is set as a reference position. This is because the photosensitive belt 1 and the developing roller 2
Photoreceptor belt 1 and developing roller 2 due to unnecessary contact 3
This is a position for preventing deterioration and damage of No. 3 and for preventing adhesion and fixation of toner outside a predetermined area.

By the way, when there is replacement or maintenance work due to the life of the developing device, or when abnormal development ends such that the process of the image forming apparatus is stopped halfway due to clogging of the transfer paper. In some cases, the positional relationship between each color of each developing unit of the developing device and the photoconductor may be random. In this case, the developing device is rotated to the reference position of the developing device and stopped before starting the image forming operation to prepare for the image forming operation.

FIG. 5 is a flow chart for controlling the rotation direction of the rotary developing device in the image forming apparatus of the present invention.
For example, in the operation when the image information is a single black color, the developing device rotates clockwise by 40 degrees from the reference position shown in FIG. 4 to the developing position of the black developing device. After the development is completed, the developing device rotates to the reference position. At this time, since the moving distance is controlled to be the shortest, the developing device rotates counterclockwise by 40 degrees. If the direction of rotation is one clockwise as in the conventional case, the rotation will be 320 degrees, which will take a long time, and the cyan, magenta, and yellow developing units will come into contact with the photosensitive belt one after another. , There is a problem that color mixing of toner occurs. However, by controlling as described above, these problems can be solved.

Next, the replenishment of toner from the toner cartridge to the toner container in the image forming apparatus of the present invention will be described with reference to FIG. The toner cartridge 11 mounted on the toner container 15 rotates with the rotation of the developing device 4. Here, for example, the developing device 4 moves from the state shown in FIG. 5A in which the yellow developing device 22Y is in the developing position to the yellow developing device in the non-developing position through the states shown in FIGS. 6B and 6C. 6D, the toner accommodated in the toner cartridge 11Y attached to the toner accommodating portion 15Y of the yellow developing device 22Y moves in the toner cartridge by gravity, and
As shown in (d), the cylindrical portion 11a of the toner cartridge
It accumulates in Y and in the vicinity of the toner container 15Y. The developing device 4 further rotates from this state, and the yellow developing device 22Y
Is returned to the state shown in FIG.
The toner accumulated in the cylindrical portion 11aY falls to the toner storage portion 15Y.

According to this configuration, the toner cartridge 1
By providing one rotation of the rotary developing device clockwise without supplying any toner conveying member to 1Y, toner can be conveyed from the toner cartridge to the toner storage unit and replenished.

Next, another operation of the developing device will be described. When outputting a full-color image, black, cyan,
Since development is performed in the order of magenta and yellow, the rotation of the developing device is rotated clockwise from the reference position shown in FIG.
Degrees, 90 degrees, 90 degrees, 90 degrees, and 50 degrees. As a result, the developing device performs the development of the four colors and makes one rotation in the clockwise direction. As described above, the toner is supplied from the toner cartridge to the toner storage unit.

However, when outputting a monochromatic black image, the developing device is rotated clockwise by 40 degrees from the reference position to the developing position of the black developing device, and after the development, the moving distance is the shortest to the reference position. , So that it rotates 40 degrees counterclockwise. If such control is performed, there is no problem if monochrome and full color are printed alternately appropriately. However, if only a monochromatic black image is output in large quantities, the rotary developing device does not rotate once. Then, the toner is not supplied from the toner cartridge to the toner storage unit, and the toner in the toner storage unit is consumed, so that a sufficient toner layer may not be formed on the developing roller.

Therefore, the rotation direction control of the rotary developing device is performed as shown in the flowchart of FIG. In this image forming apparatus, a high-speed mode and a normal mode can be selected as a print mode on a control panel.
When the high-speed mode is selected, the rotation direction of the rotary developing device can be rotated counterclockwise, and when the normal mode is selected, the counter-clockwise rotation is prohibited. For example, when printing a black monochrome image, if the high-speed mode is selected, the rotation of the rotary developing device is first rotated clockwise by 40 degrees from the reference position to the black developing position, and then from the black developing position to the reference position after development. Rotate 40 degrees counterclockwise until

As a result, the rotation type developing device does not execute once, so that the printing operation is completed earlier in time, and there is no problem of color mixing of toner in the developing device. However, as described above, when black monochrome printing continues for a certain number or more, there is a possibility that the toner to be supplied to the developing roller is insufficient and the image becomes thin or faint. In such a case, if the normal mode is selected, the rotary developing device makes one rotation clockwise, so that the toner is supplied as described above, and the shortage of the toner on the developing roller can be solved.

As still another embodiment, the control of the rotation direction of the rotary developing device is performed as shown in the flowchart of FIG. In this image forming apparatus, the clockwise rotation angle from the developing position of the last developing unit to the reference position is 18 degrees.
When the angle is larger than 0 degrees and the number of continuous prints of a single color is less than 20, the rotation of the rotary developing device is rotated counterclockwise. Otherwise, the rotation is rotated clockwise. In this case, 20 sheets are the number of sheets that can be printed only with the toner in the toner storage section even if the toner is not newly supplied to the toner storage section.

Of course, since the amount of toner accommodated varies depending on the volume of the toner accommodating portion, the number of sheets can be appropriately set in consideration of the size of the developing device. Further, the number of continuous printings of a single color is counted and counted until one rotation of the rotary developing device is performed clockwise, and after the number of printings reaches 20 or more and the rotary developing device is rotated, a new single color printing is performed. May be counted. Also, since the clockwise rotation of the rotary developing device is very infrequent,
There is almost no occurrence of color mixing on the photoreceptor or horizontal band-like portions on the toner layer on the developing roller. As further prevention,
More preferably, a bias is applied to the developing position or the photosensitive member is rotated while the rotary developing device is rotating.

According to this control, the rotary developing device is always rotated clockwise before the toner in the toner container runs short, and toner is supplied from the toner cartridge to the toner container. In this case, there is no shortage of toner in the toner container.

[0037]

The image forming apparatus according to the present invention can form a high quality image.

[Brief description of the drawings]

FIG. 1 illustrates an example of a full-color printer including a developing device in an image forming apparatus according to the present invention.

FIG. 2 is an embodiment of a developing device in the image forming apparatus of the present invention.

FIG. 3 is an embodiment of a developing device in the image forming apparatus of the present invention.

FIG. 4 is a diagram showing a reference position of a developing device in the image forming apparatus of the present invention.

FIG. 5 is a flowchart of the rotation direction control of the rotary developing device in the image forming apparatus of the present invention.

FIG. 6 is a diagram illustrating toner replenishment from a toner cartridge to a toner storage unit in the image forming apparatus of the present invention.

FIG. 7 is a flowchart of a rotation direction control of the rotary developing device in the image forming apparatus of the present invention.

FIG. 8 is a flowchart of a rotation direction control of the rotary developing device in the image forming apparatus of the present invention.

[Explanation of symbols]

1: photoreceptor belt, 2: charging roller, 3:
Laser optical device, 4: rotary developing device, 5: intermediate transfer belt, 6: transfer roller, 7: fixing device,
8: paper feed cassette, 9: paper feed roller, 10: registration roller, 11: toner cartridge, 15: toner container, 20: casing, 22: developing unit, 23: developing roller, 31: supply roller, 3
2: thin layer blade, 33: first toner conveying member, 3
4: toner transport space, 35: second toner transport member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ugitsu Fujishiro 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Ricoh Co., Ltd. (72) Mayumi Miyao Inventor Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-4-199164 (JP, A) JP-A-6-250484 (JP, A) JP-A-5-158320 (JP, A) JP-A-6-258910 (JP, A) JP-A-3-171165 (JP, A) JP-A-60-254063 ( JP, A) JP-A-61-151564 (JP, A) JP-A-64-62672 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/01-15/01 117

Claims (2)

(57) [Claims] A plurality of developing devices each containing a developer are arranged around a rotation axis, and an arbitrary developing device is rotated around the rotation axis to a development position facing a latent image carrier to perform development and development. In a rotary image forming apparatus that replenishes toner, the rotating body is rotated so that the distance for moving any developing device to a predetermined reference position after development is completed is minimized, or the rotating body is moved in only one direction. An image forming apparatus comprising a selection unit for selecting whether to rotate. 2. The image forming apparatus according to claim 1, wherein
The image forming apparatus is characterized in that the selection of the selecting unit is performed by performing a predetermined image forming operation.