JP2811088B2 - Color image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a color image in which a toner image is formed on a belt-shaped image forming body by an electrophotographic method and transferred to a transfer material to obtain an image. The present invention relates to a forming apparatus.

[Background of the Invention]

Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, as disclosed in JP-A-61-100770, a latent image is formed and developed according to the number of color separations of a document image on a photosensitive drum as an image carrier,
There is a method in which a multicolor image is formed on a transfer drum by transferring the image on a transfer drum each time development is performed and then transferred onto a recording paper to obtain a color copy. In the apparatus according to this method, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface in addition to the photosensitive drum, and the apparatus has a large and complicated structure. Inevitable.

Further, as disclosed in, for example, JP-A-61-149972, a latent image is formed and developed on a photosensitive drum in accordance with the number of separated colors of an original image, and is transferred onto a transfer material each time development is performed. This is a method of obtaining a multi-color copy. In this method, it is difficult to accurately superimpose multi-color images, and a high-quality color copy cannot be obtained.

In addition, there is a method in which a latent image is formed on the photosensitive drum in accordance with the number of separated colors of the original image and development with color toner is repeated, and a color image is obtained by superimposing and transferring a color toner image on the photosensitive drum. The basic process of this multicolor image formation is described in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-76766 by the present applicant,
Nos. 60-95456, 60-95458, 60-158475 and the like.

In a multi-color image forming image in which a color image is obtained by such superposition, a plurality of developing devices containing color toners of different colors are arranged on the periphery of the photosensitive drum. The photosensitive drum is rotated a plurality of times to develop a latent image on the photosensitive drum to obtain a color image.

As for the image forming body, a belt-shaped image forming body in which a photoconductor is applied or mounted on a flexible belt together with a photosensitive drum having a photoconductor applied or deposited on the drum peripheral surface as described above. Has also been proposed. The shape of a belt-shaped image forming body (hereinafter also referred to as a photoreceptor belt) is determined by being stretched between rotating rollers including a driving roller.
This is effective when a compact color image forming apparatus is configured by effectively utilizing the space.

[Object of the invention]

In a color image forming apparatus using a photoreceptor belt, an image forming unit such as a charging unit, an image exposing unit, and a developing unit including a plurality of developing units is provided on a peripheral portion of the photoreceptor belt. The iso-image forming means faces the rotating photoreceptor belt with a certain gap.

However, a set of charging means, an image exposing means and a plurality of developing units are arranged on the peripheral portion of the photoreceptor belt, so that the photoreceptor belt needs to rotate many times to obtain a multicolor image. It takes a considerable amount of time to obtain one image.

In addition, in the above-described image forming process, it is necessary to provide independent operation timings for charging and developing, which causes problems such as an increase in the size of a power supply, an increase in driving, and an increase in cost such as complicated control. is there.

On the other hand, it has been empirically shown that such a color image forming apparatus has an extremely large number of opportunities to form an image using only black toner in addition to a color image. When an image forming unit using only the black toner is operated up to the other unused color toner developing units, the developer is unnecessarily deteriorated,
An increase in toner scattering is inevitable.

 An object of the present invention is to solve the above problems.

[Configuration of the invention]

The object of the present invention is to form a color image by arranging a plurality of image forming means in units of a charger, an image exposing device, and a developing device on a peripheral edge of a belt-shaped image forming body stretched and moved between two rotating rollers. In the apparatus, the image forming means using each color toner controls at the same timing, while the image forming means using black toner controls at an independent timing so that the toner image is superimposed on the image forming body. This is achieved by a color image forming apparatus characterized in that the color image forming apparatus is formed.

〔Example〕

One embodiment of the color image forming apparatus of the present invention is shown in FIGS.

In FIG. 1, reference numeral 1 denotes a flexible photoreceptor belt serving as a belt-shaped image forming member. The photoreceptor belt 1 is provided between rotating rollers 2 and 3 and is driven clockwise by driving the rotating roller 2. Transported to

Reference numeral 4 denotes a guide member fixed to the apparatus main body so as to be inscribed in the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by a mechanical action above the tension roller 5 so that the inner peripheral surface thereof is formed. Is rubbed against the guide member 4. Further, the guide member 4 may be provided with a concave portion in a region not required for image formation, so as to reduce resistance due to rubbing. Of course, this recess need not be provided if the sliding resistance is low. In order to reduce the frictional resistance between the photosensitive belt 1 and the guide member 4, a low friction member such as Teflon is used for the photosensitive belt 1.
Alternatively, it is preferable to be provided on any surface of the guide member 4 or to be constituted by the above-mentioned low friction member.

Therefore, the photoreceptor on the outer peripheral surface of the photoreceptor belt 1 is always kept at a fixed relation to the surface of the guide member 4 even during conveyance, and a stable image forming surface having a large curvature has a long width. It is possible. Therefore, many image forming units having the same shape can be arranged in parallel. First
In the figure, the photoreceptor belt 1 behind the guide member 4
Opposite to the above, there are four chargers 110, 210, 310, 410, four image exposure devices 120, 220, 320, 420, and four (4) each containing yellow (Y), magenta (M), cyan (C), and black (BK) toners. Developing units 130, 230, 330, 430 are located. Then, four chargers, image exposing devices, and developing devices 110, 120, 130;
0, 220, 230; 310, 320, 330; 410, 420, 430 are adjacent to each other as four sets of image forming means in the form of a set and face the photosensitive belt 1. Developing device 43 with built-in black (BK) toner
In the case of 0, the consumption of the toner is large, the one-component developer is used, and the shape of the developing device including the hopper may be different, but the others are exactly the same. Since the respective chargers and the respective developing devices are arranged close to each other substantially in parallel in this manner, it is possible to use a common power source and drive.

By providing the developing device and the cleaning device below the photoreceptor belt, it is possible to prevent the developer from scattering and spilling.

Each of the chargers 110, 210, 310, and 410 is a scorotron charger having the same structure. The state of the charger 110, which is indicated by a cross section XX, facing the photosensitive belt 1 is as shown in FIG. 3A.
That is, 110A is a back plate of the charger 110, a metal member having a U-shaped cross section, and 110B is a back plate 11
Each electrode blocks attached to both ends of 0A, 110W ₁ is a wire electrode that is stretched between the electrode block 110B. 11
0 W ₂ is etched grid configured in a grid wire or mesh-like and many present stretched in front of the wire 110W _1.

Each electrode block 110B is integrally formed with a projection 110C having a predetermined height as an abutting member, and the charger 110 is arranged such that each projection 110C is pressed against the guide member 4 outside the photoreceptor belt 1. It is urged by an elastic member 110D such as a spring.

Accordingly wire the electrode 110W ₁ and grid wires 110W ₂
Is always kept at a constant interval with respect to the peripheral surface of the photoreceptor belt 1, and can reliably charge the photoreceptor to a predetermined potential.

Each of the image exposure devices 120, 220, 320, and 420 is an image exposure device having the same structure, and receives a color signal output from an image reading device separate from the printer shown in the embodiment of FIG. A bright line for image formation is formed on the peripheral surface of the photoreceptor belt 1 to which the charge is applied.
The image exposure devices 120, 220, 320, and 420 generate a laser beam with a semiconductor laser based on the input color signal, rotate and scan the laser beam with a polygon mirror, project the laser beam on the peripheral surface of the photoreceptor belt 1 through an fθ lens, and emit a bright line. Laser writing unit (not shown) that forms
Further, an image exposure optical system in which a convergent light transmitting body 120A linearly arranged and a light emitting section 120B such as an LED that emits light based on an input color signal may be integrated. FIG. 3 (C) shows a ZZ cross section of the image exposure apparatus 120 of FIG. 1. The light emitting section 120B has projections 120C having predetermined heights as abutting members at both ends of a casing. Similar to the case of the charger 110, the elastic member 120D such as a leaf spring is urged so as to be in pressure contact with the guide member 4 outside the belt 1.

Therefore, the image exposure optical system 120 is also always kept at a constant interval with respect to the peripheral surface of the photoreceptor belt 1, so that an image can be accurately formed on the photoreceptor.

The developing units 130, 230, 330, and 430, particularly the developing units 130, 230, and 330, have the same structure. Yellow (Y), magenta (M), cyan (C), black (B
This is a developing device having a two-component developer composed of the toner and the carrier of K) or a one-component developer having the same color and performing non-contact reversal development.

FIG. 4 shows a cross section of a developing device 130 containing a two-component developer. Reference numeral 130A denotes a developing sleeve containing a fixed magnet roller. , And is driven and rotated counterclockwise while maintaining a predetermined development interval. 131A is a rigid and magnetic thin layer forming member that is pressed against the developing sleeve 130A with a predetermined load without the developer interposed therebetween. 131B and 13
1C has a screw structure, and is a pair of toner conveying screws for conveying and circulating the developer in opposite directions, and has a function of sufficiently stirring and mixing the toner and the carrier and sending the toner and the developer to the developing sleeve 130A.

The toner transport screw 131B and the toner transport screw 131C are members that also serve as a stirring member that rotates in directions opposite to each other, and the toner and the carrier transported to the back side by the thrust of the toner transport screw 131B are on the toner transport screw 131C side. The toner is transported to the front side of the drawing by the thrust, and is made into a uniform triboelectric developer by the mixing action of the toner and the carrier therebetween, and adheres in a layer on the peripheral surface of the developing sleeve 130A.

This layer of the developer adhered to the peripheral surface of the developing sleeve 130A and formed into a layer becomes a thin layer in the course of passing through the thin layer forming member 131A, and the peripheral surface of the photosensitive belt 1 conveyed clockwise in the developing area. The latent image on the surface is reversibly developed in a non-contact manner with a development interval therebetween to form a toner image.

During this non-contact development, a developing bias including an AC component in addition to a DC component is applied from a power source (not shown) to the developing sleeve 13.
0A, so that only the toner in the developer is selectively transferred to and adhered to the surface of the latent image on the developing sleeve 130A.

The developer having consumed the toner component has a high carrier ratio and is conveyed by the developing sleeve 130A to be scraped by the scraper 13.
It is separated and collected by 1D, and a developer with a high toner ratio is mixed again.

FIG. 3B shows a YY section of the developing device 130 of FIG. In FIG. 3 (B), 130A is a developing sleeve of the developing device 130, 130B is a striking roller as a striking member, and the striking roller 130B is rotatably supported by the rotating shaft 9C of the developing sleeve 130A. I have.

The abutting roller 130B is slightly larger than the developing sleeve 130A so that when pressed against the guide member 4, the peripheral surface of the developing sleeve 130B can form a gap corresponding to the developing interval between the peripheral surface of the photosensitive belt 1 and the developing roller 130B. It has a large outer diameter.

Therefore, the developing sleeve 130A has a constant developing interval (0.3 to 1 mm) suitable for non-contact development between the outer circumferential surface of the photosensitive belt 1 and the developing sleeve 130A.
The developing device 130 can always perform an appropriate developing process. The same applies to the other developing devices 230, 330, and 430. Each built-in abutting roller is pressed against the guide member 4 by a well-known urging mechanism, and development is performed in a stable state.

As shown in FIG. 1, four sets of image forming means including a charger, an image exposing device, and a developing device having the structure and function described above face the photosensitive belt 1 moving at a speed V with an interval of H from each other. doing. That is, the chargers 110, 210, 310, 410 are arranged with an interval of H, and the same applies to the developing units 130, 230, 330, 430. In particular, the image exposing devices 120, 220, 320, 420
Are adjusted to the same length H on the peripheral surface of the photoreceptor belt 1 from the relation of superimposition of color images, and are arranged. Further fine adjustment is performed by electrically shifting and correcting the light emission timing of the light emitting units 120B, 220B, 320B, 420B from the basic timing shift.

The image formation by the printer is classified into a color copy classified into a full-color image formation and a functional color image formation and a black copy formed with a black image depending on a mode selection. First, the full-color image formation will be described. I do. In this embodiment, the developing device 130
Then, the developer containing the yellow (Y) toner is
Then, the developer containing the magenta (M) toner is
Then, a developer containing cyan (C) toner is supplied to the developing device 43.
At 0, the developer containing black (BK) toner is loaded,
Image formation is performed according to the time chart shown in FIG.

First, when the start switch is turned on, the photosensitive belt 1 starts rotating clockwise at a constant speed of V, and the chargers 110, 210, 31
0 is turned on at the first timing at the same time, and the charger 410 is turned on with a delay of 3H / V from the first timing (V is the moving speed of the photoconductor belt), and the charging device 410 is uniformly applied on the photoconductor. Charging is performed. Next, a latent image corresponding to the first color (Y) output from the signal processing unit by the image exposure device 120 is formed on the peripheral surface of the photosensitive belt 1. Then the developing unit
130, 230, 330 start operating simultaneously at the second timing. Regarding the developing device 430 having the black toner, the second
Is turned on with a delay of 3H / V from the timing of. The latent image corresponding to the first color (Y) is developed by the developing device 130, and a yellow (Y) toner image is formed. The yellow (Y) toner image passes under the charger 210 while being held, and is recharged. A latent image corresponding to the second color (M) is formed by the image exposure device 220 with a delay of the time H / V from the latent image formation by the previous image exposure device 120. This latent image is developed by the developing device 230.

The magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

Further, the photoreceptor belt 1 recharged by the charger 310
Above, the time H / V is longer than the latent image formation by the previous image exposure device 220.
The latent image corresponding to the third color (C) is later formed by the image exposing device 320.
Go formed by. This latent image is developed by the developing device 330, and the cyan (C) toner image is formed in the presence of the already formed yellow (Y) and magenta (M) toner images, and the three color toner images are superimposed. Formed on the photoreceptor belt 1.

Recharging by the charger 410 which is turned on with a delay of 3H / V from the first timing, and an image exposing device 420 for exposing with a time of H / V later than the latent image formation by the previous image exposing device 320;
Developing device that turns on with a delay of 3H / V from the second timing
With 430, a black toner image is superimposed and formed on the surface of the photoreceptor belt 1 by the same processing. Each of these developing devices 130, 230, 330 and 430 has a sleeve 130A, 230A, 330
A or 430A is applied with a DC or AC bias, so that jumping development is performed by a two-component developer as a visualizing means, and development is performed in a non-contact manner on the photosensitive belt 1 whose base is grounded. It has become. Incidentally, non-contact development using a one-component developer can also be used as the development.

The color toner image thus formed on the peripheral surface of the photoreceptor belt 1 is transferred to a transfer material sent from the paper feed cassette 14 via the paper feed guide 15 at the transfer section.

That is, one of the uppermost layers of the transfer material accommodated in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16, and the transfer material is transferred to the transfer device 12 via the timing roller 17 in synchronization with the image formation on the photosensitive belt 1. Is supplied to the static elimination bar 12A.

The transfer material having undergone the image transfer and the charge removal is reliably separated from the photoreceptor belt 1 which suddenly changes its direction along the rotating roller 2 and heads upward. The image is fused by the fixing roller 18 and then discharged. The paper is discharged onto a tray 20 via a paper roller 19.

On the other hand, the photoreceptor belt 1 after the transfer to the transfer material is further conveyed, and the remaining toner is removed by the cleaning device 13 in which the blade 13A and the toner conveying roller 13B are pressed against each other. In the cleaning device 13, the blade 13A and the toner conveying roller 13B are kept in pressure contact with the photoreceptor belt 1 all the time during the rotation of the photoreceptor belt 1, are kept in contact even after the retreat of the blade 13A, and retreat with a slight delay. Is controlled as follows.

FIG. 2 (a) shows a timing chart of this color image formation, and FIG. 2 (b) is a block diagram showing this control.

 The full-color image formation has been described above.

An image is formed in a functional color in the same manner. 130,230,330,430
On the other hand, the image exposure device 12 located in front (upstream) of the developing device
0,220,320,420 are blue (B), green (G), red (R), black (B
K) is performed by controlling each of the color image data to be output, and the number of operations is variably controlled.

Each of the chargers 110, 210, 310 may enter the charged state at the first timing earlier by a time corresponding to the interval between the respective image exposure devices 120, 220, 320. Therefore, in the time chart shown in FIG. 2, the chargers 110, 210, and 310 sharing the same power supply enter the charged state at the same time and at the first timing prior to the image exposure by the image exposure device 120, but it is preferred that So that it becomes charged before H / V is added to
It is better to select the timing. With such a setting, the photosensitive belt passes through the chargers 210 and 310 in a charged state after H / V from the start of charging, so that the fluctuation of the charging current is small. Since each of the chargers 110, 210, 310, and 410 uses a scorotron charger, the potential at the time of recharging is further maintained at the same level. Once in the recharged state,
Since the power supply of the charger is stable with little electrical fluctuation, the image is exposed to the photoreceptor that has entered the recharged state after H / V or more after entering the charged state as described above. Thereby, a stable latent image can be formed. When the chargers 110, 210, 310 are simultaneously turned off,
The image area where image exposure is performed by the image exposure device 320 is after charging is completed.

The driving of the developing units 130, 230, and 330 is also performed by the image exposure apparatus 120.
At the second timing before the image area formed by the image exposure device 130 passes through the developing device 130, the image exposure device 320
O after the developer 330 passes through the image area formed by
Controlled to be FF. However, when the driving of the developing units 130, 230, and 330 is started, vibration is likely to occur, and during the image exposure on the photoreceptor belt 1, an adverse effect on the image appears. Therefore, the development is performed prior to the image exposure by the image exposure device 120 corresponding to the first exposure. It is desirable that the driving of the devices 130, 230, 330 be in the ON state.

Also for the functional color, the black toner image is formed in a controlled manner separately from the formation of the blue (B), green (G), and red (R) toner images. That is, the charger 410 is turned on and recharged after a lapse of time 3H / V from the first timing, and the image exposure is performed by the image exposure device 420 after a lapse of time H / V from the previous latent image formation by the image exposure device 320. Then, the developing device 430 is turned ON with a delay of 3H / V from the second timing, and a black (BK) toner image is formed on the photosensitive belt 1 in an overlapping manner.

As described above, the color image forming apparatus of the present invention has the same toner image forming means for yellow (Y), magenta (M), cyan (C) or blue (B), green (G), and red (R). The image forming means using the black (BK) toner is configured to perform the control at an independent timing, so that the frequently used black monocolor print is formed by the black toner image forming means. It is performed by controlling and operating only one of them.

The application timing of the developing bias in the developing units 130, 230, 330, and 430 may be turned on at the same time as the driving of the developing units,
Further, control may be performed so that only the image area where the developing unit performs development is turned ON. This is because, in a developing device using non-contact development, ON-OFF control of development is possible by ON-OFF control of the developing bias applied to the developing sleeve even when the developing device is driven. The development bias is turned on by applying to the development sleeve a voltage composed of a DC component slightly lower than the charging potential required for reversal development and, if necessary, an AC component as a development bias. The development bias can be turned off by setting the development sleeve in a floating state.

When the developing bias is turned on at the same time as the driving of the developing devices 130, 230, and 330 having the color toner, it is desirable that the developing be performed in a charged area of the photoconductor in order to avoid consumption of the toner. Therefore, the first
It is desirable to set the second timing later than the timing described above by a time corresponding to the time difference between the charging device and the developing device. Further, OFF of the driving of the developing device is set so that the rear end of the charged area passes through the rear end of the image area and before the rear end of the charged area passes.

When the developing bias is controlled independently of the driving of the developing device, the driving can be set at the second timing, and the ON of the developing bias can be set at the timing at which each image area passes through each developing area. However, since color balance is important for a color image, it is desirable that the developing bias voltages of the respective developing units are controlled independently of each other instead of being common.

〔The invention's effect〕

In the color image forming apparatus according to the present invention, since the image forming unit is independently driven and controlled for monocolor using black toner, a stable black print can be obtained. As for other color image forming means, it is possible to share the power supply of the charger and the drive of the developing device, and the control timing of the control system is simplified. As a result, a color image forming apparatus capable of forming images at high speed is provided at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a color image forming apparatus of the present invention, and FIG. 2A is a timing chart of image formation, and a hatched area indicates an image area. FIG. 2 (b) is a block diagram showing the control of the present invention. FIG. 3 is a sectional view of a main part of the apparatus, and FIG. 4 is a sectional view of a developing device. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor belt, 2, 3 ... Rotating roller 4 ... Guide member, 12 ... Transfer device 13 ... Cleaning device, 14 ... Cassette 17 ... Timing roller 110,210,310,410 ... Charging device 120,220,320,420 ... Image Exposure equipment 130,230,330,430 …… Developer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-220977 (JP, A) JP-A-59-67560 (JP, A) JP-A-58-100141 (JP, A) 128447 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 B41J 2/525

Claims (2)

(57) [Claims] 1. A color image in which a plurality of sets of image forming means including a charger, an image exposing device, and a developing unit are arranged on a peripheral edge of a belt-shaped image forming member which is stretched and moved between two rotating rollers. In the forming apparatus, the image forming means using each color toner controls at the same timing, while the image forming means using black toner controls at an independent timing so that a toner image is superimposed on the image forming body. And a color image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein the number of operations of said image exposure apparatus is variably provided.