JP2896683B2 - 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.

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

[Configuration of the invention]

The above object is to provide a charger, an image exposure unit,
In a color image forming apparatus in which a plurality of developing devices are arranged as one set, the driving start timing of the plurality of developing devices is before the image exposure of the image exposure unit and before the developing area passes through the plurality of developing devices. The image forming is performed at the same timing, and the stop timing of the plurality of developing units is performed after the image exposure of the image exposure unit, and performed at the same timing after the developing area passes through the plurality of developing units. This is achieved by a color image forming apparatus characterized in that a toner image is formed so as to be superimposed on a body.

〔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 in contact with the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by a mechanical action above the tension roller 5 so that the inner periphery thereof is rotated. The surface is rubbed against the guide member 4.

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 is formed with a long width. Is possible. Therefore, many image forming units having the same shape can be arranged in parallel. In FIG. 1, four chargers 110, 210, 310, 410, four image exposure devices 120, 220, 320, 420, and four developing devices 130, 23 are opposed to the photosensitive drum 1 behind the guide member 4.
0,330,430 are located. Then, four sets of chargers, image exposure devices, developing devices 110, 120, 130; 210, 220, 230; 310, 320, 330; 410,
420 and 430 are adjacent to each other as four sets of image forming means in a set shape and face the photoreceptor belt 1. 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.

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 arranged in a straight line and a light emitting unit 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. As in 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 have the same structure. The developing device performs a non-contact reversal development and has a two-component developer including a yellow (Y), magenta (M), cyan (C), and black (BK) toner and a carrier. is there.

FIG. 4 shows a cross section of the developing device 130. Reference numeral 130A denotes a developing sleeve containing a fixed magnet roller and a predetermined developing distance between the peripheral surface of the photoreceptor belt 1 and a coaxial abutting roller 130B. It is driven and rotated counterclockwise while maintaining the 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 131C have a screw structure, and are a pair of toner conveying screws for conveying and circulating the developer in opposite directions to each other, and have a function of sending the toner and the carrier to the developing sleeve 130A as the upper developer by sufficiently stirring and mixing. .

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 an abutting roller serving as an abutting member, and the abutting roller 130B is rotatably supported by a rotating shaft 9C of the developing sleeve 130A. ing.

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.

The four sets of image forming means including the charger, the image exposing device, and the developing device having the structure and function described above are opposed to the photosensitive belt 1 with an interval of H as shown in FIG. That is, the chargers 110, 210, 310, and 410 are arranged at intervals of H, and the same applies to the developing units 130, 230, 330, and 430. In particular, the image exposure devices 120, 220, 320, and 420 are adjusted to have the same length H on the peripheral surface of the photoreceptor belt 1 due to superposition of color images. Are located. Further fine adjustment is performed by electrically shifting the light emission timing of the light emitting units 120B, 220B, 320B, 420B more than the basic timing shift.

In the image formation by the printer, full-color image formation, functional color image formation, and single-color image formation are performed according to the mode selection. First, full-color image formation will be described. In this embodiment, the developing device 130 contains a developer containing a yellow (Y) toner, the developing device 230 contains a developer containing a magenta (M) toner, the developing device 330 contains a developer containing a cyan (C) toner, and Developer 430
In FIG. 2, a developer containing black (BK) toner is loaded, and an image is formed according to a 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
0,410 are simultaneously turned on at the first timing, and the photosensitive member is uniformly charged. 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. Next, the developing units 130, 230, 330, and 430 simultaneously start operating at the second timing. The first latent image is developed by the developing device 130, and a yellow (Y) toner image is formed. Charger while holding yellow (Y) toner image
Passes below 210 and is recharged.

The latent image corresponding to the second color (M) is delayed by the time H / V from the latent image formation by the image
Go formed by. 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.

Similarly, re-charging by the charger 410 and the same processing by the image exposure device 420 and the developing device 430 form a black toner image on the surface of the photoreceptor belt 1 in a superimposed manner. Each of these developing units 130, 230, 330 and 430 has a sleeve 130A, 230A, 33
DC or further AC bias is applied to 0A and 430A, 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 that has undergone image transfer and charge removal is separated from the photoreceptor belt 1 that suddenly changes its direction along the rotating roller 2 and moves upward, and the image is fused by the fixing roller 18. The paper is discharged onto the tray 20 via the paper discharge rollers 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 pressure contact of the blade 13A and the toner conveying roller 13B to the photosensitive belt 1 may be controlled so as to be continuously performed during the rotation of the photosensitive belt 1.

The full-color image formation has been described above. When a single-color image is formed, the number of operations of the image exposure apparatus is variably controlled. When forming a single color image of any of the yellow (Y), magenta (M), cyan (C), and black (BK) colors, an image exposure before a specific development, for example, a single color image formation of cyan (C) is performed. At this time, the image exposure device 3 located in front (upstream) of the developing device 330 having the cyan (C) toner
By controlling so as to perform only image exposure by 20, a monochromatic image of cyan (C) is formed.

When forming a single-color image of any of the blue (B), green (G), and red (R) colors, the image exposure using the same image data is performed before (upstream) two specific developing units. This is performed by controlling the operation by two positioned image exposure apparatuses. For example, when trying to obtain a red (R) monochromatic image, the image exposure device 120 and the image exposure device 220 are controlled to output the same image data, so that the yellow (Y) and magenta (M) images are output. , A red (R) single-color image is formed.

An image is formed in a functional color in the same manner, but in this case, a developer containing blue (B), green (G), red (R), and black (BK) toners is developed instead of the above toner. 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 charger 110, 210, 310, 410 is an image exposure device 120, 220, 32
It is sufficient to enter the charged state at the first timing earlier by the time corresponding to the interval between 0,420. Therefore, in the time chart shown in FIG. 2, the chargers 110, 210, 310,
410 enters the charged state at the first timing at the same time and prior to the image exposure by the image exposure apparatus 120, but it is preferable that the 410 be in the charged state at the time before H / V is added to the above-mentioned time. It is better to select the timing of 1. With this setting, the photosensitive belt passes through the chargers 210, 310, and 410 in a charged state after H / V from the start of charging, so that the charging current fluctuates little. Chargers 110, 210, 310,
Since each of the 410s uses a scorotron charger, the potential at the time of recharging can be kept even. When entering the recharged state in this way, the electric power of the charger becomes stable with little electrical fluctuation, so after entering the charged state as described above, the passage of H / V or more elapses to the recharged state. By performing image exposure on such a photoconductor, a stable latent image can be formed. The point in time when the chargers 110, 210, 310, and 410 are simultaneously turned off is after the end of charging in the image area where image exposure is performed by the image exposure device 420.

Regarding the driving of the developing units 130, 230, 330, and 430, the image area formed by the image exposing device 120 is simultaneously turned on at the second timing before passing through the developing unit 130, and the image exposing device
It is controlled to be OFF after the developing device 430 has passed through the image area formed by 420. However, developing units 130, 230, 330, 4
Vibration is likely to occur at the start of driving of the 30 and the photosensitive belt 1
During the image exposure, an adverse effect on the image appears. Therefore, it is preferable that the driving of the developing units 130, 230, 330, and 430 is in an ON state prior to the image exposure by the image exposure apparatus 120 corresponding to the first exposure.

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 developing device drive is turned on, it is desirable that the operation be performed in a charged area of the photoconductor in order to avoid consumption of toner. Therefore,
It is desirable to set the second timing later than the first timing by a time corresponding to the time difference between the charger 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, the common power source for the charger and the common drive for the developing device can be used, 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 the color image forming apparatus of the present invention, and FIG. 2 is a timing chart of image formation. The hatched area indicates an image area. FIG. 3 is a sectional view of an essential part of the apparatus, and FIG.
The figure is a sectional configuration diagram of the 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 device 130,230,330,430 ... Developing device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-151561 (JP, A) JP-A-1-112265 (JP, A) JP-A-59-15945 (JP, A) JP-A-58-158 57139 (JP, A) JP-A-63-8659 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/00 303 G03G 21/00 370 G03G 21/14

Claims (2)

(57) [Claims] In a color image forming apparatus in which a plurality of chargers, image exposing means, and developing units are arranged as a set on the periphery of an image forming body, the drive start timing of the plurality of developing units is determined by the image of the image exposing means. Before the exposure, the development area is performed at the same timing before passing through the plurality of developing devices, the stop timing of the plurality of developing devices is after the image exposure of the image exposure means, the developing area is A color image forming apparatus, wherein the toner image is formed so as to be superimposed on the image forming body at the same timing after passing through a developing device. 2. The color image forming apparatus according to claim 1, wherein timings for applying and stopping the developing bias of said plurality of developing units are different for each of said plurality of developing units.