JPH02154278A - Color picture forming device - Google Patents

Abstract

PURPOSE:To prevent color shade and color slurring by providing a rotational speed smoothing means including a flywheel which is integrally joined with a photosensitive drum. CONSTITUTION:The device is provided with the rotational speed smoothing means including the flywheel 142 which is integrally joined with the photosensitive drum 121. A brake 144 is slightly applied to the photosensitive drum 121 via a flywheel 142 all the time. Therefore, the photosensitive drum 121 has no oscillating due to backlash which is caused in a gear 136 and a driving gear 137, etc., and is energized on its delay side and driven. Thereby, the photosensitive drum is free of the trivial periodical fluctuation by intermittent driving and is rotated by a pulse motor in accurate synchronization with an optical system. In respect of the picture quality, a picture is formed without jitter, irregularity and color slurring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to image forming apparatuses such as color copying machines and color printers that apply electrophotography.

Conventional technology Copiers, printers, etc. that apply electrophotography require accurate rotation of the photoreceptor drum, which rotates while holding an electrostatic image, without small speed fluctuations, and these fluctuations cause jitter and unevenness in the image. Occurs. In addition, especially in devices that create color images, images are usually formed for each color and then superimposed to create a single color image, so the images for each color must be aligned accurately both partially and as a whole. There is a need. Therefore, while the photoreceptor rotates many times, it is necessary to rotate it very accurately with respect to the time axis. 2. Description of the Related Art Conventionally, in order to reduce speed fluctuations of a photoreceptor in a copying machine, a photoreceptor drive device is known in which an induction motor is used as a drive source and a flywheel is connected to the shaft of a photoreceptor drum.

Problems to be Solved by the Invention However, with conventional induction motors or speed-controlled DC motors equipped with flywheels, small periodic speed fluctuations can be reduced by increasing the inertia of the flywheel to a certain extent. However, there is a problem in that slow speed fluctuations with large periods remain.

In this case, especially in devices such as color copiers and color printers that create a single color image by overlapping images of multiple colors, the positions of the images of each color may shift relative to each other, resulting in color unevenness or color shift. The problem was that it resulted in an ugly colored image.

Additionally, a flywheel attached to the outside of the photoreceptor on the shaft of the photoreceptor drum requires additional space, making the device larger and the structure more complex.

The present invention aims to solve the problems of the prior art.

In other words, the first aspect of the present invention is that the photoreceptor does not have speed fluctuations in small periods and does not have speed fluctuations in large periods. It is an object of the present invention to provide a color image forming apparatus that can produce high-quality images without color shift.

A second object of the present invention is to provide a color image forming apparatus which is small in size and has a simple configuration, and has high image quality without jitter or unevenness.

Means for Solving the Problems The first invention provides a photoreceptor drum that rotates while holding an electrostatic image, a plurality of developing means for alternately developing a plurality of colors, and a drive for driving the photoreceptor drum. The color image forming apparatus has a rotational speed smoothing means including a pulse motor and a flywheel integrally connected to the photoreceptor drum.

A second aspect of the present invention provides a photoreceptor drum that rotates while holding an electrostatic image, a plurality of developing means at least one of which combines and develops images of different colors on the photoreceptor drum in a non-contact manner, and the photoreceptor drum. The color image forming apparatus has rotational speed smoothing means including a flywheel integrally coupled to the photoreceptor drum inside the body drum.

Effects The first aspect of the present invention has the above-described configuration to reduce rotational fluctuations of the photosensitive drum as a whole from small cycles to large cycles, thereby eliminating unevenness, jitter, and ivy in image quality, and eliminating brownish shift and color unevenness. The present invention provides an excellent color image forming apparatus capable of producing beautiful color images.

A second aspect of the present invention provides an excellent color image forming apparatus that is compact and simple and free from jitter and unevenness.

Embodiment FIG. 1 is a front view showing the overall configuration of a digital color copying machine according to an embodiment of the present invention. Its configuration and operation will be explained below.

Reference numeral 1 denotes a reading section of a digital color copying machine, which mainly includes a document table 2, a document illumination lamp 3, a lens 4, a color line sensor 5, a drive system 6 for moving these in the sub-scanning direction for scanning, and an image processing circuit ( (not shown in this figure).

10 is a writing section of the digital color copying machine.

Reference numeral 11 denotes a Se-based photoreceptor which has increased sensitivity to laser light having a wavelength of 780 to 810 nm, and is rotatably supported in the direction indicated by the arrow. Reference numeral 12 indicates a first charger for charging the surface of the photoreceptor 11 to a predetermined positive potential, and reference numeral 26 indicates a laser beam.

Reference numeral 20 denotes a laser optical unit, and the laser beam 26 is emitted from a laser heating block 21, passes through a polygon scanner 22, a lens system 23, and mirrors 24, 25, and scans the photoreceptor 11. A part of the scanning light of the laser beam light 26 is reflected by the mirror 27, and the scanning light of the laser beam light 26 is reflected by the starting edge detection sensor 2.
8 is irradiated. There is a developing section 30 on the right side of the photoreceptor 11, and along the periphery of the photoreceptor 11, from the top, there are a Y developer 31 for developing yellow color, an M developer 32 for developing magenta color, and a C developer for developing cyan color. A developing device 33 (hereinafter collectively referred to as a color developing device) and a developing device 34 for developing black color are arranged. The Y developing device 3L, the M developing device 32, and the C developing device 33 are non-contact developing devices that use non-magnetic one-component toner, and are capable of developing while flying the toner onto the photoreceptor 11 without contacting it. be. I (The developing device 34 is a developing device that uses a two-component developer and develops while bringing the developer into contact with each other. As the eccentric cams 35 to 38 rotate, the Y developing device 3LM developing device 32 and C developing device 33 are pushed at their rear portions and moved horizontally to approach the photoreceptor, while the K developing device 34 is moved closer to the photoconductor. It rotates counterclockwise about 39 and approaches the photoreceptor and becomes ready for development. FIG. 1 shows the case where only the M developing device 32 is in the state capable of development.

40 is an eccentric cam 35, 36, 37, 38 and a developing device 31
．． This is the motor that drives 32, 33, and 34.

50 is the paper feed section (cassette) 51.52 and manual paper feed section 5
It is now possible to feed one sheet of paper from each of the cassettes 51 and 56, and this figure shows a case where a sheet of paper 56 is fed from the cassette 51. Paper 56 is fed to the lower surface of photoreceptor 11 via registration rollers 54 .

Reference numeral 60 denotes a transfer conveyance section, in which a semiconductive belt 63 suspended between rollers 61 and 62 can be in two states: a state in which a portion thereof is lightly pressed against the photoreceptor 11, and a state in which it is separated from the photoreceptor 11. It is also possible to move in the direction of arrow B at the same speed as the outer peripheral surface of the photoreceptor 11. In this figure, photoreceptor 1
1 shows the state of pressure contact. -164 is the second for transcription
A charger connects the belt 63 and the photoreceptor 11 via the belt 63.
A high negative potential is applied to the back side of the paper 56 being fed during this period. Reference numeral 65 denotes a cleaning blade for cleaning toner remaining on the belt, and a collection box 66 is disposed below the cleaning blade.

69 is a third charger that sprinkles negative corona when the paper 56 is separated from the belt 63.

Reference numeral 70 is a fixing and paper ejecting section, in which a heat roller 72 heated by a fixing lamp 71 and a rubber roller 73 are rotatable while being in pressure contact with each other, and paper ejection rollers 74 and 75 are provided at the rear thereof.
and a paper discharge tray 76 are provided.

Is 80 a cleaner? - The brush 81 can be in two states, a state in which it is lightly in contact with the photoreceptor pair 11 and a state in which it is separated from the photoreceptor 11, and is rotatable in the direction indicated by the arrow. This figure shows a state in which it is in contact with the photoreceptor 11.

Furthermore, a collection roller 82 is rotatably disposed while contacting the fur brush 81, and the collection roller 82 is rotatably disposed in contact with the fur brush 81. - A negative voltage is applied to the brush 81 and the collection roller 82, respectively, with respect to the photoreceptor 11. A recovery screw 8 knee 3 is installed at the bottom of the recovery roller 82, and a vibrator 84 is connected to the end of the recovery screw 83 and is connected to a recovery box 85 through this.

A fourth charger 8 is located at the bottom of the cleaner 80 and opposite the photoconductor for positively charging the toner on the photoconductor ll.
6, and a static elimination lamp 87 for neutralizing the photoreceptor 11.

Cooling fans 91 and 92 suck air from the lower and upper parts of the writing section 10 and discharge it to the outside of the apparatus.

The above is an overview of the overall configuration of a digital color copying machine to which the present invention is applied.Next, its operation will be explained with a focus on the writing section.

When the original is placed on the document table 2 and the copying operation begins,
A document is read by the reading section 1, and an image to be recorded by the writing section 1O is determined accordingly.

In the writing section, signals to be recorded are input in the order of black, yellow, magenta, and cyan, and recording is performed. First, a black signal is manually applied to the laser oscillation block 21, and the photoreceptor 11 is irradiated with a laser beam 26 modulated according to the black signal.

The photoreceptor 11 is rotated in the direction of the arrow while the first charger 12
After being uniformly charged to +850V, the area irradiated with the laser beam 26 according to the signal becomes +50V.
Static electricity is removed to a certain extent. Main scanning of the laser beam light 26 on the photoreceptor 11 is performed by a polygon scanner 22,
Sub-scanning is performed by rotating the photoreceptor 11 in the direction of arrow A, forming a latent image on the photoreceptor. When the latent image is first formed on the photoreceptor, the developing unit 30 is set to develop black, and only the K developer 34 approaches the photoreceptor 11 by the operation of the eccentric cam 38, and the developing device 34 approaches the photoreceptor 11. is in a state of separation. Therefore, the latent image corresponding to the black signal formed by the laser beam 26 is developed with black toner by the developer 334 and passes through other developing devices without being affected. At this time, the timing of contact and separation of the developing device 34 is controlled so that the developing device 34 approaches the photoreceptor 11 before the laser beam 26 starts exposing it, and moves away after development. The image developed with black toner reaches the transfer conveyance section 60 as the photoreceptor 11 rotates, but at this time, the rollers 61, 67, and 68 rotate slightly clockwise around the axis of the roller 62 in the transfer conveyance section 60. in the position where the belt 63 is attached to the photoreceptor 11.
It is spaced apart from the surface, and the image passes through it without being disturbed. Further, the fur brush 81 is rotated slightly counterclockwise around the axis of the collection screw 83, and the photoreceptor 11 is
Here, too, the black toner image passes without being disturbed and passes under the first charger 12 again. The portion of the photoreceptor 11 where the black toner image is formed is recharged from the top of the toner by the first charger 12, and the portion without toner is +850■, and the portion with toner is also apparently +85
It is charged to 0■.

The leading edge of the black toner image is recharged and exposed to the laser beam 2 again.
When the laser beam 11 reaches the irradiation position 6, the light 26 of the laser beam 11 is modulated according to the yellow signal and is exposed from above the black toner image on the photoreceptor 11. Since the leading edges of the images are aligned and the scanning speed is constant, the black toner image and the latent image based on the yellow signal are formed in positional alignment. Since only the Y developing device 31 of the developing section 30 is close to the photoconductor 11 and the other developing devices are separated, the latent image formed by the yellow signal is developed only with yellow toner and is deposited on the photoconductor. A yellow toner image is formed in addition to a black toner image.

At this time, in the Y developing device 31, the photoreceptor 11 is exposed to the laser beam 26.
The approach and separation timings are controlled so that the proximity operation is performed before the start of exposure, and the ATM is performed after development. Further, since the yellow development is performed in a non-contact manner, the previous black toner image is not disturbed. Thereafter, recharging, latent image formation using a magenta signal, magenta development, recharging, latent image formation using a cyan signal, and cyan development are repeated in the same manner.

At this time, since the yellow toner and magenta toner pass through the laser light, if necessary, exposure is performed to remove static electricity from that part of the photoreceptor, and the magenta and cyan toners are placed on top of the yellow toner, and the cyan toner is added to the old magenta toner. Can you lay down one toner? After the last cyan toner image is formed, just before the leading edge of the toner image reaches the transfer conveyance section,
The transfer conveyance unit 60 is brought into a state of being lightly pressed against the photoconductor 11, and the paper 56 enters between the photoconductor 11 and the belt 63 by the registration roller 54 at the timing when the leading edge of the toner image and the leading edge of the paper 56 match. It is fed as follows.

While the toner image is transferred to the paper 56 by the electric field generated by the second charger 64, the paper 56 is conveyed while being attached to the belt 63, but since the curvature of the roller 62 is large, it separates from the belt 63 and is separated from the fixing paper discharge section. Enter. At this time, in order to prevent the toner image on the paper 56 from being disturbed by the separation charge generated on the paper 56 when it is separated from the belt, negative corona is sprinkled from above by a third charger.

The toner image on the paper 56 is fixed when it passes through the fixing paper discharge section and is then stacked on the wandering paper tray. - The untransferred toner image remaining on the photoconductor 11 is positively charged by the fourth charger 86, which starts operating as the leading edge approaches the photoconductor 11, and almost simultaneously moves into contact with the photoconductor 11. The electric field applied to the fur brush 81 and the photoreceptor 11 moves the photoreceptor to the fur brush 81 while being rubbed by the fur brush 81 . Furthermore, the toner inside the fur brush 81 is collected by a collection roller 82.
Due to the electric field applied to the fur brush 81, the fur brush moves to the collection roller 82 and is dropped into the collection screw 83, and the vibrator 8
4 and placed in the collection box.

The surface of the photoreceptor 11 is thereby cleaned, and on the other hand, the charge is removed by the charge removal lamp 87, and the photoreceptor 11 is returned to the initial state Q, and preparation for the next copy is completed.

On the other hand, toner that is loose or normally accumulates in a small amount on the belt 63 of the transfer conveyance section 60 is cleaned by a cleaning blade 65 and collected in a collection box 63.
It's down to the 6th factor.

The above is an overview of the overall configuration and operation of a digital color copying machine to which the present invention is applied. Next, the structure and operation of the developing section of this digital color copying machine will be explained in detail.

FIG. 2 is a detailed view of the photoreceptor 1 and the developing section 30 in FIG. 1, and this figure shows the M developing device 32 in the developing state.

Each developing device 31, 32, 33, 34 has a developing rack 41.
The developing rack 41 is partially cut away in this figure.

Reference numeral 101 is a handle for pulling out the developing rack 41 from the main body. The developing rack 41 is a rail 4 fixed to the main body.
2 and can be pulled out. Reference numeral 102 denotes a lock knob which can be rotated in the E direction around a shaft 103, and in the state shown in FIG. 2, the developing rack 41 is pushed out of the drawer.

When the color fJt imagers 31, 32, and 33 are in a free state without applying any external force, they are the Y developer 31 and CIJI in Fig. 2.
It is biased by a return spring (not shown) installed in the developing rack 41 so as to return to the imager-like position. Furthermore, when the developing device is supported by a shaft 39 and is not pushed by the eccentric cam 38, it is in a position as shown in FIG. 2 due to its own weight. Eccentric cams 35, 36, 37, and 38 are installed in the main body of the copying machine and move the stored developing device to each plate spring 4.
4.45, 46, and 47 from the rear, and the developing device is pressed by turning the rotation stop about every 180 degrees around the shafts 35a, 36a, 37a, and 38a, respectively. and a separate state.

Next, the structure and operation of the photoreceptor portion of this digital color copying machine will be explained in detail. FIG. 3 is an axial cross-sectional view of a portion of a photoreceptor according to an embodiment of the first invention.

Reference numeral 121 denotes a photoreceptor drum, which has a cylindrical surface with a Se-based photoconductive layer deposited on its surface, and a rear flange 122 and a front flange 123 are fitted at both ends of the drum, respectively, and these flanges 122 and 123 are the shafts]24 The photoreceptor drum 121 is supported by engaging with. The shaft 124 has both ends connected to a rear side plate 127 via bearings 125 and 126, respectively.
It is rotatably supported by the front lid 128. The front lid 128 further has a thumbscrew 130 on the front side plate 129.
131. - A pin 132 is implanted in the blade shaft 124 at the position of the rear flange, and both ends of this pin 132 are engaged with grooves 133 carved in the rear flange 122, and the pins 132 are inserted around the hinge between the rear flange 122 and the shaft 124. It is stopped.

shaft! A screw 134 is cut in the other part of 24, and a nut 135 is engaged with the screw 134. When the nut 135 is tightened, a force is applied between the pin 132 and the nut 135 in a direction in which the rear flange 122 and the front flange 123 approach each other, thereby sandwiching and fixing the photosensitive drum 121. A gear 136 is integrally fixed to the rear flange 122 and is rotationally driven by a drive gear 137. Drive gear 1
37 is further driven by a pulse motor 13B.

On the other hand, one end of the rear side of the shaft 124 is connected to the rear side plate 127 via a bearing 139 that is engaged with a relatively large gap.
A bearing integrally fixed to is supported by plate 140. This bearing 139 is attached to the front lid 128 during maintenance.
It supports the shaft 124 when it is removed. Furthermore, the shaft 12
A D cut is formed at the end of 4, and the flywheel 142 is engaged with this and is integrally screwed to the shaft 124. Further, a brake shoe 144 attached to a leaf spring 143 fixed to a plate 140 is pressed against the inner surface of the flywheel 142 .

The structure of the photoreceptor portion has been described above. Next, the operation of this structure will be explained. During operation, the photosensitive drum 121 is driven by a pulse motor 138 in precise synchronization with the bow wagon scanner 22 in the optical section. Therefore, during the multiple rotations during which a color image is formed on the photoreceptor drum, color images are formed in which the images of each color are closely overlapped without any displacement.

On the other hand, for one step of the pulse motor 138, the photoreceptor 121 is decelerated so that its outer peripheral surface advances by half the pitch of the line scan of the polygon scanner. The photoreceptor 121 is intermittently driven by a pulse motor at very fine pitches, one step at a time. However, since the flywheel 142 is integrally connected to the photoreceptor 121 through the shaft 124, the photoreceptor 121 has a large inertia and rotates smoothly despite intermittent driving. Further, as described above, the developing device, the cleaner, etc. are brought into contact with and separated from the photoreceptor 121, but there are times during operation when these are separated and the photoreceptor rotates freely without being subjected to any external load.

However, the photoreceptor 121 has a flywheel 142.
Since a light brake is always applied through the gear 13
6, the drive gear 137, etc., and the photoreceptor is always biased toward the lag side and driven.

Therefore, from the above, the photoreceptor does not have small circumferential fluctuations due to intermittent driving, and the large pulse motor enables rotation in precise synchronization with the optical system, resulting in image quality that is free from jitter and unevenness. Further, excellent images without color shift can be formed.

FIG. 4 is a cross-sectional view showing the structure of a photoreceptor portion according to an embodiment of the second invention. The structure and function of other parts are the first.
This is similar to the embodiment of the invention. Components having the same contents as those in the previous embodiment are given the same numbers. A flywheel 142 is integrally connected to the rear flange 122 to achieve the same effect as described above. Normally, a flywheel must have a large diameter or its inertia will be small and it will not be able to produce the desired effect. In the present invention, images of each color are superimposed on the photoreceptor and developed to form a color composite image on the photoreceptor, which is then transferred all at once to paper, so the photoreceptor must be as large as the maximum copy image size. It is. Therefore, the diameter of the photoreceptor is also increased accordingly. In this embodiment, in order to obtain an A3 copy, the diameter of the photosensitive drum 121 is 152 mm. Therefore, a flywheel with a large diameter can be placed inside the photoreceptor.
The flywheel effect can be achieved without requiring any special external space.

As described in detail, according to the present invention, the rotational fluctuations of the photosensitive drum can be reduced as a whole from those with short cycles to those with large cycles, and there is no unevenness or jitter in image quality, and there is no color shift or uneven color. This is an excellent product that allows you to obtain beautiful color images without any blemishes. Furthermore, the effects of the present invention are small and simple, and are excellent in that they are free from jitter and unevenness.

[Brief explanation of the drawing]

FIG. 1 is a side view of a digital color copying machine according to an embodiment of the present invention, FIG. 2 is a side view showing details of its developing section, and FIG. 3 is a portion of a photoreceptor according to an embodiment of the first invention. FIG. 4 is a sectional view showing in detail a portion of a photoreceptor according to an embodiment of the second invention. 1...Reading section, 2...Writing section, 11...
Photoreceptor, 30...Developing section, 31...Y developing device, 32
...M developer, 33...C developer, 34...Developer at -, 35-3 days...Eccentric cam, 121...Photosensitive drum, 122...Rear flange, 123...・Moe flange, 124...shaft, 135...nut, 132・
... Pin, 136 ... Gear, 137 ... Drive gear,
138...Pulse motor, 142...Flywheel, 144...Brake shoe 152...Flywheel. Name of agent: Patent attorney Shigetaka Awano (1 person)

Claims (3)

[Claims] (1) A photoreceptor drum that rotates while holding an electrostatic image, a plurality of developing means for alternately developing a plurality of colors, a pulse motor that drives the photoreceptor drum, and an integral part of the photoreceptor drum. 1. A color image forming apparatus comprising: a rotational speed smoothing means including a flywheel coupled to the flywheel; (2) A photoreceptor drum that rotates while holding an electrostatic image, a plurality of developing means, at least one of which combines and develops images of different colors on the photoreceptor drum in a non-contact manner, and an interior of the photoreceptor drum. and rotation speed smoothing means including a flywheel integrally coupled to the photosensitive drum. (3) The rotational speed smoothing means includes a flywheel integrally coupled to the photoreceptor drum, and a brake acting on the photoreceptor drum or a member that rotates integrally with the photoreceptor drum. 3. The color image forming apparatus according to 1 or 2.