JPS62136672A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate a shift in image position and to obtain an excellent image by moving plural developing devices which are arranged at the periphery of a photosensitive body by a moving means selectively between development operation positions and development nonoperation positions. CONSTITUTION:Either of developing devices 3 and 4 is selected and the developing roller 3a or 4a of the selected device is brought into contact with the photosensitive body 1 to develop, transfer, and fix an electrostatic latent image on the photosensitive body. The anchor 27 of the device is linked to the anchor 33 of eccentric rollers 8 and 9 by a spring 28, and a roller 8 is rotated clockwise around a center 25 by the clockwise rotation of a motor; and the motor is stopped when a point 33 comes to above the line l connecting the anchor 27 and center 25, and the developing device is rotated around centers 29 and 30 of rotation with the force of the spring 28 to bring either of the rollers 3a and 4a into contact with the photosensitive body. Therefore, the movement of the developing device and the rotation to and stop at the developing roller are not performed in an exposing process and a transfer process, so an excellent image having no shift is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a photographic image forming apparatus, in particular an image forming apparatus having one or more image bearing members such as an electrophotographic photoreceptor. It has a developing device, and each developing device is movable between a developing operating position where it is close to the image carrier and develops the latent image on the image carrier, and a developing non-operating position which is remote from the image carrier. The present invention relates to an image forming apparatus. The present invention is 2
It can be suitably applied not only to image forming apparatuses for color or medium color to three or more colors, so-called multi-color image forming apparatuses, but also for full-color image forming apparatuses. In this specification, 1, the term "image forming apparatus" refers to various color printing apparatuses such as a color copying apparatus, a color printing printer constituting the output unit of a computer, a facsimile machine, etc., and furthermore, an ordinary image forming apparatus that is not a color printing apparatus. shall also be included.

Conventional technology and problems Recently, the demand for color copying and printing has increased rapidly not only in special fields but also in general and general inspection fields, and the need for good operability has increased.
There is a need for a color image forming apparatus that can provide f) good image quality. In particular, 2-color or 3-color Buddhist utensils 1. Sometimes it is required to copy or print a full-color original in 91 colors at the same time as a medium-color original, and full-color image forming apparatuses including multi-color image forming apparatuses also use selective methods to meet these demands. Are there two colors or three Buddhist altar fittings? It is required to be able to efficiently copy or print in li color.

In order to satisfy such requirements, conventional color image forming apparatuses arrange a plurality of developers each containing a different developer around an image carrier such as an electrophotographic photoreceptor, and each developer has a It is configured to be able to move i+1 between a developing operating position which is close to the image carrier and develops the latent image on the image carrier, and a developing non-operating position where heat is removed from the image carrier.

The selected developing device is moved to the developing operating position and the latent image on the image carrier is visualized. It is necessary to place a developer carrier, such as a developing roller, and an image carrier, such as a photosensitive drum, close to each other with a certain gap therebetween. There are various ways to do this, but usually, for example, a method is adopted in which rollers are arranged coaxially with the developing roller at both ends of the developing roller and the rollers are brought into contact with the photosensitive drum. . These are Japanese Patent Application Laid-Open No. 51-15444, r
This is a known method by et al. At this time, the other developing devices that have not been selected are retracted from the photosensitive drum to prevent color mixture and are placed in a developing non-operating position.

However, when the developing device is moved as described in L, an impact is often applied to the photosensitive drum, resulting in image blurring.

In addition, in order to maintain a constant gap between the developing roller and an image carrier such as a photosensitive drum, the positions and shapes T of the developing roller and photosensitive drum are adjusted so that the roller coaxial with the developing roller does not hit the photosensitive drum. Even in a system that achieves this by increasing precision, the movement of the developing unit creates an impact on the photosensitive drum, causing image blurring. Normally, when the developing device is in the non-developing position, the developing roller stops rotating to prevent toner from scattering, and the developing roller is rotated during development, but when the developing roller starts rotating, A large ++W was applied to the developing device, which sometimes caused image blurring.

An eleventh object of the present invention is to provide an image forming apparatus that can obtain good images with less image blur.

To summarize, the present invention includes at least an image exposure step for forming a latent image, a development step for making the latent image visible, and a step for transferring the developed image to a transfer material. In an image forming apparatus having two transfer units, one or more developing units are arranged around an image carrier carrying a latent image and a developed image, and each developing unit has a developing roller. a developing operation position in which the developing roller is rotated to develop the latent image on the image bearing member j2, and a developing position in which the developing roller is located away from the image carrier and the developing roller stops rotating; The image forming apparatus is movable between the developing roller and the inoperative position, and is characterized in that (1) the rotation of the developing roller is started except during the image exposure process or the transfer process.

Next, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

An image forming apparatus according to the present invention includes at least an image exposure step for forming a latent image, a developing step for making the latent image visible, and a transfer step for transferring the developed image to a transfer material. Although the present invention can be suitably embodied in a device, this embodiment will be described assuming that the device is applied to a color electrophotographic copying device for obtaining two-color images of black and red. or.

Such color "1" sub-photocopying apparatus performs various electrostatic latent image forming processes, such as primary charging, secondary charging, color separation exposure, etc.
Including steps of full-surface exposure, steps of i7 NF process or steps of primary +i'f electro-color separation exposure.

Although the so-called Carlson process and others may be used, in this embodiment, an electronic/photocopying apparatus to which the Carlson process is applied will be described.

FIG. 1 shows a schematic cross-sectional view of a color electrophotographic copying apparatus for obtaining two-color images of black and red.

First, the overall structure of a color electrophotographic copying apparatus will be described. An image carrier, in this embodiment, a photosensitive drum 1 having an electrophotographic photosensitive layer formed on its surface is arranged approximately in the center of the copying apparatus. The photosensitive drum 1 has a rotation center O in a well-known manner.
It is rotatably and removably attached to a rotation support shaft (not shown) having a rotation support shaft (not shown), and is driven by a drive motor (not shown).

In this embodiment, it is assumed that the photosensitive drum 1 rotates in the direction of arrow X, that is, clockwise in FIG.

A primary charger 2 is located approximately directly above the photosensitive drum 1, developers 3 and 4 are located on the right side of the photosensitive drum 1 in FIG. 1, and a transfer discharger 10 and a photosensitive drum 1 are located approximately directly below the photosensitive drum 1.
A cleaning device 11 is disposed on the left side in FIG. An optical system 5 is disposed on the L side of the electrophotographic copying apparatus, and an optical system 5 is arranged to place an original image between the primary charger 2 and the developer 3.

The image is projected onto the photosensitive drum 1 using an exposure unit placed therein. Optical system 5 can use any optical system. Further, a blank exposure device 6 for erasing charges in unnecessary parts outside the image area and a potential sensor 7 for measuring the surface potential of the photosensitive drum 1 are provided between the exposure section and the developing device 3.
Next, a light source 12 is provided between the electric appliance 2 and the cleaning device 11 for erasing residual charges on the photosensitive tram 11-.

Since the color copying apparatus described here is a color electrophotographic copying apparatus for obtaining two-color images of black and red as described above, it has a developing device 3.4 as a developing device. is not limited to this configuration, and may have one developing device or three or more developing devices.

The operation of the color electrophotographic copying apparatus configured as described above will be briefly explained.

The photosensitive drum 1 begins to rotate in the direction of the arrow X at the start of operation, and is charged by the primary charger 2 (charging process). The charged photosensitive drum 1 further rotates, and a light image is slit-exposed at the exposure section by the action of the optical system 5 ('A light step), so that electrostatic latent images of each color are formed on the photosensitive drum 17. At this time, the blank exposure device 6 erases charges in unnecessary portions outside the image area, and the potential sensor 7 measures the surface potential of the photosensitive drum l. The latent image on the photosensitive drum 1 is then brought by rotation of the photosensitive drum 1 to a developing area in which a developing device 3.4 is arranged, and the electrostatic latent image on the photosensitive drum 17 is transferred by the selected one developing device. is visualized as a toner image (
development process).

The toner image on the photosensitive drum is transferred to a transfer material P fed from a paper feeding device (not shown) in a transfer area where a transfer discharger 1O is arranged (transfer step).

The transfer material P carrying the toner image is then conveyed to the fixing device 14 and fixed 71. The subsequent movement of the transfer material P is 3
It is divided into two parts. First, in the first case, a new copy is not made on the transfer material P, and the flapper 15 (solid line position)
It passes through the flapper 17 (solid line position) and is discharged out of the machine.

The second case is in a mode called multiplexing,
This is a case where another copy image is formed on one side of the transfer material P.

In this case, the flapper 15 is at the position indicated by the broken line, and the course of the transfer material P is corrected in the f direction by the flapper 15.
The copies are stacked on the intermediate tray 21 via the conveyance rollers 20 with the copy side facing down. Next, in order to form a copy image of the second original, the transfer material P is fed by the feeding roller 22, passes through the feeding roller 24, stops once at the registration roller 1-, and then
It is discharged outside the machine after going through a transfer process and a regular process.

The third case is a mode called double-sided mode, in which a copy image is formed on the other side of the transfer material P. In this case, the flapper 15 and the flapper 17 are at the solid line position, and the transfer material P fixed by the fixing roller 14 is conveyed to the discharge roller 18. Flapper 15 and Flapper 17
There is a trailing edge detection sensor 16 between the transfer material P and the discharge roller 18 stops after a certain set time after the trailing edge detection sensor 16 detects the trailing edge of the transfer material P. This stop position F is a position where the rear end of the transfer material P is between the flapper 17 and the loss roller 18. Next, the flapper 17 moves to the position shown by the broken line, and the discharge roller 18 begins to reverse rotation. Then, the copies are stacked on the intermediate tray 21 by the conveyance rollers 20 with the clear side facing up. A copy image of the original of the second section 2 is formed, but the movement of the transfer material P is the same as that of the second section.

The photosensitive tram 1 is operated by a cleaning device 11 and a light source 12, and then performs the next image forming process 11f.

Next, the developing device 3.4 will be explained. This developing device can have any configuration, but in order to explain it in a cylinder for wood, it basically has the same structure and uses the developer. It is assumed that the developing rolls 3a and 4a that are carried and conveyed face the same surface.

The developing rolls 3a, 4a are composed of, for example, a fixed magnet (not shown) and a rotating developing sleeve (not shown) surrounding the magnet. The developer sleeve may be made of a non-magnetic material such as aluminum or stainless steel.

In the configuration described above, for example, the developing device 3 stores red toner, and the developing device 4 stores black toner.

Further, as schematically illustrated in FIG. 2, the developing device 3.4 is moved to the operating position (29° and 30°, respectively) by rotating the developing device moving means, for example eccentric rollers 8 and 9, respectively, about the rotation center 29° and 30°. The I'rT off position is located at the single-point line position) and the developing non-operating position (solid line position).

Here, the eccentric rollers 8 and 9 are driven by motors M, M2 (not shown).
are connected to each other via a deceleration chain, and by controlling the rotation of motors Ml and M2 in forward and reverse directions, it is possible to move the developing units 3 and 4 between a developing operating position and a developing non-operating position. The setting of the operating position will be explained based on the developing device 3 shown in FIG. 3. First, when the developing device 3 is moved from the non-developing position to the developing active position, the eccentric roller 8 begins to rotate clockwise about the rotation center 25 from the position shown by the solid line due to the rotation of the motor M1.

Also, a spring anchor 33 is fixed to the eccentric roller 8, and a spring 28 is placed between it and the spring anchor 27 fixed to the device, so that force is applied in the direction of the line connecting the spring anchors 27 and 33. is recieving.

After the motor M□ continues to rotate clockwise and the line connecting the spring anchors 33 and 27 reaches a position in the clockwise direction from the edge connecting the rotation center 25 of the eccentric roller and the spring anchor 27, the motor M1 After that, the force of the spring 28 is applied to the developing roll 3a, which is coaxial with the developing roll 3a.
The developing device 3 stops at a position (developing operation position) where an abutting roller (not shown) disposed at is in contact with the photosensitive drum.

Next, when moving the developing device 3 from the developing operating position to the developing non-operating position, the motor M1 is rotated counterclockwise. The line connecting spring anchors 33 and 27 is eccentric and connects the rotation center 25 of the roller and the spring anchor 27! 3
After reaching a position in the counterclockwise direction than al, the motor M,
Even if the energization is stopped, the developing unit 3 continues to rotate counterclockwise due to the force of the spring 28, and the developing unit 3 stops at the position where the eccentric roller 8 comes into contact with the stopper 26 (phenomenon operation position device).

By the way, it has been mentioned that the developing roller 3a rotates around the rotation center 29, but there is a southeast 31 located coaxially with the rotation center, and the rotation is performed in the south east 31, which is coaxial with the rotation center of the developing roller 3a. 1 (transmitted to the developing roller 3a via 32. Also, the tooth 11t 31 is connected to i&7 which is coaxial with the motor M3 (not shown).
The rotation of the motor M3 is transmitted to the gear 31.

FIG. 4 is a schematic diagram of a control circuit for a copying apparatus according to the present invention. 40 is a central processing unit (CPU); 41 is a developer selection switch for selecting the color of the toner image to be formed on the copy sheet;
, 42 is a print SW, 451 to 457 are amplifiers, 50
．． 51 are motors M1 and M2, which move the developing machines (3 and 4) between the development operating position and the development non-operation position, respectively;
．． 53 is a motor M that rotates the developing rollers 3a and 3b.
3, M4, 54 is a charger, 55 is an exposure lamp, and 56 is a transfer device.

Next, as an example to explain the copying operation mainly with reference to FIGS. 4 and 5, the developing device 4 is in the developing operation position, and one copy
Let us consider the case where one original is to be copied in red and the second original in black, and the number of copies is one.

First, select developer selection SW41 to red, and print 5W4.
2 to start the copy operation. Upon the start of the copying operation, the photosensitive drum 1 and the drive motor (not shown) are energized at time T0 (t=o), and the photosensitive drum 1 starts rotating. Next, in order to select a developing device, the CPU is used to rotate the eccentric rollers 8 and 9 in the forward and reverse directions, respectively, at Tll.
The Iha signal is transmitted to amplifiers 454 and 452 and then to motor M1.

M2 starts rotating and one rotation continues until Tl2. As a result, the developing device 3 reaches the developing operating position at Tl3, and the developing device 4 reaches the developing device if (after Tll+ΔT1).
After that, it is placed in a developing non-operating position.

At Tl when the developing unit 3 reaches the developing operating position, a signal to rotate the developing roller 3a is sent from the CPU, and the motor M
3 starts rotating. During this time, the motor M4 that rotates the developing roller 4a is in a stopped state. After this, the image forming process progresses, and the primary charger is turned on at Tl5, the lamp is turned on at Tl6, and the transfer charger is turned on at T+r, and Tls, TIQ, and Tll0 are turned on.
each is turned off. Then, at Tll, the energization to the photosensitive tram drive motor is cut off, thereby stopping the rotation of the photosensitive tram, and the energization to the motor M3 is also cut off, so that the rotation of the developing roller 3a is stopped F-.

During this time, the transfer material P developed with the red developer is fixed by the fixing roller 14 and stacked on the intermediate tray 21 with the copy side facing down.

Next, after placing the second original on a document table (not shown), the developer selection switch 41 is selected to black, and the print switch 42 is turned on to restart the copying operation. The photosensitive drum drive motor is T
At o o, electricity is applied and the photosensitive drum l begins to rotate.

Next, in order to perform UJ exchange of the developing device, signals are sent from the CPU to the amplifiers 45, . 452 and motor M 1
, M2 starts rotation, and rotation continues until T72. As a result, the developing device 4 reaches the developing operating position at T23, and the developing device 3 moves to the non-developing position after T21+ΔT2, and is then fixed at the non-developing position.

At T2a when the developing device 4 reaches the developing operating position, a signal to rotate the developing roller 4a is sent from the CPU, and the motor M4 starts rotating. During this time, motor M3 is in a stopped state. After this, the image forming process proceeds, and the primary charger is activated at T25, the lamp is activated at T2b, and the primary charger is activated at T25.
At 21, the transfer chargers each enter the on-state state,
They are turned off at T2O, T791 and T210, respectively. In parallel with the image forming process described in L, the transfer material P is transferred to the intermediate tray 21.
The black torch image on the photosensitive drum is transferred to the transfer material P in the transfer area where the transfer number cv device 10 is arranged, and then fixed by the fixing device 71 before being discharged to the outside of the machine. . Finally, at T211, the power to the photosensitive drum drive motor is cut off and the rotation of the photosensitive drum is stopped +L, and the developing device moves to the developing operation position before the start of the forming process, and the developing roller starts rotating again. After that, the predetermined rotation is performed by the photosensitive drum t.
・Rotation stops] If no, the same jl! Stop 1- at F.

Therefore, according to the present invention, the developing device is not moved during the image exposure process and the transfer process, and the rotation of the developing roller is not stopped during the image exposure process and the transfer process.

Effects of the Invention By setting the rotation start timing of the roller to a time other than image exposure or image transfer 1111, a good image with less image blur can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a copying apparatus having a plurality of 4i developing units. FIG. 2 is a schematic cross-sectional view showing how the developing device moves. FIG. 3 is a schematic cross-sectional view illustrating the movement of the developing unit between the developing operating position and the developing non-operating position and the rotation of the developing roller. FIG. 4 is a diagram schematically showing the control circuit. FIG. 5 is a timing chart showing the timing of movement of the developing device to the developing operating position and developing non-operating position, and the relationship between the rotation of the developing roller and other units. 3.4: Developing device 8.9: Developing device movement 1 stage

Claims (1)

[Claims] An image forming apparatus comprising at least an image exposure step for forming a latent image, a developing step for making the latent image visible, and a transfer step for transferring the developed image to a transfer material. One or more developing devices are disposed around an image bearing member carrying an image, and each developing device has a developing roller, and rotates the developing roller in proximity to the image bearing member to generate the image. The developing roller is movable between a developing operating position where the latent image on the carrier is developed and a developing non-operating position where the developing roller is separated from the image carrier and stops rotating, and the developing roller starts rotating. An image forming apparatus characterized in that the process is performed except during an image exposure process or a transfer process.