JPH02226265A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent soiling by preventing the sticking of developer to a photosensitive drum or a transferring drum as an image carrier when an abnormality generates in a driving system of a developing device by providing a constitution which eliminates napping of the developer on a developing sleeve as a developer carrier. CONSTITUTION:Each developing device 1M, 1C, 1Y, and 1BK are provided so that they can travel against the photosensitive drum 2, and when each developer is in the developing position, each light shielding plate 302 to 305 shields a light sensor 301. When the developing device is not operated normally, output from the light sensor is inputted to CPU 210, and a pulse motor 201 is stopped and the traveling of the developing device is stopped. The developing device is provided with the developing sleeve 401 which rotates as the developer carrier at an opening part of a developing container 400, a pulse motor 201 is stepped out, and when a transferring carrying system is activated for ejecting of a transferring material if the developing sleeve 401 is rotated once in the direction of an arrow 407, the developer napped over the sleeve 401 are returned to inside of the developer container 400.

Description

[Detailed Description of the Invention] 1. The present invention relates to an image forming apparatus using an electrophotographic method,
In particular, a developed image is obtained by moving a developing device equipped with at least one developing device to develop a latent image formed on an image bearing member such as a photosensitive drum, and this developed image is transferred to a recording paper. It can be suitably applied to an image forming apparatus that forms an image by transferring the image to such a transfer material.

[Kandai] Conventionally, in an image forming apparatus using an electrophotographic method, a developing device equipped with a plurality of developing devices is used, for example, when developing two colors or when performing full color development. It is used.

As an example of a full-color copying machine for performing such full-color development, as shown in FIG. close to, let
2. Description of the Related Art Multicolor image forming apparatuses that develop a latent image formed on a photosensitive drum to sequentially obtain a multicolor image have been considered.

The multicolor image forming apparatus shown in FIG. 5 includes a horizontally moving developing device 1 and a photosensitive drum 2 as an image carrier.
This developing device 1 includes a moving body 1a and a magenta developing device IM, a cyan developing device 1C, a yellow developing device ty, and a black developing device IBk mounted on the moving body 1a.

During development, the required developing devices are sequentially moved to the position directly below the photosensitive drum 2 on which a latent image is formed through a predetermined process, that is, to the developing position, and a developing operation is performed. At this time, the distance between the photosensitive drum 2 and the developing sleeve of the developing device as a developer carrier is usually about 7
00#Lm, and this developing sleeve has a developing bias of approximately 500V (7) DC voltage and approximately 2KV, 1.
An AC voltage of 5KH2 is applied.

Here, the developing device 1 in the multicolor image forming apparatus indicated by L
As shown in FIG. 6, a pulse motor 201 is used as a means of moving the motor, and a gear (
(not shown) and the developing device l so as to engage with this gear.
The developing device 1 is movable in the direction of the arrow by a rack and pinion system via a gear 204 attached to the side of the moving body 1a.

However, in the above example, the movement of the developing device 1 is
This is done by driving the pulse mode controller 201, which is a so-called open loop control. □Therefore, if the load torque is stable, there will be no problem, but if unexpected excessive torque is applied to the pulse motor 201, or if the entire multicolor image forming apparatus vibrates, the developing device l may be moved. The pulse motor 201 may not be able to be controlled, resulting in an adjustment phenomenon of the pulse motor 201.

Such a step-out phenomenon can be detected using an optical sensor or the like, depending on whether the developing device moved by the pulse motor 201 is stopped at a predetermined position.
Conventionally, when a step-out occurred, an abnormal condition was displayed and the entire multicolor image forming apparatus was stopped, but this resulted in several sheets of transfer material remaining inside the multicolor image forming apparatus without being ejected, and the user This is extremely inconvenient because the next copying operation can only be performed after all of the transfer materials have been removed.

Also, when a tax adjustment occurs, the developing device is stopped, but
All the transfer material transport systems including the photosensitive drum 2 and the transfer drum 13 as a transfer material carrier in FIG. 5 are operated, and all the transfer materials inside the multicolor image forming apparatus are discharged, and then a multicolor image is formed. When stopping the apparatus, if the pulse motor loses synchronization with the developing unit clearly far away from the predetermined stop position, no particular problem will occur. Therefore, the developing sleeve is often stopped very close to the photosensitive drum 2.

In such a state, when the pulse motor is out of synchronization, the photosensitive drum 2 is activated to operate the transfer material conveyance system and discharge the transfer material.
When you rotate the developing sleeve, even if it is not rotating,
Due to the process up to that point, spikes of two-component developer, for example, have formed on the surface of the developing sleeve, and due to friction etc., the toner as the developer may adhere to the photosensitive drum 2, and furthermore, the toner may adhere to the photosensitive drum 2. This has the disadvantage that it adheres to the transfer drum 13 that is in contact with it, resulting in dirt on the back of the transfer material, resulting in a defective copy.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to prevent the remaining power from remaining in the multicolor image forming apparatus when an abnormality occurs in the drive source such as the pulse motor that drives the developing device. Even when operating a drive system other than the drive system of the developing device in order to remove the transfer material from the transfer material transport system, it is possible to prevent the developer from adhering to the image carrier and prevent the development from occurring on the transfer material carrier. An object of the present invention is to provide an image forming apparatus equipped with a developing device that can also prevent material from adhering.

The second object of "Hands for Divination" is achieved by the multicolor image forming apparatus according to the present invention. That is, to summarize, the present invention provides a movable developing device provided with at least one developing device, an image carrier carrying a latent image formed through a predetermined process, and a transfer material carrying a transfer material. and a transfer material carrier that rotates while moving the developing device, develops the latent image formed on the image carrier by moving the developing device to obtain a developed image, and transfers the developed image to the transfer material. In an image forming apparatus that forms an image by performing an image forming process, if the developing device does not move to a predetermined developing position, a means for stopping a moving means of the developing device, and a means for rotating to discharge the transfer material. The image forming apparatus is further provided with means for preventing unnecessary adhesion of developer onto the image carrier or the transfer material carrier.

That is, according to the present invention, by providing a mechanism for eliminating spikes of developer on the developing sleeve as a developer carrier, it is possible to prevent the developer from adhering to the photosensitive drum as an image carrier, and to prevent the developer from adhering to the photosensitive drum or This can prevent the transfer drum from becoming dirty.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on one embodiment thereof with reference to the accompanying drawings.

FIG. 1 shows an overall configuration diagram of an electrophotographic full-color electrophotographic copying machine as an embodiment of an image forming apparatus according to the present invention. Referring to FIG. 1, the copying machine is
The apparatus includes a developing device 1 that moves horizontally and two photosensitive drums serving as image carriers that are rotationally driven in the direction of arrow X (counterclockwise). This photosensitive drum 2 has an electrophotographic photosensitive layer on its surface.

Further, the developing device l has a moving body 1a, and this moving body la
A magenta developer 1M, a cyan developer IC, a yellow developer lY, and a black developer IBk are mounted on the top. Further, each developing device has a developer (toner) replenishing device (not shown) on the front side, and is connected to the developing device by a flexible means, so that the developing device comes into contact with the photosensitive drum 2 for a developing operation. Developer can be replenished at any time, even when moved to different locations.

Around the photosensitive drum 2, along the direction of rotation thereof, there are arranged things necessary for the image forming process, such as a charger 3, the above-mentioned developing device 1, and a transfer drum 13 as a transfer device.

The image forming process of a full-color electrophotographic copying machine having such a configuration will be described below. First, in FIG. 1, the photosensitive drum 2 rotating in the direction of the arrow
The surface is uniformly charged. Next, an original (not shown) is scanned while being irradiated with an original illumination lamp 4, and the reflected light is imaged onto a color image sensor 8 through a lens system 7 using a first mirror 5 and a folding mirror 6. let

This color image sensor 8 performs image exposure on the surface of the photosensitive drum 2 with laser light E modulated by color-separated magenta image signals, and an electrostatic latent image corresponding to magenta color is formed on the photosensitive drum 2. be done. Also, in synchronization with the image position on the photosensitive drum 2, the magenta developer IM of the developing device 1 is moved from the home position to the developing position where it comes into contact with the photosensitive drum 2, and the electrostatic latent image on the photosensitive drum 2 is developed. and visualized.

On the other hand, the recording paper T as a transfer material fed from the paper feed unit via the paper feed guide 9 and the registration roller 10, that is, the transfer paper, is transferred to the adsorption charger 11 in synchronization with a predetermined timing. It is electrostatically wound around a transfer drum 13 as a transfer material carrier by a contact roller 12 and held. This transfer drum 13 rotates in the direction of the arrow shown in FIG. 1 in synchronization with the photosensitive drum 2, and the developed image on the photosensitive drum 2 developed by the magenta developing device IM is
The image is transferred onto the transfer paper T held on the transfer drum 13 by the transfer charger 14 . The transfer drum 13 is a transfer paper T.
With the magenta toner image transferred thereon, it continues to rotate in preparation for transferring the next color.

On the other hand, the photosensitive drum 2 is neutralized by the charger 15, the toner on the photosensitive drum 2 that has not been transferred is cleaned by the cleaning member 16, and the image forming process for the -color is completed.

However, the photosensitive drum 2 continues to rotate and is charged by the charger 3 for the next color image forming process, and in the same manner as described above, in the second image forming process of the present invention, The photosensitive drum 2 is exposed to laser light E modulated by a cyan image signal, and an electrostatic latent image corresponding to cyan is formed on the photosensitive drum 2. During this time, the developing device l moves horizontally in the direction of the arrow shown in the figure, and the cyan developing device IC
is placed at a predetermined developing position and performs a developing operation.

The above process is also performed for yellow and black colors, and when the transfer of four colors is completed, the developed image on the transfer paper T is as follows.
Chargers 17 and 18 remove static electricity, and charger 19
The developed image on the transfer paper T is recharged by
is separated from the transfer drum 13 by a separating claw 20 and sent to a fixing device 22 by a conveyor belt 21, completing a series of full-color copying processes and forming a desired full-color image.

Here, the above-mentioned developing device 1 will be explained in more detail.

As shown in FIG. 2, the developing device 1 includes a motor (not shown) for rotating four color developing units LM, IC, 'lY, and IBk and a developing sleeve as a developer carrier on a moving body 1a. is installed. And pulse motor 2
01, a gear (not shown) attached to the pulse motor shaft and a gear 204 attached to the side of the moving body la of the developing device l are engaged with the gear (not shown).
The developing device 1 is movable in the direction of the arrow via a rack and pinion system.

Further, FIG. 2 shows the magenta developing device IM just at the developing position, and the magenta developing device LM is provided with a flat spring-shaped fixed electrode 203 provided and fixed on the main body side. In order to prevent the electrode 205 connected to the developing sleeve from coming into contact with the developing sleeve and causing image fogging,
An alternating developing bias is applied in which a DC voltage of about 500 V having the same polarity as the potential on the photosensitive drum is superimposed on an AC voltage of 1112 KV and a frequency of 1.5 KHz.

As for the other three color developing devices IC, IY, and 1Bk, due to the movement of the developing device 1, the electrodes 206, 207, 2 of each developing device
08 are configured to come into contact with the fixed electrode 203 one after another.

Here, as described above, the developing device 1 is driven using the pulse motor 201, and is controlled by so-called oven loop control. Therefore, there is no problem as long as the load torque is stable, but the pulse motor 201 may
may cause a step-out phenomenon.

Therefore, in the above-mentioned developing device, as shown in FIG.
Each developer is provided with a light shielding plate 302, 303, 304, 305, and an optical sensor 301 is placed on the main body side at a position where light is blocked by each light shielding plate when each developer is in the development position.
Fixed location.

With this configuration, it is possible to detect a step-out phenomenon of the pulse motor 2Of. That is, when the light shielding plate of each developer blocks the optical sensor 301, this
1, and the output of this optical sensor 301 is:
The data is input as is to the CPU (central processing unit) 210, which drives the pulse motor 201 via the motor driver 209 according to a predetermined method, and also changes the light sensor 301 from the light-blocking state to the light-receiving state. When the pulse motor 201 stops, it is determined whether the developing device has operated normally or not, depending on whether the light is blocked again.

If the developing device is not operating normally, that is, if the developing device deviates even slightly from the predetermined developing position and stops, the developing device Since there is some abnormality in the drive system of the developing device, the movement of the developing device is immediately stopped. However, the movement of the developing device is stopped after all the transfer material in the transfer material transport system inside the image forming apparatus is discharged. The photosensitive drum 2 and the transfer drum 13 are rotated, the separation claw 20 is operated, and the transfer material conveying belt 21 and the fixing device 2 are rotated.
The transfer material is discharged through 2.

The pulse motor 2 is in a state where the developing device does not stop at a predetermined position, that is, an abnormality in the drive system of the developing device.
As mentioned above, the step-out phenomenon of 01 is caused by the pulse motor 20
This mostly occurs during acceleration and deceleration. That is, when the load torque of the pulse motor 201 becomes large, the acceleration torque of the pulse motor 201 becomes insufficient, but after the pulse motor 201 reaches a steady speed, the moment of inertia of the load acts, causing step-out. There are few. Therefore, when the developing device is at a predetermined developing position, the distance between the photosensitive drum 2 and the developing sleeve is approximately 700 pLm, as described above, but even if the pulse motor 201 steps out, From the above, the developing sleeve is often located close to the photosensitive drum 2, and in this case, even if the developing sleeve is not rotating, the charged photosensitive drum is rotated to discharge the transfer material. Since spikes of developer are formed on the surface of the developing sleeve, a considerable amount of toner ends up adhering to the photosensitive drum.

The toner that has adhered to the photosensitive drum 2 in this manner adheres to the transfer drum 13 that is rotating in contact with the photosensitive drum 2, and becomes a stain on the back of the transfer material during the next copying operation.

Therefore, in the present invention, if the developing device l does not stop at a predetermined position, it is assumed that an abnormality has occurred in the drive system of the developing device.
At the same time as stopping the movement of the developing device 1, the developing sleeve drive motor (not shown) provided on the developing device 1 similarly to the developing device 1 is reversely rotated, that is, the developing sleeve is reversely rotated, thereby removing the developing image on the developing sleeve. The spikes of developer are returned to the developing device, and the spikes of developer on the surface of the developing sleeve are removed to eliminate toner on the surface, and the photosensitive drum 2 is rotated to discharge the transfer material. This prevents toner from adhering to the drum 2.

This prevention of toner adhesion will be explained with reference to FIG. 4.

FIG. 4 is a schematic cross-sectional view of a developing device of a developing device used in the image forming apparatus of the present invention. Referring to FIG. 4, the developing device includes a developing container 400 having an opening, and a partition wall is provided in the center of the developing container 400 to divide the inside of the developing container 400 into two chambers, A chamber and B chamber. In addition, a rotating developing sleeve 401 serving as a developer carrier is disposed at the opening of the developing container 400 . A fixed magnet 402 that does not rotate is disposed inside the developing sleeve 401 to cause spikes of developer containing magnetic carrier particles and toner to stand on the developing sleeve 401 . As can be easily understood by referring to FIG. 4, the magnetic pole arrangement of the fixed magnet 402 is 31, Sz,
S and N poles called Nl, Nz, and N3 are arranged alternately. Further, a regulating member 405 is disposed in the developing container 400 so as to face the opening and be close to the developing sleeve 401 to regulate the spikes of developer on the developing sleeve 401 . Note that a screw rod 40 is provided in chamber A and chamber B of the developing container 400 for stirring and transporting the developer in the developing device.
3.404 is installed.

- Since the developing device is configured as described above, during normal development, the developing sleeve 401 rotates in the direction of the arrow 406 shown by the solid line, and as a result, N3→Sz+NI→
By switching the polarity of the magnetic poles in the order of SI+NZ, the developer in the developer container A chamber is sequentially conveyed onto the sleeve 401, and is made to stand up to a certain height by the upsetting regulating plate 405. . Then, the developer whose toner has been consumed by the developing operation has the N3 pole with simultaneous polarity next to the Nz pole, so the developer magnetized by the N and poles is also repelled by the N3 pole and is transported. It does not lose its strength and falls into the developer container B chamber. The developer in the developer container B chamber is stirred and conveyed by the screw 403 together with toner supplied from a toner replenishing means (not shown), and returned to the developer container A chamber.

Next, when the pulse motor that drives the developing device is out of step and the transfer material conveyance system is operated to eject the transfer material, the toner is transferred to the photosensitive drum 2 and the transfer drum by rotating the photosensitive drum 2. In order to prevent adhesion, it is necessary to eliminate the developer on the developing sleeve 401. To eliminate the developer on the developing sleeve 401, when the developing sleeve 401 is rotated in the direction of an arrow 407 shown by a dotted line, As mentioned above, since the fixed magnet has the same polarity as the N3→Nz pole, there is no developer conveying force. therefore,
No developer exits from the developer container B chamber to the outside of the developer container. In addition, the developer that has already stood up on the developing sleeve 401 is exposed to the magnetic pole NZ + of the fixed magnet 402.
It is transported in the order of 31→N, →sz+N3 and returns to the developer container.

Therefore, when the developing device l does not stop at a predetermined position, when the developing sleeve is reversely rotated to return the developer on the surface of the developing sleeve into the developing container, there is no need to reversely rotate the sleeve drive motor for a long time. The developing sleeve only needs to rotate once.

Next, another embodiment of the image forming apparatus according to the present invention will be described.

This embodiment also has almost the same configuration as the above-mentioned embodiment, but in the above-mentioned embodiment, when the developing device l does not stop at a predetermined position due to step-out of the pulse motor, the developing sleeve is rotated in the reverse direction. This prevents toner from adhering to the photosensitive drum by trimming the developer on the developing sleeve 7. However, in this embodiment, the developing sleeve is reversed for exchanging the developer, etc. We have described the case where the developing device is equipped with a rotating mechanism, but in the future, if the developing device is made into a cartridge and the developer does not need to be replaced, it will not be used when the image forming device is operating normally and the developing device will be replaced. Providing a mechanism for rotating the developing sleeve in the opposite direction only for use when the pulse motor that drives the apparatus is out of synchronization would be wasteful in terms of cost.

Therefore, in such a case, the same effect can be obtained by controlling the developing bias applied to the developing sleeve instead of rotating the developing sleeve in the opposite direction as in the above embodiment.

That is, in the developing means of the image forming apparatus according to the present invention, as shown in FIG.
A DC voltage having the same polarity as the potential of the photosensitive drum is applied in a superimposed manner to an AC voltage for causing toner to adhere to the photosensitive drum through a jumping operation, in order to prevent image fogging.

Here, referring to FIG. 2, the developing sleeve includes an AC
Voltages from a voltage power source 213 and a DC voltage power source 217 are applied, and this voltage application is controlled by the CPU 210. That is, the AC voltage applied to the developing sleeve is set to 0N10F by the CPU 210 via the signal line 212.
The DC voltage applied to the developing sleeve is controlled by the 8-bit digital signal 214 from the CPU 210.
The output potential of the DC voltage power source 217 can be controlled by the level of an analog signal 216 that is input to the /A converter 215 and output therefrom.

Note that during normal copying, the ACC voltage is approximately 2KV, 1
．． 5KHz, DC voltage is approximately 500V<.

In the image forming apparatus of the above embodiment configured in this way,
When the pulse motor steps out and the developing device does not stop at a predetermined position, the AC voltage is changed by the output signal 212 of the CPU 210 in order to prevent toner from adhering to the photosensitive drum, that is, to prevent the developer from jumping. Turn off. In addition, if the DC voltage is set to OV, the carrier in the developer may adhere to the photosensitive drum instead of the toner, so the electric field that electrostatically attracts the carrier to the sleeve rather than the photosensitive drum is For example, the maximum output value (approximately 700 V in the multicolor image forming apparatus of this embodiment) is set so as to form the image. By means of the above-described operation, it is possible to obtain an effect similar to that obtained by cutting the spikes on the developing sleeve, as in the above-mentioned embodiments.

Next, still another embodiment of the image forming apparatus according to the present invention will be described.

In the first and second embodiments described above, the action was taken to prevent toner from adhering to the photosensitive drum, but the pulse motor that drives the developing device went out of step, resulting in ejection of the transfer material, etc. When operating the transfer material conveyance system for this purpose, in order to prevent toner from adhering to the transfer drum, the current applied to the transfer charger 14 shown in FIG. By controlling it to about A, that is, by making it lower than during normal copying, it is possible to prevent toner from adhering to the transfer drum 13.

Therefore, although some toner is wasted due to the toner adhering to the photosensitive drum 2, it is possible to prevent the back side of the transfer material from being smudged due to toner adhering to the transfer drum, which is our objective.

In the above embodiments, a full-color electrophotographic copying machine using an electrophotographic method was shown as an example, but the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Of course, the present invention can also be applied to image forming apparatuses.

As described above, according to the image forming apparatus of the present invention, when the developing device including at least one developing device is moved to the developing position to perform development and obtain an image. If the developing device does not stop at a predetermined developing position, by preventing toner from adhering to the photosensitive drum or the transfer drum, it is possible to prevent the back of the transfer material from being stained during the next copying operation.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional overall configuration diagram of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram schematically illustrating the structure of a developing device used in the image forming apparatus shown in FIG. FIG. 3 is a schematic partial perspective view illustrating step-out detection by the pulse motor of the developing device shown in FIG. 2. FIG. FIG. 4 is a schematic cross-sectional view of the developing unit of the developing device shown in FIG. 3. FIG. FIG. 5 is a schematic cross-sectional overall configuration diagram of an example of a conventional image forming apparatus. FIG. 6 is a schematic structural explanatory diagram of a developing device portion used in the image forming apparatus shown in FIG. 5. FIG. l: developing device la: moving body 1M, IC, IY, lBk: developing device 2: photosensitive drum 13: transfer drum 201: pulse motor 210: CPU 213.217: voltage power supply 214.216: signal 301: optical sensor 302. 303.304.305: Light shielding plate 401: Developing sleeve 402: Fixed magnet

Claims (1)

[Claims] 1) A movable developing device equipped with at least one developing device, an image carrier that carries a latent image formed through a predetermined process, and a transfer material carrier that rotates while supporting a transfer material. An image is formed by moving the developing device to develop a latent image formed on the image carrier to obtain a developed image, and transferring the developed image to the transfer material. In the forming apparatus, when the developing device does not move to a predetermined developing position, means for stopping the moving means of the developing device, and the image carrier or the transfer material that rotates to discharge the transfer material. 1. An image forming apparatus comprising: means for preventing unnecessary adhesion of developer onto a carrier.