JPH03271770A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent charge up phenomenum of developer by providing a mode which makes the developer on a developer carrier consumed forcibly responding to a selected transfer material carrying path. CONSTITUTION:After one side is fixed in a case of one side copying, a recording paper 21 is ejected being passed through a first and a second paper ejecting rolls 22 and 23, but in the case of both side copying, the recording paper 21 is carried to an intermediate tray 25 and is fed again by a paper refeeding roll 26. In a device provided with a multiple number of carrying paths which carry a transfer material 21, a means is provided which makes the developer on the developer carrier in developing devices 13 and 14 consumed by force according to selection of the transfer material carrying path. Thus, even when the driven time of the developing device 13 and 14 are made longer in comparison with developer consumption quantity, the charging up phenomenon of the developer is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to an image forming apparatus using an electrophotographic method or an electrostatic recording method, and particularly an apparatus for developing an electrostatic latent image formed on an image carrier with a developer. The present invention relates to an image forming apparatus having a feature of controlling image density at the time of image forming.

Conventionally, a well-known image forming apparatus that includes a step of attaching toner to an electrostatic latent image formed on the surface of an image carrier and making it visible uses a two-dimensional image forming apparatus that includes toner and a magnetic carrier as a developer. Those using component-based developers have been widely put into practical use. By the way, conventional image forming apparatuses that use such a two-component developer are generally equipped with a stirring member in the developer storage section of the developing device, and after the toner is supplied to the developer storage section, this stirring member is provided. The developer was configured to be stirred by a stirring member to uniformly disperse the toner in the magnetic carrier. Therefore, the toner generates friction with the magnetic carrier due to the above-mentioned stirring, and is charged to a desired amount of charge.

However, in the above-mentioned conventional image forming apparatus, the stirring operation of the developing device is for circulating the developer, and therefore, the stirring operation of the developing device is performed during the continuous developing operation regardless of toner replenishment. The stirring operation was performed continuously or intermittently. In this way, in a system where the toner charge amount gradually increases in proportion to the stirring time, for example, when copying a document with extremely low toner consumption, toner is not replenished and over-stirring occurs. As a result, the amount of charge on the toner becomes very large, resulting in a phenomenon of low image density due to so-called toner charge-up.

On the other hand, as copiers have become more multi-functional in recent years, there are now copiers that have a double-sided copying function that copies on both sides of a transfer material, and a multiple copying function that copies images from multiple originals on one side of the transfer material. It has increased. For copying machines with such functions,
Generally, a transfer material conveyance path for duplex and multiple copying modes is often provided separately, and the conveyance distance of the transfer material is longer during duplex and multiple copying than during normal single-sided copying. For this reason,
When performing double-sided or multiple copying, the stirring time of the developer becomes longer, and there is a risk of excessive stirring. Moreover, the driving of the developing device is
Normally, this is linked to the driving of the copying machine main body, which inevitably lengthens the driving time of the developing device, which has the problem of accelerating the charge-up phenomenon of the developer.

Additionally, a copying machine that can copy an image that does not exist on the original by superimposing it on the original image has also been commercialized (for example, Canon NP4835). This copying machine uses a laser optical system to form and synthesize a "one-point image" with a small image ratio, such as "secret", "important", "circular", etc., on a part of the original image. When such images with a small image ratio are continuously copied, the amount of developer consumed is small compared to the operating time of the developing device, so there is still a problem that the charge-up phenomenon of the developer is accelerated. Ta.

Therefore, an object of the present invention is to provide an image forming apparatus having a plurality of transfer material transport paths with a mode for forcibly consuming the developer on a developer carrier according to the selected transfer material transport path, and to An object of the present invention is to provide an image forming apparatus in which a developer charge-up phenomenon does not occur even if the device driving time becomes longer than the amount of developer consumed.

Another object of the present invention is to provide an image forming apparatus having an add-on mode with a mode that forcibly consumes the developer on the developer carrier when the add-on mode is selected, so that even when the amount of developer consumed is small, the developer is An object of the present invention is to provide an image forming apparatus in which a charge-up phenomenon does not occur.

The above-mentioned object is achieved by an image forming apparatus according to the present invention. In summary, in one aspect, the present invention provides an electrostatic latent image carrier, a latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and a developer carrying a developer. In an image forming apparatus, the image forming apparatus includes a developing device that is carried on a body and visualizes an electrostatic latent image on the electrostatic latent image carrier, and a plurality of conveyance paths that convey a transfer material. The image forming apparatus is characterized in that it has means for forcibly consuming the developer on the developer carrier according to the selection.

In another aspect of the present invention, an electrostatic latent image carrier;
a latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier; a developer supported on the developer carrier to visualize the electrostatic latent image on the electrostatic latent image carrier; In the image forming apparatus, the image forming apparatus has a developing device for overlapping a digital image on a part of the original image, and an add-on mode for superimposing a digital image on a part of the original image, including means for forcibly consuming the developer on the developer carrier according to the selection of the add-on mode. An image forming apparatus is characterized by comprising:

4凰E Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to an electrophotographic copying machine. As usual, this copying machine is equipped with a document pressure plate 1 on the upper part, and a document platen glass 3. The original (photo original, original consisting of photos and text, etc.) 2 placed on the screen is pressed.

Note that the surface of the document pressure plate 1 that comes into contact with the document table glass 3 is white. The document 2 is illuminated by a document illumination lamp 4 such as a halogen lamp, and the reflected light passes through mirrors 5a to 5C1, optical lenses 6, and mirrors 5d to 5f to form a cylindrical image rotating at a constant speed in the direction of the arrow in the figure. The image is formed on a carrier, in this example a photosensitive drum 9. Note that the original illumination lamp 4 and the mirror 5a together constitute a scanning unit, and are reciprocated for scanning by driving a motor (not shown) in the horizontal direction at a predetermined speed according to a set magnification. In addition, a lamp 4, mirrors 5a to 5f, and an optical lens 6
The first optical system is configured by the following.

In this example, a semiconductor laser, a polygon mirror,
A laser light source section 7 consisting of an imaging lens, a scanner motor, etc. is provided, and emits a laser beam based on exposure data output from a controller 12 to expose a photoreceptor drum 9 via a folding mirror 8. . This laser light source section 7 constitutes a second optical system.

Image forming means for an electrophotographic process is arranged around the photosensitive drum 9. That is, a static elimination lamp 10 that eliminates residual charges on the photoreceptor drum 9 in preparation for the image forming process, a primary charger 11 that uniformly charges the photoreceptor drum 9, and a primary charger 11 that stores, for example, a red developer, and the photoreceptor drum 9 A first developing device 1 that develops an electrostatic latent image formed in red color.
3. A second developing device 14 that stores, for example, a black developer and develops the electrostatic latent image formed on the photoreceptor drum 9 in black color.
, transfer the developed image on the photoreceptor drum 9, that is, the toner image, to a transfer material,
In this example, a transfer charger 15 that transfers to the recording paper 21, a separation charger 16 that separates the recording paper from the photoreceptor drum 9, and a cleaner 1 that collects toner remaining on the photoreceptor drum 9.
7 are sequentially arranged along the rotational direction of the photoreceptor drum 9.

Note that one of the first developing device 13 and the second developing device 14 is disposed close to the photosensitive drum 9, and the other one is disposed close to the photosensitive drum 9, depending on a developing control signal from the controller 12. The developing device is arranged at a retracted position with respect to the photosensitive drum 9.

The recording paper 21 is conveyed via the conveyance guide 20, first stops at the registration roller position, and after being synchronized with the leading edge of the toner image formed on the photoreceptor drum 9, it is fed again and transferred to the transfer area. The toner image on the photosensitive drum 9 is transferred onto the recording paper 21 by the action of the transfer charger 15. After the recording paper 21 is separated from the photosensitive drum 9 by the separation charger 16, it is transported to the fixing device 19 by the transport belt 18. The fixing device 19 fixes the toner image transferred to the recording paper 21.
Pressure is applied using a heat roller and a pressure roller.

The image is thermally fixed onto the recording paper 21. Recording paper 21 with a fixed image
The paper passes through the first paper discharge roller 22 and the second paper discharge roller 23 and is discharged.

Here, the path of the recording paper when copying on both sides of the recording paper will be explained. In the case of single-sided copying, the first side of the recording paper 21 is fixed as described above, and then is ejected through the first paper ejection roller 22 and the second paper ejection roller 23, but in the case of double-sided copying, After the trailing edge of the recording paper 21 passes through the first paper ejection roller 22 and the transfer material deflection plate 24, the second
The paper discharge roller 23 rotates in the opposite direction, and the transfer material deflection plate 24 rotates to the position shown by the broken line in the figure, so the recording paper 21 is conveyed to the intermediate tray 25, where the second layer (the negative side is Wait for copying of the opposite side).

When copying of the second layer starts, the recording paper 21 is re-fed by the re-feed roller 26, and the toner image is transferred and fixed to the second layer in the same way as for the - side, and the toner image is transferred to the paper ejection roller 22 and The paper is ejected by 23.

Next, the path of the recording paper when multiple copies are made on one side of the recording paper will be explained. After the -th transfer image is fixed, the recording paper 21 passes through the first paper discharge roller 22 and is sent to the transfer material deflection plate 24 . Transfer material deflection plate 2 for multiple copying
4 has been rotated in advance to the position shown by the broken line in the figure, the recording paper 21 is deflected downward by the deflection plate 24 and is conveyed to the intermediate tray 25 in preparation for the second copying.

The second copy is performed in the same manner as the second copy. When multiple copying is performed more than twice, the above-described copying process is repeated a predetermined number of times without ejecting the recording paper after the second transferred image is fixed, and then the paper is ejected.

FIG. 2 is a sectional view of the developing device 13. Developing device 13
The interior thereof is partitioned by a partition wall 35 into a toner storage section, which is a toner storage chamber for storing toner, and a developer storage section C, which is a developer storage chamber for storing a two-component developer containing a magnetic carrier. ing. Note that the toner stored in the toner storage portion and the developer in the developer storage portion C are omitted for clarity.

The developer storage section C is divided by a partition wall 34 into a developer stirring section C8 and a developer supply section C8 to the developer carrying member 31, which is a developer carrying member. The stored toner in the toner storage section is transferred from the toner replenishment port 36 to the developer storage section C by rotationally driving the toner transport member 39, which is a transporting means.
will be replenished within. Among the replenishment ports 36, the toner supplied from the replenishment port located on the most downstream side of the screw 33 (see FIG. 3) begins to be conveyed onto the developer carrying member 31 within a few seconds. Therefore, when the replenished toner reaches the developer carrying member 31, it must be sufficiently stirred and mixed with the developer.

Therefore, in this embodiment, as shown in FIG. 3, the toner supply port 36 disposed at the most downstream side of the screw 33 and the developer stirring section C1 are connected to the developer carrying member 31 and the developer supply section C2. A fin-like member 33b is disposed on the screw 33 between the developer amount and the opening 34b, which is a transfer portion.

According to the above configuration, a temporary turbulent flow of the developer causes a stagnation state at the position where the fin-like member 33b is disposed, and in this turbulent flow state, the developer and the supplied toner are sufficiently mixed. After that, the receiver is transported to the transfer section 34b.

The developer carrying member 31 is disposed within the developer storage section C,
It has a developing sleeve 31a made of a non-magnetic material and containing a magnet roll 31b. N in the diagram, N wealth, Ns
, S, , 5R1Ss is the IF of the magnet roll 31b
Indicates magnetic position. Since the magnet roll 31b is fixedly supported at both ends, it does not rotate, and the developing sleeve 31a disposed on the outside thereof is driven to rotate around the magnet roll 31b at a predetermined circumferential speed in the direction of the arrow in the figure.

The screws 32 and 33 are connected to the developing sleeve 31, respectively.
The two screws 32 and 33 function as a developer stirring and conveying means arranged substantially parallel to a, and the developer conveying directions of these two screws 32 and 33 are set to be opposite to each other.

In this embodiment, the developer is set to be conveyed in the direction of the arrow in FIG.

As shown in FIG. 3, the partition wall 34 provided in the developer storage section C has openings 34a and 34b (34
(described above), and between the screws 32 and 33, the developer flows through the openings 34a and 34b.
The developer is conveyed through the screws, and the developer is received and transferred between these screws. The screws 32 and 33 are provided with fin-like members 3 so that the developer can be quickly transferred.
2a, 3.2b and 33a, 33b (33b was described above) are attached at the positions shown in the figure.

Furthermore, developer storage portion C of the developing device 13 is provided with developer amount regulating members 41 and 45 for specifying a developer circulation area on the circumferential surface of the developing sleeve 31a.

A portion of the developer on the circumferential surface of the developing sleeve 31a is scraped off by a developer scraping member 43, and the rest is transported toward the developing section. The developer scraped off by the scraping member 43 is conveyed while being mixed with the developer conveyed by the developer conveyance screw 32. Further, a portion of the developer transported by the transport screw 32 passes through the opening 47 and is transported toward the developing sleeve 31a. As the developing sleeve 31a rotates, the developer transported toward the developing section facing the photoreceptor drum 9 is pushed into the gap between the developer circulation regulating member 41 and the developing sleeve 31a, and is densely and quickly delivered. transported to. Further, the height of the brush of the developer is regulated by the doctor blade 46, and the developer is conveyed to the outside of the developing device 13.

Further, at a predetermined position within the same plane as the surface of the developer amount regulating member 41 facing the developing sleeve 31a, a developer amount detecting member 42 as a developer concentration detecting means is disposed.

By arranging the developer amount detection member 42 at the above position, the developer can be quickly conveyed to the developer amount detection member 42 necessary for toner concentration control, and the developer can be properly conveyed to the developer amount detection member 42. The conditions of stirring, mixing state, and uniformity of a predetermined amount of developer and its density necessary for detection by the developer amount detection member 42 are satisfied.

In particular, since the detection surface of the developer amount detection member 42 is disposed in the same plane as the surface facing the developing sleeve, the flow of developer in the detection area and the flow of developer outside the detection area are the same, and the developer amount detection member 42 is disposed close to the developing sleeve 31a can be eliminated.

FIG. 4 shows an enlarged sectional view of the developer amount detection member 42. As shown in FIG. In this embodiment, the developer amount detection member 42 includes a lamp 42a as a light emitting body for measuring the amount of toner in the developer, the amount of light reflected by the developer from the lamp 42a, and the amount of direct light from the lamp. It is equipped with sensors 42b and 42c that respectively detect the amount of light. The housing 48 is formed of a light-shielding member, and the detection window 44 is formed of a light-transmitting member at a predetermined location on the same surface as the surface of the developer amount regulating member 41 facing the developing sleeve 31a. It is located at the location of Sensors 42b and 42c
The amount of light incident on the is converted into voltage by a predetermined circuit.

The voltages from the sensors 42b and 42c are V, , V, respectively.
C, and the reference value at which the developer reaches the specified concentration is VC.
In this case, v6 increases or decreases in accordance with the increase or decrease in toner concentration. Now, turn on toner supply so that V, = Ve.
Toner density control circuit (not shown) that provides an off signal
When ve is adjusted, the toner concentration control circuit determines that since ve is always constant, when v;1=vc, the toner concentration is high and the toner concentration is appropriate.
A signal for turning off toner supply is supplied to a controller (not shown) that drives toner transport members 39 and 4o. Further, when V b < VC, the toner concentration control circuit supplies a toner replenishment signal to the controller, and the controller supplies a toner replenishment signal having a predetermined replenishment pattern to the toner replenishment control section. The toner replenishment control section operates the toner conveying member 39 in synchronization with the replenishment pattern signal.
．． 4 degrees and supplies toner to the developer storage section C, the toner concentration of the developer is controlled to a predetermined value.

The results of implementing the present invention using such a copying machine will be described below. With this copier, it takes about 10 seconds to make an A4 size copy, and about 15 seconds to make the first multiple copy.
The second copy takes about 10 seconds, the first side of duplex copying takes about 17 seconds, and the second copy takes about 10 seconds. The time required for this copying is the driving time of the main motor and the developing device.

FIG. 5 shows the change in image density by the developing device 13 when copying -sheets is repeated using a document with developer consumption of approximately 0.05 g/sheet (A4 size). . In the figure, a graph (a) indicated by a solid line is a case where single-sided copying is repeated using only the first developing device 13, and a graph (b) indicated by a broken line is a case where the first developing device 13 is used for the -th copying. is used, and the second developing device i1 is used for the second copying.
4, a blank sheet of paper was used as the original for the second copy, and multiple copies were repeated. Graph (C) shown by the dotted line is the same copy mode as graph (b), but In this experiment, we used a mode in which a latent image was formed that consumed 0.025 g of developer after the first original image development by the first developing device 13, and was then developed by the second developing device 14. This figure shows the change in image density when multiple copying (in which a solid latent image is formed and about 0.025 g of developer is consumed by developing this latent image) is repeated.

As is clear from Figure 5, the image density is stable in single-sided copying of graph (a), whereas in multiple copying of graph (b) using a blank original for the second time, as the number of copies increases, It can be seen that the image density is decreasing. However, in graph (C) using the original using the present invention, that is, consuming 0.025 g of developer for the second time, the graph (
It can be seen that the image density is stable despite the same multiple copying as in b).

A possible cause of this is charge-up of the developer. FIG. 6 shows the correlation between the rotation time of the developing device and the amount of charge of the developer. The graph (a) shown by the solid line in the figure is the graph (b) when no developer is consumed, and the graph (b) shown by the - dotted chain line.
) shows the change in the amount of charge of the developer when the developer is consumed at a rate of 0.05 g/10 seconds.

In this experiment, it was confirmed that when the amount of charge of the developer exceeds 20 μC/g, the image density becomes less than 1.0. As is clear from Figure 6, when the developer is not consumed, the same developer is always stirred and mixed, so the amount of charge increases, whereas when the developer is consumed, the amount of charge increases. It can be seen that the amount of charge becomes stable because the amount of developer is newly supplied and the developer is replaced.

Thus, in the present invention, when it is known in advance that the driving time of the developing device will be long, that is, when multiple copying or double-sided copying mode is selected, the forced consumption of developer is performed in conjunction with the mode selection button. When this mode was executed, the developer charge-up phenomenon did not occur, and therefore, the drawback of low image density due to developer charge-up could be prevented. Similarly, if you know in advance what kind of latent image it is and the amount of developer consumed, that is, in add-on mode, the developer is forced to be consumed in conjunction with the selection of the add-on character or mark. Even when this mode was executed, it was possible to prevent image density loss due to developer charge-up.

In this example, conversion was performed using the driving time of the developing device and the amount of developer consumed so that the amount of developer consumed per one-sided copy (A4 size) was approximately 0.05 g. In other words, based on the standard development device drive time of 10 seconds for single-sided copying (A4 size) - sheet, the development device drive time is 15 seconds when multiple copy mode is selected, so 50% of 0.05g. A solid latent image of 1 mm width was formed and developed using 0.025 g of developer, and the developer was forcibly consumed. Also, since the developing device driving time is 17 seconds when double-sided copying mode is selected, 70% of 0.05g
A solid latent image with a width of 1.4 mm was formed and developed using 0.035 g of developer material, and the developer was forcibly consumed. Furthermore, if you select the character "Secret" in add-on mode, the developer consumption for this image is approximately 0.01
g, so 0, which is 0.01g from 0.05g,
A solid latent image with a width of 1.6 mm was formed and developed using 0.04 g of developer bone, and the developer was forcibly consumed.

The solid image is formed by operating the primary charger 11 in the non-transfer area after the image formation is completed, and by exposing the area other than the necessary solid image to light with the second optical system 7 to remove the charged charges. Ta. Further, in this embodiment, the developed solid image is not transferred onto the recording paper, but is removed as it is by the cleaning member. Of course, it is also possible to adopt a configuration in which a solid image is transferred onto recording paper.

A flowchart of this embodiment is shown in FIG. This flowchart is a summary of the operations described above, so I don't think there is any need to explain it, but I would like to add that in the judgment box "Double-sided copy", the case of output rNOJ corresponds to the selection of multiple copy mode. .

In the first embodiment described above, an apparatus using a developer having a magnetic carrier and a toner, that is, a two-component developer, is described, but the present invention is not limited to this, and the amount of charge of the developer is This is effective for all devices that vary depending on the operating time of the developing device or the amount of developer consumed.

Further, in the first embodiment, a digital optical system using a laser is used as the second optical system, but the present invention is not limited to this, and for example, other exposure means such as LE'D, etc. can also be applied to devices without a second optical system. Further, the conveyance path of the transfer material is not limited to a conveyance path for double-sided copying or multiple copying, and can be applied to an apparatus having conveyance paths with different lengths even for single-sided copying.

In the first embodiment described above, the present invention was applied to one developing device, but the present invention may be applied to multiple developing devices.In addition, in the case where there is a plurality of developing devices, the present invention can be applied to all developing devices. The present invention can also be applied to some developing devices. moreover,
The forced consumption amount of developer may be the same for all developing devices, or may be changed depending on the characteristics of the developer.

The method of forced consumption is not limited to the development of a solid image, and instead of developing a certain pattern latent image or consuming it on an electrostatic latent image carrier, an electrode is provided opposite the developer carrier, and this method is used. It is also possible to develop the electrode. Further, the method is not limited to forcibly consuming the developer for each copy, but may be forcibly consumed once for each copy of a plurality of sheets.

In the first embodiment described above, toner is forcibly consumed when the add-on mode is selected, but for example, a button for selecting the density of the document and the type of document, such as a solid image or a character image, is provided as a user selection button, and the user can select the button. The presence or absence of forced consumption or the amount of consumption may be controlled in conjunction with the button.

In the first embodiment, the present invention is applied to an electrophotographic copying machine, but the present invention can also be applied to other image forming apparatuses such as printers, and image forming apparatuses of other types such as electrostatic recording. can be applied, and of course the configuration of the image forming apparatus is not limited to that of the first embodiment.

As explained above, in the image forming apparatus according to the present invention, which has a plurality of transfer material conveyance paths having different lengths, the image forming apparatus according to the present invention is capable of carrying the developer depending on the selected transfer material conveyance path. Since we have set up a mode that forcibly consumes the developer on the body,
Even if the driving time of the developing device is longer than the amount of developer consumed, the charge-up phenomenon of the developer can be prevented, and the disadvantage of low image density due to the charge-up of the developer can be avoided, which is a remarkable effect.

In addition, when it is known in advance that a latent image with predicted developer consumption will be copied, such as in add-on mode,
Since we have provided a mode that forcibly consumes the developer according to the consumption amount, it is also possible to prevent the developer charge-up phenomenon, which has the remarkable effect of eliminating the drawback of low image density due to developer charge-up. There is.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view of the developing device of the image forming apparatus shown in FIG. FIG. 3 is a top view of essential parts of the developing device shown in FIG. 2. FIG. 4 is an enlarged sectional view of the developer concentration detection section of the developing device shown in FIG. 2. FIG. 5 is a diagram showing the difference in the transition of image density depending on the copy mode. FIG. 6 is a diagram showing the correlation between the rotation time of the developing device and the amount of charge of the developer due to the difference in developer consumption. FIG. 7 is a flowchart illustrating the operation of the image forming apparatus according to the present invention. 7: Second optical system 9: Photosensitive drum (image carrier) 11 Primary charger 12: First optical system 13: First developing device 14: Second developing device 21: Recording paper 31: Developing Agent carrying member

Claims (1)

[Scope of Claims] 1) an electrostatic latent image carrier, a latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and a developer carried on the developer carrier; In an image forming apparatus that includes a developing device that visualizes an electrostatic latent image on an electrostatic latent image carrier and a plurality of conveyance paths that convey a transfer material, the An image forming apparatus comprising means for forcibly consuming the developer on the developer carrier. 2) an electrostatic latent image carrier, a latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, a developer supported on the developer carrier; In an image forming apparatus that has a developing device that visualizes an electrostatic latent image on the developer carrier, and an add-on mode that superimposes a digital image on a part of the original image, the amount of the electrostatic latent image on the developer carrier changes depending on the selection of the add-on mode. An image forming apparatus comprising means for forcibly consuming developer.