JPH0954535A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a deterioration in image quality caused by the fact that toner in a state where first and second toners are mixed is reused in a first developing device normally using the first toner by selectively carrying the toner recovered with a cleaning device to a waste toner bottle or the first developing device. SOLUTION: The toner in the state where red and black toners are mixed, which is recovered by the cleaning device 10 is carried to a waste toner tank 14 with a pipe 13 and the toner of only the black toner recovered by the cleaning device 10 is carried to the first developing device 4 with a pipe 11. The state where the toner of a mixture of the red and black toners does not remain in the cleaning device 10 is obtained, the toner of only the black toner is carried to the first developing device 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.
The present invention relates to an image forming apparatus having a plurality of developing devices and capable of forming an image formed by superposing a plurality of toner images formed by the respective developing devices.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this type, a first toner image obtained by developing a first latent image formed by a latent image forming means on a latent image carrier by a first developing device and a latent image carrier. It is known that the second latent image formed by the latent image forming means is superposed with a second toner image developed by a second developing device to form a plural toner image in which plural toner images are superposed (hereinafter , Known device 1). In the known apparatus 1, for example, a latent image corresponding to an image portion desired to be formed in black is formed as a first latent image, and a latent image corresponding to an image portion desired to be formed in red is formed as a second latent image. By forming and developing each latent image with black toner or red toner, it is possible to form a plurality of toner images in which the black toner image as the first toner image and the red toner image as the second toner image are superimposed. .

Further, the toner remaining on the surface of the latent image carrier after the transfer of the toner image is collected by the cleaning device, and the collected toner is conveyed to the developing device by the toner conveying means, and this toner is collected. An image forming apparatus used for forming an image again is known (hereinafter, known apparatus 2).
In the known device 2, waste of toner can be eliminated.

However, when the known device 1 and the known device 2 are used in combination, a new problem occurs. That is, both the first toner and the second toner remain on the latent image carrier after the transfer of the first toner image and the second toner image when forming a plurality of toner images.
Therefore, when the cleaning device collects the residual toner and conveys it to the developing device, toner different from the toner originally used in the developing device is mixed in the developing device. Specifically, when the collected toner is conveyed to the first developing device, not only the first toner, which is the toner originally used in the developing device, but also the second toner is conveyed, and the collected toner is collected. When the toner is conveyed to the second developing device, not only the second toner which is the toner originally used in the developing device but also the first toner is conveyed. In such a case, in the subsequent developing operation, the toner mixed with the toner different from the toner originally used is used for the development, which causes a problem that the image quality of the formed image is deteriorated.

Some of the publicly known documents have a description related to such problems, so that they will be introduced. For example, JP
No. 2-9383, JP-A-62-163084, and JP-A-5-165380, a toner collected from a latent image carrier by a cleaning device is separated into a first toner and a second toner, The toner is collected in the first developing device, but the second toner is discarded.
Known device 3) is disclosed.

Further, for example, Japanese Patent Laid-Open No. 58-130373.
No. 6-118845, Japanese Utility Model Laid-Open No. 58-1130.
No. 61, No. 58-115763, No. 58-1
No. 15764 and No. 58-180566, the toner collected by the cleaning device is sorted by, for example, the difference in the physical properties, the first toner is sent to the first developing device, and the second toner is sent to the second toner. An image forming apparatus (hereinafter, referred to as a known apparatus 4) that conveys to a second developing device is disclosed.

[0007] Further, for example, JP-A-54-113340
In the publication, an image forming apparatus (hereinafter referred to as a known apparatus 5) collects the toner in a state in which the first toner and the second toner collected by the cleaning device are collected in the first developing device without performing a separation process. It is disclosed. The known device 5 does not include a device for separating the first toner and the second toner, so that the structure of the device can be simplified.

[0008]

Certainly, according to the known device 3 and the known device 4 described above, the toner collected by the cleaning device is separated into the first toner and the second toner, which is different. It seems that it is possible to prevent the deterioration of the image quality due to the toner containing a mixture of toners being conveyed to each developing device and being developed by the toner. However, even if these known devices are used, problems still remain. That is, even if the known device 3 or the known device 4 is used, it is difficult to completely separate the first toner and the second toner, and the toner after the separation processing contains some other types of toner to some extent. Exists. Therefore, an image formed using such toner does not always have a satisfactory quality.

Further, in the known device 5, priority is given to simplifying the structure of the device, and the deterioration of the image quality caused when the image is formed by using the toner in the state where the first toner and the second toner are mixed is solved. It is abandoned to do. Therefore, it cannot be used at all for the purpose of improving the image quality.

The present invention has been made in view of the above problems. An object of the present invention is to form an image by forming a plurality of developing devices by superposing toner images formed by the developing devices. In this device, it is possible to prevent deterioration of image quality due to image formation due to toner mixed with different kinds of toner, which occurs when the toner remaining on the surface of the latent image bearing member is recovered and reused. An object is to provide an image forming apparatus that forms a good image.

[0011]

In order to achieve the above object, an image forming apparatus according to any one of claims 1 to 6 has a latent image carrier and a first latent image and a first latent image on the surface of the latent image carrier. A latent image forming unit capable of forming two latent images, a first developing device for developing the one latent image to form a first toner image, and a second toner image for developing the second latent image. A second developing device for forming a first latent image by the latent image forming means, and developing the latent image by the first developing device to form a single toner image consisting of only the first toner image. A toner image forming mode, a first latent image and a second latent image are formed by the latent image forming means, and each latent image is developed by the first developing device and the second developing device, respectively. And an image forming apparatus capable of switching between a plurality of toner image forming modes for forming a plurality of toner images including a second toner image. A cleaning device for collecting the toner remaining on the latent image carrier after the single toner image or the plurality of toner images are transferred, and a first device for conveying the toner collected by the cleaning device to the first developing device. A toner conveying unit, a second toner conveying unit that conveys the toner collected by the cleaning device to a waste toner tank, a first state in which the cleaning device and the first developing device communicate with each other, and the cleaning device. Switching means for switching between a second state for communicating with the second conveying means and a second state for forming the plurality of toner images. The device is kept in the second state for a certain period of time after completion.

Here, in order to "switchable" between the single-toner image forming mode and the plural-toner image forming mode, for example, a mode changeover switch is provided on the operation panel of the apparatus casing, and the switch is operated by the operator. It is possible to adopt a configuration in which the mode is switched by operation. Further, as the “first toner transporting device” and the “second toner transporting device”, for example, a configuration in which a screw, an auger or the like for transporting toner by rotation is provided in a toner transporting pipe can be adopted. As the "switching means", for example, a valve is provided in the vicinity of the branch point between the pipe forming the first toner conveying means and the pipe forming the second toner conveying means, and the valve is moved by a solenoid. A configuration that brings the device into a desired state can be adopted. In addition, in order to "keep the device in the second state by the switching means when forming a plurality of toner images and keep the device in the second state for a certain period of time after the formation of the plurality of images is completed", For example, it is possible to adopt a configuration in which a microprocessor causes the solenoid to move the valve at a desired timing.

Further, as the "fixed time", the toner remaining on the latent image carrier after the transfer of the plurality of toner images collected in the cleaning device by the cleaning device is carried out from the cleaning device by the first toner conveying means. Thus, it is possible to employ a sufficient time so that the image quality of the next single toner image is not adversely affected.
Further, more specifically, as the “certain time”, the toner remaining on the latent image carrier after the transfer of the plurality of toner images collected by the cleaning device does not remain in the cleaning device, and the second conveying unit As a result, it is possible to make the time sufficient to convey the toner to the waste toner tank. Further, this “fixed time” may be taken immediately after the formation of the plural toner images and the apparatus may be set to the second state at this point, or the apparatus may be set to the “fixed time” second state at the time after the formation of the plural toner images. May be set.

In the image forming apparatus according to any one of claims 1 to 6, when the single toner image is formed, the apparatus is in the first state, that is, the cleaning device and the first developing device are communicated by the first toner conveying means. Is in a state. Therefore, the first toner collected from the latent image carrier in the state where the transfer of the single toner image is completed is conveyed to the first developing device,
It will be used for subsequent image formation. Further, in such an image forming apparatus, the apparatus is kept in the second state for a certain period of time after the formation of a plurality of toner images is completed. Therefore, the toner in a state in which the first toner and the second toner collected from the latent image carrier after the transfer of the plurality of toner images are reliably conveyed to the waste toner bottle without remaining in the cleaning device. It

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the single toner image is formed after the formation of a plurality of toner images is completed, the aforesaid fixed time has elapsed. It is characterized in that the apparatus is brought into the first state by using the switching means and thereafter the formation of a single toner image is started. Here, in order to "set the apparatus to the first state using the switching means after a lapse of a fixed time and then start the formation of a single toner image", for example, a microprocessor uses the solenoid. The valve may be moved at a desired timing, and the driving member including the first developing device may be driven and stopped at a desired timing.

In the image forming apparatus according to claim 2,
The toner is kept in the first state for a certain period of time after the formation of a plurality of toner images, and the toner in the state where the first toner and the second toner collected from the latent image carrier are mixed in the cleaning device. It is reliably conveyed to the waste toner bottle without remaining. Then, during the subsequent formation of the single toner image, the first toner is collected from the latent image carrier after the single toner image is transferred by the cleaning device in an empty state, and the first toner is conveyed. It is conveyed to the first developing device by the means.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, wherein the single toner image is formed after the formation of the plurality of toner images is completed, the aforesaid predetermined time has elapsed. It is characterized in that formation of a single toner image is started prior to bringing the apparatus into the first state by using the switching means. Here, in order to "start the formation of a single toner image before the apparatus is brought into the first state by using the switching means after a lapse of a fixed time", for example, the image of claim 2 As with the forming device, the microprocessor moves the valve at a desired timing using the solenoid, and
Drive the driving member including the first developing device at the desired timing.
A configuration of stopping can be adopted.

In the image forming apparatus according to claim 3,
The formation of a single toner image is started before the lapse of a certain period of time in which the apparatus is kept in the second state after the formation of a plurality of toner images is completed. Therefore, the waiting time required to start the formation of a single toner image after the completion of formation of a plurality of toner images, which is required in an apparatus that starts the formation of a single toner image after the lapse of the certain time, becomes unnecessary. In addition, since the apparatus is kept in the second state for a certain period of time after the formation of the plural toner images is completed, the first toner and the second toner in the cleaning apparatus are kept. The mixed toner is not conveyed to the first developing device.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect, wherein negatively charged toner is used as the first toner and the second toner, and the cleaning device includes a housing portion. A screw for discharging the toner collected from the casing, the screw being provided so as to come into contact with the casing, and the portion of the casing and the screw in contact with the negatively charged toner is made of a fluorine resin. It is characterized by that. Here, in order to “make the portion in contact with the negatively-charged toner consist of a fluorine resin” between the casing and the screw, for example, each member is formed of a material containing a fluorine resin, or each member is made of a fluorine resin. It may be coated.

According to the image forming apparatus of the fourth aspect, since the negatively charged toner is less likely to adhere to the portion of the casing or the screw which is in contact with the negatively charged toner, and the toner is easily released from the fluorine resin. The negatively charged toner hardly adheres to the portion, and the negatively charged toner is properly discharged from the cleaning device.

An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the first aspect, wherein positively charged toner is used as the first toner and the second toner, and the cleaning device includes a housing portion. A screw for discharging the toner collected from the casing, the screw being provided so as to come into contact with the casing, and the portion of the casing and the screw in contact with the positively charged toner is made of a silicone resin. It is characterized by that. Here, in order to "make the portion in contact with the positively charged toner of the silicone resin" of the casing and the screw, for example, each member is formed of a material containing a silicone resin, or each member is made of a silicone resin. It may be coated.

According to the image forming apparatus of the fifth aspect, since the positively charged toner is less likely to adhere to the portion of the housing or the screw that is in contact with the positively charged toner, the silicone resin has good releasability from the toner. The positively charged toner hardly adheres to the portion, and the positively charged toner is satisfactorily discharged from the cleaning device.

An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the first aspect, wherein charged toner is used as the first toner and the second toner, and the cleaning device includes the housing portion and the second toner. A screw for discharging the toner collected from the casing, the screw being provided so as to come into contact with the casing, and the resistance of the casing and the portion of the screw in contact with the charged toner is 10 ¹⁰ Ωcm. It is characterized by the following. Here, “the resistance value of the portion of the casing and the screw in contact with the charged toner is 10 ¹⁰
For example, each member may be formed of a material having a resistance value of 10 ¹⁰ Ωcm or less, or each member may be coated with a material of 10 ¹⁰ Ωcm or less.

According to the image forming apparatus of the sixth aspect, the resistance value of the portion of the casing or the screw in contact with the charged toner is 1
Since it is 0 ¹⁰ Ωcm or less, its resistance value is 10 ¹⁰ Ωcm
As compared with the above case, the charged toner is less likely to adhere to the portion, and the positively charged toner is favorably discharged from the cleaning device. (Hereinafter, margin)

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus.
An embodiment, which is one of the things that the applicant thinks is the best, will be described. FIG. 1 is a schematic configuration diagram of a copying machine according to this embodiment, and FIG. 2 is a perspective view showing a main part of the copying machine.

First, the schematic construction of this copying machine will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, this copying machine is charged by a photosensitive drum 1 as a latent image carrier that rotates in the direction of the arrow, a first charging charger 2 that charges the surface of the drum, and a first charging charger 2. Photoconductor drum 1
An optical writing device (not shown) as a latent image forming means for forming a first latent image on the surface of the sheet, and develops the first latent image formed by the optical writing device to form a black toner image as the first toner image. A first developing device 4 for forming, a second charging charger 5 for charging the surface of the photosensitive drum 1 on which black toner is formed, and a second latent image formed by the above-mentioned optical writing device for developing and second The second developing device 7 for forming a toner image and the like. Here, as the photosensitive drum 1,
A photosensitive layer having a negatively charged organic photosensitive layer is used. Further, as the above-mentioned optical writing device, a device for forming the first latent image and a device for forming the second latent image may be configured as separate bodies, or they may be integrally formed.

This copying machine also transfers a toner image formed on the surface of the photosensitive drum 1 onto a transfer paper 8 which is conveyed from the right side in FIG. 1 by a conveying device (not shown). Photosensitive drum 1 after the toner image is transferred
Cleaning device 1 for collecting the toner remaining on the surface of the sheet
0 is provided. And this cleaning device 10
Is connected to the first developing device 4 via a pipe 11 forming a first toner conveying means, and is also connected to a waste toner tank 14 via a pipe 13 forming a second toner conveying means. In addition, a valve 21 driven by a solenoid 20 (see FIG. 2) is provided in the vicinity of the branch portion between the pipe 11 and the pipe 13. This valve 2
1 functions as a switching unit that switches between a first state in which the cleaning device 10 and the first developing device 4 communicate with each other and a second state in which the cleaning device 10 and the waste toner tank 14 communicate with each other.

As shown in FIGS. 1 and 2, the cleaning device 10 comprises a casing 10a and a blade 10b for scraping off the toner remaining on the surface of the photosensitive drum 1 attached to the casing. . Further, a screw 12 for transporting the toner cut off by the blade 10b to the outside of the casing is installed in the casing 10a. Also,
Inside the pipe 11, an auger 11 a for conveying the toner forming the first toner conveying means to the first developing device 4 is provided.

This copying machine having the above-mentioned structure forms a single toner image consisting of only a black toner image and a plural toner image forming mode for forming a plural toner image in which a black toner image and a red toner image are superposed. The copying machine is capable of switching between the single toner image forming mode and the single toner image forming mode. Then, for example, the operator can selectively form a plurality of toner images and a single toner image by operating a mode changeover switch (not shown) provided on the operation panel. The image forming operation (copying operation) of each of the plural toner image forming mode and the single toner image forming mode will be described below.

First, the copying operation in the multi-toner image forming mode will be described. In this mode, the surface of the photosensitive drum 1 is set to −80 by the first charging charger 2.
A latent image for forming a negative N / P black toner image as a first latent image is formed on the surface of the drum, which is charged to 0 V and subjected to this charging process, by the exposure light 3 from the optical writing device. . Then, this latent image is developed by the first developing device 7 using negatively charged toner, and a black toner image is formed on the surface of the photosensitive drum 1. Further, the surface of the drum on which the black toner image is formed is recharged by the second charging charger 5 so as to have a substantially uniform potential including the portion where the black toner is attached, and the exposure light 6 from the optical writing device is charged. Thus, a latent image for N / P red toner image formation is formed as a second latent image. Then, this latent image is developed by the second developing device 7, and a red toner image is formed on the surface of the photosensitive drum 1. When a device that directly writes by the reflected light when the original is irradiated is adopted as the optical writing device,
The exposure light 3 and the exposure light 6 are read at the same time. Further, since the non-contact developing device is adopted as the second developing device 7, when the red toner image is formed, the black toner image formed on the surface of the photosensitive drum 1 prior to this is not disturbed. .

A plurality of toner images formed by superposing the black toner image and the red toner image thus formed on the surface of the photosensitive drum 1 are transferred to the transfer paper 8 by the transfer device 9 and are not shown. The image is fixed by the fixing device and copying is completed. On the other hand, the toner remaining on the surface of the photoconductor drum 1 after the transfer is removed by the blade 10c and the casing 10a.
Collected inside.

The toner collected in the housing 10a is
By the rotation of the screw 12, the screw 12 is conveyed to the outside of the casing and drops into the waste toner bottle 14 via the pipe 13. In the multi-toner image mode, the valve 21 is located at a position where the cleaning device 10 communicates with the waste toner bottle 14 (position shown by a dotted line in FIG. 2), and a position where the cleaning device 10 communicates with the first developing device 4. (The position indicated by the solid line in FIG. 2) is not present. Therefore, the toner in a state in which the collected black toner and red toner are mixed is not conveyed to the first developing device 4, and drops into the waste toner bottle 14 as described above. As a result, not only the black toner but also the red toner is transported to the first developing device 4, and the image quality is not deteriorated due to the transport of the red toner to the first developing device 4. The state in which the cleaning device 10 and the waste toner bottle 14 communicate with each other corresponds to the second state, and the state in which the cleaning device 10 and the first developing device 4 communicate with each other corresponds to the first state.

Next, the copying operation in the single toner image forming mode will be described. In the copying operation in this mode, although the charging by the second charging charger 5, the formation of the second latent image by the exposure light 6 and the development by the second developing device 7 performed in the multi-toner image forming mode are not performed, The operation is the same as in the multiple image forming mode. That is, the surface of the photoconductor drum 1 is charged by the first charging charger 2, the first latent image is formed by the exposure light 3, and the latent image is developed by the first developing device 7 and is transferred to the surface of the photoconductor drum 1. A black toner image is formed.

Then, the single toner image consisting only of the black toner image is transferred onto the transfer paper by the transfer device 9 and fixed by the fixing device (not shown) to complete the copying. Also,
The toner remaining on the surface of the photosensitive drum 1 after the transfer is removed by the blade 10c and collected in the housing 10a as in the multiple image forming mode.

The collected toner is conveyed to the waste toner bottle 14 in the plural image forming mode, but is conveyed to the first developing device 4 in this mode. That is,
The toner collected in the casing 10a is conveyed to the outside of the casing by the rotation of the screw 12, and is further conveyed to the first developing device 4 by the rotation of the auger 11a via the pipe 11. In this mode, the cleaning device 10 and the first developing device 4 communicate with each other (the position shown by the solid line in FIG. 2). As a result, the cleaning device 1
The black toner collected at 0 comes to be reused in the first developing device 4. Note that the toner collected by the cleaning device 10 in the single-toner image forming mode does not contain red toner, so that the image quality does not deteriorate even if it is reused by the first developing device 4.

As described above, in this copying machine, in the multi-toner image forming mode, the toner in the state in which the black toner and the red toner collected by the cleaning device 10 are mixed is conveyed to the waste toner bottle 14 and discarded. While doing
Cleaning device 1 in single toner image forming mode
The black toner collected at 0 is conveyed to the first developing device 4 and reused. Therefore, it is possible to prevent the occurrence of an image defect due to the red toner being conveyed to the developing device 4 and being used by the developing device 4 while effectively utilizing the toner.

However, even when the image formation is performed by the operation described above, when the image formation in the single image formation mode is performed after the image formation in the image formation mode in the plural toner image formation mode is completed, Image quality may be degraded in a single toner image formed in the single image forming mode. This is because in such a case, the red toner may be conveyed from the cleaning device 10 to the first developing device 4, and the red toner may be used for forming a black toner image in the first developing device. That is, at the time when the image formation in the plural image formation mode is completed, the toner in which the red toner and the black toner are mixed remains in the cleaning device 10. Therefore, if an image is formed in the single-toner image forming mode immediately in this state, the toner is conveyed to the first developing device 4 and causes an image defect.

Therefore, in this copying machine, after the formation of a plurality of toner images is completed, the apparatus is put in the second state for a fixed time t1, that is, the cleaning device 10 and the waste toner bottle 1.
4 is maintained in communication with each other, and at least the screw 12 is brought into a driven state (rotated state) in this state. As a result, the toner containing the red toner remaining in the cleaning device 10 at the time when the formation of the multiple toner images is completed is conveyed to the waste toner bottle 14, and when the single toner image is formed, the toner becomes the first toner. It is designed so that it is not conveyed to one developing device 4.

Here, the fixed time t1 is the length of the cleaning device 10 in the width direction (depth direction in FIG. 1),
Although it cannot be uniformly set because it depends on the toner conveying speed of the screw 12 and the like, the toner including the red toner remaining in the cleaning device 10 when the formation of the plurality of toner images is completed is completely removed from the cleaning device 10. It may be sufficient time to be discharged to. For example, when the toner transport speed of the screw 12 is v (mm / sec) and the distance to be transported to discharge the toner including the red toner from the cleaning device 10 is L (mm), t1 is L / v (seconds).

FIGS. 3 (a) and 3 (b) are timing charts showing the operation of the copying machine when a single toner image is formed after the formation of a plurality of toner images as described above. is there. In both figures, the time when both the first developing device and the second developing device are in the ON state indicates that the device is in the process of forming a multi-toner image (multi-toner image forming mode). Then, when only the first developing device is in the ON state and the second developing device is in the OFF state, it indicates that the device is in the process of forming a single toner image (single toner image forming mode). Even in the multi-toner image forming mode, however, the photoconductor drum 1 is close to the end thereof.
Only the second developing device located downstream of is ON.

In the operation shown in FIG. 3A, after the red toner is removed from the cleaning device 10 after a predetermined time t1 has elapsed from the time A when the formation of the plural toner images is completed, the operation B is performed.
At this point, formation of a single toner image is started. On the other hand, in the operation shown in FIG. 3B, although the formation of the single toner image is started immediately at the time A when the formation of the plurality of toner images is completed, even if the single toner image is being formed,
The device is kept in the second state from the time point until a certain time t1 has elapsed. In any operation, since the toner including the red toner is discharged from the cleaning device 10 and the toner is conveyed from the cleaning device 10 to the first developing device 4, the red toner is mixed in the first developing device 4. There is no such thing. However, if the operation shown in FIG. 3B is adopted, the waiting time t2 from the completion of formation of a plurality of toner images to the formation of a single toner image required in the operation shown in FIG. 3A is unnecessary. Therefore, the time required for copying can be shortened.

In the above description, the surface of the photosensitive drum 1 is negatively charged and a negative N / P latent image is formed on the surface.
Although the configuration in which the latent image is developed using the negatively charged toner has been described, instead of this, the surface of the photosensitive drum 1 is positively charged to form a positive N / P latent image on the surface, and the latent image is formed. It is also possible to adopt a configuration in which the toner is developed using positively charged toner.

[0043]

【Example】

[Example 1] Hereinafter, a first example showing the copying machine according to the exemplary embodiment more specifically will be described.

In the copying machine of this embodiment, the surface of the photosensitive drum 1 is negatively charged and a negative N / P latent image is formed on the surface.
The latent image is developed using negatively charged toner. In addition, as shown in FIG. 4 which is an explanatory view of the cleaning device in which an area A surrounded by a dotted line in FIG.
The screw 12 attached to a is the bottom 10 of the housing.
It is provided so as to lightly contact c. Here, the angle θ of the region where the screw 12 and the housing bottom portion 10c are in contact with each other with respect to the rotation axis of the screw is 200 degrees. In addition, it is desirable to set θ in the range of 120 degrees to 240 degrees. If θ is larger than this, the toner in the housing 10a is less likely to reach the screw 12, and if θ is smaller than this, the toner reaching the screw 12 is not properly conveyed by the screw. This is because the above-mentioned harmful effect is likely to occur.

As the material for the bottom part 10c of the housing, a baitlon rubber plate (commercially available from Inei Seieidou) having a thickness of 2 mm, which is fluorine rubber, is used. And screw 12
As a SUS screw, a mixture of Lumiflon F200 (Fusso resin manufactured by Asahi Glass Co., Ltd.) dissolved in a solvent and 10 wt% of Ketchin black (carbon manufactured by Akzosimy) was applied by a spray method, and further 100 ° A coating-treated product by drying at C for 30 minutes is used. The coating thickness of the screw 12 is about 10 to 100 μm, and the resistance is about 10 ⁷ to 10 ⁸ Ωcm.

In this example, in which the screw 12 was coated with the above coating, it took 15 to 30 seconds when the screw without the coating was used.
The time for discharging the toner from the cleaning device 10 having a length of 35 cm in the width direction (depth direction in FIG. 1) is
It is reduced to about 10 seconds. Further, after the toner is discharged, the toner does not adhere to or remains on the screw 12 or the housing bottom portion 10c, and the toner is properly removed. This is screw 1
This is because the portions of the housing 2 and the housing bottom portion 10c that come into contact with toner are made of fluorine that is difficult to adhere to the negatively charged toner. Further, the screw 12 and the housing bottom portion 10c have an electric resistance of 1
The fact that it is made of a material of 0 ¹⁰ Ωcm or less also contributes to making it difficult for toner to adhere.

In this embodiment, since rubber which is an elastic body is used for the bottom 10c of the housing, the bottom and the screw 12 are used.
Can be brought into contact with each other without any gap, the toner conveyance failure due to the leakage of the toner from the gap does not occur, and the toner is satisfactorily discharged from the cleaning device. Further, since rubber, which is an elastic body, is used for the casing bottom portion 10c, the toner is crushed at the portion where the casing bottom portion 10c is in contact with the screw 12, as in the case where the casing bottom portion 10c is formed of a rigid body. The image quality will not be deteriorated due to the reuse of the toner.

In this embodiment, the housing bottom portion 10c is made of an elastic material and the screw 12 is made of a rigid material. However, instead of this, the housing bottom portion 10c may be made of a rigid material and the screw 12 is made of an elastic material. .

Further, Lumiflon F20 is attached to the screw 12.
Instead of applying 0, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA),
Tetrafluoroethylene hexafluoropropylene copolymer (FEP), or FEVE, PVdF, PVF
Fluoro resin such as may be used. In addition, the bottom 1 of the housing
As the material of 0c, other fluorocarbon rubbers such as fluorinated acrylate polymers, fluorinated ester polymers, trifluorinated polymers, and hexafluorinated acrylate polymers may be used instead of the Baytron rubber plate. good.

[Second Embodiment] A second embodiment, which more specifically shows the copying machine according to the embodiment, will be described below.

In the copying machine of this embodiment, the surface of the photosensitive drum 1 is positively charged to form a positive N / P latent image on the surface,
The latent image is developed using positively charged toner. Also in this copying machine, as in the copying machine of the first embodiment, the screw 12 is provided so as to come into light contact with the bottom portion 10c of the casing, and the rotation of the screw in the region where the screw 12 and the casing bottom portion 10c contact each other. The angle θ to the axis is 20
It is 0 degree.

As the material of the bottom 10c of the housing, SE6758U (manufactured by Toray Silicone Co., Ltd.) having a thickness of 2 mm, which is silicone rubber, is used. As the screw 12, a SUS screw and SR dissolved in a solvent are used.
2411 (Silicone resin made by Toray Silicone Co., Ltd.) and 1 Ketchin black (carbon made by Akzosimie Co.)
Apply a mixture of 0 weight percent by spraying,
Further, a product subjected to coating treatment by drying at 100 ° C. for 30 minutes is used. This screw 1
The coating No. 2 has a thickness of about 30 to 100 μm and a resistance of about 10 ⁷ to 10 ⁸ Ωcm.

In this example, in which the screw 12 was coated with the above coating, it took 15 to 30 seconds when the screw without the coating was used.
The time for discharging the toner from the cleaning device 10 having a length of 35 cm in the width direction (depth direction in FIG. 1) is
It is reduced to about 10 seconds. Further, after the toner is discharged, the toner does not adhere to or remains on the screw 12 or the housing bottom portion 10c, and the toner is properly removed. This is screw 1
This is because the portions of the housing 2 and the bottom 10c of the housing that come into contact with the toner are made of silicon that does not easily adhere to the positively charged toner.

Instead of applying SR 2411 to the screw 12, another silicone resin such as condensation reaction type silicone, addition reaction type silicone, and peroxide curing reaction type silicone may be used. In addition, the housing bottom portion 10
Instead of SE6758U as the material of c, another silicone-based rubber agent may be used.

[0055]

According to the inventions of claims 1 to 6,
Since the first toner collected from the latent image carrier in the state where the transfer of the single toner image is completed is conveyed to the first developing device and the toner is used for the subsequent image formation,
The toner consumption amount can be reduced and the image forming cost can be suppressed. Further, according to these inventions, the toner reused in the first developing device is composed of only the first toner and not the second toner. Therefore, the toner in which different types of toner are mixed is reused. Therefore, the image quality does not deteriorate. According to these inventions,
Since the toner in the state where the first toner and the second toner collected from the latent image carrier after the transfer of the plurality of toner images is mixed is reliably conveyed to the waste toner bottle without remaining in the cleaning device. The image quality is not deteriorated by the toner being conveyed to the first developing device and reused.

Particularly, according to the second aspect of the invention, the first toner is collected by the cleaning device in which the toner in which the first toner and the second toner are mixed is conveyed to the waste toner bottle and becomes empty. Then, the toner is conveyed to the first developing device and used for the subsequent development. Therefore, like a device that collects the first toner with the cleaning device in a state where the toner in which the first toner and the second toner are mixed and remains, and conveys the collected toner to the first developing device and reuses it, There is no adverse effect that the second toner is mixed with the first toner in the cleaning device and the image quality of an image formed by the toner is deteriorated.
Good image formation is achieved even when the toner is reused.

In particular, according to the third aspect of the present invention, the plural toner image required for the apparatus for starting the formation of the single toner image after the elapse of a certain time after the cleaning device becomes empty after the plural toner images are formed. A waiting time until the formation of a single toner image is started after the formation is completed is unnecessary. Therefore, by eliminating the waiting time, the time required for image formation can be shortened.

In particular, according to the inventions of claims 4 to 6, it becomes difficult for the charged toner to adhere to the portion of the housing or the screw that is in contact with the charged toner, so that the charged toner is satisfactorily discharged from the cleaning device. Become. As a result, the toner in a state in which the first toner and the second toner remaining in the cleaning device are conveyed to the first developing device and reused, it is better to deteriorate the image quality. Will be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a copying machine according to an embodiment.

FIG. 2 is a perspective view showing a main part of the copying machine.

3A and 3B are timing charts showing the operation of the copying machine.

FIG. 4 is an explanatory diagram of a cleaning device included in the copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 First charging charger 3 Exposure light 4 First developing device 5 Second charging charger 6 Exposure light 7 Second developing device 8 Transfer paper 9 Transfer device 10 Cleaning device 10a Housing 10b Blade 10c Housing bottom 11 Pipe 11a auger 12 screw 13 pipe 14 waste toner tank 20 solenoid 21 valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Koinuma 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Atsuko Komaba 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (6)

[Claims] 1. A latent image carrier, latent image forming means capable of forming a first latent image and a second latent image on the surface of the latent image carrier, and a first latent image developed to develop the first latent image. A first developing device for forming a toner image; and a second developing device for developing the second latent image to form a second toner image, wherein the latent image forming means forms the first latent image. A single toner image forming mode in which the latent image is developed by the first developing device to form a single toner image consisting of only the first toner image, and the latent image forming means forms a first latent image and a second latent image. Then, it is possible to switch between a plural toner image forming mode in which each latent image is developed by the first developing device and the second developing device to form a plural toner image including a first toner image and a second toner image. An image forming apparatus, wherein the single toner image or the plurality of toner images remain on the latent image carrier after being transferred. A cleaning device for recovering the toner, a first toner carrying means for carrying the toner collected by the cleaning device to the first developing device, and a first toner carrying means for carrying the toner collected by the cleaning device to a waste toner tank. Two toner transporting means, a switching means for switching between a first state in which the cleaning device and the first developing device are in communication, and a second state in which the cleaning device and the second transporting device are in communication. The image forming apparatus is characterized in that when forming the plurality of toner images, the apparatus is brought into the second state by the switching means, and the apparatus is kept in the second state for a certain period of time after the formation of the plurality of toner images is completed. . 2. The image forming apparatus according to claim 1, wherein when the single toner image is formed after the formation of the plurality of toner images is completed, the switching means is used to cause the first toner image to be formed. The image forming apparatus is characterized in that the formation of a single toner image is started after that. 3. The image forming apparatus according to claim 1, wherein when the single toner image is formed after the formation of the plurality of toner images is completed, the first means is used by using the switching means after the lapse of the predetermined time. An image forming apparatus characterized in that formation of a single toner image is started prior to bringing into a state. 4. The image forming apparatus according to claim 1, wherein negatively charged toner is used as the first toner and the second toner, and the cleaning device is provided so as to be in contact with a casing part and the casing part. And a screw for discharging the toner collected from the casing, wherein the casing and a portion of the screw in contact with the negatively charged toner are made of a fluorine resin. 5. The image forming apparatus according to claim 1, wherein positively charged toner is used as the first toner and the second toner, and the cleaning device is provided so as to be in contact with a casing part and the casing part. And a screw for discharging the toner collected from the casing, wherein the casing and a portion of the screw in contact with the positively charged toner are made of a silicone resin. 6. The image forming apparatus according to claim 1, wherein charged toner is used as the first toner and the second toner.
The cleaning device includes a casing and a screw for discharging the toner collected from the casing, the screw being provided so as to contact the casing, and the charged toner of the casing and the screw. The resistance value of the part in contact with is 10
An image forming apparatus having a resistance of ¹⁰ Ωcm or less.