JPH0772717A - Cleanerless image forming device - Google Patents

Abstract

PURPOSE:To prevent the accumulation of developer on a latent image holding body, to restrain the deterioration of the electrostatic life of the latent image holding body and to prevent the deterioration in image recording quality. CONSTITUTION:This device is provided with the latent image holding body 11 where a photoreceptor layer is provided, and a developing device 13 where a developer holding body 18 carrying the developer 16 on a conductive layer is oppositely arranged on the holding body 11 so as to form a developer layer on a latent image formed on the photoreceptor layer of the holding body 11. In the device, residual developer remaining on the holding body 11 after transfer is attracted and recovered as soon as the developer layer is formed on the latent image by the developing device 13. Regulating members 22a and 22b are arranged to abut on both edge parts of the holding body 11 with which the holding body 18 is not in contact. The developer existing at the edge part of the holding member 11 is guided to the contact part with the holding body 18 by the members 22a and 22b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleanerless image forming apparatus which does not require a cleaning device for cleaning a residual developer remaining on a latent image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus based on an electrophotographic method, an image forming apparatus which sucks and collects a transfer residual developer at the same time as development by a developing apparatus without using a cleaning apparatus, a so-called cleanerless image forming apparatus is disclosed in JP-A-59-133573 and JP-A-59-15766.
It is known from the publication No. 1 and the like.

In the image forming apparatus, a well-known reversal development method is often used. A cleanerless image forming apparatus using the reversal developing method uses developer particles 2 charged to the same polarity as the latent image carrier 1 as shown in FIG.
Development is performed by attaching the developer particles 2 to a portion of the surface of the latent image carrier 1 where no electric charge is present or a portion having a small amount of electric charge, and not attaching the developer particles 2 to a portion where an electric charge is present.

In order to realize such selective adhesion of the developer, the potential V0 of the charged portion on the surface of the latent image carrier 1 and the potential V of the non-charged portion of the developer holder 4 in the developing device 3 are realized.
The voltage Vb (| Vl | <| Vb | <| V0 |) between the two is applied to suppress the adhesion of the developer to the latent image carrier 1 by the electric field between the charged portion and the non-charged portion. The developer particles 2 are attached to the latent image carrier 1 by the electric field between them. At this time, the developer holding member 4 is in contact with the latent image holding member 1. The developer particles 2 attached to the latent image carrier 1 are transferred onto the recording paper 6 by a known transfer device 5.

In the transfer step, generally not all the developer is transferred, and the untransferred developer particles 2'are image-wise distributed on the surface of the latent image carrier 1 after the transfer.

Then, the untransferred developer particles 2'are brought to a developing step, and at the same time as the development, the untransferred developer particles 2'are collected in the developing device 3 by the developer holder 4. That is, in the latent image formed by the exposure of the light beam 7 from the exposure means, the transfer residual developer particles 2 ′ existing in the charged portion (unexposed portion or non-image portion) have the same polarity as the latent image by the charging device 8. In order to reliably charge the developer, the electric field (the electric field due to the potential difference between V0 and Vb) that suppresses the transfer of the developer particles 2 from the developer holder 4 to the latent image holder 1 is transferred to the developer holder 4 side. . At the same time, the transfer residual developer particles 2 ′ existing in the non-charged portion (exposed portion or image portion) receive a force from the developer holding member 4 toward the latent image holding member 1 and remain on the surface of the latent image holding member 1.

In such a reversal development method, in order to form a recorded image satisfactorily, the width of the photosensitive layer of the latent image carrier is set so that the developer can be supplied to the maximum usable recording paper range. Therefore, the length of the latent image carrier 1 in the direction of the rotation axis is set longer than the maximum usable recording paper width, and the developer is sufficiently supplied on the surface of the latent image carrier in this direction. I am able to do it.

[0008]

In such a conventional apparatus, as shown in FIG. 9, the width 1 of the photosensitive layer of the latent image holding member 1 is set longer than the width m of the conductive layer of the developer holding member 4. ing.
Then, the developer existing in the developing device 3 flows out from the end portion of the developer holding body 4 little by little onto the latent image holding body 1 as the developer holding body 4 rotates. That is, the developer adheres to the area 9 shown by the diagonal lines in the figure. Further, in this apparatus, the conductive layer of the developer holder 4 carries out the cleaning step, so that the developer attached to the region 9 is accumulated without being cleaned.

Further, as the number of recording sheets on the recording paper 6 increases, the electrical characteristics of the charging device 8 and the developer holder 4 deteriorate from the end. That is, when a scorotron charger is used as the charging device 8, deterioration of the corona wire tends to appear particularly from the end. For this reason, the charging potential V0 of the latent image carrier 1 tends to decrease from both ends. Further, the developer holding member 4 also has a mechanical wear loss from the end portion, which affects the voltage Vb.

In the cleanerless image forming apparatus, the voltage V0
, Vl, and Vb, the developer is selectively supplied or collected between the development carrier 4 and the latent image carrier 1, so that an image is formed due to deterioration of electrical characteristics of the charging device 8 and the developer carrier 4. At both ends of the forming area, the fog phenomenon on the surface of the latent image holding member is increased due to the decrease of V0, and the developer collecting ability of the developer holding member 4 is also decreased, so that the developer remaining on the surface of the latent image holding member is The amount of the developer becomes larger than that in the central portion, and the residual developer moves to the outside of the image forming area, so that the developer accumulates in the area 9 indicated by the diagonal lines in the drawing.

Since the area 9 is located outside the maximum usable width p of the recording paper 6, there is no problem in the normal case where the recording paper 6 is normally conveyed, but the recording paper 6 may skew or meander. Then, a part of the recording paper 6 is located in the area 9, whereby the developer accumulated in the area 9 is transferred to a part of the recording paper and becomes dirty, which deteriorates the image recording quality. was there. Further, even if the recording paper 6 does not skew or meander, if the accumulation of the developer in the area 9 progresses, the influence also affects the inside of the area 9 and the recording paper is conveyed normally. However, there is a problem that a part of the accumulated developer is transferred to the recording paper and becomes dirty, which deteriorates the image recording quality. Further, there is a problem that the developer accumulated in the area 9 is scattered around and pollutes the inside of the apparatus.

Furthermore, the surface of the photosensitive layer of the latent image carrier 1 is constantly exposed to the atmosphere, and during development, it is affected by positive and negative charges due to discharge of the charging device 8 and the transfer device 5, ozone, or a developer. Further, the surface of the photosensitive layer of the latent image carrier 1 is activated by being worn by contact of the recording paper 6 and the conductive layer of the developer carrier 4, but the area 9 is not worn by contact, and thus is activated. However, there is a problem that the electrostatic characteristics of the latent image holding member 1 are deteriorated due to uneven charging, a decrease in charging property and a decrease in exposure sensitivity at both ends of the photosensitive layer. FIG. 10 is a graph showing the electrostatic characteristics of the latent image carrier as a function of the number of prints and the amount of variation in charging unevenness (voltage). 1
50V, the amount of change in charging unevenness at the center and both ends of the latent image carrier 1 with respect to the number of printed sheets when character image images are continuously printed is shown. Graph a shows the characteristics of the central portion of the photosensitive layer of the latent image carrier, graph b shows the characteristics of the portion of the latent image carrier which is located within 10 mm from the right end of the photosensitive layer, and graph c shows the latent image carrier. It shows the characteristics of a portion that is inwardly about 10 mm from the left end of the photosensitive layer of the body.

As can be seen from this graph, when the number of printed sheets exceeds 10,000, the amount of change in charging unevenness becomes large at both ends of the photosensitive layer. Such deterioration of the electrostatic characteristics of the latent image carrier causes an increase in the amount of the developer adhered to the area 9, and as a result, black streaks or fogging occur when an image is recorded on the recording paper. However, there is a problem in that the image recording quality is deteriorated due to stains and stains.

Therefore, the present invention prevents the accumulation of the developer on the latent image holding member and suppresses the deterioration of the electrostatic life of the latent image holding member, thereby preventing the deterioration of the image recording quality. Provide a device.

[0015]

The invention according to claim 1 is
A latent image holding member provided with a photosensitive layer, a means for forming a latent image on the photosensitive layer of the latent image holding member, and a developer holding member holding a developer in a conductive layer are arranged in a width of the developer holding member. Is also placed in contact with a latent image carrier having a wide width, and a developing device for forming a developer layer on the latent image formed on the latent image carrier, and the developer layer formed on the latent image on the recording paper. A transfer device for transferring to
In a cleanerless image forming apparatus for forming a developer layer on a latent image by a developing device and at the same time sucking and collecting the residual developer remaining on the latent image holding member after transfer by a transfer device,
On both sides of the latent image holding member, regulating members for guiding the developer at the edge of the latent image holding member at least into the width of the developer holding member are arranged in contact with each other.

According to the second aspect of the invention, a trapping means for trapping the developer falling from the regulating member is further provided below the arrangement position of the regulating member.

[0017]

In the present invention having such a structure, the developer adhering to the edge of the latent image carrier moves to at least the region within the width of the developer carrier by the regulating member, so that the latent image carrier on the latent image carrier is The residual developer is cleaned simultaneously with development by the developing device. Thus, the accumulation of the developer on the edge of the latent image carrier is prevented. Further, since the regulating member is in contact with the edge portion of the latent image holding member which is not in contact with the developer holding member, appropriate contact abrasion is performed over the entire photosensitive layer of the latent image holding member to activate it.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic structure of a cleanerless image forming apparatus, in which a latent image carrier 11 rotating clockwise in the figure.
A charging device 12 equipped with a scorotron charging charger, a developing device 13, and a transfer device 14 equipped with a transfer charger are sequentially arranged around the periphery of the device in the clockwise direction in the figure. The charging device 12 is arranged above the latent image carrier 11, and the developing device 13 is arranged on the side of the latent image carrier 11.

An exposure device (not shown) having a laser unit is provided above the latent image carrier 11 and a laser beam 15 from the exposure device is placed between the charging device 12 and the developing device 13. Irradiation is performed on the photosensitive layer surface of the image carrier. That is, the laser beam 15 is applied to the photosensitive layer surface of the latent image carrier 11 that is uniformly negatively charged by the charging device 13 to form an electrostatic latent image based on the recorded information.

The developing device 13 is a one-component developer 1
A developer container 17 accommodating 6 and a developer holder 1 provided in contact with the surface of the latent image carrier 11 and rotating counterclockwise.
8, a developer supply roller 19 for supplying the developer 16 in the container 17 to the conductive layer of the developer holder 18, and the developer 1 supplied from the developer supply roller 19 to the developer holder 18.
It is constituted by a blade 20 which regulates 6 and forms a substantially uniform developer layer on the developer holder 18. The developing device 13 supplies the developer 16 from the developer holder 18 to the electrostatic latent image formed on the photosensitive layer of the latent image holder to form a visible image.

The recording paper 21 is conveyed in the direction shown by the arrow in the figure via the space between the latent image carrier 11 and the transfer device 14. The recording paper 21 is fed from, for example, a paper feed cassette (not shown). When the recording paper 21 passes between the latent image carrier 11 and the transfer device 14, the transfer device 14 operates to move the latent image carrier 11 from the developer 16 to the developer 16.
The visible image is transferred by.

The recording paper 21 on which the visible image is transferred is heat-fixed by a heat-fixing device (not shown) and discharged to the outside.

A pair of regulating members 22a, 22 located on both sides of the latent image holding member 11 and upstream of the charging device 12 are provided.
b is abutted and arranged.

The relationship between the width 1 of the latent image holding member 11, the width m of the developer holding member 18 and the width p of the maximum recording paper is as shown in FIG. 9, and the restriction members 22a and 22b are shown in FIG. Three
As shown in FIG. 3, the rectangular image holding member 11 is arranged obliquely so as to be contracted at an angle θ with respect to the rotation direction of the latent image holding member 11 (direction indicated by an arrow in the figure), and both edge portions of the latent image holding member 11 are arranged. The existing developer is introduced into the width of the developer holder 18. The angle θ is, for example, about 30 °.

As shown in FIG. 2, each of the regulating members 22a and 22b is mainly composed of an elastic body 23a such as silicon rubber, urethane rubber, ethylene propylene rubber, NBR or the like, and the latent image holding member 11 is supported by the supporting member 23b. It is designed to press against the surface of. The elastic body 23a preferably has a thickness of about 1 to 5 mm, and the contact area with the latent image holding body 11 is about 5 mm × 20 mm.

The contact portion of the elastic body 23a with the latent image carrier 11 has a rounded edge located upstream in the rotational direction of the latent image carrier 11 so that the developer on the latent image carrier 11 is scraped off. Are prevented. This roundness is, for example, R = 1.
It is about 0 mm.

Each of the regulating members 22a and 22b has a function of removing the developer existing on the edge portion of the latent image holding member 11 and guiding it into the width of the developer holding member 18, and a function of removing the developer on the edge portion of the latent image holding member 11. A function of appropriately activating the photosensitive layer and a function of withstanding long-term use are required, and in order to satisfy such requirements, it is preferable that the elastic body 23a is mainly composed of silicone rubber or urethane rubber, In particular, silicone rubber exerts a function capable of withstanding extremely long-term use due to its releasing property.

The supporting member 23b is made of a metal body such as phosphor bronze, stainless steel, or aluminum, a hard or soft resin such as phenol resin, acrylic resin, or a composite thereof, and the supporting member 23b is fixed to the fixing member 23c.
Is pressed through. A pressing force such as a spring is applied to the fixing member 23c, and this pressing force is applied to the supporting member 23c.
It is transmitted to b.

The shape of the restricting members 22a and 22b is not limited to the rectangular shape, but may be a triangular shape having an inclined inner side as shown in FIG. 4 (a). As shown in FIG. 4 (b), the inside may be curved.

After the transfer of the visible image by the transfer device 14, a part of the developer 16 remains on the latent image carrier 11 as a residual developer 16 '. The residual developer 16 'is charged again by the charging device 12 to have the same polarity as the surface of the latent image holding member 11. Then, the laser beam 1 is applied to the surface of the latent image carrier 11
5 is exposed to form an electrostatic latent image, and the electrostatic latent image is visualized by the developer 16 from the developer holder 18 of the developing device 13 and transferred to the recording paper 21 again by the transfer device 14.

In this series of image recording operations, the residual developer 16 'is collected in the developing device 13. That is, of the surface potential of the latent image holding member 11, the potential of the non-image portion (unexposed portion) is V0, the potential of the image portion (exposed portion) is Ver, and the developing bias voltage applied to the developer holding member 18 is Vb. , The surface potential Ve of the developer holder 18 is set to the developing bias Vb.
Equal to. And the electrostatic latent image obtained by exposure,
The reversal development is performed by the one-component developer 16 that is negatively charged.

In this reversal development, generally, the effective developing voltage bias Ve is set so as to satisfy | V0 |> | Ve |> | Ver |, and the potential difference | V0-Ver | -Ve | suppresses the adhesion of the developer 16 to the non-image area (unexposed area) (suppresses fogging).

Although the negatively charged residual developer 16 'is adhered to the surface of the latent image carrier 11, the non-image area (unexposed area)
At the developing position 13, the residual developer 16 'existing in 1) is attracted by the potential difference | V0 -Ve | and is transferred to the surface of the developer holding member 18 on the higher potential side.

On the other hand, in the image area (exposure area), the potential difference | Ve
By the action of -Ver |, the development is performed with the residual developer 16 'still attached, and the developer is transferred from the developer holder 18 to the surface of the latent image holder 11.

In this way, the image area (exposed area) is developed, and at the same time, the residual developer in the non-image area (unexposed area) is collected in the developing device.

The photosensitive layer surface of the latent image carrier 11 has a CT layer composed of a polycarbonate (manufactured by Teijin Chemicals) resin as a binder, and the developer 16 is a one-component developer composed of a polyester resin. There is.

In the embodiment having such a structure, the photosensitive layer of the latent image carrier 11 is uniformly charged by the charging device 12, and then the photosensitive layer is exposed by the laser beam 15 to record an image on the photosensitive layer. The information is formed as an electrostatic latent image. This electrostatic latent image is visualized with the developer 16 from the developer holder 18 of the developing device 13 and transferred onto the recording paper 21 by the transfer device 14. In this way, the image recording on the recording paper 21 is performed.

On the other hand, the residual developer 16 'remaining on the latent image carrier 11 during transfer is charged again by the charging device 12. Then, the electrostatic latent image is formed by the laser beam 15 and the development by the developing device 13 is sequentially performed. At the time of development, the residual developer in the non-image portion (unexposed portion) is simultaneously collected in the developing device.

In this series of operations, the developer which is not collected by the developer holding body 18 adheres to the edge portion of the latent image holding body 11 which does not come into contact with the developer holding body 18, that is, the region 9 shown by the diagonal lines in FIG. However, the developer adhering to the edge portion is guided to the portion in contact with the developer holder 18 by the regulating members 22a and 22b. In this way, the developer remaining on the surface of the latent image carrier is surely used by the developer carrier 18 for re-development or collected.

In this way, the developer remaining on the edge of the latent image carrier 11 is prevented from adhering and accumulating. Therefore, the phenomenon that the recording paper 21 is stained by the accumulated developer and the image recording quality is deteriorated does not occur. Further, the phenomenon that the accumulated developer is scattered around and the inside of the device is soiled does not occur.

Further, since the edge portions of the latent image holding body 11 which do not contact the developer holding body 18 are in contact with the regulating members 22a and 22b, they are worn by the regulating members 22a and 22b and activated.

As a result, the photosensitive layer of the latent image carrier 11 is evenly worn over the entire area, and the photosensitive layer is activated over the entire area. As a result, the central portion of the latent image carrier 11 with respect to the number of printed sheets, As shown in FIG. 5, the variation in charging unevenness at both ends, particularly the variation in charging unevenness at both ends, does not increase even when the number of printed sheets exceeds 10,000. In FIG. 5, the charging charger grid voltage Vcg of the charging device 13 is -420V, and the effective developing bias Ve is -1.
The charge variation is 50 V, and the variation amount of charging unevenness at the central portion and both ends of the latent image holding body 18 is shown with respect to the number of printed sheets when the character image images are continuously printed. In the figure, a graph a'represents the characteristics of the central portion of the photosensitive layer of the latent image carrier 11, and a graph b'represents the characteristics of the portion of the latent image carrier 11 which is located within 10 mm from the right end of the photosensitive layer. A graph c'represents a characteristic of a portion of the latent image holding member 11 which is inwardly about 10 mm from the left end of the photosensitive layer.

As described above, the electrostatic characteristics of the latent image carrier 11 are not deteriorated even if the total number of printed sheets is increased, that is, the deterioration of the electrostatic life can be suppressed, and therefore, when the image is recorded on the recording paper 21, black streaks are generated. No fogging, fogging, stains, etc. will occur.

Next, another embodiment of the present invention will be described with reference to the drawings. The same parts as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 6 shows the restriction members 24a, 24.
b is arranged in contact with the edge of the latent image carrier 11. The restriction members 24a and 24b are made of polyurethane,
An elastic body 25a composed mainly of a foam such as silicone, chloroprene, NBR is pressed against the surface of the latent image holding body 11 and brought into contact therewith, and the elastic body 25a is made of phosphor bronze having a thickness of about 0.1 to 0.5 mm or The support member 25b made of a spring member such as stainless steel is supported at one end side, and the other end of the support member 25b is fixed to the fixing member 25c.

The elastic body 25a has foam cells having an average cell diameter of several μm to several mm inside and on the surface thereof, and the thickness thereof is determined in consideration of the number of foam cells, but about 1 mm to 10 mm is practical. is there.

Also in this embodiment, the regulating members 24a, 2
The shape and arrangement of 4b are similar to those shown in FIGS.

Also in this embodiment, the regulating members 24a, 24a
b prevents the residual developer from adhering or accumulating on the edge of the latent image carrier 11. Further, the developer holder and the regulating member 24
With a and 24b, the photosensitive layer of the latent image carrier 11 is uniformly worn over the entire area, and the photosensitive layer is activated over the entire area.

Therefore, also in this embodiment, the same effect as that of the above embodiment can be obtained.

FIG. 7 shows the restriction members 24a, 24.
b, the developer receiving tray 2 is provided below the contact portion between the latent image holding member 11b.
6 is arranged so that the regulating members 24a and 24b capture the developer that falls when regulating the residual developer.

By doing so, the regulating member 24
It is possible to prevent the developer falling from a and 24b from polluting the inside of the apparatus.

It is needless to say that the same effects as those of the above-mentioned embodiment can be obtained in this embodiment as well.

[0054]

As described above, according to the present invention, the regulating member is brought into contact with the edge portion of the latent image holding body which is not in contact with the developer holding body, and the developer attached to the edge portion is brought into contact with the developer holding body. Since the toner is guided to the portion, it is possible to prevent the developer from accumulating on the latent image holding member, suppress the deterioration of the electrostatic life of the latent image holding member, and prevent the deterioration of the image recording quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a restriction member of the embodiment.

FIG. 3 is a diagram showing an arrangement relationship between a regulation member and a latent image holding member of the embodiment.

4A and 4B are views showing various examples of the restriction member of the embodiment.

FIG. 5 is a graph showing characteristics of variation in charging unevenness at the central portion and both end portions of the latent image carrier with respect to the number of printed sheets in the example.

FIG. 6 is a configuration diagram of main parts showing another embodiment of the present invention.

FIG. 7 is a main part configuration diagram showing another embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a conventional example.

FIG. 9 is a development view showing the relationship between the widths of a latent image carrier, a developer carrier, and recording paper.

FIG. 10 is a graph showing characteristics of variation in charging unevenness at the central portion and both end portions of the latent image holding member with respect to the number of printed sheets in the related art.

[Explanation of symbols]

 11 ... Latent image holder 12 ... Charging device 13 ... Developing device 14 ... Transfer device 16 ... Developer 18 ... Developer holder 21 ... Recording paper 22a, 22b ... Regulation member

Claims (2)

[Claims] 1. A latent image holding member provided with a photosensitive layer, a means for forming a latent image on the photosensitive layer of the latent image holding member, and a developer holding member holding a developer on a conductive layer. A developing device, which is disposed so as to be in contact with the latent image holding member having a width wider than that of the holding member, and forms a developer layer on the latent image formed on the latent image holding member, and formed on the latent image. A transfer device for transferring the developer layer onto the recording paper is provided, and the developer layer is formed on the latent image by the developing device, and at the same time, the residual developer remaining on the latent image carrier after the transfer by the transfer device is collected by suction. In the cleanerless image forming apparatus, the regulating members for guiding the developer at the edge of the latent image holding member at least into the width of the developer holding member are arranged on both sides of the latent image holding member in contact with each other. A cleanerless image forming apparatus characterized by the above. 2. A latent image holding member having a photosensitive layer, a means for forming a latent image on the photosensitive layer of the latent image holding member, and a developer holding member holding a developer on a conductive layer. Provided with a developing device that is placed in contact with the body and forms a developer layer on the latent image formed on the latent image carrier, and a transfer device that transfers the developer layer formed on the latent image onto recording paper. In the cleanerless image forming apparatus, the developer layer is formed on the latent image by the developing device, and at the same time, the residual developer remaining on the latent image holder after transfer by the transfer device is sucked and collected. Regulating members for guiding the developer at the edge portion of the latent image holding member to at least the width of the developer holding member are arranged in contact with each other on both sides of the latent image holding member, and the regulating member is positioned below the position where the regulating member is arranged. Providing capture means for capturing the developer falling from the member A cleanerless image forming apparatus.