JPH0916048A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus capable of preventing a recording material from rushing into a cleaning unit and resulting in defective cleaning. [Structure] Photosensitive drum (image carrier) 1, corona charger (charging means) 2, laser exposure optical system (exposure means) 3
And developing devices (developing means) 4Y, 4C, 4M, 4BK,
In the image forming apparatus having the recording material carrying sheet (recording material carrying body) 5f, the transfer device (transfer means) 5, the cleaning device (cleaning means) 6, and the transfer peeling sensor (detection means) 5h, the pre-cleaning sensor 6d The presence or absence of the recording material P on the photosensitive drum 1 is detected at a timing different from the detection timing of the transfer peeling sensor 5h. According to the invention, the pre-cleaning sensor 6d
Is used to detect the presence or absence of the recording material P on the photosensitive drum 1 at a timing different from the detection timing of the transfer peeling sensor 5h. Therefore, the recording material P is rushed into the cleaning device 6 and the cleaning failure associated therewith is detected. Etc. can be prevented.

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 for transferring a visible image formed on an image carrier to a recording material to form an image.

[0002]

2. Description of the Related Art FIG. 9 shows an example of a conventional full-color image forming apparatus.

That is, FIG. 9 is a vertical cross-sectional view of a conventional full-color image forming apparatus. The full-color image forming apparatus has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the digital color image reader section, the original 30 is placed on the original table glass 31, and the exposure lamp 32 is used.
The original 30 is exposed and scanned by
The reflected light image from the lens 33 is used by the full-color sensor 3
The color separation image signal is obtained by condensing the light on the image pickup device 4. This color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and then sent to the digital color image printer section.

In the digital color image printer unit, a photosensitive drum 1 which is an image carrier is rotatably supported in the direction of an arrow shown in the figure. A pre-exposure lamp 11 is provided around the photosensitive drum 1 and a corona charging as a charging means. A device 2, a laser exposure optical system 3, a surface potential sensor 12, four developing devices 4Y, 4C, 4M and 4BK of different colors, a photosensitive drum light amount detection means 13, a transfer device 5 and a cleaning device 6 are provided. There is.

In the laser exposure optical system 3, the image signal from the reader section is converted into an optical signal for image scan exposure by a laser output section (not shown), and the converted laser light is reflected by the polygon mirror 3a. Then, the light is projected onto the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c.

At the time of image formation, the photosensitive drum 1 is rotated in the direction of the arrow, and the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly charged negatively by the charger 2 and light is separated for each separated color. The image E is irradiated to form a latent image on the photosensitive drum 1.

Next, a predetermined developing device (4Y, 4C, 4M,
4BK) to develop the latent image on the photosensitive drum 1,
A negatively charged toner image using a resin as a base is formed on the photosensitive drum 1. Incidentally, the developing devices 4Y, 4C, 4M,
4BK is configured to selectively approach the photosensitive drum 1 according to each separated color by the operation of the eccentric cams 24Y, 24C, 24M, and 24BK.

On the other hand, the recording material P is supplied from the recording material cassette 7 to a position facing the photosensitive drum 1 via the conveying system and the transfer device 5, and the toner image on the photosensitive drum 1 is transferred onto the recording material P. It

The transfer device 5 includes a transfer drum 5a as a recording material carrier, a transfer brush charger 5b as transfer means, an adsorption corona charger 5c for electrostatically adsorbing the recording material P, and the adsorption corona. It is configured to include a suction roller 5g facing the charger 5c, an inner charger 5d, an outer charger 5e, a separation charger 5j, and a transfer peeling sensor 5h. The transfer drum 5a is rotatably supported, and a recording material carrying sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in an opening area of its peripheral surface. A dielectric sheet such as a polycarbonate film is used as the recording material carrying sheet 5f.

Then, as the transfer drum 5a is rotated, the toner image on the photosensitive drum 1 is transferred to the transfer brush charger 5.
The image is transferred onto the recording material P carried on the recording material carrying sheet 5f by b. In this way, a desired number of color toner images are transferred to the recording material P adsorbed to the recording material carrying sheet 5f, and an unfixed full-color toner image is formed on the recording material P.

In the case of forming a full-color image, when the transfer of the four color toner images onto the recording material P is completed as described above,
The recording material P is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b, and the separation charger 5j, and after the toner image is fixed by the heat roller fixing device 9, the recording material P is discharged to the tray 10 outside the machine. To be done. After the transfer, the residual toner on the surface of the photosensitive drum 1 is removed by a cleaning device 6 including a cleaning blade 6a and a squeegee sheet 6b, and then the photosensitive drum 1 is subjected to an image forming process again.

When images are formed on both sides of the recording material P, immediately after the recording material P is discharged from the heat roller fixing device 9, the conveying path switching guide 19 is driven to convey the recording material P in the longitudinal direction. After being once guided to the reversing path 21a via the path 20, the reversing roller 21b is reversed to cause the trailing end when the recording material P is fed to be the leading end and to retreat in the opposite direction to the feeding direction. P is stored in the intermediate tray 22. After that, an image is formed on the other surface of the recording material P again by the above-described image forming process.

The recording material carrying sheet 5 of the transfer drum 5a
In order to prevent scattering of powder on f, adhesion of oil on recording material P, and the like, a backup brush 15 facing the fur brush 14 via the fur brush 14 and the recording material carrying sheet 5f, and an oil removing roller. The recording material carrying sheet 5f and the recording material P are cleaned by the backup brush 17 facing the oil removing roller 16 via the recording material carrying sheet 16 and the recording material carrying sheet 5f. It should be noted that such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in the color image forming apparatus, the eccentric cam 25 is operated at a desired timing and the cam follower 5i integrated with the transfer drum 5a is operated, so that the recording material carrying sheet 5f and the photosensitive drum 1 are separated from each other. The configuration that can arbitrarily set the gap of is adopted. For example, during standby or when the power is off, the transfer drum 5
a and the photosensitive drum 1 are separated from each other.

Here, in this color image forming apparatus, pre-exposure by the pre-exposure lamp 11, primary charging by the corona charger 2, latent image formation by the laser exposure optical system 3, and developing device 4 are performed.
Development formation by Y, 4C, 4M, 4BK, transfer by transfer brush charger 5b, and transfer peeling sensor 5 of recording material P
Each sequence of the detection of h is shown in FIG.

In the transfer peeling sensor 5h, the recording material P electrostatically attracted to the recording material carrying sheet 5f is electrostatically attracted to the photosensitive drum 1 rather than electrostatically attracted to the recording material carrying sheet 5f. Is provided in order to prevent the recording material P from being peeled off from the recording material carrying sheet 5f when it becomes large, adsorbed by the photosensitive drum 1 and rushing into the cleaning device 6.

After the image formation start signal is input by the copy button or the like, and after the rotation of the photosensitive drum 1 is started,
First, pre-exposure is started, and the primary charging is started in synchronization with the rotation of the photosensitive drum 1 and the leading edge of the image forming portion (the portion that contacts the leading edge of the recording material P during transfer) reaches the primary charging position. Then, the latent image formation for the magenta image is started in synchronization with the leading end of the image forming portion of the photosensitive drum 1 reaching the latent image forming position, and the latent image is reached in the developing device 4M position in synchronization with the latent image forming position. The operation of the developing device 4M is started, and the transfer brush charger 5b starts the transfer in synchronization with the arrival of the toner image at the transfer position. Furthermore, the transfer peeling sensor 5h operates in synchronization with the front end of the recording material P on the transfer drum 5a reaching the position of the transfer peeling sensor 5h. Similarly, cyan,
Images of respective colors of yellow and black are formed, and the toner images of all the colors are superimposed and transferred onto the recording material P.

Next, FIG. 11 shows the operation when the transfer peeling sensor 5h detects the transfer peeling. In addition, FIG.
1) and (a2) show states during normal image formation.

The recording material P is peeled off from the recording material carrying sheet 5f and stuck to the side of the photosensitive drum 1, and the transfer peeling sensor 5h.
When the transfer peeling is detected by FIG. 11 (b1),
As shown in (b2), the photosensitive drum 1 immediately stops and then reverses. After rotating to a position where the recording material P can be easily removed as shown in FIGS. 11 (c1) and 11 (c2), FIG. 11 (d2).
The operation ends as shown in.

[0021]

However, in the above conventional example, when two recording materials P are carried on the recording material carrying sheet 5f, the transfer peeling sensor 5h detects the recording material P in the state as shown in FIG. It cannot detect peeling,
The recording material P plunges into the cleaning device 6, and the cleaning failure and the like caused by the plunging of the recording material P into the cleaning device 6 occur.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing a recording material from rushing into a cleaning means and a cleaning failure associated therewith. It is in.

[0023]

In order to achieve the above object, the invention according to claim 1 includes a rotating image carrier, a charging unit for charging the image carrier, and a charged image carrier. Exposure means for exposing, developing means for converting the electrostatic latent image formed on the image carrier by exposure into a visible image, and recording material carrier for carrying the recording material and conveying it to the transfer position. Body, transfer means for transferring a visible image from the image carrier to the recording material carried by the recording material carrier, and developer remaining on the image carrier without being transferred by the transfer means. In the image forming apparatus, there is provided a cleaning unit for detecting the density of the developer on the image carrier between the transfer unit and the cleaning unit. Timing to detect the developer concentration on Characterized by being adapted to detect the presence or absence of the recording material on said image bearing member at a timing different from that of the.

According to a second aspect of the present invention, a rotating image carrier, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and an image carrier by exposure. Developing means for converting the electrostatic latent image formed above into a visible image, a recording material carrier that carries a recording material and conveys it to a transfer position, and recording carried by the recording material carrier Transfer means for transferring a visible image from the image carrier to the material, cleaning means for removing the developer remaining on the image carrier without being transferred by the transfer means, the transfer means and the cleaning means And a first detection unit for detecting the developer concentration on the image carrier, and a state on the image carrier between the transfer unit and the cleaning unit separately from the first detection unit. Second placed to detect
In an image forming apparatus having a detection unit, the second detection unit 2 detects the recording material on the image carrier at a timing different from the timing at which the first detection unit detects the developer density on the image carrier. The feature is that the presence or absence is detected.

According to a third aspect of the present invention, a rotating image carrier, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and an image carrier by exposure. Developing means for converting the electrostatic latent image formed above into a visible image, a recording material carrier that carries a recording material and conveys it to a transfer position, and recording carried by the recording material carrier A transfer unit for transferring a visible image from the image carrier to the material, a cleaning unit for removing the developer remaining on the image carrier without being transferred by the transfer unit, and a carrier for the recording material carrier. First detecting means arranged downstream of the transfer position in the recording material rotation direction to detect the peeling of the recorded recording material, and the transfer means and the cleaning means to detect the state on the image carrier. An image having a second detection means arranged between In the forming apparatus, after the second detecting means detects the presence or absence of the recording material on the image carrier, the first detecting means detects the presence or absence of the recording material on the image carrier. Characterize.

The invention according to claim 4 is characterized in that, in the invention according to claim 3, the first detecting means 1 is arranged in the recording material carrying body.

According to a fifth aspect of the present invention, in the first, second or third aspect of the invention, the presence or absence of the recording material is detected by the detecting means, and when the recording material is not present at a desired position,
It is characterized in that the image carrier is rotated to a predetermined position in a direction opposite to that at the time of image formation.

[0028]

According to the present invention, the presence or absence of the recording material on the image bearing member is detected at a timing different from the timing at which the detecting means detects the developer concentration on the image bearing member.
It is possible to prevent the recording material from rushing into the cleaning means and the resulting cleaning failure.

[0029]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a vertical sectional view of a color image forming apparatus according to the present invention. In this figure, the same elements as those shown in FIG. 9 are designated by the same reference numerals. A description thereof will be omitted.

In this embodiment, in order to detect the presence or absence of the recording material P on the photosensitive drum 1 between the transfer device 5 and the cleaning device 6, a pre-cleaning sensor 6d is provided upstream of the cleaning device 6 in the photosensitive drum rotation direction. The pre-cleaning sensor 6d is set at the same distance from the transfer position to the detection position as the transfer peeling sensor 5h.

Here, the pre-exposure lamp 1 in this embodiment is used.
1 pre-exposure, corona charger 2 primary charging, laser exposure optical system 3 latent image formation, developing units 4Y, 4C, 4
FIG. 2 shows each sequence of development formation by M, 4BK, transfer by the transfer brush charger 5b, detection of the transfer peeling sensor 5h of the recording material P, and detection of the recording material P by the pre-cleaning sensor 6d.

After the rotation of the photosensitive drum 1 is started after the image forming start signal is input by the copy button or the like, the pre-exposure is started first, and the front end of the image forming portion (the recording material P at the time of transfer P is transferred in accordance with the rotation of the photosensitive drum 1 The primary charging is started in synchronization with the arrival of the portion contacting the tip) at the primary charging position. Then, the latent image formation for the magenta color image is started in synchronization with the leading edge of the image forming portion of the photosensitive drum 1 reaching the latent image forming position, and the magenta color image is synchronized with the arrival of the position of the developing device 4M. The operation of the developing device 4M is started, and the transfer of the toner image onto the recording material P by the transfer brush charger 5b is started in synchronization with the arrival of the toner image developed by the developing device 4M at the transfer position. Further, the pre-cleaning sensor 6d operates in synchronization with the image forming front end portion on the photosensitive drum 1 reaching the position of the pre-cleaning sensor 6d, and then the transfer peeling sensor 5h operates. Thereafter, toner images of cyan, yellow, and black are similarly formed in the same manner, and the full-color toner image is transferred onto the recording material P in a superimposed manner.

As a result of the above, even when the transfer peeling sensor 5h cannot detect the transfer peeling when two recording materials P are carried on the recording material carrying sheet 5f, the cleaning device 6 is detected by the pre-cleaning sensor 6d. It was possible to prevent the cleaning failure and the like caused by the rush of the recording material P and the rush of the recording material P into the cleaning device 6.

When the pre-cleaning sensor 6d is mounted at the position shown in FIG. 3, the toner not transferred on the photosensitive drum 1 is scraped off by the second squeegee sheet 6c and adheres to the detection surface of the pre-cleaning sensor 6d. As the toner adheres to the detection surface as it becomes durable, it becomes impossible to detect the presence or absence of the recording material P on the photosensitive drum 1 as shown in FIG. 4, and therefore the pre-cleaning sensor 6d as shown in FIG. The distance from the photosensitive drum 1 on the detection surface of the
A partition member 6e is provided on the upstream side of the pre-cleaning sensor 6d in the photosensitive drum rotation direction in order to prevent the toner scattered by the separation discharge between the recording material P after transfer and the photosensitive drum 1 from being attached to the detection surface. There is. Furthermore, as shown in FIG. 6, it is preferable to provide a partition 6f around the detection surface of the pre-cleaning sensor 6d. As a result, as shown in FIG. 7, the detection surface of the pre-cleaning sensor 6d is less likely to get dirty, and the regular cleaning interval can be lengthened.

The most preferable example in which the pre-cleaning sensor 6d coexists with the transfer peeling sensor 5h has been described above, but the transfer peeling sensor 5h may be omitted in order to prevent the recording material P from entering the cleaning device 6. I do not care.

<Second Embodiment> Next, a second embodiment of the present invention will be described.

In this embodiment, a patch detection sensor for detecting the developer concentration on the photosensitive drum 1 at the same position is used instead of the pre-cleaning sensor 6d in the first embodiment. Also, the same effect as in Example 1 was obtained.

Here, the pre-exposure lamp 1 in this embodiment is used.
1 pre-exposure, corona charger 2 primary charging, laser exposure optical system 3 latent image formation, developing units 4Y, 4C, 4
FIG. 8 shows the respective sequences of development formation by M and 4BK, transfer by the transfer brush charger 5b, and detection of the recording material P by the patch detection sensor.

After the rotation of the photosensitive drum 1 is started after the image forming start signal is input by the copy button or the like, the pre-exposure is first started, and the front end of the image forming portion (the recording material at the time of transfer is transferred according to the rotation of the photosensitive drum 1). The primary charging is started in synchronism with the arrival of the portion (contacting the tip of P) at the primary charging position. Then, the latent image formation for the magenta color image is started in synchronization with the leading edge of the image forming portion of the photosensitive drum 1 reaching the latent image forming position, and the magenta color image is synchronized with the arrival of the position of the developing device 4M. Then, the operation of the developing device 4M is started, and the transfer by the transfer brush charger 5b is started in synchronization with the arrival of the magenta toner image developed by the developing device 4M at the transfer position. Further, the pre-cleaning sensor 6d operates in synchronization with the image forming front end portion on the photosensitive drum 1 reaching the position of the pre-cleaning sensor 6d, and then the transfer peeling sensor 5h operates. Thereafter, in the same manner, cyan, yellow, and black color images are formed, and the toner images of all the colors are superimposed and transferred onto the recording material P.

Thus, also in this embodiment, it is possible to prevent the recording material P from entering the cleaning device 6.

The patch detection sensor is used only for detecting the toner density on the photosensitive drum 1, and the recording material P on the photosensitive drum 1 is used.
The present invention is also applied to the case where a pre-cleaning sensor is separately provided to detect the presence or absence of the above, and the same effect as described above can be obtained.

[0043]

As is apparent from the above description, according to the present invention, the presence or absence of the recording material on the image bearing member is different from the timing at which the detecting means detects the developer concentration on the image bearing member. Since the above is detected, it is possible to obtain an effect that it is possible to prevent the recording material from rushing into the cleaning means and the cleaning failure caused thereby.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a color image forming apparatus according to a first embodiment of the invention.

FIG. 2 shows pre-exposure, primary charging, latent image formation, development formation, transfer, in the color image forming apparatus according to the first embodiment of the present invention.
6 is a timing chart showing the respective sequences of detection by a transfer peeling sensor and detection by a pre-cleaning sensor.

FIG. 3 is a cross-sectional view of a main part of a color image forming apparatus showing a mounted state of a transfer peeling sensor.

FIG. 4 is a diagram showing a relationship between a reflected light amount (V) and a durable number of sheets.

FIG. 5 is a cross-sectional view of a main part of a color image forming apparatus showing a mounted state of a transfer peeling sensor.

FIG. 6 is a cross-sectional view of a main part of a color image forming apparatus showing a mounted state of a transfer peeling sensor.

FIG. 7 is a diagram showing the relationship between the amount of reflected light (V) and the number of durable sheets.

FIG. 8 is a timing chart showing each sequence of pre-exposure, primary charging, latent image formation, development formation, transfer, and patch detection sensor detection in the color image forming apparatus according to the second embodiment of the present invention.

FIG. 9 is a vertical sectional view of a conventional color image forming apparatus.

FIG. 10: Pre-exposure in a conventional color image forming apparatus,
6 is a timing chart showing each sequence of primary charging, latent image formation, development formation, transfer, and detection of a transfer peeling sensor.

FIG. 11 is a diagram for explaining the state of the recording material and the operation of the photosensitive drum and the transfer device at the time of transfer peeling in the conventional image forming apparatus.

FIG. 12 is an explanatory diagram showing a state where the recording material peeling cannot be detected in the conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Corona charger (charging means) 3 Laser exposure optical system (exposure means) 4 Developing device (developing means) 5 Transfer device (transfer means) 5f Recording material carrying sheet (recording material carrying body) 5h Transfer peeling sensor 6 Cleaning device (cleaning means) 6d Pre-cleaning sensor P Recording material

Claims (5)

[Claims] 1. A rotating image carrier, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and a static image formed on the image carrier by the exposure. Developing means for converting a latent image into a visible image, a recording material carrier that carries a recording material and conveys the recording material to a transfer position, and a recording material carried by the recording material carrier from the image carrier. A transfer unit for transferring a visible image, a cleaning unit for removing a developer remaining on the image carrier without being transferred by the transfer unit, and an image carrier between the transfer unit and the cleaning unit. An image forming apparatus having a detection unit arranged to detect the developer concentration on the body, wherein the detection unit detects the concentration of the developer on the image carrier at a different timing. Presence or absence of recording material in An image forming apparatus characterized in that the so that. 2. A rotating image carrier, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and a static image formed on the image carrier by the exposure. Developing means for converting a latent image into a visible image, a recording material carrier that carries a recording material and conveys the recording material to a transfer position, and a recording material carried by the recording material carrier from the image carrier. A transfer unit for transferring a visible image, a cleaning unit for removing a developer remaining on the image carrier without being transferred by the transfer unit, and an image carrier between the transfer unit and the cleaning unit. A first detection unit for detecting the developer concentration on the body, and a unit for detecting the state on the image carrier between the transfer unit and the cleaning unit, separately from the first detection unit. In the image forming apparatus having the second detecting means, The second detection unit 2 detects the presence or absence of a recording material on the image carrier at a timing different from the timing at which the first detection unit detects the developer concentration on the image carrier. A characteristic image forming apparatus. 3. A rotating image carrier, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and a static image formed on the image carrier by the exposure. Developing means for converting a latent image into a visible image, a recording material carrier that carries a recording material and conveys the recording material to a transfer position, and a recording material carried by the recording material carrier from the image carrier. Transfer means for transferring a visible image, cleaning means for removing the developer remaining on the image carrier without being transferred by the transfer means, and peeling of the recording material carried on the recording material carrier. First detection means arranged downstream of the transfer position in the recording material rotation direction to detect this, and arranged between the transfer means and the cleaning means to detect the state on the image carrier. In the image forming apparatus having the second detecting means, An image characterized in that the second detecting means detects the presence or absence of a recording material on the image carrier, and then the first detecting means detects the presence or absence of a recording material on the image carrier. Forming equipment. 4. The image forming apparatus according to claim 3, wherein the first detection unit 1 is arranged inside the recording material carrier. 5. The detection means detects the presence / absence of a recording material, and when the recording material is not present at a desired position, the image carrier is rotated to a predetermined position in a direction opposite to that at the time of image formation. The image forming apparatus according to claim 1, 2, or 3.