JPH11305636A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the local temperature rise of an intermediate transfer body, to prolong the life of the intermediate transfer body and to stably obtain a high-quality image without lowering the preheating temperature of a fixing device during standing-by by rotating and driving either a developing means or a transfer means every given time during standing by image formation. SOLUTION: This image forming device which finishes initial sequence maintains the standing-by state (standby state) until the standing-by time (standby state elapsed time) of the image forming device attains previously set standby state continuing time by the control of a controller 40. When the standing-by time of the image forming device attains the previously set standby state continuing time, an intermediate transfer drum 9 and the developing rotary 23 of a developing device 20 are respectively rotated at a previously set angle by the control of the controller 40. When a printing signal is inputted from the standby state, the image forming device starts printing sequence and forms an image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine or a printer for forming an image by an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art In an electrophotographic color image forming apparatus (for example, a copying machine or a printer), a toner image of each color sequentially formed on an electrophotographic photosensitive member is transferred to an intermediate transfer member (an intermediate transfer drum or an intermediate transfer drum). There is known an image forming apparatus of a system in which primary transfer is sequentially performed on a belt, a plurality of toner images are superimposed on an intermediate transfer body, and these toner images are collectively secondary-transferred onto a transfer material such as paper. .

FIG. 3 is a schematic diagram showing a conventional image forming apparatus (color laser printer) having an intermediate transfer member.

In this image forming apparatus, a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) 100 made of OPC (organic semiconductor) or the like is rotationally driven in the direction of arrow R1, and the surface thereof is charged by applying a voltage. After being uniformly charged by the roller 102, the scanner unit 103a and the reflection mirror 103b
The exposure is performed by the laser beam L according to the image information input by the exposure device 103 having an electrostatic latent image.

A developing device 104 for developing an electrostatic latent image is provided with a rotatable developing rotary 104A for magenta, cyan, and cyan.
Developing devices 104a, 104b, 104c, and 104d respectively containing yellow and black toners are rotatably supported, and are used for developing an electrostatic latent image on the photosensitive drum 100 by rotating a developing rotary 104A. A developing unit (for example, a yellow developing unit 104a) is arranged at a developing position facing the photosensitive drum 100, and toner is adhered to the electrostatic latent image to develop as a yellow toner image.

[0006] the yellow toner image is primarily transferred to the intermediate transfer drum 105 which is an intermediate transfer member, the toner image of yellow on the photosensitive drum 100 is primarily transferred at the primary transfer portion t ₁ to the intermediate transfer drum 105 surface Is done. The transfer residual toner remaining on the surface of the photosensitive drum 100 after the primary transfer is removed by the cleaning device 106.

The above-described charging, exposure, development, primary transfer, and cleaning are similarly performed for the remaining three colors, that is, magenta, cyan, and black, and the four color toner images are superimposed on the intermediate transfer drum 105.

[0008] These four color toner images are stored in a paper cassette 1
The transfer material P conveyed through the paper feed roller 110 and the like from 09, at the secondary transfer portion t _2, are secondarily transferred collectively by the secondary transfer device 107.

The transfer material P after the secondary transfer is transferred to a transfer device 111.
After the toner images of four colors are heated and pressed between the heating roller 112a and the pressing roller 112b of the fixing device 112 and fixed on the surface thereof, the toner images are then transferred to a paper discharge tray (not shown). Is discharged.

[0010]

In the above-described conventional image forming apparatus, the first print time (the time from when a print signal is received to when the first transfer material P is output) is reduced. During the standby state of the apparatus, temperature control for preheating the heating roller 112a of the fixing device 112 is performed.

For this reason, the developing device 104 and the intermediate transfer drum 105 installed in the vicinity of the fixing device 112 are heated during standby, so that the image quality is degraded due to the deterioration and fusion of the toner used in the developing device 104. And also
There is a problem that the life of the intermediate transfer drum 105 is shortened due to the deterioration of the surface layer of the intermediate transfer drum 105.

Therefore, the present invention suppresses the local temperature rise of the intermediate transfer member and the developing device without lowering the preheating temperature of the fixing device during standby, thereby extending the life of the intermediate transfer member and improving the quality of the image. To provide an image forming apparatus that can stably obtain the image.

[0013]

In order to achieve the above object, the present invention provides an electrophotographic photosensitive member on which an electrostatic latent image is formed, and a method for developing a toner image by developing the electrostatic latent image. In an image forming apparatus provided with a rotatable developing unit having a developing unit and a rotatable transfer unit for transferring the toner image onto a transfer material, at least a predetermined time interval between the developing unit and It is characterized by having control means for controlling one of the transfer means to be rotationally driven.

Further, at least one of the developing means and the transfer means is provided close to a heat source.

Further, the heat source is a fixing means for fixing the toner image transferred onto the transfer material by heating and pressing.

The developing unit includes at least a yellow developing device supported by a rotatable developing rotary;
It has a magenta developing device and a cyan developing device.

The transfer means abuts on the electrophotographic photosensitive member to primarily transfer the toner image at a primary transfer nip portion, and transfers the toner image primarily transferred at a secondary transfer nip portion with its own rotation by a transfer material. It is characterized in that it is an intermediate transfer member for secondary transfer.

Further, the intermediate transfer member is a drum-shaped intermediate transfer drum.

(Operation) According to the structure of the present invention, at the time of standby of the image forming apparatus, at least one of the developing means and the transfer means is driven to rotate at predetermined time intervals, so that thermal deterioration of the surface layer of the transfer means can be prevented. In addition, it is possible to prevent thermal deterioration and fusion of the toner used for the developing means, and also to prevent plastic deformation of the surface layer of the transfer means at the contact portion between the electrophotographic photosensitive member and the transfer means.

[0020]

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

FIG. 1 is a schematic configuration diagram showing an image forming apparatus (in this embodiment, a four-color full-color laser printer) according to an embodiment of the present invention.

The image forming apparatus includes a drum type electrophotographic photosensitive member (photosensitive drum) 15 which is driven to rotate at a constant speed. Around the photosensitive drum 15, a charging device 17,
An exposure device 30, a developing device 20, an intermediate transfer drum 9, and a cleaning device 13 are provided. Also, paper and OH
A sheet cassette 1, a secondary transfer roller 10, and a fixing device 25 are arranged in this order from the upstream side in the transport direction of the transfer material P such as P.

Next, the configuration of each section of the image forming apparatus will be sequentially described in detail.

The photosensitive drum 15 is integrally formed with a cleaner container 14 of a cleaning device 13 which also serves as a holder for the photosensitive drum 15, is supported detachably with respect to the apparatus main body 2, and extends the life of the photosensitive drum 15. In addition, the unit can be easily replaced. In the present embodiment, the photosensitive drum 15 is formed by applying an organic photoconductor layer to the outer periphery of an aluminum cylinder having a diameter of about 60 mm, and is rotated at a predetermined process speed.

In the present embodiment, the charging device 17 uses a conductive charging roller as a contact charging means.
Is brought into contact with the photosensitive drum 15, and a voltage is applied to the charging device 17 to uniformly charge the surface of the photosensitive drum 15.

An exposure device 30 for exposing the surface of the photosensitive drum 15 by irradiating a laser beam irradiates a polygon mirror 31 with a laser beam (image beam) L corresponding to an image signal.
The polygon mirror 31 is rotated at high speed by the scanner motor 31a, and the laser light L reflected by the polygon mirror 31
Selectively exposes the surface of the photosensitive drum 15 rotating at a constant speed via the imaging lens 32 and the reflection mirror 33 to form an electrostatic latent image on the photosensitive drum 15.

Developing device 20 for visualizing the electrostatic latent image
Is provided with rotatable developing units 20Y, 20M, and 20C that respectively perform yellow, magenta, and cyan color development, and a black developing unit 21B that performs black development.

The black developing device 21B is a fixed developing device, and has a sleeve 21 at a position facing the photosensitive drum 15.
The BS is arranged at a minute interval (about 300 μm) with respect to the photosensitive drum 15, and forms a visible image on the photosensitive drum 15 using black toner.

The black developing unit 21B feeds the toner by a feed mechanism (not shown), applies a thin layer of the toner to the outer periphery of the sleeve 21BS by the coating blade 21BB pressed against the outer periphery of the sleeve 21BS, and gives a charge to the toner (friction). Charge). Further, by applying a developing bias to the sleeve 21BS, toner is attached to the electrostatic latent image on the photosensitive drum 15 and developed as a toner image.

Each of yellow, magenta and cyan developing units 2
0Y, 20M, and 20C are detachably held by a developing rotary 23 that rotates about a rotating shaft 22, respectively.
At the time of image formation, the developing units 20Y, 20M, and 20C are rotated around the rotary shaft 22 while being held by the developing rotary 23, and a predetermined developing unit is stopped at a position facing the photosensitive drum 15, and the developing sleeve is further stopped. Is the photosensitive drum 15
Then, toner is attached to the electrostatic latent image on the photosensitive drum 15 and developed as a toner image.

When a color image is formed, the developing rotary 23 rotates for each rotation of the intermediate transfer drum 9 as an intermediate transfer member, and the yellow developing device 20Y and the magenta developing device 20 are rotated.
M, cyan developing device 20C, then black developing device 20B
The development process is performed in this order.

FIG. 1 shows a state in which the yellow developing unit 20Y is positioned at a position facing the photosensitive drum 15 and is stationary. The yellow developing device 20Y sends the toner to the coating roller 20YR by a feeding mechanism (not shown), and the sleeve 20YB is pressed against the outer periphery of the coating roller 20YR and the sleeve 20YS by a sleeve 20YB.
A thin layer of toner is applied to the outer periphery of S, and a charge is applied to the toner (friction band weight). Photosensitive drum 15 on which latent image is formed
By applying a developing bias to the sleeve 20YS opposed to the photosensitive drum 15, toner development is performed on the photosensitive drum 15 in accordance with the electrostatic latent image. In the magenta developing device 20M and the cyan developing device 20C, toner development is performed in the same manner as described above.

The respective sleeves of the yellow, magenta, and cyan developing units 20Y, 20M, and 20C are connected to a high-voltage power supply and a driving device (not shown) for developing each color when each of the developing units is rotated to the developing position. In this case, a voltage is sequentially and selectively applied to each color development and driven to rotate. Developing device 2
The 0Y, 20M, and 20C and the black developing device 21B are detachably mounted in the apparatus main body 2. The developing rotary 23 is rotated by driving means such as a motor (not shown), and the developing devices 20 for yellow, magenta, and cyan are rotated.
Y, 20M, and 20C sequentially move to the position facing the photosensitive drum 15.

The intermediate transfer drum 9 as an intermediate transfer member is
At the time of color image forming operation, 20Y, 20
Since the toner image on the photosensitive drum 15 visualized by the M, 20C, and the black developing device 21B is subjected to multiple transfer four times (images of four colors of yellow, magenta, cyan, and black), the outer peripheral speed of the photosensitive drum 15 It rotates in synchronization with. The intermediate transfer drum 9 that has received the multiple transfer transfers the transfer material P between the secondary transfer roller 10 to which the voltage is applied and conveys the transfer material P, thereby simultaneously multiple transferring the toner images of the respective colors on the intermediate transfer drum 9 to the transfer material P. I do.

In the present embodiment, the intermediate transfer drum 9 has a structure in which the outer circumference of an aluminum cylinder 12 having a diameter of 180 mm is covered with an elastic layer 11 such as a medium resistance sponge or medium resistance rubber. Further, the intermediate transfer drum 9 rotates by being driven by a gear (not shown) which is rotatably supported and integrally fixed. The intermediate transfer drum 9 is detachably mounted in the apparatus main body 2.

The cleaning device 13 cleans the transfer residual toner remaining on the photosensitive drum 15 after the toner visualized on the photosensitive drum 15 by the developing device 20 is transferred to the intermediate transfer drum 9. The cleaned waste toner is stored in the cleaner container 14.
The amount of waste toner stored in the cleaner container 14 does not fill the cleaner container 14 earlier than the life of the photosensitive drum 15. Therefore, the cleaner container 14 is simultaneously replaced when the life of the photosensitive drum 15 is replaced.

The feeding means for feeding the transfer material P between the intermediate transfer drum 9 and the secondary transfer roller 10 includes a paper feed cassette 1 containing a plurality of transfer materials P, a paper feed roller 3, and a feeder. A roller 4, a retard roller 5 for preventing double feed, a paper feed guide 6, a transport roller 7, and a registration roller 8 are provided.

At the time of image formation, the paper feed roller 3 is driven and rotated in accordance with the image forming operation, and the transfer material P in the paper feed cassette 1 is rotated.
Are separated and fed one by one, guided by a paper feed guide 6, and fed to a registration roller 8 via a transport roller 7. The registration roller 8 performs, in a predetermined sequence, a non-rotating operation of stopping the transfer material P in a standby state during the image forming operation and a rotating operation of conveying the transfer material P toward the intermediate transfer drum 9 in a predetermined sequence. The image and the transfer material P in a certain transfer step are aligned.

The secondary transfer roller 10 is formed by winding a medium-resistance foam elastic body around a metal shaft (not shown), and is movable in a direction facing the intermediate transfer drum 9. The secondary transfer roller 10 is rotatable by a connected driving device (not shown).

While forming the four-color toner image on the intermediate transfer drum 9, that is, while the intermediate transfer drum 9 rotates a plurality of times, the transfer roller 10 is, as shown by a solid line in FIG. It is separated from the intermediate transfer drum 9. Also,
After the four color toner images have been formed on the intermediate transfer drum 9, the secondary transfer roller 10 is moved by a cam member (not shown) to a position indicated by a dotted line in FIG. That is, the intermediate transfer drum 9 is pressed against the intermediate transfer drum 9 with a predetermined pressure via the transfer material P.

At this time, a bias is applied to the secondary transfer roller 10 at the same time, and the toner image on the intermediate transfer drum 9 is transferred to the transfer material P. Since the intermediate transfer drum 9 and the secondary transfer roller 10 are each driven to rotate, the transfer material P sandwiched between them is conveyed at a predetermined speed to the left in the figure at the same time as the transfer process is performed. It is sent to the fixing device 25 which is a process.

The fixing device 25 fixes the toner image transferred onto the transfer material P by the secondary transfer roller 10, and a fixing roller 26 for applying heat to the transfer material P.
And a pressure roller 27 for pressing the transfer material P against the fixing roller 26. Each roller 26, 27
It is rotatable by a connected driving device (not shown), and has heaters 28 and 29 inside, respectively.

The transfer material P to which the toner image has been transferred is nipped and conveyed between the rotating fixing roller 26 and the pressing roller 27, and the toner image is fixed on the transfer material P by applying heat and pressure. You.

In addition, a control device (CP
U) 40, and the control device 40 controls the image forming operation and controls the rotation of the intermediate transfer drum 9 and the developing device 20 during standby of the device (details will be described later).

Next, an image forming operation by the image forming apparatus configured as described above will be described.

At the time of image formation, the photosensitive drum 1 is driven to rotate at a predetermined process speed by driving means (not shown), and is charged to a predetermined polarity and potential by a charging device 17 to which a predetermined charging bias is applied.

Then, image exposure with laser light L is given to the charged photosensitive drum 1 by the exposure device 3 through the polygon mirror 31, the image forming lens 32 and the reflection mirror 33, and the first color image of the target color image is given. An electrostatic latent image corresponding to a color component image (for example, a yellow component image) is formed. Next, the electrostatic latent image is developed with the yellow toner of the first color by the yellow developing device 20Y.

The yellow toner image of the first color formed and carried on the photosensitive drum 1 passes through the primary transfer nip T1 between the photosensitive drum 1 and the intermediate transfer drum 9, and is primarily transferred onto the intermediate transfer drum 9. Will be done. Hereinafter, similarly, the magenta toner image of the second color, the cyan toner image of the third color, and the fourth color of the third color formed and carried on the photosensitive drum 1 by the magenta developing device 20M, the cyan developing device 20C, and the black developing device 21B, respectively. Are sequentially superimposed and transferred onto the intermediate transfer drum 9 to form a composite color toner image corresponding to the target color image.

At this time, in the process of superimposing and transferring the toner images of the first to fourth colors from the photosensitive drum 1 to the intermediate transfer drum 9, the secondary transfer roller 10 is separated from the intermediate transfer drum 9.

Then, the transfer material P such as paper is separated one by one from the paper cassette 1 by the paper feed roller 3, and the registration material P is fed through the feed roller 4, the retard roller 5, the paper feed guide 6, and the transport roller 7. The sheet is fed to the roller 8 and is conveyed by the registration roller 8 to the secondary transfer nip T2 between the intermediate transfer drum 9 and the secondary transfer roller 10 at a predetermined timing. At this time, a secondary transfer bias is applied to the secondary transfer roller 10, and the composite color toner image is transferred from the intermediate transfer drum 9 onto the transfer material P.

The transfer material P to which the composite color toner image has been transferred is conveyed to the fixing device 25 and is nipped and conveyed between the fixing roller 26 and the pressure roller 27 of the fixing device 25, whereby the transfer material P is transferred onto the transfer material P. The composite color toner image is fixed. The transfer material P on which the composite color toner image is fixed is
The paper is output onto a paper output tray 37 via paper output rollers 34, 35, and 36.

The transfer residual toner remaining on the intermediate transfer drum 9 is removed by the cleaning blade 16 of the cleaning device 13, and the removed waste toner is stored in the cleaner container 14.

Next, a sequence during standby for image formation, which is a feature of the present invention, will be described with reference to a flowchart shown in FIG.

First, in the image forming apparatus which has completed the initial sequence in step S1, the standby time (elapsed time of the standby state) of the image forming apparatus under the control of the control device 40 is set to a standby state continuation time t (sec.).
The standby state (standby state) is maintained until the time reaches (Steps S2 and S3).

When the standby time (elapsed time of the standby state) of the image forming apparatus reaches a preset standby state duration time t in step S 2, the control of the controller 40 controls the intermediate transfer drum 9 and the developing device 20. The developing rotary 23 is moved to a predetermined angle θ _l , θ _R
(Deg.) (Step S4).

On the other hand, when a print signal is input from the standby state of step S3 (step S5), the image forming apparatus enters a print sequence and performs the above-described image forming operation (step S6). In the print sequence of step S6, the position of the developing rotary 23 of the developing device 20 is the home position (the position where the developing rotary 23 is held when the image forming apparatus is on standby. In the present embodiment, the yellow developing device 20Y And cyan developing unit 2
If not, the operation to move to the home position is performed first.

This corresponds to the developing rotary 2 of the developing device 20.
The position of the developing rotary 23 is detected by a home position sensor (not shown) provided on the side plate supporting the camera 3 and is moved to the home position. On the other hand, in the present embodiment, since the intermediate transfer drum 9 does not need to move to the home position, the printing operation starts from the position when the print signal is input.

In the above-described flowchart of the sequence during standby of the image forming apparatus, in the present embodiment,
The standby state continuation time t in step S2 is set to 1800 seconds, and the rotation angle θ _l of the intermediate transfer drum 9 in step S4 is set.
deg. Is 85 ° and the rotation angle θ _{R of the} developing rotary 23 is
deg. Was set to 120 °.

The maximum temperature of the surface layer of the intermediate transfer drum 9 in the vicinity of the fixing device 25 was measured when the above sequence during standby of the image forming apparatus was performed and when this sequence was not performed. The maximum temperature of the surface layer of the drum 9 was suppressed from 60 ° C to 45 ° C. Similarly, the developing device 2 near the fixing device 25
When the maximum temperature of 0 was measured, the maximum temperature of the developing device 20 was suppressed from 45 ° C. to 38 ° C.

As described above, in the present embodiment, a rise in temperature on the surface of the intermediate transfer drum 9 during standby of the apparatus can be suppressed, and at the same time, plastic deformation of the surface of the intermediate transfer drum 9 by the photosensitive drum 15 can be prevented. The deterioration of the surface material of the intermediate transfer drum 9 is suppressed, and the life of the intermediate transfer drum 9 can be extended.

Similarly, a rise in the temperature of the developing device 20 during standby of the device can be suppressed, and thermal deterioration and fusion of the toner can be prevented.

The optimum values of the time t during which the image forming apparatus is kept on standby and the rotational angles θ _l and θ _R of the intermediate transfer drum 9 and the developing rotary 23 of the developing device 20 are optimal depending on the configuration of the image forming apparatus. Since they are different, they can be set to values suitable for the configuration of the image forming apparatus.

[0063]

As described above, according to the present invention, at the time of standby of the image forming apparatus, at least one of the developing means and the transfer means is driven to rotate at predetermined time intervals, whereby the heat on the surface layer of the transfer means is obtained. Since deterioration and thermal deterioration and fusion of the toner used in the developing unit can be prevented, the life of the transfer unit can be extended and a high-quality image can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart during standby of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an image forming apparatus in a conventional example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 paper feed cassette 2 apparatus main body 3 paper feed roller 4 feed roller 5 retard roller 6 paper feed guide 7 transport roller 8 registration roller 9 intermediate transfer drum (transfer means, intermediate transfer body) 10 secondary transfer roller 11 elastic layer 12 aluminum Cylinder 13 Cleaning device 14 Cleaner container 15 Photosensitive drum (electrophotographic photosensitive member) 16 Cleaning blade 17 Charging device 20 Developing device (developing means) 20Y Yellow developing device 20YB Coating blade 20YR Coating roller 20YS Developing sleeve 20M Magenta developing device 20MB Coating blade 20MR Coating roller 20MS Developing sleeve 20C Cyan developing device 20CB Coating blade 20CR Coating roller 20CS Developing sleeve 21B Black developing device 21BB Coating blade 21BR Coating roller 21BS Developing three 22 rotation shaft 23 developing rotary 25 fixing device (heating source, fixing means) 26 fixing roller 27 pressure roller 28, 29 heater 30 exposure device 31 polygon mirror 32 imaging lens 33 reflection mirror 34, 35, 36 discharge roller 37 discharge Tray 40 control device (control means)

Claims (6)

[Claims] An electrophotographic photosensitive member on which an electrostatic latent image is formed; a rotatable developing unit having a plurality of developing units for developing the electrostatic latent image to form a toner image; Control means for controlling at least one of the developing means and the transfer means to be rotationally driven at predetermined time intervals during standby for image formation in an image forming apparatus provided with a rotatable transfer means for transferring an image to a transfer material. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein at least one of the developing unit and the transfer unit is provided near a heat source. 3. The image forming apparatus according to claim 2, wherein the heat source is a fixing unit that fixes the toner image transferred to the transfer material by heating and pressing. 4. The image forming apparatus according to claim 1, wherein the developing unit has at least a yellow developing device, a magenta developing device, and a cyan developing device supported by a rotatable developing rotary. 5. The transfer means contacts the electrophotographic photoreceptor and primarily transfers a toner image at a primary transfer nip portion, and transfers the toner image primary-transferred at a secondary transfer nip portion together with its own rotation to a transfer material. The image forming apparatus according to claim 1, wherein the image forming apparatus is an intermediate transfer member that performs secondary transfer to the image forming apparatus. 6. The image forming apparatus according to claim 5, wherein the intermediate transfer member is a drum-shaped intermediate transfer drum.