JP4788383B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image by an electrophotographic process, and more particularly to an image forming apparatus that includes a transfer unit having a contact transfer member that contacts a back surface of a transfer member to transfer a toner image.

  Conventionally, as a transfer means, corona discharge is performed from the back side of a transfer body such as recording paper, and a charge for attracting the toner image is applied to the back side of the transfer body opposite to the surface on which the toner image is transferred. Non-contact transfer means for transferring an image has been widely used.

  In contrast, as a transfer means that solves the problem of ozone generated by corona discharge, a contact transfer member made of a roller or a belt is used, and a transfer voltage for moving the toner image to the transfer member is applied to the contact transfer member. Contact-type transfer means that presses the transfer body against the image carrier while applying the pressure has come to be used.

  Thus, in the contact type transfer means, there is a problem that the toner adheres to the surface of the contact transfer member, and the adhered toner is retransferred to the back surface of the transfer body and becomes dirty on the back surface. A transfer member cleaning means for cleaning the surface of the contact transfer member is used.

  The transfer member cleaning means includes a blade and electric field cleaning that applies a cleaning voltage for returning toner from the contact transfer member to the image carrier.

The cleaning voltage is applied while pressing the transfer unit against the image carrier. However, in Patent Document 1, in order to effectively perform the cleaning, the pressure of the contact transfer member against the image carrier is applied to the toner image from the image carrier. It has been proposed that the toner image to be transferred to the transfer member is transferred differently from the cleaning of the transfer member for returning the toner from the contact transfer member to the image carrier.
JP-A-8-101588

  As in Patent Document 1, when the transfer unit is cleaned, the cleaning performance is improved by bringing the transfer unit into contact with the image carrier at a higher pressure than when the toner image is transferred, but it is still not sufficient.

  When recovering after a jam has occurred or when resuming operation after an emergency stop, a large amount of toner may adhere to the surface of the transfer means. It was confirmed that it was not removed.

An object of the present invention is to provide an image forming apparatus provided with a transfer member cleaning unit that performs good cleaning even when a large amount of toner adheres to the transfer unit, such as during recovery after a jam has occurred. .

The object is achieved by the following invention.
1.
Image carrier,
Toner image forming means for forming a toner image on the image carrier;
A transfer means for transferring the toner image on the image carrier to a transfer body, the transfer means having a contact transfer member that contacts the back surface of the transfer body for transfer; and
In the image forming apparatus having a transfer member cleaning means for cleaning the toner attached on the contact transfer member,
The transfer member cleaning means has a power source for applying a pressing means and voltage to the contact transfer member to press the contact transfer member to said image bearing member,
In the transfer member cleaning step, the pressing unit presses the contact transfer member against the image carrier with a plurality of gradually increasing pressures, and the power source applies a plurality of gradually decreasing voltages to the contact transfer member. An image forming apparatus.
2.
Photoconductor,
Toner image forming means for forming a toner image on the photoreceptor;
Intermediate transfer member,
First transfer means for transferring a toner image on the photosensitive member to the intermediate transfer member;
A second transfer means for transferring a toner image on the intermediate transfer body to a recording material, the second transfer means having a contact transfer member for transferring in contact with the back surface of the recording material ;
In the image forming apparatus having a transfer member cleaning means for cleaning the toner attached on the contact transfer member,
The transfer member cleaning means has a power source for applying a pressing means and voltage to the contact transfer member to press the contact transfer member to the intermediate transfer member,
In the transfer member cleaning step, the pressing means presses the contact transfer member against the intermediate transfer body with a plurality of pressures that are gradually increased , and the power source applies a plurality of voltages that are gradually decreased to the contact transfer member. An image forming apparatus.
3 .
3. The image forming apparatus according to 1 or 2 , wherein the power supply applies an alternating voltage in a transfer member cleaning step.
4 .
2. The image forming apparatus according to 1, wherein the transfer unit transfers a toner image to the transfer body that is a recording material.
5 .
5. The image forming apparatus according to any one of claims 1 to 4 , wherein the transfer member cleaning step is performed during a jam recovery operation after removing the recording material after the jam has occurred .
6 .
The image forming apparatus according to any one of claims 1 to 5 , wherein the transfer member cleaning step is performed at the time of restart after an emergency stop .
7 .
2. The image forming apparatus according to 1 above, wherein the contact transfer member rotates following the image carrier.
8 .
3. The image forming apparatus according to 2, wherein the contact transfer member rotates following the intermediate transfer member.

  According to the present invention, since the transfer member is satisfactorily cleaned in any case where toner adheres to the contact transfer member, it is possible to always stably obtain a high-quality image recording body with very little backside contamination.

  The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments.

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

  Around the rotating photoreceptor 1 as an image carrier, a charging unit 2, an exposure unit 3, a developing unit 4, a transfer unit 5 and a cleaning unit 6 are disposed.

  The recording material P is conveyed to the transfer position formed by the transfer means 5, and the recording material P to which the toner image has been transferred passes through the fixing means 24 and is fixed.

  As the photosensitive member 1, any known one such as an OPC photosensitive member or an aSi photosensitive member can be used. In the illustrated example, a negatively chargeable OPC photosensitive member is used. In addition to the drum-like material, a belt-like photoconductor can also be used as the photoconductor. As the charging means 2, a well-known device such as a corotron or a scorotron is used. In the illustrated example, a scorotron charger is used. As the exposure means 3, any known laser or LED array can be used. In the illustrated example, a semiconductor laser is used as a light source, and an exposure means using a deflecting device and an imaging optical system is used. As the developing means 4, any known developing means such as a developing means using a two-component developer or a developing means using a one-component developer can be used. However, in the illustrated example, a two-component developer is used, and the inversion is performed. Developing means for forming a toner image by development is used. The developing bias applied to the developer carrying member of the developing unit 4 is preferably a developing bias in which alternating current is superimposed on direct current. As the transfer unit 5, a transfer unit having a transfer roller 50 as a contact transfer member that contacts the back surface of the recording material P and performs transfer by bringing the recording material P into contact with the photoreceptor 1 is used.

  In image formation, the photosensitive member 1 is driven to rotate by a motor M1 and rotates clockwise as indicated by an arrow, and the rotating photosensitive member 1 is uniformly charged by the charging unit 2 and the image is exposed by the exposing unit 3. As a result, an electrostatic latent image is formed on the photoreceptor 1. The formed electrostatic latent image is developed by the developing means 4 to form a toner image.

  In synchronism with the rotation of the photosensitive member 1, the toner image on the photosensitive member P is transferred to the conveyed recording material P by the transfer unit 5.

  The recording material P to which the toner image has been transferred is supplied to the fixing unit 24. In the fixing unit 24, the toner image on the recording material P is heated, melted, and fixed on the recording material P.

  After the toner image has been transferred, the photosensitive member 1 passes through the cleaning means 6 and is cleaned to remove residual toner.

  The transfer unit 5 includes a transfer roller 50 as a contact transfer member. In addition to the transfer roller, a transfer belt can be used as the contact transfer member.

The transfer roller 50 is made of solid rubber such as silicone rubber, urethane rubber, EPDM (ethylene-propylene-diene rubber) or foamed rubber, and has a constant volume resistance of 10 ⁵ to 10 ⁹ Ω · cm, rubber hardness of 20 to 70 ° (Asker) C) is preferably used.

  The rotation shaft 51 of the transfer roller 50 is slidably supported by a bifurcated guide support member 52, and the guide support member 52 is urged by a compression spring 53 constituting a pressing means.

  The guide support member 52 is further slidable within a cylindrical support member 55 and has an action pin 54. The action pin 54 is in contact with the cam 56, and the cam 56 is rotationally driven by the motor M2.

  The spring 53, the cam 56, and the motor MT2 constitute a pressing unit that presses the transfer roller 50 against the photosensitive member 1 with a pressure of two or more levels. Set to standard.

  Reference numeral 57 denotes a cleaning blade as a cleaning means for cleaning the surface of the transfer roller 50.

  TE1 and TE2 are power supplies for applying a transfer voltage and a cleaning voltage to the transfer roller 50.

  In the image forming process, a positive voltage is applied to the transfer roller 50 by the power source TE1, and a toner image made of negatively charged toner is transferred from the photoreceptor 1 to the recording material P. In the transfer process, the cleaning blade 57 is in contact with the transfer roller 50 and cleans the toner adhering to the transfer roller 50.

  As will be described later, when toner adheres to the transfer roller 50, a transfer member cleaning process is performed to remove the adhering toner. In the transfer member cleaning process, basically, the toner is supplied from the power source TE2. A cleaning voltage is applied to transfer the toner from the transfer roller 50 to the photoreceptor 1.

Further, as will be described later, in order to remove not only negatively charged toner but also positively charged adhering toner called reversely charged toner, a cleaning voltage composed of positive and negative alternating voltages is applied to the transfer roller 50. As a result, the transfer roller 50 is cleaned more satisfactorily.
<Embodiment 1>
The transfer member cleaning process for cleaning the transfer roller 50 is executed in the following cases (a) to (d).
(A) Upon completion of image formation Before image formation is completed and rotation of the photosensitive member 1 is stopped, a cleaning voltage is applied to the rotating transfer roller 50 by TE2 to clean the transfer roller 50. The
(B) At the time of completion of preliminary rotation Prior to starting the image forming process, preliminary rotation for rotating the photosensitive member 1 is performed. The preliminary rotation mainly erases the history of the photosensitive member 1. In this preliminary rotation, the photosensitive member is charged and the developing bias (DC) is applied. Therefore, solid development is performed, a band-like toner image is formed on the photosensitive member 1, and the toner image is transferred to the transfer roller 50 and attached.

At the end of the preliminary rotation, the belt-like toner image is transferred to the photoreceptor 1 by rotating the transfer roller 50 while applying a cleaning voltage to the transfer roller 50 and cleaned by the cleaning device 6.
(C) During jam recovery When a jam occurs, the photosensitive member 1 operates to forcibly discharge the recording material remaining in the apparatus when the jam occurs, so that the toner on the photosensitive member 1 is transferred to the transfer roller 50. The toner adheres onto the transfer roller 50 due to the transfer. Further, after the jam is released, the photosensitive member 1 is operated to clean these surfaces. At this time, the toner adheres to the surface of the transfer roller 50. Accordingly, a transfer member cleaning process for removing the toner from the transfer roller 50 at the time of jam recovery is performed.
(D) At the time of restart after an emergency stop The transfer roller 50 is cleaned at the time of restart after an emergency stop due to an abnormal transfer current, turning of the cleaning blade of the cleaning device 6 or the like.

In the cases (a) and (b) among the cases (a) to (d), the amount of toner adhering to the transfer roller 50 is relatively small. Therefore, in the case of (a) and (b), the following A mode transfer member cleaning process is executed.
A mode A cycle in which a voltage of ± 2 kV is applied to the transfer roller 50 by the power sources TE1 and TE2 is repeated four times. In each cycle, the transfer roller 50 is rotated twice, and the transfer roller 50 is driven with a pressure of 20 N through four cycles. Press to 1. Such a transfer member cleaning process is shown in FIG.

As a result, the transfer roller 50 is cleaned well.
B mode In the cases (c) and (d), there is a possibility that the toner that forms a solid image may be transferred to and adhered to the transfer roller 50 as it is, and a transfer member cleaning process capable of cleaning a large amount of toner is performed. Need to be implemented.

  In the B mode, the cycle in which a voltage of ± 2 kV is applied to the transfer roller 50 by the power supplies TE1 and TE2 is repeated four times, and the transfer roller 50 is rotated twice in each cycle, but the transfer mode is the same as in the A mode. In the transfer member cleaning process, the pressure of the transfer roller 50 is gradually increased so that the pressure of the roller 50 is 20 N in the first half of the cleaning process and 50 N in the second half.

  FIG. 3 shows the cleaning process in the B mode.

  When a large amount of toner adheres to the transfer roller 50, if the transfer roller 50 is brought into contact with the photoconductor 1 with a large pressure from the beginning, the toner may be compressed and a portion that does not transfer to the photoconductor 1 may appear. As shown in FIG. 3, more effective cleaning can be performed by gradually increasing the pressure of the transfer roller 50.

  With the cleaning shown in FIG. 3, the transfer roller 50 can be satisfactorily cleaned even when toner for forming a solid image adheres to the transfer roller 50.

  The cleaning in the A and B modes is set based on the experimental results described below.

FIG. 4 shows the cleaning performance for a solid toner image adhering to the transfer roller 50 when the pressure of the transfer roller 50 is 50N. In FIG. 4, the vertical axis represents the amount of toner (g / m ² ) on the transfer roller 50, and the horizontal axis represents the number of cleanings. Regarding the number of cleanings, one rotation of the transfer roller 50 was set to one cleaning. Ie upon 2 and the negative voltage or a negative voltage from a positive voltage and one change periodically cleaning count once indicated by C to the positive voltage.

  FIG. 5 shows the cleaning performance for a solid toner image attached to the transfer roller 50 when the pressure of the transfer roller 50 is 20N. 4 and 5, “x” indicates a poor cleaning, Δ indicates a substantially good cleaning result, and ○ indicates a good cleaning result.

  As is clear from the figure, the area below the curve L is the area where good cleaning is performed, and good cleaning is performed when the number of cleanings is increased, but a relatively small number of cleanings is performed by increasing the pressure. It can be seen that good cleaning is performed.

  However, in the case of a high pressure, that is, 50 N, when the number of cleanings is increased, a phenomenon in which toner partially remains on the transfer roller 50 was observed. For this reason, if the pressure of the transfer roller 50 is increased, the transfer roller 50 and the backup roller 74 may be deformed. Therefore, it is preferable to reduce the number of times of lack of high pressure as much as possible.

As shown in FIG. 5, in the cleaning step of the transfer roller 50, by changing the pressure, without causing faulty cleaning, good cleaning is performed, it is possible to prevent the back surface contamination of the recording material.

In the A mode, the transfer roller 50 is cleaned depending on each of the cases (a) to (d) so as to be constant at a relatively low pressure and constant at a relatively high pressure in the B mode. It is also possible to set the pressure to two or more levels and perform cleaning at a constant pressure.
<Embodiment 2>
6 and 7 show a transfer member cleaning process in the second embodiment.

  In the present embodiment, the same cleaning of the transfer roller 50 as in the first embodiment was performed at the end of (a) image formation and (b) at the end of preliminary rotation, but (c) at the time of jam recovery and (D) At the time of restart after the emergency stop, the applied voltage was gradually decreased from 4 kV to 2 kV.

  FIG. 8 shows the cleaning performance for a solid toner image attached to the transfer roller 50 when the voltage applied to the transfer roller 50 is changed. As is apparent from FIG. 8, the upper right of the curve L, that is, the voltage is high, and the cleaning cycle is increased, so that a good cleaning is performed.

  Based on the cleaning test results of FIGS. 4, 5 and 8, as shown in FIG. 7, the pressure of the transfer roller 50 and the cleaning are compared with the cases (c) and (d) in which a large amount of toner may adhere. By performing the transfer member cleaning in which the voltage is changed during the transfer member cleaning step, it is possible to satisfactorily remove the toner attached to the transfer roller 50. In the latter half of the cleaning process, the amount of toner remaining on the transfer roller 50 is reduced, so that the cleaning voltage can be gradually reduced to perform good cleaning.

  FIG. 9 is a diagram showing an outline of another example of the image forming apparatus according to the embodiment of the present invention.

  The image forming apparatus 100 is called a tandem full-color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer body unit 7, a paper feeding / conveying unit 21, and a fixing device. 24. A document image reading device SC is disposed above the image forming apparatus 100.

  The image forming apparatus 100 is provided with a housing 8 that can be pulled out via support rails 82L and 82R. Inside the housing 8, image forming units 10Y, 10M, 10C, and 10K, and an intermediate transfer member are provided. A unit 7 is provided. Note that the housing 8 may be used as a member that can be separated and replaced from the image forming unit A called a process cartridge.

  In FIG. 9, the image forming units 10Y, 10M, 10C, and 10K are vertically arranged in the vertical direction, and the intermediate transfer member unit 7 is disposed on the left side of the photosensitive member constituting each image forming unit. The intermediate transfer body unit 7 is an intermediate transfer of an endless belt-like intermediate transfer body 70 wound around rollers 71, 72, 73, 74 (backup rollers), 76, 77, and toner images formed by the respective image forming units. The primary transfer rollers 5Y, 5M, 5C, and 5K to be transferred onto the body 70 and the cleaning means 6A that removes the toner remaining on the intermediate transfer body 70 are configured. Next, image formation performed by the image forming apparatus 100 will be described.

  The image forming unit 10Y for forming a yellow image includes a drum-shaped photoconductor 1Y, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y, and a cleaning unit 6Y arranged around the photoconductor 1Y. Have The image forming unit 10M for forming a magenta image includes a drum-shaped photoconductor 1M, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M, and a cleaning unit 6M arranged around the photoconductor 1M. Have The image forming unit 10C for forming a cyan image includes a drum-shaped photoconductor 1C, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C, and a cleaning unit 6C arranged around the photoconductor 1C. Have The image forming unit 10K for forming a black image includes a drum-shaped photosensitive member 1K, a charging unit 2K, an exposing unit 3K, a developing unit 4K, a primary transfer roller 5K, and a cleaning unit 6K disposed around the photosensitive unit 1K. .

  The intermediate transfer body unit 7 includes a semiconductive endless belt-like intermediate transfer body 70 that is wound around a plurality of rollers and is rotatably supported.

  The single color toner images formed in the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K, and are synthesized. An image is formed.

  The recording material P such as paper stored in the paper feed cassette 20 is sent out one by one by the first paper feed roller 21 and conveyed by the paper feed rollers 22A, 22B, 22C, 22D. Pause at the upstream position. After the temporary stop, the recording material P is conveyed to the transfer position by the registration roller 23 in synchronization with the image formation in the image forming units 10Y, 10M, 10C, and 10K. The color toner image is transferred onto the recording material P at the transfer position formed by the roller 74 that supports the intermediate transfer body 70 and the transfer roller 5A.

  Reference numeral 22E denotes a manual sheet feeder.

  The recording material P onto which the color toner image has been transferred is fixed by a fixing device 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  In the double-sided image formation, the recording material P on which the image is formed on the front surface travels downward after passing through the fixing device 24, reverses in the reverse conveyance path 27, and then is fed again to the registration roller 23. After the back image is formed and fixed on the re-recorded recording material P, the recording material P is discharged to the discharge tray 26.

  On the other hand, after the color toner image is transferred to the recording material P by the secondary transfer roller 5A, the residual toner is removed from the intermediate transfer body 70 from which the recording material P has been separated by the cleaning means 6A.

  In this example, the toner image is transferred to the intermediate transfer member 70 as the image carrier by the primary transfer rollers 5Y, 5M, 5C, and 5K as the toner image forming unit. The secondary transfer member is a contact transfer member of the transfer unit. As described above, the transfer member cleaning process for the transfer roller 5A is executed in the A mode and the B mode.

  In this example, the transfer means is composed of a secondary transfer roller 5A as a contact transfer member and a power source TE1, and the transfer member cleaning means is a spring 53 as shown in FIG. 1 and described above with reference to the image forming apparatus of FIG. The transfer member cleaning process is executed in the A mode and the B mode, which includes a cam 56 and a motor M2, and includes pressing means and power supplies TE1 and TE2 for applying a cleaning voltage.

  As shown in FIG. 10, the transfer voltage and the cleaning voltage applied to the transfer roller 5 </ b> A as the contact transfer member are applied by applying voltages from the power sources TE <b> 1 and TE <b> 2 to the backup roller 74.

1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a transfer member cleaning process in the A mode of the first embodiment. FIG. 6 is a diagram illustrating a transfer member cleaning process in the B mode according to the first embodiment. 6 is a graph showing a cleaning performance for a solid toner image attached to a transfer roller. 6 is a graph showing a cleaning performance for a solid toner image attached to a transfer roller. FIG. 10 is a diagram illustrating a transfer member cleaning process in the A mode of the second embodiment. FIG. 10 is a diagram illustrating a transfer member cleaning process in the B mode of the second embodiment. 6 is a graph showing a cleaning performance for a solid toner image attached to a transfer roller. It is a figure which shows the outline of the other example of the image forming apparatus which concerns on embodiment of this invention. It is a figure which shows the transfer member cleaning process in B mode. FIG. 10 is a diagram illustrating a transfer unit of the image forming apparatus illustrated in FIG. 9.

Explanation of symbols

1, 1Y, 1M, 1C, 1K Photoconductor 5 Transfer means 5A Secondary transfer roller 53 Spring 50 Transfer roller 53 Spring 56 Cam M1, M2 Motor TE1, TE2 Power supply

Claims (8)

Image carrier,
Toner image forming means for forming a toner image on the image carrier;
A transfer means for transferring the toner image on the image carrier to a transfer body, the transfer means having a contact transfer member that contacts the back surface of the transfer body for transfer; and
In the image forming apparatus having a transfer member cleaning means for cleaning the toner attached on the contact transfer member,
The transfer member cleaning means has a power source for applying a pressing means and voltage to the contact transfer member to press the contact transfer member to said image bearing member,
In the transfer member cleaning step, the pressing unit presses the contact transfer member against the image carrier with a plurality of gradually increasing pressures, and the power source applies a plurality of gradually decreasing voltages to the contact transfer member. An image forming apparatus. Photoconductor,
Toner image forming means for forming a toner image on the photoreceptor;
Intermediate transfer member,
First transfer means for transferring a toner image on the photosensitive member to the intermediate transfer member;
A second transfer means for transferring a toner image on the intermediate transfer body to a recording material, the second transfer means having a contact transfer member for transferring in contact with the back surface of the recording material ;
In the image forming apparatus having a transfer member cleaning means for cleaning the toner attached on the contact transfer member,
The transfer member cleaning means has a power source for applying a pressing means and voltage to the contact transfer member to press the contact transfer member to the intermediate transfer member,
In the transfer member cleaning step, the pressing means presses the contact transfer member against the intermediate transfer body with a plurality of pressures that are gradually increased , and the power source applies a plurality of voltages that are gradually decreased to the contact transfer member. An image forming apparatus. Wherein the power source, the transfer member in the cleaning step, the image forming apparatus according to claim 1 or 2, characterized in that an alternating voltage is applied.   The image forming apparatus according to claim 1, wherein the transfer unit transfers a toner image to the transfer body that is a recording material. The transfer member cleaning step, the image forming apparatus according to any one of claims 1 to 4, characterized in that takes place when a jam recovery action after removal of the recording material after the occurrence of a jam. The transfer member cleaning step, the image forming apparatus according to any one of claims 1 to 5, characterized in that is carried out when restarting after an emergency stop.   The image forming apparatus according to claim 1, wherein the contact transfer member rotates following the image carrier.   The image forming apparatus according to claim 2, wherein the contact transfer member rotates following the intermediate transfer member.

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