JP6394738B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that transfers a toner image on an image carrier to a recording medium.

  As an image forming apparatus for transferring a toner image on the surface of an image carrier to a recording material sandwiched in a transfer nip, an image forming apparatus described in Japanese Patent Application Laid-Open No. 2006-267486 is known. . The image forming apparatus described in Patent Document 1 records a toner image formed on the surface of a drum-shaped photosensitive member serving as an image carrier via an endless intermediate transfer belt that is an image carrier and an intermediate transfer member. This is an intermediate transfer type apparatus for transferring to a medium (for example, transfer paper). Further, a direct transfer type image forming apparatus that transfers a toner image formed on the surface of a photoconductor as an image carrier directly from a photoconductor to a recording medium is also well known.

  As a method for transferring a toner image carried by an image carrier such as a photoreceptor or an intermediate transfer belt to a recording medium, a contact transfer method is widely used today. In the contact transfer method, a transfer member such as a transfer roller is disposed at a position facing the image carrier in the transfer region, and a transfer nip is formed between the image carrier and the transfer member. Then, by applying a transfer bias to the transfer nip, the toner image carried on the image carrier is electrostatically transferred to the recording medium in the nip.

  The transfer member contacts the surface of the image carrier when the recording medium does not exist in the transfer nip, and contacts the back surface of the recording medium when the recording medium exists in the transfer nip. Therefore, when the recording medium is not present in the transfer nip, the toner on the surface of the image carrier adheres to the surface of the transfer member, and if the toner adheres to the back surface of the recording medium, the recording medium becomes dirty. May occur.

  A technique for performing bias cleaning of the transfer member is known as a technique for suppressing the back contamination of the recording medium without providing a cleaning device for the transfer member. For example, Patent Document 2 (Japanese Patent Laid-Open No. 2011-158785) and Patent It is disclosed in Document 3 (Japanese Patent Laid-Open No. 2001-83853) and the like. In the bias cleaning, a cleaning bias is applied to the transfer area during non-image formation to transfer toner or the like to the surface of the image carrier, and this is cleaned using a cleaning mechanism of the image carrier. The bias cleaning method is advantageous in terms of downsizing and cost reduction of the image forming apparatus because the backside contamination of the transfer paper can be suppressed without providing a transfer member cleaning device.

However, in bias cleaning, the optimum cleaning conditions differ when the environment or changes with time occur. For example, in a low temperature environment or over time, the cleaning performance deteriorates due to an increase in the resistance of the transfer member and a deterioration in the surface property of the roller .

SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can satisfactorily clean a transfer member even when environmental conditions fluctuate.

In order to solve the above problems, the present invention provides an image carrier on which a toner image is carried, a transfer member, and a power source for applying a transfer bias to a transfer portion where the image carrier and the transfer member face each other. And an image forming apparatus for transferring the toner image on the image carrier to a recording medium, and recording the toner image on the image carrier. When applying a bias having a polarity opposite to that when the toner image is transferred to the recording medium from the power source, or when transferring the toner image to the recording medium at a timing different from when transferring to the medium. the opposite polarity and the same polarity of the bias be those applied alternately performing bias cleaning of the transfer member, said control means, said bias when the temperature detected by said temperature detecting means is low When performing cleaning, the temperature detected by said temperature detecting means is compared with the case of performing the bias cleaning if not cold, characterized in that the operating speed before Kizo carrier and the transfer member are both low .

In order to solve the above problems, the present invention provides an image carrier for carrying a toner image, a transfer member, and a transfer bias applied to a transfer portion where the image carrier and the transfer member face each other. In an image forming apparatus, comprising: a power source; a control unit that controls the power source; and a temperature / humidity detection unit that detects temperature and humidity, wherein the toner image on the image carrier is transferred to a recording medium. A bias having a polarity opposite to that when the toner image is transferred to the recording medium is applied from the power source to the transfer unit at a timing different from that when the toner image is transferred to the recording medium, or the toner image is transferred to the recording medium. The biasing of the transfer member is performed by alternately applying a bias of the opposite polarity and the same polarity as when transferring to the transfer member, and the control means has a low temperature and humidity detected by the temperature and humidity detection means. When in the case of humidity performing the bias cleaning, temperature and humidity detected by said temperature detecting means is compared with the case of performing the bias cleaning if not cold low humidity, operating speed before Kizo carrier and the transfer member It is characterized by lowering both.

According to the image forming apparatus of the present invention, it is possible to provide an image forming apparatus that can satisfactorily clean the transfer member even when the environmental conditions fluctuate.

1 is a schematic configuration diagram of a printer as an example of an image forming apparatus according to the present invention. The enlarged view which shows another form of the power supply and voltage supply for secondary transfer. FIG. 2 is a block diagram illustrating a part of a printer control system. It is a flowchart which shows an example of the control of the bias cleaning performed at the time of jam recovery operation | movement. It is a wave form diagram which shows an example of the basic unit of cleaning bias. It is a wave form diagram which shows a mode that the basic unit is repeatedly applied in multiple cycles. It is a flowchart which shows an example of control of the bias cleaning in 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an electrophotographic color printer (hereinafter simply referred to as “printer”) as an example of an image forming apparatus according to the present invention.

  In the figure, the printer includes four image forming units 1Y, 1M, 1C, and 1K for forming yellow (Y), magenta (M), cyan (C), and black (K) toner images, and a transfer device. As a transfer unit 30, an optical writing unit 80, a fixing device 90, a paper feed cassette 100, a registration roller pair 101, and a control unit 60 serving as control means.

  The four image forming units 1Y, 1M, 1C, and K use Y, M, C, and K toners of different colors as image forming materials, but other than that, they have the same configuration and are replaced when the lifetime is reached. Is done. The image forming unit 1K for forming a K toner image will be described as an example. This unit includes a drum-shaped photosensitive member 2K as an image carrier, a drum cleaning device 3K, a charge eliminating device (not shown), a charging device 6K, a developing device. The apparatus 8K etc. are provided. The image forming unit 1K is configured such that these components are held in a common casing and can be integrally attached to and detached from the printer body, and these components can be replaced at the same time.

  The photoreceptor 2K is rotationally driven in a clockwise direction in the drawing by a driving unit (not shown). The charging device 6K uniformly charges the surface of the photoreceptor 2K. In this printer, the toner is uniformly charged to the same negative polarity as the normal charging polarity of the toner. Instead of a method of bringing a charging member such as a charging roller into contact with or close to the photosensitive member 2K, a charging method using a charging charger may be adopted.

  The surface of the photoreceptor 2 </ b> K uniformly charged by the charging device 6 </ b> K is optically scanned by a laser beam emitted from the optical writing unit 80 to carry an electrostatic latent image for K. The electrostatic latent image for K is developed by the developing device 8K using K toner to become a K toner image. Then, the toner image is primarily transferred onto an intermediate transfer belt 31 which is an intermediate transfer member which will be described later and is a belt-like image carrier.

  In the Y, M, and C image forming units 1Y, 1M, and 1C, Y, M, and C toner images are respectively formed on the photoreceptors 2Y, 2M, and 2C in the same manner as the K image forming unit 1K. Is done.

  Above the image forming units 1Y, 1M, 1C, and 1K, an optical writing unit 80 serving as a latent image writing unit is disposed. The optical writing unit 80 optically scans the photosensitive members 2Y, 2M, 2C, and 2K with laser light emitted from a light source such as a laser diode based on image information. By this optical scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 2Y, 2M, 2C, and 2K. As the exposure means, one that performs optical writing on the photoreceptors 2Y, 2M, 2C, and 2K by LED light emitted from a plurality of LEDs of the LED array may be employed.

  Below the image forming units 1Y, 1M, 1C, and 1K, there is disposed a transfer unit 30 that moves the endless intermediate transfer belt 31 endlessly in the counterclockwise direction in the drawing. In addition to the intermediate transfer belt 31 as an image carrier, the transfer unit 30 includes a driving roller 32, a repulsive roller 33, a cleaning backup roller 34, four primary transfer rollers 35Y, 35M, 35C, and 35K serving as primary transfer members, a transfer member Secondary transfer roller 36, belt cleaning device 37, and the like.

  A primary transfer bias is applied to the primary transfer rollers 35Y, 35M, 35C, and 35K by a primary transfer bias power source (not shown). As a result, transfer electric fields are formed between the Y, M, C, and K toner images on the photoreceptors 2Y, 2M, 2C, and 2K and the primary transfer rollers 35Y, 35M, 35C, and 35K. The Y toner formed on the surface of the Y photoconductor 2Y enters the Y primary transfer nip as the photoconductor 2Y rotates. Then, due to the action of the transfer electric field and the nip pressure, the image is moved from the photoreceptor 2Y onto the intermediate transfer belt 31 to be primarily transferred. The intermediate transfer belt 31 on which the Y toner image is primarily transferred in this way then passes sequentially through the primary transfer nips for M, C, and K. Then, the M, C, and K toner images on the photoreceptors 2M, 2C, and 2K are sequentially superimposed and superimposed on the Y toner image. By this primary transfer of superposition, a four-color superposed toner image is formed on the intermediate transfer belt 31. Instead of the primary transfer rollers 35Y, 35M, 35C, and 35K, a transfer charger, a transfer brush, or the like may be employed as the primary transfer member.

  The secondary transfer roller 36 of the transfer unit 30 is disposed outside the loop of the intermediate transfer belt 31, and the intermediate transfer belt 31 is sandwiched between the repulsive roller 33 inside the loop. As a result, a secondary transfer nip N is formed in which the front surface of the intermediate transfer belt 31 and the secondary transfer roller 36 abut. In the example shown in FIG. 1, the secondary transfer roller 36 is grounded, while the repulsive roller 33 is applied with a secondary transfer bias as a voltage by a power supply 39 of the secondary transfer bias. As a result, a secondary transfer electric field is formed between the repulsive roller 33 and the secondary transfer roller 36 to cause the negative polarity toner to electrostatically move from the repulsive roller 33 side toward the secondary transfer roller 36 side.

  Below the transfer unit 30, a paper feed cassette 100 that stores a plurality of recording papers P in a stacked state is disposed. In the paper feed cassette 100, a paper feed roller 100a is brought into contact with the top recording paper P in the paper bundle, and the recording paper P is directed to the paper feed path by being driven to rotate at a predetermined timing. And send it out. A registration roller pair 101 is disposed near the end of the paper feed path. The registration roller pair 101 sends the recording paper P toward the secondary transfer nip N at a timing at which the recording paper P can be synchronized with the four-color superimposed toner image on the intermediate transfer belt 31 in the secondary transfer nip N. The four-color superimposed toner image on the intermediate transfer belt 31 brought into close contact with the recording paper P at the secondary transfer nip N is collectively transferred onto the recording paper P by the action of the secondary transfer electric field and nip pressure, and recorded. Combined with the white color of the paper P, a full color toner image is obtained. When the recording paper P having the full color toner image formed on the surface in this way passes through the secondary transfer nip N, the recording paper P is separated from the secondary transfer roller 36 and the intermediate transfer belt 31 by curvature.

  The power source 39 outputs a voltage (hereinafter referred to as “secondary transfer bias”) for transferring the toner image on the intermediate transfer belt 31 to the recording material P sandwiched in the secondary transfer nip N. In this embodiment, as shown in FIG. 1, the secondary transfer roller 36 is grounded while the secondary transfer bias is applied to the repulsive roller 33.

  The supply form of the secondary transfer bias is not limited to the form shown in FIG. 1, and the repulsive roller 33 is applied while applying the secondary transfer bias from the power source 39 to the secondary transfer roller 36 as shown in FIG. 2. May be grounded. In this case, the polarity of the DC voltage is made different from that in FIG.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 31 after passing through the secondary transfer nip N. This transfer residual toner is cleaned from the belt surface by a belt cleaning device 37 in contact with the front surface of the intermediate transfer belt 31.

  A fixing device 90 is disposed on the right side in FIG. 1, which is downstream of the secondary transfer nip N in the recording paper conveyance direction. The fixing device 90 forms a fixing nip with a fixing roller 91 containing a heat source such as a halogen lamp and a pressure roller 92 that rotates while contacting with the fixing roller 91 with a predetermined pressure. The recording paper P fed into the fixing device 90 is sandwiched between the fixing nips in such a posture that the carrying surface of the unfixed toner image is in close contact with the fixing roller 91. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full-color image is fixed. The recording paper P discharged from the fixing device 90 passes through a post-fixing conveyance path and is then discharged outside the apparatus.

  In this printer, the standard mode and the high image quality mode are set in the control unit 60. The “standard speed” which is the process linear speed in the standard mode (the linear speed of the photosensitive member and the intermediate transfer belt) is set to 352.8 [mm / s]. Further, the “low speed” which is the process linear speed in the high image quality mode in which higher image quality is given priority than the print speed is set to 158.8 [mm / s]. Switching between the standard mode and the high image quality mode is performed by a user key operation on an operation panel 50 (see FIG. 3) provided in the printer or a printer property menu on the personal computer connected to the printer.

  FIG. 3 is a block diagram showing a part of the control system of the printer. In the figure, a control unit 60 constituting a part of the transfer bias output means includes a CPU 60a (Central Processing Unit) as a calculation means, a RAM 60c (Random Access Memory) as a nonvolatile memory, and a ROM 60b (Read Only Memory) as a temporary storage means. And a flash memory 60d. Various components and sensors are electrically connected to the control unit 60 that controls the entire printer so as to be communicable. In FIG. 3, only components related to the characteristic configuration of the printer are shown. Is shown.

  A power source 39 for secondary transfer outputs a secondary transfer bias supplied to the secondary transfer nip N. In the form of FIG. 1, a secondary transfer bias to be applied to the repulsive roller 33 is output. The power supply 39 constitutes a transfer bias output means together with the control unit 60. The operation panel 50 includes a touch panel (not shown) and a plurality of key buttons. The operation panel 50 can display an image on the screen of the touch panel. The operation panel 50 receives an input operation by the operator using the touch panel and the key button, and inputs the input information to the control unit 60. It has a function to send. The operation panel 50 can also display an image on the touch panel based on a control signal sent from the control unit 60. The secondary transfer bias by the power supply 39 and the application of a cleaning bias, which will be described later, are also controlled by the CPU 60b of the control unit 60.

  By the way, in this embodiment, the secondary transfer roller 36 as a transfer member has a foam roller configuration in which foam rubber (elastic layer) is laminated on a core metal. The secondary transfer roller 36 is not provided with a cleaning means, and bias cleaning is performed by applying a cleaning bias to the secondary transfer region (to the repulsive roller 33 in the embodiment of FIG. 1). The toner transferred from the secondary transfer roller 36 to the intermediate transfer belt 31 by the bias cleaning is cleaned by a belt cleaning device 37.

  In this embodiment, the secondary transfer roller 36 is not provided with a cleaning unit, but the secondary transfer roller 36 may be provided with a cleaning unit (both bias cleaning and cleaning by the cleaning unit may be performed). Good).

  The present invention is characterized in that the operating linear velocity when performing bias cleaning of the transfer member is changed according to the environmental conditions (first embodiment). Further, the operation linear velocity when performing bias cleaning of the transfer member is changed according to the time-dependent condition (second embodiment).

  First, as a first embodiment of the transfer member bias cleaning (in which the operation linear velocity when performing bias cleaning of the transfer member is changed according to the environmental conditions), the transfer member that performs bias cleaning is the second member in the configuration of FIG. A case where a DC bias as a cleaning bias is applied to the transfer area (to the repulsive roller 33 in the secondary transfer portion in the configuration of FIG. 1) as the next transfer roller 36 will be described as an example.

  In the embodiment, as the application control of the cleaning bias, (1) a DC component having a polarity opposite to that of the image transfer is applied, (2) a DC component having a positive / negative polarity (reverse polarity to the image transfer and the same polarity as that of the image transfer) by switching the polarity. The two controls of alternately applying can be performed. In each of the above (1) and (2), the bias value to be applied and the bias application time are changed according to the environmental conditions. Note that the bias application time is simply changed in the case of (1) above. In the case of (2) above, the number of times of polarity switching (number of cycles) is changed.

  In this embodiment, a DC component (DC bias) is used as a cleaning bias. However, a DC component having a polarity opposite to that of image transfer is controlled by a constant voltage, and a DC component having the same polarity as that of image transfer is controlled by a constant current. .

  Furthermore, in the present embodiment, there are two operation modes, ie, a normal speed mode (hereinafter referred to as a cleaning standard mode) and a low speed mode (hereinafter referred to as a cleaning low speed mode) as operation modes for the transfer member bias cleaning. The operating linear velocity in the standard cleaning mode is set to 352.8 [mm / s], which is the same as the “standard velocity” that is the linear velocity in the standard mode during image formation. Further, the operation linear velocity in the cleaning low speed mode is set to 158.8 [mm / s], which is the same as the “low speed” which is the linear velocity in the high image quality mode at the time of image formation.

  In the present invention, the linear speed in bias cleaning is changed by changing both the linear speeds of the image carrier (here, the intermediate transfer belt 31) and the transfer member (here, the secondary transfer roller 36) in contact therewith. It is assumed that the relative speed of is not changed.

  In the embodiment, the apparatus linear speed at which the bias cleaning of the transfer member is performed is the same as the operation linear speed (“standard speed” and “low speed”) in the image forming mode. May be an operation linear velocity different from the operation linear velocity at the time of image formation. In the present embodiment, “standard speed” and “low speed”, which are the operation linear speeds in the image forming mode, are used as they are as the operation linear speeds of the bias cleaning in order to suppress increase in control load and cost.

  Further, when a plurality of linear velocities are provided as the operation linear velocity at the time of image formation and the operation linear velocity for bias cleaning, either one is made the same and the other is made different, or any one is made different and the others are the same. It is good.

  As described above, the present embodiment has the cleaning standard mode and the cleaning low speed mode, and the operation linear speed is changed based on the detection result of the temperature sensor or the temperature / humidity sensor mounted on the image forming apparatus. Specifically, when the detection result of the temperature sensor or temperature / humidity sensor is a predetermined low temperature environment or low temperature / low humidity environment, the bias cleaning of the transfer member is performed in the cleaning low speed mode, and in the case of other environmental conditions It shall be carried out in the cleaning standard mode. Predetermined conditions for carrying out in the cleaning low speed mode will be described later.

Next, the timing for performing bias cleaning of the transfer member is set to be performed at a timing different from the printing operation in the embodiment. As the “timing different from the printing operation”, the following two timings a) and b) can be considered.
a) A paper jam occurs while being conveyed from the paper feed unit to the paper discharge unit. → Jam removed paper is removed. → Timing when cleaning is performed by a return operation (= when a jam recovery operation is performed).
b) Timing when the device is abnormally terminated by applying a large impact or power failure and turning on the power of the device → recovering operation (= recovery operation from abnormal termination of the device).

  In addition, as the “timing different from the printing operation”, the bias cleaning can be performed before printing, after printing, or at other appropriate “timing different from the printing operation”.

  As an example of classification of environmental conditions, in the embodiment, classification is performed based on temperature and humidity detected by a temperature and humidity sensor, and HH (high temperature and high humidity), MH (room temperature and high humidity), MM (room temperature and normal humidity), ML (Normal temperature and low humidity), LL (low temperature and low humidity), and LLL (low temperature and low humidity than LL). When the detection result of the temperature / humidity sensor is determined to be an HH, MH, or MM environment, bias cleaning is performed in the cleaning standard mode. When the detection result is an ML, LL, or LLL environment, bias cleaning is performed in the cleaning low speed mode. To do.

FIG. 4 is a flowchart showing an example of bias cleaning control executed during the jam recovery operation.
In this flowchart, when jam recovery occurs (S1), a return operation execution flag is set (S2). Then, jam recovery is canceled (S3), and environmental conditions are detected by a temperature / humidity sensor or the like (S4). If it is determined that the detected environmental condition is a predetermined environmental condition (in this embodiment, one of the ML, LL, and LLL environments), the process proceeds to S6, and the bias cleaning mode is set to the cleaning low speed mode. If the detected environmental condition is other than the above, the process proceeds to S7, and the bias cleaning mode is set to the cleaning standard mode. Then, the secondary transfer roller 36 as a transfer member is brought into contact with the intermediate transfer belt 31 as an image carrier (S8), and a predetermined cleaning bias is applied to perform bias cleaning (S9).

  FIG. 5 shows a case where polarity is switched as a cleaning bias for bias cleaning of the transfer member (secondary transfer roller 36), and positive and negative (image transfer reverse polarity and image transfer same polarity) DC components are alternately applied. FIG. 5 is a waveform diagram showing a basic unit of a cleaning bias. In the illustrated example, the bias having the same polarity (−) as the image transfer is applied for 0.9 turn of the secondary transfer roller 36, and the bias having the opposite polarity (+) to the image transfer is 1.0 turn of the secondary transfer roller 36. Application is made to the repulsive roller 33 for a period of minutes. By switching the polarity of the cleaning bias, not only the normally charged toner but also the reversely charged toner is cleaned.

  FIG. 6 shows how the basic unit of the cleaning bias is repeatedly applied for a plurality of cycles. The number of repetitions is set to 12 in the jam recovery operation, but is not limited to this and can be changed as appropriate. The waveform of the cleaning bias is not limited to the illustrated example, and can be changed as appropriate. For example, in the basic unit, the application time of the reverse polarity (+) to the image transfer is set to 1.8 laps (1.8 laps of the secondary transfer roller 36).

Next, an evaluation experiment conducted by the inventor will be described.
The evaluation experiment is performed with the machine having the configuration shown in FIG. 1, and the machine is forcibly stopped at a predetermined timing during printing of a two-color solid image, and a jam occurs so that the secondary transfer roller 36 is soiled with toner. As a result, the secondary transfer roller 36 is soiled with a solid image of two-color toner (100% cyan and 100% magenta in the experiment). Then the jammed paper is removed and the machine is returned. At this time, the recovery cleaning described in FIG. 4 is executed. After that, print a blank image and check the backside of the paper.

The experimental environment was performed under two conditions of 23 ° C. 50% and 10 ° C. 15%.
The paper used for the evaluation was a high-quality paper for full-color copying (TYPE6000 <70W>) manufactured by Ricoh Co., Ltd.

  The cleaning bias is a method in which the polarity of the DC component is repeatedly switched as described above, and is 1000 V on the opposite polarity (+) side to the image transfer in the cleaning standard mode (standard speed), and -80 μA on the same polarity (−) side as the image transfer. . In the cleaning low speed mode (low speed), the reverse polarity (+) side to the image transfer is 1000 V, and the same polarity (−) side as the image transfer is −36 μA.

  The evaluation results are shown in Table 1 below. The determination is based on ranks 1 to 5, with rank 5 being the best, no back dirt, and rank 4 or higher being the allowable range.

  As shown in Table 1, in the environment of 23 ° C. and 50%, the standard bias speed was out of the allowable range at rank 3.5 when the number of reciprocations of polarity switching of the cleaning bias was 3. By changing the speed to a low speed, the cleaning performance was improved, and the rank 4.5 was satisfied. In addition, it can be seen that the ranks of the switching reciprocation times of 6 and 12 are also improved, and the cleaning property is improved.

  Also, in an environment of 10 ° C and 15%, the cleaning speed is reduced by switching the linear speed to a low speed while the rank does not satisfy the allowable range in any case where the number of reciprocations of the polarity switching of the cleaning bias is any standard speed. Is improved and the rank satisfies the allowable range.

  As described above, it has been confirmed that the cleaning performance is improved by reducing the operating linear velocity of the apparatus during the bias cleaning. Therefore, the transfer member can be satisfactorily cleaned without increasing the cost of the power source or increasing the size by changing the apparatus operating linear velocity at the time of bias cleaning execution based on the detection result of the environmental condition detection sensor mounted on the apparatus. It becomes possible.

  Next, a second embodiment of bias cleaning will be described in which the operation linear velocity when performing bias cleaning of the transfer member is changed according to the time-dependent conditions. In addition, the description which overlaps with 1st Embodiment demonstrated above is abbreviate | omitted suitably, and it demonstrates focusing on a different part.

  The transfer member that performs bias cleaning is the secondary transfer roller 36 in the configuration of FIG. 1, and the DC bias as the cleaning bias is applied to the transfer region (in the configuration of FIG. 1, to the repulsive roller 33 of the secondary transfer portion). Is the same as in the first embodiment.

  Also, as the cleaning bias application control, (1) Apply a DC component with the opposite polarity to the image transfer, (2) Switch the polarity and alternate between the positive and negative DC components (the opposite polarity to the image transfer and the same polarity as the image transfer). The same is true in that the two controls can be applied. In the second embodiment, for each of the above (1) and (2), the bias value to be applied and the bias application time are changed according to the aging conditions. Note that the bias application time is simply changed in the case of (1) above. In the case of (2) above, the number of times of polarity switching (number of cycles) is changed.

Further, it is the same as the first embodiment in that the DC component having the opposite polarity to the image transfer is controlled with constant voltage and the DC component having the same polarity as the image transfer is controlled with constant current.
Further, the operation mode of the transfer member bias cleaning is the same in that it includes two operation modes of a cleaning standard mode and a cleaning low speed mode. The linear velocity value in each mode is also set to [mm / s] at 352.8 [mm / s] and 158.8 as in the first embodiment.

  Note that the line speed at which the bias cleaning is performed may be an operation line speed different from the operation line speed at the time of image formation. Also, in the case where a plurality of linear velocities are provided as the operation linear velocity at the time of image formation and the bias cleaning operation linear velocity, either one is made the same and the other is made different, or any one is made different and the others are the same. It is good.

  In the second embodiment, the cumulative travel distance of the transfer member or the number of printed sheets in the image forming apparatus can be used as the time condition. The accumulated travel distance of the transfer member may be provided in the control unit 60 of FIG. 3 as a counter. The number of prints can also be grasped by the control unit 60.

  Then, the operation linear speed of bias cleaning is changed based on the time-dependent conditions such as the cumulative travel distance of the transfer member and the number of prints. Specifically, when the travel distance or the number of printed sheets after replacement of the transfer member reaches a predetermined value (for example, travel distance of 5000 hours or 10,000 prints), the subsequent time (until the transfer member is replaced next time). Bias cleaning is performed in the cleaning low speed mode.

The bias cleaning is performed at a timing different from the printing operation. As the “timing different from the printing operation”, the following two timings a) and b) can be considered.
a) A paper jam occurs while being conveyed from the paper feed unit to the paper discharge unit. → Jam removed paper is removed. → Timing when cleaning is performed by a return operation (= when a jam recovery operation is performed).
b) Timing when the device is abnormally terminated by applying a large impact or power failure and turning on the power of the device → recovering operation (= recovery operation from abnormal termination of the device).

  In addition, as the “timing different from the printing operation”, the bias cleaning can be performed before printing, after printing, or at other appropriate “timing different from the printing operation”.

FIG. 7 is a flowchart showing an example of bias cleaning control executed during the jam recovery operation.
In this flowchart, when jam recovery occurs (S1), a return operation execution flag is set (S2). Then, the jam recovery is canceled (S3), and the travel distance or the number of printed sheets after the transfer member replacement stored in the counter or the like in the control unit 60 is read (S4). If it is determined that the detected time condition is a predetermined condition, the process proceeds to S6, and the bias cleaning mode is set to the cleaning low speed mode. If the read time condition is other than the above, the process proceeds to S7, and the bias cleaning mode is set to the cleaning standard mode. Then, the secondary transfer roller 36 as a transfer member is brought into contact with the intermediate transfer belt 31 as an image carrier (S8), and a predetermined cleaning bias is applied to perform bias cleaning (S9).

  As the cleaning bias, as in the first embodiment, the basic unit and basic unit of the cleaning bias shown in FIG. 5 can be repeatedly applied for a plurality of cycles. The number of repetitions is set to 12 in the jam recovery operation, but is not limited to this and can be changed as appropriate. The waveform of the cleaning bias is not limited to the illustrated example, and can be changed as appropriate. For example, in the basic unit, the application time of the reverse polarity (+) to the image transfer is set to 1.8 laps (1.8 laps of the secondary transfer roller 36).

Next, an evaluation experiment conducted by the inventor will be described.
The apparatus used for the evaluation experiment, the procedure of the experiment, and the like are the same as in the first embodiment. However, the secondary transfer roller 36 as a transfer member is not a new product, but is a product that has been used for 600000 hours (life product).

The experimental environment and the evaluation sheet are the same as in the first embodiment. The same applies to the cleaning bias.
The evaluation results are shown in Table 2 below. The determination is based on ranks 1 to 5, with rank 5 being the best, no back dirt, and rank 4 or higher being the allowable range.

  As shown in Table 2, in the environment of 23 ° C. and 50%, the standard speed was out of the allowable range at rank 3 when the number of reciprocations of polarity switching of the cleaning bias was 3, but the linear speed was reduced even with the same number of reciprocations. By switching to a low speed, the cleaning performance was improved and the rank 4 and the allowable range were satisfied. In addition, it can be seen that the ranks of the switching reciprocation times of 6 and 12 are also improved, and the cleaning property is improved.

  Also, in an environment of 10 ° C and 15%, the cleaning speed is reduced by switching the linear speed to a low speed while the rank does not satisfy the allowable range in any case where the number of reciprocations of the polarity switching of the cleaning bias is any standard speed. Is improved and the rank satisfies the allowable range.

  As described above, by changing the apparatus operating linear velocity at the time of bias cleaning based on the detection result of the aging condition detecting means mounted on the apparatus, it is possible to improve the transfer member without causing an increase in power supply cost or an increase in size. It becomes possible to clean.

  Next, a description will be given of a third embodiment characterized in that the operation linear velocity at the time of bias cleaning of the transfer member is changed according to the environmental condition and the aging condition. In addition, the description which overlaps with 1st Embodiment described above and 2nd Embodiment is abbreviate | omitted, and it demonstrates focusing on a different part.

  In the third embodiment, as a condition for changing the apparatus operation linear speed at the time of bias cleaning execution, the determination of the linear speed change is performed based on a combination of environmental conditions and time-dependent conditions. For example, a reference table as shown in the following Table 3 is stored in the memory in the control unit 60 of FIG. 3 and is compared with the values of the temperature / humidity sensor and the travel distance counter by referring to the reference table when jam recovery occurs. Then, when a predetermined condition is satisfied, the bias cleaning mode is set to the cleaning low speed mode. The example shown in Table 3 is an example in which the cleaning low-speed mode is set under conditions that apply to the shaded portion, and the cleaning standard mode is set under other conditions.

  In the third embodiment, since the change of the linear velocity is determined based on the combination of the environmental condition and the aging condition, the operation linear velocity at the time of bias cleaning appropriate for both the environmental condition and the aging condition is set. The member can always be cleaned well.

  Next, there is provided a means for detecting the resistance of the transfer member, and the operation linear velocity when performing bias cleaning of the transfer member is changed according to the transfer member resistance value detected by the resistance detection means. Four embodiments will be described. In addition, the description which overlaps with 1st Embodiment-3rd Embodiment demonstrated above is abbreviate | omitted, and it demonstrates centering on a different part.

  In the fourth embodiment, a voltage detection circuit is provided in the power source 39 in the apparatus configuration of FIG. 1, and the resistance of the transfer member can be detected by this voltage detection circuit. That is, a predetermined current is passed through the secondary transfer roller 36 during non-image formation, and the voltage value at that time is detected by the voltage detection circuit of the power source 39. Based on the detected voltage value, the resistance of the secondary transfer roller 36 is calculated. When the calculated resistance of the secondary transfer roller is less than the specified value, the bias cleaning mode is set to the cleaning low speed mode. When the resistance of the secondary transfer roller is higher than the specified value, the bias cleaning mode is set to the cleaning standard mode. To do.

  Since the resistance of the transfer member varies depending on environmental conditions and aging conditions, according to the fourth embodiment, by changing the operation linear velocity when performing bias cleaning of the transfer member according to the resistance of the transfer member, In addition, since it is set to an appropriate operation linear velocity at the time of bias cleaning in both of the aging conditions, it is possible to always clean the transfer member satisfactorily.

  In the first to fourth embodiments described above, the time for performing bias cleaning of the transfer member depends on the environmental conditions in the case of the first embodiment, and depends on the aging conditions in the case of the second embodiment. In the case of the third embodiment, the cleaning execution time is adjusted to be shorter or longer than the standard time according to the environmental condition and the aging condition, and in the case of the fourth embodiment, according to the resistance value of the transfer member. Is preferable.

  For example, in the case of a low temperature and low humidity condition, the execution time is lengthened, and in the high temperature and high humidity condition, the execution time is shortened. Further, as the aging condition, the cleaning execution time may be increased stepwise as the running time or the number of printed sheets increases. The same applies to a combination of environmental conditions and aging conditions. Also in the case of the resistance value of the transfer member, the cleaning execution time may be lengthened stepwise as the resistance value increases.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. The present invention can be applied not only to the intermediate transfer system but also to a direct transfer system. Further, an appropriate configuration can be adopted as the configuration of the transfer portion, and the opposing member side may be configured by a belt. A power supply capable of outputting a superimposed bias is well known, and a power supply having an appropriate configuration can be used.

  In a direct transfer type image forming apparatus, a toner image formed on a photoreceptor (image carrier) is directly transferred onto a sheet (recording medium). In a general configuration, the sheet is transferred to a photoreceptor. The image is transferred by a transfer member such as a transfer roller and a transfer conveyance belt arranged opposite to each other, and is sent to a subsequent fixing device by the transfer roller, the transfer conveyance belt, or the like. When the present invention is applied to such a configuration, a cleaning bias is applied to the transfer member to transfer toner or the like on the transfer member to the photoconductor, and the transferred toner or the like is provided in the photoconductor. Can be cleaned. Note that the polarity of the cleaning bias applied to the transfer member may be set so as to correspond to the toner charging polarity set in the direct transfer type image forming apparatus.

  The configuration of each part of the image forming apparatus is also arbitrary, and the arrangement order of the color image forming units in the tandem system is arbitrary. The present invention can be applied not only to a four-color machine but also to a full-color machine using three-color toners and a multi-color machine using two-color toners. Applicable to monochrome devices. Of course, the image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions.

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photosensitive drum 30 Transfer unit 31 Intermediate transfer belt (image carrier)
33 Repulsive roller 36 Secondary transfer roller (transfer member)
39 Power supply 60 Control means 70 I / O control unit 101 Registration roller pair P Recording material N Transfer nip

JP 2006-267486 A JP 2011-158785 A JP 2001-83853 A

Claims (7)

An image carrier on which a toner image is carried;
A transfer member;
A power source for applying a transfer bias to a transfer portion where the image carrier and the transfer member face each other;
Control means for controlling the power source;
Temperature detecting means for detecting the temperature,
In the image forming apparatus for transferring the toner image on the image carrier to a recording medium,
Applying a bias having a polarity opposite to that when the toner image is transferred to the recording medium from the power source to the transfer unit at a timing different from when the toner image on the image carrier is transferred to the recording medium, or A bias cleaning of the transfer member is performed by alternately applying a bias of the opposite polarity and the same polarity as when transferring the toner image to the recording medium,
Wherein, when the temperature detected by said temperature detecting means performs the bias cleaning in the case of low temperature, the temperature detected by said temperature detecting means is compared with the case of performing the bias cleaning if not cold, before An image forming apparatus characterized in that both the image carrier and the transfer member are operated at a low speed.   The image forming apparatus according to claim 1, wherein an execution time of the bias cleaning is adjusted according to a temperature. An image carrier on which a toner image is carried;
A transfer member;
A power source for applying a transfer bias to a transfer portion where the image carrier and the transfer member face each other;
Control means for controlling the power source;
Temperature and humidity detection means for detecting temperature and humidity,
In the image forming apparatus for transferring the toner image on the image carrier to a recording medium,
Applying a bias having a polarity opposite to that when the toner image is transferred to the recording medium from the power source to the transfer unit at a timing different from when the toner image on the image carrier is transferred to the recording medium, or A bias cleaning of the transfer member is performed by alternately applying a bias of the opposite polarity and the same polarity as when transferring the toner image to the recording medium,
When the temperature and humidity detected by the temperature and humidity detection means is low temperature and low humidity, the control means performs the bias cleaning, and when the temperature and humidity detected by the temperature and humidity detection means is not low temperature and low humidity, the bias cleaning is performed. the than when performed before Kizo carrier and an image forming apparatus characterized by both lowering the operating speed of the transfer member.   The image forming apparatus according to claim 3, wherein an execution time of the bias cleaning is adjusted according to temperature and humidity.   The timing different from when the toner image on the image carrier is transferred to the recording medium is a timing at the time of the return operation after the occurrence of the jam or a timing at the time of the return operation after the abnormal end of the apparatus. The image forming apparatus according to claim 1. An image carrier on which a toner image is carried;
A transfer member;
A power source for applying a transfer bias to a transfer portion where the image carrier and the transfer member face each other;
Control means for controlling the power source;
Temperature detecting means for detecting the temperature,
In the image forming apparatus for transferring the toner image on the image carrier to a recording medium,
Bias of opposite polarity and the same polarity are applied alternately to the transfer unit from the power source to the transfer unit at a different timing from when the toner image on the image carrier is transferred to the recording medium. And performing bias cleaning of the transfer member,
When the bias cleaning is performed when the temperature detected by the temperature detecting means is low, the control means is more effective than when the bias cleaning is performed when the temperature detected by the temperature detecting means is not low. Reduce the operating speed of both the image carrier and the transfer member,
An image forming apparatus, wherein a plurality of cycles for alternately applying the bias are performed. An image carrier on which a toner image is carried;
A transfer member;
A power source for applying a transfer bias to a transfer portion where the image carrier and the transfer member face each other;
Control means for controlling the power source;
Temperature and humidity detection means for detecting temperature and humidity,
In the image forming apparatus for transferring the toner image on the image carrier to a recording medium,
Bias of opposite polarity and the same polarity are applied alternately to the transfer unit from the power source at the timing different from when the toner image on the image carrier is transferred to the recording medium. And performing bias cleaning of the transfer member,
When the temperature and humidity detected by the temperature and humidity detection means is low temperature and low humidity, the control means performs the bias cleaning, and when the temperature and humidity detected by the temperature and humidity detection means is not low temperature and low humidity, the bias cleaning is performed. Compared with the time of performing both the operation speed of the image carrier and the transfer member,
An image forming apparatus, wherein a plurality of cycles for alternately applying the bias are performed.

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