JP2010066687A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent cleaning failure caused by a large quantity of developer conveyed into a cleaning part all at a time, by selecting an auxiliary cleaning mode when having a condition in which cleaning failure is highly likely to occur, in an image forming apparatus having a cleaning means for removing developer on an intermediate transfer body. <P>SOLUTION: The image forming apparatus has the auxiliary cleaning mode, which is carried out in the manner described below. When developer on the intermediate transfer body is removed without being secondarily transferred to a transfer material, some of the developer on the intermediate transfer body is recovered to a secondary transfer member. Then, the developer remaining on the intermediate transfer body is recovered by the cleaning means. Subsequently, developer recovered to the secondary transfer member is retransferred onto the intermediate transfer body. The developer retransferred to the intermediate transfer body is recovered by the cleaning means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, and relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

A plurality of color developer images formed on a photoconductor as an image carrier are sequentially superimposed on an intermediate transfer body to perform primary transfer, and a color image (or a plurality of color developer images formed on the intermediate transfer body (or There is known a color image forming apparatus that obtains a color image by collectively transferring a multicolor image) onto a transfer material. However, in the image forming apparatus using the intermediate transfer member described above, after the secondary transfer from the intermediate transfer member to a transfer material such as paper, a transfer residual developer exists on the intermediate transfer member. Developer removal and processing methods are a technical issue. As means for solving the above-mentioned problems, an image forming apparatus that scrapes the remaining developer on the intermediate transfer member by bringing an elastic blade into contact with the intermediate transfer member is disclosed in Japanese Patent Application Laid-Open Nos. 56-153357 and 5 -303310. Further, a fur brush that contacts and separates from the intermediate transfer member is provided, and a developer having a polarity opposite to that of the secondary transfer residual developer on the intermediate transfer member is applied to the fur brush to collect the developer. There is also a configuration in which after being attached to a bias roller such as a metal roller, it is scraped off by a blade.
JP-A-56-153357 JP-A-5-303310

  In the method of cleaning the developer by bringing an elastic blade into contact with the intermediate transfer member as described in JP-A-56-153357 and JP-A-5-303310, a pickup material pickup mistake, When post-processing such as when a jam occurs, that is, when the developer is not transferred to the transfer material and a large amount of developer is sent to the elastic blade, the developer cannot be scraped sufficiently and the developer slips through. As a result, poor cleaning may occur. Also, in the method of collecting the developer on the intermediate transfer member using a fur brush, when a large amount of developer is fed, the developer cannot be completely collected and a cleaning failure may occur.

  An object of the present invention is to provide an image forming apparatus capable of suppressing an increase in size, complexity, and cost of an image forming apparatus, and capable of cleaning well even when a large amount of developer is sent to a cleaning unit. It is in.

  In order to achieve the above object, an image forming apparatus of the present invention constitutes an image forming apparatus as follows.

(1) In an image forming apparatus having transfer means for transferring a developed image on an image carrier to a transfer material, and cleaning means for removing the developer on the image carrier.
When the developer on the image carrier is removed without being transferred to a transfer material, a voltage that makes the direction of the electric field equal to that during transfer is applied to the transfer member, so that one of the developers on the image carrier is removed. After the developer is collected on the transfer member and the developer remaining on the image carrier is collected by the cleaning unit, a voltage is applied to the transfer member so that the direction of the electric field is opposite to that during transfer. A mode in which the developer collected on the member is re-transferred onto the image carrier, and the developer re-transferred on the image carrier is collected by the cleaning unit, and a mode in which only normal cleaning is performed is provided. The mode can be switched and selected.

  (2) It has means for detecting at least temperature or humidity, or both temperature and humidity, and the mode is selected according to the detection result of the detection means. Image forming apparatus.

  (3) A developer amount detecting means for detecting the amount of developer on the image carrier is provided, and the mode is selected according to the detection result of the developer amount detecting means (1). ).

  (4) The image forming apparatus according to any one of (1) to (3), wherein the image carrier is an intermediate transfer member.

  According to the present invention, in the image forming apparatus having a cleaning unit for removing the developer on the intermediate transfer member, when the developer on the intermediate transfer member is removed without being secondarily transferred to the transfer material, Part of the developer on the intermediate transfer member is collected on a secondary transfer member, and the developer remaining on the intermediate transfer member is collected by the cleaning unit, and then developed on the secondary transfer member. The cleaning assist mode has a cleaning assist mode in which the developer is retransferred onto the intermediate transfer member and the developer retransferred onto the intermediate transfer member is collected by the cleaning unit. The mode is selected, and the occurrence of poor cleaning due to a large amount of developer being sent to the cleaning unit at a time is suppressed. On the other hand, when the condition is such that a cleaning failure is unlikely to occur, the mode is not selected and the normal cleaning means is entered.

  By making this mode switching selectable, unnecessary cleaning assistance operations can be avoided, and cleaning assistance operations can be performed only when necessary.

  Furthermore, by providing means for detecting temperature and humidity, the mode can be optimally selected according to the situation.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Examples of the present invention will be described below.

  In this embodiment, in an image forming apparatus having a cleaning unit for removing the developer on the intermediate transfer member, when the developer on the intermediate transfer member is removed without being secondarily transferred to a transfer material, Part of the developer on the intermediate transfer member is collected on the secondary transfer member, and the developer remaining on the intermediate transfer member is collected by the cleaning unit, and then the developer collected on the secondary transfer member And a cleaning assist mode for collecting the developer retransferred on the intermediate transfer member by the cleaning unit, and according to the performance of the cleaning unit with respect to the detected outside air temperature. Thus, by making the mode switching selectable, a method of appropriately suppressing the occurrence of defective cleaning due to a large amount of developer being fed to the cleaning unit at a time is necessary. It described Te.

  FIG. 1 is a cross-sectional view illustrating the overall configuration of the color image forming apparatus according to the first embodiment. As shown in the figure, this apparatus is a tandem color image forming apparatus that employs an intermediate transfer member 27 that is an example of an electrophotographic color image forming apparatus. The color image forming apparatus includes an image forming unit shown in FIG. 1 and an image processing unit (not shown).

  Hereinafter, the operation of the image forming unit in the electrophotographic color image forming apparatus will be described with reference to FIG.

  The image forming unit forms an electrostatic latent image with exposure light that is turned on based on the exposure time converted by the image processing unit, and develops the electrostatic latent image to form a single color developer image. The multi-color developer image is formed by superimposing the images, the multi-color developer image is transferred to the transfer material 21, and the multi-color developer image on the transfer material 21 is fixed. Photoconductors (22Y, 22M, 22C, 22K) for each station arranged side by side for development color, injection charging means (23Y, 23M, 23C, 23K) as primary charging means, developer cartridges (25Y, 25M, 25C, 25K) , Developing means (26Y, 26M, 26C, 26K), an intermediate transfer member 27, a transfer roller 28, a cleaning means 29, and a fixing unit 30.

  The photosensitive drums (photoconductors) 22Y, 22M, 22C, and 22K are configured by applying an organic optical conductive layer to the outer periphery of an aluminum cylinder, and are rotated by the driving force of a driving motor (not shown) being transmitted. Rotates the photosensitive drums 22Y, 22M, 22C, and 22K in the counterclockwise direction in accordance with the image forming operation.

  As the primary charging means, four injection chargers 23Y, 23M, 23C, and 23K for charging the yellow (Y), magenta (M), cyan (C), and black (K) photoreceptors are provided for each station. In configuration, each injection charger is provided with a sleeve 23YS, 23MS, 23CS, 23KS.

  Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and the electrostatic latent images are selectively exposed by exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. An image is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing devices 26Y, 26M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, Each developing device is provided with a sleeve 26YS, 26MS, 26CS, and 26KS. Each developing device is detachably attached.

  The intermediate transfer member 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and rotates clockwise when forming a color image. The intermediate transfer member 27 rotates with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K, and is monochrome. The developer image is transferred. Thereafter, a transfer roller 28 (to be described later) comes into contact with the intermediate transfer member 27 to sandwich and convey the transfer material 21, and the multicolor developer image on the intermediate transfer member 27 is transferred to the transfer material 21.

  The transfer roller 28 contacts the transfer material 21 at the position 28a while the multicolor developer image is transferred onto the transfer material 21, and is separated to the position 28b after the printing process.

  The fixing unit 30 melts and fixes the transferred multi-color developer image while conveying the transfer material 21, and fixes the transfer material 21 and the fixing roller 31 that heats the transfer material 21 as shown in FIG. 1. A pressure roller 32 is provided for pressure contact with the roller 31. The fixing roller 31 and the pressure roller 32 are formed in a hollow shape, and heaters 33 and 34 are incorporated therein, respectively. That is, the transfer material 21 holding the multicolor developer image is conveyed by the fixing roller 31 and the pressure roller 32, and heat and pressure are applied to fix the developer on the surface.

  After the developer image is fixed, the transfer material 21 is discharged to a discharge tray (not shown) by a discharge roller (not shown) and the image forming operation is finished.

  The cleaning unit 29 cleans the developer remaining on the intermediate transfer member 27, and waste development after transferring the four-color multicolor developer image formed on the intermediate transfer member 27 onto the transfer material 21. The agent is stored in a cleaner container.

  Next, the cleaning means 29 used in this embodiment will be described. In the embodiment of the present invention, as the cleaning unit 29, a method of cleaning the developer by bringing an elastic blade into contact with the intermediate transfer member 27 is used. Further, urethane rubber is used as the material of the elastic blade.

  Other cleaning means include means using a fur brush as described above, but the cleaning means and material are optimally determined according to the configuration of the image forming apparatus and are particularly limited. It is not a thing.

  In general, it is known that the performance of the cleaning means varies depending on the outside air temperature, and the cleaning performance deteriorates in a low temperature environment. FIG. 2 shows the relationship between the outside air temperature and the performance of the cleaning means. FIG. 2 shows a case in which a developer is primarily transferred onto the intermediate transfer member 27 and cleaning is performed without secondary transfer onto the transfer material, assuming a pickup mistake or jam in the transfer material. The experiment was conducted by changing the conditions of the outside air temperature from 1 ° C. to 10 to 25 ° C., and experimenting how many times the cleaning failure occurred out of 10 times. At this time, the image is obtained by placing a secondary color solid on an A4 size transfer material, and the amount of developer is equivalent to 574 mg. Further, the intermediate transfer member rotation speed is 140 mm / s, the cleaning member uses a rubber blade, and the blade contact pressure is 40 gf / cm.

  From this result, by detecting the outside temperature, a threshold value for the outside temperature that requires the cleaning assist mode is determined.

Hereinafter, when a transfer material pickup error, jam, or the like, which is a feature of the present invention, occurs, that is, when the developer is not transferred to the transfer material, the developer collection procedure by the secondary transfer member, the cleaning procedure, and the outside air temperature A mode selection procedure based on detection will be described with reference to the flowchart of FIG.
STEP1
The ambient temperature is detected by the environmental sensor.
STEP2
It is determined whether or not to select the cleaning assist mode from the detected temperature. In this embodiment, the cleaning assist mode is selected when 15 ° C. or lower is detected, and when 16 ° C. or higher is detected, the process moves to the normal cleaning means 29, and the waste developer is collected at once in a short time. In this embodiment, the mode selection temperature is 15 ° C., but it differs depending on the configuration of the image forming apparatus to which the present invention is applied, and is not uniquely determined.

Hereinafter, a control flow when the cleaning assist mode is selected will be described.
STEP3
The transfer roller 28 is moved to the position 28a and brought into contact with the intermediate transfer member 27, and a voltage is applied to the transfer roller 28 so that the electric field direction is equal to that in the secondary transfer. In this embodiment, the voltage applied to the transfer roller 28 is 1.2 kV.
STEP4
The intermediate transfer member 27 is rotated in the same clockwise direction as in image formation, and the developer is sandwiched between the transfer roller 28 and the intermediate transfer member 27 to which a voltage is applied, whereby a part of the developer is collected on the transfer roller 28. The voltage application to the transfer roller 28 is performed in the image area formed on the intermediate transfer body 27. When the applied voltage is reduced, the developer recovery amount of the transfer roller 28 decreases, and when the voltage is increased, the developer recovery amount increases. Therefore, the optimum value is set according to the desired recovery amount. In this embodiment, by applying a voltage of 1.2 kV to the transfer roller 28, about 70% of the developer is collected on the transfer roller 28.
STEP5
The developer that has not been collected by the transfer roller 28 is removed from the intermediate transfer member 27 by the cleaning unit 29.
STEP6
Over the time of one round of the intermediate transfer member 27, a voltage having a different electric field direction from that at the time of secondary transfer is applied to the transfer roller 28, and the development collected on the transfer roller 28 from the transfer roller 28 onto the intermediate transfer member 27 by STEP2. Retransfer agent. In this embodiment, the voltage applied to the transfer roller 28 is set to -1.2 kV. Here, if the voltage applied to the transfer roller 28 is too small, the retransfer efficiency is lowered. If it is too large, the charging polarity of the developer is reversed, and the retransfer efficiency is also lowered. Therefore, it is preferable that the voltage value applied to the transfer roller 28 is set to an optimum value so that retransfer is efficiently performed according to the configuration of the image forming apparatus to which the present invention is applied. In this embodiment, the time for transferring the developer again from the transfer roller 28 to the intermediate transfer member 27 is set as one turn of the intermediate transfer member 27, but this time is not particularly limited. Depending on the configuration of the image forming apparatus to which the present invention is applied, it is desirable to set the time for the developer of the transfer roller 28 to be sufficiently retransferred to the intermediate transfer member 27.
STEP7
The developer transferred again by the transfer roller 28 is removed from the intermediate transfer member 27 by the cleaning unit 29.

  As described above, in this embodiment, in the image forming apparatus having the cleaning unit for removing the developer on the intermediate transfer member, the developer on the intermediate transfer member is not secondarily transferred to the transfer material. In the case of removing the developer on the intermediate transfer member, a part of the developer on the intermediate transfer member is collected on a secondary transfer member, and the developer remaining on the intermediate transfer member is collected by the cleaning unit, and then the secondary transfer member is collected. The cleaning unit recovers the developer collected on the member onto the intermediate transfer member, and collects the developer re-transferred onto the intermediate transfer member by the cleaning unit. By making it possible to select the mode switching according to the performance of the means, it is possible to appropriately suppress the occurrence of defective cleaning due to a large amount of developer being sent to the cleaning unit at a time. It was described law.

  In this embodiment, there is provided a developer amount detecting means for detecting the amount of developer on the intermediate transfer member, and the mode switching can be selected according to the detection result of the developer amount detecting means. A method for suppressing the occurrence of cleaning failure in the image forming apparatus used in Example 1 will be described.

  When the amount of the developer on the intermediate transfer member 27 is different, the cleaning performance is different even if the outside air temperature is constant. Therefore, in this embodiment, the switching of the cleaning assist mode can be selected in accordance with the amount of the developer on the intermediate transfer member 27, so that a large amount of developer is sent to the cleaning unit at a time, resulting in poor cleaning. A method for appropriately suppressing the occurrence only when necessary will be described.

  The color image forming apparatus according to the second embodiment is a tandem color image forming apparatus that employs an intermediate transfer member 27 that is an example of an electrophotographic color image forming apparatus, as in the first embodiment. The color image forming apparatus includes an image forming unit and an image processing unit. The operation of the image forming unit in the color image forming apparatus used in the present embodiment is the same as that of the image forming apparatus described in the first embodiment, and a description thereof is omitted.

  The second embodiment is different from the first embodiment in that it has a developer amount detecting means for detecting the amount of developer on the intermediate transfer member 27, and selects the mode switching according to the detection result. It is possible.

  In this embodiment, the amount of developer on the intermediate transfer body 27 is detected by calculating the printing rate of each process color.

  FIG. 4 shows a means for calculating the printing rate of each process color from the image signal.

  4A is a time transition of an image signal sent from the host computer, and FIG. 4B is a magenta converted by the printer main body CPU based on the signal of FIG. 4A. Time transition of the color image signal (not shown for each color of C, Y, Bk), and equations (1) to (4) are calculation equations for calculating the printing rate of each process color.

  Formula (1) is a formula for calculating the print ratio of each process color of magenta, Formula (2) is cyan, Formula (3) is yellow, and Formula (4) is black. The image signal sent to the printer is converted into Y, M, C, and Bk image signals by the main body CPU of the printer according to the image processing method of the main body. For the image converted in FIG. 4B, the image density and area are calculated from the signal level and time, and the printing rate in the drawing area is calculated.

  Here, in a printer that handles the control signal as a binary signal (the density gradation is controlled by the amount of developer per area and does not have gradation in units of 1 dot), the signal level is always 0 or a constant value. Therefore, the print rate can be obtained by accumulating the signal on time in the drawing time.

  On the other hand, in a printer that handles a control signal as a multi-value signal (having a density gradation of several bits per dot), the product of the signal level and time is accumulated to obtain the printing rate.

  The amount of developer that is actually primary-transferred onto the intermediate transfer body 27 differs depending on the process color even if the printing rate is the same. Therefore, the amount of developer is calculated from the printing rate for each process color and added. By combining them, the total amount of the developer that is primarily transferred onto the intermediate transfer member 27 can be calculated.

  In general, the performance of the cleaning means varies depending on the amount of developer on the intermediate transfer member, and the cleaning performance deteriorates when a certain threshold is exceeded under various conditions. FIG. 5 shows the relationship between the developer amount and the performance of the cleaning means. FIG. 5 shows a case in which a developer is primarily transferred onto the intermediate transfer member 27 and cleaning is performed without secondary transfer onto the transfer material, assuming a pickup mistake or jam in the transfer material. The developer amount was changed from 30 mg to 110 to 570 mg in increments of 30 mg, and an experiment was conducted to determine how many times cleaning failure occurred in 10 times. At this time, the outside air temperature is 10 ° C., the intermediate transfer member rotational speed is 140 mm / s, the cleaning member uses a rubber blade, and the blade contact pressure is 40 gf / cm.

  From this result, by detecting the amount of developer on the intermediate transfer member, the threshold value of the amount of developer that requires the cleaning assist mode is determined.

Hereinafter, the developer recovery procedure and cleaning procedure by the secondary transfer member and the mode selection procedure by detecting the developer amount, which are the features of the present invention, will be described with reference to the flowchart of FIG.
STEP1
The amount of developer on the intermediate transfer member 27 is calculated by the above method.
STEP2
It is determined whether or not to select the cleaning assist mode from the detected amount of developer. In this embodiment, the cleaning assist mode is selected when 140 mg or less is detected, and when 141 mg or more is detected, the process moves to the normal cleaning unit 29 and the waste developer is collected at once in a short time. In this embodiment, the mode selection developer amount is 140 mg. However, it differs depending on the configuration of the image forming apparatus to which the present invention is applied and various conditions such as the outside air temperature, and is not uniquely determined.

Hereinafter, a control flow when the cleaning assist mode is selected will be described.
STEP3
The transfer roller 28 is moved to the position 28a and brought into contact with the intermediate transfer member 27, and a voltage is applied to the transfer roller 28 so that the electric field direction is equal to that in the secondary transfer.
STEP4
The intermediate transfer member 27 is rotated in the same clockwise direction as in image formation, and the developer is sandwiched between the transfer roller 28 and the intermediate transfer member 27 to which a voltage is applied, whereby a part of the developer is collected on the transfer roller 28. The voltage application to the transfer roller 28 is performed in the image area formed on the intermediate transfer body 27.
STEP5
The residual developer not collected by the transfer roller 28 is removed from the intermediate transfer member 27 by the cleaning unit 29. A voltage having a different electric field direction from the secondary transfer is applied to the transfer roller 28.
STEP6
A voltage of −1.2 kV is applied to the transfer roller 28 over a period of one round of the intermediate transfer member 27, and the developer collected on the transfer roller 28 in STEP 4 is retransferred onto the intermediate transfer member 27.
STEP7
The developer transferred again by the transfer roller 28 is removed from the intermediate transfer member 27 by the cleaning unit 29.

  As described above, in this embodiment, there is a developer amount detecting means for detecting the amount of developer on the intermediate transfer member, and the secondary transfer is performed according to the detection result of the developer amount detecting means. In the image forming apparatus used in the first embodiment, which is characterized in that the voltage value applied to the member is set, the method for suppressing the occurrence of defective cleaning has been described.

  The method of selecting the mode by detecting the amount of developer performed in the present embodiment and the method of selecting the mode by detecting the outside air temperature described in the first embodiment are performed at the same time, thereby improving the accuracy. Since the mode selection can be determined, the first and second embodiments may be combined.

  In the first and second embodiments, the intermediate transfer member is taken as an example of the image carrier to be cleaned, but another image carrier such as a photosensitive member may be used.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus according to Embodiment 1. FIG. The relationship diagram between outside temperature and cleaning performance. 3 is a flowchart for explaining the procedure of the first embodiment. The figure explaining the calculation method of a printing rate. FIG. 6 is a relationship diagram of developer amount and cleaning performance. 9 is a flowchart for explaining the procedure of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Paper feeding part 21 Transfer material 22 Photosensitive body, Photosensitive drum 23 Charger 24 Scanner part 25 Toner cartridge 26 Developing means 27 Intermediate transfer body 28 Transfer roller 29 Cleaning means 30 Fixing device 31 Fixing roller 32 Pressure roller 33, 34 Heater

Claims (4)

In an image forming apparatus comprising: a transfer unit that transfers a developed image on an image carrier to a transfer material; and a cleaning unit that removes the developer on the image carrier.
When the developer on the image carrier is removed without being transferred to a transfer material, a voltage that makes the direction of the electric field equal to that during transfer is applied to the transfer member, so that one of the developers on the image carrier is removed. After the developer is collected on the transfer member and the developer remaining on the image carrier is collected by the cleaning unit, a voltage is applied to the transfer member so that the direction of the electric field is opposite to that during transfer. A mode in which the developer collected on the member is re-transferred onto the image carrier, and the developer re-transferred on the image carrier is collected by the cleaning unit, and a mode in which only normal cleaning is performed is provided. An image forming apparatus characterized in that the mode can be switched and selected.   2. The image forming apparatus according to claim 1, further comprising means for detecting at least temperature, humidity, or both temperature and humidity, and selecting the mode according to a detection result of the detection means.   2. The mode according to claim 1, further comprising developer amount detection means for detecting the amount of developer on the image carrier, wherein the mode is selected according to a detection result of the developer amount detection means. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member.

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