JP2009139700A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of efficiently collecting a toner image which is not transferred in a short time if the toner image formed on an image carrier can not be transferred to a recording medium. <P>SOLUTION: The image forming apparatus includes a rotatable image carrier 30, a transfer means 32 transferring the toner image formed on the image carrier to the recording medium, a cleaning means 34 removing toner remaining on the image carrier after transferring the toner image, and a control means 40. If the toner image formed on the image carrier can not be transferred to the recording medium, the control means sets the rotating time of the image carrier until starting image formation next from an image carrier stop state to be longer than the rotating time of the image carrier until starting image formation next from the image carrier stop state when the toner image formed on the image carrier is transferred to the recording medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer or an electrophotographic copying machine.

  In an image forming apparatus such as a printer or a copying machine using an electrophotographic method, a toner image formed on a photosensitive member is transferred directly or once onto an intermediate transfer member and then transferred onto the recording medium from the intermediate transfer member. Then, by further fixing, an image fixed on the recording medium is obtained. Generally, the transfer efficiency of toner from an image carrier such as a photoconductor or an intermediate transfer member to a recording medium such as paper does not reach 100%, so some toner remains on the photoconductor or intermediate transfer member. To do. Therefore, in order to avoid the influence on the subsequent image formation, it is necessary to provide a cleaning means for collecting the transfer residual toner remaining on the image carrier after the transfer to the recording medium. As a cleaning means, a method that physically scrapes off using a rubber cleaning blade or a method that electrostatically recovers by applying a bias is known.

  The configuration using the cleaning blade is adopted in many image forming apparatuses because it has an advantage that the configuration is simpler than other configurations and can be manufactured at low cost. However, in the method using the cleaning blade, even if the performance is sufficient to remove a small amount of toner remaining after transfer (hereinafter referred to as transfer residual toner), it remains as it is without being transferred onto the recording medium. There is a problem that a large amount of toner images may not be collected at once. There are three cases where it is necessary to collect a large amount of toner image as compared with the untransferred toner. One is a case where the image forming operation is interrupted due to an abnormal operation such as a jam of the recording medium on the conveyance path, and the toner image formed on the image carrier has to be cleaned once. The other is a case where a control image (toner image for adjusting the image quality) that is not transferred to the recording medium is formed on the image carrier and the control image has to be cleaned once. The other one is that the toner image formed on the image carrier has to be cleaned once because there are not enough recording media prepared in the image forming apparatus for the number of sheets to be output by the user. This is the case.

  When it is necessary to collect a large amount of toner image compared to the untransferred toner, it is conceivable to increase the idling of the image carrier so that the same portion is cleaned a plurality of times. However, since the time until the next image forming operation can be resumed becomes longer, and the sliding time between the cleaning blade and the image carrier becomes longer, the durable life of the cleaning blade becomes shorter. It is desirable to keep the idle rotation of the as short as possible.

In view of this, Japanese Patent Application Laid-Open No. H10-228688 proposes an image forming apparatus that provides another cleaning unit on the image carrier and collects it twice. In Patent Document 2, when an image forming operation is interrupted due to an abnormal operation such as a jam, the same bias is applied to the transfer roller as when transferring to a recording medium, and a part of the toner is moved onto the transfer roller to perform cleaning. An image forming apparatus in which the amount of toner collected by the means is reduced has been proposed. In Patent Document 3, after a part of toner is moved onto a transfer roller, a bias having a reverse polarity is applied to the transfer roller and moved again onto the image carrier, thereby cleaning the image carrier. Have proposed an image forming apparatus that reduces the amount of toner collected at one time.
JP-A-63-137286 JP 2002-174967 A Japanese Patent Laid-Open No. 2005-242009

  However, newly providing another cleaning unit leads to an increase in the cost of the image forming apparatus. Further, even in a system in which a part of the toner is moved onto the transfer roller, a means for removing the toner on the transfer roller or a means for applying a bias having a polarity opposite to that at the time of image formation to the transfer roller is required. Providing a means for removing toner and a means for applying a reverse polarity bias to move a part of the toner onto the transfer roller also leads to an increase in the cost of the image forming apparatus.

  An object of the present invention is to provide an image forming apparatus capable of efficiently collecting a toner image in a short time when a toner image formed on an image carrier is not transferred to a recording medium.

  In order to achieve the above object, there are provided a rotatable image carrier, transfer means for transferring a toner image formed on the image carrier to a recording medium, and the image carrier after the toner image is transferred. When the toner image formed on the image carrier is not transferred to a recording medium in an image forming apparatus having a cleaning unit for removing toner remaining on the control unit and a control unit, the control unit The rotation time of the image carrier from the carrier stopped state to the start of the next image formation is determined from the image carrier stopped state when the toner image formed on the image carrier is transferred to the recording medium to the next image formation start. The rotation time is longer than the rotation time of the image carrier.

  In addition, a configuration for achieving the above object includes a rotatable image carrier, transfer means for transferring a toner image formed on the image carrier to a recording medium, and the image after transfer of the toner image. When the toner image formed on the image carrier is not transferred to a recording medium in an image forming apparatus having a cleaning unit for removing toner remaining on the carrier and a control unit, the control unit The rotation of the image carrier for cleaning is continued from the start of rotation of the image carrier for the start of the next image formation without stopping the rotation of the image carrier.

  According to the present invention, it is possible to provide an image forming apparatus capable of efficiently collecting a toner image in a short time when the toner image formed on the image carrier is not transferred to a recording medium.

  The present invention will be described with reference to the drawings.

[Example 1]
(1) Overall Configuration of Image Forming Apparatus FIG. 1 is an overall configuration model diagram of an example of an image forming apparatus according to the present invention.

  This image forming apparatus is a full-color laser printer that forms four color images of yellow, magenta, cyan, and black on a recording medium such as recording paper and an OHP sheet using an electrophotographic method.

  The color laser printer shown in this embodiment is a tandem type printer in which first to fourth image forming stations SY, SM, SC, and SK are arranged in parallel in the horizontal direction.

  The first image forming station SY is for yellow (Y) image formation, and the second image forming station SM is for magenta (M) image formation. The third image forming station SC is for forming a cyan (C) image, and the fourth image forming station SK is for forming a black (K) image.

  Each of the image forming stations SY, SM, SC, SK has a rotatable photosensitive member (electrophotographic photosensitive member) 22Y, 22M, 22C, 22K as a first image carrier. The photoconductors 22Y, 22M, 22C, and 22K are configured in a drum shape by applying an organic photoconductive layer to the outer periphery of a cylindrical aluminum cylinder. Hereinafter, the photosensitive members 22Y, 22M, 22C, and 22K are referred to as photosensitive drums 22Y, 22M, 22C, and 22K.

  Further, the image forming stations SY, SM, SC, and SK include chargers 23Y, 23M, 23C, and 23K as charging means along the rotation direction of the photosensitive drums 22Y, 22M, 22C, and 22K. Further, laser scanner units 24Y, 24M, 24C and 24K are provided as exposure means. In addition, developing devices 26Y, 26M, 26C, and 26K as developing means and drum cleaning devices 41Y, 41M, 41C, and 41K are provided. On the developing units 26Y, 26M, 26C, and 26K, toner cartridges 25Y, 25M, 25C, and 25K that supply toner to the developing units 26Y, 26M, 26C, and 26K are provided as developing cartridges. Each of the drum cleaners 41Y, 41M, 41C, and 41K includes a cleaning blade 42 in contact with the outer peripheral surface (surface) of the corresponding photosensitive drum 22Y, 22M, 22C, and 22K in the cleaner container 43 (FIG. 7).

  Below the image forming stations SY, SM, SC, and SK, as a second image carrier, an intermediate transfer member 30 made of a dielectric material and capable of rotating an endless belt having flexibility is provided. The intermediate transfer member 30 has three rollers 29a and 29b so that the outer peripheral surface (front surface) of the intermediate transfer member 30 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K of the image forming stations SY, SM, SC, and SK. , 29c. 29a is a driving roller, 29b is a driven roller, and 29c is a tension roller.

  Reference numerals 31Y, 31M, 31C and 31K denote primary transfer rollers as first transfer means. The primary transfer rollers 31Y, 31M, 31C, and 31K are disposed opposite to the photosensitive drums 22Y, 22M, 22C, and 22K inside the intermediate transfer member 30, and are opposed to the photosensitive drums 22Y, 22M, and 22C across the intermediate transfer member 30. , 22K and the primary transfer nip portion T1.

  Reference numeral 32 denotes a secondary transfer roller as second transfer means. The secondary transfer roller 32 is disposed opposite to the driving roller 29a on the outside of the intermediate transfer member 30, and contacts the surface of the intermediate transfer member 30 to form a secondary transfer nip portion T2. The secondary transfer roller 32 can be brought into contact with and separated from the surface of the intermediate transfer member 30, is brought into contact when transferring the toner image from the intermediate transfer member 30 to the recording medium 11, and is separated in other cases. Is done. By separating the secondary transfer roller 32 from the surface of the intermediate transfer body 30 at times other than during transfer, it is possible to suppress wear of the secondary transfer roller 32 and toner adhesion. As a means for bringing the secondary transfer roller 32 into contact with or separating from the surface of the intermediate transfer body 30, a driving means such as a solenoid can be used.

  A cleaning device 33 cleans the surface of the intermediate transfer member 30. The cleaning device 33 is disposed opposite to the driving roller 29 a outside the intermediate transfer member 30. The cleaning device 33 includes a cleaning blade 34 as a cleaning means in a cleaner container 36 (FIG. 2).

  Reference numeral 21a denotes a feeding cassette in which the recording medium 11 is loaded and stored. 21b is a manual feed tray.

  Reference numeral 28 denotes transport means for transporting the recording medium 11. The transport unit 28 includes feeding rollers 28a and 28b, a registration roller 28c, a transport roller 28d, a discharge roller 28e, and the like.

  Reference numeral 40 denotes a control unit as control means. The control unit 40 includes a CPU and a memory such as a ROM and a RAM. The memory stores an image formation control sequence executed during image formation, a jam detection / recovery operation control sequence executed when a jam occurs, and the like.

  Reference numeral 50 denotes a fixing device. The fixing device 50 is provided between the secondary transfer roller 32 and the conveyance roller 28d. The fixing device 50 includes a fixing roller 51 that is heated by a heating source (not shown) such as a heater, and a pressure roller 52 that contacts the fixing roller 51 to form a fixing nip portion.

  In the printer of this embodiment, when the control unit 40 captures an image signal from an external device (not shown) such as a host computer, the control unit 40 executes an image formation control sequence.

  First, a motor M (FIG. 2) as a driving unit is rotationally driven to move the photosensitive drums 22Y, 22M, 22C, and 22K, the intermediate transfer member 30, the rollers of the conveying unit 28, and the rollers of the fixing device 50 in the direction of the arrow. Rotate. Further, the scanner units 24Y, 24M, 24C, and 24K are driven.

  Next, the surface of the photosensitive drum 22Y of the first color, for example, the yellow image forming station SY is uniformly charged to a predetermined polarity and potential by the charger 23Y. Next, the scanner unit 24Y scans and exposes the surface of the photosensitive drum 22Y with a laser beam modulated in accordance with an image signal. As a result, an electrostatic latent image corresponding to the image signal is formed on the surface of the photosensitive drum 22Y. The latent image is developed with yellow toner by the developing device 26Y, and a yellow toner image is formed on the surface of the photosensitive drum 22Y. The toner image formed on the surface of the photosensitive drum 22Y is transferred from the surface of the photosensitive drum 22Y to the surface of the intermediate transfer member 30 at the primary transfer nip T1 by a transfer bias applied to the primary transfer roller 31Y from a transfer bias power source (not shown). The The toner (transfer residual toner) remaining on the surface of the photosensitive drum 22Y after the transfer of the toner image is removed by the cleaning blade 42 of the drum cleaner 41Y. The removed toner is collected in the cleaner container 43 of the drum cleaner 41Y. Thus, the photosensitive drum 22Y is used for the next image formation.

  A similar image forming process is performed in each of the magenta, cyan, and black image forming stations SM, SC, and SK. In each of the image forming stations SM, SC, and SK, the magenta, cyan, and black toner images formed on the surfaces of the photosensitive drums 22M, 22C, and 22K are converted into the toner images previously transferred to the surface of the intermediate transfer member 30. Transferred in order.

  On the other hand, the recording medium 11 is fed from the feeding cassette 21a to the registration roller 28c by the feeding roller 28a, or the recording medium 11 is fed from the manual feeding tray 21b to the registration roller 28c by the feeding roller 28b. The recording medium 11 is conveyed to the nip portion T2 by the registration roller 28c at a predetermined timing. The recording medium 11 is nipped and conveyed by the secondary transfer roller 32 and the intermediate transfer body 30 at the nip portion T2. In the conveying process, a transfer bias is applied to the secondary transfer roller 32. As a result, the full-color toner image transferred onto the surface of the intermediate transfer member 30 is transferred from the surface of the intermediate transfer member 30 onto the recording medium 11 at the secondary transfer nip T2. The toner (transfer residual toner) remaining on the surface of the intermediate transfer member 30 after the transfer of the toner image is removed by the cleaning blade 34 of the cleaning device 33. The removed toner is collected in the cleaner container 36 of the cleaning device 33. Thus, the intermediate transfer member 30 is used for the next image formation.

  The recording medium 11 to which the toner image has been transferred is conveyed to the fixing device 50, and passes through the fixing nip portion between the fixing roller 51 and the pressure roller 52, whereby an unfixed toner image on the recording medium 11 is recorded on the recording medium 11. Heat-fixed on top. The recording medium 11 on which the toner image is heated and fixed is conveyed to the discharge roller 28e by the conveyance roller 28d, and is discharged onto the discharge tray 55 by the discharge roller 28e.

(2) Explanation of Cleaning of Toner Image on Surface of Intermediate Transfer Member 30 FIG. 2 is an enlarged view of the cleaning device 33 and its peripheral portion.

  The cleaning device 33 is for cleaning the surface of the intermediate transfer member 30. The cleaning device 33 includes a cleaning blade 34 that mainly scrapes and removes transfer residual toner remaining on the surface of the intermediate transfer member 30, and a scoop sheet 35 that collects the scraped toner inside the cleaner container 36. ing. The cleaning blade 34 is made of urethane rubber having a thickness of 2 mm, and the rake sheet 35 is composed of a PET sheet having a thickness of 50 μm. The transfer residual toner remaining on the surface of the intermediate transfer member 30 after the four color toner images formed on the surface of the intermediate transfer member 30 are transferred to the recording medium 11 is scraped off by the edge portion of the cleaning blade 34 and stored in the cleaner container 36. Stored.

  As a means for confirming the conveyance state of the recording medium 11 on the conveyance path of the recording medium 11 indicated by the dotted line in FIG. 1, the paper feed sensors 60a and 60b, the registration sensor 61, the fixing discharge, in order from the upstream in the recording medium conveyance direction. A paper sensor 62 and a full load detection sensor 63 are provided. The paper feed sensor 60a detects the presence / absence of the recording medium 11 in the feeding cassette 21a, and the paper feed sensor 60b detects the presence / absence of the recording medium 11 in the manual feed tray 21b. The registration sensor 61 detects the presence or absence of the recording medium 11 between the registration roller 28c and the secondary transfer roller 32, and the fixing discharge sensor 62 detects the recording medium 11 between the fixing device 50 and the conveyance roller 28d. The presence or absence is detected. The full load detection sensor 63 detects the presence / absence of the recording medium 11 after image formation discharged onto the discharge tray 55. Any of the sensors 60a, 60b, 61, 62, and 63 described above, when the recording medium 11 is passing or when the recording medium 11 exists, the recording medium 11 physically moves a resin flag, The operation is detected by a photo interrupter (not shown). The detection signal is sent to the control unit 40.

  Jam (conveyance abnormality) of the recording medium 11 is detected by the sensor group including the above five sensors. For example, if the fixing paper discharge sensor 62 does not detect the recording medium 11 after a predetermined time has elapsed after the registration sensor 61 detects the recording medium 11, the control unit 40 determines that the recording medium 11 and the registration sensor 61 are not discharged. It is determined that a jam has occurred with the paper sensor 62.

  When a jam of the recording medium 11 occurs between the registration sensor 61 and the fixing paper discharge sensor 62 during the image forming operation, the control unit 40 outputs an emergency stop signal to turn off the driving of the motor M and the transfer bias power source. The application of the transfer bias is stopped and the image forming operation is interrupted.

  After the image forming operation is interrupted, the control unit 40 displays on the display panel (not shown) that a jam has occurred and the location where the jam has occurred. The user who sees the display opens a cover (not shown) provided in the image forming apparatus so as to be openable and closable, and removes the recording medium 11 causing the jam in the image forming apparatus.

  When the user removes the recording medium 11 and closes an openable / closable cover (not shown) of the image forming apparatus or presses a predetermined button switch (not shown) of the image forming apparatus, the image forming apparatus The return operation (hereinafter referred to as jam return operation) is performed.

  Opening / closing of the cover of the image forming apparatus is detected by a detecting means such as a cover opening / closing sensor (not shown). The cover open / close sensor detects that the cover is closed and outputs a detection signal to the control unit 40. When a predetermined button switch is pressed, a signal is output to the control unit 40.

  The image forming apparatus finishes a predetermined jam recovery operation, and after the image forming operation can be performed again, the image forming apparatus re-forms an image that could not be normally formed by the jam, so that the user desired. An image can be obtained.

  In the jam recovery operation, the intermediate transfer member 30 is rotated at least one rotation or more at a rotation speed equal to the rotation speed during the image forming operation. Accordingly, the transfer residual toner image remaining on the surface of the intermediate transfer member 30 (on the intermediate transfer member) when the image forming operation is interrupted is collected by the cleaning device 33.

  FIG. 3A is an explanatory diagram showing a state in which the transfer residual toner on the surface of the intermediate transfer body 30 is removed by the cleaning blade 34 during the image forming operation. FIG. 6B is an explanatory diagram illustrating a state in which the multi-color toner image on the surface of the intermediate transfer member 30 is removed by the cleaning blade 34 when the image forming operation is interrupted.

  During normal printing without interrupting the image forming operation, the multi-color toner image formed on the surface of the intermediate transfer member 30 is transferred to the recording medium 11, so that the amount of toner remaining on the surface of the intermediate transfer member 30 is small. Therefore, the cleaning blade 34 can remove the transfer residual toner at once (FIG. 3A).

  However, when the multicolor toner image formed on the surface of the intermediate transfer member 30 cannot be transferred to the recording medium 11 due to the occurrence of a jam, such as when the image forming operation is interrupted, the multicolor toner image remains as it is. It remains on the surface of the intermediate transfer member 30. Thus, when it is necessary to collect a large amount of multicolor toner images due to the occurrence of a jam (FIG. 3B), the cleaning blade 34 cannot collect all the toner at once, and some of them are intermediate. It remains on the surface of the transfer body 30. This is because toner that should originally be scraped off from the surface of the intermediate transfer member 30 cannot be completely removed, and enters the nip portion between the cleaning blade 34 and the surface of the intermediate transfer member 30 with which the cleaning blade 34 is in contact. It depends.

  If the next image forming operation is performed in this state, the toner remaining on the surface of the intermediate transfer body 30 is transferred to the recording medium 11 to cause an image defect. Therefore, before the next image forming operation, the intermediate transfer is performed. The residual toner on the surface of the body 30 needs to be removed.

  The toner that has once entered the nip portion between the cleaning blade 34 and the intermediate transfer member 30 gradually slips out of the nip portion by idle rotation of the intermediate transfer member 30, and is scraped off by the cleaning blade 34. It can be recovered. However, since it takes a long time to collect all the toner, there is a problem that it takes a long time to obtain an image originally desired by the user.

  At the same time, since the rubbing time between the cleaning blade 34 and the intermediate transfer member 30 also becomes longer, there is a problem that the cleaning blade 34 is worn out, the cleaning performance is lowered, and the durable life of the cleaning blade 34 is shortened. is there.

  According to a study by the inventors of the present invention, it is found that the toner deposited on the edge portion of the cleaning blade 34 slips more when the intermediate transfer member 30 starts rotating than during the steady rotation of the intermediate transfer member 30. It was. This is because, as shown in FIG. 4A, when the rotation of the intermediate transfer member 30 is started, a greater shear stress (the force that the blade applies to the toner) between the cleaning blade 34, the intermediate transfer member 30, and the toner interposed therebetween. The force that the intermediate transfer member gives to the toner). For this reason, it is considered that when the rotation of the intermediate transfer member 30 is started, the force that causes the toner to slip through the nip portion is easier to work than when the intermediate transfer member 30 is rotated regularly as shown in FIG. Further, it is considered that when the rotation of the intermediate transfer member 30 is started, the behavior of the cleaning blade 34 becomes non-steady compared to that during steady rotation, and there is toner that newly enters the nip portion. In addition, once the toner slips, there is a tendency that the toner continues to slip for a while from that point. This is presumably because the cleaning blade 34 cannot be in direct contact with the surface of the intermediate transfer member 30 due to the presence of toner in the nip portion, and sufficient cleaning performance of the cleaning blade 34 cannot be obtained.

  Therefore, after cleaning a large amount of toner on the surface of the intermediate transfer member 30, even if the intermediate transfer member 30 continues to rotate idly and the toner that has passed through the nip portion has been recovered, the intermediate transfer member is formed at the start of the next image formation. When the roller 30 is rotated, the toner slips through the nip portion again. Here, the cleaning means that the toner on the surface of the intermediate transfer member 30 is scraped off by the cleaning blade 34 and removed.

  In order to prevent the toner from slipping through the nip portion, in the conventional image forming apparatus, the rotation time of the intermediate transfer body 30 after cleaning a large amount of toner on the surface of the intermediate transfer body 30 is extended, and the nip portion After the amount of toner was sufficiently reduced, the next image forming operation was performed. However, when this method is adopted, the rotation time of the intermediate transfer member 30 after cleaning is extended, so that there is a problem that the return time from the start of cleaning to the start of the next image formation becomes longer.

  In view of this, the present inventor noticed that the toner passing through the nip portion decreased during the steady rotation of the intermediate transfer member 30 (during the rotation operation), and extended the rotation time of the intermediate transfer member 30 after cleaning. The image formation is started without stopping the rotation.

(3) Rotation Control of Intermediate Transfer Body 30 During Jam Return Operation Referring to FIG. 5, the rotation control of the intermediate transfer body 30 during the jam return operation in the conventional image forming apparatus and the image forming apparatus of this embodiment will be described. To do.

  5A and 5B schematically show the relationship between the rotation control of the intermediate transfer member 30 and the amount of residual toner remaining on the surface of the intermediate transfer member 30 during the jam recovery operation in the conventional image forming apparatus. FIG. FIG. 5C schematically shows the relationship between the rotation control of the intermediate transfer member 30 and the amount of residual toner remaining on the surface of the intermediate transfer member 30 during the jam recovery operation in the image forming apparatus of this embodiment. FIG. FIG. 5D is a diagram schematically illustrating rotation control of the intermediate transfer member 30 during normal printing in the image forming apparatus of the present embodiment. In each of FIGS. 5A, 5B, 5C, and 5D, the horizontal axis indicates time. In each of FIGS. 5A, 5B, and 5C, the broken line drawn along the horizontal axis indicates the amount of residual toner on the surface of the intermediate transfer member 30 that appears as an image defect on the recording medium 11. It is. However, the residual toner amount is graphed so that the phenomenon of the residual toner amount can be easily understood, and is not a quantitative value of the actual residual toner amount.

  The conventional image forming apparatus (conventional example 1) starts the next image formation only by cleaning the surface of the intermediate transfer member 30, as shown in FIG.

  At the time of jam recovery operation, first, the intermediate transfer member 30 is rotated and started to rotate once or more in order to clean the surface of the intermediate transfer member 30 and then stopped. Although most of the large amount of toner on the surface of the intermediate transfer body 30 is collected by the cleaning blade 34 due to the rotation of the intermediate transfer body 30, residual toner that could not be cleaned exists on the surface of the intermediate transfer body 30.

  Next, the intermediate transfer member 30 is rotated again and rotated forward for a preliminary operation for the next image formation, and the next image formation is started as it is. When the rotation starts to rotate the intermediate transfer member 30 for the pre-rotation, the toner accumulated on the edge portion of the cleaning blade 34 passes through the nip portion, and the residual toner on the surface of the intermediate transfer member 30 increases (upper stage). (See the rising edge of the graph). The residual toner amount at the start of the pre-rotation of the intermediate transfer body 30 exceeds the residual toner amount that causes an image defect. Therefore, if the next image formation is started without collecting the residual toner, the residual toner on the surface of the intermediate transfer member 30 is transferred to the recording medium 11 and an image defect occurs on the recording medium 11. This is because the residual toner increased by the pre-rotation of the intermediate transfer member 30 is not sufficiently reduced to a level at which no image defect occurs only by the pre-rotation of the intermediate transfer member 30.

  Another conventional image forming apparatus (conventional example 2) extends the idle rotation of the intermediate transfer member 30 after cleaning the surface of the intermediate transfer member 30, as shown in FIG.

  At the time of jam recovery operation, first, the intermediate transfer member 30 is rotated and started to rotate one or more times in order to clean the surface of the intermediate transfer member 30, and the intermediate transfer member 30 is continuously rotated without stopping the rotation of the intermediate transfer member 30. Stops after idling. Residual toner that could not be recovered by cleaning the surface of the intermediate transfer member 30 due to the idle rotation of the intermediate transfer member 30 is recovered to a level less than the residual toner amount that causes an image defect.

  Next, the intermediate transfer member 30 is rotated again and rotated forward for a preliminary operation for the next image formation, and the next image formation is started as it is. When rotation is started to rotate the intermediate transfer member 30 forward, the toner accumulated on the edge portion of the cleaning blade 34 passes through the nip portion, and the residual toner on the surface of the intermediate transfer member 30 increases (rise of the graph in the upper diagram). Section). However, the residual toner at the start of the pre-rotation of the intermediate transfer member 30 is less than the residual toner at the start of the pre-rotation of the intermediate transfer member 30 shown in FIG. The level is less than the amount of residual toner that becomes defective. Accordingly, even if the intermediate transfer member 30 is rotated forward and the next image formation is started without stopping the rotation of the intermediate transfer member 30, no image defect occurs on the recording medium 11.

  That is, the image forming apparatus extends the idle rotation of the intermediate transfer body 30 after collecting a large amount of toner on the surface of the intermediate transfer body 30 and cleaning the surface of the intermediate transfer body 30, After that, the next image formation is started. Therefore, before starting the next image formation, it is necessary to idle the intermediate transfer body 30 to the extent that the toner passing through the nip portion again does not cause an image defect, and it takes a long time before starting the next image formation. Needed.

  As shown in FIG. 5C, the image forming apparatus according to the present embodiment performs the pre-rotation of the intermediate transfer body 30 before starting the next image formation, and the pre-rotation of the intermediate transfer body 30 during normal printing (see FIG. 5C). It is longer than (d) in FIG.

  During normal printing, as shown in FIG. 5D, first, in order to clean the surface of the intermediate transfer body 30, the intermediate transfer body 30 is started to rotate, and then stopped after being rotated one or more times. Next, the intermediate transfer member 30 is rotated again and rotated forward for a preliminary operation for the next image formation, and the next image formation is started as it is.

  At the time of jam recovery operation, first, the intermediate transfer member 30 is started to rotate and rotated after one rotation or more in order to clean the surface of the intermediate transfer member 30 and then stopped. Although most of the large amount of toner on the surface of the intermediate transfer body 30 is collected by the cleaning blade 34 due to the rotation of the intermediate transfer body 30, residual toner that could not be cleaned exists on the surface of the intermediate transfer body 30.

  Next, the intermediate transfer member 30 is started to rotate and pre-rotated for the preliminary operation of the next image formation, and the intermediate transfer member 30 is continuously idled without stopping the rotation of the intermediate transfer member 30 and the intermediate transfer. The next image formation is started without stopping the rotation of the body 30. Here, the rotation time of the intermediate transfer member 30 during the jam recovery operation (pre-rotation + rotation time of idle rotation) is set longer than the rotation time of the intermediate transfer member 30 during normal printing (rotation time of the pre-rotation). Yes. When rotation is started to rotate the intermediate transfer member 30 forward, the toner accumulated on the edge portion of the cleaning blade 34 passes through the nip portion, and the residual toner on the surface of the intermediate transfer member 30 increases (rise of the graph in the upper diagram). Section). Although the residual toner at the start of the pre-rotation of the intermediate transfer body 30 exceeds the residual toner amount that causes image failure, the residual toner amount that is recovered by pre-rotation and idle rotation of the intermediate transfer body 30 and causes image failure The level will be less. Therefore, even if the intermediate transfer member 30 is idled after the previous rotation and the next image formation is started continuously without stopping the rotation of the intermediate transfer member 30, no image defect occurs on the recording medium 11.

  In the image forming apparatus of this embodiment, the intermediate transfer before the start of the next image formation is performed without extending the rotation time of the intermediate transfer body 30 after the cleaning as in the conventional image forming apparatus (see FIG. 5B). The rotation time of the body 30 is extended (see FIG. 5C). That is, when the toner image formed on the surface of the intermediate transfer body 30 is not transferred to the recording medium 11, the rotation time of the intermediate transfer body 30 after cleaning at the time of jam recovery operation is set as the intermediate transfer after cleaning at the time of normal printing. The rotation time of the body 30 is longer. Specifically, the rotation time of the intermediate transfer member 30 during the jam recovery operation (pre-rotation + rotation time of idle rotation) is at least longer than the rotation time of the intermediate transfer member 30 during normal printing (rotation time of the pre-rotation). The intermediate transfer body 30 is longer than one rotation. Accordingly, the rotation time of the intermediate transfer member 30 during the jam recovery operation is longer than the rotation time of the intermediate transfer member 30 during normal printing by the amount of idle rotation of the intermediate transfer member 30. Here, the rotation time of the intermediate transfer member 30 during normal printing refers to the rotation time for rotating the intermediate transfer member 30 in the preparatory operation before image formation. That is, the intermediate transfer member from the intermediate transfer member stop state (image carrier stop state) when the toner image formed on the surface of the intermediate transfer member 30 (on the image carrier) is transferred to the recording medium 11 to the start of the next image formation. 30 rotation times.

  FIG. 6 is a flowchart of an example of a jam detection / return operation control sequence executed by the control unit 40 when a jam occurs during the image forming operation.

  In S101, a jam of the recording medium 11 is detected by a sensor group including five sensors 60a, 60b, 61, 62, and 63 during the image forming operation.

  In S <b> 102, an emergency stop signal is output, the driving of the motor M and the application of the transfer bias are stopped, the image forming operation is interrupted, and the secondary transfer roller 32 is separated from the intermediate transfer body 30.

  In S103, the fact that a jam has occurred and the location where the jam has occurred are displayed on the display panel.

In S104, it is determined that the user has removed the jammed recording medium 11 by taking in the detection signal from the cover open / close sensor or the output signal of the button switch, and the process proceeds to Step 105.

  In S105, the motor M is stopped after being driven for a predetermined time. In the state where each roller of the conveying means 28 is rotated by driving the motor M, if the recording medium 11 causing the jam is not detected by the sensors 60a, 60b, 61, 62, 63, the recording medium 11 is removed from the conveying path. It is determined that it has been removed and the process proceeds to step 106. When the jammed recording medium 11 is detected by the sensors 60a, 60b, 61, 62, and 63, it is determined that the recording medium 11 has not been removed from the conveyance path, and the process returns to step 103.

  In step S106, the motor M is driven to rotate the intermediate transfer member 30 one or more times, and then stopped to clean the toner image remaining on the surface of the intermediate transfer member 30.

  In S107, a signal for starting the next image formation is output.

  In S108, the motor M is driven to perform the pre-rotation and idling of the intermediate transfer member 30.

  With the above procedure, the image forming apparatus returns from the jam and can form again an image that could not be formed due to the jam based on the signal output in S107.

  In S102, the secondary transfer roller 32 is separated from the intermediate transfer member 30 when a jam occurs. As a result, the user can easily remove the recording medium 11 causing the jam. Further, even if the intermediate transfer member 30 is rotated one or more times in order to clean the toner image remaining on the surface of the intermediate transfer member 30, the toner image can be prevented from adhering to the secondary transfer roller 32.

(4) Evaluation In the conventional image forming apparatus (FIG. 5B), the rotation of the intermediate transfer member 30 after cleaning the toner image remaining on the surface of the intermediate transfer member 30 is extended during the jam recovery operation. . In contrast, in the image forming apparatus of this embodiment (FIG. 5C), during the jam recovery operation, the rotation of the intermediate transfer body 30 before the start of the next image formation is extended to perform the next image formation. ing.

  Table 1 shows that the surface of the intermediate transfer member 30 remains at the time of the next image formation when the rotation of the intermediate transfer member 30 after cleaning is extended and when the rotation of the intermediate transfer member 30 before the next image formation is extended. This represents the amount of toner.

  The amount of toner remaining on the surface of the intermediate transfer body 30 due to the occurrence of a jam and having to be cleaned by the cleaning blade 34 is equivalent to a solid image of an A4 size yellow single color.

  In the table, ◯ is a state in which the residual toner on the surface of the intermediate transfer member 30 is almost completely removed, Δ is a state in which a very small amount of residual toner is present on the surface of the intermediate transfer member 30, and x is a residual toner on the surface of the intermediate transfer member 30. Indicates the presence of.

  As can be seen from Table 1, when only the rotation time of the intermediate transfer body 30 before the next image formation is extended as in this embodiment, the residual toner on the surface of the intermediate transfer body 30 is completely removed in 30 seconds. It is possible to perform image formation. On the other hand, when the rotation time of the intermediate transfer member 30 after cleaning is extended as in the prior art, it can be seen that the removal of the residual toner is not completed even after 60 seconds of idling.

  As described above, according to the image forming apparatus of the present embodiment, the intermediate transfer member 30 is continuously idled without stopping the rotation of the intermediate transfer member 30 following the pre-rotation of the intermediate transfer member 30. As a result, the residual toner at the start of the pre-rotation of the intermediate transfer body 30 (at the start of re-rotation) can be collected and reduced to a level at which no image defect occurs. As a result, it is possible to shorten the return time from the start of cleaning to the start of the next image formation, while preventing the occurrence of image defects, and the rotation time of the intermediate transfer member 30 can be shortened. The rubbing time can be shortened. Further, since the sliding time of the cleaning blade 34 with the intermediate transfer member 30 can be shortened, the durability life of the blade 34 can be improved. Therefore, when the toner image formed on the surface of the intermediate transfer member 30 (on the image carrier) is not transferred to the recording medium 11, the toner image can be efficiently collected in a short time.

  Further, the image forming apparatus according to the present exemplary embodiment does not rotate the intermediate transfer body 30 during the normal image formation (normal printing) in which only a small amount of transfer residual toner is cleaned. The extension of the rotation time of the transfer body 30 is avoided.

[Example 2]
Another example of the image forming apparatus according to the present invention will be described.

  The image forming apparatus shown in the present embodiment has the same configuration as that of the image forming apparatus of the first embodiment except for the rotation control of the intermediate transfer body 30 during the jam return operation. In the present embodiment, the same members and portions as those in the image forming apparatus of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The rotation control of the intermediate transfer body 30 during the jam recovery operation in the image forming apparatus of the present embodiment is different from the first embodiment in that the intermediate transfer body 30 is rotated between the cleaning of a large amount of toner and the start of the next image formation. The difference is that the intermediate transfer member 30 is continuously rotated without stopping.

  The inventors pay attention to the fact that the toner passing through the nip portion decreases during the steady rotation of the intermediate transfer member 30 (during the rotation operation), and continuously without stopping the rotation of the intermediate transfer member 30 from the start of cleaning. Then, the next image formation is started.

  With reference to FIG. 8, the rotation control of the intermediate transfer member 30 during the jam recovery operation in the image forming apparatus of this embodiment will be described. FIG. 8 shows the difference between the rotation control of the intermediate transfer body 30 during the jam recovery operation of the image forming apparatus according to the present embodiment and the image forming apparatus according to the first embodiment. The same figure as (c) is described.

  FIG. 8A schematically shows the relationship between the rotation control of the intermediate transfer member 30 and the amount of residual toner remaining on the surface of the intermediate transfer member 30 during the jam recovery operation in the image forming apparatus of the first embodiment. FIG. FIG. 8B schematically shows the relationship between the rotation control of the intermediate transfer member 30 during the jam recovery operation and the residual toner amount remaining on the surface of the intermediate transfer member 30 in the image forming apparatus of this embodiment. FIG.

  As shown in FIG. 8A, the image forming apparatus according to the first exemplary embodiment performs the next image formation by extending the rotation of the intermediate transfer body 30 before starting the next image formation during the jam recovery operation.

In the image forming apparatus of this embodiment, as shown in FIG. 8B, during the jam recovery operation, the intermediate transfer member 30 is rotated and started to rotate one or more times in order to clean the surface of the intermediate transfer member 30. The intermediate transfer member 30 is continuously idled without stopping the rotation of the transfer member 30. Then, without rotating the idling intermediate transfer body 30, the next image formation is performed as it is by rotating it for the preliminary operation of the next image formation. That is, when the toner image formed on the surface of the intermediate transfer body 30 is not transferred to the recording medium 11, the next image is not stopped without stopping the rotation of the intermediate transfer body 30 from the start of the rotation of the intermediate transfer body 30 for cleaning. This is continued until the rotation of the intermediate transfer member for the start of formation (pre-rotation start). Here, the rotation continuation time for continuing the rotation of the intermediate transfer member 30 is set to be longer than at least the rotation time of the intermediate transfer member 30 corresponding to two rotations or more.
The residual toner that could not be recovered by cleaning the surface of the intermediate transfer member 30 due to idling and pre-rotation of the intermediate transfer member 30 after cleaning a large amount of toner on the surface of the intermediate transfer member 30 is less than the residual toner amount that causes image defects. Recovered to level.

  FIG. 9 is a flowchart illustrating an example of a jam detection / recovery operation control sequence executed by the control unit 40 when a jam occurs during the image forming operation.

  S201 to S205 are the same as S101 to S105 in FIG.

  In S206, the motor M is driven so as to rotate the intermediate transfer member 30 one or more times to clean the toner image remaining on the surface of the intermediate transfer member 30, and the intermediate transfer member 30 is rotated forward and idle. . The intermediate transfer member 30 is rotated one or more times by the forward rotation and idling of the intermediate transfer member 30.

  In S207, a signal for starting the next image formation is output.

  Through the above procedure, the image forming apparatus returns from the jam and can form again an image that could not be formed due to the jam based on the signal output in S207.

  As described above, according to the image forming apparatus of the present embodiment, the rotation of the intermediate transfer body 30 for cleaning starts from the start of rotation, and the rotation of the intermediate transfer body 30 is not stopped before starting the next rotation for image formation. It continues until. Thereby, the residual toner at the time of the next image formation on the intermediate transfer body 30 can be collected and reduced to a level at which no image defect occurs. As a result, it is possible to shorten the return time from the start of cleaning to the start of the next image formation, while preventing the occurrence of image defects, and the rotation time of the intermediate transfer member 30 can be shortened. The rubbing time can be shortened. Further, since the sliding time of the cleaning blade 34 with the intermediate transfer member 30 can be shortened, the durability life of the blade 34 can be improved. Therefore, the same effect as that of the image forming apparatus of the first embodiment can be obtained.

Example 3
Another example of the image forming apparatus according to the present invention will be described.

  The image forming apparatus shown in the present embodiment extends the rotation time (previous rotation + rotation time of idling) of the intermediate transfer member 30 before starting the next image formation described in the first embodiment only under a specific temperature condition. The configuration is the same as that of the image forming apparatus according to the first exemplary embodiment except that it is executed. Also in this embodiment, the same members / portions as those in the image forming apparatus of Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 10 is an explanatory view showing the cleaning blade 34 used in the image forming apparatus of this embodiment.

  The cleaning blade 34 includes a general urethane rubber 34a as a blade material and a metal portion 34b for fixing the same. The rebound resilience of the urethane rubber 34a has temperature dependence, and the rebound resilience tends to be low in a low temperature environment and high in a high temperature environment.

  When the impact resilience is lowered, the coefficient of friction of the cleaning blade 34 against the surface of the intermediate transfer body 30 decreases, and the contact pressure applied to the surface of the intermediate transfer body 30 by the cleaning blade 34 tends to decrease, whereby the cleaning performance tends to decrease. .

  On the other hand, when the resilience increases, the friction coefficient of the cleaning blade 34 against the surface of the intermediate transfer body 30 increases, and the cleaning blade 34 is unsteady, and thus the cleaning performance tends to be lowered.

  Therefore, even in the environment of around 20 ° C., even if the cleaning blade 34 has a performance capable of cleaning a large amount of toner after the occurrence of a jam or the shortage of the recording medium 11 at a time, the cleaning performance in the low temperature or high temperature environment. May decrease.

  Therefore, in this embodiment, the temperature inside the image forming apparatus is detected by a temperature sensor (not shown) provided in the image forming apparatus, and the control unit 40 captures the output signal of the temperature sensor. Based on the output signal from the temperature sensor, the control unit 40 determines whether the in-machine temperature is in a low temperature environment of less than 15 ° C or a high temperature environment of 27 ° C or higher. The control unit 40 sets the rotation time of the intermediate transfer body 30 before the start of the next image formation as in the first embodiment only when the internal temperature is a low temperature environment of less than 15 ° C. or a high temperature environment of 27 ° C. or more. Extend to the rotation time of rotation + idling. That is, the control unit 40 determines whether or not the rotation time of the intermediate transfer body 30 before the start of the next image formation is longer than the rotation time of the intermediate transfer body during normal printing according to the internal temperature.

  According to the image forming apparatus of this embodiment, sufficient cleaning performance can be obtained without performing the operation of extending the rotation time of the intermediate transfer body 30 before the start of the next image formation. The above operation is not performed in the environment. As a result, while ensuring sufficient cleaning performance of the cleaning blade 34, the return time from the start of cleaning to the start of the next image formation can be shortened, the rotation time of the intermediate transfer body 30 can be shortened, and the blade 34 and the intermediate transfer can be shortened. The rubbing time of the body 30 can be shortened. Therefore, the same effect as that of the image forming apparatus of the first embodiment can be obtained.

[Others]
1) In the first to third embodiments, the intermediate transfer member used in the color image forming apparatus is exemplified as the image carrier. However, the image carrier is not limited to this, and the above-described photosensitive drum or single color image forming apparatus is used. A drum-shaped photosensitive member (electrophotographic photosensitive member (photosensitive drum)) may be used. Then, the intermediate transfer before the start of the next image formation is performed only when the jam detection / return operation control sequence described above, the internal temperature is lower than 15 ° C., or higher than 27 ° C. An operation of extending the rotation time of the body 30 may be applied. Thus, the same operational effects as those described above can be obtained for the photosensitive drum.

  2) In the image forming apparatus according to the first embodiment, assuming that the toner image formed on the surface of the intermediate transfer member, which is an image carrier, is not transferred to the recording medium, the image is formed by the abnormal operation (conveyance abnormality) of the conveyance unit due to jam An example is given where the operation is interrupted. As another example of the case where the toner image formed on the surface of the intermediate transfer member is not transferred to the recording medium, as described in the third embodiment, the surface of the intermediate transfer member is caused by a shortage of the recording medium prepared in advance. In some cases, the formed toner image is removed by the cleaning blade 34. In some cases, an image for adjusting image quality and image position (a control image for density detection and image position adjustment for adjusting image quality) is formed on the surface of the intermediate transfer member. In each of the above cases, the same effect can be obtained by controlling the rotation operation of the intermediate transfer member 30 described in the first to third embodiments.

  3) In the image forming apparatus of the second embodiment, whether or not to perform the operation of extending the rotation time of the intermediate transfer body 30 before the start of the next image formation is determined according to the in-machine temperature. The determination may be made according to the continuous use time of the image forming apparatus) or the number of image formations. That is, it is predicted whether or not the operation of extending the rotation time of the intermediate transfer body 30 before the start of the next image formation is performed by predicting a decrease in cleaning performance due to wear of the cleaning blade 34 by a timer or a counter in the image forming apparatus. It may be determined.

Overall configuration model diagram of an example of an image forming apparatus according to Embodiment 1 Enlarged view of the cleaning device and its surroundings (A) is an explanatory view showing a state in which the transfer residual toner on the surface of the intermediate transfer member is removed by a cleaning blade during normal printing (during normal image formation), and (b) is an intermediate transfer member by the cleaning blade when the image forming operation is interrupted. Explanatory drawing showing a state of removing a multicolor toner image on the surface (A) is an explanatory diagram showing the force acting on the cleaning blade and the surface of the intermediate transfer member when the intermediate transfer member starts to rotate, and (b) is an explanation showing the force acting on the surface of the cleaning blade and the intermediate transfer member during steady rotation of the intermediate transfer member. Figure FIG. 6 is a diagram for explaining rotation control of an intermediate transfer member during a jam recovery operation in a conventional image forming apparatus and the image forming apparatus according to the present exemplary embodiment. 7 is a flowchart illustrating an example of a jam detection / return operation control sequence of the image forming apparatus according to the first exemplary embodiment. Explanatory drawing showing the relationship between the photosensitive drum and drum cleaning FIG. 6 is a diagram illustrating rotation control of an intermediate transfer member during a jam recovery operation in the image forming apparatus according to the second embodiment. 7 is a flowchart illustrating an example of a jam detection / return operation control sequence of the image forming apparatus according to the second embodiment. Explanatory drawing showing the cleaning blade used for the image forming apparatus of Example 3. FIG.

Explanation of symbols

11: recording medium, 22Y, 22M, 22C, 22K: photosensitive drum (photosensitive member), 30: intermediate transfer member, 32: secondary transfer roller, 34: cleaning blade, 40: control unit

Claims (12)

A rotatable image carrier; transfer means for transferring a toner image formed on the image carrier to a recording medium; and cleaning means for removing toner remaining on the image carrier after the toner image is transferred. And an image forming apparatus having a control unit.
When the toner image formed on the image carrier is not transferred to the recording medium, the control means determines the rotation time of the image carrier from the image carrier stopped state to the start of the next image formation. An image forming apparatus characterized in that the rotation time of the image carrier from the stopped state of the image carrier when the toner image formed on the body is transferred to a recording medium is set longer than the rotation time of the image carrier. A rotatable image carrier; transfer means for transferring a toner image formed on the image carrier to a recording medium; and cleaning means for removing toner remaining on the image carrier after the toner image is transferred. And an image forming apparatus having a control unit.
When the toner image formed on the image carrier is not transferred to the recording medium, the control means does not stop the rotation of the image carrier from the start of the rotation of the image carrier for cleaning. An image forming apparatus that continues until the rotation of an image carrier for starting image formation is started.   The image forming apparatus according to claim 1, wherein a rubber blade is used as the cleaning unit.   The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member.   The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor.   The control means determines the rotation time of the image carrier from the image carrier stopped state to the start of the next image formation, from the image carrier stopped state when the toner image formed on the image carrier is transferred to a recording medium. 9. The image forming apparatus according to claim 1, wherein the rotation time of the image carrier is increased by at least one rotation of the image carrier before the start of the next image formation.   3. The image according to claim 1, wherein the case where the toner image formed on the image carrier is not transferred to a recording medium is a case where image formation is interrupted due to an abnormal operation. Forming equipment.   The image forming apparatus according to claim 3, wherein the abnormal operation is a jam of a recording medium.   The case where the toner image formed on the image carrier is not transferred to a recording medium is a case where the number of recording media prepared in advance is insufficient with respect to the number of images to be formed. The image forming apparatus according to claim 1 or 2.   The case where the toner image formed on the image carrier is not transferred to a recording medium is a case where a control image for adjusting image quality is formed on the image carrier. The image forming apparatus according to claim 1 or 2.   The control means determines the rotation time of the image carrier from the image carrier stopped state to the start of the next image formation in accordance with the in-machine temperature of the image forming apparatus, and uses the toner image formed on the image carrier as a recording medium. 2. The image forming apparatus according to claim 1, wherein it is determined whether or not the rotation time of the image carrier from the image carrier stopped state at the time of transfer to the start of the next image formation is longer.   According to the continuous use time or the number of times of image formation of the image forming apparatus, the control means determines the rotation time of the image carrier from the image carrier stopped state to the start of the next image formation, and the toner formed on the image carrier. 2. The image formation according to claim 1, wherein it is determined whether or not the rotation time of the image carrier from the image carrier stop state when the image is transferred to the recording medium to the start of the next image formation is longer. apparatus.