JP6234246B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and is suitably applied to an intermediate transfer type image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine.

  Conventionally, an intermediate transfer type image forming apparatus transfers an image formed of a toner image to an intermediate transfer belt (this transfer is called primary transfer), and then travels the intermediate transfer belt to convey the transferred image. The image is transferred onto a recording medium (for example, paper) (this transfer is referred to as secondary transfer).

  In such an intermediate transfer type image forming apparatus, since the image conveyance path is longer than the recording medium conveyance path, the primary transfer of the image to the intermediate transfer belt is started first, and then the intermediate transfer Secondary transfer is performed by matching the conveyance timing of the recording medium with the conveyance timing of the image primarily transferred to the belt (see, for example, Patent Document 1).

JP 2010-277308 A

  By the way, in the conventional intermediate transfer type image forming apparatus, the conveyance of the recording medium may be delayed due to the decrease in the conveying ability of the pickup roller for feeding the recording medium from the tray, the type and quality of the recording medium, and the like. .

  In fact, if the conveyance of the recording medium is delayed, the conveyance timing of the recording medium cannot be matched with the conveyance timing of the image primarily transferred to the intermediate transfer belt, and as a result, the image is primarily transferred to the intermediate transfer belt. The transferred image cannot be secondarily transferred to the recording medium, and the first transferred image is wasted.

  As described above, the conventional intermediate transfer type image forming apparatus has a problem that if the conveyance of the recording medium is delayed, the primary transferred image is wasted and the toner is wasted.

  The present invention has been made in consideration of the above points, and intends to propose an image forming apparatus capable of reducing wasteful toner consumption.

In order to solve such a problem, in the present invention, an image forming unit that forms an image composed of a toner image, a primary transfer unit that primarily transfers an image formed by the image forming unit to an intermediate transfer member, and the intermediate An image conveying means for conveying an image primarily transferred to the transfer body via an annular conveyance path, a recording medium conveying means for conveying a recording medium, and the intermediate transfer body conveyed by the image conveying means. An operation of conveying the recording medium by the recording medium conveying means, comprising: a secondary transfer means for secondarily transferring the primary transferred image to the recording medium conveyed by the recording medium conveying means; The recording medium does not reach the predetermined position on the medium side for performing the secondary transfer even if the image transferred to the intermediate transfer body reaches the predetermined position on the image side for performing the secondary transfer. If the secondary Without secondary transfer by shooting means, wherein it together with transporting the primary transferred image on the intermediate transfer member, onto the recording medium is the medium upstream point continues to perform the operation of transporting the recording medium When the recording medium reaches the predetermined position on the medium side , the image transferred to the intermediate transfer member is transported again to the predetermined position on the image side and transferred to the recording medium by the secondary transfer means. Even if the first image primary-transferred to the intermediate transfer member reaches the predetermined position on the image side for performing the secondary transfer by performing the secondary transfer of If the position does not reach the position, the first image is at least at the contact position between the image forming unit and the intermediate transfer body with respect to the image that follows the first image and has not yet completed the primary transfer. Before reaching It was to determine whether the next transfer is completed.

As described above, in the present invention, when the recording medium does not reach the predetermined position on the medium side for performing the secondary transfer even when the operation of transporting the recording medium is performed, the secondary transfer by the secondary transfer unit is performed. Without waiting, the recording medium waits for the medium side predetermined position to be reached, and after the recording medium reaches the medium side predetermined position, the secondary transfer means performs the secondary transfer to the recording medium. I did it. In this way, even if the conveyance of the recording medium is delayed, the image that has been primarily transferred to the intermediate transfer member as in the past can be more reliably transferred to the recording medium without being wasted. If the recording medium does not reach the predetermined position on the medium side, the first image is at least between the image forming means and the intermediate transfer body for the image that follows the first image and has not yet been subjected to the primary transfer. It is determined whether primary transfer is completed before reaching the contact position. In this way, among the images following the first image, the image in which the primary transfer is completed before the first image reaches the contact position between the image forming unit and the intermediate transfer member is interrupted halfway. The primary transfer to the intermediate transfer member can be performed as usual without discarding or discarding, and the primary transfer is performed before the first image reaches the contact position between the image forming unit and the intermediate transfer member. For images that are not completed, and for which primary transfer has not yet been performed, the primary transfer is suspended and wasteful toner consumption can be reduced.

According to the present invention, even if the conveyance of the recording medium is delayed, the first image (toner image) primarily transferred to the intermediate transfer member and the image following the first image are more reliably stored on the recording medium without being wasted. Since secondary transfer can be performed, an image forming apparatus capable of reducing wasteful toner consumption can be realized.

1 is a schematic cross-sectional view illustrating an overall configuration of a printer. FIG. 2 is a block diagram illustrating a functional configuration of a printer. 6 is a flowchart illustrating a printing operation procedure of the printer. FIG. 4 is a flowchart illustrating a printing operation procedure of the printer following the flowchart of FIG. 3. It is a schematic sectional drawing which shows each position on a conveyance path. It is a timing chart which shows the operation timing (pattern 1 and pattern 2) of each part. It is a timing chart which shows the operation timing (pattern 3 and pattern 4) of each part. It is a timing chart which shows the operation timing (pattern 5) of each part.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1. Overall configuration of image forming apparatus]
FIG. 1 shows the overall configuration of a printer 1 which is one specific example of an intermediate transfer type image forming apparatus. FIG. 1 mainly shows the structure of a mechanical part as the overall structure of the printer 1. As shown in FIG. 1, the printer 1 has a substantially box-shaped housing 2.

  In the following description, the left side when viewed from the front of the housing 2 is the left side of the housing 2, and the right side when viewed from the front of the housing 2 is the right side of the housing 2. Further, the direction from the left side to the right side of the housing 2 is the right direction, the direction from the right side to the left side of the housing 2 is the left direction, the direction from the lower side to the upper side of the housing 2 is the upward direction, and the upper side of the housing 2 The direction from the lower side to the lower side is the downward direction, the direction from the back side to the front side of the housing 2 is the front direction, and the direction from the front side to the back side of the housing 2 is the back direction.

  An image drum unit (toner image) for forming developer images (toner images) of each color of black (K), yellow (Y), magenta (M), and cyan (C) handled by the printer 1 is provided in the upper part of the housing 2. 3A to 3D (hereinafter referred to as ID units) are provided side by side in the front-rear direction. These four ID units 3 </ b> A to 3 </ b> D are detachably attached to the housing 2.

  The four ID units 3A to 3D have the same configuration, and each includes an image drum 4, a charging roller 5, an LED head (exposure means) 6, a developing roller 7, a supply roller 8, a toner cartridge 9, a cleaning blade 10, and the like. ing.

  The charging roller 5, the developing roller 7, and the cleaning blade 10 are provided around the image drum 4 so as to be in contact with the surface of the image drum 4.

  The charging roller 5 is configured to negatively charge the surface of the image drum 4 by applying a negative charging voltage. The LED head 6 is disposed above the image drum 4, and selectively irradiates light on the surface of the charged image drum 4, thereby forming an electrostatic latent image based on print image data on the surface of the image drum 4. ing. The developing roller 7 is applied with a negative voltage and develops the electrostatic latent image formed on the surface of the image drum 4 with toner, thereby forming a toner image on the surface of the image drum 4.

  During the development, the supply roller 8 supplies the toner contained in the toner cartridge 9 to the developing roller 7 and negatively frictionally charges the toner by a stirring operation at that time. The toner cartridge 9 is a container that is detachably attached to each of the ID units 3A to 3D and stores toner of a corresponding color.

  The cleaning blade 10 scrapes and removes residual toner adhering to the surface of the image drum 4 after primary transfer described later.

  Further, an intermediate transfer belt 11 is provided inside the housing 2 below the four ID units 3 </ b> A to 3 </ b> D, that is, at the center inside the housing 2. The intermediate transfer belt 11 is positioned at the front side (upstream side) of the ID unit 3D, which is positioned in front of the ID unit 3D. The intermediate transfer belt 11 is positioned behind the driving roller 12 and at the rearmost side (downstream side). The side surface is driven by three rollers: a belt driven roller 13 positioned below the ID unit 3A and a secondary transfer backup roller 14 positioned below the driving roller 12 and below the belt driven roller 13. An annular endless belt stretched in an inverted triangular shape as viewed, and made of, for example, a high-resistance semiconductive plastic film.

  The position of the secondary transfer backup roller 14 in the front-rear direction is closer to the belt driven roller 13 than the drive roller 12.

  The intermediate transfer belt 11 includes an image drum 4 of each of the ID units 3A to 3D and a primary transfer roller 15 disposed opposite to the lower side of each image drum 4 at the upper surface between the driving roller 12 and the belt driven roller 13. It is arranged to pass between.

  The intermediate transfer belt 11 travels in the clockwise direction in the drawing as the driving roller 12 is driven. The intermediate transfer belt 11 is connected to the image drum 4 and the primary transfer roller 15 of each of the ID units 3A to 3D. When passing, the toner images formed on the surface of the image drum 4 of each of the ID units 3A to 3D are primarily transferred onto the surface. The toner image primarily transferred to the intermediate transfer belt 11 is conveyed as the intermediate transfer belt 11 travels. In other words, the intermediate transfer belt 11 is provided along the conveyance path of the primary-transferred toner image and plays a role of conveying the primary-transferred toner image.

  Each of the four ID units 3 </ b> A to 3 </ b> D rotates the image drum 4, the charging roller 5, the developing roller 7, and the supply roller 8 by driving an ID motor (not shown), and separates the image drum 4 from the intermediate transfer belt 11. Or can be brought into contact with the intermediate transfer belt 11.

  Further, a cleaning blade 16 is disposed oppositely behind the belt driven roller 13, and the intermediate transfer belt 11 passes between the belt driven roller 13 and the cleaning blade 16.

  The cleaning blade 16 has a plate shape, and the tip portion of the cleaning blade 16 abuts on the surface of the intermediate transfer belt 11, thereby scraping off toner adhering to the surface of the intermediate transfer belt 11 after the secondary transfer described later. To be removed.

  Further, below the cleaning blade 16, a cleaner container 17 is provided for storing deposits such as toner scraped off by the cleaning blade 16.

  The cleaning blade 16 can be separated from or abutted on the intermediate transfer belt 11 by a solenoid (not shown).

  Further, a secondary transfer roller 19 is disposed below the secondary transfer backup roller 14 so as to face the recording medium conveyance path 18 therebetween. The intermediate transfer belt 11 passes between the secondary transfer backup roller 14 and the secondary transfer roller 19 so as to convey the primary transferred toner image to the secondary transfer roller 19. It has become.

  On the other hand, the recording medium passes between the intermediate transfer belt 11 and the secondary transfer roller 19. When the recording medium passes between the intermediate transfer belt 11 and the secondary transfer roller 19, the recording medium passes through the intermediate transfer belt 11. The transferred toner image is secondarily transferred.

  The secondary transfer roller 19 can be separated from or in contact with the intermediate transfer belt 11 by a solenoid (not shown). The secondary transfer roller 19 is made of, for example, a conductive rubber material, is rotatably supported by a metal shaft (not shown), and is connected (grounded) to the housing 2 through the metal shaft.

  Further, below the secondary transfer roller 19, a cleaning roller 20 is disposed so as to face the upper end of the cleaning roller 20 so that the upper end thereof is in contact with the lower end of the secondary transfer roller 19. For example, a metal roller is used as the cleaning roller 20. Further, a cleaning blade 21 is disposed opposite to the cleaning roller 20.

  The cleaning blade 21 has a plate shape like the cleaning blade 16, and the tip portion of the cleaning blade 21 abuts on the lower end of the cleaning roller 20, thereby scraping off and removing the toner adhering to the surface of the cleaning roller 20. It is like that.

  Further, below the cleaning blade 21, there is provided a cleaner container 22 that accommodates deposits such as toner scraped off by the cleaning blade 21.

  Further, a recording medium storage cassette 23 for loading recording media is detachably attached to the casing 2 at the bottom of the casing 2. Further, a hopping roller 24 for feeding the recording media stacked in the recording medium accommodation cassette 23 one by one to the transport path 18 is provided near the recording medium outlet at the front end of the recording medium accommodation cassette 23. ing.

  The conveyance path 18 extends upward from the vicinity of the recording medium outlet of the recording medium accommodating cassette 23, bends backward near the center of the housing 2, and extends rearward as it is. The secondary transfer backup roller 14 and the secondary transfer roller 19 To pass between.

  On the downstream side of the hopping roller 24 in the conveyance path 18, the recording medium fed out from the recording medium accommodating cassette 23 is adjacent to a portion bent backward, and the intermediate transfer belt 11 and the secondary transfer belt are transferred at a predetermined timing. A pair of upper and lower registration rollers 25 are provided for conveyance to the contact position P0 with the roller 19.

Further, a pair of upper and lower transport rollers 26 and a pair of upper and lower transport rollers 27 for transporting the recording medium are provided between the registration roller 25 and the contact position P0 of the transport path 18. The transport roller 27 is provided below flow side of the conveying roller 26.

  Further, a sensor 28 is provided between the transport roller 26 and the transport roller 27 for detecting the presence or absence of a recording medium passing through a position near the transport roller 27 (hereinafter referred to as a sensor position) P1. . The sensor 28 is, for example, a photoelectric sensor. When the recording medium passes through the sensor position P1 on the conveyance path 18, the sensor 28 detects the change in the light emitted from the photoelectric sensor, thereby determining the sensor position P1. The presence or absence of a passing recording medium is detected.

  Further, a fixing device 29 for fixing the toner image secondarily transferred to the recording medium to the recording medium is provided behind the secondary transfer backup roller 14 and the secondary transfer roller 19. The fixing device 29 is provided with a heat roller 30 that heats and melts the toner on the recording medium with a built-in heater (not shown) on the upper side, and further melted below the heat roller 30. A pressure roller 31 that pressurizes the toner and fixes the toner on the recording medium is disposed oppositely.

  Further, the fixing device 29 is provided with a thermistor 32 that detects the temperature of the heat roller 30 in the vicinity of the surface of the heat roller 30.

  The conveyance path 18 passes between the secondary transfer backup roller 14 and the secondary transfer roller 19, extends to a fixing device 29 located behind the secondary transfer roller 14, and further extends upward via the fixing device 29. Is connected to a recording medium discharge port provided at the upper rear end of the recording medium.

  Accordingly, the recording medium passes between the secondary transfer backup roller 14 and the secondary transfer roller 19, and after the toner image primarily transferred onto the surface of the intermediate transfer belt 11 is secondarily transferred, the fixing device 29 The toner image that has been secondarily transferred at this time is fixed between the heat roller 30 and the pressure roller 31 and then conveyed to the recording medium discharge port and discharged to the outside of the housing 2. ing.

[2. Printer functional configuration]
Next, the functional configuration of the printer 1 will be described with reference to FIG. The printer 1 controls communication with a host computer 100 as a host device, receives an print data from the host computer 100 and analyzes it, and a mechanism control unit 102 that controls operation of a mechanical part of the printer 1. It consists of.

  Further, the mechanical control unit 102 includes a main control unit 103, an image forming unit 104, an image conveyance unit 105, a fixing control unit 106, a medium conveyance unit 107, a secondary transfer control unit 108, and a cleaning blade control unit. 109 and an ID unit control unit 110.

  The main control unit 103 instructs each unit to perform an image forming operation based on print information obtained by receiving and analyzing print data by the interface unit 101. The image forming unit 104 forms images (that is, toner images) using the ID units 3A to 3D. The image transport unit 105 drives the intermediate transfer belt 11 to transport the primary transferred image. The fixing control unit 106 controls the fixing temperature of the fixing device 29 and the like. The medium transport unit 107 transports the recording medium. The secondary transfer control unit 108 controls the secondary transfer and separates / contacts the secondary transfer roller 19. The cleaning blade control unit 109 separates / contacts the cleaning blade 16. The ID unit controller 110 separates / contacts the ID units 3A to 3D (that is, separates / contacts the image drum 4).

[3. Printer printing procedure]
Next, a printing operation procedure (referred to as a printing operation procedure) of the printer 1 will be described with reference to flowcharts shown in FIGS. This printing operation is started when the interface unit 101 receives and analyzes print data transmitted from the host computer 100, and the mechanical control unit 102 acquires print information obtained as a result from the interface unit 101. The

  When the printing operation is started, in step SP1 of the printing operation procedure, the main control unit 103 of the mechanical control unit 102 instructs the image forming unit 104 to form an image, thereby starting primary transfer. At this time, the main control unit 103 instructs the image conveying unit 105 to convey an image, thereby driving the intermediate transfer belt 11 to convey a toner image that has been primarily transferred (hereinafter referred to as a primary transfer image). To do. At this time, the image transport unit 105 identifies the position of the primary transfer image from the travel amount of the intermediate transfer belt 11 and manages this. The travel amount of the intermediate transfer belt 11 can be calculated from the rotation amount of the drive roller 12, for example.

  When the print data includes a plurality of pages, the main control unit 103 performs image formation and image conveyance for the next page with a predetermined image interval (for example, 70 mm) after the primary transfer of the image of the previous page is completed. It is like that.

  In subsequent step SP2, the main control unit 103 instructs the medium transport unit 107 to transport the medium, thereby starting the medium transport. At this time, the medium transport unit 107 drives the hopping roller 24 and feeds the recording medium from the recording medium storage cassette 23 one by one. Further, the medium transport unit 107 drives the registration roller 25 and the transport rollers 26 and 27, removes the skew of the recording medium by the registration roller 25, and transports the recording medium to the downstream side by the transport rollers 26 and 27.

  Here, the medium transport unit 107 specifies the position of the recording medium based on the output (ON / OFF) of the sensor 28 and manages this. Note that it is difficult to specify the exact position of the recording medium based on the rotation amount of the transport rollers 26 and 27 and the like because slipping may occur during the transport. Therefore, the medium transport unit 107 specifies the position of the recording medium based on the output of the sensor 28.

  Actually, the sensor 28 is turned on when the recording medium passes through the sensor position P1 between the conveying roller 27 and the conveying roller 26. When the sensor 28 is turned on, the medium conveying unit 107 is turned on by the hopping roller 24, The registration roller 25 and the conveyance rollers 26 and 27 are stopped to make the recording medium stand by.

  At this time, the medium transport unit 107 waits for the recording medium in a state where the leading end portion of the recording medium is positioned at the position P2 of the transport roller 27. At this time, the leading end portion of the recording medium is sandwiched between the upper and lower transport rollers 27. Here, as shown in FIG. 5, when the distance from the secondary transfer roller 19 to the conveyance roller 27 on the conveyance path 18 (that is, the distance from the position P0 to the position P2) is d1, the recording medium is subjected to the secondary transfer. It waits at a position at a distance d1 from the roller 19.

The printer 1 conveys the image primarily transferred to the intermediate transfer belt 11 together with the recording medium. However, the main controller 103 determines that the image transferred by the primary transfer is a distance d1 from the secondary transfer roller 19. Before reaching the position P3, the recording medium for secondary transfer of this image is transported from the secondary transfer roller 19 to the position P2 at a distance d1 and is put on standby.

  Further, when the print data is a plurality of pages, the medium transport unit 107 feeds the recording medium of the next page with a predetermined medium interval (for example, 50 mm) after completing the feeding of the recording medium of the previous page. It is like that.

  As described above, in the printer 1, the image interval (70 mm) is made larger than the medium interval (50 mm) so as to have a certain amount of margin (70 mm−50 mm = 20 mm). The reason is that while the image primarily transferred to the intermediate transfer belt 11 is accurately conveyed, the conveyance of the recording medium may be delayed due to sliding or the like. Therefore, in the printer 1, by providing a margin for the conveyance of the recording medium, even if a slip of a margin (20 mm) occurs in the recording medium, the conveyance of the recording medium is synchronized with the conveyance of the image to perform the secondary transfer. Can be done.

  In this manner, after the conveyance of the recording medium is started in step SP2 (FIG. 3), the process proceeds to step SP3. In step SP3, the main control unit 103 determines whether or not the image primarily transferred to the intermediate transfer belt 11 can be secondarily transferred to the recording medium. When the print data is a plurality of pages and there are a plurality of primary-transferred images, the main control unit 103 sequentially determines whether the secondary transfer is possible for each primary-transferred image. It has become.

  Specifically, the main control unit 103 determines that the recording medium is separated from the secondary transfer roller 19 by a distance d1 when the image primarily transferred to the intermediate transfer belt 11 reaches a position P3 at a distance d1 from the secondary transfer roller 19. If the position P2 is reached (that is, if the sensor 28 is on), it is determined that the image primarily transferred to the intermediate transfer belt 11 can be secondarily transferred to the recording medium.

  On the other hand, when the image primarily transferred to the intermediate transfer belt 11 reaches the position P3 at a distance d1 from the secondary transfer roller 19, the recording medium is still at a position P2 at a distance d1 from the secondary transfer roller 19 due to sliding or the like. If it has not reached (that is, if the sensor 28 is not turned on), it is determined that the recording medium is not in time for transporting the primary transferred image, and that secondary transfer is impossible. Hereinafter, the position P2 is referred to as a medium side secondary transfer start position P2, and the position P3 is referred to as an image side secondary transfer start position P3.

  In fact, when the main control unit 103 determines that the secondary transfer is possible because the sensor 28 is on, the main control unit 103 obtains a positive result in step SP3, moves to step SP4, and turns off the sensor 28. If it is determined that secondary transfer is impossible, a negative result is obtained in step SP3, and the process proceeds to step SP8 (FIG. 4).

  In step SP4, when the secondary transfer is determined to be possible, the main control unit 103 conveys the waiting recording medium to the secondary transfer roller 19 and instructs the secondary transfer control unit 108 to perform secondary transfer. Thus, the secondary transfer of the primary transferred image to the recording medium is started. The recording medium on which the secondary transfer of the image has been completed is subsequently conveyed to the fixing device 29 in order, and is discharged after the image is fixed.

  In subsequent step SP5, the main control unit 103 makes an inquiry to the image transport unit 105 to determine whether or not the images of all pages that have been primarily transferred have been secondarily transferred. If the image of all pages has not yet been secondarily transferred, the main control unit 103 waits until the image of all pages is secondarily transferred.

  When the images of all pages are secondarily transferred, the main control unit 103 obtains an affirmative result at step SP5 and proceeds to step SP6. In step SP6, the main control unit 103 inquires of the image forming unit 104 and determines whether or not all received print data has been primarily transferred.

  Here, if the primary transfer of all the print data is completed, the main control unit 103 obtains a positive result in step SP6, proceeds to step SP7, and if not completed, proceeds to step SP22.

  In step SP7, which is shifted when it is determined that all print data has been primarily transferred, the main control unit 103 stops driving each unit and ends the printing operation.

  On the other hand, when it is determined that the primary transfer of all print data has not been completed, the main control unit 103 inquires of the ID unit control unit 110 in step SP22, and the ID units 3A to 3D make the intermediate transfer belts. 11 is determined whether it is separated from 11 or not.

  Here, when the ID units 3A to 3D are separated from each other, this will be described in detail later, but there is an image in which the primary transfer of all print data is not completed and the primary transfer is suspended. Means that. In this case, the main control unit 103 obtains a positive result in step SP22, and proceeds to step SP23. The processing after step SP23 will be described later.

  On the other hand, if the ID units 3A to 3D are not separated, this simply means that the primary transfer of all print data has not yet been completed. In this case, the main control unit 103 returns to step SP1 and starts primary transfer of the remaining print data.

  Further, when a negative result is obtained in the above-described step SP3, that is, when it is determined that the transfer of the recording medium is not in time for the transfer of the primary transfer image and the secondary transfer to the recording medium is impossible, step SP8 ( In FIG. 4), the main control unit 103 instructs the secondary transfer control unit 108 and the cleaning blade control unit 109 to once separate the secondary transfer roller 19 and the cleaning blade 16 from the intermediate transfer belt 11. At this time, the main control unit 103 starts counting a timer (not shown).

  In the printer 1 of the present embodiment, as will be described in detail later, the secondary transfer is canceled once for the primary transfer image that is determined to be impossible to perform the secondary transfer due to the conveyance of the recording medium being delayed. Thus, the conveyance path (that is, the intermediate transfer belt 11) is rotated once and the secondary transfer is attempted again. Therefore, here, when the secondary transfer of the primary transfer image (hereinafter referred to as the secondary transfer retry image) is canceled once and the conveyance path is made to make one round, the secondary transfer retry image is the secondary transfer image. The secondary transfer roller 19 and the cleaning blade 16 are once separated from the intermediate transfer belt 11 so as not to be deteriorated or discarded by adhering to the transfer roller 19 or being scraped off by the cleaning blade 16. .

  In subsequent step SP9, the main control unit 103 makes contact with the intermediate transfer belt 11 of the ID unit 3A where the leading edge of the secondary transfer retry image is located on the rearmost side (the side closest to the cleaning blade 16) (FIG. 5), it is determined whether or not there is an image in which the primary transfer is not completed.

  In fact, when the secondary transfer retry image is rotated once to retry the secondary transfer, the ID units 3A to 3D are also separated from the intermediate transfer belt 11 so that the primary transfer image is not overwritten on the secondary transfer retry image. It is necessary to let On the other hand, if the ID units 3 </ b> A to 3 </ b> D are separated from each other as described above, it is naturally impossible to perform primary transfer.

  That is, in order to make the secondary transfer retry image make one round, the ID units 3A to 3A to 3D are required until at least the front end of the secondary transfer retry image reaches the contact position P4 of the rearmost (upstream side) ID unit 3A. The 3D must be separated, and for the image for which the primary transfer is not completed by this time, the primary transfer must be suspended or stopped.

  Therefore, an image in which the primary transfer is not completed before the leading edge of the secondary transfer retry image reaches the contact position P4 of the rearmost ID unit 3A means that the secondary transfer retry image is retried. In this case, it is an image for which primary transfer needs to be suspended or stopped, and this image is hereinafter referred to as a primary transfer suspension target image.

  On the other hand, an image in which the primary transfer is completed until the leading edge of the secondary transfer retry image reaches the contact position P4 of the rearmost ID unit 3A will be described in detail later, but the secondary transfer retry image will be described later. When the secondary transfer is retried, the secondary transfer is continuously performed.

  Strictly speaking, when the leading edge of the secondary transfer retry image reaches the contact position P4 of the rearmost ID unit 3A, the leading edge of the secondary transfer retry image contacts the ID unit 3A. May deteriorate. Therefore, in practice, the main control unit 103 does not complete the primary transfer yet when the leading edge of the secondary transfer retry image reaches a predetermined position P5 that is a predetermined distance away from the contact position P4 of the ID unit 3A. It is supposed to judge whether there is.

  Note that, as the predetermined position P5 is moved away from the contact position P4, the number of images for which the primary transfer is completed before the secondary transfer retry image reaches the predetermined position P5 decreases. It is desirable to be close.

  At this time, the secondary transfer retry image is still being conveyed and is located in the vicinity of the image side secondary transfer start position P3. Therefore, at this point, the main control unit 103 predicts whether there is a primary transfer suspension target image based on the print data or the like.

  Specifically, based on the print data, the main control unit 103 is an image of an image for which primary transfer has not yet been completed among images of all pages (hereinafter referred to as primary transfer incomplete image). Calculate the length. This image length means a length parallel to the traveling direction of the intermediate transfer belt 11. Then, the main control unit 103 predicts whether there is a primary transfer suspension target image based on the image length of the primary transfer incomplete image and the interval between the images.

  Here, if it can be predicted that there is a primary transfer pending target image, this means that when the secondary transfer retry image is retried, the primary transfer is not completed in all pages of the image. Means that there is an image whose primary transfer should be suspended or canceled. At this time, the main control unit 103 obtains a positive result in step SP9 and proceeds to step SP19. On the other hand, if it can be predicted that there is no primary transfer suspension target image, this means that when the secondary transfer retry image is retried, the primary transfer of the images on all pages is completed and 1 This means that there is no image for which the next transfer should be suspended or canceled. At this time, the main control unit 103 obtains a negative result in step SP9 and proceeds to step SP10.

  In step SP19, which is shifted to when it can be predicted that there is a primary transfer pending image, the main control unit 103 determines whether the primary transfer pending target image is the secondary transfer retry image itself.

  Here, when the primary transfer hold target image is the secondary transfer retry image itself, the leading edge of the secondary transfer retry image is the contact position P4 (actually the contact position P4 of the rearmost ID unit 3A). This is a case where the image length of the secondary transfer retry image is so long that the primary transfer on the rear end side of the secondary transfer retry image is not yet completed even after reaching the predetermined position P5 near the position P4. The primary transfer of the secondary transfer retry image cannot be completed and the secondary transfer cannot be retried.

  Therefore, when the primary transfer suspension target image is determined to be the secondary transfer retry image itself, the main control unit 103 obtains a positive result in step SP19 and proceeds to step SP21 to print, for example, when an abnormality occurs. A process for notifying the user by displaying on the screen (not shown) that this could not be performed normally (this is called an abnormality detection process) is executed, and the printing operation is terminated.

  On the other hand, when determining that the primary transfer suspension target image is not the secondary transfer retry image itself, the main control unit 103 obtains a negative result in step SP19, and proceeds to step SP20. In step SP20, the main control unit 103 instructs the image forming unit 104 to hold the primary transfer of the primary transfer hold target image, and moves to step SP10.

  Note that the primary transfer suspension target image that is not the secondary transfer retry image can still be 1 at the present time (that is, when the secondary transfer retry image is located in the vicinity of the image side secondary transfer start position P3). An image in which the primary transfer is not completed before the secondary transfer is performed and the secondary transfer retry image reaches the predetermined position P5, or the secondary transfer retry image is in the middle of the primary transfer being performed at the present time. This is an image in which the primary transfer is not completed until the predetermined position P5 is reached.

  Among these, for the primary transfer suspension target image that has not been subjected to the primary transfer at this time, the primary transfer is not performed this time, and the secondary transfer retry image is retried for the secondary transfer, and then the primary transfer is performed. I do. On the other hand, for the primary transfer suspension target image that is already undergoing primary transfer at the present time, the primary transfer is interrupted when the ID units 3A to 3D are separated. In the case of the primary transfer suspension target image, the primary transfer is performed on the intermediate transfer belt 11 in an incomplete state. Therefore, the secondary transfer is not performed, and the intermediate transfer belt 11 is scraped off by the cleaning blade 16 or the like. After the secondary transfer of the secondary transfer retry image is retried, primary transfer is performed again, and then secondary transfer is performed.

  From step SP10, when the main control unit 103 determines that the secondary transfer is impossible due to the delay of the recording medium based on the count value of a timer (not shown) and the output (ON / OFF) of the sensor 28. It is determined whether or not the recording medium has reached the medium side secondary transfer start position P2 within a predetermined time.

  As shown in FIG. 5, the predetermined time in this case is, for example, that the leading edge of the secondary transfer retry image is a distance d2 (however, d2 <d1) from the image side secondary transfer start position P3 to the position P3. It is set to the time required to reach the position P6.

  Here, when the recording medium does not reach the medium side secondary transfer start position P2 within a predetermined time, this means that the conveyance of the recording medium is not delayed due to mere sliding or the like, but a jam (paper jam) or the like. This means that there is a high possibility that the recording medium cannot be conveyed. At this time, the main control unit 103 obtains a negative result in step SP10, moves to step SP21, executes abnormality detection processing, and ends the printing operation.

  On the other hand, if the recording medium reaches the medium side secondary transfer start position P2 within a predetermined time, this means that the conveyance of the recording medium is delayed due to mere sliding or the like. At this time, the main control unit 103 obtains an affirmative result in step SP10, moves to step SP11, and stops the medium conveyance to the medium conveyance unit 107 so that the recording medium waits at the medium side secondary transfer start position P2. Instruct and move to step SP12.

  In step SP12, the main control unit 103 temporarily drives the intermediate transfer belt 11 when the leading edge of the secondary transfer retry image reaches a predetermined position P5 near the contact position P4 of the rearmost ID unit 3A. The image conveying unit 105 is instructed to stop, and the process proceeds to step SP13.

In step SP13, the main control unit 103 instructs the ID unit control unit 110 to separate the ID units 3A to 3D, and proceeds to step SP14. In step SP14, the main control unit 103 drives the intermediate transfer belt 11 again until the leading edge of the secondary transfer retry image reaches a predetermined position P7 set in the vicinity of the image side secondary transfer start position P3, and the predetermined position P7. so as to suspend the intermediate transfer belt 11 when it reaches a instructs the image-bearing portion 105. The predetermined position P7 is set so that, for example, all of the image primarily transferred onto the intermediate transfer belt 11 passes through the contact position P8 of the cleaning blade 16.

In subsequent step SP15, the main control unit 103 instructs the secondary transfer control unit 108 and the cleaning blade control unit 109 to bring the secondary transfer roller 19 and the cleaning blade 16 into contact with the intermediate transfer belt 11, and then performs the next transfer. proceeds to the step SP16, by re-driving the intermediate transfer belt 11 so as to resume the conveyance of the image, and instructs the image-bearing portion 105, and proceeds to step SP17.

  In step SP17, the main control unit 103 makes an inquiry to the image transport unit 105 and waits for the leading end of the secondary transfer retry image to reach the image side secondary transfer start position P3, so that the leading end of the secondary transfer retry image is on the image side. When the secondary transfer start position P3 is reached, an affirmative result is obtained in step SP17, and the process proceeds to step SP18.

  In step SP18, the main control unit 103 instructs the medium conveyance unit 107 to resume conveyance of the recording medium waiting at the medium side secondary transfer start position P2, and proceeds to step SP4 (FIG. 3). Thereafter, the secondary transfer retry image is subjected to secondary transfer by the processing after step SP4. In this case, since the secondary transfer is performed after confirming that the recording medium has reached the medium side secondary transfer start position P2, the secondary transfer basically succeeds. Further, when there is a primary transfer image following the secondary transfer retry image, the primary transfer image is also subjected to secondary transfer to the recording medium. The primary transfer image is subjected to secondary transfer after determining again whether secondary transfer is possible for each image.

  Further, at this time, if there is a primary transfer suspension target image in which the primary transfer is interrupted in the middle of the primary transfer image following the secondary transfer retry image, the main control unit 103 performs the primary transfer. The image to be held is passed through the secondary transfer roller 19 without being subjected to the secondary transfer to the recording medium, and scraped off from the intermediate transfer belt 11 by the cleaning blade 16 or the like.

  By the way, as described above, in the printer 1, the primary transfer is suspended for the image that is not the secondary transfer retry image itself among the primary transfer suspension target images. When there is an image for which such primary transfer is suspended, the printer 1 does not complete the primary transfer of all print data, and the ID units 3A to 3D are removed from the intermediate transfer belt 11 by the process of step SP13 described above. It is in a separated state.

  In this case, the main control unit 103 obtains a negative result in step SP6 (FIG. 3), obtains a positive result in step SP22, and proceeds to step SP23. Thereafter, in order to start primary transfer of an image for which primary transfer is suspended, the main control unit 103 instructs the image transport unit 105 to temporarily stop driving the intermediate transfer belt 11 in step SP23. . Upon confirming that the driving of the intermediate transfer belt 11 has been temporarily stopped, the main control unit 103 causes the ID unit control unit 110 to contact the ID units 3A to 3D with the intermediate transfer belt 11 again in the subsequent step SP24. Instruct. When the contact of the ID units 3A to 3D is confirmed, the main control unit 103 instructs the image conveying unit 105 to re-drive the intermediate transfer belt 11 in the subsequent step SP25.

  With the processing in steps SP23 to SP25 thus far, preparation for starting the primary transfer of the image for which the primary transfer is suspended is completed, and then the main control unit 103 returns to step SP1 to return to the primary transfer. The primary transfer of the image whose transfer is suspended is started.

  The procedure of the printing operation of the printer 1 is as described above. As described so far, in the printer 1, when the conveyance of the recording medium is not in time for the conveyance of the primary transfer image, the secondary transfer of the primary transfer image is canceled once and the conveyance path is rotated once. The secondary transfer is attempted again.

[4. Operation timing of each part during printing operation]
Next, the timing at which each unit actually operates by the above-described printing operation will be described by taking some patterns as examples. First, the operation timing of each part in the pattern 1 in which the image of all one page is normally printed will be described with reference to the timing chart shown in FIG.

  In this case, first, the driving of the intermediate transfer belt 11 is started at time t1-1, and then the primary transfer of the image to the intermediate transfer belt 11 is started at time t1-2, and 1 of the image is started at time t1-4. The next transfer is completed (processing corresponding to step SP1 of the printing operation).

  On the other hand, the conveyance of the recording medium is started at time t1-3 after the primary transfer of the image to the intermediate transfer belt 11 is started at time t1-2. Thereafter, when the recording medium reaches the medium side secondary transfer start position P2 at time t1-5, the conveyance of the recording medium is temporarily stopped (step SP2).

  Thereafter, when the primary transfer image reaches the image side secondary transfer start position P3 at time t1-6, conveyance of the recording medium is resumed, and secondary transfer to the recording medium is started at t1-7 (step SP3). ~ SP4). When the secondary transfer is completed at time t1-8, the driving of the intermediate transfer belt 11 is stopped at time t1-9, and the image transferred to the recording medium is fixed and discharged, and at time t1-10. Then, the conveyance of the recording medium is completed (steps SP5 to SP7).

  Next, FIG. 6B shows the operation timing of each part in the pattern 2 in which the conveyance of the recording medium is delayed and the secondary transfer of this image is retried when attempting to perform the secondary transfer of the image of all one page. This will be described with reference to the timing chart shown.

  In this case, first, the driving of the intermediate transfer belt 11 is started at time t2-1, and then the primary transfer of the image to the intermediate transfer belt 11 is started at time t2-2, and 1 of the image is started at time t2-4. Next transfer is completed (step SP1).

  On the other hand, the conveyance of the recording medium is started at time t2-3 after the primary transfer of the image to the intermediate transfer belt 11 is started at time t2-2 (step SP2). After that, even if the primary transfer image reaches the image side secondary transfer start position P3, if the recording medium does not reach the medium side secondary transfer start position P2, the secondary transfer of the primary transfer image is canceled once. At time t2-5, the secondary transfer roller 19 is separated from the intermediate transfer belt 11 (steps SP3 and SP8). Thereafter, when the recording medium reaches the medium side secondary transfer start position P2 at time t2-6 within a predetermined time, the conveyance of the recording medium is temporarily stopped (steps SP9 to SP11).

  Thereafter, when the secondary transfer retry image reaches a predetermined position P5 in the vicinity of the contact position P4 of the rearmost ID unit 3A at time t2-7, the driving of the intermediate transfer belt 11 is stopped (step SP12). At time t2-8, the ID units 3A to 3D are separated from the intermediate transfer belt 11 (step SP13). Thereafter, the driving of the intermediate transfer belt 11 is resumed at time t2-9, and when the secondary transfer retry image reaches a predetermined position P7 in the vicinity of the image side secondary transfer start position P3 at time t2-10, the intermediate transfer belt 11 again. Is stopped (step SP14). At time t2-11 while the driving of the intermediate transfer belt 11 is stopped, the secondary transfer roller 19 is again brought into contact with the intermediate transfer belt 11 (step SP15). Then, the driving of the intermediate transfer belt 11 is resumed at time t2-12, and when the secondary transfer retry image reaches the image side secondary transfer start position P3 at time t2-13, conveyance of the recording medium is resumed (step). SP16-SP18).

  Thereafter, secondary transfer to the recording medium is started at time t2-14. When the secondary transfer is completed at time t2-15, the driving of the intermediate transfer belt 11 is stopped at time t2-16, and the image transferred to the recording medium is fixed and discharged. At time t2-17, the transfer is performed. The ID units 3A to 3D are brought into contact with the intermediate transfer belt 11 again, and the conveyance of the recording medium is completed at time t2-18 (steps SP4 to SP7).

  Next, each part of the pattern 3 in which the transfer of the recording medium is delayed and the second transfer of the image of the first page is retried when the image of the first page is to be subjected to the secondary transfer among the images of all the two pages. Will be described with reference to a timing chart shown in FIG. The pattern 3 is a pattern in which the image on the second page is not the primary transfer suspension target image, and after the second transfer of the image on the first page is retried, the image on the second page is subsequently transferred on the secondary transfer. It is.

  In this case, first, the driving of the intermediate transfer belt 11 is started at time t3-1, and then the primary transfer of the image of the first page to the intermediate transfer belt 11 is started at time t3-2, and time t3-4. The primary transfer of the first page image is completed at time t3-5, and the first transfer of the second page image is started at time t3-5. Step SP1).

  On the other hand, the conveyance of the recording medium is started at time t3-3 after the primary transfer of the image to the intermediate transfer belt 11 is started at time t3-2 (step SP2). After that, even if the primary transfer image of the first page reaches the image side secondary transfer start position P3, if the recording medium does not reach the medium side secondary transfer start position P2, the secondary transfer of the primary transfer image is 1 The secondary transfer roller 19 is separated from the intermediate transfer belt 11 at time t3-6 (steps SP3 and SP8). Thereafter, when the recording medium reaches the medium side secondary transfer start position P2 at time t3-7 within a predetermined time, the conveyance of the recording medium is temporarily stopped (steps SP9 to SP11).

  Thereafter, when the secondary transfer retry image of the first page reaches a predetermined position P5 in the vicinity of the contact position P4 of the rearmost ID unit 3A at time t3-9, the driving of the intermediate transfer belt 11 is stopped ( Step SP12). At time t3-10, the ID units 3A to 3D are separated from the intermediate transfer belt 11 (step SP13). Thereafter, the driving of the intermediate transfer belt 11 is resumed at time t3-11, and when the secondary transfer retry image reaches a predetermined position P7 in the vicinity of the image side secondary transfer start position P3 at time t3-12, the intermediate transfer belt 11 again. Is stopped (step SP14). At time t3-13 while the driving of the intermediate transfer belt 11 is stopped, the secondary transfer roller 19 is again brought into contact with the intermediate transfer belt 11 (step SP15). Then, the driving of the intermediate transfer belt 11 is resumed at time t3-14, and when the secondary transfer retry image reaches the image side secondary transfer start position P3 at time t3-15, conveyance of the recording medium is resumed (step). SP16-SP18).

  Thereafter, the secondary transfer of the primary transfer image of the first page to the recording medium is started at time t3-16, and the secondary transfer of the first page is completed at time t3-17. The secondary transfer of the eye is started, and the secondary transfer of the second page is completed at time t3-19. Subsequent operations are the same as those in the pattern 2, and thus description thereof is omitted.

  Next, each part of the pattern 4 in which the transfer of the recording medium is delayed and the second transfer of the image of the first page is retried when the image of the first page is to be secondarily transferred among the images of all three pages. Will be described with reference to a timing chart shown in FIG. The pattern 4 is a pattern in which the image on the third page becomes the primary transfer suspension target image and is not primarily transferred.

  In this case, first, the driving of the intermediate transfer belt 11 is started at time t4-1, and then the primary transfer of the image of the first page to the intermediate transfer belt 11 is started at time t4-2, and time t4-4. Then, the primary transfer of the first page image is completed, the primary transfer of the second page image is started at time t4-5, and the primary transfer of the second page image is completed at time t4-8 ( Step SP1).

  On the other hand, the conveyance of the recording medium is started at time t4-3 after the primary transfer of the image to the intermediate transfer belt 11 is started at time t4-2 (step SP2). After that, even if the primary transfer image of the first page reaches the image side secondary transfer start position P3, if the recording medium does not reach the medium side secondary transfer start position P2, the secondary transfer of the primary transfer image is 1 The secondary transfer roller 19 is separated from the intermediate transfer belt 11 at time t4-6 (steps SP3 and SP8). Here, for the image on the third page, the primary transfer is not completed until the secondary transfer retry image for the first page reaches a predetermined position P5 in the vicinity of the contact position P4 of the ID unit 3A on the first rear side. By being predicted, the image is set as the primary transfer suspension target image (steps SP9 and SP2). At this time, since the image on the third page has not yet been primarily transferred, the primary transfer is suspended without being performed at all. If the image on the third page is in the primary transfer at this time, a part of the image is held in the primary transfer state.

  Thereafter, when the recording medium reaches the medium side secondary transfer start position P2 at time t4-7 within a predetermined time, the conveyance of the recording medium is temporarily stopped (steps SP9 to SP11). Subsequent operations are the same as those in the pattern 2, and thus description thereof is omitted.

  For the third page image set as the primary transfer suspension target image, the secondary transfer of the second page image is completed, and the driving of the intermediate transfer belt 11 is stopped at time t4-20. The ID units 3A to 3D are again brought into contact with the intermediate transfer belt 11 at time t4-21, and after conveyance of the recording medium is completed at time t4-22, primary transfer and secondary transfer are performed at the same operation timing as pattern 1. Done.

  Next, when the image of the entire page is to be subjected to the secondary transfer, the conveyance of the recording medium is delayed and the secondary transfer of the image is retried, but the primary transfer of the image itself cannot be completed. Therefore, the operation timing of each part in the pattern 5 in which neither primary transfer nor secondary transfer can be performed will be described with reference to the timing chart shown in FIG.

  In this case, first, the driving of the intermediate transfer belt 11 is started at time t5-1, and then the primary transfer of the image to the intermediate transfer belt 11 is started at time t5-2 (step SP1).

  On the other hand, conveyance of the recording medium is started at time t5-3 after the primary transfer of the image to the intermediate transfer belt 11 is started at time t5-2 (step SP2). After that, even if the primary transfer image reaches the image side secondary transfer start position P3, if the recording medium does not reach the medium side secondary transfer start position P2, the secondary transfer of the primary transfer image is canceled once. At time t5-4, the secondary transfer roller 19 is separated from the intermediate transfer belt 11 (steps SP3 and SP8). Here, this image is still undergoing primary transfer, and the primary transfer must be completed before the leading edge of this image reaches a predetermined position P5 near the contact position P4 of the ID unit 3A on the rearmost side. By the prediction, the primary transfer is interrupted at time t5-5, and the abnormality detection process is executed (steps SP9, SP19, SP20). Further, the driving of the intermediate transfer belt 11 is stopped at time t5-6, the medium conveyance is stopped at time t5-7, and the secondary transfer roller 19 is brought into contact with the intermediate transfer belt 11 at time t5-8.

[5. Summary and Effect]
As described above, when the primary transfer image transferred to the intermediate transfer belt 11 reaches the image side secondary transfer start position P3, the printer 1 still reaches the medium side secondary transfer start position P2. If not, it is determined that the secondary transfer cannot be performed, and the secondary transfer of the primary transfer image to the recording medium is canceled once.

  Thereafter, when the recording medium reaches the medium side secondary transfer start position P2 within a predetermined time with a delay, the printer 1 waits for the recording medium at the medium side secondary transfer start position P2, while performing the secondary transfer. For the canceled primary transfer image (that is, the secondary transfer retry image), the annular transfer path is rotated once along with the intermediate transfer belt 11.

  When the secondary transfer retry image reaches the image side secondary transfer start position P3 again, the printer 1 starts transporting the recording medium waiting at the medium side secondary transfer start position P2, The secondary transfer retry image and the recording medium conveyance timing are synchronized, and the secondary transfer retry image is secondarily transferred to the recording medium.

  In this way, even if the conveyance of the recording medium is delayed, the printer 1 does not waste the primary transfer image (toner image) transferred to the intermediate transfer belt 11 as in the prior art, and the recording medium Secondary transfer can be performed and wasteful toner consumption can be reduced.

  In addition, the printer 1 does not immediately determine that the recording medium is transported as a jam, but only determines that the recording medium does not reach the medium-side secondary transfer start position P2 after waiting for a predetermined time. The printing operation was stopped. By doing so, it is possible to avoid as much as possible the situation in which the conveyance delay of the recording medium is erroneously determined as a jam. Thereby, the printer 1 can reduce the number of recording media discarded as a jam as compared with the conventional one, and can reduce the printing cost.

  Further, when the printer 1 makes the secondary transfer retry image once together with the intermediate transfer belt 11, the secondary transfer roller 19, the cleaning blade 16, and the ID units 3 </ b> A to 3 </ b> D are separated from the intermediate transfer belt 11 to perform the secondary transfer. The transfer retry image was passed. Thus, in the printer 1, when the secondary transfer retry image is rotated once, the secondary transfer retry image is scraped from the intermediate transfer belt 11 by the secondary transfer roller 19, the cleaning blade 16, and the ID units 3 </ b> A to 3 </ b> D. It is possible to prevent the image from being deteriorated by avoiding being dropped or peeled off.

  Further, since the ID units 3A to 3D are separated from the intermediate transfer belt 11, the consumption of the ID units 3A to 3D can be prevented.

  Further, the printer 1 temporarily stops the intermediate transfer belt 11 immediately before the secondary transfer retry image reaches the ID unit 3A on the most upstream side, and separates the ID units 3A to 3D. In this way, with respect to the image following the secondary transfer retry image, the primary transfer can be continued until immediately before the secondary transfer retry image reaches the most downstream ID unit 3A.

  As a result, the printer 1 is in the middle of the image following the secondary transfer retry image for which the primary transfer is completed immediately before the secondary transfer retry image reaches the most downstream ID unit 3A. The primary transfer to the intermediate transfer belt 11 can be performed as usual without being interrupted or discarded.

  On the other hand, among the images following the secondary transfer retry image, the printer 1 performs intermediate transfer for an image in which the primary transfer is not completed immediately before the secondary transfer retry image reaches the ID unit 3A on the most upstream side. The primary transfer to the belt 11 cannot be performed as usual.

  Therefore, when the printer 1 determines that the secondary transfer of the primary transfer image is impossible due to a delay in the conveyance of the recording medium, the secondary transfer retry image is one of the images following the secondary transfer retry image. It is predicted whether or not there is an image in which primary transfer is not completed immediately before reaching the upstream ID unit 3A.

  Then, the printer 1 does not complete the primary transfer immediately before the secondary transfer retry image reaches the ID unit 3A and has not yet performed the primary transfer. The primary transfer is suspended at a time point before the primary transfer.

  By doing so, the primary transfer of the image that is not completed by the primary transfer retry image immediately before the secondary transfer retry image reaches the ID unit 3A among the images following the secondary transfer retry image is performed. A situation in which the primary transfer is interrupted in the middle can be avoided.

  As a result, it is possible to prevent an image interrupted during the primary transfer, that is, an image that needs to be discarded, from remaining on the intermediate transfer belt 11 as much as possible, thereby reducing wasteful toner consumption. .

[6. Other Embodiments]
[6-1. Other Embodiment 1]
In the above-described embodiment, when the primary transfer image reaches the image side secondary transfer start position P3, if the recording medium has not yet reached the medium side secondary transfer start position P2, the primary transfer image has reached the primary transfer image. to cancel once the secondary transfer of the transferred image, a predetermined time until the primary transfer image (i.e. secondary transfer retry image) reaches the position P6 of the distance d 2 from the image side secondary transfer start position P3, Waiting for the conveyance of the recording medium.

  For example, the transfer of the recording medium may be waited for a predetermined time until the secondary transfer retry image reaches the predetermined position P5 in the vicinity of the contact position P4 of the ID unit 3A. The conveyance of the recording medium may be waited for a predetermined time until the next transfer image reaches a predetermined position between the image side secondary transfer start position P3 and the contact position P4 of the ID unit 3A.

  In this case, the closer to the contact position P4 of the ID unit 3A, the longer the waiting time for the recording medium, and the closer to the image side secondary transfer start position P3, the shorter the waiting position for the recording medium. .

[6-2. Other Embodiment 2]
In the above-described embodiment, when the primary transfer image reaches the image side secondary transfer start position P3, if the recording medium has not yet reached the medium side secondary transfer start position P2, the primary transfer image has reached the primary transfer image. to cancel once the secondary transfer of the transferred image, a predetermined time until the primary transfer image (secondary transfer retry image) reaches the position P6 of the distance d 2 from the image side secondary transfer start position P3, the recording When the recording medium reaches the medium side secondary transfer start position P2 within a predetermined time after waiting for the conveyance of the medium, the recording medium waits at the medium side secondary transfer start position P2 and the secondary transfer retry image is displayed as 1. The secondary transfer is retried.

  Not limited to this, the secondary transfer retry image may be retried without making one round of the secondary transfer retry image.

In this case, the predetermined time until the secondary transfer retry image reaches the position P6 of the distance d 2 from the image side secondary transfer start position P3, waits for the conveyance of the recording medium, the recording medium within the predetermined time medium side 2 If it reaches the next transfer start position P2 with a delay, at that time, the drive of the intermediate transfer belt 11 is temporarily stopped to stop the conveyance of the secondary transfer retry image.

At this time, the recording medium is conveyed from the medium side secondary transfer start position P2 to a position (not shown) at a distance d2 and stopped. Then, by re-driving the intermediate transfer belt 11 to resume conveyance of the secondary transfer retry images, when the secondary transfer retry image reaches the position P6 of the distance d 2 from the image side secondary transfer start position P3, the medium the conveyance of the recording medium that is stopped from the side secondary transfer start position P2 at a distance d 2 is resumed, synchronization of the transfer timing of the secondary transfer retry image and the recording medium, to perform the secondary transfer .

  In this way, it is possible to retry the secondary transfer without making the secondary transfer retry image one round, and as a result, it is possible to reduce the time required for printing.

[6-3. Other Embodiment 3]
Further, in the above-described embodiment, when the secondary transfer retry image is rotated once with the intermediate transfer belt 11, the secondary transfer roller 19 and the ID units 3A to 3D are separated from the intermediate transfer belt 11 to perform the secondary transfer. The retry image was passed.

  This is because when the secondary transfer roller 19 and the ID units 3A to 3D are in contact with the intermediate transfer belt 11, the secondary transfer roller 19 and the ID units 3A to 3D are secondary when the secondary transfer retry image passes. This is because the transfer retry image is deteriorated.

  On the other hand, for example, even if the secondary transfer roller 19 and the ID units 3A to 3D are in contact with the intermediate transfer belt 11, if the mechanism does not deteriorate the secondary transfer retry image, the secondary transfer retry image is rotated once. When doing so, the secondary transfer roller 19 and the ID units 3A to 3D need not be separated.

  Further, even when the secondary transfer retry image is deteriorated, there is no problem (for example, it is not deterioration that can be recognized by the user), and when the secondary transfer retry image is rotated once, the secondary transfer roller 19 and the ID unit 3A to 3D may not be separated.

[6-4. Other Embodiment 4]
Further, in the above-described embodiment, when the secondary transfer retry image reaches the predetermined position P5 in the vicinity of the contact position P4 of the ID unit 3A, the driving of the intermediate transfer belt 11 is temporarily stopped and the secondary transfer retry image is displayed. The conveyance was stopped and the ID units 3 </ b> A to 3 </ b> D were separated from the intermediate transfer belt 11.

  Not limited to this, among the images following the secondary transfer retry image, when the primary transfer of the last image of the image where the primary transfer is completed before the secondary transfer retry image reaches the position P5 is completed. Alternatively, the driving of the intermediate transfer belt 11 may be temporarily stopped to stop the conveyance of the secondary transfer retry image, and the ID units 3A to 3D may be separated from the intermediate transfer belt 11.

  Further, when it is determined that the secondary transfer of the primary transfer image is impossible and must be retried, the image following the primary transfer image (that is, the secondary transfer retry image) is already in the primary transfer. If the secondary transfer retry image is a primary transfer suspension target image whose primary transfer is not completed before reaching the position P5, the primary transfer of the primary transfer suspension target image is not continued unnecessarily. As described above, the driving of the intermediate transfer belt 11 may be temporarily stopped to stop the conveyance of the secondary transfer retry image, and the ID units 3A to 3D may be separated from the intermediate transfer belt 11.

[6-5. Other Embodiment 5]
Further, in the above-described embodiment, the printer 1 is configured to have one recording medium accommodating cassette 23. However, the configuration is not limited to this, and the printer 1 may be configured to include two or more recording medium accommodating cassettes 23. Even in such a configuration, by performing the same printing operation as in the above-described embodiment, even if the conveyance of the recording medium is delayed, the secondary transfer can be retried, and wasteful toner consumption is reduced. be able to.

[6-6. Other Embodiment 6]
Furthermore, in the above-described embodiment, it is determined whether or not the recording medium has reached the medium side secondary transfer start position P2 by turning on / off the sensor 28 that is a photoelectric sensor. Any other sensor may be used as long as it can determine whether or not the recording medium has reached the medium-side secondary transfer start position P2, and it may be determined by a method different from the sensor. You may do it.

[6-7. Other Embodiment 7]
Further, in the above-described embodiment, the present invention is applied to the intermediate transfer type printer 1, but an intermediate transfer type image forming apparatus such as a facsimile, an MFP (Multi Function Product), a copier, or the like. It can also be applied to an image forming apparatus.

[6-8. Other Embodiment 8]
Further, in the above-described embodiment, the ID units 3A to 3D are used as specific examples of the image forming unit that forms an image. However, the present invention is not limited to this, and an image forming unit having a mechanism different from that of the ID units 3A to 3D may be used as long as it has a function of forming an image.

  Further, in the above-described embodiment, the intermediate transfer belt 11 is used as a specific example of the intermediate transfer member on which the image is primarily transferred. For example, a drum-like intermediate transfer member may be used instead of the intermediate transfer belt 11 as long as it functions as an intermediate transfer member.

  Furthermore, in the above-described embodiment, the primary transfer roller 15 is used as a specific example of the primary transfer unit that primarily transfers an image to the intermediate transfer member. Not limited to this, a primary transfer unit having a mechanism different from that of the primary transfer roller 15 may be used as long as it has a primary transfer function.

  Furthermore, in the above-described embodiment, the drive roller 12 is used as a specific example of the image conveying unit that conveys the image primarily transferred to the intermediate transfer member. However, the present invention is not limited to this, and an image conveying unit having a mechanism different from that of the driving roller 12 may be used as long as it has a function of conveying an image.

  Furthermore, in the above-described embodiment, the hopping roller 24, the registration roller 25, and the conveyance rollers 26 and 27 are used as specific examples of the recording medium conveyance unit that conveys the recording medium. However, the present invention is not limited to this, and a recording medium conveying unit having a mechanism different from those may be used as long as it has a function of conveying a recording medium.

  Further, in the above-described embodiment, the secondary transfer roller 19 is used as a specific example of the secondary transfer unit that secondarily transfers the image to the recording medium. Not limited to this, a secondary transfer unit having a mechanism different from that of the secondary transfer roller 19 may be used as long as it has a primary transfer function.

  Further, in the above-described embodiment, the main control unit 103 is used as a specific example of the predicting unit that predicts whether or not the primary transfer of the image is completed. However, the present invention is not limited to this, and a prediction unit different from the main control unit 103 may be used as long as it has a function of predicting whether or not primary transfer of an image is completed.

[6-9. Other Embodiment 9]
Furthermore, the present invention is not limited to the above-described embodiment and other embodiments. That is, the scope of application of the present invention extends to embodiments in which some or all of the above-described embodiments and other embodiments are arbitrarily combined, and embodiments in which some are extracted.

  The present invention can be widely used in an intermediate transfer type image forming apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3A, 3B, 3C, 3D ... ID unit, 4 ... Image drum, 11 ... Intermediate transfer belt, 12 ... Drive roller, 15 ... Primary transfer roller, 18 ... Conveyance path , 19 ... secondary transfer roller, 24 ... hopping roller, 25 ... registration roller, 26, 27 ... transport roller, 103 ... main controller.

Claims (7)

An image forming means for forming an image comprising a toner image;
Primary transfer means for primarily transferring an image formed by the image forming means to an intermediate transfer member;
Image conveying means for conveying the image primarily transferred to the intermediate transfer member via an annular conveying path;
A recording medium conveying means for conveying the recording medium;
Secondary transfer means for secondary transfer to the recording medium transported by the recording medium transporting means and secondary transferred to the recording medium transported by the image transfer means, ,
The recording medium is transported by the recording medium transporting means, and even if the image primarily transferred to the intermediate transfer body reaches a predetermined position on the image side for secondary transfer, the recording medium When the predetermined position on the medium side for performing the secondary transfer is not reached, the secondary transfer by the secondary transfer means is not performed, and the image that is primarily transferred to the intermediate transfer member is conveyed as it is, and the recording medium The recording medium is continuously executed to wait for the recording medium to reach the predetermined position on the medium side, and when the recording medium reaches the predetermined position on the medium side, the image primarily transferred to the intermediate transfer member is displayed. The second image is conveyed again to a predetermined position on the image side, and the second image is transferred to the recording medium by the second transfer unit, so that the first image transferred first to the intermediate transfer member performs the second transfer. Reached the specified position on the image side However, if the recording medium does not reach the predetermined position on the medium side, the first image is at least the image forming means for the image that follows the first image and has not yet undergone the primary transfer. An image forming apparatus that determines whether primary transfer is completed before reaching a contact position between the intermediate transfer member and the intermediate transfer member. An image forming means for forming an image comprising a toner image;
Primary transfer means for primarily transferring an image formed by the image forming means to an intermediate transfer member;
Image conveying means for conveying the image primarily transferred to the intermediate transfer member via an annular conveying path;
A recording medium conveying means for conveying the recording medium;
Secondary transfer means for secondary transfer to the recording medium transported by the recording medium transporting means and secondary transferred to the recording medium transported by the image transfer means, ,
The image forming unit and the secondary transfer unit are capable of contacting and separating from the intermediate transfer member,
The recording medium is transported by the recording medium transporting means, and even if the image primarily transferred to the intermediate transfer body reaches a predetermined position on the image side for secondary transfer, the recording medium When the predetermined position on the medium side for performing the secondary transfer is not reached, the secondary transfer unit and the image forming unit are separated from the intermediate transfer member without performing the secondary transfer by the secondary transfer unit. The image that has been primarily transferred to the intermediate transfer member is transported as it is, and the operation of transporting the recording medium is continued to wait until the recording medium reaches a predetermined position on the medium side. When the medium side predetermined position is reached, the image transferred primary to the intermediate transfer member is conveyed again to the image side predetermined position, and secondary transfer onto the recording medium is performed by the secondary transfer unit, Intermediate transfer If the recording medium does not reach the predetermined position on the medium side even if the first image that has been primarily transferred to the medium reaches the predetermined position on the image side for performing the secondary transfer, the image following the first image And determining whether primary transfer is completed before the first image reaches at least the contact position between the image forming means and the intermediate transfer body for an image for which primary transfer has not yet been completed. Image forming apparatus. Said first without and still the primary transfer is completed by the image following the image, 1 before the previous SL first image further to reach the contact position with the at least the image forming means and said intermediate transfer member 3. The image forming apparatus according to claim 1, wherein, for an image that is determined to have completed the next transfer, the primary transfer is performed as usual, and the second transfer is performed after the second transfer of the first image. . Said first without and still the primary transfer is completed by the image following the image, 1 before the previous SL first image further to reach the contact position with the at least the image forming means and said intermediate transfer member The image forming apparatus according to claim 1, wherein the primary transfer is suspended for an image for which it is determined that the next transfer is not completed. For the image on which the primary transfer is suspended, the first transfer and the image that has been subjected to the primary transfer with the image following the first image are subjected to the secondary transfer, and then the primary transfer and the secondary transfer are performed. The image forming apparatus according to claim 4. The intermediate transfer member is annular and is provided along the transport path.
The image conveying means is configured to convey the image primarily transferred to the intermediate transfer body by driving the intermediate transfer body, and without performing the secondary transfer by the secondary transfer means, When the image primarily transferred to the intermediate transfer member is conveyed as it is and again to the predetermined position on the image side, the image before the image reaches the contact position between the image forming unit and the intermediate transfer member. At that point, the drive of the intermediate transfer member is temporarily stopped,
The image forming apparatus according to claim 2, wherein the image forming unit is separated from the intermediate transfer member when the driving of the intermediate transfer member is temporarily stopped by the image conveying unit. If the recording medium does not reach the predetermined position on the medium side even when the image primarily transferred to the intermediate transfer body reaches the predetermined position on the image side for performing the secondary transfer, the secondary transfer means 2 The image that has been primarily transferred to the intermediate transfer member is transported as it is without performing the next transfer, and the recording medium before the image reaches at least the contact position between the image forming unit and the intermediate transfer member. 7. When the medium reaches a predetermined position on the medium side, the image primarily transferred to the intermediate transfer member is conveyed again to the predetermined position on the image side, and secondary transfer onto the recording medium is performed by the secondary transfer unit. The image forming apparatus described in 1.

Images