JP2015184651A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an image forming apparatus that can reduce unnecessary consumption of toner.SOLUTION: An image forming apparatus conveys, prior to the current printing, a preliminary recording medium to a conveyance path through which a normal conveyance recording medium does not pass during the printing to be held on the conveyance path. During the printing, when the image forming apparatus has determined that the conveyance of the normal conveyance recording medium has been delayed for some reason and does not meet a secondary transfer timing, immediately conveys the preliminary recording medium separately held on the conveyance path to a secondary transfer unit 19 so as to perform secondary transfer onto the preliminary recording medium in place of the normal conveyance recording medium. With this configuration, the situation can be avoided in which a toner image primarily transferred to an intermediate transfer belt 10 is not transferred to a recording medium unnecessarily.

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 this problem, in the image forming apparatus of the present invention, an analysis unit that analyzes an image forming job, an image forming unit that forms an image based on an analysis result by the analysis unit, and the image forming unit The recording medium conveyance path is determined based on a primary transfer section that primarily transfers the image to the intermediate transfer member, a recording medium conveyance path having a plurality of conveyance paths, and an analysis result by the analysis section. A recording medium conveying unit that conveys the recording medium according to the conveying path determined by the conveying path determining unit, and an image primarily transferred to the intermediate transfer member by the recording medium conveying unit. A secondary transfer unit that performs secondary transfer to the recording medium being conveyed, and the recording medium conveyance unit before conveying the first recording medium according to the conveyance path determined by the conveyance path determination unit. The standby second recording medium is transported to a place that does not pass through the transport path of the first recording medium, and the standby is performed, and the recording medium transporting section performs an operation of transporting the first recording medium. However, when the first recording medium is not normally conveyed, the second recording medium that is waiting is conveyed by the recording medium conveying unit, and the image primarily transferred to the intermediate transfer member is transferred to the intermediate transfer member. A control unit for performing secondary transfer onto the second recording medium by the secondary transfer unit is provided.

  As described above, according to the present invention, for example, when the first recording medium is not normally conveyed due to a delay, the second recording medium that is waiting in a place that does not pass through the conveying path of the first recording medium is provided. Even if the image transferred primary to the intermediate transfer member cannot be secondarily transferred to the first recording medium due to the conveyance of the first recording medium, the image is delayed. Can be secondarily transferred to the second recording medium, so that a situation where the image primarily transferred to the intermediate transfer member is wasted can be avoided.

  According to the present invention, even when the conveyance of the first recording medium is delayed and the image primarily transferred to the intermediate transfer member cannot be secondarily transferred to the first recording medium, the image is Since the secondary transfer can be performed on the second recording medium, it is possible to avoid the situation where the image primarily transferred to the intermediate transfer member is wasted, and thus image formation that can reduce wasteful toner consumption. A device can be realized.

1 is a schematic cross-sectional view illustrating an overall configuration of a printer. 2 is a schematic cross-sectional view illustrating a configuration of an image forming unit. FIG. FIG. 6 is a schematic cross-sectional view illustrating a recording medium conveyance path during double-sided printing. FIG. 6 is a schematic cross-sectional view showing a recording medium conveyance path during two-pass printing. FIG. 2 is a block diagram illustrating a functional configuration of a printer. It is a flowchart which shows printing start operation | movement. It is a schematic sectional view showing a standby position of a preliminary recording medium during two-pass printing. It is a schematic sectional view showing a standby position of a preliminary recording medium during single-sided printing and double-sided printing. It is a flowchart which shows printing operation. 6 is a timing chart illustrating the operation timing of each unit during a printing start operation before performing two-pass printing. It is a timing chart which shows the operation timing of each part at the time of the printing start operation | movement before performing single-sided printing or double-sided printing. 6 is a timing chart showing the operation timing of each unit during a printing operation when performing single-sided printing and when a normal conveyance recording medium is normally conveyed. 6 is a timing chart showing the operation timing of each unit during a printing operation when using a preliminary recording medium that is waiting on a conveyance path for duplex printing. 6 is a timing chart showing the operation timing of each unit during a printing operation when using a preliminary recording medium that is waiting on a conveyance path for two-pass printing.

  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 right side of FIG. 1 is the front side of the casing 2, the left side when viewed from the front of the casing 2 is the left side of the casing 2, and the right side when viewed from the front of the casing 2 is the casing 2. On the right side. 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.

  Formed on the upper part inside the housing 2 are developer images (toner images) of four colors (for example, black (K), yellow (Y), magenta (M), and cyan (C)) handled by the printer 1. Image forming units 3A to 3D for this purpose are provided side by side in the front-rear direction. These four image forming units 3 </ b> A to 3 </ b> D are detachably attached to the housing 2. The four image forming units 3A to 3D have the same configuration, and each includes a photosensitive drum 4, a charging roller 5, an LED head 6, a developing roller 7, a supply roller 8, a toner cartridge 9 and the like as shown in FIG. Has been. The charging roller 5 and the developing roller 7 are provided around the photosensitive drum 4 so as to be in contact with the surface of the photosensitive drum 4.

  The charging roller 5 is configured to negatively charge the surface of the photosensitive drum 4 by applying a negative charging voltage. The LED head 6 is disposed above the photosensitive drum 4 and selectively irradiates light onto the surface of the charged photosensitive drum 4 to form an electrostatic latent image based on the print image data on the surface of the photosensitive drum 4. It is like that. The developing roller 7 is applied with a negative voltage and develops the electrostatic latent image formed on the surface of the photosensitive drum 4 with toner, thereby forming a toner image on the surface of the photosensitive 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 image forming units 3A to 3D and stores toner of a corresponding color.

  Further, as shown in FIG. 1, an intermediate transfer belt 10 is provided inside the housing 2 below the four image forming units 3 </ b> A to 3 </ b> D. The intermediate transfer belt 10 has an annular shape, and includes a driving roller 11 positioned in front of the first image forming unit 3D, a driven roller 12 positioned in the rear of the first rear image forming unit 3A, and a front-rear direction. A secondary transfer backup roller 13 whose position is between the drive roller 11 and the driven roller 12 and whose vertical position is below these, and a pair of driven rollers positioned between the driven roller 12 and the secondary transfer backup roller 13 14 is stretched in a substantially inverted triangular shape in a side view.

  The intermediate transfer belt 10 has an upper surface portion extending in the front-rear direction between the photosensitive drums 4 of the image forming units 3 </ b> A to 3 </ b> D and the primary transfer roller 15 disposed to face the lower side of the photosensitive drums 4. It is arranged to pass. The intermediate transfer belt 10 runs in the clockwise direction in the drawing as the drive roller 11 is driven, and the photosensitive drum 4 and the primary transfer roller 15 of each of the image forming units 3A to 3D. , The toner images formed on the surface of the photosensitive drum 4 of each of the image forming units 3A to 3D are primarily transferred onto the surface.

  The toner image primarily transferred to the intermediate transfer belt 10 is conveyed as the intermediate transfer belt 10 travels. In other words, the intermediate transfer belt 10 is provided along the conveyance path of the primary-transferred toner image and plays a role of conveying the primary-transferred toner image.

  Further, a cleaning blade 16 is disposed opposite to the rear end of the upper surface portion of the intermediate transfer belt 10. The cleaning blade 16 has a plate shape, and the tip portion of the cleaning blade 16 comes into contact with the surface of the intermediate transfer belt 10 to scrape off toner or the like adhering to the surface of the intermediate transfer belt 10 after the secondary transfer described later. To be removed.

  Furthermore, a secondary transfer roller 18 is sandwiched between a conveyance path 17 for a recording medium (for example, paper) at a lower apex portion (a portion in contact with the secondary transfer backup roller 13) of the intermediate transfer belt 10. Are arranged opposite to each other. That is, the intermediate transfer belt 10 passes between the secondary transfer backup roller 13 and the secondary transfer roller 18 at the lower apex portion and travels in the clockwise direction in FIG. The toner image primarily transferred by 3A to 3D is conveyed to the secondary transfer roller 18. Note that the secondary transfer backup roller 13 and the secondary transfer roller 18 are a part of the secondary transfer unit 19, and the secondary transfer unit 19 is connected to the intermediate transfer belt by a solenoid (not shown). It can be separated from 10 or abutted.

  Further, the recording medium passes between the intermediate transfer belt 10 and the secondary transfer roller 18 along the conveyance path 17, and the secondary transfer unit 19 is configured to supply a voltage of the charged toner image on the intermediate transfer belt 10. By applying a voltage having the opposite attribute to the secondary transfer roller 18, the toner image primarily transferred to the intermediate transfer belt 10 is secondarily transferred to the recording medium.

  Furthermore, a recording medium storage tray 20 on which recording media are loaded is detachably attached to the casing 2 at the bottom of the casing 2. Further, a pickup roller 21 is provided in the vicinity of the recording medium outlet near the front end of the recording medium accommodation tray 20 for feeding the recording media stacked in the recording medium accommodation tray 20 one by one to the conveyance path 17. Yes.

  The conveying path 17 curves backward from the vicinity of the recording medium outlet of the recording medium accommodation tray 20 toward the upper side and extends rearward as it passes between the secondary transfer backup roller 13 and the secondary transfer roller 18. It has become. On the downstream side of the pickup roller 21 in the conveyance path 17, the skew of the recording medium fed out from the recording medium storage tray 20 is corrected near the end of the curve, and the contact between the intermediate transfer belt 10 and the secondary transfer roller 18 is corrected. A pair of registration rollers 22 for transporting to the contact position (that is, the secondary transfer position) P is provided.

  Further, a pair of transport rollers 23 and a pair of transport rollers 24 for transporting the recording medium are provided between the pickup roller 21 and the registration rollers 22 in the transport path 17. The transport roller 23 is provided on the upstream side (side closer to the pickup roller 21) than the transport roller 24. Further, a sensor (referred to as an IN sensor) 25 for detecting a recording medium passing between the transport roller 23 and the transport roller 24 is provided between the transport roller 23 and the transport roller 24 in the transport path 17. An IN sensor 26 for detecting a recording medium passing therethrough is also provided between the conveying roller 24 and the registration roller 22.

  Further, a pair of transport rollers 27 for transporting the recording medium is provided between the registration roller 22 and the secondary transfer position P in the transport path 17, and the transport roller 27 and the secondary transfer position P An IN sensor 28 for detecting the presence or absence of a recording medium passing therethrough is provided in between. 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 unit 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.

  The conveyance path 17 passes between the secondary transfer backup roller 13 and the secondary transfer roller 18, extends to the fixing device 29 located behind the secondary transfer roller 13, passes through the fixing device 29, and then curves upward. It extends upward as it is and is connected to a discharge port provided at the rear upper end of the housing 2. Further, a portion of the transport path 17 extending upward between the fixing device 29 and the discharge port is provided with a pair of discharge transport rollers (referred to as discharge rollers) 32. In the vicinity of the fixing device 29 between the fixing device 29 and the fixing device 29, a sensor 33 (referred to as an EXIT sensor) for detecting a recording medium passing therethrough is provided, and between the discharge roller 32 and the discharge port. Is provided with an EXIT sensor 34 for detecting a recording medium passing therethrough.

  Actually, the recording medium is conveyed between the secondary transfer backup roller 13 and the secondary transfer roller 18 in accordance with the conveyance timing of the toner image primarily transferred to the intermediate transfer belt 10, where the intermediate transfer belt After the toner image primarily transferred to the toner image 10 is secondarily transferred, the toner image passes between the heat roller 30 and the pressure roller 31 of the fixing device 29, where the secondly transferred toner image is fixed. The sheet is conveyed to a discharge port, and discharged from the discharge port to a recording medium integrated stacker 35 provided on the top plate portion of the housing 2.

  Further, the housing 2 is provided with a recording medium accommodation tray for manual feeding (referred to as a manual feeding tray) 40 at the front end thereof so as to be exposed to the outside. The manual feed tray 40 is provided with a pickup roller 42 for feeding the recording media stacked in the manual feed tray 40 one by one to the conveyance path 41 in the vicinity of the recording medium intake port at the rear end. . The conveyance path 41 extends rearward from the vicinity of the recording medium intake port of the manual feed tray 40 and joins near the end of the curve on the front side of the conveyance path 17. The transport path 41 is provided with a pair of transport rollers 43. Note that the above-described IN sensor 26 may be provided in the transport path 41 and the IN sensor 26 may detect a recording medium passing therethrough.

  In fact, in the printer 1, the recording medium stacked on the manual feed tray 40 is also moved between the secondary transfer backup roller 13 and the secondary transfer roller 18 in the same manner as the recording medium stacked on the recording medium storage tray 20. The toner image that is conveyed and primarily transferred onto the surface of the intermediate transfer belt 10 is secondarily transferred.

  The configuration of the printer 1 described so far is a basic configuration when performing single-sided printing on a recording medium. In addition to such a basic configuration, in the inside of the housing 2 of the printer 1, double-sided printing or two-pass printing is performed on the recording medium in the space between the conveyance path 17 and the recording medium containing tray 20. The double-sided printing unit 50 is provided. The duplex printing unit 50 has a conveyance path 51 through which a recording medium passes when performing duplex printing or two-pass printing. Double-sided printing is printing that prints on both sides of a recording medium, and two-pass printing is printing that prints on one side of the recording medium and then prints again on this single side.

  The conveyance path 17 is provided with a branch point of the conveyance path 51 of the duplex printing unit 50 between the sensor 33 in the vicinity of the fixing device 29 and the conveyance roller 27. A separator (referred to as a DUP (Double Printing) separator) 52 for switching to the side or the conveyance path 51 side is provided. This branching point is the entrance of the duplex printing unit 50. When performing duplex printing or two-pass printing on the recording medium, the fixing device 29 is switched by turning on the DUP separator 52 and switching the conveyance direction to the conveyance path 51 side. The recording medium that has passed is conveyed to the conveyance path 51 of the duplex printing unit 50.

  Further, a junction point with the conveyance path 51 is provided in the conveyance path 17 between the registration roller 22 and the conveyance roller 27. This junction is the exit of the duplex printing unit 50, and the recording medium transported to the transport path 51 of the duplex printing unit 50 exits from this exit and is again upstream from the secondary transfer position P of the transport path 17. It is supposed to be returned to. At this time, in the case of double-sided printing, the double-sided printing unit 50 turns the recording medium upside down and returns it to the conveyance path 17 so that the recording surface becomes the opposite surface. On the other hand, in the case of two-pass printing, the recording medium is conveyed so that its recording surface does not change and returned to the conveying path 17.

  Specifically, the duplex printing unit 50 includes a duplex printing conveyance path 51A that serves as a duplex conveyance path, and a two-pass printing conveyance path 51B that serves as a single-sided two-time conveyance path. Note that the conveyance path 17 is referred to as a single-sided conveyance path when expressed in contrast with the conveyance path 51A for double-sided printing and the conveyance path 51B for two-pass printing. The two-pass printing transport path 51B has a substantially racetrack shape that connects the entrance and the exit of the duplex printing unit 50 so that the recording medium that has entered from the entrance can be directly returned from the exit to the transport path 17. . That is, the two-pass printing conveyance path 51B curves forward while going downward from the entrance, extends forward, and further curves toward the rear while going upward from near the bottom of the exit. It is connected.

  Further, the two-pass printing conveyance path 51B is provided with a pair of conveyance rollers (referred to as DUP reversing rollers) 53 at the center of the rear curve, and further in the middle of the portion extending forward. A pair of conveying rollers (referred to as two-pass conveying rollers) 54 is provided, a pair of conveying rollers 55 is provided immediately before the front curve, and a pair of registration rollers is provided at the center of the front curve portion. 56 is provided. Further, a sensor (referred to as a two-pass sensor) 57 for detecting a recording medium passing therethrough is provided between the DUP reverse roller 53 and the two-pass transport roller 54 in the two-pass printing transport path 51B. In addition, a two-pass sensor 58 is provided between the two-pass conveyance roller 54 and the conveyance roller 55, and a sensor 59 is also provided between the two-pass conveyance roller 55 and the registration roller 56.

  On the other hand, the double-sided printing conveyance path 51A has a first conveyance path 51Aa for turning back the recording medium with its leading end dead end so that the recording medium that has entered from the entrance can be turned over and returned to the conveyance path 17 from the exit. The second recording path 51Ab is configured to convey the folded recording medium upside down. The first conveyance path 51Aa branches outward from the center of the curve on the rear side of the two-pass printing conveyance path 51B and extends downward, and its tip is a dead end. On the other hand, the second transport path 51Ab branches inward from the center of the curve on the rear side of the 2-pass printing transport path 51B toward the entrance and extends downward under the front slant, and the tip of the second transport path 51Ab extends to the front. At the position immediately before the curve on the front side of the transport path 51B for printing, the two-pass printing transport path 51B is joined.

  Further, at the branch point between the first conveyance path 51Aa for duplex printing and the conveyance path 51B for two-pass printing, the conveyance direction of the recording medium is changed to the first conveyance path 51Aa side for duplex printing or the conveyance path for two-pass printing. A separator (this is called a two-pass separator) 60 for switching to the 51B side is provided, and a branch point between the second conveyance path 51Ab for double-sided printing and the conveyance path 51B for two-pass printing is provided on the recording medium. A DUP separator 61 is provided for switching the conveyance direction to the second conveyance path 51Ab side for two-sided printing or the two-pass printing conveyance path 51B side.

  Further, the second conveyance path 51Ab for double-sided printing is provided with a pair of conveyance rollers (referred to as DUP conveyance rollers) 62 at the center thereof, and further, the DUP conveyance roller 62 and the two-pass printing conveyance path 51B. Is provided with a sensor (referred to as a DUP sensor) 63 for detecting a recording medium passing therethrough.

  The configuration of the duplex printing unit 50 of the printer 1 is as described above. Here, the conveyance path in the case of duplex printing and two-pass printing of the recording medium fed out from the recording medium accommodation tray 20 will be described in more detail.

  First, the conveyance path in the case of duplex printing will be described with reference to FIG. In the case of double-sided printing, as indicated by an arrow Ar 1, the recording medium is fed one by one from the recording medium storage tray 20 to the transport path 17 by the pickup roller 21 and passes through the secondary transfer unit 19. At this time, an image is formed on one recording surface of the recording medium. Thereafter, the recording medium passes through the fixing device 29. Here, in the case of duplex printing, the DUP separator 52 positioned immediately after the fixing device 29 is turned on, and the recording medium conveyance direction is switched to the conveyance path 51 side of the duplex printing unit 50. The medium is conveyed into the duplex printing unit 50 as indicated by an arrow Ar2.

  Here, in the case of double-sided printing, the two-pass separator 60 is off, and the recording medium is indicated by an arrow Ar3 because the conveyance direction of the recording medium is switched to the first conveyance path 51Aa for double-sided printing. Thus, it is conveyed to the first conveyance path 51Aa. Thereafter, when the rotation direction of the DUP reversing roller 53 is reversed (that is, reversed), the recording medium conveyed to the first conveying path 51Aa is in the direction opposite to the direction in which the recording medium has advanced, as indicated by an arrow Ar4. It is conveyed by turning back. At this time, since the DUP separator 61 is turned on and the conveyance direction of the recording medium is switched to the second conveyance path 51Ab for double-sided printing, the recording medium is printed on both sides as indicated by an arrow Ar5. Is transported to the second transport path 51Ab. At this time, the recording medium is turned upside down by being conveyed by folding the first conveying path 51Aa for double-sided printing.

  The reversed recording medium passes through the second conveyance path 51Ab as it is, and returns to the conveyance path 17 again through the curve on the front side of the two-pass printing conveyance path 51B as indicated by an arrow Ar6. Then, the recording medium passes through the secondary transfer unit 19 again. At this time, an image is formed on the other recording surface of the recording medium. Thereafter, the recording medium passes through the fixing device 29. At this time, since the DUP separator 52 is turned off and the conveyance direction of the recording medium is switched to the conveyance path 17 side, the recording medium passes through the conveyance path 17 and is recorded as indicated by an arrow Ar7. It is conveyed to the medium accumulation stacker 35. In the case of duplex printing, such a conveyance path is used. In the case of double-sided printing, the recording medium is folded to the first conveyance path 51Aa for double-sided printing and conveyed to the second conveyance path 51Ab. Therefore, the length of the first conveyance path 51Aa is the recording medium. It is desirable that the length is sufficiently longer than the length in the transport direction (for example, the length of the long side).

  Next, the conveyance path in the case of 2-pass printing will be described with reference to FIG. Also in the case of two-pass printing, as indicated by an arrow Ar 10, the recording medium is fed one by one from the recording medium storage tray 20 to the transport path 17 by the pickup roller 21 and passes through the secondary transfer unit 19. At this time, an image is formed on the recording surface of the recording medium. Thereafter, the recording medium passes through the fixing device 29. Here, since the DUP separator 52 located immediately after the fixing device 29 is turned on and the recording medium transport direction is switched to the transport path 51 side of the duplex printing unit 50, the recording medium is indicated by the arrow Ar11. As shown in FIG. 2, the sheet is conveyed into the duplex printing unit 50.

  Here, in the case of two-pass printing, since the two-pass separator 60 is turned on and the recording medium conveyance direction is switched to the two-pass printing conveyance path 51B side, the recording medium is indicated by an arrow Ar12. It is conveyed to the two-pass printing conveyance path 51B. Thereafter, the recording medium passes through the two-pass printing conveyance path 51B as it is and is returned to the conveyance path 17 again as indicated by an arrow Ar13. Then, the recording medium passes through the secondary transfer unit 19 again. At this time, an image is overwritten on the recording surface of the recording medium. Thereafter, the recording medium passes through the fixing device 29. At this time, since the DUP separator 52 is turned off and the recording medium conveyance direction is switched to the conveyance path 17 side, the recording medium passes through the conveyance path 17 as shown by an arrow Ar14 and is recorded. It is conveyed to the medium accumulation stacker 35. In the case of two-pass printing, such a conveyance path is used.

[2. Printer functional configuration]
Next, the functional configuration of the printer 1 will be described with reference to FIG. The printer 1 includes a control unit 100, a storage unit 101, an input unit 102, a display unit 103, and a communication unit 104 as main functional units. The control unit 100 includes a CPU or the like, and includes a plurality of modules (which may be software or hardware) as an image analysis unit 105, a conveyance control unit 106, an image control unit 107, a medium standby processing control unit 108, a transfer control unit 109, and the like. A fixing control unit 110 is included. The image analysis unit 105 analyzes a print job received from an external host device (for example, a personal computer) via the communication unit 104 to specify a printing method, and generates print image data based on the print job. In the printing method, it is assumed that one of single-sided printing, double-sided printing, and two-pass printing is designated.

  The conveyance control unit 106 determines the conveyance path of the recording medium based on the printing method specified in the print job, and the rollers 21, 22, 23, 24, 27, 32, 42, 43, 53, 54, 55, 56, 62, sensors 25, 26, 28, 33, 34, 57, 58, 59, 63 and separators 52, 60, 61, respectively, and recording media in the transport paths 17, 41, 51 Control the transport of The driving of the intermediate transfer belt 10 is also controlled. The image control unit 107 controls the operation of the image forming units 3A to 3D. Specifically, the voltage applied to each of the charging roller 5, the developing roller 7, and the supply roller 8 and the light amount of the LED head 6 are controlled. The medium standby process control unit 108 determines a standby position for standby of the spare recording medium based on the printing method of the print job specified by the image analysis unit 105. Details of the operation for waiting the spare recording medium at the predetermined standby position will be described later. The transfer control unit 109 controls the transfer voltage and transfer timing of the intermediate transfer belt 10 and the secondary transfer unit 19. The fixing control unit 110 controls the driving of the fixing device 29. Specifically, the temperature of the fixing device 29 and the heating timing are controlled.

  The storage unit 101 includes a work memory 111, a program storage unit 112, and a setting information storage unit 113. The work memory 111 is composed of, for example, a RAM, and is a work memory that is necessary for the control unit 100 to control the printer 1. The program storage unit 112 is configured by a ROM, for example, and stores a control program executed by the control unit 100. The setting information storage unit 113 is configured by a flash memory, for example, and stores various setting values and setting information regarding the printer 1.

  The input unit 102 includes a touch panel 114, an operation keyboard 115, and the like, and receives an operation input from a user. The display unit 103 includes, for example, a liquid crystal panel 116, and displays various types of information related to the printer 1. Note that the input unit 102 and the display unit 103 are provided, for example, at the upper front of the housing 2 of the printer 1. The communication unit 104 is an interface unit such as a USB or LAN, and receives a print job by controlling communication with a host device such as a personal computer.

[3. Printer printing start operation]
Next, an operation at the start of printing of the printer 1 (referred to as a printing start operation) will be described in detail with reference to the flowchart shown in FIG. This printing start operation is an operation performed by the control unit 100 of the printer 1 executing a control program stored in the program storage unit 112 to control each unit.

  In step SP <b> 1, the control unit 100 receives a print job transmitted from the higher-level device through the communication unit 104. In subsequent step SP2, the image analysis unit 105 of the control unit 100 analyzes the received print job to specify a printing method and generates print image data. In subsequent step SP3, each module (the image analysis unit 105, the conveyance control unit 106, the image control unit 107, the medium standby processing control unit 108, the transfer control unit 109, and the fixing control unit 110) of the control unit 100 starts printing. Start warming up for the first time. In this case, for example, the image forming units 3A to 3D are activated, the secondary transfer unit 19 is activated, the fixing unit 29 is activated, and the intermediate transfer belt 10, each roller, sensor, separator, and the like are driven. It is assumed that at least one of activation (not shown) or the like is included.

  In subsequent step SP4, the image analysis unit 105 of the control unit 100 determines whether the print method specified for the print job is single-sided printing, double-sided printing or two-pass printing based on the printing method obtained by analyzing the print job. To determine which one of them. When it is determined that the printing method is two-pass printing, the control unit 100 proceeds from step SP4 to step SP5. Here, the medium standby processing control unit 108 of the control unit 100 instructs the transport control unit 106 to perform transport control from steps SP5 to SP8. That is, in step SP5, the conveyance control unit 106 first drives the pickup roller 21 to feed one recording medium to the conveyance path 17.

  In subsequent step SP6, the conveyance control unit 106 switches the conveyance direction of the recording medium into the duplex printing unit 50 by turning on the DUP separator 52. Further, at this time, the recording rollers 22, 23, 24 and 27 on the conveyance path 17 are driven to convey the recording medium into the duplex printing unit 50. At this time, the recording medium passes through the secondary transfer unit 19 and the fixing device 29, but these pass through without forming an image because they are still warming up.

  In subsequent step SP7, the transport control unit 106 rotates the DUP reversing roller 53 in the normal direction to transport the recording medium to the first transport path 51Aa for duplex printing, and then reverses the DUP reversing roller 53 and the second By driving the DUP conveyance roller 62 on the conveyance path 51Ab, the recording medium is conveyed from the first conveyance path 51Aa to the second conveyance path 51Ab. That is, here, the recording medium is conveyed to the duplex printing conveyance path 51A.

  In subsequent step SP8, when the recording medium is detected (turned on) by the DUP sensor 63 on the second conveyance path 51Ab, the conveyance control unit 106 stops the DUP conveyance roller 62, as shown in FIG. Then, the recording medium 120 is stopped in the second transport path 51Ab and waited. At this time, the conveyance control unit 106 stops the recording medium 120 so that the tip of the recording medium 120 is located at a predetermined distance from the junction point between the second conveyance path 51Ab and the two-pass printing conveyance path 51B. The recording medium 120 that waits in the second conveyance path 51Ab in this way is referred to as a preliminary recording medium 120. After waiting the standby recording medium 120 in this way, the control unit 100 moves to step SP13 and waits for the end of warming up. When the warming up ends, the control unit 100 moves to step SP14 and starts a printing operation. Details of the printing operation will be described later.

  On the other hand, if it is determined that the printing method of the print job is single-sided printing or double-sided printing, the control unit 100 proceeds from step SP4 to step SP9. Here, the medium standby processing control unit 108 of the control unit 100 instructs the transport control unit 106 to perform transport control from steps SP9 to SP12. That is, in step SP9, the conveyance control unit 106 first drives the pickup roller 21 to feed one recording medium to the conveyance path 17.

  In subsequent step SP10, the conveyance control unit 106 switches the recording medium conveyance direction into the duplex printing unit 50 by turning on the DUP separator 52. Further, at this time, the recording rollers 22, 23, 24 and 27 on the conveyance path 17 are driven to convey the recording medium into the duplex printing unit 50. At this time, the recording medium passes through the secondary transfer unit 19 and the fixing device 29, but these pass through without forming an image because they are still warming up. In subsequent step SP11, the conveyance control unit 106 turns on the two-pass separator 60, rotates the DUP reversing roller 53 normally, and further drives the two-pass conveyance roller 54 on the two-pass printing conveyance path 51B. The recording medium is conveyed to the two-pass printing conveyance path 51B.

  In step SP12, when the recording medium is detected (turned on) by the two-pass sensor 58 on the two-pass printing conveyance path 51B, the conveyance control unit 106 stops the two-pass conveyance roller 54 as shown in FIG. As shown, the recording medium 120 is stopped in the two-pass printing conveyance path 51B and is put on standby. At this time, the conveyance control unit 106 stops the recording medium 120 so that the tip of the recording medium 120 is located at a predetermined distance from the junction point between the second conveyance path 51Ab and the two-pass printing conveyance path 51B. In this way, the recording medium 120 that stands by in the two-pass printing conveyance path 51B is also referred to as a preliminary recording medium 120. Note that the distance from the joining point of the second conveyance path 51Ab and the two-pass printing conveyance path 51B to the leading edge of the standby recording medium 120 that is stopped is waiting for the preliminary recording medium 120 in the duplex printing conveyance path 51A. The same length is also used when waiting in the transport path 51B for two-pass printing. After waiting the standby recording medium 120 in this way, the control unit 100 moves to step SP13 and waits for the end of warming up. When the warming up ends, the control unit 100 moves to step SP14 and starts a printing operation. Details of the printing operation will be described later.

  As described so far, the printer 1 specifies a transport path through which the recording medium does not pass in the current printing based on the print job printing method during warm-up at the start of printing, and reserves the transport path in advance. The recording medium is transported and kept waiting. In order to distinguish the recording medium conveyed by the normal conveyance path from the preliminary recording medium, it is hereinafter referred to as a normal conveyance recording medium.

  In other words, if the printing method of the print job is two-pass printing, the preliminary recording medium is conveyed and waited in the double-sided printing conveyance path 51A that does not pass through the two-pass printing, and the printing method of the print job is single-sided printing or double-sided printing. In the case of printing, the preliminary recording medium is transported and kept in a two-pass printing transport path 51B that cannot pass in single-sided printing and double-sided printing. The preliminary recording medium will be described in detail later, but when the printing is actually performed, the normal transfer recording medium fed from the recording medium storage tray 20 to the transfer path 17 is delayed in conveyance for some reason, and the secondary transfer timing. When it is determined that the time is not in time, the normal transfer recording medium is transported to the secondary transfer unit 19 for secondary transfer.

  Therefore, it is sufficient to transport the preliminary recording medium after it is determined that the transport of the normal transport recording medium is sent and the secondary transfer timing is not in time, and from the standby position of the preliminary recording medium so as to be in time for the secondary transfer timing. The distance to the secondary transfer unit 19 is shorter than the distance from the recording medium storage tray 20 (that is, the normal conveyance recording medium conveyance start position) to the secondary transfer unit 19.

[4. Printer printing operation]
Next, a printing operation performed after the printing start operation of the printer 1 (referred to as a printing operation) will be described in detail with reference to the flowchart shown in FIG. This printing operation is also performed by the control unit 100 of the printer 1 executing a control program stored in the program storage unit 112 to control each unit.

  In step SP20, the conveyance control unit 106 of the control unit 100 starts driving the intermediate transfer belt 10. In subsequent step SP21, the image control unit 107 of the control unit 100 forms a toner image on the photosensitive drum 4 by controlling the operations of the image forming units 3A to 3D. Then, the transfer control unit 109 of the control unit 100 transfers the toner image formed on the photosensitive drum 4 onto the intermediate transfer belt 10.

  In subsequent step SP <b> 22, the conveyance control unit 106 drives the pickup roller 21 to feed the normal conveyance recording medium to the conveyance path 17. In subsequent step SP23, the control unit 100 determines whether or not the normal conveyance recording medium is normally conveyed. Specifically, when the IN sensor 25 arranged at the center of the curve on the front side of the conveyance path 17 does not turn on within a predetermined time after the driving of the pickup roller 21 is started, the normal conveyance recording medium is normally conveyed. It is determined that it has not been done. That is, it is determined that the secondary transfer onto the normal conveyance recording medium is impossible. The error at this time is a hopping error or a medium feed timeout error.

  When an affirmative result is obtained in step SP23, that is, when it is determined that the normal transport recording medium is transported normally, the control unit 100 proceeds from step SP23 to step SP24. In step SP24, the transfer control unit 109 performs secondary transfer on the normal transport recording medium transported to the secondary transfer unit 19. In subsequent step SP25, the fixing controller 110 fixes the toner image secondarily transferred to the normal transport recording medium by the fixing device 29 to the normal transport recording medium. In subsequent step SP26, the control unit 100 determines whether or not primary transfer of all pages designated in the print job has been completed.

  If there is a page for which the primary transfer has not been completed yet, the control unit 100 returns to step SP21 to perform the primary transfer for the page that has not been completed. On the other hand, if the primary transfer of all pages instructed in the print job has been completed, the control unit 100 moves to step SP27 and stops driving the intermediate transfer belt 10 under the control of the conveyance control unit 106. This printing operation is terminated.

  On the other hand, if a negative result is obtained in step SP23 described above, that is, if it is determined that the normal conveyance recording medium is not normally conveyed due to a hopping error or the like, the control unit 100 proceeds from step SP23 to step SP28. In step SP28, the conveyance control unit 106 first stops driving the pickup roller 21 and the conveyance rollers 23 and 24 in order to temporarily stop conveyance of the normal conveyance recording medium. In addition, the conveyance control unit 106 determines whether the printing method obtained by analyzing the print job by the image analysis unit 105, that is, the printing method of the currently processed print job is one of simplex printing, duplex printing, and two-pass printing. Is determined.

  If it is determined that the printing method is two-pass printing, the conveyance control unit 106 moves from step SP28 to step SP29, and at this time, in order to convey the standby recording medium waiting on the duplex printing conveyance path 51A. The DUP conveyance roller 62 is driven. As a result, the preliminary recording medium is transported to the secondary transfer unit 19 instead of the normal transport recording medium, and the secondary transfer is performed on the preliminary recording medium through the processing of steps SP24 to SP27 described above.

  On the other hand, if it is determined that the printing method is double-sided printing, the conveyance control unit 106 moves from step SP28 to step SP30, and at this time, in order to convey the standby recording medium waiting on the two-pass printing conveyance path 51B. The two-pass conveyance roller 54 is driven. As a result, the preliminary recording medium is transported to the secondary transfer unit 19 instead of the normal transport recording medium, and the secondary transfer is performed on the preliminary recording medium through the processing of steps SP24 to SP27 described above.

  By the way, the case where the secondary transfer is performed on the preliminary recording medium as described above is a case where the normal conveyance recording medium is not normally conveyed. In this case, for example, the normal conveyance recording medium is conveyed to the conveyance path 17. There is a high possibility of jamming (that is, medium jam) in the middle of the process. Therefore, in this case, when the secondary transfer to the preliminary recording medium is completed, the control unit 100 stops the printing operation and displays, for example, a message for instructing the user to remove the jam on the display unit 103. Then, after allowing the user to remove the jam, the printing is started again from the printing start operation. Note that if the printing operation is stopped due to a jam before printing all pages of the print job, the control unit 100 starts printing from a page that has not been printed, for example.

  On the other hand, when the control unit 100 performs the primary transfer of the last page of the print job without using the preliminary recording medium, the secondary recording unit 19 transfers the preliminary recording medium instead of the normal conveyance recording medium at this time. And the secondary transfer of the last page is performed on the preliminary recording medium. In other words, the printer 1 uses a preliminary recording medium for the last page of the print job even if the normal conveyance recording medium is not jammed. This is because the printing method may change for each print job, and when the printing method changes, it is necessary to change the standby position of the preliminary recording medium.

  As described so far, in the printer 1, when it is determined that the secondary transfer onto the normal transport recording medium is impossible due to a delay in the transport of the normal transport recording medium during printing, the standby recording medium that is on standby Are transferred to the secondary transfer unit 19 and secondary transfer is performed on the preliminary recording medium instead of the normal conveyance recording medium. As described above, even when the normal conveyance recording medium is delayed and the secondary transfer cannot be performed on the normal conveyance recording medium, the printer 1 uses the image primarily transferred to the intermediate transfer belt 10 as a preliminary recording medium. Since the secondary transfer can be performed, it is possible to avoid a situation where the toner image primarily transferred to the intermediate transfer belt 10 is wasted.

  By the way, as described above, in the printer 1, when the IN sensor 25 in the vicinity of the pickup roller 21 is not turned on within a predetermined time after the drive of the pickup roller 21 is started, that is, the medium feeding is started. When the normal conveyance recording medium did not reach the position of the IN sensor 25 within the time, the preliminary recording medium was conveyed to the secondary transfer unit 19 instead of the normal conveyance recording medium.

  Here, in actuality, in the printer 1, a time corresponding to a predetermined margin is set in the time from the start of driving the pickup roller 21 to the arrival of the IN sensor 25 when the normal conveyance recording medium is normally conveyed. The added time is set as a standby time for determining whether or not the normal recording medium is normally conveyed. The margin refers to a distance that can be made in time for the secondary transfer by increasing the conveyance speed when the normal conveyance recording medium is delayed. Specifically, in the printer 1, the margin is 20 mm. In other words, the printer 1 can keep the normal conveyance recording medium in time for the secondary transfer timing even if conveyance is delayed by a maximum of 20 mm.

  In the case of the printer 1, the distance from the IN sensor 25 to the secondary transfer position P is 317 mm. Therefore, when the standby recording medium is transported from the standby position to the secondary transfer position P after the standby time elapses, the preliminary recording medium is transported at the normal transport speed of the normal transport recording medium in time for the secondary transfer timing. The distance from the standby position of the preliminary recording medium to the secondary transfer position P must be at least 317 mm or less.

  Further, in consideration of the above-mentioned margin of 20 mm, the distance from the standby position of the preliminary recording medium to the secondary transfer position P needs to be at least 317-20 = 297 mm or less. Here, in fact, the preliminary recording medium is made to stand by at a standby position where the head of the preliminary recording medium is 10 mm before the DUP conveyance roller 55. Since the distance from the DUP conveyance roller 55 to the secondary transfer position P is 219 mm, the distance from the standby position of the preliminary recording medium to the secondary transfer position P is 219 + 10 = 229 mm.

  Thus, the distance (229 mm) from the standby position of the preliminary recording medium to the secondary transfer position P is the distance (297 mm) obtained by subtracting the margin (20 mm) from the distance (317 mm) from the IN sensor 25 to the secondary transfer position P. ) By 297-229 = 68 mm. That is, the distance from the standby position of the preliminary recording medium to the secondary transfer position P has a margin of 68 mm. Thus, in the printer 1, even if the preliminary recording medium is transported from the time when it is determined that the normal transport recording medium is not normally transported, the preliminary recording medium can be sufficiently in time for the secondary transfer timing. . Further, in the printer 1, it takes some time for the transport speed of the preliminary recording medium to reach a predetermined transport speed. In consideration of this time, the distance from the standby position of the preliminary recording medium to the secondary transfer position P is considered. In addition, there is a sufficient margin.

[5. Operation timing of each part during printing start operation and printing operation]
Next, the timing at which each unit actually operates during the above-described printing start operation and printing operation will be briefly described by taking some patterns as examples. First, the operation timing of each unit during the printing start operation before performing two-pass printing will be described with reference to the timing chart shown in FIG.

  In this case, first, at time t1, driving of the pickup roller 21 is started in order to convey the preliminary recording medium. Thereafter, at time t2, the driving of the registration roller 22 is started, and the IN sensor 25 is turned on by the preliminary recording medium. Thereafter, the driving of the secondary transfer roller 18 is started at time t3. Thereafter, when the IN sensor 28 in front of the secondary transfer unit 19 is turned on by the preliminary recording medium at time t4, at this time, in order to transport the preliminary recording medium to the duplex printing conveyance path 51A in the duplex printing unit 50, The DUP separator 61 is turned on, and the DUP reversing roller 53 is driven to rotate in the normal rotation direction (+ direction in the timing chart).

  Thereafter, when the EXIT sensor 33 in front of the DUP separator 61 is turned on at time t5, driving of the DUP conveyance roller 62 in the duplex printing conveyance path 51A is started. Thereafter, until time t6, the DUP reversing roller 53 is rotated in the normal direction, and at time t6, the rotation direction of the DUP reversing roller 53 is switched to the reversing direction (− direction in the timing chart). Thus, the preliminary recording medium is conveyed to the second conveyance path 51Ab by folding the first conveyance path 51Aa of the duplex printing conveyance path 51A.

  Thereafter, when the DUP sensor 63 of the first transport path 51Aa is turned on by the preliminary recording medium at time t7, the DUP separator 61 is turned off and the driving of the DUP reversing roller 53 is stopped. Thereafter, by continuing to drive the DUP transport roller 62 until time t8, the preliminary recording medium is transported to the standby position, and then the drive of the DUP transport roller 62 is stopped to stop the preliminary recording medium at this standby position.

  Next, the operation timing of each unit during the printing start operation before performing duplex printing will be described with reference to the timing chart shown in FIG. In this case, first, at time t10, driving of the pickup roller 21 is started in order to transport the preliminary recording medium. Thereafter, at time t11, the driving of the registration roller 22 is started, and the IN sensor 25 is turned on by the preliminary recording medium. Thereafter, the driving of the secondary transfer roller 18 is started at time t12. Thereafter, at time t13, when the IN sensor 28 in front of the secondary transfer unit 19 is turned on by the preliminary recording medium, at this time, the preliminary recording medium is transported to the two-pass printing transport path 51B in the duplex printing unit 50. The DUP separator 61 is turned on, the two-pass separator 60 is turned on, and the DUP reversing roller 53 is driven to rotate in the forward direction.

  Thereafter, at time t14, when the EXIT sensor 33 in front of the DUP separator 61 is turned on, driving of the two-pass conveyance roller 54 in the two-pass printing conveyance path 51B is started. Thereafter, when the two-pass sensor 58 of the two-pass printing conveyance path 51B is turned on by the preliminary recording medium at time t15, the DUP separator 61 and the two-pass separator 60 are turned off and the driving of the DUP reversing roller 53 is stopped. Thereafter, by continuing to drive the two-pass transport roller 54 until time t16, the preliminary recording medium is transported to the standby position, and then the drive of the two-pass transport roller 54 is stopped to stop the preliminary recording medium at this standby position. Let

  Next, the operation timing of each unit during the printing operation when performing single-sided printing and when the normal conveyance recording medium is normally conveyed will be described with reference to the timing chart shown in FIG. In this case, first, at time t20, the drive of the pickup roller 21 is started in order to convey the normal conveyance recording medium. Thereafter, at time t21, the driving of the registration roller 22 is started and the IN sensor 25 is turned on by the normal conveyance recording medium.

  Thereafter, the driving of the secondary transfer roller 18 is started at time t22. Thereafter, at time t23, the IN sensor 28 in front of the secondary transfer unit 19 is turned on by the normal conveyance recording medium. Thereafter, the normal conveyance recording medium passes through the secondary transfer portion 19 to secondary transfer the toner image, and further passes through the fixing device 29 to fix the toner image. At time t24, when the EXIT sensor 33 is turned on by the normal conveyance recording medium that has passed through the fixing device 29, the discharge roller 32 is turned on to convey the normal conveyance recording medium to the recording medium accumulation stacker 35 at this time. At this time, since the DUP separator 52 is off, the normal conveyance recording medium is not conveyed into the duplex printing unit 50. Thereafter, from time t24 to time t25, the EXIT sensor 33 in front of the DUP separator 61 is turned on by the normal transport recording medium. Thereafter, the discharge roller 32 is driven until time t26, whereby the normal conveyance recording medium is conveyed to the recording medium accumulation stacker 35.

  Next, the operation timing of each part during the printing operation when the standby recording medium that is waiting on the conveyance path for duplex printing is transported instead of the normal transport recording medium after the transport of the normal transport recording medium is delayed. The timing chart shown in FIG. In this case, first, at time t30, the drive of the pickup roller 21 is started in order to convey the normal conveyance recording medium. Thereafter, at time t31, the driving of the registration roller 22 is started. At this time, the IN sensor 25 is supposed to be turned on by the normal conveyance recording medium, but the IN sensor 25 is not turned on because the normal conveyance recording medium is delayed.

  After that, at time t32 when a predetermined time has elapsed from time t30 when driving of the pickup roller 21 is started, it is determined that the normal conveyance recording medium is not in time for the secondary transfer timing because the IN sensor 25 is not yet turned on. At this time, driving of the DUP conveyance roller 62 is started in order to convey the standby recording medium waiting on the conveyance path for duplex printing. At this time, driving of the secondary transfer roller 18 is also started.

  Thereafter, at time t33, the IN sensor 28 in front of the secondary transfer unit 19 is turned on by the preliminary recording medium. Further, at time t34, the DUP sensor 63 that has been turned on by the preliminary recording medium is turned off because the preliminary recording medium has been transported to the transport path 17. Thereafter, the preliminary recording medium passes through the secondary transfer portion 19 to secondary transfer the toner image, and further passes through the fixing device 29 to fix the toner image. At time t35, when the EXIT sensor 33 is turned on by the preliminary recording medium that has passed through the fixing device 29, the discharge roller 32 is turned on to convey the preliminary recording medium to the recording medium accumulation stacker 35 at this time. At this time, since the DUP separator 52 is off, the preliminary recording medium is not conveyed into the duplex printing unit 50. Thereafter, from time t35 to time t36, the EXIT sensor 33 in front of the DUP separator 61 is turned on by the preliminary recording medium. Thereafter, the discharge roller 32 is driven until time t37, whereby the preliminary recording medium is conveyed to the recording medium stacking stacker 35.

  Next, regarding the operation timing of each part during the printing operation in the case of transporting the spare recording medium waiting on the transport path for 2-pass printing instead of the normal transport recording medium after the transport of the normal transport recording medium is delayed This will be described with reference to the timing chart shown in FIG. In this case, first, at time t40, the drive of the pickup roller 21 is started to convey the normal conveyance recording medium. Thereafter, at time t41, driving of the registration roller 22 is started. At this time, the IN sensor 25 is supposed to be turned on by the normal conveyance recording medium, but the IN sensor 25 is not turned on because the normal conveyance recording medium is delayed.

  Thereafter, at time t42 when a predetermined time has elapsed from time t40 when driving of the pickup roller 21 is started, it is determined that the normal conveyance recording medium is not in time for the secondary transfer timing because the IN sensor 25 is not yet turned on. At this time, the drive of the two-pass transport roller 54 is started in order to transport the standby recording medium that is waiting on the transport path for two-pass printing. At this time, driving of the secondary transfer roller 18 is also started.

  Thereafter, at time t43, the IN sensor 28 in front of the secondary transfer unit 19 is turned on by the preliminary recording medium. Further, at time t44, the two-pass sensor 58 that has been turned on by the preliminary recording medium is turned off because the preliminary recording medium has been transported to the transport path 17. Thereafter, the preliminary recording medium passes through the secondary transfer portion 19 to secondary transfer the toner image, and further passes through the fixing device 29 to fix the toner image. At time t45, when the EXIT sensor 33 is turned on by the preliminary recording medium that has passed through the fixing device 29, the discharge roller 32 is turned on to convey the preliminary recording medium to the recording medium stacker 35 at this time. At this time, since the DUP separator 52 is off, the preliminary recording medium is not conveyed into the duplex printing unit 50. Thereafter, from time t45 to time t46, the EXIT sensor 33 in front of the DUP separator 61 is turned on by the preliminary recording medium. Thereafter, the discharge roller 32 is driven until time t47, whereby the preliminary recording medium is conveyed to the recording medium accumulation stacker 35.

[6. Summary and Effect]
As described above, when the printer 1 determines that the normal conveyance recording medium is delayed in conveyance for some reason and is not in time for the secondary transfer timing at the time of printing, the printer 1 immediately puts the standby recording medium on standby as a secondary transfer unit. Then, secondary transfer was performed on the preliminary recording medium instead of the normal conveyance recording medium.

  As a result, even when the normal conveyance recording medium is delayed and the secondary transfer cannot be performed on the normal conveyance recording medium, the printer 1 uses the image that has been primarily transferred to the intermediate transfer belt 10 as a preliminary recording medium. Since the next transfer can be performed, it is possible to avoid a situation where the toner image primarily transferred to the intermediate transfer belt 10 is wasted. In this way, the printer 1 can avoid a situation where the toner image primarily transferred to the intermediate transfer belt 10 is wasted, and thus can reduce wasted toner consumption.

  Further, before printing based on the received print job, the printer 1 transports the standby recording medium to a standby path through which the normal transport recording medium does not pass in the printing method specified in the print job and waits. I did it. That is, if the printing method specified in the print job is single-sided printing or double-sided printing, the printer 1 uses a two-pass printing conveyance path (two-pass printing conveyance path 51B) that does not pass through single-sided printing or double-sided printing. If the designated printing method is two-pass printing, the spare recording medium is transported to a standby state (two-sided printing conveyance path 51A) that does not pass through two-pass printing. Was made to wait.

  In this way, in any printing method, when the conveyance of the normal conveyance recording medium is delayed, the preliminary recording medium is conveyed instead of the normal conveyance recording medium, and the primary transferred toner image is wasted. The secondary transfer can be performed on the pre-recording medium without the need for the recording.

  Further, the printer 1 conveys the preliminary recording medium to the standby position and waits during the warming up of the image forming units 3A to 3D, the secondary transfer unit 19, and the fixing device 29, which are executed before printing. I made it. As a result, the printer 1 can make the user wait for the warm-up time only before the printing, so that the user can be unaware of the time for transporting the preliminary recording medium to the standby position. Printing can be performed immediately after the warm-up.

[7. Other Embodiments]
[7-1. Other Embodiment 1]
In the above-described embodiment, when the normal conveyance recording medium as the first recording medium does not reach the position of the IN sensor 25 within a predetermined time after the driving of the pickup roller 21 is started, Instead of the normal conveyance recording medium, a preliminary recording medium as the second recording medium is conveyed to the secondary transfer unit 19. In this case, it is necessary to start transporting the preliminary recording medium to reach the secondary transfer position P between the time after a predetermined time has elapsed after the pickup roller 21 is driven and the secondary transfer timing.

  Therefore, in the above-described embodiment, the conveyance of the preliminary recording medium is started and moved to the secondary transfer position P between the time after the predetermined time elapses after the driving of the pickup roller 21 is started and the secondary transfer timing. The distance from the standby position of the preliminary recording medium to the secondary transfer position P is made sufficiently shorter than the distance from the IN sensor 25 to the secondary transfer position so that it can be reached.

  On the other hand, instead of shortening the distance as described above, the pickup roller is configured so that the conveyance speed when conveying the preliminary recording medium from the standby position to the secondary transfer position P is higher than the conveyance speed of the normal conveyance recording medium. 21 may be started so that the preliminary recording medium can be transported to reach the secondary transfer position P between the time after a predetermined time has elapsed and the secondary transfer timing. In this way, for example, the internal structure is such that the distance from the standby position of the preliminary recording medium to the secondary transfer position P cannot be made sufficiently shorter than the distance from the IN sensor 25 to the secondary transfer position. This printer can make the preliminary recording medium in time for the secondary transfer timing. Further, the preliminary recording medium may be made in time for the secondary transfer timing by combining such a shortening of the distance and an increase of the conveying speed.

[7-2. Other Embodiment 2]
Further, in the above-described embodiment, when printing is performed using the normal transport recording medium stacked on the recording medium storage tray 20, if it is determined that the normal transport recording medium is delayed and not in time for the secondary transfer timing, Printing was performed using a recording medium. Not limited to this, even when printing is performed using the normal transport recording medium stacked on the manual feed tray 40, if it is determined that the normal transport recording medium is delayed and not in time for the secondary transfer timing, the preliminary recording medium is used. Printing may be performed.

  In this case, an IN sensor is provided in the transport path 41 connecting the manual feed tray 40 and the transport path 17, and the transport status of the normal recording medium transported from the manual feed tray 40 is detected by the IN sensor. For example, the conveyance status of the normal recording medium conveyed from the manual feed tray 40 may be detected by the IN sensor 26 shown in FIG.

  Then, if the normal transport recording medium does not reach the position of the IN sensor 26 within a predetermined time after the driving of the pickup roller 42 of the manual feed tray 40 is started, a spare recording medium is used instead of the normal transport recording medium. The recording medium is conveyed to the secondary transfer unit 19. Also in this case, as a matter of course, the conveyance of the preliminary recording medium is started and reaches the secondary transfer position P between the time after the predetermined time elapses after the pickup roller 42 is driven and the secondary transfer timing. In order to achieve this, the distance from the standby position of the preliminary recording medium to the secondary transfer position P is sufficiently shorter than the distance from the IN sensor 26 to the secondary transfer position P, or the transport speed of the preliminary recording medium is increased. It is sufficient to make it sufficiently faster than the conveyance speed of the normal conveyance recording medium.

[7-3. Other Embodiment 3]
Further, in the above-described embodiment, the preliminary recording medium is made to wait in the duplex printing unit 50 originally provided in the printer 1. However, the present invention is not limited to this. For example, a dedicated conveyance path for waiting for the preliminary recording medium may be provided separately, and the preliminary recording medium may be conveyed and waited on the conveyance path.

[7-4. Other Embodiment 4]
Further, in the above-described embodiment, when the preliminary recording medium is not used until the last page of the print job, the preliminary recording medium is used for printing the final page. This is because the printing method for the next print job may be different from the printing method for the current print job, and it is necessary to reset the standby position of the preliminary recording medium once. That is, in the above-described embodiment, it is necessary to transport the preliminary recording medium again for each print job.

  The present invention is not limited to this, and even if the preliminary recording medium is not used until the last page of the print job, the preliminary recording medium can be not used for printing the final page. In this case, if the printing method of the current print job is the same as the printing method of the previous print job, the remaining spare recording medium that has not been used last time is kept waiting. A new preliminary recording medium may be transported and waited on a transport path that does not pass through the print job, and the remaining preliminary recording medium that has not been used last time may be used for the first page of the current print job. . In this way, when a plurality of printing methods print the same print job continuously, it is possible to save time and trouble of re-transporting the preliminary recording medium for each print job, thereby enabling more rapid printing. Become.

[7-5. Other Embodiment 5]
Furthermore, in the above-described embodiment, the preliminary recording medium is transported to the 2-pass printing transport path 51B and waits for both single-sided printing and double-sided printing. When performing single-sided printing, the preliminary recording medium may be transported to the double-sided printing transport path 51A and waited.

[7-6. Other Embodiment 6]
Furthermore, in the above-described embodiment, the present invention is applied to the printer 1 that can perform printing by three types of printing methods of single-sided printing, double-sided printing, and two-pass printing. The present invention can also be applied to a printer that can perform printing by a printing method, a printer that can perform printing by various types of printing methods, and the like.

  Furthermore, in the above-described embodiment, the present invention is applied to the printer 1 that prints using toner of four colors. However, the invention is not limited to this, and printing is performed using toner of three colors or less, or five colors or more. It can also be applied to a printer.

  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. The present invention can be applied to an image forming apparatus, and can also be applied to an image forming apparatus that forms an image on a recording medium other than paper.

[7-7. Other Embodiment 7]
Furthermore, in the above-described embodiment, the image analysis unit 105 of the control unit 100 is used as a specific example of the analysis unit that analyzes a print job as an image forming job. The present invention is not limited to this, and an image analysis unit different from the image analysis unit 105 may be used as long as it has a function of analyzing an image forming job.

  Furthermore, in the above-described embodiment, the image forming units 3A to 3D are used as specific examples of the image forming unit that forms an image. The present invention is not limited to this, and an image forming unit having a mechanism different from that of the image forming 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 10 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 10 as long as it functions as an intermediate transfer member.

  Further, in the above-described embodiment, the primary transfer roller 15 is used as a specific example of the primary transfer portion that primarily transfers the 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 transport control unit 106 of the control unit 100 is used as a specific example of the transport path determination unit that determines the transport path. The present invention is not limited to this, and a transport path determination unit different from the transport control unit 106 may be used as long as it has a function of determining a transport path.

  Furthermore, in the above-described embodiment, the rollers 21, 22, 23, 24, 27, 32, 42, 43, 53, 54, 55, 56, 62, as specific examples of the recording medium transport unit that transports the recording medium. Separator 52, 60, 61 was used. However, the present invention is not limited to this, and a recording medium conveyance unit having a mechanism different from these may be used as long as it has a function of conveying a recording medium.

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

  Furthermore, in the above-described embodiment, the control unit 100 and the medium standby processing unit 108 are used as specific examples of the control unit. The present invention is not limited to this, and a control unit different from the control unit 100 may be used as long as it has a function equivalent to that of the control unit 100.

  Further, in the above-described embodiment, the IN sensor 25 is used as a specific example of the detection unit for detecting the arrival of the first recording medium. However, the present invention is not limited to this, and a detection unit different from the IN sensor 25 may be used as long as it has a function of detecting the arrival of the recording medium.

[7-8. Other Embodiment 8]
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 ... Image forming unit, 10 ... Intermediate transfer belt, 15 ... Primary transfer roller, 17, 41, 51 ... Conveyance path, 19 ... Secondary Transfer section, 21, 42 ... Pickup roller, 22, 56 ... Registration roller, 23, 24, 43, 55 ... Conveyance roller, 25, 26, 28 ... IN sensor, 29 ... Fixing device, 50 ... Double-sided printing unit, 51A... Double-sided printing conveyance path, 51B... Two-pass printing conveyance path, 100... Control unit, 105... Image analysis unit, 106. 120... Preliminary recording medium.

Claims (8)

An analysis unit for analyzing an image forming job;
Based on the analysis result by the analysis unit, an image forming unit that forms an image;
A primary transfer unit that primarily transfers an image formed by the image forming unit to an intermediate transfer member;
A recording medium conveyance path having a plurality of conveyance paths;
A transport path determining unit that determines a transport path of the recording medium based on an analysis result by the analysis unit;
A recording medium transport unit that transports the recording medium according to the transport path determined by the transport path determination unit;
A secondary transfer unit that secondary-transfers the image primarily transferred to the intermediate transfer member onto a recording medium conveyed by the recording medium conveyance unit;
Before transporting the first recording medium according to the transport path determined by the transport path determination unit, the recording medium transport unit reserves a second recording that is reserved in a location that does not pass through the transport path of the first recording medium. The medium is transported and kept in standby, and the recording medium transport unit performs standby when the first recording medium is not transported normally even if the recording medium transport unit performs the operation of transporting the first recording medium. A control unit that transports the second recording medium by the recording medium transport unit, and secondarily transfers the image primarily transferred to the intermediate transfer member to the second recording medium by the secondary transfer unit. An image forming apparatus. The controller is
2. The second recording medium is transported to a place where it does not pass through the transport path of the first recording medium during a warm-up performed before the image formation by the image forming apparatus, and waits. Image forming apparatus. The conveyance path includes a one-sided conveyance path for forming an image once on one side of the recording medium, a duplex conveyance path for forming an image once on both sides, and an image twice on one side. A single-sided two-way transport path when forming,
The controller is
When the image forming job is instructed to form an image once on one side of the recording medium, the second recording medium is placed at a predetermined position on the duplex conveying path or the single-sided twice conveying path. Let it be transported and wait,
If the image forming job is instructed to form an image once on both sides of the recording medium, the second recording medium is transported to a predetermined position on the one-sided twice transport path and is made to wait. ,
When the image forming job is instructed to form an image twice on one side of the recording medium, the second recording medium is transported to a predetermined position on the double-side transport path and waited. The image forming apparatus according to claim 1. The transport path is provided with a detection unit for detecting arrival of the first recording medium at a predetermined position,
The controller is
Transporting the second recording medium when the detection unit does not detect the arrival of the first recording medium even after a predetermined time has elapsed since the operation of transporting the first recording medium was performed. The image forming apparatus according to claim 1. The distance from the standby position of the second recording medium to the secondary transfer position is shorter than the distance from the position of the detection unit to the secondary transfer position by the secondary transfer unit. The image forming apparatus according to claim 4. The distance from the standby position of the second recording medium to the secondary transfer position is shorter than the distance obtained by subtracting a predetermined margin from the distance from the position of the detection unit to the secondary transfer position by the secondary transfer unit. The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus. The image forming apparatus according to claim 4, wherein the control unit conveys the second recording medium at a conveyance speed faster than a conveyance speed of the first recording medium. The controller is
When the image of the last page of the image forming job is primarily transferred to the intermediate transfer member, the second recording medium that is waiting is transported and the last page that is primarily transferred to the intermediate transfer member The image forming apparatus according to claim 1, wherein the image is secondarily transferred to the second recording medium.

Images