Printing apparatus and control method

A printing apparatus includes a conveyance unit configured to convey a sheet along a conveyance path, a printing unit configured to print an image by discharging ink to the sheet conveyed by the conveyance unit, a heating unit configured to, in a heating section on the conveyance path, heat the sheet on which the image has been printed by the printing unit, and a control unit configured to control the heating unit so that the heating section is changed in accordance with a print condition.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure is related to a printing technique.

Description of the Related Art

In methods in which ink is discharged to a sheet to thereby print an image, there are cases in which the sheet curls due to moisture included in the ink. Accordingly, techniques for heating the sheet to accelerate drying have been proposed. For example, a technique in which drying is accelerated by blowing hot air onto a sheet on which an image has been printed is disclosed in the specification of U.S. Pat. No. 10,201,985.

The form of heating that is suitable to drying a sheet may differ depending on print conditions. For example, when the sheet conveyance path differs depending on one-side printing and double-side printing, if a sheet is heated in the same section on the conveyance path in both cases, the sheet may be heated unnecessarily or unsuitably. There are cases in which this results in an excess or deficiency in the drying of the sheet, or results in the internal temperature of the apparatus rising unnecessarily or in unnecessary power consumption.

SUMMARY OF THE INVENTION

The present invention provides a technique capable of controlling heating of a sheet in accordance with a print condition.

According to an aspect of the present invention, there is provided a printing apparatus, comprising: a conveyance unit configured to convey a sheet along a conveyance path; a printing unit configured to print an image by discharging ink to the sheet conveyed by the conveyance unit; a first heating unit configured to, in a heating section on the conveyance path, heat the sheet on which the image has been printed by the printing unit; and a control unit configured to control the first heating unit so that the heating section is changed in accordance with a print condition.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1is a front surface view of a printing system1according to an embodiment of the present invention. An arrow X in each figure includingFIG. 1indicates left and right directions, and an arrow Y indicates the depth direction, and these are orthogonal to each other. An arrow Z indicates a vertical direction.

The printing system1includes an apparatus main body2and a post-processing apparatus3. The apparatus main body2of the present embodiment is an apparatus that configures a multi-function device, and the apparatus main body2comprises a copy function, a scanner function, and a printer function. The apparatus main body2includes a reading apparatus4, a printing apparatus5, and a feeding apparatus6, and an operation unit7is provided on a front portion of the apparatus main body2. The operation unit7is a user input/output interface, and, for example, includes hard keys, a display unit, or a touch panel that receives user input and displays information, and includes an output unit such as a voice generator.

The reading apparatus4includes an ADF (automatic document feeder) and the reading apparatus4conveys stacked originals and reads original images. The feeding apparatus6is an apparatus for feeding a recording medium to the printing apparatus5. The recording medium, in the case of the present embodiment, is a sheet of paper or film or the like, and in particular is a cut sheet. There are cases where the recording medium is referred to as a sheet. The feeding apparatus6includes a plurality of cassettes6aon which sheets are stacked, and a feeding mechanism (not shown) for feeding sheets from the cassettes6ato the printing apparatus5on a conveyance path RT.

The printing apparatus5prints an image on a sheet. The printing apparatus5includes a printing unit30for printing an image by discharging ink onto a sheet and drying acceleration units40and50for accelerating drying of sheets. Details of the printing apparatus5will be described later.

The post-processing apparatus3is attached disconnectably to a side of the apparatus main body2as an optional apparatus, and is a finisher (sheet processing apparatus) for performing sheet post-processing. The post-processing may be, for example, stacking processing in which sheets discharged from the printing apparatus5are stacked on a tray3a, sorting processing in which a plurality of sheets discharged from the printing apparatus5are read in order and aligned in a bundle form, stapling processing in which a bundled sheet bundle is bound by a stapler, binding processing, or punch press processing.

FIG. 2is an explanatory view illustrating an internal structure of the printing apparatus5. The printing apparatus5includes, as frames for supporting internal mechanisms, a bottom wall portion5a, a top wall portion5b, a right wall portion5c, a left wall portion5d, and a back wall portion5e. These walls define the internal space of the printing apparatus5. The internal space of the printing apparatus5is further separated into a bottom space SP1and a top space SP2by a partition wall5h. The space SP1and the space SP2are not divided hermetically, and communicate with each other.

The bottom wall portion5ahas an opening5fthrough which a sheet that is fed from the feeding apparatus6passes. The right wall portion5chas an opening5gthrough which a sheet that is discharged to the post-processing apparatus3passes. The left wall portion5dand the right wall portion5cmay be supported so as to be able to open/close, in the form of a door, for maintenance.

The printing apparatus5includes a conveyance unit20, the printing unit30, the drying acceleration units40and50, a straightening unit60, and an exhaust unit70.

The conveyance unit20is a mechanism for conveying a sheet along a conveyance path RT. The conveyance path RT is a path along which sheets are conveyed whose upstream end is the opening5fand whose downstream end is the opening5gin the case of the present embodiment. The conveyance path RT includes main paths RT1and RT2, a redirecting path RT3, and an inversion path RT4. The main paths RT1and RT2are paths that connect the opening5fto the opening5gthrough a midpoint M1, and the main path RT1is from the opening5fto the midpoint M1and the main path RT2is from the midpoint M1to the opening5g. The main paths RT1and RT2are paths for conveying a sheet leftward and then upward and then rightward, and the sheet passes, in order, through the printing unit30, then the drying acceleration unit40, then the drying acceleration unit50, and then the straightening unit60. In the case of one-side printing, in which only one side of the sheet is printed on, the sheet is conveyed through the main paths RT1and RT2.

The redirecting path RT3and the inversion path RT4are paths that are formed to branch from the main path RT1, and along which a sheet is conveyed after one-side printing in the case of double-side printing, in which both sides of the sheet are printed on. The redirecting path RT3, from the midpoint M1, forms a path separate from the main path RT2. Also, the inversion path RT4is a path from the midpoint M1to a merging point M2part way through the main path RT1, and, via the inversion path RT4, the front and back of a sheet are inverted and the sheet is returned once again to the main path RT1.

When the downstream side and the upstream side are referred to in the discussion below, the conveyance direction of the sheet in the conveyance path RT is the reference.

The conveyance unit20includes a driving mechanism that biases a conveying force in relation to a sheet, and a guide that guides the conveyance of the sheet along the conveyance path RT, and part of that is illustrated inFIG. 2. The driving mechanism includes a plurality of conveyance rollers21which are driven by a driving source such as a motor. A driven roller or spur is arranged to face each of the conveyance rollers21. A sheet is conveyed so as to be sandwiched between the conveyance roller21and the driven roller or spur. The spur, in order to maintain the quality of a printed image, is arranged so as to contact the side of the printing surface in a region on the downstream side of the printing unit30. The guide includes guide members22to24. The guide member24is supported by the left wall portion5d. Part of the conveyance path RT is formed between the guide member23and the guide member24, and part of the path RT1is formed between the guide member22and the guide member24.

The conveyance unit20includes path switching units25and26. The path switching units25and26are units for switching the sheet guidance path, and operate by a driving source such as an electromagnetic solenoid, a motor, or the like. The path switching units25and26guide the sheet from the main path RT1to the main path RT2in the case of one-side printing and, in the case of double-side printing, guide the sheet from the main path RT1to the redirecting path RT3, and then guide the redirected sheet to the inversion path RT4.FIG. 3illustrates path switching states of the path switching units25and26. The path switching units25and26respectively include pivotable flaps, and switch the path by positioning of the flaps. The positioning illustrated in solid lines is the positioning in the case of one-side printing, and the positioning illustrated in dashed lines is the positioning in a case of double-side printing. Sheet sensors for detecting the presence or absence of a sheet at respective locations on the conveyance path RT are arranged, and the position of the sheet on the conveyance path RT is identified by sheet sensor detection results.

Returning toFIG. 2, the printing unit30includes a printhead31, and the printhead31is an inkjet head for forming images (ink images) by discharging ink onto a sheet. The ink that the printhead31discharges is contained in a plurality of ink tank units T. The ink tank units T are arranged for each type of ink, and the types of ink are, for example, yellow, magenta, cyan, and black color types.

The printhead31is arranged for each type of ink. In the case of the present embodiment, each printhead31is a full-line head arranged to extend in a Y direction, and nozzles are arranged in a range covering a width of an image printing area of a sheet of a maximum size that can be used. A printhead includes a bottom surface that faces the sheet via a minute gap (of several mm, for example), and an ink discharge surface in which a nozzle is open is formed in this bottom surface.

A discharging element is arranged in each nozzle. The discharging element is, for example, an element that causes pressure to form within the nozzle to discharge ink within the nozzle, and a publicly known inkjet head technique can be applied thereto. The discharging element may be, for example, an element that discharges ink by forming air bubbles by causing film boiling to occur in the ink by an electrothermal transducer, an element that discharges ink by an electromechanical transducer, an element that discharges ink using static electricity, or the like. It is possible to perform high-density printing at high-speed by using a discharging element that uses an electrothermal transducer.

Note that the printing unit30may be a serial printing unit in which printing is performed by the reciprocal movement of a printhead arranged on a carriage in a sheet width direction. Also, the ink to be discharged may be of a single type such as when it is only black. It is possible to select a single ink printing mode and a multiple ink type printing mode as the printing mode of the printing unit30. The ink may mainly contain a coloring agent (a dye or a pigment) and a solvent component. A water-based material or an oil-based material may be used for the solvent component. As the dye, a water-soluble dye as typified by, for example, a direct dye, an acidic dye, a basic dye, a reactive dye, a food dye, or the like, is preferable, and the dye may be anything that provides an image that satisfies a fixing characteristic, colorability, vividness, stability, lightfastness, or other desired characteristics in combination with the above-described recording medium. A carbon black or the like is preferable for the pigment. A method for using a pigment and a dispersing agent together may be a method using self dispersion pigment or a method of microencapsulation. Also, for the ink, it is possible to add various additives, as necessary, such as a solvent component, a solubilizer, a viscosity modifier, a surfactant, a surface tension adjuster, a pH adjuster, a resistivity adjusting agent, and the like. Also, rather than arranging the printhead31for every type of ink, nozzles may be arranged for every type of ink on a single printhead.

A sheet, after an image has been printed thereon by the printing unit30, may expand due to the liquid in the ink and an undulation may form therein. Such a sheet may become the cause of a paper jam in the printing apparatus5or of a deterioration in stacking performance/alignment performance in the post-processing apparatus3. By accelerating sheet drying, it is possible to prevent the expansion of the sheet due to liquid in the ink. The printing apparatus5of the present embodiment comprises a plurality of drying acceleration units40and50that are similar in that they heat the sheet, but whose methods of drying the sheet differ. Note that a predetermined moisture is included in the liquid of the ink.

The drying acceleration unit40is a unit that is arranged on the downstream side of the printing unit30and that heats the sheet by blowing hot air onto the sheet in a predetermined heating section on the conveyance path RT, thereby accelerating drying of the sheet without contacting the sheet. This structure will be described with reference toFIG. 2,FIG. 3A, andFIG. 3B.

The drying acceleration unit40includes a hollow body41that defines an internal space and a fan42and a heating element43arranged within the hollow body41. The hollow body41comprises an air intake port41aon a right side. The wall41bthat forms the left side of the hollow body41is a guide wall portion that is also used as a sheet conveyance guide, and the wall41bextends in a Y direction so as to cover the width of the maximum size sheet. A guide wall portion41bhas C-shaped cross-sectional shape (cross-section on the X-Z plane), and has a wall surface that faces the guide members22to24. Between this wall and the guide members22to24, a part of the conveyance path RT is formed and the midpoint M1is present at that part of the conveyance path RT. A large number of hot air outlets N that communicate with the internal space of the hollow body41are formed in the guide wall portion41b.

The fan42is an electrically driven fan for which a motor is made to be a driving source, and the fan42is, for example, a sirocco fan. The fan42introduces air into the hollow body41from the intake port41a. The air pressure within the hollow body41increases due to the introduced air, and the air within the hollow body41is blown out of the hollow body41from the outlets N. There may be one fan42or there may be a plurality of fans42arranged adjacently in a Y direction.

The heating element43heats the air introduced into the hollow body41from the intake port41aby the fan42. In the case of the present embodiment, the heating element43is a rod-like heating element such as an infrared light lamp heater or the like, and the heating element43extends in the Y direction. Also, a plurality of heating43elements are arranged in a Z direction. The plurality of the heating element43are arranged between the fan42and the intake port41a, and the air introduced within the hollow body41from the intake port41ais heated when passing through the heating element43. A temperature sensor44is provided in the drying acceleration unit40, and driving of the heating element43is controlled according to a result of detection by the temperature sensor44.

By such a configuration, the drying acceleration unit40blows hot air from the outlets N whose air flow is indicated by the arrows inFIG. 3. By this, the sheet that passes through the conveyance path RT is heated to promote evaporation of the liquid included in the ink image on the sheet, and thereby drying of the sheet can be accelerated.

In the drying acceleration unit40, a shutter unit45that changes the outlets N that blow out hot air is arranged. It is possible to change the heating section on the conveyance path by changing the outlets N that blow out hot air.

FIG. 3Ais an explanatory view for the heating section. In the example of the figure, a heating section R1and a heating section R2are exemplified. The heating section R2is all sections in which hot air can be blown out from the drying acceleration unit40, and the heating section R1is a part of the heating section R2. Accordingly, the heating section R2is a section that is longer than the heating section R1. The heating section R2includes a portion on the downstream side of the main path RT1(from the starting point for blowing of hot air by the drying acceleration unit40until the midpoint M1) and a portion on the upstream side of the main path RT2(the surrounding part of the midpoint M1) and the redirecting path RT3. The heating section R1includes a portion on the downstream side of the main path RT1(from the starting point for blowing hot air by the drying acceleration unit40until the midpoint M1) and the portion on the upstream side of the main path RT2(the surrounding part of the midpoint M1).

Note that while in the present embodiment it is possible to change between two types of heating sections, there may be three or more types of heating sections that it is possible to change between. The three or more types of heating sections may have different lengths from each other, and a shorter heating section may be a portion of a larger heating section.

The shutter unit45includes a shutter450and a drive unit451for reciprocally moving the shutter450in a Y direction.FIG. 3Bis a view that illustrates movement states of the shutter450, and shows a part of the wall41bin a direction of an arrow D1inFIG. 3A. The shutter450is arranged on the inner side of the wall41b, and is a plate-like member having a form that follows the inner surface of the wall41b. The shutter450has a size that overlaps only a part of the top side of the wall41b, and its width (the width in the Y direction) reaches the entirety of the region in which the outlets N are formed on the wall41b. InFIG. 3B, a pattern is added to the shutter450positioned in the background of the wall41bso that the shutter450can be easily visually distinguished. The shutter450has a plurality of holes OP corresponding to the plurality of outlets N provided on the wall41b. There is no pattern added for the holes OP.

The drive unit451is a driving mechanism such as a pull solenoid or an electrically-driven cylinder/ball screw mechanism/rack pinion mechanism for which a motor is a driving source, and the drive unit451causes the shutter450to slide in the Y direction. InFIG. 3B, a state STO indicates a state in which the shutter450is positioned at an open position, and a state STC indicates a state in which the shutter450is positioned at a closed position. In a case where the shutter450is positioned in an open position, the holes OP overlap the respective outlets N, and so the outlets N are in an open state in which hot air can be blown therethrough. The heating section is then R2. In the case where the shutter450is positioned in the closed position, the respective outlets N do not overlap the holes OP but rather overlap the body portion of the shutter450, and the outlets N are in a closed state in which the hot air substantially cannot be blown therethrough. The heating section is then R1. In this fashion, by changing the outlets N through which the hot air is blown, the heating section can be switched between R1and R2.

The drying acceleration unit50is arranged on the downstream side of the drying acceleration unit40, and is a heat fixing device for heating the sheet by contacting the sheet and thereby accelerating the drying. Its structure is described with reference toFIG. 2.

The drying acceleration unit50includes a heating member51and a roller56, and these extend in a Y direction so as to cover the width of the sheet of the maximum size. The heating member51includes a support member53for supporting a heating element54which is a heat source. The heating element54is, for example, a ceramic heater, and extends in a Y direction. The temperature of the heating element54is detected by a temperature sensor55as typified by a thermistor, and driving of the heating element54is controlled based on detection results.

The support member53supports a film52. The film52is configured in a cylindrical shape and extends in a Y direction. The film52is supported by the support member53so as to be able to freely rotate around the support member53, and is interposed between the roller56and the heating element54. The film52, for example, is a single layered film or a multi-layered film whose thickness is 10 μm or more and 100 μm or less. In a case of a single layered film, the material may be PTFE, PFA, or FEP, for example. In the case of a multi-layered film, PTFE, PFA, FEP, or the like, for example, may be coated on a layer of polyimide, polyamide-imide, PEEK, PES, PPS, or the like, or a film of a layered structure to which a coating is applied may be used.

Note that the configuration of the heating member51is not limited to this structure, and, for example, configuration may be taken such that a structure comprising a heating element such as a halogen heater is comprised within a hollow metal core axis, and an elastic body such as silicone rubber is coated around the core axis.

The roller56is configured to coat the circumferential surface of the core metal56aby the elastic body56bwhich may be silicone rubber. The roller56is crimped to the heating member51with a predetermined pressing force, and a nipping portion is formed by the roller56and the heating member51. The roller56rotates with a motor as its driving source, and the film52rotates together with the roller56. By such a configuration, it is possible to heat the sheet while it is being conveyed in the nipping portion, and thereby promote drying of the sheet.

In the present embodiment, the sheet is dried in two stages by the drying acceleration units40and50, but configuration may be such that only one of the drying acceleration units is arranged.

The straightening unit60is a mechanism for straightening the curvature (“curl” here) of the sheet. In the case of the present embodiment, the straightening unit60includes a large-diameter drive roller61and a small-diameter driven roller62. The drive roller61is a roller in which the circumference of a core metal is coated by an elastic body such as silicone rubber. The driven roller62is a metal roller. The drive roller61and the driven roller62press against each other. When a sheet passes between the drive roller61and the driven roller62, pressure is applied to the sheet by these rollers, and it is possible to straighten a curl in the sheet. The straightening unit60can add a straightening force in a direction of projection, upward, for example, in relation to the sheet. In such a case, it is possible to straighten a sheet having a convex curl downward by the straightening unit60so that the sheet has a flatter shape.

The exhaust unit70is a unit for discharging air within the printing apparatus5to the outside of the apparatus. The printing apparatus5of the present embodiment comprises the drying acceleration units40and50, and these increase the temperature within the apparatus. Also, these act to cause moisture in the ink to evaporate. In a case where printing is performed consecutively in relation to a large number of sheets, the humidity level within the apparatus may rise. A high humidity level may cause curving of sheets. Between the drying acceleration unit50and the opening5g, the sheet conveyance distance is comparably long, and moreover, the sheet is conveyed within the upper space SP2in which water vapor tends to be retained. There are cases in which sheets are exposed to a high humidity level environment in the space SP2. The humidity level within the apparatus can be lowered by discharging air within the space SP2to the outside of the apparatus by the exhaust unit70.

The exhaust unit70of the present embodiment is a structure that naturally discharges air within the space SP2by the plurality of exhaust ducts71to73. However, configuration may be taken such that the exhaust unit70forcibly discharges air within the apparatus by a fan or the like. With reference toFIG. 2andFIG. 4, the structure of the exhaust unit70will be described.FIG. 4is a plan view illustrating the vicinity of the exhaust unit70, and the top wall portion5bis omitted from the illustration.

An exhaust duct71is a tubular member including an extension71athat extends in a Y direction and an extension7bthat extends from the end on the far side in the Y direction of the extension71ato the right side in the X direction. The extension71aextends at a position in the vicinity of the sheet discharge position in the drying acceleration unit50and below the main path RT2. The extension71ais an air intake portion in which a plurality of slits for air intake ports are formed on the upper left-side and bottom. From the upper left-side slit, air that was warmed by the drying acceleration unit50, for example, is introduced, and from the bottom slit, for example, it is possible for hot air blown out from the outlets N of the drying acceleration unit40to be introduced. The extension71ais arranged to extend across the back wall portion5e, and its end on the far side in the Y direction and the extension7bare positioned outside (the far side in the Y direction) of the space SP2. Note that the extension71amay be of a form that extends at a position on the top side of the main path RT2.

An exhaust duct72is a tubular member that includes an extension72athat extends in the Y direction, a collection unit72bthat extends from the extension72ato the right side, and an extension72cthat extends from the right end of the collection unit72bto the far side of the Y direction. The extension72aextends at a position in the vicinity of the sheet discharge position in the drying acceleration unit50and above the main path RT2. The bottom of the extension72aopens to form an air intake port, and for example, air warmed by the drying acceleration unit50and water vapor in the space SP2is introduced. The extension72acrosses the top wall portion5band protrudes above the top wall portion5b.

For the collection unit72b, the extension72aside in the plan view has a wide triangular shape, and its entirety is positioned above the top wall portion5b. The collection unit72bcollects air introduced to the extension72ain the center in the Y direction on the right end. The collected air flows to the extension72c. The entirety of the extension72calso is positioned above the top wall portion5b, and partially warped and extends to the far side of the back wall portion5e. In the far side of the back wall portion5e, the extension7bof the exhaust duct71is connected to the extension72cof the exhaust duct72, and these internal spaces communicate. The extension72cis connected to an exhaust duct73.

The exhaust duct73extends in the X direction and is an exhaust member open to the far side in the Y direction. The opening of the exhaust duct73faces a cover8that forms the exterior of the rear side of the apparatus main body2. A large number of slits (louver)8aare formed in the cover8, and the air that has flowed into the exhaust duct73is discharged to the outside of the apparatus from the rear side of the apparatus main body2through the slits8a.

A control system of the apparatus main body2will be described.FIG. 5is a block diagram of a control unit9of the apparatus main body2. The control unit9comprises a processing unit10, a storage unit11, a read control unit13, an image processing unit14, a head controller15, an engine control unit16, and a drying control unit17. The processing unit10is a processor as typified by a CPU (central processing unit), and comprehensively controls operation of each unit of the apparatus main body2. The storage unit11is a storage device such as a ROM or a RAM, for example. In the storage unit11, programs for the processing unit10to execute and fixed data (for example, data related to the type of sheets stored in each cassette6a) necessary for various operations of the apparatus main body2are stored. Also, the storage unit11stores various setting data in a work area for the processing unit10or a temporary storage region for various received data.

The read control unit13controls the reading apparatus4. The image processing unit14performs image processing for image data that the apparatus main body2handles. The inputted image data color space (for example, YCbCr) is converted into a standard RGB color space (for example, sRGB). The print data obtained by such image processing is stored in the storage unit11. The head controller15performs control for driving the printing unit30in accordance with print data based on control commands received from the processing unit10. The engine control unit16performs sheet conveyance control and the like. The drying control unit17performs control for driving the drying acceleration units40and50. Each of these control units includes a processor such as a CPU, a storage device such as a RAM or a ROM, and an interface for an external device.

An I/O12is an interface (I/F) for connecting the control unit9with a host apparatus18and the post-processing apparatus3, and is a local I/F or a network I/F. The host apparatus18is an apparatus that is an image data supply source for causing the printing apparatus5to perform a printing operation. The host apparatus18may be a general-purpose or dedicated computer, and may be a dedicated image device such as an image capturing device having an image reader unit, a digital camera, or a photo storage.

<Control to Change Heating Section>

The redirecting path RT3included in the heating section R2is a path over which sheets are conveyed in the case of double-side printing, and a path over which sheets are not conveyed in the case of one-side printing. Assuming that the heating section of the drying acceleration unit40is uniformly made to be the heating section R2, in a case where one-side printing over which a sheet is not conveyed to the redirecting path RT3, hot air that does not contribute to the drying of the sheet is blown to the redirecting path RT3. This is a waste (a waste of power consumption) of the heat generated by the heating element43. Also, in the case of the present embodiment, since the redirecting path RT3does not communicate with the space SP2, hot air blown to the redirecting path RT3flows to the space SP2. The hot air that does not contribute (by which heat exchange with the moisture does not occur) to the drying of the sheet causes an unnecessary rise in the temperature of the space SP2. Cases are envisioned where, when the temperature of the space SP2rises, another sheet that is conveyed via the drying acceleration unit50towards the straightening unit60will be heated, and the intended curvature of the other sheet will not be achieved by the straightening unit60.

Conversely, assuming that the heating section of the drying acceleration unit40is uniformly made to be the heating section R1, in the case of double-side printing in which a sheet is conveyed to the redirecting path RT3, it is envisioned that there will be cases where drying of the sheet will be insufficient.

Accordingly, in the present embodiment, the heating section is changed depending on one of the sheet print conditions, namely one-side printing or double-side printing. In other words, in the plurality of conveyance paths, the heating section is changed in accordance with the current sheet conveyance path. By this, it is possible to control heating of the sheet in accordance with the print condition, and it is possible to achieve drying of the sheet as intended.FIG. 10Ais a flowchart that illustrates an example of control for changing the heating section. Processing ofFIG. 10Ais a process for controlling the drying acceleration unit40that is executed by the drying control unit17, for example.

In step S1, it is determined whether a print condition for an image on a sheet that is the current print target is one-side printing or double-side printing. In the case of one-side printing, the processing advances to step S2, and in the case of double-side printing, the processing advances to step S3. In step S2, the drive unit451is driven, and the shutter450is positioned at a closed position. The heating section R1ends up being selected. In step S3, it is determined whether printing of an image on a front surface (hereinafter a first surface), on which an image is printed first among front/back surfaces of the sheet that is the current target of printing, has completed, and it is the stage in which an image is to be printed on the back surface (hereinafter, second surface).

If it is the stage in which the image is to be printed on the second surface, the processing advances to step S2, and the shutter450is positioned in the closed position. The heating section R1becomes selected. If it is not the stage in which the image is to be printed on the second surface, and rather it is the stage in which an image is to be printed on the first surface, the processing advances to step S4. In step S4, the drive unit451is driven and the shutter450is thereby positioned in the open position. The heating section R2becomes selected. The above processing is repeated, and the heating section is changed according to whether it is one-side printing or double-side printing. In the case of the double-side printing, the heating section is also changed according to whether it is the stage for printing the first surface or it is the stage for printing the second surface.

Operation Example

An example of a printing operation by the printing apparatus5according to control by the control unit9will be described with reference toFIG. 6toFIG. 9. First, with reference toFIG. 6andFIG. 7, operation in a case where an image is printed on one side of a sheet will be described. In a case of printing an image on one side of a sheet, the path switching units25and26are set at the positions for the case of the one-side printing (the positioning illustrated in solid lines inFIG. 3A). By the processing ofFIG. 10A, the shutter450is positioned in the closed position and the heating section R1is set. The heating element43of the drying acceleration unit40and the heating element54of the drying acceleration unit50may be kept at a temperature that is predetermined in advance.

The state ST1ofFIG. 6indicates a state in which a sheet P fed from the feeding apparatus6is conveyed by the conveyance unit20on the main path RT1to the printing unit30, and printing by the printing unit30is started. The printing unit30prints the image by discharging ink to the sheet P as illustrated by the arrow. The sheet P is conveyed towards the drying acceleration unit40. The drying acceleration unit40starts operating, and hot air is blown (state ST2ofFIG. 6) to the sheet P in the heating section R1. Drying of the sheet P which is wet from the ink is accelerated by the hot air.

The sheet P is further conveyed toward the drying acceleration unit50on the main path RT2. The drying acceleration unit50starts operating, and the sheet P is conveyed by the roller56rotating as illustrated in the state ST3ofFIG. 7and the sheet P is heated by the heating member51. The drying of the sheet P is further accelerated thereby.

The sheet P is further conveyed toward the straightening unit60on the main path RT2as illustrated in the state ST4ofFIG. 7. The straightening unit60starts operating, a curl in the sheet P is straightened, and the sheet P is discharged to the post-processing apparatus3from the opening5g.

Next, with reference toFIG. 8andFIG. 9, operation in a case where an image is printed on both sides of a sheet will be described. The state ST11ofFIG. 8indicates a state in which a sheet P fed from the feeding apparatus6is conveyed by the conveyance unit20on the main path RT1to the printing unit30, and printing by the printing unit30is started. The printing unit30prints the image by discharging ink to a first surface of the sheet P as illustrated by the arrow. The path switching unit26is set to the position for the case of double-side printing (the positioning illustrated by dashed lines inFIG. 3A). By the processing ofFIG. 10A, the shutter450is positioned in the open position and the heating section R2is set.

The sheet P is conveyed towards the drying acceleration unit40. The drying acceleration unit40starts operating, and hot air is blown (state ST12ofFIG. 8) to the sheet P in the heating section R2. Drying of the sheet P which is wet from the ink is accelerated by the hot air. By the guidance of the path switching unit26, the sheet P, rather than being conveyed to the drying acceleration unit50, is conveyed to the redirecting path RT3. Since the heating section R2is set, hot air is blown onto the sheet P in the redirecting path RT3. When the trailing edge of the sheet P passes the position of the path switching unit25, the path switching unit25is set to the position for double-side printing. Then, the conveyance unit20conveys (redirecting conveyance) the sheet P on the redirecting path RT3in the reverse direction.

By guidance of the path switching unit25, the sheet P is conveyed to the inversion path RT4as indicated by the state ST13ofFIG. 8. Also, the sheet P is returned to the main path RT1as illustrated by the state ST14ofFIG. 8. The path switching unit25is set to the position (the positioning illustrated by the solid lines inFIG. 3A) in the case of the one-side printing. The printing unit30prints the image by discharging ink to a second surface of the sheet P as illustrated by the arrow. The operation after that is the same as in the states ST2to ST4of the case of one-side printing.

Regarding the heating and drying in relation to the sheet P, the configuration of the present embodiment is summarized as follows. The drying acceleration unit50of the present embodiment is a configuration in which the heating member51(the heating element54) is arranged on one side of the conveyance path RT of the sheet P, and the heating member51contacts only one side of the sheet P and heats it. Accordingly, while heat reaches both sides of the sheet P and drying is accelerated, the drying is more accelerated on the one side that the heating member51contacts directly. In the case of one-side printing, the heating member51contacts the image printing surface of the sheet P.

In the case of double-side printing, the heating element54faces the second surface of the sheet P, and the heating member51contacts only the back surface, and there is no stage in which the heating member51contacts the first surface of the sheet P. Accordingly, in the case of double-side printing, if the other conditions are the same, drying of the sheet P by the drying acceleration unit50will be more accelerated for the second surface than the first surface.

Meanwhile, the drying acceleration unit40of the present embodiment is arranged on one side of the conveyance path RT of the sheet P, and is a configuration in which hot air is blown only on one side of the sheet P. Accordingly, while drying of both sides is accelerated, the drying on the one side that the hot air directly hits is more accelerated. In the case of one-side printing, the hot air is blown on the image printing surface of the sheet P in the heating section R1.

In the case of the double-side printing, in the stage in which an image is printed on the first surface of the sheet P, hot air is blown on the first surface in the heating section R2, and in the stage in which an image is printed on the second surface, hot air is blown on the second surface in the heating section R1.

Regarding the drying in both the drying acceleration units40and50in the case of double-side printing, in the drying by the drying acceleration unit40, drying of the first surface of the sheet P is accelerated more than the second surface by using the length of the heating section. In the drying by the drying acceleration unit50, the drying of the second surface of the sheet P is accelerated more than the first surface at the point of the contact surface. Accordingly, it is possible to reduce the difference in drying between the front/back surfaces.

Second Embodiment

In the first embodiment, the difference (conveyance path difference) between one-side printing and double-side printing is given as an example of the print condition upon which the heating section change is based, but the print condition is not limited thereto. For example, the heating section may change depending on the discharge amount of ink onto the sheet P. Specifically, in a case where the ink discharge amount is large and the drying capability should be increased, a longer heating section may be selected, and in the case where the ink discharge amount is smaller, a shorter heating section may be selected. In the example ofFIG. 10A, in the case where it is determined that it is not the stage in which an image is printed on the second surface of the sheet in step S3, the processing does not advance to the step S4immediately, and further determines whether the ink discharge amount corresponding to the first surface is equal to a threshold or more. If the ink discharge amount is equal to the threshold or more, the processing advances to step S4, and if it is less than the threshold, the processing advances to step S2.

Third Embodiment

In the first embodiment, the driving condition for the fan42and the heating element43of the hot air drying unit40is not changed even in a case where both the heating sections R1and R2have been set, but configuration may be taken to change it. If the driving condition is the same for these, the drying capability per unit area of sheet may be increased for when the heating section R1is set. Accordingly, in the case where the heating section R1is set, output of at least one of the fan42and the heating element43may be reduced. It is possible to achieve a reduction in power consumption thereby.

Fourth Embodiment

Configuration may be taken so as not to continuously heat the heating element54of the drying acceleration unit50, and to stop the heating in the time period in which heat-drying of the sheet P is not performed by the drying acceleration unit50.FIG. 10Bis a flowchart that illustrates an example of control for driving the heating element54, and processing inFIG. 10Bis executed by the drying control unit17, for example. To outline the details of the control, the heating element54starts heating the sheet when it reaches the midpoint M1, and when the sheet passes the drying acceleration unit50, the heating is stopped. However, in the case of double-side printing, even after the sheet reaches the midpoint M1immediately after the image is printed on the first surface, the heating is not started; the heating is started when the sheet reaches the midpoint M1after the image is printed on the second surface. Until the sheet reaches the drying acceleration unit50, there is a period in which the heating of the heating element54is stopped, and therefore it is possible to reduce the power consumption and to prevent a rise in the internal temperature of the apparatus.

In step S11, it is determined whether a print condition for an image on a sheet that is the current print target is one-side printing or double-side printing. In the case of one-side printing, the processing advances to step S12, and in the case of double-side printing, the processing advances to step S16. In step S12, it is determined whether the sheet reached the midpoint M1. This determination is performed based on the result of detection by the sheet sensor described above. In the case where it is determined that the sheet has reached the midpoint M1, the processing advances to step S13, and in a case where it is determined not to have been reached, or when it had already been reached, the processing advances to step S14.

In step S13, the heating element54is driven and the heating is thereby started. In step S14, it is determined whether a sheet has passed the drying acceleration unit50. This determination is performed based on the above-described sheet sensor detection results. In the case where the sheet is determined to have passed the drying acceleration unit50, the processing advances to step S15, and in the case where it is determined to not have passed yet, the processing ends. In step S15, driving of the heating element54driven in step S14is stopped, and the heating is ended.

In step S16, printing of the image on the first surface of the sheet in the double-side printing ends and it is determined that whether the inversion of the sheet has ended (whether the sheet has passed the inversion path RT4). This determination is performed based on the result of detection by the sheet sensor described above. In the case where the inversion of the sheet has ended, the processing advances to step S12, and in the case where it has not ended, the processing ends. By this, in the case of double-side printing, an image is printed on the second surface of the sheet, and the heating of the heating element54is stopped until the midpoint M1is reached.

Fifth Embodiment

In the first embodiment, the shutter unit45was used to change the heating section, but other methods maybe be used.FIG. 11illustrates an example of another configuration of the drying acceleration unit40. In the drying acceleration unit40of the figure, a partition wall46which separates the internal space of the hollow body41vertically is provided. As configurations corresponding to the fan42and the heating element43of the first embodiment, fans42A and42B which are driven independently and heating elements43A and43B are provided. The fan42A and the heating element43A are arranged in the lower space in the internal space of the hollow body41separated by the partition wall46, and the fan42B and the heating element43B are arranged in the upper space separated by the partition wall46.

When the heating section R1is set, the fan42A and the heating element43A are driven when drying the sheet, and the fan42B and the heating element43B are not driven. When the heating section R2is set, the fan42A and the heating element43A are driven when drying the sheet, and the fan42B and the heating element43B are driven.

FIG. 12illustrates an example of yet another configuration of the drying acceleration unit40. The drying acceleration unit40of the figure is a configuration that corresponds to the heating element43of the first embodiment, and heating elements43A and43B which are driven independently are provided. The heating element43A is arranged in the lower space of the internal space of the hollow body41, and the heating element43B is arranged in the upper space. The partition wall46illustrated inFIG. 11is not arranged, and the fan42is not separated into upper and lower spaces. By driving the fan42, the air flow generated in the internal space of the hollow body41becomes a crosscurrent, but it is possible to produce a temperature difference within the space in accordance with which of the heating elements43A and43B are driven. If the configuration is such that the air flow generated in the internal space of the hollow body41by driving the fan42becomes closer to a laminar flow, it is possible to more clearly produce this temperature difference.

When the heating section R1is set, the fan42and the heating element43A are driven when drying the sheet, and the heating element43B is not driven. The hot air is sent from each outlet N and is blown to the redirecting path RT3as well, but since the heating element43B is not driven, the temperature of the hot air sent to the redirecting path RT3is comparably lower. Since the heating element43B is not driven, it is possible to prevent unnecessary power consumption and a rise in the internal temperature of the apparatus.

When the heating section R2is set, the fan42and the heating elements43A and43B are driven when drying the sheet. Since the heating element43B is driven, hot air whose temperature does not differ from other sections is sent to the redirecting path RT3.

OTHER EMBODIMENTS

This application claims the benefit of Japanese Patent Application No. 2019-154973, filed Aug. 27, 2019, which is hereby incorporated by reference herein in its entirety.