Conveying device, image forming apparatus, liquid discharge device

A conveying device includes a rotator, a drier, and a conveyance direction changer. The rotator winds a web-shaped recording medium around a predetermined region of an outer peripheral surface of the rotator with one side of the web-shaped recording medium facing outward and conveys the recording medium with rotation. The drier is disposed downstream from the rotator in a direction of conveyance of the recording medium, to dry and convey the recording medium. The conveyance direction changer is disposed on a conveyance path of the recording medium between the rotator and the drier. The conveyance direction changer has an outer peripheral surface that includes an opposed region opposed to the one side of the recording medium. The opposed region has openings to blow gas toward the one side of the recording medium. The rotator and the drier are disposed at positions not overlapping with each other in a plan view.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2017-153280, filed on Aug. 8, 2017 in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relate to a conveying device, an image forming apparatus, and a liquid discharge device.

Related Art

An image forming apparatus is known that forms an image using so-called ultraviolet (UV) ink that is irradiated and cured with ultraviolet rays.

For example, an image forming apparatus includes an inkjet head to discharge UV ink and a UV lamp to cure UV ink. Such an image forming apparatus includes a conveying device including a platen drum that winds and conveys a web-shaped recording medium around an outer peripheral surface of the platen drum.

On the other hand, an image forming apparatus using aqueous ink is known. Since the aqueous ink is difficult to dry, the image forming apparatus using the aqueous ink typically includes a drying section to dry the aqueous ink. To prevent the image from being disturbed, the web-shaped recording medium is conveyed to the drying section so that an image formation surface of the web-shaped recording medium on which the image is formed by the aqueous ink does not contact any component.

SUMMARY

In an aspect of the present disclosure, there is provided a conveying device that includes a rotator, a drier, and a conveyance direction changer. The rotator winds a web-shaped recording medium around a predetermined region of an outer peripheral surface of the rotator with one side of the web-shaped recording medium facing outward and conveys the web-shaped recording medium with rotation of the rotator. The drier is disposed downstream from the rotator in a direction of conveyance of the web-shaped recording medium, to dry and convey the web-shaped recording medium. The conveyance direction changer is disposed on a conveyance path of the web-shaped recording medium between the rotator and the drier. The conveyance direction changer has an outer peripheral surface that includes an opposed region opposed to the one side of the web-shaped recording medium. The opposed region has openings to blow gas toward the one side of the web-shaped recording medium. The rotator and the drier are disposed at positions not overlapping with each other in a plan view.

In another aspect of the present disclosure, there is provided an image forming apparatus that includes the conveying device and an image forming unit opposed to the outer peripheral surface of the rotator, to form an image on the one side of the web-shaped recording medium.

In another aspect of the present disclosure, there is provided a liquid discharge apparatus that includes the conveying device and a liquid discharge unit opposed to the outer peripheral surface of the rotator, to discharge liquid onto the one side of the web-shaped recording medium.

DETAILED DESCRIPTION

Below, embodiments of the present disclosure are described with reference to accompanying drawings. In each of the drawings, the same reference codes are allocated to components or portions having the same configuration and redundant descriptions of the same components may be omitted.

First Embodiment

FIG. 1is a schematic diagram of an example of an image forming apparatus according to a first embodiment of the present disclosure. As illustrated inFIG. 1, an image forming apparatus1according to the present embodiment includes, as main components, a feed conveyor10, a platen drum20, an image forming unit30, an air turn bar system40, a drier50, an ejection conveyor60, and a controller70. Note that a section including the platen drum20, the air turn bar system40, and the drier50is referred to as a conveying device100in the first embodiment. In some embodiments, the conveying device100may include the feed conveyor10(first conveyor) and the ejection conveyor60(second conveyor).

FIG. 2is a diagram of an example of a hardware configuration of the controller. As illustrated inFIG. 2, the controller70includes a central processing unit (CPU)71, a read only memory (ROM)72, a random access memory (RAM)73, an interface (I/F)74, and a bus line75as main components. The CPU71, the ROM72, the RAM73, and the I/F74are mutually connected via the bus line75. The controller70is connected to various controlled objects, various sensors, and the like.

The CPU71controls functions of the controller70. The ROM72as a storage device stores programs executed by the CPU71to control functions of the controller70and various information. The RAM73as a storage device is used as a work area or the like of the CPU71. The RAM73can temporarily store predetermined information. The I/F74is an interface for connecting with other devices and the like, and is connected to, for example, an external network.

Note that a part or the whole of the controller70may be constituted by hardware. Examples of the hardware include an application specific integrated circuit (ASIC), a digital signal processor (DSP), and a field programmable gate array (FPGA).

FIG. 3is a diagram of an example of functional blocks of the controller. As illustrated inFIG. 3, the controller70includes, for example, a rotation control unit710, a discharge control unit720, a drying control unit730, and a gas supply control unit740as main functional blocks. Specific functions of each function block are described later in the descriptions of the drawings. Note that the controller70may have other functional blocks as necessary.

With reference back toFIG. 1, the image forming apparatus1includes an introduction port101and an exit port102. The image forming apparatus1introduces a web-shaped recording medium300, which is unwound from an unwinding device disposed outside the image forming apparatus1in a direction indicated by arrow A (hereinafter, direction A) inFIG. 1, from the introduction port101. After forming an image on a surface (one side) of the web-shaped recording medium300, the image forming apparatus1sends out the web-shaped recording medium300from the exit port102in a direction indicated by arrow B (hereinafter, direction B) inFIG. 1. The web-shaped recording medium300is, for example, continuous paper. However, the material of the web-shaped recording medium300is not limited to paper.

The web-shaped recording medium300sent out in the direction B is delivered to a subsequent processing apparatus disposed outside the image forming apparatus1. Examples of the subsequent processing apparatus include a turn bar that inverts the front and back sides of the web-shaped recording medium300to form an image on the back surface (back side) of the web-shaped recording medium300on which an image has been formed on the front surface, a winding device to wind the web-shaped recording medium300, on which the images have been formed, on a roll, and a post-processing device, such as a cutter or a laminator.

The web-shaped recording medium300introduced from the introduction port101in the direction A passes, for example, the feed conveyor10including a plurality of conveyance idler rollers11, paired conveyance drive rollers12, an edge position control (EPC) device13, and a tension roller14, and is wound around the platen drum20and conveyed by the platen drum20.

The paired conveyance drive rollers12include, for example, a driving roller12aand a pinch roller12b. The rotation control unit710of the controller70controls a driving source to drive the driving roller12aand rotates the driving roller12aat a predetermined rotation speed. Thus, the web-shaped recording medium300is conveyed. The EPC device13is a device to adjust the position of the web-shaped recording medium300to a specified position with respect to the width direction of the web-shaped recording medium300. The tension roller14includes a pressure detector, such as a load cell, in a bearing portion, and detects the tension of the web-shaped recording medium300.

The platen drum20is a rotator that winds the web-shaped recording medium300around a predetermined region on the outer peripheral surface of the platen drum20with an image formation surface of the web-shaped recording medium300, on which an image is formed, facing outward, and conveys the web-shaped recording medium while rotating. More specifically, the rotation control unit710of the controller70controls a driving source for driving the platen drum20and rotates the platen drum20at a predetermined rotation speed. The tension of the web-shaped recording medium300caused by the rotation of the platen drum20is detected by the tension roller14and input to the controller70. The rotation control unit710of the controller70controls the rotation speed of the paired conveyance drive rollers12so that the tension detected by the tension roller14reaches a preset value. Thus, the web-shaped recording medium300is conveyed while maintaining a predetermined tension.

The image forming unit30is disposed above the platen drum20in the vertical direction and opposite an outer peripheral surface of the platen drum20. The image forming unit30forms an image on the web-shaped recording medium300. The image forming unit30can form an image with, for example, aqueous ink. The aqueous ink is an ink using water as a solvent, for example, an aqueous dye ink or an aqueous pigment ink.

The image forming unit30includes, for example, a plurality of inkjet recording head arrays (IJ head arrays) arranged in a conveyance direction of the web-shaped recording medium300along the outer periphery of the platen drum20. Each IJ head array includes, for example, a plurality of IJ heads arranged side by side in a direction orthogonal to the conveyance direction of the web-shaped recording medium300.

InFIG. 1, the image forming unit30discharges an IJ head array31to discharge black (K) ink, an IJ head array32to discharge cyan (C) ink, and an IJ head array33to discharge magenta (M) ink, an IJ head array34to discharge yellow (Y) ink, and an IJ head array35to discharge special color ink.

The image forming unit30is controlled by the controller70. A discharge control unit720of the controller70allocates nozzles to be discharged to each of the IJ heads constituting the IJ head arrays31to35according to print data500received from the outside of the image forming apparatus1and controls discharge timing of each IJ head.

The platen drum20is provided with a detector25to detect the movement amount of a drum surface (outer peripheral surface) of the platen drum20. A detection signal of the detector25is input to the controller70. The discharge control unit720of the controller70detects the correlation between the discharge timing of each of the IJ heads constituting the IJ head arrays31to35and the movement amount of the platen drum20, based on the detection signal of the detector25. Thus, the discharge control unit720can correct the discharge timing in accordance with the conveyance amount of the web-shaped recording medium300.

FIG. 4Ais an illustration of the relationship between the winding angle θ and the conveying force F.FIG. 4Bis a graph illustrating an example of the relationship between the winding angle θ and the conveying force F in conveyance of the web-shaped recording medium300that is wound around the platen drum20at a tension T1. T1represents a tension on the tension roller14side, and T2is a tension on the air turn bar system40side.

Assuming that the width of the web-shaped recording medium300is W and the coefficient of static friction between the web-shaped recording medium300and the platen drum20is μ, the relationship between T1and T2and the conveying force F are expressed by the following Equation 1 and Equation 2, respectively.

To accurately reflect the corrected discharge timing, which has been corrected by the discharge control unit720of the controller70, on printing, the web-shaped recording medium300is conveyed while maintaining close contact with or a micro slip state against the platen drum20. Therefore, preferably, the conveying force F is set to be sufficiently greater than the tension T1.

The graph ofFIG. 4represents the relationship between the winding angle θ and the safety of the conveying force F against the tension. The static friction coefficient μ is empirically about 0.3, but in consideration of variation, μ is set to be 0.2. The graph ofFIG. 4represents that, when the winding angle θ is 200 degrees or more, the safety is twice or more than when the winding angle θ is zero degree. In other words,FIG. 4illustrates that, if the web-shaped recording medium300is wound around the platen drum20by 200 degrees or more, a conveying force F that can withstand an external force of twice or more than the tension without slipping can be obtained.

Accordingly, by designing the winding angle θ of the web-shaped recording medium300to the platen drum20to be 200 degrees or more, the web-shaped recording medium can be conveyed with a sufficient margin for slipping.

Further, with the above-described configuration, the web-shaped recording medium300is tightly wound around the outer peripheral surface of the platen drum20and conveyed, thus preventing fluttering of the web-shaped recording medium300. Accordingly, since the IJ head arrays31to35constituting the image forming unit30do not contact the web-shaped recording medium300, the IJ head arrays31to35can be disposed proximate to the platen drum20to the extent that vibration of the platen drum20does not cause the contact of the web-shaped recording medium300with the IJ head arrays31to35.

Since each of the IJ heads constituting the IJ head arrays31to35varies in discharge angle between nozzles, reducing the distance between each IJ head and the platen drum20can reduce the variation of landing positions of ink droplets, thus allowing printing with higher image qualities.

Returning toFIG. 1, the web-shaped recording medium300passing through the platen drum20is conveyed substantially downward from the platen drum20. The web-shaped recording medium300is wound around an outer peripheral surface (for example, an outer peripheral surface having an arc-shaped region in side view) of an air turn bar41constituting the air turn bar system40, and the conveyance direction of the web-shaped recording medium300is changed substantially upward. The web-shaped recording medium300, the conveying direction of which has been changed substantially upward, is conveyed to the drier50through a conveyance idler roller49. Details of the air turn bar system40is described later.

The drier50is disposed downstream from the platen drum20and the air turn bar41in the conveyance direction of the web-shaped recording medium300. The drier50dries the image formed on the web-shaped recording medium300by the image forming unit30, and conveys the web-shaped recording medium300. The drier50dries, for example, undried aqueous ink in the image formed by the image forming unit30. The drier50is disposed at a position not overlapping with the platen drum20in a plan view and includes a tension roller51, a drying drum52, a heater53, and a plurality of air nozzles54.

Note that the term “plan view” means a view from the normal direction of a horizontal plane on which the image forming apparatus1is disposed in a normally usable state.

The tension roller51includes a pressure detector, such as a load cell, in a bearing portion, and detects the tension of the web-shaped recording medium300extended between the platen drum20and the drying drum52. The tension roller51is a typical example of the tension detector according to an embodiment of the present disclosure.

The drying drum52winds the web-shaped recording medium300around a predetermined region on an outer peripheral surface of the drying drum52with an image formation surface of the web-shaped recording medium300, on which the image is formed, facing outward, and conveys the web-shaped recording medium300as the drying drum52rotates. The drying drum52is a typical example of a second rotator according to an embodiment of the present disclosure.

The rotation control unit710of the controller70controls the rotation speed of the drying drum52. For example, the rotation control unit710controls a driving source to drive the drying drum52, and rotates the drying drum52at a predetermined rotation speed. The tension of the web-shaped recording medium300caused by the rotation of the drying drum52is detected by the tension roller51and input to the controller70. The rotation control unit710of the controller70controls the rotation speed of the drying drum52so that the tension detected by the tension roller51becomes a preset value. Accordingly, the web-shaped recording medium300can be conveyed while maintaining the tension of the web-shaped recording medium300between the platen drum20and the drier50at a predetermined value.

The tension detector of the tension roller51is not limited to the load cell. The tension of the web-shaped recording medium300may be detected, for example, by swingably supporting the tension roller51, pressing the tension roller51with an elastic member in a tensioning direction of the web-shaped recording medium300, and measuring the pressure of the tension roller51to detect the tension of the web-shaped recording medium300.

A heater53made of, for example, a halogen lamp or the like is disposed inside the drying drum52. The air nozzles54are arranged to surround the periphery of the drying drum52. The heating amount of the heater53and the blowing amount of the air nozzles54are controlled by the drying control unit730of the controller70. The web-shaped recording medium300wound around the drying drum52is heated from the rear side (back side) of the image formation surface by the heater53and air (at normal temperature) or hot air is blown to the image formation surface (front side) by the air nozzles54. Thus, the ink discharged onto the web-shaped recording medium300can be dried.

Note that, from viewpoints from the physical properties of ink and the productivity required for the apparatus, drying may be promoted by installing a technique of drying the drier50with thermal radiation of an infrared heater or the like to the drier50.

When the ink is dried by the drier50, a contactable film is formed on a surface of the ink. After drying, the web-shaped recording medium300passes through the ejection conveyor60including, for example, a plurality of conveyance idler rollers61, a tension roller62, and paired conveyance driving rollers63. The web-shaped recording medium300is ejected in the direction indicated by arrow B from the exit port102, and is delivered to a post-processing device or the like in the subsequent stage.

The paired conveyance driving rollers63include, for example, a driving roller63aand a pinch roller63b. The rotation control unit710of the controller70controls a driving source to drive the driving roller63ato rotate the driving roller63aat a predetermined rotation speed. The tension of the web-shaped recording medium300caused by the rotation of the driving roller63ais detected by the tension roller62and input to the controller70. The rotation control unit710of the controller70controls the rotation speed of the driving roller63aso that the tension detected by the tension roller62becomes a preset value. Thus, the web-shaped recording medium300is conveyed while maintaining a predetermined tension.

Here, the air turn bar system40is described in detail.FIGS. 5A and 5Bare schematic diagrams of a configuration example of the air turn bar system according to the first embodiment.FIG. 5Ais a illustration of an example of the entire configuration of the air turn bar system.FIG. 5Bis an enlarged upside-down view of the air turn bar41.

As illustrated inFIG. 5A, the air turn bar system40includes the air turn bar41, a blower42, a filter43, a gas flow path44, and a pressure sensor45.

The air turn bar41is disposed on a conveyance path of the web-shaped recording medium300between the platen drum20and the drier50, and can change the conveyance direction of the web-shaped recording medium300, for example, by 180 degrees. The air turn bar41is a typical example of a conveyance direction changer according to an embodiment of the present disclosure.

The blower42is connected to the air turn bar41via the gas flow path44, and can supply gas to the air turn bar41. The supply amount of gas supplied from the blower42is controlled by the gas supply control unit740of the controller70. The blower42is a typical example of the gas supplier according to an embodiment of the present disclosure.

The filter43is inserted into the gas flow path44between the air turn bar41and the blower42, and can remove foreign matters and the like contained in the gas supplied from the blower42. The gas flow path44is a flow path of the gas supplied from the blower42. Here, the gas is, for example, air.

The pressure sensor45is disposed near the air turn bar41and can detect the internal pressure of the air turn bar41. The detected value of the internal pressure of the air turn bar41detected by the pressure sensor45is input to the controller70. As the pressure sensor45, for example, a sensor having a piezoresistance can be used. The pressure sensor45is a typical example of a pressure detector according to an embodiment of the present disclosure.

An outer peripheral surface411of the air turn bar41around which the web-shaped recording medium300is wound has an opposed region opposed to the image formation surface of the web-shaped recording medium on which an image is formed. The opposed region may be a part or the whole of the outer peripheral surface411. The opposed region includes a plurality of air blowing holes412, which are openings for blowing gas toward the image formation surface of the web-shaped recording medium300on which an image is formed. The shape and arrangement pattern of the air blowing holes412are not particularly limited and can be appropriately determined as necessary.

The gas supplied from the blower42is introduced into the air turn bar41via the filter43and blown out from the plurality of air blowing holes412of the outer peripheral surface411. The blown gas flows into between the image formation surface of the web-shaped recording medium300wound around the outer peripheral surface411of the air turn bar41and the outer peripheral surface411of the air turn bar41, brings the web-shaped recording medium300into contact with the air turn bar41, and floats the web-shaped recording medium300from the outer peripheral surface411of the air turn bar41.

In the air turn bar system40, to reliably float and convey the web-shaped recording medium300, a gas having a pressure sufficient to float the web-shaped recording medium300is supplied to the air turn bar41.

In the present embodiment, the pressure sensor45to measure the internal pressure of the air turn bar41is disposed near the air turn bar41. The gas supply control unit740of the controller70compares a detection result of the internal pressure of the air turn bar41by the pressure sensor45with a preset numerical value, and controls the amount of gas supplied by the blower42according to the comparison result.

For example, as illustrated in step S100ofFIG. 6, the gas supply control unit740obtains a detection result (a detection value “a” of the pressure sensor45) of the internal pressure of the air turn bar41by the pressure sensor45.

Next, in step S101, the gas supply control unit740compares the detection value “a” of the pressure sensor45with a preset numerical value (a pressure setting value “b”), and determines whether the detection value “a” of the pressure sensor45is smaller than the pressure setting value “b”. Note that the pressure setting value “b” is stored in, for example, the RAM73, and the gas supply control unit740can read the pressure setting value “b” from the RAM73as necessary.

If the gas supply control unit740determines in step S101that the detection value “a” is smaller than the pressure setting value “b” of the pressure sensor45(YES in step S101), the process proceeds to step S102. The gas supply control unit740increases the supply amount of gas of the blower42by Δp.

When the gas supply control unit740determines in step S101that the detection value “a” of the pressure sensor45is equal to or greater than the pressure setting value “b” (NO in step S101), the process proceeds to step S103and the gas supply control unit740decreases the supply amount of gas of the blower42by Δp. The processing from step S100to step S103is repeatedly executed. The gas supply control unit740can interrupt or stop the processing at desired timing.

Performing the control illustrated inFIG. 6allows the gas having a pressure sufficient to float the web-shaped recording medium300to be stably supplied to the air turn bar41, thus allowing the web-shaped recording medium300to be reliably floated and conveyed.

Note that the above-described process is an example of a method of stabilizing the internal pressure of the air turn bar41, and the internal pressure of the air turn bar41may be stabilized by another method. For example, a plurality of pressure check points may be set in the air turn bar41, and the gas supply control unit740may measure the internal pressure of the air turn bar41at the respective pressure check points. Alternatively, a method may be employed that controls the supply amount of the gas supplied by the blower42such that the gas supply control unit740matches the measured value of each pressure check point with a predetermined pressure setting value.

In the image forming apparatus1, the air turn bar system40allows the web-shaped recording medium300conveyed from the platen drum20to be conveyed while floating from the outer peripheral surface411of the air turn bar41. Accordingly, an image formed with undried ink on the image formation surface of the web-shaped recording medium300is introduced to the drier50without being disturbed. The undried ink on the image formation surface of the web-shaped recording medium300is dried by the drier50, and a contactable film is formed on the surface of the ink.

Note that, inFIG. 1, the configuration is illustrated in which the detection mechanism disposed on the tension roller51detects the tension of the web-shaped recording medium300between the platen drum20and the drier50to control the tension. However, in the configuration ofFIGS. 5A and 5B, the internal pressure of the air turn bar41can be detected. Therefore, instead of controlling the tension of the web-shaped recording medium300according to the tension detection result of the tension roller51as illustrated inFIG. 1, for example, the following control may be performed.

That is, the rotation control unit710of the controller70may detect the tension of the web-shaped recording medium300extended between the platen drum20and the drying drum52, based on the detection result of the internal pressure of the air turn bar41by the pressure sensor45, and control the rotational speed of the drying drum52based on the detected tension. For example, the rotation control unit710may detect the tension of the web-shaped recording medium300extended between the platen drum20and the drying drum52, based on the correlation between the internal pressure of the air turn bar41and the tension of the web-shaped recording medium300wound around the outer peripheral surface411of the air turn bar41, and control the rotational speed of the drying drum52based on the detected tension.

More specifically, as illustrated in step S200ofFIG. 7, the rotation control unit710obtains a detection result of the internal pressure of the air turn bar41by the pressure sensor45(a detection value “a” of the pressure sensor45) and converts the detection value “a” to a tension S. The conversion can be carried out, for example, based on conversion data of the detection value “a” and the tension S stored in the RAM73.

Next, in step S201, the rotation control unit710compares the tension S with a preset numerical value (tension setting value T), and determines whether the tension S is smaller than the tension setting value T. Note that the tension setting value T is stored in, for example, the RAM73, and the rotation control unit710can read the tension setting value T from the RAM73as necessary.

If the rotation control unit710determines in step S201that the tension S is smaller than the tension setting value T (YES in step S201), the process proceeds to step S202. The rotation control unit710increases the rotation speed of the drying drum52by Δv.

If the rotation control unit710determines in step S201that the tension S is equal to or greater than the tension setting value T (NO in step S201), the process proceeds to step S203. The rotation control unit710decreases the rotation speed of the drying drum52by Δv. The processing from step S200to step S203is repeatedly executed. The rotation control unit710can interrupt or stop the processing at desired timing.

As illustrated inFIG. 7, the detected value of the internal pressure of the air turn bar41is converted into a tension and compared with a preset numerical value, and the rotational speed of the drying drum52(conveyance speed of the web-shaped recording medium300) is adjusted, thus allowing tension control. Accordingly, the tension control can be performed by an inexpensive configuration in which a pressure detection mechanism, such as a load cell, arranged on the tension roller51is omitted.

The process illustrated inFIG. 7is effective to handle a homogeneous web recording medium300since the internal pressure varies with the air permeability of the web-shaped recording medium300wound around the air turn bar41.

Likewise, since the air turn bar41is a system in which the web-shaped recording medium300is floated by air pressure, the floating amount varies with the air permeability of a material constituting the web-shaped recording medium300. When the floating amount is excessively low due to a material having an extremely high air permeability, an undried ink image may contact the outer peripheral surface411of the air turn bar41and disturb the image. In addition, ink attached to the outer peripheral surface411may stain the surface of the subsequent web-shaped recording medium300. Alternatively, a material having a low air permeability may cause an excessively large floating amount, thus causing meandering due to fluttering of the web-shaped recording medium300. Therefore, the floating amount of the web-shaped recording medium300is preferably controlled to an appropriate range.

Here, a comparative example is described.FIG. 8is a schematic view of an example of an image forming apparatus according to Comparative Example 1. As illustrated inFIG. 8, an image forming apparatus1X according to Comparative Example 1 includes web support rollers17including seven rollers to bridge the web-shaped recording medium300. The image forming unit30is disposed above the web support rollers17.

A length measuring roller16with an encoder15is disposed upstream from the image forming unit30in the conveyance direction of the web-shaped recording medium300. Based on a detection signal of the encoder15, the discharge timing is corrected according to the conveyance amount of the web-shaped recording medium300, and an image is formed on the web-shaped recording medium300.

InFIG. 8, the positional relationship between the web-shaped recording medium300and the image forming unit30is maintained only by the tension of the web-shaped recording medium300on the web support rollers17. Accordingly, in the web-shaped recording medium300, a parallelism error between the web support rollers17and fluttering or meandering due to the influence of the deflection occurs.

If fluttering occurs, the distance between each IJ head of the image forming unit30and the web-shaped recording medium300varies, thus causing an error in landing position of ink droplets in the conveyance direction. If meandering occurs, an error occurs in landing position of ink droplets in the width direction of the web-shaped recording medium300. Furthermore, if the web-shaped recording medium300contacts the nozzle surface of the IJ head, print dot missing occurs due to nozzle clogging. Therefore, the distance between each IJ head and the recording medium is set in consideration of fluttering of the web-shaped recording medium300, which may become a factor of deterioration of landing position accuracy.

Setting high tension of the web-shaped recording medium300can reduce fluttering and meandering. However, since too high tension cause a harmful effect, the restrictions on the use of the web-shaped recording medium300may occur if conditions cannot be satisfied. For example, if the tension is extremely increased with a paper medium, depending on the printing coverage of ink on the upstream side, the elastic modulus may decrease due to penetration of ink. Elongation may occur in the printing medium, and an error in landing position of the ink may occur due to lack of the conveyance amount.

In the case of oriented polypropylene (OPP) having a thickness of 20 μm, which is a soft packaging medium, when the tension exceeds 100 N/m, tension wrinkles are generated, thus causing an error in landing position. As described above, the system illustrated inFIG. 8has a simple configuration. However, the restrictions on applicable recording media may increase.

FIG. 9is a schematic view of an example of an image forming apparatus according to Comparative Example 2. As illustrated inFIG. 9, an image forming apparatus1Y according to Comparative Example 2 includes the platen drum20as inFIG. 1. However, unlikeFIG. 1, the image forming apparatus1Y does not include the air turn bar system40.

In the image forming apparatus1Y, the web-shaped recording medium300printed by the image forming unit30is wound around the platen drum20at a winding angle at which sufficient conveying force is obtained, and conveyed. Below the platen drum20, the web-shaped recording medium300is further conveyed downward from the platen drum20to the drier50.

Since an undried ink image is formed on the image formation surface of the web-shaped recording medium300sent out of the platen drum20, the web-shaped recording medium300cannot contact any conveying member until the ink is dried and a contactable film is formed on the surface of the ink.

Here, the IJ head arrays31to35of the image forming unit30are arranged along the outer periphery of the platen drum20. The left end portion of the image forming unit30in the conveyance direction is located below a horizontal tangent passing an uppermost portion of the outer periphery of the platen drum20.

Such a configuration hampers the drier50from being disposed on the left side of the platen drum20so as not to overlap with the platen drum20in plan view, and the web-shaped recording medium300from being horizontally conveyed from the platen drum20toward the drier50. This is because the image formation surface of the web-shaped recording medium300would contact the left end portion of the image forming unit30in the conveyance direction.

Therefore, inFIG. 9, the drier50is disposed substantially below the platen drum20so that the image formation surface of the web-shaped recording medium300can be introduced into the drier50without contacting any portion.

Meanwhile, to dry the ink with the drier50, the heating temperature and the heating time are set in accordance with the physical properties of ink and a printing medium. In a high-speed image forming apparatus, a long heating conveyance distance is set according to the conveyance speed in order to ensure the heating time, and the apparatus tends to be large.

Accordingly, in the configuration in which the drier50is disposed below the platen drum20as in the image forming apparatus1Y, the height of the image forming apparatus would increase and may exceed 2 m. An increase in the height of the image forming apparatus would cause deterioration in operability of, e.g., loading of the web-shaped recording medium300. For the transportation of the image forming apparatus, the height of a shipping container is generally about 2.5 m. Therefore, when the image forming apparatus exceeding 2 m is packed, the packed image forming apparatus is highly likely to exceed 2.5 m, which may hamper the image forming apparatus to be transported in assembled state.

Since the image forming apparatus exceeding the allowable height of the shipping container is disassembled and then transported, the image forming apparatus would be assembled on site after transportation, thus causing a failure of an increase in the installation time of the apparatus.

As an arrangement to avoid an increase in height of the apparatus, the web-shaped recording medium300may be drawn out in the right direction from the lowermost point of the platen drum20in the image forming apparatus1Y. However, in such a case, to arrange the drier50on the right side of the platen drum20, the length of the conveyance path of the feed conveying unit to the platen drum20and the length of the conveyance path from the drier50to the exit port102increase, thus causing a failure of increasing spoilage (broke, wasted paper) at the time of stopping printing startup.

On the other hand, the image forming apparatus1illustrated inFIG. 1includes the air turn bar system40. The air turn bar system40includes the air turn bar41and the blower42downstream from the platen drum20. The air turn bar41has the plurality of air blowing holes412on the outer peripheral surface411around which the web-shaped recording medium300is wound. The blower42blows air to the air turn bar41.

Accordingly, even if the image formation surface (printed surface) of the web-shaped recording medium300on which an image has been formed by the image forming unit30is conveyed facing the outer peripheral surface411of the air turn bar41, a non-contact state of the image formation surface and the air turn bar41can be maintained. Thus, the conveyance direction can be turned along the outer peripheral surface411of the air turn bar41without disturbing the image formed on the image formation surface.

As a result, the platen drum20and the drier50can be disposed at positions not overlapping in a plan view, thus suppressing an increase in height and size of the apparatus while shortening the length of the conveyance path. In addition, since the length of the conveyance path length can be shortened, an image forming apparatus can be achieved that does not increase spoilage (broke, wasted paper).

In the image forming apparatus1, the web-shaped recording medium300is wound around the platen drum20, and the image forming unit30including, for example, the IJ head arrays31to35is arranged around the platen drum20. Such a configuration can reduce the influence of variations due to the characteristics of the web-shaped recording medium300and stretching vibration during conveyance, and furthermore, the distance between the IJ head arrays31to35and the web-shaped recording medium300can be set small.

Accordingly, variations in landing of ink when forming an image on the web-shaped recording medium300are reduced, and high image quality of the image formed on the web-shaped recording medium300can be achieved. In addition, since there is no limitation on the type of web-shaped recording medium300, complicated landing position adjustment for each web-shaped recording medium300can be obviated, thus allowing the accuracy of landing positions of ink to be stably maintained.

Variation of First Embodiment

As a variation of the first embodiment, an example is described in which an air turn bar system having a specification different from the specification of the first embodiment is used. Note that, in the variation of the first embodiment, descriptions of the same constituent parts as in the above-described embodiments may be omitted.

FIG. 10is a schematic diagram of a configuration example of an air turn bar system according to a variation of the first embodiment. As illustrated inFIG. 10, an air turn bar system40A according to the variation of the first embodiment is different from the air turn bar system40(seeFIG. 5A) in that a displacement sensor46is disposed opposite the back surface of the web-shaped recording medium300so as to sandwich the web-shaped recording medium300between the air turn bar system40A and the outer peripheral surface411of the air turn bar41).

The displacement sensor46is configured to be able to detect the floating amount of the web-shaped recording medium300. As the displacement sensor46, for example, an optical-type or an ultrasonic-type non-contact displacement sensor can be used. The displacement sensor46is a typical example of the floating amount detector according to an embodiment of the present disclosure.

The floating amount of the web-shaped recording medium300floated by the air turn bar41is likely to be smaller in the vicinity of a top of an arc of the outer peripheral surface411having an arc-shaped region in a side view of the outer peripheral surface411of the air turn bar41and end portions of the web-shaped recording medium300in the width direction of the web-shaped recording medium300(perpendicular to the conveyance direction) than other portions.

Therefore, although the displacement sensor46may be singular or plural, the displacement sensor46is preferably arranged in the vicinity of at least one of the top of the arc of the outer peripheral surface411of the air turn bar41and the end portions of the web-shaped recording medium300in the width direction of the web-shaped recording medium300. Such a configuration can reliably prevent an undried ink image from contacting the outer peripheral surface411of the air turn bar41due to an insufficient floating amount of the web-shaped recording medium300.

In the air turn bar system40A, the gas supply control unit740of the controller70compares the floating amount of the web-shaped recording medium300detected by the displacement sensor46with a preset numerical value, and controls the supply amount of gas of the blower42based on the comparison result.

For example, as illustrated in step S300inFIG. 11, the gas supply control unit740of the controller70obtains a detection result (a detected value “d” of the floating amount of the web-shaped recording medium300) of the displacement sensor46.

Next, in step S301, the gas supply control unit740compares the detection value “d” of the displacement sensor46with a preset numerical value (displacement amount setting value “e”) and determines whether the detection value “d” of the displacement sensor46is smaller than the displacement amount setting value “e”. Note that the displacement amount setting value “e” is stored in, for example, the RAM73and can be read out by the gas supply control unit740as needed.

If the gas supply control unit740determines in step S301that the detection value “d” of the displacement sensor46is smaller than the displacement amount setting value “e” (YES in step S301), the process proceeds to step S302and the gas supply control unit740increases the amount of gas to be supplied by the blower42by Δp.

If the gas supply control unit740determines in step S301that the detection value “d” is equal to or greater than the displacement amount setting value “e” of the displacement sensor46) (NO in step S301), the process proceeds to step S303and the gas supply control unit740decreases the supply amount of gas to be supplied by the blower42by Δp. Although the processing from step S300to step S303is repeatedly executed, the gas supply control unit740can suspend or stop the processing at necessary timing.

The control illustrated inFIG. 11allows the floating amount of the web-shaped recording medium300to be controlled within an appropriate range.

On the other hand, the floating amount of the web-shaped recording medium300also varies with the tension of the web-shaped recording medium300. For example, when the tension of the web-shaped recording medium300is large, the floating amount decreases, and when the tension is small, the floating amount increases.

Hence, in addition to the control of the output of the blower42by the controller70, the rotation speed of the drying drum52is controlled so that the tension detected by the tension roller51falls within an appropriate range, thus allowing the floating amount of more various types of media to be controlled by the air turn bar41.

Specifically, in step S400ofFIG. 12A, the gas supply control unit740of the controller70sets variable i to i=1. Next, in step S401, the gas supply control unit740sets variable j to j=1. Next, in step S402, the gas supply control unit740compares i with N and determines whether i is equal to or smaller than N. Here, N is the number of retries.

When the gas supply control unit740determines in step S402that i is equal to or smaller than N (YES in S402), the process proceeds to step S403. In step S403, the gas supply control unit740compares j with M and determines whether j is equal to or smaller than M. Here, M is the number of retries.

If the gas supply control unit740determines in step S403that j is equal to or smaller than M (YES in step S403), the process proceeds to step S404. In step S404, the gas supply control unit740of the controller70obtains whether the detection result of the displacement sensor46(the detection value “d” of the floating amount of the web-shaped recording medium300).

Next, in step S405, the gas supply control unit740compares the detection value “d” of the displacement sensor46with a preset numerical value (displacement amount setting value “e”), and determines whether the detection value “d” of the displacement sensor46is smaller than the displacement amount setting value “e”. Note that the displacement amount setting value “e” is stored in, for example, the RAM73and can be read out by the gas supply control unit740as needed.

If the gas supply control unit740determines in step S405that the detection value “d” of the displacement sensor46is smaller than the displacement amount setting value “e” (YES in step S405), the process proceeds to step S406and the gas supply control unit740increases the supply amount of gas to be supplied by the blower42by Δp. Then, in step S407, the gas supply control unit740sets i=i+1, proceeds to step S402, and repeats the same processing thereafter.

If the gas supply control unit740determines in step S405that the detection value “d” of the displacement sensor46is equal to or greater than the displacement amount setting value “e” (NO in step S405), the process proceeds to step S408and the gas supply control unit740decreases the supply amount of gas to be supplied by the blower42by Δp. Then, in step S409, the gas supply control unit740sets j=j+1, proceeds to step S403, and repeats the same processing thereafter.

On the other hand, if the gas supply control unit740determines in step S402that i is greater than N (NO in step S402), the process proceeds to step S410ofFIG. 12Band the rotation control unit710of the controller70lowers the tension setting value T to T−α. Here, α is a change amount of the tension that is appropriately set.

Next, in step S411, the rotation control unit710obtains the tension S detected by the tension roller51. Next, in step S412, the rotation control unit710compares the tension S with the tension setting value T after the change in step S410, and determines whether the tension S is smaller than the tension setting value T.

If the rotation control unit710determines in step S412that the tension S is smaller than the tension setting value T (YES in step S412), the process proceeds to step S400and the rotation control unit710repeats the same processing thereafter.

If the rotation control unit710determines in step S412that the tension S is equal to or greater than the tension setting value T (NO in step S412), the process proceeds to step S413and the rotation control unit710decreases the rotation speed of the drying drum52by Δv. Then, the process proceeds to step S411, and the rotation control unit710repeats the same processing thereafter.

If the gas supply control unit740determines in step S403that j is greater than M (NO in step S403), the process proceeds to step S420ofFIG. 12Cand the rotation control unit710of the controller70increases the tension setting value T to T+α.

Next, in step S421, the rotation control unit710obtains the tension S detected by the tension roller51. Next, in step S422, the rotation control unit710compares the tension S with the tension setting value T after the change in step S420, and determines whether the tension S is equal to or greater than the tension setting value T.

If the rotation control unit710determines in step S422that the tension S is equal to or greater than the tension setting value T (YES in step S422), the process proceeds to step S400and the rotation control unit710repeats the same processing thereafter.

If the rotation control unit710determines in step S422that the tension S is smaller than the tension setting value T (NO in step S422), the process proceeds to step S423and the rotation control unit710increases the rotational speed of the drying drum52by Δv. Then, the process proceeds to step S421, and the rotation control unit710repeats the same processing thereafter.

The control illustrated inFIGS. 12A to 12Callows the floating amount the floating amount of a wider variety of media to be controlled by the air turn bar. Thus, an image forming apparatus with high media compatibility can be provided.

Although some embodiments and variation have been described above, embodiments of the present disclosure are not limited to the above-described embodiments and variation. Various modifications and substitutions may be made to the above-described embodiments without departing from the scope described in the appended claims.

For example, in the above-described embodiments and variation, the image forming apparatus including the conveying device has been described. However, the conveying device according to an embodiment of the present disclosure can be widely applied to liquid discharge apparatuses including an image forming apparatus.

The term “liquid discharge apparatus” or “apparatus for discharging liquid” used herein is an apparatus including a liquid discharge head, which is a liquid discharge unit, or a liquid discharge device to discharge liquid by driving the liquid discharge unit. The liquid discharge apparatus may be, for example, an apparatus capable of discharging liquid to a material to which liquid can adhere and an apparatus to discharge liquid toward gas or into liquid.

The liquid discharge apparatus may include devices to feed, convey, and eject the material on which liquid can adhere. The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged.

The “liquid discharge apparatus” may be, for example, an image forming apparatus to form an image on a sheet by discharging ink, or a three-dimensional fabricating apparatus to discharge a fabrication liquid to a powder layer in which powder material is formed in layers, so as to form a three-dimensional fabrication object.

The liquid discharge apparatus is not limited to an apparatus to discharge liquid to visualize meaningful images, such as letters or figures. For example, the liquid discharge apparatus includes an apparatus to form meaningless images, such as meaningless patterns, or fabricate three-dimensional images.

The above-described term “material on which liquid can be adhered” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate. Examples of the “material on which liquid can be adhered” include recording media, such as paper sheet, recording paper, recording sheet of paper, film, and cloth, electronic component, such as electronic substrate and piezoelectric element, and media, such as powder layer, organ model, and testing cell. The “material on which liquid can be adhered” includes any material on which liquid is adhered, unless particularly limited.

Examples of the material on which liquid can be adhered include any materials on which liquid can be adhered even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic.

Examples of the liquid are, e.g., ink, treatment liquid, DNA sample, resist, pattern material, binder, fabrication liquid, or solution and dispersion liquid including amino acid, protein, or calcium.

The term “liquid discharge apparatus” may be an apparatus to relatively move a head and a medium on which liquid can be adhered. However, the liquid discharge apparatus is not limited to such an apparatus. For example, the liquid discharge apparatus may be a serial head apparatus that moves the liquid discharge head or a line head apparatus that does not move the liquid discharge head.

Examples of the “liquid discharge apparatus” further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat the treatment liquid on the surface of the sheet to reform the sheet surface and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is injected through nozzles to granulate fine particles of the raw materials.

The “liquid discharge device” is an integrated unit including the liquid discharge head, such as an IJ head and functional parts or mechanisms, and is an assembly of parts relating to liquid discharge. For example, the “liquid discharge device” may be a combination of the liquid discharge head with at least one of the head tank, the carriage, the supply unit, the maintenance unit, and the main scan moving unit.

Here, examples of the integrated unit include a combination in which the liquid discharge head and a functional part(s) are secured to each other through, e.g., fastening, bonding, or engaging, and a combination in which one of the liquid discharge head and a functional part(s) is movably held by another. The liquid discharge head may be detachably attached to the functional part(s) or unit(s) each other.

In addition, “the liquid discharging head” has no specific limit to the pressure generator used in the liquid discharge head. The liquid discharge head may use, as the pressure generator, for example, a piezoelectric actuator (which may use a laminated piezoelectric element), a thermal actuator using an electrothermal transducer, such as a heating resistor, and an electrostatic actuator including a diaphragm and opposed electrodes.

The terms “image formation”, “recording”, “printing”, “image printing”, and “fabricating” used herein may be used synonymously with each other.

Each of the functions of the described embodiments may be implemented by one or more processing circuits. A processing circuit includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.