Liquid jetting apparatus and method of coping with floating of medium

There are provided a liquid jetting apparatus in which the deterioration of production efficiency is suppressed in a case in which the floating of a medium occurs, and a method of coping with the floating of a medium. A medium is fed; liquid is jetted to the medium, which is transported by a medium transport unit including a medium support surface on which the medium is supported and transporting the fed medium in a medium transport direction, by a liquid jet head; drying processing is performed on the medium, to which the liquid jetted from the liquid jet head adheres, at a position on the downstream side of the liquid jet head in the medium transport direction; and in a case in which the floating of the medium is detected at a position on the upstream side of the liquid jet head in the medium transport direction, the medium continues to be fed, the liquid jet head is moved to a retreat position from a liquid jet position, and the intensity of drying processing is suppressed in comparison with that in a liquid-drying processing-performing state in which drying processing is performed on the medium.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid jetting apparatus and a method of coping with the floating of a medium, and more particularly, to a technique for coping with a case in which floating occurs on a medium.

2. Description of the Related Art

In a case in which mediums are successively fed and liquid is successively jetted to the plurality of mediums in a liquid jetting apparatus including liquid jet heads, the floating of a medium may occur. For example, in a case in which the floating of a medium occurs, the medium is in contact with the liquid jetting surface of the liquid jet head. For this reason, the liquid jetting surface of the liquid jet head may be damaged.

A technique for making the liquid jet head retreat to avoid the contact between the liquid jetting surface of the liquid jet head and the medium in a case in which the floating of a medium is detected is known.

JP2007-136726A discloses a liquid jetting apparatus that includes a plurality of liquid jet heads. The liquid jetting apparatus disclosed in JP2007-136726A stops transporting a medium and moves the liquid jet heads in a direction in which the liquid jet heads are away from a transport belt for transporting the medium in a case in which the floating of the medium is detected.

Since the liquid jet heads are moved in the direction in which the liquid jet heads are away from the transport belt for transporting the medium, a collision between the liquid jet heads and the medium is avoided. Further, since the transport of the medium is stopped, the generation of waste sheets is suppressed.

The term of “liquid jet head” in this specification corresponds to the term of “ink jet head” in JP2007-136726A. The term of “liquid jetting apparatus” in this specification corresponds to the term of “ink jet recording apparatus” in JP2007-136726A. The term of “medium” in this specification corresponds to the term of “sheet” in JP2007-136726A. The term of “the floating of a medium” in this specification corresponds to the term of “the floating of a sheet” in JP2007-136726A.

SUMMARY OF THE INVENTION

However, the liquid jetting apparatus disclosed in JP2007-136726A stops transporting a medium in a case in which the floating of the medium is detected. In this case, processing associated with drawing needs to be stopped.

For example, it is necessary to stop feeding a medium to stop transporting a medium. Since some time is taken until the processing associated with drawing is resumed in a case in which processing associated with drawing is stopped as described above, there is a concern that production efficiency may deteriorate.

The invention has been made in consideration of the above-mentioned circumstances, and an object of the invention is to provide a liquid jetting apparatus in which the deterioration of production efficiency is suppressed in a case in which the floating of a medium occurs, and a method of coping with the floating of a medium.

The following aspects of the invention are provided to achieve the object.

A liquid jetting apparatus of a first aspect comprises: a medium feed unit that feeds a medium; a medium transport unit that includes a medium support surface on which the medium fed by the medium feed unit is supported and transports the medium, which is fed by the medium feed unit, in a medium transport direction; a liquid jet head that jets liquid to the medium transported by the medium transport unit; a head moving unit that moves the liquid jet head between a liquid jet position where liquid is jetted to the medium and a retreat position which is more distant from the medium transport unit than the liquid jet position; a liquid-drying processing section that performs drying processing on the medium to which the liquid jetted from the liquid jet head adheres and is disposed at a position on a downstream side of the liquid jet head in the medium transport direction; a medium floating detection unit that is disposed at a position on an upstream side of the liquid jet head in the medium transport direction, and detects a floating of the medium indicating whether or not at least a part of the medium transported by the medium transport unit is away from the medium support surface by a distance equal to or longer than a predetermined distance; a medium feed control unit that allows the medium feed unit to continue to feed the medium in a case in which the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit; a head movement control unit that allows the head moving unit to move the liquid jet head to the retreat position from the liquid jet position in a case in which the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit; and a liquid-drying processing control unit that switches the liquid-drying processing section to a liquid-drying processing-suppression state in which an intensity of drying processing is suppressed in comparison with that in a liquid-drying processing-performing state in which drying processing is performed on the medium, in a case in which the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit.

According to the first aspect, since a medium continues to be fed in a case in which the floating of the medium is detected, a period between the elimination of the floating of the medium and a time when the jet of liquid can be resumed can be made shorter than that in a case in which the feed of a medium is interrupted or stopped at the time of detection of the floating of the medium. As a result, the deterioration of production efficiency can be suppressed.

Further, since the liquid-drying processing section is switched to the liquid-drying processing-suppression state in which the intensity of liquid-drying processing is suppressed in a case in which the floating of a medium is detected, a period between the elimination of the floating of the medium and the resumption of the drying processing of the liquid-drying processing section can be made shorter than that in a case in which the liquid-drying processing section is completely stopped at the time of detection of the floating of the medium. As a result, the deterioration of production efficiency can be suppressed.

It is preferable that the liquid jetting apparatus includes a jetting control unit for controlling the jet of the liquid jet head. The jetting control unit allows the liquid jet head to be in a state in which the liquid jet head can jet liquid in a case in which the liquid jet head is disposed at the liquid jet position, and allows the liquid jet head to be in a state in which the jet of liquid from the liquid jet head is stopped in a case in which the liquid jet head is disposed at the retreat position.

According to a second aspect, the liquid jetting apparatus of the first aspect may further comprise a jetting state detection unit that detects whether or not a state of the liquid jet head is a state in which predetermined jetting quality is obtained, the head movement control unit may allow the head moving unit to move the liquid jet head to the liquid jet position from the retreat position in a case in which an elimination of the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit, and the liquid-drying processing control unit may switch the liquid-drying processing section to the liquid-drying processing-performing state from the liquid-drying processing-suppression state in a case in which the jetting state detection unit determines that the state of the liquid jet head is a state in which predetermined jetting quality is obtained.

According to the second aspect, the jet of liquid is resumed in a case in which it is determined that the state of the liquid jet head is a state in which predetermined jetting quality is obtained. Accordingly, the deterioration of jetting quality, which is caused by an influence in at least one of a case in which the liquid jet head is made to retreat to the retreat position or a case in which the liquid jet head returns to the liquid jet position, can be suppressed.

According to a third aspect, in the liquid jetting apparatus of the second aspect, the jetting state detection unit may include a pressure detection unit that detects internal pressure of the liquid jet head, and the head movement control unit may determine that the state of the liquid jet head is a state in which predetermined jetting quality is obtained in a case in which the elimination of the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit and the internal pressure of the liquid jet head detected by the pressure detection unit is in a predetermined range.

According to the third aspect, the jetting state of the liquid jet head in which the internal pressure of the liquid jet head is used can be detected.

The pressure in a common flow passage, which communicates with a plurality of jetting elements, of the internal flow passage of the liquid jet head can be applied as the internal pressure of the liquid jet head.

According to a fourth aspect, the liquid jetting apparatus of any one of the first to third aspects may further comprise: a treatment liquid-application section that applies treatment liquid, which aggregates or insolubilizes the liquid jetted to the medium, to the medium and is disposed at a position on an upstream side of the liquid jet head in the medium transport direction; and a treatment liquid-application control unit that controls an operation of the treatment liquid-application section and performs switching between a treatment liquid-application processable state which is a state in which the treatment liquid is capable of being applied to the medium from the treatment liquid-application section and a treatment liquid-application standby-fixed state in which the treatment liquid-application section is fixed in a treatment liquid-application standby state which is a state in which the treatment liquid is not applied to the medium from the treatment liquid-application section. The treatment liquid-application control unit may switch the treatment liquid-application section to the treatment liquid-application standby-fixed state from the treatment liquid-application processable state in a case in which the floating of the medium is detected by the medium floating detection unit.

According to the fourth aspect, in an aspect in which the treatment liquid-application section for applying treatment liquid, which aggregates or insolubilizes the liquid jetted to the medium, to the medium is provided, a period between the elimination of the floating of the medium and a time when the jet of liquid can be resumed can be made shorter than that in a case in which the treatment liquid-application section is stopped. As a result, the deterioration of production efficiency is suppressed.

According to a fifth aspect, in the liquid jetting apparatus of the fourth aspect, the treatment liquid-application section may include an application member that is in contact with the medium to apply the treatment liquid to the medium. In a case in which the treatment liquid-application section is in the treatment liquid-application processable state, the treatment liquid-application control unit may move the application member from a standby position, which is distant from a treatment liquid-application position where the application member and the medium are in contact with each other, to the treatment liquid-application position at a timing when the medium enters a treatment liquid-application region of the treatment liquid-application section and may move the application member to the standby position from the treatment liquid-application position at a timing when the medium gets out of the treatment liquid-application region of the treatment liquid-application section.

According to the fifth aspect, in the treatment liquid-application section that makes the application member be in contact with the medium in a case in which treatment liquid is to be applied to the medium and that makes the application member not be in contact with the medium in a case in which treatment liquid is not to be applied to the medium, the treatment liquid-application device can be switched to the treatment liquid-application standby-fixed state from the treatment liquid-application processable state in a case in which the floating of the medium is detected.

According to a sixth aspect, in the liquid jetting apparatus of the fifth aspect, the treatment liquid-application control unit may switch the treatment liquid-application section to the treatment liquid-application processable state from the treatment liquid-application standby-fixed state in a case in which an elimination of the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit.

According to the sixth aspect, in the treatment liquid-application section that makes the application member be in contact with the medium in a case in which treatment liquid is to be applied to the medium and that makes the application member not be in contact with the medium in a case in which treatment liquid is not to be applied to the medium, the treatment liquid-application device can be switched to the treatment liquid-application processable state from the treatment liquid-application standby-fixed state in a case in which the floating of the medium is detected.

According to a seventh aspect, the liquid jetting apparatus of any one of the fourth to sixth aspects may further include a treatment liquid-drying processing section and a treatment liquid-drying processing control unit. The treatment liquid-drying processing section may perform drying processing on the medium to which the treatment liquid is applied by the treatment liquid-application section. The treatment liquid-drying processing section may be disposed at a position on a downstream side of the treatment liquid-application section in the medium transport direction and on an upstream side of the liquid jet head in the medium transport direction. The treatment liquid-drying processing control unit may switch the treatment liquid-drying processing section to a treatment liquid-drying processing-suppression state in which an intensity of drying processing is suppressed in comparison with that in a treatment liquid-drying processing-performing state in which drying processing is performed on the medium, in a case in which the floating of the medium transported by the medium transport unit is detected by the medium floating detection unit.

According to the seventh aspect, in an aspect in which the treatment liquid-drying processing section for drying the treatment liquid applied to the medium is provided, a period between the elimination of the floating of the medium and a time when the jet of liquid can be resumed can be made shorter than that in a case in which the treatment liquid-drying processing section is stopped. As a result, the deterioration of production efficiency is suppressed.

According to an eighth aspect, the liquid jetting apparatus of the seventh aspect may further comprise a jetting state detection unit that detects whether or not a state of the liquid jet head is a state in which predetermined jetting quality is obtained, and the treatment liquid-drying processing control unit may switch the treatment liquid-drying processing section to the treatment liquid-drying processing-performing state from the treatment liquid-drying processing-suppression state in a case in which the jetting state detection unit determines that the state of the liquid jet head is a state in which predetermined jetting quality is obtained.

According to the eighth aspect, in an aspect in which the treatment liquid-drying processing section for drying the treatment liquid applied to the medium is provided, the treatment liquid-drying processing section can be switched to the treatment liquid-drying processing-performing state from the treatment liquid-drying processing-suppression state in a case in which it is determined that the state of the liquid jet head is a state in which predetermined jetting quality is obtained.

According to a ninth aspect, in the liquid jetting apparatus of any one of the first to eighth aspects, the liquid-drying processing section may include a heater radiating heat, and the liquid-drying processing control unit may suppress radiant energy of heat radiated from the heater in comparison with radiant energy of heat, which is radiated from the heater in the liquid-drying processing-performing state, at a timing when the liquid-drying processing control unit switches the liquid-drying processing section to the liquid-drying processing-suppression state.

According to the ninth aspect, since the radiant energy of heat radiated from the heater is suppressed, the liquid-drying processing-suppression state can be realized.

According to a tenth aspect, in the liquid jetting apparatus of any one of the first to ninth aspects, the liquid-drying processing section may include a fan that generates wind, and the liquid-drying processing control unit may suppress a flow rate of air sent from the fan in comparison with a flow rate of air, which is sent from the fan in the liquid-drying processing-performing state, at a timing when the liquid-drying processing control unit switches the liquid-drying processing section to the liquid-drying processing-suppression state.

According to the tenth aspect, since the flow rate of air sent from the fan is suppressed, the liquid-drying processing-suppression state can be realized.

According to an eleventh aspect, in the liquid jetting apparatus of any one of the first to tenth aspects, the liquid jet head may be an ink jet head that jets ink to a medium.

According to the eleventh aspect, in an aspect in which an ink jet head is provided as the liquid jet head, the same effects as the first aspect can be obtained.

According to a twelfth aspect, the liquid jetting apparatus of any one of the first to eleventh aspects may further comprise a waste sheet-number setting unit that sets the number of mediums passing through a liquid jet region of the liquid jet head in a head retreat period between a timing when the liquid jet head is moved to the retreat position from the liquid jet position by the head moving unit and a timing when the liquid jet head is moved to the liquid jet position from the retreat position by the head moving unit, by using the head retreat period, a feed timing of the medium fed by the medium feed unit, and a transport speed of the medium transported by the medium transport unit. The liquid-drying processing control unit may switch the liquid-drying processing section to the liquid-drying processing-suppression state in a period in which mediums of which the number is set by the waste sheet-number setting unit from mediums detected by the medium floating detection unit pass through a drying processing region of the liquid-drying processing section.

According to the twelfth aspect, since the number of waste sheets passing through the jet region of the liquid jet head is set in the head retreat period, the liquid-drying processing section can be switched to the liquid-drying processing-suppression state and the liquid-drying processing-performing state on the basis of the number of waste sheets.

A method of coping with floating of a medium according to a thirteenth aspect comprises: a medium feeding step of feeding a medium; a liquid jetting step of jetting liquid to the medium, which is fed in the medium feeding step and is transported by a medium transport unit, by a liquid jet head, the medium transport unit including a medium support surface on which the medium fed in the medium feeding step is supported and transporting the medium in a medium transport direction; a liquid-drying processing step of performing drying processing on the medium, to which the liquid jetted from the liquid jet head adheres, at a position on a downstream side of the liquid jet head in the medium transport direction; a medium floating detection step of detecting a floating of the medium, which indicates whether or not at least a part of the medium transported by the medium transport unit is away from the medium support surface by a distance equal to or longer than a predetermined distance, at a position on an upstream side of the liquid jet head in the medium transport direction; and a head moving step of moving the liquid jet head between a liquid jet position where the liquid is jetted to the medium and a retreat position that is more distant from the medium transport unit than the liquid jet position. In a case in which the floating of the medium transported by the medium transport unit is detected in the medium floating detection step, the medium continues to be fed in the medium feeding step, the head moving step is performed to move the liquid jet head to the retreat position from the liquid jet position, and a state is switched to a liquid-drying processing-suppression state in which an intensity of drying processing is suppressed in comparison with that in a liquid-drying processing-performing state in which drying processing is performed on the medium in the liquid-drying processing step.

According to the thirteenth aspect, the same effects as the first aspect can be obtained.

In the thirteenth aspect, the same items as the items specified in the second to twelfth aspects can be appropriately combined. In this case, components taking on the processing or functions specified in the liquid jetting apparatus can be grasped as components, which take on processing or functions corresponding to the above-mentioned processing or functions, of the method of coping with the floating of a medium.

According to the invention, since a medium continues to be fed in a case in which the floating of a medium is detected, a period between the elimination of the floating of the medium and a time when the jet of liquid can be resumed can be made shorter than that in a case in which the feed of a medium is interrupted or stopped at the time of detection of the floating of the medium. As a result, the deterioration of production efficiency can be suppressed.

Further, since a liquid-drying processing section is switched to a liquid-drying processing-suppression state in which the intensity of liquid-drying processing is suppressed in a case in which the floating of a medium is detected, a period between the elimination of the floating of the medium and the resumption of the drying processing of the liquid-drying processing section can be made shorter than that in a case in which the liquid-drying processing section is completely stopped at the time of detection of the floating of the medium. As a result, the deterioration of production efficiency can be suppressed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Description of Ink Jet Recording Apparatus]

FIG. 1is a diagram showing the schematic configuration of the entire ink jet recording apparatus. The ink jet recording apparatus10shown inFIG. 1is an image forming apparatus that applies an ink jet system to perform drawing on a sheet-like medium.

The sheet-like medium is a material on which drawing can be performed or a pattern can be formed using an ink jet system, such as paper, a sheet-like fiber, a sheet-like metal material, or a sheet-like resin material. Hereinafter, the term of “medium” can be substituted with the term of “sheet”. Further, the term of “image forming” can be substituted with the term of “drawing”.

The ink jet recording apparatus10shown inFIG. 1includes a sheet feed unit12, a treatment liquid-application section14, a treatment liquid-drying processing section16, a drawing unit18, an ink-drying processing section20, and a sheet discharge unit24. The sheet feed unit12, the treatment liquid-application section14, the treatment liquid-drying processing section16, the drawing unit18, the ink-drying processing section20, and the sheet discharge unit24are arranged along a sheet transport direction, which is the transport direction of a sheet36, in the order of the sheet feed unit12, the treatment liquid-application section14, the treatment liquid-drying processing section16, the drawing unit18, the ink-drying processing section20, and the sheet discharge unit24.

The structure of each section of the ink jet recording apparatus10will be described in detail below. The ink jet recording apparatus10shown inFIG. 1is one aspect of a liquid jetting apparatus. Ink is one aspect of liquid.

The sheet feed unit12shown inFIG. 1includes a stocker30, a sheet feed sensor32, and a feeder board34. Sheets36are stored in the stocker30. The sheet feed sensor32detects the sheet36taken out from the stocker30.

An optical sensor can be applied as the sheet feed sensor32, and examples of the optical sensor include a light projection type passage sensor that includes a light projecting part and a light receiving part. Information on a sheet36, which is acquired using the sheet feed sensor32, can be used for the measurement of the number of sheets36that are fed from the sheet feed unit12.

Further, in a case in which a plurality of sheets36are successively fed, information on a sheet36, which is acquired using the sheet feed sensor32, can be applied to the detection of the feed timing of each sheet36. The feed timing of the sheet36is one aspect of the feed timing of a medium.

The feeder board34corrects the posture of a sheet36that is taken out from the stocker30. The sheet36of which the posture is corrected by the feeder board34is delivered to the treatment liquid-application section14. An arrow line, which is shown above the feeder board34, indicates the sheet transport direction on the feeder board34.

A sheet36is one aspect of a medium. A sheet, which uses a material other than paper, such as sheet-like metal or a sheet-like resin, may be applied instead of a sheet36. The medium is a concept that includes a base material or a substrate. The sheet feed unit12is one aspect of a medium feed unit.

The treatment liquid-application section14shown inFIG. 1includes a treatment liquid drum42and a treatment liquid-application device44. The treatment liquid drum42has a columnar shape. The treatment liquid drum42is supported so as to be rotatable about a columnar central shaft as a rotating shaft42A.

The entire length of the treatment liquid drum42in a direction parallel to the rotating shaft42A corresponds to the maximum width of a sheet36having the maximum size. The width of a sheet36is the length of the sheet36in a direction orthogonal to the sheet transport direction. A direction parallel to the rotating shaft42A of the treatment liquid drum42inFIG. 1is a direction perpendicular to the plane ofFIG. 1.

The term of “orthogonal” or “perpendicular” in this specification includes “substantially orthogonal” or “substantially perpendicular” where the same effects as the effects, which are obtained in a case in which two directions cross each other at an angle of 90°, are obtained in a case in which two directions cross each other at an angle exceeding 90° or a case in which two directions cross each other at an angle less than 90°.

Further, the term of “parallel” in this specification includes “substantially parallel” where two directions are not parallel to each other but the same effects as the effects, which are obtained in a case in which the two directions are parallel to each other, are obtained. Furthermore, the term of “the same” in this specification includes “substantially the same” where components are different from each other but the same effects as the effects, which are obtained in a case in which the components are the same, are obtained.

The treatment liquid drum42includes a gripper (not shown). The gripper includes a plurality of claws that are arranged along the direction parallel to the rotating shaft42A of the treatment liquid drum42. The plurality of claws grips the front end portion of a sheet36. The sheet36of which the front end portion is gripped by the gripper is supported on an outer peripheral surface42B of the treatment liquid drum42. The sheet36, which is supported on the outer peripheral surface42B of the treatment liquid drum42, is not shown.

In a case in which the treatment liquid drum42is rotated while supporting the sheet36on the outer peripheral surface42B, the treatment liquid drum42transports the sheet36along the outer peripheral surface42B. An arrow line, which is shown in the treatment liquid drum42, indicates the sheet transport direction in the treatment liquid-application section14. The treatment liquid drum42is one aspect of a medium transport unit. The outer peripheral surface42B of the treatment liquid drum42is a component of a medium support surface on which a medium is supported.

The treatment liquid-application device44includes an application roller44A, a measurement roller44B, and a treatment liquid container44C. The application roller44A is in contact with the sheet36, which is transported by the treatment liquid drum42, and applies treatment liquid, which is retained on the outer peripheral surface42B of the treatment liquid drum42, to the sheet36.

The measurement roller44B draws up treatment liquid, which is stored in the treatment liquid container44C and aggregates or insolubilizes ink, by a predetermined volume, and supplies the treatment liquid to the application roller44A. The sheet36to which the treatment liquid is applied by the treatment liquid-application section14, is delivered to the treatment liquid-drying processing section16.

The treatment liquid-application device44shown inFIG. 1performs an operation for applying treatment liquid during a period in which the sheet36passes through a processing region. Further, during a period in which the sheet36does not pass through the processing region, the treatment liquid-application device44is in a standby state without performing an operation for applying treatment liquid. The details of the operation of the treatment liquid-application device44will be described later.

The application roller is one aspect of an application member. A structure, which includes an application roller and a measurement roller, is one aspect of an application member.

The treatment liquid-drying processing section16shown inFIG. 1includes a treatment liquid-drying processing drum46, transport guides48, and a treatment liquid-drying processing device50. The treatment liquid-drying processing drum46has a columnar shape. The treatment liquid-drying processing drum46is supported so as to be rotatable about a columnar central shaft as a rotating shaft46A. A direction parallel to the rotating shaft46A of the treatment liquid-drying processing drum46inFIG. 1is a direction perpendicular to the plane ofFIG. 1.

The treatment liquid-drying processing drum46includes a gripper that has the same structure as the gripper of the treatment liquid drum42. The gripper of the treatment liquid-drying processing drum46is not shown. The gripper of the treatment liquid-drying processing drum46grips the front end portion of the sheet36.

In a case in which the treatment liquid-drying processing drum46is rotated while gripping the front end portion of the sheet36by the gripper, the treatment liquid-drying processing drum46transports the sheet36along an outer peripheral surface46B thereof. An arrow line, which is shown in the treatment liquid-drying processing drum46, indicates the sheet transport direction in the treatment liquid-drying processing section16.

The sheet36, which is transported by the treatment liquid-drying processing drum46, passes under the treatment liquid-drying processing drum46.

The transport guides48are disposed on the lower side of the treatment liquid-drying processing drum46. The transport guides48support the sheet36that passes under the treatment liquid-drying processing drum46. The term of “lower” in this specification indicates the direction of gravity. Further, the term of “upper” indicates a direction opposite to the direction of gravity.

The treatment liquid-drying processing drum46and the transport guides48are components of the medium transport unit. The transport guides48are components of the medium support surface on which a medium is supported.

The treatment liquid-drying processing device50is disposed in the treatment liquid-drying processing drum46. The treatment liquid-drying processing device50performs processing for drying treatment liquid on the sheet36that passes under the treatment liquid-drying processing drum46and that is supported by the transport guides48.

As in the case of the ink-drying processing section20, the treatment liquid-drying processing section16can be switched to a treatment liquid-drying processing-performing state and a treatment liquid-drying processing-suppression state.

The sheet36, which has passed through the processing region of the treatment liquid-drying processing device50, is delivered to the drawing unit18. The sheet36, which has been subjected to the processing for drying treatment liquid by the treatment liquid-drying processing device50, is not shown inFIG. 1.

The drawing unit18shown inFIG. 1includes a drawing drum52. The drawing drum52has a columnar shape. The drawing drum52is supported so as to be rotatable about a columnar central shaft as a rotating shaft52A. A direction parallel to the rotating shaft52A of the drawing drum52inFIG. 1is a direction perpendicular to the plane ofFIG. 1.

The drawing drum52includes a plurality of suction holes on an outer peripheral surface52B thereof. The plurality of suction holes are connected to a suction flow passage formed in the drawing drum52. The suction flow passage formed in the drawing drum52is not shown. The outer peripheral surface52B of the drawing drum52is a component of the medium support surface on which a medium is supported.

The suction flow passage formed in the drawing drum52is connected to a suction pressure generating device (not shown) through a pipe (not shown). In a case in which the suction pressure generating device is operated, the drawing drum52can generate suction pressure in the plurality of suction holes provided on the outer peripheral surface52B.

The drawing drum52includes a gripper (not shown). Since the structure of the gripper of the drawing drum52is the same as the structure of the gripper of the treatment liquid drum42and the structure of the gripper of the treatment liquid-drying processing drum46, the description thereof will be omitted.

The gripper of the drawing drum52is disposed in a recessed portion that is formed on the outer peripheral surface52B of the drawing drum52. The recessed portion formed on the outer peripheral surface52B of the drawing drum52is not shown.

Suction pressure, which is generated in the plurality of suction holes provided on the outer peripheral surface52B of the drawing drum52, acts on the sheet36of which the front end portion is gripped by the gripper of the drawing drum52, so that the sheet36is closely attached to the outer peripheral surface52B of the drawing drum52. The sheet36, which is closely attached to the outer peripheral surface52B of the drawing drum52, is not shown inFIG. 1.

In a case in which the drawing drum52is rotated while the sheet36is closely attached to the outer peripheral surface52B, the drawing drum52transports the sheet36along the outer peripheral surface52B. An arrow line, which is shown in the drawing drum52, indicates the sheet transport direction in the drawing unit18. The drawing drum52is a component of the medium transport unit.

The drawing unit18shown inFIG. 1includes a sheet floating sensor55. The sheet floating sensor55detects the floating of a sheet36that is delivered to the drawing unit18. The floating of a sheet36includes a state in which at least a part of the sheet36is away from a sheet support surface, which is the outer peripheral surface52B of the drawing unit18, by a distance equal to or larger than a predetermined distance due to the bending of a corner portion of the sheet36, the curvature of the sheet36, or the like.

The sheet floating sensor55is disposed at a position on the upstream side of a liquid jet head56C that is disposed at the most upstream position in the drawing unit18in the sheet transport direction. The sheet floating sensor55detects the floating of a sheet36that does not yet enter the liquid jet region of the liquid jet head56C.

The drawing unit18shown inFIG. 1includes a liquid jet head56C, a liquid jet head56M, a liquid jet head56Y, and a liquid jet head56K. Each of the liquid jet heads56C,56M,56Y, and56K includes nozzle portions that jet liquid.

The nozzle portion is not shown inFIG. 1. The nozzle portion is denoted inFIG. 5by reference numeral281.

Here, an alphabet, which is added to the reference numeral of the liquid jet head, represents a color. C represents cyan. M represents magenta. Y represents yellow. K represents black.

The liquid jet heads56C,56M,56Y, and56K are arranged above the drawing drum52. The liquid jet heads56C,56M,56Y, and56K are arranged along the sheet transport direction from the upstream side in the sheet transport direction in the order of the liquid jet heads56C,56M,56Y, and56K.

An ink jet head may be applied as each of the liquid jet heads56C,56M,56Y, and56K. The liquid jet heads56C,56M,56Y, and56K jet liquid to one surface of the sheet36that is transported by the drawing drum52. Jetted liquid is applied to one surface of the sheet36, so that drawing is realized. One surface of the sheet36is the surface of the sheet36that is opposite to the surface of the sheet36supported by the drawing drum52.

The liquid jet heads56C,56M,56Y, and56K are mounted on head moving units. The head moving units are not shown inFIG. 1. The head moving unit is denoted inFIG. 7by reference numeral400. The detail of the head moving unit will be described later.

The drawing unit18shown inFIG. 1includes an in-line sensor58. The in-line sensor58is disposed at a position on the downstream side of the liquid jet head56K that is disposed at the most downstream position in the sheet transport direction. The in-line sensor58includes an imaging element, a peripheral circuit of the imaging element, and a light source.

A solid-state imaging element, such as a CCD image sensor or a CMOS image sensor, can be applied as the imaging element. The imaging element, the peripheral circuit of the imaging element, and the light source are not shown. CCD is an abbreviation for Charge Coupled Device. CMOS is an abbreviation for Complementary Metal-Oxide Semiconductor.

The peripheral circuit of the imaging element includes a processing circuit for an output signal of the imaging element. Examples of the processing circuit include a filter circuit that removes noise components from the output signal of the imaging element, an amplifier circuit, a waveform shaping circuit, and the like. The filter circuit, the amplifier circuit, or the waveform shaping circuit is not shown.

The light source is disposed at a position where the light source can irradiate an object, which is to be read by the in-line sensor, with illumination light. An LED, a lamp, or the like can be applied as the light source. LED is an abbreviation for light emitting diode.

An imaging signal, which is output from the in-line sensor58, is sent to a system controller100shown inFIG. 8. An imaging signal, which is output from the in-line sensor58, can be used for the detection of abnormalities of the liquid jet heads56C,56M,56Y, and56K, the detection of density unevenness, and the like. The sheet36subjected to drawing in the drawing unit18is delivered to the ink-drying processing section20. The sheet36subjected to drawing in the drawing unit18is not shown.

The ink-drying processing section20shown inFIG. 1includes a drying processing device21and a sheet transport member22. The drying processing device21is disposed above the sheet transport member22that transports a sheet in the ink-drying processing section20.

The drying processing device21performs drying processing on the sheet36to which ink is made to adhere by the drawing unit18and which is transported by the sheet transport member22. A heater that radiates heat or a fan that generates wind can be applied as the drying processing device21. The drying processing device21may include both a heater and a fan. An infrared heater, an ultraviolet lamp, or the like can be applied as the heater.

The sheet transport member22transports the sheet36in the ink-drying processing section20. A chain transport, a belt transport, a roller transport, or the like can be applied as the sheet transport member22. The sheet transport member22is a component of the medium transport unit. The sheet36, which has been subjected to drying processing by the drying processing device21, is delivered to the sheet discharge unit24.

The drying processing device21can be switched to an ink-drying processing-performing state that is a state in which processing for drying ink is performed and an ink-drying processing-suppression state that is a state in which substantive processing for drying ink is not performed.

The ink-drying processing-performing state is a state in which drying processing is performed under a set drying processing condition. The ink-drying processing-suppression state is a state in which at least one of setting the temperature of the heater, setting the temperature of dry gas, or setting the flow rate of dry gas is lowered in the ink-drying processing-performing state.

Examples of the drying processing-suppression state include the turn-off of the heater of the drying processing device21and the turn-off of the fan. Further, other examples of the drying processing-suppression state include blocking that is performed between the drying processing device21and a sheet36by a blocking member, such as a shutter.

In other words, the drying processing device21, which is in the ink-drying processing-suppression state, is in an unstopped state in which a system is activated. Examples of a state in which the system is activated include a state in which a control section for controlling the drying processing device21is activated. The control section for controlling the drying processing device21is shown inFIG. 8as an ink-drying processing control unit122.

Furthermore, the drying processing device21, which is in the ink-drying processing-suppression state, is in a state in which the intensity of the drying processing is made lower than that in the ink-drying processing-performing state in which the drying processing is performed on the sheet36. The state in which the intensity of drying processing is made lower is a heat-remaining state in which the radiant energy of heat radiated from the heater is reduced or a state in which the flow rate of air sent from the fan is reduced.

Moreover, the drying processing device21, which is in the ink-drying processing-suppression state, is in a state in which substantive drying processing is not performed. The sheet36having passed through the processing region of the drying processing device21, which is in the ink-drying processing-suppression state, is not subjected to substantive drying processing as in the case in which drying processing is not performed.

The sheet36having passed through the processing region of the ink-drying processing section20is transported to the sheet discharge unit24. The sheet36, which is subjected to the processing for drying ink by the ink-drying processing section20, is not shown inFIG. 1. The ink-drying processing section is one aspect of a liquid-drying processing section. The ink-drying processing-performing state is one aspect of a liquid-drying processing-performing state. The ink-drying processing-suppression state is one aspect of a liquid-drying processing-suppression state.

The sheet36, which has been subjected to drying processing by the ink-drying processing section20, is stored in the sheet discharge unit24shown inFIG. 1. The sheet discharge unit24classifies a sheet36that has been subjected to normal drawing and a sheet36that is a waste sheet.

Here, the waste sheet includes a sheet36that is determined as a sheet of which the floating occurs. Further, the waste sheet may include a sheet36that is fed subsequently to a sheet36determined as a sheet of which the floating occurs and that is not subjected to normal processing in any one of the treatment liquid-application section14, the treatment liquid-drying processing section16, the drawing unit18, and the ink-drying processing section20.

An aspect in which a sorting device is provided may be provided as an example in which a sheet36subjected to normal drawing and a sheet36determined as a waste sheet are classified. In the aspect in which a sorting device is provided, a sheet36subjected to normal drawing and a waste sheet are stored at separate sheet discharge positions.

Further, an aspect in which a tape inserter for inserting a tape into a sheet36determined as a waste sheet is provided may be provided as another example. A sheet36into which a tape is inserted is removed in the aspect in which a tape inserter is provided. The removal of a sheet36into which a tape is inserted may be automatically performed and may be manually performed.

The ink jet recording apparatus10, which includes the treatment liquid-application section14and the treatment liquid-drying processing section16, is shown inFIG. 1, but the treatment liquid-application section14and the treatment liquid-drying processing section16may be omitted.

Further, inFIG. 1, a structure, such as a structure for transporting a sheet by a belt or a structure for transporting a sheet by a transport drum, may be applied as a structure that transports a sheet36subjected to drawing.

[Structure of Liquid Jet Head]

Next, the structures of the liquid jet heads shown inFIG. 1will be described in detail.

FIG. 2is a perspective plan view of the liquid jetting surface of the liquid jet head. The same structure can be applied to the liquid jet head56C for jetting a cyan ink, the liquid jet head56M for jetting a magenta ink, the liquid jet head56Y for jetting a yellow ink, and the liquid jet head56K for jetting a black ink that are shown inFIG. 1.

In a case in which the liquid jet heads56C,56M,56Y, and56K do not need to be distinguished from each other, the liquid jet heads are denoted by reference numeral56.

As shown inFIG. 2, the liquid jet head56is a line type head. The line type head has a structure in which a plurality of nozzle portions are arranged over a length exceeding the entire width Lmaxof the sheet36in a direction orthogonal to the sheet transport direction. The nozzle portions are not shown inFIG. 2. The nozzle portions are denoted inFIG. 5by reference numeral281.

A direction, which is denoted inFIG. 2by reference letter X, is a direction orthogonal to the sheet transport direction. A direction, which is denoted inFIG. 2by reference letter Y, is the sheet transport direction. Hereinafter, the direction orthogonal to the sheet transport direction may be referred to as a sheet width direction or an X direction. Further, the sheet transport direction may be referred to as a Y direction. The sheet transport direction corresponds to the medium transport direction.

The liquid jet head56shown inFIG. 2includes a plurality of head modules200. The plurality of head modules200are arranged in a line along the sheet width direction.

The same structure may be applied to the plurality of head modules200. Further, the head module200may have a structure that can function alone as a liquid jet head.

The liquid jet head56in which the plurality of head modules200are arranged in a line along the sheet width direction is shown inFIG. 2, but the plurality of head modules200may be arranged in two lines so that the phases of the head modules200are shifted from each other in the sheet transport direction.

A plurality of nozzle openings are arranged on liquid jetting surfaces277of the head modules200of the liquid jet head56. The nozzle openings are not shown inFIG. 2. The nozzle openings are shown inFIG. 4and denoted by reference numeral280.

The full-line type liquid jet head56is exemplified in this embodiment, but a serial system may be applied. In the serial system, a short serial type liquid jet head shorter than the entire width Lmaxof a sheet36is moved in the sheet width direction to perform drawing corresponding to one time in the sheet width direction, the sheet36is transported in the sheet transport direction by a certain distance so that drawing in the sheet width direction is formed in the next region in a case in which the drawing corresponding to one time in the sheet width direction is completed, and this operation is repeated so that drawing is performed on the entire surface of the sheet.

<Example of Structure of Head Module>

Next, the head module will be described in detail.

FIG. 3is a perspective view of the head module including a partial cross-sectional view.FIG. 4is a plan perspective view of the liquid jetting surface of the head module.

As shown inFIG. 3, the head module200includes an ink supply unit. The ink supply unit includes an ink supply chamber232and an ink circulation chamber236.

The ink supply chamber232and the ink circulation chamber236are disposed on the side opposite to a liquid jetting surface277of a nozzle plate275. The ink supply chamber232is connected to an ink tank (not shown) through a supply-side individual flow passage252. The ink circulation chamber236is connected to a collection tank (not shown) through a collection-side individual flow passage256.

Only some of the nozzle openings280are shown inFIG. 4. A plurality of nozzle openings280are two-dimensionally arranged on the liquid jetting surface277of the nozzle plate275of one head module200.

That is, the head module200has the planar shape of a parallelogram that has a long-side end face extending in a V direction having an inclination of an angle β with respect to the X direction and a short-side end face extending in a W direction having an inclination of an angle α with respect to the Y direction, and the plurality of nozzle openings280are arranged in the form of a matrix in a row direction parallel to the V direction and a column direction parallel to the W direction.

The arrangement of the nozzle openings280is not limited to the aspect shown inFIG. 4, and the plurality of nozzle openings280may be arranged in a row direction parallel to the X direction and a column direction obliquely crossing the X direction.

Here, the matrix arrangement of the nozzle openings280is the arrangement of the nozzle openings280where the intervals between the nozzle openings280are uniform in an X-direction projection nozzle array280A in which the plurality of nozzle openings280are arranged along the X direction in a case in which the plurality of nozzle openings280are projected to the X direction.

In the liquid jet head56shown in this embodiment, nozzle openings280belonging to one head module200and nozzle openings280belonging to the other head module200are mixed at a connecting portion between the adjacent head modules200in the X-direction projection nozzle array.

In a case in which there is no error in the mounting position of each head module200, the nozzle openings280, which belong to one head module200, and the nozzle openings280, which belong to the other head module200, of a connecting region are arranged at the same positions. Accordingly, the arrangement of the nozzle openings280is uniform even in the connecting region.

In the following description, it is assumed that the head modules200of the liquid jet head56are mounted with no error in the mounting positions thereof.

<Internal Structure of Head Module>

FIG. 5is a cross-sectional view showing the internal structure of the head module. The head module200includes an ink supply passage214, individual supply passages216, pressure chambers218, nozzle communication passages220, individual circulation flow passages226, a common circulation flow passage228, piezoelectric elements230, and a vibrating plate266.

The ink supply passage214, the individual supply passages216, the pressure chambers218, the nozzle communication passages220, the individual circulation flow passages226, and the common circulation flow passage228are formed in a flow passage structure210. The nozzle portion281may include the nozzle opening280and the nozzle communication passage220.

The individual supply passage216is a flow passage that connects the pressure chamber218to the ink supply passage214. The nozzle communication passage220is a flow passage that connects the pressure chamber218to the nozzle opening280. The individual circulation flow passage226is a flow passage that connects the nozzle communication passage220to the common circulation flow passage228.

The vibrating plate266is provided on the flow passage structure210. The piezoelectric elements230are disposed on the vibrating plate266with an adhesive layer267therebetween. The piezoelectric element230has a structure in which a lower electrode265, a piezoelectric layer231, and an upper electrode264are laminated. The lower electrode265is called a common electrode, and the upper electrode264is called an individual electrode.

The upper electrode264is formed of an individual electrode that is patterned so as to correspond to the shape of each pressure chamber218, and the piezoelectric element230is provided for each pressure chamber218.

The ink supply passage214is connected to the ink supply chamber232described inFIG. 3. Ink is supplied to the pressure chamber218from the ink supply passage214through the individual supply passage216. In a case in which a drive voltage is applied to the upper electrode264of the piezoelectric element230to be operated according to image data, the piezoelectric element230and the vibrating plate266are deformed and the volume of the pressure chamber218is changed.

The head module200can jet ink droplets from the nozzle openings280through the nozzle communication passages220due to a change in pressure that is caused by a change in the volume of the pressure chamber218.

In a case in which the drive of the piezoelectric elements230corresponding to the respective nozzle openings280is controlled according to dot data that is generated from the image data, the head module200can jet ink droplets from the nozzle openings280.

In a case in which jetting timings of ink droplets from the respective nozzle openings280shown inFIG. 4are controlled according to the transport speed of a sheet36while the sheet36shown inFIG. 2is transported in the sheet transport direction at a certain speed, a desired image is formed on the sheet36.

Although not shown, the planar shape of the pressure chamber218provided so as to correspond to each nozzle opening280is a substantially square shape, an outlet, which is to be connected to the nozzle opening280, is provided at one corner portion of both corner portions positioned on a diagonal line, and the individual supply passage216, which is an inlet for ink to be supplied, is provided at the other corner portion thereof.

The shape of the pressure chamber is not limited to a square shape. The planar shape of the pressure chamber may be various shapes, such as a quadrangular shape (a rhombic shape, a rectangular shape, and the like), a pentagonal shape, a hexagonal shape, other polygonal shapes, a circular shape, an elliptical shape, and the like.

A circulation outlet (not shown) is formed at the nozzle portion281that includes the nozzle opening280and the nozzle communication passages220. The nozzle portion281communicates with the individual circulation flow passage226through the circulation outlet. Ink, which is not used for jetting, of ink of the nozzle portion281is collected to the common circulation flow passage228through the individual circulation flow passage226.

The common circulation flow passage228is connected to the ink circulation chamber236described inFIG. 4. Since ink is normally collected to the common circulation flow passage228through the individual circulation flow passage226, the thickening of ink of the nozzle portion during a period in which ink is not jetted is prevented.

The piezoelectric element230having a structure individually separated so as to correspond to each nozzle portion281is exemplified inFIG. 5as an example of a piezoelectric element. Of course, a structure in which the piezoelectric layer231is integrally formed so as to correspond to the plurality of nozzle portions281, the individual electrode is formed so as to correspond to each nozzle portion281, and an active region is formed for each nozzle portion281may be applied.

The head module200may include a heater, which is provided in the pressure chamber218, as a pressure generating element instead of the piezoelectric element. A thermal system, which supplies a drive voltage to the heater to allow the heater to generate heat and uses a film boiling phenomenon to jet ink present in the pressure chamber218from the nozzle opening280, may be applied to the head module200.

<Description of Ink Supply Section>

FIG. 6is a block diagram showing the configuration of an internal flow passage of the liquid jet head and the configuration of an ink supply system. An ink supply section127shown inFIG. 8includes the internal flow passage of the liquid jet head and the ink supply system shown inFIG. 6.

As shown inFIG. 6, the liquid jet head56includes the plurality of head modules200. Some head modules200of the plurality of head modules200are not shown inFIG. 6.

The supply-side individual flow passage252of each head module200is connected to a supply-side manifold308through a supply-side damper304and a supply-side valve306. Likewise, the collection-side individual flow passage256of each head module200is connected to a collection-side manifold318through a collection-side damper314and a collection-side valve316.

For the convenience of illustration, inFIG. 6, reference numerals are given to only one of the supply-side individual flow passages252, only one of the supply-side dampers304, only one of the supply-side valves306, the supply-side manifold308, only one of the collection-side individual flow passages256, only one of the collection-side dampers314, only one of the collection-side valves316, and the collection-side manifold318.

The supply-side manifold308is a flow passage structure in which ink to be supplied to the head modules200is temporarily stored and which is common to the plurality of head modules200in the liquid jet head56.

The collection-side manifold318is a flow passage structure in which ink to be collected from the head modules200is temporarily stored and which is common to the plurality of head modules200in the liquid jet head56.

A supply-side pressure sensor320is mounted on the supply-side manifold308as means for measuring the pressure of liquid that is stored in the supply-side manifold308. A collection-side pressure sensor322is mounted on the collection-side manifold318as means for measuring the pressure of liquid that is stored in the collection-side manifold318.

The collection-side manifold318is connected to the supply-side manifold308through a first bypass flow passage valve330and a first bypass flow passage332. The supply-side manifold308is connected to the collection-side manifold318through a second bypass flow passage valve334and a second bypass flow passage336.

The supply-side manifold308is connected to a supply back pressure tank342through a supply-side flow passage340. The detailed structure of the supply back pressure tank342is not shown. Examples of structure of the supply back pressure tank342include a sealed structure of which an internal space is partitioned into a gas chamber and a liquid chamber by an elastic film.

The gas chamber of the supply back pressure tank342may be connected to an air tank through a valve and a flow passage. A flow passage, on which a valve is mounted and which is opened to the atmosphere, may be connected to the air tank. The air tank can be opened to the atmosphere in a case in which a valve opened to the atmosphere is opened.

The collection-side manifold318is connected to a collection back pressure tank362through a collection-side flow passage360. The detailed structure of the collection back pressure tank362is not shown. The same structure as the supply back pressure tank342can be applied to the collection back pressure tank362.

The supply back pressure tank342and the collection back pressure tank362can function as dampers for flow passages that communicate with the supply back pressure tank342and the collection back pressure tank362.

The supply back pressure tank342is connected to a common flow passage377through a supply flow passage valve376. The collection back pressure tank362is connected to the common flow passage377through a collection flow passage valve378.

The common flow passage377is connected to a direction-switching valve329. A second supply flow passage309is connected to a first output port329A of the direction-switching valve329. A second collection flow passage319is connected to a second output port329B of the direction-switching valve329.

The second supply flow passage309is connected to a supply tank311through a supply pump313. Further, the second collection flow passage319is connected to a collection tank321through a collection pump323. The supply tank311and the collection tank321communicate with each other through a pump325.

The direction-switching valve329is switched to connect the second supply flow passage309to the common flow passage377or to connect the second collection flow passage319to the common flow passage377. The supply of ink to the liquid jet head56from the supply tank311and the collection of ink to the collection tank321from the liquid jet head56can be switched by the switching of the direction-switching valve329.

Filters for capturing foreign materials, deaerators for removing air bubbles present in ink, check valves for preventing the back flow of ink, and the like are appropriately disposed in the ink supply system shown inFIG. 6.

[Description of Head Moving Unit]

FIG. 7is a schematic diagram schematically showing the schematic configuration of the head moving units. Only any one of the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1is denoted inFIG. 7by reference numeral56.

The head moving units400shown inFIG. 7move the liquid jet head56between a drawing position and a retreat position by moving the liquid jet head56in a vertical direction. InFIG. 7, the moving direction of the liquid jet head56is indicated by an arrow line.

The drawing position is the position of the liquid jet head56in a case in which the liquid jet head56jets liquid to the sheet36transported by the drawing drum52. A distance between the liquid jet head56that is disposed at the drawing position and the sheet36that is supported by the drawing drum52is 1 mm or less. The drawing position is one aspect of a liquid jet position.

The retreat position is a position to which the liquid jet head56is to be moved in a case in which the floating of a sheet36is detected. The retreat position is the position of the liquid jet head56where the sheet36and the liquid jetting surface277of the liquid jet head56are not in contact with each other even in a case in which the floating of a sheet36occurs. A broken line denoted inFIG. 7by reference numeral56A shows a liquid jet head that is moved to the retreat position.

Further, the retreat position is a position from which the liquid jet head56can return to the drawing position in a short period of time in a case in which the floating of a sheet36is eliminated.

The head moving units400are disposed outside both ends of the liquid jet head56in a longitudinal direction of the liquid jet head56. The longitudinal direction of the liquid jet head56is the width direction of a sheet36that is denoted by reference letter X, and is a direction orthogonal to the sheet transport direction.

The head moving unit400includes a head support member402that supports a raising/lowering support member302mounted on the liquid jet head56, and an actuator404that raises and lowers the head support member402in the vertical direction.

The actuator404includes a raising/lowering mechanism and a drive source for the raising/lowering mechanism. A ball screw or the like can be applied as the raising/lowering mechanism. A rotary motor can be applied as the drive source. A linear motor in which a raising/lowering mechanism and a drive source are integrated with each other may be applied.

The head moving units400, which raise and lower the liquid jet head56in the vertical direction, are shown in this embodiment, but the head moving units400may move the liquid jet head56in an oblique direction having a vertical component. For example, the head moving units400may move the liquid jet head56in a normal direction of the outer peripheral surface52B of the drawing drum52.

The head moving units400shown inFIG. 7may be adapted to collectively raise and lower the four liquid jet heads56C,56M,56Y, and56K in a case in which the four liquid jet heads56C,56M,56Y, and56K shown inFIG. 1are to be raised and lowered.

The head moving units400shown inFIG. 7may be adapted to individually raise and lower the four liquid jet heads56C,56M,56Y, and56K shown inFIG. 1.

[Description of Control System]

FIG. 8is a block diagram showing the schematic configuration of a control system. As shown inFIG. 8, the ink jet recording apparatus10includes a system controller100. Although not shown, the system controller100may include a CPU, a ROM, and a RAM.

CPU is an abbreviation for Central Processing Unit. ROM is an abbreviation for Read Only Memory. RAM is an abbreviation for Random Access Memory.

The system controller100functions as a total control section that generally controls the respective parts of the ink jet recording apparatus10. Further, the system controller100functions as a calculation section that performs various kinds of calculation processing. Furthermore, the system controller100functions as a memory controller that controls the reading of data of a memory and the writing of data.

The ink jet recording apparatus10shown inFIG. 8includes a communication unit102and an image memory104. The communication unit102includes a communication interface (not shown). The communication unit102can transmit and receive data to and from a host computer103connected to the communication interface.

The image memory104functions as a temporary storage section for various kinds of data including image data. Data is read from and written in the image memory104through the system controller100. Image data, which is taken from the host computer103through the communication unit102, is temporarily stored in the image memory104.

The ink jet recording apparatus10shown inFIG. 8includes a sheet feed control unit110, a transport control unit112, a treatment liquid-application control unit116, a treatment liquid-drying processing control unit117, a drawing control unit118, a head movement control unit120, an ink-drying processing control unit122, and a sheet discharge control unit124.

The sheet feed control unit110allows the sheet feed unit12to be operated according to a command sent from the system controller100. The sheet feed control unit110controls an operation for starting feeding the sheet36, an operation for stopping feeding the sheet36, and the like. The sheet feed control unit110is one aspect of a medium feed control unit.

The transport control unit112controls the operation of a transport unit114for the sheet36of the ink jet recording apparatus10. The transport unit114shown inFIG. 8includes the treatment liquid drum42, the treatment liquid-drying processing drum46, the drawing drum52, and the sheet transport member22shown inFIG. 1.

The treatment liquid-application control unit116allows the treatment liquid-application section14to be operated according to a command sent from the system controller100. The treatment liquid-application control unit116controls the amount of treatment liquid to be applied, a treatment liquid-application timing, and the like.

The treatment liquid-drying processing control unit117allows the treatment liquid-drying processing section16to be operated according to a command sent from the system controller100. The treatment liquid-drying processing control unit117controls drying temperature, the flow rate of dry gas, the injection timing of dry gas, and the like.

The treatment liquid-drying processing control unit117controls the switching of the treatment liquid-drying processing-performing state and the treatment liquid-drying processing-suppression state of the treatment liquid-drying processing device50of the treatment liquid-drying processing section16shown inFIG. 1. The treatment liquid-drying processing control unit117is not stopped in the treatment liquid-drying processing-suppression state of the treatment liquid-drying processing device50of the treatment liquid-drying processing section16.

The drawing control unit118controls the operation of the drawing unit18according to a command sent from the system controller100. That is, the drawing control unit118controls the jet of ink from the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1.

The drawing control unit118includes an image processing section (not shown). The image processing section generates dot data from input image data. The image processing section includes a color separation processing section, a color conversion processing section, a correction processing section, and a halftoning section (not shown).

In the color separation processing section, color separation processing is performed on the input image data. For example, in a case in which the input image data is represented in RGB, the input image data is separated into data of the respective colors of R, G, and B. Here, R represents red. G represents green. B represents blue.

In the color conversion processing section, image data, which are separated into the data of R, G, and B and correspond to the respective colors, are converted into C, M, Y, and K corresponding to the colors of inks. Here, C represents cyan. M represents magenta. Y represents yellow. K represents black.

In the correction processing section, correction processing is performed on the image data that are converted into C, M, Y, and K and correspond to the respective colors. Examples of the correction processing include gamma correction processing, processing for correcting density unevenness, processing for correcting an abnormal recording element, and the like.

In the halftoning section, image data represented by multiple numbers of gradations in the range of, for example, 0 to 255 are converted into dot data represented by a binary value or a multi-level value that is a ternary value or more and is smaller than the number of gradations of the input image data.

In the halftoning section, a predetermined halftoning rule is applied. Examples of the halftoning rule include a dither method, an error diffusion method, and the like. The halftoning rule may be changed according to image recording conditions, the contents of image data, or the like.

The drawing control unit118includes a waveform generation unit, a waveform storage unit, and a drive circuit (not shown). The waveform generation unit generates a waveform of a drive voltage. The waveform of the drive voltage is stored in the waveform storage unit. The drive circuit generates a drive voltage having a drive waveform corresponding to dot data. The drive circuit supplies the drive voltage to the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1.

That is, a jetting timing and the amount of ink to be jetted at the position of each pixel are determined on the basis of dot data generated through the processing that is performed by the image processing section, a drive voltage corresponding to the jetting timing and the amount of ink to be jetted at the position of each pixel and a control signal determining the jetting timing at each pixel are generated, this drive voltage is supplied to the liquid jet heads, and dots are formed by the ink jetted from the liquid jet heads. The drawing control unit is one aspect of a jetting control unit.

The ink-drying processing control unit122allows the ink-drying processing section20to be operated according to a command sent from the system controller100. The ink-drying processing control unit122controls the temperature of dry gas, the flow rate of dry gas, the injection timing of dry gas, or the like. The ink-drying processing control unit122is one aspect of a liquid-drying processing control unit.

The ink-drying processing control unit122controls the switching of the ink-drying processing-performing state and the ink-drying processing-suppression state of the drying processing device21of the ink-drying processing section20shown inFIG. 1. The ink-drying processing control unit122is not stopped in the ink-drying processing-suppression state of the drying processing device21of the ink-drying processing section20.

The sheet discharge control unit124allows the sheet discharge unit24to be operated according to a command sent from the system controller100. The sheet discharge control unit124controls the sorting of a sheet36that is subjected to normal drawing and a sheet36that is determined as a waste sheet.

The ink jet recording apparatus10shown inFIG. 8includes an ink supply control unit126. The ink supply control unit126controls the operation of the ink supply section127, which includes the internal flow passage of the liquid jet head and the ink supply system shown inFIG. 6, according to a command sent from the system controller100.

That is, the ink supply control unit126functions as a pump control section that controls the operation of a pump, such as the supply pump313shown inFIG. 6. Examples of the control of the operation of a pump include the off-on control of a pump, the control of the flow rate of a pump, and the like.

Further, the ink supply control unit126shown inFIG. 8functions as a valve control section that controls the operation of a valve, such as the supply-side valve306shown inFIG. 6. Examples of the control of the operation of a valve include the off-on control of a valve.

The ink jet recording apparatus10shown inFIG. 8includes an operation unit130and a display section132.

The operation unit130includes operation members, such as an operation button, a keyboard, or a touch panel. The operation unit130may include plural kinds of operation members. The operation members are not shown.

Information, which is input through the operation unit130, is sent to the system controller100. The system controller100performs various kinds of processing according to the information that is sent from the operation unit130.

The display section132includes a display device, such as a liquid crystal panel, and a display driver. The display device and the display driver are not shown. The display section132allows the display device to display various kinds of information, such as various kinds of configuration information of the apparatus or information on abnormalities of the apparatus, according to a command sent from the system controller100.

The ink jet recording apparatus10shown inFIG. 8includes a parameter storage unit134and a program storage unit136.

Various parameters, which are used in the ink jet recording apparatus10, are stored in the parameter storage unit134. Various parameters, which are stored in the parameter storage unit134, are read through the system controller100and are set in respective parts of the apparatus.

Various programs, which are used in the respective parts of the ink jet recording apparatus10, are stored in the program storage unit136. Various programs, which are stored in the program storage unit136, are read through the system controller100and are executed in respective parts of the apparatus.

The ink jet recording apparatus10shown inFIG. 8includes a sheet floating detection unit140. The sheet floating detection unit140includes the sheet floating sensor55shown inFIG. 1. The sheet floating detection unit140determines whether or not the floating of a sheet36having passed through a detection region of the sheet floating sensor55occurs on the basis of an output signal of the sheet floating sensor55.

The sheet floating detection unit140sends the detection information on a sheet36, of which the floating occurs, to the system controller100. In a case in which the system controller100acquires the detection information on a sheet36of which the floating occurs, the system controller100sends commands, which allow the liquid jet heads56M,56Y, and56K shown inFIG. 1to retreat to the retreat positions, to the head movement control unit120. The sheet floating detection unit140is one aspect of a medium floating detection unit.

Further, in a case in which the system controller100acquires information on a sheet36of which the floating occurs, the system controller100sends commands, which change processing, to the treatment liquid-application control unit116, the treatment liquid-drying processing control unit117, the drawing control unit118, and the ink-drying processing control unit122. The details of the change of processing will be described later.

The ink jet recording apparatus10shown inFIG. 8includes a pressure detection unit142.

The pressure detection unit142includes the supply-side pressure sensor320and the collection-side pressure sensor322shown inFIG. 6. The pressure detection unit142shown inFIG. 8sends pressure information, which represents the pressure of the supply-side manifold308shown inFIG. 6, and pressure information, which represents the pressure of the collection-side manifold318, to the system controller100shown inFIG. 8. The pressure detection unit142is one aspect of a jetting state detection unit.

The ink jet recording apparatus10shown inFIG. 8includes a waste sheet-number setting unit144. In a case in which a sheet36of which the floating occurs is detected by the sheet floating detection unit140, the waste sheet-number setting unit144derives the number of sheets36as waste sheets while regarding the sheet36of which the floating occurs as a first waste sheet and sets the derived number of waste sheets.

For example, the number of sheets36passing through the drawing regions of the liquid jet heads56C,56M,56Y, and56K in a head retreat period, which is a period between a timing when the liquid jet heads56C,56M,56Y, and56K start to retreat from the drawing positions and a timing when the liquid jet heads56C,56M,56Y, and56K have completely returned to the drawing positions and is a period in which the liquid jet heads56C,56M,56Y, and56K are retreating from the drawing positions, can be calculated from the feed timing of the sheet36and the transport speed of the sheet36.

The drawing regions of the liquid jet heads56C,56M,56Y, and56K are regions positioned on the transport path of the sheet36, and mean regions in which the liquid jet heads56C,56M,56Y, and56K jet liquid.

The number of waste sheets, which is set, is displayed on the display section132and can be notified to an operator. In a case in which the operator grasps the number of waste sheets displayed on the display section132, the operator can add the number of waste sheets to the number of sheets subjected to drawing.

A sensor146shown inFIG. 8includes various sensors, such as the sheet feed sensor32shown inFIG. 1. For example, the system controller100acquires sheet feed information that is sent from the sheet feed sensor32and represents the feed of a sheet36. The sheet feed information acquired by the system controller100can be used for the control of the transport of the sheet36, and the like.

[Description of Method of Coping with Floating of Sheet]

First Embodiment

Next, a method of coping with the floating of a sheet according to a first embodiment, which is applied to the above-mentioned ink jet recording apparatus10, will be described. The method of coping with the floating of a sheet corresponds to a method of coping with the floating of a medium. The method of coping with the floating of a sheet to be described below can be applied to a case in which drawing is successively performed on a plurality of sheets36.

FIG. 9is a flowchart showing a procedure of drawing to which the method of coping with the floating of a sheet according to the first embodiment is applied.

After image data and drawing, which includes the number of sheets to be subjected to drawing, are set the start of drawing is determined, it is determined in a sheet-number determination step S10whether or not a preset number of sheets36are subjected to drawing. If a preset number of sheets36are not subjected to drawing, the determination of the sheet-number determination step S10is determined as YES. If the determination of the sheet-number determination step S10is determined as YES, processing proceeds to a sheet feed step S12.

On the other hand, if a preset number of sheets36are subjected to drawing, the determination of the sheet-number determination step S10is determined as NO. If the determination of the sheet-number determination step S10is determined as NO, processing proceeds to an end processing step S14. Then, drawing ends.

In the sheet feed step S12, sheets36are fed from the sheet feed unit12shown inFIG. 1at predetermined sheet feed timings. The predetermined sheet feed timings may be regular intervals and may be irregular intervals.

The feed timings of the sheets36, which are fed in the sheet feed step S12, are detected by the sheet feed sensor32shown inFIG. 1. Further, the number of the sheets36fed in the sheet feed step S12is measured by a counter (not shown).

Further, the positions of the sheets36fed in the sheet feed step S12can be found out by the sheet feed control unit110shown inFIG. 8.

After the sheets are fed in the sheet feed step S12, processing proceeds to a sheet floating detection step S16. The sheet feed step S12is one aspect of a medium feeding step.

In the sheet floating detection step S16, the sheet floating sensor55shown inFIG. 1detects whether or not the floating of a sheet36occurs. The sheet floating detection step S16shown inFIG. 9is performed on all the sheets36passing through the detection region of the sheet floating sensor55shown inFIG. 1.

A criterion, which is used to determine whether or not the floating of a sheet occurs in the sheet floating detection step S16shown inFIG. 9, is determined from a condition where the sheet36is not in contact with the liquid jetting surface277shown inFIG. 4in a period in which the sheet36passes through the drawing regions of the liquid jet heads56C,56M,56Y, and56K disposed at the drawing positions.

A period in which the sheet36passes through the drawing region can be set as a period between a timing when the front end of the sheet36enters the drawing region and a timing when the rear end of the sheet36has gotten out of the drawing region. The front end of the sheet36and the rear end of the sheet36may be any position of the sheet36.

It is preferable that the criterion, which is used to determine whether or not the floating of a sheet occurs, is determined according to the type of each sheet36. The thickness of the sheet36, the material of the sheet36, or the like can be applied as the type of the sheet36. Further, it is preferable that a criterion used to determine the floating of a sheet is set in units of a job for forming an image.

If the floating of a sheet is not detected in the sheet floating detection step S16shown inFIG. 9, the determination of the sheet floating detection step S16is determined as NO. If the determination of the sheet floating detection step S16is determined as NO, processing proceeds to the sheet-number determination step S10. That is, the sheet36of which the floating is not detected in the sheet floating detection step S16is sent to the sheet discharge unit24shown inFIG. 1through a drawing step (not shown) and an ink-drying processing step (not shown). The drawing step is one aspect of a liquid jetting step. The ink-drying processing step is one aspect of a liquid-drying processing step.

On the other hand, if the floating of a sheet is detected in the sheet floating detection step S16shown inFIG. 9, the determination of the sheet floating detection step S16is determined as YES. If the determination of the sheet floating detection step S16is determined as YES, coping with the floating of a sheet is performed. The coping with the floating of a sheet includes the retreat of the heads in a head retreat step S18. The heads mentioned here are the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1.

In the head retreat step S18, the head moving units400shown inFIG. 7are operated to move the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1to the retreat positions before the sheet36of which the floating is detected reaches the drawing regions of the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1.

Further, if the floating of a sheet is detected in the sheet floating detection step S16, the number of waste sheets is set in a waste sheet-number setting step S19. The number of waste sheets is the number of sheets36passing through the drawing regions of the liquid jet heads56M,56Y, and56K in a period that is obtained by adding up a period in which the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1are moved to the retreat positions from the drawing positions, a period in which the retreat of the liquid jet heads56C,56M,56Y, and56K to the retreat positions is continued, a period in which the liquid jet heads56C,56M,56Y, and56K are moved to the drawing positions from the retreat positions, and a period in which the drawing of the liquid jet heads56C,56M,56Y, and56K is prepared.

After the number of waste sheets is set in the waste sheet-number setting step S19shown inFIG. 9, processing proceeds to an ink-drying processing-suppression switching step S20. In the ink-drying processing-suppression switching step S20, the drying processing device21of the ink-drying processing section20shown inFIG. 1is switched to the ink-drying processing-suppression state. Then, the sheet36of which the floating is detected in the sheet floating detection step S16shown inFIG. 9is regarded as a first sheet, and the ink-drying processing-suppression state is maintained until a timing when a sheet36corresponding to the order of the number of waste sheets, which is set in the waste sheet-number setting step S19, from the first sheet36gets out of the drying processing region of the drying processing device21.

The timing when the sheet36gets out of the drying processing region of the drying processing device21may be a timing when the front end of the sheet36gets out of the drying processing region of the drying processing device21. Further, the timing when the sheet36gets out of the drying processing region of the drying processing device21may be a timing when the rear end of the sheet36gets out of the drying processing region of the drying processing device21. The front end of the sheet36and the rear end of the sheet36may be any position of the sheet36.

The orders of the head retreat step S18and the waste sheet-number setting step S19shown inFIG. 9may be exchanged with each other. The period of the head retreat step S18and the period of the waste sheet-number setting step S19may overlap each other. The head retreat step S18is a component of a head moving step.

In the method of coping with the floating of a sheet described in this embodiment, a sheet continues to be fed if the floating of the sheet is detected in the sheet floating detection step S16. That is, even though the floating of a sheet is detected in the sheet floating detection step S16, the sheet feed step S12is not interrupted or stopped.

In a case in which the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1retreat to the retreat positions in the head retreat step S18shown inFIG. 9and the drying processing device21of the ink-drying processing section20shown inFIG. 1is switched to the ink-drying processing-suppression state in the ink-drying processing-suppression switching step S20, it is determined in a sheet floating-elimination determination step S22whether or not the floating of a sheet36is eliminated.

If sheets36of which the floating is detected are continuous to each other among sheets36that successively pass through the detection region of the sheet floating sensor55shown inFIG. 1, it can be determined in the sheet floating-elimination determination step S22that the floating is not eliminated.

A detection signal of the sheet floating sensor55shown inFIG. 1is used for the detection of the elimination of the floating of a sheet in the sheet floating-elimination determination step S22. That is, in a case in which a detection signal, which represents the non-detection of the floating of a sheet, is output from the sheet floating sensor55, it can be determined that the floating of a sheet is eliminated.

If it is determined in the sheet floating-elimination determination step S22that the floating of a sheet36is not eliminated, the determination of the sheet floating-elimination determination step S22is determined as NO. If the determination of the sheet floating-elimination determination step S22is determined as NO, the determination of the elimination of the floating of a sheet is continued in the sheet floating-elimination determination step S22.

That is, it is determined in the sheet floating-elimination determination step S22whether or not the floating of all the sheets36passing through the detection region of the sheet floating sensor55shown inFIG. 1occurs is determined.

On the other hand, if it is determined in the sheet floating-elimination determination step S22that the floating of a sheet36is eliminated, the determination of the sheet floating-elimination determination step S22is determined as YES. If the determination of the sheet floating-elimination determination step S22is determined as YES, processing proceeds to a head position-return step S24.

In the head position-return step S24, the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1are moved to the drawing positions from the retreat positions. The head position-return step S24is a component of the head moving step.

Further, if it is determined in the sheet floating-elimination determination step S22shown inFIG. 9that the floating of a sheet36is eliminated, an ink-drying processing-performing state-return step S26is performed. In the ink-drying processing-performing state-return step S26, the drying processing device21of the ink-drying processing section20is switched to the ink-drying processing-performing state from the ink-drying processing-suppression state after the elapse of a period in which all waste sheets pass through the processing region of the ink-drying processing section20shown inFIG. 1.

A timing when the drying processing device21is switched to the ink-drying processing-performing state from the ink-drying processing-suppression state may be determined in consideration of a processing period in a case in which the drying processing device21is switched to the ink-drying processing-performing state from the ink-drying processing-suppression state.

In the head position-return step S24shown inFIG. 9, the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1return to the drawing positions. Then, in a case in which the drying processing device21of the ink-drying processing section20shown inFIG. 1is switched to the ink-drying processing-performing state in the ink-drying processing-performing state-return step S26, processing proceeds to the sheet-number determination step S10.

Further, drawing to which the method of coping with the floating of a sheet is applied is performed until a preset number of sheets36are subjected to drawing.

The number of waste sheets, which is set in the waste sheet-number setting step S19shown inFIG. 9, can be displayed on the display section132shown inFIG. 8. Furthermore, the number of sheets36, which are not subjected to drawing, is measured, and the measured number of sheets36may be displayed on the display section132shown inFIG. 8as the number of waste sheets.

Whether or not a sheet is a sheet not actually subjected to drawing can be determined using the imaging result of a sheet36that is obtained from the in-line sensor58shown inFIG. 1. An operator can set the number of waste sheets, which is displayed on the display section132shown inFIG. 8, as a shortfall in the number of sheets subjected to drawing. The ink jet recording apparatus10shown inFIG. 1can perform drawing on sheets36of which the number corresponds to a shortfall in the number of sheets caused by the generation of waste sheets.

Effects of First Embodiment

In a case in which the floating of a sheet is detected in the method of coping with the floating of a sheet that is adapted as described above, the sheet continues to be fed and the liquid jet heads are moved to the retreat positions. The ink-drying processing section is switched to the ink-drying processing-suppression state from the ink-drying processing-performing state. After that, in a case in which the floating of a sheet is eliminated, the liquid jet heads return to the drawing positions. Moreover, the ink-drying processing section returns to the ink-drying processing-performing state from the ink-drying processing-suppression state.

Accordingly, since the liquid jet heads retreat to the retreat positions in a case in which the floating of a sheet is detected, a collision between the sheet and the liquid jet heads is avoided. Further, since a sheet continues to be fed in a case in which the floating of the sheet is detected, a period between the elimination of the floating of the sheet and a time when drawing can be resumed can be made shorter than that in a case in which the feed of a sheet is interrupted or stopped at the time of detection of the floating of the sheet. As a result, the deterioration of production efficiency can be suppressed.

Furthermore, since the ink-drying processing section is switched to the ink-drying processing-suppression state in which the intensity of drying processing of the ink-drying processing section is suppressed in a case in which the floating of a sheet is detected, a period between the elimination of the floating of the sheet and the resumption of the processing of the ink-drying processing section can be made shorter than that in a case in which the ink-drying processing section is completely stopped at the time of detection of the floating of the sheet. As a result, the deterioration of production efficiency can be suppressed.

A case in which the ink-drying processing section is completely stopped, which is mentioned here, is a case in which the entire system of the ink-drying processing section including the processing of the control system is stopped by emergency stop or the like. In a case in which the ink-drying processing section is completely stopped, processing requiring a long period, such as initialization processing, is required at the time of the restart of the ink-drying processing section.

Second Embodiment

Next, a method of coping with the floating of a sheet according to a second embodiment will be described. The same components of the method of coping with the floating of a sheet according to the second embodiment to be described below as the components of the method of coping with the floating of a sheet according to the first embodiment will be denoted by the same reference numerals as those of the first embodiment, and the description thereof will be appropriately omitted.

FIG. 10is a flowchart showing a procedure for coping with the floating of a sheet according to the second embodiment. In the flowchart shown inFIG. 10, a drawing-start-possibility determination step S25is added to the flowchart shown inFIG. 9.

That is, in a case in which the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1are moved to the drawing positions from the retreat positions in the head position-return step S24, processing proceeds to the drawing-start-possibility determination step S25shown inFIG. 10.

It is determined in the drawing-start-possibility determination step S25whether or not the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1satisfy drawing start conditions.

If the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1do not satisfy the drawing start conditions in the drawing-start-possibility determination step S25shown in FIG.10, the determination of the drawing-start-possibility determination step S25shown inFIG. 10is determined as NO. If the determination of the drawing-start-possibility determination step S25is determined as NO, the determination of whether or not the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1satisfy the drawing start conditions is continued in the drawing-start-possibility determination step S25.

If the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1satisfy the drawing start conditions in the drawing-start-possibility determination step S25shown inFIG. 10, the determination of the drawing-start-possibility determination step S25shown inFIG. 10is determined as YES. If the determination of the drawing-start-possibility determination step S25is determined as YES, processing proceeds to the ink-drying processing-performing state-return step S26.

Then, the processing state of the ink-drying processing section20shown inFIG. 1returns to the ink-drying processing-performing state and drawing is resumed.

In the waste sheet-number setting step S19shown inFIG. 10, the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1return to the drawing positions and the number of waste sheets is set in consideration of a period until the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1satisfy the drawing start conditions.

FIG. 11is a graph illustrating drawing start conditions. An example in which the internal pressures of the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1are applied as parameters of the drawing start conditions will be described below.

A horizontal axis of the graph shown inFIG. 11represents a period. The unit of the horizontal axis of the graph shown inFIG. 11is second. A vertical axis of the graph shown inFIG. 11represents a pressure in the internal flow passage of the liquid jet head56. The unit of the vertical axis of the graph shown inFIG. 11is Pascal.

The liquid jet head56, which is mentioned here, is any one of the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1. The same applies to the following description.

The graph shown inFIG. 11represents a pressure in the internal flow passage of the liquid jet head56in a case in which the liquid jet head56is moved up from the drawing position in the vertical direction, is stopped at a stop position above the drawing position, and is moved to the upper side of the stop position in the vertical direction.

In a case in which the upper limit and the lower limit of the pressure in the internal flow passage of the liquid jet head56are set and the measured value of a pressure measured by the supply-side pressure sensor320shown inFIG. 6and the measured value of a pressure measured by the collection-side pressure sensor322are in the range of the lower limit to the upper limit as shown inFIG. 11, it can be determined that the drawing start conditions are satisfied.

The pressure in the internal flow passage of the liquid jet head56shown inFIG. 11tends to change on the basis of the measured value of a pressure measured by the supply-side pressure sensor320shown inFIG. 6and the measured value of a pressure measured by the collection-side pressure sensor322.

The liquid jet head56starts to be moved up in the vertical direction at t1, is stopped at the stop position above the drawing position at t2, starts to be moved down in the vertical direction at t3, and returns to the drawing position at t4. 1 second is provided as an example of a period between t1and t2, a period between t2and t3, and a period between t3and t4inFIG. 11.

InFIG. 11, 200 Pa is exemplified as the upper limit of the pressure in the internal flow passage of the liquid jet head56. Further, −200 Pa is exemplified as the lower limit of the pressure in the internal flow passage of the liquid jet head56.

The upper limit and the lower limit of the pressure in the internal flow passage of the liquid jet head56can be set according to a drawing condition, such as drawing resolution or image quality. Further, the upper limit and the lower limit of the pressure in the internal flow passage of the liquid jet head56can be set according to the type of ink.

For example, in a case in which drawing resolution is relatively fine and in a case in which image quality is relatively high, a range between the upper limit and the lower limit of the pressure in the internal flow passage of the liquid jet head56may be set to be narrow line.

In regard to the liquid jet heads56C,56M,56Y, and56K shown inFIG. 1, the same value may be set as the value of the range between the upper limit and the lower limit and different individual values may be set as the value.

In a case in which the liquid jet head56is moved in the vertical direction, the jetting state of ink is changed due to a change in the pressure in the internal flow passage and image quality is negatively affected. Accordingly, in a case in which the pressure in the internal flow passage of the liquid jet head56is used as the parameter of the drawing start conditions, the deterioration of image quality caused by the retreat of the liquid jet head56can be suppressed.

The temperature of liquid in the liquid jet head56, a period in which the liquid jet head56retreats to the retreat position, or the like can be applied as another example of the parameter of the drawing start conditions.

Effects of Second Embodiment

The same effects as the first embodiment can be obtained in the method of coping with the floating of a sheet that is adapted as described above. Further, the liquid jet head56retreats in a case in which the floating of a sheet is detected, the liquid jet head56returns to the drawing position in a case in which the floating of a sheet is eliminated, and drawing is resumed in a case in which the drawing start conditions are satisfied. Accordingly, it is possible to suppress the deterioration of image quality that is caused by at least one of a case in which the liquid jet head56retreats to the retreat position or a case in which the liquid jet head56returns to the drawing position. Image quality is one aspect of jetting quality. The drawing start condition is one aspect of a jetting start condition.

Third Embodiment

Next, a method of coping with the floating of a sheet according to a third embodiment will be described. The same components of the method of coping with the floating of a sheet according to the third embodiment to be described below as the components of the methods of coping with the floating of a sheet according to the first and second embodiments will be denoted by the same reference numerals as those of the first and second embodiments, and the description thereof will be appropriately omitted.

FIG. 12is a flowchart showing a procedure for coping with the floating of a sheet according to the third embodiment. In the flowchart shown inFIG. 12, a treatment liquid-application standby-fixed state switching step S21and a treatment liquid-application processable state return step S27are added to the flowchart shown inFIG. 9.

In a case in which the floating of a sheet is detected in the sheet floating detection step S16and the number of waste sheets set in the waste sheet-number setting step S19exceeds the number of sheets36having passed through the treatment liquid-application section14shown inFIG. 1, the treatment liquid-application device44of the treatment liquid-application section14is switched to a treatment liquid-application standby-fixed state from a treatment liquid-application processable state.

That is, in a case in which sheets36not yet subjected to treatment liquid-application processing are included in sheets determined as waste sheets, the treatment liquid is not applied to the sheets determined as waste sheets.

Further, if it is determined in the sheet floating-elimination determination step S22shown inFIG. 12that the floating of a sheet is eliminated, the treatment liquid-application device44of the treatment liquid-application section14is switched to the treatment liquid-application processable state from the treatment liquid-application standby-fixed state after all the sheets36determined as waste sheets pass through the treatment liquid-application section14.

FIG. 13is a diagram illustrating the operation of the treatment liquid-application device. Here, the treatment liquid-application processable state and the treatment liquid-application standby-fixed state of the treatment liquid-application device44will be described. The application roller44A of the treatment liquid-application device44shown inFIG. 13starts to be in contact with a sheet36at a timing when the front end of the sheet36reaches a treatment liquid-application region.

That is, the treatment liquid-application device44moves the application roller44A to a treatment liquid-application position from a standby position in a case in which the sheet36enters the treatment liquid-application region. The standby position is the position of the application roller44A that is denoted by reference numeral44D.

The treatment liquid-application region is a region between the position of the rear end of a sheet36in a case in which the front end of the sheet36reaches the treatment liquid-application position and the position of the front end of the sheet36in a case in which the rear end of the sheet36reaches the treatment liquid-application position, on the transport path of the sheet36in the treatment liquid-application device44.

The treatment liquid-application position is a position where the application roller44A is in contact with the sheet36, and is the position of the application roller44A that is shown by a solid line.

Further, the treatment liquid-application device44allows the application roller44A to be away from the sheet36at a timing when the rear end of the sheet36gets out of the treatment liquid-application region. That is, in a case in which the sheet36gets out of the treatment liquid-application region, the treatment liquid-application device44moves the application roller44A to the standby position from the treatment liquid-application position. An arrow line given to the application roller44A indicates the moving direction of the application roller44A.

Furthermore, the treatment liquid-application device44allows the measurement roller44B to be in contact with the application roller44A in a period in which treatment liquid is to be supplied to the application roller44A from the measurement roller44B. Moreover, the treatment liquid-application device44allows the measurement roller44B to be away from the application roller44A in a period in which treatment liquid is not to be supplied to the application roller44A from the measurement roller44B.

InFIG. 13, the measurement roller44B, which is present at a position denoted by reference numeral44E, is the measurement roller44B that is away from the application roller44A. A treatment liquid-application standby state may include a state in which the measurement roller44B is away from the application roller44A. An arrow line given to the measurement roller44B ofFIG. 13indicates the moving direction of the measurement roller44B.

The treatment liquid-application standby-fixed state, which is switched in the treatment liquid-application standby-fixed state switching step S21shown inFIG. 12, is a state in which the treatment liquid-application device44is fixed in the treatment liquid-application standby state in a period in which a sheet36passes through the treatment liquid-application region of the application roller44A shown inFIG. 13.

In a case in which the treatment liquid-application device44is fixed in the treatment liquid-application standby state, the treatment liquid is not applied to the sheet36passing through the treatment liquid-application region of the application roller44A.

The treatment liquid-application processable state, which is switched in the treatment liquid-application processable state return step S27shown inFIG. 12, is a state in which the application roller44A shown inFIG. 13is movable between the treatment liquid-application position and the standby position. In the treatment liquid-application processable state, the treatment liquid is applied to the sheet36passing through the treatment liquid-application region of the application roller44A.

In a case in which the floating of a sheet is detected and the treatment liquid-application device44of the treatment liquid-application section14is switched to the treatment liquid-application standby-fixed state, it is preferable that the treatment liquid-drying processing section16is switched to the ink-drying processing-suppression state from the ink-drying processing-performing state.

Further, in a case in which the treatment liquid-application device44of the treatment liquid-application section14is switched to the treatment liquid-application processable state in the treatment liquid-application processable state return step S27, it is preferable that the treatment liquid-drying processing section16is switched to the treatment liquid-drying processing-performing state from the treatment liquid-drying processing-suppression state.

Effects of Third Embodiment

In a case in which the floating of a sheet is detected in the method of coping with the floating of a sheet that is adapted as described above, the treatment liquid-application device44of the treatment liquid-application section14is in the treatment liquid-application standby-fixed state. Further, in a case in which the floating of a sheet is eliminated, the treatment liquid-application device44of the treatment liquid-application section14is switched to the treatment liquid-application processable state.

Accordingly, a period between the elimination of the floating of a sheet and a time when drawing can be resumed can be made shorter than that in a case in which a treatment liquid-application processing section is stopped at the time of detection of the floating of the sheet. As a result, the deterioration of production efficiency can be suppressed.

Further, since treatment liquid is not applied in a case in which a sheet36determined as a waste sheet passes through the processing region of the treatment liquid-application section14, the waste sheet to which treatment liquid is not applied can be reused.

Contact type treatment liquid application, which uses the application roller, is exemplified in this embodiment, but an application member, such as a blade or an ink jet head, can also be used.

The third embodiment and the second embodiment are combined with each other, and the internal pressure of the liquid jet head may be applied to the treatment liquid-application device44of the treatment liquid-application section14under a condition where the treatment liquid-application device44of the treatment liquid-application section14is switched to the treatment liquid-application processable state from the treatment liquid-application standby-fixed state.

The embodiments of the invention described above can be properly subjected to the modification, addition, and deletion of components without departing from the scope of the invention. The invention is not limited to the above-mentioned embodiments, and can be modified in various ways by those skilled in the art without departing from the scope of the invention.

EXPLANATION OF REFERENCES