JP2024072545A - Suction device - Google Patents

Abstract

[Problem] To provide a suction device that can reduce a decrease in suction force. [Solution] A platen 31 is formed with a plurality of suction holes. A pressure chamber 33 is connected to each of the suction holes of the platen 31. A fan 34 generates negative pressure in the pressure chamber 33. A control unit 5 executes a cleaning operation in which a pressure is generated in the pressure chamber 33 by the fan 34 for cleaning the suction holes 31b with the paper P placed on the transport surface 21b so as to indirectly block at least a portion of all of the suction holes 31b of the platen 31. [Selected Figure] Figure 1

Description

The present invention relates to a suction device.

Suction devices that perform air suction are known. For example, in a line-type inkjet printing device that prints by ejecting ink from an inkjet head onto paper while transporting the paper, a suction device is used that uses air suction to adhere the paper to a transport belt and transport the paper (see Patent Document 1).

In the inkjet printing device described above, a platen with many suction holes is placed under a conveyor belt with many belt holes. Air is sucked in through the belt holes and suction holes by driving a fan, and the paper is attracted to the conveyor belt by the suction force generated by the belt holes.

JP 2006-206309 A

In the inkjet printing device described above, air containing ink mist generated by the ejection of ink is sucked in through the belt holes and suction holes, which can cause the suction holes to become clogged with ink. In particular, in platens with small suction holes, the suction holes are prone to becoming clogged with ink.

If sufficient pressure is applied to the ink clogged in the suction hole by operating the fan, the pressure will remove the ink from the suction hole and the clog will be cleared. However, if there are many suction holes on the platen that are not yet clogged with ink, even if the fan is operating, the suction holes that are not clogged with ink will become air passages, and almost no pressure will be applied to the ink in the clogged suction hole.

As a result, the ink blockage in the suction holes is not cleared, the suction power of the suction device decreases, and as a result, the paper may float off the conveyor belt.

The present invention has been made in consideration of the above, and aims to provide a suction device that can reduce the decrease in suction power.

To achieve the above object, the suction device of the present invention is characterized by comprising a suction hole member having multiple suction holes formed therein, a pressure chamber communicating with the multiple suction holes, a pressure generating unit that generates negative pressure in the pressure chamber, and a control unit that executes a cleaning operation in which the pressure generating unit generates pressure in the pressure chamber for cleaning the multiple suction holes while a blocking member is disposed so as to directly or indirectly block at least a portion of the multiple suction holes.

The suction device of the present invention can reduce the decrease in suction power.

1 is a schematic configuration diagram of an inkjet printing apparatus according to an embodiment; 2 is a partially enlarged plan view of a transport section of the inkjet printing apparatus shown in FIG. 1 . 3 is a partially enlarged cross-sectional view of the conveying section taken along line AA in FIG. 2. FIG. 13 is a diagram showing a state in which the maintenance unit is placed at a maintenance position. FIG. 13 is a diagram showing a state in which a suction hole in the platen is clogged with ink. 13A and 13B are diagrams illustrating a state in which pressure is applied to ink clogged in a suction hole of a platen by a cleaning operation. 13A and 13B are diagrams showing a state in which ink clogged in the suction holes of the platen has been removed by a cleaning operation.

The following describes an embodiment of the present invention with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

The embodiments shown below are examples of devices that embody the technical idea of this invention, and the technical idea of this invention does not specify the materials, shapes, structures, arrangements, etc. of each component part to those described below. The technical idea of this invention can be modified in various ways within the scope of the claims.

Figure 1 is a schematic diagram of an inkjet printing device provided with a suction device according to an embodiment of the present invention. Figure 2 is a partially enlarged plan view of the transport section of the inkjet printing device shown in Figure 1. Figure 3 is a partially enlarged cross-sectional view of the transport section taken along line A-A in Figure 2. In the following description, the direction perpendicular to the paper surface of Figure 1 is referred to as the front-rear direction, and the front direction of the paper surface is referred to as the forward direction. Additionally, the top, bottom, left, and right directions of the paper surface in Figure 1 are referred to as the top, bottom, left, and right directions. In Figure 1, the direction from left to right is the paper transport direction.

As shown in FIG. 1, the inkjet printing device 1 according to this embodiment includes a printing unit 2, a conveying unit 3, a maintenance unit 4, and a control unit 5. The suction device includes the conveying unit 3 and the control unit 5.

The printing unit 2 prints on the paper P transported by the transport unit 3. The printing unit 2 has multiple line heads 11. In this embodiment, the printing unit 2 has four line heads 11.

The line heads 11 eject ink onto the paper P to print an image. Each of the four line heads 11 ejects ink of a different color (e.g., black, cyan, magenta, yellow). The four line heads 11 are arranged in parallel above the transport unit 3 along the transport direction (left-right direction) of the paper P. Each line head 11 has multiple inkjet heads (corresponding to droplet ejection units) 12.

In the line head 11, the inkjet heads 12 are arranged in a staggered pattern along the front-to-rear direction. That is, in each line head 11, the inkjet heads 12 arranged along the front-to-rear direction are arranged with their positions shifted alternately in the left-to-right direction.

The inkjet head 12 is disposed opposite a platen (corresponding to a suction hole member) 31, which will be described later, with a conveyor belt 21, which will be described later, between them. The inkjet head 12 has a number of nozzles (not shown) that open to an ejection surface 12a, which is the lower surface facing the conveyor surface 21b of the conveyor belt 21, which will be described later, and ejects ink from the nozzles.

The conveying unit 3 conveys paper P (corresponding to the conveyed object) fed from a paper feed unit (not shown) while adsorbing and holding the paper by air suction. The conveying unit 3 includes a conveying belt (corresponding to a moving body) 21, a driving roller 22, driven rollers 23 to 25, a conveying motor (corresponding to a motor) 26, and a suction unit 27.

The conveyor belt 21 suctions and holds the paper P and conveys it. The conveyor belt 21 is a circular belt stretched over the drive roller 22 and driven rollers 23 to 25. As shown in FIG. 2, the conveyor belt 21 has a large number of belt holes (corresponding to suction holes) 21a formed therein. The conveyor belt 21 holds the paper P on the conveyor surface 21b by the suction force generated in the belt holes 21a by the drive of the fan 34 of the suction section 27 described later. The conveyor surface 21b is the surface on which the paper P of the conveyor belt 21 is placed, and is the upper surface of the horizontal part of the conveyor belt 21 between the drive roller 22 and the driven roller 23. The conveyor belt 21 rotates in the clockwise direction in FIG. 1 and moves (endless movement) along the platen 31 to convey the paper P held on the conveyor surface 21b.

The belt holes 21a are arranged at a predetermined pitch in each row along the transport direction (left-right direction) of the paper P. In addition, two rows of belt holes 21a adjacent to each other in the paper width direction (front-back direction) perpendicular to the transport direction are arranged so that they are shifted by half a pitch in the left-right direction.

The drive roller 22 rotates the conveyor belt 21. The driven rollers 23 to 25 support the conveyor belt 21 together with the drive roller 22. The driven rollers 23 to 25 rotate in response to the conveyor belt 21. The driven roller 23 is disposed to the left of the drive roller 22 at the same height as the drive roller 22. The driven rollers 24 and 25 are disposed below the drive roller 22 and the driven roller 23, spaced apart from each other in the left-right direction, at the same height.

The conveyor motor 26 rotates the drive roller 22 to move the conveyor belt 21 (endless movement) along the platen 31.

The suction unit 27 adheres the paper P to the conveyor belt 21 by air suction. The suction unit 27 includes a platen 31, a platen plate 32, a pressure chamber 33, and a fan (corresponding to a pressure generating unit) 34.

The platen 31 is a plate-shaped member that is disposed below the conveyor belt 21 between the drive roller 22 and the driven roller 23 and slidably supports the conveyor belt 21. The platen 31 has multiple recesses 31a and multiple suction holes 31b.

The recesses 31a are formed by digging down from the front surface (upper surface) of the platen 31, which is the surface facing the conveyor belt 21, toward the back surface (lower surface). The recesses 31a are the part where air is sucked in by driving the fan 34 to generate negative pressure. The recesses 31a are formed in a rectangular shape in a plan view. The recesses 31a are arranged at a predetermined pitch in the left-right direction. Furthermore, two rows of recesses 31a adjacent to each other in the front-rear direction are arranged so that they are shifted by half a pitch in the left-right direction. The pitch of the recesses 31a in the front-rear direction is equal to the pitch of the belt holes 21a in the front-rear direction. The recesses 31a are arranged at the points where the belt holes 21a of the conveyor belt 21 pass through.

The suction holes 31b are holes for sucking air through the recesses 31a and the belt holes 21a. The suction holes 31b are formed so as to penetrate from a part of the bottom surface of the recesses 31a to the back surface of the platen 31. The suction holes 31b are formed so as to open one by one to the bottom surface of each recess 31a. The suction holes 31b are formed so as to have a smaller area in a plan view than the belt holes 21a.

The platen plate 32 is a plate-shaped member that is disposed below the platen 31 and supports the platen 31 via a number of spacers 36. The platen plate 32 has a number of through holes 32a formed therein to allow air drawn in by the fan 34 to pass through. The planar area of the through holes 32a is larger than the planar area of the belt holes 21a and the planar area of the suction holes 31b.

The pressure chamber 33 forms a space in which negative pressure is generated to generate an adhesive force in the belt holes 21a of the conveyor belt 21. The pressure chamber 33 is provided on the back side (lower side) of the platen 31, between the drive roller 22 and the driven roller 23. The pressure chamber 33 communicates with each suction hole 31b of the platen 31. An ink absorbing sheet (not shown) that absorbs ink is disposed on the bottom surface of the pressure chamber 33.

The fan 34 exhausts air from the pressure chamber 33 to generate a negative pressure in the pressure chamber 33. This causes the fan 34 to suck air through the suction holes 31b and the belt holes 21a, generating an adsorption force in the belt holes 21a, and adsorbs the paper P to the conveyor belt 21.

The maintenance unit 4 performs maintenance of the inkjet head 12. When the inkjet printing device 1 is in a printing operation, the maintenance unit 4 is located in a retracted position, which is the position of the maintenance unit 4 shown in FIG. 1. When performing maintenance on the inkjet head 12, the maintenance unit 4 is located in a maintenance position, which is the position of the maintenance unit 4 shown in FIG. 4. The maintenance unit 4 is configured to be movable by a motor (not shown).

The maintenance unit 4 includes an ink receiving section (corresponding to a liquid receiving section) 41 and multiple wipers (not shown) that wipe the ejection surface 12a of the inkjet head 12.

The ink receiving section 41 receives ink that falls from the inkjet head 12 when the wiper wipes the ejection surface 12a during maintenance of the inkjet head 12. When the maintenance section 4 is placed in the maintenance position, the ink receiving section 41 is placed on the transport surface 21b of the transport belt 21 and covers each belt hole 21a in the transport surface 21b.

The control unit 5 controls the operation of each part of the inkjet printing device 1. The control unit 5 is configured with a CPU, RAM, ROM, hard disk, etc.

Specifically, the control unit 5 controls the conveying unit 3 to move the paper P while ejecting ink from each inkjet head 12 to print on the paper P.

The control unit 5 also executes a cleaning operation in which the fan 34 generates pressure (negative pressure) in the pressure chamber 33 to clean the suction holes 31b while the paper P is placed on the transport surface 21b so as to indirectly block at least a portion of all the suction holes 31b of the platen 31.

Next, the operation of the inkjet printing device 1 will be described.

When a print job is input, the control unit 5 starts driving the transport motor 26. This starts driving the drive roller 22. The control unit 5 also starts driving the fan 34.

Driven by the drive roller 22, the conveyor belt 21 rotates in the clockwise direction in FIG. 1 and moves in the conveying direction of the paper P between the drive roller 22 and the driven roller 23. As the conveyor belt 21 rotates, the belt holes 21a pass over the recesses 31a of the platen 31 from left to right.

On the other hand, when the fan 34 is driven to exhaust air from the pressure chamber 33, negative pressure is generated within the pressure chamber 33.

The recess 31a of the platen 31 is connected to the pressure chamber 33 via the suction hole 31b and the through hole 32a of the platen plate 32. Therefore, when negative pressure is generated in the pressure chamber 33, negative pressure is generated in the recess 31a where the belt holes 21a do not overlap and are blocked by the conveyor belt 21. The recess 31a where the belt holes 21a overlap is open to the atmosphere by the belt holes 21a, and no negative pressure is generated.

After the drive roller 22 and the fan 34 start to drive, when paper P is fed from a paper feed section (not shown) to the transport section 3, some of the belt holes 21a are covered by the fed paper P. The recesses 31a overlapping the belt holes 21a covered by the paper P are blocked by the transport belt 21 and the paper P, so the recesses 31a are in a negative pressure state. This generates an adhesive force at the belt holes 21a, and the paper P is attracted to the belt holes 21a.

The conveyor belt 21 attracts and holds the paper P on the conveyor surface 21b by the suction force generated in the belt holes 21a covered by the paper P. The conveyor belt 21 rotates in the clockwise direction in FIG. 1 to convey the attracted and held paper P to the right.

Based on the print job, the control unit 5 controls each inkjet head 12 to eject ink onto the paper P transported by the transport belt 21 to print an image. The printed paper P is discharged by a paper discharge unit (not shown).

During the printing operation as described above, ink mist is generated by the ejection of ink from the inkjet head 12. Some of the generated ink mist is sucked into the pressure chamber 33 together with air in the area between the transported sheets of paper P through the belt holes 21a, the recesses 31a of the platen 31, the suction holes 31b, and the through holes 32a of the platen plate 32.

When the ink mist is sucked in in this manner, as shown in FIG. 5, the suction hole 31b, which has a relatively small area in a plan view, may become clogged with ink 51, which is liquefied ink mist.

When sufficient pressure is applied to the ink 51 clogged in the suction hole 31b, the pressure removes the ink 51 from the suction hole 31b, clearing the clog. However, if there are many suction holes 31b in the platen 31 that are not yet clogged with ink, as shown in Figure 5, the suction holes 31b that are not clogged with ink will become a passageway for air, even if the fan 34 is driven. For this reason, almost no pressure is applied to the ink 51 in the clogged suction hole 31b.

As a result, the suction force of the suction section 27 decreases because the blockage of ink 51 in the suction hole 31b where ink 51 is clogged is not cleared, and as a result, there is a risk that the paper P will float off the conveyor belt 21.

In response to this, the inkjet printing device 1 performs a cleaning operation to remove the ink 51 that has become clogged in the suction hole 31b.

The above cleaning operation will be explained.

During printing operation, if the suction force of the suction unit 27 is reduced due to clogging of the suction holes 31b as described above, the frictional force between the conveyor belt 21 and the platen 31 is reduced. This reduces the load (load current value) of the conveyor motor 26. Therefore, the control unit 5 executes a cleaning operation when the load of the conveyor motor 26 during the movement of the conveyor belt 21 during printing operation is reduced to a predetermined threshold value. Here, the threshold value of the load of the conveyor motor 26 is a value set based on experiments, etc., as the load of the conveyor motor 26 in a situation where cleaning of the suction holes 31b is required and paper P may float from the conveyor belt 21 due to a reduction in the suction force of the suction unit 27.

When the load on the transport motor 26 drops to a threshold value during printing operation, the control unit 5 controls the transport motor 26 to stop the paper P on the transport surface 21b of the transport belt 21.

The suction hole 31b of the recess 31a that overlaps with the belt hole 21a blocked by the paper P stopped on the conveying surface 21b is indirectly blocked by the paper P. Note that this state in which the suction hole 31b is indirectly blocked by the paper P (the paper P indirectly blocks the suction hole 31b) is sometimes simply described as the suction hole 31b being blocked by the paper P (the paper P blocks the suction hole 31b).

If the size of the paper P is such that it can cover all of the suction holes 31b of the platen 31, the control unit 5 stops the paper P at a position that covers all of the suction holes 31b. Here, the control unit 5 controls the stopping position of the paper P based on the timing at which a paper sensor (not shown) provided upstream of the conveying unit 3 in the conveying direction of the paper P detects the leading edge of the paper P.

If the size of the paper P is such that it is not possible to block all of the suction holes 31b, the control unit 5 stops the paper P at a position where the blocking ratio, which is the ratio of the suction holes 31b blocked by the paper P, is equal to or greater than a predetermined value. Depending on the size of the paper P, multiple sheets of paper P may be stopped. Here, the predetermined value of the blocking ratio is a value set based on experiments, etc., as the lower limit of the blocking ratio at which the ink 51 clogged in the suction holes 31b can be removed by driving the fan 34.

Next, the control unit 5 controls the fan 34 to generate a cleaning pressure in the pressure chamber 33, which is a pressure (negative pressure) for cleaning the suction hole 31b. Here, the cleaning pressure is preset as a pressure capable of destroying the meniscus of the ink 51 that has clogged the suction hole 31b.

As described above, by generating a cleaning pressure in the pressure chamber 33 while the paper P is stopped on the transport surface 21b, pressure is applied uniformly to the lower surface of the platen 31 and the inner wall surface of the pressure chamber 33, and as shown in FIG. 6, pressure is also applied to the ink 51 clogged in the suction hole 31b. Then, by breaking the meniscus of the ink 51 clogged in the suction hole 31b, as shown in FIG. 7, the ink 51 is removed from the suction hole 31b, and the clog of the ink 51 is cleared. The ink 51 removed from the suction hole 31b falls from the through hole 32a of the platen plate 32 and is absorbed by the ink absorption sheet on the bottom surface inside the pressure chamber 33.

The control unit 5 ends the cleaning operation when a predetermined cleaning time has elapsed since the start of generating the cleaning pressure. Specifically, the control unit 5 controls the fan 34 so that the pressure (negative pressure) in the pressure chamber 33 becomes the pressure during paper transport (printing operation), and causes the transport unit 3 to transport the paper P and the paper discharge unit to discharge the paper.

At least one of the cleaning pressure and cleaning time may be adjusted according to the blockage rate depending on the size of the paper P.

As described above, in the inkjet printing device 1, the control unit 5 executes a cleaning operation in which the fan 34 generates cleaning pressure in the pressure chamber 33 while the paper P is placed on the transport surface 21b so as to block at least a portion of all of the suction holes 31b of the platen 31. This can eliminate ink clogging of the suction holes 31b, thereby reducing the decrease in the suction power of the suction unit 27. As a result, the occurrence of the paper P floating off the transport belt 21 can be suppressed.

The control unit 5 also executes the cleaning operation when the load on the conveyor motor 26 during the movement of the conveyor belt 21 drops to a threshold value. This allows the cleaning operation to be executed at an appropriate timing when a drop in the suction force of the suction unit 27 occurs.

In addition, the control unit 5 performs the cleaning operation by using paper P as a blocking member that blocks at least a portion of the suction hole 31b. This allows cleaning of the suction hole 31b without providing a new dedicated blocking member.

In the above-described embodiment, the paper P is stopped on the transport surface 21b during the cleaning operation, but the cleaning operation may be performed while the paper P is being transported. In this case, the control unit 5 may determine the timing to end the cleaning operation based on the load on the transport motor 26. For example, the cleaning operation may be ended when the load on the transport motor 26 becomes the same value as when the inkjet printing device 1 was shipped. This makes it possible to avoid performing an excessively long cleaning operation.

In addition, in the above-described embodiment, paper P is used as the blocking member, but the ink receiving portion 41 may be used as the blocking member. In this case, the control portion 5 places the maintenance portion 4 at the maintenance position and performs the cleaning operation. Even in this way, cleaning of the suction holes 31b can be achieved without providing a new dedicated blocking member. Here, the ink receiving portion 41 may be large enough to block all of the suction holes 31b of the platen 31 but to provide a blocking ratio of a predetermined value or more.

A dedicated member may also be used as the blocking member. For example, a dedicated sheet may be placed on the conveying surface 21b to perform the cleaning operation.

In addition, in the above-described embodiment, the cleaning operation is performed when the load on the conveyor motor 26 during the movement of the conveyor belt 21 drops to a threshold value, but the timing for performing the cleaning operation is not limited to this. For example, the cleaning operation may be performed periodically at a predetermined period of time, or after a predetermined number of printed sheets.

In the above-described embodiment, an example was shown in which clogging of the suction hole 31b caused by ink was cleared by the cleaning operation. However, the cleaning operation can also clear clogging of the suction hole 31b caused by things other than ink. For example, the cleaning operation can also clear clogging of the suction hole 31b caused by paper powder.

In the above-described embodiment, during the cleaning operation, the belt holes 21a are blocked by paper P as a blocking member, thereby indirectly blocking the suction holes 31b. However, the cleaning operation may be performed by removing the conveyor belt 21 and placing a blocking member on the platen 31 that can directly block the suction holes 31b.

In the above-described embodiment, the inkjet printing device 1 is described as adsorbing the paper P to the conveyor belt 21 by the suction force of the suction unit 27. However, the present invention is not limited to this, and any suction device that sucks air through multiple suction holes formed in the suction hole member may be used. Furthermore, the moving body that moves along the suction hole member is not limited to the conveyor belt 21 that conveys the paper P. Furthermore, the moving body is not limited to a body that conveys an object to be conveyed.

The present invention can also be applied to a suction device provided in a droplet ejection device that has a droplet ejection part other than an inkjet head. In such a suction device, a liquid receiving part that receives liquid that falls from the droplet ejection part during maintenance of the droplet ejection part may be used as a blocking member.

The present invention is not limited to the above-described embodiment as it is, and in the implementation stage, the components can be modified and embodied without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment.

[Additional Notes]
This application discloses the following inventions.

(Appendix 1)
A suction hole member having a plurality of suction holes formed therein;
a pressure chamber communicating with the plurality of suction holes;
a pressure generating unit that generates a negative pressure in the pressure chamber;
a control unit that executes a cleaning operation in which a blocking member is disposed so as to directly or indirectly block at least a portion of the plurality of suction holes, and the pressure generating unit generates pressure in the pressure chamber for cleaning the plurality of suction holes.

(Appendix 2)
The suction device described in Appendix 1 is characterized in that the control unit performs the cleaning operation by using a liquid receiving portion as the blocking member, which receives liquid falling from the droplet ejection portion arranged opposite the suction hole member during maintenance of the droplet ejection portion.

(Appendix 3)
A moving body that moves along the suction hole member;
A motor for moving the moving body is further provided,
The suction device according to claim 1 or 2, wherein the control unit executes the cleaning operation when a load on the motor during movement of the movable body falls to a predetermined threshold value.

(Appendix 4)
the movable body has a plurality of suction holes, and holds and transports an object to be transported by suction force generated in the suction holes by driving the pressure generating unit,
The suction device according to claim 3, wherein the control unit performs the cleaning operation by using the transported object as the blocking member.

REFERENCE SIGNS LIST 1 Inkjet printing device 2 Printing section 3 Conveying section 4 Maintenance section 5 Control section 11 Line head 12 Inkjet head 21 Conveying belt 21a Belt hole 21b Conveying surface 22 Driving roller 23 to 25 Driven roller 26 Conveying motor 27 Suction section 31 Platen 31a Recess 31b Suction hole 32 Platen plate 32a Through hole 33 Pressure chamber 34 Fan 41 Ink receiving section

Claims (4)

A suction hole member having a plurality of suction holes formed therein;
a pressure chamber communicating with the plurality of suction holes;
a pressure generating unit that generates a negative pressure in the pressure chamber;
a control unit that executes a cleaning operation in which a blocking member is disposed so as to directly or indirectly block at least a portion of the plurality of suction holes, and the pressure generating unit generates pressure in the pressure chamber for cleaning the plurality of suction holes. The suction device according to claim 1, characterized in that the control unit performs the cleaning operation by using a liquid receiving portion, which receives liquid that falls from the droplet discharge portion during maintenance of the droplet discharge portion arranged opposite the suction hole member, as the blocking member. A moving body that moves along the suction hole member;
A motor for moving the moving body is further provided,
3. The suction device according to claim 1, wherein the control unit executes the cleaning operation when a load on the motor during the movement of the moving body falls to a predetermined threshold value. the movable body has a plurality of suction holes, and holds and transports an object to be transported by suction force generated in the suction holes by driving the pressure generating unit,
The suction device according to claim 3 , wherein the control unit executes the cleaning operation by using the transported object as the blocking member.