Suction fan control

Abstract

The present invention provides a suction fan control device capable of suppressing vibration of a plurality of suction fans. The suction fan control device comprises: a suction unit having first to fourth suction fans (85a-85d) which generate negative pressure for adsorbing a printing medium; and a control unit (70) which controls the first to fourth suction fans (85a-85d), wherein the control unit (70) controls the rotation speeds of the first to fourth suction fans (85a-85d) to be different from each other and to be such a rotation speed as to suppress resonance of vibration caused by the rotation of the first to fourth suction fans (85a-85d).

Description

Technical Field

[0001] The present invention relates to a suction fan control device for controlling a plurality of suction fans for generating negative pressure for sucking a printing medium. Background Art

[0002] Conventionally, there has been proposed an inkjet printing apparatus that performs printing by ejecting ink from an inkjet head onto the printing medium while conveying a printing medium made of paper, film, or the like.

[0003] As a conveying device for printing media in such an inkjet printing device, a conveying device using a conveyor belt has been proposed. Specifically, the following conveying device has been proposed: a suction fan is provided opposite to the back side of the conveyor belt on which the printing media is placed, and a plurality of suction holes formed in the conveyor belt are rotated to generate negative pressure, thereby causing the printing media to be adsorbed on the conveyor belt (for example, refer to Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-127364 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Here, when the suction fan used in the above-mentioned conveying device is started and the rotating body has a deviation (eccentricity) in the center of gravity relative to the rotating shaft, vibration occurs in accordance with the rotation speed. This is because the force generated by the eccentricity generates a back-and-forth vibration during one rotation of the rotating body.

[0009] Moreover, in a conveying device using a suction fan, there is a situation in which, when the suction fan vibrates, the vibration is transmitted to the conveyor belt, thereby affecting the position where the ink lands on the printing medium conveyed by the conveyor belt. Specifically, since the conveyor belt leans toward the conveying direction when the suction fan vibrates in the conveying direction of the printing medium, the printing medium is conveyed faster than before, and the ink landing interval becomes loose. On the other hand, since the suction fan vibrates in the opposite direction to the conveying direction of the printing medium, the conveyor belt leans toward the opposite direction to the conveying direction, the printing medium is conveyed slower than before, and the ink landing interval becomes dense. In particular, in the case of a suspended belt platen, it is easily affected by the vibration of the suction fan.

[0010] Furthermore, particularly when a plurality of identical suction fans are provided and used at the same rotation speed, vibrations caused by the rotation of the plurality of suction fans resonate, and the influence thereof is further intensified. Fig.13A in FIG. 1 is a diagram showing a state of resonance generation when four suction fans are rotated at the same speed. Fig.13 A in the figure represents the occurrence of resonance when each suction fan vibrates about 70 times during the conveyance of an A3 size print medium. Fig.13 The graph shown in B in FIG. 1 shows the vibration cycle of each suction fan. Fig.13 The diagram shown in A shows Fig.13 The composite wave of the vibration cycles of the four suction fans shown in B in FIG. Since the vibration cycles of the four suction fans are the same, they resonate in the composite wave and are strengthened four times. When such vibration resonance occurs, Fig.14 Such periodic density unevenness as shown leads to a decrease in printing quality.

[0011] In view of the above situation, an object of the present invention is to provide a suction fan control device capable of suppressing vibration of a plurality of suction fans.

[0012] Means used to solve problems

[0013] The suction fan control device of the present invention comprises: a suction unit, which has multiple suction fans, which generate negative pressure for adsorbing printing media; and a control unit, which controls the suction fans, and the control unit controls the rotation speeds of the multiple suction fans to different rotation speeds from each other and to a rotation speed that suppresses the resonance of vibrations caused by the rotation of the multiple suction fans.

[0014] Effects of the Invention

[0015] According to the suction fan control device of the present invention, the rotation speeds of the plurality of suction fans are controlled to be different from each other and to be rotation speeds that suppress resonance of vibrations caused by rotation of the plurality of suction fans, thereby suppressing vibrations of the plurality of suction fans. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram showing a schematic configuration of an inkjet printing apparatus using an embodiment of the suction fan control device of the present invention.

[0017] Figure 2 This is a diagram of the transport unit as seen from above.

[0018] Figure 3 Yes means Figure 1 A block diagram showing a schematic configuration of a control system for an inkjet printing apparatus shown.

[0019] Figure 4 This is a diagram showing the occurrence of resonance when the duty ratios of the driving voltages of the first to fourth suction fans are controlled by shifting them by 10%.

[0020] Figure 5 It means forming Figure 4 FIG. 1 is a diagram showing an example of the vibration cycles of the first to fourth suction fans of the synthetic wave.

[0021] Figure 6 The diagram shows a state of resonance generation when the four rotational frequencies of the first to fourth suction fans are controlled to be frequencies corresponding to four pitches that form dissonant sounds.

[0022] Figure 7 It means forming Figure 6 FIG. 1 is a diagram showing an example of the vibration cycles of the first to fourth suction fans of the synthetic wave.

[0023] Figure 8 This is a diagram showing an example in which four first to fourth suction fans are provided with respect to one air chamber.

[0024] Fig. 9 This is a diagram showing a graph indicating changes in the uneven interval corresponding to changes in the rotation speed of the suction fan for each conveying speed.

[0025] Fig.10 This is a diagram showing an example of a table for setting the duty ratios of the first to fourth suction fans in consideration of the vibration of the conveying motor.

[0026] Fig.11 This is a diagram showing an example in which three air cells are arranged in parallel in a direction perpendicular to the conveyance direction of the print medium.

[0027] Fig.12 This is a flowchart for explaining the flow of operations of the transport unit.

[0028] Fig.13 This is a diagram showing the occurrence of resonance when four suction fans are rotated at the same speed and the vibration period of each suction fan.

[0029] Fig.14 This is a diagram showing an example of density unevenness caused by resonance of vibrations due to rotation of a plurality of suction fans.

[0030] Description of Reference Numerals

[0031] 1: Inkjet printing device;

[0032] 10: Side paper feeding unit;

[0033] 11: Paper supply table;

[0034] 12: primary paper feed roller;

[0035] 14: registration roller;

[0036] 20: Internal paper supply unit;

[0037] 21a, 21b, 21c, 21d: paper supply table;

[0038] 22a, 22b, 22c, 22d: primary paper feed rollers;

[0039] 30: image forming unit;

[0040] 31: nozzle unit;

[0041] 32a, 32b, 32c, 32d: linear nozzles;

[0042] 32: first switching mechanism;

[0043] 33: nozzle holding part;

[0044] 40: upper paper discharge unit;

[0045] 41: paper delivery table;

[0046] 42: paper discharge roller;

[0047] 43: second switching mechanism;

[0048] 50: turning part;

[0049] 51: Turning table;

[0050] 52: turning roller;

[0051] 53: conveying roller;

[0052] 60: side paper discharge unit;

[0053] 61: paper delivery table;

[0054] 62: paper discharge roller;

[0055] 70: Control unit;

[0056] 71: Operation panel;

[0057] 80: conveying unit;

[0058] 81: conveyor belt;

[0059] 82: embossing roller;

[0060] 83: First air chamber;

[0061] 84: Second air chamber;

[0062] 85a: first suction fan;

[0063] 85b: third suction fan;

[0064] 85c: second suction fan;

[0065] 85d: fourth suction fan;

[0066] 86: air chamber;

[0067] 87: conveying motor;

[0068] 90: first air chamber;

[0069] 91: Second air chamber;

[0070] 92: The third air chamber;

[0071] 93a: first suction fan;

[0072] 93b: second suction fan;

[0073] 93c: third suction fan;

[0074] 93d: fourth suction fan;

[0075] 93e: fifth suction fan;

[0076] 93f: sixth suction fan;

[0077] CR: Circular conveying path;

[0078] FR: paper feeding path;

[0079] P: Printing medium. DETAILED DESCRIPTION

[0080] Hereinafter, an inkjet printing device using an embodiment of the suction fan control device of the present invention will be described in detail with reference to the accompanying drawings. The inkjet printing device of this embodiment is characterized by a control method of a suction fan of a printing medium conveying unit. First, the overall structure of the inkjet printing device will be described. Figure 1 1 is a schematic structural diagram of the inkjet printing device 1 of this embodiment. Figure 1 The up, down, left, and right directions indicated by the arrows are the up, down, left, and right directions in the inkjet printing device 1 of this embodiment. Figure 1 The paper surface has the near front side as the front direction and the far side as the rear direction.

[0081] like Figure 1 As shown, the inkjet printing device 1 of this embodiment includes a side paper feed unit 10, an internal paper feed unit 20, an image forming unit 30, an upper paper discharge unit 40, a reversing unit 50, a side paper discharge unit 60, a control unit 70, an operation panel 71, and a transport unit 80.

[0082] The side paper feed unit 10 includes: a paper feed table 11 on which print media P such as paper or film are stacked; a primary paper feed roller 12 which guides the print media P stacked on the paper feed table 11 one by one from the top and conveys them toward a registration roller 14 described later; and a registration roller 14 which separates the print media P delivered by the primary paper feed roller 12 at a predetermined paper interval and transfers them to the image forming unit 30.

[0083] The internal paper supply unit 20 includes: paper supply tables 21a, 21b, 21c, and 21d, on which print media P are placed; and primary paper supply rollers 22a, 22b, 22c, and 22d, which respectively guide the print media P stacked on the paper supply tables 21a, 21b, 21c, and 21d one by one from the top and transport them to the paper supply transport path FR.

[0084] The print medium P fed out from the primary paper feed rollers 22 a , 22 b , 22 c , and 22 d of the internal paper feed unit 20 is also transported toward the registration roller 14 . Furthermore, the print medium P is also transported from the reversing unit 50 toward the registration roller 14 .

[0085] There is a confluence point where the conveying path of the supplied print medium P and the path where the paper having one side printed thereon circulates and is conveyed from the reversing unit 50 merge before the conveying direction of the registration roller 14. Based on this confluence point, the path on the paper supply mechanism side is referred to as the paper supply conveying path FR, and the other paths are referred to as the circulation conveying path CR.

[0086] The printing medium P supplied from the registration roller 14 is transported to the transport unit 80. The transport unit 80 includes a transport belt 81, a platen roller 82, a first air chamber 83, a second air chamber 84, and first to fourth suction fans 85a to 85d. In addition, in the present embodiment, the first air chamber 83, the second air chamber 84, and the first to fourth suction fans 85a to 85d correspond to the suction unit of the present invention.

[0087] The conveyor belt 81 and the platen roller 82 are supported by being suspended directly from the housing of the inkjet printing apparatus 1 or indirectly from a member provided in the housing other than the housing.

[0088] The conveyor belt 81 is an endless belt having a plurality of suction holes formed therein for sucking the print medium P. The platen roller 82 is a roller extending in a direction perpendicular to the conveying direction of the print medium P. Figure 1 As shown, four embossing rollers 82 are provided. Specifically, one embossing roller 82 is provided near the downstream side of the registration roller 14 and near the upstream side of the first switching mechanism 32 described later, and another group of embossing rollers 82 is provided below the group of embossing rollers 82.

[0089] like Figure 1As shown, the conveyor belt 81 is mounted on the four platen rollers 82 . The four platen rollers 82 rotate, so that the conveyor belt 81 moves to convey the printing medium P attracted to the conveyor belt 81 .

[0090] A first air chamber 83 and a second air chamber 84 for generating negative pressure are provided on the back side of the suction surface of the conveyor belt 81 for the printing medium P. The first air chamber 83 and the second air chamber 84 are box-shaped members forming a closed space, are connected to the suction holes of the conveyor belt 81, and are provided with two suction fans respectively.

[0091] Figure 2 This is a diagram showing the conveying unit 80 as viewed from above. Figure 2 As shown, the first air chamber 83 is provided upstream in the conveying direction of the printing medium P, and the second air chamber 84 is provided downstream in the conveying direction of the printing medium P. The first air chamber 83 and the second air chamber 84 are formed across half of the range where the printing medium P can be placed in the conveyor belt 81.

[0092] Furthermore, a first suction fan 85 a and a second suction fan 85 c are provided at the bottom of the first air chamber 83 , and a third suction fan 85 b and a fourth suction fan 85 d are provided at the bottom of the second air chamber 84 .

[0093] The first suction fan 85 a and the second suction fan 85 c rotate to generate negative pressure in the first air chamber 83 and the suction holes of the conveyor belt 81 distributed in the range of the first air chamber 83 , so that the print medium P is sucked onto the conveyor belt 81 .

[0094] In addition, the third suction fan 85b and the fourth suction fan 85d rotate to generate negative pressure in the second air chamber 84 and the suction holes of the conveyor belt 81 distributed in the range of the second air chamber 84, so that the print medium P is adsorbed to the conveyor belt 81. In this way, the conveyor belt 81 moves in a state where the print medium P is adsorbed to the conveyor belt 81, so that the print medium P is conveyed from the upstream side to the downstream side at a predetermined conveying speed.

[0095] Then, as described above, the printing medium P is conveyed by the conveyor belt 81 , and ink is ejected from the head unit 31 onto the printing medium P, whereby a printing process is performed on the printing medium P.

[0096] The image forming unit 30 is provided at a position facing the conveyor belt 81 of the conveyor unit 80 , and includes a head unit 31 and a head holding unit 33 .

[0097] The head unit 31 includes four line heads 32a, 32b, 32c, and 32d. Each of the line heads 32a to 32d includes a plurality of inkjet heads having a plurality of nozzles for ejecting ink.

[0098] Each of the line heads 32a to 32d is extended in a direction perpendicular to the conveying direction of the printing medium P, and ejects ink to the printing medium P conveyed by the conveying unit 80. Figure 1 As shown, four line heads 32a to 32d are arranged at predetermined intervals along a conveying path of the printing medium P. The four line heads 32a to 32d eject inks of different colors (for example, black, cyan, magenta, and yellow), respectively.

[0099] The nozzle holding part 33 is a member for installing each linear nozzle 32a to 32d. The nozzle holding part 33 is composed of a box-shaped support member, and a plurality of installation holes for inserting and installing each inkjet head of each linear nozzle 32a to 32d are formed on the bottom surface of the nozzle holding part 33. The installation holes are through holes formed so that the ink ejection surface of each inkjet head is exposed to the outside of the bottom surface of the nozzle holding part 33.

[0100] After the print medium P printed by the image forming unit 30 is delivered from the conveying unit 80, it is conveyed by conveying rollers or the like arranged on the circulating conveying path CR. A first switching mechanism 32 is provided on the circulating conveying path CR, and the first switching mechanism 32 switches whether the print medium P subjected to the printing process is guided to the side paper discharge unit 60 or guided to the upper circulating conveying path CR. Furthermore, a second switching mechanism 43 is provided on the circulating conveying path CR, and the second switching mechanism 43 switches whether the print medium P subjected to the printing process and conveyed to the upper circulating conveying path CR is guided to the upper paper discharge unit 40 or guided to the circulating conveying path CR on the side of the reversing unit 50.

[0101] The side paper discharge unit 60 includes a paper discharge table 61 protruding from the housing of the inkjet printing device 1, and a pair of paper discharge rollers 62 that guide the printed print medium P to the paper discharge table 61. The printed print medium P guided to the side paper discharge unit 60 by the first switching mechanism 32 is conveyed to the paper discharge table 61 by the paper discharge rollers 62, and is placed on the paper discharge table 61 with the printed surface facing up.

[0102] The upper paper discharge unit 40 includes a paper discharge table 41 protruding from the housing of the inkjet printing device 1, and a pair of paper discharge rollers 42 that guide the printed print medium P to the paper discharge table 41. The printed print medium P guided to the upper paper discharge unit 40 by the second switching mechanism 43 is conveyed to the paper discharge table 41 by the paper discharge rollers 42, and is placed on the paper discharge table 41 with the printed surface facing downward.

[0103] The reversing unit 50 includes a reversing table 51 for reversing the print medium P, and reversing rollers 52 for conveying the print medium P from the circulating conveyance path CR to the reversing table 51 or conveying the print medium P from the reversing table 51 to the circulating conveyance path CR.

[0104] The print medium P guided to the reversing unit 50 by the second switching mechanism 43 is conveyed from the circulating conveying path CR to the reversing table 51 by the reversing roller 52, and after a predetermined time, is conveyed again from the reversing table 51 to the circulating conveying path CR to be reversed. Then, the reversed print medium P is conveyed toward the image forming unit 30 by a plurality of rollers such as the conveying roller 53 provided on the circulating conveying path CR.

[0105] The operation panel 71 is composed of, for example, a touch panel having a liquid crystal display, and receives various setting inputs from the user. In particular, the operation panel 71 of this embodiment receives setting inputs of a suction force required for the conveyor belt 81 and a conveying speed of the conveyor belt 81 .

[0106] Figure 3 This is a block diagram showing the schematic structure of the control system of the inkjet printing device 1 of this embodiment. The control unit 70 includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, etc. The control unit 70 executes a program pre-stored in a storage medium such as a semiconductor memory or a hard disk, and activates an electrical circuit to control the operation of each part of the inkjet printing device 1.

[0107] In particular, the control unit 70 of the present embodiment controls the rotation speeds of the first to fourth suction fans 85a to 85d by changing the duty ratio of the drive voltage applied to the drive motors. Specifically, the control unit 70 controls the rotation speeds of the first to fourth suction fans 85a to 85d to different rotation speeds, respectively, and to such rotation speeds as to suppress the resonance of the vibrations caused by the rotation of the first to fourth suction fans 85a to 85d.

[0108] This can suppress the vibration of the plurality of suction fans as described above, thereby suppressing the occurrence of density unevenness caused by the vibration, and improving the printing quality.

[0109] In the present embodiment, the duty ratios of the driving voltages applied to the driving motors of the first to fourth suction fans 85a to 85d are shifted by 10% so that the fans are controlled to have different rotation speeds.

[0110] Specifically, the control unit 70 sets the duty ratio of the drive voltage applied to the drive motors of the first to fourth suction fans 85a to 85d to a magnitude as shown in Table 1 below, for example.

[0111] Table 1

[0112] Duty Cycle First suction fan 70％ Second suction fan 80％ The third suction fan 50％ Fourth suction fan 60％

[0113] Figure 4This is a diagram showing the occurrence of resonance when the duty ratio of the drive voltage applied to the drive motors of the first to fourth suction fans 85a to 85d is controlled as shown in Table 1 above. Figure 5 A to Figure 5 The graph shown in D in FIG. 8 shows the vibration cycle of the first to fourth suction fans 85a to 85d. Figure 4 The graph shown in FIG. 8 shows the composite wave of the vibration cycles of the first to fourth suction fans 85a to 85d. Figure 4 As shown, if and Fig.13 By comparing the resonance generated when the four suction fans shown in A in FIG. 1 are set to the same rotation speed, it can be seen that the amplitude of the synthetic wave is locally reduced, which can suppress the resonance. As a result, the concentration unevenness caused by the resonance of the vibration of the first suction fan to the fourth suction fan 85a to 85d can be suppressed. In addition, it can be seen from the experiment that Figure 4 as well as Fig.13 The amplitude of the composite wave indicated by A in FIG. 1 starts to affect the printed image when it reaches 75% or more of the amplitude of three suction fans (three-quarters).

[0114] In addition, in this embodiment, as shown in Table 1 above, the duty cycle (rotation speed) of the first suction fan 85a and the second suction fan 85c arranged in the first air chamber 83 is greater (higher) than the duty cycle (rotation speed) of the third suction fan 85b and the fourth suction fan 85d arranged in the second air chamber 84.

[0115] Thus, the negative pressure generated in the first air chamber 83 on the upstream side can be made higher than the negative pressure generated in the second air chamber 84 on the downstream side. In other words, the suction force of the conveyor belt 81 in the range corresponding to the first air chamber 83 on the upstream side can be made stronger than the suction force of the conveyor belt 81 in the range corresponding to the second air chamber 84 on the downstream side.

[0116] Here, since the printing medium P entering the conveyor belt 81 has high rigidity, the printing medium P warped on the suction surface of the conveyor belt 81 needs to be flattened and sucked, and thus a stronger suction force is required.

[0117] Therefore, as in the present embodiment, by making the suction force of the conveyor belt 81 in the range corresponding to the first air chamber 83 on the upstream side stronger than the suction force of the conveyor belt 81 in the range corresponding to the second air chamber 84 on the downstream side, the printing medium P can be fully adsorbed on the entrance side of the conveyor belt 81, thereby ensuring flatness.

[0118] On the other hand, for the outgoing side of the printing medium P in the conveyor belt 81, since the sucked printing medium P is simply held, a strong suction force is not required.

[0119] Therefore, by controlling the rotation speeds of the first to fourth suction fans 85a to 85d as described above, the negative pressure generated in the second air chamber 84 on the downstream side can be made lower than the negative pressure generated in the first air chamber 83 on the upstream side. That is, the suction force of the conveyor belt 81 in the range corresponding to the second air chamber 84 on the downstream side can be made weaker than the suction force of the conveyor belt 81 in the range corresponding to the first air chamber 83 on the upstream side.

[0120] This can reduce the power consumption of the third suction fan 85b and the fourth suction fan 85d on the outgoing side of the conveyor belt 81, and also reduce the load of the conveyor motor 87 that drives the platen roller 82, thereby further reducing power consumption.

[0121] In addition, the duty ratio of the driving voltage of the first suction fan to the fourth suction fan 85a~85d is not limited to the value shown in the above Table 1, and the resonance can be further suppressed by setting it to the duty ratio shown in the following Table 2. Each duty ratio of the driving voltage shown in the following Table 2 is a combination of duty ratios corresponding to the ratio of the rotational frequencies of the first suction fan to the fourth suction fan 85a~85d that can further suppress the resonance. Specifically, it is set in such a way that the four rotational frequencies of the first suction fan to the fourth suction fan 85a~85d determined by the four duty ratios become the relationship between the four frequencies corresponding to the four intervals that form the inharmonic sound.

[0122] It can be seen that when the frequency of the dissonant sound is synthesized, the resonance is suppressed and the amplitude of the synthesized wave becomes smaller. Therefore, by setting the four rotation frequencies of the first to fourth suction fans 85a to 85d to the relationship of four frequencies corresponding to the four intervals that form the dissonant sound as described above, the frequency of the vibration caused by the rotation of the first to fourth suction fans 85a to 85d can be set to the relationship of the four frequencies of the dissonant sound. That is, the resonance of the vibration caused by the rotation of the first to fourth suction fans 85a to 85d can be suppressed. In addition, as long as the relationship between the rotation frequencies (duty cycles) of the first to fourth suction fans 85a to 85d is a relationship in which the resonance of the vibration caused by the rotation of the first to fourth suction fans 85a to 85d is suppressed, any combination may be used.

[0123] Table 2

[0124] Duty Cycle First suction fan 72％ Second suction fan 100％ No. = Suction fan 50％ Fourth suction fan 36％

[0125] Figure 6 This is a diagram showing the occurrence of resonance when the duty ratio of the drive voltage applied to the drive motors of the first to fourth suction fans 85a to 85d is controlled as shown in Table 2 above. Figure 7 A to Figure 7The graph shown in D in FIG. 8 shows the vibration cycle of the first to fourth suction fans 85a to 85d. Figure 6 The graph shown in FIG. 8 shows the composite waveform of the vibration cycles of the first to fourth suction fans 85a to 85d. Figure 6 As shown, if the resonance is generated when the duty ratio is set as shown in Table 1 above (refer to Figure 4 ) shows that the portion of the amplitude of the synthetic wave exceeding 75% is further reduced, and the resonance can be further suppressed. Thus, the concentration unevenness can be further suppressed.

[0126] Furthermore, when the duty ratios of the first to fourth suction fans 85a to 85d are set as shown in Table 2 above, it is preferred that the duty ratios of the first suction fan 85a and the second suction fan 85c provided in the first air chamber 83 are set to 100% and 72%, and the duty ratios of the third suction fan 85b and the fourth suction fan 85d provided in the second air chamber 84 are set to 50% and 36%. Thus, the negative pressure generated in the first air chamber 83 on the upstream side can be made higher than the negative pressure generated in the second air chamber 84 on the downstream side.

[0127] In addition, when the duty ratios of the first to fourth suction fans 85a to 85d are set as described above, if the suction amount of the second air chamber 84 on the downstream side cannot be ensured, for example, the duty ratios of the first to fourth suction fans 85a to 85d may be set separately at intervals of more than ±5% from the duty ratios in Table 2 above, thereby ensuring the suction amount of the second air chamber 84 on the downstream side.

[0128] In the inkjet printing apparatus 1 of the above embodiment, two air chambers, namely the first air chamber 83 and the second air chamber 84, are provided. However, the present invention is not limited thereto, and a single air chamber may be provided. Figure 8 1 is a diagram showing an example in which four first to fourth suction fans 85a to 85d are provided for one air chamber 86. Figure 8 In the illustrated example, since there is only one air chamber, negative pressure generated by the rotation of the first to fourth suction fans 85a to 85d is evenly generated on the placement surface of the printing medium P of the conveyor belt 81, and the suction force is also even.

[0129] exist Figure 8 In the case of a structure in which the air chamber is one as shown, the control unit 70 preferably controls the average value of the rotational speeds of the first suction fan to the fourth suction fan 85a~85d to be close to the same rotational speed so as to obtain the same suction force as that generated when, for example, the rotational speeds of the first suction fan to the fourth suction fan 85a~85d are all set to the same rotational speed as mentioned above.

[0130] Thus, a desired suction force can be obtained and the duty ratios of the first to fourth suction fans 85a to 85d can be calculated by simple calculation processing.

[0131] In addition, in the inkjet printing device 1 of the above-mentioned embodiment, the duty ratio (rotation speed) is controlled by considering the resonance of the vibration of the first to fourth suction fans 85a to 85d, but the duty ratio (rotation speed) of the first to fourth suction fans 85a to 85d may also be set by considering the vibration caused by the rotation of the conveying motor 87 that drives the platen roller 82. That is, the duty ratio (rotation speed) of the first to fourth suction fans 85a to 85d may also be set in a manner that also suppresses the resonance of the vibration of the conveying motor 87 and the vibration caused by the rotation of the first to fourth suction fans 85a to 85d. In this way, the uneven concentration caused by the resonance of the vibration of the conveying motor 87 and the vibration of the first to fourth suction fans 85a to 85d can be suppressed, and the printing quality can be further improved. The resonance of the vibration of the suction fan and the vibration of the conveying motor of the platen roller is described below.

[0132] Fig. 9 The graph showing the change in the uneven interval corresponding to the change in the rotation speed of the suction fan is the graph showing the conveying speed (hereinafter simply referred to as conveying speed) of the conveying motor for each platen roller. Fig. 9 The horizontal axis of the graph shown is the rotation speed of the suction fan, and the vertical axis represents the change in the interval of the above-mentioned unevenness. In addition, the rotation speed of the suction fan is represented by frequency (Hz). Fig. 9 Graph a shown is a case where the conveying speed is 700 mm / s, graph b is a case where the conveying speed is 600 mm / s, and graph c is a case where the conveying speed is 500 mm / s.

[0133] like Fig. 9 As shown, the faster the rotation speed of the suction fan is, the narrower the interval of unevenness caused by the vibration caused by its rotation is. In addition, the faster the conveying speed is, the wider the interval of unevenness caused by the vibration of the suction fan is.

[0134] On the other hand, it is known that the uneven interval caused by the vibration of the conveying motor of the platen roller is determined by the vibration generation period of the conveying motor itself and the ratio of the gears connected to the conveying motor and the platen roller, and is fixed regardless of the speed change of the conveying motor. In addition, the interval of the vibration of the conveying motor is set to 6 mm.

[0135] In this case, the case where the vibration caused by the rotation of the suction fan and the vibration caused by the conveying motor resonate refers to, for example, the case where the conveying speed is 700 mm / s and the duty cycle of the suction fan is 70%. That is, when the conveying speed is 700 mm / s, if there is a suction fan with a duty cycle of 70% among the first to fourth suction fans 85a to 85d, the vibration of the suction fan and the vibration of the conveying motor 87 resonate, that is, the uneven intervals of the suction fan and the uneven intervals of the conveying motor overlap, and the concentration unevenness becomes larger. Similarly, when the conveying speed is 600 mm / s, if there is a suction fan with a duty cycle of 40%, the vibration of the suction fan and the vibration of the conveying motor 87 resonate, and the concentration unevenness becomes larger. In addition, when the conveying speed is 500 mm / s, if there is a suction fan with a duty cycle of 20%, the vibration of the suction fan and the vibration of the conveying motor 87 resonate, and the concentration unevenness becomes larger.

[0136] That is, the relationship between the conveying speed and the duty ratio of the suction fan to be avoided at the conveying speed is shown in Table 3 below.

[0137] Table 3

[0138]

[0139] Therefore, when there is a duty ratio corresponding to the conveying speed shown in Table 3 among the duty ratios of the first to fourth suction fans 85a to 85d, the duty ratio may be corrected and set. The correction of the duty ratio of the suction fan will be described in detail below.

[0140] Fig.10 The table shows an example of setting the duty ratio so that the rotation frequencies of the first to fourth suction fans 85a to 85d have a relationship with the frequencies of the inharmonic sound as described above. Fig.10 The duty ratios of the first to fourth suction fans 85a to 85d in the table shown are values ​​calculated so that the average value thereof approaches the set value in the table.

[0141] Fig.10 The setting values ​​in the table shown are appropriately set according to the suction force required for the conveyor belt 81 , and are set according to, for example, the type of the print medium P. The setting values ​​are set and input by, for example, the user on the operation panel 71 . Fig.10 The average value in the table shown indicates an actual average value when the duty ratios of the first to fourth suction fans 85a to 85d are calculated as described above.

[0142] For example, when the setting value is 20%, the four duty ratios calculated in a manner that becomes the frequency relationship of the dissonant sound are 24%, 33%, 17%, and 12%, and the average value thereof is approximately 22%. In this case, if the four duty ratios are compared with the duty ratios to be avoided shown in Table 3 above, the difference between the duty ratios 24% and 17% among the four duty ratios and the duty ratio 20% to be avoided corresponding to the conveying speed of 500 mm / s in Table 3 above is less than 5%.

[0143] Therefore, when the set value is set to 20% and the conveying speed is set to 500 mm / s, the control unit 70 changes the duty cycle of the first suction fan 85a from 24% to 15%, and changes the duty cycle of the third suction fan 85b from 17% to 15%, so that the difference from the duty cycle of 20% that should be avoided is more than 5%.

[0144] In addition, when the difference between the duty ratio of the first to fourth suction fans 85a to 85d and the duty ratio to be avoided is less than 5%, as a method of changing the duty ratio, there is a method of making the duty ratio Fig.10 The method of changing the duty ratio to a larger value and a smaller value is shown in the figure, but it is preferable to decide which value to change to based on the relationship between the set value and the average value. That is, when the set value is 20% and the average value is 22%, since the average value is larger than the set value, it is preferable to change the duty ratio to a value smaller than the set value. Fig.10 The duty ratio shown is small. This allows the duty ratio to be changed so that the average value approaches the set value.

[0145] In addition, when the setting value is 20%, when the conveying speed is set to 700 mm / s or 600 mm / s, the control unit 70 sets the duty ratio of the first to fourth suction fans 85a to 85d to Fig.10 The four duty cycles are shown in the table.

[0146] In addition, for example, when the setting value is 30%, the four duty ratios calculated in a manner that becomes the frequency relationship of the dissonant sound are 36%, 50%, 25%, and 18%, and the average value thereof is approximately 32%. In this case, if the four duty ratios are compared with the duty ratios to be avoided shown in Table 3 above, the difference between the duty ratio 18% among the four duty ratios and the duty ratio 20% to be avoided corresponding to the conveying speed of 500 mm / s in Table 3 above is less than 5%. In addition, the difference between the duty ratio 36% and the duty ratio 40% to be avoided corresponding to the conveying speed of 600 mm / s in Table 3 above is less than 5%.

[0147] Therefore, when the set value is set to 30% and the conveying speed is set to 500 mm / s, the control unit 70 changes the duty cycle of the fourth suction fan 85d from 18% to 15%, so that the difference between it and the duty cycle of 20% that should be avoided is more than 5%. In addition, when the set value is set to 30% and the conveying speed is set to 600 mm / s, the control unit 70 changes the duty cycle of the first suction fan 85a from 36% to 35%, so that the difference between it and the duty cycle of 40% that should be avoided is more than 5%. In addition, when the set value is set to 30% and the conveying speed is set to 700 mm / s, the control unit 70 sets the duty cycles of the first to fourth suction fans 85a to 85d to Fig.10 The four duty cycles are shown in the table.

[0148] In addition, for example, when the setting value is 40%, the four duty ratios calculated in a manner that becomes the frequency relationship of the dissonant sound are 48%, 67%, 33% and 24%, and the average value thereof is about 43%. In this case, if the four duty ratios are compared with the duty ratios to be avoided shown in Table 3 above, the difference between the duty ratio 24% among the four duty ratios and the duty ratio 20% to be avoided corresponding to the conveying speed of 500 mm / s in Table 3 above is less than 5%. In addition, the difference between the duty ratio 67% and the duty ratio 70% to be avoided corresponding to the conveying speed of 700 mm / s in Table 3 above is less than 3%.

[0149] Therefore, when the set value is set to 40% and the conveying speed is set to 500 mm / s, the control unit 70 changes the duty cycle of the fourth suction fan 85d from 24% to 15%, so that the difference between it and the duty cycle of 20% that should be avoided is more than 5%. When the set value is set to 40% and the conveying speed is set to 700 mm / s, the duty cycle of the second suction fan 85c is changed from 67% to 65%, so that the difference between it and the duty cycle of 70% that should be avoided is more than 5%. In addition, when the set value is set to 40% and the conveying speed is set to 600 mm / s, the control unit 70 sets the duty cycles of the first to fourth suction fans 85a to 85d to Fig.10 The four duty cycles are shown in the table.

[0150] In addition, when the set value is 50%, 60%, 70% and 80%, the control unit 70 is also based on the same idea. Fig.10 As shown in the column of the change method of the table shown in the figure, the duty ratios of the first to fourth suction fans 85a to 85d are changed and set. In other cases, the duty ratios are set to Fig.10The four duty ratios in the table shown in FIG. 1 are shown in FIG. 1 . In addition, when the set value is 80%, the average value is 78%, which is smaller than the set value. Therefore, when the control unit 70 changes the duty ratio of the third suction fan 85b from 67%, it does not change it to 65%, but changes it to 75% to make the average value close to the set value.

[0151] In addition, according to Fig.10 When the duty ratios of the first to fourth suction fans 85a to 85d are set in the table shown, the number of air chambers may be two as described above or may be one.

[0152] In the inkjet printing device 1 of the above embodiment, the first air chamber 83 is provided on the upstream side in the conveying direction of the printing medium P, and the second air chamber 84 is provided on the downstream side in the conveying direction. However, the present invention is not limited to this. Fig.11 As shown in FIG. 1 , three air chambers, namely, a first air chamber 90 , a second air chamber 91 , and a third air chamber 92 , are arranged side by side in a direction perpendicular to the conveyance direction of the print medium P.

[0153] In this case, the first suction fan 93a and the second suction fan 93b may be provided in the first air chamber 90, the third suction fan 93c and the fourth suction fan 93d may be provided in the second air chamber 91, and the fifth suction fan 93e and the sixth suction fan 93f may be provided in the third air chamber 92. Furthermore, the duty ratio may be set so that the rotation frequencies of the first to sixth suction fans 93a to 93f become the frequencies of the inharmonic sound.

[0154] In addition, if Fig.11 As shown, when three air chambers, namely, the first air chamber 90, the second air chamber 91, and the third air chamber 92, are provided, it is preferable to set the duty ratios of the first to sixth suction fans 93a to 93f so that the suction forces of the first air chamber 90 and the third air chamber 92 on both sides are higher than the suction force of the second air chamber 91 in the center. In this way, the warping of the ends on both sides extending in the conveying direction of the printing medium P can be suppressed, the jamming of the printing medium P caused by the warping can be prevented, and the reduction in printing quality can be suppressed.

[0155] In addition, in the inkjet printing device 1 of the above embodiment, when setting the rotation speeds of the plurality of suction fans, it is preferred to actually check the intensity of the influence on the printed matter in a state where the suction fans are individually stopped in advance, check the strength of the vibration of each suction fan, and set the rotation speed of the suction fan with greater vibration to a value lower than the average value of the rotation speeds of all the suction fans. In this way, the vibration caused by the rotation of the suction fans can be effectively suppressed.

[0156] Next, refer to Fig.12The flowchart shown explains the flow of the operation of the transport unit 80 of the inkjet printing apparatus 1 according to the above embodiment.

[0157] First, before starting to feed the print medium P, the conveying speed of the conveying unit 80 is set ( S10 ). Then, the control unit 70 drives the conveying motor 87 , and the platen roller 82 rotates at a rotation speed corresponding to the conveying speed set in S10 , and the conveying belt 81 moves ( S12 ).

[0158] Next, the control unit 70 sets the duty ratio of the driving voltage of the first to fourth suction fans 85a to 85d to the above-mentioned duty ratio (S14).

[0159] Next, the control unit 70 applies the driving voltage of the duty ratio set in S14 to the driving motors of the first to fourth suction fans 85a to 85d, and starts driving the first to fourth suction fans 85a to 85d (S16). Then, the control unit 70 starts the paper feeding operation of the printing medium P (S18).

[0160] The following additional remarks are also disclosed regarding the suction fan control device of the present invention. (Additional remarks)

[0161] The suction fan control device of the present invention may include a conveying unit that sucks and conveys the printing medium, and the suction unit may generate negative pressure for sucking the printing medium onto the conveying unit.

[0162] In the suction fan control device of the present invention, the suction unit can have air chambers that generate negative pressure through the rotation of the suction fan on the upstream side and the downstream side of the conveying direction of the printing medium, respectively, and the control unit can make the rotation speed of the suction fan that generates negative pressure in the air chamber on the upstream side higher than the rotation speed of the suction fan that generates negative pressure in the air chamber on the downstream side.

[0163] In addition, in the suction fan control device of the present invention, the suction part can have an air chamber that generates negative pressure through the rotation of multiple suction fans, and the control part can control the average value of the rotation speeds of the multiple suction fans to be close to the same rotation speed so as to obtain the same suction force as the suction force generated when the rotation speeds of the multiple suction fans are all set to the above-mentioned same rotation speed.

[0164] Furthermore, in the suction fan control device of the present invention, the control unit can set the rotation speeds of the plurality of suction fans based on the conveyance speed of the print medium.

[0165] Furthermore, in the suction fan control device of the present invention, the control unit can set the rotational frequencies of the plurality of suction fans to frequencies corresponding to the plurality of pitches that form the dissonant sound.

Claims

1. A suction fan control device, characterized in that: The suction fan control device comprises: a suction section having a plurality of suction fans that generate negative pressure for sucking the printing medium; and a control unit, which controls the suction fan, The suction unit has air chambers on the upstream side and the downstream side of the conveying direction of the printing medium, respectively, for generating negative pressure by the rotation of the suction fan, and the plurality of suction fans are directly mounted on the air chambers, respectively. The control unit controls the rotation speeds of the plurality of suction fans to be different from each other and to be rotation speeds such that resonance of vibrations caused by rotation of the plurality of suction fans is suppressed. The control unit makes the rotation speed of the suction fan for generating negative pressure in the upstream air chamber higher than the rotation speed of the suction fan for generating negative pressure in the downstream air chamber. The control section sets the rotation speeds of the plurality of suction fans based on a conveyance speed of the print medium so as to suppress vibration caused by rotation of the suction fans and vibration resonance caused by a conveyance motor for conveying the print medium.

2. The suction fan control device according to claim 1, characterized in that: The suction fan control device includes a conveying unit for sucking and conveying the printing medium. The suction unit generates negative pressure for causing the printing medium to be attracted to the conveying unit.

3. The suction fan control device according to claim 1 or 2, characterized in that: In order to obtain the same suction force as that generated when the rotation speeds of the plurality of suction fans are all set to the same rotation speed, the control unit performs control so that an average value of the rotation speeds of the plurality of suction fans approaches the same rotation speed.

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