JP2022100083A - Suction fun control device - Google Patents

Abstract

To provide a suction fan control device capable of suppressing vibration of a plurality of suction fans.SOLUTION: A suction fan control device includes: a suction part having first to fourth suction fans 85a to 85d for generating a negative pressure for sucking a print medium; and a control part 70 that controls the first to fourth suction fans 85a to 85d. The control part 70 has the rotation speeds of the first to fourth suction fans 85a to 85d at different rotation speeds from each other, and controls the rotation speed so as to suppress the resonance of vibration due to the rotation of the first to fourth suction fans 85a to 85d.SELECTED DRAWING: Figure 1

Description

The present invention relates to a suction fan control device that controls a plurality of suction fans that generate a negative pressure for sucking a print medium.

Conventionally, an inkjet printing apparatus has been proposed in which ink is ejected from an inkjet head onto a printing medium to perform printing while conveying a printing medium made of paper or film.

As a transfer device for a print medium in such an inkjet printing device, a transfer device using a transfer belt has been proposed. Specifically, a suction fan is provided so as to face the surface of the transport belt on the back side of the installation surface of the print medium, and the rotation of the suction fan generates a negative pressure in a large number of suction holes formed in the transport belt. A transport device for sucking a print medium on a transport belt has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2019-127364

Here, the rotating body, including the suction fan used in the transport device as described above, vibrates according to the number of rotations when the center of gravity is deviated (eccentric) with respect to the rotation axis. This is because the force generated by the eccentricity causes one reciprocating vibration during one rotation of the rotating body.

When a suction fan vibrates in a transfer device using a suction fan, the vibration propagates to the transfer belt and may affect the landing position of ink on the print medium conveyed by the transfer belt. .. Specifically, when the suction fan vibrates in the transport direction of the print medium, the transport belt moves toward the transport direction, so that the print medium is transported faster than it should be, and the ink landing interval becomes coarser. On the other hand, when the suction fan vibrates in the direction opposite to the transfer direction of the print medium, the transfer belt moves in the direction opposite to the transfer direction, so that the transfer of the print medium becomes slower than it should be and the ink landing intervals become dense. .. In particular, the hanging belt platen is easily affected by the vibration of the suction fan.

Further, in particular, when a plurality of the same suction fans are installed and used at the same rotation speed, the vibration due to the rotation of the plurality of suction fans resonates, and the influence thereof is further emphasized. FIG. 13A is a diagram showing a state of resonance generation when four suction fans have the same rotation speed. FIG. 13A shows a state in which resonance occurs when each suction fan vibrates about 70 times in the process of transporting an A3 size print medium. The graph shown in FIG. 13B shows the vibration cycle of each suction fan, and the graph shown in FIG. 13A shows the combined wave of the vibration cycle of the four suction fans shown in FIG. 13B. Since the vibration cycles of the four suction fans are the same, they resonate in the combined wave and are emphasized four times. When such vibration resonance occurs, periodic density unevenness as shown in FIG. 14 occurs, which causes deterioration of print quality.

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

The suction fan control device of the present invention includes a suction unit having a plurality of suction fans for generating a negative pressure for sucking the print medium, and a control unit for controlling the suction fan, and the control unit is a plurality of suction fans. The number of rotations of the above is controlled to be different from each other and to suppress the resonance of vibration due to the rotation of a plurality of suction fans.

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 suppress the resonance of vibration due to the rotation of the plurality of suction fans. Therefore, it is possible to suppress the vibration of a plurality of suction fans.

The figure which shows the schematic structure of the inkjet printing apparatus which used one Embodiment of the suction fan control apparatus of this invention. Top view of the transport unit A block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. The figure which shows the occurrence state of resonance when the duty ratio of the drive voltage of the 1st to 4th suction fans is controlled by shifting by 10%. The figure which shows an example of the vibration period of the 1st to 4th suction fans which form the synthetic wave shown in FIG. The figure which shows the occurrence state of resonance when the four rotation frequencies of the 1st to 4th suction fans are controlled to be the frequency corresponding to the 4 pitches forming a dissonant sound. The figure which shows an example of the vibration period of the 1st to 4th suction fans which form the synthetic wave shown in FIG. The figure which shows the example which provided four 1st to 4th suction fans for one air chamber. A graph showing the change in the uneven interval according to the change in the rotation speed of the suction fan for each transfer speed. The figure which shows an example of the table which sets the duty of the 1st to 4th suction fans in consideration of the vibration of a transfer motor. The figure which shows the example which provided three air chambers side by side in the direction orthogonal to the transport direction of a print medium. Flow chart to explain the operation flow of the transport unit The figure which shows the occurrence state of resonance and the vibration cycle of each suction fan when four suction fans have the same rotation speed. The figure which shows an example of the density unevenness generated by the resonance of vibration by the rotation of a plurality of suction fans.

Hereinafter, an inkjet printing apparatus using an embodiment of the suction fan control device of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of the present embodiment is characterized by a method of controlling a suction fan of a transfer unit of a printing medium. First, the configuration of the entire inkjet printing apparatus will be described. FIG. 1 is a schematic configuration diagram of the inkjet printing apparatus 1 of the present embodiment. The vertical and horizontal directions indicated by the arrows in FIG. 1 are the vertical and horizontal directions in the inkjet printing apparatus 1 of the present embodiment. Further, the front side is the front direction and the back side is the rear direction with respect to the paper surface of FIG.

As shown in FIG. 1, the inkjet printing apparatus 1 of the present 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, an inversion unit 50, and a side surface. It includes a paper ejection unit 60, a control unit 70, an operation panel 71, and a transport unit 80.

The side paper feed unit 10 feeds out the paper feed table 11 on which the print medium P such as paper or film is loaded and the print medium P loaded on the paper feed table 11 one by one from the upper part, and the registration roller 14 described later. It is provided with a primary paper feed roller 12 that conveys the print medium P toward the image forming unit 30 and a registration roller 14 that delivers the print medium P sent out by the primary paper feed roller 12 to the image forming unit 30 at predetermined paper intervals.

The internal paper feed unit 20 has one sheet from the top of each of the paper feed trays 21a, 21b, 21c, 21d on which the print medium P is placed and the print media P loaded on the paper feed trays 21a, 21b, 21c, 21d. It is provided with primary paper feed rollers 22a, 22b, 22c, 22d that are fed out one by one and conveyed onto the paper feed transfer path FR.

The print media P sent out from the primary paper feed rollers 22a, 22b, 22c, 22d of the internal paper feed unit 20 are also conveyed toward the resist roller 14, and further, the print medium is also conveyed from the reversing unit 50 toward the resist roller 14. P is transported.

In front of the register roller 14 in the transport direction, there is a confluence point where the transport path of the fed print medium P and the path in which the paper printed on one side circulates and is conveyed from the reversing section 50 meet. exist. Based on this confluence, the path on the paper feed mechanism side is called the paper feed transfer path FR, and the other paths are called the circulation transfer path CR.

The print medium P fed from the resist roller 14 is conveyed to the transfer unit 80. The transport unit 80 includes a transport belt 81, a platen roller 82, a first air chamber 83 and a second air chamber 84, and first to fourth suction fans 85a to 85d. 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.

The transport 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 other than the housing provided in the housing.

The transport belt 81 is an annular belt, and has a large number of suction holes for sucking the print medium P. The platen roller 82 is a roller extended in a direction orthogonal to the transport direction of the print medium P. In this embodiment, as shown in FIG. 1, four platen rollers 82 are provided. Specifically, one platen roller 82 is installed in the vicinity of the downstream side of the resist roller 14 and in the vicinity of the upstream side of the first switching mechanism 32, which will be described later, and below the set of platen rollers 82, Another set of platen rollers 82 is installed.

As shown in FIG. 1, the transport belt 81 is hung on the four platen rollers 82 described above, and when the four platen rollers 82 rotate, the transport belt 81 moves and is attracted to the transport belt 81. The print medium P is conveyed.

A first air chamber 83 and a second air chamber 84 that generate a negative pressure are provided on the back side of the suction surface of the print medium P in the transport belt 81. The first air chamber 83 and the second air chamber 84 are box-shaped members forming a closed space, and communicate with the suction holes of the transport belt 81 and are provided with two suction fans, respectively. There is.

FIG. 2 is a view of the transport unit 80 as viewed from above. As shown in FIG. 2, the first air chamber 83 is provided on the upstream side of the print medium P in the transport direction, and the second air chamber 84 is provided on the downstream side of the print medium P in the transport direction. The first air chamber 83 and the second air chamber 84 are formed over half the range in which the print medium P can be installed in the transport belt 81, respectively.

A first suction fan 85a and a second suction fan 85c are provided at the bottom of the first air chamber 83, and a third suction fan 85b and a third suction fan 85b are provided at the bottom of the second air chamber 84. The suction fan 85d of No. 4 is provided.

The rotation of the first suction fan 85a and the second suction fan 85c causes a negative pressure to be generated in the suction holes of the transport belt 81 distributed in the range of the first air chamber 83 and the first air chamber 83. As a result, the print medium P is attracted to the transport belt 81.

Further, the rotation of the third suction fan 85b and the fourth suction fan 85d causes a negative pressure to be generated in the suction holes of the transport belt 81 distributed in the range of the second air chamber 84 and the second air chamber 84. As a result, the print medium P is attracted to the transport belt 81. By moving the transfer belt 81 with the print medium P adsorbed on the transfer belt 81 in this way, the print medium P is conveyed from the upstream side to the downstream side at a predetermined transfer speed.

Then, as described above, while the print medium P is conveyed by the transfer belt 81, ink is ejected from the head unit 31 to the print medium P, whereby the print process is applied to the print medium P.

The image forming unit 30 is provided at a position facing the transport belt 81 of the transport unit 80, and includes a head unit 31 and a head holder 33.

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

Each of the line heads 32a to 32d extends in a direction orthogonal to the transport direction of the print medium P, and ejects ink to the print medium P conveyed by the transfer unit 80. As shown in FIG. 1, the four line heads 32a to 32d are arranged at predetermined intervals along the transport path of the print medium P. The four line heads 32a to 32d eject inks of different colors (for example, black, cyan, magenta, and yellow).

The head holder 33 is a member on which each line head 32a to 32d is installed. The head holder 33 is composed of a box-shaped support member, and a plurality of installation holes in which the inkjet heads of the line heads 32a to 32d are fitted and installed are formed on the bottom surface of the head holder 33. There is. The installation hole is a through hole, and is formed so that the ink ejection surface of each inkjet head is exposed on the outside of the bottom surface of the head holder 33.

The print medium P printed by the image forming unit 30 is carried out from the transport unit 80 and then transported by a transport roller or the like arranged on the circulation transport path CR. On the circulation transport path CR, a first switching mechanism 32 for switching whether to guide the print medium P subjected to the printing process to the side paper ejection unit 60 or on the upper circulation transport path CR is provided. Has been printed. Further, a printing process is performed on the circulation transport path CR, and the print medium P conveyed on the upper circulation transfer path CR is guided to the upper paper ejection section 40, or the circulation transfer path on the reversing section 50 side. A second switching mechanism 43 for switching whether to guide on the CR is provided.

The side paper ejection unit 60 has a paper ejection table 61 protruding from the housing of the inkjet printing apparatus 1, and a pair of paper ejection rollers 62 for guiding the printed print medium P to the paper ejection table 61. Then, the printed print medium P guided to the side paper ejection unit 60 by the first switching mechanism 32 is conveyed to the paper ejection table 61 by the paper ejection roller 62, and the printing surface is turned up on the paper ejection table 61. It will be placed.

The upper paper ejection unit 40 has a paper ejection table 41 protruding from the housing of the inkjet printing apparatus 1, and a pair of paper ejection rollers 42 for guiding the printed print medium P to the paper ejection table 41. Then, the printed print medium P guided to the upper paper ejection unit 40 by the second switching mechanism 43 is conveyed to the paper ejection table 41 by the paper ejection roller 42, and the printing surface is turned down on the paper ejection table 41. It will be placed.

The inversion unit 50 is an inversion table 51 that inverts the print medium P, and an inversion that conveys the print medium P from the circulation transfer path CR to the inversion table 51, or conveys the print medium P from the inversion table 51 onto the circulation transfer path CR. It is equipped with a roller 52.

The print medium P guided to the reversing section 50 by the second switching mechanism 43 is transported from the circulation transport path CR to the reversing table 51 by the reversing roller 52, and after a predetermined time elapses, the printing medium P is again transferred from the reversing table 51 to the circulation transport path CR. By being transported, the front and back are reversed. Then, the print medium P whose front and back sides are reversed is conveyed toward the image forming unit 30 by a plurality of rollers such as a transfer roller 53 provided on the circulation transfer path CR.

The operation panel 71 is composed of, for example, a touch panel having a liquid crystal display, and accepts various setting inputs by the user. In particular, the operation panel 71 of the present embodiment receives the setting value of the suction force required for the transport belt 81 and the setting input of the transport speed of the transport belt 81.

FIG. 3 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1 of the present embodiment. The control unit 70 includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, and the like. The control unit 70 controls the operation of each unit of the inkjet printing apparatus 1 by executing a program stored in advance in a storage medium such as a semiconductor memory or a hard disk and operating an electric circuit.

In particular, the control unit 70 of the present embodiment controls the rotation speed by changing the duty ratio of the drive voltage applied to the drive motors of the first to fourth suction fans 85a to 85d. Specifically, the control unit 70 vibrates the rotation speeds of the first to fourth suction fans 85a to 85d at different rotation speeds due to the rotation of the first to fourth suction fans 85a to 85d. The rotation speed is controlled so as to suppress the resonance of.

This makes it possible to suppress the vibration of the plurality of suction fans as described above. Therefore, it is possible to suppress the occurrence of density unevenness due to the vibration, and it is possible to improve the print quality.

In the present embodiment, the duty ratios of the drive voltages applied to the drive motors of the first to fourth suction fans 85a to 85d are shifted by 10% to control the rotation speeds to be different from each other.

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

FIG. 4 is a diagram showing a state of resonance generation 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. The graphs shown in FIGS. 5A to 5D represent the vibration cycles of the first to fourth suction fans 85a to 85d, and the graph shown in FIG. 4 shows the vibration cycles of the first to fourth suction fans 85a to 85d. Shows the combined wave of. As shown in FIG. 4, the amplitude of the combined wave is partially smaller than that in the case where the four suction fans shown in FIG. 13A have the same rotation speed, and the resonance can be suppressed. You can see that there is. Thereby, the density unevenness generated by the resonance of the vibration of the first to fourth suction fans 85a to 85d can be suppressed. It has been experimentally found that the amplitude of the synthetic wave shown in FIGS. 4 and 13A affects the printed image from around 75% or more, which is equivalent to three suction fans (three-quarters).

Further, in the present embodiment, as shown in Table 1 above, the duty ratio (rotation speed) of the first suction fan 85a and the second suction fan 85c provided in the first air chamber 83 is the second. It is set to be larger (higher) than the duty ratio (rotation speed) of the third suction fan 85b and the fourth suction fan 85d provided in the air chamber 84 of 2.

As a result, 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. That is, the suction force of the transport 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 transport belt 81 in the range corresponding to the second air chamber 84 on the downstream side. can.

Here, the entry side of the print medium P in the transport belt 81 has a strong stiffness, and the print medium P that is warped against the suction surface of the transport belt 81 needs to be flattened and sucked, so that the suction force is strong. Is required.

Therefore, as in the present embodiment, the suction force of the transport belt 81 in the range corresponding to the first air chamber 83 on the upstream side is the suction force of the transport belt 81 in the range corresponding to the second air chamber 84 on the downstream side. By making the force stronger than the force, the print medium P can be sufficiently attracted on the approach side of the transport belt 81, and the flatness can be ensured.

On the other hand, the carry-out side of the print medium P in the transport belt 81 does not require a strong suction force because it only holds the print medium P once adsorbed.

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 transferred to the first air chamber on the upstream side. It can be lower than the negative pressure generated in 83. That is, the suction force of the transport belt 81 in the range corresponding to the second air chamber 84 on the downstream side may be weaker than the suction force of the transport belt 81 in the range corresponding to the first air chamber 83 on the upstream side. can.

As a result, on the carry-out side of the transport belt 81, the power consumption of the third suction fan 85b and the fourth suction fan 85d can be reduced, and the load of the transport motor 87 for driving the platen roller 82 is also reduced. As a result, the power consumption can be further reduced.

Further, the duty ratio of the drive voltage of the first to fourth suction fans 85a to 85d is not limited to the value shown in Table 1 above, but by setting the duty ratio as shown in Table 2 below, resonance is further caused. It can be suppressed. Each duty ratio of the drive voltage shown in Table 2 below is a combination of duty ratios according to the ratio of the rotation frequencies of the first to fourth suction fans 85a to 85d capable of further suppressing resonance. Specifically, the four rotation frequencies of the first to fourth suction fans 85a to 85d, which are determined by the four duty ratios, are set to have a relationship of four frequencies according to the four pitches forming the dissonance. ing.

It is known that when the frequency of the dissonant sound is synthesized, the resonance is suppressed and the amplitude of the synthesized wave becomes small. Therefore, as described above, by making the four rotation frequencies of the first to fourth suction fans 85a to 85d into a relationship of four frequencies corresponding to the four pitches forming the dissonance, the first to fourth suction fans The frequency of vibration caused by the rotation of the suction fans 85a to 85d can be related to the four frequencies of the dissonant sound. That is, it is possible to suppress the resonance of vibration caused by the rotation of the first to fourth suction fans 85a to 85d. The relationship between the rotation frequencies (duty ratios) of the first to fourth suction fans 85a to 85d is such that the resonance of vibration caused by the rotation of the first to fourth suction fans 85a to 85d is suppressed. Any combination may be used.

FIG. 6 is a diagram showing the state of resonance generation 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. The graphs shown in FIGS. 7A to 7D represent the vibration cycles of the first to fourth suction fans 85a to 85d, and the graph shown in FIG. 6 shows the vibration cycles of the first to fourth suction fans 85a to 85d. The composite waveform of is shown. As shown in FIG. 6, when compared with the resonance occurrence state (see FIG. 4) when the duty ratio is set as shown in Table 1 above, the portion where the amplitude of the combined wave exceeds 75% is further reduced, and the resonance is further reduced. It can be seen that can be suppressed. Thereby, the density unevenness can be further suppressed.

When the duty ratios of the first to fourth suction fans 85a to 85d are set as shown in Table 2 above, the first suction fan 85a and the second suction fan 85c provided in the first air chamber 83 are provided. Duty ratios can be 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 can be set to 50% and 36%. preferable. As a result, 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.

If the duty ratios of the first to fourth suction fans 85a to 85d are set as described above and the suction amount of the second air chamber 84 on the downstream side cannot be secured, for example, the first to fourth suction fans The duty ratios of the suction fans 85a to 85d may be set at intervals of ± 5% or more from the duty ratios in Table 2 above so that the suction amount of the second air chamber 84 on the downstream side can be secured. ..

Further, in the inkjet printing apparatus 1 of the above embodiment, two air chambers, a first air chamber 83 and a second air chamber 84, are provided, but the present invention is not limited to this, and one air chamber is provided. You may do it. FIG. 8 is a diagram showing an example in which four first to fourth suction fans 85a to 85d are provided for one air chamber 86. In the case of the example shown in FIG. 8, since there is only one air chamber, the negative pressure generated by the rotation of the first to fourth suction fans 85a to 85d is evenly distributed on the installation surface of the print medium P of the conveyor belt 81. It is generated and the suction force becomes even.

When the air chamber is configured as one as shown in FIG. 8, the control unit 70 has, for example, the suction force generated when the rotation speeds of the first to fourth suction fans 85a to 85d are all the same rotation speed. It is preferable to control so that the average value of the rotation speeds of the first to fourth suction fans 85a to 85d approaches the same rotation speed so that the same suction force can be obtained.

As a result, 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 a simple calculation process.

Further, in the inkjet printing apparatus 1 of the above embodiment, the duty ratio (rotational speed) is controlled in consideration of the vibration resonance of the first to fourth suction fans 85a to 85d, but the platen roller 82 is used. The duty ratio (rotational speed) of the first to fourth suction fans 85a to 85d may be set in consideration of the vibration due to the rotation of the driven transfer motor 87. That is, the duty ratio (rotation speed) of the first to fourth suction fans 85a to 85d so as to suppress the resonance between the vibration of the transfer motor 87 and the vibration due to the rotation of the first to fourth suction fans 85a to 85d. May be set. As a result, density unevenness due to resonance between the vibration of the transfer motor 87 and the vibration of the first to fourth suction fans 85a to 85d can be suppressed, and the print quality can be further improved. Hereinafter, the resonance between the vibration of the suction fan and the vibration of the transfer motor of the platen roller will be described.

FIG. 9 shows a graph showing a change in the interval of unevenness according to a change in the rotation speed of the suction fan, and shows the above graph for each transfer speed (hereinafter, simply referred to as a transfer speed) of the transfer motor of the platen roller. .. The horizontal axis of the graph shown in FIG. 9 is the rotation speed of the suction fan, and the vertical axis shows the change in the above-mentioned unevenness interval. The rotation speed of the suction fan is expressed in frequency (Hz). The graph a shown in FIG. 9 is the case where the transport speed is 700 mm / s, the graph b is the case where the transport speed is 600 mm / s, and the graph c is the case where the transport speed is 500 mm / s.

As shown in FIG. 9, the faster the rotation speed of the suction fan, the narrower the interval of unevenness generated by the vibration due to the rotation. Further, the faster the transport speed, the wider the interval of unevenness due to the vibration of the suction fan.

On the other hand, the interval of unevenness due to the vibration of the transfer motor of the platen roller is determined by the mechanism such as the vibration generation cycle of the transfer motor itself and the ratio of the gear connected to the transfer motor and the platen roller, regardless of the speed change of the transfer motor. It is known to be constant. Here, the vibration interval of the transfer motor is set to 6 mm.

In this case, the case where the vibration due to the rotation of the suction fan and the vibration due to the transfer motor resonate is, for example, when the transfer speed is 700 mm / s and the duty ratio of the suction fan is 70%. That is, when the transfer speed is 700 mm / s, if a suction fan having a duty ratio of 70% exists in the above-mentioned first to fourth suction fans 85a to 85d, the suction fan vibrates and the transfer motor 87 vibrates. Resonates with each other, that is, the interval between the unevenness of the suction fan and the interval of the unevenness of the conveyor motor overlap, and the density unevenness becomes large. Similarly, when the transfer readability is 600 mm / s, if a suction fan having a duty ratio of 40% exists, the vibration of the suction fan and the vibration of the transfer motor 87 resonate, and the density unevenness becomes large. Further, when the transfer readability is 500 mm / s, if a suction fan having a duty ratio of 20% exists, the vibration of the suction fan and the vibration of the transfer motor 87 resonate, and the density unevenness becomes large.

That is, the relationship between the transfer speed and the duty ratio of the suction fan to be avoided in the case of the transfer speed is as shown in Table 3 below.

Therefore, if there is a duty ratio with respect to the transfer speed shown in Table 3 above in the duty ratios of the first to fourth suction fans 85a to 85d, the duty ratio may be modified and set. good. Hereinafter, the modification of the duty ratio of the suction fan will be described in detail.

FIG. 10 shows an example of a table in which the duty ratio is set so that the rotation frequencies of the first to fourth suction fans 85a to 85d are related to the frequency of the dissonant sound as described above. The duty ratios of the first to fourth suction fans 85a to 85d in the table shown in FIG. 10 are values calculated so that the average value thereof is close to the set value in the above table.

The set value of the table shown in FIG. 10 is a value appropriately set according to the suction force required for the transport belt 81, and is set according to, for example, the type of the print medium P. The above set values are set and input by the user, for example, on the operation panel 71. The average value in the table shown in FIG. 10 shows the actual average value when the duty ratios of the first to fourth suction fans 85a to 85d are calculated as described above.

For example, when the set value is 20%, the four duty ratios calculated to be related to the frequency of the dissonant sound are 24%, 33%, 17% and 12%, and the average value is about 22%. .. In this case, when the four duty ratios and the duty ratios to be avoided shown in Table 3 above are compared, the duty ratios 24% and 17% of the four duty ratios correspond to the transport speed of 500 mm / s in Table 3 above. The difference from the duty ratio of 20% to be avoided is less than 5%.

Therefore, when the set value is 20% and the transfer speed is set to 500 mm / s, the control unit 70 changes the duty ratio 24% of the first suction fan 85a to 15%, and the third By changing the duty ratio 17% of the suction fan 85b to 15%, the difference from the duty ratio 20% to be avoided is set to 5% or more.

When the difference between the duty ratios of the first to fourth suction fans 85a to 85d and the duty ratio to be avoided is less than 5%, the method of changing the duty ratio is better than the duty ratio shown in FIG. There are a method of increasing and a method of decreasing, but it is desirable to decide which value to change 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%, the average value is smaller than the set value. Therefore, the duty ratio can be changed to be smaller than the duty ratio shown in FIG. It is desirable to change it so that it becomes. As a result, the duty ratio can be changed so that the average value approaches the set value.

Further, when the set value is 20% and the transfer speed is set to 700 mm / s or 600 mm / s, the control unit 70 sets the duty ratios of the first to fourth suction fans 85a to 85d in FIG. Set to the four duty ratios in the table shown in.

Further, for example, when the set value is 30%, the four duty ratios calculated to be related to the frequency of the dissonant sound are 36%, 50%, 25% and 18%, and the average value is about 32%. Is. In this case, when the four duty ratios and the duty ratios to be avoided shown in Table 3 above are compared, the duty ratio 18% of the four duty ratios should be avoided corresponding to the transport speed of 500 mm / s in Table 3 above. The difference from the duty ratio of 20% is less than 5%. Further, the difference between the duty ratio of 36% and the duty ratio of 40% to be avoided corresponding to the transport speed of 600 mm / s in Table 3 above is less than 5%.

Therefore, when the set value is 30% and the transfer speed is set to 500 mm / s, the control unit 70 avoids it by changing the duty ratio 18% of the fourth suction fan 85d to 15%. The difference from the duty ratio to be 20% is 5% or more. Further, when the set value is 30% and the transfer speed is set to 600 mm / s, the control unit 70 avoids it by changing the duty ratio 36% of the first suction fan 85a to 35%. The difference from the duty ratio to be 40% is 5% or more. When the set value is 30% and the transfer speed is set to 700 mm / s, the control unit 70 sets the duty ratios of the first to fourth suction fans 85a to 85d in the table shown in FIG. Set to 4 duty ratios.

Further, for example, when the set value is 40%, the four duty ratios calculated to be related to the frequency of the dissonant sound are 48%, 67%, 33% and 24%, and the average value is about 43%. Is. In this case, when the four duty ratios and the duty ratios to be avoided shown in Table 3 above are compared, the duty ratio 24% of the four duty ratios should be avoided corresponding to the transport speed of 500 mm / s in Table 3 above. The difference from the duty ratio of 20% is less than 5%. Further, the difference between the duty ratio of 67% and the duty ratio of 70% to be avoided corresponding to the transfer speed of 700 mm / s in Table 3 above is less than 3%.

Therefore, when the set value is 40% and the transfer speed is set to 500 mm / s, the control unit 70 avoids it by changing the duty ratio 24% of the fourth suction fan 85d to 15%. The difference from the duty ratio to be 20% is 5% or more. When the set value is 40% and the transfer speed is set to 700 mm / s, the duty ratio of the second suction fan 85c is changed from 67% to 65%, so that the duty ratio to be avoided is 70%. The difference between the two is 5% or more. When the set value is 40% and the transfer speed is set to 600 mm / s, the control unit 70 sets the duty ratios of the first to fourth suction fans 85a to 85d in the table shown in FIG. Set to 4 duty ratios.

In addition, when the set values are 50%, 60%, 70%, and 80%, the control unit 70 uses the same concept, and the control unit 70 sucks the first to fourth suctions as shown in the column of the table changing method shown in FIG. The duty ratios of the fans 85a to 85d are changed and set, and in other cases, the duty ratios are set to four in the table shown in FIG. When the set value is 80%, the average value is 78%, which is smaller than the set value. Therefore, when changing the duty ratio 67% of the third suction fan 85b, the control unit 70 changes the duty ratio to 75% instead of 65% so that the average value approaches the set value.

Further, when the duty ratios of the first to fourth suction fans 85a to 85d are set according to the table shown in FIG. 10, the number of air chambers may be two or one as described above.

Further, in the inkjet printing apparatus 1 of the above embodiment, the first air chamber 83 is provided on the upstream side of the print medium P in the transport direction, and the second air chamber 84 is provided on the downstream side in the transport direction. For example, as shown in FIG. 11, three air chambers, a first air chamber 90, a second air chamber 91, and a third air chamber 92, are arranged in a direction orthogonal to the transport direction of the print medium P. It may be provided side by side.

In this case, the first suction fan 93a and the second suction fan 93b are provided in the first air chamber 90, and the third suction fan 93c and the fourth suction fan 93d are provided in the second air chamber 91. The fifth suction fan 93e and the sixth suction fan 93f may be provided in the air chamber 92 of 3. Then, the duty ratio may be set so that the rotation frequencies of the first to sixth suction fans 93a to 93f are related to the frequency of the dissonant sound.

Further, as shown in FIG. 11, when three air chambers of the first air chamber 90, the second air chamber 91 and the third air chamber 92 are provided, the first air chamber 90 and the third air chamber 90 on both sides are provided. It is preferable to set the duty ratios of the first to sixth suction fans 93a to 93f so that the suction force of the air chamber 92 is higher than the suction force of the second air chamber 91 in the center. As a result, it is possible to suppress the warp of both end portions extending in the transport direction of the print medium P, prevent jamming of the print medium P due to the warp, and suppress deterioration of print quality.

Further, when setting the rotation speeds of a plurality of suction fans in the inkjet printing apparatus 1 in the above embodiment, the strength of the influence on the printed matter is actually confirmed with the suction fans individually stopped in advance. Therefore, it is preferable to check the strength of the vibration of each suction fan and set the rotation speed of the suction fan having a large vibration to a value lower than the average value of the rotation speeds of all the suction fans. As a result, vibration due to rotation of the suction fan can be efficiently suppressed.

Next, the operation flow of the transport unit 80 of the inkjet printing apparatus 1 of the above embodiment will be described with reference to the flowchart shown in FIG.

First, the transport speed of the transport unit 80 is set before the start of the paper feed operation of the print medium P (S10). Then, the transfer motor 87 is driven by the control unit 70, the platen roller 82 rotates at a rotation speed corresponding to the transfer speed set in S10, and the transfer belt 81 moves (S12).

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

Subsequently, the control unit 70 applies a drive voltage having a duty ratio set in S14 to the drive motors of the first to fourth suction fans 85a to 85d to drive the first to fourth suction fans 85a to 85d. Start (S16). Then, the control unit 70 starts the paper feeding operation of the print medium P (S18).

The following additional notes are further disclosed with respect to the suction fan control device of the present invention.
(Additional note)

The suction fan control device of the present invention can be provided with a transport unit that sucks and conveys the print medium, and the suction unit can generate a negative pressure for sucking the print medium on the transport unit.

In the suction fan control device of the present invention, the suction unit can have air chambers that generate a negative pressure by the rotation of the suction fan on the upstream side and the downstream side in the transport direction of the print medium, respectively. The rotation speed of the suction fan that generates a negative pressure in the air chamber on the upstream side can be made higher than the rotation speed of the suction fan that generates a negative pressure in the air chamber on the downstream side.

Further, in the suction fan control device of the present invention, the suction unit can have one air chamber that generates a negative pressure by the rotation of a plurality of suction fans, and the control unit can control all the rotation speeds of the plurality of suction fans. It is possible to control the average value of the rotation speeds of the plurality of suction fans to approach the same rotation speed so that the same suction force as the suction force generated when the rotation speeds are the same can be obtained.

Further, in the suction fan control device of the present invention, the control unit can set the rotation speeds of a plurality of suction fans based on the transport speed of the print medium.

Further, in the suction fan control device of the present invention, the control unit can set the rotation frequency of the plurality of suction fans to a frequency corresponding to a plurality of pitches forming a dissonant sound.

1 Inkjet printing device 10 Side paper feed unit 11 Paper feed table 12 Primary paper feed roller 14 Resist roller 20 Internal paper feed unit 21a, 21b, 21c, 21d Paper feed table 22a, 22b, 22c, 22d Primary paper feed roller 30 Image forming unit 31 Head unit 32a, 32b, 32c, 32d Line head 32 First switching mechanism 33 Head holder 40 Upper paper ejection unit 41 Paper ejection table 42 Paper ejection table 42 Second switching mechanism 50 Reversing unit 51 Reversing table 52 Reversing roller 53 Conveying roller 60 Side paper ejection unit 61 Disposal stand 62 Paper ejection roller 70 Control unit 71 Operation panel 80 Conveying unit 81 Conveying belt 82 Platen roller 83 First air chamber 84 Second air chamber 85a First suction Fan 85b Third suction fan 85c Second suction fan 85d Fourth suction fan 86 Air chamber 87 Conveyor motor 90 First air chamber 91 Second air chamber 92 Third air chamber 93a First suction fan 93b 2nd suction fan 93c 3rd suction fan 93d 4th suction fan 93e 5th suction fan 93f 6th suction fan CR Circulation transfer path FR Paper feed transfer path P Printing medium

Claims (5)

A suction unit having a plurality of suction fans that generate a negative pressure for sucking the print medium,
A control unit that controls the suction fan is provided.
A suction fan control device in which the control unit controls the rotation speeds of the plurality of suction fans to be different rotation speeds from each other and to suppress vibration resonance due to rotation of the plurality of suction fans. A transport unit that adsorbs and conveys the print medium is provided.
The suction fan control device according to claim 1, wherein the suction unit generates a negative pressure for sucking the print medium on the transport unit. The suction unit has air chambers that generate a negative pressure by the rotation of the suction fan on the upstream side and the downstream side in the transport direction of the print medium, respectively.
The first or second claim, wherein the control unit makes the rotation speed of the suction fan that generates a negative pressure in the air chamber on the upstream side higher than the rotation speed of the suction fan that generates a negative pressure in the air chamber on the downstream side. Suction fan control device. The suction unit has one air chamber that generates a negative pressure by the rotation of the plurality of suction fans.
The average value of the rotation speeds of the plurality of suction fans is the average value so that the control unit can obtain the same suction force as the suction force generated when the rotation speeds of the plurality of suction fans are all the same. The suction fan control device according to claim 1 or 2, wherein the suction fan control device is controlled so as to approach the same rotation speed. The suction fan control device according to any one of claims 1 to 4, wherein the control unit sets the rotation speed of the plurality of suction fans based on the transport speed of the print medium.

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