JP6027501B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus.

  In general, an ink jet recording apparatus includes a transport mechanism that sucks a sheet and transports the belt, and a recording head on which a plurality of nozzles that can eject ink are formed. An ink jet recording apparatus capable of color recording includes a plurality of recording heads corresponding to a plurality of colors.

  However, a nozzle that has not ejected ink for a while tends to have a high ink viscosity within the nozzle, resulting in poor ink ejection. As a result, there is a problem that the formed image is disturbed.

  For example, in an inkjet recording apparatus capable of color recording, for example, when performing monochrome recording of only black, recording heads of colors other than black are not used. However, since the nozzles of the recording heads of other colors are open even when not in use, the viscosity of the ink increases in the nozzles, and the nozzles are easily clogged.

  Thus, it is known to eliminate nozzle clogging by forcibly ejecting ink with increased viscosity from the nozzle. However, a large amount of ink was consumed at that time.

  On the other hand, in Patent Document 1, the cap moving mechanism is controlled during monochromatic recording so that the cap member is disposed opposite to the nozzle of another recording head that is not in use, and the nozzle is covered with the cap member. It is described. As a result, it is attempted to suppress clogging of nozzles in other recording heads while suppressing ink consumption.

JP 2011-136468 A

  However, the ink jet recording apparatus has a problem that paper dust is generated and conveyed when the paper is conveyed, and the paper dust adheres to the nozzles of the recording head and clogs the nozzles.

  The present invention has been made in view of such points, and an object thereof is to suppress nozzle clogging due to paper dust of paper.

An ink jet recording apparatus according to the present invention includes a recording unit having a recording head in which a plurality of nozzles for ejecting ink are formed, and a transport mechanism that is disposed to face the recording unit and transports paper along the recording unit. And a discharge unit that discharges a transparent liquid containing at least water to the paper transported to the transport mechanism, a humidity sensor that detects relative humidity around the nozzle, and the humidity sensor When the relative humidity is equal to or lower than a predetermined threshold value, the liquid discharge amount per unit time is larger than the liquid discharge amount per unit time when the relative humidity is larger than the threshold value. and a discharge portion control means for controlling the ejection portions so as to shorten the time interval for discharging liquid, the ink jet recording apparatus, the discharge unit control means The discharge unit is controlled to discharge the liquid only to a region other than the recording region where the ink is recorded on the paper, and the region other than the recording region is a peripheral edge of the paper. Ru margin area der part.

  According to this configuration, the transport mechanism transports the paper along the recording unit. On the other hand, ink is ejected from a plurality of nozzles formed in the recording head of the recording unit. The ink ejected from the nozzles adheres to the paper transported facing the recording unit. As a result, an image is recorded on the paper.

  At this time, the discharge unit discharges a transparent liquid containing at least water to the paper transported to the transport mechanism. Then, the moisture of the liquid adhering to the paper evaporates, and the relative humidity around the nozzles facing the paper increases. Therefore, it is possible to suppress the increase in the viscosity of the ink in the nozzles with a relatively simple configuration of a discharge unit that discharges the liquid.

  In addition, paper dust is generated when the paper is transported, but since the discharge unit discharges liquid to the paper, the generated paper powder can be attached to the paper together with the liquid. . Therefore, it becomes difficult for paper dust to fly up from the paper, and it is possible to suppress clogging of the nozzles due to paper dust.

  That is, according to the above configuration, it is possible not only to suppress clogging of the nozzles due to ink thickening but also to suppress clogging of the nozzles due to paper dust of the paper with a relatively simple configuration.

  According to this configuration, since a transparent liquid containing at least water is discharged onto the paper by the discharge unit, an increase in relative humidity around the nozzle can be suppressed. However, for example, when the environmental temperature decreases, the relative humidity may decrease.

  On the other hand, in the above configuration, when the relative humidity around the nozzle detected by the humidity sensor is equal to or lower than the predetermined threshold, the discharge amount of the liquid per unit time by the discharge unit is set to be less than the above threshold. Since the discharge unit is controlled by the discharge unit control means so as to be larger than the discharge amount of the liquid per unit time when it is large, when the relative humidity becomes equal to or less than the threshold value, The amount of water evaporation can be increased. Accordingly, the relative humidity can be maintained larger than the above threshold value, and thus the ink viscosity increase at the nozzle is suitably suppressed.

In addition , since the ejection unit controlled by the ejection unit control unit ejects liquid to an area other than the recording area on the paper, the liquid does not adhere to the image recorded in the recording area. Therefore, it is possible to prevent the image from being disturbed by the liquid adhering to the paper while suppressing clogging of the nozzles.

  It is preferable that the discharge unit is constituted by an inkjet head.

  According to this configuration, since the discharge unit can be configured using the existing structure used for the recording unit, it is possible to suppress an increase in manufacturing cost due to the provision of the discharge unit.

  The recording unit is preferably a line head type.

  According to this configuration, since the recording unit is a line head type, it is possible to perform recording by conveying the sheet at high speed. However, if paper is transported at high speed, more paper dust is generated. On the other hand, in the above configuration, since the discharge unit for discharging the liquid is provided on the paper, even if a large amount of paper dust is generated, the generated paper powder can be adhered to the paper together with the liquid. Become. Therefore, since paper dust hardly rises from the paper, it is possible to suitably suppress clogging of the nozzles in the line head type recording unit while conveying the paper at high speed.

  According to the present invention, it is possible to suppress clogging of nozzles due to paper dust of paper.

FIG. 1 is a longitudinal sectional view schematically showing an image forming apparatus as an ink jet recording apparatus in the present embodiment. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus. FIG. 3 is a bottom view schematically showing the line head and the discharge unit. FIG. 4 is an enlarged side view showing the vicinity of the nozzle of the discharge unit. FIG. 5 is a plan view showing a sheet on which liquid is ejected to the non-recording area. FIG. 6 is a plan view illustrating a sheet on which liquid is ejected to the recording area and the non-recording area.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

  FIG. 1 schematically shows an image forming apparatus 1 as an ink jet recording apparatus in the present embodiment. FIG. 2 shows the configuration of the image forming apparatus 1. FIG. 3 is a bottom view schematically showing the line heads 6Y, 6M, 6C, and 6K.

  As shown in FIG. 1, the image forming apparatus 1 includes an inkjet head 2 as a recording unit, a paper feed cassette 3 that accommodates a paper P that is a recording medium, and a paper that is disposed to face the inkjet head 2. A transport mechanism 4 and a paper discharge tray 5 for discharging the paper P on which an image is formed are provided.

  The inkjet head 2 is configured as a line head type. That is, the inkjet head 2 has a plurality of line heads 6Y, 6M, 6C, and 6K as recording heads arranged in the sub-scanning direction (left and right direction in FIG. 1). Each of the line heads 6Y, 6M, 6C, and 6K is configured to form an image by ejecting yellow (Y), magenta (M), cyan (C), and black (K) ink onto the paper P, respectively. ing.

  As shown in FIG. 3, the line heads 6 </ b> Y, 6 </ b> M, 6 </ b> C, and 6 </ b> K are formed with a plurality of nozzles 12 that eject ink onto the lower surface facing the paper transport mechanism 4. In FIG. 3, the number of nozzles 12 is reduced for the sake of explanation, but in reality, a large number of nozzles 12 are provided in a matrix.

  The line heads 6Y, 6M, 6C, and 6K discharge ink from each nozzle 12 by changing the volume of the pressure chamber filled with ink by a piezoelectric element.

  As shown in FIG. 1, the paper feed cassette 3 is provided at the lower part of the apparatus and can accommodate a plurality of sheet-like papers P in a stacked manner. The paper feed cassette 3 is provided with a paper feed roller 7 for feeding paper.

  A transport path L for guiding the paper P fed from the paper feed cassette 3 to the paper transport mechanism 4 is provided on the side of the paper feed roller 7. The conveyance path L is constituted by a guide plate 8. In the transport path L, a pair of first transport rollers 9, a pair of second transport rollers 10, and a pair of registration rollers 20 are provided in order from the paper feed cassette 3 side to the paper transport mechanism 4 side. The registration roller 20 supplies the paper P to the paper transport mechanism 4 at a predetermined timing. A pair of paper discharge rollers 11 and a paper discharge tray 5 are provided on the side of the paper transport mechanism 4.

  As shown in FIG. 1, the paper transport mechanism 4 is arranged on the inner side in the radial direction of the transport belt 18, which is looped around a plurality of rollers 13 to 16 and holds and transports the paper P. And a negative pressure generator 19. The paper transport mechanism 4 is arranged to face the ink jet head 2 and is configured to transport the paper P in the paper transport direction A along the ink jet head 2.

  The plurality of rollers 13 to 16 include two tension rollers 13 and 14, a driving roller 15, and a driven roller 16.

  The driving roller 15 is a roller for transmitting a driving force to the conveying belt 18, and is disposed on the downstream side in the sheet conveying direction A from the inkjet head 2. As shown in FIG. 2, the drive roller 15 is coupled to the drive motor 23 so that power can be transmitted.

  The driven roller 16 is disposed upstream of the inkjet head 2 in the paper transport direction A. The driven roller 16 is disposed at substantially the same height as the drive roller 15. The tension rollers 13 and 14 are rollers for adjusting the tension of the transport belt 18, and are disposed below the driving roller 15 and the driven roller 16.

  The upper surface of the transport belt 18 forms a paper transport surface for transporting the paper P. The upper surface of the conveyance belt 18 extends substantially parallel to the lower surface of the inkjet head 2. The transport belt 18 transports the paper P while adsorbing and holding the paper P on its upper surface.

  A number of vent holes (not shown) are formed in the transport belt 18. Each air hole penetrates the conveyor belt 18 in the belt thickness direction. Each vent has a function of causing the negative pressure generated by the negative pressure generator 19 to act on the paper P.

  The negative pressure generator 19 has a fan case 25 to which a fan 24 is attached. The fan case 25 includes a case body 26 that opens upward, and a top plate portion 27 that covers the upper side of the case body 26.

  The fan 24 is attached below the case body 26. The fan 24 generates negative pressure in the fan case 25 by being driven by a fan drive motor (not shown).

  The top plate portion 27 is in contact with the inner peripheral surface of the conveyor belt 18. The paper P held on the upper surface (outer peripheral surface) of the conveyor belt 18 is supported from below via the conveyor belt 18.

  A plurality of suction holes (not shown) are formed through the top plate portion 27. When the fan 24 is activated, a negative pressure is generated in the fan case 25, and this negative pressure acts on the paper P on the transport belt 18 through the suction holes and the vent holes of the transport belt 18. As a result, the paper P is attracted and held on the upper surface of the transport belt 18.

  Then, the paper P fed from the paper feed cassette 3 by the paper feed roller 7 is transported along the transport path L by the first and second transport rollers 9 and 10 and is supplied to the paper transport mechanism 4 by the registration roller 20. . The paper P supplied to the paper transport mechanism 4 is discharged in the paper discharge tray 5 by the paper discharge roller 11 after an image is formed by the inkjet head 2 while being transported in the sub-scanning direction.

  The image forming apparatus 1 further includes a discharge unit 34 that discharges a transparent liquid containing at least water onto the paper P transported to the paper transport mechanism 4. The discharge unit 34 is arranged to face the paper transport mechanism 4 on the upstream side in the paper transport direction A from the inkjet head 2. The discharge part 34 is comprised by the inkjet head.

  Here, FIG. 4 shows an enlarged view of the vicinity of the nozzle 31 of the discharge unit 34. As shown in FIGS. 3 and 4, similarly to the line heads 6Y, 6M, 6C, and 6K, the discharge unit 34 includes a plurality of nozzles 31 that face the paper transport mechanism 4, and a pressure chamber 32 that communicates with the nozzles 31. And a piezoelectric element (not shown) that varies the volume of the pressure chamber 32. In FIG. 3, the number of nozzles 31 is described to be small for the sake of explanation.

  The pressure chamber 32 is filled with a transparent liquid 33 containing at least water, such as water or a storage liquid. And the discharge part 34 discharges the liquid 33 inside the pressure chamber 32 from the nozzle 31 by contracting the pressure chamber 32 with the said piezoelectric element.

  Further, the image forming apparatus 1 has a liquid tank (not shown) connected to the pressure chamber 32 of the discharge unit 34. The liquid 33 stores the liquid 33 and is configured to sequentially supply the liquid 33 from the liquid tank to the pressure chamber 32.

  Further, as shown in FIG. 2, the image forming apparatus 1 includes a discharge unit drive circuit 35 as a discharge unit control unit 35 that controls the discharge unit 34.

  The ejection unit drive circuit 35 drives the ejection unit 34 so that the liquid 33 is ejected onto the paper P by operating the piezoelectric element of the ejection unit 34 when the paper P faces the ejection unit 34. Control. For example, the ejection unit drive circuit 35 controls the ejection unit 34 so that the liquid 33 is intermittently ejected from the nozzle 31. Whether or not the paper P faces the ejection unit 34 can be detected by a sensor such as an optical sensor.

  Further, the image forming apparatus 1 includes a humidity sensor 38 that detects the relative humidity around the nozzles 12 of the line heads 6Y, 6M, 6C, and 6K, as shown in FIG.

  The ejection unit drive circuit 35 is a unit in which the ejection amount of the liquid 33 per unit time is greater than the threshold when the relative humidity detected by the humidity sensor 38 is equal to or less than a predetermined threshold. The ejection unit 34 is controlled so as to be larger than the ejection amount of the liquid 33 per time.

  For example, the ejection unit drive circuit 35 controls the ejection unit 34 that intermittently ejects the liquid 33 to shorten the time interval at which the liquid 33 is ejected when the relative humidity is equal to or lower than the above threshold. . Thereby, the discharge amount of the liquid 33 per unit time can be increased and the relative humidity can be increased.

  The threshold value can be appropriately set according to the ink characteristics. That is, the relative humidity at which the ink viscosity increases to such an extent that the nozzle 12 is clogged is measured in advance, and the relative humidity may be set as the threshold value. A plurality of threshold values may be set.

  Here, FIG. 5 and FIG. 6 show a region where the liquid 33 on the paper P is discharged. As shown in FIG. 5, the ejection unit drive circuit 35 controls the ejection unit 34 to eject the liquid 33 to the non-recording area 52 other than the recording area 51 where recording with ink is performed on the paper P. The non-recording area 52 is, for example, a margin area in the peripheral portion of the paper P.

Note that the ejection unit drive circuit 35 may control the ejection unit 34 to eject the liquid 33 to both the recording area 51 and the non-recording area 52 as shown in FIG. Since the liquid 33 is transparent, even if the liquid 33 adheres to the recording area 51, it is difficult for the user to visually recognize it. Further, since the amount of the liquid 33 supplied to the paper P increases, the relative humidity can be increased more suitably.
-Control system configuration-

  As shown in FIG. 2, the image forming apparatus 1 includes a control unit 40 that controls the conveyance belt 18, the line heads 6Y, 6M, 6C, and 6K, the discharge unit 34, and the like. The discharge unit drive circuit 35, the humidity sensor 38, the interface 41, the ROM 42, the RAM 43, the encoder 44, the drive motor control circuit 45, the line head control circuit 46, the fan motor control circuit 47, and the like are connected to the control unit 40. ing.

  The interface 41 transmits / receives data to / from a host device such as a personal computer (not shown). The control unit 40 converts the image signal received via the interface 41 into image data, and outputs the control signal to various control circuits described later.

  The ROM 42 stores a control program and the like for recording the image by driving the line heads 6Y, 6M, 6C, and 6K. The RAM 43 stores the image data converted by the control unit 40 in a predetermined area.

  The encoder 24 is connected to the paper discharge side drive roller 15 that drives the transport belt 18, and outputs a pulse train according to the rotational displacement amount of the rotation shaft of the drive roller 15. The controller 40 calculates the rotation amount by counting the number of pulses transmitted from the encoder 44, and grasps the sheet feed amount (sheet position). The control unit 40 outputs a control signal to the drive motor control circuit 45 and the line head control circuit 46 based on the signal input from the encoder 44.

  The drive motor control circuit 45 drives the drive motor 23 based on the output signal of the control unit 40. The drive motor 23 rotates the drive roller 15 to rotate the transport belt 18 and transport the paper P in the transport direction A.

  The line head control circuit 46 controls ink ejection by the line heads 6Y, 6M, 6C, and 6K based on the output signal of the control unit 40 and the image data stored in the RAM 43. By the control of the line heads 6Y, 6M, 6C, and 6K and the conveyance control of the paper P by the drive motor 23, the recording process for the paper P is performed.

  The fan motor control circuit 47 drives the fan motor 48 based on the output signal of the control unit 40. The fan motor 48 rotates the fan 24 to generate a negative pressure inside the fan case 25 and cause the paper P to be attracted to the transport belt 18.

  The ejection unit drive circuit 35 drives and controls the ejection unit 34 based on the output signal of the control unit 40 to which the detection signal of the humidity sensor 38 is input. That is, the ejection unit drive circuit 35 intermittently ejects the liquid 33 onto the paper P by operating the piezoelectric element of the ejection unit 34 when the paper P faces the ejection unit 34. In addition, the ejection unit drive circuit 35 shortens the time interval at which the ejection unit 34 ejects the liquid 33 when the relative humidity becomes equal to or lower than the threshold value. As a result, the discharge amount of the liquid 33 per unit time by the discharge unit 34 is increased.

  As described above, if the viscosity of the ink in the nozzle 12 increases, ink ejection defects are likely to occur. On the other hand, in the present embodiment, the discharge unit 34 that discharges the transparent liquid 33 containing at least water is provided on the paper P being transported to the paper transport mechanism 4. As a result, the moisture of the liquid 33 adhering to the paper P evaporates, so that the relative humidity around the nozzles 12 facing the paper P can be increased. Therefore, it is possible to suppress the increase in the viscosity of the ink in the nozzle 12 with a relatively simple configuration of the ejection unit 34 that ejects the liquid 33.

  In addition, paper dust is generated when the paper P is conveyed, but since the discharge unit 34 discharges the liquid 33 to the paper P, the generated paper dust is attached to the paper P together with the liquid 33. It is possible to leave. Therefore, it is difficult for paper dust to rise from the paper P. Assuming that the paper dust rises from the paper P, the paper dust can be captured by the liquid 33 ejected from the ejection unit 34. Therefore, according to this embodiment, clogging of the nozzles 12 due to paper dust can be suppressed.

  That is, according to the present embodiment, the nozzle 12 can be prevented from clogging due to paper dust of the paper P as well as the nozzle 12 from being clogged due to thickening of the ink by a relatively simple configuration.

  By the way, for example, when the environmental temperature decreases, the relative humidity may decrease. In contrast, in the present embodiment, when the relative humidity around the nozzle 12 detected by the humidity sensor 38 is equal to or less than a predetermined threshold, the discharge amount of the liquid 33 per unit time by the discharge unit 34 is set as the relative humidity. The discharge unit 34 is controlled by the discharge unit control means so that the discharge amount of the liquid 33 per unit time when the value is larger than the above threshold value. As a result, the amount of water evaporation of the liquid 33 from the paper P can be increased when the relative humidity is equal to or lower than the threshold value. Accordingly, the relative humidity can be maintained larger than the above threshold value, so that nozzle clogging due to ink thickening in the nozzles 12 can be suitably suppressed.

  Further, the ejection unit drive circuit 35 controls the ejection unit 34 to eject the liquid 33 to the non-recording area 52 of the paper P, so that the liquid does not adhere to the image recorded in the recording area 51. It is possible to prevent image disturbance due to the liquid 33 adhering to the paper P while suppressing clogging of the nozzles 12.

  Furthermore, since the ejection part 34 is configured using an inkjet head having an existing structure used for the inkjet head 2, an increase in manufacturing cost due to the provision of the ejection part 34 can be suppressed.

  Further, since the inkjet head 2 is a line head type, it is possible to perform recording by conveying the paper P at a high speed. If the paper P is transported at high speed, more paper dust is generated, and the wind speed of the transport air generated along with the paper transport increases. However, as described above, since the discharge unit 34 is provided in the present embodiment, the paper Even if a lot of powder is generated, the paper powder can be adhered to the paper P together with the liquid 33. Therefore, since paper dust does not easily rise from the paper P, the clogging of the nozzles 12 in the line head type inkjet head 2 can be suitably suppressed while the paper P is conveyed at high speed.

  In the above embodiment, a line head type ink jet recording apparatus has been described as an example. However, the present invention is not limited to this, and a serial head type ink jet recording apparatus may be used.

  As described above, the present invention is useful for an ink jet recording apparatus.

P Paper 1 Image forming device (inkjet recording device)
2 Inkjet head (recording part)
4 Paper transport mechanism 6Y, 6M, 6C, 6K Line head (recording head)
12 Nozzle 33 Liquid 34 Discharge part 35 Discharge part drive circuit (discharge part control means)
38 Humidity sensor 51 Recording area 52 Non-recording area

Claims (3)

A recording unit having a recording head on which a plurality of nozzles for discharging ink are formed;
A transport mechanism disposed opposite the recording unit and configured to transport a sheet along the recording unit;
A discharge unit that discharges a transparent liquid containing at least water to the paper transported to the transport mechanism;
A humidity sensor that detects the relative humidity around the nozzle;
When the relative humidity detected by the humidity sensor is equal to or lower than a predetermined threshold, the amount of liquid discharged per unit time is greater than the amount of liquid discharged per unit time when the relative humidity is greater than the threshold. And a discharge unit control means for controlling the discharge unit so as to shorten the time interval of discharging the liquid ,
The ejection unit control means is configured to control the ejection unit so that the liquid is ejected only to an area other than a recording area where the ink is recorded on the paper.
Region other than the recording region, Ru margin area der circumferential portion of the paper, the ink jet recording apparatus. The inkjet recording apparatus according to claim 1 , wherein
The ejection unit is an inkjet recording apparatus configured by an inkjet head. In the ink jet recording apparatus according to any one of claims 1 and 2 ,
The ink jet recording apparatus, wherein the recording unit is a line head type.

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