JP6024440B2 - Empty discharge receiver and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly, to an empty discharge receiver provided when flushing ink droplet (droplet) discharge ports of a recording head in an ink jet recording apparatus.

  2. Description of the Related Art As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, and a multifunction machine having these functions, for example, an ink jet recording apparatus (liquid discharge recording type image forming apparatus) having a recording head for discharging ink droplets is known. . In such a liquid ejection type image forming apparatus, the recording head performs image recording by ejecting ink pressurized in a pressure generating chamber from a nozzle onto a recording material (also referred to as recording medium or paper). For this reason, there is a problem that the ink viscosity rises due to the evaporation of the solvent from the nozzle, the ink solidifies, the dust adheres, and the air bubbles are mixed, resulting in a discharge failure and a recording failure. . Therefore, in order to keep the ejection state of the recording head normal, a maintenance recovery operation is necessary. The maintenance / recovery operation includes wiping and idle discharge after suction of the head, in addition to a discharge recovery operation in which the nozzle of the recording head is sealed with a cap member, and ink is sucked and discharged (head suction) from the nozzle with a negative pressure. Wiping is an operation of wiping with a wiping member residual ink that adheres to the nozzle surface of the recording head and causes the flying state of ink droplets to change. The idle ejection is an operation for ejecting ink droplets that do not contribute to image formation in order to return the meniscus of the nozzle to a normal state after wiping.

  When idle ejection is performed, so-called satellite droplets and mist smaller than the main droplets are generated from the ink droplets in addition to the main droplets that reach the idle ejection receptacle almost linearly. Mist originates from ink droplets, just like main droplets and satellite droplets, but is finer and floats in the air, and its properties differ greatly from main droplets and satellite droplets. This causes the inside of the machine to become contaminated, causing image quality degradation and device failure.

  As a conventional solution to such a problem, for example, in Patent Document 1, an air flow generated by dragging ambient air by ejecting ink droplets is guided to the filter-attached opening wall side of the empty ejection receiver, and then rides on the air flow. It proposes to collect mist with a filter. This prevents mist from splashing outside. However, the configuration disclosed in Patent Document 1 has a problem in that the cost is increased because the filter portion is provided in the idle discharge receiver, and there is a problem that replacement is necessary because there is a lifetime due to filter clogging.

  Here, the ink jet recording apparatus includes a serial type image forming apparatus that forms an image by ejecting ink droplets while the recording head moves in the main scanning direction, and a state in which the recording heads arranged in a line do not move. There is a line-type image forming apparatus that uses a line-type head that ejects ink droplets. In serial type recording devices, the number of heads is small and the number of idle ejections as a whole is small. However, when a line type recording device, especially a large machine, the number of idle ejections until the machine life is large, the replacement frequency increases. . For this reason, if the line type is intended to reduce the size of the idle discharge receptacle, the service life is quickly reached.

  Moreover, even if it guide | induces an airflow to the wall side in the structure of patent document 1, not all the airflow goes to the wall side but there is what rises and flows out from the opening part of an empty discharge receptacle. Mist also flows out of the opening along a gentle air flow. In particular, when the idle discharge receptacle is downsized, the pressure inside the idle discharge receptacle is likely to increase, and an ascending air current is generated immediately, and more mist is likely to be scattered from the opening to the outside. In general, since only two nozzle rows are arranged in the short direction of the recording head, the influence of the descending air flow due to the idle ejection is strong, and the mist is hardly scattered. On the other hand, in the longitudinal direction of the recording head, only the influence of the descending airflow due to the idle ejection of the nozzles at the end of the many nozzles is caused, and mist is more likely to be scattered than in the lateral direction. Therefore, in the configuration of Patent Document 1, when the airflow is guided to the outside in the longitudinal direction of the head, the mist that does not adhere to the filter rides on the rising airflow as it is, flows out from the end of the opening in the longitudinal direction of the head, and the amount is large. It is.

  An object of the present invention is to provide an empty discharge receptacle that can minimize the external scattering of mist due to empty discharge even if it is downsized.

An object of the present invention is to provide an empty discharge receptacle for storing a droplet discharged from a recording head, and having a passage wall provided with a wall extending from the droplet inlet to the inside of the housing along the droplet traveling direction. Formed in an outer peripheral region of the introduction passage, a guide piece having a slope located inside the casing on the downstream side in the droplet traveling direction of the discharge droplet introduction passage, and a passage wall of the discharge droplet introduction passage, A mist airflow circulation space defined by a top surface inside the housing and a free end of the passage wall, and a mist recovery port formed on a side surface of the mist airflow circulation space, the mist The problem is solved by having the upper end of the recovery port located below the top surface inside the housing and the lower end thereof located above the lower end of the passage wall, and the mist recovery port is connected to the mist recovery chamber .

The downdraft generated by the droplets ejected in the air collides with the inner surface of the housing of the empty ejection receptacle, and the energy is attenuated while being spirally diffused throughout the housing with the mist derived from the droplets. According to the present invention, in that case, in the mist air circulation space as the energy attenuating space, the air current energy is efficiently attenuated, and the energy is utilized to the maximum to prevent the mist from being scattered outside and the mist recovery port to be Mist can be collected in the mist collection chamber . Further, it is not necessary to use a suction means or a large-capacity storage chamber with a larger flow rate than the air flow generated by the idle discharge.

1 is a schematic configuration diagram of an entire ink jet recording apparatus according to an example of the present invention. It is a schematic sectional drawing of the idle discharge receptacle which concerns on an example of this invention. It is a figure of the simulation result which confirms the external leakage of the mist airflow by the difference in the attachment position of a mist circulation port, a is a thing which made the mist collection | recovery port downward, and b is a structure concerning this invention. It is a conceptual diagram explaining pump suction of a recovery droplet. FIG. 5 is a cross-sectional view taken along a cross-sectional line XX in FIG. 4. It is sectional drawing of the sectional line YY of FIG.

  An example of the present invention will be described below. In FIG. 1, the paper 100 stacked on the paper feed tray 101 is transported by a paper feed roller 102 to a transport path indicated by a dotted line. The paper 100 transported to the transport path is transported to the belt transport unit 104 via a timing alignment / skew correction roller (so-called registration roller) pair 103.

  The belt conveyance unit 104 includes a conveyance roller 105 driven at a predetermined timing, a tension roller 106, and an endless conveyance belt 107 wound around these rollers. In order to hold the paper 100 by the belt conveyance unit 104, means by electrostatic adsorption, adsorption by air suction, or other known means can be used. The paper 100 is transported to the belt transport unit 104 and passes under the recording head unit 108 to form an image.

  On the paper 100 on which an image has been formed by the recording head unit 108, undried ink constituting the image is adhered. In order to dry the undried ink, although not shown, a drying mechanism such as a heater or hot air can be provided between the decurler unit 109 and the like. After image formation by the recording head unit 108, the paper 100 is conveyed to the decurler unit 109 and decurled. When the paper 100 that has passed through the decurler unit 109 is discharged as it is, it is conveyed by the separation claw 110 via the conveyance path 111 to the paper discharge roller 112 and discharged. In the case of reverse paper discharge or reverse side printing, the separation claw 110 switched from the illustrated position counterclockwise passes through the conveyance path 113, passes through the guide member 114, and is sent to the tapping roller 115. The paper 100 sent to the tapping roller 115 is conveyed in the reverse direction by the tapping roller 115 whose rotation direction has been switched. In the case of reverse paper discharge, the paper 100 passes through the conveying path 117 via the second separation claw 116. The paper is sent to the paper discharge roller 112 and discharged. When printing on the reverse side, the sheet conveyed in the reverse direction by the tapping roller 115 passes through the conveyance path 119 via the second separation claw 116 and the double-side reversing roller 118 that are switched counterclockwise from the illustrated position. Are sent to the registration roller pair 103.

  The recording head unit 108 is composed of a line type liquid discharge head having a nozzle row in which a plurality of nozzles for discharging ink droplets are arranged in a length corresponding to the paper width. The recording head unit 108 includes a recording head 108my for yellow (Y) and magenta (M), and a recording head 108kc for cyan (C) and black (K). In the recording head unit 108, the respective heads are arranged in a staggered manner in odd and even columns. It should be noted that the recording head can be mounted on the carriage as a serial type image forming apparatus.

  A maintenance / recovery unit 200 is provided to maintain and recover the performance of the recording head unit 108. The maintenance / recovery unit 200 includes a cap 201 for sucking ink of the recording head unit 108, a wiper 202 for wiping off ink adhering to the head when sucked, and an empty discharge receiver 300 for storing empty discharge ink. When performing the maintenance recovery, the recording head unit 108 rises, and the maintenance recovery unit 200 moves below each recording head, and a maintenance recovery operation is performed. The cap 201 of the maintenance / recovery unit 200 also serves as a moisture retention cap that maintains the humidity of the recording head 108 kc during standby, while the humidity of the recording head 108 my is maintained by another moisture retention cap unit 203. At the time of non-printing, the recording head unit 108 rises, and the maintenance / recovery unit 200 and the moisture retaining cap unit 203 move to below each recording head to perform moisture retention capping.

  FIG. 2 is a cross-sectional view showing an outline of the idle discharge receiver according to an embodiment of the present invention, with the short direction (direction perpendicular to the longitudinal direction) of the recording head aligned with the paper surface. An ink droplet 301 as a droplet is ejected downward from the nozzle hole 108b of the nozzle plate 108a of the recording head. The ink droplet 301 is generated by a droplet inlet 303 on the surface of the casing while generating an air flow 302 and a passage wall 304 having a wall extending from the inlet to the casing of the empty discharge receptacle 300 along the droplet traveling direction. It passes through a defined discharge droplet introduction passage 305. The inner wall surface of the passage wall 304 extends along the liquid droplet traveling direction, but does not have to be strictly parallel to the liquid droplet traveling direction and extends so as not to hinder the liquid droplet traveling. The ink droplet 301 is divided into a main droplet, a satellite droplet, and a mist during idle ejection. The main droplet and the satellite droplet collide with the landing inclined surface 307 of the guiding portion piece 306 located downstream of the ejection droplet introduction passage 305 in the droplet traveling direction, that is, below, and thereafter, the ink reservoir inside the empty ejection receiver 300. It flows down to the part 309. On the other hand, the mist is pulled by the air current 302 and guided to the landing slope 307 of the guide piece 306 and enters the droplet storage chamber 310 inside the empty discharge receptacle 300. The airflow containing mist becomes a spiral airflow 312 in the droplet storage chamber 310 and attenuates energy while diffusing.

  It is desirable that the apex 308 of the guide piece 306 is substantially at the same height as the lower end position 320 of the passage wall 304 of the discharge droplet introduction passage 305 in order to smoothly guide the airflow. If the apex 308 protrudes into the ejection droplet introduction passage 305, the entry of the ejection droplet is hindered, and if it is lower than the lower end position 320, it is guided to the landing slope 307 starting from the apex 308 and accommodates the droplet. This is because the airflow traveling through the chamber 310 is difficult to spiral and tends to be turbulent. The mist contained in the air flow 312 that is spiraled and attenuated in the droplet storage chamber 310 is guided to the mist recovery port 340 formed on the side surface of the droplet storage chamber 310 and collected in the mist recovery chamber 350. At this time, it is important to form a mist airflow circulation space 325 as an energy attenuation space for preventing the mist from scattering outside. The mist airflow circulation space 325 is a space formed in the outer peripheral region of the passage wall 304 of the discharge droplet introduction passage 305, and is a free end of the top surface 311 of the droplet storage chamber 310 and the passage wall 304, that is, a lower end position 320. The upper and lower areas are defined by. Since the mist airflow circulation space 325 is at a position higher than the lower end position 320 of the passage wall 304, the airflow 312 containing mist is difficult to return to the ejection droplet introduction passage 305. In other words, when there is no mist airflow circulation space 325 or when the height of the mist airflow circulation space 325 is not sufficient, an effective attenuation effect cannot be obtained, and the mist flows backward from the ejection droplet introduction passage 305. It will be scattered outside.

  Further, by providing the mist recovery port 340 in the mist airflow circulation space 325, the mist-containing airflow in a state where the continuous airflow due to continuously ejected droplets is mixed and moderately attenuated is introduced to the mist recovery port 340. It is burned. The mist collection chamber 350 connected to the mist collection port 340 is formed as a continuous space common to a plurality of recording heads, as will be described later with reference to FIG. The mist is collected here.

  The mist collection port 340 is located on the side surface of the mist air circulation space 325, that is, its upper end is the same as or lower than the top surface 311 of the droplet storage chamber 310, and its lower end is lower than the lower end position 320 of the tsu road wall 304. Located on the top. When the mist collection port 340 is formed away from the top surface 311 of the droplet storage chamber 310 and the lower end position 320 of the passage wall 304, as shown in FIG. The recovery port 340 is reached. Therefore, the mist is not guided to the mist collection chamber 350 through the mist collection port 340 but flows from the mist airflow circulation space 325 to the discharge droplet introduction passage 305, and the mist is scattered to the outside at a considerable rate. Since the mist collection port 340 is positioned on the side surface of the mist airflow circulation space 325, as shown in FIG. 3b, the mist collection port 340 is guided to the mist collection chamber 350 through the mist collection port 340, and external scattering is suppressed.

  Incidentally, if the mist discharge through the mist collection port 340 is not performed well, the mist-containing air current continues to circulate in the mist air current circulation space 325 and the droplet storage chamber 310 and stays. Then, in a configuration in which the space is reduced and only a small space can be secured in the empty discharge receptacle, the pressure inside the droplet storage chamber 310 is increased by the subsequent mist-containing air flow entering the droplet storage chamber 310. As a result, a reverse flow occurs in the discharge droplet introduction passage 305, causing mist scattering from the discharge droplet introduction passage 305 to the outside. According to experiments by the present inventors, it has been found that to prevent mist scattering, it is necessary to suppress the pressure increase in the droplet storage chamber 310 to 10 Pa or less, particularly as close to 0 Pa as possible. In order to suppress such a low pressure increase, the capacity of the mist airflow circulation space 325 and the opening diameter of the mist collection port 340 that are adapted to the strength and amount of the airflow generated by the discharged droplets are specifically set in each case. The capacity of the mist airflow circulation space 325 leads to securing a set position of the mist recovery port 340 having a necessary opening diameter, and is also related to a space height for effective energy attenuation. By appropriately setting the capacity of the mist airflow circulation space 325 and the opening diameter of the mist recovery port 340, it is possible to recover the mist continuously and efficiently.

  The main droplet and satellite droplet that have flowed down to the ink reservoir 309 may be recovered through the droplet recovery port 360, which will be described below. In FIG. 4, after flowing down into the ink reservoir 309, the main droplets and satellite droplets are sucked by the attached ink suction pump 400 from the droplet recovery port 360 formed on the bottom surface of the droplet storage chamber 310. The liquid droplet collection port 360 is used for the waste liquid mainly composed of main droplets, and the mist collection port 340 has a larger tube diameter and a smaller channel resistance with a focus on securing a flow rate rather than a pressure point for mist collection. Is significantly different from The droplet recovery port 360 is located on the bottom of the chamber where the flow due to gravity can be used, and is required to have a function of efficiently discharging the accumulated waste liquid. When the ink suction pump 400 performs suction, a strong suction pressure is generated even at a low flow rate. A high resistance and therefore a narrow opening cross section is required. If both recovery ports are hole-shaped, mist recovery diameter B> droplet recovery diameter A. That is, the opening area of the mist collecting port 340 is larger than the opening area of the droplet collecting port 360. By increasing the opening area, the flow path resistance can be significantly reduced. In addition, there is no problem even if a plurality of droplet recovery ports 360 are provided, but it is desirable to provide one for each droplet storage chamber 310 in order to increase suction efficiency.

  FIG. 5 and FIG. 6 show states cut along the XX and YY sectional lines in FIG. That is, FIGS. 5 and 6 are cross-sectional views in the nozzle row direction (head longitudinal direction) of the recording head, and the configuration of the idle discharge receptacle 300 for a plurality of recording heads, and thus for the respective nozzle plates 108ax, 108ay, 108az. Represents. A mode (one-head idle discharge receiver) may be used in which each of the plurality of recording heads corresponds to one idle discharge receiver. However, as in this example, a common idle discharge receiver can correspond to a plurality of recording heads. This is advantageous because it is easy to approximate the mist collection chamber 350 to an open state.

  5 and 6, there are a discharge droplet introduction passage 305, a droplet storage chamber 310, a mist airflow circulation space 325, a mist collection port 340, and a droplet collection port 360, respectively, separately for a plurality of recording heads. On the other hand, the mist collection chamber 350 connected to each mist collection port 340 is common to a plurality of recording heads and has a large capacity, and the mist whose energy is attenuated in the mist airflow circulation space 325 is further attenuated and collected. Can do. The increased capacity mist collection chamber 350 can be laid out effectively according to the empty space in the apparatus.

  Further, the main droplets and satellite droplets flowing down from the droplet recovery ports 360 formed on the bottom surface of each droplet storage chamber 310 pass through the droplet recovery passage 410 that is a connection structure by the common ink suction pump 400. It is collected in the place.

  Incidentally, the surface portion where ink droplets or mist may come into contact may be configured to be ink repellency (water repellency). Specifically, the passage wall 304 of the discharge droplet introduction passage 305, the guide piece 306 including the landing slope 307, the droplet storage chamber 310, the mist collection port 340, the mist collection chamber 350, the droplet collection port 360, the droplet Each of the collection passages 410. This prevents the ink from sticking to the surface and depositing. The ink repellency is imparted by, for example, the hydrophobicity of the material itself such as a fluororesin or surface processing by fluorine processing.

  With the configuration as described above, even a line type liquid discharge head having a large number of recording heads can perform low-cost, high-efficiency, and high-reliability empty discharge collection while suppressing an increase in size.

108a Nozzle plate 108b Nozzle hole 300 Empty discharge receptacle 301 Ink droplet 303 Droplet inlet 304 Passage wall 305 Discharged droplet introduction passage 306 Guide piece 307 Landing slope 309 Ink reservoir portion 310 Droplet storage chamber 311 Top surface 325 Mist airflow circulation space 340 Mist collection port 350 Mist collection chamber 360 Droplet collection port

JP 2009-137227 A

Claims (7)

An empty discharge receiver for storing droplets discharged from the recording head, and a discharge droplet introduction passage having a passage wall provided with a wall surface extending from the droplet inlet to the inside of the housing along the droplet traveling direction; A guide piece having an inclined surface located inside the casing on the downstream side in the droplet traveling direction of the discharge droplet introduction passage, and an outer peripheral region of the passage wall of the discharge droplet introduction passage, A mist airflow circulation space defined by an upper surface and a free end of the passage wall, and a mist recovery port formed on a side surface of the mist airflow circulation space, the upper end of the mist recovery port The empty discharge receptacle , wherein the lower end of the housing is located above the lower end of the passage wall, and the mist recovery port is connected to the mist recovery chamber . A discharge droplet introduction passage, a mist airflow circulation space, and a mist recovery port are formed separately for each of the plurality of recording heads, and a mist recovery chamber connected to each mist recovery port is provided in common for the plurality of recording heads. The empty discharge receiver according to claim 1 , wherein the empty discharge receiver is provided. Wherein the bottom surface of the housing part receiving spit according to claim 1 or 2, characterized by providing a droplet collection ports. 4. The idle discharge receptacle according to claim 3 , wherein an opening area of the mist collecting port is larger than an opening area of the droplet collecting port. 5. The idle discharge receiver according to claim 3, wherein an ink suction pump is attached to the droplet recovery port. Receiving idle discharge according to any one of claims 1 to 5, characterized in that ink repellency is given to the surface in contact with liquid droplets or a mist flow. An image forming apparatus having a blank ejection receiver according to any one of claims 1-6.