JP2015016557A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent contamination by liquid mist without narrowing a width of material selection of a member constituting a liquid discharge device.SOLUTION: A liquid discharge device includes: a discharge head 114 for discharging liquid to a sheet 103; a protection object member 116 being an object to be protected from contamination due to adhering of liquid mist of the liquid floating without landing on the sheet 103; and a contamination prevention part 150 configured separately from the protection object member 116 and having an electrically neutral characteristic, the contamination prevention part 150 is provided facing a path of the liquid mist ranging from a source of the liquid mist to the protection object member 116.

Description

  The present invention relates to a liquid ejecting apparatus, and more particularly to a technique for preventing contamination of liquid mist generated from liquid ejected from the liquid ejecting apparatus.

  In recent years, in an image forming apparatus such as a printer or a copying machine, an ink jet recording type liquid ejecting apparatus that performs image forming output on a recording medium by ejecting ink droplets from an ejecting head having a nozzle array has been mounted. Sometimes. In such a liquid ejection device, when droplets are ejected from the ejection head, some of the droplets cannot be merged and separated during ejection or flight, or by rebounding that occurs when ink lands on the recording medium. Or separate from the main drop. A part of the separated droplets rapidly decreases in speed due to the viscous resistance of air, and may be scattered as mist without reaching the recording medium and may adhere to the inside of the image forming apparatus. Such a phenomenon is not limited to a mechanism using a piezoelectric vibrator as a mechanism for ejecting ink droplets, but also occurs in a pressure generating unit that operates by applying a driving voltage such as a heating element.

  The mist adhering to the inside of the image forming apparatus becomes dirty, and when the user touches the inside of the image forming apparatus to replace the ink cartridge, the mist adheres to the hand and becomes dirty. In addition, if it adheres to each sensor such as an optical sensor that detects the paper inside the image forming apparatus and an encoder sensor that detects the carriage position, the detection accuracy of each sensor decreases due to the dirt.

  Therefore, as a technique for suppressing adhesion of mist to the encoder sensor, for example, Patent Document 1 collects a discharge electrode for charging the ink mist and a charged ink mist for the purpose of collecting the ink mist. There has been proposed a technique of supplying a high voltage to each electrode from a high voltage circuit that includes a dust collecting electrode for generating a high voltage for charging a conveying belt that conveys a recording medium.

  Patent Document 2 proposes a technique for forming a linear scale of an encoder sensor using a material having the same polarity as that of ink mist for the purpose of suppressing mist contamination of the encoder sensor.

  According to Patent Document 1, the flow of mist can be controlled and recovered by electrostatic force, but it is necessary to provide a discharge electrode and a dust collecting electrode separately, which increases the cost due to the increase in the size of the device and the number of parts. There was a problem of being connected.

  According to Patent Document 2, since the scale portion (encoder sheet) of the encoder sensor is charged with the same polarity as the ink, the material of the encoder is limited to a chargeable material. A material having transparency may be used as the encoder sheet. However, if there is a restriction that a material having the same polarity as the ink mist must be selected, the materials that can be used as the encoder sheet are further limited. Therefore, there is a problem of narrowing the range of material selection. On the other hand, from the viewpoint of expanding the range of material selection, it is conceivable to use a material that does not have transparency. However, in that case, there is a problem that machining for providing a through hole for transmitting light is required. Arise.

  Further, Patent Document 2 does not solve the problem of avoiding mist contamination inside the upper surface cover of the casing that is easy for the user to touch, among the exterior covers of the image forming apparatus. Note that the problem caused by the mist contamination as described above can occur not only in the image forming apparatus but also in an apparatus that ejects liquid.

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent contamination by liquid mist without narrowing the material selection range of members constituting the liquid ejection apparatus.

  In order to solve the above-described problems, a liquid ejection apparatus according to the present invention includes an ejection head that ejects liquid onto a recording medium, and a liquid mist that floats without landing on the recording medium. A protection target member to be protected from contamination, and a contamination prevention unit configured separately from the protection target member and having electrically neutral characteristics, wherein the contamination prevention unit includes the liquid mist. It is provided so as to face the path of the liquid mist from the generation source to the member to be protected.

  According to the present invention, contamination by liquid mist can be prevented without narrowing the material selection range of members constituting the liquid ejection device.

1 is a block diagram showing a hardware configuration of an image forming apparatus according to the present embodiment. 1 is a block diagram showing a functional configuration of an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram of an entire mechanism unit of an image forming apparatus according to a first embodiment. Diagram showing the configuration of the image forming unit A diagram schematically showing an optical linear encoder An explanatory perspective view showing the configuration of the ejection head Diagram showing the configuration of the conveyor belt The figure which shows the operation which discharges the droplet from the discharge head FIGS. 4A and 4B are diagrams illustrating a phenomenon in which mist is generated, in which FIG. 4A illustrates a nozzle plate surface of an ejection head having a plurality of nozzle holes, and FIG. 4B illustrates a state where ink is landed on a sheet. Diagram showing the path of mist drops It is the figure which showed the relationship between the charge amount of the upper surface cover of a housing | casing, and the mist adhesion amount, (a) is a graph which shows the relationship between the charge amount and mist adhesion amount, (b) is a linear encoder. Indicates the measurement position of the amount of mist contamination on the measuring medium installed nearby Functional block diagram showing the configuration of the static eliminator according to the second embodiment Schematic configuration diagram of the entire mechanism of the image forming apparatus according to the second embodiment It is a figure which shows the structure of the static elimination part which concerns on 2nd embodiment, Comprising: (a) shows a brush-shaped static elimination member on one side, (b) shows a roll-shaped static elimination member, (c) shows a static elimination member. The operation of removing the charge by moving it is shown. 8 is a flowchart illustrating an operation example of the image forming apparatus according to the second embodiment. 7 is a flowchart illustrating an operation example of an image forming apparatus according to another aspect of the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image forming apparatus as an MFP (Multi Function Peripheral) will be described as an example. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus, and includes an ink jet recording apparatus (liquid ejecting apparatus) as an image forming output mechanism, and among inks (recording liquid) ejected from the ink jet recording apparatus. The gist of the present invention is to prevent contamination by ink mist that does not land on a recording medium (for example, a paper medium) but floats in a mist.

  FIG. 1 is a block diagram illustrating a hardware configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes an engine that executes image formation in addition to the same configuration as an information processing terminal such as a general server or a PC (Personal Computer). That is, the image forming apparatus 1 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an engine 13, an HDD (Hard Disk Drive) 14, and an I / O. F15 is connected via the bus 18. Further, an LCD (Liquid Crystal Display) 16 and an operation unit 17 are connected to the I / F 15.

  The CPU 10 is a calculation unit and controls the operation of the entire image forming apparatus 1. The RAM 11 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 12 is a read-only nonvolatile storage medium, and stores programs such as firmware. The engine 13 is a mechanism that actually executes image formation in the image forming apparatus 1.

  The HDD 14 is a nonvolatile storage medium capable of reading and writing information, and stores an OS (Operating System), various control programs, application programs, and the like. The I / F 15 connects and controls the bus 18 and various hardware and networks. The LCD 16 is a visual user interface for the user to check the state of the image forming apparatus 1. The operation unit 17 is a user interface such as a keyboard and a mouse for the user to input information to the image forming apparatus 1.

  In such a hardware configuration, a program stored in a recording medium such as the ROM 12, the HDD 14, or an optical disk (not shown) is read into the RAM 11 and operates according to the control of the CPU 10, thereby configuring a software control unit. A functional block that realizes the functions of the image forming apparatus 1 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware.

  Next, the functional configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment includes a controller 20, an ADF (Auto Document Feeder) 21, a scanner unit 22, a paper discharge tray 23, a display panel 24, and a paper feed tray. 25, a print engine 26, a paper discharge tray 27, and a network I / F 28.

  The controller 20 includes a main control unit 30, an engine control unit 31, an input / output control unit 32, an image processing unit 33, and an operation display control unit 34. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment is configured as a multifunction machine having a scanner unit 22 and a print engine 26. In FIG. 2, the electrical connection is indicated by solid arrows, and the flow of paper is indicated by broken arrows.

  The display panel 24 is an output interface that visually displays the state of the image forming apparatus 1 and is an input when the user directly operates the image forming apparatus 1 or inputs information to the image forming apparatus 1 as a touch panel. It is also an interface (operation unit). The network I / F 28 is an interface for the image forming apparatus 1 to communicate with other devices via the network, and uses an Ethernet (registered trademark) or a USB (Universal Serial Bus) interface.

  The controller 20 is configured by a combination of software and hardware. Specifically, a control program such as firmware stored in a nonvolatile recording medium such as the ROM 12 and the nonvolatile memory and the HDD 14 and the optical disk is loaded into a volatile memory (hereinafter referred to as a memory) such as the RAM 11 to control the CPU 10. The controller 20 is configured by a software control unit configured according to the above and hardware such as an integrated circuit. The controller 20 functions as a control unit that controls the entire image forming apparatus 1.

  The main control unit 30 plays a role of controlling each unit included in the controller 20 and gives a command to each unit of the controller 20. The engine control unit 31 serves as a drive unit that controls or drives the print engine 26, the scanner unit 22, and the like.

  The input / output control unit 32 inputs a signal or a command input via the network I / F 28 to the main control unit 30. The main control unit 30 controls the input / output control unit 32 and accesses other devices via the network I / F 28.

  The image processing unit 33 generates drawing information based on the print information included in the input print job under the control of the main control unit 30. The drawing information is information for drawing an image to be formed in the image forming operation by the print engine 26 as an image forming unit. The print information included in the print job is image information converted into a format that can be recognized by the image forming apparatus 1 by a printer driver installed in an information processing apparatus such as a PC. The operation display control unit 34 displays information on the display panel 24 or notifies the main control unit 30 of information input via the display panel 24.

  When the image forming apparatus 1 operates as a printer, first, the input / output control unit 32 receives a print job via the network I / F 28. The input / output control unit 32 transfers the received print job to the main control unit 30. When receiving the print job, the main control unit 30 controls the image processing unit 33 to generate drawing information based on the print information included in the print job.

  When drawing information is generated by the image processing unit 33, the engine control unit 31 performs image formation on the paper conveyed from the paper feed tray 25 based on the generated drawing information. That is, the print engine 26 functions as an image forming unit. A document on which an image has been formed by the print engine 26 is discharged to a discharge tray 27.

  When the image forming apparatus 1 operates as a scanner, the operation display control unit 34 or the input / output unit is operated in accordance with a user operation on the display panel 24 or a scan execution instruction input from an external PC or the like via the network I / F 28. The control unit 32 transfers a scan execution signal to the main control unit 30. The main control unit 30 controls the engine control unit 31 based on the received scan execution signal.

  The engine control unit 31 drives the ADF 21 and conveys the document set on the ADF 21 to the scanner unit 22. Further, the engine control unit 31 drives the scanner unit 22 and images a document conveyed from the ADF 21. If no original is set on the ADF 21 and the original is directly set on the scanner unit 22, the scanner unit 22 takes an image of the set original under the control of the engine control unit 31. That is, the scanner unit 22 operates as an imaging unit.

  In the imaging operation, an imaging element such as a CCD included in the scanner unit 22 optically scans the document, and imaging information generated based on the optical information is generated. The engine control unit 31 transfers the imaging information generated by the scanner unit 22 to the image processing unit 33. The image processing unit 33 generates image information based on the imaging information received from the engine control unit 31 according to the control of the main control unit 30.

  The image information generated by the image processing unit 33 is stored in the HDD 14 or the like as it is according to a user instruction or transmitted to an external device via the input / output control unit 32 and the network I / F 28.

  Further, when the image forming apparatus 1 operates as a copying machine, the image processing unit 33 generates drawing information based on the imaging information received by the engine control unit 31 from the scanner unit 22 or the image information generated by the image processing unit 33. To do. Based on the drawing information, the engine control unit 31 drives the print engine 26 as in the case of the printer operation. In this embodiment, an ink jet recording apparatus is used as the print engine 26. This ink jet recording apparatus corresponds to a liquid ejection apparatus.

<First embodiment>
The first embodiment is an embodiment in which an antistatic member (a member subjected to antistatic processing) is disposed on the upper portion of the ink jet recording apparatus. The structure of the image forming apparatus according to this embodiment will be described below with reference to FIGS. FIG. 3 is a schematic configuration diagram of the entire mechanism unit of the image forming apparatus according to the first embodiment. FIG. 4 is a diagram illustrating a configuration of the image forming unit. FIG. 5 is a diagram schematically showing an optical linear encoder. FIG. 6 is a perspective explanatory view showing the configuration of the ejection head. FIG. 7 is a diagram illustrating a configuration of the conveyance belt. FIG. 8 is a diagram illustrating an operation of ejecting droplets from the ejection head.

  As shown in FIG. 3, the image forming apparatus 1 according to the present embodiment includes a housing 101 that is placed on a floor surface, and an ADF 21 and a paper discharge tray 23 that discharges a document read by the ADF 21 on the top. To do. The housing 101 includes an inkjet recording apparatus 102 as the print engine 26 and a transport mechanism 105 that transports a recording medium (hereinafter referred to as “paper”). A paper feed tray 25 on which a large number of recording media (hereinafter referred to as “paper”) 103 can be stacked is provided below the housing 101. Then, the sheet 103 fed from the sheet feeding tray 25 is taken in, and an image forming output is performed by the inkjet recording apparatus 102 while the sheet 103 is conveyed by the conveying mechanism 105, and then the sheet is mounted on the side of the casing 101. The paper 103 is discharged to the paper discharge tray 27. A cover member that is located on the upper side of the ink jet recording apparatus 102 and has a surface (opposing surface) facing the ink jet recording apparatus 102 among the exterior covers constituting the housing 101 is referred to as an upper surface cover 101a.

  Further, the image forming apparatus 1 according to the present embodiment includes a duplex unit 107 that can be attached to and detached from the housing 101. When performing duplex printing, after the printing of one side (front side) of the paper 103 is completed, the paper 103 can be taken into the duplex unit 107 while being conveyed in the reverse direction by the transport mechanism 105 and reversed to print the other side (back side). The sheet is again fed into the transport mechanism 105 as a surface. Then, after the printing on the other side (back side) is completed, the sheet 103 is discharged to the discharge tray 27.

  The ink jet recording apparatus 102 includes guide shafts 111 and 112 made of a long member, a carriage 113, an ejection head 114, and an ink cartridge 115. The guide shafts 111 and 112 are arranged so that their major axis directions coincide with a direction (hereinafter referred to as “main scanning direction”) orthogonal to the conveyance direction (hereinafter referred to as “sub-scanning direction”) of the sheet 103. Be placed. A carriage 113 is slidably held on the guide shafts 111 and 112, and the carriage 113 is moved in a direction orthogonal to the conveyance direction of the sheet 103 by a main scanning motor (not shown). That is, the main scanning motor and the carriage 113 correspond to a moving unit that moves the ejection head 114 relative to the paper 103.

  The carriage 113 is detachably mounted with an ejection head 114 and an ink cartridge 115 that supplies liquid to the ejection head 114. Note that a subtank may be mounted instead of the ink cartridge 115, and ink may be supplementally supplied from the main tank to the subtank.

  Further, as shown in FIG. 4, a linear encoder 116 is arranged along the long axis direction of the guide shaft 111. In FIG. 4, the ink cartridge 115 is not shown for the sake of simplicity. The linear encoder 116 is read by a reading sensor (not shown) provided in the discharge head 114, and the discharge head 114 is positioned. That is, the linear encoder 116 corresponds to a movement amount measuring member for measuring the movement amount of the ejection head. The detection method of the linear encoder 116 includes an optical method and a magnetic method, but the method is not particularly limited. In this embodiment, an optical linear encoder 116 shown in FIG. 5 is used. The longitudinal direction of the linear encoder 116 is installed in a direction parallel to the main scanning direction. The linear encoder 116 uses, for example, a transparent film material, and includes a light-transmitting portion 116a that can transmit light, and a light-shielding portion 116b that is printed in a slit shape that is long in the band width direction (painted with paint or the like). Alternatively, the detection pattern may be formed alternately along the main scanning direction. When the linear encoder 116 is made of an opaque material, for example, a slit-shaped through hole may be provided, and light may be transmitted through the through hole to form a detection pattern. The linear encoder 116 is a member to be protected from contamination caused by the ink mist adhering, that is, a so-called protection target member. Details will be described later.

  The ejection head 114 uses four independent inkjet heads 114y, 114m, 114c, and 114k that eject ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (Bk). You may comprise, and you may comprise so that the 1 or several discharge head which has a some nozzle row which discharges the ink droplet of each color may be used. The number of colors and the order of arrangement are not limited to this. In the present embodiment, the ejection head 114 is configured as an ejection head in which nozzle holes 114n (see FIG. 6), which are a plurality of ejection openings for ejecting ink droplets, are arranged.

  The inkjet heads 114y, 114m, 114c, and 114k that constitute the ejection head 114 include a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal conversion element such as a heating resistor, Any system may be used as long as it has an energy generating means for ejecting ink, such as a shape memory alloy actuator using a metal phase change due to a temperature change or an electrostatic actuator using an electrostatic force.

  As shown in FIG. 3, the upper part of the ink jet recording apparatus 102 (ADF 21 side), more specifically, the upper part of the ink cartridge 115 is formed on the paper 103 out of the ink ejected from the ink jet heads 114y, 114m, 114c, 114k. A contamination prevention unit 150 is provided for preventing contamination by ink mist floating without landing. In the present embodiment, the contamination prevention unit 150 is configured by using a planar member using an antistatic member, for example, a film, and the upper part of the ink jet recording apparatus 102, that is, the ink cartridge 115 and the upper surface 101 a of the housing 101. Arranged between. The shape of the contamination prevention unit 150 is not limited to a planar member, and the shape thereof is not limited, such as a rod shape or a mesh shape.

  The transport mechanism 105 includes a paper feed roller (half-moon roller) 121, a transport guide portion 123, a transport roller 124, a pressure roller 125, guide members 126 and 127, and a pressing roller 128 (see FIG. 3).

  The paper 103 in the paper feed tray 25 is separated one by one by a paper feed roller (half-moon roller) 121 and a separation pad (not shown), fed into the housing 101, and sent to the conveyance guide unit 123.

  The conveyance guide unit 123 includes a guide surface 123 a that guides the fed sheet 103 upward toward the conveyance roller 124 and a guide surface 123 b that guides the sheet 103 fed from the duplex unit 107 toward the conveyance roller 124. Including. The transport roller 124 transports the sheet 103 fed from the guide surface 123 a or the guide surface 123 b along the rotation direction of the transport roller 124. At this time, the pressure roller 125 presses the conveyance roller 124 against the sheet 103, and the guide member 126 guides the sheet 103 along the rotation direction of the conveyance roller 124. Then, the sheet 103 is sent out to the conveying belt 133 while being pressed against the conveying roller 124 by the pressing roller 128. Further, between the guide member 126 and the pressing roller 128 is provided a guide member 127 that guides the sheet 103 that is returned during double-sided printing (sent out in the direction opposite to the conveyance direction) to the duplex unit 107.

  Further, in order to convey the sheet 103 with the ejection head 114 while maintaining the flatness of the sheet 103, the conveyance mechanism 105 charges the conveyance belt 133 that is stretched between the driving roller 131 and the driven roller 132, and the conveyance belt 133. A charging roller 134 for causing the charging roller 134 to face, a guide roller 135 facing the charging roller 134, a guide member (not shown) that guides the transport belt 133 at a portion facing the ink jet recording apparatus 102, and a transport belt 133. And a cleaning roller made of a porous material, which is a cleaning means for removing ink (recording liquid) adhering to the ink.

  Here, the conveying belt 133 is an endless belt, and is stretched between a driving roller 131 that is rotationally driven by a driving motor (not shown) and a driven roller (tension roller) 132, and is in a direction indicated by an arrow a in FIG. It is configured to circulate in the paper conveyance direction). The transport belt 133 may be configured as a single layer or as shown in FIG. 7, a two-layer configuration of a first layer (outermost layer: a surface layer serving as a suction surface of the paper 103) 133a and a second layer (back layer) 133b. Moreover, it can be set as the structure of three or more layers. When the transport belt 133 is configured by a laminated structure, the first layer is a pure resin material having a thickness of about 40 μm that is not subjected to resistance control, for example, ETFE pure material (ETFE: ethylene tetrafluoroethylene copolymer). And the second layer may be constituted by a back layer (medium resistance layer, earth layer) that is made of the same material as the first layer and is subjected to resistance control by carbon.

  The charging roller 134 is disposed so as to come into contact with the first layer of the transport belt 133 and to rotate following the rotation of the transport belt 133. A high voltage is applied to the charging roller 134 in a predetermined pattern from a high voltage circuit (high voltage power source) (not shown).

  Further, a paper discharge roller 138 for sending the paper 103 on which an image is recorded to the paper discharge tray 27 is provided on the downstream side from the transport mechanism 105. In the image forming apparatus 1 configured as described above, the conveying belt 133 circulates in the direction of arrow a, and comes into contact with the charging roller 134 to which a high potential applied voltage (AC bias voltage) is applied. Positively charged. In this case, by switching the polarity of the charging roller 134 at a predetermined time interval, the conveying belt 133 is charged while switching the polarity at a predetermined charging pitch.

  Here, when the sheet 103 is fed onto the conveying belt 133 charged to this high potential, the inside of the sheet 103 is in a polarized state, and the charge opposite in polarity to the charge on the conveying belt 133 is transferred to the conveying belt of the sheet 103. The charge on the transport belt 133 and the charge on the transported paper 103 are electrostatically attracted to each other, and the paper 103 is electrostatically attracted to the transport belt 133. Adsorbed. In this way, the sheet 103 strongly adsorbed to the transport belt 133 is calibrated for warpage and unevenness, and a highly flat surface is formed.

  Accordingly, the sheet 103 is moved by circling the conveying belt 133, and the ejection head 114 is driven in accordance with the image signal while moving and scanning the carriage 113 in one direction or in both directions. As shown in FIG. Then, the ink droplet 141 is ejected (ejected), and the ink droplet is landed on the stopped paper 103 to form the dot Di and record one line. Thereafter, after the sheet 103 is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 103 reaches the recording area, the recording operation is ended. In this way, the sheet 103 on which the image is recorded is discharged to the discharge tray 27 by the discharge roller 138.

  Next, a phenomenon in which mist is generated from ink droplets will be described with reference to FIG. 9A and 9B are diagrams illustrating a phenomenon in which mist is generated. FIG. 9A illustrates a nozzle plate surface of an ejection head having a plurality of nozzle holes, and FIG. 9B illustrates ink landing on a sheet. Show the state. As shown in FIG. 9A, the main causes of the occurrence of mist are due to the trailing edge cut of the droplet 141 and the bounce after landing as shown in FIG. 9B.

  As shown in FIG. 9A, of the ink droplets 141 ejected from the nozzle holes 114n, the mist droplet 141b split from the main droplet 141a suddenly loses speed and floats in the air. At that time, if a uniform electric field exists, even if the original droplet 141 is electrically neutral, electrostatic induction occurs due to charging of the conveyor belt 133, and the charge distribution of the mist droplet 141b is unidirectional. It will be biased to. For example, when the transport belt 133 side has a positive charge, a negative charge is induced on the transport belt 133 side of the droplet 141, and a positive charge is induced on the droplet on the nozzle plate side of the droplet 141. Since the mist droplet 141b is constituted by a part of the droplet 141 on the side opposite to the conveying belt 133 of the droplet 141, it is positively charged. That is, it is not electrically neutral. Accordingly, the mist droplet 141b is easily adsorbed by the charged housing 101 and the members accommodated therein, and the mist droplet 141b accumulates to cause mist contamination. The mist droplet 141b is a so-called liquid mist.

  Therefore, the image forming apparatus 1 according to the present embodiment repels the mist droplet 141b by the contamination prevention unit 150 described above, suppresses reaching the protection target member, and prevents mist contamination. The contamination prevention unit 150 has an electrically neutral characteristic, and is arranged on the path of the mist droplet 141b from the ink landing point on the generation source of the mist droplet 141b, for example, the ejection head 114 and the paper 103, to the protection target member. To do. Hereinafter, a linear encoder 116 is taken as an example of a member to be protected, and an embodiment using a planar member that is configured separately from the linear encoder 116 and covers the ejection head 114 and the conveyor belt 133 as the contamination prevention unit 150. explain.

  FIG. 10 is a diagram showing the path of the mist droplet. For simplicity of explanation, the guide shaft 112 and the carriage 113 are not shown. The discharge head 114 reciprocates along the guide shaft 111 in the direction of the arrow 148 (main scanning direction), and the linear encoder 116 is disposed on the back side of the guide shaft 111 (upstream side in the conveyance direction of the paper 103). . Here, when the contamination prevention unit 150 according to the present invention is not disposed, the mist droplet 141b ejected from the ejection head 114 is charged as described above. When charged with the opposite polarity to the electric charge of the droplet 141b, the mist droplet 141b is attracted and rises. The raised mist droplet 141b passes through the guide shaft 111 and reaches the linear encoder 116. By continuing to adhere to the linear encoder 116 as mist contamination, reading of the encoder sensor is hindered. That is, the mist droplet 141 b arrives at the linear encoder 116 through the paths indicated by the arrows 146 and 147.

  The inventors of the present invention determined the relationship between the amount of mist droplet adhesion and the charge amount of the top cover by experiments. The result will be described with reference to FIG. FIG. 11 is a graph showing the relationship between the charge amount of the reverse polarity charge on the top cover 101a and the mist adhesion amount, and FIG. 11A is a graph showing the relationship between the charge amount and the mist adhesion amount. b) shows the mist contamination amount measurement position of the measurement medium installed near the linear encoder. On the measurement medium 136 shown in FIG. 11B, the interval between the adjacent measurement positions 136a of the amount of mist contamination is set to 5 cm, and the horizontal axis of the graph of FIG. The distance from the center of each to each measurement position 136a is shown. The vertical axis of the graph is a measured value of an index representing the amount of mist droplets attached, and the higher the value, the greater the amount of mist attached. From the result of FIG. 11, the larger the charge amount of the upper surface cover 101a, the more the amount of mist droplets rises. As a result, the mist drops rise around the back of the guide shaft 111 (in the direction of the arrow 147 in FIG. 10) and adhere to the linear encoder 116. It is estimated that the amount to be increased also increases.

  Therefore, in the image forming apparatus 1 according to the present embodiment, the antistatic contamination preventing unit 150 is disposed on the upper side of the ejection head 114, thereby suppressing the charged mist droplet 141b from being attracted and raised. It becomes possible. That is, the flow of the mist droplet 141b can be controlled to some extent by making the contamination prevention unit 150 electrically neutral. Note that the “electrically neutral state” includes not only a completely uncharged state but also a state where the mist droplet 141b is charged so as not to attract (more specifically, a state where the absolute value of the surface potential is close to 0). including.

  The contamination prevention unit 150 is formed, for example, by containing metal particles or a metal material inside the material of the contamination prevention unit 150, or is coated with an antistatic agent on the surface of the contamination prevention unit 150, particularly the surface facing the paper 103. Thus, an uncharged state can be realized. The type of metal particles or metal material is not particularly limited, but is preferably grounded in order to maintain an uncharged state. Further, as the antistatic agent, known materials can be applied, for example, fatty acid salts, higher alcohol sulfate esters, aliphatic amines and aliphatic amide sulfates, aliphatic alcohol phosphate esters, dibasic fatty acids. Anionic surfactants such as ester sulfonates, aliphatic amide sulfonates, alkylallyl sulfonates, cationic surfactants such as aliphatic amine salts, quaternary ammonium salts, alkylpyridinium salts, carboxybetaines , Betaine types such as sulfobetaine, amphoteric surfactants such as aminocarboxylates and imidazoline derivatives, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, poly Carboxymethyl nonionic surfactants such as polyoxyethylene sorbitan alkyl esters.

  In the present embodiment, the contamination prevention unit prevents the mist droplet from rising, and thus can be prevented from reaching the linear encoder and being contaminated. Further, by configuring the contamination prevention unit separately from the linear encoder, it is possible to prevent mist contamination without narrowing the range of material selection of the linear encoder.

  In the above-described embodiment, a flat film is used as the contamination prevention unit 150 and is disposed on the upper part of the ejection head 114. However, the arrangement position of the contamination prevention unit is not limited to the upper part of the ejection head 114. You may arrange | position to the side of. Furthermore, the member which comprises the pollution prevention part 150 is not limited to said planar film. For example, the upper surface cover 101a of the housing 101 or the exterior cover that forms the side surface of the housing 101 can be used as the contamination prevention unit. In this case, the types of metal particles and metal materials included in the upper surface cover 101a are not particularly limited, but are preferably grounded in order to maintain an uncharged state. Examples of the antistatic material include an antistatic film made of vinyl chloride resin, an antistatic sheet made of vinyl chloride resin or acrylic copolymer, an antistatic curtain, and the like. As a result, mist contamination can be prevented without increasing the number of parts. In addition, mist contamination of the top cover 101a of the housing 101 and the exterior cover itself that can be touched most by the user can be avoided, so that when the user touches the inside of the image forming apparatus, mist contamination of the top cover 101a and the exterior cover is possible. Can be prevented from adhering to the hand.

<Second embodiment>
The second embodiment is an embodiment in which neutralization is performed according to the electrical characteristics of the exterior cover of the housing to prevent mist contamination. The configuration of the image forming apparatus according to the second embodiment will be described below with reference to FIGS. FIG. 12 is a functional block diagram illustrating a configuration of the static eliminating unit according to the second embodiment. FIG. 13 is a schematic configuration diagram of the entire mechanism unit of the image forming apparatus according to the second embodiment. FIG. 14 is a diagram illustrating a configuration of a static eliminating unit according to the present embodiment, where (a) illustrates a brush-shaped static eliminating member on one side, (b) illustrates a roll-shaped static eliminating member, and (c) illustrates The operation of removing the charge by moving the charge removal member will be described. In addition, about the structure similar to 1st embodiment, the same code | symbol is attached | subjected and duplication description is abbreviate | omitted.

  As shown in FIG. 12, the image forming apparatus according to the second embodiment includes a neutralization unit 160 that neutralizes the exterior cover inside the print engine 26. The neutralization unit 160 is electrically connected to the main control unit 30 and operates in response to a control signal from the main control unit 30. The static elimination unit 160 measures the surface potential of the static elimination member 161 that performs static elimination by contacting the surface of the static elimination target member, the driving device 162 that moves the static elimination member 161 along the surface, and the static elimination target member. And an electrometer 163. That is, the electrometer 163 corresponds to a potential measurement unit. The static elimination member 161 and the drive device 162 are mechanically connected. In addition, each of the driving device 162 and the electrometer 163 is electrically connected to the main control unit 30. In the present embodiment, an exterior cover that constitutes the casing 101, in particular, an upper surface cover 101a is used as a member to be neutralized.

  Therefore, as shown in FIG. 13, an electrometer 163 for measuring the surface potential is provided on the inner surface of the upper surface cover 101a of the image forming apparatus 1a. The static elimination member 161 is disposed so as to come into contact with the inner surface of the top cover 101a. Then, the drive unit 162 removes the charge by moving the charge removal member 161 in contact with the inner surface of the upper surface cover 101a.

  The neutralization member 161 may use a neutralization member 161a (see FIG. 14A) having a brush on one side, or a neutralization member 161b composed of a roll-shaped brush (see FIG. 14B). May be used, and the material of the brush is not particularly limited. By removing the charge removal member 161 while being in contact with the inner surface of the upper surface cover 101a by the driving device 162 (see FIG. 14C), the upper surface cover 101a can be discharged. In order to increase the charge removal effect, the charge removal member 161 is preferably grounded.

  Next, an operation flow of the image forming apparatus according to the second embodiment will be described with reference to FIG. FIG. 15 is a flowchart illustrating an operation example of the image forming apparatus according to the second embodiment.

  Prior to image formation output by the image forming apparatus 1a, power is first turned on (S1501), the surface potential [kV] of the inner surface of the upper surface cover 101a is measured by the electrometer 163 (S1502), and based on the measurement result, It is determined whether or not the top cover 101a has a reverse polarity with respect to the electrical characteristics (polarity) of the mist droplet (S1503). That is, when the mist droplet is positively charged, it is determined whether or not the upper surface cover 101a is negatively charged.

  When the upper surface cover 101a is charged with the opposite polarity to the electrical characteristics of the mist droplet (S1503 / Yes), the upper surface cover 101a is discharged (S1504). Then, the surface potential of the upper surface cover 101a is measured again (S1502), and it is determined whether or not it is charged with a reverse polarity.

  When the upper surface cover 101a is not charged with the opposite polarity to the polarity of the mist droplet (S1503 / No), that is, when it is electrically neutral or positively charged, printing is possible on the display panel 24. A signature is displayed (S1505).

  In the above example, the surface potential of the top cover 101a is measured with an electrometer. Instead, a predicted value of the surface potential of the top cover 101a is calculated from the humidity inside the housing 101 of the image forming apparatus 1a. Also good. Since the image forming apparatus 1a is usually provided with a humidity sensor for detecting the state of the ejection head 114, the surface potential can be obtained without using a new apparatus by using the output value of the humidity sensor. Can be predicted. The humidity sensor corresponds to a humidity measuring unit that detects the humidity inside the housing. Hereinafter, an operation process for predicting the surface potential using the measurement value of the humidity sensor will be described with reference to FIG. FIG. 16 is a flowchart illustrating an operation example of the image forming apparatus according to another aspect of the second embodiment.

  Prior to image formation output by the image forming apparatus 1a, first, the power is turned on (S1601), the humidity in the housing 101 is measured using the humidity sensor provided in the housing 101 (S1602), and the measurement result is displayed. Based on this, a predicted value of the surface potential of the top cover 101a is calculated (S1603). The prediction of the surface potential may be calculated by the main control unit 30 applying the humidity measured in step S1602 to a table or function obtained by measuring the humidity and the corresponding surface potential of the upper surface cover 101a in advance. Good. Therefore, the main control unit 30 has a function as a predicted value calculation unit that calculates a predicted value of the surface potential of the top cover.

  If the upper surface cover 101a is expected to have a reverse polarity to the mist droplet (S1604 / Yes), the upper surface cover is neutralized (S1605), and a printable sign is displayed on the display panel 24 (S1606). Even when the upper surface cover is expected not to have a reverse polarity (S1604 / No), a printable sign is displayed on the display panel 24 (S1606).

  In the above description, the charge removal is performed when it is determined or predicted that the top cover has the reverse polarity. However, the top cover may be discharged when the power is turned on. Moreover, you may use the planar member of the pollution prevention part with which it replaced with the upper surface cover and was provided in 1st embodiment.

  According to this embodiment, it is possible to prevent mist from adhering to the protection target member (for example, a linear encoder) or the upper surface cover by attracting the mist droplets to the upper surface cover.

  In addition to the above embodiments, a mist collecting mechanism may be formed by providing a region having a polarity opposite to that of the mist droplet 141b in a part of the contamination prevention unit 150 and adsorbing the mist droplet 141b in the region. In order to provide a region having a reverse polarity, for example, in the second embodiment, a region that is not neutralized, that is, a non-static region may be secured in a partial region of the upper surface cover 101a. In this case, since the non-static area is not neutralized, it has reverse characteristics and functions as a mist collecting mechanism. The configuration of the mist collecting mechanism may be a configuration in which a cleaning unit is provided and cleaning is automatically performed after a predetermined time has elapsed, or a configuration in which the droplet absorbing material absorbs the mist collecting mechanism.

  In the above embodiment, the embodiment in which the liquid ejection apparatus according to the present invention is applied to the MFP has been described. However, the liquid ejection apparatus according to the present invention is not limited to the MFP, and in an apparatus for ejecting liquid droplets such as a three-dimensional printer, It can be widely applied to technology for preventing contamination by droplet mist.

1 Image forming apparatus 10 CPU
11 RAM
12 ROM
13 Engine 14 HDD
15 I / F
16 LCD
17 Operation unit 18 Bus 20 Controller 21 ADF
22 Scanner unit 23 Paper output tray 24 Display panel 25 Paper feed tray 26 Print engine 27 Paper output tray 28 Network I / F
30 Main Control Unit 31 Engine Control Unit 32 Input / Output Control Unit 33 Image Processing Unit 34 Operation Display Control Unit 101 Case 101a Top Cover 102 Inkjet Recording Device 103 Paper 105 Conveying Mechanism 107 Duplex Unit 111, 112 Guide Shaft 113 Carriage 114 Discharge Head 115 Ink Cartridge 116 Linear Encoder 121 Paper Feed Roller 123 Transport Guide Portion 124 Transport Roller 125 Pressure Roller 126, 127 Guide Member 128 Press Roller 131 Drive Roller 132 Followed Roller 133 Transport Belt 134 Charging Roller 135 Guide Roller 136 Measuring Medium 136a Measurement Position 138 Discharge roller 141 Droplet 141a Main drop 141b Mist drop 160 Static elimination unit 161 Static elimination member 162 Driving device 163 Electrometer

JP 2005-349799 A JP 2012-240255 A

Claims (10)

An ejection head for ejecting liquid onto a recording medium;
Among the liquids, a protection target member that is a target to be protected from contamination due to adhesion of floating liquid mist without landing on the recording medium;
Constructed separately from the member to be protected, and having a pollution prevention part having electrically neutral characteristics,
The liquid discharge apparatus according to claim 1, wherein the contamination prevention unit is provided facing a path of the liquid mist from the liquid mist generation source to the member to be protected.   The liquid ejection apparatus according to claim 1, wherein the contamination prevention unit is disposed on a side opposite to the recording medium with the ejection head interposed therebetween. A moving unit that moves the ejection head relative to the recording medium;
A movement amount measuring member for measuring the movement amount of the ejection head, and
The liquid ejection apparatus according to claim 1, wherein the protection target member is the movement amount measurement member. A transport mechanism for transporting the recording medium;
4. The liquid ejection apparatus according to claim 1, wherein the contamination prevention unit is formed by a planar member that covers the ejection head and the transport mechanism. 5.   The liquid ejecting apparatus according to claim 4, wherein the planar member is configured using an antistatic member. A housing for accommodating the liquid ejection device;
The liquid ejecting apparatus according to claim 4, wherein the planar member is formed by using a facing surface that constitutes the casing and faces the liquid ejecting apparatus.   The liquid ejecting apparatus according to claim 6, further comprising a static eliminating unit that removes charges by removing charges accumulated on the facing surface. It further includes a potential measuring unit that measures the surface potential of the facing surface,
The neutralization of the opposing surface is performed by the static elimination unit when the opposing surface is determined to have a polarity opposite to the polarity of the liquid mist as a result of measurement by the potential measuring unit. The liquid discharge apparatus as described. A humidity measuring unit for detecting humidity in the housing;
A predicted value calculation unit that calculates a predicted value of the surface potential of the facing surface based on the detected humidity;
Based on the predicted value calculated by the predicted value calculation unit, when it is determined that the facing surface has a polarity opposite to the polarity of the liquid mist, the charge removal unit performs charge removal on the facing surface. The liquid ejection device according to claim 7.   A part having a reverse polarity with respect to the electrical characteristics of the liquid mist is provided in a part of the contamination prevention unit, and a mist collecting mechanism for adsorbing and collecting the liquid mist is formed in the area. The liquid ejection device according to claim 1.