JP2014172370A - Liquid discharge head and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge head which can more reliably suppress pressure variations in individual liquid chambers from propagating, thereby solving a problem that it is impossible to sufficiently suppress pressure variations in individual flow channels from propagating by only providing a damper region in a common liquid chamber.SOLUTION: A flow channel plate is provided with individual flow channels 5 which are formed on it and include a liquid supply passage 70 constituted of an individual liquid chamber 6, a fluid resistance part 7 and a liquid introduction part 8. Buffer chambers 41 holding gas are provided between the fluid resistance parts 7, 7 of the flow channel plate, and the buffer chambers 41 are connected with the liquid introduction parts 8 via passages 42. The cross-sectional area of the opening of the passages 42 connecting the buffer chambers 41 and the liquid introduction parts 8 is smaller than the cross-sectional area of the opening of the liquid introduction parts 8.

Description

  The present invention relates to a liquid discharge head and an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying apparatus, a plotter, and a complex machine of these, for example, a liquid discharge recording type image forming apparatus using a recording head composed of a liquid discharge head (droplet discharge head) for discharging droplets An ink jet recording apparatus or the like is known.

  In the liquid discharge head, when the individual flow path is pressurized to discharge droplets, the pressure fluctuation generated in the individual flow path becomes a pressure wave, and the common liquid that supplies the liquid to the plurality of individual flow paths It also propagates to the chamber (common flow path). When the pressure wave propagated to the common liquid chamber propagates back to the individual flow path, the pressure of the individual flow path is fluctuated, and the meniscus of the nozzle cannot be controlled, so that the liquid droplet with the required drop speed and drop volume (drop volume) Can no longer be discharged, or it causes non-discharge of drops. In addition, if the pressure wave propagated to the common liquid chamber propagates to the adjacent individual flow paths and causes mutual interference that affects the liquid, it may cause unintended leakage of liquid droplets from the nozzle, ejection, and instability of the ejection state. Will trigger.

  Therefore, conventionally, a part of the wall surface of the common liquid chamber is used as a deformable damper region (Patent Document 1), or a buffer chamber volume expansion portion is provided upstream of the common flow path. (Patent Document 2).

JP 2007-307774 A JP 2011-161934 A

  However, as described above, there is a problem that it is not possible to sufficiently suppress propagation of pressure fluctuations in the individual flow paths simply by providing a damper region in the common liquid chamber (common flow path).

  The present invention has been made in view of the above problems, and an object thereof is to more reliably suppress the propagation of pressure fluctuations in the individual liquid chambers.

In order to solve the above-described problem, a liquid discharge head according to the present invention includes:
A flow path plate that forms a plurality of individual flow paths including a separate liquid chamber that communicates with each of a plurality of nozzles that discharge droplets and a liquid supply path that communicates with the individual liquid chamber;
The flow path plate is provided with a buffer chamber that communicates with the liquid supply path and holds gas,
The opening cross-sectional area of the passage through the buffer chamber and the liquid supply path is configured to be smaller than the opening cross-sectional area of the liquid supply path.

  According to the present invention, it is possible to more reliably suppress propagation of pressure fluctuations in the individual liquid chambers.

FIG. 2 is an external perspective view for explaining an example of a liquid discharge head according to the present invention. FIG. 2 is a cross-sectional explanatory diagram in a direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction along the line AA in FIG. 1. It is a cross-sectional explanatory drawing of the nozzle arrangement direction (liquid chamber short direction) along the BB line of FIG. It is a plane explanatory view of a channel board in a 1st embodiment of the present invention. It is a plane explanatory view of a channel board in a 2nd embodiment of the present invention. It is a plane explanatory view of a channel board in a 3rd embodiment of the present invention. It is a plane explanatory view of a channel board in a 4th embodiment of the present invention. FIG. 4 is a side explanatory view of a mechanism portion for explaining an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. An example of a liquid discharge head according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective explanatory view of the head, FIG. 2 is a cross-sectional explanatory view in a direction (longitudinal direction of the liquid chamber) orthogonal to the nozzle arrangement direction along the line AA in FIG. 1, and FIG. It is sectional explanatory drawing of the nozzle arrangement | sequence direction (liquid chamber short direction) in alignment with a line.

  In this liquid discharge head, a nozzle plate 1, a flow path plate (liquid chamber substrate) 2, and a vibration plate member 3 as a thin film member are laminated and joined. And the piezoelectric actuator 11 which displaces the diaphragm member 3 and the frame member 20 are provided as a common flow path member.

  The nozzle plate 1, the flow path plate 2, and the vibration plate member 3, the individual liquid chamber 6 that communicates with the plurality of nozzles 4 that discharge droplets, the fluid resistance portion 7 that supplies the liquid to the individual liquid chamber 6, and the fluid resistance A liquid supply path 70 including a liquid introduction part 8 connected to the part 7 is formed. Here, the individual flow path 5 is constituted by the individual liquid chamber 6, the fluid resistance section 7, and the liquid introduction section 8 (liquid supply path 70). The individual liquid chamber is also referred to as a pressurizing chamber, a pressure chamber, a pressurized liquid chamber, or the like.

  Then, the liquid (ink) is supplied to the plurality of individual liquid chambers 6 through the liquid introduction portion 8 and the fluid resistance portion 7 through the filter portion 9 formed in the diaphragm member 3 from the common liquid chamber 10 as a common flow path of the frame member 20. ).

  Here, the nozzle plate 1 is formed of a nickel (Ni) metal plate and is manufactured by an electroforming method (electroforming). Not limited to this, other metal members, resin members, laminated members of resin layers and metal layers, and the like can be used. In the nozzle plate 1, for example, nozzles 4 having a diameter of 10 to 35 μm are formed corresponding to the respective liquid chambers 6 and bonded to the flow path plate 2 with an adhesive. Further, a water repellent layer is provided on the droplet discharge side surface (surface in the discharge direction: discharge surface or the surface opposite to the liquid chamber 6 side) of the nozzle plate 1.

  For example, the flow path plate 2 is formed by pressing a metal plate such as a SUS substrate to form a groove that becomes the individual flow path 5. Note that the metal plate can be formed by etching with an acidic etching solution, or the silicon substrate can be formed by etching.

  The vibration plate member 3 also serves as a wall surface member that forms a part of the wall surface of the individual liquid chamber 6 of the flow path plate 2, and has a deformable vibration region 30 at a portion corresponding to the individual liquid chamber 6. The diaphragm member 3 is also formed from a nickel (Ni) metal plate and is manufactured by an electroforming method (electroforming). Not limited to this, other metal members, resin members, laminated members of resin layers and metal layers, and the like can be used.

  A piezoelectric actuator 11 including an electromechanical conversion element as a driving means (actuator means, pressure generating means) for deforming the vibration region 30 of the diaphragm member 3 on the opposite side of the diaphragm member 3 from the individual liquid chamber 6. Is arranged.

  The piezoelectric actuator 11 has a plurality of laminated piezoelectric members 12 bonded with adhesive on a base member 13, and the piezoelectric member 12 is grooved by half-cut dicing to have a required number of piezoelectric members 12. Piezoelectric columns 12A and 12B are formed in a comb shape at a predetermined interval.

  The piezoelectric columns 12A and 12B of the piezoelectric member 12 are the same, but a piezoelectric column that is driven by giving a driving waveform is a driving piezoelectric column (driving column) 12A, and a piezoelectric column that is used as a simple column without giving a driving waveform. It is distinguished as a non-driving piezoelectric column (non-driving column) 12B.

  The drive column 12A is joined to an island-shaped convex portion 30a formed in the vibration region 30 of the diaphragm member 3. Further, the non-driving column 12B is joined to the convex portion 30b of the diaphragm member 3.

  This piezoelectric member 12 is formed by alternately laminating piezoelectric layers and internal electrodes, and each internal electrode is pulled out to the end face to be provided with an external electrode, and can be used to supply a drive signal to the external electrode of the drive column 12A. An FPC 15 as a flexible wiring board having flexibility is connected.

  The frame member 20 is formed by injection molding using, for example, epoxy resin or thermoplastic resin such as polyphenylene sulfite, and a common liquid chamber 10 to which liquid is supplied from a head tank or a liquid cartridge (not shown) is formed.

  In the liquid discharge head configured as described above, for example, the drive column 12A contracts by lowering the voltage applied to the drive column 12A from the reference potential, and the vibration region 30 of the diaphragm member 3 descends, so that the individual liquid chambers 6 As the volume expands, the liquid flows into the individual liquid chamber 6.

  Thereafter, the voltage applied to the drive column 12A is increased to extend the drive column 12A in the stacking direction, the vibration region 30 of the diaphragm member 3 is deformed in the nozzle 4 direction, and the volume of the individual liquid chamber 6 is contracted. The liquid in the individual liquid chamber 6 is pressurized, and droplets are ejected (jetted) from the nozzle 4.

  Then, by returning the voltage applied to the drive column 12A to the reference potential, the vibration region 30 of the diaphragm member 3 is restored to the initial position, and the individual liquid chamber 6 expands to generate a negative pressure. The liquid is filled into the individual liquid chamber 6 from the liquid chamber 10 through the liquid introducing portion 8 and the fluid resistance portion 7. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (pulling-pushing), and it is also possible to perform striking or pushing depending on the direction to which the driving waveform is given.

  Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 4 is an explanatory plan view of the flow path plate in the same embodiment. In FIG. 4, the channel portion is shown with surface coating (hereinafter the same).

  In the flow path plate 2, a buffer chamber 41 that holds gas is formed in a partition wall (partition wall region) 40 between adjacent fluid resistance units 7 and 7. The buffer chamber 41 communicates with the liquid introduction part 8 upstream of the fluid resistance part 7 through the passage 42. Note that gas is also retained in the passage 42.

  Here, the opening cross-sectional area of the passage 42 is smaller than the opening cross-sectional area of the liquid introduction part 8 constituting the liquid supply path 70.

  The opening cross-sectional area of the passage 42 is the cross-sectional area of the cross section along the line CC in FIG. 4, and the open cross-sectional area of the liquid introduction portion 8 is the cross-sectional area of the cross section along the line DD in FIG. That is, the “opening cross-sectional area” is a cross-sectional area in the direction along the plate thickness direction of the flow path plate 2. The opening cross-sectional area of the buffer chamber 41 is the same as the opening cross-sectional area of the passage 42.

  As a result, when the ink is initially filled, the flow of ink from the liquid introduction portion 8 toward the passage 42 can be blocked at a location where the cross-sectional area changes due to the surface tension of the ink. Gas can remain (enclose).

  In addition, the upper and lower surfaces of the buffer chamber 41 in the liquid discharge direction (the front-rear direction in the drawing) are closed by the vibration plate member 3 and the nozzle plate 4. At this time, the opening cross-sectional area of the passage 42 communicating with the buffer chamber 41 is set to be small so that the air accumulated in the buffer chamber 41 is not released when the head is assembled. Thereby, when the head is assembled, air is held in the buffer chamber 41. In addition, the buffer chamber 41 can be filled with a gas different from air.

  With this configuration, the pressure fluctuation generated in the individual liquid chamber 6 is propagated to the common liquid chamber 10 side by the gas in the buffer chamber 41 or backpropagated from the common liquid chamber 10 side to the individual liquid chamber 6 side. In doing so, the gas in the buffer chamber 41 exhibits a damper function, and the propagation of pressure fluctuations can be more reliably suppressed.

  In this case, only the damper function of the buffer chamber 41 causes the pressure fluctuation generated in the individual liquid chamber 6 to propagate to the common liquid chamber 10 side or to propagate backward from the common liquid chamber 10 side to the individual liquid chamber 6 side. Can be suppressed, a damper is not provided on the common liquid chamber 10 side.

  By not providing a damper on the common liquid chamber 10 side, a thin member serving as a damper region becomes unnecessary, and the yield can be improved and the frame member forming the common liquid chamber can be downsized.

  However, a damper region (deformable wall surface) can be provided on the common liquid chamber 10 side and used together with the buffer chamber 41.

  And by using together with the damper on the common liquid chamber 10 side, the damper part on the common liquid chamber 10 side can be reduced in size, and accordingly, the frame member can be reduced in size.

  In the example of FIG. 4, the buffer chamber 41 is formed in a direction bent with respect to the passage 42. However, the present invention is not limited to this, and the buffer chamber 41 may be formed on a straight line of the passage 42.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory plan view of the flow path plate in the same embodiment.

  In the present embodiment, the opening sectional area of the buffer chamber 41 is formed larger than the opening sectional area of the passage 42.

  The opening cross-sectional area of the buffer chamber 41 is the cross-sectional area of the cross section along the line EE in FIG. 5, and the open cross-sectional area of the passage 42 is the cross-sectional area of the cross section along the line CC in FIG. is there.

  Thereby, in this embodiment, a bigger damper function can be exhibited than the said 1st Embodiment.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is an explanatory plan view of the flow path plate in the same embodiment.

  In the present embodiment, the fluid resistance parts 7 of the individual flow paths 5 are alternately arranged in different directions in the nozzle arrangement direction. A common buffer chamber 41 leading to the liquid introduction sections 8 and 8 constituting the adjacent liquid supply paths 70 and 70 is disposed between the two adjacent fluid resistance sections 7 and 7 where the bias of the fluid resistance section 7 is opposite. have.

  Here, the common buffer chamber 41 communicates with the adjacent liquid introduction portions 8 and 8 through independent passages 42 and 42, respectively.

  Since it comprised in this way, the volume of the one buffer chamber 41 can be enlarged rather than the said 1st, 2nd embodiment, and a bigger damper function can be exhibited.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is an explanatory plan view of the flow path plate in the same embodiment.

  In the present embodiment, in the third embodiment, the passage 42 that passes through the common buffer chamber 41 and the adjacent liquid introduction portions 8 and 8 includes the common passage portion 42a that leads to the common buffer chamber 41, and the common passage portion 42a. It is set as the structure which has the separate channel | path parts 42b and 42b which branch from and adjoins the liquid introduction parts 8 and 8 which adjoin.

  With this configuration, the gas can be reliably sealed in the buffer chamber 41.

  That is, the gas held in the buffer chamber 41 is a gas that remains as a result of the ink being prevented from flowing into the buffer chamber 41 during the initial ink filling as described above. Here, since the initial ink filling is performed by pressurizing the ink, in the configuration of the third embodiment, there is a possibility that the ink flows from one passage 42 to the other passage 42 via the buffer chamber 41. is there.

  Therefore, by joining the two passages and integrating them before reaching the buffer chamber 41, the gas does not flow in from one side and flow out from the other, and the gas can reliably remain in the buffer chamber 41. .

  In addition, the opening cross-sectional area of the common channel | path part 42a can be made smaller than the opening cross-sectional area of the individual channel | path part 42b.

  In the above embodiment, the liquid introduction part has been described as an example of constituting an individual flow path, but the liquid introduction part communicates with each other every two or more, and all the liquid introduction parts The present invention can be applied in the same manner even if the configuration is communicated.

  Next, an example of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 8 is an explanatory side view of the mechanism unit of the apparatus, and FIG. 9 is an explanatory plan view of the main part of the mechanism unit.

  This image forming apparatus is a serial type image forming apparatus, and a carriage 233 is slidably held in a main scanning direction by main and slave guide rods 231 and 232 which are guide members horizontally mounted on left and right side plates 221A and 221B. . Then, the main scanning motor (not shown) moves and scans in the direction indicated by the arrow (carriage main scanning direction) via the timing belt.

  The carriage 233 is supplied with ink supplied to the same head as the liquid discharge head according to the present invention for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). A recording head 234 in which a storage tank is integrated is mounted. The recording head 234 is mounted with a nozzle row composed of a plurality of nozzles arranged in the sub-scanning direction orthogonal to the main scanning direction and the ink droplet ejection direction facing downward.

  Each recording head 234 has two nozzle rows. Then, one nozzle row of one recording head 234a discharges black (K) droplets, and the other nozzle row discharges cyan (C) droplets. Also, one nozzle row of the other recording head 234b discharges magenta (M) droplets, and the other nozzle row discharges yellow (Y) droplets. Here, a configuration in which droplets of four colors are ejected in a two-head configuration is used, but it is also possible to arrange four nozzle rows per head and eject each of the four colors with one head.

  Further, the ink of each color is replenished and supplied from the ink cartridge 210 of each color to the tank 235 of the recording head 234 via the supply tube 236 of each color.

  On the other hand, as a paper feeding unit for feeding the paper 242 stacked on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feeding) that separates and feeds the paper 242 one by one from the paper stacking unit 241. Paper roller) 243 and a separation pad 244 facing the paper feed roller 243.

  A guide 245 for guiding the paper 242, a counter roller 246, a conveyance guide member 247, and a tip pressure roller 249 are used to feed the paper 242 fed from the paper feeding unit to the lower side of the recording head 234. And a pressing member 248 having Further, a transport belt 251 is provided as a transport unit for electrostatically attracting the fed paper 242 and transporting it at a position facing the recording head 234.

  The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction). In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A double-sided unit 271 is detachably attached to the back surface of the apparatus main body. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272.

  Further, a maintenance / recovery mechanism 281 for maintaining and recovering the nozzle state of the recording head 234 is disposed in a non-printing area on one side in the scanning direction of the carriage 233.

  The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a and 282b (hereinafter referred to as “caps 282” when not distinguished) for capping the nozzle surfaces of the recording head 234. . The maintenance and recovery mechanism 281 includes a wiper blade 283 that is a blade member for wiping the nozzle surface. The maintenance / recovery mechanism 281 includes an empty discharge receiver 284 that receives droplets when performing empty discharge for discharging droplets that do not contribute to recording in order to discharge the thickened recording liquid.

  Further, in the non-printing area on the other side in the scanning direction of the carriage 233, there is an empty space for receiving a liquid droplet when performing an empty discharge for discharging a liquid droplet that does not contribute to the recording in order to discharge the recording liquid thickened during the recording. A discharge receiver 288 is disposed. The idle discharge receiver 288 includes an opening 289 along the nozzle row direction of the recording head 234 and the like.

  In this image forming apparatus configured as described above, the sheets 242 are separated and fed one by one from the sheet feeding tray 202, and the sheet 242 fed substantially vertically upward is guided by the guide 245, and is conveyed to the conveyor belt 251 and the counter. It is sandwiched between the rollers 246 and conveyed. Further, the leading edge of the sheet 242 is guided by the conveying guide 237 and pressed against the conveying belt 251 by the leading end pressing roller 249, and the conveying direction is changed by approximately 90 °.

  When the paper 242 is fed onto the charged transport belt 251, the paper 242 is attracted to the transport belt 251, and the paper 242 is transported in the sub-scanning direction by the circular movement of the transport belt 251.

  Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  As described above, since the image forming apparatus includes the liquid discharge head according to the present invention as a recording head, a high-quality image can be stably formed.

  In the present application, “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, and the like, and can be attached to ink droplets and other liquids. This includes recording media, recording media, recording paper, recording paper, and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  The “image forming apparatus” means an apparatus that forms an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics or the like. In addition, “image formation” not only applies an image having a meaning such as a character or a figure to a medium but also applies an image having no meaning such as a pattern to the medium (simply applying a droplet to the medium). It also means to land on.

  The “ink” is not limited to an ink unless otherwise specified, but includes any liquid that can form an image, such as a recording liquid, a fixing processing liquid, or a liquid. Used generically, for example, includes DNA samples, resists, pattern materials, resins, and the like.

  In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Flow path plate 3 Vibration plate member 4 Nozzle 5 Individual flow path 6 Individual liquid chamber 7 Fluid resistance part 8 Liquid introduction part 10 Common liquid chamber 12 Piezoelectric member 20 Frame member 40 Partition part between fluid resistance parts 41 Buffer chamber 42 passage 70 liquid supply passage 233 carriage 234a, 234b recording head

Claims (7)

A flow path plate that forms a plurality of individual flow paths including a separate liquid chamber that communicates with each of a plurality of nozzles that discharge droplets and a liquid supply path that communicates with the individual liquid chamber;
The flow path plate is provided with a buffer chamber that communicates with the liquid supply path and holds gas,
The liquid discharge head according to claim 1, wherein an opening cross-sectional area of a passage through the buffer chamber and the liquid supply path is smaller than an opening cross-sectional area of the liquid supply path. The liquid supply path has a fluid resistance portion on the upstream side of the individual liquid chamber,
The buffer chamber is disposed between the fluid resistance portions of the adjacent individual flow paths,
The liquid discharge head according to claim 1, wherein the buffer chamber communicates with the liquid supply path on an upstream side of the fluid resistance portion.   The liquid discharge head according to claim 1, wherein an opening cross-sectional area of the buffer chamber is larger than an opening cross-sectional area of the passage.   4. The liquid discharge head according to claim 1, comprising the common buffer chamber communicating with the adjacent liquid supply passages. 5.   The liquid discharge head according to claim 4, wherein the common buffer chamber communicates with the adjacent liquid supply paths through independent passages.   A passage through the common buffer chamber and the adjacent liquid supply passage includes a common passage portion that communicates with the common buffer chamber, and an individual passage portion that branches from the common passage portion and communicates with the adjacent liquid supply passage. The liquid discharge head according to claim 4, wherein the liquid discharge head is provided.   An image forming apparatus comprising the liquid discharge head according to claim 1.

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