JP2017087708A - Droplet discharge head and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge head which can suppress shortage in a discharge amount of droplets due to recovery of ink in a pressure generation chamber 12 to a circulation liquid chamber.SOLUTION: A droplet discharge head comprises: a plurality of pressure generation chambers 12 which individually communicate with a plurality of nozzles 13; a supply liquid chamber 10 which stores ink to be supplied to the pressure generation chambers; a plurality of supply paths 11 which make the pressure generation chambers 12 communicate with the supply liquid chamber 10; a circulation liquid chamber 15 which receives ink recovered from each of the plurality of pressure generation chambers 12; and a plurality of circulation paths 14 which make the plurality of pressure generation chambers 12 communicate with the circulation liquid chamber 15. Each of the plurality of circulation paths 14 is provided with a small diameter part 14b whose diameter becomes small in a partial region in the whole region in the longitudinal direction.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a droplet discharge head that discharges droplets from each of a plurality of discharge holes, and an image forming apparatus that forms an image using the droplet discharge head.

  Conventionally, a plurality of pressure generation chambers that individually apply pressure to a plurality of discharge holes for discharging droplets, a supply liquid chamber that stores liquid supplied to them, and a plurality of pressure generation chambers, respectively. A droplet discharge head having a circulating liquid chamber for receiving a collected liquid is known.

  For example, a droplet discharge head described in Patent Document 1 includes a plurality of nozzles that are discharge holes for discharging ink droplets, a plurality of pressure generation chambers that individually communicate with them and apply pressure to ink, and generate these pressures. And a common supply channel serving as a supply liquid chamber for storing ink to be supplied to the chamber. In addition, a common recovery channel that is a circulating fluid chamber that receives ink recovered from a plurality of pressure generation chambers, a plurality of individual supply channels that individually communicate a plurality of pressure generation chambers and a common supply channel, and a plurality of pressure generation chambers And a plurality of individual recovery channels that individually communicate with the common recovery channel. The ink sent from the common supply channel to the pressure generating chamber through the individual supply channel is liquidated from the nozzle communicating with the pressure generating chamber when pressure is applied by driving a piezoelectric element fixed to the outer wall of the pressure generating chamber. Discharge as drops. At the same time, bubbles in the ink in the pressure generating chamber enter the individual recovery channel together with a part of the ink, and are then recovered in the common recovery channel. Thereafter, the ink in the common recovery channel is returned to the common supply channel and reused.

  In such a configuration, if the bubbles collected together with the ink from the pressure generation chamber are defoamed by some means and the defoamed ink is returned to the common supply path, the ink is not wasted and the bubbles caused by the bubbles are not discarded. The occurrence of discharge can be suppressed.

  However, when pressure is applied to the ink in the pressure generating chamber, the ink may enter the individual recovery channel or the common recovery channel ahead of the ink, thereby causing a shortage of droplet discharge from the nozzles. There is.

  In order to solve the above-described problems, the present invention provides a plurality of discharge holes for discharging droplets, a plurality of pressure generation chambers for individually applying pressure to the discharge holes, and applying pressure to the internal liquid, and these pressures. A supply liquid chamber for storing a liquid to be supplied to each of the generation chambers, a plurality of supply passages through each of the pressure generation chambers and the supply liquid chamber, and a liquid recovered from each of the plurality of pressure generation chambers A droplet discharge head having a circulating fluid chamber for receiving the fluid, and a plurality of circulation passages for communicating each of the plurality of pressure generating chambers with the circulating fluid chamber. A small-diameter portion having a small diameter in a partial region in the entire region is provided.

  According to the present invention, there is an excellent effect that it is possible to suppress the shortage of the discharge amount of droplets due to the recovery of the ink in the pressure generation chamber to the circulating liquid chamber such as the common recovery flow path.

1 is a main part configuration diagram showing a main part configuration of an image forming apparatus according to an embodiment. The top view which shows the principal part structure. FIG. 3 is a cross-sectional view showing a droplet discharge head 434 of the image forming apparatus. FIG. 4 is a plan sectional view showing a section A-A ′ of FIG. 3. FIG. 4 is a plan sectional view showing a B-B ′ section in FIG. 3. The perspective view which shows the droplet discharge head. FIG. 3 is a cross-sectional view showing a droplet discharge head of the image forming apparatus according to the first embodiment. FIG. 8 is a plan sectional view showing a B-B ′ section in FIG. 7. FIG. 9 is a cross-sectional view illustrating a droplet discharge head of an image forming apparatus according to a second embodiment. FIG. 10 is a cross-sectional view illustrating a droplet discharge head of an image forming apparatus according to a third embodiment. FIG. 10 is a cross-sectional view illustrating a droplet discharge head of an image forming apparatus according to a fourth embodiment. 1 is a block diagram showing a supply / circulation mechanism of an image forming apparatus according to an embodiment together with a droplet discharge head.

Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described.
Note that the recording sheet is not limited to paper, but includes OHP, cloth, glass, a substrate, and the like, which means that ink droplets, other liquids, and the like can be attached. Including recording paper, recording paper and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  An “image forming apparatus” is 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” includes not only the application of an image having a meaning such as a character or a figure to a medium but also an aspect of applying an image having no meaning such as a pattern to a recording medium (simply a liquid). A mode in which drops are landed on a medium).

  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. The “liquid” used by the image forming apparatus is not limited to recording liquid and ink, and is not particularly limited as long as it becomes a fluid when ejected. A “droplet discharge device” is a device that discharges liquid from a droplet discharge head, and is a conventional recording device, printing device, image forming device, droplet discharge device, liquid discharge device, treatment liquid application device, three-dimensional modeling. All devices called devices are included and are not limited to those that perform image formation.

  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. The serial type image forming apparatus performs recording by moving a droplet discharge head mounted on a carriage in a main scanning direction orthogonal to a sheet feeding direction. The line-type image forming apparatus uses a line-type head in which a plurality of ejection ports (nozzles) that eject droplets over substantially the entire width of a recording area are arranged. In the embodiment, an example in which a serial type is employed will be described, but the present invention is not limited to the serial type.

  Liquid ejection heads are roughly classified into several types according to the type of actuator means for ejecting ink droplets (recording liquid). For example, a part of the wall of the liquid chamber is made into a thin diaphragm, and a piezoelectric element as an electromechanical conversion element is arranged correspondingly, and the diaphragm is deformed by deformation of the piezoelectric element that occurs when voltage is applied. There is a piezo type that discharges ink droplets by changing the pressure in the pressure generating chamber. In addition, there is a bubble jet (registered trademark) type in which a heating element is disposed in the liquid chamber, bubbles are generated by heating the heating element by energization, and ink droplets are ejected by the pressure of the bubbles. In addition, an electric field is formed between the diaphragm that forms the wall surface of the liquid chamber and the individual electrode outside the liquid chamber that is disposed to face the diaphragm, so that the diaphragm is deformed so that the pressure and volume in the liquid chamber are reduced. There is also an electrostatic type in which ink droplets are ejected from the nozzles by changing. In the embodiment, an example in which the piezo method is adopted will be described, but the embodiment is not limited to the piezo method.

  First, a basic configuration of the image forming apparatus according to the embodiment will be described. FIG. 1 is a main part configuration diagram showing a main part configuration of the image forming apparatus according to the embodiment. FIG. 2 is a plan view showing the configuration of the main part.

  The image forming apparatus according to the embodiment is a serial type ink jet recording apparatus, and the carriage 433 can be reciprocated in the main scanning direction (arrow direction) by main and slave guide rods 431 and 432 horizontally mounted on the left and right side plates 421A and 421B. Hold on. The carriage 433 is equipped with two droplet discharge units 430A and 430B that hold a droplet discharge head 434 as a droplet discharge member. The droplet discharge head 434 sets the nozzle arrangement direction of the nozzle row composed of a plurality of nozzles (discharge holes) to the sub-scanning direction (droplet discharge head longitudinal direction) orthogonal to the main scanning direction, and the droplet discharge direction downward. It is attached.

  Each of the two droplet discharge units 430A and 430B has two nozzle rows. The droplet discharge head 434 of one droplet discharge unit 430A discharges black (K) ink droplets from each nozzle in one nozzle row, and cyan (C) ink droplets from each nozzle in the other nozzle row. Is discharged. The droplet discharge head 434 of the other droplet discharge unit 430B discharges magenta (M) ink droplets from each nozzle of one nozzle row, and yellow (Y) from each nozzle of the other nozzle row. Ink droplets are ejected.

  Note that the image forming apparatus according to the embodiment ejects four color ink droplets using two droplet ejection heads, and four nozzle rows are arranged in one droplet ejection head, It is also possible to eject four colors of ink from one droplet ejection head.

  A supply / circulation mechanism 404 described later is mounted on the apparatus main body side. A supply tank or circulation tank, which will be described later, disposed in the supply / circulation mechanism 404 and a droplet discharge head 434 on the carriage 433 can circulate ink via a tube bundle 436. .

  The image forming apparatus according to the embodiment includes a paper feeding unit for feeding a recording sheet 442 as a recording medium stacked on the sheet stacking unit 441 of the paper feeding tray 402. The sheet feeding unit includes a sheet feeding roller 443 that separates and feeds recording sheets 442 from the sheet stacking unit 441 one by one, a separation pad 444 that faces the sheet feeding roller 443, and the like.

  The image forming apparatus according to the embodiment also includes a guide 445 that conveys and guides the fed recording sheet 442, a counter roller 446, a conveyance guide member 447, and a pressing member 448 having a tip pressure roller 449. Further, a transport belt 451 is also provided as a transport means for sucking the transported recording sheet 442 and transporting the recording sheet 442 at a position facing the droplet discharge head 434 of the droplet discharge unit 430.

  The conveyor belt 451 is an endless belt, and is configured to wrap around the conveyor roller 452 and the tension roller 453 so as to circulate in the belt conveyance direction (sub-scanning direction). As the transport belt 451, an electrostatic transport belt charged by a charging roller 456 serving as a charging unit is used. However, the conveyance belt 451 may be a conveyance belt that is attracted by air suction. Moreover, as a conveyance means, you may convey by a roller, without using a conveyance belt.

  A separation claw 461 for separating the recording sheet 442 from the conveyance belt 451, a discharge roller 462, and a discharge roller 463 are provided on the downstream side of the tension roller 453 around which the conveyance belt 451 is wound, and the discharge roller 462. Is provided with a paper discharge tray 403 below. A double-sided unit 471 is detachably attached to the back surface of the apparatus main body. The duplex unit 471 takes in the recording sheet 442 returned by the reverse rotation of the conveying belt 451, reverses it, and feeds it again between the counter roller 446 and the conveying belt 451. The upper surface of the duplex unit 471 is a manual feed tray 472. Further, a maintenance / recovery mechanism 481 for maintaining and recovering the state of the nozzles of the droplet discharge heads 434 in the droplet discharge units 430A and 430B is disposed in the non-print region on one side in the scanning direction of the carriage 433. .

  The maintenance / recovery mechanism 481 includes caps 482a and 482b for capping the nozzle surface of the droplet discharge head 434. The maintenance / recovery mechanism 481 includes a blade member 483 for wiping the nozzle surface. Further, the maintenance / recovery mechanism 481 includes a blank discharge receptacle 484 for receiving ink when performing blank discharge for discharging ink that does not contribute to image formation in order to discharge thickened ink. In the non-printing area on the other side in the scanning direction of the carriage 433, an empty discharge receiver 488 is disposed to receive ink when empty discharge is performed during image formation. The idle discharge receiver 488 is provided with an opening 489 along the nozzle arrangement direction of the droplet discharge head 434 and the like.

  In the image forming apparatus according to the embodiment, the recording sheets 442 are separated and fed one by one from the sheet feeding tray 402, and the recording sheet 442 fed substantially vertically upward is guided by the guide 445, and includes the conveyance belt 451 and the counter. It is sandwiched between the rollers 446 and conveyed. Further, the leading edge of the recording sheet 442 is guided by the conveying guide 437 and pressed against the conveying belt 451 by the leading edge pressing roller 449, and the conveying direction is changed by approximately 90 °. When the recording sheet 442 is fed onto the charged conveying belt 451, the recording sheet 442 is attracted to the conveying belt 451, and the recording sheet 442 is conveyed in the sub-scanning direction by the circumferential movement of the conveying belt 451. Therefore, by driving the droplet discharge heads 434 of the droplet discharge units 430A and 430B in accordance with the image signal while moving the carriage 433, ink is discharged onto the recording sheet 442 that has stopped, and an image for one row is obtained. Record. Then, after the recording sheet 442 is conveyed by a predetermined amount, image formation of the next row is performed. Upon receiving a recording end signal or a signal that the trailing edge of the recording sheet 442 has reached the recording area, the recording operation is terminated and the recording sheet 442 is discharged onto the discharge tray 403.

  FIG. 3 is a cross-sectional view showing the droplet discharge head 434. FIG. 4 is a plan sectional view showing the A-A ′ section of FIG. 3. FIG. 5 is a plan sectional view showing a B-B ′ section of FIG. 3. 4 and 5, the outline of the object above the cross-sectional position is indicated by a two-dot chain line, and the perspective outline of the object below is indicated by a dotted line.

  In FIG. 3, the droplet discharge head 434 includes a base plate member 1, a first plate member 2, a second plate member 3, a third plate member 4, and a fourth plate member 5 that are stacked and joined to each other. And a fifth plate-like member 6.

  As shown in FIG. 4, the fifth plate-like member 6 includes a supply liquid chamber 10 formed by a slit extending in the head longitudinal direction, a circulating liquid chamber 15 formed by a slit extending in the head longitudinal direction, and the head longitudinal direction. The piezoelectric element mounting portion 19 is formed by a slit extending in the direction.

  In FIG. 3, the fourth plate member 5 on which the fifth plate member 6 is directly laminated is formed with a diaphragm portion 5 a that is half-etched into a thin thickness, a vibration transmission portion 5 b that rises from the diaphragm portion 5 a, and the like. Yes. As shown in FIG. 4, the vibration transmitting portion 5b has a long and narrow box shape, and is formed so that a plurality of vibration transmitting portions 5b are arranged in a posture in which the short side direction is along the longitudinal direction of the head. A laminated piezoelectric element 7 is fixed on the vibration transmitting portion 5b. The fifth plate-like member 6 is formed by stacking two Ni alloy plating films by electroforming.

  Two laminated piezoelectric elements 7 are arranged along the longitudinal direction of the head. A structure in which piezoelectric layers made of lead zirconate titanate (PZT) having a thickness of 10 to 50 [μm] and internal electrode layers made of silver and palladium (AgPd) having a thickness of several [μm] are alternately laminated. It has become. The internal electrode layer is connected to the external electrode at both ends. The laminated piezoelectric element 7 is divided into comb teeth by half-cut dicing (hereinafter referred to as a divided element), and each is joined to a different vibration transmission portion 5b to individually apply vibrations thereto. The length of the outer electrode is limited by cutting or the like so as to be divided by half-cut dicing, and these function as a plurality of individual electrodes. By individually applying a voltage to each individual electrode, it is possible to individually vibrate a plurality of divided elements. The inside of the external electrode functions as a common electrode without being divided by dicing.

  In FIG. 3, the second plate member 3 is directly laminated on the upper surface of the first plate member 2, and the third plate member 4 is laminated directly on the upper surface of the second plate member 3. The above-described fourth plate member 5 is directly laminated on the upper surface of the plate member 4. Each of the first plate-like member 2, the second plate-like member 3, and the third plate-like member 4 is made of stainless steel, and a combination thereof forms a supply path 11, a pressure generation chamber 12, and a circulation path 14. Are stacked on each other.

  The supply path 11 is formed by a slit and a half-etched portion (concave portion) provided in the third plate-like member 4. As shown in FIG. 4, a large-diameter portion 11a having a relatively large diameter and a relatively small-diameter small portion 11b communicating with the large-diameter portion 11a are provided. A diameter portion 11a is formed. Moreover, the small diameter part 11b is formed by the above-mentioned half etching part.

  In FIG. 3, the pressure generation chamber 12 is formed by a slit provided in each of the third plate-like member 4, the second plate-like member 3, and the first plate-like member 2 so as to communicate with the small diameter portion 11 b of the supply path 11. Has been.

  Further, the circulation path 14 is a slit provided in the first plate-like member 2 so as to communicate with the pressure generating chamber 12, a slit provided by pressing in the second plate-like member 3 so as to communicate with this, and It is formed by a slit provided in the third plate-like member 4 so as to communicate with this. As shown in FIG. 4, a relatively small diameter small diameter portion 14b formed by a slit provided in the first plate-like member 2 and a relatively large diameter large diameter portion 14a communicating therewith are provided. Yes.

  As shown in FIG. 4, a plurality of combinations of the supply passage 11 and the pressure generation chamber 12 communicating with the supply passage 11 are formed along the longitudinal direction of the head. A vibration transmitting portion 5b is individually formed on each of the upper walls of the pressure generating chambers 12. As a result, the diaphragm portions 5a in the individual pressure generation chambers 12 are individually vibrated, and pressure is individually applied to the ink in the individual pressure generation chambers 12.

  A plurality of circulation paths 14 are also formed along the longitudinal direction of the head, and these are individually communicated with any one of the plurality of pressure generating chambers 12.

  The slits of the third plate-like member 4 and the slits of the fifth plate-like member 6 are formed by cutting.

  The first plate member 2 is directly laminated on the upper surface of the base plate member 1. The base plate member 1 made of stainless steel is formed with a plurality of nozzles 13 communicating with each of the plurality of pressure generating chambers 12 by press working. The nozzle 13 is tapered so that the ink droplet ejection side is narrower than the receiving side. The diameter is about 20 to 35 [μm], and the arrangement pitch is 150 [dpi].

  The plurality of supply paths 11 shown in FIG. 4 communicate with one supply liquid chamber 10 extending in the head longitudinal direction. More specifically, as shown in FIG. 3, a plurality of supply paths 11 and supply liquid chambers 10 are provided in the fourth plate member 5 so as to individually correspond to the plurality of supply paths 11. The supply opening 5c communicates.

  Further, the plurality of circulation paths 14 shown in FIG. 4 communicate with one circulation liquid chamber 15 extending in the longitudinal direction of the head. More specifically, as shown in FIG. 3, a plurality of circulation paths 14 and a circulation fluid chamber 15 are provided in the fourth plate member 5 so as to individually correspond to each of the plurality of circulation paths 14. The recovery opening 5d communicates.

  FIG. 6 is a perspective view showing the droplet discharge head 434. The droplet discharge head 434 is mounted on the carriage (433) so that the plurality of nozzles (13) are directed vertically downward. This figure shows the droplet discharge head 434 in the above-described posture. The droplet discharge head 434 has a supply-side base material 18, and this supply-side base material 18 is bonded onto the fifth plate-like member 6 shown in FIG. In FIG. 6, the supply-side base material 18 includes screw holes 18a at both ends in the longitudinal direction. The screw passed through the screw hole is fixed to the carriage (433).

  In addition to the two screw holes 18, the supply-side base material 18 includes an ink supply hole and an ink circulation hole. The ink supply hole is formed at the end of the supply-side base material 18 and communicates with the supply liquid chamber 10 shown in FIG. A supply pipe 16 is joined to the upper surface of the supply-side base material 18 so as to communicate with each ink supply hole (see FIG. 3). The supply pipe 16 communicates with the supply tank via the tube of the tube bundle 436 and the supply side pressure sensor.

  The ink circulation hole is formed at the end of the supply-side base material 18 and communicates with the circulation liquid chamber 15 shown in FIG. And the circulation pipe 17 is joined to the upper surface of the supply side base material 18 so that it may connect with the circulation hole (refer FIG. 3). The circulation pipes 17 communicate with the circulation tank via the tubes of the tube bundle 436 (see FIG. 2) and the circulation side pressure sensor.

  When a driving voltage (pulse voltage of 10 to 50 V) is applied to the above-described individual electrode of the laminated piezoelectric element 7, a displacement in the stacking direction of the dividing element corresponding to the individual electrode is caused, and the vibration transmitting unit 5b. The diaphragm portion 5a is also displaced in the same direction. As a result, the ink stored in the pressure generation chamber 12 corresponding to the individual electrode is pressurized, and the ink droplet 99 is ejected from the nozzle 13 communicating with the pressure generation chamber 12. Thereafter, when the dividing element returns to the original position, the ink pressure in the pressure generating chamber 12 is reduced, and the ink pressure is changed to a negative pressure due to the inertia of the ink flow and the attenuation of the driving voltage. As a result, the ink discharge process shifts to the ink filling process. At this time, ink is supplied from the supply tank to the supply liquid chamber 10 via the supply-side pressure sensor, and ink in the supply liquid chamber 10 is filled into the pressure generation chamber 12 via the supply path 11.

  In the ink discharge process described above, part of the ink in the pressure generation chamber 12 enters the circulation path 14 from the pressure generation chamber 12 together with the bubbles. A part of the ink in the large-diameter portion 14a of the circulation path 14 flows into the circulating liquid chamber 15 from the large-diameter portion 14a together with the bubbles. The ink in the circulating fluid chamber 15 is fed into the circulation tank through the circulation pipe 17 and the circulation side pressure sensor. The ink in the circulation tank is supplied to the supply liquid chamber 10 via the supply tank and the pressure side pressure sensor via the liquid feed pump.

  As shown in FIG. 4, the circulation path 14 is provided with a small diameter portion 14b having a smaller diameter than the large diameter portion 14a. In such a configuration, the small-diameter portion 14 b gives resistance to the ink that is about to enter the circulation path 14 from the pressure generation chamber 12, and is collected from the pressure generation chamber 12 to the circulation liquid chamber 15 via the circulation path 14. Regulate the amount of ink. Thereby, it is possible to suppress the shortage of the ink droplet ejection amount from the nozzle 13 due to the recovery of the ink in the pressure generation chamber 12 to the circulating fluid chamber 15.

  When the ink in the pressure generating chamber 12 is pressurized, the ink is discharged as an ink droplet from the nozzle 13, the ink entering the circulation path 14 from the pressure generating chamber 12, and the supply path 11 from the pressure generating chamber 12. Ink that reverts back to the position is also generated. Further, the reverse movement may cause a shortage of the discharge amount of the droplets from the nozzle 13. Therefore, in the image forming apparatus according to the embodiment, the supply path 11 is also provided with a small diameter portion 11b having a smaller diameter than the large diameter portion 11a. In this configuration, the small diameter portion 11b applies resistance to the ink that is about to enter the supply path 11 from the pressure generation chamber 12, and regulates the amount of ink that returns from the pressure generation chamber 12 back to the supply path 11. To do. Thereby, it is possible to suppress the shortage of the discharge amount of the liquid droplets from the nozzle 13 caused by returning the ink in the pressure generation chamber 12 back to the supply path 11.

  The small-diameter part 11b of the supply path 11 and the small-diameter part 14b of the circulation path 14 can also have an effect of attenuating residual pressure vibration after ink droplet ejection. However, in the ink filling process, resistance is applied to the ink to be returned from the supply path 11 or the circulation path 14 to the pressure generation chamber 12 to inhibit the flow thereof, so that the pressure in the pressure generation chamber 12 is restored. Prolong the time until. Therefore, the residual pressure is attenuated and the refill time is adjusted by adjusting the resistance applied to the ink by the small diameter portion 11b of the supply path 11 and the resistance applied to the ink by the small diameter section 14b of the circulation path 14. It is desirable to balance with By doing so, it is possible to shorten the time (drive cycle) until the transition to the next ink droplet ejection operation.

  Next, each example in which a more characteristic configuration is added to the image forming apparatus according to the embodiment will be described. Note that the configuration of the image forming apparatus according to each example is the same as that of the embodiment unless otherwise specified.

[First embodiment]
When the laminated piezoelectric element 7 is driven, the amount of ink droplets ejected from the nozzle 13, the amount of ink returning from the pressure generation chamber 12 to the supply path 11, and the amount of ink traveling from the pressure generation chamber 12 to the circulation path 14 Is determined by the ratio of the channel resistances. Specifically, it is determined by the ratio of the flow path resistance of the small diameter portion 14 b of the circulation path 14, the flow path resistance of the small diameter section 11 b of the supply path 11, and the flow path resistance of the nozzle 13. Further, the pressure applied to the meniscus of the nozzle 13 is determined based on the ratio of the above-mentioned flow path resistance, the pressure ratio between the positive pressure and the negative pressure, and the like with respect to the nozzle position. When actually handling the circulation type droplet discharge head 434, it is desirable that the pressure ratio between the positive and negative pressures is 1: 1 from the viewpoint of ease of pressure control. For this purpose, the ratio of the flow path resistance of the small diameter portion 14b of the circulation path 14 to the flow path resistance of the small diameter section 11b of the supply path 11 must also be 1: 1.

  FIG. 7 is a cross-sectional view showing the droplet discharge head 434 of the image forming apparatus according to the first embodiment. FIG. 8 is a plan sectional view showing a B-B ′ section in FIG. 7. In FIG. 7, the droplet discharge head 434 sandwiches the intermediate plate member 20 between the first plate member 2 and the second plate member 3. The intermediate plate member 20 is provided with a plurality of slits individually communicating with the plurality of pressure generation chambers 12 and a plurality of slits for functioning as a part of the respective large diameter portions 14a in the plurality of circulation paths 14. It has been.

  As shown in FIG. 8, the large diameter portion 14a and the small diameter portion 14a of the circulation path 14 have the same size in the width direction. Even if the size in the width direction is the same, in order to make the small diameter portion 14b smaller in diameter than the large diameter portion 14a, as shown in FIG. 7, the depth of the small diameter portion 14b is larger than the depth of the large diameter portion 14a. Shallow. In the slit of the first plate-like member 2, the portion where the slit of the intermediate plate-like member 20 is overlapped functions as the large-diameter portion 14a, while the non-slit portion of the intermediate plate-like member 20 is overlapped shallower than the large-diameter portion 14a. The above-mentioned part is made to function as the small diameter part 14b.

  In such a configuration, since the size in the width direction of the small diameter portion 14b is not made smaller than the size in the width direction of the large diameter portion 14a, the width of the slit provided for the small diameter portion 14b in the first plate member 2 is set for the large diameter portion 14a. The width of the slit can be the same. Thereby, as a drilling process of the 1st plate-shaped member 2 for forming the small diameter part 14b, the low cost can be achieved by adopting an inexpensive method that does not require high dimensional accuracy and weak impact property. Further, by adjusting the thickness of the first plate-like member 2, the flow resistance of the small diameter portion 14b can be easily adjusted, and the ratio of the flow resistance to the large diameter portion 14a can be easily adjusted to 1: 1. it can.

[Second Example]
In the image forming apparatus according to the second embodiment, as in the first embodiment, the large-diameter portion 14a and the small-diameter portion 14b of the circulation path 14 have the same size in the width direction. And the small diameter part 14b is made smaller diameter than the large diameter part 14a by making the depth of the small diameter part 14b of the circulation path 14 shallower than the depth of the large diameter part 14a.

  FIG. 9 is a cross-sectional view showing the droplet discharge head 434 of the image forming apparatus according to the second embodiment. Unlike the image forming apparatus according to the first embodiment, the droplet discharge head 434 does not provide an intermediate plate member between the first plate member 2 and the second plate member 3. Instead, the small-diameter portion 14a and the large-diameter portion 14b of the circulation path 14 are provided as follows. That is, the second plate-shaped member 3 is provided with a half-etched portion (concave portion) functioning as a part of the large-diameter portion 14a on the first surface (lower surface). And the part which overlapped the half etching part of the 2nd plate-shaped member 3 and the slit of the 1st plate-shaped member 2 among the whole area in the length direction of the circulation path 14 is functioned as the large diameter part 14a. Further, the half-etched portion of the second plate-like member 3 or the portion where the portion that is not a slit and the slit of the first plate-like member are overlapped is made to function as a small-diameter portion 14b that is shallower than the large-diameter portion 14a.

  In such a configuration, the large-diameter portion 14a and the small-diameter portion 14b of the circulation path 14 can be provided without providing an intermediate plate member. Therefore, the number of parts and man-hours can be reduced compared with the first embodiment, and the cost can be reduced. In addition, the flow resistance of the small-diameter portion 14b can be adjusted not only by the length of the small-diameter portion 14b but also by adjusting the depth, so that the degree of freedom in design can be increased.

[Third embodiment]
The image forming apparatus according to the third embodiment has the same configuration as that of the image forming apparatus according to the second embodiment except for the following points.
FIG. 10 is a cross-sectional view showing the droplet discharge head 434 of the image forming apparatus according to the third embodiment. In the figure, the second plate-like member 3 has a plurality of half-etched portions formed on the first surface for forming the respective large diameter portions 14a in the plurality of circulation paths 14 as in the second embodiment. Yes. Moreover, unlike the second embodiment, a plurality of half-etched portions for forming the respective large diameter portions 11a in the plurality of supply paths 11 are formed on the second surface (upper surface).

  Similar to the second embodiment, the image forming apparatus according to the third embodiment overlaps the slits of the first plate-like member 2 and the half-etched portion of the first surface of the second plate-like member 3 so as to circulate a plurality of circulations. Each large diameter part 14a in the path 14 is formed. Further, unlike the second embodiment, as the third plate-like member 4, a half-etched portion for forming the small diameter portion 11 b in each of the plurality of supply paths 11 and a large diameter portion in each of the plurality of supply paths 11. What provided the slit for forming 11a is used. And the half-etching part of the 2nd surface of the 2nd plate-shaped member 3 and the part which is not a slit, and the half-etching part of the 3rd plate-shaped member 4 are piled up, and the small diameter part 11b of the supply path 11 is formed. . Further, the large-diameter portion 11 a of the supply path 11 is formed by overlapping the half-etched portion on the second surface of the second plate-like member 3 and the slit of the third plate-like member 4.

  In such a configuration, the capacity of the large-diameter portion 11a of the supply path 11 can be easily adjusted by adjusting the depth in the half-etched portion of the second surface of the second plate-like member 3. Further, when manufacturing the droplet discharge heads 434 individually corresponding to models having different ink viscosity specifications, the other plate-like members of the second plate-like member 3 can be used in common among those models. Specifically, in order to eject inks having different viscosities, it may be necessary to make the capacity of the large diameter part 11a of the supply path 11 different from the capacity of the large diameter part 14a of the circulation path 14. Even in such a case, as the second plate-like member 3, other than using the one having a different depth of the half-etched portion on the first surface and the half-etched portion on the second surface, The same plate-like member can be used.

[Fourth embodiment]
The image forming apparatus according to the fourth embodiment has the same configuration as that of the image forming apparatus according to the second embodiment except for the following points.
FIG. 11 is a cross-sectional view showing the droplet discharge head 434 of the image forming apparatus according to the fourth embodiment. The droplet discharge head 434 has a second plate-like member 3 provided with a plurality of half-etched portions (concave portions) functioning as a part of the plurality of pressure generating chambers 12 on the second surface (upper surface). Used. A location where the slit of the third plate-like member 4 and the half-etched portion of the second surface of the second plate-like member 3 are superposed functions as the pressure generating chamber 12.

  In such a configuration, the capacity of the large-diameter portion 11a of the supply path 11 can be easily adjusted by adjusting the depth in the half-etched portion of the second surface of the second plate-like member 3. Further, when manufacturing the droplet discharge heads 434 individually corresponding to models having different ink viscosity specifications, the other plate-like members of the second plate-like member 3 can be used in common among those models. Specifically, in order to eject inks having different viscosities, it may be necessary to make the capacity of the pressure generating chamber 12 and the capacity of the large diameter portion 14a of the circulation path 14 different from each other. Even in such a case, as the second plate-like member 3, other than using the one having a different depth of the half-etched portion on the first surface and the half-etched portion on the second surface, The same plate-like member can be used.

  In the fourth embodiment, the convex portion adjacent to the half-etched portion provided on the second surface of the second plate-like member 3 is used as the floor surface of the small diameter portion 11 b of the supply path 11. In such a configuration, by adjusting the length of the half-etched portion, the length of the small diameter portion 11b of the supply path 11 can be easily adjusted, and the flow path resistance of the small diameter portion 11b can be easily adjusted.

In addition, in the image forming apparatus according to the embodiment and each example, a system in which ink is circulated by driving a pump is employed, but a system in which ink is circulated only by the pressurizing force of the laminated piezoelectric element 7 may be employed. Good. For reference, a circulation system employed in the image forming apparatus according to the embodiment and each example will be described.
FIG. 12 is a block diagram showing the supply / circulation mechanism 404 together with the droplet discharge head 434. As illustrated, the supply / circulation mechanism 404 includes a main tank, a supply tank, a circulation tank, a compressor, a vacuum pump, a liquid feed pump, a regulator (R), a supply side pressure sensor, a circulation side pressure sensor, and the like. .

  The supply side pressure sensor is connected between the supply tank and the droplet discharge head 434 and on the supply flow path side connected to the supply pipe 16 (see FIG. 6) of the droplet discharge head 434. The circulation side pressure sensor is connected between the droplet discharge head 434 and the circulation tank, and is connected to the circulation channel side connected to the circulation pipe 17 (see FIG. 6) of the droplet discharge head 434.

  One of the circulation tanks is connected to the supply tank via a liquid feed pump, and the other of the circulation tanks is connected to the main tank via a second liquid feed pump. As a result, the liquid flows from the supply tank through the supply pipe 16 into the droplet discharge head 434, is discharged from the circulation pipe 17 and discharged to the circulation tank, and further from the circulation tank to the supply tank by the first liquid feed pump. The liquid circulates by being sent.

  In addition, a compressor is connected to the supply tank, and the supply side pressure sensor is controlled to detect a predetermined positive pressure. On the other hand, a vacuum pump is connected to the circulation tank, and control is performed so that a predetermined negative pressure is detected by the circulation side pressure sensor. Thereby, the negative pressure of the meniscus can be kept constant while circulating the liquid through the droplet discharge head 434.

  When liquid droplets are ejected from the nozzles of the liquid droplet ejection head 434, the amount of liquid in the supply tank and the circulation tank decreases. Therefore, liquid is appropriately transferred from the main tank to the circulation tank using the second liquid feed pump. It is desirable to replenish. The timing of liquid replenishment from the main tank to the circulation tank depends on the detection result of the liquid level sensor etc. provided in the circulation tank, such as liquid replenishment when the ink level in the circulation tank falls below a predetermined level. Can be controlled.

  The circulation of the liquid can be performed not only when the droplet discharge head 434 is operating but also when the operation is stopped. Circulation during operation stop is preferable because the liquid in the individual liquid chamber is always refreshed and aggregation and sedimentation of components contained in the liquid can be suppressed.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
[Aspect A]
Aspect A includes a plurality of discharge holes (for example, nozzles 13) for discharging droplets (for example, ink droplets) and a plurality of pressure generations for individually applying pressure to the liquid (for example, ink) through the discharge holes. A chamber (for example, the pressure generation chamber 12), a supply liquid chamber (for example, the supply liquid chamber 10) that stores a liquid to be supplied to each of the pressure generation chambers, and each of the pressure generation chambers and the supply liquid chamber. A plurality of supply passages (for example, supply passage 11), a circulating fluid chamber (for example, circulating fluid chamber 15) that receives liquid collected from each of the plurality of pressure generating chambers, each of the plurality of pressure generating chambers, and the circulation. In a droplet discharge head (for example, the droplet discharge head 434) having a plurality of circulation paths (for example, the circulation path 14) communicating with the liquid chamber, each of the plurality of circulation paths has a lengthwise region. Kicking is characterized in the provision of the small diameter portion whose diameter in some areas are thinner (e.g., small diameter portion 14b).

  In such a configuration, the small diameter portion of the circulation path provides resistance to the ink that is about to enter the circulation path from the pressure generation chamber, and the amount of ink collected from the pressure generation chamber through the circulation path to the circulation liquid chamber is reduced. regulate. Thereby, it is possible to suppress the shortage of the discharge amount of the liquid droplets from the discharge holes due to the recovery of the ink in the pressure generation chamber into the circulating liquid chamber.

[Aspect B]
Aspect B is a first aspect in which a plurality of slits or recesses for forming each of the small diameter portions in the plurality of circulation paths and a large diameter portion (for example, large diameter portion 14a) larger than this are provided in aspect A. A plate-like member (for example, the first plate-like member 2) and a second plate-like member (for example, the second plate-like member 3) provided with a plurality of slits or recesses for forming the large-diameter portion are overlaid, A portion where the slit or recess of the first plate member and the slit or recess of the second plate member are overlapped functions as the large diameter portion, and the slit or recess of the first plate member and the second A portion where a portion that is not a slit or a recess of the plate member is overlapped is made to function as the small diameter portion. In such a configuration, the small-diameter portion is made smaller in diameter than the large-diameter portion by making the depth of the small-diameter portion shallower than the large-diameter portion without making the width of the small-diameter portion narrower than that of the large-diameter portion. Thereby, as a drilling process of the first plate-like member for forming the small diameter portion, it is possible to reduce the cost by adopting an inexpensive method that does not require high dimensional accuracy and weak impact property. Further, by adjusting the thickness of the first plate-like member, it is possible to easily adjust the flow resistance of the small diameter portion and easily adjust the flow resistance ratio to the large diameter portion.

[Aspect C]
Aspect C uses the one provided with a plurality of the concave portions as the second plate-like member in aspect B, and includes a slit or a concave portion of the first plate-like member and a portion that is not a concave portion of the second plate-like member. The overlapped portion is made to function as the small diameter portion. In such a configuration, the capacity of the large-diameter portion of the circulation path can be easily adjusted by adjusting the depth of the concave portion of the second plate-like member.

[Aspect D]
Aspect D is characterized in that, in aspect C, each of the plurality of supply paths is provided with a small-diameter portion having a small diameter in a partial region in the entire region in the length direction. In such a configuration, the flow path resistance of the liquid flow returning from the pressure generation chamber to the supply path side and the flow path resistance of the liquid flow proceeding from the pressure generation chamber to the circulation path side are adjusted by adjusting the length and depth of each small diameter portion. The ratio can be easily adjusted.

[Aspect E]
Aspect E provides a plurality of recesses in the first surface (for example, the upper surface) as a second plate-shaped member in the first surface (for example, an upper surface) and a plurality of the second plate-shaped members. The first plate-like member and the second member are provided with a plurality of recesses on the second surface for forming the respective large-diameter portions (for example, the large-diameter portion 14a) in the supply channel (for example, the supply channel 14). A plurality of circulation paths are formed by overlapping the first surface of the plate-like member, and a plurality of slits or recesses for forming the respective large diameter portions and small diameter portions in the plurality of supply paths are provided. A third plate-like member (for example, the third plate-like member 4) and the second surface of the second plate-like member are overlapped, and a slit or recess of the third plate-like member and a recess of the second surface are formed. Let the overlapped part function as the large diameter part of the supply path Together it is characterized in that to function the locations of repeated non recess portion of the slit or recess and said second surface of said third plate-like member as a small-diameter portion of said supply path (e.g., 11b). In such a configuration, the capacity of the large-diameter portion of the supply path can be easily adjusted by adjusting the depth of the concave portion of the second surface of the second plate-shaped member.

[Aspect F]
Aspect F provides a plurality of concave portions for forming the large diameter portions of the plurality of circulation paths in the first surface as the second plate-shaped member in aspect C, and a plurality of the pressure generating chambers. What used the thing which provided the some recessed part for forming each in the 2nd surface is used. In such a configuration, the capacity of the pressure generating chamber can be easily adjusted by adjusting the depth of the concave portion of the second surface of the second plate-shaped member.

[Aspect G]
Aspect G includes a droplet discharge head that discharges droplets from a plurality of discharge holes, a sheet transport unit that transports a recording sheet, and transports the droplet discharge head along the surface of the recording sheet by the sheet transport unit. In an image forming apparatus that includes a head moving unit that moves in a direction orthogonal to the direction, and forms an image on a recording sheet by droplets ejected from a plurality of ejection holes, the droplet ejection heads of modes A to F are used. Any one of them is used.

DESCRIPTION OF SYMBOLS 10: Supply liquid chamber 11: Supply path 11a: Large diameter part of supply path 11b: Small diameter part of supply path 12: Pressure generation chamber 13: Nozzle (discharge hole)
14: Circulation path 14a: Large diameter section of the circulation path 14b: Small diameter section of the circulation path 15: Circulating liquid chamber 16: Supply pipe 17: Circulation pipe 434: Droplet discharge head

JP 2014-210373 A

Claims (7)

A plurality of discharge holes for discharging droplets, a plurality of pressure generation chambers for individually applying pressure to the discharge holes and applying pressure to the liquid inside, and a liquid for supplying to each of the pressure generation chambers are accommodated A supply liquid chamber, a plurality of supply passages through each of the pressure generation chambers and the supply liquid chamber, a circulating liquid chamber for receiving liquid recovered from each of the plurality of pressure generation chambers, and a plurality of the pressure generation chambers In a droplet discharge head having a plurality of circulation paths that communicate with each of the circulating fluid chambers,
A droplet discharge head, characterized in that each of the plurality of circulation paths is provided with a small-diameter portion having a small diameter in a partial region in the entire length direction. The droplet discharge head according to claim 1.
A first plate-like member provided with a plurality of slits or recesses for forming each of the small-diameter portions in the plurality of circulation paths and a large-diameter portion having a larger diameter, and a plurality of plates for forming the large-diameter portions. The second plate-like member provided with the slit or the concave portion of the first plate-like member is overlapped, and the portion where the slit or the concave portion of the first plate-like member and the slit or the concave portion of the second plate-like member are overlapped functions as the large-diameter portion. And a portion where the slits or recesses of the first plate-shaped member and the slits or recesses of the second plate-shaped member are overlapped functions as the small-diameter portion. The droplet discharge head according to claim 2,
A portion provided with a plurality of the concave portions as the second plate-shaped member, and a portion where the slit or the concave portion of the first plate-shaped member and the portion which is not the concave portion of the second plate-shaped member are overlapped is defined as the small diameter portion. A droplet discharge head characterized by functioning. The droplet discharge head according to claim 3.
A droplet discharge head, wherein each of the plurality of supply paths is provided with a small-diameter portion having a small diameter in a partial region in the entire length direction. The droplet discharge head according to claim 4,
As the second plate-shaped member, a plurality of concave portions for forming the large diameter portions in the plurality of circulation paths are provided on the first surface and the large diameter portions in the plurality of supply paths are formed. A plurality of recesses are provided on the second surface, and the first plate member and the first surface of the second plate member are overlapped to form the plurality of circulation paths, and The third plate member provided with a plurality of slits or recesses for forming the large diameter portion and the small diameter portion in the supply path is overlapped with the second surface of the second plate member, and the third plate The portion where the slit or recess of the plate member and the recess of the second surface are overlapped functions as the large diameter portion of the supply path, and is not the slit or recess of the third plate member and the recess of the second surface The place where the parts are overlapped is the small diameter part of the supply path Droplet discharge head is characterized in that to function Te. The droplet discharge head according to claim 3.
As the second plate-like member, a plurality of recesses for forming the large-diameter portions in the plurality of circulation paths are provided on the first surface, and a plurality of pressure generating chambers are formed. A droplet discharge head using a recess provided on a second surface. A droplet ejection head that ejects droplets from a plurality of ejection holes, a sheet conveyance unit that conveys a recording sheet, and a direction perpendicular to the conveyance direction of the sheet conveyance unit while passing the droplet ejection head along the surface of the recording sheet In an image forming apparatus comprising a head moving means for moving in a direction, and forming an image on a recording sheet by droplets ejected from a plurality of ejection holes,
An image forming apparatus using the droplet discharge head according to claim 1 as the droplet discharge head.

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