JP2010201709A - Liquid droplet discharging head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet discharging head which can prevent the liquid filling speed from dropping and attain high throughput while reducing the crosstalk. <P>SOLUTION: The liquid droplet discharging head 64 includes a plurality of nozzles 90 for discharging the liquid droplet to a recording medium, a plurality of pressure chambers 84 which are prepared for each nozzle 90, connected with communication and filled up with liquid, a diaphragm 86 which is actuated by a pressure generating element 88 and makes the volume of each pressure chamber 84 changed, a common liquid chamber 60 wherein the liquid supplied to each pressure chamber 84 is stored, a liquid channel 94 for making the communicating connection between each pressure chamber 84 and the common liquid chamber 60, a plurality of branch channels 96, 98 formed in the halfway section of the liquid channel 94, and a reflection part 102 which is formed in the branch channel 98 except at least one of two or more branch channels 96, 98 and reflects a pressure wave generated with the volume change of the pressure chamber 84. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a droplet discharge head.

  In a droplet discharge head, when one pressure generating element is moved and a droplet is discharged from a nozzle, the return pressure wave affects an adjacent nozzle (particularly a meniscus) through a liquid flow path. The so-called crosstalk problem has been known for some time.

  As a countermeasure against the crosstalk, for example, the ejection is not performed until the vibration is settled. However, in this case, there remains a problem with respect to the high throughput. Therefore, by providing a storage-type common liquid chamber, it is possible to prevent propagation of pressure waves to adjacent nozzles (see, for example, Patent Document 1), or to provide a return pressure wave by providing protrusions in the liquid flow path. (For example, see Patent Document 2).

JP 2008-126420 A JP 2005-131843 A

  However, in the case of Patent Document 1, since the nozzles are formed close to each other, an expected crosstalk improvement effect cannot be expected. In addition, it was considered to provide two liquid flow paths that connect the common liquid chamber and the pressure chamber, and to consider the straightness of the droplet by making the pressure distribution symmetrical. However, since the pressure wave is superimposed, the vibration itself Can not be weakened.

  In the case of Patent Document 2, since the pressure wave returned to the pressure wave generation source is reflected, meniscus vibration is induced in the target nozzle, resulting in an increase in throughput. In addition, if a protrusion is provided in the liquid flow path connecting the common liquid chamber and the pressure chamber instead of the common liquid chamber, the liquid flow path is narrowed and limited (the flow resistance increases). The liquid filling rate was reduced.

  In view of the above circumstances, an object of the present invention is to provide a liquid droplet ejection head that can reduce crosstalk, prevent a decrease in liquid filling speed, and achieve high throughput.

  In order to achieve the above object, a liquid droplet ejection head according to claim 1 of the present invention is provided with a plurality of nozzles for ejecting liquid droplets onto a recording medium and is connected to and communicated with each nozzle. A plurality of pressure chambers filled with liquid; a vibration plate driven by a pressure generating element to change the volume of each pressure chamber; a common liquid chamber storing liquid supplied to each pressure chamber; Excluding at least one of a liquid flow path that connects each pressure chamber and the common liquid chamber in communication, a plurality of branch flow paths formed in the middle of the liquid flow path, and the plurality of branch flow paths And a reflection portion that is formed in the branch flow path and reflects a pressure wave generated with a change in volume of the pressure chamber.

  According to the first aspect of the present invention, the branch flow path excluding at least one of the plurality of branch flow paths formed in the middle of the liquid flow path that connects the pressure chamber and the common liquid chamber in communication with each other, Since the reflection part that reflects the pressure wave generated with the volume change of the pressure chamber is formed, the pressure wave that propagates through the branch flow path where the reflection part is formed and the branch where the reflection part is not formed A phase difference can be given to the pressure wave propagating through the flow path.

  Therefore, the amplitude (vibration) can be reduced when pressure waves are superimposed at the junction of each branch flow path. Therefore, it is possible to reduce crosstalk that affects another nozzle adjacent through the common liquid chamber. In addition, since it is not necessary to provide a protrusion as in the prior art in the liquid flow path (branch flow path), the liquid filling speed does not decrease, and high throughput can be achieved.

  According to a second aspect of the present invention, in the liquid droplet ejection head according to the first aspect, the plurality of branch flow paths are symmetric when viewed from a direction orthogonal to the liquid flow direction of the liquid flow path. It is characterized by its shape.

  According to the second aspect of the present invention, the confluence of the pressure waves propagating through the branch flow paths is symmetrical with the start point of the pressure wave when starting to propagate through the branch flow paths. Therefore, a phase difference can be reliably imparted between the pressure wave propagating through the branch flow path in which the reflection portion is formed and the pressure wave propagating through the branch flow path in which no reflection portion is formed.

  According to a third aspect of the present invention, the liquid droplet ejection head according to the first aspect is substantially the same as the plurality of branch flow paths when viewed from a direction orthogonal to the liquid flow direction of the liquid flow path. It is characterized by a triangular shape.

  According to the third aspect of the present invention, the channel resistance in at least one branch channel can be reduced. Therefore, it is possible to further prevent a decrease in the liquid filling rate. Further, the phase difference can be easily given to the pressure wave propagating through each branch flow path due to the difference in flow path length.

  According to a fourth aspect of the present invention, in the liquid droplet ejection head according to any one of the first to third aspects, the reflecting portion is configured by a wall portion of the common liquid chamber. It is characterized by having.

  According to invention of Claim 4, the attenuation effect of a pressure wave can be heightened.

  As described above, according to the present invention, it is possible to provide a droplet discharge head that can reduce crosstalk, prevent a decrease in liquid filling speed, and achieve high throughput.

Schematic side view showing the overall configuration of an image forming apparatus provided with a droplet discharge head Schematic side sectional view showing the internal structure of the droplet discharge head Explanatory drawing showing the channel structure in the droplet discharge head Graph showing the combined waveform of pressure waves out of phase Explanatory drawing showing another channel structure in the droplet discharge head Explanatory drawing showing another channel structure in the droplet discharge head Explanatory drawing showing another channel structure in the droplet discharge head Explanatory drawing showing another channel structure in the droplet discharge head

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention will be described in detail based on examples shown in the drawings. FIG. 1 is a schematic side view showing an overall configuration of an image forming apparatus 10 including an inkjet line head 64 as a droplet discharge head. First, the overall configuration of the image forming apparatus 10 will be described.

  As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment includes a paper feed conveyance unit that feeds and conveys paper upstream of a sheet as a recording medium (hereinafter referred to as “paper”) in the conveyance direction. 12 is provided. On the downstream side of the paper feeding / conveying unit 12, a processing liquid applying unit 14 for applying a processing liquid to the recording surface of the paper along the paper conveying direction, an image forming unit 16 for forming an image on the recording surface of the paper, An ink drying unit 18 for drying the image formed on the recording surface of the paper, an image fixing unit 20 for fixing the dried image on the paper, and a discharge unit 21 for discharging the paper on which the image is fixed are provided.

  The paper feeding / conveying unit 12 is provided with a stacking unit 22 on which sheets are stacked. The stacking unit 22 is disposed downstream of the stacking unit 22 in the sheet conveying direction (hereinafter, “paper conveying direction” may be omitted). A paper feed unit 24 that feeds the sheets stacked on the unit 22 one by one is provided. The sheet fed by the sheet feeding section 24 is transported to the processing liquid coating section 14 via a transport section 28 composed of a plurality of pairs of rollers 26.

  In the treatment liquid application unit 14, a treatment liquid application drum 30 is rotatably disposed. The processing liquid coating drum 30 is provided with a holding member 32 that holds the paper by sandwiching the leading end of the paper, and the paper is held on the surface of the processing liquid coating drum 30 via the holding member 32. In this state, the sheet is conveyed downstream by the rotation of the treatment liquid coating drum 30.

  Note that an intermediate conveying drum 34, an image forming drum 36, an ink drying drum 38, and an image fixing drum 40, which will be described later, are also provided with a holding member 32 in the same manner as the processing liquid coating drum 30. The holding member 32 transfers the paper from the upstream drum to the downstream drum.

  A processing liquid coating device 42 and a processing liquid drying device 44 are disposed above the processing liquid coating drum 30 along the circumferential direction of the processing liquid coating drum 30. The treatment liquid is applied to the surface, and the treatment liquid is dried by the treatment liquid drying device 44. This treatment liquid has an effect of reacting with the ink to aggregate the color material (pigment) and promoting separation of the color material (pigment) and the solvent.

  The treatment liquid application device 42 is provided with a storage portion 46 for storing the treatment liquid, and a part of the gravure roller 48 is immersed in the treatment liquid. A rubber roller 50 is disposed in pressure contact with the gravure roller 48, and the rubber roller 50 comes into contact with the recording surface (front surface) side of the paper to apply the processing liquid. In addition, a squeegee (not shown) is in contact with the gravure roller 48 to control the amount of treatment liquid applied to the recording surface of the paper.

  Here, the film thickness of the treatment liquid is ideally sufficiently smaller than the droplets of the head droplets. For example, in the case of a droplet ejection amount of 2 pl, the average diameter of the droplets of the head droplet is 15.6 μm, and when the treatment liquid film thickness is thick, the ink dots are not contacted with the recording surface of the paper in the treatment liquid. Float. In order to obtain a landing dot diameter of 30 μm or more with a droplet ejection amount of 2 pl, the treatment liquid film thickness is preferably 3 μm or less.

  On the other hand, in the treatment liquid drying device 44, a hot air nozzle 54 and an infrared heater 56 (hereinafter referred to as “IR heater 56”) are disposed close to the surface of the treatment liquid application drum 30. The hot air nozzle 54 and the IR heater 56 evaporate a solvent such as water in the processing liquid to form a solid or thin film processing liquid layer on the recording surface side of the paper.

  By thinning the treatment liquid in the treatment liquid drying step, the dots deposited by ink in the image forming unit 16 come into contact with the surface of the paper to obtain the required dot diameter and react with the thinned treatment liquid. In addition, it is easy to obtain an effect that the color material aggregates and is fixed to the paper surface. In this way, the sheet on which the processing liquid has been applied and dried on the recording surface by the processing liquid application unit 14 is conveyed to an intermediate conveyance unit 58 provided between the processing liquid application unit 14 and the image forming unit 16.

  An intermediate transport drum 58 is rotatably provided in the intermediate transport unit 58, and a sheet is held on the surface of the intermediate transport drum 34 via a holding member 32 provided in the intermediate transport drum 34. The sheet is conveyed downstream by the rotation of 34.

  An image forming drum 36 is rotatably provided in the image forming unit 16, and a sheet is held on the surface of the image forming drum 36 via a holding member 32 provided on the image forming drum 36. The sheet is conveyed downstream by the rotation of 36.

  Above the image forming drum 36, a head unit 66 composed of a single-pass inkjet line head 64 is disposed adjacent to the surface of the image forming drum 36. In this head unit 66, at least YMCK inkjet line heads 64, which are basic colors, are arranged along the circumferential direction of the image forming drum 36, and on the processing liquid layer formed on the recording surface of the paper by the processing liquid application unit 14. Then, an image of each color is formed.

  The inkjet line head 64 has a length corresponding to the maximum paper width of the paper targeted by the image forming apparatus 10, and the nozzle surface has a length exceeding at least one side of the maximum size paper (within the drawable range). A plurality of nozzles 90 (see FIG. 2) for discharging ink are arranged over the entire width.

  The treatment liquid has an effect of aggregating the color material (pigment) dispersed in the ink and latex particles, and forms an aggregate so that no color material flow occurs on the paper. As an example of the reaction between the ink and the treatment liquid, an acid is contained in the treatment liquid, the pigment dispersion is destroyed by PH down, and the mechanism of agglomeration is used, color material bleeding, color mixing between each color ink, ink droplet landing Avoid droplet ejection interference due to liquid coalescence.

  The inkjet line head 64 performs droplet ejection in synchronization with an encoder (not shown) that detects the rotational speed disposed on the image forming drum 36, thereby determining the landing position with high accuracy and at the same time. Irregular droplet ejection can be reduced without depending on the shake, the accuracy of the rotary shaft 68, and the drum surface speed.

  The head unit 66 can be retracted from the upper part of the image forming drum 36, and maintenance operations such as cleaning the nozzle surface of the inkjet line head 64 and discharging the thickened ink, the head unit 66 is moved to the upper part of the image forming drum 36. It is carried out by evacuating from.

  The sheet on which the image is formed on the recording surface is conveyed to an intermediate conveyance unit 70 provided between the image forming unit 16 and the ink drying unit 18 by the rotation of the image forming drum 36. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof is omitted.

  An ink drying drum 38 is rotatably provided in the ink drying unit 18, and a plurality of hot air nozzles 72 and IR heaters 74 are arranged on the upper portion of the ink drying drum 38 in proximity to the surface of the ink drying unit 18. It is installed.

  Here, as an example, the pair of IR heaters 74 arranged in parallel with the hot air nozzles 72 are alternately arranged so that the hot air nozzles 72 are arranged on the upstream side and the downstream side. In addition to this, a large number of IR heaters 74 are arranged on the upstream side to irradiate a large amount of heat energy on the upstream side, the moisture temperature is increased, and a large number of hot air nozzles 72 are arranged on the downstream side to blow off saturated water vapor. May be.

  Here, the hot air nozzle 72 is arranged so that the blowing angle of the hot air is inclined toward the rear end side of the paper. Thus, the flow of hot air from the hot air nozzle 72 can be collected in one direction, and the paper is pressed against the ink drying drum 38 side, and the state where the paper is held on the surface of the ink drying drum 38 can be maintained. it can. With the hot air from the hot air nozzle 72 and the IR heater 74, the solvent separated by the color material aggregating action is dried in the image forming portion of the paper, and a thin image layer is formed.

  Although the warm air varies depending on the paper conveyance speed, it is normally set to 50 ° C. to 70 ° C., and the ink surface temperature is set to 50 ° C. to 60 ° C. by setting the temperature of the IR heater 74 to 200 ° C. to 600 ° C. It is set to be. The evaporated solvent is discharged together with air to the outside of the image forming apparatus 10, but the air is recovered. This air may be cooled by a cooler / radiator or the like and recovered as a liquid.

  The sheet on which the image on the recording surface is dried is conveyed to an intermediate conveyance unit 76 provided between the ink drying unit 18 and the image fixing unit 20 by the rotation of the ink drying drum 38. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof is omitted.

  An image fixing drum 40 is rotatably provided in the image fixing unit 20. The image fixing unit 20 has a function of fixing the latex particles in the thin image layer formed on the ink drying drum 38 by being heated / pressurized to be melted.

  A heating roller 78 is disposed above the image fixing drum 40 in the vicinity of the surface of the image fixing drum 40. The heating roller 78 has a halogen lamp incorporated in a metal pipe made of aluminum or the like having a good thermal conductivity. The heating roller 78 applies thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex. As a result, the latex particles are melted and pressed into the irregularities on the paper for fixing, and the irregularities on the surface of the image are leveled to obtain glossiness.

  A fixing roller 80 is provided on the downstream side of the heating roller 78. The fixing roller 80 is disposed in pressure contact with the surface of the image fixing drum 40 so as to obtain a nip force with the image fixing drum 40. I have to. For this reason, at least one of the fixing roller 80 and the image fixing drum 40 has an elastic layer on the surface and a uniform nip width with respect to the paper.

  The sheet on which the image on the recording surface is fixed by the above-described process is conveyed to the discharge unit 21 provided on the downstream side of the image fixing unit 20 by the rotation of the image fixing drum 40. In the present embodiment, the configuration including the image fixing unit 20 has been described. However, if the image formed on the recording surface can be dried and fixed by the ink drying unit 18, the image fixing unit 20 may be omitted. .

  Next, the inkjet line head 64 which is an example of a droplet discharge head according to the present embodiment will be described in detail. As shown in FIG. 2, the inkjet line head 64 includes a long common flow path (common liquid chamber) 60 that stores ink supplied from an ink tank (not shown). In the common channel 60, an air layer partitioned by a diaphragm is formed. That is, this air layer serves as the air damper 62 in the common flow path 60.

  In addition, the inkjet line head 64 includes a pressure chamber 84 above the common flow path 60, and is provided on the vibration plate 86 constituting the upper surface of the pressure chamber 84 and the upper surface of the vibration plate 86. And a piezoelectric actuator (pressure generating element) 88 that vibrates (drives) the diaphragm 86 in the vertical direction.

  The inkjet line head 64 includes an ink flow path 92 that connects the nozzle 90 and the pressure chamber 84, an ink flow path (liquid flow path) 94 that connects the common flow path 60 and the pressure chamber 84, and It has.

  The pressure chamber 84 has a substantially square planar shape, an ink flow path 94 communicating with the common flow path 60 is connected to one of the diagonal corners, and an ink flow communicating with the nozzle 90 is connected to the other. A path 92 is connected. The shape of the pressure chamber 84 is not limited to this, and the planar shape may take various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse.

  An individual electrode (not shown) for driving the piezoelectric actuator 88 is provided on the upper surface of the piezoelectric actuator 88. That is, by applying a driving voltage between the individual electrode and the diaphragm 86 as a common electrode, the piezoelectric actuator 88 deforms the diaphragm 86 to change the volume of the pressure chamber 84, and the pressure change associated therewith. Thus, an ink droplet is ejected from the nozzle 90. In addition, when the displacement of the vibration plate 86 returns to the original state after ink droplet ejection, new ink is refilled into the pressure chamber 84 from the common channel 60 through the ink channel 94.

  Further, a plurality of (two in the drawing) branch channels 96 and 98 are formed in the middle of the ink channel 94 between the common channel 60 and the pressure chamber 84. Each of the branch channels 96 and 98 is formed in a substantially “<” shape and a substantially “>” shape in a front view shown in FIG. 3 (viewed from a direction orthogonal to the ink flow direction of the ink channel 94). Has been. That is, each of the branch channels 96 and 98 is formed in a rhombus (square) having a line-symmetric shape in the front view shown in FIG.

  A damper portion 100 having a diaphragm 102 as a reflection portion is integrally connected to one of the branch channels 96, 98, for example, a bent portion 98A (swells outward) of the branch channel 98. That is, a part of the wall portion constituting the branch flow path 98 is made of a material different from the other wall portions, for example, polyethylene (PE) having a density different from that of silicon (Si) constituting the branch flow paths 96 and 98. The configured diaphragm (reflecting portion) 102 is used.

  And the cover part 104 which covers the diaphragm 102 is provided integrally. The inside of the cover 104 is in an airtight state, and the hardness of the diaphragm 102 can be adjusted by adjusting the size (volume). That is, when the size (volume) of the cover portion 104 is large, the diaphragm 102 can be softened, and when the size (volume) of the cover portion 104 is small, the diaphragm 102 can be hardened.

  When such a damper portion 100 is provided only in one branch flow path 98, when one piezoelectric actuator 88 is moved to eject ink droplets from the nozzle 90 (when pressure is generated), the pressure chamber 84 is provided. Since the return pressure wave propagated from the ink flow path 94 to the branch flow path 98 is reflected (bounced back) by the diaphragm 102, the pressure wave propagated through the branch flow path 98, A phase difference can be given to the pressure wave that has propagated through the branch channel 96.

  Therefore, since the pressure waves that have propagated can be canceled and reduced at the junction (combining point) of the branch channels 96 and 98, the propagation of the pressure wave to the common channel 60 side is suppressed. (Attenuation effect of pressure wave is obtained with respect to the common flow channel 60 side). In other words, this can reduce crosstalk that affects another nozzle 90 adjacent through the common flow channel 60.

  The cover portion 104 is larger in volume, and the diaphragm 102 is softer and softer (for example, even if the material of the diaphragm 102 is the same polyethylene and the same film thickness, the lighter the specific gravity). This is desirable because it is easy to shift the phase and can be close to a reversal that is 180 ° out of phase.

  Further, the damper unit 100 may not be provided with the cover unit 104. That is, the outer surface of the diaphragm 102 may be open to the atmosphere (the air interface). In this case, however, the hardness of the diaphragm 102 is adjusted by the material, film thickness, etc. of the diaphragm 102 itself.

  Further, the diaphragm 102 may be made of the same material as the material (for example, Si) constituting the branch flow path 98 as long as the film thickness is different. That is, a part of the wall portion of the branch flow path 98 may be formed thinner than other portions to form the diaphragm 102. In this case, there is an advantage that the ink flow path 94 can be easily configured (the inkjet line head 64 can be easily manufactured).

  Next, the operation of the flow path structure (ink flow path 94) of the inkjet line head 64 configured as described above will be described. When one piezoelectric actuator 88 is driven to vibrate the vibration plate 86 and ink droplets are ejected from the nozzle 90 (when pressure is generated), a return pressure wave generated in the pressure chamber 84 passes through the ink flow path 94. Then, it is propagated to the common flow channel 60 on the ink supply side.

  Here, branch channels 96 and 98 are formed in the middle of the ink channel 94 between the pressure chamber 84 and the common channel 60, and a damper unit 100 is formed on one of them. That is, the wall portion in the bent portion 98A of the branch flow path 98 is a diaphragm 102 made of polyethylene (PE) or the like. Therefore, a phase difference can be provided between the pressure wave propagating through the branch flow path 98 and the pressure wave propagating through the branch flow path 96.

  That is, the pressure wave propagating through the branch flow path 98 is reflected (bounced back) by the diaphragm 102 formed at the bent portion 98A of the branch flow path 98, so that the diaphragm 102 (damper portion 100) is formed. The phase is shifted between the pressure wave that has propagated through the branched flow path 98 and the pressure wave that has propagated through the branch flow path 96 where the diaphragm 102 (damper portion 100) is not formed. be able to.

  Moreover, as shown in FIG. 3, the branch channels 96 and 98 are configured in line symmetry, in other words, the confluence of the pressure waves propagating through the branch channels 96 and 98 is The pressure wave propagating through the branch flow path 98 in which the diaphragm 102 is formed, and the diaphragm 102, are symmetrical with the starting point of the pressure wave when starting to propagate through the branch flow paths 96 and 98. A phase difference can be surely given to the pressure wave propagating through the branch flow path 96 in which is not formed.

  Therefore, when the pressure waves propagating through the branch channels 96 and 98 are superimposed at the junction of the branch channels 96 and 98, the pressure waves cancel each other out due to the phase difference. The amplitude (vibration) is reduced, and the propagation of the pressure wave to the common channel 60 side is suppressed (the pressure wave propagated to the common channel 60 side is attenuated). Therefore, crosstalk that affects another nozzle 90 adjacent via the common flow channel 60 can be reduced.

  Further, since the protrusions and the like as shown in the prior art are not formed in the branch flow paths 96 and 98, the decrease in the ink filling speed is small (the ink filling speed does not decrease). Therefore, high throughput can be achieved by using this inkjet line head 64.

  As an example, FIG. 4 shows a combined waveform when a pressure wave whose phase is 0 ° and a pressure wave whose phase is shifted by 120 ° are superimposed. In the combination with the phase shifted by 180 ° (the phase is inverted), the propagation of the pressure wave to the common flow path 60 does not occur, but the amplitude (vibration) is also generated when the phase is shifted by 120 °. ) Is halved. Therefore, the channel structure according to the present embodiment is effective.

  The number of branch channels 96 and 98 formed in the ink channel 94 is not limited to the two shown in FIGS. 2 and 3, and may be three as shown in FIG. 5, for example. That is, between the branch channel 96 and the branch channel 98, a branch channel 97 having a narrower channel than the branch channels 96, 98 (different from the branch channels 96, 98 in channel resistance) is formed. A three-pronged shape may be used.

  In this case, among the three branch channels 96, 97, 98, the diaphragm 102 is provided at each of the bent portions 96A, 98A of the two branch channels 96, 98 excluding at least the branch channel 97, and each diaphragm is provided. The pressure wave propagating through the branch flow path 96 is changed by changing the size of the cover section 104 provided in 102 (for example, making the cover section 104 on the branch flow path 96 side smaller than the cover section 104 on the branch flow path 98 side). And the pressure wave propagating through the branch flow path 98 can be shifted in phase, so that different pressure differences can be imparted to the pressure waves propagating through the branch flow paths 96, 97, and 98, respectively.

  Moreover, the shape of the branch flow paths 96 and 98 is not limited to the line symmetrical shape as shown in FIG. 3, for example, as shown in FIG. 6, the branch without the diaphragm 102 (damper portion 100) is provided. You may form in the substantially triangular shape made into linear form, without making only the flow path 96 bend. With such a configuration, the flow resistance in the branch flow path 96 can be reduced, so that the ink filling speed can be further prevented from decreasing. Further, the phase difference can be easily given to the pressure wave propagating through the branch flow channels 96 and 98 due to the difference in flow channel length.

  The shape of the branch channels 96 and 98 is, for example, a substantially triangular shape in which only the branch channel 96 without the diaphragm 102 (damper portion 100) is formed in an arc shape (expands outward) as shown in FIG. You may form in (fan shape). Even with such a configuration, the same effect as described above can be obtained. However, when the branch flow paths 96 and 98 are not line-symmetrical as shown in FIG. 3, the ink flow rate and the phase shift width are considered. Thus, it is necessary to design the ink flow path 94.

  Further, as shown in FIG. 8, the air damper 62 formed above the common flow path 60 may be shared as the damper portion 100 of the branch flow path 98. That is, a part of the wall portion of the branch flow path 98 may be configured by the wall portion of the common flow path 60 and may be used as the diaphragm 102. In this case, the attenuation effect of the pressure wave propagated to the common channel 60 can be further enhanced.

  Further, with such a configuration, it is not necessary to separately provide the cover 104 shown in FIGS. 2, 3, and 5 to 7, so that the number of parts can be reduced. Further, as shown in FIG. 8, the size of the air damper 62 at this time corresponds to the height dimension H of the portion from the diaphragm 86 to the nozzle 90 (material is Si or the like) is about 600 μm. It is made a size.

  The flow path structure in the liquid droplet ejection head (inkjet line head 64) according to the present embodiment has been described above. However, the flow path structure in the liquid droplet ejection head according to the present embodiment is limited to the illustrated examples. However, the design can be changed as appropriate without departing from the scope of the present invention.

  That is, each branch flow path is caused by a return pressure wave generated along with the volume change of the pressure chamber 84 and propagating through the branch flow paths 96 and 98 of the ink flow path 94 communicating with the common flow path 60. It is only necessary that the flow path structure has a configuration (shape, material, etc.) capable of providing a phase difference up to 96 and 98 confluences.

10 Image forming device 60 Common flow path (Common liquid chamber)
62 Air damper 64 Inkjet line head (droplet discharge head)
84 Pressure chamber 86 Diaphragm 88 Piezoelectric actuator (pressure generating element)
90 Nozzle 92 Ink channel 94 Ink channel (liquid channel)
96 Branching channel 97 Branching channel 98 Branching channel 100 Damper part 102 Diaphragm (reflection part)
104 Cover part

Claims (4)

A plurality of nozzles for discharging droplets onto a recording medium;
A plurality of pressure chambers provided for each of the nozzles and connected in communication and filled with liquid;
A diaphragm that is driven by a pressure generating element to change the volume of each pressure chamber;
A common liquid chamber in which the liquid supplied to each pressure chamber is stored;
A liquid flow path connecting the pressure chambers to the common liquid chamber;
A plurality of branch channels formed in the middle of the liquid channel;
A reflection part that is formed in a branch flow path excluding at least one of the plurality of branch flow paths and reflects a pressure wave generated in accordance with a volume change of the pressure chamber;
A liquid droplet ejection head comprising:   2. The droplet discharge head according to claim 1, wherein the plurality of branch flow paths have a symmetrical shape when viewed from a direction orthogonal to a liquid flow direction of the liquid flow path.   2. The droplet discharge head according to claim 1, wherein when viewed from a direction orthogonal to the liquid flow direction of the liquid flow path, the plurality of branch flow paths have a substantially triangular shape.   4. The liquid droplet ejection head according to claim 1, wherein the reflection portion is configured by a wall portion of the common liquid chamber. 5.

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