JP2007136839A - Ink-jet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording device that has a nozzle capable of breaking ink into particulates with a stable drive voltage even when acoustic velocity in the ink is changed due to temperature change in the ink-jet recording device of a continuous system. <P>SOLUTION: The nozzle is composed of an orifice for jetting out the ink, a stepped ink flow passage composed by coupling three or more columnar holes respectively having a different inner diameter with each other so as to introduce the ink to the orifice, and a vibration means joined at the outer peripheral part of the ink flow passage so as to vibrate the ink. The ink flow passage comprises a cylindrical tube, which is internally provided with three or more parts respectively having a different inner diameter, and a joint machined so as to allow its one end to be inserted into the cylindrical tube. A nozzle gravity position is set to be located inside the joint inserted into the cylindrical tube. It is composed so as to allow vibration of a piezoelectric element to be easily transmitted by setting an interval between the nozzle gravity position and the orifice to about one forth of a wavelength that mechanically resonates the nozzle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nozzle structure of an ink jet recording apparatus that performs printing by ejecting ink continuously from a nozzle.

  Continuous ink jet recording devices that eject ink continuously from nozzles, charge ink droplets that separate during flight, and deflect the ink droplets with an electric field for printing. Is widely used as a printing device. Conventionally, as shown in Patent Document 1, pressurized ink is supplied to the ink chambers of the nozzles of the ink jet recording apparatus, and the inks are vibrated using vibration amplification by fluid resonance of the ink chambers. Ink droplets are known which are made to fly from an orifice present at the end of a chamber.

JP-A-5-254117

  In the above prior art, the nozzle drive frequency (80 kHz) is set between two fluid resonance frequencies (70 kHz and 90 kHz). By vibrating the ink chamber with the piezoelectric element at this driving frequency, the ink flying from the orifice is made into particles.

  However, the speed of sound in ink generally used in an ink jet recording apparatus is 1200 to 1400 m / s at room temperature, but varies depending on the temperature. In the temperature range of 0 to 45 ° C., which is the operating temperature range of the ink jet recording apparatus, the speed of sound in the ink changes by about ± 10% with respect to the normal temperature. Since the fluid resonance frequency in the same ink flow path is proportional to the sound velocity, the fluid resonance frequency also changes by about ± 10% when the sound velocity changes. Therefore, the two fluid resonance frequencies change in the range of 70 ± 7 kHz and 90 ± 9 kHz, and the amplification factor of the ink vibration at the driving frequency of 80 kHz varies greatly depending on the temperature, and the particle formation becomes unstable. was there. In order to reduce this instability, if the two fluid resonance frequencies are greatly separated from the nozzle drive frequency, a sufficient amplification factor cannot be obtained, so that the amplitude of the piezoelectric element has to be increased. For this purpose, another problem has arisen that it is essential to increase the size of the piezoelectric element and increase the input voltage.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus having a nozzle that can atomize ink with a stable driving voltage even if the sound speed in the ink changes due to a temperature change in a continuous inkjet recording apparatus. is there. Another object is to provide an ink jet recording apparatus having a small nozzle that can atomize ink with a low driving voltage.

  In order to achieve the above object, the nozzle of the ink jet recording apparatus has the following configuration. The nozzle is an orifice that ejects ink, a stepped ink flow path that connects three or more cylindrical holes with different inner diameters that guide the ink to the orifice, and a vibration for exciting the ink on the outer periphery of the ink flow path. The structure (cylindrical piezoelectric element) was joined. The ink flow path was composed of a cylindrical tube having three or more portions having different inner diameters and a joint processed so that one end was inserted into the cylindrical tube, and the cylindrical tube and the joint were joined with an adhesive. The nozzle is configured to supply ink from the end of the joint and to eject ink from the orifice. The length of the portion having the same inner diameter inside the cylindrical tube was set to such a length that fluid resonance does not occur there.

  Also, in order to atomize ink at the nozzle mechanical resonance frequency, the distance between the center of gravity of the nozzle and the orifice is divided by the mechanical resonance length of the nozzle (the speed of the sound wave propagating through the nozzle material is divided by the ink particleization frequency). The vibration of the piezoelectric element is amplified to about a quarter of the value obtained. In addition, a part having a large diameter is provided in a part of the joint of the nozzle, and the nozzle holder is fixed to the nozzle holder at that position, and the nozzle holder is fixed to the print head.

  According to the present invention, the distance between the center of gravity of the nozzle and the orifice is set to about one-fourth of the wavelength when the nozzle mechanically resonates, so that the mechanical resonance frequency of the nozzle vibrates the piezoelectric element that is the vibration means. Therefore, the vibration of the piezoelectric element can be amplified and transmitted to the ink. As a result, the piezoelectric element can be made small, and the nozzle can be miniaturized. In addition, by making a difference between the fluid resonance frequency of the ink flow path in the nozzle and the drive frequency of the nozzle, even if the sound velocity in the ink changes due to temperature change, stable particle formation is not affected by fluid resonance. There is an effect that becomes possible. Further, by fixing the nozzle at a position closer to the ink supply than the position of the center of gravity of the nozzle, there is an effect that a change in mechanical resonance frequency is small and a stable resonance state can be maintained.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 6 shows an overview of the ink jet recording apparatus. An ink jet recording apparatus control system and an ink circulation system exist inside the main body 100, and maintenance work can be performed by opening and closing the door 105. A cable 103 extends from the main body 100. The cable 103 includes a pipe that sends ink from the main body 100 to the print head 101, a pipe that collects ink from the print head 101 to the main body 100, and a wiring that sends electric signals to the print head 101. Furthermore, the main body 100 includes a touch panel type liquid crystal panel 104 for a user to input print contents, print specifications, and the like. While the recording device is in operation, the liquid crystal panel 104 displays the control contents of the recording device, the operation status, and the like. The print head 101 is made of stainless steel, and a printing unit that creates ink particles and controls the flying of the ink particles is housed therein. The ink particles created inside the print head 101 are ejected from an opening 102 provided on the bottom surface and adhere to a recording medium (not shown) to form an image.

  Next, the internal configuration of the main body 100 will be described with reference to FIG.

  On the upper part of the main body 100, electrical parts such as the control board 109 are arranged. Further, circulation system control parts such as the electromagnetic valve 108 and the pump unit 106 are disposed in the lower part 110 of the main body, and an ink container 1 that stores ink to be supplied to the nozzles is housed in the vicinity thereof. The door 105 can be opened and closed, the ink container can be pulled out to the door 105 side, and maintenance work such as ink supply and disposal can be easily performed.

  Next, a schematic configuration of the ink circulation system and the printing unit of the ink jet recording apparatus will be described with reference to FIG.

  The ink supply path 21 contains an ink container 1 that contains ink, a supply pump 2 that pumps ink, a pressure regulating valve 3 that adjusts ink pressure, a pressure gauge 4 that measures and displays the pressure of the supplied ink, and catches foreign matter in the ink. It consists of a filter 5 and supplies ink to the nozzle 6. The nozzle 6 is provided with a piezoelectric element. By applying a sine wave of about 70 kHz to the piezoelectric element, ink is ejected from an orifice present at the end of the nozzle 6, and the ejected ink is divided into particles during flight. . A recording signal source (not shown) is connected to the charging electrode 7, and by applying a recording signal voltage to the charging electrode 7, the ink particles 8 ejected regularly from the nozzle 6 are charged. Since the upper deflection electrode 9 is connected to a high voltage source (not shown) and the lower deflection electrode 10 is grounded, an electrostatic field is formed between the upper deflection electrode 9 and the lower deflection electrode 10. The ink particles 8 charged by the charging electrode 7 are deflected according to the charge amount of the ink particles 8 while passing through the electrostatic field, and adhere to a recording medium (not shown) to form an image.

  The ink recovery path 22 includes a backlash 11, a filter 12, and a recovery pump 14, and ink particles 8 that are not charged by the charging electrode 7 and are not deflected while passing through the electrostatic field are recovered by the gutter 11. Return to the ink container 1 to be reused. The ink recovery path 22 including the filter 12 is formed inside the print head 101, and therefore exists at a position where it cannot be seen from the outer surface.

  Next, the nozzle 6 of this invention is demonstrated using FIG. 1 and FIG. FIG. 1 is a sectional view of a nozzle 6 of the present invention. The nozzle 6 includes a cylindrical tube 30 provided with an orifice 31 on one end side, a piezoelectric element 29 serving as a vibration means disposed on the outer periphery of the cylindrical tube 30, and one end of the cylindrical tube 30 opposite to the orifice 31 side. The joint 27 is arranged. The joint 27 is joined to the cylindrical tube 30 by an adhesive.

  The ink is supplied from the joint 27 to the cylindrical tube 30, passes through the ink flow paths 37, 38, and 39 that gradually decrease in diameter in three stages inside the cylindrical tube 30, and is ejected from the orifice 31 ahead. The material of the cylindrical tube 30 is stainless steel, and the ink flow path whose diameter gradually decreases in three stages is manufactured by drilling. The orifice 31 beyond that is manufactured by pressing. The reason for providing the flow paths 37, 38, and 39 having a small diameter in three stages will be described later.

  The cylindrical tube 30 can be divided into cylindrical tubes 30a and 30b. This is because the solvent used in the ink used has high volatility, and if the ink ejection is stopped for a long time, the orifice 31 is clogged. Therefore, only the cylindrical tube 30b is separated and the orifice 31 portion is separated. It is because it is necessary to wash. When cleaning the orifice 31, the nozzle 6 is removed from the print head, and the cylindrical tubes 30a and 30b are separated and ultrasonically cleaned. By cleaning, clogging of the orifice 31 can be removed.

  FIG. 3 is an enlarged view of the nozzle tip of FIG. Cylindrical tubes 30 a and 30 b are structured to be joined by screws 50. That is, a male screw is cut on the cylindrical tube 30a side, and a female screw is cut on the cylindrical tube 30b side. Further, a seal member (using a rubber plate 40 in the present embodiment) is attached to the boundary between the flow path 38 and the flow path 39 (the connecting portion between the cylindrical tube 30a and the cylindrical tube 30b) to prevent ink leakage.

  Next, the piezoelectric element 29 will be described in detail with reference to FIG. The piezoelectric element 29 has a cylindrical shape, and electrodes are provided on the inner and outer surfaces. The inner surface electrode 51 of the piezoelectric element 29 is provided on the entire inner surface and end surface of the cylindrical portion. Further, in order to maintain electrical insulation between the outer surface electrode 52 and the inner surface electrode 51, there is an electrodeless portion 54 on the outer surface of the piezoelectric element 29. The piezoelectric element 29 is adhesively bonded to the cylindrical tube 30 at the portion of the inner surface electrode 51 so that the vibration of the piezoelectric element 29 can be efficiently transmitted to the cylindrical tube 30. Since the inner surface electrode 51 of the piezoelectric element 29 contacts the cylindrical tube 30 through a thin adhesive layer with negligible electrical resistance, the cylindrical tube 30 and the inner surface electrode 51 are electrically connected. Therefore, the piezoelectric element 29 can be vibrated by connecting a transmitter that generates a sinusoidal electric signal between the outer electrode 52 and the cylindrical tube 30.

  Next, a method for designing the flow path structure will be described.

The manner in which the vibration is transmitted to the ink flowing in the cylindrical tube 30 when the piezoelectric element 29 is vibrated by applying a high frequency voltage will be described. In the voltage range that can be applied to the piezoelectric element 29, vibration is very small and insufficient for particle formation. For this reason, the cylindrical tube 30 is configured to amplify the vibration so that the axial resonance frequency f _b (mechanical resonance) is close to the nozzle drive frequency (frequency at which ink is atomized) f _n . . The axial resonance frequency f _b can be obtained by the following equation.

f _b = nV _b / 4 (L + k ₁ ) (Equation 1)
Here, n is an integer value determined by a resonance mode, L is distance between the position of the center of gravity and the orifice of the cylindrical tube 30, V _b are those speed of sound in the cylindrical tube 30, k ₁ is determined experimentally by the correction factor. In general, the resonance frequency f in the axial direction of a round rod that is thin with respect to the length is inversely proportional to the entire length of the rod, but the outer diameter is not uniform as in this embodiment, and there is no hole inside. It was confirmed experimentally that the cylindrical nozzle was inversely proportional to the position of the center of gravity and the distance to the nozzle end (orifice). The sound velocity V _b in this embodiment is V _b = 5800 to 5900 m / s because the material of the cylindrical tube is stainless steel. The speed of sound in a solid depends on the Young's modulus, and since the Young's modulus changes little with temperature, the speed of sound in a solid is less affected by temperature.

The optimum value of the nozzle drive frequency f _n is almost determined by the orifice diameter (the hole diameter in this embodiment is φ0.065 mm), and f _n = 70 kHz. By bringing f _b and f _n closer, the vibration of the piezoelectric element 31 is amplified by the cylindrical tube 30 and the ink is vibrated, thereby enabling efficient particle formation.

When n = 1 in Equation ₁ , L + k ₁ is about 20 to 22 mm, and this length is L5 in FIG. Further, by transforming Equation ₁ , L + k ₁ is a value obtained by dividing the sound velocity V _b in the cylindrical tube 30 by the resonance frequency f _b in the axial direction of the cylindrical tube 30 (resonant wavelength in the axial direction of the cylindrical tube 30). It becomes a quarter. This value and λ _b.

As described above, k ₁ is experimentally determined, and is determined by the inner diameter of the cylindrical hole in the cylindrical tube 30 and the size of the vibration means, and is within ± 10% of L. Therefore, the value of L5 enters the range of 0.9 to 1.1 times of lambda _b.

  Hereinafter, a method for designing the lengths L1 to L4 will be specifically described.

  First, a design method for the lengths L2 to L4 inside the cylindrical tube 30 will be described.

  As described above, the nozzle has a shape in which the cylindrical tube 30 and the joint 27 are connected, and the ink is introduced into the ink flow paths 37, 38, and 39 of the cylindrical tube 30. The ink flow paths 37, 38, and 39 have a stepped structure with different inner diameters. That is, the inner diameter becomes smaller as going to the orifice 31 side. This is because, when the ink flow path having the same inner diameter is divided into short, the fluid resonance frequency generated in the ink flow path is increased, and the ink is vibrated at the drive frequency that particles the ink. This is to prevent fluid resonance with a large property.

The fluid resonance in the ink flow path will be described. The fluid resonance frequency f _i of the ink flow path is obtained by the following equation.

f _i = nV _i / 4 (l + k ₂ ) (Equation 2)
Here, V _i is the speed of sound in the ink, l is the length of the ink flow path, k ₂ is the correction factor, are those determined by experiment. n is an integer value determined by the resonance mode. In the case of the ink flow path 39, the orifice diameter is sufficiently small with respect to the inner diameter. Therefore, the boundary condition of one end closing and one end opening is taken, and n = 1, 2 in the primary mode. In the next mode, n = 3, and in the third mode, n = 5. Further, since the ink flow paths 37 and 38 are boundary conditions with both ends open, n = 2 in the primary mode, n = 4 in the secondary mode, and n = 6 in the tertiary mode. In general, the speed of sound in ink is 1200 to 1400 m / s at room temperature, but the speed of sound in ink varies depending on the temperature. The amount of change is about ± 10% at 0 to 45 ° C., which is the operating temperature range of the ink jet recording apparatus. Therefore, in this embodiment, in order to prevent the particle formation from being affected by fluid resonance, the flow path length l is set so that the fluid resonance frequency is separated from the driving frequency. The primary mode l in the ink flow paths 37 and 38 is 9 to 10 mm, and the primary mode in the ink flow path 39 is 4 to 5 mm. Furthermore, in order to avoid higher-order mode fluid resonance, L2 and L3 were set to the middle of the above two ranges, and L4 was set to be smaller than the above 4 to 5 mm.

  By setting in this way, the fluid resonance frequency of the ink flowing through each flow path can be made higher than the drive frequency. In this embodiment, the diameter of the flow path is divided into three stages. However, even if the number of stages is increased, no problem occurs.

  Next, a design method for the joint length L1 will be described.

  One end of the joint 27 is inserted into the cylindrical tube 30 and joined with an adhesive. A pipe for introducing ink is connected to the other end. Since the sum of the lengths from L2 to L4 is shorter than L5, the center of gravity of the nozzle exists at the portion where the joint 27 is inserted into the cylindrical tube 30. When the outer diameter of the joint is the same as the outer diameter of the cylindrical tube, the center of gravity is at the center of the entire nozzle, so the distance between the orifice position and the ink inlet of the joint is twice L5. As a result, L1 is L5. (L1 becomes 2 × L5-L2-L3-L4). However, since the shorter nozzle is easier to handle, it is preferable that the length of L1 is as short as possible. As for the portion where the ink pipe is connected by the joint, it is sufficient that the outer diameter is about 5 to 10 mm in accordance with the inner diameter of the ink pipe. Therefore, in order to shorten the length of L1, the joint is connected. It is necessary to increase the weight by increasing a part of the diameter. Here, if the nozzle diameter is adjusted to about 8 to 10 mm, which is the height of the character to be printed, it can be applied to an inkjet printer having a plurality of nozzles arranged in multiple stages. Is about 8 to 10 mm (an example of an ink jet printer in which a plurality of nozzles are arranged in multiple stages on the recording head will be described later). From the above conditions, the lower limit value of L1 is approximately the same as L5.

As described above, the range of the length of L1 is determined by the ratio with respect to L5, but the following must be further considered. Since the joint portion having a length L1 becomes an ink flow path having a constant inner diameter, fluid resonance in this portion must be avoided. Since this part is a boundary condition with both ends open, the above-mentioned n in Equation 2 is n = 2 in the primary mode, n = 4 in the secondary mode, and n = 6 in the tertiary mode. For n = _2, l + _k 2 becomes about 8.5～10Mm, since this length is equal to or less than the lower limit value of is shorter than L5 L1, 1-order mode does not exist. When n = 4, l + k ₂ is about 17 to 20 mm (l + k ₂ when n = 4 is equal to a value obtained by dividing the speed of sound in ink by the ink particleization frequency. This value is assumed to be λi). Therefore, the length of L1 needs to avoid this range.

Since the lower limit value of L1 is substantially the same as L5, the set value of L1 is longer than λi. K 2 in Equation ₂ is a value determined by experiment, and varies depending on the inner diameter of the joint, and the fluctuation range is within ± 10% of l. Based on the above results, L1 may be set to 1.1 times or more of λi.

When n = 6 in Equation ₂ , l + k2 is about 25.5 to 30 mm, and L1 needs to avoid this range. In this case, since the range of 0.9 to 1.1 times L1 avoids 1.5 times λi, L1 is 1.4 times or less of λi or 1.7 times or more of λi. Become.

  Considering that the shorter L1 is easier to handle when the set value of L1 is determined by combining the above ranges, it is preferable to set L1 to 1.1 times or more and 1.4 times or less of λi.

  By setting L1 to L4 as described above, the influence of fluid resonance can be reduced, so that even if the temperature changes, there is an effect that the fluctuation of the driving voltage for atomizing ink is small.

  Next, a method for attaching the nozzle will be described.

  In order to fix the nozzle to the print head, it is common to fix the nozzle to the nozzle holder and attach the nozzle holder to the print head.

  FIG. 2 is a sectional view showing a state in which the nozzle of the present invention is fixed to the nozzle holder. The nozzle 6 is fixed to the nozzle holder 32 by a screw 33 at a position where the diameter of the cylindrical tube 30 is the largest. Since this position is on the ink supply side with respect to the center of gravity of the nozzle, there is a feature that stable vibration can be maintained without weakening the mechanical resonance state of the nozzle. The nozzle holder 32 is provided with an opening 34 which is a lead wire outlet for supplying a signal to the piezoelectric element 29.

  FIG. 9 is an external view of the front end portion of the print head 101. The nozzle 6 attached to the nozzle holder 32 is fixed to the mounting substrate 41 with screws, and the mounting substrate 41 is fixed to the print head 101 with screws. In addition to the nozzles, the charging electrode 7, the upper deflection electrode 9, and the lower deflection electrode 10 are fixed to the mounting substrate 41 with screws. Ink particles that have not been used for printing are collected by the gutter 11 and return to the ink tank in the main body via an ink collection path (not shown) inside the print head 101.

  By manufacturing the nozzle 6 as described above, vibration amplification using mechanical resonance with little change with respect to temperature can be obtained, so that stable particle formation is possible. At the same time, the nozzle having the above-described configuration has a feature that it is not affected by fluid resonance that varies greatly with temperature.

  Next, an example of the nozzle 6 different from FIG. 1 will be described.

  FIG. 4 shows the appearance of the nozzle 6 having a configuration different from that in FIG. The configuration in FIG. 1 is a configuration in which the inner diameter of the piezoelectric element 29 and the outer diameter of the nozzle 6 are combined, but the configuration in this figure is a configuration in which the outer diameter of the piezoelectric element 29 and the outer diameter of the nozzle 6 are combined. The setting method of L1 to L5 is not different from the case of FIG. In such a configuration, the nozzle outer shape of the attachment portion of the piezoelectric element 29 needs to be the same as that in FIG. 1, and the other nozzle outer shapes are larger. Therefore, the configuration in FIG. Becomes larger. For this reason, although the voltage which makes ink particle | grains becomes high, the variation between solids has the characteristic that it becomes small.

  Next, a print head equipped with a plurality of nozzles 6 will be described.

  Since the nozzles shown in FIGS. 1 and 4 have a small diameter, a print head capable of simultaneously printing more than twice as many regions can be configured by juxtaposing two or more nozzles in the print head.

  FIG. 10 shows a schematic configuration of an ink circulation system and a printing unit of an ink jet recording apparatus having two nozzles.

  As in FIG. 8, the ink supply path 21 includes an ink container 1 that contains ink, a supply pump 2 that pumps ink, a pressure regulating valve 3 that adjusts ink pressure, a pressure gauge 4 that displays the pressure of the supplied ink, The ink that exits the filter 5 is divided into a first nozzle 6a and a second nozzle 6b. The ink that has entered the first nozzle 6a is split into particles in the air after being ejected from the orifice by the vibration of the piezoelectric element. The ink particles 8a are charged by the charging electrode 7a and deflected by the electrostatic field formed by the upper deflection electrode 9a and the lower deflection electrode 10a. Ink particles that have not been used for printing are collected from the gutter 11 a by suction of a pump disposed in the main body 100. The collected ink passes through the filter 12a to remove foreign matters such as dust. The 2nd nozzle 6b is arrange | positioned below the nozzle 6a, and the distance is equal to the magnitude | size of the character printed with the 1st nozzle 6a. The method of printing using the second nozzle 6b and the method of collecting ink particles not used for printing are the same as in the case of using the first nozzle 6a.

  Next, the reason why two recovery paths are provided for ink recovery will be described. When the ink is collected by a pump, a large amount of air is simultaneously sucked at the same time as the ink. In that case, the ratio of the amount of air and ink in the collection path is constantly changing, and the flow path resistance at the time of collection is also constantly changing. If the suction force of one pump is branched into two and collected, the flow rate from the side with less collection resistance increases and the other collection amount decreases. In order to reliably recover from a recovery path with a small recovery amount, it is necessary to increase the suction amount of the pump. Therefore, by using two pumps without branching the suction force of one pump into two, the sum of the pump recovery amounts becomes smaller than the recovery amount of one pump. Since the ink solvent used in this inkjet printer is highly volatile, the amount of ink solvent that volatilizes out of the inkjet recording device increases and the environmental impact is adversely affected if the pump recovery volume increases. Become. Therefore, by using two pumps, the amount of volatilization of the solvent can be reduced, and there is an effect that the environment is not adversely affected.

  In this embodiment, an example in which two pumps are provided in the main body of the ink jet recording apparatus has been described. However, the position of the pumps may be in the recording head if a place for arranging the pump in the recording head can be secured. . When a pump is arranged in the recording head, ink and air are sent to the main body at a position away from the recording head. In general, the pump performance is higher than the suction capacity, so the discharge capacity is higher than the suction capacity.Therefore, when the pump is placed in the recording head, a pump with a smaller recovery capacity can be selected than in the main body. There is an effect that it can be suppressed.

It is sectional drawing of the nozzle which is one Example of this invention. It is sectional drawing of the state which fixed the nozzle which is one Example of this invention to the holder. It is sectional drawing of the front-end | tip part of the nozzle which is one Example of this invention. It is sectional drawing of the nozzle which is one Example of this invention different from FIG. It is sectional drawing of the piezoelectric element used for the nozzle which is one Example of this invention. It is a general-view figure of an inkjet recording device. It is a figure which shows the inside of the main body of an inkjet recording device. It is a figure explaining the mode of the ink circulation in an inkjet recording device. It is a figure explaining the method to fix the nozzle of this invention to a recording head. It is a figure explaining the mode of the ink circulation in an inkjet recording device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ink container, 2 ... Pump, 6 ... Nozzle, 7 ... Charging electrode, 8 ... Ink particle, 9 ... Deflection electrode, 11 ... Gutter, 27 ... Joint, 29 ... Piezoelectric element, 30 ... Cylindrical tube, 31 ... Orifice

Claims (5)

In an ink jet recording apparatus having an orifice that ejects ink, an ink flow path that guides ink to the orifice, and a nozzle that includes vibration means for applying vibration to the ink,
The nozzle includes a cylindrical tube having a stepped ink flow path in which three or more cylindrical holes having different inner diameters are connected, a joint having one end inserted and joined to the inside of the cylindrical tube, and an outer peripheral portion of the cylindrical tube An ink jet recording apparatus having a structure in which a vibration means is joined to vibrate ink, and the center of gravity of the nozzle is on the joint side where one end is inserted into the inside of the cylindrical tube and joined. In an ink jet recording apparatus having an orifice that ejects ink, an ink flow path that guides ink to the orifice, and a nozzle that includes vibration means for applying vibration to the ink,
The nozzle includes a cylindrical tube having a stepped ink flow path in which three or more cylindrical holes having different inner diameters are connected, a joint having one end inserted and joined to the inside of the cylindrical tube, and an outer peripheral portion of the cylindrical tube In this structure, the gap between the nozzle center of gravity and the orifice is the mechanical resonance length of the nozzle (the velocity of the sound wave propagating in the nozzle material is divided by the ink particleization frequency). An ink jet recording apparatus characterized by being in a range of 0.9 to 1.1 times the value of a quarter of the value.   3. The ink jet recording apparatus according to claim 1, wherein a length L1 of a joint having a structure in which one end is inserted into the inside of the cylindrical tube is a value obtained by dividing the velocity of a sound wave propagating in the ink by the particleization frequency of the ink. An ink jet recording apparatus having a range of 1.1 times to 1.4 times.   4. The ink jet recording apparatus according to claim 1, wherein the nozzle is fixed to the recording head at a position closer to the ink introduction port than the position of the center of gravity of the nozzle. 5. 5. The inkjet recording apparatus according to claim 1, wherein a plurality of the nozzles are provided, a charging electrode for individually charging the ink particles with respect to each nozzle, and an electrostatic field for deflecting the ink particles. An ink jet recording apparatus comprising: a deflection electrode for forming a nozzle; a gutter for collecting ink individually for each nozzle; and a pump.

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