JP2004181656A - Liquid ejecting method and liquid ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a method for ejecting liquid in a liquid channel as a liquid drop group from a liquid ejection hole in which the ejection quantity of each liquid drop in the liquid drop group being ejected continuously from the liquid ejection hole toward one shooting point is stabilized over a wide frequency band of a pulse signal. <P>SOLUTION: In the liquid ejection method, ink in an ink channel 21 is ejected as a group of continuous ink liquid drops 30, 30... from a nozzle 20, and the ejection quantity of each ink liquid drop 30 in the group of ink liquid drop 30, 30... being ejected continuously from the nozzle 20 toward one dot D in response to a pulse signal is made constant or approximately constant over a wide frequency band of that pulse signal thus ejecting liquid by varying the driving frequency of the pulse signal within that frequency band. Ejection quantity of each ink liquid drop 30 can thereby be stabilized over a wide frequency band of the pulse signal and a print image having a high image quality can be formed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid ejection method and a liquid ejection device for ejecting a liquid in a liquid flow path from a liquid ejection hole as a group of liquid droplets, and more specifically, continuously ejecting liquid from the liquid ejection hole toward one impact point. The present invention relates to a liquid discharge method and a liquid discharge apparatus capable of stabilizing the discharge amount of each droplet of a liquid droplet group in a wide frequency band of a pulse signal.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an ink jet recording apparatus has been known as an example of a liquid ejection apparatus that ejects a liquid in a liquid flow path from a liquid ejection hole as a droplet group. 2. Description of the Related Art Ink jet recording apparatuses, for example, ink jet printers, are widely used in terms of high recording speed, low running cost, and easy colorization of printed images. Techniques for forming images have been developed.
[0003]
For example, in the case of a serial print head that forms a print image by discharging ink from a discharge unit (nozzle) formed in the print head while reciprocating the print head in the full width direction of the recording medium, a so-called multi-type print head is used. The path method is used. The multi-pass method is a method in which, when a print image is formed by ejecting ink while reciprocating a print head, ink is ejected from a plurality of ejection units to one line constituting the print image. It is. Accordingly, it is possible to make it difficult to see the variation in the ejection amount of the ink ejected from each ejection unit of the print head.
[0004]
On the other hand, in the case of a line type print head in which a number of head chips are arranged corresponding to the entire width of the recording medium, the recording medium is moved only in the length direction with respect to this print head and printing is performed. Since an image is formed, the multi-pass method cannot be applied, and a so-called PNM (Pulse Number Modulation) method is used. The PNM system is a system in which the number of ink droplets ejected from each ejection unit is increased or decreased to vary the size of the diameter of a dot (pixel) constituting a print image to express a gradation. In order to form a high-quality print image using such a PNM method, it is important to stabilize the ejection amount of each ink droplet ejected from each ejection unit. For example, Japanese Patent Application Laid-Open No. H11-163,087 discloses a technique for making the amount of each ink droplet constant when ink is continuously ejected.
[0005]
[Patent Document 1]
Patent No. 3157945 (Page 3, FIGS. 5, 8)
[0006]
[Problems to be solved by the invention]
However, in the technique described in Patent Document 1, the pulse interval of a pulse signal for continuously ejecting a plurality of independent ink droplets as a group of ink droplets per pixel from the same ejection portion is determined by the following: In a frequency band in which the ejection amount per droplet increases when the length of the ink droplet is increased, the amount of each ink droplet of the ink droplet group is reduced when a single ink droplet is ejected. The pulse interval is equal to the amount. Thereby, the pulse interval at which the ejection amount per droplet of the continuously ejected ink droplet group becomes the same is selected from the graph of the ink ejection amount characteristic with respect to the driving frequency, and each of the ink liquids is used by using the selected pulse interval. The drop volume can be constant, but this pulse interval was uniquely determined. Therefore, the pulse interval cannot be set arbitrarily, and when the pulse interval is applied to the above-described line type print head, the pulse is applied to the heating elements provided in each ejection section as the number of ejection sections increases. Power was sometimes concentrated. In this case, the voltage of the power supply that supplies power to each heating element fluctuates, and as a result, a high-quality printed image may not be formed.
[0007]
Further, in the technique described in Patent Document 1, when a pulse interval at which the amount of each ink droplet of an ink droplet group ejected from each ejection unit is the same is selected from the graph of the ink ejection amount characteristic, Also, the amount of each ink droplet tends to fluctuate due to variations in individual products in the manufacturing process of the print head, or changes in temperature during use, and each ink droplet of the ink droplet group ejected from each ejection unit. It has been difficult to stabilize the discharge amount of the droplet.
[0008]
Accordingly, the present invention addresses such a problem, and discharges each droplet of a droplet group that is continuously discharged from a liquid discharge hole that discharges liquid in a liquid flow path to one impact point. It is an object of the present invention to provide a liquid ejection method and a liquid ejection device capable of stabilizing the amount in a wide frequency band of a pulse signal.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a liquid discharge method according to the present invention refills a liquid in a liquid flow path formed corresponding to a liquid discharge hole for discharging a liquid, and applies a negative pressure to the liquid in the liquid flow path. To prevent the liquid from spontaneously leaking from the liquid discharge hole, and supply a pulse signal to the discharge energy generating means provided in the liquid flow path to discharge the liquid in the liquid flow path. A liquid discharge method of discharging as a continuous droplet group from a hole, the discharge amount of each droplet of the droplet group continuously discharged from the liquid discharge hole toward one impact point by the pulse signal. A predetermined frequency band of the pulse signal is fixed or approximated to the predetermined frequency band, and the driving frequency of the pulse signal is changed within the frequency band to discharge the liquid.
[0010]
According to such a method, the ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point by the pulse signal generated by the pulse signal generation unit is determined by the pulse signal. Each of the liquids of the continuously discharged liquid droplet group is discharged by discharging the liquid by changing the driving frequency of the pulse signal within the frequency band so as to be constant or approximate to a predetermined frequency band. The ejection amount of the droplet can be stabilized in a wide frequency band of the pulse signal.
[0011]
In addition, a liquid ejection device according to the present invention includes a nozzle member having a liquid ejection hole for ejecting liquid, a member forming a liquid flow path formed corresponding to the liquid ejection hole, And a discharge energy generating means for generating energy for discharging the liquid in the liquid flow path from the liquid discharge holes as liquid droplet groups, and a pulse signal generating means for generating a pulse signal to be supplied to the discharge energy generating means. Means, and a negative pressure generating means for applying a negative pressure to the liquid in the liquid flow path to prevent the liquid from leaking spontaneously from the liquid discharge hole. The ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point is fixed or approximated to a predetermined frequency band of the pulse signal, and the frequency band is Inside The driving frequency of the pulse signal is obtained as a variable to perform discharge of the liquid.
[0012]
With such a configuration, the ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point by the pulse signal generated by the pulse signal generation unit is determined by the pulse signal. The liquid droplets are ejected continuously by making the driving frequency of the pulse signal variable and ejecting the liquid within the frequency band so as to be constant or close to a predetermined frequency band. Can be stabilized for a wide frequency band of the pulse signal.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing an embodiment of a liquid discharging method according to the present invention. This liquid discharge method discharges liquid in a liquid flow path from a liquid discharge hole as a continuous droplet group. In FIG. 1, a nozzle 20 for discharging ink is formed on a nozzle member 19 described later, A heating element 18 is provided in an ink flow path 21 formed corresponding to the nozzle 20. In such a state, a pulse signal is supplied to the heating element 18 to discharge the ink in the ink flow path 21 from the nozzle 20 as a continuous ink droplet group 30, 30,.
[0014]
Here, in the liquid discharging method according to the present invention, the ink droplet groups 30, 30,... Which are continuously discharged from the nozzle 20 toward one impact point on the recording paper P by a continuous pulse signal. The ejection amount of each droplet is constant or approximated to a predetermined frequency band of the pulse signal, and the ink is ejected by changing the driving frequency of the pulse signal within the frequency band.
[0015]
That is, the replenishment of the ink into the flow path 21 is to replenish the same amount of liquid as the ejection amount of the ink droplet 30 ejected from the nozzle 20 in the predetermined frequency band of the pulse signal. Further, the negative pressure applied to the liquid in the ink flow path 21 is set so that the surface (meniscus) of the liquid in the nozzle 20 is not returned to the liquid flow path side in the predetermined frequency band of the pulse signal. A specific configuration for realizing this will be described later in detail.
[0016]
FIG. 2 is a partially cutaway perspective view showing a specific embodiment of an ink jet printer as an apparatus directly used for implementing the liquid discharging method according to the present invention. This ink-jet printer forms a print image by forming liquid ink into particles, discharging the ink droplets from a discharge unit as ink droplets, and depositing the ink droplets on a recording paper (recording medium) P. Inside, a paper tray 2, paper feeding means 3, paper feeding means 4, an electric circuit section 5, and a print head 6 are provided.
[0017]
The housing 1 is a box-shaped body housing components of an ink jet printer and has, for example, a rectangular parallelepiped shape. One end face is provided with a tray entrance 1a for mounting a paper tray 2 described later, Is provided with a paper discharge port 1b for discharging the printed recording paper P '. A paper tray 2 is housed inside the housing 1. The paper tray 2 is capable of accommodating a plurality of sheets of, for example, A4 size recording paper P, and the leading end thereof lifts the recording paper P upward. The paper tray 2 can be mounted in the housing 1 from a tray entrance 1a provided on one end surface of the housing 1.
[0018]
A paper feeding unit 3 is provided above the leading end of the paper tray 2 housed in the housing 1. The paper feed unit 3 supplies the recording paper P stored in the paper tray 2 to a paper feed unit 4 described later, and includes a paper feed roller 7 and a paper feed motor 8. The paper feed roller 7 is formed, for example, in a substantially semi-cylindrical shape, and supplies only the topmost recording paper P among the recording papers P stored in the paper tray 2 in the direction of the paper feeding means 4. It has become. The paper feed motor 8 rotates the paper feed roller 7 by a gear (not shown), and is disposed, for example, above the paper feed roller 7.
[0019]
A paper feeding means 4 is provided below a print head 6 described later in a direction in which the paper feeding means 3 supplies the recording paper P. The paper feed unit 4 conveys the recording paper P supplied from the paper feed unit 3 toward the paper discharge port 1 b provided on the other end surface of the housing 2. , A paper feed guide 10 and a second paper feed roller 11. The first paper feed roller 9 conveys the recording paper P supplied from the paper feeding means 3 to a paper feed guide 10 described later, and sandwiches the recording paper P between a pair of upper and lower roller members that are in contact with each other. It is designed to rotate. The paper feed guide 10 guides the recording paper P conveyed from the first paper feed roller 9 to the second paper feed roller 11 described later, and is formed in a flat plate shape. Are arranged at a predetermined interval below. Further, the second paper feed roller 11 transports the recording paper P guided by the paper feed guide 10 to the paper discharge port 1b provided on the other end surface of the housing 2, and a pair of upper and lower contacts which are in contact with each other. The recording paper P is rotated between roller members.
[0020]
Further, an electric circuit section 5 is disposed above the paper tray 2. The electric circuit unit 5 controls the operation of the paper feed unit 3 and the paper feed unit 4 and outputs a pulse signal for discharging ink from a discharge unit (not shown) arranged on a print head 6 described later. It constitutes a pulse signal generating means for generating, and includes, for example, a power supply for generating a continuous pulse signal, an arithmetic device such as a CPU, a memory for storing various correction data, and the like.
[0021]
A print head 6 is provided above the paper feeding means 4. The print head 6 forms a print image by ejecting liquid ink into fine particles and spraying the ink droplets on the recording paper P. The number of ink droplets constitutes a print image. It has a PNM modulation function of expressing gradation by changing the size of the diameter of (pixel), and accommodates, for example, four color inks of yellow Y, magenta M, cyan C, and black K. Further, a line head (see FIG. 3) for ejecting the four colors of YMCK ink is provided for each color. In the following description, the print head 6 is described as a line type in which a head chip having a discharge unit (not shown) for discharging ink is arranged corresponding to the entire width of the recording paper P.
[0022]
FIG. 3 is an explanatory diagram showing the structure of the line head 12 for one color provided in the print head 6 shown in FIG. The line head 12 discharges ink of each color into fine particles and discharges the ink. A discharge unit (nozzle) for discharging ink droplets is disposed so as to face downward. As shown, the recording paper P is covered by an outer casing 13 having a length corresponding to the entire width of the recording paper P shown in FIG. The electric wiring 14 is connected to the electric circuit unit 5 shown in FIG. 2 and receives a continuous pulse signal generated by the electric circuit unit 5 so as to supply the pulse signal to a head chip 17 described later. Has become. As shown in FIG. 3B, a linear head frame 15 is provided on the bottom surface of the line head 12, and a slit-shaped ink supply extending in the longitudinal direction of the head frame 15 is provided. On the left and right sides of the hole 16, a plurality of head chips 17, 17,... On the bottom surface of each head chip 17, a large number of heating elements 18 for generating energy for discharging ink from nozzles 20 described later are arranged.
[0023]
Also, sheet-shaped nozzle members 19 are provided on the bottom surfaces of the head chips 17, 17,... The nozzle member 19 is provided with a nozzle 20 for discharging liquid ink, and is formed by, for example, electroforming of nickel, and is subjected to corrosion-resistant plating with palladium, gold, or the like to prevent corrosion by the ink. . A large number of nozzles 20 are formed in the nozzle member 19 along the longitudinal direction. The nozzles 20 serve as liquid ejection holes for ejecting liquid ink, and are one-to-one with a large number of heating elements 18 provided on each of the head chips 17 arranged alternately on the bottom surface of the line head 12. It is formed at the corresponding position. Here, it is assumed that the nozzles 20 are arranged such that the print resolution of a print image formed on the recording paper P ′ shown in FIG. 2 is, for example, 600 dpi.
[0024]
The cross-sectional structure of such a line head 12 will be described with reference to FIGS. FIG. 4 is a sectional view taken along line AA of FIG. 3B, and FIG. 5 is a sectional view taken along line BB of FIG. 3B. As shown in FIG. 4 or 5, an ink flow path 21 is formed at a position corresponding to the nozzle 20 (see FIG. 3B) formed on the sheet-shaped nozzle member 19. The ink flow path 21 supplies the ink in the ink supply hole 16 (see FIG. 3B) to an ink liquid chamber 22 formed between the head chip 17 and the nozzle member 19, and a barrier described later. It is constituted by a layer 26. As shown in FIG. 4, a spring member 23 is provided between the outer casing 13 (see FIG. 3A) and the bag member 24 containing the ink. The spring member 23 serves as a negative pressure generating means for applying a negative pressure to the ink replenished in the ink flow path 21 to prevent the ink from leaking from the nozzle 20 spontaneously. It is designed to spread. The spring member 23 can freely set the negative pressure applied to the ink in the ink flow path 21 by the strength of the force for expanding the bag member 24 outward.
[0025]
In FIG. 4 or FIG. 5, reference numeral 25 denotes a filter for filtering dust and agglomerates of ink components mixed in the ink stored in the bag member 24, and is attached so as to cover the ink supply holes 16. ing. The filter 25 prevents dust and the like mixed in the ink from dropping to the ink supply hole 16 side, so that clogging of the nozzle 20 can be prevented.
[0026]
FIG. 6 is an enlarged view of a main part of the line head 12 shown in FIG. The heating elements 18 (see FIG. 3B) are formed on the bottom surfaces of the left and right head chips 17 as described above. The heating element 18 serves as an ejection energy generating means for generating energy for ejecting the ink replenished in the ink flow path 21 from the nozzle 20 as an ink droplet group, and is provided on the bottom side of the head chip 17 made of silicon. It is formed by performing a semiconductor process, and is provided so as to be arranged at a position facing the nozzle 20 in the ink flow path 21.
[0027]
Further, a barrier layer 26 having a predetermined thickness H is provided between the head chip 17 and the nozzle member 19. The barrier layer 26 is a member constituting the ink flow path 21 formed corresponding to the nozzle 20 and, as shown in FIG. The heating element 18 is arranged between the comb teeth 26a, 26a,. The thickness H of the barrier layer 26 is the height H of the ink flow path 21 (see FIG. 6). As described above, when the nozzles 20 formed in the nozzle member 19 are arranged so as to have a resolution of 600 dpi, the comb teeth 26a of the comb-shaped barrier layer 26 have approximately 42 comb teeth. .. 3 μm. In addition, as shown in FIG. 7, the tip side of the comb teeth 26 a of the comb-shaped barrier layer 26 becomes an opening for replenishing the ink into the ink flow path 21.
[0028]
Then, as shown in FIG. 6, a pulse signal is generated by the electric circuit section 5 (see FIG. 2), so that the heat generating element 18 formed on the bottom surface of the head chip 17 generates heat and replenishes the ink flow path 21. The ink thus heated is heated to generate bubbles, whereby ink having the same volume as the bubbles is pushed out, and the ink droplets 30 are ejected from the nozzles 20. Then, as shown by an arrow J, the ink is replenished from the ink supply hole 16 into the ink flow path 21, the heating element 18 is cooled, and the bubbles disappear by cooling.
[0029]
In addition, by generating a continuous pulse signal in the electric circuit unit 5 (see FIG. 2) and supplying the pulse signal to the heating element 18 (see FIG. 6), as shown in FIG. The ink in 21 is ejected from the nozzle 20 toward one dot D on the recording paper P as a continuous ink droplet group 30, 30,. The ink droplet groups 30, 30,... Discharged on the recording paper P spread in the direction of arrow S to form one dot D, as shown in FIG. At this time, by increasing or decreasing the number of times of generation of the pulse signal to increase or decrease the number of the ink droplets 30 ejected from the nozzle 20, the size of the diameter of the dot D attached to the recording paper P is changed, Can be expressed.
[0030]
Here, in the liquid discharge apparatus according to the present invention, as shown in FIG. 1, each liquid of a liquid droplet group continuously discharged from the liquid discharge hole toward one impact point by the continuous pulse signal is used. The ejection amount of the droplet is fixed or approximated to a predetermined frequency band of the pulse signal, and the driving frequency of the pulse signal is changed within the frequency band to eject the liquid.
[0031]
Specifically, the ink flow path 21 shown in FIG. 6 has an opening on the side of replenishing the ink in the ink flow path 21 with an ink droplet ejected from the nozzle 20 in a predetermined frequency band of the pulse signal. Are formed at a height that allows replenishment of the same amount of ink as the ejection amount of the groups 30, 30,. For example, the height of the ink flow path 21, that is, the height H of the barrier layer 26 is set to 11 μm.
[0032]
Here, the reason why the height H of the ink flow path 21 is formed to be 11 μm will be described with reference to FIGS. FIG. 8 is a graph showing the relationship between the driving frequency of the pulse signal and the ink ejection amount when the height H of the ink flow path 21 shown in FIG. 6 is formed at 11 μm. FIG. 9 is a graph showing the relationship between the driving frequency of the pulse signal and the ink ejection amount when the height H of the ink flow path 21 is 7 μm. 8 and 9, the negative pressure of the spring member 23 shown in FIG. ₂ The ink discharge amount characteristic at O is indicated by a circle (丸), and the negative pressure of the spring member 23 is −60 mmH. ₂ The ink ejection amount characteristic at the time of O is indicated by a square mark (□), and the negative pressure of the spring member 23 is −30 mmH. ₂ A triangular mark (△) shows the ink discharge amount characteristic at the time of O.
[0033]
As shown in FIG. 8, when the height H of the ink flow path 21 (see FIG. 6) is formed to be 11 μm, the ejection frequency of the pulse signal from the nozzle 20 is set to a wide frequency band of about 1 KHz to 10 KHz. The discharge amount of the ink droplet to be discharged can be constant or approximated. On the other hand, as shown in FIG. 9, when the height H of the ink flow path 21 is 7 μm, the ink ejection amount decreases as the driving frequency of the pulse signal becomes higher than, for example, 5 KHz. There is a tendency. This is because when the height H of the ink flow path 21 shown in FIG. 6 is as low as 7 μm, when the driving frequency of the pulse signal is high, the ejection amount of the ink droplet ejected from the nozzle 20 is the same. This is because it is difficult for the liquid to be refilled into the ink flow path 21 again. In this case, the amount of ink that is replenished in the ink flow path 21 is reduced again, so that the ink ejection amount is reduced as compared with the case where the driving frequency of the pulse signal is lower than 5 KHz. Therefore, it is desirable that the height H of the ink flow path 21 be high, for example, 11 μm.
[0034]
Further, the spring member 23 shown in FIG. 4 applies a negative pressure to the ink in the ink flow path 21 so that the surface of the ink in the nozzle 20 is not returned to the ink flow path 21 in the predetermined frequency band of the pulse signal. The size is set. For example, the negative pressure of the spring member 23 is -30 mmH ₂ Set to O.
[0035]
Here, the negative pressure of the spring member 23 is set to -30 mmH. ₂ The reason for setting O will be described with reference to FIGS. 10 and 11. FIG. 10 shows that the negative pressure of the spring member 23 shown in FIG. ₂ 9 is a graph illustrating a relationship between a driving frequency of a pulse signal and an ink ejection amount when set to O; FIG. 11 shows that the negative pressure of the spring member 23 is -150 mmH. ₂ 9 is a graph illustrating a relationship between a driving frequency of a pulse signal and an ink ejection amount when set to O; In FIGS. 10 and 11, the triangular mark (△) shows the ink ejection amount characteristics when the height H of the ink flow path 21 shown in FIG. 6 is 7 μm, and the height H of the ink flow path 21 is 11 μm. The ink ejection amount characteristics when formed are indicated by square marks (□).
[0036]
As shown in FIG. 10, the negative pressure of the spring member 23 (see FIG. 4) is reduced to -30 mmH. ₂ When O is set and the height H of the ink flow path 21 is 11 μm, the driving frequency of the pulse signal is about 1 KHz to 10 KHz. The discharge amount can be constant or approximated. On the other hand, as shown in FIG. 11, the negative pressure of the spring member 23 (see FIG. 4) is reduced by -150 mmH. ₂ When set to O, regardless of whether the height H of the ink flow path 21 is set to 7 μm or 11 μm, as the driving frequency of the pulse signal becomes lower than 5 KHz, for example, The ink ejection amount tends to decrease. This is because the negative pressure of the spring member 23 shown in FIG. ₂ This is because if the driving frequency of the pulse signal is low, the surface of the ink in the nozzle 20 is easily pulled back to the ink flow path 21 when the driving frequency of the pulse signal is low. In this case, the amount of ink that is replenished into the ink flow path 21 is reduced again, and therefore, the ink ejection amount is reduced as compared with the case where the driving frequency of the pulse signal is higher than 5 KHz. Therefore, the negative pressure of the spring member 23 is reduced, for example, -30 mmH ₂ It is desirable to set to O.
[0037]
In the above description, the height H of the ink flow path 21 is set to 11 μm, and the negative pressure of the spring member 23 is set to −30 mmH. ₂ Although described as being set to O, the present invention is not limited to this, and the height H of the ink flow path 21 is determined by the ink liquid ejected from the nozzle 20 in a predetermined frequency band (high frequency side) of the pulse signal. The height may be any height as long as the same amount of ink as the ejection amount of the droplet groups 30, 30,. Specifically, it is determined by the relationship between the width of the ink flow path 21 shown in FIG. 7 and the interval between the comb teeth 26a formed on the comb-shaped barrier layer 26, that is, the flow path resistance. Therefore, in order to increase the printing resolution, when the interval between the comb teeth 26a of the barrier layer 26 is further narrowed, it is necessary to make the channel shape such that the channel resistance does not increase. As one method, the height H of the ink flow path 21 may be increased. The negative pressure of the spring member 23 is -30 mmH ₂ The size is not limited to O, and may be set to a size such that the surface (meniscus) of the ink in the nozzle 20 does not return to the ink flow path 21 side in a predetermined frequency band (low frequency side) of the pulse signal.
[0038]
Next, the operation of the ink jet printer as the liquid ejection device thus configured will be described. First, in FIG. 2, the recording paper P stored in the paper tray 2 is supplied by the paper feeding means 3 in the direction of the paper feeding means 4 and passes below the print head 6. At this time, the print head 6 ejects the four colors of YMCK ink as ink droplets from the ejection unit (see FIG. 3B), and forms a print image on the recording paper P. The printed recording paper P ′ is discharged from a discharge port 1 b provided on the other end surface of the housing 2.
[0039]
Here, the operation of the print head 6 will be described. First, as shown in FIG. 6, ink is replenished in the ink flow path 21 formed corresponding to the nozzle 20, and a continuous pulse signal is generated by the electric circuit unit 5 (see FIG. 2). The heat is supplied to the heating element 18 provided in the flow path 21, and the heating element 18 repeatedly generates heat. Thus, as shown in FIG. 1, the ink in the ink flow path 21 is ejected from the nozzles 20 as ink droplet groups 30, 30,.
[0040]
As described above, the height H of the ink flow path 21 is formed, for example, at 11 μm. As a result, as shown by arrow J, the same amount of liquid as the amount of ink droplets ejected from the nozzle 20 in the predetermined frequency band (high frequency side) of the continuous pulse signal Is replenished again. The negative pressure of the spring member 23 is, for example, -30 mmH. ₂ Set to O. Thereby, the surface of the liquid in the nozzle 20 is moved toward the ink flow path 21 in a predetermined frequency band (low frequency side) of the continuous pulse signal by the negative pressure applied to the ink in the ink flow path 21 by the spring member 23. Can be prevented from being pulled back.
[0041]
Therefore, the ejection amount of each ink droplet of the ink droplet groups 30, 30,... Continuously ejected from the nozzle 20 toward one dot D by the continuous pulse signal is determined by the wide frequency band of the pulse signal. Can be quantified to be constant or close thereto. Specifically, as shown by a triangle (△) in FIG. 8, the ejection amount of each ink droplet 30 is constant or approximately equal to a predetermined frequency band (for example, about 1 KHz to 10 KHz) of the pulse signal. (E.g., 5 to 4.8 picoliters). Then, the liquid can be ejected by varying the driving frequency of the pulse signal within the wide frequency band. From this, it is possible to arbitrarily set the drive frequency of the continuous pulse signal, and to distribute and print the pulse signal to be supplied to the heating element 18 (see FIG. 3B) provided in the nozzle 20. An image can be formed. In this case, the voltage of the power supply that supplies power to each heating element 18 does not fluctuate, the ejection amount of ink droplets ejected from each nozzle 20 can be stabilized, and good gradation printing can be performed. Thus, a high quality print image can be formed.
[0042]
In addition, since the driving frequency of the continuous pulse signal can be set arbitrarily, it is not affected by variations in individual products in the manufacturing process of the print head, or changes in temperature during use, and the like. The ejection amount of the ejected ink droplets can be stabilized, and a high-quality print image can be formed by performing favorable gradation recording.
[0043]
In the above description, an example applied to an ink jet printer has been described.However, the present invention is not limited to this, and any liquid that discharges a liquid in a liquid flow path from a liquid discharge hole as a droplet group may be used. Such a thing may be used. For example, the present invention is also applicable to an image forming apparatus such as a facsimile apparatus or a copying machine of which the recording method is an ink jet method. Further, the present invention can be applied to an apparatus for discharging a DNA-containing solution for detecting a biological sample.
[0044]
Although the print head has been described as a line type print head, the present invention is not limited to this, and is applicable to a serial type print head. Further, the liquid discharged from the liquid discharge holes is not limited to ink, and may be any liquid that discharges the liquid in the liquid flow path as a group of droplets.
[0045]
Furthermore, although the spring member 23 has been described as being a negative pressure generating means for applying a negative pressure to the ink in the ink flow path 21, the present invention is not limited to this. Any material may be used as long as it prevents natural leakage, and for example, it may be based on the arrangement position of the bag member 24 for storing ink and the ink supply hole 16. The heating element 18 has been described as a discharge energy generating unit that discharges the ink droplets from the discharge unit. However, the present invention is not limited to this. It may be of a mechanical conversion type or the like, and may be formed into fine particles and discharged.
[0046]
【The invention's effect】
Since the present invention is configured as described above, according to the liquid discharge method according to the first aspect, the liquid is continuously discharged from the liquid discharge hole toward one impact point by the pulse signal generated by the pulse signal generating means. The ejection amount of each droplet of the droplet group to be ejected is fixed or approximated to a predetermined frequency band of the pulse signal, and the driving frequency of the pulse signal is varied within the frequency band to eject the liquid. By doing so, it is possible to stabilize the ejection amount of each droplet of the continuously ejected droplet group in a wide frequency band of the pulse signal. Therefore, the driving frequency of the pulse signal can be set arbitrarily, and by forming the print image by dispersing the pulse signal, it is possible to perform good gradation recording and form a high-quality print image. In addition, it is possible to quantify the ejection amount of each droplet of a continuously ejected droplet group without being affected by variations in individual products in a manufacturing process of a print head or a temperature change during use. It is possible to form a high quality print image by performing good gradation recording.
[0047]
According to the second aspect of the present invention, the replenishment of the liquid into the liquid flow path is performed by the same amount of liquid discharged from the liquid discharge hole in the predetermined frequency band of the pulse signal. By replenishing, it is possible to quantify the ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one dot with respect to the frequency band on the high frequency side of the pulse signal. it can.
[0048]
Further, according to the third aspect of the present invention, the negative pressure applied to the liquid in the liquid flow path is such that the surface of the liquid in the liquid ejection hole is not returned to the liquid flow path side in the predetermined frequency band of the pulse signal. With the size, the ejection amount of each droplet of a droplet group continuously ejected from the liquid ejection hole toward one dot is quantified with respect to the frequency band on the low frequency side of the pulse signal. Can be.
[0049]
According to the fourth aspect of the invention, the liquid droplet group discharged from the liquid discharge hole is extruded and discharged by heating the liquid in the liquid flow path to generate bubbles. By increasing or decreasing the number of times the pulse signal is generated, the number of droplet groups continuously ejected from the liquid ejection hole toward one dot is increased or decreased, and the size of the dot diameter of the recording paper is changed. Can be expressed in gradation.
[0050]
Further, according to the liquid ejecting apparatus of the fifth aspect, each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point by the pulse signal generated by the pulse signal generating means. The discharge amount of the pulse signal is made constant or approximated to a predetermined frequency band of the pulse signal, and the drive frequency of the pulse signal is changed within the frequency band to discharge the liquid, whereby the continuous It is possible to stabilize the ejection amount of each droplet of the droplet group which is ejected in a wide frequency band of the pulse signal. Therefore, it is possible to arbitrarily set the drive frequency of the continuous pulse signal, and to form a print image by dispersing the pulse signal, thereby forming a good gradation record and forming a high-quality print image. Can be. In addition, it is possible to quantify the ejection amount of each droplet of a continuously ejected droplet group without being affected by variations in individual products in a manufacturing process of a print head or a temperature change during use. It is possible to form a high quality print image by performing good gradation recording.
[0051]
Further, according to the invention according to claim 6, the member constituting the liquid flow path replenishes the same amount of liquid as the amount of liquid droplets discharged from the liquid discharge holes in the predetermined frequency band of the pulse signal. By being formed at a possible height, the ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one dot can be adjusted to the frequency band on the high frequency side of the pulse signal. Can be quantified.
[0052]
Still further, according to the invention as set forth in claim 7, the negative pressure generating means applies a negative pressure to the liquid in the liquid flow path to the surface of the liquid in the liquid discharge hole in a predetermined frequency band of the pulse signal. Is set so as not to be drawn back to the liquid flow path side, so that the ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one dot is determined by a pulse signal. Can be quantified with respect to the frequency band on the low frequency side.
[0053]
According to the invention according to claim 8, the discharge energy generating means heats the liquid in the liquid flow path to generate bubbles, thereby extruding the liquid from the liquid discharge holes and discharging the liquid. By increasing or decreasing the number of times the pulse signal is generated, the number of droplet groups continuously ejected from the liquid ejection hole toward one dot is increased or decreased, and the size of the dot diameter of the recording paper is changed. Can be expressed in gradation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of a liquid ejection method according to the present invention, and shows a state in which ink in an ink flow path is ejected from an ejection unit as an ink droplet group.
FIG. 2 is a partially cutaway perspective view showing a specific embodiment of an ink jet printer as an apparatus directly used for implementing a liquid discharging method according to the present invention.
3A and 3B are explanatory diagrams showing the structure of a line head for one color provided in the print head shown in FIG. 2, wherein FIG. 3A is a plan view and FIG. 3B is a bottom view.
FIG. 4 is a sectional view taken along line AA of FIG. 3 (b).
FIG. 5 is a sectional view taken along line BB of FIG. 3 (b).
FIG. 6 is an enlarged view of a main part of the line head shown in FIG. 4;
7 is an exploded perspective view showing a structure of an ink flow path formed corresponding to the ejection unit shown in FIG.
8 is a graph showing a relationship between a driving frequency of a pulse signal and an ink ejection amount when the height of the ink flow path shown in FIG. 6 is formed to be 11 μm.
9 is a graph showing a relationship between a driving frequency of a pulse signal and an ink ejection amount when the height of the ink flow path shown in FIG. 6 is formed to 7 μm.
FIG. 10 shows that the negative pressure of the spring member shown in FIG. ₂ 6 is a graph showing a relationship between a driving frequency of a pulse signal and an ink ejection amount when the value is set to O.
FIG. 11 shows that the negative pressure of the spring member shown in FIG. ₂ 6 is a graph showing a relationship between a driving frequency of a pulse signal and an ink ejection amount when the value is set to O.
[Explanation of symbols]
1 ... housing
2. Paper tray
3. Paper feeding means
4: Paper feeding means
5. Electric circuit
6 ... Print head
12 ... Line head
13 ... outer casing
14 ... Electrical wiring
15 ... Head frame
16 ... Ink supply hole
17 ... Head chip
18. Heating element
19 ... Nozzle member
20 ... Discharge unit
21 ... Ink flow path
22 ... Ink liquid chamber
23 ... Spring member
24 ... bag member
26 ... Barrier layer
30 ... Ink droplet

Claims (8)

Replenish the liquid in the liquid flow path formed corresponding to the liquid discharge hole for discharging the liquid,
By applying a negative pressure to the liquid in the liquid flow path to prevent the liquid from leaking spontaneously from the liquid ejection holes,
A liquid discharge method for supplying a pulse signal to a discharge energy generating means provided in the liquid flow path and discharging the liquid in the liquid flow path from the liquid discharge holes as a continuous droplet group,
The ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point by the pulse signal is fixed or approximated to a predetermined frequency band of the pulse signal. And discharging the liquid by changing the driving frequency of the pulse signal within the frequency band. 2. The liquid replenishing method according to claim 1, wherein the replenishment of the liquid in the liquid flow path is performed by replenishing the same amount of liquid as the amount of liquid droplets discharged from the liquid discharge hole in a predetermined frequency band of the pulse signal. The liquid discharging method according to the above. 2. The liquid supply apparatus according to claim 1, wherein the negative pressure applied to the liquid in the liquid flow path is such that the surface of the liquid in the liquid discharge hole is not pulled back to the liquid flow path side in a predetermined frequency band of the pulse signal. The liquid discharging method according to the above. 2. The liquid discharging method according to claim 1, wherein the liquid droplet group discharged from the liquid discharging hole is extruded and discharged by heating the liquid in the liquid flow path to generate bubbles. A nozzle member having a liquid ejection hole for ejecting liquid,
A member forming a liquid flow path formed corresponding to the liquid ejection hole,
A discharge energy generating unit that is provided in the liquid flow path and generates energy for discharging the liquid in the liquid flow path from the liquid discharge hole as a droplet group;
Pulse signal generating means for generating a pulse signal for supplying to the ejection energy generating means;
Negative pressure generating means for applying a negative pressure to the liquid in the liquid flow path to prevent the liquid from leaking spontaneously from the liquid ejection hole,
A liquid ejection device comprising:
The ejection amount of each droplet of the droplet group continuously ejected from the liquid ejection hole toward one impact point by the pulse signal is fixed or approximated to a predetermined frequency band of the pulse signal. A liquid discharge device for discharging a liquid by changing a drive frequency of a pulse signal within the frequency band. The member constituting the liquid flow path is formed at a height capable of replenishing the same amount of liquid as the discharge amount of the liquid droplet discharged from the liquid discharge hole in a predetermined frequency band of the pulse signal. The liquid ejecting apparatus according to claim 5, wherein: The negative pressure generating means sets a negative pressure applied to the liquid in the liquid flow path to a size such that the surface of the liquid in the liquid ejection hole is not pulled back to the liquid flow path side in a predetermined frequency band of the pulse signal. The liquid ejecting apparatus according to claim 5, wherein the liquid ejecting apparatus is used. 6. The liquid discharge apparatus according to claim 5, wherein the discharge energy generating means heats the liquid in the liquid flow path to generate bubbles, thereby extruding the liquid from the liquid discharge holes to discharge the liquid. .

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