JP2003260796A - Inkjet recording head and image recorder using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording head which prevents large effects on discharge characteristics of nozzle openings even when an end of a common ink chamber is tapered. <P>SOLUTION: The common ink chamber 26 sets a reduced region 36 having a sectional area reduced more than that of the other region at the end. An ink supply path 27 communicating with the region has at least one of a sectional area and a length made different from that of a plurality of ink supply paths of the same shape which communicate with the other region. Accordingly, an inertance of the ink supply path 27 communicating with the end of the common pressure chamber 26 is set to be smaller than that of ink supply paths communicating with the other region, whereby an ink pressure resonance period of time in each of all separate pressure generation chambers 20 is uniformed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet image recording apparatus and an inkjet recording head used as an inkjet printer or an inkjet plotter.

[0002]

2. Description of the Related Art In a conventional recording head, a plurality of pressure generating chambers having nozzle openings are formed side by side, and a long and narrow common ink chamber is formed along the arrangement direction of these pressure generating chambers. A structure in which an ink supply path communicates with the generation chamber, a pressure generation element is provided in each pressure generation chamber via a vibration plate, and ink droplets are ejected from a nozzle opening due to pressure fluctuations in the pressure generation chamber caused by the pressure generation element. Take. The common ink chamber has a tapered shape by narrowing the channel width at the left and right ends that are farthest from the ink supply pipe that supplies the ink to the common ink chamber. This is to eliminate residual air bubbles when filling ink or cleaning by suction from nozzle openings.

A large compliance is given by partitioning one surface of the common ink chamber with an elastic film. This is to absorb the pressure of the ink flowing back from the ink supply path when ejecting the ink, and to quickly supply the ink to each pressure generating chamber.

[0004]

[Patent Document 1] JP-A-6-297701

[Patent Document 2] Japanese Unexamined Patent Publication No. 9-057961

[Patent Document 3] Japanese Unexamined Patent Publication No. 9-099557

[0005]

However, in the above-described conventional recording head, even if the pressure generating element is driven under the same conditions, the end portions of the common ink chamber (the end portions far from the ink supply tube) communicate with each other. A phenomenon occurs in which the ejection characteristics of the ink droplets ejected from the nozzle openings of the existing pressure generating chamber differ from the ejection characteristics of the other nozzle openings, and the variation range is about + -15% of the target value. It is presumed that such a phenomenon causes a pressure loss at the end of the common ink chamber and a negative pressure at the inlet of the ink supply passage. Then, in order to eliminate this, it is conceivable to increase the compliance of the common ink chamber, but the end of the common ink chamber needs to be tapered in order to enhance the bubble elimination property, so the compliance portion is simply It is difficult to expand. Also, there is a tendency to increase the number of nozzles per row due to demands such as higher image recording speed and larger recording objects, but the amount of ink to be removed when the cleaning pump is enlarged and bubble discharge capacity is increased. Therefore, it is unavoidable to taper the tip of the common ink chamber.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to have an ink jet recording head having a plurality of nozzle openings and capable of achieving uniform discharge characteristics of each of these nozzle openings. An object is to provide an image recording device using this recording head.

[0007]

In order to achieve the above-mentioned object, according to a first aspect of the present invention, a plurality of pressure generating chambers having nozzle openings are formed side by side and a common ink is provided on one side of these pressure generating chambers. A chamber is formed, and a common ink chamber and each pressure generating chamber are connected by an ink supply path,
An ink jet that has a pressure generating element corresponding to each pressure generating chamber, connects an ink supply pipe to the common ink chamber, and discharges ink in the pressure generating chamber from a nozzle opening due to pressure fluctuation in the pressure generating chamber caused by the pressure generating element. In the ink-jet recording head, among the ink supply passages, the ink supply passage communicating near the end of the common ink chamber is compared with the plurality of ink supply passages having the same shape communicating outside the vicinity of the end of the common ink chamber. The inkjet recording head is characterized in that at least one of the sectional area and the length is different.

According to a second aspect of the present invention, the pressure generating chambers are formed so that the longitudinal direction is the arrangement direction of the pressure generating chambers, the ink supply pipe communicates with the substantially center of the longitudinal direction, and the ink supply pipes communicate with the vicinity of both ends of the common ink chamber. 2. The ink supply path to be formed is different in at least one of the cross-sectional area and the length from the ink supply path communicating with the other part of the common ink chamber. Is an inkjet recording head.

According to a third aspect of the present invention, in the vicinity of the end portion of the common ink chamber is a throttle area having a reduced cross-sectional area as compared with other portions, and the ink jet apparatus according to the first or second aspect. It is a recording head.

According to a fourth aspect of the present invention, the damping coefficient Mn / Rn of the ink supply path communicating with the vicinity of the end of the common ink chamber is provided.
4. The ink jet recording head according to any one of claims 1 to 3, wherein the value of and the value of the attenuation coefficient Mn / Rn of the ink supply path communicating with the other part of the common ink chamber are made uniform. is there.

According to a fifth aspect of the present invention, there is provided the ink jet recording head according to any one of the third to fourth aspects, wherein the plurality of stages are narrowed so as to be tapered.

According to a sixth aspect of the present invention, there is provided an ink jet recording head according to any one of the first to fifth aspects, wherein a plurality of ink supply paths are provided for one pressure generating chamber. is there.

According to a seventh aspect of the present invention, the ink supply path is divided into a flow path on the nozzle opening side and a flow path on the opposite side of the nozzle opening side. The inkjet recording head described above.

According to an eighth aspect of the present invention, the volume of each pressure generating chamber is made uniform by adjusting the position of the outlet of the ink supply passage of the passage located on the nozzle opening side. The inkjet recording head described in 1.

According to a ninth aspect of the present invention, the inertance of the flow passage on the nozzle opening side and the inertance of the flow passage on the opposite side are set separately.
Alternatively, it is the inkjet recording head described in 8.

A tenth aspect of the present invention is an image recording apparatus comprising the ink jet recording head according to any one of the first to ninth aspects.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an image recording apparatus 2 using an inkjet recording head (hereinafter referred to as recording head 1). The image recording device 2 is used in a state of being connected to a computer (not shown) together with a scanner (not shown) and the like. By loading and executing a predetermined program on this computer,
The entire device functions as a recording device as a whole. In a computer, an application program operates under a predetermined operating system and displays an image on a CRT display (not shown) while performing a predetermined process on an image read from a scanner. When the application program issues a print command, the computer outputs to the image recording device 2 the image data read via the scanner, the character data input via the keyboard, and the like.

In the image recording apparatus 2, the carriage 3 is connected to the carriage motor 5 via the timing belt 4,
It is configured to be guided by the guide member 6 and reciprocate in the paper width direction of the recording paper 7. Further, the image recording apparatus 2 is also provided with a paper feed mechanism using a paper feed roller 7 '. The carriage 3 has a surface facing the recording paper 7,
That is, in this embodiment, the recording head 1 is attached to the lower surface, and the recording head 1 receives the ink from the ink cartridge 9 set in the holder 8 attached to the upper portion of the carriage 3 and receives the ink from the carriage 3. Images and characters are printed by ejecting ink droplets onto the recording paper 7 as it moves.

Further, a capping device 10 is arranged in a non-printing area (non-recording area) separated from the recording paper 7 and seals the nozzle opening of the recording head 1 during the suspension of printing. Therefore, during the suspension of printing, the capping device 10
By virtue of the sealing of the nozzle opening by means of the ink, it is possible to prevent the ink from thickening or forming an ink film. Also,
Although not shown in the drawing, the capping device 10 is connected to a pump via a suction pipe, and is sucked from a nozzle opening at the time of filling ink or cleaning, and bubbles in the ink flow path in the recording head 1 are sucked. Eliminate. Then, the wiping device 11 arranged in the vicinity of the capping device 10 is configured to wipe the surface of the recording head 1 (the lower surface with the nozzle openings) to remove the ink dregs, paper dust and the like adhering thereto. ing.

FIG. 2 is an exploded perspective view of the recording head 1 of the ink jet type image recording apparatus 2 shown in FIG. 1, FIG. 3 is a sectional view of an actuator of the recording head 1, and FIG. 4 is a flow path formation of the recording head 1. It is a plan view of the plate 12. 2 and 3
In order to manufacture the recording head 1 shown in FIG. 1, a nozzle plate 14 in which nozzle openings 13 are formed in a plurality of rows, a flow path forming plate 12 in which a pressure generating chamber 20 communicating with each of the nozzle openings 13 is formed, and a pressure are formed. After the elastic plate 21 in which the vibration regions overlapping each of the generation chambers 20 are formed in an island shape is laminated in this order to form the flow path unit 22, the flow path unit 22 is supported by the head case 24 in which the pressure generating element 23 is supported.
Then, the tip portions of the pressure generating elements 23 are brought into contact with and bonded to the respective vibration areas of the elastic plate 21, and the edge cover 25 is put on the nozzle plate 14 side.

The nozzle plate 14 is a thin plate such as a stainless plate having nozzle openings 13 having a diameter of 20 μm to 30 μm formed at a pitch corresponding to the dot formation density. Further, as shown in FIG. 4, the flow path forming plate 12 is formed by forming a through hole in a silicon substrate having a thickness of about 400 μm by wet etching or the like. The through hole allows the common ink chamber 26, This common ink chamber 2
The ink supply path 27 and the pressure generating chamber 20 are formed to be elongated from 6 to a position overlapping the nozzle opening 13 of the nozzle plate 14.

In the elastic plate 21, a stainless steel part is left as an island-shaped vibrating region (island part) 31 in a region overlapping the pressure generating chamber 20 with respect to the composite plate composed of the stainless plate 29 and the resin film 30, and this vibration is generated. Only the resin film 30 is left around the area 31. In addition, an ink supply hole 32 is formed in the elastic plate 21 in a region overlapping the common ink chamber 26.

The head case 24 has a window 3 at its tip.
3 is opened, and when the pressure generating element 23 having a plurality of comb teeth formed by fixing the base end to the stainless steel fixed substrate 34 is inserted into the head case 24, the pressure generating element 23 is placed inside the window 33. The tip part of the. An ink supply pipe 35 is formed in the head case 24.

In the recording head 1 thus constructed, when a voltage pulse is applied to the pressure generating element 23, the pressure generating element 23 bends, that is, contracts, so as to expand the volume of the pressure generating chamber 20. A negative pressure is generated in the generation chamber 20. As a result, the meniscus of the ink is
3, the ink is drawn into the inside of the nozzle 3, and the ink flows from the common ink chamber 26 into each pressure generating chamber 20 through each ink supply passage 27. On the other hand, when a discharge pulse is applied, the pressure generating element 2
3 bends, that is, extends in a direction of contracting the volume of the pressure generating chamber 20, and a positive pressure is generated in the pressure generating chamber 20. As a result, ink droplets are ejected from the nozzle openings 13. In both of these operations, the expansion and contraction of the pressure generating element 23 are transmitted via the vibration area 31 of the elastic plate 21.

The feature of the embodiment of the flow path forming plate 12 shown in FIG. 4 is that since the ink supply pipe 35 communicates with one end of the common ink chamber 26, the other far from the ink supply pipe 35. That is, the width of the ink supply path 27 communicating with the end area of the nozzle is gradually widened from the nozzle number # 4 to the nozzle number # 1. In other words, the width of the common ink chamber 26 gradually increases as it is located closer to the tip from the center side.

Since the depth of the common ink chamber 26 formed in the flow path forming plate 12 is uniform, the cross-sectional area of the inlet of the ink supply passage 27 (the supply opening corresponding to # 1 to # 4) is gradually increased. Therefore, it is possible to suppress the fluctuations in the ink speed and the ink amount that occur in the nozzle numbers # 4 to # 1.

Here, the principle will be described with reference to FIG. Mn, Ms, and Ma are inertances of the nozzle opening 13, the ink supply passage 27, and the pressure generating element 23, respectively. Rn, Rs, and Ra are nozzle openings 1 respectively.
3, resistance of the ink supply path 27 and the pressure generating element 23. Cn, Cc, and Ca are the compliances of the nozzle opening 13, the pressure generating chamber 20, and the pressure generating element 23, respectively. Us and Un are volume velocities of the inks flowing to the nozzle opening 13 side and the ink supply path 27 side, respectively. Ua is the volumetric velocity of ink generated in the pressure generating chamber 20 per unit time when the pressure generating element 23 operates. Therefore, the sum of the volume velocities Un and Us is Ua.

The vibration frequency (Fink) of the ink flowing in the pressure generating chamber 20 is expressed by the following equation. Fink = 1 / 2π · √ (Mn · Ms) / √ {Cc (M
n + ms)} In the present embodiment, Mn = 1.27 × 10 ⁸ (kg
/ M ⁴ ), Ms = 1.50 × 10 ⁸ (kg / m ⁴ ), Cc
= 2.44 × 10 ⁻²⁰ (m ⁵ / N), so the Fink
Is estimated to be about 123 kHz.

The ratio of Un to Us is determined by the ratio of the impedance Zn on the nozzle side and the impedance Zs on the ink supply side, but since the fink is very fast, it should be considered that Zn≈Mn and Zs≈Ms. You can

Therefore, Un / Us≈Mn / Ms holds, and Un / U can be adjusted by adjusting Ms of the ink supply port.
s can be controlled. The ink velocity ejected from the nozzle opening 13 is equal to the volume velocity Un (m ³ / s) /
Since it can be considered as the nozzle opening area (m ² ), U
The ink velocity can be reduced by reducing n. Similarly, the ink amount can be reduced by decreasing Un.

Ms can be expressed by the following equation. Ms = ρ × 1 / S here, ρ: Specific gravity of ink l: Length of ink supply path 27 S: sectional area of the ink supply path 27 Is.

Therefore, by increasing the cross-sectional area S of the ink supply passage 27, Ms becomes smaller, and the ink speed and the ink amount can be controlled. As described above, the same effect can be obtained even if the length of the ink supply path 27 is shortened.

Next, a second embodiment shown in FIG. 6 will be described. The feature of this second embodiment is that the ink supply pipe 3
5 is located substantially in the center with respect to the longitudinal direction of the common ink chamber 26. With such a configuration, the length from the ink supply pipe 35 to the end of the common ink chamber 26 can be reduced to about half of that in the first embodiment, and the length and cross-sectional area of the common ink chamber 26 can be changed. The problem of head loss can be avoided even if the nozzle row becomes long. In this embodiment, since the distances from the ink supply pipe 35 to the end of the common ink chamber 26 are the same, both ends have a tapered shape whose cross-sectional area gradually decreases,
The width of the ink supply path 27 communicating with the tapered end region (throttle region 36) is gradually widened from the center side toward the tip, that is, from # 4 to # 1. .

Next, a third embodiment shown in FIG. 7 will be described. The feature of this third embodiment is that the ink supply path 2
That is, a plurality of pressure generating chambers 7 are formed in one pressure generating chamber 20. In the description of the first embodiment, it is explained that the common ink chamber 26 is excellent in bubble discharging property, and the ink amount and the ink speed at the end can be corrected, but it is intended to further increase the recording speed. If the pressure generation chamber 20
It is necessary to efficiently damp the vibration of ink inside.

Generally, the damping coefficient can be expressed as Ms / Rs. Here, Rs can be expressed by the following equation. Rs = 12 × η × l / (W × t ³ ) η: Ink viscosity (Pa × s) l: Length of supply port (ink supply path 27) (m) W: Long side of supply port cross section (supply When the mouth has a rectangular cross section) t: The short side of the cross section of the feed opening (when the feed opening has a rectangular cross section).

In this embodiment, since the thickness of the flow path forming plate 12 is 200 to 500 μm and the width of the ink supply path 27 is 10 to 50 μm, as shown in the first embodiment, the ink supply is performed. If Ms is reduced in the width of the path 27, Rs is reduced in proportion to the cube of the width.

The smaller the damping coefficient Mn / Rn, the faster the ink vibration can be dampened.
With the width of 7, even if the ink speed and the ink amount can be reduced, the attenuation is deteriorated, which is an obstacle to realization of high-speed printing.

However, the third embodiment is characterized in that a plurality of ink supply passages 27 are provided for one pressure generating chamber 20, so Mn can be considered in parallel, and the ink supply passages can be considered. By adjusting the length l, width W, and depth t of 27, the damping coefficient Mn / Rn
It is possible to adjust Mn at the end portion to be small while making the same as that of the ink supply path 27 without correction.

In the above embodiment, the ink supply path 27 is used.
However, the inside of one ink supply path 27 may be divided into upper and lower parts or left and right parts so as to join in the pressure generating chamber 20.

In each of the above-described embodiments, the ink supply path 27 communicating with the common ink chamber 26 is the same as the ink supply path 27 communicating with the end of the common ink chamber 26. Compared with a plurality of ink supply passages 27 of the same shape that communicate with other portions 26 other than the above-mentioned end portions, at least one of the cross-sectional areas or the lengths is made different, whereby the ink is ejected from each nozzle opening 13. It is configured so that the discharge characteristics of the ink droplets are uniform. That is, the amount of ink supplied and the speed of ink droplets are made uniform so as to improve the recording quality. This is to communicate with the common ink chamber 26 individually, and to communicate with the pressure supply chamber 27 from the ink supply passage 27. Among the ink paths reaching the nozzle opening 13 via 20, the ink path communicating with the diaphragm area 36 has at least one of shape, length, and cross-sectional area, and the common ink other than the diaphragm area 36 has the same shape. This means that the velocity of the ink droplets ejected from each nozzle opening 13 is made uniform by making it different from that of the ink path communicating with the chamber 26. In each of the embodiments described below, the recording quality is further improved. It should be noted that, for ease of understanding, the description partially overlaps with the above-described embodiment, but will be described in detail.

The recording head 1 shown in FIGS. 8 and 9 is similar to that of the above-described embodiment in that the piezoelectric vibrator 41 is inserted into one of the storage chambers 40 of the head case 24 from one opening as a pressure generating element and combs. The tooth-shaped tip faces the other opening (window 33), the flow path unit 22 is bonded to the surface (lower surface) of the head case 24 on the opening side, and the comb-teeth-shaped tip of the piezoelectric vibrator 41 is flowed respectively. The unit 22 is roughly configured by abutting and fixing it on a predetermined portion of the unit 22.

The channel unit 22 is constructed by laminating the nozzle plate 14 and the elastic plate 21 on both sides with the channel forming plate 12 sandwiched therebetween, as in the above embodiment.

The nozzle plate 14 is a thin plate made of stainless steel in which a plurality of nozzle openings 13 are opened in a row at a pitch corresponding to the dot formation density. In this embodiment, one row is formed at a pitch of 0.141 mm (180 dpi). Five rows of 96 nozzle openings 13 are opened. The nozzle plate 14 may be integrally formed with other members such as the flow path forming plate 12.

The flow path forming plate 12 laminated on one surface of the nozzle plate 14 corresponds to the nozzle opening 13 of the nozzle plate 14 by wet etching or the like on a silicon substrate having a thickness of about 400 μm. A plurality of vacant spaces to be 20 are formed side by side in a state of being partitioned by partition walls, and a vacant space to be the common ink chamber 26 is formed along the arrangement direction of the pressure generating chambers 20.
6 is a plate-shaped member that forms an empty portion that serves as an ink supply path 27 that connects the pressure generation chamber 20 and the pressure generation chamber 20.

The common ink chamber 26 is a chamber for supplying the ink stored in the ink cartridge 9 to each of the pressure generating chambers 20, and the ink supply pipe 35 is provided substantially at the center in the longitudinal direction.
As shown in FIG. 10, a narrowed region 36 in which the cross-sectional area is narrowed by narrowing the width of the flow channel is reduced at the end portions (left and right end portions) far from the ink supply pipe 35. Set. In order to form this throttle area 36, the pressure generating chamber 2
It is formed by bending or bending the side located on the side opposite to the pressure generating chamber 20 while keeping the side on the 0 side linear and moving the side closer to the pressure generating chamber 20 side. The ink supply pipe 3
5, the left and right neighboring portions (that is, the central portion) and the aperture area 3
6 is connected with an appropriate inclination, but in the present embodiment, the side of the front portion of the throttle region 36 is inclined toward the pressure generating chamber 20 side at a steeper angle than the other portions, so that it is divided into a plurality of stages. Is forming.

The pressure generating chamber 20 is a chamber elongated in the direction orthogonal to the row of the nozzle openings 13, and a part of the chamber (on the nozzle opening 13 side) is a rectangle penetrating in the thickness direction of the flow path forming plate 12. Of the through hole 20a of the
The flow path forming plate 12 is composed of a flat concave chamber which is vertically divided by an upper and lower chamber partition wall 42 formed at the center in the thickness direction.
The pressure generating chambers 20 in the present invention are formed so that all 96 pressure generating chambers 20 have the same volume.

The ink supply passage 27 is a passage for connecting the common ink chamber 26 and each pressure generating chamber 20. In the embodiment shown in FIG. 11, the inlet 2 opened to the common ink chamber 26 side.
7a and the outlet 27b opened to the pressure generating chamber 20 side, a partition (central state portion) 43 is formed, and the flow passage width and the flow passage length are adjusted according to the dimensions of the intermediate state portion 43, whereby individual inertance is achieved. Is being adjusted. Particularly, in the present embodiment, the inlet 27 of the ink supply path 27 communicating with the throttle area 36.
The respective inertances between the a and the outlet 27b are set to be smaller than the inertances of the other ink supply passages 27 communicating with the common ink chamber 26 other than the throttle region 36, and the above-mentioned common ink chamber 26 is The ink supply path 27 located closer to the tip side is set smaller, and
The volume of the pressure generating chamber 20 that communicates with the ink supply path 27 having a small inertance is made equal to the volume of another pressure generating chamber 20 that communicates with the common ink chamber 26 other than the throttle region 36.

More specifically, the three pressure generating chambers 20A, 20 communicating with each other in the throttle area 36 shown in FIG.
Of the B and 20C, the width of the middle state portion 43A of the ink supply path 27A at the end is set to the minimum and the length is set to the minimum, and thus the inertance of the ink supply path 27A is set to the minimum, and the ink supply The width of the second middle state portion 43B located next to the road 27A from the end is set to the above-mentioned middle state portion 43.
It is made slightly wider (standard width) than A, and the length is set to the shortest, thereby setting the inertance of the ink supply passage 27B to the second smallest value.
The width of the third intermediate state portion 43C from the end located next to 7B is set to the standard width, and the length is set to be slightly longer (intermediate length) than the first and second portions. The inertance of 27C is set to the third smallest.

In this way, the dimensions of the central area 43 are changed to change the cross-sectional area of the flow path between the inlet 27a and the outlet 27b of the ink supply path 27, so that the inertance of each end portion (the tip of the narrowed region 36) is increased. ) Was set smaller, but
By aligning the position of the outlet 27b of the ink supply path 27, that is, the position of the pressure chamber side end of the central state portion 43 on the virtual straight line L1 along the arrangement direction of the pressure generating chambers 20, the volume of each pressure generating chamber 20 is reduced. I have it. Incidentally, the middle state portion 43 of the ink supply path 27 of the pressure generating chambers 20D, 20E, ... Communicating except the throttle region 36 has the same standard width as the second and third middle state portions 43B and 43C, The length is set to the same standard length as that of the third middle state portion 43C. Therefore, the inertance of these ink supply passages 27 has three pressure generating chambers 20A, 20A communicating with each other in the throttle region 36.
The value is larger than the inertance of B and 20C.

In this embodiment, the elastic plate 21 is laminated on the other surface of the flow path forming plate 12 located on the opposite side of the nozzle plate 14 as shown in FIG.
A sealing plate that seals one opening face of the common ink chamber 26, and an elastic film (thin film portion) that is laminated on the other face of the flow path forming plate 12 and seals one opening face of the common ink chamber 26. Doubles as
Polymer film 30 such as PPS on stainless plate 29
It has a laminated double structure. Since the sealing plate and the elastic film are made of the same material, the portion of the stainless plate 29 that functions as the sealing plate, that is, the portion of the stainless plate 29 that overlaps with the pressure generating chamber 20 is etched to form the piezoelectric vibrator 4.
1 for contacting and fixing the tip of 1 (island portion 3
1) is formed in an island shape, and the portion of the stainless plate 29 that functions as an elastic film, that is, the portion that overlaps the common ink chamber 26 is removed by etching to leave only the film 30 (elastic film). Then, an ink supply hole 32 (see FIG. 10) which communicates with the ink supply pipe 35 and supplies ink into the common ink chamber 26 is formed in a region overlapping the common ink chamber 26.

In the recording head 1 having the above structure, the island portion 31 is pressed toward the nozzle plate 14 by extending the piezoelectric oscillator 41 in the oscillator longitudinal direction, and the film (elastic film) around the island portion 31 is pressed. ) 30
Is deformed and the pressure generating chamber 20 contracts. Further, when the piezoelectric vibrator 41 is contracted in the vibrator longitudinal direction, the elastic film 32
The elasticity of the pressure generating chamber 20 expands. Then, ink droplets are ejected from the nozzle openings 13 by controlling expansion / contraction of the pressure generating chamber 20.

The nozzle opening 1 is operated by the operation of the capping device 10 at the time of filling ink or cleaning.
When the ink is sucked from No. 3, since the throttling regions 36 are formed at the left and right ends of the common ink chamber 26, the ink flow velocity in this portion is increased, whereby bubbles are eliminated without being caught and residual bubbles are eliminated. You can

Thus, in this embodiment, the common ink chamber 2
The end of 6 is squeezed to reduce residual air bubbles.
Even if the end of the common ink chamber 26 is narrowed, the ink supply passage 27
The discharge characteristics of the nozzle openings 13 are made uniform by adjusting (correcting) the inertance. Hereinafter, this ejection characteristic will be described.

The vibration system of this recording head 12 is shown in FIG.
This can be represented by the equivalent circuit shown in FIG. In Figure 5
And the symbol M is the inertance [Kg
/ M ^Four] And Ma is the inertia in the piezoelectric vibrator 41.
Stance, Mn is inertance at the nozzle opening 13,
Ms is inertance in the ink supply path 27.
The symbol R is the resistance [N · s /
m^Five], And Rn is a register at the nozzle opening 13.
The resistance Rs is the resistance in the ink supply path 27.
is there. The symbol C is the volume change per unit pressure
Alliance [m ^Five/ N], and Cc is the pressure generation chamber 20.
Compliance, Ca is the
Compliance, Cn is the nozzle plate 14
Iansu. The symbol P indicates that the piezoelectric vibrator 41 has been aged.
Generated pressure, in other words, applied to the piezoelectric vibrator 41.
The voltage pulse is converted into an equivalent pressure.

The compliance Cc of the pressure generating chamber 20 mainly consists of the compliance Cs of the elastic plate 21 and the ink compliance C.ink. V is the volume of the pressure generating chamber 20, ρ is the ink density, and c is the sound velocity in the ink.
Then, the ink compliance C.ink can be expressed by the following equation (1). C.ink = V / ρ · c ² (1) Here, since ρ and c are constant, it can be expressed as C.ink = k · V (k; constant) (2) it can.

The compliance Cc of the pressure generating chamber 20 constitutes the pressure generating chamber 20, that is, the partition wall of the flow path forming plate 12, which functions as the inner wall surface of the pressure generating chamber 20, the elastic plate 21, and the nozzle plate 14. And the compliance of these pressure generating chamber 20 constituent members is C.str, this C.str is the pressure change Δ.
It is a volume change ΔV with respect to P and can be expressed as in the following equation (3). C.str = ΔV / ΔP (3) Here, among the compliance components of the recording head 1,
The proportion of the ink compliance C.ink in the pressure generating chamber 20 is made higher than the proportion of the compliance C.str of the pressure generating chamber 20 constituent members such as the partition wall and the elastic plate 21 that configure the pressure generating chamber 20. (C.ink> C.str)
And the processing accuracy of pressure generating components such as the partition walls of the flow path forming plate 12 and the elastic plate 21, especially the island portion 31 of the elastic plate 21.
It becomes difficult to be influenced by the processing condition of the above and the error of the thickness of the film 30. In other words, among the factors that determine the compliance of the recording head 1, if the ratio that depends on the compliance of the ink in the pressure generating chamber 20 is relatively increased, the ratio that depends on the machining accuracy of the recording head 1 becomes relatively large. It is possible to reduce the fluctuation of the compliance of the recording head 1.

Further, it is necessary to match the ejection characteristics of the nozzle openings 13 of the pressure generating chamber 20 connected to the throttle area 36 of the common ink chamber 26 with the ejection characteristics of the nozzle opening 13 of the pressure generating chamber 20 connected to another area. If the volume of the pressure generating chambers 20 is made constant, this can be achieved by aligning the ink pressure resonance cycle in each pressure generating chamber 20. The ink pressure resonance period Tc can be expressed by the following equation (4). Further, the inertance Ms of the ink supply path 27 can be represented by the equation (5), where ρ is the ink density, S is the cross-sectional area of the ink supply path 27, and n is the number of parallel flow paths of the ink supply port 24. , Inertance Mn and Ms are calculated in parallel using equation (6).
Can be expressed as Tc = 2π√ (MCc) ... (4) Ms = ρ.L / n.S ... (5) M = (Mn + Ms) / (Mn.Ms) ... (6) Ink pressure resonance cycle From the above formula (4), it is necessary to align the inertance and the pressure in order to align Tc. In this regard, in this embodiment, as described above, the ink supply path 27 connected to the throttle area 36 of the common ink chamber 26 has the inlet 2 of the ink supply path 27.
The inertance between 7a and the outlet 27b can be adjusted by adjusting the size of the central region 43.
It is corrected so that the ones arranged at the ends of are smaller.

For this reason, the inertance added at this portion is corrected by the diaphragm (tapering) of the common ink chamber 26 so that the inertance of the ink supply path 27 is corrected to be small. Furthermore, since the positions of the outlets 27b of the ink supply path 27 are aligned, the compliance Cc of the pressure generating chamber 20 is also the same. Therefore, by the above correction, the ink pressure resonance cycle of the ink supply passage 27 connected in the throttle area 36 of the common ink chamber 26 is the same as the ink pressure resonance cycle of the ink supply passage 27 connected in the area other than the throttle area 36. Will be equivalent. As a result, the ejection characteristics of the individual nozzle openings 13 can be made uniform, and high-quality images can be expected.

In order to make the discharge characteristics uniform in more detail, the above-mentioned throttle area is provided in the flow passage between the inlet 27a and the outlet 27b of the ink supply passage 27 which are in communication with each other in the throttle area 36 of the common ink chamber 26. Each entrance 27 from the beginning of the throttle 36
The ink supply passages 2 are formed by adding the passages up to the length a.
7, and the inertances in these virtual flow paths are set to the common ink chamber 26 in areas other than the throttle area 36.
The inertance in the flow path from the inlet 27a to the outlet 27b of the other ink supply path 27 communicating with the ink supply path 27 is aligned.

According to this structure, the common ink chamber 26 can be adjusted including the inertance added by narrowing the end portion of the common ink chamber 26 to form the narrowed region 36, reducing residual bubbles and reducing the nozzle openings 13. It is possible to make the ejection characteristics constant.

Regarding the compliance of the common ink chamber 26, when the end of the common ink chamber 26 is narrowed, the width of the film 30 (compliance region 50) near the ink supply path 27 connected by the narrowed region 36 becomes narrower. Therefore, the compliance is locally reduced in the vicinity of the ink supply paths 27. Therefore, at the end of the common ink chamber 26, the ability to absorb the pressure of the ink flowing back from the ink supply path 27 at the time of ink ejection is reduced, which is one of the causes that the ink ejection characteristics change at the end. For the purpose of supplementing this, as shown in FIG. 12, for example, the common ink chamber 26 of the middle state portions 43A, 43B, 43C is formed.
The end portion on the side (the end portion on the inlet 27a side) is retracted toward the pressure generating chamber 20 side (the length is short), and accordingly, the compliance region 50 of the common ink chamber 26 is set to the ink supply path 27. It may be enlarged to the ink supply path 27 side according to the shortened length.

In this way, the compliance replenishment area 50
If a is increased, the compliance of the aperture area 36 of the common ink chamber 26 is replenished, the additional inertance of the aperture area 36 is substantially reduced, and the correction amount of the ink supply path 27 connected to the aperture area 36 is reduced. Can be reduced.

Note that, due to the processing of the flow path forming plate 12, as shown in FIG. 13, the tip of the throttle area 36 of the common ink chamber 26 may be formed obliquely in the direction away from the pressure generating chamber 20. However, in this case, even if the side of the film 30 (compliance region 50) on the pressure generating chamber 20 side is aligned to the end, or if it is expanded to the pressure generating chamber 20 side and the compliance replenishing region 50a is increased. Good.

As shown in FIGS. 8 and 9, when the ink supply path 27 is divided into a flow path 27dn on the nozzle opening 13 side (nozzle plate 14 side) and a flow path 27up on the elastic plate 21 side, In order to avoid interference with the island portion 31, the middle state portion 43 provided in the flow path 27up on the elastic plate 21 side.
Regulated in position. Therefore, as shown in FIG. 9, the middle state portion 43up of the elastic plate 21 side is retracted to the common ink chamber 26 side, and the middle state portion 43dn of the nozzle opening 13 side is moved forward to the pressure generating chamber 20 side. The volume of the generation chamber 20 may be made uniform. The inertance between the inlet and the outlet of the ink supply passage 27up on the side of the elastic plate 21 and the inertance between the inlet and the outlet of the ink supply passage 27dn on the side of the nozzle opening 13 are defined as the middle state portion 43u.
It may be corrected by adjusting the width and length dimensions of p and 43dn. Therefore, the inertance of the ink supply passage 27up on the side of the elastic plate 21 may be different from the inertance of the ink supply passage 27dn on the side of the nozzle opening 13,
Greater flexibility in design.

In the above-described embodiment, the ink supply path 27 is used.
Although the ink supply flow path is divided by providing the middle state portion 43 in the middle of the above, the ink supply path 27 in the present invention is not limited to this, and the inertance between the inlet 27a and the outlet 27b of the ink supply path 27 is not limited to this. It suffices if it can be configured to correct. For example, as shown in FIG. 14, the correction may be performed by changing the flow path width of the ink supply path 27, that is, by setting the flow path located at the tip of the narrowed region 36 to be wider. In this way, the ink supply path 27
When the flow channel width of is changed, as can be seen from the equation (5),
Inertance can be corrected.

In each of the embodiments described above,
Although the inertance between the inlet 27a and the outlet 27b of the ink supply path 27 is corrected, the present invention is not limited to this, and the inertance in the range including the throttle area 36 of the common ink chamber 26 may be adjusted. In addition, in each of the embodiments, the piezoelectric vibrator 41 is described as an example of the pressure generating element 23, but the pressure generating element 23 of the present invention is not limited to this. For example, the pressure in the pressure generating chamber 20 may be changed by providing a heating element and generating bubbles in the ink.

Although one common ink chamber 26 is provided for each row of nozzle openings 13, as shown in FIG.
The nozzle openings 13 in a row may be divided into a plurality of groups, and a common ink chamber may be provided for each group. That is,
A plurality of common ink chambers (three in this embodiment) may be provided for one row of nozzle openings, and a plurality of colors of ink may be ejected through one row of nozzle openings. Also in this embodiment, similarly to the above-described embodiment, the throttle region 3 is provided at the end of the common ink chamber 26 farther from the ink supply pipe 35.
6 is formed, and the cross-sectional area and the length of the ink supply passage 27 communicating with the throttle area 36 are made different from those of the ink supply passage 27 communicating with the supply ink chamber 26 outside the throttle area 36. The speed and the amount of ink droplets ejected from each nozzle opening 13 are made uniform.

[0068]

As described above, according to the present invention, even if the number of nozzles per row is increased and the length of the common ink chamber is increased, the ideal shape of the common ink chamber which is excellent in bubble discharging property is maintained. It is possible to equalize the ink speed and the ink amount at the nozzle openings at the end portions, and it is possible to efficiently damp the vibration of the ink, which makes it possible to perform high-speed image recording with excellent recording quality. can do. That is, in the common ink chamber, a squeezed region having a cross-sectional area smaller than that of the other part is set at a portion far from the ink supply pipe, and bubbles are generated at the time of filling the ink or cleaning by suction from the nozzle opening. Can be prevented from remaining and the recording quality can be improved. Then, the inertance relating to the ink supply path communicating with the throttle area is set to be smaller than the inertance of the other ink supplying paths communicating with the common ink chamber other than the throttle area, and the tip of the common ink chamber is set. The ink supply passage 27 located at the lower position is set to have a smaller volume, and the volume of the pressure generating chamber communicating with the ink supply passage 27 having a smaller inertance is set to another pressure that communicates with the common ink chamber in a region other than the throttle region. When the volume of the pressure generating chamber is made uniform, the ink pressure resonance cycle in each pressure generating chamber can be made uniform. Therefore, the ejection characteristics of the nozzle openings located at the end portions and the ejection characteristics of the nozzle opening in the central portion can be made uniform. Therefore, the image quality is further improved, and it is possible to respond to the increase in size and speed of the recording target. As described above, according to the present invention, it is possible to achieve both the bubble discharge property and the discharge property uniformity at the end of the common ink chamber. In particular, when the pressure generating chamber is pressurized by the pressurizing unit using the substantially same drive signal, the ejection speed of the ink droplet from the nozzle opening is + -5% of the target value. It can fit within the range.

[Brief description of drawings]

FIG. 1 is a perspective view of an image recording apparatus using an inkjet recording head.

FIG. 2 is an exploded perspective view of a recording head.

FIG. 3 is a cross-sectional view of an actuator formed on a recording head.

FIG. 4 is a plan view of the first embodiment of the flow path forming plate.

FIG. 5 is an explanatory diagram of an equivalent circuit.

FIG. 6 is a plan view of a second embodiment of a flow path forming plate.

FIG. 7 is a plan view of a third embodiment of a flow path forming plate.

FIG. 8 is a cross-sectional view taken along the arrow X in FIG. 10 showing the main part of the recording head.

FIG. 9 is a cross-sectional view showing the main part of the recording head as viewed in the direction of the arrow in FIG. 10Y.

FIG. 10 is a plan view of a fourth embodiment of a flow path forming plate.

FIG. 11 is an enlarged view of the vicinity of the throttle area of the common ink chamber.

FIG. 12 is an explanatory diagram of a main part of an embodiment in which a compliance replenishment area is formed in accordance with a shortened ink supply path.

FIG. 13 is an explanatory diagram of a main part of another embodiment in which a compliance replenishment area is formed according to the shortening of the ink supply path.

FIG. 14 is an explanatory diagram of an embodiment in which the compliance of the ink supply path is corrected by changing the width of the ink supply path.

FIG. 15 is a plan view of an embodiment in which one row of nozzle openings is divided into a plurality of groups and a common ink chamber is provided for each group.

[Explanation of symbols]

1 Inkjet recording head 2 Image recording device 3 carriage 4 Timing belt 5 Carriage motor 6 Guide member 7 Recording paper 7'paper feed roller 8 holder 9 ink cartridges 10 Capping device 11 Wiping device 12 Flow path forming plate 13 nozzle opening 14 nozzle plate 20 Pressure generation chamber 21 elastic plate 22 Channel unit 23 Pressure generating element 24 head case 25 edge cover 26 common ink chamber 27 ink supply path 27a entrance 27b exit 29 stainless steel plate 30 resin film 31 Vibration area (island part) 32 ink supply hole 33 windows 34 Fixed board 35 ink supply pipe 36 Aperture area 40 storage room 41 Piezoelectric vibrator 42 Upper and lower chamber partition 43 Central Region 50 Compliance area 50a Compliance replenishment area

   ─────────────────────────────────────────────────── ─── Continued front page    (31) Priority claim number Japanese Patent Application 2000-16180 (P2000-16180) (32) Priority date January 25, 2000 (January 25, 2000) (33) Priority claiming country Japan (JP)

Claims (10)

[Claims] 1. A plurality of pressure generating chambers having nozzle openings are formed side by side, a common ink chamber is formed on one side of these pressure generating chambers, and an ink supply path is provided between the common ink chamber and each pressure generating chamber. A pressure generating element is provided corresponding to each pressure generating chamber, an ink supply pipe is connected to the common ink chamber, and the ink in the pressure generating chamber is nozzle-opened due to the pressure variation in the pressure generating chamber caused by the pressure generating element. In the ink jet recording head ejecting from the ink supply path, the ink supply path communicating with the ink supply path in the vicinity of the end of the common ink chamber has a plurality of ink shapes of the same shape communicated with other than the vicinity of the end of the common ink chamber. An ink jet recording head characterized in that at least one of a cross-sectional area and a length thereof is different from a path. 2. The common ink chamber is formed with the arrangement direction of the pressure generating chambers as a longitudinal direction, and an ink supply pipe communicates with a substantially center of the longitudinal direction, and communicates with both ends of the common ink chamber. 2. The ink supply path to be formed is different in at least one of the cross-sectional area and the length from the ink supply path communicating with the other part of the common ink chamber. Inkjet recording head. 3. The ink jet recording head according to claim 1, wherein the vicinity of the end portion of the common ink chamber is a throttle area having a cross-sectional area smaller than that of other portions. 4. The value of the attenuation coefficient Mn / Rn of the ink supply passage communicating with the vicinity of the end of the common ink chamber and the attenuation coefficient Mn of the ink supply passage communicating with the other portion of the common ink chamber.
4. The value of / Rn is set to be the same.
An ink jet recording head according to any one of 1. 5. The ink jet recording head according to claim 3, wherein the narrowed region is narrowed in a plurality of stages so as to be tapered. 6. The ink jet recording head according to claim 1, wherein a plurality of the ink supply passages are provided for one pressure generating chamber. 7. The ink jet recording head according to claim 1, wherein the ink supply path is divided into a flow path on the nozzle opening side and a flow path on the opposite side. 8. The ink jet recording head according to claim 7, wherein the volume of each pressure generating chamber is made uniform by adjusting the position of the outlet of the ink supply passage of the passage located on the nozzle opening side. . 9. The ink jet recording head according to claim 7, wherein the inertance of the flow path on the nozzle opening side and the inertance of the flow path on the opposite side are set separately. 10. An image recording apparatus comprising the ink jet recording head according to any one of claims 1 to 9.