FR2717738A1 - Ink jet printer head - Google Patents

Abstract

The printer head has a flow section with a partition (6), a jet plate (11) and an elastic plate (4). The partition has a series of pressure chambers (7) in a row, all lying in the same plane, and the jet plate has a series of nozzles which are linked to the pressure chambers. The head incorporates a piezoelectric vibrator (2) which is designed to provide selective modification of the pressure chambers' volume, and a housing (5) to fix the piezo-electric elements to the flow section. The housing is connected to the flow section by an adhesive strip lying perpendicular to the row of pressure chambers, with a groove in the strip's surface set parallel to the row.

Description

 The invention relates to an ink jet recording head for use in recording apparatuses such as printers for forming an ink image on a recording medium such as an inkjet recording paper. recording by projecting droplets of ink.

 An ink jet recording head, which is adapted to deform an elastic plate constituting a surface of a pressure producing chamber in a piezoelectric vibration element moving direction so that a droplet of ink is expelled from a nozzle communicating with the pressure producing chamber, may have the possibility of being controlled at low voltage, having a high density, etc.

 However, to expel an ink droplet, it is necessary to cause a piezoelectric vibrating element to change the capacity of a pressure producing chamber. Therefore, a flow passage unit constituting these pressure producing chambers should have as little stiffness as possible. As a result, upon receiving a displacement of a piezoelectric vibrating element as an ink droplet is expelled, the flow passage unit is deformed as a whole in an unnecessary manner. ; more particularly, large stresses are applied to areas where the flow passage unit is attached to a head body which is an element for connecting the flow passage unit to the piezo-vibrating element. electric.

 Thus, if the flow passage unit is formed by gluing a nozzle plate, a spacer, and the elastic plate one over the other, the bonded surface is separated or split, which is a problem.

 In addition, if the piezoelectric vibrating element is stuck on a vibration plate at a high temperature, there is a difference between the temperature at the time of manufacture of the recording head and the temperature at the time of use. of the recording head, which in turn causes the flow passage unit to be permanently recalled to the piezoelectric vibrating element due to a difference in thermal expansion between the head body and the piezoelectric vibration element. This not only results in the ink expulsion performance becoming inconsistent, but also that the bonded surface is likely to separate.

 In addition, the deformation of the flow passage unit causes inconsistencies in the direction of the nozzle opening at the time of the expulsion of an ink droplet on both end portions of the d-line. nozzle opening and in the middle thereof, or inconstancies in the force applied to the pressure producing chamber, which in turn causes fluctuations in the droplet positions of ink droplets on a support of and the amount of ink expelled, which is another problem.

 In order to overcome these problems, an ink jet recording head is proposed for example in Japanese Unexamined Patent Publication Number Hei 4-361045. This ink jet recording head is characterized in that it forms not only dummy pressure producing chambers which have nothing to do with printing at the two end portions of the opening row. nozzle, but also in that it provides piezoelectric pressure vibration elements for these, so that printing is performed only with pressure producing chambers which are towards the middle relative to these chambers of dummy pressure production.

 According to this example, the deformation values of an area related to the print may be uniformly reduced to prevent the print quality from being affected. However, the dummy pressure chambers and the piezoelectric vibration elements therefor must be provided, which in turn makes the size of the recording head complete and reduces the efficiency while the number of coins is increased.

 The invention has been made with regard to the problems mentioned above. Therefore, the object of the invention is to provide an ink jet recording head which can maintain print quality not only with stresses received at the moment when the piezoelectric vibration elements are controlled but also with changes in room temperature without complicating the structure thereof, and which can remain reliable with significant changes in ambient temperature.

In order to achieve the above object, the invention is applied to an ink jet recording head comprising: a flow passage unit which is constituted by a spacer, a nozzle plate and an elastic plate the spacer having a plurality of pressure producing chambers in a single plane in the form of a row, the nozzle plate having nozzles communicating with the pressure producing chambers and being laminated on a surface of the spacer, the elastic plate being laminated on the other surface of the spacer; a piezoelectric vibration element for selectively modifying a capacity of the pressure producing chamber while abutting the elastic plate; and a head body for fixing the piezoelectric vibrating elements on the flow passage unit. In such an ink jet recording head, a bonding width
L of the head body on the flow passage unit in a direction perpendicular to the row of pressure producing chambers is set to
0.5b <L <5a if it is assumed that a distance from the bonding end to one end of a piezoelectric vibration element closest to the leading body is a and that a gap between the bonding ends of the head body flanking the piezoelectric vibration element is b.

 The head body thus has a rigidity to suppress the deformation of the flow passage unit when necessary in order to maintain the print quality as well as the absorption function of the internal stresses of the passage unit. flow caused by a change in ambient temperature.

Fig. 1 is a sectional view showing an embodiment of the invention;
Fig. 2 is an exploded perspective view showing the embodiment of the invention;
Figure 3 (a) is a sectional view along a line AA of Figure 1;
Fig. 3 (b) is a sectional view along a line BB of Fig. 1;
Fig. 4 is a diagram showing how a flow passage unit is connected to a head body;
Fig. 5 is a sectional view showing how the flow passage unit is deformed at the moment of expulsion of an ink droplet in the invention.

 Figs. 6 (a) to (c) are diagrams respectively showing how flow passage units are deformed at the moment of expulsion of an ink droplet into jet recording heads. conventional ink.

 Fig. 7 is a diagram showing how the flow passage unit in a direction of a row of nozzle openings is deformed at the moment of expulsion of an ink droplet in the invention.

 Fig. 8 is a diagram showing nozzle tip deformation values by nozzle position of the ink jet recording head of the invention and the conventional ink jet recording head.

 Fig. 9 is a diagram showing the offset of a shape dot on a recording medium caused by deformation of a nozzle plate in the conventional ink jet recording head.

Figs. 10 (a) to (c) are diagrams showing other respective embodiments of the invention;
Fig. 11 is a diagram showing another structure of a bonding zone between the flow passage unit and the head body;
Fig. 12 is a diagram showing another embodiment of the bonding zone between the flow passage unit and the head body.

 The ink jet recording heads, which are embodiments of the invention, will now be described with reference to the drawings.

 Figures 1 and 2 show an ink jet recording head, which is an embodiment of the invention. In Figures 1 and 2, references 2, 2, ... designate piezoelectric vibration elements, which expand and contract each in a longitudinal direction (in vertical directions as seen in Figures 1 and 2). It is the upper half of the piezoelectric vibrating element that functions as an active zone, that is to say, that expands and contracts. The lower half serves as an inactive area. The inactive zone is fixed on fixing plates 3 which are made of a relatively rigid material, for example steel or ceramic. The piezoelectric vibration elements thus constructed are grouped together in a vibration element unit.

 The fixing plates 3 are housed in a piezoelectric vibration element receiving chamber 14 of a head body 5 with the front end of each piezoelectric vibration element 2 which abuts against an island-shaped projection. 4a of an elastic plate 4 which will be described later, and are fixed on the head body 5 with an epoxy resin adhesive.

 Reference 6 denotes a spacer forming pressure producing chambers 7, a common ink chamber 8 and ink supply inlets 9. Spacer 6 has groove portions and through holes formed by removing portions unnecessary while subjecting a material, such as a resinous composition that cures by irradiation of an active energy beam, glass, or silicon, to etching using a predetermined mask pattern or the like; desired groove portions and through-holes may also be formed by injection molding using a resin or the like.

 On one surface of the spacer 6 is the elastic plate 4, and on the other surface thereof there is a nozzle plate 11 glued to be watertight. The nozzle plate 11 has nozzle openings 10 each having a diameter of 30 to 70 ssm. These three elements constitute a flow passage unit 12.

 The flow passage unit 12 is such that one side of the elastic plate 4 is fixed on an opening end surface of the head body 5 by an adhesive so that displacements of each vibration element piezoelectric 2, that is to say a dilation and a contraction thereof, can be accepted.

 Figs. 3 (a) and (b) show cross-sectional structures along a line A-A and a line B-B respectively in Fig. 1.

 The structure of the nozzle openings in the arrangement direction will be described first in more detail with reference to Fig. 3 (a).

 In Fig. 3 (a), references 13, 13 denote recesses. Each recess is positioned such that a portion thereof faces each of the two ends of the pressure producing chambers 7, 7, i.e., the head body 5 serves as a support point of the flow passage unit 12 and a portion thereof extends to the piezoelectric vibration element receiving chamber 14.

 The recesses 13, 13 are formed by providing through holes similar to the pressure producing chambers 7, 7, ... in the spacer 6. The recesses 13, 13 are designed to reduce the stiffness of the fixed parts in the vicinity of the head body 5, that is to say the rigidity of the flow passage unit 12 in the vicinity of the end pressure production chambers 7 ', 7' with respect to the rigidity thereof in the middle part.

 The recesses 13, 13 also serve as dummy ink flow passages to help remove bubbles at the time of ink loading by feeding the ink supply inlets or the nozzle openings communicating with the ink chamber. common ink 8 to communicate therewith in a manner similar to the pressure producing chambers 7, 7 'if necessary.

 In addition, the width of the recess 13 may desirably be chosen to be 1/2 to 3 times the thickness of the spacer 6 for the following reasons. Too large a width, which decreases the rigidity of attachment between the flow passage unit 12 and the head body 5, prevents reliable fixing between them, while a too small width, which increases excessively the rigidity near the fixed areas, prevents uniform deformation of the flow passage unit 12 at the time of expulsion of the ink.

 On the other hand, in a direction perpendicular to the direction in which the nozzle openings 10, 10, 10, i.e. in the longitudinal direction of the pressure producing chambers 7, are disposed, the piezoelectric vibration elements 2 are arranged at predetermined distances from the head body 5 with spaces formed by the piezoelectric vibration element receiving chamber 14 interposed therebetween as shown in Fig. 3 (a).

That is, the width L along which the head body 5 is glued to the flow passage unit 12 is chosen so that
0.5b <L <5a where a is the distance between the surface opposite the piezoelectric vibration element 2 and that of the head body 5, that is to say the distance from the bonding end from the flow passage unit 12 to the piezoelectric vibration element 2 closest to the head body 5; and b is a width of the piezoelectric vibration element receiving chamber 14 which surrounds the piezoelectric vibration element 2, i.e. the distance between the bonding ends of the head body 5 which frame the piezoelectric vibration element 2.

 The reasons for which the relation 0.5b <L <5a is chosen for the gluing zone of the flow passage unit 12 will be described later.

 The piezoelectric vibrating elements 2, 2, 2 are glued to the flow passage unit 12 with an epoxy resin adhesive which makes it possible to obtain a relatively high bond strength.

In order to shorten the bonding time, these elements are usually heated to 40 to 60 C.

Thus, if the fully assembled recording head is exposed to a temperature of -200C, the head body 5 contracts as shown in Fig. 6 (a) to the point of bringing the piezoelectric vibration element 2 to push up the island-shaped protrusion 4a of the elastic plate 4 due to a difference in material between the head body 5 and the piezoelectric vibrating element 2. That is, the coefficient of linear expansion of the
5 head body 5 is 2 x 10 (1 / OC), while the linear expansion coefficient of the piezoelectric vibration element 2 is 6 x 10-6 (1/0 C), a difference greater than an order of magnitude.

 Since the bonding width L is chosen in a range as described above in the invention, the rigidity of the flow passage unit 12 acts effectively on the head body 5. That is, that is, the rigidity of the flow passage unit 12 pulls the bonding zone from the head body 5 to the flow passage unit 12, so that part of a difference in the value of deformation that can be attributed to a difference in coefficient of thermal expansion between the head body 5 and the piezoelectric vibration element 2 can be absorbed by the expansion of the head body 5.

 That is, because the section of the bonding surface of the head body 5 is small, the head body 5 in this area can easily expand, which in turn effectively prevents deformation of the flow passage unit 12, the deformation being capable of causing a separation of the bonding surface between the spacer 6 and the elastic plate 4 which constitute the flow passage unit 12.

 In contrast, a recording head having the bonding width L between the head body and the chosen flow passage unit at a value greater than 5a gives too little dilatation to the head body 5 to absorb the stress of the flow passage unit 12. As a result, the difference in deformation value due to the difference in coefficient of thermal expansion between the head body 5 and the piezoelectric vibration element 2 is directly transformed into a deformation of the flow passage unit 12, and the deformation acts as a separating force of the elastic plate 4 of the spacer 6, both constituting the flow passage unit 12, as shown in Figure 6 (a), resulting in a separation 40 in a portion where the spacer 6 is glued to the elastic plate 4, the portion being close to the ink supply inlet 9 whose bonding surface is pa particularly low in the flow passage unit 12.

 On the other hand, if the distance a from the inner surface of the head body 5 to the side surface of the piezoelectric vibrating element 2 is small, the spacer 6 is separated from the elastic plate 4 in a manner similar to the case mentioned above, or a crack 41 develops in the spacer 6 if the spacer 6 is made of a material such as a photoresist or equivalent whose friability increases at low temperatures when exposed at temperatures significantly different from a bonding temperature, because shear stresses applied to the portion of the flow passage unit 12 over the distance a are increased (Fig. 6 (b)) while the value deformation due to the difference in coefficient of thermal expansion remains unchanged.

 In order to study these conditions, a total of 50 ink jet recording heads were manufactured, each ink jet recording head having the bonding width L between the head body 5 and the unit 12 and the distance a between the bonding end and the lateral surface of a piezoelectric vibration element 2 closest to the head body 5 set at different values. These 50 ink-jet recording heads were placed at -20 C, which is a critical operating temperature, reducing the temperature from a bonding temperature of 500C to study the incidence of separations and cracks. at the interface in the flow passage unit 12. The result of the study is shown in Table 1.

Table 1

<tb> Width <SEP> of <SEP> Distance <SEP> (a) <SEP> between <SEP> L / a <SEP> Rate
<tb> gluing <SEP> (L) <SEP> the <SEP> surface <SEP> in <SEP> of appearance
<tb> between <SEP> the <SEP> body <SEP> look <SEP> from <SEP> of
<tb> of <SEP> head <SEP> and <SEP> the <SEP> element of <SEP> separations
<tb><SEP> unit <SEP> vibration <SEP> piezo <SEP>;<SEP> and <SEP> of
<tb> passage <SEP> electrical <SEP> and <SEP> cracks
<SEQ><SEP> flow <SEP> of <SEP><SEP><SEP><SEP>
<tb> (mm) <SEP> head <SEP> (mm) <SEP> 50 <SEP> heads
<tb><SEP> 1.2 <SEP> 0.3 <SEP>;<SEP> 4 <SEP> 0/50
<tb><SEP> 1.5 <SEP> 0.3 <SEP> 5 <SEP> 0/50
<tb><SEP> 1.8 <SEP> 0.3 <SEP> 6 <SEP> 2/50
<tb><SEP> 3.0 <SEP> 0.3 <SEP> 10 <SEP> 25/50
<tb><SEP> 1.2 <SEP> 0.24 <SEP> 5 <SEP> 0/50
<tb><SEP> 1.2 <SEP> 0.15 <SEP> 6 <SEP> 7/50
<tb><SEP> 1,2 <SEP> 0,15 <SEP> j <SEP> 8 <SEP> 27/50
<Tb>
As a result, it is verified that if L / a is set to 5 or less, cracks in the spacer 6 and separation in the flow passage unit can be prevented.

 On the other hand, if the bonding width L is reduced in order to decrease the value L / a (FIG. 6 (c)), the rigidity at the bonding surface between the head body 5 and the passage unit The flow path 12 is then reduced, which in turn reduces the function of preventing deformation of the flow passage unit 12 at the time of the ink expulsion which is essentially necessary for the head body 5. , thus causing overlaps, which is a phenomenon whereby an ink droplet is expelled from a piezoelectric vibration element 2 on which no printing signal is applied, or causing what is calls a misfire, which is a phenomenon whereby an ink droplet is not expelled even if a print signal is applied.

 In order to study these conditions, a total of 50 ink jet recording heads were made in a similar fashion, each ink jet recording head having the distance b between the body's sticking ends. head 5 framing the piezoelectric vibration element 2 set at 1.1 mm, while the bonding width L between the head body 5 and the flow passage unit 12 is set to different values. The incidence of defective ink droplet expulsion operations is controlled. The result is shown in Table 2.

Table 2

<tb> Width <SEP> of <SEP> Distance <SEP> (b) <SEP> | <SEP> L / b <SEP> Rates
<tb> gluing <SEP> (L) <SEP> between <SEP><SEP> appearing <SEP>
<tb> between <SEP> the <SEP> body <SEP> ends <SEP> of <SEP> misses <SEP> (%)
<tb> of <SEP> head <SEP> and <SEP> gluing <SEP> (number <SEP> of
<tb><SEP> unit <SEP> of <SEP> element of <SEP><SEP> nozzles with
<tb> passage <SEP> vibration <SEP> (mm) <SEP><SEP> failed <SEP> / number
<tb> flow <SEP> of <SEP> nozzles
<tb> (mm) <SEP> studied) * 100 <SEP>
<tb><SEP> 0.33 <SEP> 1.1 <SEP> 0.3 <SEP> 40 <SEP> to <SEP> 50
<tb><SEP> 0.45 <SEP> 1.1 <SEP> 0.4 <SEP> 5 <SEP> to <SEP> 10
<tb><SEP> 0.55 <SEP> 1.1 <SEP> 0.5 <SEP> 0 <SEP> to <SEP> 1
<tb><SEP> 1,1 <SEP> 1,1 <SEP> 1 <SEP> O
<Tb>
It is verified from Table 2 that the head body 5 has a rigidity to accommodate the deformation of the flow passage unit 12 at the time of the expulsion of an ink droplet without causing an operation. Defective ink droplet expulsion if L / b is set to at least 0.5 or higher.

 From the foregoing, it is concluded that the bonding width L between the head body 5 and the flow passage unit 12, the distance a from the bonding end of the head body 5 to the piezoelectric vibration element closest to the head body 5, and the space b between the bonding ends of the head body 5 flanking the piezoelectric vibrating element are desirably determined so that the following relationship is established.

0.5b <L v 5a
As a result of this design, the head body 5 has a rigidity such that there is no defective ink droplet expulsion operation and can accommodate the deformation of the pass-through unit. flow 12 at the time of the ink droplet expulsion caused by a change in ambient temperature. Therefore, the print quality is not affected, and the occurrence of separations and cracks in the flow passage unit with a temperature change can be prevented.

In this embodiment, when printing signals are applied to all piezoelectric vibrating elements 2, 2, 2 ... rows of nozzle openings to cause displacements Na (of about 0, 5 to 3 ssm) on the piezoelectric vibration elements 2, the ink in the respective pressure producing chambers 7 is
Pressurizing to about 1 to 3 105 Pa and the ink droplets are expelled from the nozzle openings 10, 10, 10 ....

 The Na expansion displacements of the piezoelectric vibration elements 2, 2, 2 act as a force intended to deform the flow passage unit 12 as a whole. However, the presence of the recesses 13 near the zone bonding between the flow passage unit 12 and the head body 5 causes the recesses 13 to bend, and this provides a region where the nozzle openings 10, 10, 10 ... are formed to flex as a whole uniformly as shown in Figure 7.

Example
An ink jet recording head having 16 pressure producing chambers 7 has been prepared under the following conditions. The nozzle plate 11 is made in a stainless steel plate 80 Am thick; the spacer 6 is made of a photosensitive resin approximately 200 ssm thick; the elastic plate 4 is made of a sheet of nickel 20s thick; the head body 5 is made of a liquid crystal polymer; the length of the pressure producing chamber 7 is set at about 1.2 mm; the width of it at about 200 ssm; and the width of the recess 13 is set at about 300 m.

 When the piezoelectric vibrating element 2 is controlled so that the displacement amount Na thereof is equal to about 0.6 μm, a desired ink droplet can be obtained.

 The amount of deformation of the surface of the nozzle plate 11 is measured, using a laser Doppler displacement measuring device, while an ink droplet is expelled. A deformation value Nm in the middle portion is equal to about 0.14 ssm and a deformation value Ne in the nozzle openings 10 ', 10' on both end portions is equal to about 0.1 ssm like this. is indicated by the solid line in Figure 8.

A difference between the ink droplet expulsion rate at the nozzle openings in the middle portion and that at both end portions is about 7%.

 In addition, when a horizontal line is printed on a recording medium, there are differences of about 5 to 10 ssm in the line width produced by the ink droplets on the end portion and in the middle part.

 In contrast, the conventional ink jet recording head having no recesses 13 has a deformation value Nm of about 0.1 Mm in the middle part of the nozzle plate and a deformation value Ne. about 0.05 ssm on both end parts. That is, the difference between these values is about twice that of the invention as indicated by a dashed line in Figure 8. A difference between the ink droplet expulsion rate in the middle part and that on both end parts is as strong as about 17%. As a result, points formed by the respective nozzle apertures are arranged in a curve as shown in Fig. 9 in the conventional example. When a horizontal line is printed on a recording medium, there are differences of about 15 to 30 ssm in the line width produced by the ink droplets on the end portion and in the middle portion.

 As described above, it is verified that the ink in the pressure producing chambers 7 can be compressed substantially at the same pressure and that consequently the speed of the ink droplets expelled from each nozzle opening 10 and the volume of the ink droplet are made constant in the invention. As a result, the invention can form points closely following the mode of arrangement of the nozzle openings.

On the other hand, the shift of a dot formed on a recording medium is caused by the difference in speed of ink droplet expulsion. Therefore, in order to obtain an image whose resolution is for example 360 dots per inch, an offset value D of one point is given by
D = Vh x AG x 1 / Vm1 - 1 / Vm21 if it is assumed that the repetition frequency of the ink droplet expulsion operation is set to about 7.2 kHz; that the head movement speed Vh is set at about 0.5 m / s; that the upper and lower limits of the ink droplet expulsion rate are set to Vml and Vm2 respectively; and that the gap AG between the nozzle opening 10 and the recording medium is actually present, the rate of ink droplet expulsion rate fluctuation should be limited to about 15% or less, or preferably at 10% or less considering these factors causing variations.

 Considering the above conditions, in order to reduce the offsets of the ink droplets formed by the pressure producing chambers 7 ', 7' on the two end portions of the nozzle opening rows and the production chambers pressure 7, 7 in the middle part, the difference in deformation value INm - Ne between the deformation value Ne of the nozzle plate 11 on the end portions of the nozzle opening row and the deformation value Nm near the middle part of the nozzle opening rows should be limited to a low value, preferably less than or equal to 01 x Na.

 That is, because an ink droplet is expelled by the displacement amount Na of the piezoelectric vibration element 2, the strain value Nm must be smaller than Na because the ink pressure is not increased and because the ink droplet expulsion speed becomes extremely low, even though the ink droplet can hardly be expelled, thus rendering the expulsion operation unstable of ink droplet.

 In addition, the difference in amplitude of the displacement Na of the piezoelectric vibration element 2 leads to a difference in speed of expulsion and volume of an ink droplet.

That is, the larger the Na displacement of the piezoelectric vibrating element 2, the higher the expulsion rate and the volume of the ink droplet become respectively high and large.

 In addition, as described above, it is the deformation value of the nozzle plate 11 that causes the difference in speed and volume of an expelled ink droplet.

 Considering the above, different studies have also been conducted. From the results of these studies, it is verified that it is extremely efficient to control the difference in deformation value Nm-Nel between the deformation value Ne of the nozzle plate 11 on the end portions and the value of Nm deformation near the middle portion of the nozzle opening rows at 10% Na displacement of the piezoelectric vibration element 2 to suppress variations in the expulsion rate and the volume of the ink droplet.

 As a means of achieving this, it is effective to form the recesses 13 near the fixed points of the flow passage unit 12 with respect to the head body 5 as described above, so that areas more likely to deform than fixed points may be formed between the fixed points and the nozzle opening row area.

 Figures 10 (a) to (c) show further embodiments of the invention. FIG. 10 (a) shows an ink jet recording head characterized in that it has slots 20, 20 near fixed areas of the nozzle plate 11 with respect to the head body 15 formed by stamping, engraving or equivalent, the slots serving as through holes. Fig. 10 (b) is an ink jet recording head characterized by having recesses 21 which form thin wall portions.

 The slots 20 and recesses 21 are disposed at the boundary of the flow passage unit 12 relative to the head body 5 where the stresses are more concentrated when the piezoelectric vibrating elements 2, 2, 2 expand. ; a portion of these are disposed at the piezoelectric vibration element receiving chamber 14; and a portion thereof are arranged to face the head body 5. The width of the slot or recess ranges from about 50 to 300 ssm.

 The presence of the slots 20 and the recesses 21 cause these parts to deform intensely due to the expansion of the piezoelectric vibration elements 2. Therefore, the area forming an opening which is inward with respect to these parts can flex uniformly, thus making the difference Nm - Ule | No deformation value on the end part and in the lower middle part.

 In addition, an embodiment shown in Fig. 10 (c) is characterized in that it comprises thin wall portions 22, each having a width such that it extends over the element receiving chamber. piezoelectric vibration 14 and the head body 5 at the limit of the elastic plate 4 with respect to the head body 5. In this embodiment also, the thin wall portions 22 are intensely deformed, which allows its turn to the deformation value of the nozzle opening row area to be made uniform.

While the thin wall portions 22 are disposed on a side facing the head body 5, it is obvious that similar effects can be obtained by disposing thin wall portions 23 in the spacer 6.

 Further, while in the case where the recesses 13, the slots 20, the recesses 21 and the thin wall portions 22 are uniquely shaped in the embodiments mentioned above, it is evident that a combination of recesses with slots, recesses or thin-walled parts can provide better effects.

Figure 11 shows yet another embodiment of the invention. This embodiment is characterized by forming a groove 25 which extends in the pressure producing chamber arrangement direction in a head body 5a on the ink supply inlet side 9 so that a zone 26 is formed in an area of the head body 5 which is capable of undergoing interface and equivalent separation on the piezoelectric vibration element receiving chamber side 14, the zone 26 being provided for selectively absorbing the deformation caused by the difference in the coefficient of thermal expansion while maintaining the bonding width L between the flow passage unit 12 and the head body 5, the distance a between the surface facing the the piezoelectric vibration element 2 and that of the head body 5, and the width b of the piezoelectric vibration element receiving chamber 14 between the piezoelectric vibration element 2 of said so the relationship
0.5b <L -> 5a can be established.

 According to this embodiment, the head body 5 can be deformed to such a degree that it removes as much as possible the deformation of the flow passage unit 12 due to a temperature change due to the zone 26 defined by the groove 25, while the head body 5 has sufficient rigidity as a whole. Therefore, the deformation of the flow passage unit can be prevented to such a degree that it maintains the satisfactory ink droplet expelling performance while preventing the flow passage unit 12 from being damaged due to a change in ambient temperature.

Figure 12 shows another embodiment of the invention. This embodiment is characterized by making the bonding width Lb of the head body 5b on the side of the nozzle opening 10 of the flow passage unit 12 greater than the width La of the head body 5a on the ink supply input side 9 while maintaining the bonding width L of the flow passage unit 12 on the head body 5, the distance a between the surfaces facing the element piezoelectric vibration 2 and the head body 5, and the width b of the piezoelectric vibration element receiving chamber 14 in the direction of interposition of the piezoelectric vibration element 2 being determined in such a way that that the relationship
0.5b <L i 5a
can be established.

 According to this embodiment, the stiffness of the head body 5a on the side of the ink supply inlets 9 is relatively small, which in turn more effectively suppresses the development of cracks in the spacer 6 and the separation of the spacer 6 of the elastic plate 4 due to a change in ambient temperature.

In addition, because the rigidity of the head body 5b on the nozzle opening side 10 strongly affects the control of the deformation of the flow passage unit 12 at the time of the expulsion of a droplet droplet. ink, it is more efficient to increase the bonding width
Lb of the head body 5b on the nozzle opening side to improve the print quality.

 As has been described in the foregoing, the invention is characterized in that the bonding width L of the head body with respect to the flow passage unit in the direction perpendicular to the rows of chambers is determined. pressure producing at 0.5b s L s 5a if it is assumed that the distance from the bonding end to the end of the piezoelectric vibration element 2 closest to the head body 5 is a and that the space between the sticking ends of the head body which surround the piezoelectric vibration element 2 is b. Therefore, the absorption function of the internal stresses in the flow passage unit caused by a change in ambient temperature can be given to the head body while maintaining a rigidity such that it eliminates the deformation of the unit of flow. flow passage required to maintain the print quality, which in turn helps to prevent the spacer from cracking or the spacer to be separated from the elastic plate while maintaining the print quality .

Claims (8)

1. Ink jet recording head, characterized in that it comprises  a flow passage unit (12) consisting of a spacer (6), a nozzle plate (11) and an elastic plate (4), the spacer (6) having a plurality of production chambers (6). pressure (7) in a single plane in the form of a row, the nozzle plate (11) having nozzles which communicate with the pressure producing chambers (7) and being laminated on a surface of the spacer (6). ), the elastic plate (4) being laminated on the other surface of the spacer (6);  a piezoelectric vibration element (2) for selectively modifying a capacity of the pressure producing chamber (7) while abutting against the elastic plate (4); and  a head body (5) for fixing the piezoelectric vibration elements (2) to the flow passage unit (12);  a bonding width L of the head body (5) on the flow passage unit (12) in a direction perpendicular to the row of pressure producing chambers (7) is set to 0.5b 'LL 5a where a is a distance from the bonding end to one end of a piezoelectric vibrating element (2) closest to the head body (5), and b a gap between the bonding ends of the head body (5). 5) flanking the piezoelectric vibration element (2). An ink jet recording head according to claim 1, characterized in that a groove (25) is formed parallel to the row of pressure producing chambers (7) in the bonding surface of the head body ( 5) on the flow passage unit (12). An ink jet recording head according to claim 1, characterized in that a bonding width (Lb) of the head body (5) on the side of the nozzle opening (10) of the flow passage unit (12) is made larger than a bonding width (La) of the head body (5) on an ink supply input side (9) of the flow passage unit flow (12), the ink supply inlet side (9) communicating with the pressure producing chamber (7). 4. Ink jet recording head, characterized in that it comprises  a flow passage unit (12) consisting of a spacer (6), a nozzle plate (11) and an elastic plate (4), the spacer (6) having a plurality of production chambers (6). pressure (7) in a single plane in the form of a row, the nozzle plate (11) having nozzles which communicate with the pressure producing chambers (7) and being laminated on a surface of the spacer (6). ), the elastic plate (4) being laminated on the other surface of the spacer (6);  a piezoelectric vibration element (2) for selectively modifying a capacity of the pressure producing chamber (7) while abutting against the elastic plate (4); and  a head body (5) for fixing the piezoelectric vibration elements (2) to the flow passage unit (12);  a rigidity of the flow passage unit (12) in areas around the fixed parts between the flow passage unit (12) and the head body (5) being relatively small compared to that of the flow passage unit (12) in a nozzle opening formation area and areas on both sides of the flow passage unit (12) in a row direction of openings of nozzle. An ink jet recording head according to claim 4, characterized in that a slot (20) or a recess (21) is formed in parts of the nozzle plate (11) and the parts are around the fixed parts between the head body (5) and the flow passage unit (12) in the nozzle opening row direction. The ink jet recording head according to claim 4, characterized in that thin wall portions (22) are formed in portions of the elastic plate (4) and the parts are around the fixed parts between the head body (5) and the flow passage unit (12) in the nozzle opening row direction. An ink jet recording head according to claim 4, characterized in that thin wall portions (23) are formed in spacer portions (6) and the portions are around the fixed portions between the head body (5) and the flow passage unit (12) in the nozzle opening row direction. 8. Ink jet recording head, characterized in that it comprises  a flow passage unit (12) consisting of a spacer (6), a nozzle plate (11) and an elastic plate (4), the spacer (6) having a plurality of production chambers (6). pressure (7) in a single plane in the form of a row, the nozzle plate (11) having nozzles which communicate with the pressure producing chambers (7) and being laminated on a surface of the spacer (6). ), the elastic plate (4) being laminated on the other surface of the spacer (6);  a piezoelectric vibration element (2) for selectively modifying a capacity of the pressure producing chamber (7) while abutting against the elastic plate (4); and  a head body (5) for fixing the piezoelectric vibration elements (2) to the flow passage unit (12);  a deformation value Ne of a vibration plate in an area facing a pressure producing chamber (7) on an outer end of the row of nozzle openings, a deformation value Nm of the vibration plate in a zone facing a pressure producing chamber (7) in the middle of the row of nozzle openings, and a displacement amount Na of the piezoelectric vibrating element (2) being set to  Nm - Do not 0.1 x Na.