EP0774355B1 - Appareil à jet d'encre - Google Patents

Appareil à jet d'encre Download PDF

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Publication number
EP0774355B1
EP0774355B1 EP97101749A EP97101749A EP0774355B1 EP 0774355 B1 EP0774355 B1 EP 0774355B1 EP 97101749 A EP97101749 A EP 97101749A EP 97101749 A EP97101749 A EP 97101749A EP 0774355 B1 EP0774355 B1 EP 0774355B1
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EP
European Patent Office
Prior art keywords
ink
manifold
ink jet
chambers
jet apparatus
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EP97101749A
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German (de)
English (en)
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EP0774355A2 (fr
EP0774355A3 (fr
Inventor
Qiming C/O Brother Kogyo K. K. Zhang
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Brother Industries Ltd
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Brother Industries Ltd
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Priority claimed from JP5022571A external-priority patent/JPH06234216A/ja
Application filed by Brother Industries Ltd filed Critical Brother Industries Ltd
Priority to EP97114688A priority Critical patent/EP0810093B1/fr
Priority to EP97114689A priority patent/EP0810094B1/fr
Publication of EP0774355A2 publication Critical patent/EP0774355A2/fr
Publication of EP0774355A3 publication Critical patent/EP0774355A3/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/14—Structure thereof only for on-demand ink jet heads
    • B41J2/14201—Structure of print heads with piezoelectric elements
    • B41J2/14209—Structure of print heads with piezoelectric elements of finger type, chamber walls consisting integrally of piezoelectric material

Definitions

  • the present invention relates to an ink jet apparatus that prints by ejecting ink droplets under pressure from nozzles.
  • Non-impact printers Traditional impact printers are now being replaced with non-impact printers, and the market of the non-impact printers is being expanded.
  • One known kind of non-impact printers is an ink jet printer simple in principle and that can easily effect multi-scale or color printing.
  • a drop-on-demand type ink jet printer capable of jetting ink droplets at a required time during printing has rapidly spread owing to its good jetting efficiency and its low running cost.
  • Typical examples of such drop-on-demand type ink jet printers are a Kaiser type disclosed in Japanese Patent Publication No. Sho 53-12138 and a thermal jet type disclosed in Japanese Patent Publication No. Sho 61-59914, for example.
  • the former is hard to reduce in size, and the latter is required to have a high heat resistance of ink because the ink undergoes a high temperature.
  • both types have very severe problems in application.
  • Fig. 16 shows a shear mode type ink jet apparatus 1 in the prior art.
  • the ink jet apparatus 1 is constructed of a piezoelectric ceramics plate 2, a cover plate 10, a nozzle plate 14, and a substrate 41.
  • the piezoelectric ceramics plate 2 is provided with a plurality of grooves 3 by grinding with use of a diamond blade or the like. Accordingly, a plurality of side walls 6 extend along the grooves 3 in such a manner that each side wall 6 is formed between adjacent ones of the grooves 3. Each side wall 6 is polarized in a direction indicated by an arrow 5. All the grooves 3 have the same depth, and they are parallel to each other. The depth of each groove 3 is gradually reduced as it approaches a rear end surface 15 of the piezoelectric ceramics plate 2 to form a shallow groove 7 near the rear end surface 15.
  • a pair of metal electrodes 8 are formed on opposed side surfaces of each groove 3 at an upper half portion thereof by sputtering or the like.
  • a metal electrode 9 is formed on opposed side surfaces and a bottom surface of each shallow groove 7 by sputtering or the like.
  • the pair of metal electrodes 8 formed on the opposed side surfaces of each groove 3 are connected with the metal electrode 9 formed on the opposed side surfaces and the bottom surface of the corresponding shallow groove 7 contiguous to the groove 3.
  • the cover plate 10 is formed of a ceramics material, a resin material, etc.
  • the cover plate 10 is provided with an ink inlet hole 16 and a manifold 18 communicating with the ink inlet hole 16 by grinding, cutting, etc.
  • the lower surface of the cover plate 10, on which the manifold 18 is formed is bonded to the upper surface of the piezoelectric ceramics plate 2 on which the grooves 3 are formed by an epoxy adhesive 20 (see Fig. 18).
  • a plurality of individual ink chambers 4 functioning as ink channels are defined by the grooves 3 of the piezoelectric ceramics plate 2 and the lower surface of the cover plate 10 to be transversely equally spaced from each other.
  • each ink chamber 4 is rectangular in vertical section, and it is filled with ink in operation.
  • the nozzle plate 14 is bonded to the front end surface of the assembly of the piezoelectric ceramics plate 2 and the cover plate 10.
  • the nozzle plate 14 is provided with a plurality of nozzles 12 at laterally spaced positions corresponding to the front end positions of the ink chambers 4.
  • the nozzle plate 14 is formed of a plastic material such as polyalkylene terephthalate (e.g., polyethylene terephthalate), polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.
  • the substrate 41 is bonded to the lower surface of the piezoelectric ceramics plate 2 on the opposite side of the cover plate 10 by an adhesive such as an epoxy adhesive.
  • a plurality of individual conductor film patterns 42 are formed on the substrate 41 at transversely spaced positions corresponding to the rear end positions of the ink chambers 4.
  • Each conductor film pattern 42 is connected through a conductor wire 43 to the metal electrode 9 formed on the bottom surface of the shallow groove 7 in the corresponding ink chamber 4 by wire bonding.
  • Fig. 17 shows a schematic diagram of a control section for controlling the ink jet apparatus 1.
  • the conductor film patterns 42 formed on the substrate 41 are individually connected to an LSI chip 51.
  • a clock line 52 Also connected to the LSI chip 51 are a clock line 52, a data line 53, a voltage line 54, and a ground line 55.
  • the LSI chip 51 determines from which nozzle 12 the ink droplets are to be jetted according to data appearing on the data dine 53 on the basis of continuous clock pulses supplied from the clock line 52. Then, according to the result of determination, the LSI chip 51 applies a voltage V of the voltage line 54 to the conductor film pattern 42 connected to the metal electrode 8 in the ink chamber 4 to be driven. Further, the LSI chip 51 applies a zero volt of the ground line 55 to the other conductor film patterns 42 connected to the metal electrodes 8 in the other ink chambers 4 not to be driven.
  • a positive driving voltage V is applied to the metal electrodes 8e and 8f and the metal electrodes 8d and 8g are grounded.
  • a driving electric field in a direction indicated by an arrow 13b is generated in the side wall 6b, and a driving electric field in a direction indicated by an arrow 13c is generated in the side wall 6c.
  • the side walls 6b and 6c are rapidly deformed inwardly of the ink chamber 4b by a piezoelectric thickness shear effect. This deformation of the side walls 6b and 6c reduces the volume of the ink chamber 4b to rapidly increase the pressure of the ink filled in the ink chamber 4b and thereby generate a pressure wave. As a result, the ink droplets are jetted from the nozzle 12 (see Fig. 19) communicating with the ink chamber 4b.
  • Fig. 14 is a sectional side view of the ink jet apparatus according to the invention
  • the ink is forced from the corresponding nozzle 12 simultaneously, the ink reversely flows from the manifold 18 into the ink inlet hole 15.
  • the pressure near the manifold 18 is rapidly reduced to generate a negative pressure wave.
  • this negative pressure wave reaches the nozzle 12, the ink jet from the nozzle 12 is stopped. The shorter the distance y between the front side surface of the manifold 18 and the inner surface of the nozzle plate 14, the shorter the time of reach of the negative pressure wave to the nozzle 12.
  • the distance y when the distance y is reduced, the ink jet from the nozzle 12 is quickly stopped to result in a reduction in volume of ink droplets, causing a deterioration in print quality.
  • the distance x between the front side surface of the manifold 18 and the rear end surface of each ink chamber 4 becomes very small. Accordingly, the ink flow from the manifold 18 into each ink chamber 4 becomes difficult, so that a necessary amount of ink cannot be supplied to each ink chamber 4. As a result, the volume of ink droplets is reduced to cause deterioration in print quality.
  • EP-A-0 364 136 upon which the precharacterising portion of appended claim 1 is based, discloses another ink jet apparatus such as defined above.
  • an ink jet printing apparatus comprising:
  • the distance between the front side surface of the manifold and the nozzle comprises a distance between the front side surface of the manifold and an opening of the nozzle on a side exposed to the ink chamber.
  • ink jet apparatus off the present invention having the above construction, pressure necessary for jetting ink droplets can be maintained for a relatively long period of time. A flow resistance to the ink flowing from the manifold into each ink chamber can be reduced.
  • the distance between the front side surface of the manifold and the nozzle is set so that the pressure near the nozzle can be maintained for a necessary period of time upon jetting of the ink, thereby ensuring a sufficient volume of ink droplets to be jetted. Accordingly, print quality is improved. Further, since a necessary amount of ink is supplied to each ink chamber, the volume of ink droplets to be jetted can be made into a desired value, thereby improving print quality.
  • Figs. 1A and 1B are enlarged views of an ink inlet hole 16 and a manifold 18 in the preferred embodiment.
  • Fig. 1A is a cross section taken from the side of an ink jet apparatus 1
  • Fig. 1B is a cross section taken along the line I-I in Fig. 1A.
  • the ink jet apparatus 1 includes a piezoelectric ceramics plate 2 and a cover plate 10.
  • the piezoelectric ceramics plate 2 has a plurality of grooves 3 and a plurality of side walls 6 partitioning the grooves 3.
  • the cover plate 10 has the ink inlet hole 16 and the manifold 18.
  • the piezoelectric ceramics plate 2 and the cover plate 10 are bonded together by an adhesive 20 to thereby define a plurality of ink chambers 4 as ink channels.
  • ink is supplied from an ink tank (not shown) through an ink supply tube (not shown) into the ink inlet hole 16 having a diameter d. Then, the ink is supplied from the ink inlet hole 16 through the manifold 18 into each ink chamber 4. Since the manifold 18 has a sectional area larger than that of the ink inlet hole 16 as shown, the ink flowing from the ink inlet hole 16 into the manifold 18 is jetted therein. Accordingly, the ink undergoes a divergent flow loss due to rapid enlargement of a channel.
  • a total flow loss occurring in the ink flowing from the ink inlet hole 16 into the manifold 18 varies according to the state the ink is jetted in.
  • the total flow loss is equal to the divergent flow loss.
  • the total flow loss is equal to the sum of the divergent flow loss and a turbulent flow loss.
  • a Reynolds number Re which is an important parameter deciding the flow state of a fluid, must be reduced to about 30 or less (see for example, Dynamics of Viscous Fluid , Takefumi Ikui and Masahiro Inoue, p. 206, Rikogaku-sha).
  • the velocity u is in inverse proportion to the square of the diameter d of the ink inlet hole 16.
  • the Reynolds number Re is, therefore, in inverse proportion to the diameter d of the ink inlet hole 16, as shown in Fig. 2.
  • the maximum consumption of the ink per unit time was set so that ink droplets in a volume of 40pl were simultaneously jetted from 25 nozzles at a frequency of 5kHz.
  • a value of 10cps of pigment ink containing tripropylene glycol monomethylether (TPM) as a base at ordinary temperature was used as the coefficient of kinematic viscosity ⁇ of the ink.
  • TPM tripropylene glycol monomethylether
  • the Reynolds number Re is influenced not only by the diameter d of the ink inlet hole 16 but also by the consumption of the ink per unit time and the coefficient of kinematic viscosity ⁇ of the ink.
  • the consumption of the ink per unit time cannot be reduced because a printing speed and clearness must be maintained.
  • the coefficient of kinematic viscosity ⁇ of the ink cannot be largely increased due to the need for stability of the jet of ink droplets. In particular, it is desired to prevent generation of unduly small ink droplets called satellites. Accordingly, there is a possibility that the relation between the Reynolds number Re and the diameter d of the ink inlet hole 16 may shift upwards as shown by a broken line 34 in Fig. 2 according to a change in printing speed or ink viscosity. However, there is no possibility that the relation may shift downwards from the solid line 32 calculated by using a minimum printing speed and a minimum ink viscosity.
  • the diameter d of the ink inlet hole 16 must be set to 0.2mm or more to reduce the Reynolds number Re to 30 or less.
  • the jet state of the ink flowing from the ink inlet hole 16 into the manifold 18 can be made into a laminar flow state by setting the diameter d of the ink inlet hole 16 to 0.2 mm or more. Accordingly, the total flow loss occurring in the ink flowing from the ink inlet hole 16 into the manifold 18 becomes the divergent flow loss, so that the total flow loss can be minimized, resulting in no turbulence of the ink flow in the manifold 18. Accordingly, the pressure of the ink in the manifold 18 becomes constant, and the pressure of the ink in each ink chamber 4 therefore becomes constant. As a result, the volume and the flying speed of ink droplets to be jetted become constant, thereby improving print quality. Further, since a desired amount of ink is supplied to each ink chamber 4, the volume of ink droplets to be jetted becomes a desired amount, thereby improving a print quality.
  • the size of the ink inlet hole 16 having a circular shape is decided to reduce the Reynolds number Re to 30 or less.
  • the Reynolds number Re that will not cause a turbulent flow of ink may be obtained by carrying out a test to decide the size of the ink inlet hole 16.
  • the ratio of pressure generated in each ink chamber 4 to driving voltage applied to each electrode 8 is large. Further, the ink flow into each ink chamber 4 is stable, and a resistance to the ink flow is small. Accordingly, a high pressure can be generated in each ink chamber 4 by applying a low driving voltage, and ink droplets can be jetted with a speed and a volume sufficient to form print images. According to the ink jet apparatus 1 of this preferred embodiment, ink droplets can be stably jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl by applying a low driving voltage of about 20 to 50 volts. Thus, a driving circuit can be manufactured at a low cost with a small size. The ink jet apparatus 1 as a whole can therefore be manufactured at a low cost with a small size.
  • ink is supplied from an ink tank (not shown) through an ink supply tube (not shown) into the ink inlet hole 16. Then, the ink is supplied from the ink inlet hole 16 through the manifold 18 into each ink chamber 4. At this time, the ink in the manifold 18 flows, as shown by arrows 31 in Fig. 3B, into each ink chamber 4. Since ink chambers 4a and 4b directly face the ink inlet hole 16, the ink pressures in the ink chambers 4a and 4b are changed by the jet of the ink flowing from the ink inlet hole 16.
  • Fig. 4 shows a change in central speed of the ink jet when the ink flows from the ink inlet hole 16 through the manifold 18 into the ink chambers 4a and 4b directly facing the ink inlet hole 16.
  • the axis of the abscissa represents the depth h of the manifold 18, and the axis of the ordinate represents the central speed of the jet.
  • a test was carried out using three values of the diameter d of the ink inlet hole 16 and setting a maximum ink consumption so that ink droplets in a volume of 40pl were simultaneously jetted from 20 nozzles at a frequency of 5kHz.
  • Solid lines 35, 36, and 37 shown in Fig. 4 correspond to the diameter d of the ink inlet hole 16 set to 0.7, 1.0, and 1.4mm, respectively.
  • the central speed u of the ink jet flowing from the ink inlet hole 16 is maximum in each case.
  • the central speed u of the ink jet is in inverse proportion to the square of the diameter d of the ink inlet hole 16.
  • the central speed u relatively rapidly decreases with an increase in depth h from zero.
  • the depth h becomes about 0.2mm or more, especially, 0.3mm or more, the central speed in becomes sufficiently small in each case. Even when the depth h is further increased, the central speed u hardly decreases in each case. Further, as far as the diameter d of the ink inlet hole 16 is 0.2mm or more, a tendency similar to that shown in Fig. 4 is exhibited.
  • the flow velocity of the jet is proportional to the ink consumption per unit time, which varies according to a print pattern. Accordingly, unless the depth h of the manifold 18 is set to a value enough to diminish the influence of the ink jet flowing from the ink inlet hole 16, the ink pressures in the ink chambers 4a and 4b directly facing the ink inlet hole 16 would vary according to the print pattern, causing instability of jetting of the ink droplets.
  • the depth h of the manifold 18 for distributing the ink flowing from the inlet hole 16 to each ink chamber 4 is set to 0.2mm or more, preferably 0.3mm or more.
  • the ink flow into each ink chamber becomes stable and uniform. Accordingly, the pressure generated in each ink chamber 4 upon application of a driving voltage to each electrode 8 becomes constant, and ink droplets can be jetted with a speed and a volume sufficient to form print images. According to the ink jet apparatus 1 of this preferred embodiment, ink droplets can be stably and uniformly jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl by applying a driving voltage of about 20 to 50 volts.
  • the ink flow into each ink chamber 4 is stable and uniform, it is not necessary to provide a function for correcting the ink flow in the driving circuit.
  • the driving circuit can be simplified and made compact.
  • the ink jet apparatus 1 can therefore be stabilized and manufactured at a low cost with a small size.
  • sectional area of the manifold 18 means the area of a cross section perpendicular to the longitudinal direction of the manifold 18, and the total sectional area of the ink chambers 4 means the total areas of the cross sections perpendicular to the longitudinal directions of all of the ink chambers 4.
  • ink is supplied from an ink tank (not shown) through an ink supply tube (not shown) into the ink inlet hole 16. Then, the ink is supplied from the ink inlet hole 16 through the manifold 18 into each ink chamber 4. At this time, the ink in the manifold 18 flows as shown by arrows 31 in Fig. 5B into each ink chamber 4.
  • a flow resistance increases proportionally to the length of a channel and rapidly decreases with a decrease in sectional area of the channel.
  • the channel has a rectangular cross section as in the manifold 18 and each ink chamber 4, the flow resistance to the ink in a unit length of the channel is in substantially inverse proportion to the square of the sectional area of the channel, as shown in Fig. 6.
  • the ink flowing from the ink inlet hole 16 undergoes a flow resistance in the manifold 18 and a flow resistance in each ink chamber 4 until the ink reaches each nozzle (not shown).
  • the total flow resistance to the ink is the sum of the flow resistance in the manifold 18 and the flow resistance in all of the ink chambers 4.
  • a flow distance from the ink inlet hole 16 to an ink chamber 4c is larger than a flow distance from the ink inlet hole 16 to an ink chamber 4a, for example. Therefore, the flow resistance to the ink that will flow into the ink chamber 4c becomes larger than the flow resistance to the ink that will flow into the ink chamber 4a. Further, the ink that will flow into another ink chamber 4 more distant from the ink inlet hole 16 than the ink chamber 4c undergoes a larger flow resistance.
  • the manifold 18 is designed in such a manner that the flow resistance in the manifold 18 becomes uniform regardless of the position of each ink chamber 4.
  • the manifold 18 is designed to have a sectional area such that the flow resistance in the manifold 18 is insignificant compared with the flow resistance in each ink chamber 4.
  • Fig. 7 shows a change in total flow resistance to the ink in this preferred embodiment, in which the axis of abscissa represents a sectional area ratio S1/SA between the manifold 18 and all the ink chambers 4.
  • the sectional area SA of all of the ink chambers 4 is equal to the product of the sectional area S2 of each ink chamber 4 and the number of all of the ink chambers 4.
  • the maximum ink consumption per unit time was set so that ink droplets in a volume of 40pl were simultaneously jetted from 50 nozzles at a frequency of 2.5kHz.
  • a value of 10cps of pigment ink containing tripropylene glycol monomethylether (TPM) as a base at ordinary temperature was used as the coefficient of kinematic viscosity ⁇ of the ink.
  • the dimensions of each ink chamber 4 were the height H of 400 ⁇ m, the width b of 80 ⁇ m, and the length of 12mm.
  • a solid line 38 is a curve showing the total flow resistance to the ink
  • a broken line 39 is a line showing the flow resistance in the ink chambers 4 only with no flow resistance in the manifold 18.
  • the total flow resistance rapidly increases on the left side of the sectional area ratio S1/SA with respect to a boundary value of about 1, that is, it rapidly increases with a decrease in sectional area ratio S1/SA from about 1.
  • the sectional area ratio S1/SA increases from about 1
  • the total flow resistance rapidly approaches the flow resistance in the ink chambers 4 only as shown by the broken line 39.
  • the sectional area ratio S1/SA decreases from 1
  • the flow resistance in the manifold 18 rapidly increases; while, when the sectional area S1/SA increases from 1, the flow resistance in the manifold 18 rapidly decreases.
  • the sectional area ratio S1/SA needs to be set to 1 or more to reduce the flow resistance in the manifold 18. Further, in an ink jet apparatus having a structure like that of this preferred embodiment, there is no possibility that the inks in the adjacent ink chambers 4 will be simultaneously jetted. Accordingly, the total sectional area of all of the ink chambers 4 becomes half in reality. Even considering this fact, the sectional area ratio S1/SA needs to be set to 0.5 or more.
  • the increase in the sectional area ratio S1/SA is necessary for a reduction in flow resistance in the manifold 18.
  • the sectional area ratio S1/SA becomes about 5 or more, the flow resistance in the manifold 18 is greatly reduced to 1% or less of the flow resistance in the ink chambers 4, which is substantially insignificant.
  • an increase in sectional area ratio S1/SA from about 5 merely causes enlargement of the ink jet apparatus 1 and is hardly effective for the reduction in the total flow resistance.
  • each ink chamber 4 were set to 400 ⁇ m in height H, 80 ⁇ m in width b, and 12mm in length. However, even when the dimensions of each ink chamber 4 are changed, the above preferable sectional area ratio S1/SA is unchanged. That is, as shown in Fig. 7, the curve 38 showing a pressure loss is merely expanded or contracted in a vertical direction on the basis of the axis of abscissa as shown by a broken line 38a or 38b.
  • the sectional area of the manifold 18 for distributing the ink having flowed from the ink inlet hole 16 into each ink chamber 4 is set to about 0.5 to 5 times the total sectional area of all of the ink chambers 4.
  • the ink jet apparatus 1 Because the sectional area of the manifold 18 is set to about 0.5 to 5 times the total sectional area of all the ink chambers 4, the ink is substantially uniformly distributed through the manifold 18 into each ink chamber 4 with a low flow resistance. Accordingly, the ink can be smoothly introduced into each ink chamber 4, and a high pressure can be generated in each ink chamber 4 by applying a low driving voltage. Thus, ink droplets are jetted with a sufficient speed and a uniform volume to form print images. According to the ink jet apparatus 1 of this preferred embodiment, ink droplets can be stably jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl by applying a low driving voltage of about 20 to 50 volts. Thus, a driving circuit can be manufactured at a low cost with a small size. The ink jet apparatus 1 as a whole can therefore be manufactured at a low cost with a small size.
  • Fig. 8 is a sectional view of a part of the ink jet apparatus 1 showing the shapes of the grooves 3, the side walls 6, the metal electrodes 8, and the cover plate 10.
  • Reference character b represents the width of each groove 3 formed on the piezoelectric ceramics plate 2
  • reference character H represents the depth of each groove 3.
  • each metal electrode 8 is formed on the upper half portion of each side wall 6, the length from the upper end to the lower end of each metal electrode 8 becomes half of the depth H of each groove 3, that is, becomes H/2.
  • reference character k represents the thickness of the cover plate 10 made of the same material as that of the piezoelectric ceramics plate 2.
  • each piezoelectric ceramics plate 2 having different groove depths H of 0.2, 0.4, and 0.6mm was used.
  • the width of each side wall 6 was set to 80 ⁇ m
  • the width b of each groove 3 was set to 80 ⁇ m.
  • Lead zirconate titanate (PZT) piezoelectric ceramics were used as the materials of the piezoelectric ceramics plate 2 and the cover plate 10.
  • An aluminum film having a thickness of about 1 ⁇ m formed by vacuum deposition was used as each metal electrode 8, and an epoxy adhesive was used as the adhesive 20.
  • four kinds of cover plates 10 having different thicknesses k of 0.25, 0.5, 1, and 2mm were used.
  • ink jet apparatus 1 twelve kinds were totally prepared by using the three kinds of piezoelectric ceramics plate 2 and the four kinds of cover plates 10 in combination. Further, pigment ink containing tripropylene glycol monomethylether (TPM) as a base was used as the ink, and a driving voltage to be applied to each metal electrode 8 was set to 40 volts.
  • TPM tripropylene glycol monomethylether
  • the flying speed of ink droplets was calculated by emitting light from a light emitting diode in synchronism with a driving voltage pulse to form a still image of the droplets and shifting a timing of the light emission to the driving voltage pulse to obtain a travel of the still image of the ink droplets.
  • Fig. 9 The flying speeds of ink droplets in the various kinds of ink jet apparatus 1 prepared above were measured.
  • the result of measurement is shown in Fig. 9, in which the axis of abscissa represents the product H x k of the depth H of each groove 3 and the thickness k of the cover plate 10 and the axis of ordinate represents the flying speed of ink droplets.
  • solid lines 40, 42, and 44 correspond to the ink jet apparatuses 1 having the depths H of 0.2, 0.4, and 0.6mm, respectively.
  • each side wall 6 was set to 80 ⁇ m in the above test according to this preferred embodiment, a tendency similar to that shown in Fig. 9 is exhibited even when the width of each side wall 6 varies from the above value.
  • the product of the depth of each groove 3 and the thickness of the cover plate 10 is set to 0.2 (mm x mm) or more.
  • the ratio of the pressure generated in each ink chamber 4 to the driving voltage to be applied to each metal electrode 8 can be increased. Accordingly, a high pressure can be generated in each ink chamber 4 by applying a low driving voltage, and ink droplets can be jetted with a speed and a volume enough to form print images.
  • ink droplets can be jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl by applying a low driving voltage of about 20 to 50 volts.
  • a driving circuit can be manufactured at a low cost with a small size.
  • the ink jet apparatus 1 as a whole can therefore be manufactured at a low cost with a small size.
  • each side wall 6 is integral at a lower end thereof with the piezoelectric ceramics plate 2, and an upper end of each side wall 6 is bonded to the cover plate 10 by the adhesive 20.
  • the surface of the cover plate 10 is smooth, a very thin film of the adhesive 20 is formed between each side wall 6 and the cover plate 10, and a bonded portion formed by the adhesive 20 has a high rigidity.
  • the surface of the cover plate 10 is rough, a large amount of the adhesive 20 is interposed between each side wall 6 and the cover plate 10 as shown in Fig. 10B to cause a low rigidity of the bonded portion.
  • the pressure generated in each ink chamber 4 upon jetting of ink droplets cannot be sufficiently increased, so that a desired volume of the ink droplets cannot be obtained.
  • the volume of ink droplets jetted was measured by using the cover plates 10 having different surface roughnesses.
  • each side wall 6 was set to 80 ⁇ m
  • the depth H of each groove 3 equal to the height of each side wall 6 was set to 400 ⁇ m
  • the width b of each groove 3 was set to 80 ⁇ m.
  • Lead zirconate titanate (PZT) piezoelectric ceramics were used as the materials of the piezoelectric ceramics plate 2 and each cover plate 10.
  • An aluminum film having a thickness of about 1 ⁇ m formed by vapor deposition was used as each metal electrode 8. Further, an epoxy adhesive was used as the adhesive 20.
  • the thickness k of each cover plate 10 was set to 1mm, and the surface roughness of the surface to be bonded to each side wall 6 was changed from 1 to 8 ⁇ m.
  • the adhesive 20 was applied uniformly and thinly in all the cover plates 10 having the different surface roughnesses.
  • the volume of ink droplets was calculated by measuring the weight of a predetermined number of the ink droplets with use of a high-precision analysis balance and by using the weight thus measured and the density of the ink.
  • the volume of the ink droplets is maximum and substantially constant. In comparison with this, when the surface roughness increases to about 4 ⁇ m, the volume of the ink droplets decreases about 10%. Further, when the surface roughness increases to about 5 ⁇ m or more, the volume of the ink droplets decreases 20% or more, causing a remarkable reduction in formation efficiency of the ink droplets.
  • the surface roughness of the cover plate 10 is set to 5 ⁇ m or less, preferably 3 ⁇ m or less.
  • the ratio of the pressure generated in each ink chamber 4 to the driving voltage applied to each metal electrode 8 is large. Accordingly, a high pressure can be generated in each ink chamber 4 by applying a low driving voltage, and ink droplets can be jetted with a speed and a volume enough to form print images. According to the ink jet apparatus 1 of this preferred embodiment, ink droplets can be jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl, which depends on the length of each ink chamber 4, by applying a low driving voltage of about 20 to 50 volts. Thus, a driving circuit can be manufactured at a low cost with a small size. The ink jet apparatus 1 as a whole can therefore be manufactured at a low cost with a small size.
  • the piezoelectric ceramics plate 2 of the ink jet apparatus 1 is formed with a plurality of grooves 3 each forming an ink chamber 4 and with a plurality of side walls 6 partitioning the grooves 3.
  • the width b of each groove 3 is set to 80 ⁇ m, and the depth H of each groove 3 is set to 400 ⁇ m.
  • the width W of each side wall 6 is set to 80 ⁇ m.
  • the upper end surface of each side wall 6 is bonded to the cover plate 10 by an adhesive 20.
  • a thermosetting adhesive such as an epoxy adhesive is used as the adhesive 20.
  • the adhesive 20 is hardened by heating up to about 160°C.
  • the thickness of the cover plate 10 is set to 1mm.
  • the material of the piezoelectric ceramics plate 2 is not necessarily the same as the material of the cover plate 10. Accordingly, when the material of the piezoelectric ceramics plate 2 has a coefficient of linear expansion different from that of the material of the cover plate 10, the deformation of both members becomes nonuniform when the temperature of the adhesive 20 after being hardened by heating is returned to ordinary temperature. As a result, even when each side wall 6 is bonded to the cover plate 10 at about 160°C in such a manner that the adjacent side walls 6 are parallel to each other as shown in Fig. 12A, the side walls 6 are deformed after reaching ordinary temperatures as shown in Fig. 12B, a residual stress is generated in each side wall 6 and the adhesive 20 reducing the strength of a bonded portion, in particular.
  • the magnitude of the residual stress is dependent upon not only a difference in coefficient of linear expansion but also an elastic modulus (Young's modulus) of material.
  • the cover plate 10 is sufficiently thick as compared with each side wall 6.
  • Young's modulus due to a difference in material of the cover plate 10 is substantially insignificant.
  • Fig. 13 The result of measurement is shown in Fig. 13.
  • the difference in coefficient of linear expansion between the piezoelectric ceramics plate 2 and the cover plate 10 is 6.0ppm/°C or less
  • the life of the ink jet apparatus 1 is 30 x 10 8 times.
  • the difference in coefficient of linear expansion becomes 8.5ppm/°C
  • the life decreases to 20 x 10 8 times.
  • the difference in coefficients of linear expansion becomes larger, the life decreases more remarkably.
  • thermosetting adhesive such as a phenol adhesive
  • a tendency similar to that shown in Fig. 13 is exhibited.
  • the difference in coefficients of linear expansion between the piezoelectric ceramics plate 2 and the cover plate 10 is set to 8.5ppm/°C or less, preferably 6.0ppm/°C or less.
  • the jet life of the ink jet apparatus 1 becomes at least about 20 x 10 8 times, preferably 30 x 10 8 times which is sufficient in practical use. Accordingly, the ink jet apparatus 1 can be sufficiently applied to not only printing of character images but also printing of graphics images requiring a great frequency of jets of ink. Accordingly, the number of replacements of the ink jet apparatus 1 in a printer can be reduced, and the reliability of the printer can be improved.
  • Fig. 14 shows a cross section of the ink jet apparatus 1 as viewed from one side thereof.
  • ink is supplied from an ink tank (not shown) through an ink supply tube (not shown) into the ink inlet hole 16. Then, the ink is supplied from the ink inlet hole 16 through the manifold 18 into each ink chamber 4.
  • PZT lead zirconate titanate
  • each ink jet apparatus 1 To examine a change in volume of ink droplets due to a change in relative positional relationship between the manifold 18 and each ink chamber 4, various ink jet apparatuses 1 were prepared having different distances x from the front side surface of the manifold 18 to the rear end surface of each ink chamber 4. However, in each ink jet apparatus 1, the full length L of each ink chamber 4 was set to 17mm. Further, in each ink jet apparatus 1, the depth h of the manifold 18 was set to 0.5mm, and the width w of the manifold 18 was set to 5mm. The volume of ink droplets was calculated by measuring the weight of a predetermined number of the ink droplets jetted with use of a high-precision analysis balance and by using the weight thus measured and the density of the ink.
  • Fig. 15 in which the axis of abscissa represents the distance x between the front side surface of the manifold 18 and the rear end surface of each ink chamber 4, and the axis of ordinate represents the volume of ink droplets.
  • the distance x ranges between 1mm and 6mm, the volume of ink droplets reaches a maximum value of 60pl, which is kept substantially constant.
  • x 1 means that the distance of overlap between the manifold 18 and each ink chamber 4 is equal to 1mm, and a decrease in the distance x down from 1mm causes the ink flow into each ink chamber 4 to become rapidly hard.
  • the distance x becomes 6mm or more, the volume of ink droplets does not decrease as rapidly. This is due to the fact that an increase in the distance x results in an approach of the manifold 18 to a nozzle plate 14, that is, the distance y between the front side surface of the manifold 18 and the inner surface of the nozzle plate 14.
  • the pressure in each ink chamber 4 is increased to jet the ink droplets from a nozzle 12 formed through the nozzle plate 14, the ink in each ink chamber 4 is forced from the nozzle 12. Simultaneously, it reversely flows from the manifold 18 into the ink inlet hole 16. As a result, the pressure near the manifold 18 is rapidly reduced to generate a negative pressure wave.
  • the volume of ink droplets becomes about 30pl, i.e., half of the maximum value.
  • the relative positional relationship between the manifold 18 and each ink chamber 4 must be defined so that the distance x is set to 0.2mm or more and the distance y is set to 3mm or more, preferably 6mm or more.
  • the position of the manifold 18 to be formed in the cover plate 10 relative to each ink chamber 4 is such that the distance between the front side surface of the manifold 18 and the rear end surface of each ink chamber 4 is set to 0.2mm or more. Also, the distance between the front side surface of the manifold 18 and the inner surface of the nozzle plate 14 is set to 3mm or more, preferably 6mm or more.
  • the ink droplets can be efficiently jetted and the ink can be smoothly supplied to each ink chamber 4. Accordingly, the ink droplets can be jetted with a speed and a volume sufficient to form print images. According to the ink jet apparatus 1 of this preferred embodiment, ink droplets can be jetted with a speed of about 3 to 8m/sec and a volume of about 30 to 90pl by applying a low driving voltage of about 20 to 50 volts. Thus, a driving circuit can be manufactured at a low cost with a small size. The ink jet apparatus 1 as a whole can therefore be manufactured at a low cost with a small size.
  • the ink jet apparatus 1 of the preferred embodiment is of a shear mode type, such that the ink in each ink chamber 4 is jetted by the shear mode deformation of each side wall 6 made of piezoelectric ceramics
  • the ink jet apparatus according to the present invention may be another type, such as a Kaiser type or a thermal jet type as mentioned previously.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)

Claims (11)

  1. Imprimante à jet d'encre comprenant :
    une plaque (2) ayant une pluralité de parois droites s'étendant longitudinalement (6) définissant des chambres d'encre parallèles (4), chacune des dites chambres d'encre (4) comportant une extrémité avant et une extrémité arrière ;
    un ensemble de buses (14) couplé à la dite plaque (2) à la dite extrémité avant des dites chambres d'encre (4) et ayant, formées en lui, des buses (12), les dites buses (12) étant alignées avec les dites chambres d'encre (4) ; et
    un couvercle (10) couplé à la dite plaque (2) et fermant les dites chambres d'encre (4), le dit couvercle (10) incluant un collecteur d'encre (18) comportant un côté avant et un côté arrière et étant en communication avec les dites chambres d'encre (4) et incluant une entrée d'encre (16) dans le dit collecteur (18) pour introduire de l'encre dans le dit collecteur (18) ; caractérisée en ce que
    une distance (X) entre le dit côté avant du dit collecteur (18) et la dite extrémité arrière des dites chambres d'encre (4) est comprise entre 0,2 mm et 6 mm, et une distance (Y) entre le dit côté avant du dit collecteur (18) et la dite extrémité avant des dites chambres d'encre (4) à la dite buse (12) est au moins de 3 mm.
  2. Imprimante à jet d'encre selon la revendication 1, dans laquelle la dite distance (Y) entre le dit côté avant du dit collecteur (18) et la dite extrémité avant des dites chambres d'encre (4) à la dite buse (12) est au moins de 6 mm.
  3. Imprimante à jet d'encre selon la revendication 1 ou 2, dans laquelle chacune des dites chambres d'encre (4) a une profondeur (H) et le dit couvercle (10) a une épaisseur (K), et dans laquelle la dite profondeur (H) multipliée par la dite épaisseur (K) est égal à 0,2 mm2 ou plus, ce qui supprime la déformation du dit couvercle.
  4. Imprimante à jet d'encre selon la revendication 1, 2 ou 3, dans laquelle le dit couvercle a une surface qui est tournée vers la dite plaque (2) et la dite surface a une rugosité de 5 µm ou moins.
  5. Imprimante à jet d'encre selon la revendication 4, dans laquelle la dite surface a une rugosité de 3 µm ou moins.
  6. Imprimante à jet d'encre selon l'une quelconque des revendications précédentes, dans laquelle la dite entrée d'encre (16) est dimensionnée pour créer un écoulement laminaire d'encre dans le dit collecteur.
  7. Imprimante à jet d'encre selon l'une quelconque des revendications précédentes, dans laquelle le dit collecteur (18) a une profondeur qui permet à l'encre de s'écouler dans les dites chambres d'encre (4) sans variation de pression.
  8. Imprimante à jet d'encre selon l'une quelconque des revendications précédentes, dans laquelle la dite entrée d'encre (16) a un diamètre d'au moins 0,2 mm.
  9. Imprimante à jet d'encre selon l'une quelconque des revendications précédentes, dans laquelle le dit collecteur (18) a une profondeur d'au moins 0,2 mm.
  10. Imprimante à jet d'encre selon la revendication 9, dans laquelle le dit collecteur (18) a une profondeur d'au moins 0,3 mm.
  11. Imprimante à jet d'encre selon l'une quelconque des revendications précédentes, dans laquelle la dite plaque (2) et le dit couvercle (10) sont liés ensemble par un agent adhésif thermodurcissable.
EP97101749A 1993-02-10 1994-02-10 Appareil à jet d'encre Expired - Lifetime EP0774355B1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP97114688A EP0810093B1 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre
EP97114689A EP0810094B1 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2257193 1993-02-10
JP5022571A JPH06234216A (ja) 1993-02-10 1993-02-10 インク噴射装置
JP22571/93 1993-02-10
EP94300968A EP0611154B2 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre

Related Parent Applications (2)

Application Number Title Priority Date Filing Date
EP94300968A Division EP0611154B2 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre
EP94300968.8 Division 1994-02-10

Related Child Applications (2)

Application Number Title Priority Date Filing Date
EP97114689A Division EP0810094B1 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre
EP97114688A Division EP0810093B1 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre

Publications (3)

Publication Number Publication Date
EP0774355A2 EP0774355A2 (fr) 1997-05-21
EP0774355A3 EP0774355A3 (fr) 1997-11-19
EP0774355B1 true EP0774355B1 (fr) 1999-11-17

Family

ID=26136921

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97101749A Expired - Lifetime EP0774355B1 (fr) 1993-02-10 1994-02-10 Appareil à jet d'encre

Country Status (1)

Country Link
EP (1) EP0774355B1 (fr)

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5912828B2 (ja) 1976-07-19 1984-03-26 株式会社大林組 鉄筋コンクリ−ト構造骨組の柱・梁接合部
US4887100A (en) 1987-01-10 1989-12-12 Am International, Inc. Droplet deposition apparatus
GB8824014D0 (en) * 1988-10-13 1988-11-23 Am Int High density multi-channel array electrically pulsed droplet deposition apparatus
JPH04363250A (ja) * 1991-03-19 1992-12-16 Tokyo Electric Co Ltd インクジェットプリンタヘッド及びその製造方法
JP2744535B2 (ja) * 1991-07-08 1998-04-28 株式会社テック インクジェットプリンタヘッドの製造方法
JPH06159914A (ja) 1992-11-24 1994-06-07 Sanyo Electric Co Ltd 薬用保冷庫

Also Published As

Publication number Publication date
EP0774355A2 (fr) 1997-05-21
EP0774355A3 (fr) 1997-11-19

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