JP2007075998A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head which enables efficient cleaning. <P>SOLUTION: This inkjet head has a plurality of channels which are composed of a pressure chamber and an orifice plate 33 with an ink ejection port 33a. In the inkjet head, a plurality of grooves communicating with respective channels are provided, and a common liquid chamber is provided on the upper part of the grooves. The inkjet head comprises: a partition plate which brings about channel resistance along the grooves by separating the common chamber in a direction orthogonal to the grooves; a liquid supply port for supplying the liquid to a first common liquid chamber on the pressure-chamber side of the partition plate; and a liquid ejection port for ejecting the liquid from a second common liquid chamber on the backside of the pressure-chamber of the partition plate. The flow of the liquid along the grooves is formed by making the liquid flow to the liquid ejection port from the liquid supply port. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet head having improved detergency.

  Various apparatuses for cleaning the inside of an inkjet head are known (see, for example, Patent Document 1).

  A general inkjet head cleaning method will be described with reference to FIGS. This example shows an inkjet head 14 without a filter. It is shown in AA sectional view 22 of FIG.

  21 and 22, an ink supply port 15 and a discharge port 16 are provided on the upper part of an inkjet head 14 in which an orifice plate 13 having a pressure chamber 12 and an ink discharge port 13a is bonded to the opening end of the groove 10. .

  That is, a pressure chamber 12 surrounded by the partition wall of the groove 10, the top plate 17, and the orifice plate 13 is formed, and an actuator (not shown) is provided in the pressure chamber 12 to generate pressure, and from the ink discharge port 13a. Ink is ejected.

  The groove 10 continues to the back of the pressure chamber 12 (right side in the figure), and gradually becomes shallower with R due to the diameter of the blade used to generate the groove 10. This portion is regarded as an open end in the operation of the pressure chamber, and is opened to the common liquid chamber 16 at the top.

On the other hand, when the inkjet head 14 has a filter, a filter 21 is installed in the common liquid chamber 18 as shown in FIG. In some cases, liquid is caused to flow into the inkjet head 14 from the supply port 15 and discharged from the discharge port 16. By doing so, cleaning in the inkjet head 14, replacement of ink in the inkjet head 14, and discharge of bubbles in the inkjet head 14 are performed. Here, the fluid to be flowed is ink, ink solvent, or cleaning liquid.
Japanese Patent No. 3108788 JP 2002-144576 A

  When the liquid flows from the supply port 15 toward the discharge port 16 through the inkjet head 14 having the cross section shown in FIG. 22, there are the following problems.

  That is, the liquid flow in the common liquid chamber 18 occurs in the direction in which the nozzles are arranged, that is, in the direction perpendicular to the grooves 10. At this time, depending on the viscosity of the flowing liquid, the flow velocity becomes the maximum near the center of the cross section of the common liquid chamber 18 in FIG. It is. This becomes a problem. When cleaning the inkjet head 14, the place where dirt is most likely to adhere is the upper part of the groove 10. This is because although the upper portion of the groove 10 is a surface in contact with the common liquid chamber 18, no flow velocity is generated in this portion.

  At the same time, the surface where the upper portion of the groove 10 is in contact with the common liquid chamber 18 is the portion where ink is most difficult to replace, and is also the portion where small bubbles are likely to adhere, so the reason for flowing ink becomes a problem in any of the above cases. .

  Further, as shown in FIG. 23, in the head having the filter 21 in the common liquid chamber 16, the liquid flows only on the primary side of the filter 21, and the secondary side of the filter 21 cannot be cleaned at all.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an inkjet head capable of performing efficient cleaning.

  The invention according to claim 1 is an inkjet head having a plurality of channels comprising an orifice plate having a pressure chamber and a discharge port, having a plurality of grooves communicating with each channel, and having a common liquid chamber above the grooves. A partition plate that separates the common liquid chamber in a direction perpendicular to the groove and has flow resistance along the groove, and a liquid that supplies the liquid to the first common liquid chamber on the pressure chamber side of the partition plate A supply port; and a liquid discharge port for discharging liquid from a second common liquid chamber on the back side of the pressure chamber of the partition plate, and the groove is formed by flowing the liquid from the liquid supply port to the liquid discharge port. It is characterized by creating a flow of liquid along the line.

  According to a second aspect of the present invention, the cross-sectional area of the first common liquid chamber according to the first aspect varies along the channel, and the cross-sectional area of the second common liquid chamber varies along the channel. It changes in the direction opposite to the common liquid chamber.

  According to a third aspect of the present invention, the cross-sectional area of the first common liquid chamber according to the first aspect changes so as to decrease along the channel from the side where the liquid supply port is provided. The cross-sectional area of the chamber is changed so as to decrease along the channel from the side where the liquid discharge port is provided.

  According to a fourth aspect of the present invention, the first common liquid chamber according to the first aspect has a filter.

  According to a fifth aspect of the present invention, the cross-sectional area of the second common liquid chamber according to the fourth aspect varies along the channel, and the cross-sectional area of the supply path on the primary side of the filter varies along the channel. It changes in the reverse direction.

  According to a sixth aspect of the present invention, the cross-sectional area of the second common liquid chamber according to the fourth aspect changes so as to decrease along the channel from the side on which the liquid discharge port is provided. The cross-sectional area of the chamber is changed so as to decrease along the channel from the side where the liquid supply port is provided.

  The invention according to claim 7 is characterized in that the liquid discharge port according to any one of claims 1 to 6 is sealed during use.

  According to the present invention, since the flow to the discharge port along the groove can be made in the groove portion behind the pressure chamber, which could not be cleaned conventionally, cleaning, ink replacement, and bubble discharge are effectively effective. Can be done.

  Further, since a vortex can be created in the groove, the cleaning effect can be further enhanced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In FIGS. 1 and 2, reference numeral 34 denotes an ink jet head. In the inkjet head 34, a piezoelectric member 34a is laminated on a substrate 34d. The piezoelectric member 34a is formed of a piezoelectric member made of PZT that is vertically polarized, and has a plurality of grooves 30 that open at the front surface (left side in the figure) and gradually become shallower at the rear portion with R. .

A top plate 34b is bonded so as to surround the groove 30 of the laminated piezoelectric member 34a, and the top plate 34b
The upper opening is closed by a lid member 34c. The common liquid chamber 41 formed in this way is divided into a first common liquid chamber 42 located on the orifice plate 33 side by a partition plate 41 described later and a second common liquid in a direction away from the orifice plate (right side in the figure). Separated into chamber 43.

    A liquid supply port 35 is connected to the first common liquid chamber 42, and a discharge port 36 is connected to the second common liquid chamber 43. The discharge port 36 may be sealed after cleaning.

  An orifice plate 33 having an ink discharge port 33a at a position corresponding to each groove 30 is bonded to the front surface of the inkjet head.

  Further, the pressure chamber 32 is formed by the space surrounded by the partition walls of each groove 30, the common liquid chamber 41, and the orifice plate 33. Then, electrodes are formed on both sides of the partition wall, and ink is supplied to the pressure chamber 32, and a drive pulse is applied to the partition wall forming the pressure chamber 32 to deform the partition wall so that the inside of the pressure chamber 32 By pressurizing the ink, the ink is ejected from the ink ejection port 33a.

  Each channel 31 is constituted by the pressure chamber 32 and the groove 30. In this embodiment, 318 channels # 1 to # 318 are provided.

  The common liquid chamber 41 is separated into left and right as used in FIG. 2 by a partition plate 44 disposed in a direction orthogonal to the groove 30. Note that the liquid chamber on the orifice plate 33 side from the partition plate 44 is the first common liquid chamber 42, and the liquid chamber farther from the partition plate 44 from the orifice plate 33 (right side in the figure) is the second common liquid chamber 43. To tell.

  The supply port 35 is connected to the # 1 side of the first common liquid chamber 42 closer to the pressure chamber 32 (left side in the figure).

  The discharge port 36 is connected to the # 318 side of the second common liquid chamber 43 on the back side (right side in the drawing) of the pressure chamber.

  The orifice surface may be left open if an ink receiver is provided to allow ink to drip, but here it is assumed to be sealed by a cap (not shown) for simplicity. That is, there is no liquid flow toward the orifice plate 33.

  As shown in FIG. 2, the depth d of the groove 30 is, for example, 0.3 mm, the width w of the groove 30 in the depth direction is, for example, 0.08 mm, the channel pitch is 0.169 mm, and the number of channels is, for example, 318.

  For example, a gap s of 0.5 mm is provided between the partition plate 44 and the upper part of the channel 31. The gap s is preferably narrow, but is set appropriately according to the accuracy of the members constituting the head 34. Alternatively, a structure may be adopted in which the accuracy of each member is increased so that the gap is 0 mm, and the member is bonded to the column portion of the groove.

  The dimension of the partition plate 44 in the channel arrangement direction, that is, the channel arrangement direction is 0.169 * 318 = 54 mm.

  As shown in FIG. 3, the ceiling of the first common liquid chamber 42 is lowered from the supply side, that is, from the # 1 side toward the # 318 side. This is a structure for making the flow in the first common liquid chamber 42 smooth. For example, the height of the ceiling on the # 1 side is 4 mm, and the height of the ceiling on the # 318 side is 1 mm.

  The dimensions of the second common liquid chamber 43 on the right side of the partition plate 44 are 2 mm in the direction along the groove 30 and 0.169 * 318 = 54 mm in the direction orthogonal to the channels, that is, the channel arrangement direction.

  As shown in FIG. 4, the ceiling of the second common liquid chamber 43 is lowered from the discharge side, that is, from the # 318 side to the # 1 side. For example, the height at the # 318 side is 4 mm, The height is 1mm.

  FIG. 5 is an enlarged view of one channel of the flow path in the vicinity of the partition plate 44 and the first common liquid chamber 42. In FIG. 5, the flow resistance of the upper part of the groove 30 below the partition plate 44 is Ru, the flow resistance inside the groove is RL, and the flow paths corresponding to the channels 1 to 318 orthogonal to the grooves of the first common liquid chamber. Assuming that the resistances are Rf1 to Rf318 and the flow resistances corresponding to the channels 1 to 318 orthogonal to the grooves 30 of the second common liquid chamber 43 are Rs1 to Rs318, an equivalent circuit of the entire head is as shown in FIG. . In FIG. 6, Pt is a differential pressure (Pt = 10 kPa) applied between the supply port 35 and the discharge port 36, it is a flow rate (Ml / s) flowing at that time, and Ps # and Pf # are based on the discharge port 36. The pressure of each part, is #, if #, iu #, iL # is the flow rate (mL / s) flowing through each part, and the unit of flow path resistance is Pa · s / mL.

When Ru and RL were calculated for a liquid with a viscosity of 10 Pa · s, they were 21739 Pa · s / mL and 793650 Pa · smL, respectively. The values of Rs # and Rf # are different for each channel, and are the values in the second and third columns of Table 1, respectively.

  In Table 1, d, e, f, a, b, c are equivalent resistances of the equivalent circuit of FIG. 8 modified as shown in FIGS. 7 to 10, and is, if, iu, iL are Pt = 10 kPa. The flow rate, Ps, and Pf of each part when given are the pressures of each part based on the discharge port.

  When the value of iL is plotted along the channel, the liquid flows in the range of the flow rate of 1 to 2 μL / s as shown in FIG.

  Thus, the balance of the flow rate for each channel can be adjusted by adjusting the height of the common liquid chamber 41.

  For example, if the height of the first and second common liquid chambers 42 and 43 is 0.7 to 4 mm along the channel, as shown in FIG. Further improvement can be achieved if the first and second common liquid chambers 42 and 43 are formed with undulations.

The flow velocity vector corresponding to FIG. 5 is as shown in FIG. As shown in FIG.
It can be seen that a flow toward the discharge port 36 occurs in the groove. Further, a vortex flow 51 is generated under the first common liquid chamber 42, and a cleaning effect by the vortex flow 51 can also be expected.

  As described above, according to the first embodiment, the ceiling inclination of the first common liquid chamber 42 on the supply side and the second common liquid chamber 43 on the discharge side, that is, the cross-sectional area of the flow path is along the channel. Therefore, the liquid flow from the supply port 35 to the discharge port 36 can be adjusted to be uniform for each channel. Further, if the change profile is adjusted, the liquid flow from the supply port 35 to the discharge port 36 can be made uniform for each channel.

  Next, a second embodiment will be described. The second embodiment is characterized in that a filter 61 is provided in the first common liquid chamber 42 of the first embodiment. The filter 61 is provided at a height h (for example, 1 mm) from the upper surface of the channel 31. The filter has a mesh size of 10 μm, a flow resistance of 5560 Pa · s / mL, and 100000 Pa · s / mL per channel.

  Since the configuration other than the filter 61 is the same as that of the first embodiment, its detailed configuration is omitted. That is, the filter 61 is disposed in the first common liquid chamber 42 close to the pressure chamber 32. The supply port 35 is provided on the primary side of the filter 61, that is, above the filter 61.

  Ink is supplied from the primary side of the filter 61. Since the flow resistance on the primary side of the filter 61 is sufficiently smaller than the flow path resistance of the filter 61, the flow resistance on the primary side of the filter 61 is ignored in the following calculation for simplicity.

  The flow resistance in the upper part of the groove 30 below the partition plate 44 is Ru, the flow resistance in the groove 30 is RL, the flow resistance per channel of the filter 61 is Rf, and the direction perpendicular to the groove 30 in the lower flow path of the filter 61 FIG. 17 shows an equivalent circuit of the entire head, where Rp is the flow resistance per channel and Rs is the flow resistance corresponding to channels 1 to 318 orthogonal to the channel of the second common liquid chamber 43. It becomes like this. In FIG. 17, Pt is a differential pressure (Pt = 10 kPa) applied between the supply port 35 and the discharge port 36, it is a flow rate (Ml / s) flowing at that time, and Ps # and Pf # are based on the discharge port 36. The pressure of each part, is #, if #, ip #, iu #, iL # is the flow rate (mL / s) flowing through each part, and the unit of flow path resistance is Pa · s / mL.

When Ru and RL were calculated for a liquid with a viscosity of 10 Pa · s, they were 21739 Pa · s / mL and 793650 Pa · smL, respectively. As described above, it is 1800000 Pa · s / mL. The values of Rf, Rs #, and Rf # are different for each channel, and are the values in the second and third columns of Table 2, respectively.

  In Table 2, e ′, f ′, a ′, a, b, c ′, c, d, e, and f are resistance values of equivalent circuits obtained by modifying the equivalent circuit of FIG. 17 as shown in FIGS. is, if, ip, iu, iL are the flow rates of the respective parts when Pt = 10 kPa is given, and Ps, Pf are the pressures of the respective parts based on the discharge port.

  When the value of iL is plotted along the channel, the liquid flows in a flow rate range of about 1 to 3 μL / s as shown in FIG. Although there is a difference in flow rate between the channels, the ratio is suppressed and made uniform within a range of about three times or less due to the flow path resistance of the filter 61.

  The flow rate flowing in the groove 30 increases toward the # 318 channel because the pressure loss is small because the # 318 side is close to the discharge port 36.

  In the second embodiment, for the sake of simplicity, the flow resistance on the primary side of the filter 61 is calculated to be sufficiently small. However, the supply port 35 is provided on the # 1 channel side, and the primary side of the filter 61 is calculated. As shown in FIG. 15, the ceiling can be lowered from the # 1 side to the # 318 side as in the first embodiment, and a slight improvement can be achieved by calculating in consideration of this.

  As described above, according to the second embodiment, the flow rate of the liquid flowing from the supply port 35 to the discharge port 36 is determined for each channel by the flow path resistance of the filter 61 provided in the first common liquid chamber 42 on the supply side. Differences can be reduced.

   Further, by changing the cross-sectional area of the primary pressure chamber of the filter 61 provided in the first common liquid chamber 41 on the supply side along the channel, the channel of the liquid flow from the supply port 35 to the discharge port 36 is changed. Each difference can be reduced.

  If the difference in the flow of liquid from the supply port 35 to the discharge port 36 is reduced in this way, cleaning, ink replacement, and bubble discharge can be performed more effectively.

  Since the ink flow along the groove generated by the first and second embodiments described above is washed away from the upper part of the groove where dirt is most likely to adhere, the head can be effectively cleaned.

  In addition, after washing | cleaning using a discharge port, in order to prevent a foreign material from flowing backward from a discharge port, you may seal a discharge port.

  Further, the discharge port 36 can be connected to the ink path of the printing apparatus so that it can be cleaned in the printing apparatus using a pump or the like.

  Further, the discharge port 36 is not limited to cleaning use, and may be used for ink replacement for the purpose of color change or the like. At this time, since the conditions necessary for neatly replacing the ink are substantially the same as the conditions necessary for the cleaning, a similar effect can be expected. Here, since the upper portion of the groove is a portion where small bubbles are easily attached, it is effective even when used for discharging the bubbles.

  In the above-described embodiment, the cleaning liquid is supplied from the supply port 35, but the nozzle may suck it.

  The present invention is not applied to the ink jet head having the structure shown in FIGS. 2 and 14, but a pressure chamber is formed on the opening side of a groove formed in the head material, and a heating element is formed on the bottom surface of the pressure chamber. The present invention can also be applied to an inkjet head configured to pressurize ink in the pressure chamber by providing an electromechanical converter and an actuator.

1 is a perspective view of an inkjet head according to a first embodiment of the present invention. Sectional drawing along the BB line of the inkjet head of FIG. FIG. 2 is a cross-sectional view of the inkjet head of FIG. 1 taken along line CC. FIG. 2 is a cross-sectional view taken along line DD of the ink jet head of FIG. 1. The enlarged view for 1 channel of a 1st common liquid chamber from the partition plate which concerns on the same embodiment. FIG. 3 is an equivalent circuit diagram of the entire head according to the same embodiment. FIG. 3 is an equivalent circuit diagram according to the embodiment. FIG. 3 is an equivalent circuit diagram according to the embodiment. FIG. 3 is an equivalent circuit diagram according to the embodiment. FIG. 3 is an equivalent circuit diagram according to the embodiment. The figure which shows the flow volume for every channel which concerns on the same embodiment. The figure which shows the flow vector of the 1st common liquid chamber and partition plate lower side which concerns on the same embodiment. The perspective view of the inkjet head which concerns on the 2nd Embodiment of this invention. FIG. 14 is a cross-sectional view of the inkjet head of FIG. 13 along the line EE. FIG. 14 is a cross-sectional view taken along line FF of the inkjet head of FIG. FIG. 14 is a cross-sectional view taken along line GG of the inkjet head of FIG. FIG. 6 is an equivalent circuit diagram of the ink jet head according to the second embodiment. FIG. 6 is an equivalent circuit diagram according to the second embodiment. FIG. 6 is an equivalent circuit diagram according to the second embodiment. The figure which shows the flow volume for every channel which concerns on the 2nd Embodiment. The perspective view of the conventional inkjet head. FIG. 22 is a cross-sectional view of the inkjet head of FIG. 21 taken along line AA. Sectional drawing along the AA line of the inkjet head which has the conventional filter.

Explanation of symbols

  34 ... Inkjet head, 35 ... Liquid supply port, 36 ... Discharge port, 41 ... Common liquid chamber, 42 ... First common liquid chamber, 43 ... Second common liquid chamber, 44 ... Partition plate, 61 ... Filter.

Claims (7)

In an inkjet head having a plurality of channels composed of an orifice plate having a pressure chamber and an ink discharge port, having a plurality of grooves communicating with each channel, and having a common liquid chamber above the grooves,
A partition plate that separates the common liquid chamber in a direction orthogonal to the groove and has flow resistance along the groove;
A liquid supply port for supplying liquid to the first common liquid chamber on the pressure chamber side of the partition plate;
A liquid discharge port for discharging liquid from the second common liquid chamber on the back side of the pressure chamber of the partition plate;
An ink jet head, wherein a liquid flow along a groove is created by flowing a liquid from the liquid supply port to the liquid discharge port. The cross-sectional area of the first common liquid chamber changes along the channel, and the cross-sectional area of the second common liquid chamber changes along the channel in a direction opposite to the first common liquid chamber. The inkjet head according to claim 1. The cross-sectional area of the first common liquid chamber changes so as to decrease along the channel from the side where the liquid supply port is provided, and the cross-sectional area of the second common liquid chamber is provided with the liquid discharge port. 2. The ink jet head according to claim 1, wherein the ink jet head is changed so as to decrease along the channel from the opposite side. The inkjet head according to claim 1, wherein the first common liquid chamber has a filter. 5. The cross-sectional area of the second common liquid chamber changes along the channel, and the cross-sectional area of the supply path on the primary side of the filter changes in the opposite direction along the channel. The inkjet head as described. The cross-sectional area of the second common liquid chamber changes so as to decrease along the channel from the side where the liquid discharge port is provided, and the cross-sectional area of the first common liquid chamber is provided with the liquid supply port. 5. The ink jet head according to claim 4, wherein the ink jet head is changed so as to decrease along the channel from the opposite side. The inkjet head according to claim 1, wherein the liquid discharge port is sealed during use.

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