JP2005081597A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inkjet head capable of ejecting uniform liquid drops by making the ink temperature uniform in an inkjet head thereby making the ink viscosity uniform. <P>SOLUTION: The inkjet head 4 comprises an inkjet head chip 41 having a nozzle array 42a arranged with ink ejection openings 42 on the forward end face 41a, a manifold 48 bonded to the side part of the inkjet head chip and introducing ink thereto, a housing frame 53 for containing the manifold, and an ink heater 49 for heating ink in the manifold through the manifold between the manifold and the housing frame. Heat generation density of the ink heater varies in the nozzle array direction X. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet head, and more particularly to an inkjet head that discharges heated ink.

  2. Description of the Related Art Conventionally, ink jet printers that record predetermined images by ejecting ink onto recording media such as paper and plastic thin plates have been proposed and put into practical use. The ink jet printer includes an ink jet head having an ink ejection port, and ejects ink from the ink ejection port toward the recording medium while moving the ink jet head in a predetermined direction, thereby obtaining a predetermined image on the recording medium. It is recorded.

  In the ink jet printer, ink is ejected by an ink jet head using a piezoelectric element (piezo element) or the like. The inkjet head includes an inkjet head chip in which a nozzle array in which ink ejection ports for ejecting ink are arranged is provided on a front end surface, and is bonded and fixed to a side portion of the inkjet head chip to guide the ink to the inkjet head chip. A manifold and a housing frame that houses the manifold are provided.

By the way, since the viscosity of the ink used in the ink jet printer increases at low temperatures, it is necessary to heat the ink to reduce the viscosity and maintain the viscosity at a predetermined viscosity for the purpose of good ink ejection.
Therefore, conventionally, an ink heater is provided in an ink tank, or an ink heater (ink heating device) for heating a filter case of an inkjet head (nozzle head) is provided as described in Patent Document 1. .
JP-A-10-790

  However, in the ink heater provided in the ink tank as described above, the temperature of the ink may change before being ejected from the ink ejection port, and there is a possibility that good ink ejection cannot be performed. In addition, in the case of an ink heater that heats the filter case of the ink jet head, it is difficult to change the heating amount with respect to the temperature of the ink, thereby making it difficult to maintain the ink at a predetermined temperature and performing good ink ejection. Was the cause that can not.

In order to solve these problems, it has been considered that an ink heater is provided on the side of the manifold, and the ink inside the manifold is heated by the ink heater to keep the ink temperature at a predetermined temperature.
Here, the ink inside the manifold has a portion where the temperature tends to be low because the heat dissipation conditions of the inkjet head differ depending on the location, and a portion where the temperature is difficult to decrease. Also, the portion near the ink supply port has a feature that the temperature tends to be low.
However, the ink heater provided on the side of the manifold has the same heat generation density at any position of the heater, and all parts of the manifold are heated in the same manner, resulting in variations in ink temperature in the inkjet head. There was a thing. As a result, variations in ink viscosity may occur, and ink ejection with uniform droplets may not be possible, which hinders good image formation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head that can make the ink viscosity uniform by making the ink temperature inside the ink jet head uniform, and can eject ink with uniform droplets. .

The invention described in claim 1
An inkjet head chip having a nozzle row in which ink discharge ports are arranged on the front end surface;
A manifold that is adhesively fixed to a side portion of the inkjet head chip and guides ink to the inkjet head chip;
A housing frame for housing the manifold;
An ink heater for heating ink inside the manifold via the manifold between the manifold and the housing frame;
An inkjet head comprising:
The ink heater is characterized in that the heat generation density changes in the nozzle row direction.

The invention according to claim 2 is the ink jet head according to claim 1,
The ink heater includes a heating wire formed in a wave shape, and the heat generation density is changed by changing the number of waveforms of the heating wire with respect to a predetermined area.

The invention according to claim 3 is the inkjet head according to claim 1 or 2,
The ink heater is characterized in that the heat density at both ends of the nozzle row is increased.

The invention according to claim 4
An inkjet head comprising an ink heater for heating supplied ink,
The ink heater is characterized in that the heat generation density near the ink supply port for supplying ink to the ink jet head is increased.

  According to the first aspect of the present invention, an inkjet head chip having a nozzle row in which ink discharge ports are arranged on the front end surface, a manifold that is bonded and fixed to a side portion of the inkjet head chip and guides ink to the inkjet head chip, and a manifold The ink heater has an ink heater that heats ink inside the manifold via the manifold between the manifold and the housing frame. The heat density of the ink heater changes in the nozzle row direction. Therefore, the ink temperature inside the inkjet head can be made uniform, thereby making it possible to make the ink viscosity uniform and eject ink with uniform droplets. As a result, good ink discharge can be performed and good image formation can be performed.

  According to the second aspect of the present invention, the ink heater includes the heating wire formed in a wave shape, and the heat generation density is changed by changing the number of heating wire waveforms with respect to a predetermined area. The effect of the invention described in claim 1 can be achieved with a simple configuration.

  According to the invention described in claim 3, since the heat density of the ink heater is increased at both ends of the nozzle row, the ink temperature at both ends of the nozzle row that easily dissipates heat can be increased. The ink temperature inside the inkjet head can be made uniform.

  According to the fourth aspect of the present invention, in the ink jet head provided with the ink heater for heating the supplied ink, the ink heater increases the heat generation density on the side close to the ink supply port for supplying the ink to the ink jet head. Therefore, the ink temperature on the side close to the ink supply port that easily radiates heat can be raised, and as a result, the ink temperature inside the inkjet head can be made uniform. Thereby, the ink viscosity can be made uniform, and ink can be ejected with uniform droplets. Thus, good ink discharge can be performed, and good image formation can be performed.

  An embodiment of the present invention will be described below with reference to the drawings. However, the following is one embodiment of the present invention and does not limit the present invention.

  First, an overall configuration of an ink jet printer according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an ink jet printer according to an embodiment of the present invention.

  The ink jet printer 1 ejects ink onto a recording medium P and records an image on the recording medium P. The ink jet printer 1 includes a transport unit (not shown), and the transport unit transports the recording medium P in the sub-scanning direction orthogonal to the main scanning direction A while passing through the recording area C in FIG. ing.

  Above the recording area C, a carriage rail 2 extending along the main scanning direction A is arranged. A carriage 3 guided by the carriage rail 2 is movably provided on the carriage rail 2. Yes.

  The carriage 3 is mounted with an inkjet head 4 that ejects ink onto the recording medium P, and moves in the direction of arrow A from the home position area B to the maintenance area D along the carriage rail 2.

  In the ink jet printer 1 according to the present embodiment, a total of four ink jet heads 4 are arranged in the carriage 3 so that four colors of ink of black (K), yellow (Y), magenta (M), and cyan (C) can be ejected. Is installed. In the present embodiment, two inkjet heads 4, 4 are arranged in a line in the front-rear direction, and the other two inkjet heads 4 are arranged on both sides of the center of the inkjet heads 4, 4 aligned in the front-rear direction. , 4 are arranged.

  Each of these inkjet heads 4 is connected to an ink tank 5 for storing black, yellow, magenta, and cyan inks via an ink supply pipe 6. That is, the ink in the ink tank 5 is supplied to each inkjet head 4 by the ink supply pipe 6.

  In the maintenance area D, a maintenance unit 7 that performs maintenance on the inkjet head 4 is provided. The maintenance unit 7 includes a plurality of suction caps 8 that cover the discharge surface 41a of the inkjet head 4 and suck ink in the nozzles, a cleaning blade 9 that wipes off ink adhering to the discharge surface 41a, and an inkjet head. An ink receiver 10 that receives ink ejected from 4, a suction pump 11, and a waste ink tank 12 are provided.

The suction cap 8 communicates with the waste ink tank 12 via the suction pump 11 and is raised during the maintenance operation so as to cover the ejection surface 41a of the inkjet head 4. Four suction caps 8, 8,... Are arranged so as to correspond to the respective ink-jet heads 4 so as to cover the ejection surfaces 41a of all the ink-jet heads 4 when raised as described above.
The suction pump 11 includes a cylinder pump and a tube pump, and operates in a state where the suction cap 8 covers the discharge surface 41a, so that the ink inside the ink jet head 4 is discharged from the ink discharge port 42 (described later). A suction force for sucking together with the foreign matter is generated.

  In the home position area B, a moisturizing unit 13 for moisturizing the inkjet head 4 is provided. The moisturizing unit 13 is provided with four moisturizing caps 14 that moisturize the ink of the ink jet head 4 by covering the ejection surface 41a when the ink jet head 4 is in a standby state. These four moisturizing caps 14, 14,... Are arranged corresponding to the arrangement of the inkjet heads 4 so as to simultaneously cover the ejection surfaces 41a of the four inkjet heads 4.

  The control unit is configured to include a CPU (Central Processing Unit) and a memory, and controls each component of the inkjet printer 1. The memory stores image data to be formed on the recording medium P and a program for controlling each component of the inkjet printer 1, and controls each component based on the image data and program in the memory. A signal is transmitted.

Next, the inkjet head 4 according to the present invention will be described with reference to FIGS.
FIG. 2 is an exploded perspective view of the inkjet head 4 of the present embodiment, and FIG. 3 is a side view of the inkjet head 4 of the present embodiment. FIG. 4 is an enlarged perspective view of the vicinity of the inkjet head chip 41 and the manifold 48 of the inkjet head 4 of the present embodiment. 5 is a diagram showing an example of an arrangement pattern of heating wires 49a in the ink heater 49, and FIG. 6 is a diagram showing another example of an arrangement pattern of heating wires 49a in the ink heater 49. As shown in FIG.

The inkjet head 4 of the present embodiment is provided with an inkjet head chip (hereinafter referred to as “head chip”) 41 that ejects ink. The head chip 41 has a long outer shape in the arrow X direction, and a large number of ink discharge ports 42 are arranged in the arrow X direction on its discharge surface (tip surface) 41a. The ink discharge port 42 continuously provided in the arrow X direction and the nozzle row having the ink discharge ports 42 are referred to as a nozzle row 42a. In the inkjet head 4 of the present embodiment, two nozzle rows 42a are provided. The inkjet head 4 is mounted on the carriage 3 so that the arrow X direction (nozzle row direction) and the main scanning direction A shown in FIG.
As shown in FIG. 3, ink supply ports 43 are provided on both side surfaces of the head chip 41, and the ink supply ports 43 and the ink discharge ports are connected via an ink flow path 44 formed inside the head chip 41. 42 is continuous. A part of the ink flow path 44 forms a pressure chamber, and has a structure in which an ink droplet is ejected from the ink ejection port 42 by changing the pressure by the action of a piezoelectric element (not shown).

  On both sides of the head chip 41, two sets of manifolds 48 that are connected to the ink supply port 43 and guide the ink from the outside to the head chip 41 are bonded and fixed. An inlet 481 through which ink flows is provided at one end of the manifold 48.

Further, an ink heater 49 is provided on the side of the manifold 48 between the manifold 48 and the housing frame 53 so as to contact the manifold 48 as shown in FIGS. The ink heater 49 is provided for heating the ink introduced into the manifold 48 to a predetermined temperature.
Further, an adhesive is filled between the manifold 48 and the housing frame 53 so as to include at least the ink heater 49, whereby the housing frame 53, the ink heater 49, and the manifold 48 are bonded and fixed. Yes.
Here, the manifold 49 is often made of resin, and the housing frame 53 is often made of metal or the like. Therefore, usually, a large amount of heat generated from the ink heater 49 is transmitted to the housing frame 53. In the present invention, the ink is filled between the ink heater 49 and the housing frame 53, so that the ink Heat conduction from the heater 49 to the housing frame 53 is suppressed, and heat generated from the ink heater 49 is appropriately transmitted to the ink inside the manifold 48 via the manifold 48.

Further, in the present embodiment, the ink heater 49 is configured in a sheet shape in which a heating wire 49a formed in a wave shape is disposed on an appropriate sheet.
The ink heater 49 is configured such that the heat generation density changes in the nozzle row direction X. In the present embodiment, the heat generation density is changed by changing the number of waveforms of the heating wire 49a of the ink heater 49 with respect to a predetermined area. Specifically, as shown in FIG. 5, in the ink heater 49, the heat generation density on both end sides (left and right end sides E and G in the nozzle row direction X) of the nozzle row 42 a is the center portion (nozzle). The arrangement pattern increases the number of waveforms per unit area of the heating wire 49a on both ends of the nozzle row 42a so as to be larger than the central portion F) in the row direction X. As a result, the ink temperature at both ends of the nozzle row 42a that easily dissipates heat can be raised particularly.
Further, in order to heat the ink uniformly through the ink heater 49 and the manifold 48, it is desirable that the thermal coupling between the ink heater 49 and the manifold 48 is uniform within the heater surface. Therefore, for example, the ink heater 49 and the manifold 48 may be in contact via a predetermined member. Further, a predetermined amount of adhesive may be filled between the ink heater 49 and the manifold 48 instead of the members.
In the example shown in FIGS. 3 and 4, the ink heater 49 is provided in contact with the manifold 48, but the ink heater 49 may be disposed away from the manifold 48.
The ink heater 49 may be installed on each of the two side portions of the manifold 48, or may be installed on only one of them.

Further, as shown in FIG. 6, the ink heater 49 generates heat on the side close to the ink supply port (inlet port of the manifold 48) 481 for supplying ink to the inkjet head 4 (right end side J in the nozzle row direction X). An arrangement pattern that particularly increases the number of waveforms per unit area of the heating wire 49b on the side close to the ink supply port 481 may be used so that the density becomes particularly large. In FIG. 6, the number of waveforms per unit area of the heating wire 49 b on the left end side H in the nozzle row direction X is also increased from the central portion I in the nozzle row direction X. Thereby, the ink temperature on the side close to the ink supply port 481 that easily dissipates heat due to the cooling effect by the ink flow can be further increased.
5 and 6 corresponds to the right front side of the nozzle row direction X in FIG. 2 and the upper right side of the nozzle row direction X in FIG.

Then, each of the two sets of head drive substrates 46 that transmit a control signal from the control unit to each piezoelectric element (not shown) of the head chip 41 is connected via a flexible wiring board 47. A heater circuit for supplying power to the ink heater 49 is formed on the head drive substrate 46, and the heating wire 49 a of the ink heater 49 is electrically connected to the heater circuit via the electric wire 50. It is connected. Similarly, the temperature sensor 45 for detecting the temperature is electrically connected to the heater circuit by an electric wire (not shown). The temperature sensor 45 is disposed closer to the head chip 41 than the ink heater 49.
The two sets of head drive boards 46 are each provided with a connector 461, and each of these connectors 461 has an output terminal 62 of a flexible wiring board 60 having one input terminal 61 and two output terminals 62. It is connected. A power source and a control unit (not shown) are electrically connected to the input terminal 61 of the flexible wiring board 60, and a control signal and power are supplied to the head drive substrate 46 via the flexible wiring board 60. It is like that.

  A holding plate 51 for holding the manifold 48 and the head chip 41 is attached to the lower part of the head chip 41 so that the discharge surface 41a is exposed. At one end of the holding plate 51, an ink receiving portion 52 that holds the inlet 481 of the manifold 48 and allows ink to flow into the inlet 481 is formed.

As shown in FIG. 2, the inkjet head 4 is provided with the components of the inkjet head 4 such as the head chip 41, the manifold 48, the head drive substrate 46, and the holding plate 51. A frame 53 and a cover 54 that covers the housing frame 53 are provided. The casing frame 53 is provided with a frame ink flow path 55 that supplies ink by being connected to the ink receiving portion 52 of the holding plate 51, and the ink supply pipe 6 is connected to the frame ink flow path 55. It has come to be. In addition, support beams 56 that support two sets of head drive substrates 46 are provided inside the housing frame 53.
An opening 57 is provided in the upper part of the cover 54, and the input terminal 61 of the flexible wiring board 60 is exposed to the outside from the opening 57 after the ink jet head 4 is assembled.

Next, the operation of this embodiment will be described.
When the power of the ink jet printer 1 is turned on, power is supplied to each part of the ink jet printer 1. Accordingly, when power is supplied to the ink heater 49, the heating wire 49a of the ink heater 49 generates heat, and the ink in the manifold 48 is heated via the manifold 48 to reduce the viscosity.
Thereafter, when an instruction to start image recording is input, the control unit transmits a control signal based on the image data to the head driving substrate 46 and other driving units to start image recording. Ink is ejected from the inkjet head 4 onto the recording medium P that is transported to the transporting means. When this ink is ejected, the ink is preheated to reduce the viscosity, so that stable ejection and high image quality are achieved. An image is formed.

Here, the ink heater 49 having the arrangement pattern of the heating wire 49a shown in FIG. 5 and the conventional arrangement pattern of the heating wire (that is, the arrangement pattern in which the number of waveforms per unit area is the same and the heat generation density is uniform at any position) The result of the comparison experiment of the ink temperature with the ink heater which has) is shown. Here, an inkjet head having a length of 42 mm in the longitudinal direction of the inkjet head, that is, the nozzle row direction X was used, and a predetermined heater heating power was applied.
FIG. 7 is a graph showing the temperature distribution at each position in the nozzle row direction of the tip surface provided with the ink discharge ports by a conventional ink heater.
FIG. 8 is a graph showing the temperature distribution at each position in the nozzle row direction X of the tip surface 41a provided with the ink discharge ports 42 by the ink heater 49 of the present invention shown in FIG.
As is apparent from FIGS. 7 and 8, it was found that the ink heater 49 having the arrangement pattern of the heating wire 49a in the present invention can make the ink temperature inside the inkjet head uniform compared to the conventional ink heater.

  As described above, according to the ink jet head in the present embodiment, an ink jet head chip having a nozzle row in which the ink discharge ports are arranged on the front end surface, and an ink is attached to the side portion of the ink jet head chip and ink is applied to the ink jet head chip. An ink jet head comprising: a leading manifold; a housing frame that houses the manifold; and an ink heater that heats ink inside the manifold via the manifold between the manifold and the housing frame. In this case, since the heat generation density changes, the ink temperature inside the ink jet head can be made uniform, whereby the ink viscosity can be made uniform and ink can be ejected with uniform droplets. As a result, good ink discharge can be performed and good image formation can be performed.

  In this embodiment, the ink heater includes a heating wire formed in a wave shape, and the heat generation density is changed by changing the number of heating wire waveforms for a predetermined area. The effects described above can be achieved.

  Furthermore, in this embodiment, since the ink heater increases the heat generation density at both ends of the nozzle array, the ink temperature at both ends of the nozzle array that easily dissipates heat can be increased. The ink temperature can be made uniform.

  Furthermore, in an ink jet head having an ink heater for heating the supplied ink, if the heat density of the ink heater close to the ink supply port for supplying ink to the ink jet head is increased, the ink supply is easy to dissipate heat. The ink temperature on the side close to the mouth can be raised, and as a result, the ink temperature inside the inkjet head can be made uniform. Thereby, the ink viscosity can be made uniform, and ink can be ejected with uniform droplets. Thus, good ink discharge can be performed, and good image formation can be performed.

The ink jet head and the ink jet printer according to the present invention are not limited to the above-described embodiments, and can be applied to other configurations.
For example, the ink jet head is not limited to a configuration including a piezoelectric element in a head chip, and may be configured to include a heater, for example.
In addition, the shape and positional relationship of the ink jet head and the ink heater can be changed as appropriate. For example, in order to change the heat generation density of the ink heater, not only the number of heating wire waveforms but also the effective number of turns of the ink heater may be changed. In addition, a thin-film ink heater may be used as the ink heater. At this time, the heat generation density is changed by changing the distribution of the specific resistance of the heater.

1 is a plan view illustrating an outline of an inkjet printer according to an embodiment of the present invention. 1 is an exploded perspective view of an inkjet head according to an embodiment of the present invention. It is a side view of the ink jet head concerning one embodiment of the present invention. FIG. 2 is an enlarged perspective view of the vicinity of a head chip and a manifold of an inkjet head according to an embodiment of the present invention. It is a figure which shows an example of the arrangement pattern of the heating wire in an ink heater. It is a figure which shows the other example of the arrangement pattern of the heating wire in an ink heater. It is a graph which shows the temperature distribution in each position in the nozzle row direction of the front end surface in which the ink discharge port was provided by the conventional ink heater. It is a graph which shows the temperature distribution in each position in the nozzle row direction of the front end surface provided with the ink discharge port by the ink heater of the present invention.

Explanation of symbols

1 Inkjet printer 4 Inkjet head 41 Head chip (inkjet head chip)
41a Discharge surface (tip surface)
42 Ink Ejection Port 42a Nozzle Row 48 Manifold 49 Ink Heater 49a Heating Wire 53 Housing Frame P Recording Medium X Nozzle Row Direction

Claims (4)

An inkjet head chip having a nozzle row in which ink discharge ports are arranged on the front end surface;
A manifold that is adhesively fixed to a side portion of the inkjet head chip and guides ink to the inkjet head chip;
A housing frame for housing the manifold;
An ink heater for heating ink inside the manifold via the manifold between the manifold and the housing frame;
An inkjet head comprising:
The ink jet head according to claim 1, wherein the heat density of the ink heater changes in the nozzle row direction. The inkjet head according to claim 1,
An ink jet head, wherein the ink heater includes a heating wire formed in a wave shape, and the heat generation density is changed by changing the number of waveforms of the heating wire with respect to a predetermined area. The inkjet head according to claim 1 or 2,
The ink jet head according to claim 1, wherein the ink heater has a large heat generation density at both ends of the nozzle row. An inkjet head comprising an ink heater for heating supplied ink,
The ink-jet head is characterized in that the ink heater increases the heat generation density on the side close to the ink supply port for supplying ink to the ink-jet head.

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