JP2017061112A - Recording head and liquid droplet ejection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording head for a liquid droplet ejection device, in which variance in difference in an amount of displacement of recording elements is suppressed, the difference being caused by difference in voltage drop between the recording elements.SOLUTION: There is provided a recording head 120 ejecting a liquid droplet on the basis of a drive signal supplied from a drive signal source. The recording head 120 comprises a plurality of recording elements 5 that generate pressure on the basis of a drive signal; and a vibration plate 2 that is joined to the plurality of recording elements 5, propagates pressure to a liquid chamber 4, and causes a liquid droplet to be ejected. The area of the joining portion between each recording element 5 and the vibration plate 2 in a recording element 5 with a long path for supplying the drive signal from the drive signal source to each recording element 5 is larger than that in a recording element 5 with a short path.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a recording head and a droplet discharge device.

A recording head (droplet discharge head) is used in a droplet discharge recording apparatus, and one that forms and discharges discharge droplets by various methods is known. For example, the discharge means is a piezoelectric element, the liquid droplets are heated to generate bubbles, and the liquid droplets are discharged by the pressure, or the drive means uses electrostatic force.
A recording head using such an ejecting means can realize high-density multi-nozzle relatively easily and can form a high-definition image on a recording medium.

With respect to such a multi-nozzle recording head, for example, Patent Document 1 discloses a liquid transfer device including a piezoelectric actuator having excellent driving efficiency. In this piezoelectric actuator, a concave portion is formed in a region on the pressure chamber side surface of the diaphragm that overlaps the central portion of the pressure chamber, and the rigidity of the diaphragm is partially reduced in the portion where the concave portion is formed. The diaphragm can be greatly deformed with a lower driving voltage.
Further, Patent Document 2 discloses a recording head and an image forming apparatus of a droplet discharge device that can satisfactorily maintain droplet discharge characteristics with the current head component configuration. In this recording head, in addition to the common electrode section on the ground side of each actuator element, a conductive loop is provided by a head component that performs a function different from the conductive purpose, and the actuators arranged in a row are driven. The on-resistance of the drive is reduced as the distance from the connection portion increases.

In a recording head, a recording element with a long closed-loop wiring viewed from the drive signal source has a higher wiring resistance value than a recording element with a short closed-loop wiring. Therefore, when a large number of recording elements are driven, each recording element There is a problem in that the liquid droplets ejected by the ink vary.
In Patent Document 1, although the driving efficiency is increased by changing the shape of the diaphragm in each of the plurality of pressure chambers, it does not cause a difference for each pressure chamber, and all the liquid chambers have the same shape. Yes.
In Patent Document 2, the IC on-resistance of the drive is changed according to the loop length of the circuit. However, since the conductive loop is provided by the head component that performs a function different from the conductive purpose, It is necessary to consider sex.

  The present invention has been made in view of the above-described problems, and provides a recording head that suppresses variations in the amount of displacement of recording elements due to variations in voltage drop between recording elements, and a droplet discharge apparatus using the recording head. Objective.

  In order to solve the above-described problem, one aspect of the recording head of the present invention is a recording head that discharges droplets based on a driving signal supplied from a driving signal source, and applies pressure based on the driving signal. A plurality of recording elements to be generated; and a vibration plate that is bonded to the plurality of recording elements and that propagates the pressure to a liquid chamber and discharges the liquid droplets, and a bonding area between each recording element and the vibration plate Is characterized in that a recording element having a long path for supplying the driving signal from the driving signal source to each recording element is larger than a short recording element.

  According to the present invention, it is possible to provide a recording head that suppresses variation in the displacement amount of the recording element due to variation in voltage drop between the recording elements, and a droplet discharge apparatus using the recording head.

It is an external view which shows an example of the droplet discharge apparatus of one Embodiment. It is the figure which looked at the internal structural example of the droplet discharge apparatus of one Embodiment from the upper surface. FIG. 2 is an overview diagram illustrating a recording head according to an embodiment. It is a fragmentary sectional view of a droplet discharge part of a recording head of one embodiment. FIG. 3 is a diagram illustrating a configuration example of a circuit of a recording head viewed from a driving signal source. It is a schematic diagram showing an example of a landing image in the configuration of a conventional recording head. FIG. 3 is a diagram illustrating a recording head according to the first embodiment. FIG. 3 is a schematic diagram illustrating an example of a landing image in the configuration of the recording head according to the first embodiment. 3 is a diagram illustrating an example of a bonding area between a recording element and a diaphragm in the recording head of Embodiment 1. FIG. 6 is a graph showing an example of a bonding area of each channel in the recording head of Embodiment 2.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted.
First, an outline of a droplet discharge device according to an embodiment will be described with reference to FIGS. FIG. 1 is an external view showing an example of a droplet discharge device, and FIG. 2 is a view of the inside of the droplet discharge device as viewed from above.
The droplet discharge device 100 includes a plurality of ink cartridges (ink supply sources) 110 and a number of recording heads 120 corresponding to the number of colors of the ink cartridges 110. In FIG. 2, a recording head 120 corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) is arranged in a carriage 130 inside the droplet discharge device 100. An example is shown. By applying a drive waveform for driving the recording head 120, the droplet discharge device 100 is configured to discharge the droplet from the recording head 120 to form an image. The droplet discharge device 100 records characters, images, and the like on the recording medium by reciprocating the recording head 120 in the carriage movement direction and moving the recording medium such as paper in the belt conveyance direction.

Next, a configuration example of the recording head 120 will be described with reference to FIGS. FIG. 3 is a schematic view of the recording head 120, and FIG. 4 is a partial cross-sectional view of the ejection portion of the recording head 120.
3 or 4, among the components of the recording head 120, the flow path plate 1, the vibration plate 2, the nozzle plate 3, the recording element 5, the FPC (Flexible Printed Circuits) 6, the driving IC (Integrated Circuit) 7, and the FFC. (Flexible Flat Cable) 8, the droplet supply part 9, and the base member 10 are represented. A liquid chamber 4 is formed by the flow path plate 1 and the vibration plate 2. Description of other components is omitted here.
In the recording head 120, the droplets are supplied from the ink cartridge 110 to the droplet supply port 91 of the droplet supply unit 9 and filled into the liquid chamber 4. The recording head 120 is supplied with a drive waveform composed of one drive signal or a plurality of drive signals from a control unit (not shown) that controls the entire droplet discharge apparatus 100. The supplied driving waveform is applied to the recording element 5 as a driving signal through a wiring board such as the FFC 8 and the FPC 6 and the driving IC 7 on the wiring board. In the recording head 120, the recording element 5 is displaced by the drive signal, and the diaphragm 2 is deformed, whereby the pressure in the liquid chamber 4 is changed and the liquid droplets are ejected from the nozzle port 31.

FIG. 5 shows a configuration example of the circuit of the recording head 120 as viewed from the drive signal source in one embodiment. The circuit shown in FIG. 5 is a configuration example in which the recording head 120 includes n channels (drive channels) from the first channel to the n-th channel. The circuit includes a drive signal source 71, n drive elements PZT1 to PZTn (referred to as “drive element PZT” if not distinguished), and n switches SW1 to SWn (giving signals to arbitrary channels (drive channels)). When not distinguished, it is described as “switch SW”). Each channel includes one corresponding driving element PZT and one switch SW. The nozzle plate 3 is formed with n nozzle ports 31 corresponding to the respective channels.
The drive signal source 71 is included in the drive IC 7. The drive IC 7 receives a drive signal constituting a drive waveform from the control unit described above, and selectively applies the drive signal to the drive element PZT of each channel by the switch SW.
The drive element PZT is an example of a piezoelectric element included in the recording element 5 and shows an example using lead zirconate titanate (PZT).
The switch SW switches on / off of a drive signal supplied from the drive signal source 71 to the drive element PZT.

  As shown in FIG. 5, depending on the channel number, a path through which a drive signal is supplied from the drive signal source 71 to each of the drive elements PZT1 to PZTn (hereinafter also referred to as “wiring path” or “closed loop” as appropriate). ) Different lengths. Specifically, the center m-th channel driving element PZTm has a long closed loop viewed from the driving signal source 71, and the first channel driving element PZT1 and the n-th channel driving element PZTn at the ends are the driving signal source. The closed loop viewed from 71 has a short configuration. As the length of the closed loop viewed from the drive signal source 71 is shorter, the wiring resistance of the path is smaller, so that the droplets can be efficiently ejected with less deterioration of the drive signal. Conversely, the longer the length of the closed loop viewed from the drive signal source 71, the greater the wiring resistance of the path, and the greater the deterioration of the drive signal. As a result, as compared with a channel having a short path, the displacement of the diaphragm is reduced, and droplets are discharged with low efficiency.

FIG. 6 shows an example of a landing image in the configuration of the conventional recording head. As described above, a channel having a long wiring path has a lower ejection efficiency than a channel having a shorter wiring path, and the droplet speed is low even when a droplet is ejected at the same time. Therefore, landing deviation occurs in the carriage movement direction as in the landing image example of FIG. This is a problem caused by a difference in diaphragm displacement due to deterioration of the drive waveform.
More specifically, in the recording head used in the droplet discharge device, as the number of channels of the piezoelectric element, which is a recording element, increases with the increase in the number of nozzles, the amount of drive current increases. It is known that the amount of voltage drop increases and distortion occurs in the drive waveform. A channel having a long wiring path (high wiring resistance) has a particularly large influence. The reason for this is that when the number of channels increases, the amount of current flowing through the entire circuit increases, so the voltage drop due to the wiring resistance corresponding to this increases in a channel with a long wiring path, which is larger than that in a short channel, and the ejection efficiency increases. It is because it falls.

  Therefore, in the recording head 120 according to an embodiment, a channel with a long wiring path (high wiring resistance) has a larger bonding area between the diaphragm 2 and the recording element 5 than a channel with a short wiring path (low wiring resistance). Enlarge. As a result, the ejection efficiency of the channel having a long wiring path is improved, and the variation in the ejection speed and droplet amount of each channel is reduced. In other words, one embodiment of the recording head 120 has a large junction area in a channel with a long wiring path and low ejection efficiency, and a small junction area in a channel with a short wiring path and high ejection efficiency, thereby enabling ejection during multi-channel driving. Reduce efficiency and discharge variation.

In one embodiment, the description will be made on the assumption that there are two drive signal sources 71, the number of channels n is 3 or more, and the number m of a channel having a long wiring length is 2 or more. However, this does not exclude a configuration example in which the number of drive signal sources 71 is one, the number of channels n is 2 or more, and the number m is 1 or more, or a configuration example in which the number of drive signal sources 71 is 3 or more. One embodiment can be applied even in the configuration example.
Each embodiment will be described below using the configuration example of the recording head 120 described above.

Embodiment 1. FIG.
The recording head 120 according to the first embodiment will be described with reference to FIGS.
In FIG. 7, symbols PZT1, PZTm, and PZTn are shown on the upper recording head 120 (same as in FIG. 3), and the correspondence with the drive element PZT of the lower circuit is shown. In the recording head 120, a recording area in which each recording element 5 and the diaphragm 2 are joined has a long path length for supplying a driving signal from the driving signal source 71 to the driving elements PZT 1 to PZTn (each recording element 5). The diaphragm 2 is formed so that the element 5 is larger than the short recording element 5. For example, since the length of the wiring path of the mth channel is longer than that of the first and nth channels, the junction area is increased.

  FIG. 8 shows an example of a landing image in the configuration of the recording head of the first embodiment. In the landing image example of FIG. 8, the junction area is increased for the m-th channel and any number of channels close thereto, which are channels arranged in the center of the circuit, and the ejection efficiency is increased compared to the first and n-th channels. An example is shown. Thereby, compared with the conventional landing image example shown in FIG. 6, the landing point of the channel arranged in the center can be brought closer to the first and n channels. Note that the junction area between the channels arranged in the center is more preferably formed so as to increase the junction area of a channel having a long wiring path.

FIG. 9 shows an example of the bonding area between the recording element 5 and the diaphragm 2. An enlarged view of the diaphragm 2 and the recording element 5 (portion surrounded by a one-dot chain line) of the recording head 120 shown in the upper part of FIG. 9 is shown in the lower part. The lower diagram shows the bonding state of the diaphragm 2 and each recording element 5, and shows a short channel on the left side and a long channel on the right side. First, a configuration example of the diaphragm 2 will be described.
The diaphragm 2 includes, as an example, a thin portion 21, a plurality of thick portions 22, and a plurality of joint portions (thick portions) 23a and 23b (referred to as “join portions 23” if not distinguished). One surface of the thin portion 21 forms the wall surface of the liquid chamber 4, and the other surface faces each recording element, and a plurality of thick portions 22 and joint portions 23 are formed. Each joint 23 is joined to the recording element 5 of the corresponding channel. A part of the thin portion 21 is bonded to the flow path plate 1 with an adhesive, and the bonding portion 23 is bonded to the recording element 5 and the like with an adhesive.
The diaphragm 2 can be formed of a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method).
As shown in FIG. 9, the junction 23a corresponding to the channel with the long wiring path is formed so that the bonding area with the recording element 5 is larger than the junction 23b corresponding to the channel with the short wiring path.
Although FIG. 9 shows a configuration example in which the number of layers of the diaphragm 2 is three layers of the thin portion 21, the thick portion 22, and the joint portion 23, the number of layers is not limited to three layers, and three layers or more. Alternatively, it may be configured by two layers of the thin portion 21 and the joint portion 23.

  As described above, the recording head 120 of the present embodiment changes the bonding area between the diaphragm 2 and each recording element 5 based on the length of the wiring path. As a result, it is possible to reduce variations in droplet velocity due to the difference in the length of the wiring path when the number of channels increases. In this embodiment, since the ejection efficiency is improved by providing a difference in the bonding area between the channels, the structure or control of the recording head (for example, control when a drive signal is applied to the recording element) is complicated. This can be avoided and an increase in manufacturing cost can be suppressed.

Embodiment 2. FIG.
In the present embodiment, another mode in which the bonding area between the recording element 5 and the diaphragm 2 is changed between channels will be described. FIG. 10 shows an example of the bonding area of each channel in the recording head of the second embodiment. The configuration example of the circuit viewed from the drive signal source 71 is the same as that in FIG. 5. Here, among the n channels, the first and n-th channel wiring paths are the shortest, and the m-th channel wiring path is the most. A long case is assumed. In the first embodiment, one mode of increasing the bonding area corresponding to an arbitrary number of channels arranged at the center of the nozzle plate 3 has been described. In the second embodiment, an aspect in which the junction area is changed stepwise for all channels will be described. For example, as shown in FIG. 10, the junction area is changed stepwise in accordance with the length of the wiring path from the drive signal source 71 to the recording element 5 of each channel.

FIG. 10 shows an example of a stepwise change in the bonding area. For example, all channels are divided into a plurality of groups according to the length of the wiring path, and the bonding area is stepwise for each group. May be changed. Furthermore, the junction area may be increased at a uniform rate or the ratio of increasing the junction area may be changed according to the length of the wiring path from the drive signal source 71. The difference in junction area between all channels is not limited to these, and there are at least two channels having different junction areas among all channels, and the junction area between adjacent channels has a long wiring path. The relationship that the channel is larger or the same as the short channel may be established.
According to the recording head of this embodiment, variation in ejection between channels can be suppressed more finely by changing the bonding area between the diaphragm 2 and the recording element 5 in stages.

Embodiment 3. FIG.
When the bonding area described in each of the above embodiments is changed between channels, in addition to changing the size of the bonding portion 23 of the diaphragm 2, the compliance value between the channels of the thin portion 21 of the diaphragm 2 is changed. It is preferable to make it uniform. The configuration of the diaphragm 2 is the same as the configuration shown in FIG.
The compliance value is a value serving as an index of rigidity and indicates the ease of deformation. By making the compliance component of the thin portion 21 of the diaphragm 2 joined to the recording element 5 the same between the channels, the natural period of the liquid chamber 4 (individual liquid chamber) for each channel varies, and the sensitivity to the drive signal is increased. Droplets can be ejected without change. Further, the natural period Tc is proportional to the square root of the multiplier of the inertance component M and the compliance component C as shown in the following equation.

Embodiment 4 FIG.
By mounting the recording head 120 described in each of the above embodiments on the droplet discharge device 100, it is possible to correct discharge variations between channels as shown in the landing image example of FIG. The droplet discharge device is not limited to that shown in FIGS. 1 and 2, and includes a carriage 130 on which the recording head 120 can be mounted and an ink supply source that can supply droplets to the droplet supply port 91. As long as it is a device.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Flow path plate 2 Vibrating plate 3 Nozzle plate 4 Liquid chamber 5 Recording element 6 FPC
7 Drive IC
8 FFC
9 Droplet supply part 10 Base member 21 Thin part 22 Thick part 23a, 23b Joint part 31 Nozzle port 71 Drive signal source 91 Droplet supply port 100 Droplet discharge device 110 Ink cartridge 120 Recording head 130 Carriage PZT1 to PZTn Drive element SW1 to SWn switch

JP 2006-321174 A JP 2009-154519 A

Claims (5)

A recording head that ejects droplets based on a drive signal supplied from a drive signal source,
A plurality of recording elements that generate pressure based on the drive signal;
A vibration plate that is bonded to the plurality of recording elements and that propagates the pressure to a liquid chamber to discharge the droplets;
With
The recording head is characterized in that the bonding area between each recording element and the diaphragm is such that a recording element having a long path for supplying the drive signal from the drive signal source to each recording element is larger than a short recording element.   The recording head according to claim 1, wherein the bonding area is changed stepwise according to the length of the path. The diaphragm has a thin portion facing the liquid chamber, and a plurality of joints that join the plurality of recording elements,
2. The plurality of bonding portions are formed so that the bonding area is larger than a bonding portion where a bonding portion that is bonded to a recording element having a long path length is bonded to a recording element that is short. Or the recording head of 2.   The recording head according to claim 3, wherein the thin portion has a uniform compliance.   A liquid droplet ejection apparatus comprising the recording head according to claim 1.

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