JP2020157756A - Liquid discharge device - Google Patents

Abstract

To improve discharge characteristics of liquid in a liquid discharge device.SOLUTION: A liquid discharge device comprises: a recording head for discharging liquid; a drive waveform generation part for generating a head drive waveform signal to be supplied to the recording head; a transmission path in which plural transmission lines are paired, and which transmits the head drive waveform signal generated by the drive waveform generation part to the recording head; a switching part which is disposed between the drive waveform generation part and the transmission path, and switches directions of an electric current of the transmission path; and a switching control part for controlling the switching part in accordance with changes in load capacity of the recording head.SELECTED DRAWING: Figure 5

Description

The present invention relates to a liquid discharge device.

Conventionally, as an example of an inkjet printer, a liquid discharge device including a liquid discharge head or a liquid discharge unit and driving the liquid discharge head to discharge a liquid is known. The liquid discharge device includes not only a device capable of discharging a liquid to a device to which the liquid can adhere, but also a device for discharging the liquid toward the air or the liquid.

The head drive waveform signal applied to the liquid discharge head such as the inkjet head oscillates in combination with the inductance component of the transmission line due to the fluctuation of the capacitance load component of the liquid discharge head, so that the oscillation is suppressed and the ink etc. It is desired to improve the discharge characteristics of the liquid.

By switching between two types of resistors in front of the transmission line that transmits the head drive waveform signal for the purpose of improving the ejection characteristics of ink, etc., the oscillation of the head drive waveform signal is suppressed against fluctuations in the load capacitance component of the head. (See, for example, Patent Document 1 and the like).

However, when the transmission line for transmitting the head drive waveform signal to the liquid discharge head is long, the impedance of the transmission line itself is large, so that the resistance value hardly fluctuates only by switching the resistance value in front of the transmission line. Therefore, it becomes difficult to adjust the impedance of the transmission line, and the oscillation of the head drive waveform signal cannot be sufficiently suppressed.

The present invention has been made in view of the above, and an object of the present invention is to improve the liquid discharge characteristics of the liquid discharge device.

In order to solve the above-mentioned problems and achieve the object, the present invention has a recording head that discharges a liquid, a drive waveform generator that generates a head drive waveform signal to be supplied to the recording head, and a drive waveform generator. A transmission line in which a plurality of transmission lines are paired to transmit the head drive waveform signal generated in the above to the recording head, and a current of the transmission line provided between the drive waveform generator and the transmission line. It is characterized by including a switching unit for switching the direction of the above and a switching control unit for controlling the switching unit according to a change in the load capacitance of the recording head.

According to the present invention, it is possible to improve the liquid discharge characteristics of the liquid discharge device.

FIG. 1 is a perspective view showing the inside of the liquid discharge device as seen through. FIG. 2 is a top view showing the mechanical configuration inside the liquid discharge device. FIG. 3 is a diagram illustrating an arrangement example of a recording head mounted on the carriage. FIG. 4 is an enlarged view of the bottom surface of the recording head. FIG. 5 is a block diagram showing a configuration example of the liquid discharge device. FIG. 6 is a diagram showing an example of an equivalent circuit of a transmission line and an inkjet head. FIG. 7A is a diagram (1) showing an example of a head drive waveform signal applied to the inkjet head. FIG. 7B is a diagram (2) showing an example of a head drive waveform signal applied to the inkjet head. FIG. 7C is a diagram (3) showing an example of a head drive waveform signal applied to the inkjet head. FIG. 8 is a diagram showing an example of the relationship between the number of ejection nozzles of the inkjet head and the ejection characteristics (ejection speed) of the ink. FIG. 9 is a diagram (1) showing an example of impedance adjustment of the transmission line. FIG. 10 is a diagram (2) showing an example of impedance adjustment of the transmission line. FIG. 11 is a diagram (3) showing an example of impedance adjustment of the transmission line.

Hereinafter, embodiments of the liquid discharge device will be described in detail with reference to the accompanying drawings.

<Mechanical configuration of liquid discharge device>
First, the mechanical configuration of the liquid discharge device 100 of the present embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view showing the inside of the liquid discharge device 100 as seen through. FIG. 2 is a top view showing the mechanical configuration inside the liquid discharge device 100. FIG. 3 is a diagram illustrating an arrangement example of the recording head 6 mounted on the carriage 5. FIG. 4 is an enlarged view of the bottom surface of the recording head 6.

As shown in FIG. 1, the liquid discharge device 100 of the present embodiment includes a carriage 5 that reciprocates in the main scanning direction (direction of arrow A in the drawing). The carriage 5 is supported by a main guide rod 3 extending along the main scanning direction. Further, the carriage 5 is provided with a connecting piece 5a. The connecting piece 5a engages with the sub-guide member 4 provided in parallel with the main guide rod 3 to stabilize the posture of the carriage 5.

As shown in FIG. 2, the carriage 5 ejects a recording head 6y that ejects yellow ink, a recording head 6m that ejects magenta ink, a recording head 6c that ejects cyan ink, and black ink. A recording head 6k (hereinafter, when the recording heads 6y, 6m, 6c, and 6k are collectively referred to as "recording head 6") is mounted. The recording head 6 is mounted on the carriage 5 so that its ejection surface (nozzle surface) faces downward (the medium M side such as recording paper).

Returning to FIG. 1, the cartridge 7, which is an ink supply body for supplying ink to the recording head 6, is not mounted on the carriage 5, but is arranged at a predetermined position in the liquid ejection device 100. The cartridge 7 and the recording head 6 are connected by a pipe, and ink is supplied from the cartridge 7 to the recording head 6 through the pipe.

The carriage 5 is connected to a timing belt 11 stretched between the drive pulley 9 and the driven pulley 10. The drive pulley 9 is rotated by driving the main scanning motor 8. The driven pulley 10 has a mechanism for adjusting the distance between the driven pulley 10 and the drive pulley 9, and has a role of applying a predetermined tension to the timing belt 11. The carriage 5 reciprocates in the main scanning direction by the timing belt 11 being fed by driving the main scanning motor 8. The movement of the carriage 5 in the main scanning direction is controlled based on the encoder value obtained by detecting the mark on the encoder sheet 14 by the encoder sensor 13 provided on the carriage 5, as shown in FIG. 2, for example.

In FIG. 1, the liquid discharge device 100 of the present embodiment includes a maintenance mechanism 15 for maintaining the reliability of the recording head 6. The maintenance mechanism 15 cleans and caps the ejection surface of the recording head 6, ejects unnecessary ink from the recording head 6, and the like.

A platen 16 is provided at a position facing the discharge surface of the recording head 6. The platen 16 is for supporting the medium M when ejecting ink from the recording head 6 onto the medium M. The liquid discharge device 100 of the present embodiment is a wide machine having a long moving distance in the main scanning direction of the carriage 5. Therefore, the platen 16 is configured by connecting a plurality of plate-shaped members in the main scanning direction (moving direction of the carriage 5). The medium M is sandwiched by a transfer roller driven by a sub-scanning motor, and is intermittently transported on the platen 16 in the sub-scanning direction (arrow B in the drawing).

The recording head 6 includes a plurality of nozzle rows, and forms an image on the medium M by ejecting ink from the nozzle rows on the medium M conveyed on the platen 16. In the present embodiment, in order to secure a large width of the image that can be formed on the medium M by one scanning of the carriage 5, as shown in FIG. 3, the carriage 5 is recorded on the upstream side recording head 6 and the downstream side. The head 6 is mounted. Further, in order to increase the printing speed of black, the recording heads 6k for ejecting black ink are mounted on the carriage 5 twice as many as the recording heads 6y, 6m, and 6c for ejecting color ink. Further, the recording heads 6y and 6m are arranged separately on the left and right sides. This is to match the overlapping order of the colors by the reciprocating operation of the carriage 5 so that the colors do not change between the outward route and the return route. The arrangement of the recording heads 6 shown in FIG. 3 is an example, and is not limited to the arrangement shown in FIG.

Each of the above-mentioned components constituting the liquid discharge device 100 of the present embodiment is arranged inside the exterior body 1. A cover member 2 is provided on the exterior body 1 so as to be openable and closable. By opening the cover member 2 during maintenance of the liquid discharge device 100 or when a jam occurs, it is possible to perform work on each component provided inside the exterior body 1.

The liquid discharge device 100 of the present embodiment intermittently conveys the medium M on the platen 16 in the sub-scanning direction, and while the transfer of the medium M in the sub-scanning direction is stopped, moves the carriage 5 in the main scanning direction. While moving, ink is ejected from the nozzle row of the recording head 6 mounted on the carriage 5 onto the medium M on the platen 16 to form an image on the medium M.

The liquid discharge device 100 of the present embodiment includes a two-dimensional image sensor 20 having a function of capturing an image of a color measurement pattern formed on the medium M and calculating a color measurement value. As shown in FIG. 2, the two-dimensional image sensor 20 is supported by the carriage 5 on which the recording head 6 is mounted, and moves integrally. Then, when the two-dimensional image sensor 20 moves on the medium M on which the color measurement pattern is formed by the transport of the medium M and the movement of the carriage 5, and comes to a position facing the color measurement pattern, the image is displayed. Take an image of. Then, the color measurement value of the color measurement pattern is calculated based on the RGB value of the color measurement pattern obtained by imaging.

In FIG. 4, a large number of printing nozzles 6b are arranged in a staggered pattern on the nozzle surface (bottom surface) 6a of the recording head 6, and in this embodiment, 64 printing nozzles 6b are arranged in a staggered pattern in two rows. .. By arranging a large number of printing nozzles 6b in a staggered manner in this way, high resolution can be supported.

FIG. 5 is a block diagram showing a configuration example of the liquid discharge device 100. In FIG. 5, the liquid discharge device 100 is provided with a drive control board 39, a transmission line 44, a head relay board 45, and an inkjet head 47. One end of the transmission line 44 is connected to the drive control board 39, and the inkjet head 47 is connected to the other end of the transmission line 44 via the head relay board 45. The transmission line 44 has a plurality of transmission lines paired with each other, and is composed of, for example, a flexible flat cable (FFC). The transmission line 44 has locations where currents flow in different directions in a plurality of transmission lines. The inkjet head 47 corresponds to the recording head 6 described above.

The drive control board 39 includes a drive control unit 40, a drive waveform generation unit 41, a switching control unit 42, and a switching unit 43. The drive control unit 40 generates a timing control signal and drive waveform data for driving the piezoelectric element 50 of the inkjet head 47 based on the image data to be printed. The drive waveform generation unit 41 DA-converts the drive waveform data of the digital value generated by the drive control unit 40, and amplifies the voltage and the current. The switching control unit 42 controls the switching unit 43 according to the number of simultaneous drives of the piezoelectric element 50 (the number of nozzles that simultaneously discharge liquid). Changes in the number of nozzles that discharge liquid at the same time and the load capacity are calculated based on the image data input to the liquid discharge device 100. The switching unit 43 switches the path of the head drive waveform signal in the transmission line 44.

The head drive waveform signal whose voltage is amplified and current is amplified by the drive waveform generation unit 41 is sent to the path of the transmission line 44 switched by the switching unit 43. Digital signals such as timing control signals generated by the drive control unit 40 of the drive control board 39 are transmitted to the head relay board 45 by serial communication, and are deserialized by the head control unit 46 on the head relay board 45. It is transmitted to the inkjet head 47.

The signal transmitted to the inkjet head 47 is input to the piezoelectric element drive IC 49 on the piezoelectric element support portion 48 in the inkjet head 47. The head drive waveform signal generated by the drive waveform generation unit 41 of the drive control board 39 is input to the piezoelectric element 50 by turning on / off the piezoelectric element drive IC 49 according to the timing control signal.

FIG. 6 is a diagram showing an example of an equivalent circuit of the transmission line 44 and the inkjet head 47. In FIG. 6, the transmission line 44 is represented as a series circuit of the resistance component R and the inductance component L, and the inkjet head 47 is represented as the capacitance component C. The overall impedance seen from the drive control board 39 side is the impedance of the series circuit of the resistance component R, the inductance component L, and the capacitance component C. The absolute value is expressed by the following equation (1).

The resistance component R increases in proportion to the length of the transmission line 44, and the length of the transmission line 44 is a fixed value because it is fixed in the liquid discharge device 100. The inductance component L will be described in detail later, but in the case of a transmission line in which a plurality of transmission lines are paired, there are places where the current flows in different directions, so that the direction of the current flowing in each transmission line is different. The mutual inductance acts and the inductance components L cancel each other out, so that the value of the inductance component L of the entire transmission line 44 can be adjusted. The capacitance component C fluctuates because it increases as the number of ejection nozzles of the inkjet head 47 (the number of nozzles that eject liquid at the same time) increases.

Therefore, when the number of discharge nozzles is small (when the capacitance component C is small), the value of ωL-1 / ωC can be reduced by increasing the inductance component L. When the number of discharge nozzles is large (when the capacitance component C is large), the value of ωL-1 / ωC can be reduced by reducing the inductance component L. In this way, by changing the inductance component L with respect to the increase or decrease of the capacitance component C, it is possible to maintain a constant impedance, and the oscillation of the head drive waveform signal due to the fluctuation of the load capacitance of the inkjet head 47 is suppressed. It is possible to supply a head drive waveform signal with stable behavior to the inkjet head 47.

7A to 7C are diagrams showing an example of a head drive waveform signal applied to the inkjet head 47. As described above, the head drive waveform signal is generated in the drive waveform generation unit 41 of the drive control board 39.

FIG. 7A is an example of a head drive waveform signal when the load of the inkjet head 47 is low (when the number of ejection nozzles is small). Since the capacitive load component is small, the current value flowing into the inkjet head 47 is also small, and the impedance including the inkjet head 47 and the transmission line 44 is small, so that the head drive waveform signal is less affected by oscillation. Therefore, the waveform is stable at the low level voltage VL and the high level voltage VH. The ink ejection speed at this time is assumed to be
V _j0
And.

FIG. 7B is a head drive waveform signal when the inkjet head 47 has a medium load (when the number of ejection nozzles is medium). The capacitive load component is larger than that in FIG. 7A, the current value flowing into the inkjet head 47 also increases, the impedance including the inkjet head 47 and the transmission line 44 increases, and the head drive waveform signal is affected by oscillation. Therefore, the waveform amplitude becomes large. Therefore, the waveform is over the voltage VL'that is lower than the low level voltage VL, and the waveform is over the voltage VH'that is higher than the high level voltage VH. Assuming that the ink ejection speed at this time is V _j1 , the waveform amplitude becomes large. Therefore, in relation to the case of FIG. 7A,
V _j1 > V _j0
Will be.

FIG. 7C is a head drive waveform signal when the inkjet head 47 has a large load (when the number of ejection nozzles is large). The capacitive load component is larger than that in FIG. 7B, the current value flowing into the inkjet head 47 also increases, the impedance including the inkjet head 47 and the transmission line 44 increases, and the head drive waveform signal is affected by oscillation. Therefore, the waveform amplitude becomes even larger. Therefore, the waveform is over the voltage VL "that is lower than the low level voltage VL", and the waveform is over the voltage VH "that is higher than the high level voltage VH". Assuming that the ink ejection speed at this time is V _j2 , the waveform amplitude becomes large. Therefore, in relation to the cases of FIGS. 7A and 7B,
V _j2 ＞ V _j1 ＞ V _j0
Will be.

In addition, in FIGS. 7A to 7C, it was explained that the waveform amplitude increases due to oscillation, but in reality, as the number of ejection nozzles increases, the waveform becomes dull (the slew rate at the rising edge of the waveform becomes smaller), and the amplitude may become smaller. is there. In order to simplify the explanation, the case where the waveform oscillates and the waveform amplitude becomes large is described, but it is the same in that the waveform deviates from the normal state even when the waveform is blunted.

FIG. 8 is a diagram showing an example of the relationship between the number of ejection nozzles of the inkjet head 47 and the ejection characteristics (ejection speed) of ink. In FIG. 8, the broken line shows the ideal relationship between the number of ejection nozzles and the ink ejection speed V _j, and is the case where the ejection speed V _j is constant with respect to the number of ejection nozzles. The solid line shows the relationship between the actual number of ejection nozzles and the ink ejection speed _Vj . As the number of ejection nozzles increases, as described in FIGS. 7A to 7C, the waveform amplitude increases due to oscillation, so that the ink ejection speed _Vj increases, resulting in behavior like a solid line. If the ink ejection speed _Vj changes depending on the number of ejection nozzles, the image becomes uneven and the image quality deteriorates.

9 to 11 are views showing an example of impedance adjustment of the transmission line 44, and it is assumed that the transmission line 44 is composed of 16 transmission lines. The number of transmission lines is not limited to this.

As described above, even when the transmission line 44 is long, the inductance component can be adjusted by changing the direction in which the current flows. When a current flows in the opposite direction, mutual induction (mutual inductance) action works, and the inductance components cancel each other out.

In FIG. 9, the head drive waveform signal generated by the drive waveform generation unit 41 is connected to the transmission line 44 by the switching unit 43 controlled by the switching control unit 42, and is transmitted to the head relay board 45. The arrows in each transmission line constituting the transmission line 44 indicate the direction of the current, and the transmission line pointing to the right in the figure indicates the path through which the current of the head drive waveform signal flows into the inkjet head 47. The transmission line facing to the left shows a path for drawing the current of the head drive waveform signal from the inkjet head 47. In order to adjust the inductance component of the transmission line 44 by using the mutual inductance, the switching unit 43 changes the current flow method.

In FIG. 9, depending on the contact state of the switching unit 43, the first to eighth transmission lines from the top of the transmission line 44 flow into the inkjet head 47, and the ninth to 16th transmission lines are inkjet. It is a route that pulls in from the head 47. Let L1 be the inductance component of the transmission line 44 in this state.

In FIG. 10, depending on the contact state of the switching unit 43, the transmission lines from the first to the fourth and the ninth to the twelfth from the top of the transmission line 44 are the paths flowing into the inkjet head 47, and the fifth to the eighth. The transmission lines up to the thirteenth and the thirteenth to the sixteenth are the paths drawn from the inkjet head 47. By changing the flow of the current flowing through each transmission line of the transmission line 44 by the switching unit 43 controlled by the switching control unit 42, the inductance components cancel each other out due to the action of mutual inductance, and the inductance component is reduced. Assuming that the inductance component of the transmission line 44 in this state is L2, in relation to the case of FIG. 9,
L1> L2
Will be. The reason for this is that the number of places where mutual inductance acts (the part of the pair in which the current flows in opposite directions) increases as compared with FIG.

In FIG. 11, the 1st, 2nd, 5th, 6th, 9th, 10th, 13th, and 14th transmission lines from the top of the transmission line 44 flow into the inkjet head 47 due to the contact state of the switching unit 43. The 3rd, 4th, 7th, 8th, 11th, 12th, 15th, and 16th transmission lines are routes that are drawn from the inkjet head 47. By changing the flow of the current flowing through each transmission line of the transmission line 44 by the switching unit 43 controlled by the switching control unit 42, the inductance components cancel each other out due to the action of mutual inductance, and the inductance component is reduced. Assuming that the inductance component of the transmission line 44 in this state is L3, in relation to the cases of FIGS. 9 and 10,
L1 ＞ L2 ＞ L3
Will be. The reason for this is that the number of places where mutual inductance acts increases as compared with FIG.

In this way, the switching control unit 42 and the switching unit 43 change the flow of the current of the head drive waveform signal flowing through the transmission line 44 according to the fluctuation of the load capacity (capacitive component) of the inkjet head 47, thereby changing the load capacity. Even if the head drive waveform signal fluctuates, the oscillation of the head drive waveform signal can be suppressed, and the head drive waveform signal having stable behavior can be supplied to the inkjet head 47.

The above description has mainly taken an inkjet printer as an example of the liquid ejection device, but the present invention is not limited to this.

This liquid discharge device can also include means related to feeding, transporting, and discharging paper to which a liquid can adhere, as well as a pretreatment device, a posttreatment device, and the like.

As a liquid ejection device, for example, an image forming apparatus which is a device for ejecting ink to form an image on paper, and a powder layer in which powder is formed in layers in order to form a three-dimensional model (three-dimensional model). There is a three-dimensional modeling device (three-dimensional modeling device) that discharges the modeling liquid.

Further, the liquid discharge device is not limited to the one in which a significant image such as characters and figures is visualized by the discharged liquid. For example, those that form patterns that have no meaning in themselves and those that form a three-dimensional image are also included.

The above-mentioned "material to which a liquid can adhere" means a material to which a liquid can adhere at least temporarily, such as one that adheres and adheres, and one that adheres and permeates. Specific examples include media such as paper, recording paper, recording paper, film, cloth and other recording media, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and inspection cells. Yes, including anything to which the liquid adheres, unless otherwise specified.

The material of the above-mentioned "material to which liquid can be attached" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics or the like as long as the liquid can be attached even temporarily.

The "liquid" may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. It is preferable to have. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, polymerizable compounds, resins, functionalizing materials such as surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural dyes, etc. These are, for example, inks for inkjets, surface treatment liquids, constituents of electronic elements and light emitting elements, and formation of electronic circuit resist patterns. It can be used for applications such as liquids for three-dimensional modeling.

Piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heat-generating resistors, and electrostatic actuators that consist of a vibrating plate and counter electrodes are used as energy sources for discharging liquid. Includes what to do.

Further, the liquid discharge device includes, but is not limited to, a device in which the liquid discharge head and the device to which the liquid can adhere move relatively. Specific examples include a serial type device that moves the liquid discharge head, a line type device that does not move the liquid discharge head, and the like.

In addition, as a liquid discharge device, a treatment liquid coating device that discharges a treatment liquid onto a paper in order to apply the treatment liquid to the surface of the paper for the purpose of modifying the surface of the paper, and a raw material in the solution. There is an injection granulator that injects a dispersed composition liquid through a nozzle to granulate fine particles of raw materials.

Further, in the present application, image formation, recording, printing, printing, printing, modeling, etc. are all synonymous terms.

100 Liquid discharge device 6 Recording head 39 Drive control board 40 Drive control unit 41 Drive waveform generator 42 Switching control unit 43 Switching unit 44 Transmission line 45 Head relay board 46 Head control unit 47 Inkjet head 48 Piezoelectric element support 49 Piezoelectric element drive IC
50 Piezoelectric element

Japanese Unexamined Patent Publication No. 2014-218019

Claims (7)

A recording head that discharges liquid and
A drive waveform generator that generates a head drive waveform signal to be supplied to the recording head,
A transmission line in which a plurality of transmission lines are paired to transmit a head drive waveform signal generated by the drive waveform generator to the recording head, and
A switching unit provided between the drive waveform generation unit and the transmission line to switch the direction of the current in the transmission line,
A switching control unit that controls the switching unit according to a change in the load capacity of the recording head,
A liquid discharge device. The transmission line is a flexible flat cable.
The liquid discharge device according to claim 1. The switching unit switches one end of a plurality of transmission lines constituting the transmission line on the switching unit side between a path connected to the output of the drive waveform generation unit and a path grounded.
The liquid discharge device according to claim 1 or 2. The switching control unit controls the switching unit according to the number of nozzles at which the recording head simultaneously discharges liquid.
The liquid discharge device according to any one of claims 1 to 3. The switching control unit determines the number of nozzles that the recording head simultaneously discharges the liquid based on the discharge data instructing the discharge of the liquid from the recording head.
The liquid discharge device according to claim 4. When the number of nozzles that the recording head simultaneously discharges liquid is equal to or less than the first threshold value, the switching control unit switches the switching unit so that the number of places where mutual inductance acts is reduced.
The liquid discharge device according to claim 4 or 5. When the number of nozzles that the recording head simultaneously discharges liquid is equal to or greater than the second threshold value, the switching control unit switches the switching unit so as to increase the number of places where mutual inductance acts.
The liquid discharge device according to any one of claims 4 to 6.

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