JP2024040826A - Inkjet head and inkjet recording device - Google Patents

Abstract

[Problem] To provide an inkjet head and inkjet recording device capable of effectively generating a plurality of voltages to be applied to an actuator. [Solution] According to an embodiment, an inkjet head includes an actuator, a first switch, a second switch, and a control circuit. The actuator changes the volume of a pressure chamber. The first switch connects a first power line supplying a first voltage to the actuator. The second switch connects a second power line supplying a second voltage different from the first voltage to the actuator. The control circuit turns the first switch off and then turns the second switch on while the first voltage is applied to the actuator, and turns the second switch off before the required time has elapsed since turning on the second switch, with a resolution of less than or equal to half the required time for the voltage applied to the actuator to rise or fall from the first voltage to the second voltage. [Selected Figure] Figure 3

Description

Embodiments of the present invention relate to an inkjet head and an inkjet recording apparatus.

Some inkjet heads apply a driving waveform to an actuator that drives a pressure chamber to eject ink droplets from a nozzle that communicates with the pressure chamber. Inkjet heads sometimes control the voltage of the drive waveform in order to control the amount of ink droplets.

Conventionally, inkjet heads need to use a plurality of potentials that output different voltages.

Japanese Patent Application Publication No. 2014-113783

In order to solve the above problems, an inkjet head and an inkjet recording apparatus are provided that can effectively generate a plurality of voltages to be applied to an actuator.

According to the embodiment, the inkjet head includes an actuator, a first switch, a second switch, and a control circuit. The actuator changes the volume of the pressure chamber. A first switch connects the actuator to a first power line that supplies a first voltage. A second switch connects the actuator to a second power line that supplies a second voltage different from the first voltage. The control circuit turns on the second switch after turning off the first switch in a state where the first voltage is applied to the actuator, and the control circuit turns on the second switch when the first voltage is applied to the actuator. Turning off the second switch before the required change time elapses after the second switch is turned on with a resolution that is less than half the time required for the change to rise or fall from the voltage to the second voltage. .

FIG. 1 is a diagram schematically showing a configuration example of an inkjet recording apparatus according to an embodiment. FIG. 2 is a block diagram showing a configuration example of a control system of an inkjet recording apparatus according to an embodiment. FIG. 3 is a block diagram showing a configuration example of an inkjet head according to an embodiment. FIG. 4 is a diagram showing an equivalent circuit of a channel group according to the embodiment. FIG. 5 is a diagram showing an equivalent circuit of the control switch according to the embodiment. FIG. 6 is a timing chart showing an example of the operation of the inkjet head according to the embodiment.

Embodiments will be described below with reference to the drawings.
The inkjet recording apparatus according to the embodiment forms an image on a medium such as paper using an inkjet head. An inkjet recording device prints an image on a medium by ejecting ink droplets in a pressure chamber of an inkjet head onto a medium from a nozzle. Examples of the inkjet recording device include an office inkjet recording device, a barcode inkjet recording device, a POS inkjet recording device, an industrial inkjet recording device, a 3D inkjet recording device, and the like. Note that the medium on which the inkjet recording device forms an image is not limited to a specific configuration. The inkjet head included in the printer according to the embodiment is an example of a liquid ejection head, and the ink is an example of a liquid.

FIG. 1 is a schematic diagram showing an example of the configuration of an inkjet recording apparatus 1 according to an embodiment. The inkjet recording apparatus 1 forms an image on an image forming medium S using a recording material such as ink. As an example, the inkjet recording apparatus 1 includes a plurality of liquid ejection sections 2, a head support mechanism 3 that movably supports the liquid ejection sections 2, and a medium support mechanism 4 (support mechanism) that movably supports the image forming medium S. ) and. The image forming medium S is, for example, a sheet made of paper, cloth, resin, or the like.

As shown in FIG. 1, the plurality of liquid ejecting units 2 are supported by the head support mechanism 3 while being arranged in parallel in a predetermined direction. The head support mechanism 3 is attached to an endless belt 3b wrapped around a roller 3a. The inkjet recording apparatus 1 can move the head support mechanism 3 in the main scanning direction A perpendicular to the conveyance direction of the image forming medium S by rotating the roller 3a.

The liquid ejection unit 2 integrally includes an inkjet head 10 and a circulation device 20.
The inkjet head 10 ejects ink droplets made of ink I onto an image forming medium S.
Further, the circulation device 20 supplies the ink I to the inkjet head 10 and collects the ink I from the inkjet head 10.

The liquid ejecting unit 2 performs an ejecting operation of ejecting ink I from the inkjet head 10 as a liquid. As an example, the inkjet recording apparatus 1 uses a scanning method in which a desired image is formed on an image forming medium S disposed facing each other by performing an ink ejection operation while reciprocating the head support mechanism 3 in the main scanning direction A. It is. Alternatively, the inkjet recording apparatus 1 may be of a single-pass type in which the ink ejecting operation is performed without moving the head support mechanism 3. In this case, it is not necessary to provide the roller 3a and the endless belt 3b. Further, in this case, the head support mechanism 3 is fixed to, for example, the casing of the inkjet recording apparatus 1.

The plurality of liquid ejecting units 2 eject, for example, four color inks corresponding to CMYK (cyan, magenta, yellow, and key (black)), that is, cyan ink, magenta ink, yellow ink, and black ink, respectively.

Next, the control system of the inkjet recording apparatus 1 will be explained.
FIG. 2 is a block diagram showing a configuration example of a control system of the inkjet recording apparatus 1. As shown in FIG.
As shown in FIG. 2, the inkjet recording apparatus 1 includes a processor 201, ROM 202, RAM 203, operation panel 204, communication interface 205, transport motor 206, motor drive circuit 207, pump 208, pump drive circuit 209, inkjet head 10, etc. Be prepared.

The inkjet recording apparatus 1 also includes bus lines 211 such as an address bus and a data bus. The processor 201 is connected to the ROM 202, RAM 203, operation panel 204, communication interface 205, motor drive circuit 207, pump drive circuit 209, and inkjet head 10 via a bus line 211, either directly or via an input/output circuit. Motor drive circuit 207 is connected to transport motor 206 . Further, the pump drive circuit 209 is connected to the pump 208.

The processor 201 has a function of controlling the overall operation of the inkjet recording apparatus 1 . Processor 201 may include an internal cache, various interfaces, and the like. The processor 201 implements various processes by executing programs stored in advance in an internal cache or ROM 202. The processor 201 implements various functions of the inkjet recording apparatus 1 according to the operating system, application programs, and the like.

Note that some of the various functions realized by the processor 201 executing programs may be realized by a hardware circuit. In this case, processor 201 controls the functions performed by the hardware circuits.
Further, the processor 201 functions as a higher-level controller of the inkjet head 10.

The ROM 202 is a nonvolatile memory in which control programs, control data, and the like are stored in advance. The control program and control data stored in the ROM 202 are installed in advance according to the specifications of the inkjet recording apparatus 1. For example, the ROM 202 stores an operating system, application programs, and the like.

RAM 203 is volatile memory. The RAM 203 temporarily stores data being processed by the processor 201. The RAM 203 stores various application programs based on instructions from the processor 201. Further, the RAM 203 may store data necessary for executing the application program, results of executing the application program, and the like. Further, the RAM 203 may function as an image memory in which print data is expanded.

The operation panel 204 is an interface that accepts input instructions from an operator and displays various information to the operator. The operation panel 204 includes an operation section that accepts input of instructions and a display section that displays information.

The operation panel 204 transmits a signal indicating an operation received from an operator to the processor 201 as an operation of the operation unit. For example, the operation unit has function keys such as a power key, a paper feed key, and an error release key arranged thereon.

The operation panel 204 displays various information based on the control of the processor 201 as an operation of the display unit. For example, the operation panel 204 displays the status of the inkjet recording apparatus 1 and the like. For example, the display section is composed of a liquid crystal monitor.
Note that the operation unit may be configured from a touch panel. In this case, the display section may be integrally formed with a touch panel as an operation section.

The communication interface 205 is an interface for transmitting and receiving data to and from an external device via a network such as a LAN (Local Area Network). For example, communication interface 205 is an interface that supports LAN connection. For example, the communication interface 205 receives print data from a client terminal via a network. For example, when an error occurs in the inkjet recording apparatus 1, the communication interface 205 transmits a signal notifying the client terminal of the error.

A motor drive circuit 207 controls driving of the transport motor 206 according to a signal from the processor 201. For example, motor drive circuit 207 sends power or control signals to transport motor 206.

The transport motor 206 is driven under the control of a motor drive circuit 207. The transport motor 206 functions as a drive source for the head support mechanism 3, the medium support mechanism 4, and the like. For example, when the transport motor 206 is driven, the medium support mechanism 4 transports the medium. Further, when the transport motor 206 is driven, the head support mechanism 3 transports the inkjet head 10.

Pump drive circuit 209 controls the drive of pump 208 according to signals from processor 201. For example, pump drive circuit 209 sends power or control signals to pump 208.

Pump 208 is driven under the control of pump drive circuit 209. The pump 208 is a pump for circulating the ink I in the circulation device 20. When the pump 208 is driven, the ink I is supplied from the circulation device 20 to the inkjet head 10, and the ink I is collected from the inkjet head 10.

Note that the inkjet recording apparatus 1 may further include other configurations as needed in addition to the configurations shown in FIGS. 1 and 2, or a specific configuration may be excluded from the inkjet recording apparatus 1.

Next, the inkjet head 10 will be explained.
FIG. 3 shows an example of the configuration of the inkjet head 10. As shown in FIG. 3, the inkjet head 10 includes a channel group 11, a control switch 12, a logic circuit 13, and the like.

The channel group 11 is composed of a plurality of channels that eject ink. Here, the channel group 11 is No. It consists of channels 001, 002, ..., x. Each channel is composed of a pressure chamber filled with ink, a piezoelectric element (actuator) that changes the volume of the pressure chamber, an electrode that applies voltage to the piezoelectric element, and the like.

Each channel inputs a drive waveform via a control switch 12. A driving waveform is applied to the piezoelectric element of each channel through electrodes. When a driving waveform is applied to the piezoelectric element, the piezoelectric element is driven to change the volume of the pressure chamber. Pressure vibrations caused by changes in the volume of the pressure chamber cause ink droplets to be ejected from a nozzle communicating with the pressure chamber.
The channel will be explained in detail later.

The control switch 12 is a switch that controls the connection between the power line that supplies voltage and the electrode of each channel. The control switch 12 controls the connection between the power line and the electrode for each channel. Here, the control switch 12 connects a power line (first power line) that supplies voltage V1, a power line (second power line) that supplies voltage V2, and a power line (third power line) that supplies voltage VSS (for example, ground). power lines) and the channel electrodes. The control switch 12 switches connections according to a control signal supplied from the logic circuit 13.

Here, it is assumed that voltage V1>voltage V2>voltage VSS.
The control switch 12 will be explained in detail later.

The logic circuit 13 (control circuit) supplies a control signal to the control switch 12. The logic circuit 13 receives print data, clock/reset signals, and the like. Logic circuit 13 supplies a control signal to control switch 12 so that a drive waveform is applied to the channel. The logic circuit 13 transmits a control signal for controlling the connection between the first to third power lines and the electrodes for each channel.

The control circuit turns on the second switch after turning off the first switch in a state where the first voltage is applied to the actuator, and the voltage applied to the actuator changes from the first voltage to the second switch. The second switch is turned off before the required change time elapses after the second switch is turned on with a resolution that is less than half the time required for the change to rise or fall to the voltage.

Next, the channel group 11 will be explained.
FIG. 4 shows an equivalent circuit of the channel group 11. Here, No. The x channel will be explained. As shown in FIG. The x channel is composed of a first electrode 17, a second electrode 18 and a piezoelectric element 19.

The first electrode 17 is connected to the control switch 12 . The first electrode 17 receives a voltage V1, a voltage V2, or a voltage VSS (first voltage, second voltage, third voltage) through the control switch 12.
The second electrode 18 is connected to the reference voltage COM.

A piezoelectric element 19 that changes the volume of the pressure chamber is formed between the first electrode 17 and the second electrode 18. A voltage difference between the first electrode 17 and the second electrode 18 is applied to the piezoelectric element 19 .
Further, the piezoelectric element 19 corresponds to a capacitor.

Next, the control switch 12 will be explained.
FIG. 5 shows an equivalent circuit of the control switch 12. Here, No. The switch connected to channel x will be explained. As shown in FIG. 5, the control switch 12 includes transistors 22 to 24 (a first switch, a second switch, a third switch), and the like.

The transistor 22 connects the first power line supplying the voltage V1 and the first electrode 17. The transistor 22 has a source connected to the first power line, a drain connected to the first electrode 17 , and a gate connected to the logic circuit 13 .

The transistor 22 controls the connection between the first power line and the first electrode 17 according to the control signal (No. x SW V1) supplied by the logic circuit 13.

When the transistor 22 is turned on according to the control signal from the logic circuit 13, the first power line and the first electrode 17 are connected. As a result, the voltage V1 is applied to the first electrode 17.

Transistor 23 connects first electrode 17 to a second power line that supplies voltage V2. The transistor 23 has a source connected to the second power line, a drain connected to the first electrode 17 , and a gate connected to the logic circuit 13 .

When the transistor 23 is turned on based on the control signal (No. x SW V2) from the logic circuit 13, the second power line and the first electrode 17 are connected. As a result, the voltage V2 is applied to the first electrode 17.

Transistor 24 connects first electrode 17 to a third power line that supplies voltage VSS. The transistor 24 has a source connected to the third power line, a drain connected to the first electrode 17 , and a gate connected to the logic circuit 13 .

When the transistor 24 is turned on based on the control signal (No. x SW VSS) from the logic circuit 13, the third power line and the first electrode 17 are connected. As a result, the voltage VSS is applied to the first electrode 17.

Further, the drains of the transistors 22 to 24 are connected to each other.
Furthermore, when the transistors 22 to 24 are turned off based on the control signal from the logic circuit 13, the first electrode 17 becomes high impedance.

Control switch 12 includes transistors 22 to 24 for each channel.

Next, an example of the operation of the inkjet head 10 will be described.
FIG. 6 is a timing chart for explaining an example of the operation of the inkjet head 10. FIG. 6 shows an example of operation for generating a drive waveform to be applied to the piezoelectric element 19 of a predetermined channel.

FIG. 6 shows a clock input to the logic circuit 13, SW V1, SW V2, and SW VSS output from the logic circuit 13, and a drive waveform applied to the piezoelectric element 19. Here, the logic circuit 13 applies a voltage smaller than the voltage V1 from a state in which the voltage V1 is applied to the first electrode 17 as a drive waveform, and then applies the voltage V1 again.

Here, the time period during which the voltage applied to the piezoelectric element 19 reaches the voltage VSS after the third power line and the first electrode 17 are connected while the voltage V1 (or voltage V2) is applied to the piezoelectric element 19 is described. Let be the change time.

The logic circuit 13 receives a clock (input clock) having a predetermined frequency. The input clock has a shorter wavelength than the transition time. Here, the input clock has a wavelength that is less than half the time it takes to change.

In the initial state, the logic circuit 13 turns on SW V1 and turns off SW V2 and SW VSS. That is, the logic circuit 13 applies the voltage V1 to the piezoelectric element 19.

The logic circuit 13 turns off SW V1 at a predetermined timing. At this time, SW V1, SW V2, and SW VSS are all temporarily turned off. Through this operation, the logic circuit 13 prevents the first power line, the second power line, and the third power line from shorting.

When a predetermined time has elapsed after turning off SW V1, the logic circuit 13 turns on SW VSS. When the logic circuit 13 turns on SW VSS, the voltage applied to the piezoelectric element 19 drops from the voltage V1 to the voltage VSS.

The logic circuit 13 counts input clocks when SW VSS is turned on. The logic circuit 13 turns off SW VSS when the counted value reaches a predetermined threshold (count threshold). Here, the logic circuit 13 turns off SW VSS before the required change time elapses after turning on SW VSS.

When SW VSS is turned off, the voltage applied to the piezoelectric element 19 is maintained at the voltage at the time SW VSS was turned off.

The logic circuit 13 controls the time from turning on SW VSS to turning off SW VSS by counting input clocks. Therefore, the logic circuit 13 controls the time using the wavelength of the input clock as the minimum resolution.

Furthermore, the logic circuit 13 stores a count threshold value in advance. Further, the logic circuit 13 may store a plurality of count threshold values depending on the gradation. For example, the logic circuit 13 may select one count threshold from a plurality of count thresholds based on print data from the processor 201 or the like.

Furthermore, the logic circuit 13 may change the count threshold depending on the number of channels to be simultaneously driven. Through this operation, even if the required change time changes due to the piezoelectric elements 19 of multiple channels being connected to the third (or first and second) power lines at the same time, the logic circuit 13 can perform the appropriate operation. Gradation can be maintained.

When a predetermined time has elapsed since SW VSS was turned off, the logic circuit 13 turns on SW V1. When the logic circuit 13 turns on SW V1, the voltage applied to the piezoelectric element 19 increases to voltage V1.

Note that the logic circuit 13 may turn off SW V1 and SW VSS and turn on SW VSS in the initial state. That is, the logic circuit 13 applies the voltage VSS to the piezoelectric element 19.

In this case, the change letter time is the voltage applied to the piezoelectric element 19 after the first (or second) power line and the first electrode 17 are connected while the voltage VSS is applied to the piezoelectric element 19. This is the time when the voltage becomes V1 (or voltage V2).

The logic circuit 13 turns off SW VSS at a predetermined timing. At this time, SW V1, SW V2, and SW VSS are all temporarily turned off.

When a predetermined time has elapsed after turning off SW VSS, the logic circuit 13 turns on SW V1 (or SW V2). When the logic circuit 13 turns on SW V1, the voltage applied to the piezoelectric element 19 increases from the voltage VSS to the voltage V1.

The logic circuit 13 counts input clocks when SW V1 is turned on. The logic circuit 13 turns off SW V1 when the counted value reaches the count threshold. Here, the logic circuit 13 turns off SW V1 before the required change time elapses after turning on SW V1.

When SW V1 is turned off, the voltage applied to the piezoelectric element 19 is maintained at the voltage at the time SW V1 was turned off.

When a predetermined time has elapsed after turning off SW V1, the logic circuit 13 turns on SW VSS.

Furthermore, the input clock may have a wavelength that is 1/3 times or less the time required for the change. In this case, the logic circuit 13 can apply a voltage to the piezoelectric element 19 with a resolution of 1/3 or less of the voltage V1. Therefore, even if the voltage V1 is twice the voltage V2, the logic circuit 13 can apply a voltage other than the voltage V1 and the voltage V2 to the piezoelectric element 19.

Further, the inkjet head 10 does not need to include the second power line.
Furthermore, the inkjet head 10 may include four or more power lines that supply different voltages.

Further, the processor 201 may adjust the gradation of print data according to the number of channels driven simultaneously. In this case, the logic circuit 13 does not need to change the count threshold according to the number of channels to be simultaneously driven.

The inkjet head configured as described above stops applying voltage to the piezoelectric element during the rise or fall of the voltage applied to the piezoelectric element. As a result, the inkjet head can maintain the voltage applied to the piezoelectric element at the voltage at the time when the voltage application stopped. Therefore, the inkjet head can apply a plurality of voltages to the piezoelectric element using a potential that outputs a predetermined voltage.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 1... Inkjet recording device, 2... Liquid discharge part, 3... Head support mechanism, 3a... Roller, 3b... Endless belt, 4... Medium support mechanism, 10... Inkjet head, 11... Channel group, 12... Control switch, 13... Logic circuit, 17... First electrode, 18... Second electrode, 19... Piezoelectric element, 20... Circulation device, 22... Transistor, 23... Transistor, 24... Transistor, 201... Processor, 202... ROM, 203... RAM , 204...Operation panel, 205...Communication interface, 206...Transport motor, 207...Motor drive circuit, 208...Pump, 209...Pump drive circuit, 211...Bus line, I...Ink, S...Image forming medium.

Claims (5)

an actuator that changes the volume of the pressure chamber;
a first switch connecting a first power line supplying a first voltage and the actuator;
a second switch connecting the actuator to a second power line that supplies a second voltage different from the first voltage;
turning on the second switch after turning off the first switch while the first voltage is applied to the actuator;
The required change time has elapsed since the second switch was turned on, with a resolution of less than half of the change time required for the voltage applied to the actuator to rise or fall from the first voltage to the second voltage. turning off the second switch before
a control circuit;
An inkjet head equipped with. The control circuit includes:
inputting a clock having a wavelength shorter than half of the change time;
counting the clock after turning on the second switch;
turning off the second switch when the counted value reaches a predetermined threshold;
The inkjet head according to claim 1. a third switch that connects the actuator to a third power line that supplies a third voltage different from the first voltage and the second voltage;
The control circuit turns on the second switch and turns off the second switch before the required change time elapses with a resolution of ⅓ times or less of the required change time.
The inkjet head according to claim 1. The control circuit turns on the second switch after a predetermined time has elapsed after turning off the first switch.
The inkjet head according to claim 1. An inkjet recording device that discharges ink droplets onto a medium,
a support mechanism that supports the medium;
The inkjet head according to any one of claims 1 to 4,
An inkjet recording device comprising: