Patent Application
20210053349
Embodiments described herein relate generally to a liquid discharge apparatus and an ink jet printer.
Liquid discharge apparatuses that supply a predetermined amount of liquid to predetermined positions are known. A liquid discharge apparatus is mounted on, for example, an ink jet printer, a 3D printer, a dispensing apparatus, or the like. The ink jet printer discharges ink droplets from an ink jet head to form an image or the like on the surface of a recording medium. The 3D printer discharges droplets of a molding material from a molding material discharge head and hardens the droplets to forma three-dimensional modeled object. The dispensing apparatus supplies a predetermined amount of droplets of a sample to a plurality of containers or the like.
The liquid discharge apparatus drives an actuator to discharge a liquid from a nozzle formed in a nozzle plate. The actuator including a piezoelectric body is driven by the piezoelectric body being deformed due to a piezoelectric effect when a driving signal is supplied thereto from a driving circuit. When a liquid is discharged from the nozzle, the liquid may be attached to the nozzle plate. The liquid attached to the nozzle plate is removed by a cleaning apparatus.
However, when the nozzle plate is cleaned using a cleaning member such as a wiper blade, the nozzle plate is deformed due to stress such as a pressing force and a frictional force, and the piezoelectric body of the actuator is further generated, which may generate charge due to a piezoelectric effect. When charge is generated in the piezoelectric body of the actuator, there is a concern that adverse influences maybe exerted due to a voltage applied to the driving circuit. In some cases, there is a concern that elements and the like of the driving circuit may be broken.
Embodiments provide a liquid discharge apparatus capable of protecting a driving circuit when stress is applied due to external factors, such as at the time of cleaning of a nozzle plate in which a plurality of nozzles for discharging a liquid are arranged, and an ink jet printer.
In general, according to one embodiment, a liquid discharge apparatus includes a nozzle plate configured such that a plurality of nozzles is arranged, a liquid supply unit, an actuator, a driving circuit, and a low impedance circuit. The nozzles arranged in the nozzle plate discharge a liquid. The liquid supply unit communicates with the nozzles. The actuator is provided for each nozzle in the nozzle plate. The actuator includes a piezoelectric element. The driving circuit supplies a driving signal to the piezoelectric element of the actuator and drives the actuator to discharge a liquid from the nozzles. The low impedance circuit is connected to the piezoelectric element of the actuator while stress is applied to the nozzle plate due to external factors.
Hereinafter, liquid discharge apparatuses according to embodiments will be described with reference to the accompanying drawings. Meanwhile, in the drawings, the same components will be denoted by the same reference numerals and signs.
As an example of an image forming apparatus having a liquid discharge apparatus 1 according to an embodiment mounted thereon, an ink jet printer 10 that prints an image on a recording medium will be described.
Image data to be printed on the sheet S is generated by, for example, a computer 2 which is external connection equipment. The image data generated by the computer 2 is transmitted to the control unit 17 of the ink jet printer 10 through a cable 21 and connectors 22B and 22A.
A pick-up roller 23 supplies the sheets S from the cassette 12 to the upstream transport path 13 one by one. The upstream transport path 13 is constituted by feed roller pairs 13a and 13b and sheet guide plates 13c and 13d. The sheet S is transmitted to an upper surface of the transport belt 14 through the upstream transport path 13. In the drawing, an arrow A1 indicates a transport path of the sheet S from the cassette 12 to the transport belt 14.
The transport belt 14 is a net-like endless belt having a large number of through holes formed in the surface thereof. Three rollers including a driving roller 14a and driven rollers 14b and 14c rotatably support the transport belt 14. A motor 24 rotates the transport belt 14 by rotating the driving roller 14a. The motor 24 is an example of a driving apparatus. In the drawing, A2 indicates a rotation direction of the transport belt 14. A negative pressure container 25 is disposed on the back side of the transport belt 14. The negative pressure container 25 is continuous with a decompression fan 26 and is configured such that the inside of the container changes to a negative pressure due to an air current formed by the fan 26. The sheet S is adsorbed and held by the upper surface of the transport belt 14 due to the inside of the negative pressure container 25 changing to a negative pressure. In the drawing, A3 indicates a flow of an air current. The transport belt 14 is an example of a recording medium transport apparatus.
The ink jet heads 1A to 1D are disposed so as to face the sheet S adsorbed and held on the transport belt 14 through a narrow gap of, for example, 1 mm. The ink jet heads 1A to 1D individually discharge ink droplets toward the sheet S. An image is formed on the sheet S when the sheet S passes below the ink jet heads 1A to 1D. The ink jet heads 1A to 1D have the same structure except that colors of ink to be discharged are different from each other. The colors of the ink are, for example, cyan, magenta, yellow, and black.
The ink jet heads 1A to 1D are respectively connected to ink tanks 3A to 3D and ink supply pressure adjustment apparatuses 32A to 32D through ink flow channels 31A to 31D. The ink flow channels 31A to 31D are, for example, resin tubes. The ink tanks 3A to 3D are containers in which ink is stored. The ink tanks 3A to 3D are respectively disposed above the ink jet heads 1A to 1D. The ink supply pressure adjustment apparatuses 32A to 32D adjust the insides of the ink jet heads 1A to 1D to a negative pressure, for example, −1 kPa with respect to atmospheric pressure so that ink does not leak from nozzles 51 (see
Each of the ink jet heads 1A to 1D includes a maintenance unit. The maintenance units respectively include cleaning apparatuses 33A to 33D that clean the ink jet heads 1A to 1D, and caps 34A to 34D that protect nozzle surfaces of the ink jet heads 1A to 1D. The cleaning apparatuses 33A to 33D remove attached substances attached to the nozzle surfaces of the ink jet heads 1A to 1D. The attached substances are, for example, ink. In addition, for example, dust, sheet dust, and the like may be attached. The ink jet heads 1A to 1D are configured to be movable to cleaning execution positions above the cleaning apparatuses 33A to 33D by head movement apparatuses 35A to 35D (not shown in
After an image is formed, the sheet S is transmitted from the transport belt 14 to the downstream transport path 15. The downstream transport path 15 is constituted by feed roller pairs 15a, 15b, 15c, and 15d and sheet guide plates 15e and 15f for specifying a transport path of the sheet S. The sheet S is transmitted from an outlet 27 to an ejection tray 16 through the downstream transport path 15. In the drawing, an arrow A4 indicates a transport path of the sheet S.
Subsequently, a configuration of an ink jet head 1A will be described with reference to
An actuator 8 serving as a driving source of an operation of discharging ink is provided for each nozzle 51. The actuators 8 are formed to have an annular shape and are arranged such that the nozzles 51 are positioned at the center thereof. For example, the actuator 8 has sizes of an inner diameter of 30 μm and an outer diameter of 140 μm. The actuators 8 are electrically connected to individual electrodes 81, respectively. Further, regarding the actuators 8, eight actuators 8 lined up in the Y-axis direction are electrically connected to each other through common electrodes 82. The individual electrodes 81 and the common electrodes 82 are further electrically connected to a mounting head 9. The mounting head 9 serves as an input port for supplying a driving signal (electrical signal) to the actuators 8. The individual electrodes 81 respectively supply driving signals to the actuators 8, and the actuators 8 are driven in response to the driving signals. Meanwhile, for convenience of description, the actuators 8, the individual electrodes 81, the common electrodes 82, and the mounting head 9 are shown as solid lines in
The mounting head 9 is electrically connected to a wiring pattern formed in the flexible substrate 6 through, for example, an anisotropic contact film (ACF). Further, the wiring pattern of the flexible substrate 6 is electrically connected to the driving circuit 7. The driving circuit 7 is, for example, an integrated circuit (IC). The driving circuit 7 generates a driving signal to be applied to the actuator 8.
The vibration plate 53 is formed of an insulating inorganic material. The insulating inorganic material is, for example, silicon dioxide (SiO2). The thickness of the vibration plate 53 is, for example, 2 to 10 μm, and preferably 4 to 6 μm. Although details will be described later, the vibration plate 53 and the protection layer 52 are bent inwards in association with deformation in a d31 mode of the piezoelectric body 85 having a voltage applied thereto. In addition, the piezoelectric body 85 is returned to its original state when the application of a voltage thereto is stopped. The capacity of the pressure chamber (individual pressure chamber) 41 expands and contracts due to the reversible deformation of the piezoelectric body. When the capacity of the pressure chamber 41 is changed, ink pressure in the pressure chamber 41 changes.
The protection layer 52 is formed of polyimide having a thickness of, for example, 4 μm. The protection layer 52 covers one surface of the nozzle plate 5 on the bottom side and covers an inner circumferential surface of the hole of the nozzle 51.
A wiper blade 104 is attached to a support base 105 provided on the rotary belt 100. The wiper blade 104 and the support base 105 are rotated integrally with the rotary belt 100. In the wiper blade 104, the upper portion thereof is disposed at a height in contact with the bottom surface of the ink jet head 1A, that is, the surface of the nozzle plate 5. The wiper blade 104 is an example of a cleaning member that cleans the nozzle surface of the nozzle plate 5. The wiper blade 104 is disposed such that a side in the longitudinal direction (Y-axis direction) intersects the longitudinal direction (X-axis direction) of the ink jet head 1A. Further, in the wiper blade 104, for example, the length of a side in the longitudinal direction (Y-axis direction) is equal to or greater than the width of the ink jet head 1A in a shorter direction (Y-axis direction). The thickness in the X-axis direction and the height in the Z-axis direction can be appropriately determined in accordance with the size of the ink jet head 1A, and the like.
The wiper blade 104 is formed of, for example, an elastic member having flexibility. The elastic member is, for example, rubber, fluororesin, or the like. A material having liquid repellency to ink and a material having a lyophilic property on the contrary may be selected.
The support base 105 is formed of a resin material such as plastic. For example, the wiper blade 104 is configured to be detachable by being fitted to an upper opening of the support base 105. The wiper blade 104 is replaced when deterioration due to continuous use proceeds. A guide rail 106 is disposed above rotary belt 100 in the longitudinal direction (X-axis direction) of the ink jet head 1A. For example, the guide rail 106 engages with a concave portion formed in the side surface of the support base 105. When cleaning is performed, the motor 103 reciprocates the wiper blade 104 and the support base 105 in the X-axis direction and the −X-axis direction, for example, by rotating the driving pulley 101 forward and reversely. The guide rail 106 guides the support base 105 so that the upper portion of the wiper blade 104 moves while maintaining a fixed height. The wiper blade 104 may be circled in one direction instead of reciprocation. In addition, a container that collects ink and the like removed by the wiper blade 104 may be provided.
When cleaning is performed, the ink jet head 1A is moved to a cleaning execution position shown in
The driving circuit 7 includes a data buffer 71, a decoder 72, and a driver 73. The data buffer 71 stores image data for each actuator 8 in time series. The decoder 72 controls the driver 73 on the basis of the image data stored in the data buffer 71 for each actuator 8. The driver 73 outputs a driving signal for operating the actuators 8 under the control of the decoder 72. The driving signal is a voltage to be applied to the actuators 8.
In the driving signal supply circuit 200, three switches 201, 202, and 203 are disposed in parallel. The switches 201, 202, and 203 are driving circuit elements. The first switch 201 is electrically connected to a driving voltage power supply. The second switch 202 is electrically connected to an intermediate voltage power supply. The third switch 203 is grounded. The driving signal supply circuit 200 supplies control signals 1 to 3 to the switches 201, 202, and 203 to control switching between turn-on and turn-off of the switches 201, 202, and 203. The switches 201, 202, and 203 are, for example, transistors. The transistors are, for example, electric field effect transistors (MOS-FET).
Meanwhile, the above-described driving voltage is a voltage V1 in a driving waveform of
Subsequently, a relationship between a waveform (driving waveform) of a driving signal to be supplied to the actuator 8 and an operation of discharging ink from the nozzle 51 will be described with reference to
The driving circuit 7 turns on the first switch 201 of the driving signal supply circuit 200 from time t0 to time t1 to apply a bias voltage V1 to the actuator 8. That is, the voltage V1 is applied between the lower electrode 86 and the upper electrode 84. In addition, after the third switch 203 of the driving signal supply circuit 200 is turned on from time t1 at which an ink discharge operation is started to time t2 to apply a voltage V3 (=0 V), the second switch 202 of the driving signal supply circuit 200 is turned on from time t2 to time t3 and a voltage V2 is applied to perform first ink dropping. Further, after the third switch 203 of the driving signal supply circuit 200 is turned on from time t3 to time t4 to apply a voltage V3 (=0 V), the second switch 202 of the driving signal supply circuit 200 is turned on from time t4 to time t5 and a voltage V2 is applied to perform second ink dropping. Further, after the third switch 203 of the driving signal supply circuit 200 is turned on from time t5 to time t6 and a voltage V3 (=0 V) is applied, the second switch 202 of the driving signal supply circuit 200 is turned on from time t6 to time t7 and a voltage V2 is applied to perform third ink dropping. The first switch 201 of the driving signal supply circuit 200 is turned on at time t7 after the termination of dropping and a bias voltage V1 is applied to attenuate residual vibration inside the pressure chamber 41.
The voltage V2 is a voltage lower than the bias voltage V1, and a voltage value is determined on the basis of, for example, an attenuation rate of pressure vibration of ink inside the pressure chamber 41. A period of time between time t1 and time t2, a period of time between time t2 and time t3, a period of time between time t3 and time t4, a period of time between time t4 and time t5, a period of time between time t5 and time t6, and a period of time between time t6 and time t7 are set to a half cycle of a specific vibration cycle λ determined depending on characteristics of ink and an internal structure of the head. The half cycle of the specific vibration cycle λ is also called an acoustic length (AL). Meanwhile, the voltage of the grounded common electrode 82 is fixed to 0 V during a series of operations.
When a voltage V3 (=0 V) as an expansion pulse is applied at time t1, the actuator 8 returns to a state before deformation as schematically shown in
When a voltage V2 as a contraction pulse is applied at time t2, the piezoelectric body 85 of the actuator 8 is deformed again, and thus the capacity of the pressure chamber 41 is reduced. As described above, ink pressure increases between time t1 and time t2, and ink pressure is increased by pressing the pressure chamber 41 using the actuator 8 so as to reduce the capacity of the pressure chamber 41, and thus ink is pushed out from the nozzle 51 as schematically shown in
After a voltage V3 (=0 V) is applied from time t3 to time t4, second ink dropping is performed using the same operations and actions as when a voltage V2 is applied from time t4 to time t5 (
When the third ink dropping is performed, a voltage V1 as a cancellation pulse is applied at time t7. Ink pressure inside the pressure chamber 41 is decreased by discharging ink. Further, vibration of the ink remains inside the pressure chamber 41. Consequently, the actuator 8 is driven so that the capacity of the pressure chamber 41 is reduced by lowering a voltage from the voltage V2 to the voltage V1, and ink pressure inside the pressure chamber 41 is substantially set to 0 so as to forcibly attenuate residual vibration of ink inside the pressure chamber 41.
As an example, the cleaning of the ink jet head 1A is performed according to a procedure shown in
When it is determined that a printing job is not executed and any printing job is not also received (Act10, no), the control unit 17 moves the ink jet head 1A in the Z-axis direction and the Y-axis direction by the head movement apparatus 35A and positions the ink jet head 1A at the cleaning execution position shown in
Subsequently, the control unit 17 controls the driving signal supply circuit 200 so as to turn on the third switch 203 as shown in
Subsequently, the control unit 17 rotates the rotary belt 100 to move the wiper blade 104 in the X-axis direction as shown in
When cleaning is performed while moving the wiper blade 104 in the X-axis direction, the nozzle plate 5 may be deformed as if, for example, a wave moves forward due to stress such as a pressing force or a frictional force from the wiper blade 104. Further, in a region in which the actuators 8 are disposed, the piezoelectric bodies 85 of the actuators 8 may be deformed together with the nozzle plate 5, and charge may be generated due to the action of a piezoelectric effect. In this case, when all of the switches 201, 202, and 203 are kept turned off for a reason to reduce power consumption, there is a concern that circuits on sides of output ends of the switches 201, 202, and 203 may be set to be in a high impedance state and may exert adverse influences on the driving circuit 7. In some cases, there is a concern that the switches 201, 202, and 203 which are driving circuit elements may be broken. On the other hand, when the third switch 203 is turned on, a low impedance state is set, and thus charge generated by the piezoelectric body 85 escapes to a ground line.
When the cleaning performed by the wiper blade 104 is completed, the control unit 17 returns the wiper blade 104 to a standby position and then stops the motor 103. Further, the third switch 203 is turned off to terminate the cleaning (Act14). That is, all of the switches 201, 202, and 203 are turned off again to reduce power consumption of the printing apparatus. The ink jet head 1A having terminated cleaning is returned to the ink discharge position shown in
Meanwhile, in the above-described embodiment, cleaning is performed in a state where the third switch 203 is turned on, but cleaning may be performed in a state where the second switch 202 is turned on and connected to the intermediate voltage power supply as shown in
According to the above-described embodiment, cleaning is performed in a state where any one of the switches 201, 202, and 203 of the driving signal supply circuit 200 is turned on and the piezoelectric body 85 of the actuator 8 is connected to a ground or a power supply through the driving signal supply circuit 200. In this manner, a circuit on a side of an output end of the driving signal supply circuit 200 is set to be in a low impedance state, and thus charge can be released to a ground line or a power supply even when the piezoelectric body 85 unexpectedly generates the charge during cleaning. As a result, it is possible to prevent the circuit from being set to be in a high impedance state and exerting adverse influences. In addition, it is possible to prevent driving circuit elements such as the switches 201, 202, and 203 from being broken.
In this manner, in a configuration in which any one of the switches 201, 202, and 203 of the driving signal supply circuit 200 is turned on to set a low impedance state, the driving signal supply circuit 200 functions as a low impedance circuit that connects the piezoelectric body 85 of the actuator 8 to a ground or a power supply during cleaning. Therefore, design change for newly providing a low impedance circuit may not be performed, and there is an advantage in that the number of components is not increased. In addition, when the third switch 203 is turned on, the nozzle plate 5 is in a flat state as schematically shown in
Subsequently, a liquid discharge apparatus 1 according to a second embodiment will be described by taking an ink jet head 1A as an example.
The driving signal supply circuit 300 includes a fourth switch 204. The fourth switch 204 is connected to a resistance element 205, and the resistance element 205 is grounded. In addition, a control unit 17 supplies a control signal 4 to turn on the fourth switch 204 during cleaning. In addition, cleaning is performed in a state where a piezoelectric body 85 of an actuator 8 is connected to the resistance element 205. That is, in the present embodiment, a circuit to which the fourth switch 204 and the resistance element 205 are connected constitutes a low impedance circuit. An element other than the resistance element 205 may be used. Even with such a configuration, a circuit on a side of an output end of the driving signal supply circuit 300 is set to be in a low impedance state, and thus charge can be released to a low impedance circuit even when the piezoelectric body 85 unexpectedly generates the charge during cleaning.
Subsequently, a liquid discharge apparatus 1 according to a third embodiment will be described by taking an ink jet head 1A as an example.
The suction member 400 is disposed on a rotary belt 100 and is movable in the X-axis direction, similar to the wiper blade 104. In the suction member 400, a suction port 401 is decompressed by a decompression apparatus not shown in the drawing while the suction member is moving in the X-axis direction. Attached substances attached to the surface of the nozzle plate 5 are suctioned from the suction port 401. Cleaning performed by the suction member 400 is performed in a state where any one of first to fourth switches 201 to 204 is turned on, similar to the first embodiment or the second embodiment. Even when the nozzle plate 5 is deformed due to a suction force and charge is generated in a piezoelectric body 85 of an actuator 8, the charge can be released to any one of a ground line, a driving voltage power supply, an intermediate voltage power supply, and a resistance element 205, similar to the first embodiment or the second embodiment. Meanwhile, suction-type cleaning can also be used to eliminate clogging inside the nozzle 51.
Subsequently, a liquid discharge apparatus 1 according to a fourth embodiment will be described by taking an ink jet head 1A as an example.
A cleaning apparatus according to the fourth embodiment has a configuration in which a suction function is added to a cap 34A protecting the nozzle surface, as an example. That is, the cap 34A functions as a cleaning member. The cap 34A has a concave shape by a bottom surface 500 facing the nozzle surface of the nozzle plate 5 and an erected wall 501 formed along the outer circumference of the bottom surface 500. In the drawing, the cap 34A is shown in a longitudinal sectional view. The cap 34A is mounted from below the ink jet head 1A to form a sealed space 502 surrounding the nozzle surface of the nozzle plate 5. A decompression apparatus 503 that decompresses the inside of the sealed space 502 in order to perform suction is connected to an exhaust hole 505 formed in the bottom surface of the cap 34A through an exhaust passage 504. The decompression apparatus 503 is, for example, a decompression pump. A container 506 collecting ink is provided in the middle of the exhaust passage 504. Besides, a valve, a pressure sensor, and the like may be provided.
Cleaning is performed by mounting the cap 34A on the ink jet head 1A and then operating the decompression apparatus 503 for a predetermined period of time. As an example, cleaning is performed when a printing job is not performed for a long period of time, when clogging occurs in a nozzle 51, and the like. It is possible to clean the nozzle surface of the nozzle plate 5 by suctioning the sealed space 502 surrounding the nozzle surface to particularly discharge ink in the vicinity of the nozzle 51 or an object which is the cause of clogging. Similarly to the first to third embodiments, cleaning is performed in a state where any one of first to fourth switches 201 to 204 is turned on. Even when the nozzle plate 5 is deformed due to a suction force and charge is generated in a piezoelectric body 85 of an actuator 8, the charge can be released to any one of a ground line, a driving voltage power supply, an intermediate voltage power supply, and a resistance element 205, similar to the first to third embodiments.
Although the ink jet heads 1A according to the first to fourth embodiments have been described in detail, the pressure chambers (individual pressure chambers) 41 may be omitted and the nozzle plate 5 may directly communicate with the common ink chamber 42 as shown in
In the first to fourth embodiments, the protection of the driving circuit 7 when charge is generated due to deformation of the actuator 8 during cleaning of the ink jet head 1A has been described. However, for example, when there is a concern that the nozzle plate 5 may be deformed due to stress caused by external factors such as a case where the cap 34A protecting the nozzle surface is attached to the ink jet head 1A, it is possible to protect the driving circuit 7 even when the actuator 8 unexpectedly generates charge in a state where any one of the first to fourth switches 201 to 204 is turned on.
Cleaning may also be manually performed without being automatically performed as in the first to fourth embodiments.
Further, in the ink jet head 1A, both the actuator 8 and the nozzle 51 may not be disposed on the surface of the nozzle plate 5. For example, an ink jet head including an actuator of any one driving type among a drop on demand piezo type, a share wall type, and a share mode type may be used.
Further, in the above-described embodiments, the ink jet head 1A of the ink jet printer 1 has been described as an example of a liquid discharge apparatus, but the liquid discharge apparatus may be a molding material discharge head of a 3D printer or a sample discharge head of a dispensing apparatus.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-208557 | Nov 2018 | JP | national |
This application is a Division of application Ser. No. 16/550,460 filed on Aug. 26, 2019, the entire contents of which are incorporated herein by reference. This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-208557, filed Nov. 6, 2018, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16550460 | Aug 2019 | US |
| Child | 17091191 | US |
