JP2013158960A - Liquid droplet ejection head and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid droplet ejection head capable of stably performing minute driving operation for generating a pressure to vibrate an ejection liquid in an ejection liquid chamber without ejecting a liquid droplet from an ejection hole, and to provide an image forming device having the liquid droplet ejection head.SOLUTION: A recording head 51 includes: a plurality of ejection CHs each having a nozzle hole 20, an individual liquid chamber 14 storing ink liquid ejected from the nozzle hole 20, and a piezoelectric actuator 200 for pressurizing the inside of the individual liquid chamber 14; a common liquid chamber 18 communicated with the plurality of individual liquid chambers 14; a supply port 102b for supplying the ink liquid to the common liquid chamber 18; and a driving control means for controlling driving of the piezoelectric actuators 200 so as to perform ejection operation and minute driving operation. A pressurizing frequency in minute driving operation of the piezoelectric actuator 200 is decreased in a position away from the supply port 102b on the downstream side compared to the vicinity of the supply port 102b on the upstream side of a passage of the ink liquid in the common liquid chamber 18.

Description

  The present invention relates to a droplet discharge head that discharges droplets and an image forming apparatus including the droplet discharge head.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a liquid ejection head that ejects ink droplets, and ejects ink droplets while conveying a medium. There is an ink jet recording apparatus that forms an image by adhering to a medium. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  An inkjet head in an inkjet recording apparatus, which is an example of an image forming apparatus, includes a plurality of ejection holes that eject ink droplets, an ejection liquid chamber that communicates with the outside through the ejection holes and contains ink that becomes ink droplets; Pressure generating means for generating pressure to pressurize the ink liquid in the discharge liquid chamber. Then, by driving the pressure generating means, the ink liquid in the discharge liquid chamber is pressurized and ink droplets are discharged from the discharge holes. As such an ink jet recording apparatus, an ink-on-demand system that ejects ink droplets only when recording is necessary is the mainstream.

Inkjet heads are roughly classified into several types depending on the type of pressure generating means for ejecting ink droplets.
Japanese Patent Application Laid-Open No. H10-228561 describes a piezoelectric type in which a part of the wall of the discharge liquid chamber is a thin diaphragm and a piezoelectric element as an electromechanical conversion element is arranged correspondingly. In the piezo method, an ink droplet is ejected by changing the pressure in the ejection liquid chamber by deforming the diaphragm by the deformation of the piezoelectric element that occurs with voltage application.
Japanese Patent Application Laid-Open No. 2004-228561 describes an electrostatic type that includes a diaphragm that forms a wall surface of a discharge liquid chamber and an individual electrode outside the liquid chamber that is disposed to face the diaphragm. In the electrostatic method, the diaphragm is deformed by an electrostatic force generated by applying an electric field between the diaphragm and the electrode, and ink droplets are ejected from the ejection holes by changing the pressure / volume in the ejection liquid chamber. .
A bubble jet (registered trademark) type in which a heating element is disposed in the discharge liquid chamber, bubbles are generated by heating the heating element by energization, and ink droplets are discharged by the pressure of the bubbles is generally well known. Yes.

  In such an ink jet head, if the state in which the ink liquid in the discharge liquid chamber is not discharged continues, the ink liquid near the discharge hole may increase in viscosity. If the ink liquid in the vicinity of the discharge hole in the discharge liquid chamber is thickened, the discharge hole may be clogged, and there may be a problem that the ink droplet is bent or non-discharged in the next discharge. As a configuration for preventing a problem caused by thickening of the ink liquid in the vicinity of the ejection hole, Patent Document 3 generates a pressure for vibrating the ink liquid in the ejection liquid chamber to such an extent that no liquid droplet is ejected from the ejection hole. A configuration for performing a fine driving (fine vibration) operation is described. In addition, it is described that the ink liquid in the vicinity of the ejection holes is agitated in the ejection liquid chamber to prevent clogging of the ejection holes by performing fine driving at a predetermined time such as when printing is started.

  As the temperature of the ink liquid increases, the viscosity decreases, and as the temperature decreases, the viscosity increases.When the drive control such as the magnitude of the pressure generated during fine driving and the frequency of generation is set constant, the following is performed: Problems arise. In other words, if the same micro-driving that can sufficiently stir ink liquid with low temperature and high viscosity is performed in the same way for ink liquid with high temperature and low viscosity, the stirred ink liquid leaks from the ejection holes. There is a risk of release. In addition, if the same fine driving as the fine driving in which the ink liquid having a high temperature and low viscosity does not leak from the ejection hole is performed in the same manner for the ink liquid having a low temperature and high viscosity, the stirring of the ink liquid becomes insufficient. The clogging described above may occur.

  Patent Document 3 describes a configuration in which the temperature of an inkjet head is detected and the driving of a fine driving operation is controlled according to the detection result. Thereby, even if the temperature of the ink liquid in the ink jet head changes due to a change in the environmental temperature or the like, it is possible to prevent the ink liquid from leaking out and clogging due to insufficient stirring.

  However, in an inkjet head including a plurality of discharge liquid chambers, the internal temperature may be different depending on the discharge liquid chamber. In the configuration described in Patent Document 3, since the drive control of uniform fine driving is performed for the entire inkjet head, if the temperature of the ink liquid inside differs depending on the discharge liquid chamber, the ink liquid in each discharge liquid chamber Depending on the temperature, there is a possibility that the ink liquid leaks out or clogging due to insufficient stirring occurs.

  The present invention has been made in view of the above problems, and its purpose is to stably perform a fine driving operation that generates a pressure that oscillates the discharge liquid in the discharge liquid chamber without discharging droplets from the discharge holes. It is an object of the present invention to provide a droplet discharge head that can be performed and an image forming apparatus including the droplet discharge head.

In order to achieve the above object, the invention of claim 1 includes a discharge hole for discharging a droplet, a discharge liquid chamber communicating with the outside through the discharge hole and containing a discharge liquid to be the droplet, A plurality of droplet discharge mechanisms, each of which includes a pressure generating means for generating pressure in the discharge liquid chamber, communicated with each of the plurality of droplet discharge mechanisms, and supplied to the discharge liquid chamber A common flow path through which the discharge liquid passes, a liquid supply port for supplying the discharge liquid to the common flow path, and a drive control means for controlling the drive of the pressure generating means of the plurality of droplet discharge mechanisms, The drive control means generates a pressure that generates a pressure that discharges the droplet from the discharge hole, and generates a pressure that vibrates the discharge liquid in the discharge liquid chamber without discharging the droplet from the discharge hole. The pressure generating means of the droplet discharge mechanism is controlled so as to perform a fine driving operation. In the liquid droplet discharge head, the fine generating operation of the pressure generating means for generating a pressure in the discharge liquid chamber communicating with the common flow path upstream of the passage path of the discharge liquid in the common flow path, The fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path downstream of the discharge liquid passage in the common flow path has a higher frequency of generating pressure. It is characterized by few.
In order to achieve the above object, a second aspect of the present invention provides a discharge hole for discharging a droplet, a discharge liquid chamber communicating with the outside through the discharge hole and containing a discharge liquid to be the droplet. A plurality of droplet discharge mechanisms, each of which is connected to the discharge liquid chambers of the plurality of droplet discharge mechanisms, and is supplied to the discharge liquid chambers. A common flow path through which the discharged liquid passes, a liquid supply port for supplying the discharged liquid to the common flow path, and a drive control means for controlling the driving of the pressure generating means of the plurality of droplet discharge mechanisms. A discharge operation in which the drive control means generates a pressure for discharging a droplet from the discharge hole, and the discharge liquid in the discharge liquid chamber including the inside of the discharge hole without discharging the droplet from the discharge hole. The liquid droplet ejection mechanism so as to perform a fine driving operation for generating a pressure that vibrates the liquid. In the droplet discharge head for controlling the driving of the force generating means, the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path upstream of the passage path of the discharge liquid in the common flow path The fine drive operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path downstream of the discharge liquid passage path in the common flow path is more than the fine drive operation of The generated pressure is small.

As a result of extensive investigations by the present inventors, in a state where the internal temperature differs depending on the discharge liquid chamber, the discharge liquid chamber communicates with a plurality of discharge liquid chambers and a common flow path through which the discharge liquid supplied to each discharge liquid chamber passes. Thus, it was found that the temperature of the discharge liquid chamber communicating with the common flow path on the downstream side of the passage path of the discharge liquid becomes higher. This is due to the following reason.
That is, the pressure generating means generates Joule heat at the time of driving, and the drive control means for controlling the driving of the pressure generating means generates Joule heat at the time of exchanging signals when performing control. For this reason, when the discharge liquid passes through the common flow path, it is heated by the heat generated by the pressure generating means and the drive control means, and the temperature of the discharge liquid rises. Since the discharge liquid supplied to the discharge liquid chamber communicating with the common flow path on the downstream side of the passage path of the discharge liquid has a longer flow path until reaching the discharge liquid chamber and is heated for a longer time, The rise is remarkable.

In the invention having the configuration of claim 1 of the present application, the discharge communicated with the common flow path downstream of the discharge liquid passage path rather than the discharge liquid chamber communicated with the common flow path upstream of the discharge liquid passage path. In the liquid chamber, the pressure generating means generates less pressure during the fine driving operation, so that the temperature is high and the viscosity is low while sufficiently stirring the upstream discharge liquid having a low temperature and a high viscosity. It is possible to prevent the discharge liquid from leaking due to the pressure applied to the discharge liquid on the downstream side excessively.
Further, in the invention having the configuration of claim 2 of the present application, it communicates with the common flow path downstream of the discharge liquid passage path rather than the discharge liquid chamber communicating with the common flow path upstream of the discharge liquid passage path. Since the pressure generated by the pressure generating means during the fine driving operation is smaller in the discharge liquid chamber, the temperature is high and the viscosity is low while sufficiently stirring the upstream discharge liquid having a low temperature and a high viscosity. It is possible to prevent the discharge liquid from leaking due to excessive pressure applied to the discharge liquid on the downstream side.

  According to the present invention, the downstream discharge liquid can be prevented from leaking while sufficiently stirring the upstream discharge liquid, so that the discharge liquid in the discharge liquid chamber is not discharged from the discharge hole. There is an excellent effect that the fine driving operation for generating the pressure to vibrate can be stably performed.

FIG. 4 is an exploded perspective view of the recording head showing the temperature distribution of the ink liquid, (a) is an explanatory diagram of a nozzle substrate, (b) is an explanatory diagram of a liquid chamber substrate, and (c) is an explanatory diagram of a protective substrate. 1 is a schematic perspective view of an ink jet printer. 1 is a schematic sectional view of an ink jet printer. FIG. 4 is an exploded perspective view of a droplet discharge head, (a) is an explanatory view of a nozzle substrate, (b) is an explanatory view of a liquid chamber substrate, and (c) is an explanatory view of a protective substrate. Cross-sectional explanatory view of the droplet discharge head, (a) is a cross-sectional explanatory view corresponding to the XX 'cross section in FIG. 4, (b) is a cross-sectional explanatory view corresponding to the YY' cross section shown in FIG. Figure. FIG. 3 is a block explanatory diagram of a control unit of the printer. An explanatory diagram showing an example of a drive waveform, (a) is an explanatory diagram of a generated drive waveform, (b) is an explanatory diagram of an input drive waveform for fine driving, and (c) is an input drive waveform for ejecting small ink droplets. FIG. 7D is an explanatory diagram of input drive waveforms for ejecting large ink droplets. FIG. 4 is an explanatory diagram of falling and rising from a reference potential in a drive signal, (a) is an explanatory diagram of an example of a drive signal, and (b) is an enlarged view of a part of (a). Schematic which shows the shape of the diaphragm layer in the state in which the voltage is not applied to the piezoelectric element, and the state in which the voltage is applied. An explanatory view of a change in ink liquid near the nozzle hole, (a) is an explanatory view of a state where a reference potential is applied, (b) is an explanatory view of a state where the potential is lowered, and (c) is a reference potential. Explanatory drawing of the state which raised the electric potential to. Explanatory drawing of the other example of a generation drive waveform. Explanatory drawing of ejection of ink droplets, (a) is an explanatory diagram of ink droplets ejected from one nozzle hole at different timings, and (b) is a paper on which an image is formed by ejection of ink droplets of (a) FIG. 9C is an explanatory diagram of an example of the formed image. FIG. 3 is a cross-sectional view of a recording head for explaining a state where heat is transmitted to a common liquid chamber. FIG. 3 is an explanatory perspective view of a recording head showing a positional relationship between a common liquid chamber and a head driver. FIG. 5A is an explanatory diagram of a drive waveform used in the first embodiment, FIG. 5A is an explanatory diagram of a generated drive waveform, FIG. 5B is an explanatory diagram of a fine drive input drive waveform, and FIG. Illustration. Explanatory drawing of the temporal control of the droplet control signal MN and the drive waveform of the first embodiment, (a) is an explanatory diagram of the control for the discharge CH near the supply port, and (b) is for the discharge CH at a position far from the supply port. Explanatory drawing of control. FIG. 6A is an explanatory diagram of a drive waveform used in the second embodiment, FIG. 5A is an explanatory diagram of a generated drive waveform, FIG. 5B is an explanatory diagram of an input drive waveform for fine driving, and FIG. Explanatory drawing of a drive waveform. Explanatory drawing of the temporal control of the droplet control signal MN and the drive waveform of the second embodiment, (a) is an explanatory diagram of the control for the discharge CH near the supply port, and (b) is for the discharge CH at a position far from the supply port. Explanatory drawing of control. Explanatory drawing which shows an example of grouping of discharge CH in Example 3. FIG.

Hereinafter, an ink jet printer (hereinafter, printer 100) will be described as an embodiment of an image forming apparatus to which the present invention is applicable.
First, the basic configuration of the printer 100 will be described. FIG. 2 is a perspective view of the printer 100, and FIG. 3 is a schematic cross-sectional view including the ink cartridge 102 when viewed from the front side in FIG.
The printer 100 includes a printing mechanism 103 that includes a carriage 101, a recording head 51, and an ink cartridge 102 inside the main body. The carriage 101 is a member that can move in the scanning direction that is orthogonal to the conveyance direction of the paper 30 inside the printer 100 main body. The recording head 51 is an ink jet head which is an example of a droplet discharge head mounted on the carriage 101, and the ink cartridge 102 supplies ink liquid in the tank portion 102a to the recording head 51 described later.

  As shown in FIG. 3, the printer 100 includes a paper feed mechanism unit 104 below the printing mechanism unit 103. Although details will be described later, the printer 100 takes in the paper 30 fed from the paper feed tray 230 or the manual feed tray 105 of the paper feed mechanism unit 104, records a required image by the print mechanism unit 103, and then on the rear side. The paper is discharged onto the mounted paper discharge tray 106.

The recording head 51 is an ink discharge head that discharges yellow (Y), magenta (M), cyan (C), and black (B) ink liquids, and includes a plurality of ink discharge holes (described later, “nozzle holes 20”). Are arranged in a direction (arrow B direction in the figure) orthogonal to the main scanning direction (arrow A direction in FIG. 2, direction orthogonal to the paper surface in FIG. 3). The recording head 51 is mounted on the carriage 101 so that the ink discharge direction is downward.
Further, the carriage 101 of the printing mechanism unit 103 includes four ink cartridges 102 each containing ink liquids of yellow (Y), magenta (M), cyan (C), and black (B) in the recording head 51. It is installed so that it can be replaced.

  Above the tank portion 102a of the ink cartridge 102 (above in FIG. 3), an air port (not shown) communicating with the air is provided. A supply port 102b for supplying the ink liquid in the tank 102a to the recording head 51 is provided below the tank 102a. Further, the tank portion 102a has a porous body (not shown) filled with ink liquid, and the ink liquid supplied to the recording head 51 is made to have a slight negative pressure by the capillary force of the porous body. Is maintained.

  As the ink cartridge 102, the tank unit 102 a and the recording head 51 may be integrated, or the tank unit 102 a may be separated from the recording head 51. Further, in the present embodiment, the recording head 51 is configured to use a plurality of head portions corresponding to the respective colors, but may be a single head portion having nozzle holes for discharging ink liquids of the respective colors.

  The printing mechanism unit 103 includes a main guide rod 107 and a sub guide rod 108 as guide members horizontally mounted on both side plates (100a and 100b) in the main scanning direction of the main body of the printer 100 as a holding unit that holds the carriage 101. The main guide rod 107 passes through the rear side of the carriage 101 (downstream side in the paper conveyance direction, right side in FIG. 3). The sub guide rod 108 extends in parallel with the main guide rod 107 at a predetermined interval, and is placed on the front side of the carriage 101 (upstream side in the sheet conveying direction, left side in FIG. 3). The carriage 101 is slidably held by a main guide rod 107 and a sub guide rod 108 so as to be movable in the main scanning direction.

  Further, the printing mechanism unit 103 rotates the timing belt 112, the driving pulley 110 and the driven pulley 111 that stretch the timing belt 112, and the driving pulley 110 as moving means for moving and scanning the carriage 101 in the main scanning direction. And a main scanning motor 109 to be driven. As shown in FIG. 2, the driving pulley 110 is disposed on one side plate (100b) side of the printer 100 main body, and the driven pulley 111 is disposed on the other side plate (100a) side of the main body. Extends in parallel with the main scanning direction. A carriage 101 is fixed to the timing belt 112.

  The main scanning motor 109 is a driving source that rotates the driving pulley 110 forward and backward. When the driving pulley 110 rotates, the timing belt 112 moves endlessly in the main scanning direction. Since the carriage 101 is fixed to the timing belt 112, the carriage 101 moves in the main scanning direction together with the timing belt 112. Therefore, the carriage 101 is reciprocated in the main scanning direction by rotating the driving pulley 110 forward and backward by the main scanning motor 109.

On the other hand, the paper feed mechanism unit 104 includes a paper feed tray 230 on which the paper 30 is stacked, a paper feed roller 113, a friction pad 114, a guide member 115, and a transport roller 116. The paper feed tray 230 is capable of stacking a bundle of a plurality of sheets 30 from the right side in FIG. 3, and is detachably attached to the printer 100 main body.
The paper feed roller 113 and the friction pad 114 separate and feed the uppermost sheet of the bundle of paper 30 set in the paper feed tray 230 in order to transport the paper 30 below the recording head 51. The guide member 115 guides the paper 30 separated and fed from the paper feed tray 230 to an area where the paper is conveyed by the conveyance roller 116.

  The transport roller 116 feeds the paper 30 fed by the paper feed roller 113 and guided by the guide member 115, and transports the paper 30 to a position facing the lower surface of the recording head 51. A transport roller 117 and a front roller 118 are disposed around the transport roller 116. The conveyance roller 117 presses the paper 30 against the conveyance roller 116 to prevent the paper 30 from being separated from the conveyance roller 116. The leading end roller 118 feeds the paper 30 at a predetermined feed angle to a position facing the lower surface of the recording head 51. The conveyance roller 116 is rotated by a sub-scanning motor 130 via a gear train (not shown), and rotates in the clockwise direction in FIG.

  At a position facing the lower surface of the recording head 51, a mark is a sheet guide member that guides the sheet 30 fed from the conveying roller 116 corresponding to the movement range of the carriage 101 in the main scanning direction on the lower side of the recording head 51. A copying member 119 is provided. A discharge roller 120 for sending the paper 30 in the discharge direction and a discharge spur 121 opposed to the discharge roller 120 are disposed on the downstream side of the printing receiving member 119 in the paper conveyance direction. Furthermore, a paper discharge roller 123 that discharges the paper 30 fed by the discharge roller 120 to the paper discharge tray 106 and a paper discharge spur 124 that faces the paper discharge roller 123 are provided. A lower guide member 125 and an upper guide member 126 are disposed between the discharge roller 120 and the paper discharge roller 123 as a pair of guide members that form a paper discharge path.

  Further, the printer 100 is provided with a manual feed tray 105 for manually feeding the paper 30. The manual feed tray 105 is attached to the printer 100 main body about the tray opening / closing shaft 105b so as to be foldable. ing. The paper 30 on the manual feed tray 105 is transported to the transport roller 116 by the manual paper feed roller 105a.

  A recovery device 127 for recovering the ejection failure of the recording head 51 is provided at a position outside the recording area on the right front side in FIG. 2, which is one end of the moving range of the carriage 101 in the main scanning direction in the printing mechanism 103. It is arranged. The recovery device 127 includes a cap unit, a suction unit, and a cleaning unit. The carriage 101 is moved to the recovery device 127 side during printing standby, and the recording head 51 is capped by a capping unit (not shown), and the nozzle hole is kept in a wet state to prevent ejection failure due to ink drying. It has a configuration. In addition, by moving the carriage 101 to a position facing the recovery device 127 during recording or the like and discharging ink liquid that is not related to recording, the ink viscosity of all nozzle holes is made constant and stable discharge performance is maintained. can do.

  When a discharge failure occurs, the nozzle hole on the lower surface of the recording head 51 is sealed by the capping unit, and bubbles and the like are sucked out from the nozzle hole by the suction unit through a tube (not shown) provided in the capping unit. Further, ink liquid and dust adhering to the head surface (lower surface) where the nozzle holes are opened are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink liquid is discharged to a waste ink tank (not shown) installed at the lower part of the printer 100 main body, and is absorbed and held by an ink absorber inside the waste ink tank.

Next, the printing operation of the printer 100 will be described.
The printer 100 receives a signal such as image information from an external device such as a personal computer and executes a printing operation. When the printing operation is executed, the paper 30 is fed from the manual feed tray 105 by the manual feed roller 105a or from the paper feed tray 230 by the paper feed roller 113. The paper 30 fed from the paper feed tray 230 is guided by the guide member 115 and the transport roller 117, reversed while being transported by the transport roller 116, and transported to a position facing the recording head 51. On the other hand, the paper 30 supplied from the manual feed tray 105 is guided to the transport roller 117, transported to the transport roller 116, and transported to a position facing the recording head 51.

When the paper 30 transported to the position facing the recording head 51 reaches a predetermined position, the rotation of the transport roller 116 is stopped and the movement of the paper 30 is stopped. Then, while the carriage 101 reciprocates in the main scanning direction according to the image signal, a predetermined ink liquid is ejected to a predetermined position of the stopped paper 30 to form an image for one line on the paper 30. Here, one line refers to a range in the sub-scanning direction (the moving direction of the sheet 30 at a position facing the recording head 51) in which the recording head 51 can record on the sheet 30.
When image formation for one line is completed in the main scanning direction, the conveyance roller 116 is rotated for a predetermined time, and the sheet 30 is moved by one line in the direction of the paper discharge tray 106 and stopped. Then, the carriage 101 forms an image for one line while reciprocating in the main scanning direction according to the image signal.

  Such a process is repeated a predetermined number of times to print a desired image on the paper 30. When a recording end signal is received from an external device and a desired image is printed, or when a signal indicating that the trailing edge of the paper 30 has reached the recording area is received, the paper 30 is discharged from the discharge roller 120 and the discharge spur 121. , The paper discharge roller 123 and the paper discharge spur 124, and are discharged to the paper discharge tray 106. After the image formation, the carriage 101 moves to a position facing the recovery device 127 on the right front side in FIG. 2, and capping the nozzle holes of the recording head 51 by a capping unit (not shown).

Next, the recording head 51 will be described. The recording head 51 of this embodiment is a thin film piezo head.
FIG. 4 is an exploded perspective view of a part of the recording head 51 described above. The recording head 51 shown in FIG. 4 uses a piezoelectric actuator 200 and shows an example of a side shooter system in which ink droplets are ejected from nozzle holes provided on a surface portion (head surface) of a substrate. . 2 and 3, the recording head 51 in which the ink discharge holes (“nozzle holes 20”) are installed downward is drawn upward in FIG. 4 for convenience of explanation.

  As shown in FIG. 4, the recording head 51 is formed by stacking three substrates. 4A is an explanatory diagram of the nozzle substrate 2 having the nozzle holes 20 for discharging ink liquid, and FIG. 4B is an individual liquid chamber 14, a diaphragm layer 55, a fluid resistance unit 15, and individual ink supply holes. FIG. 4C is an explanatory view of the protection substrate 3 forming the piezoelectric element protection space 22 and the common liquid chamber. As described above, the recording head 51 has a laminated structure in which the three substrates of the nozzle substrate 2, the liquid chamber substrate 1 and the protective substrate 3 are stacked. FIGS. 4B and 4C are partially sectional views.

  FIG. 5 is an explanatory cross-sectional view of the recording head 51 shown in FIG. FIG. 5A is a cross-sectional explanatory view corresponding to the XX ′ cross section in FIG. 4 and shows only a part corresponding to two individual liquid chambers 14 for convenience, and the ink in one individual liquid chamber 14 is shown. Is schematically shown as being ejected through the nozzle hole 20 toward the paper 30 as ink droplets. FIG. 5B is a cross-sectional explanatory diagram corresponding to the Y-Y ′ cross section shown in FIG. 4. In Fig.5 (a), the area | region corresponding to the fluid resistance part 15 where the flow path is narrow is shown with the broken line.

A silicon substrate 4 is used for the liquid chamber substrate 1, and groove portions serving as ink flow paths such as the individual liquid chamber 14 and the fluid resistance portion 13 are formed.
The liquid chamber substrate 1 uses an SOI substrate in which silicon is bonded to a silicon substrate 4 via a silicon oxide film. The diaphragm layer 55 is obtained by applying a pyro-oxidation method to the surface of the silicon layer (Si layer) of the SOI substrate to form a silicon oxide film. A piezoelectric element 56 is formed on the diaphragm layer 55. The piezoelectric actuator 200 is configured. The piezoelectric element 56 has a multilayer structure of a platinum film serving as the lower electrode layer 151, a PZT (lead zirconate titanate) film serving as the piezoelectric layer 152, and a platinum film serving as the upper electrode layer 153 on the diaphragm layer 55. It is formed by stacking. The piezoelectric element 56 is formed in a region facing the individual liquid chamber 14 formed by etching the silicon substrate 4.

  The liquid chamber substrate 1 includes a wiring member 154 that applies a potential to each of the lower electrode layer 151 and the upper electrode layer 153. As the wiring member 154, a first wiring member 154a that electrically connects the lower electrode pad portion 157 to the lower electrode layer 151, and a second wiring member 154b that electrically connects the upper electrode pad portion 158 to the upper electrode layer 153. And are provided. The liquid chamber substrate 1 also includes an interlayer insulating film 155 disposed between the lower electrode layer 151 and the upper electrode layer 153 and the wiring member 54. Further, a passivation film 156 for protecting the wiring member 154 is disposed on the liquid chamber substrate 1 so as to cover the upper surface and side surfaces of the piezoelectric actuator 200.

The nozzle substrate 2 is made of a SUS substrate having a thickness of 30 to 50 [μm], and the nozzle holes 20 are formed by pressing and polishing. The nozzle hole 20 faces the individual liquid chamber 14 of the liquid chamber substrate 1 when the nozzle substrate 2 and the liquid chamber substrate 1 are assembled, and communicates the individual liquid chamber 14 and the external space.
The protective substrate 3 enhances the rigidity of the groove portion serving as the ink flow path as the common liquid chamber 18, the piezoelectric element protection space 22 for preventing protection and displacement of the piezoelectric element 56, and the flow path partition 4 a of the liquid chamber substrate 1. Therefore, a reinforcing wall 23 that reinforces the flow path partition wall 4 a is formed through the diaphragm layer 55.

Hereinafter, the operation of the recording head 51 shown in FIGS. 4 and 5 will be described.
The ink liquid supplied from the tank 102a to the recording head 51 via the supply port 102b is supplied from the common liquid chamber 18 to the individual liquid chambers 14 via the individual ink supply holes 24. The
A potential having a predetermined driving waveform is applied between the upper electrode layer 153 and the lower electrode layer 151 of the piezoelectric element 56 in a state where the interior of the individual liquid chamber 14 is filled with the ink liquid, whereby the piezoelectric layer 152 contracts. The entire diaphragm layer 55 in close contact with the piezoelectric layer 152 across the lower electrode layer 151 is deformed into a convex shape toward the individual liquid chamber 14. As a result, the volume of the individual liquid chamber 14 is reduced, the pressure in the individual liquid chamber 14 is rapidly increased, and ink droplets are ejected from the nozzle holes 20 toward the paper 30. By repeatedly applying a pulse voltage between the upper electrode layer 153 and the lower electrode layer 151 continuously, ink droplets can be continuously discharged.
Hereinafter, a droplet discharge mechanism composed of a combination of a set of piezoelectric elements 56, individual liquid chambers 14, and nozzle holes 20 is referred to as a discharge channel (discharge CH).

In the printer 100, image formation is performed by ejecting ink droplets toward the paper 30, but ink droplets are ejected when the recording head 51 is not facing the paper 30, that is, when image formation is not performed. The empty discharge operation is performed.
This idle ejection operation is performed by ejecting ink droplets by moving the carriage 101 so that the recording head 51 is positioned outside the area facing the paper surface before printing, before printing, or during printing. This is the operation of discarding the ink liquid whose viscosity has increased.

  In the printer 100 in a state where the power is not turned on, the lower surface of the recording head 51 is capped so as to cover the nozzle hole 20 in order to prevent the ink liquid in the individual liquid chamber 14 from being thickened by drying. ing. However, even if capping is performed, the ink liquid in the individual liquid chamber 14 of the ejection CH that has not been driven for a long period of time gradually increases in viscosity. For this reason, after the power is turned on, the printer 100 discharges ink droplets that do not contribute to image formation with all of the discharge channels before starting printing, and performs pre-printing empty discharge in which the thickened ink liquid in the individual liquid chamber 14 is discarded. Do.

Further, during printing, ink droplets are not necessarily ejected from all ejection CHs. Other discharge CHs may be in a discharge state, and some discharge CHs may continue to be in a non-discharge state. When the non-ejection time becomes longer for some ejection CHs, the ink liquid near the meniscus formed in the nozzle holes 20 of the ejection CHs increases in viscosity, causing the ink droplets to be bent or not to be ejected next time. There is a risk of problems such as ejection.
In the printer 100, in order to prevent the occurrence of such a problem, the ink liquid in the individual liquid chamber 14 or the nozzle hole 20 is applied to the ink liquid in the individual liquid chamber 14 by applying a pressure that does not eject ink droplets. It is configured to perform fine driving to vibrate. By causing the ink liquid in the nozzle hole 20 to vibrate, it is possible to prevent the ink liquid near the meniscus from being thickened.

  The recording head 51 during image formation performs an operation such as discharging several tens of discharge CHs out of all hundreds of discharge CHs at a certain timing, but not discharging the remaining discharge CHs. The fine driving is an operation performed by such a discharge CH that does not cause discharge. Note that, depending on the type of image forming apparatus, there is a type in which fine driving is turned on for all non-ejection CHs during a printing operation.

As described above, during printing, in the ejection CH in which the non-ejection state continues for a long time, the fine driving is performed in order to prevent the ink liquid from thickening, but the thickening alone cannot be sufficiently suppressed. For this reason, the printer 100 performs a hollow print discharge in which the head is periodically moved to the outside of the paper surface during printing, and ink droplets are discharged from all the discharge CHs to discard the thickened ink liquid.
The two operations of the pre-printing idle discharge and the printing hollow discharge described above are idle discharge operations.

Next, an example of the drive control unit 508 that controls the driving of the plurality of piezoelectric elements 56 will be described with reference to the block diagram of FIG.
The drive control unit 508 included in the control unit 500 of the printer 100 includes a drive waveform generation unit 701 and a data transfer unit 702. The data transfer unit 702 outputs image data corresponding to a print image, a clock signal, a latch signal (LAT), and a droplet control signal MN.

  The drive waveform generation unit 701 generates a predetermined drive waveform during image formation and idle ejection operation. That is, the drive waveform generation unit 701 generates and outputs a drive waveform composed of a plurality of drive pulses (drive signals) within one print ejection period during image formation. In addition, the drive waveform generation unit 701 generates and outputs a drive waveform composed of a plurality of drive pulses (drive signals) within one idle discharge period during the idle discharge operation. Since the ejection of ink droplets during the idle ejection operation is not intended to form an image, the drive waveform output from the drive waveform generation unit 701 differs between one print ejection cycle and one blank ejection cycle.

Here, one print discharge cycle and one idle discharge cycle are one cycle of a drive waveform input during printing and idle discharge, respectively, and a drive waveform of one print discharge cycle or a drive waveform of one idle discharge cycle is obtained. By inputting to one ejection CH, ink droplets are ejected from the nozzle hole 20 of this ejection CH, or a fine driving operation is performed. The size of the ink droplets to be ejected can be varied by varying the drive waveform input to the ejection CH in one printing ejection cycle (or one idle ejection cycle).
In the following description, a period of a signal for performing ink droplet ejection or fine driving and non-driving operations is not limited to either one printing ejection period or one idle ejection period.

  The clock signal is a signal serving as an operation reference of the logic circuit, and the latch signal is a signal for temporarily storing (latching) recording data in the latch circuit 712. Further, the droplet control signal MN is a signal for instructing opening and closing of the analog switch 715 that is a switch unit of the head driver 509 for each ink droplet. A drive waveform (drive signal) of a drive signal group that constitutes a drive waveform (hereinafter referred to as “generated drive waveform”) generated and output by the drive waveform generation unit 701 is selected by the droplet control signal MN. By this selection, as described above, ink droplets having different sizes can be ejected to separate dots having different sizes, or a non-ejection operation can be performed.

  The head driver 509 includes a shift register 711, a latch circuit 712, a decoder 713, a level shifter 714, an analog switch 715, and the like. The shift register 711 receives a transfer clock (shift clock) and serial image data from the data transfer unit 702, and the latch circuit 712 temporarily stores each register value of the shift register 711 by a latch signal. Is for.

Based on the image data and the data based on the droplet control signal MN, the decoder 713 determines the gradation data indicating which operation is to be performed by which piezoelectric element 56 (for each ejection CH, large droplets, medium droplets, and small droplets). Data for instructing which one of discharge driving, fine driving, or non-driving operation for discharging any droplet is performed and is output as a logic signal. The gradation data output here determines what waveform signal to be applied to the piezoelectric element 56 of which ejection CH is applied by the droplet control signal MN (details will be described later MN1 to MN9).
The level shifter 714 converts the level of the logic signal output from the decoder 713 to a level at which the analog switch 715 can operate. Here, the logic signal is a signal with a low voltage of about 3 [V] to 4 [V], and controls how each discharge CH operates. The above-described clock signal, latch signal, and droplet control signal MN are this logic signal. Since the voltage of such a logic signal is too low for the analog switch 715 to operate, the level shifter 714 amplifies the voltage to a level at which the analog switch 715 can operate.
The analog switch 715 is turned on / off (opened / closed) by the output of the decoder 713 given through the level shifter 714.

  The analog switch 715 is connected to the upper electrode layer 153 that is an individual electrode of each piezoelectric element 56 of each ejection CH, and the generated drive waveform from the drive waveform generation unit 701 is input. Therefore, by turning on the analog switch 715 according to the result of decoding the serially transferred image data (gradation data) and the droplet control signal MN by the decoder 713, a predetermined drive signal constituting the generated drive waveform is The selected potential corresponding to the drive signal is applied to each piezoelectric element 56.

Next, drive waveforms will be described.
FIG. 7 is an explanatory diagram illustrating an example of a drive waveform. FIG. 7A is an explanatory diagram of the generated drive waveform generated and output by the drive waveform generation unit 701. FIGS. 7B to 7D show the drive signal P based on the droplet control signal MN from the generated drive waveform. Is an example of an input drive waveform that is selected and input to the discharge CH. FIG. 7B shows an input drive waveform to the ejection CH that performs fine driving, FIG. 7C shows an input drive waveform to the ejection CH that ejects small ink droplets, and FIG. FIG. 6 is an input drive waveform to the discharge CH that discharges a large ink droplet.

  In the printer 100, as shown in FIG. 7A, the generated drive waveform generated by the drive waveform generation unit 701 is six drive signals (drive pulses) P output in time series within one drive cycle. (First drive signal P1 to sixth drive signal P6). Ve in FIG. 7 is a reference potential (intermediate potential), and in each ejection CH, the potential of the drive signal applied to the upper electrode layer 153 that is an individual electrode of the piezoelectric element 56 falls from the reference potential Ve, and then rises. Sometimes ink droplets are ejected.

FIG. 8 is an explanatory diagram of the fall from the reference potential Ve in the drive signal P and the subsequent rise.
FIG. 8A is an explanatory diagram showing a state in which there is only one drive signal P within one drive cycle, and FIG. 8B is an enlarged explanatory diagram of the drive signal P in FIG. 8B. . A portion where the potential is shifted in the direction in which the potential decreases like the portion indicated by β in FIG. 8B is a falling portion, and the direction where the potential increases as in the portion indicated by α in FIG. 8B. The part shifted to is the rising part.
Then, ink droplets are ejected at a timing corresponding to the signals of the rising portions indicated by α2 to α5 in FIG. In the first drive signal P1, the variation in potential at the rising portion indicated by α1 is small, the pressure is not so high that ink droplets are ejected, and the fine drive in which the ink liquid vibrates in the individual liquid chamber 14. Become.

The reference potential Ve is a potential applied to the piezoelectric element 56 (upper electrode layer 153) in a state where the drive signal P is not applied during the printing operation, and the potential is applied to the upper electrode layer 153. When a voltage is applied to the piezoelectric element 56, the diaphragm layer 55 is configured to bend toward the nozzle hole 20 side.
FIG. 9 is a schematic diagram showing the shape of the diaphragm layer 55 in a state where no voltage is applied to the piezoelectric element 56 in one ejection CH and a state where a voltage is applied. FIG. 9A is an explanatory diagram in a state where no voltage is applied to the piezoelectric element 56, and FIG. 9B is an explanatory diagram in a state where a voltage is applied to the piezoelectric element 56. The diaphragm layer 55 bends toward the nozzle hole 20 when a voltage is applied to the piezoelectric element 56 as shown in FIG. 9B from the state shown in FIG. 9A, but as shown in FIG. From the state, it is configured not to bend to the opposite side of the nozzle hole 20.

FIG. 10 is an explanatory diagram of changes in the ink liquid in the vicinity of the nozzle holes 20 when the potential is raised after the potential is lowered from the state in which the reference potential Ve is applied to the piezoelectric element 56.
10A is an explanatory diagram of a state in which the reference potential Ve is applied, FIG. 10B is an explanatory diagram of a state in which the potential is lowered, and FIG. 10C is a diagram in which the potential is raised to the reference potential Ve. It is explanatory drawing of the raised state.

In the drive signal P shown in FIG. 8, when the reference potential Ve is applied to the piezoelectric element 56, the diaphragm layer 55 is bent toward the nozzle hole 20 as shown in FIG. 9B. This is because the piezoelectric element 56 expands when a potential is applied from the state shown in FIG. 9A in which no potential is applied to the piezoelectric element 56, and the diaphragm layer 55 is pushed downward in FIG. is there. On the other hand, in the vicinity of the nozzle hole 20, when the reference potential Ve is applied, the meniscus 21a is formed in the vicinity of the outlet of the nozzle hole 20 as shown in FIG.
In this state, when the potential applied to the piezoelectric element 56 falls from the reference potential Ve as indicated by β in FIG. 8B, the piezoelectric element 56 contracts more than the state of FIG. 9B. Then, the vibration plate layer 55 is displaced in the direction in which the volume of the individual liquid chamber 14 is expanded (the direction opposite to the nozzle hole 20). As a result, the ink liquid flows from the common liquid chamber 18 into the individual liquid chamber 14, and the state shown in FIG. At this time, the meniscus 21a is drawn into the nozzle hole 20 from the state shown in FIG. 10A, and the state shown in FIG.

Thereafter, when the potential applied to the piezoelectric element 56 rises as indicated by α in FIG. 8B, the piezoelectric element 56 expands again, and the diaphragm layer 55 is deformed to bend toward the nozzle hole 20 side. The state shown in FIG. As a result, the volume of the individual liquid chamber 14 contracts, the ink liquid in the individual liquid chamber 14 is pressurized, and the ink droplets 21 are ejected from the nozzle holes 20 as shown in FIG.
As described above, the ink liquid is drawn into the individual liquid chamber 14 by the operation of changing the state in which the voltage is applied to the piezoelectric element 56 to the state in which the voltage is not applied. For this reason, at the timing when the drive signal P is not applied at the time of image formation, the reference potential Ve is always applied to the piezoelectric element 56 and the diaphragm layer 55 is bent toward the nozzle hole 20 (in FIG. 9B). State).

Of the plurality of drive signals P constituting one drive cycle shown in FIG. 7, the first drive signal P1 generates a pressure that does not eject ink droplets, thereby vibrating the ink liquid in the nozzle holes 20. This is a drive signal. The waveform element falls from the reference potential Ve, the waveform element holds the potential after the fall, and the waveform element rises linearly up to the reference potential Ve after holding the potential.
The second drive signal P2 and the third drive signal P3 are ejection drive signals for ejecting ink droplets. It comprises a waveform element that falls from the reference potential Ve, a waveform element that holds the potential after the fall, and a waveform element that rises stepwise to the reference potential Ve after holding the potential.
The fourth drive signal P4 is an ejection drive signal for ejecting ink droplets. The waveform element falls from the reference potential Ve, the waveform element holds the potential after the fall, and the waveform element rises linearly up to the reference potential Ve after holding the potential.

The fifth drive signal P5 is an ejection drive signal for ejecting ink droplets. The waveform element falls from the reference potential Ve, the waveform element held at the potential after the fall, and after holding the potential, the reference potential Ve is exceeded and a predetermined value is exceeded. Waveform element rising to potential, waveform element holding to potential after rising, waveform element rising after holding potential, waveform element holding to potential after further rising, waveform element falling to reference potential after holding potential (β5 ).
When one drop of the ink droplet 21 is ejected, the meniscus 21a vibrates by the ejected reaction. If the next ink droplet 21 is ejected while the meniscus is oscillating, there is an effect that a desired ejection speed cannot be obtained.

  In the fifth drive signal P5, the vibration of the meniscus is suppressed by the waveform element indicated by β5. This is due to the following actions. That is, by setting the potential higher than the reference potential Ve before reaching the reference potential Ve at the end of one driving cycle, the volume in the individual liquid chamber 14 becomes smaller than the state of the reference potential Ve. Thereafter, the volume in the individual liquid chamber 14 is expanded by the waveform element of β5, so that the pressure difference in which the ink liquid in the nozzle hole 20 is directed to the individual liquid chamber 14 acts, and the force for drawing the meniscus 21a acts. Meniscus vibration can be suppressed.

  7A is an example, and the drive signal P includes both a signal that rises to the reference potential Ve stepwise after falling and a signal that rises to the reference potential Ve linearly after falling. It has a waveform. As the generated drive waveform, as shown in FIG. 11, the second drive signal P2 and the third drive signal P3 may be a drive signal P that rises linearly to the reference potential Ve after the fall.

  As described above, the combination of the drive signals P (P1 to P6) constituting the generated drive waveform shown in FIG. 7A is input to the discharge CH as the input drive waveform. Controlled by MN1 to MN9). That is, the droplet control signal MN is a signal for determining the waveform of the potential applied to each piezoelectric element 56, and can be said to be a signal for cutting out the waveform from the generated drive waveform.

In the printer 100, there are nine types of droplet control signals MN including a first droplet control signal MN1, a second droplet control signal MN2,..., And a ninth droplet control signal MN9. If the total discharge CH of the recording head 51 is 400 CH, an input drive waveform determined (cut out) by any one of the nine droplet control signals MN is applied to each of all 400 CH.
What input drive waveform is applied corresponding to each droplet control signal MN is set in advance. For example, FIG. 7B shows a waveform corresponding to the first drop control signal MN1, FIG. 7C shows a waveform corresponding to the second drop control signal MN2, and FIG. 7D shows the ninth drop control signal MN9. Is a waveform corresponding to.

  In the printer 100, an analog switch switching operation for cutting out the waveform of FIG. 7B from the generated drive waveform is set in advance as the first drop control signal MN1. Accordingly, when the piezoelectric element 56 of a certain discharge CH is finely driven, the operation instruction data (“image data” in FIG. 6) of the first droplet control signal MN1 in the discharge CH is shifted. It is sent to the register 711 and sent to the decoder 713 via the latch circuit 712. Thereafter, the decoder 713 operates in accordance with the first drop control signal MN1 set in advance for the piezoelectric element 56 of the discharge CH (the input cut out from the generated drive waveform so as to have the waveform of FIG. 7B). A signal (logic signal) for instructing an operation corresponding to the drive waveform is output.

  This signal is a low voltage of about 3.5 [V], and the voltage is low to operate the analog switch 715. After that, the level shifter 714 amplifies the voltage to a level at which the analog switch 715 can operate and generates it. 7B is applied to the piezoelectric element 56 by performing a switching operation by the first droplet control signal MN1 on the driving waveform (an operation in which only the first driving signal P1 is passed among the generated driving waveforms). . As described above, when the waveform determined by the first droplet control signal MN1 is applied to the piezoelectric element 56, a fine driving operation is performed with the corresponding discharge CH.

  The same applies to the case of ejecting ink droplets, and the third drive signal P3 is a drive signal for ejecting ink liquid, but the second droplet is supplied with a droplet control signal MN that passes (cuts out) only the third drive signal P3. It is preset in the control signal MN2. Thus, when the waveform determined by the second droplet control signal MN2 (the waveform of FIG. 7C) is applied to the piezoelectric element 56, an operation of ejecting a small ink droplet is performed. Similarly, when the waveform determined by the ninth droplet control signal MN9 (the waveform of FIG. 7D) is applied to the piezoelectric element 56, an operation of ejecting a large ink droplet is performed.

  In the input drive waveform shown in FIG. 7D, there are waveform elements (α2 to α5) for performing ejection four times during one drive cycle. In the ejection CH to which such an input driving waveform is input, before the ink droplet ejected earlier in one driving cycle reaches the paper surface, the ink droplet ejected after the same one driving cycle is ejected, It catches up with the previous ink droplet and reaches the paper surface in a state where it becomes one ink droplet. For this reason, as shown in FIG. 7C, a small ink droplet is ejected in the ejection CH in which the input driving waveform is inputted as a waveform element that ejects in one driving cycle as shown in FIG. A large ink droplet is ejected in the ejection CH in which the waveform element for ejecting during one driving cycle is inputted with the input driving waveform of four times.

FIG. 12 is an explanatory diagram of ink droplet ejection.
FIG. 12A shows the second droplet control signal MN2 → second droplet control signal MN2 → ninth for one ejection CH when the recording head 51 moves in the arrow D direction with respect to the stopped paper 30. FIG. FIG. 6 is an explanatory diagram of ink droplets ejected at each timing when an input drive waveform corresponding to a droplet control signal MN in the order of droplet control signal MN9 → first droplet control signal MN1 is input.
FIG. 12B is a top view of the paper 30 on which an image is formed by the ejected ink droplets as shown in FIG.

  At the timings (i) and (ii), an input drive waveform corresponding to the second droplet control signal MN2 is input to the ejection CH, so that a small ink droplet (small droplet) is ejected from the nozzle hole 20 to the paper 30. It is discharged toward. At the timing of (iii), an input drive waveform corresponding to the ninth droplet control signal MN9 is input, so that a large ink droplet (large droplet) is ejected from the nozzle hole 20 toward the paper 30. On the other hand, since the input drive waveform corresponding to the first droplet control signal MN1 is input at the timing (iv), fine driving is performed by the ejection CH, and no ink droplet is ejected from the nozzle hole 20.

As shown in FIG. 12B, the image formed at the timings (i) and (ii) is a small-diameter image, and the image formed at the timing (iii) is a large-diameter image. An image is not formed at a position facing the nozzle hole 20 at the timing (iv).
Note that an arrow E shown in FIG. 12B indicates an area on the paper surface corresponding to one driving cycle.
In the example shown in FIGS. 12A and 12B, the interval between the ink droplets is shown wide in order to correspond to the movement of the recording head 51, but the interval between the ink droplets is actually narrower, By performing such an operation with a plurality of ejection channels, an image as shown in FIG. 12C is formed.

Next, the temperature rise of the ink liquid in the recording head 51 will be described.
FIG. 13 is a cross-sectional view of the recording head 51 in the same cross section as FIG. 5A, and is an explanatory view showing a state where heat is transferred to the common liquid chamber 18. FIG. 14 is an explanatory perspective view of the recording head 51 showing the positional relationship between the common liquid chamber 18 and the head driver 509.
FIG. 1 is an exploded perspective view of the recording head 51 showing the temperature distribution of the ink liquid. In FIG. 1, the temperature of the ink liquid is higher on the side indicated by “high” and the ink is indicated on the side indicated by “low”. It shows that the temperature of the liquid is lowered. In FIG. 1, the description of the reinforcing wall 23 that partitions the plurality of piezoelectric element protection spaces 22 is omitted.

The ink liquid supplied to the recording head 51 from the supply port 102 b passes through the common liquid chamber 18, then passes through the individual liquid chambers 14 that are discharge liquid chambers, and is discharged from the nozzle holes 20. The flow of ink liquid passing through the common liquid chamber 18 from the supply port 102b at this time is indicated by an arrow L in FIG.
The piezoelectric actuator 200 that is driven when ejecting the nozzle hole 20 and the head driver 509 that controls the potential applied to the piezoelectric element 56 of the piezoelectric actuator 200 generate heat when driven.
An arrow H1 in FIGS. 13 and 14 indicates heat transfer from the head driver 509, and an arrow H2 indicates heat transfer from the piezoelectric actuator 200.

  When the ink liquid passes through the common liquid chamber 18 indicated by an arrow L in FIG. 14, the temperature of the ink liquid in the recording head 51 rises due to heat generated by the piezoelectric actuator 200 and the head driver 509. As shown in FIGS. 13 and 14, the head driver 509 and the plurality of piezoelectric actuators 200 are arranged in the immediate vicinity of the common liquid chamber 18 and parallel to the longitudinal direction of the common liquid chamber 18. This is because the ink liquid supplied from 102 b continues to be heated by the piezoelectric actuator 200 and the head driver 509 that generate heat by driving until the ink liquid is discharged from the nozzle hole 20 through the common liquid chamber 18.

  Further, as shown in FIG. 1, the temperature of the ink liquid rises as the individual liquid chamber 14 is located farther from the supply port 102b, that is, on the downstream side of the ink liquid passage in the common liquid chamber 18. The individual liquid chambers 14 communicating with 18 are more prominent. The ink liquid flowing into the individual liquid chamber 14 at a position away from the supply port 102b has a flow path until reaching the individual liquid chamber 14 as compared with the ink liquid flowing into the individual liquid chamber 14 near the supply port 102b. Since the heating is continued for a longer time, the temperature rise becomes significant. Further, as shown in FIGS. 1 and 5, since the individual liquid chamber 14 and the common liquid chamber 18 are connected to each other, the individual liquid chamber 14 of the non-ejection discharge CH is located at a position away from the supply port 102b. However, heat is transmitted from the ink liquid on the common liquid chamber 18 side. Therefore, the temperature of the ink liquid in the individual liquid chamber 14 located farther from the supply port 102b is higher than that of the ink liquid in the individual liquid chamber 14 near the supply port 102b regardless of whether the discharge CH is discharged or not. Become.

  In general, the individual liquid chamber 14 that stores the ink liquid having a high temperature has a smaller frequency of the drive signal (pulse) of fine driving applied than the individual liquid chamber 14 that stores the ink liquid having a low temperature, and has an amplitude. Can be small. This is due to the following reason.

  That is, in the fine drive originally, when the time of the non-ejection state becomes long, the ink liquid near the meniscus 21a is thickened, so that the ink droplet is bent or non-ejection when the next ejection is performed. This is a pulse to be applied to prevent this. The ink liquid has a lower viscosity as the temperature is higher, and the viscosity is higher as the temperature is lower. Therefore, a viscosity distribution of the ink liquid corresponding to the temperature distribution of the ink liquid in the recording head 51 is generated, and the ink liquid having a high temperature and a low viscosity is thickened as compared with the ink liquid having a low temperature and a high viscosity. Hateful. Therefore, the individual liquid chamber 14 that stores the ink liquid having a high temperature may be bent when the ejection pulse is applied next, even if the meniscus 21a is not frequently shaken or shaken greatly during non-ejection. Discharge abnormalities such as non-ejection are unlikely to occur.

  In a conventional ink jet printer, a uniform fine driving pulse is applied to all ejection CHs for the entire recording head or for each column. For this reason, the same fine driving pulse as that of the piezoelectric element on the individual liquid chamber into which the low ink liquid flows is applied to the piezoelectric element on the individual liquid chamber into which the high temperature ink liquid flows. That is, more pulses than necessary are applied to the piezoelectric elements on the individual liquid chambers into which the ink liquid having a high temperature flows, and this contributes to an increase in power consumption. In addition, if the same fine driving as the fine driving that can sufficiently stir ink liquid with low temperature and high viscosity is performed in the same way for ink liquid with high temperature and low viscosity, the stirred ink liquid leaks from the nozzle hole. There is a risk of release.

[Example 1]
Next, a first embodiment of the recording head 51 to which the present invention is applied (hereinafter referred to as Embodiment 1) will be described.
As described with reference to FIG. 1, the temperature of the ink liquid in the recording head 51 becomes higher and the viscosity becomes lower as the position is farther from the supply port 102b. By utilizing this fact, in the recording head 51 of the first embodiment, the frequency of the fine driving pulse applied to the piezoelectric element on the individual liquid chamber 14 located far from the supply port 102b is set on the individual liquid chamber 14 near the supply port 102b. The number of piezoelectric elements is less than that of the piezoelectric element. With such a configuration, pulses applied more than necessary can be reduced, and power consumption can be suppressed as compared with the conventional example.

  FIG. 15 is an explanatory diagram of the drive waveform used in the recording head of Example 1, and the generated drive waveform is the same waveform as the example described with reference to FIG. FIG. 15A is an explanatory diagram of the generated drive waveform, FIG. 15B is an input drive waveform to the discharge CH that performs fine driving, and FIG. 15C illustrates the discharge CH that does not perform driving. It is an input drive waveform to. In the first embodiment, in addition to the three droplet control signals MN (MN1, MN2, and MN9) described with reference to FIG. 7, an analog switch switching operation for cutting out the waveform of FIG. 15C from the generated drive waveform is performed. An operation corresponding to the third drop control signal MN3 is set in advance.

  FIG. 16 is an explanatory diagram of the temporal control of the droplet control signal MN corresponding to the non-ejection ejection CH of the recording head 51 of Example 1 and the drive waveform applied to the ejection CH. FIG. 16A is an explanatory diagram of the control for the discharge CH near the supply port 102b, and FIG. 16B is an explanatory diagram of the control for the discharge CH at a position far from the supply port 102b.

The data transfer unit 702 outputs only the first droplet control signal MN1 as the droplet control signal MN corresponding to the non-ejection ejection CH near the supply port 102b. As a result, as shown in FIG. 16A, the non-ejection discharge CH near the supply port 102b receives the input drive waveform shown in FIG. 15B in each drive cycle, and the non-ejection discharge CH near the supply port 102b. In the discharge CH, fine driving is performed in each driving cycle.
On the other hand, as the droplet control signal MN corresponding to the non-ejection ejection CH located far from the supply port 102b, the data transfer unit 702 alternately outputs the first droplet control signal MN1 and the third droplet control signal MN3. As a result, the non-ejection discharge CH at a position far from the supply port 102b is, as shown in FIG. 16B, the input drive waveform of FIG. 15B and the input drive of FIG. Waveforms are input alternately. As a result, fine driving and non-driving are alternately performed for each non-ejection discharge CH located at a position far from the supply port 102b for each drive cycle.
Further, as described above, the timing at which the fine driving pulse is applied to which piezoelectric element is controlled by the control unit 500 in FIG.

For example, 400 individual liquid chambers 14 are arranged in the longitudinal direction of the common liquid chamber 18 (the direction of arrow B in the figure), and the supply port is provided between the 200th and 201st ends from one end in the longitudinal direction. Assume that the center of 102b is located. In this case, each of the first to 50th and 351 to 400th individual liquid chambers 14 counted from one end in the longitudinal direction is positioned far from the supply port 102b, and corresponds to these individual liquid chambers 14. The drive waveform shown in FIG. 16B is applied to each piezoelectric element 56 at the non-ejection timing. On the other hand, the other individual liquid chambers 14 (300 in the 51st to 350th) are in the vicinity of the supply port 102b, and the corresponding piezoelectric elements 56 have the drive waveform shown in FIG. Applied.
By controlling in this way, the frequency of the fine driving pulse applied to the piezoelectric element 56 on the individual liquid chamber 14 far from the supply port 102b is less than that of the piezoelectric element 56 on the individual liquid chamber 14 near the supply port 102b. Can be realized.

By reducing the frequency of the fine driving pulse, the power consumption in the piezoelectric element 56 on the individual liquid chamber 14 far from the supply port 102b can be reduced. Further, by reducing the frequency of fine driving in the discharge CH far from the supply port 102b, the frequency of stirring is reduced, and stirring is performed with the viscosity increased to some extent, so that the ink liquid leaks from the nozzle holes. This can be suppressed.
With such a configuration, the ink liquid in the individual liquid chamber 14 near the supply port 102b can be sufficiently stirred, and the ink liquid in the individual liquid chamber 14 far from the supply port 102b can be prevented from leaking. A fine driving operation that generates a pressure that vibrates the ink liquid in the individual liquid chamber 14 without ejecting ink droplets from the nozzle holes 20 can be stably performed.

In the printer 100 including the recording head 51 according to the first embodiment, variation in ejection characteristics between ejection CHs can be reduced for the following reason.
That is, as described above, when the number of fine drive pulses is reduced, the power consumed by the piezoelectric element 56 on the individual liquid chamber 14 can be suppressed. When the power consumption is reduced, the heat generation at the piezoelectric element 56 is suppressed, so the amount of heat generated from the piezoelectric element 56 disposed at a position far from the supply port 102b is reduced, and the temperature rise of the ink liquid is suppressed. Accordingly, since the difference between the ink viscosity (ink temperature) in the individual liquid chamber 14 near the supply port 102b and the ink viscosity (ink temperature) in the individual liquid chamber 14 located at a position away from the supply port 102b is small, the ejection is performed. The difference in characteristics can be reduced.
As described above, in the recording head 51 according to the first embodiment, the power consumption is reduced, the ink liquid whose viscosity is reduced can be prevented from leaking from the nozzle holes 20 of the non-ejection ejection CH, and the ejection characteristics are excellent. A droplet discharge device is realized.

[Example 2]
Next, a second embodiment (hereinafter referred to as a second embodiment) of the recording head 51 to which the present invention is applied will be described.
In the recording head 51 of Example 2, the amplitude of the fine driving pulse applied to the piezoelectric element on the individual liquid chamber 14 located far from the supply port 102b is smaller than that of the piezoelectric element on the individual liquid chamber 14 near the supply port 102b. It is configured to do. This is due to the following reason.
That is, as described above, the ink liquid in the individual liquid chamber 14 located far from the supply port 102b has a higher temperature and a lower viscosity, so that it is compared with the ink liquid in the individual liquid chamber 14 near the supply port 102b. This is because even if the amount of the meniscus is small, it is difficult to increase the viscosity, and it is difficult to affect the next applied ejection pulse.
As an example of applying different fine drive pulses to different ejection CHs in this way, the portion of the sixth drive signal P6 in FIG. 7 may be changed to a fine drive pulse having a smaller amplitude than the first drive signal P1.

  FIG. 17 is an explanatory diagram of drive waveforms used in the recording head 51 of the second embodiment, FIG. 17A is an explanatory diagram of generated drive waveforms, and FIG. 17B and FIG. It is an input drive waveform to non-discharge CH. In the second embodiment, in addition to the three droplet control signals MN (MN1, MN2, and MN9) described with reference to FIG. 7, an analog switch switching operation for cutting out the waveform of FIG. 17C from the generated drive waveform is performed. An operation corresponding to the fourth drop control signal MN4 is set in advance. The generated drive waveform in FIG. 17 is a drive signal for performing the fine drive by the sixth drive signal P6, and is different from the generated drive waveform in FIG. 7 in which the sixth drive signal P6 is a drive signal for performing the non-drive. Therefore, the input drive waveform corresponding to the droplet control signal MN other than the fourth droplet control signal MN4 is set to a drive waveform that does not include the sixth drive signal P6.

In the second embodiment, both the first drive signal P1 and the sixth drive signal are fine drive pulses, but the amplitudes of the potentials thereof are different, and the amplitude of the sixth drive pulse is smaller.
FIG. 18 is an explanatory diagram of the temporal control of the droplet control signal MN corresponding to the non-ejection ejection CH of the recording head 51 of Example 2 and the drive waveform applied to the ejection CH. FIG. 18A is an explanatory diagram of the control for the discharge CH near the supply port 102b, and FIG. 18B is an explanatory diagram of the control for the discharge CH at a position far from the supply port 102b.

The data transfer unit 702 outputs the first droplet control signal MN1 as the droplet control signal MN corresponding to the non-ejection ejection CH near the supply port 102b. As a result, in the non-ejection discharge CH near the supply port 102b, the input drive waveform in FIG. 17B is input in each drive cycle as shown in FIG. 18A, and the fine drive based on the first drive signal P1. Driving is performed.
On the other hand, the data transfer unit 702 outputs the fourth droplet control signal MN4 as the droplet control signal MN corresponding to the non-ejection ejection CH located far from the supply port 102b. Thereby, in the non-ejection ejection CH far from the supply port 102b, as shown in FIG. 18B, the input driving waveform of FIG. 17C is input in each driving cycle, and based on the sixth driving signal P6. Fine driving is performed. By setting in this way, it is possible to input fine drive pulses having different amplitudes depending on the position of the discharge CH to the discharge CH.

By reducing the amplitude of the drive pulse, the power consumption in the piezoelectric element 56 on the individual liquid chamber 14 far from the supply port 102b can be reduced. In addition, since the power consumption is reduced, the difference in discharge characteristics for each discharge CH can be reduced as in the first embodiment. Furthermore, by reducing the amplitude of fine driving in the discharge CH far from the supply port 102b, the pressure applied to the ink liquid that is easy to discharge due to its high temperature and low viscosity can be reduced, so that the ink liquid leaks from the nozzle hole. Can be suppressed.
With such a configuration, the ink liquid in the individual liquid chamber 14 near the supply port 102b can be sufficiently stirred, and the ink liquid in the individual liquid chamber 14 far from the supply port 102b can be prevented from leaking. A fine driving operation that generates a pressure that vibrates the ink liquid in the individual liquid chamber 14 without ejecting ink droplets from the nozzle holes 20 can be stably performed.
As described above, in the recording head 51 of the second embodiment, as in the first embodiment, it is possible to reduce the power consumption and suppress the leakage of the ink liquid whose viscosity has decreased from the nozzle holes 20 of the non-ejection ejection CH. Furthermore, a droplet discharge device having good discharge characteristics is realized.

  In the first embodiment, the frequency of the fine driving pulse applied to the piezoelectric element 56 on the individual liquid chamber 14 far from the supply port 102b is reduced, and in the second embodiment, the amplitude of the fine driving pulse to be applied is reduced. However, these may be combined. That is, the frequency of fine driving pulses to be applied to the piezoelectric element 56 on the individual liquid chamber 14 far from the supply port 102b is smaller than that of the piezoelectric element 56 on the individual liquid chamber 14 near the supply port 102b, and The amplitude of the fine drive pulse to be applied may be reduced. A similar effect can be obtained by such a configuration.

Example 3
Next, a third embodiment of the recording head 51 to which the present invention is applied (hereinafter referred to as Embodiment 3) will be described.
In the third embodiment, the discharge CH is divided into a plurality of groups, and input drive waveforms having different configurations of the drive signal P are applied to each group instead of each discharge CH.
FIG. 19 is an explanatory diagram illustrating an example of grouping of ejection CHs (individual liquid chambers 14 and piezoelectric actuators 200) in the third embodiment, and only the liquid chamber substrate 1 provided in the recording head 51 is illustrated.

  In Example 3, as shown in FIG. 19, among the discharge CHs arranged in a line in the longitudinal direction (the direction of arrow B in the figure), those near the left end in the figure are those near the first group G1 and the supply port 102b. The second group G2, which is near the right end in the figure, is divided into a third group G3 and three groups. For the non-ejection CH, only the second group G2 applies a fine driving pulse different from the first group G1 and the third group G3. At this time, the fine drive pulse applied to the first group G1 and the third group G3 has a smaller amplitude than the fine drive pulse applied to the second group G2.

  Thereby, in the group (G1 and G3) far from the supply port 102b, the power consumption by the fine driving applied is reduced. This is because the power consumed is smaller as the amplitude of the fine drive pulse to be applied is smaller.

Accordingly, the difference in ejection characteristics for each group can be reduced. This is due to the following reason.
That is, the electric power consumed by the piezoelectric elements 56 of the first group G1 and the third group G3 decreases as the amplitude of the fine driving pulse decreases. Accordingly, heat generation of the piezoelectric elements 56 arranged in the first group G1 and the third group G3 is suppressed as compared with the second group G2. Accordingly, the difference between the viscosity (temperature) of the ink liquid in the individual liquid chambers 14 included in the first group G1 and the third group G3 and the viscosity of the ink liquid in the individual liquid chambers 14 included in the second group G2. This is because becomes smaller.

By grouping as in the third embodiment, the processing in the drive control unit 508 can be quickly performed. For example, by controlling the temperature of each individual liquid chamber 14 with a thermistor or the like, and controlling for each group in comparison with the configuration in which the drive waveform applied to the piezoelectric element 56 is determined for each discharge CH in accordance with the detected temperature distribution, Processing in the drive control unit 508 illustrated in FIG. 6 can be simplified.
As described above, the recording head 51 according to the third embodiment is effective in reducing the power consumption and the difference in ejection characteristics as in the recording head 51 according to the first and second embodiments, and the drive control unit 508. Can be processed quickly.

In any of the configurations of the first to third embodiments described above, the boundary between the discharge CH near the supply port 102b and the discharge CH positioned far from the supply port 102b may be changed according to the change with time. This is because the entire temperature of the recording head 51 may increase when the recording head 51 is used for a long time.
In such a case, taking the configuration of Example 1 as an example, in the configuration described above, 50 pieces of the first to 50th pieces and 351 to 400th pieces from one end in the longitudinal direction are far from the supply port 102b. The discharge CH at the position is used. With such a configuration, when the entire temperature of the recording head 51 becomes higher than a predetermined state, 80 pieces of 1st to 80th pieces and 321st to 400th pieces are supplied from one end in the longitudinal direction. By changing the setting so that the discharge CH is located far from the mouth 102b, the same effect can be expected even when the temperature is changed.
Further, when the outside air temperature is high, the temperature of the entire head rises, so that the same effect can be expected by changing the boundary in the same way and performing the same control.

In the recording head 51 of the present embodiment, fine driving performed by the piezoelectric element 56 that is a driving element disposed on the individual liquid chamber 14 close to the supply port 102b, and piezoelectric disposed at a position away from the supply port 102b. The fine driving performed by the element 56 is controlled so that the vibration of the meniscus due to the latter fine driving is small and the frequency is low. By including such a recording head 51, the printer 100 can reduce the power consumption, and the image forming apparatus can exhibit an excellent ejection characteristic with a small difference in ink temperature.
Note that the recording head 51 of the present embodiment has a configuration using a piezo method using a piezoelectric actuator 200 as pressure generating means for generating pressure in the individual liquid chamber 14. The pressure generating means is not limited to the piezo method. Pressure corresponding to ink ejection, non-ejection, and fine driving at the time of non-ejection by its drive control even in bubble jet method using heat generating element or electrostatic method that deforms diaphragm by electrostatic force etc. As long as it is possible to generate

  In addition, since the printer 100 according to the present embodiment includes the recording head 51 in which the fine driving operation described in the first to third embodiments is stable, the ink can be prevented from leaking from the ejection CH in the fine driving operation state. A defective image in which ink adheres to the non-image portion of the paper 30 can be prevented. Furthermore, since the ink liquid in the individual liquid chamber 14 of the discharge CH in the fine drive operation state can be sufficiently stirred, the nozzle hole 20 can be prevented from being clogged, and ink droplets can be generated due to clogging. Defective images due to bending or non-ejection can be prevented.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A discharge hole such as a nozzle hole 20 that discharges a droplet such as an ink droplet; a discharge liquid chamber such as an individual liquid chamber 14 that communicates with the outside through the discharge hole and contains a discharge liquid that becomes a droplet; and a discharge liquid A plurality of droplet discharge mechanisms, such as a discharge CH, including pressure generating means such as a piezoelectric actuator 200 for generating pressure in the chamber, are communicated with the discharge liquid chambers of the plurality of droplet discharge mechanisms, Drives the common flow path such as the common liquid chamber 18 through which the supplied discharge liquid passes, the liquid supply ports such as the supply port 102b for supplying the discharge liquid to the common flow path, and the pressure generating means of the plurality of droplet discharge mechanisms. A drive control unit such as a drive control unit 508 for controlling, a discharge operation in which the drive control unit generates a pressure for discharging a droplet from the discharge hole, and a discharge liquid chamber without discharging the droplet from the discharge hole. Pressure to vibrate the discharged liquid In the droplet discharge head such as the recording head 51 that controls the driving of the pressure generating means of the droplet discharge mechanism so as to perform the driving operation, the common channel is communicated with the upstream side of the discharge liquid passage in the common channel. Rather than the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber (such as the individual liquid chamber 14 in the vicinity of the supply port 102b). The fine drive operation of the pressure generating means for generating pressure in the communicating discharge liquid chamber (such as the individual liquid chamber 14 at a position away from the supply port 102b) generates less pressure. According to this, as described in the first embodiment, it is possible to prevent the discharge liquid on the downstream side from leaking while sufficiently stirring the discharge liquid on the upstream side. Without this, a fine driving operation for generating a pressure that vibrates the discharge liquid in the discharge liquid chamber can be stably performed. Further, by reducing the frequency of pressure generation by the pressure generating means for generating pressure in the discharge liquid chamber on the downstream side during the fine driving operation, the power consumption is reduced as compared with the conventional example. Furthermore, by reducing the frequency with which pressure is generated by the pressure generating means, the amount of heat generated from the pressure generating means is reduced, and the temperature of the discharged liquid due to the difference in the position of the discharged liquid chamber with respect to the common flow path is reduced. The difference in characteristics can be reduced, and a liquid droplet ejection head with good ejection characteristics can be realized.
(Aspect B)
A discharge hole such as a nozzle hole 20 that discharges a droplet such as an ink droplet; a discharge liquid chamber such as an individual liquid chamber 14 that communicates with the outside through the discharge hole and contains a discharge liquid that becomes a droplet; and a discharge liquid A plurality of droplet discharge mechanisms, such as a discharge CH, including pressure generating means such as a piezoelectric actuator 200 for generating pressure in the chamber, are communicated with the discharge liquid chambers of the plurality of droplet discharge mechanisms, Drives the common flow path such as the common liquid chamber 18 through which the supplied discharge liquid passes, the liquid supply ports such as the supply port 102b for supplying the discharge liquid to the common flow path, and the pressure generating means of the plurality of droplet discharge mechanisms. A drive control unit such as a drive control unit 508 for controlling, a discharge operation in which the drive control unit generates a pressure for discharging a droplet from the discharge hole, and a discharge liquid chamber without discharging the droplet from the discharge hole. Pressure to vibrate the discharged liquid In the droplet discharge head such as the recording head 51 that controls the driving of the pressure generating means of the droplet discharge mechanism so as to perform the driving operation, the common channel is communicated with the upstream side of the discharge liquid passage in the common channel. Rather than the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber (such as the individual liquid chamber 14 in the vicinity of the supply port 102b). The fine driving operation of the pressure generating means for generating pressure in the communicating discharge liquid chamber (such as the individual liquid chamber 14 at a position away from the supply port 102b) generates a smaller pressure. According to this, as described in the second embodiment, it is possible to prevent the discharge liquid on the downstream side from leaking while sufficiently stirring the discharge liquid on the upstream side. Without this, a fine driving operation for generating a pressure that vibrates the discharge liquid in the discharge liquid chamber can be stably performed. In addition, by reducing the pressure generated by the pressure generating means for generating the pressure in the discharge liquid chamber on the downstream side during the fine driving operation, the power consumption is reduced as compared with the conventional example. Furthermore, by reducing the pressure generated by the pressure generating means, the amount of heat generated from the pressure generating means is reduced, and the temperature of the discharged liquid due to the difference in the position of the discharged liquid chamber with respect to the common flow path is reduced. The difference can be reduced, and a droplet discharge head with good discharge characteristics can be realized.
(Aspect C)
In the aspect of (Aspect A) or (Aspect B), the discharge of the individual liquid chamber 14 and the like communicating with the common flow channel upstream of the passage path of the discharge liquid such as the ink liquid in the common flow channel of the common liquid chamber 18 and the like. The pressure is generated in the discharge liquid chamber communicating with the common flow path downstream of the discharge liquid passage in the common flow path, rather than the fine driving operation of the pressure generating means such as the piezoelectric actuator 200 that generates pressure in the liquid chamber. In the fine drive operation of the pressure generating means, the frequency of generating pressure is less and the generated pressure is smaller. According to this, as described in the second embodiment, it is possible to prevent the discharge liquid on the downstream side from leaking while sufficiently stirring the discharge liquid on the upstream side. Without this, a fine driving operation for generating a pressure that vibrates the discharge liquid in the discharge liquid chamber can be stably performed. In addition, during the fine driving operation, the pressure generated by the pressure generating means for generating the pressure in the discharge liquid chamber on the downstream side is reduced and the frequency of generation is reduced, thereby reducing the power consumption compared to the conventional example. . Furthermore, by reducing the pressure generated by the pressure generating means and reducing the frequency of generation, the amount of heat generated from the pressure generating means decreases, and the temperature of the discharge liquid due to the difference in the position of the discharge liquid chamber with respect to the common flow path Therefore, the difference in ejection characteristics can be reduced, and a liquid droplet ejection head with good ejection characteristics can be realized.
(Aspect D)
In any one of the aspects (A) to (C), the droplet discharge mechanisms such as a plurality of discharge CHs are divided into two or more groups, and the fine drive operations of the droplet discharge mechanisms included in the same group are the same. The droplet discharge mechanism included in a certain group such as the first group G1 is controlled so as to be finely driven by the droplet discharge mechanism included in at least one other group such as the second group G2. The operation of is different. According to this, as described in the third embodiment, the processing by the drive control means such as the drive control unit 508 is simplified as compared with the case where the fine drive operation is controlled for each individual droplet discharge mechanism. This is effective in stabilizing the fine driving operation, reducing the power consumption, and reducing the difference in ejection characteristics, and can quickly perform the processing in the drive control means.
(Aspect E)
In an image forming apparatus such as an ink jet printer 100 equipped with an ink jet head such as the recording head 51 that ejects ink droplets, the liquid droplet ejection head according to any one of the aspects A to C is used as the ink jet head. Use. According to this, as described in the above embodiment, since the fine driving operation of the ink jet head is stabilized, the occurrence of a defective image can be prevented and high-quality image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Liquid chamber substrate 2 Nozzle substrate 3 Protection substrate 4 Silicon substrate 14 Individual liquid chamber 18 Common liquid chamber 20 Nozzle hole 21a Meniscus 51 Recording head 55 Diaphragm layer 56 Piezoelectric element 100 Printer 101 Carriage 102b Supply port 151 Lower electrode layer 152 Piezoelectric body Layer 153 Upper electrode layer 154 Wiring member 154a First wiring member 154b Second wiring member 155 Interlayer insulating film 156 Passivation film 157 Lower electrode pad portion 158 Upper electrode pad portion 200 Piezoelectric actuator 230 Paper feed tray 500 Control portion 508 Drive control portion 509 Head driver 701 Drive waveform generation unit 702 Data transfer unit 711 Shift register 712 Latch circuit 713 Decoder 714 Level shifter 715 Analog switch MN Drop control signal P Drive signal Ve Reference potential

Japanese Patent Laid-Open No. 10-100401 JP-A-2-289351 Japanese Patent No. 338452 JP 2011-37241 A

Claims (5)

A discharge hole for discharging a droplet; a discharge liquid chamber that communicates with the outside through the discharge hole and that stores a discharge liquid to be the droplet; and a pressure generating unit that generates pressure in the discharge liquid chamber. A plurality of droplet ejection mechanisms
A common flow path that communicates with each of the discharge liquid chambers of the plurality of droplet discharge mechanisms and through which the discharge liquid supplied to the discharge liquid chamber passes;
A liquid supply port for supplying the discharge liquid to the common flow path;
Drive control means for controlling the drive of the pressure generating means of the plurality of droplet discharge mechanisms,
The drive control means generates a pressure that discharges a droplet from the discharge hole, and a pressure that vibrates the discharge liquid in the discharge liquid chamber without discharging the droplet from the discharge hole. In a droplet discharge head that controls driving of the pressure generating means of the droplet discharge mechanism so as to perform a fine driving operation to be generated,
Rather than the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path upstream of the discharge liquid passage in the common flow path, A liquid characterized in that the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path downstream of the discharge liquid passage path generates less pressure. Drop ejection head. A discharge hole for discharging a droplet; a discharge liquid chamber that communicates with the outside through the discharge hole and that stores a discharge liquid to be the droplet; and a pressure generating unit that generates pressure in the discharge liquid chamber. A plurality of droplet ejection mechanisms
A common flow path that communicates with each of the discharge liquid chambers of the plurality of droplet discharge mechanisms and through which the discharge liquid supplied to the discharge liquid chamber passes;
A liquid supply port for supplying the discharge liquid to the common flow path;
Drive control means for controlling the drive of the pressure generating means of the plurality of droplet discharge mechanisms,
The drive control means generates a pressure for discharging a droplet from the discharge hole, and discharges the discharge liquid in the discharge liquid chamber including the inside of the discharge hole without discharging the droplet from the discharge hole. In a droplet discharge head that controls the driving of the pressure generating means of the droplet discharge mechanism so as to perform a fine drive operation that generates a pressure to vibrate,
Rather than the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path upstream of the discharge liquid passage in the common flow path, Droplet discharge characterized in that the pressure to be generated is smaller in the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path downstream of the passage path of the discharge liquid head. The droplet discharge head according to claim 1 or 2,
Rather than the fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path upstream of the discharge liquid passage in the common flow path, The fine driving operation of the pressure generating means for generating pressure in the discharge liquid chamber communicating with the common flow path on the downstream side of the discharge liquid passage route generates less pressure and generates pressure. A droplet discharge head characterized by having a small diameter. In the liquid droplet ejection head according to any one of claims 1 to 3,
The plurality of droplet discharge mechanisms are divided into two or more groups, and the fine drive operations of the droplet discharge mechanisms included in the same group are controlled to be the same operation, and the droplets included in a group A droplet discharge head, wherein the discharge mechanism is different in operation of the fine driving operation from the droplet discharge mechanism included in at least one other group. In an inkjet image forming apparatus equipped with an inkjet head that ejects ink droplets,
An image forming apparatus using the droplet discharge head according to claim 1 as the inkjet head.

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