JP6136006B2 - Droplet ejection apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a droplet discharge device and an image forming apparatus that discharge droplets.

  2. Description of the Related Art Conventionally, a liquid droplet ejection head having a plurality of nozzles for ejecting liquid droplets, a liquid chamber communicating with the nozzles and containing a liquid, and pressure generating means for generating pressure for pressurizing the liquid in the liquid chamber is provided. A droplet discharge device is known. In this droplet discharge device, by applying a driving signal to drive the pressure generating means, the liquid in the liquid chamber can be pressurized and the droplets can be discharged from the nozzle.

The droplet discharge head of the droplet discharge apparatus is roughly classified into several types depending on the type of pressure generation mechanism of the pressure generation means.
For example, Patent Document 1 discloses a piezoelectric type in which a part of a wall of a liquid chamber is a thin diaphragm and a piezoelectric element as an electromechanical conversion element is arranged corresponding to the diaphragm. In the piezo method, droplets are ejected from a nozzle by changing the pressure in a liquid chamber by deforming a diaphragm by deformation of a piezoelectric element that occurs with application of a drive signal.
Japanese Patent Application Laid-Open No. 2004-228561 describes an electrostatic type that includes a diaphragm that forms a wall surface of a liquid chamber and an individual electrode outside the liquid chamber that is disposed to face the diaphragm. In the electrostatic method, an electric field is formed between the diaphragm and the electrode by applying a driving signal, and the diaphragm is deformed by the electrostatic force generated by the electric field to change the pressure in the liquid chamber, and the liquid droplets are discharged from the nozzle. To discharge.
There is also known a bubble jet (registered trademark) type in which a heating element is disposed inside a liquid chamber, bubbles are generated by heating the heating element by energization, and droplets are ejected by the pressure of the bubbles.

  In a droplet discharge head provided with pressure generating means such as the above-described piezoelectric element, physical property values such as the viscosity of the liquid in the head may change depending on the environmental temperature. In this case, even if a predetermined drive signal set in advance is applied to the pressure generating means, the droplet discharge characteristics such as the droplet discharge speed and the discharge amount change and deviate from the target droplet discharge characteristics. As described above, when the droplet discharge characteristics change with the temperature change, the landing position and the adhesion amount of the droplet on the target surface to which the discharged droplet arrives change. When this droplet discharge head is used in an image forming apparatus, the change in droplet discharge characteristics accompanying the above temperature change leads to a decrease in image quality.

Therefore, conventionally, in order to compensate for the change in the droplet discharge characteristics due to the temperature change (hereinafter referred to as “temperature compensation”), the amplitude and pulse width of the drive signal applied to the pressure generating means based on the temperature detection result. Controls that change are known.
For example, Patent Document 3 discloses an inkjet head drive control device including a storage unit that stores a correspondence table between the environmental temperature of the electrostatic inkjet head and the pulse width correction value dPw of the drive signal. . This correspondence table is provided so that a pulse width correction value dPw at which the ejected ink weight characteristic is constant corresponds to each of a plurality of temperature ranges continuous at a predetermined temperature width (5 ° C.). In this drive control device, the pulse width correction value dPw corresponding to the detected temperature is retrieved from the correspondence table, the pulse width correction value dPw and the pulse width initial value Pws of the preset drive signal are added, The correction pulse width Pw = Pws + dPw is obtained. By applying a drive signal having this correction pulse width Pw between the opposing electrodes formed on the opposing plate and the diaphragm of the inkjet head, temperature compensation is performed so that the weight characteristic of the ejected ink of the inkjet head is constant. Do.
Patent Document 4 discloses an ink jet recording apparatus including an internal ROM that stores a table in which the environmental temperature of the above-described piezo ink jet head is associated with drive waveform data of a drive signal. This table is provided so that drive waveform data corresponding to each temperature range corresponds to each of a plurality of temperature ranges continuous at a predetermined temperature range (5 ° C.). In this ink jet recording apparatus, drive waveform data corresponding to the detected temperature is selected, and a drive pulse is generated based on the selected drive waveform data. By applying this drive pulse to the piezoelectric element that is the piezoelectric generating means of the ink-jet head, temperature compensation can be performed so that stable ink droplets can be ejected against environmental temperature changes.

However, even if the control of the driving signal of the pressure generating means based on the conventional detection temperature disclosed in Patent Documents 3 and 4 is executed, the droplet discharge characteristics change as shown below, and the target droplet There is a risk of deviation from the discharge characteristics.
In the conventional temperature compensation control of the drive signal, the pulse width correction value dPw and the drive waveform data are stored as temperature compensation data for each of a plurality of temperature ranges having a predetermined temperature range. Therefore, with respect to a temperature change within that temperature range, the change in the droplet discharge characteristics cannot be accurately compensated for temperature, and there is a possibility that stable liquid suitability cannot be discharged. Although it is conceivable to narrow the temperature width of each temperature range in order to increase the accuracy of temperature compensation, it is necessary to increase the capacity of a storage unit such as a ROM for storing the pulse width correction value dPw and drive waveform data. , Leading to increased costs.
Further, while maintaining the temperature range of the above temperature range, the temperature compensation data (pulse width correction value dPw and drive waveform data) corresponding to the temperature in the vicinity of the boundary of each temperature range is obtained for each temperature range on both sides of the boundary. It is conceivable to obtain linear interpolation from temperature compensation data. However, as a result of diligent experiments and examinations by the present inventors, it has been found that there are cases where temperature compensation cannot be performed with high accuracy even if the linear interpolation is performed. For example, if the relationship between the drive signal applied to the piezoelectric element and the deformation (surface displacement on the liquid chamber side) of the piezoelectric element, which is a physical parameter of the pressure generating mechanism that changes by the application of the drive signal, is nonlinear, Even if linear interpolation is performed, temperature compensation may not be performed with high accuracy.

  Note that the problem of cost increase when the temperature compensation data is increased and the problem that temperature compensation may not be performed accurately even if the linear interpolation is performed are the above-described electrostatic method and bubble jet method. The same may occur in the case of other types of droplet discharge heads. For example, in the case of an electrostatic droplet discharge head, the relationship between the drive signal applied to the individual electrode and the magnitude of the surface displacement of the diaphragm, which is a physical parameter of the pressure generating mechanism that changes as the drive signal is applied If is non-linear, the above problem can occur in the same manner. In the case of a bubble jet type droplet discharge head, the relationship between the driving signal applied to the heating element and the amount of heat generated by the heating element, which is a physical parameter of the pressure generating mechanism that changes according to the driving signal, is nonlinear. If it exists, the said subject may generate | occur | produce similarly.

  The object of the present invention is to achieve stable liquid droplet ejection that is not affected by temperature changes even when the relationship between the drive signal in the pressure generating means and the physical parameter size of the pressure generating mechanism is non-linear while reducing costs. It is an object of the present invention to provide a droplet discharge device capable of obtaining characteristics.

  In order to achieve the above object, the invention according to claim 1 is driven by the size of a physical parameter of a nozzle that discharges droplets, a liquid chamber that communicates with the nozzle, and a pressure generation mechanism that generates pressure in the liquid chamber. A droplet discharge head having a pressure generating means that changes according to a signal, a drive signal output means for outputting a drive signal applied to the pressure generating means, and drive waveform data of a drive signal corresponding to each of a plurality of temperatures are stored. Storage means; temperature detection means for detecting temperature; and control for controlling the drive signal output means to output the drive signal based on the temperature detection result of the temperature detection means and apply the drive signal to the pressure generation means A droplet discharge device comprising: a temperature detection unit configured to detect the temperature among drive waveform data corresponding to each of the plurality of temperatures stored in the storage unit; The drive waveform data corresponding to each of the temperatures Tn and Tn + 1 satisfying Tn ≦ Tx ≦ Tn + 1 for the detected temperature Tx detected in the stage is read, and the drive waveform data corresponding to each of the temperatures Tn and Tn + 1 are read out from the temperatures Tn and Tn + 1, respectively. Is converted into time change data of physical parameters of the pressure generation mechanism corresponding to the temperature Tn and Tn + 1, and the time change data of physical parameters of the pressure generation mechanism corresponding to the temperatures Tn and Tn + 1, respectively, corresponds to the detected temperature Tx. The time change data of the physical parameter of the pressure generating mechanism is obtained by linear interpolation, and the time change data of the physical parameter of the pressure generating mechanism corresponding to the detected temperature Tx is converted into the drive waveform data corresponding to the detected temperature Tx. Drive used to generate a drive signal that is converted and applied to the pressure generating means The shape data, is characterized in changing the driving waveform data corresponding to the detection temperature Tx of the converted.

In the present specification, the “physical parameter of the pressure generation mechanism” means a physical quantity that changes when pressure is generated in the liquid in the liquid chamber by the pressure generation means by applying a drive signal. For example, the “physical parameter of the pressure generating mechanism” is the surface displacement on the liquid chamber side of a piezoelectric element that is an electromechanical conversion element to which a drive signal is applied in the case of a piezo type droplet discharge head. The “physical parameters of the pressure generating mechanism” are the surface displacement of the diaphragm facing the individual electrode to which the drive signal is applied in the case of the electrostatic droplet discharge head, and the bubble jet droplet discharge head. In this case, the heat generation amount of the heating element is included.
In this specification, the “waveform” or “drive waveform” of the drive signal means the entire temporal variation in one cycle of the drive signal.
Further, in this specification, “pulse” in the drive signal is an element (part of temporal variation) constituting the waveform. In particular, “pulse” in the present specification means a portion of the waveform of one cycle of the drive signal where the instantaneous value changes with time so as to generate a pressure change in the liquid chamber.
Further, in this specification, “drive waveform data” includes a plurality of times or identifier data thereof in a drive waveform and voltage or current data corresponding to each of the plurality of times. The “time change data of physical parameters of the pressure generating mechanism” includes a plurality of times of the driving waveform or data of identifiers thereof, and data of physical parameter values of the pressure generating mechanisms corresponding to the plurality of times, respectively. Is included.

  According to the present invention, stable liquid droplet ejection that is not affected by temperature changes even when the relationship between the drive signal in the pressure generating means and the physical parameter size of the pressure generating mechanism is non-linear while reducing costs. Characteristics can be obtained.

1 is a perspective view illustrating an example of an overall schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view of the image forming apparatus. (A) is a partial top view which shows the internal structure of the droplet discharge head which concerns on this embodiment. FIG. 3B is a partial cross-sectional view as seen from the cut surface A-A ′ of the droplet discharge head of FIG. FIG. 3C is a partial cross-sectional view as seen from a cut surface B-B ′ of the droplet discharge head in FIG. Explanatory drawing of the process of diaphragm formation. Explanatory drawing of the process of lower electrode formation. Explanatory drawing of the process of piezoelectric layer (PZT) / upper electrode formation. Explanatory drawing of the process of interlayer insulation film formation. Explanatory drawing of a lead wiring formation process. Explanatory drawing of the process of passivation layer formation. Explanatory drawing of the process of a through-hole pre-etching. Explanatory drawing of the process of pad / bypass wiring formation. Explanatory drawing of the process of protective substrate joining. Explanatory drawing of the process of individual liquid chamber board | substrate grinding | polishing and liquid chamber formation. Explanatory drawing of the process of nozzle substrate joining. 2 is a block diagram illustrating a configuration example of a main part of a control system of the image forming apparatus according to the embodiment. The block diagram which shows one structural example of the part which performs head drive control accompanying selection of the drive waveform according to the detected temperature in the same control system. The graph which shows an example of the drive waveform used for temperature compensation control, and the drive waveform after temperature compensation control. 18 is a flowchart showing an example of temperature compensation control using the drive waveform data of FIG. 6 is a graph showing the relationship between the temperature of the liquid in the liquid chamber of the liquid droplet discharge head and the surface displacement amount Δδ on the liquid chamber side of the piezoelectric element necessary for discharging liquid droplets at a predetermined discharge speed Vj. The graph which shows an example of the relationship between the voltage of the drive signal applied to a lamination type piezoelectric element, and the surface displacement (delta) of the liquid chamber side of a piezoelectric element. The graph which shows an example of the relationship between the voltage of the drive signal applied to a thin film type piezoelectric element, and the surface displacement (delta) of the liquid chamber side of a piezoelectric element. The graph which shows the other example of the drive waveform used for temperature compensation control. Explanatory drawing which shows the shift | offset | difference of the landing position of the droplet at the time of performing the conventional temperature compensation control. 3 is a graph showing an example of the entire drive waveform in one cycle of a drive signal corresponding to a detected temperature of 12.5 ° C. for which temperature compensation control has been performed in the first embodiment. 6 is a graph showing an example of a drive waveform used for temperature compensation control in Examples 3 and 4;

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, an example of an image forming apparatus provided with a droplet discharge device according to an embodiment of the present invention will be described.
FIG. 1 is a perspective view showing an example of the overall schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view of the image forming apparatus. This image forming apparatus is a serial type ink jet recording apparatus, and stores a printing mechanism unit 2 as a droplet discharge apparatus. The printing mechanism unit 2 includes a carriage that can move in the main scanning direction inside the apparatus main body 1, a liquid droplet ejection head (recording head) 14 mounted on the carriage, and a liquid such as ink for image formation on the liquid droplet ejection head 14. It is composed of a liquid tank (ink cartridge) or the like for supplying the liquid. The paper 3 as a recording medium is taken into the apparatus main body by being fed from the paper feed cassette 4 or the manual feed tray 5, and after a required image is formed by the printing mechanism unit 2, it is mounted on the rear side. The paper is discharged to the paper discharge tray 6.

  The printing mechanism unit 2 holds the carriage 13 slidably in the main scanning direction (vertical direction in FIG. 2) with a main guide rod 11 and a sub guide rod 12 which are guide members horizontally mounted on left and right side plates (not shown). doing. A droplet discharge head 14 for discharging droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) is mounted on the carriage 13 with the droplet discharge direction facing downward. Yes. On the upper side of the carriage 13, each liquid tank (ink cartridge) 15 for supplying each color liquid to the head 14 is replaceably mounted.

  The liquid tank 15 has an atmosphere port communicating with the atmosphere above, a supply port for supplying liquid to the droplet discharge head 14 below, and a porous body filled with the liquid inside. ing. The liquid supplied to the droplet discharge head 14 is maintained at a slight negative pressure by the capillary force of the porous body. Liquid is supplied from the liquid tank 15 into the droplet discharge head 14.

  The carriage 13 is slidably mounted on the main guide rod 11 at the rear side of the apparatus (downstream side in the sheet conveyance direction), and is slidably mounted on the sub guide rod 12 at the front side of the apparatus (upstream side in the sheet conveyance direction). ing. In order to move and scan the carriage 13 in the main scanning direction, a timing belt 20 is stretched between a driving pulley 18 and a driven pulley 19 that are rotationally driven by a main scanning motor 17. A carriage 13 is fixed to the timing belt 20, and the carriage 13 is reciprocated by forward and reverse rotation of the main scanning motor 17.

In this embodiment, a plurality of droplet discharge heads 14 corresponding to the liquids of the respective colors are used. However, a single droplet discharge head having a plurality of nozzles for discharging the droplets of the respective colors may be used. .
In the present embodiment, a piezo-type head that is a piezo-type droplet discharge head is used as the droplet discharge head 14. As will be described later, the droplet discharge head 14 includes a vibration plate that forms at least a part of the wall surface of the liquid flow path, and a piezoelectric element as an electromechanical conversion element that deforms the vibration plate. Have. Instead of this piezo-type head, a bubble jet type droplet discharge head (thermal type head), an electrostatic type droplet discharge head (electrostatic type head), or the like can also be used.

  In addition, the image forming apparatus according to the present embodiment includes a paper feed roller 21 that separates and feeds the paper 3 from the paper feed cassette 4 and friction in order to transport the paper 3 set in the paper feed cassette 4 to the lower side of the head 14. A pad 22 and a guide member 23 for guiding the paper 3 are provided. Further, the image forming apparatus reverses and conveys the fed paper 3, a conveyance roller 25 pressed against the peripheral surface of the conveyance roller 24, and a feeding angle of the paper 3 from the conveyance roller 24. A tip roller 26 is provided. The transport roller 24 is rotationally driven by a sub-scanning motor 27 through a gear train.

  In addition, a printing receiving member 29 is provided as a paper guide member for guiding the paper 3 fed from the transport roller 24 corresponding to the movement range of the carriage 13 in the main scanning direction on the lower side of the droplet discharge head 14. Yes. A transport roller 31 and a spur 32 that are rotationally driven to send the paper 3 in the paper discharge direction are provided on the downstream side of the printing receiving member 29 in the paper transport direction. Further, a paper discharge roller 33 and a spur 34 for sending the paper 3 to the paper discharge tray 6 and guide members 35 and 36 for forming a paper discharge path are provided.

  In the image forming apparatus configured as described above, during image formation, the droplet discharge head 14 is driven in accordance with the image signal while moving the carriage 13, thereby discharging droplets onto the stopped paper 3 and corresponding to one row. After the image 3 is formed and the sheet 3 is conveyed by a predetermined amount, the next row image is formed. Upon receiving an image formation end signal or a signal that the rear end of the sheet 3 reaches the image forming area, the image forming operation is terminated and the sheet 3 is discharged.

A recovery device 37 for recovering defective ejection of the droplet ejection head 14 is disposed at a position outside the image forming area on the right end side in the movement direction of the carriage 13. The recovery device 37 includes a cap unit, a suction unit, and a cleaning unit. The carriage 13 is moved to the recovery device 37 during printing standby, and the droplet discharge head 14 is capped by the capping means. Thereby, the nozzle (discharge port) of the droplet discharge head 14 is kept in a wet state, and discharge failure due to liquid drying can be prevented. Further, by discharging (purging) a liquid that is not related to image formation in the middle of image formation or the like, the viscosity of the liquid of all the nozzles can be made constant and stable discharge performance can be maintained.
When a discharge failure occurs, the nozzle of the droplet discharge head 14 is sealed with a capping unit, bubbles and the like are sucked out from the nozzle through the tube with a suction unit, and the liquid or dust adhering to the nozzle surface is cleaned with a cleaning unit. And the defective discharge is recovered. The sucked liquid is discharged into a waste ink reservoir (not shown) installed at the lower part of the apparatus main body, and is absorbed and held by a liquid absorber inside the waste ink reservoir.

  Next, a droplet discharge head (also referred to as “thin film head” or “thin film piezo head”) that can be used in the image forming apparatus (droplet discharge device) of the present embodiment will be described.

  FIG. 3A is a partial plan view showing the internal structure of the droplet discharge head according to the present embodiment. FIG. 3B is a partial cross-sectional view as viewed from the cut surface A-A ′ of the droplet discharge head of FIG. FIG. 3C is a partial cross-sectional view as seen from the cut surface B-B ′ of the droplet discharge head of FIG. The droplet discharge head of this embodiment is an example of a side shooter system that discharges droplets from nozzles provided on the surface of the substrate.

  In FIG. 3, the droplet discharge head of this embodiment includes three substrates: a nozzle substrate 110 having a nozzle 110a for discharging droplets, an individual liquid chamber substrate 111, and a protective substrate 112 functioning as a subframe. It has a stacked structure. The individual liquid chamber substrate 111 includes an individual liquid chamber (also referred to as a “pressurized liquid chamber” or a “pressure chamber”) 111 a communicating with the nozzle 110 a, a fluid resistance portion 111 b, and a liquid supply path 111 c including a groove portion. Has been. The upper wall of the individual liquid chamber 111 a is formed by a vibration plate 113, and a piezoelectric element 114 as an electromechanical conversion element is formed on the vibration plate 113. The piezoelectric element 114 serves as an actuator unit that functions as pressure generating means for generating pressure in the liquid in the individual liquid chamber 111a. The protective substrate 112 has a recess 112a that forms a piezoelectric element protection space in which the piezoelectric element 114 is protected in a deformable manner.

  As the individual liquid chamber substrate 111, for example, an SOI (silicon on insulator) substrate in which a silicon layer is formed on a silicon substrate via a silicon oxide film is used. As the diaphragm 113, for example, a silicon oxide film is formed on the surface of the silicon layer of the SOI substrate by applying a pyro oxidation method. Furthermore, on the diaphragm 113, a platinum film that becomes the lower electrode (common electrode) 114a, a PZT (lead zirconate titanate) layer that becomes the piezoelectric layer 114b, and a platinum film that becomes the upper electrode (individual electrode) 114c Is formed. This multi-layer actuator portion is formed in a region facing the individual liquid chamber 111a formed by etching silicon.

  Further, on the individual liquid chamber substrate 111, an interlayer insulating film 115 disposed between the upper and lower electrodes 114a and 114c and each wiring material, and a passivation film 116 for protecting the material of the lead wiring are provided in the actuator portion. It arrange | positions so that an upper surface and a side surface may be covered. The upper electrode 114c is connected to an individual electrode pad 118 serving as a terminal electrode via a lead wiring 117. The lower electrode 114a is connected to a common electrode pad serving as a terminal electrode via a lead wiring 119 and a bypass wiring 120.

  For example, a SUS substrate having a thickness of 30 [μm] to 50 [μm] is used as the nozzle substrate 110, and the nozzle 110a is formed by pressing and polishing. The nozzle 110 a communicates with the individual liquid chamber 111 a of the individual liquid chamber substrate 111.

  The protective substrate 112 is formed with a concave portion 112a that forms a protective space for the piezoelectric element for preventing the piezoelectric element from being protected and displaced, and a common liquid chamber 112b that includes a groove portion serving as a liquid flow path. Further, the protective substrate 112 is formed with a column 112c for enhancing the rigidity of the flow path partition 111d of the individual liquid chamber substrate 111 and supporting the entire liquid chamber, and a wiring space 112c in which the bypass wiring 120 is disposed. .

  In the droplet discharge head configured as described above, a combination of the nozzle 110a and the individual liquid chamber 111a corresponding to each other is referred to as a discharge channel (discharge CH).

Next, a manufacturing method for a more specific example of the droplet discharge head according to the present embodiment will be described.
4 to 14 are explanatory views showing an example of a manufacturing process of the droplet discharge head of this embodiment.
In this embodiment, the actuator part is created by depositing a diaphragm material and a piezoelectric element material on a silicon substrate.
In the diaphragm film forming process of FIG. 4, first, an SOI substrate having a silicon oxide film of 0.2 [μm] and a silicon layer of 2.0 [μm] formed on the surface of a silicon substrate having a thickness of 400 [μm]. Use. A silicon oxide film of 0.3 [μm] is formed on the surface of the SOI substrate by a pyro oxidation method, and this is used as a layer of the diaphragm 113.

  In the step of forming the lower electrode in FIG. 5, a platinum (Pt) layer to be the lower electrode 114a is formed by patterning on the vibration plate 113 with a thickness of 0.2 [μm] by sputtering. Further, the piezoelectric layer 114b is formed on the lower electrode 114a by 2 [μm] by the sol-gel method, and further, the platinum (Pt) layer to be the upper electrode 114c is formed by 0.1 [μm] on the piezoelectric layer 114b.

  In the step of forming the piezoelectric layer (PZT) / upper electrode in FIG. 6, the upper electrode 114c and the piezoelectric layer 114b are patterned by a patterning method using a photolithography technique and an etching technique (hereinafter referred to as “lithoetch method”).

  In the step of forming the interlayer insulating film in FIG. 7, the interlayer insulating film 115 is formed by 0.3 [μm] by a plasma CVD (Chemical Vapor Deposition) method, and various through holes are patterned by a lithoetch method. That is, a via hole 115a is formed in the interlayer insulating film 115 for making a wiring contact between the lead wiring 117 to be formed next and the upper electrode 114c. Further, the interlayer insulating film 115 is formed with a through hole 115b serving as a conduction portion to the bypass wiring, a through hole 115c serving as a liquid supply hole, and an opening 115d exposing the upper surface of the piezoelectric element.

  In the lead wiring formation process of FIG. 8, lead wirings 117 and 119 are formed of an aluminum material. Since the lead-out wiring 117 receives stress due to the vibration of the vibration plate 113 driven by the piezoelectric element 114, the lead wiring 117 is made of a soft aluminum material and is thickened by about 1 [μm] so as not to be disconnected due to vibration.

  In the step of forming a passivation layer in FIG. 9, a silicon nitride film by plasma CVD is formed to a thickness of 2 [μm] and patterned as a passivation film 116 for protecting the aluminum wiring.

  In the through hole pre-etching step of FIG. 10, the portion 113 a serving as the liquid supply port of the diaphragm 113 is etched in advance.

  In the step of forming the pad / bypass wiring in FIG. 11, gold is laminated by a plating method, and the individual electrode pad 118 connected to the upper electrode (individual electrode) 114c and the bypass wiring 120 are simultaneously formed. By forming the individual electrode pads 118 of gold, electrical connection with a drive circuit element (driver IC) (not shown) is connected by low-temperature wire bonding. Also, gold has a low resistance value, and the effect of lowering the resistance value of the common electrode as the bypass wiring 120 is great. Note that the step of forming the individual electrode pad 118 and the step of forming the bypass wiring 120 may be separated, and copper, aluminum, or the like may be used as the material of the bypass wiring 120. In that case, a protective layer for protecting the bypass wiring 120 from corrosion may be required.

  In the protective substrate bonding step of FIG. 12, a protective substrate 112 in which a pillar is separately formed on a glass substrate by blasting is bonded to the individual liquid chamber substrate 111.

  In the individual liquid chamber substrate polishing and liquid chamber forming process of FIG. 13, the surface opposite to the protective substrate bonding surface of the individual liquid chamber substrate 111 is polished to a desired thickness. The protective substrate 112 may be a silicon substrate obtained by processing a recess by a lithoetch method, or may be a silicon substrate processed by wet etching using an alkaline etching solution such as TMAH or KOH. Further, it may be a molded part such as a resin mold or a metal injection mold. In addition, when the drive circuit is integrally formed on the actuator substrate, an oxide film is formed by a pyro-oxidation method, and an oxide film formation region is selected by a LOCOS (local oxidation of silicon) method so that the drive circuit is formed on the same substrate. It can also be formed on top. Thereafter, recesses to be the individual liquid chamber 111a, the fluid resistance portion 111b, and the liquid supply portion 111c are formed on the opposite surface of the silicon substrate by ICP (Inductive Coupled Plasma) dry etching using inductively coupled plasma.

  Finally, in the nozzle substrate bonding step of FIG. 14, a nozzle 110a is separately formed on the nozzle substrate 110 by pressing and polishing a SUS substrate having a thickness of 30 [μm] to 50 [μm]. The nozzle substrate 110 on which the nozzles 110a are formed is adhered to the flow channel partition surface of the individual liquid chamber substrate 111, and the aluminum wiring portion connected to the upper electrode and the lower electrode of the piezoelectric element is connected to the drive circuit to thereby provide the liquid. A droplet discharge head is completed.

Next, control of the image forming apparatus according to the present embodiment will be described.
FIG. 15 is a block diagram illustrating a configuration example of a main part of a control system of the image forming apparatus according to the present embodiment. In FIG. 15, a control unit as a control means includes a microcomputer (hereinafter referred to as “CPU”) 80 that controls the entire apparatus and an internal ROM (hereinafter simply referred to as “memory” that stores necessary fixed information). ROM ”) 81 and a RAM 82 as storage means used as a working memory or the like. Further, the control unit has an image memory (lass data memory) 83 as storage means for storing image data (referred to as “dot data” or “dot pattern data”) transferred from the host side such as an external computer device. I have. In addition, the control unit includes a parallel input / output (PIO) port 84, a parallel input / output (PIO) port 86, a drive signal generation circuit 87, a head drive circuit 88, and a driver 89.

  The PIO port 84 has various information and data such as image data transferred from the printer driver side of the host, various instructions from the operation panel 90, selection information, various kinds of temperature sensors 92 as temperature detecting means for detecting the environmental temperature, and the like. A detection signal or the like from the sensor is input. In addition, necessary information is sent to the host side and the operation panel 90 side via the PIO port 84. The operation panel 90 is provided with notification means 91 such as a display lamp.

  The drive signal generation circuit 87 generates and outputs a drive signal having a required drive waveform to be applied to the piezoelectric element 114 of the droplet discharge head 14. As the drive signal generation circuit 87, as will be described later, a D / A converter that D / A converts drive waveform data composed of digital signals from the CPU 80 into drive signals composed of analog signals can be used. By using this D / A converter, it is possible to generate and output a drive signal having a required drive waveform with a simple configuration.

  A head drive circuit (driver IC) 88 is a drive signal generation circuit 87 for the piezoelectric element 114 of the selected discharge channel of the droplet discharge head 14 based on various data and signals given through the PIO port 86. The drive signal output from is applied.

  The driver 89 moves and scans the carriage 13 in the main scanning direction by driving and controlling the main scanning motor 17 and the sub-scanning motor 27 in accordance with driving control data given through the PIO port 86, and the conveying roller 24. The paper 3 is rotated and conveyed by a predetermined amount.

Next, head drive control with selection of a drive waveform according to the detected temperature in the control system having the above configuration will be described.
FIG. 16 is a block diagram illustrating a configuration example of a portion that performs head drive control with selection of a drive waveform in accordance with the detected temperature in the control system having the above configuration.
The main control unit 101 having the CPU 80 processes font data (dot data) as image formation data sent from the host side, and performs corresponding vertical / horizontal conversion of the droplet discharge heads 14. Further, the main control unit 101 generates head drive by generating 2-bit drive data SD necessary for dividing the droplets ejected from the droplet ejection head 14 into three values of large droplets, small droplets, and non-printing. Output to the circuit (driver IC) 88. The main control unit 101 also outputs a clock signal CLK, a latch signal LAT, and drive waveform selection signals M1 to M3 to the head drive circuit (driver IC) 88. The drive waveform selection signals M1 to M3 are signals for selecting a drive waveform corresponding to a dot (large droplet) having a size for forming an image dot, a drive waveform corresponding to a small droplet, and a drive waveform corresponding to non-printing. .

  Further, the main control unit 101 reads out the drive waveform data stored in the internal ROM 81 and gives it to the drive signal generation circuit 87. In this case, the ROM 81 stores a plurality of types of drive waveform data having different parameters (drive conditions) according to each of a plurality of temperatures. The main control unit 101 detects and discriminates the environmental temperature based on the detection signal from the temperature sensor 92 and selects one drive waveform data from a plurality of types of drive waveform data based on the detected temperature (detected temperature). This is given to the drive signal generation circuit 87.

  The drive signal generation circuit 87 includes a D / A converter 102, an amplifier 103, and a current amplifier 104. The D / A converter 102 performs D / A conversion on the drive waveform data supplied from the main control unit 101 and outputs it as an analog signal. The amplifier 103 amplifies the analog signal output from the D / A converter 102 to a drive signal having an actual drive voltage. The current amplifier 104 amplifies the drive signal output from the amplifier 103 so that a current necessary for driving the piezoelectric element 114 of the droplet discharge head 14 can be sufficiently supplied. The drive signal generation circuit 87 generates a drive signal having a drive waveform Pv including a plurality of drive pulses within one drive cycle and supplies the drive signal to a driver IC (head drive circuit) 88.

  The driver IC (head drive circuit) 88 includes a shift register, a latch circuit, a data selector, a level shifter, and a transmission gate, which are not shown. The shift register takes in the drive data SD by the clock signal CLK from the main control unit 101. The latch circuit latches the resist value of the shift register with the latch signal LAT. The data selector selects drive waveform selection signals M1 to M3 (logic signals) based on the 2-bit drive data latched by the latch circuit. The level shifter converts the output (logic signal) of the data selector into a drive voltage level. The transmission gate is controlled to be turned on / off by the output of the level shifter. The transmission gate is given a drive waveform Pv from the drive signal generation circuit 87 and is connected to the piezoelectric elements 114 corresponding to the respective nozzles of the droplet discharge head 14.

  In the driver IC (head drive circuit) 88, one of the drive waveform selection signals M1 to M3 is selected by the data selector in accordance with the drive data SD. Then, the selected drive waveform selection signals M1 to M3, which are logic signals, are converted into drive voltage levels by the level shifter and applied to the gate of the transmission gate. As a result, the transmission gate is switched according to the length of the selected drive waveform selection signals M1 to M3. Accordingly, a drive pulse, which is a drive signal having a predetermined drive waveform Pv, is applied to the piezoelectric element 114 of the ejection channel in which the transmission gate is open.

Next, temperature compensation control in head drive control that involves selection of a drive waveform in accordance with the detected temperature will be described.
As described above, the main control unit 101 detects the environmental temperature based on the detection signal of the temperature sensor 92, reads the drive waveform data corresponding to the detected temperature from the ROM 81, and provides it to the drive signal generation circuit 87. However, normally, the ROM 81 does not store drive waveform data corresponding to all temperatures detectable by the temperature sensor 92. For example, the drive waveform data stored in the ROM 81 may be every 5 ° C. while the temperature detectable by the temperature sensor 92 is every 0.5 ° C. for cost reduction. If drive waveform data is stored in the ROM 81 for all detectable temperatures, the temperature compensation control can be performed with high accuracy. However, the ROM 81 needs to have a large capacity, leading to an increase in cost.

  When drive waveform data corresponding to the detected temperature is not stored in the ROM 81, a drive signal is generated using drive waveform data linearly interpolated using two drive waveform data corresponding to temperatures before and after the normal detected temperature. Is output.

  FIG. 17 is a graph showing drive waveforms in an example of temperature compensation control according to the present embodiment. This example is an example where the temperature detectable by the temperature sensor 92 is every 0.5 ° C. and the drive waveform data stored in the ROM 81 is every 5 ° C.

  In FIG. 17, when the detected temperature detected by the temperature sensor 92 is 12.5 ° C., the ROM 81 does not store drive waveform data corresponding to the detected temperature 12.5 ° C. Of the drive waveform data stored in the ROM 81, the drive waveform data corresponding to temperatures around 12.5 ° C. is a drive waveform corresponding to 10 ° C. indicated by symbols A and B in FIG. And a driving waveform corresponding to 15 ° C. (hereinafter also referred to as “15 ° C. waveform”). Here, the difference between the 10 ° C. waveform and the 15 ° C. waveform is the voltage between 2.0 [μs] and 3.0 [μs] in one drive cycle in the time on the horizontal axis, and the 10 ° C. waveform. Is 1.0 [V], and 15 [deg.] C. is 5.0 [V]. For this reason, the voltage of the drive waveform corresponding to 12.5 ° C. (hereinafter also referred to as “12.5 ° C. waveform”) indicated by the symbol C in FIG. 17 is the voltage (1. 0 [V], 5.0 [V]). Drive waveform data having a voltage of 3.0 [V] (between 2.0 [μs] and 3.0 [μs]) obtained by this linear interpolation is output.

  FIG. 18 is a flowchart showing an example of temperature compensation control using the drive waveform data of FIG. In FIG. 18, after the temperature is detected by the temperature sensor 92, the environmental temperature (12.5 ° C.) is detected based on the detection signal of the temperature sensor 92 (S101). Then, it is determined whether or not drive waveform data corresponding to the detected temperature (12.5 ° C.) exists in the ROM 81 (S102). In the case of the drive waveform data of FIG. 17, since drive waveform data corresponding to the detected temperature (12.5 ° C.) does not exist in the ROM 81 (N in S102), the temperature (12.5 ° C.) before and after the detected temperature (12.5 ° C.). 10 ° C. and 15 ° C. waveform data corresponding to 10 ° C. and 15 ° C.) are read out. Using these 10 ° C. waveform voltage (1.0 [V]) and 15 ° C. waveform voltage (5.0 [V]), a voltage (3.0 [V]) corresponding to the detected temperature (12.5 ° C.) is used. V]) is obtained by linear interpolation (S103). The voltage (3.0 [V]) obtained by the above linear interpolation has a drive waveform set to a voltage between 2.0 [μs] and 3.0 [μs] in one drive cycle. A drive signal is generated and output (S104).

As shown in FIG. 17 and FIG. 18, the reason why the voltage of the drive signal can be obtained by linear interpolation with respect to the detected temperature is due to the following reasons (1) and (2).
(1) In order to eject droplets at the same predetermined ejection speed Vj (= 7.0 [m / s]) at each temperature when the temperature range of the liquid in the droplet ejection head is a narrow temperature range of about 5 ° C. The surface displacement amount Δδ on the liquid chamber side of the piezoelectric element 114 required for the above can be regarded as substantially linear with respect to the temperature of the liquid. This point has been experimentally confirmed by the present inventors as shown in FIG.
(2) Further, in the case of using a laminated piezoelectric element formed by stacking a plurality of layers as the electromechanical conversion element in the pressure generating means, a piezoelectric signal is applied to the voltage V [V] of the drive signal applied to the piezoelectric element. The surface displacement δ [μm] on the liquid chamber side of the element 114 increases linearly. That is, the relationship between the voltage V [V] of the drive signal applied to the multilayer piezoelectric element and the surface displacement δ [μm] on the liquid chamber side of the piezoelectric element 114 exhibits a linear characteristic. This point has also been experimentally confirmed by the present inventors as shown in FIG.

  As described above, in the present embodiment, Tn ≦ Tx ≦ Tn + 1 is satisfied for the detected temperature Tx in which the drive waveform data is not stored in the ROM 81 under the conditions in which the points (1) and (2) are confirmed. Read drive waveform data corresponding to each of the temperatures Tn and Tn + 1. More specifically, with respect to the detected temperature Tx for which drive waveform data is not stored in the ROM 81, the drive waveform data of the temperatures T1 and T2 before and after that is read. Then, linear interpolation of the voltage of the drive signal corresponding to the detected temperature is performed using the read temperatures Tn and Tn + 1 (T1, T2). Thereby, highly accurate temperature compensation control becomes possible.

Next, temperature compensation control when a thin film type piezoelectric element 114 is used as an electromechanical conversion element (actuator) in the pressure generating means will be described.
As shown in FIG. 21, the thin film type piezoelectric element 114 is different from the above-described laminated type piezoelectric element in that the liquid of the piezoelectric element 114 as a physical parameter of the pressure generating mechanism is applied to the voltage of the applied drive signal. The chamber-side surface displacement δ increases nonlinearly. That is, the relationship between the voltage of the drive signal and the surface displacement δ on the liquid chamber side of the piezoelectric element 114 as a physical parameter of the pressure generating mechanism is a non-linear relationship. As described above, in the thin film type piezoelectric element, unlike the stacked type piezoelectric element, the voltage characteristic of the surface displacement on the liquid chamber side is not linear. Therefore, the drive signal corresponding to the detected temperature shown in FIGS. When the linear interpolation of the voltage is performed, there is a possibility that the landing position deviation of the droplet may occur. The thin film type piezoelectric element exhibits a nearly linear surface displacement characteristic in a region where the voltage of the drive signal is low, but when a high voltage is applied (near 30 V), the surface displacement is indicated by a curve B in FIG. There is a tendency for saturation of δ. This saturation tendency is considered to be due to the fact that the piezoelectric film as a driving source is a thin film of about 1 [μm] or more and 2 [μm] or less in the thin film type piezoelectric element, and the electric field strength in the film becomes very high. ing.

  FIG. 22 is a graph showing another example of drive waveforms (10 ° C. waveform, 15 ° C. waveform) of drive signals of 10 ° C. and 15 ° C. used for temperature compensation control. The 10 ° C. waveform and the 15 ° C. waveform in FIG. 22 are voltages (0 to 1.0 [μs] and 4.0 to 5.0 [μs] in one cycle of the drive signal (voltages on both sides of the pulse). The so-called intermediate potentials are different from each other. The amplitude of the 10 ° C. waveform is 0 to 15 [V], and the amplitude of the 15 ° C. waveform is 0 to 7.0 [V]. The amplitude of the 12.5 ° C. waveform obtained by performing linear interpolation on the temperature using these 10 ° C. and 15 ° C. waveforms is 0 to 11.0 [V]. Then, from FIG. 20 described above, the surface displacement Δδ corresponding to the amplitude of 0 to 11.0 [V] of the 12.5 ° C. waveform obtained by performing linear interpolation on the temperature of the thin film piezoelectric element is 0. 129 [μm]. This surface displacement amount Δδ (= 0.129 [μm]) exceeds the surface displacement amount Δδ = 0.125 [μm] required for the droplet discharge speed Vj = 7 [m / s] at 12.5 ° C. (See FIG. 19). For this reason, as shown in FIG. 23, when the detected temperature is 12.5 ° C., 7.0 [m / s] when the discharge speed Vj of the droplet D discharged from the nozzle 110a is 10 ° C. or 15 ° C. ], And the landing position of the droplet D is displaced.

  Therefore, in this embodiment, temperature compensation control can be performed with high accuracy even when a thin film type piezoelectric element as shown in the following examples is used.

Next, a specific example of temperature compensation control that can be accurately performed even when a thin film type piezoelectric element is used in the image forming apparatus (droplet discharge apparatus) of the present embodiment will be described.
[Example 1]
In the first embodiment, the nonlinear displacement characteristic indicating the relationship between the voltage V of the driving signal and the surface displacement δ in the thin film piezoelectric element 114 is approximated by the following equation (1), and based on this approximate equation (1): The drive waveform interpolation in FIG. 18 is performed. In formula (1), a is a constant.
δ = a · V ^0.5 (1)

  In the first embodiment, a case where the detected temperature detected by the temperature sensor 92 is Tx [° C.] and drive waveform data corresponding to the detected temperature Tx is not stored in the ROM 81 will be described. Here, with respect to the detected temperature Tx for which drive waveform data is not stored in the ROM 81, assuming that the temperatures Tn and Tn + 1 satisfy Tn ≦ Tx ≦ Tn + 1, in this embodiment, the drive waveform data of temperatures T1 and T2 before and after the detected temperature Tx are used. read out.

As described above, if the temperature interval in which the drive waveform data is stored is a narrow temperature interval, it can be assumed that the required displacement amount Δδ of the surface of the piezoelectric element 114 at which a predetermined discharge speed is obtained is proportional to the temperature. Therefore, the surface displacement δx of the piezoelectric element 114 at the detected temperature Tx is linear as shown by the following equation (2) using the surface displacements δ1 and δ2 of the piezoelectric element 114 at the front and rear temperatures T1 and T2, respectively. It can be obtained by interpolation.
δx = (δ2−δ1) (Tx−T1) / (T2−T1) + δ1 (2)

Here, the drive waveform data stored in the ROM 81 is time and voltage data corresponding to each of a plurality of temperatures. The voltage Vx at the detected temperature Tx is expressed by the following equations (3) and (4) using the voltages V1 and V2 corresponding to the temperatures T1 and T2, respectively.
Vx = (δx / a) ² (3)
δx = a (V2 ^0.5 −V1 ^0.5 ) (Tx−T1) / (T2−T1) + V1 ^0.5 (4)

  In the first embodiment, the voltages of the low voltage portion, the intermediate voltage portion, and the high voltage portion in one cycle of the drive signal at the temperatures T1 and T2 before and after the detected temperature Tx according to the above formulas (3) and (4). The voltage of each part of the drive signal at the detected temperature Tx is obtained by interpolation from V1 and V2. And the drive signal of the waveform which has the voltage of each part calculated | required by the interpolation is produced | generated and output as a drive signal at the detection temperature Tx.

Here, the above equation (4) corresponds to the process of converting the voltages V1, V2 corresponding to the temperatures T1, T2 into the surface displacements δ1, δ2 of the piezoelectric element 114 and the detected temperature Tx from the surface displacements δ1, δ2. This is an equation for performing processing for obtaining the surface displacement δx by linear interpolation. In the actual temperature compensation control, the process using the above equation (4) is executed on the entire drive waveform (for example, see FIG. 24 described later). That is, the above equation (4) is an equation for performing the following two processes A and B together.
Process A: A process of converting drive waveform data corresponding to the temperatures T1 and T2 into time change data of the surface displacement δ of the piezoelectric element corresponding to the temperatures T1 and T2.
Process B: A process of obtaining by linear interpolation the time change data of the surface displacement δ of the piezoelectric element corresponding to the detected temperature Tx from the time change data of the surface displacement δ of the piezoelectric element corresponding to the temperatures T1 and T2.

  Further, the above equation (3) is an equation for converting the surface displacement δx of the piezoelectric element 114 corresponding to the detected temperature Tx into a voltage Vx corresponding to the detected temperature Tx. In the actual temperature compensation control, the process using the above equation (3) is also executed for the entire drive waveform (for example, see FIG. 24 described later). That is, the above equation (3) is an equation for performing processing for converting the time change data of the surface displacement δ of the piezoelectric element corresponding to the detected temperature Tx into the drive waveform data corresponding to the detected temperature Tx.

  FIG. 24 corresponds to the detected temperature of 12.5 ° C. obtained by approximating the nonlinear displacement characteristic indicating the relationship between the voltage V of the driving signal and the surface displacement δ in the thin film type piezoelectric element by the equation (1). It is a graph which shows an example of the whole drive waveform in 1 period of a drive signal. A curve C in FIG. 24 is obtained by interpolating the voltages of the low voltage portion, the intermediate voltage portion, and the high voltage portion in one cycle of the drive signal corresponding to the detected temperature of 12.5 ° C. by the temperature compensation control of the first embodiment. It is the obtained drive waveform (12.5 ° C. waveform). Curves A and B in FIG. 24 are a 10 ° C. waveform and a 15 ° C. waveform used when the 12.5 ° C. waveform is interpolated to obtain. A curve D in FIG. 24 is a 12.5 ° C. waveform according to a comparative example obtained from a 10 ° C. waveform and a 15 ° C. waveform by conventional linear interpolation.

  As described above, in the first embodiment, the nonlinear displacement characteristic indicating the relationship between the voltage V of the drive signal and the surface displacement δ is approximated by the equation (1), and the voltage of the drive signal is calculated using the approximate equation (1). Conversion between V and the surface displacement δ is performed. Then, temperature compensation control for interpolating a drive waveform corresponding to the detected temperature Tx is performed using drive waveform data at temperatures T1 and T2 before and after the detected temperature Tx. By performing this temperature compensation control in the control unit, it is possible to perform highly accurate temperature compensation control even when an actuator having non-linear surface displacement voltage characteristics such as a thin film type piezoelectric element is used as the pressure generating means. Become.

In addition, when the above formula (1) is generalized, the following formula (5) is obtained. By using this generalized equation (5), the types of thin film piezoelectric elements to which the temperature compensation control of the first embodiment can be applied are expanded. That is, the temperature compensation control of the first embodiment can be applied to a thin film type piezoelectric element having various nonlinear characteristics as a characteristic indicating the relationship between the voltage V [V] of the drive signal and the surface displacement δ [μm]. it can. In Equation (5), a _k is a constant [μm / V], and m and n are real numbers.

[Example 2]
In the second embodiment, conversion between the voltage V of the drive signal and the surface displacement δ is performed using a δ-V conversion table stored in advance in the control unit instead of the above equation (1). In the second embodiment, similarly to the first embodiment, the detected temperature detected by the temperature sensor 92 is Tx [° C.], and drive waveform data corresponding to the detected temperature Tx is stored in the ROM 81. The case where there is not will be described. In the second embodiment, the description of the parts common to the first embodiment will be omitted.

Here, the temperatures before and after the detected temperature Tx among the temperatures in which the drive waveform data is stored in the ROM 81 are T1 and T2, respectively. Table 1 is an example of a δ-V conversion table.

  In the second embodiment, drive waveform data corresponding to temperatures around 12.5 ° C. among the drive waveform data stored in the ROM 81 are a 10 ° C. waveform and a 15 ° C. waveform (see FIG. 17). Here, the difference between the 10 ° C. waveform and the 15 ° C. waveform is a voltage between 2.0 [μs] and 3.0 [μs], and the 10 ° C. waveform is 1.0 [V] and the 15 ° C. waveform. Then, it is 5.0 [V].

  Here, from the δ-V conversion table of Table 1, the surface displacement δ of the piezoelectric element corresponding to the 12.5 ° C. waveform is 0.071 [μm]. This surface displacement δ = 0.071 [μm] can be obtained by the following procedure. From Table 1, the surface displacement δ of the piezoelectric element corresponding to 1.0 [V] of the 10 ° C. waveform is 0.044 [μm], and the surface of the piezoelectric element corresponding to 5.0 [V] of the 15 ° C. waveform. The displacement δ is 0.098 [μm]. When the surface displacement δ of the piezoelectric element corresponding to the 12.5 ° C. waveform is obtained by linear interpolation from these displacement δ values, (0.098−0.044) (12.5) according to the above-described equation (2). −10) / (15−10) + 0.044 = 0.071 [μm]. When the surface displacement δ of the piezoelectric element corresponding to the 12.5 ° C. waveform is converted into a voltage between 2.0 [μs] and 3.0 [μs] of the 12.5 ° C. waveform using Table 1, 6 [V]. This is because in the δ-V conversion table of Table 1, the voltage V corresponding to the surface displacement δ = 0.071 [μm] of the piezoelectric element is 2.6 [V].

  Note that the processing in the temperature compensation control using the δ-V conversion table in the second embodiment is performed on the entire drive waveform (see, for example, FIG. 24) as in the first embodiment. That is, using the δ-V conversion table, the drive waveform data corresponding to the temperatures T1 and T2 before and after the detected temperature Tx is converted into time change data of the surface displacement δ of the piezoelectric element corresponding to the temperatures T1 and T2. The Then, the time change data of the surface displacement δ of the piezoelectric element corresponding to the detected temperature Tx is obtained by linear interpolation from the time change data of the surface displacement δ of the piezoelectric element corresponding to the temperatures T1 and T2. Further, using the δ-V conversion table, the time change data of the surface displacement δ of the piezoelectric element corresponding to the detected temperature Tx is converted into drive waveform data corresponding to the detected temperature Tx.

  As described above, in the second embodiment, not only when using mathematical formulas as in the first embodiment described above, but also by having a δ-V conversion table in the control unit in advance, high accuracy is achieved as in the first embodiment. Temperature compensation control is possible. That is, even when an actuator having a non-linear voltage characteristic of surface displacement such as a thin film type piezoelectric element is used for the pressure generating means, highly accurate temperature compensation control can be performed.

[Example 3]
The third embodiment is an embodiment where there is no corresponding voltage in the δ-V conversion table. That is, in Example 2 described above, the voltage (1.0, 5.0 [V]) between 2.0 [μs] and 3.0 [μs] of each of the 10 ° C. waveform and the 15 ° C. waveform is δ−V. An example is given in the conversion table. In the third embodiment, at least one of these voltages (1.0, 5.0 [V]) is not in the δ-V conversion table. In the third embodiment, the description of the parts common to the first and second embodiments will be omitted.

  In the third embodiment, the temperature detected by the temperature sensor 92 is 8.5 ° C., and drive waveform data corresponding to temperatures around 8.5 ° C. among the drive waveform data stored in the ROM 81 is a 5 ° C. waveform. The waveform is 10 ° C. (see FIG. 25). The difference between the 5 ° C. waveform and the 10 ° C. waveform is the voltage between 2.0 [μs] and 3.0 [μs], which is 0.15 [V] for the 5 ° C. waveform and 1.0 for the 15 ° C. waveform. [V].

  Here, it is impossible to convert the voltage V corresponding to the 5 ° C. waveform into the surface displacement δ of the piezoelectric element. This is because the voltage 0.15 [V] between 2.0 [μs] and 3.0 [μs] of the 5 ° C. waveform does not exist in the δ-V conversion table of Table 1.

  Therefore, in the third embodiment, in order to convert the voltage V having the 5 ° C. waveform to the surface displacement δ of the piezoelectric element, the voltage closest to the voltage having the 5 ° C. waveform is used instead. In this example, the voltage in the δ-V conversion table closest to the voltage 0.15 [V] of the 5 ° C. waveform is 0.20 [V], and the surface displacement δ of the piezoelectric element from the voltage V of the 5 ° C. waveform. This value (= 0.20 [V]) is substituted in the conversion to. By performing conversion by substituting such a voltage, between 2.0 [μs] and 3.0 [μs] of the drive waveform at 8.5 ° C. (hereinafter referred to as “8.5 ° C. waveform”). Is 0.8 [V]. This voltage V = 0.8 [V] can be obtained by the following procedure. When the voltage 0.20 [V] on the δ-V conversion table of Table 1 is substituted for the voltage 0.15 [V] of the 5 ° C. waveform, the surface displacement of the piezoelectric element corresponding to the voltage 0.20 [V] δ is 0.020 [μm]. Further, from Table 1, the surface displacement δ of the piezoelectric element corresponding to 1.0 [V] of the 10 ° C. waveform is 0.044 [μm]. When the surface displacement δ of the piezoelectric element corresponding to the 8.5 ° C. waveform is obtained by linear interpolation with respect to the voltage using these surface displacement δ values, (0.044−0.020) is obtained by the above equation (2). ) (8.5-5) / (10-5) + 0.020 = 0.037 [μm]. Here, linear interpolation by voltage becomes possible by replacing T in the expression (2) with V. From Table 1, the voltage V corresponding to this surface displacement of 0.037 [μm] is 0.8 [V].

  As described above, in Example 3, even when the voltage corresponding to the voltage in the drive waveform does not exist in the δ-V conversion table, similarly to Example 2, the surface of the piezoelectric element corresponding to the detected temperature. The displacement δ can be interpolated.

[Example 4]
The fourth embodiment is another embodiment where there is no corresponding voltage V in the δ-V conversion table. In the fourth embodiment, instead of substituting the closest voltage in the δ-V conversion table as in the third embodiment, the surface displacement δ of each piezoelectric element corresponding to the voltage before and after the voltage V is the closest. The surface displacement δ of the piezoelectric element corresponding to the detected temperature is obtained by linear interpolation. That is, when the voltage V of the drive waveform data before conversion is not in the δ-V conversion table, the surface displacement δp corresponding to Vp and Vp + 1 satisfying Vp ≦ V ≦ Vp + 1 among the voltages in the δ-V conversion table and Linear interpolation of δp + 1 is performed. In the fourth embodiment, the description of the parts common to the first to third embodiments will be omitted.

  In the fourth embodiment, a case similar to that in the third embodiment will be described. That is, the temperature detected by the temperature sensor 92 is 8.5 ° C., and the drive waveform data corresponding to the temperature around 8.5 ° C. among the drive waveform data stored in the ROM 81 is the 5 ° C. waveform and 10 ° C. A waveform is used (see FIG. 25).

  Here, as described above, since the voltage 0.15 [V] between 2.0 [μs] and 3.0 [μs] of the 5 ° C. waveform is not in the δ-V conversion table, the surface displacement δ of the piezoelectric element is increased. Cannot be converted. When the surface displacement δ of the piezoelectric element corresponding to the 5 ° C. waveform is linearly interpolated from the surface displacement corresponding to voltages around 0.15 [V], it is 0.015 [μm]. This 0.015 [μm] can be determined by the following procedure. From Table 1, the voltages before and after the voltage 0.15 [V] are 0.0 [V] and 0.20 [V], respectively. The surface displacement δ of the piezoelectric element corresponding to these two voltages is 0.00 [μm] and 0.02 [μm], respectively. When the surface displacement δ of the piezoelectric element corresponding to the 5 ° C. waveform voltage is obtained by linear interpolation with respect to the voltage from the two surface displacements δ, (0.02-0.00) (0 .15-0) / (0.20-0) + 0 = 0.015 [μm]. Here, linear interpolation by voltage becomes possible by replacing T in the expression (2) with V.

  As described above, the surface displacement δ corresponding to the voltage not included in the δ-V conversion table is linearly interpolated by the front and rear voltages, so that the waveform of the 8.5 [V] waveform is 2.0 [μs] to 3.0 [μs]. The voltage between them is 0.6 [V]. This 0.6 [V] can be obtained by the following procedure. As described above, the surface displacement δ of the voltage 0.15 [V] of the 5 ° C. waveform is 0.015 [μm], and the surface displacement δ corresponding to 1.0 [V] of the 10 ° C. waveform is 0.044. [Μm]. When the surface displacement δ corresponding to the 8.5 ° C. waveform is linearly interpolated using these surface displacement values, (0.044−0.015) (8.5-5) according to the above equation (2). /(10−5)+0.015=0.035 [μm]. From Table 1, the voltage corresponding to this surface displacement of 0.035 [μm] is 0.6 [V].

  As described above, in the fourth embodiment, even when the voltage corresponding to the voltage in the drive waveform does not exist in the δ-V conversion table, as in the second and third embodiments, the piezoelectric element corresponding to the detected temperature. It is possible to interpolate the surface displacement δ.

[Example 5]
The fifth embodiment is an embodiment where there is no corresponding surface displacement δ in the δ-V conversion table. In the fifth embodiment, description of portions common to the first to fourth embodiments will be omitted.

In the fifth embodiment, the drive waveform data used for the temperature compensation control is the 10 ° C. waveform and the 15 ° C. waveform shown in FIG. 22 stored in the ROM 81, and the δ-V conversion table shown in Table 2 is used. . In the fifth embodiment, a case where the temperature detected by the temperature sensor 92 is 11 ° C. will be described.

  When the temperature detected by the temperature sensor 92 is 11 ° C., the drive waveform data corresponding to 11 ° C. is not stored in the ROM 81, and the drive waveform data stored in the ROM 81 corresponds to temperatures around 11 ° C. The drive waveform data to be performed is a 10 ° C. waveform and a 15 ° C. waveform (see FIG. 22). Here, the difference between the 10 ° C. waveform and the 15 ° C. waveform is the voltage between 0 to 1.0 [μs] and 4.0 to 5.0 [μs], and the 10 ° C. waveform is 15 [V]. In the 15 ° C. waveform, 7.0 [V]. The surface displacement δ of the piezoelectric element having an 11 ° C. waveform is calculated from these waveforms to be 0.159 [μm]. This 0.159 [μm] can be obtained by the following procedure. From Table 2, the surface displacement δ corresponding to 15 [V] of the 10 ° C. waveform is 0.170 [μm], and the surface displacement δ corresponding to 7.0 [V] of the 15 ° C. waveform is 0.116 [μm]. ]. When these surface displacements δ are used to obtain the surface displacement δ corresponding to the 11 ° C. waveform by linear interpolation, (0.170−0.116) (11-15) according to the above equation (2). /(10−15)+0.116=0.159 [μm].

  Here, it is impossible to convert the surface displacement δ (= 0.159 [μm]) corresponding to the 11 ° C. waveform into a voltage. This is because the surface displacement δ (= 0.159 [μm]) corresponding to 0 to 1.0 [μs] and 4.0 to 5.0 [μs] of the 11 ° C. waveform is δ−V in Table 2. This is because it does not exist in the conversion table.

  Therefore, in the fifth embodiment, in order to convert to voltage, the surface displacement δ closest to the surface displacement δ (= 0.159 [μm]) corresponding to the 11 ° C. waveform is used instead of the conversion. Thereby, the voltage between 0-1.0 [μs] and 4.0-5.0 [μs] of the 11 ° C. waveform is 13.0 [V]. That is, in the case of Example 5, the surface displacement δ in the δ-V conversion table of Table 2 closest to the surface displacement δ (= 0.159 [μm]) of the 11 ° C. waveform is 0.158 [μm]. . When the value of the surface displacement δ (= 0.158 [μm]) is substituted for the surface displacement δ of the 11 ° C. waveform, the corresponding voltage is 13.0 [V] according to Table 2.

  As described above, in the fifth embodiment, the case where the surface displacement δ of the piezoelectric element corresponding to the voltage in the drive waveform does not exist in the δ-V conversion table corresponds to the detected temperature as in the second embodiment. It is possible to interpolate the surface displacement δ of the piezoelectric element.

[Example 6]
The sixth embodiment is another embodiment where the corresponding surface displacement δ does not exist in the δ-V conversion table. In the sixth embodiment, the description of the parts common to the first to fifth embodiments will be omitted.

  In the sixth embodiment, instead of substituting the nearest surface displacement in the δ-V conversion table as in the fifth embodiment, linear interpolation of respective voltages corresponding to the nearest front and rear surface displacements is performed. The voltage corresponding to the surface displacement that does not exist is calculated and interpolated. That is, when the surface displacement δ on the liquid chamber side of the piezoelectric element before conversion is not in the δ-V conversion table, it corresponds to each of δq and δq + 1 satisfying δq ≦ δ ≦ δq + 1 among the surface displacements in the δ-V conversion table. Linear interpolation of Vq and Vq + 1 of the drive waveform data to be performed is performed.

  In the sixth embodiment, a case similar to that of the above-described fifth embodiment is considered. That is, the temperature detected by the temperature sensor 92 is 11 ° C., and the drive waveform data corresponding to temperatures around 11 ° C. among the drive waveform data stored in the ROM 81 is a 10 ° C. waveform and a 15 ° C. waveform ( (See FIG. 22). At this time, as described above, since the surface displacement δ (= 0.159 [μm]) corresponding to the 11 ° C. waveform is not in the δ-V conversion table of Table 2, it cannot be converted into a voltage.

  Therefore, when the voltage V corresponding to the 11 ° C. waveform is linearly interpolated from the surface displacement before and after the surface displacement δ (= 0.159 [μm]) corresponding to the 11 ° C. waveform, 13.2 [V]. It is. This voltage 13.2 [V] can be obtained by the following procedure. From Table 2, the surface displacements before and after the surface displacement of 0.159 [μm] are 0.158 [μm] and 0.161 [μm], respectively. From Table 2, the voltages V corresponding to these two surface displacements δ are 13.0 [V] and 13.5 [V], respectively. When the voltage corresponding to the 11 ° C. waveform displacement is calculated from these two voltages by linear interpolation based on the displacement, (13.5-13.0) (0.159-0.158) according to the above-described equation (2). /(0.161−0.158)+13=13.2 [V]. Here, linear interpolation by voltage can be performed by setting δ in equation (2) to V and T to δ.

  As described above, in Example 6, even when the surface displacement δ of the piezoelectric element corresponding to the voltage in the drive waveform does not exist in the δ-V conversion table, the detected temperature is the same as in Examples 2 and 5. It is possible to interpolate the surface displacement δ of the piezoelectric element corresponding to.

In the above embodiment and each example, various variations can be considered for the timing of switching the drive waveform of the drive signal output to the piezoelectric element of the droplet discharge head. For example, the timing at which the drive waveform of the drive signal output to the piezoelectric element of the droplet discharge head is switched is for every page or multiple pages of the recording medium (printed material) of the image forming apparatus, every predetermined time, and the droplet empty discharge timing You may set every.
In the above-described embodiment and each example, the temperature sensor 92 as a temperature detecting unit is installed not only inside the droplet discharge head but also outside the droplet discharge head, outside the image forming apparatus, and liquid tank ( Various variations are conceivable, such as in the ink cartridge 15.

In the above-described embodiment and each example, the case where the actuator constituting the pressure generating unit includes a piezo-type droplet discharge head that is a piezoelectric element has been described. The same applies to the case where a head is provided.
For example, the present invention can be applied to an electrostatic droplet discharge head. In this case, the physical parameter of the pressure generating mechanism that changes due to the application of the drive signal is the surface displacement of the diaphragm facing the individual electrode to which the drive signal is applied. In the present invention, even when the relationship between the drive signal applied to the individual electrode and the magnitude of the surface displacement of the diaphragm is non-linear, stable droplet ejection characteristics that are not affected by temperature changes can be obtained.
The present invention can also be applied to a bubble jet type droplet discharge head. In this case, the physical parameter of the pressure generating mechanism that changes according to the drive signal is the amount of heat generated by the heating element. In the present invention, even when the relationship between the drive signal applied to the heating element and the amount of heat generated by the heating element is non-linear, stable droplet ejection characteristics that are not affected by temperature changes can be obtained.

  Further, in the image forming apparatus described with reference to FIGS. 1 and 2 described above, a case has been described in which an image is formed by landing droplets ejected from a droplet ejection head on a sheet. It can be applied to other devices. For example, according to the present invention, the medium on which the droplets for image formation are landed and applied is a medium (recording medium, transfer material, recording paper) other than paper, such as thread, fiber, fabric, leather, metal, plastic, glass. The same applies to a medium such as wood or ceramics. The present invention is not limited to the case where an image having a meaning such as a character or a figure is applied to a medium, but also a device that applies a pattern having no meaning such as a character to the medium (simply ejects a droplet). It can also be applied to. The present invention can also be applied to an apparatus for discharging a liquid resist for patterning to land on a landing medium. The present invention can also be applied to a droplet discharge device that discharges a genetic analysis sample to land on a landing medium, a three-dimensional molding droplet discharge device, and the like.

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 nozzle 110a that discharges droplets, a liquid chamber such as an individual liquid chamber 111a that communicates with the nozzle 110a, and a physical parameter of a pressure generation mechanism that generates pressure in the liquid chamber, such as a piezoelectric element 114 that changes according to a drive signal. A droplet discharge head 14 having a pressure generating means, a driving signal output means such as a head driving circuit (driver IC) 88 that outputs a driving signal applied to the pressure generating means, and a driving signal corresponding to each of a plurality of temperatures. A storage means such as a ROM 81 in which drive waveform data is stored, a temperature detection means such as a temperature sensor 92 for detecting temperature, and a drive signal is output based on the temperature detection result of the temperature detection means and applied to the pressure generation means. And a control unit such as a main control unit 101 having a CPU 80 for controlling the drive signal output unit. Of the drive waveform data corresponding to each of a plurality of temperatures stored in the storage means, the drive waveform data corresponding to each of the temperatures Tn and Tn + 1 satisfying Tn ≦ Tx ≦ Tn + 1 for the detected temperature Tx detected by the temperature detection means , And converts the drive waveform data corresponding to the temperatures Tn and Tn + 1 to time change data of physical parameters of the pressure generating mechanism corresponding to the temperatures Tn and Tn + 1, respectively, and the pressures corresponding to the temperatures Tn and Tn + 1, respectively. The time change data of the physical parameter of the pressure generating mechanism corresponding to the detected temperature Tx is obtained by linear interpolation from the time change data of the physical parameter of the generating mechanism, and the physical parameter of the pressure generating mechanism corresponding to the detected temperature Tx is obtained. Is changed to drive waveform data corresponding to the detected temperature Tx. And the drive waveform data used for generating the drive signals to be applied to the pressure generating means, to change the driving waveform data corresponding to the detected temperature Tx after conversion.
According to this, as described in the above embodiment, when the relationship between the drive signal in the pressure generating means and the physical parameter size of the pressure generating mechanism is non-linear, the drive waveform data is stored in the storage means. Temperature compensation control is performed as follows for a detected temperature Tx that does not exist. First, drive waveform data corresponding to each of temperatures Tn and Tn + 1 satisfying Tn ≦ Tx ≦ Tn + 1 with respect to the detected temperature Tx is read. The non-linear relationship between the drive signal and the physical parameter of the pressure generation mechanism can be examined in advance. Therefore, the drive waveform data corresponding to each of the temperatures Tn and Tn + 1 can be accurately converted into time change data of physical parameters of the pressure generating mechanism corresponding to the temperatures Tn and Tn + 1. Here, the relationship between the temperature and the physical parameter of the pressure generation mechanism can be regarded as a substantially linear relationship. Therefore, the time change data of the physical parameter of the pressure generation mechanism corresponding to the detected temperature Tx can be obtained by linear interpolation with high accuracy from the time change data of the physical parameter of the pressure generation mechanism corresponding to each of the temperatures Tn and Tn + 1. it can. As described above, the time change data of the physical parameter of the pressure generating mechanism corresponding to the detected temperature Tx is obtained from the non-linear relationship between the drive signal that can be examined in advance and the physical parameter of the pressure generating mechanism. Conversion to drive waveform data corresponding to Tx is possible with high accuracy. As described above, the temperature compensation control of the drive signal can be accurately performed for the detected temperature Tx in which the drive waveform data is not stored in the storage unit. Then, the drive waveform data used for generating the drive signal applied to the pressure generating means is changed to the drive waveform data corresponding to the detected temperature Tx after the conversion subjected to the temperature compensation control with high accuracy. Therefore, stable droplet discharge characteristics that are not affected by temperature changes can be obtained. In addition, since it is not necessary to store drive waveform data for all temperature ranges that can be detected by the temperature detection means, an increase in the storage capacity of the storage means can be suppressed, and the cost can be reduced. Therefore, it is possible to obtain stable droplet discharge characteristics that are not affected by temperature changes even when the relationship between the drive signal in the pressure generating means and the physical parameter size of the pressure generating mechanism is nonlinear while reducing costs. Can do.
(Aspect B)
In the above aspect A, the pressure generating means is an electromechanical transducer in which the surface on the liquid chamber side is displaced so that the pressure for ejecting the droplets from the nozzle 110a is generated in the liquid chamber when a drive signal is applied. The physical parameter of the pressure generating mechanism is the surface displacement of the electromechanical transducer on the liquid chamber side.
According to this, as described in the above embodiment, even when the relationship between the drive signal applied to the electromechanical transducer and the magnitude of the surface displacement on the liquid chamber side of the electromechanical transducer is non-linear, the influence of the temperature change It is possible to obtain stable droplet discharge characteristics that are not subjected to the above.
(Aspect C)
In the aspect B, the surface displacement on the liquid chamber side of the electromechanical transducer is δ [μm], the voltage of the drive signal is V [V], a _k [μm / V] is a constant, m and n Is a real number, the conversion between the drive waveform data and the time change data of the surface displacement δ on the liquid chamber side of the electromechanical conversion element is performed using the above-described equation (5). According to this, as described in the above embodiment, the types of electromechanical conversion elements that can obtain stable droplet discharge characteristics that are not affected by temperature changes are expanded. That is, a plurality of types of electromechanical transducers having various non-linear characteristics as characteristics indicating the relationship between the voltage of the drive signal and the surface displacement δ on the liquid chamber side of the electromechanical transducer are also stable without being affected by temperature changes. The droplet discharge characteristics can be obtained.
(Aspect D)
In the aspect B, the conversion between the driving waveform data and the time change data of the surface displacement of the electromechanical conversion element on the liquid chamber side is performed using a conversion table provided in advance.
According to this, as described in the above embodiment, the conversion between the drive waveform data and the time change data of the surface displacement on the liquid chamber side of the electromechanical conversion element can be performed by simple data processing.
(Aspect E)
In the above aspect D, the conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other, and the voltage V of the drive waveform data before conversion is If not in the conversion table, the voltage closest to the voltage V of the drive waveform data before conversion among the voltages in the conversion table is used instead of the voltage V of the drive waveform data before conversion from the liquid chamber side of the electromechanical conversion element. Is converted into a surface displacement δ.
According to this, as described in the above embodiment, conversion from the voltage V of the drive waveform data before conversion to the surface displacement δ on the liquid chamber side of the electromechanical conversion element is performed while suppressing the data amount of the conversion table. It can be done reliably.
(Aspect F)
In the above aspect D, the conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other, and the voltage V of the drive waveform data before conversion is If not in the conversion table, linear interpolation of the surface displacements δp and δp + 1 on the liquid chamber side of the electromechanical conversion element corresponding to Vp and Vp + 1 respectively satisfying Vp ≦ V ≦ Vp + 1 among the voltages in the conversion table, The voltage V of the drive waveform data before conversion is converted into the surface displacement δ on the liquid chamber side of the electromechanical conversion element.
According to this, as described in the above embodiment, conversion from the voltage V of the drive waveform data before the conversion to the surface displacement δ on the liquid chamber side of the electromechanical conversion element while suppressing the data amount of the conversion table. Can be performed reliably.
(Aspect G)
In any one of the above aspects D to F, the conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other, and the electromechanical conversion before conversion When the surface displacement on the liquid chamber side of the element is not in the conversion table, the surface displacement closest to the surface displacement before the conversion among the surface displacements in the conversion table is substituted, and the electromechanical conversion element before the conversion The surface displacement on the liquid chamber side is converted into the voltage of the drive waveform data.
According to this, as described in the above embodiment, the conversion from the surface displacement on the liquid chamber side of the electromechanical conversion element before the conversion to the voltage of the drive waveform data is reliably performed while suppressing the data amount of the conversion table. It can be carried out.
(Aspect H)
In any one of the above aspects D to F, the conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other, and the electromechanical conversion before conversion When the surface displacement δ on the liquid chamber side of the element is not in the conversion table, Vq and Vq + 1 of the drive waveform data corresponding to δq and δq + 1 satisfying δq ≦ δ ≦ δq + 1, respectively, among the surface displacements in the conversion table. Conversion from the surface displacement δ on the liquid chamber side of the electromechanical conversion element before conversion to the voltage V of the drive waveform data is performed by linear interpolation.
According to this, as described in the above embodiment, the conversion from the surface displacement on the liquid chamber side of the electromechanical conversion element before the conversion to the voltage of the drive waveform data is reliably performed while suppressing the data amount of the conversion table. It can be carried out.
(Aspect I)
In any one of the above aspects B to H, the electromechanical conversion element is a thin film piezoelectric element in which the relationship between the drive signal and the surface displacement on the liquid chamber side is nonlinear.
According to this, as described in the above embodiment, even when the relationship between the drive signal applied to the thin film piezoelectric element and the surface displacement on the liquid chamber side of the thin film piezoelectric element is non-linear, Stable droplet ejection characteristics that are not affected can be obtained.
(Aspect J)
In any one of the above aspects A to I, the temperature detection means is provided inside the droplet discharge head. According to this, as described in the above embodiment, the detection accuracy with respect to the temperature of the liquid in the liquid chamber provided in the droplet discharge head can be increased, so that stable droplet discharge characteristics that are not affected by the temperature change can be obtained. It can be obtained more reliably.
(Aspect K)
An image forming apparatus including the droplet discharge device according to any one of the above-described aspects A to J as a droplet discharge device having a droplet discharge head for discharging droplets for image formation.
According to this, as described in the above embodiment, it is possible to achieve stable and high-quality image formation that is not affected by temperature changes while reducing costs.
(Aspect L)
In the above aspect K, the change timing of the drive waveform data based on the temperature detection result of the temperature detection means is set for each page of the recording medium such as the paper 3 on which an image is formed by droplets discharged from the droplet discharge head. Or, every plural pages.
According to this, as described in the above embodiment, it is possible to prevent the image quality from being deteriorated due to the change in the droplet discharge characteristics in the middle of the page of the recording medium.

1 Image forming apparatus main body 2 Printing mechanism (droplet discharge device)
14 Droplet ejection head 80 CPU
81 ROM
82 RAM
87 Drive signal generation circuit 88 Head drive circuit (driver IC)
92 Temperature Sensor 101 Main Control Unit 110 Nozzle Substrate 110a Nozzle 111 Individual Liquid Chamber Substrate 111a Individual Liquid Chamber 111b Fluid Resistance Unit 111c Liquid Supply Port 112 Protective Substrate 112a Recessed 112d Opening 113 Vibration Plate 114 Piezoelectric Element 114a Upper Electrode (Individual Electrode)
114b Piezoelectric layer (piezoelectric film)
114c Lower electrode (common electrode)

Japanese Patent Laid-Open No. 10-100401 JP-A-2-289351 Japanese Patent Laid-Open No. 10-202844 JP 2004-202884 A

Claims (12)

A liquid droplet ejection head having a nozzle for ejecting liquid droplets, a liquid chamber communicating with the nozzle, and a pressure generating means for changing the size of a physical parameter of a pressure generating mechanism for generating pressure in the liquid chamber according to a drive signal; ,
Drive signal output means for outputting a drive signal applied to the pressure generating means;
Storage means for storing drive waveform data of a drive signal corresponding to each of a plurality of temperatures;
Temperature detection means for detecting temperature;
Control means for controlling the drive signal output means so as to output the drive signal based on the temperature detection result of the temperature detection means and apply the drive signal to the pressure generating means,
The control means includes
Of the drive waveform data corresponding to each of the plurality of temperatures stored in the storage means, the drive corresponding to each of the temperatures Tn and Tn + 1 satisfying Tn ≦ Tx ≦ Tn + 1 for the detected temperature Tx detected by the temperature detecting means. Read waveform data,
Converting drive waveform data corresponding to each of the temperatures Tn and Tn + 1 to time change data of physical parameters of the pressure generating mechanism corresponding to the temperatures Tn and Tn + 1, respectively;
From the time change data of the physical parameters of the pressure generation mechanism corresponding to each of the temperatures Tn and Tn + 1, the time change data of the physical parameters of the pressure generation mechanism corresponding to the detected temperature Tx is obtained by linear interpolation,
Converting time change data of physical parameters of the pressure generating mechanism corresponding to the detected temperature Tx into drive waveform data corresponding to the detected temperature Tx;
A droplet discharge apparatus, wherein drive waveform data used for generating a drive signal to be applied to the pressure generating means is changed to drive waveform data corresponding to the detected temperature Tx after conversion. The droplet discharge device according to claim 1.
The pressure generating means is an electromechanical conversion element whose surface on the liquid chamber side is displaced so that a pressure for discharging a droplet from the nozzle is generated in the liquid chamber when the drive signal is applied. ,
The droplet discharge device, wherein the physical parameter of the pressure generating mechanism is a surface displacement of the electromechanical conversion element on the liquid chamber side. The droplet discharge device according to claim 2.
When the surface displacement on the liquid chamber side of the electromechanical transducer is δ [μm], the voltage of the drive signal is V [V], a _k [μm / V] is a constant, and m and n are real numbers. The liquid droplet ejection apparatus, wherein the conversion between the drive waveform data and the time change data of the surface displacement δ on the liquid chamber side of the electromechanical conversion element is performed using the following equation.
The droplet discharge device according to claim 2.
A droplet discharge apparatus, wherein conversion between the drive waveform data and time change data of surface displacement on the liquid chamber side of the electromechanical conversion element is performed using a conversion table provided in advance. The droplet discharge device according to claim 4.
The conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other,
When the voltage of the drive waveform data before conversion is not in the conversion table, the voltage closest to the voltage V of the drive waveform data before conversion among the voltages in the conversion table is substituted, and the drive waveform before conversion is converted. A droplet discharge device that performs conversion from a voltage of data into a surface displacement on a liquid chamber side of the electromechanical transducer. The droplet discharge device according to claim 4.
The conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other,
If the voltage V of the drive waveform data before conversion is not in the conversion table, the liquid chamber side of the electromechanical conversion element corresponding to Vp and Vp + 1 satisfying Vp ≦ V ≦ Vp + 1 among the voltages in the conversion table. A droplet discharge device characterized in that the voltage V of the drive waveform data before conversion is converted into the surface displacement δ on the liquid chamber side of the electromechanical conversion element by linear interpolation of surface displacements δp and δp + 1. In the droplet discharge device according to any one of claims 4 to 6,
The conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other,
When the surface displacement on the liquid chamber side of the electromechanical conversion element before conversion is not in the conversion table, the surface displacement closest to the surface displacement before conversion among the surface displacements in the conversion table is used as a substitute. A droplet discharge device that performs conversion from a surface displacement on the liquid chamber side of a previous electromechanical conversion element into a voltage of the drive waveform data. In the droplet discharge device according to any one of claims 4 to 6,
The conversion table stores the voltage of the drive waveform data and the surface displacement on the liquid chamber side of the electromechanical conversion element in association with each other,
When the surface displacement δ on the liquid chamber side of the electromechanical transducer before conversion is not in the conversion table, the drive waveforms corresponding to δq and δq + 1 satisfying δq ≦ δ ≦ δq + 1 among the surface displacements in the conversion table. A droplet discharge device characterized by converting the surface displacement δ on the liquid chamber side of the electromechanical conversion element before conversion into the voltage V of the drive waveform data by linear interpolation of data Vq and Vq + 1. In the droplet discharge device according to any one of claims 2 to 8,
The electromechanical conversion element is a thin film piezoelectric element in which the relationship between the drive signal and the surface displacement on the liquid chamber side is nonlinear. The droplet discharge device according to any one of claims 1 to 9,
The droplet discharge device, wherein the temperature detection means is provided inside the droplet discharge head.   An image forming apparatus comprising the liquid droplet ejection apparatus according to claim 1 as a liquid droplet ejection apparatus having a liquid droplet ejection head for ejecting liquid droplets for image formation. The image forming apparatus according to claim 11.
The change timing of the drive waveform data based on the temperature detection result of the temperature detecting means is every page or a plurality of pages of the recording medium on which an image is formed by droplets ejected from the droplet ejection head. An image forming apparatus.