JP2004106253A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a density difference occurs before and after switching the driving conditions in one page to cause deterioration in image quality. <P>SOLUTION: Drops stabilized against ambient temperature variation can be ejected through simple control by switching the driving conditions in units of sheet and providing a hysteresis in the switching of temperature compensation thereby eliminating such a deterioration of image quality as the density is varied in a sheet. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an inkjet recording device.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 10-202284 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-322265
2. Description of the Related Art An ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, and a plotter includes a nozzle for ejecting ink droplets and an ink flow path (ejection chamber, pressure chamber, pressurizing chamber) communicating with the nozzle. Chamber, liquid chamber, pressurizing chamber, etc.) and a pressure generating means for pressurizing the ink in the ink flow path.
[0004]
As an ink jet head, a piezoelectric element is used as a pressure generating means for pressurizing ink in an ink flow path, and a diaphragm forming a wall surface of the ink flow path is deformed to change a volume in the ink flow path to discharge ink droplets. The so-called piezo type, or the so-called thermal type, in which ink is ejected by pressure generated by heating ink in the ink flow path using an exothermic resistor to generate air bubbles, the wall of the ink flow path An electrostatic type in which a diaphragm and an electrode to be formed are opposed to each other, and the diaphragm is deformed by an electrostatic force generated between the diaphragm and the electrode, thereby changing a volume in an ink flow path and ejecting ink droplets. And others are known.
[0005]
By the way, since the ejection state of ink changes due to changes in physical properties such as viscosity depending on environmental temperature and the like, in an ink jet recording apparatus,
As disclosed in Patent Literature 1 and Patent Literature 2, drive waveforms generally provided to temperature generating means for the head based on the detected temperature are provided with temperature detecting means for detecting the environmental temperature. The temperature compensation for changing the driving conditions is performed by changing the parameters (1) and (2).
[0006]
Various methods for the temperature compensation differ depending on the head configuration, and various methods have been proposed, such as a method of changing a driving voltage of a driving waveform, a method of changing a pulse width, and a method of changing a gradation of print data.
[0007]
[Problems to be solved by the invention]
However, even when the temperature compensation is performed as described above, when the driving conditions are switched, a slight density difference occurs before and after the switching. Therefore, when the driving conditions are changed within one page, the density may become layered, and there is a problem that a slight difference greatly deteriorates the image quality.
[0008]
In this case, it is sufficient to perform compensation control as fine as possible so that the driving conditions change almost continuously. However, the control becomes complicated, and sensor accuracy is required and the cost increases. At the same time, in the ink jet recording apparatus, the driving elements (actuators and heating elements) of the recording head and the driver IC itself are heat sources, and there are various heat sources such as conveyance motors which can be disturbances in the recording apparatus. Adversely affects the image quality. Further, since the heat capacity of the ink is large, there is a certain difference between the ink temperature and the temperature detected by the sensor.
[0009]
The present invention has been made in view of the above points, and an object of the present invention is to provide an ink jet recording apparatus capable of performing stable droplet discharge regardless of an environmental temperature and easily compensating for a temperature.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, an inkjet recording apparatus according to the present invention has a configuration in which drive conditions are changed based on a detected temperature for each sheet, and switching of the drive conditions based on the detected temperature has hysteresis. is there. In this specification, the term “paper” is not limited to paper, but refers to a medium on which an image is recorded by adhering ink droplets. For example, besides paper, cloth, OHP, etc. Including films.
[0011]
Here, the width of the hysteresis is preferably in the range of 1/4 to 3/4 times the temperature compensation step width. Further, it is preferable to include a means for performing temperature detection a plurality of times within one sheet printing and notifying when the detected temperature changes by two or more temperature compensation steps. Further, when printing is started by releasing the capping of the head, it is preferable to determine the temperature compensation step at a boundary having no hysteresis.
[0012]
Further, it is preferable to set a driving condition in which the volume Mj of the ink droplet ejected from the head is small in a region lower than the image quality guarantee temperature range. Further, it is preferable that the head presses the ink in the pressurizing chamber to which the nozzle communicates with the electromechanical transducer.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus as an image recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of the mechanism.
[0014]
This ink jet recording apparatus includes a carriage that is movable in the main scanning direction inside the recording apparatus main body 1, a recording head including an inkjet head mounted on the carriage, an ink cartridge that supplies ink to the recording head, and the like. After storing the mechanism unit 2 and the like, taking in the paper 3 fed from the paper feed cassette 4 or the manual feed tray 5, recording the required image by the printing mechanism unit 2, the paper is transferred to the paper output tray 6 mounted on the rear side. Discharge paper.
[0015]
The printing mechanism 2 holds the carriage 13 slidably in the main scanning direction (the direction perpendicular to the paper surface in FIG. 2) by a main guide rod 11 and a sub guide rod 12, which are guide members that are laterally mounted on left and right side plates (not shown). The carriage 13 is provided with an ink jet head 14 for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet ejection direction directed downward. Each ink tank (ink cartridge) 15 for supplying each color ink to the head 14 is exchangeably mounted on the upper side of the carriage 13.
[0016]
The ink cartridge 15 has an upper air port that communicates with the atmosphere, a lower supply port for supplying ink to the inkjet head 14, and a porous body filled with ink inside. The ink supplied to the inkjet head 14 by the force is maintained at a slight negative pressure. The ink is supplied from the ink cartridge 15 into the head 14.
[0017]
Here, the carriage 13 is slidably fitted to the main guide rod 11 on the rear side (downstream side in the paper transport direction), and is slidably mounted on the front guide rod 12 (upstream side in the paper transport direction). are doing. 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 driven to rotate by a main scanning motor 17. , And the carriage 13 is reciprocated by the forward and reverse rotation of the main scanning motor 17.
[0018]
Although the heads 14 of each color are used here as the recording head, a single head having nozzles for ejecting ink droplets of each color may be used. Further, as described later, a diaphragm that forms at least a part of the wall surface of the ink flow path and a piezo-type inkjet head that deforms the diaphragm with a piezoelectric element are used as the head 14, but are not limited thereto. Alternatively, a thermal head, an electrostatic head, or the like can be used.
[0019]
On the other hand, in order to transport the paper 3 set in the paper cassette 4 to the lower side of the head 14, the paper 3 is guided by the paper feed roller 21 and the friction pad 22, which separate and feed the paper 3 from the paper cassette 4. A guide member 23, a transport roller 24 that reverses and transports the fed paper 3, a transport roller 25 pressed against the peripheral surface of the transport roller 24, and a leading end that defines an angle at which the paper 3 is sent out from the transport roller 24. A roller 26 is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.
[0020]
Further, there is provided a printing receiving member 29 which is a paper guide member for guiding the paper 3 sent from the transport roller 24 below the recording head 14 in accordance with the moving range of the carriage 13 in the main scanning direction. On the downstream side of the printing receiving member 29 in the paper transport direction, there are provided a transport roller 31 and a spur 32 that are driven to rotate in order to transport the paper 3 in the paper discharge direction. Rollers 33 and spurs 34 and guide members 35 and 36 forming a paper discharge path are provided.
[0021]
At the time of recording, the recording head 14 is driven in accordance with an image signal while moving the carriage 13 to discharge ink on the stopped paper 3 to record one line, and after the paper 3 is conveyed by a predetermined amount, the next paper is transported. Record the line. Upon receiving a recording end signal or a signal indicating that the rear end of the sheet 3 has reached the recording area, the recording operation is terminated and the sheet 3 is discharged.
[0022]
Further, a recovery device 37 for recovering from the ejection failure of the head 14 is disposed at a position outside the recording area on the right end side in the moving direction of the carriage 13. The recovery device 37 has a cap unit, a suction unit, and a cleaning unit. The carriage 13 is moved to the recovery device 37 side during printing standby, the head 14 is capped by the capping means, and the ejection opening (nozzle hole) is kept in a wet state, thereby preventing ejection failure due to ink drying. In addition, by discharging (purging) ink that is not related to printing during printing or the like, the ink viscosity of all the discharge ports is made constant, and stable discharge performance is maintained.
[0023]
When a discharge failure occurs, the discharge port (nozzle) of the head 14 is sealed by capping means, bubbles are sucked out of the discharge port with ink by a suction means through a tube, and ink or dust adhered to the discharge port surface. Is removed by the cleaning means, and the ejection failure is recovered. The sucked ink is discharged to a waste ink reservoir (not shown) provided at a lower portion of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.
[0024]
Next, an ink jet head constituting the recording head 14 of the ink jet recording apparatus will be described with reference to FIGS. FIG. 3 is an explanatory cross-sectional view of the head along the longitudinal direction of the liquid chamber, FIG. 4 is an explanatory cross-sectional view of the head along the lateral direction of the liquid chamber, and FIG. 5 is an explanatory plan view of a main part of the head.
[0025]
The inkjet head has a flow path plate 41 formed of a single crystal silicon substrate, a vibration plate 42 joined to the lower surface of the flow path plate 41, and a nozzle plate 43 joined to the upper surface of the flow path plate 41, With these, a nozzle 45 for ejecting ink droplets, which are liquid droplets, is connected to a pressurizing chamber 46 as an ink flow path communicating through a nozzle communication passage 45a, and a common liquid chamber 48 for supplying ink to the pressurizing chamber 46 is supplied to the ink chamber. An ink supply path 47 is formed as a fluid resistance portion that communicates via the supply port 49.
[0026]
Then, an electromechanical converter which is a pressure generating means (actuator means) for pressurizing ink in the pressurizing chamber 46 corresponding to each pressurizing chamber 46 on the outer surface side (the opposite side to the liquid chamber) of the vibration plate 42. A laminated piezoelectric element 52 as an element is joined, and this piezoelectric element 52 is joined to a base substrate 53. Further, between the piezoelectric elements 52, support columns 54 are provided corresponding to the partition walls 41a between the pressurizing chambers 46, 46. Here, the piezoelectric element member is divided into comb-tooth shapes by subjecting the piezoelectric element member to slit processing by half-cut dicing, and each of the piezoelectric element members is formed by a piezoelectric element 52 and a support portion 54. The structure of the support portion 54 is the same as that of the piezoelectric element 51, but is a simple support since no drive voltage is applied.
[0027]
Further, the outer peripheral portion of the diaphragm 42 is joined to the frame member 44 by an adhesive 50 including a gap material. The frame member 44 has a recess serving as a common liquid chamber 48 and an ink supply hole (not shown) for supplying ink to the common liquid chamber 48 from outside. The frame member 44 is formed by injection molding of, for example, epoxy resin or polyphenylene sulphite.
[0028]
Here, for example, the channel plate 41 is formed by anisotropically etching a single crystal silicon substrate having a crystal plane orientation of (110) using an alkaline etching solution such as an aqueous solution of potassium hydroxide (KOH) to form a nozzle communication passage 45a, The pressure chamber 46 and the concave portion and the hole serving as the ink supply path 47 are formed. However, the present invention is not limited to a single crystal silicon substrate, and other stainless steel substrates and photosensitive resins can be used.
[0029]
The vibration plate 42 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). However, other vibration members such as a metal plate, a resin plate, or a joining member between a metal and a resin plate may be used. It can also be used. The vibration plate 42 has a thin portion (diaphragm portion) 55 for facilitating deformation and a thick portion (island-shaped convex portion) 56 for joining with the piezoelectric element 52 at a portion corresponding to the pressurizing chamber 46. At the same time, a thick portion 57 is also formed at a portion corresponding to the support portion 54 and a joint portion with the frame member 44, the flat surface side is bonded to the flow channel plate 41 with an adhesive, and the island-shaped convex portion 56 is formed with the piezoelectric element 52. The thick portion 57 is further joined to the support portion 54 and the frame member 44 with an adhesive 50. Here, the diaphragm 42 is formed by nickel electroforming of a two-layer structure. In this case, the thickness of the diaphragm 55 is 3 μm and the width is 35 μm (one side).
[0030]
The nozzle plate 43 forms a nozzle 45 having a diameter of 10 to 35 μm corresponding to each pressurizing chamber 46 and is bonded to the flow path plate 41 with an adhesive. As the nozzle plate 43, a metal such as stainless steel or nickel, a combination of a metal and a resin such as a polyimide resin film, silicon, or a combination thereof can be used. Here, it is formed by a Ni plating film or the like by an electroforming method. Further, the inner shape (inner shape) of the nozzle 43 is formed in a horn shape (a substantially columnar shape or a substantially truncated cone shape), and the hole diameter of the nozzle 45 is about 20 to about the diameter on the ink droplet outlet side. It is 35 μm. Further, the nozzle pitch of each row was 150 dpi.
[0031]
In addition, a water-repellent treatment layer (not shown) that has been subjected to a water-repellent surface treatment is provided on the nozzle surface (surface in the discharge direction: discharge surface) of the nozzle plate 43. Examples of the water-repellent layer include PTFE-Ni eutectoid plating, electrodeposition coating of a fluororesin, evaporation-coated fluororesin (for example, pitch fluoride), silicon-based resin and fluorine-based resin. A water-repellent treatment film selected according to the physical properties of the ink, such as baking after the application of a solvent, is provided to stabilize the ink droplet shape and flying characteristics and obtain high-quality image quality.
[0032]
The piezoelectric element 52 includes a piezoelectric layer 61 of lead zirconate titanate (PZT) having a thickness of 10 to 50 μm / 1 and an internal electrode layer 62 of silver / palladium (AgPd) having a thickness of several μm / 1. The internal electrodes 62 are alternately stacked, and are electrically connected alternately to the individual electrodes 63 and the common electrodes 64 which are end electrodes (external electrodes) on the end surfaces. The pressurizing chamber 46 is contracted and expanded by the expansion and contraction of the piezoelectric element 52 whose piezoelectric constant is d33. When a drive signal is applied to the piezoelectric element 52 and charging is performed, the piezoelectric element 52 expands, and when the electric charge charged to the piezoelectric element 52 discharges, it contracts in the opposite direction.
[0033]
In addition, the end face electrode on one end face of the piezoelectric element member is divided into individual electrodes 63 by dicing processing by half-cutting, and the end face electrode on the other end face is not divided by the restriction of processing such as notch and is divided by all the piezoelectric elements 52. The conductive common electrode 64 is formed.
[0034]
An FPC cable 65 is connected to the individual electrodes 63 of the piezoelectric element 52 by solder bonding, ACF (anisotropic conductive film) bonding, or wire bonding in order to supply a drive signal. Is connected to a drive circuit (driver IC) for selectively applying a drive waveform. The common electrode 64 is provided with an electrode layer at an end of the piezoelectric element and is turned around to be connected to a ground (GND) electrode of the FPC cable 65.
[0035]
In the ink jet head configured as described above, for example, by applying a drive waveform (pulse voltage of 10 to 50 V) to the piezoelectric element 52 in accordance with a recording signal, a displacement in the stacking direction occurs in the piezoelectric element 52, and vibration is generated. The ink in the pressurizing chamber 46 is pressurized via the plate 42, the pressure increases, and ink droplets are ejected from the nozzle 45.
[0036]
Thereafter, with the end of the ink droplet ejection, the ink pressure in the pressurizing chamber 46 is reduced, and a negative pressure is generated in the pressurizing chamber 46 due to the inertia of the ink flow and the discharge process of the driving pulse, and the ink filling process is started. Transition. At this time, ink supplied from an ink tank (not shown) flows into the common liquid chamber 48, passes through the ink supply port 49 from the common liquid chamber 47, passes through the fluid resistance part 47, and is filled into the pressurizing chamber 46.
[0037]
The fluid resistance portion 47 is effective in attenuating the residual pressure vibration after ejection, but is resistant to refilling due to surface tension. By appropriately selecting the fluid resistance value of the fluid resistance unit 47, the balance between the attenuation of the residual pressure and the refill time can be achieved, and the time (drive cycle) until the transition to the next ink droplet ejection operation can be shortened.
[0038]
Next, an outline of a control unit of the inkjet recording apparatus will be described with reference to FIG.
The control unit includes a microcomputer (hereinafter, referred to as a “CPU”) 80 for controlling the entire recording apparatus, a ROM 81 storing required fixed information, a RAM 82 used as a working memory, and the like. An image memory (lass data memory) 83 for storing image data (referred to as dot data or dot pattern data) to be transferred; a parallel input / output (PIO) port 84; a parallel input / output (PIO) port 86; A generating circuit 87, a head driving circuit 88, a driver 89, and the like are provided.
[0039]
The PIO port 84 receives various information and data such as image data transferred from the printer driver of the host, various instructions from the operation panel 90, selection information, and various sensors such as a temperature sensor 92 for detecting an environmental temperature. And the like, and necessary information is transmitted to the host and the operation panel 90 through the PIO port 84. Here, the operation panel 90 is provided with notification means 91 such as a display lamp.
[0040]
The drive waveform generation circuit 87 generates and outputs a drive waveform to be applied to the piezoelectric element 52 of the recording head 14. As will be described later, the drive waveform generating circuit 87 can generate and output a required drive waveform with a simple configuration by using a D / A converter for D / A converting the drive waveform data from the CPU 80. it can.
[0041]
The head drive circuit (driver IC) 88 drives the drive waveform from the drive waveform generation circuit 87 for the piezoelectric element 52 of the selected channel of the recording head 14 based on various data and signals provided via the PIO port 86. Is applied. Further, the driver 89 moves and scans the carriage 13 in the main scanning direction by controlling the driving of the main scanning motor 17 and the sub-scanning motor 27 in accordance with the driving data provided via the PIO port 86, respectively. Is rotated to convey the sheet 3 by a predetermined amount.
[0042]
A part of the control unit related to head drive control will be described with reference to FIG.
[0043]
The main control unit 101 processes font data (dot data) as print data sent from the host side, performs vertical / horizontal conversion corresponding to the arrangement of the heads, and converts ink droplets into large droplets, small droplets, It generates 2-bit drive data SD necessary for separating the three values of printing and outputs it to the head drive circuit (driver IC) 88. In addition, for the driver IC 88, a clock signal CLK, a latch signal LAT, a driving waveform corresponding to a dot (large droplet) of a size forming an image dot as a driving waveform, and a driving waveform corresponding to a small droplet are selected. To output drive waveform selection signals M1 to M3 for performing the operation.
[0044]
Further, the main control unit 101 reads the drive waveform data stored in the internal ROM 81 and supplies the read drive waveform data to the drive waveform generation circuit 87. In this case, the internal ROM 81 stores data of a plurality of types of driving waveforms having different parameters (driving conditions) according to the temperature, and the main control unit 101 determines the environmental temperature based on a detection signal from the temperature sensor 92. Is detected, and one drive waveform data is selected from a plurality of types of drive waveform data based on the detected temperature (detected temperature) and supplied to the drive waveform generation circuit 87.
[0045]
The drive waveform generation circuit 87 D / A converts the drive waveform data supplied from the main control unit 101 and outputs it as an analog signal, and converts the analog signal from the D / A converter 102 into an actual drive voltage. And a current amplifier 104 that amplifies the amplified output so as to supply a sufficient current by driving the head, generates a drive waveform Pv including a plurality of drive pulses in one drive cycle, and generates a driver IC 88 Give to.
[0046]
Although not shown, the driver IC (head drive circuit) 88 includes a shift register that captures drive data SD in response to a clock signal CLK from the main control unit 101, and a latch circuit that latches a register value of the shift register with a latch signal LAT. A data selector for selecting drive waveform selection signals M1 to M3 (logic signals) based on the 2-bit drive data latched by the latch circuit, a level shifter for converting an output (logic signal) of the data selector to a drive voltage level, And a transmission gate whose on / off is controlled by the output of the level shifter. The transmission gate is supplied with a drive waveform Pv from a drive waveform generation circuit 87 and is connected to a piezoelectric element 52 corresponding to each nozzle of the recording head (inkjet head) 14.
[0047]
Therefore, in the head drive circuit 88, one of the drive waveform selection signals M1 to M3 is selected by the data selector according to the drive data SD, and the selected drive waveform selection signals M1 to M3, which are logic signals, are driven by the level shifter. Convert to level and give to transmission gate. As a result, the transmission gate is switched according to the length of the selected drive waveform selection signals M1 to M3, so that the drive waveform Pv is formed for the piezoelectric element 52 of the channel whose transmission gate is open. A driving pulse will be applied.
[0048]
Next, temperature compensation in the ink jet recording apparatus will be described with reference to FIG.
First, a driving waveform for temperature compensation stored in the ROM 81 of the main control unit 101 will be described with reference to FIG. This figure shows a waveform a applied when the detected temperature is 15 ° C. to 18 ° C. and a waveform b applied when the detected temperature is 10 ° C. to 15 ° C. In the other temperature ranges, drive waveforms are similarly set and drive waveform data is stored.
[0049]
In this ink jet recording apparatus, a piezoelectric element, which is an electromechanical transducer, is used as the pressure generating means of the head, so that the temperature compensation varies the voltage values of the drive waveforms, that is, the drive waveforms having different voltage waveforms are based on the detected temperature. It can be done easily by switching.
[0050]
As described above, as the head, a thermal head or an electrostatic head can be used, but these heads cannot be controlled by simple drive waveform parameters such as a voltage value or a pulse width. The head using the piezoelectric element can be set to a relatively large temperature compensation step width, the temperature compensation becomes simple, the storage capacity of the drive waveform data is small, and the capacity of the storage means is small.
[0051]
In this case, the drive waveform data for temperature compensation is stored in advance in a storage unit such as a ROM of the printing apparatus main body. However, a configuration in which the drive waveform data is transferred from the printer driver on the host side to the printing apparatus may be adopted. it can.
[0052]
Next, a first example of temperature compensation will be described with reference to FIG. In this example, the step of changing the driving condition by temperature (temperature compensation step) is divided into eight steps, one step is set to 5 ° C., and the switching of the steps is provided with hysteresis. The driving condition is switched based on the pattern c shown by the symbol. If the temperature rises, the driving condition is switched based on the pattern d shown by the broken line. The hysteresis width is set to 2 ° C.
[0053]
Therefore, for example, when the temperature rises from 12 ° C. to 18 ° C., the step is changed to 16 ° C. based on the pattern d, so that the drive waveform b for the temperature range of 10 ° C. to 15 ° C. When the temperature exceeds 16 ° C., the drive waveform a is switched to the drive waveform a for the temperature range of 15 ° C. to 20 ° C.
[0054]
On the other hand, when the temperature drops from 18 ° C. to 12 ° C., the step is changed at 14 ° C. based on the pattern c. When the temperature is lower than 14 ° C., the drive waveform is switched to the drive waveform b for the temperature range of 10 ° C. to 15 ° C.
[0055]
In addition, the temperature compensation is performed for each sheet (for each page). When recording on a sheet, (1) transporting the sheet to a predetermined position, (2) printing, and (3) discharging the sheet are one integrated basic control sequence.
[0056]
Here, the control can be performed more easily by performing temperature compensation during (1) paper transport than by a method of detecting and compensating for the temperature at regular intervals.
[0057]
On the other hand, it is conceivable that temperature compensation is not performed in a series of printing processes including a plurality of pages as a unit. In this case, since the driving waveform does not change, there is a possibility that the density gradually changes at the environmental temperature, but it is not noticeable because it does not change rapidly. However, when the ink jet recording apparatus is used as a network printer, when printing data is sent from a plurality of hosts and the printing is nested, it is necessary to determine how far a printing process should be performed. The control becomes very complicated, such as whether the print processing for one sheet and the print processing for 100 sheets may be handled as the same series, whether the number is limited, or how to handle a sheet conveyance failure (paper jam). Since the control sequence for each sheet is a basic unit of printing as in the present invention, the control can be simplified and changed easily by including the temperature compensation control therein.
[0058]
Further, when temperature compensation (drive waveform replacement) is performed for each scan of the carriage as a finer control unit, the image density may become stratified even with a slight difference in ink droplet amount Mj due to switching, so that it is conspicuous. However, the image quality is greatly deteriorated. In other words, it is better to use the same drive waveform in the paper, even if the environmental temperature changes, since there is no sudden change, the continuity is maintained, and a striking pattern like a layer does not appear on the image, This has higher image quality.
[0059]
Furthermore, even if the temperature compensation (swapping of drive waveforms) is performed for each sheet, if the drive waveform is switched for each sheet, a slight difference in density occurs, resulting in an undesirable result as a group of printed matter. In other words, although temperature compensation is necessary, it is preferable that the switching be minimized. In practice, the temperature does not change so much because the heat capacity of the ink is large.
[0060]
However, the ambient temperature may be near the boundary of the temperature compensation step, and the sensor detection temperature may frequently exceed the boundary due to disturbance. As described above, the disturbance includes a heat source such as an actuator of a recording head, a driver IC, and a paper conveyance motor, and electric noise superimposed on a temperature detecting unit.
[0061]
Therefore, in the present invention, the influence of disturbance is prevented by performing temperature compensation for each sheet and providing hysteresis at the time of switching the temperature compensation step. Further, when the environmental temperature is changing, the ink temperature can absorb a temperature difference that follows with a delay.
[0062]
Although the recording head of the electromechanical transducer has been described, switching of the temperature compensation is the same for a thermal head and an electrostatic head. Further, although a specific temperature compensation method has been described by exchanging the data of the drive waveform, the temperature compensation may be performed by a circuit such as switching of an amplifier gain, or a method of converting gradation data and transferring it to a recording head. The compensation method itself is not particularly limited.
[0063]
Here, the temperature range is set at equal intervals in eight stages of temperature compensation steps, but the number of steps may be increased or the temperature range may be set at irregular intervals.
[0064]
FIG. 10 shows an example of the processing of this example. That is, when the paper is fed, that is, when the paper is transported to the predetermined position, the temperature is detected based on the detection signal of the temperature sensor 92, and the detected temperature is compared with the previous detected temperature that is maintained. It is determined whether the temperature is rising or falling. If the temperature is rising, the temperature compensation pattern d is selected, and the drive waveform corresponding to the detected temperature is selected. Then, a drive waveform corresponding to the detected temperature is selected.
[0065]
As described above, the temperature compensation switching (switching of the driving conditions) is provided with hysteresis, and the temperature compensation is performed for each sheet. , A stable drop can be ejected, and the temperature compensation step can be prevented from changing for each sheet due to disturbance.
[0066]
Next, the hysteresis width will be described with reference to FIG.
In this example, the hysteresis width is set to 3.6 ° C. It was confirmed that even in the switching of the temperature compensation step in this case, there was no occurrence of a large density difference between the sheets, deteriorating the image quality, or causing ejection failure due to insufficient temperature compensation.
[0067]
Originally, the way to divide the temperature range when creating the temperature compensation table is such that the boundary temperature is set at a temperature interval that will extremely deteriorate the drop formation state or cause a clear density difference regardless of the classification. Setting is not preferred. It is necessary to provide a sufficient margin for a temperature change of half the temperature compensation step width.
[0068]
Therefore, when an experiment was conducted to determine how far apart the drive waveform was used, the difference in concentration and the like became clear, and it was concluded that a difference appeared when the temperature compensation step width was separated. .
[0069]
Therefore, it is preferable that the hysteresis width is within a maximum of 3/4 times the temperature compensation step.
[0070]
On the other hand, if the hysteresis width is small, the hysteresis width is more than 1/4 of the temperature compensation step, though depending on the cause of the disturbance since the influence of the disturbance is likely to occur.
[0071]
Accordingly, by setting the hysteresis width within the range of 1/4 to 3/4 of the temperature compensation step, an extreme change in density or the like does not occur when the environmental temperature changes, and the temperature assurance step can be smoothly performed. Switching can be performed, and the temperature compensation step is hardly switched due to disturbance, and droplets can be discharged stably with respect to environmental temperature changes by simple control.
[0072]
When the temperature step intervals are unequal, it is preferable to change the hysteresis width for each temperature compensation step width. However, if the temperature step interval is within the range of 1/4 to 3/4, the hysteresis width is commonly used. You can also.
[0073]
Next, considering the changing speed of the environmental temperature and the printing speed, it is extremely rare that the temperature changes as the temperature compensation step changes by two or more steps while printing one sheet of paper, and it is determined that the temperature is abnormal. be able to.
[0074]
Therefore, as described above, the temperature is detected and the temperature compensation step is switched before the start of printing, but the temperature is detected (reading of the sensor signal) for each scan (one scan). However, even if the temperature compensation step is shifted by one step in consideration of hysteresis within one sheet, the drive waveform is not switched.
[0075]
Then, it is preferable that the temperature detection is continued as it is, and when the temperature changes by two or more steps, an interrupt is issued to cause the notification means 91 of the operation panel 90 to notify the abnormality. In this case, since there is a high possibility of some malfunction such as sensor detection, the user is prompted to restart the recording device.
[0076]
The temperature detection during printing of the paper may be performed at each scan as described above, or the temperature may be detected at regular intervals after the temperature detection is performed before the printing for the temperature compensation step switching. . Further, the notification means is provided on the operation panel, but the notification means is not limited to this.
[0077]
In this way, by performing temperature detection and error determination, useless printing due to malfunction can be prevented, and time due to paper, ink, and misprint can be saved.
[0078]
When the recording head is capped by the head reliability maintaining mechanism, the capping is released and the recording is started on the first sheet, and the determination of the temperature compensation step for the first sheet has no hysteresis. It is preferable to perform at the boundary.
[0079]
That is, for example, in the relationship between the detected temperature and the temperature compensation step in FIG. 8 described above, for the detected temperature of 11 ° C., either step 2 can be interpreted when the temperature rises, and step 3 can be interpreted when the temperature falls. For the first sheet, step 3 is selected with 10 ° C. as the boundary.
[0080]
When hysteresis is used, a history of the temperature compensation step is required, and there is a method in which the temperature is detected at predetermined time intervals and the history is recorded even in a standby state in which the recording head is capped. However, in this case, there is a problem that the control becomes complicated, such as what to do with the history from power-off to power-on (even if the power-off step is stored, it does not become a temperature change history). Occurs.
[0081]
In general, the recording head is capped during standby to prevent drying of the ink in the nozzles. Simple control can be realized by defining the first sheet to be printed after releasing the capping and initializing the temperature detection result. In the case of initialization, since the subsequent temperature rise / fall cannot be predicted, it is preferable to set at a boundary where no hysteresis is used.
[0082]
As described above, for the first sheet (the first sheet after the capping is released), the temperature compensation step is determined at a boundary having no hysteresis. However, temperature compensation can be appropriately performed.
[0083]
Next, a case where the temperature is low will be described. FIG. 12 shows an example of the temperature dependence of the ink viscosity. As described above, the main purpose of the temperature compensation is to compensate for a change in the viscosity of the ink due to the temperature, and to secure the same ink droplet amount Mj and ink droplet speed Vj regardless of the temperature change.
[0084]
However, if the temperature is too low, the viscosity may be too high and a desired droplet may not be ejected, and this temperature range is outside the image quality guarantee range. At this time, it is also difficult to secure the flow rates of the common liquid chamber and the individual liquid chambers. Note that the image quality guarantee range is a temperature range that achieves the image quality specifications and is described in a catalog. In the example shown in FIG. 12, the image quality guarantee range is 5 ° C. to 32 ° C., and the temperature lower than 5 ° C. is outside the low temperature image quality guarantee range.
[0085]
In this case, the drive sequence is set in advance so that small droplets Mj are ejected without changing the control sequence even outside the image quality guarantee range. In particular, the size of the maximum amount of large ink droplets that restricts the flow rate is set small in advance.
[0086]
Originally, since the droplets are hardly ejected, they are out of the image quality assurance range. Therefore, it is difficult to forcibly adjust the ink droplet amount Mj (density in terms of an image), and unstable ejection is more likely to occur. Since the flow rate is sufficient, it is necessary to reduce the droplet amount or the printing speed, but having a separate moving speed of the carriage complicates the control. On the other hand, since the ink droplet amount Mj can be adjusted only by the driving waveform data, the control can be performed in the same manner as the image quality guarantee range only by setting the ink droplet amount Mj to a small value. Is simplified.
[0087]
In addition, for an ink having a viscosity of 5 cP or more at 20 ° C., it is particularly necessary to set the ink droplet amount Mj outside the low-temperature image quality guarantee range to a small value. That is, when the ink having a high viscosity lands on paper, the ink penetrates at a low speed due to the capillary force, whereby a high-quality image with little bleeding can be formed. However, in general, ink having a high viscosity at room temperature (around 20 ° C.) tends to have a greater change in viscosity with temperature. This is because those used for viscosity adjustment, such as glycerin, have a large change in viscosity with temperature.
[0088]
Therefore, in particular, in an ink jet recording apparatus using an ink whose viscosity is prescribed to be 5 cP or more in order to obtain high image quality while suppressing bleeding in the image quality guarantee range, the low temperature image quality is out of the guarantee range (less than 5 ° C. in this example). It is preferable to set the ink droplet amount Mj in ()) lower than the normal temperature.
[0089]
Further, as shown in FIG. 11, when the temperature is lower than 5 ° C., the viscosity increases more rapidly. Therefore, it is preferable to increase the temperature compensation steps outside the guaranteed low-temperature image quality range, such as 5 ° C. to 2 ° C. and less than 2 ° C., to decrease the ink droplet amount Mj stepwise.
[0090]
【The invention's effect】
As described above, according to the inkjet recording apparatus of the present invention, the hysteresis is provided for the switching of the temperature compensation, and the temperature is compensated for each sheet. In addition, it is possible to discharge droplets that are stable against environmental temperature changes with simple control.
[Brief description of the drawings]
FIG. 1 is an explanatory perspective view showing an example of a mechanism section of an ink jet recording apparatus according to the present invention. FIG. 2 is a side sectional explanatory view of a mechanism section of the recording apparatus. FIG. 3 is an ink jet constituting a recording head of the recording apparatus. FIG. 4 is an explanatory cross-sectional view of a head taken along a long side direction of a liquid chamber, illustrating an example of the head. FIG. 4 is an explanatory cross-sectional view of the head taken along a short side direction of a liquid chamber. FIG. 7 is a block diagram illustrating an outline of a control unit of the recording apparatus. FIG. 7 is a block diagram of a part related to head drive control of the control unit. FIG. 8 is an explanatory diagram illustrating an example of a drive waveform. FIG. 10 is a flowchart illustrating an example of a temperature compensation process. FIG. 11 is an explanatory diagram illustrating another example of a temperature compensation pattern. FIG. 12 is an explanation illustrating a relationship between ink viscosity and temperature. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 13 ... Carriage, 14 ... Recording head, 41 ... Flow path plate, 42 ... Vibration plate, 43 ... Nozzle plate, 45 ... Nozzle, 46 ... Pressurizing chamber, 47 ... Fluid resistance part, 48 ... Common liquid chamber, 52 ... Piezoelectric Element, 87 ... Drive waveform generation circuit.

Claims (6)

In an ink jet recording apparatus provided with means for changing a driving condition of a head for discharging ink droplets based on a detected temperature, a driving condition based on the detected temperature is changed for each sheet, and a driving condition based on the detected temperature is changed. An ink jet recording apparatus characterized in that switching has hysteresis. 2. The ink jet recording apparatus according to claim 1, wherein the width of the hysteresis is in a range of 1/4 to 3/4 of a temperature compensation step width. 3. The ink jet recording apparatus according to claim 1, further comprising means for performing temperature detection a plurality of times within one sheet printing, and notifying when the detected temperature changes by two or more temperature compensation steps. An inkjet recording apparatus characterized by the above-mentioned. 4. The ink-jet recording apparatus according to claim 1, wherein, when printing is started by releasing the capping of the head, the temperature compensation step is determined at a boundary having no hysteresis. apparatus. 5. The ink jet recording apparatus according to claim 1, wherein a driving condition is set such that a volume Mj of an ink droplet ejected from the head is reduced in a region lower than an image quality guarantee temperature range. apparatus. 6. An ink jet recording apparatus according to claim 1, wherein said head presses ink in a pressurized chamber to which said nozzle communicates by an electromechanical transducer.

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