JP4082541B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus capable of providing a drive waveform corresponding to an ink ambient temperature.
[0002]
[Prior art]
An ink jet recording apparatus used as an image recording apparatus or an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a plotter has a nozzle for discharging ink droplets and a discharge chamber (pressure chamber, pressurized liquid chamber, liquid chamber) communicating with the nozzle. And an energy generation means for generating energy for pressurizing the ink in the discharge chamber, and driving the energy generation means to pressurize the ink in the discharge chamber to thereby form a nozzle hole. Ink-on-demand systems, which eject ink droplets only when recording is necessary, are the mainstream.
[0003]
In such an ink jet head, the ink ejection amount and the ink droplet ejection speed are greatly influenced by the ambient temperature of the head (also referred to as the ambient temperature of the ink, which means the temperature of the head itself) or the ink temperature. The ejection amount and the ink droplet ejection speed are important factors that determine the dot diameter and dot position accuracy, and the image quality may deteriorate when the ambient temperature or the ink temperature changes.
[0004]
Therefore, conventionally, a method has been employed in which the head ambient temperature is detected and the drive waveform is controlled in accordance with the detected temperature so that the dot diameter and dot position system are constant. In a liquid jet recording apparatus in which a recording head having a temperature detecting element for detecting the temperature of the recording head is detachable as described in JP-A-2-17852, the characteristics of the temperature detecting element are related. By providing a determination means for determining a correction value, and a control means for outputting a control signal for controlling the temperature of the print head in accordance with the correction value determined by the determination means and the detection output of the temperature detection element, It is known to improve temperature detection accuracy.
[0005]
[Problems to be solved by the invention]
However, the head characteristics largely depend on changes in physical properties (surface tension, viscosity, etc.) due to temperature changes of the ink itself. For example, if a device left in a room with high temperature is moved to a room with low temperature, it takes time for the temperature of the ink itself to follow the temperature of the head and its surroundings. Then, although the temperature of the ink itself is still high, the detected temperature is low, so the ink temperature is judged to be low and the head is driven at a low temperature setting. Alternatively, when printing is started immediately after turning on the heating in the morning in winter, the detected temperature becomes high regardless of the ink temperature itself being low, so the ink temperature is judged to be high and the head is set at a high temperature setting. Will drive.
[0006]
As described above, since it takes time to follow the ink ambient temperature (detected temperature) detected by the ink temperature, image quality deteriorates if printing is started before the ink temperature follows the ink ambient temperature. become. In this case, it is very difficult to directly detect the temperature of the ink itself.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to maintain a high image quality by setting an appropriate driving waveform according to the ink temperature.
[0008]
[Means for Solving the Problems]
  In order to solve the above problems, an ink jet recording apparatus according to the present invention includes:A temperature detecting means for detecting the ambient temperature of the ink, a measuring means for measuring an elapsed time from when the power is turned off, a detected temperature before turning on after the power is turned on and before starting printing, and a detected temperature immediately before turning off the power When the difference between the detected temperatures is equal to or less than a predetermined value, the detected temperature immediately before the power is turned off is determined as the ink temperature, and when the difference between the detected temperatures exceeds a predetermined value, the detected temperature immediately before the power is turned off. And a means for determining the ink temperature based on the detected temperature and the elapsed time since the power was turned off.
[0009]
  Here, the inkjet head according to the determined ink temperatureDrop droplets fromIt is preferable to provide means for adjusting the driving waveform..
[0010]
  The inkjet recording apparatus according to the present invention isThe temperature detection means for detecting the ambient temperature of the ink is compared with two detected temperatures at each time before and after the elapse of a predetermined time after the power is turned on, and when the difference between the detected temperatures is equal to or less than a predetermined value, When the detected temperature at the time is determined as the ink temperature and the difference between the detected temperatures exceeds a predetermined value, the detected temperature at the time after the predetermined time has elapsed, the elapsed time from the same time, and the detection at this elapsed time temperatureBased onAnd a means for determining the ink temperature.
[0011]
  Here, the inkjet head according to the determined ink temperatureDrop droplets fromIt is preferable to provide means for adjusting the driving waveform..
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a mechanism portion of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side view of the mechanism portion.
[0013]
The 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 that includes an ink jet head mounted on the carriage, an ink cartridge that supplies ink to the recording head, and the like. A sheet feeding cassette (or a sheet feeding tray) 4 capable of stacking a large number of sheets 3 from the front side can be removably attached to the lower part of the apparatus main body 1. Further, the manual feed tray 5 for manually feeding the paper 3 can be opened, the paper 3 fed from the paper feed cassette 4 or the manual feed tray 5 is taken in, and a required image is displayed by the printing mechanism section 2. After recording, the paper is discharged to a paper discharge tray 6 mounted on the rear side.
[0014]
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). The carriage 13 has a head 14 composed of an inkjet head for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet discharge direction directed downward. Each ink tank (ink cartridge) 15 for supplying ink of each color to the head 14 is replaceably mounted on the carriage 13.
[0015]
Here, the carriage 13 is slidably fitted to the main guide rod 11 via a bearing 16 on the rear side (downstream side in the paper conveyance direction), and the front side (downstream side in the paper conveyance direction) is slid on the slave guide rod 12. It is placed freely. 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. It is fixed to.
[0016]
Further, although the heads 14 of the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used. Furthermore, the ink jet head used as the head 14 pressurizes the ink through a vibration plate that forms a liquid chamber wall surface by an electromechanical transducer such as a piezoelectric element, or generates a bubble by film boiling by a heating resistor to generate ink. A pressurizing device or a device that pressurizes ink by displacing the vibrating plate with an electrostatic force between a vibrating plate forming a liquid chamber wall surface and an electrode facing the vibrating plate can be used. In this embodiment, an inkjet head using a piezoelectric element is used.
[0017]
On the other hand, in order to convey the paper 3 set in the paper feed cassette 4 to the lower side of the head 14, the paper feed roller 21 and the friction pad 22 for separating and feeding the paper 3 from the paper feed cassette 4 and the paper 3 are guided. A guide member 23, a transport roller 24 that reverses and transports the fed paper 3, a transport roller 25 that is pressed against the peripheral surface of the transport roller 24, and a transport that defines the feed angle of the paper 3 from the transport roller 15. A roller 26 is provided. The transport roller 24 is rotationally driven by a sub-scanning motor 27 through a gear train.
[0018]
A printing receiving member 29 is provided as a paper guide member for guiding the paper 3 fed from the transport roller 24 below the recording head 14 in accordance with the range of movement of the carriage 13 in the main scanning direction.
[0019]
A conveyance 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 conveyance direction, and the paper 3 is further delivered to the paper discharge tray 6. A roller 33 and a spur 34, and guide members 35 and 36 that form a paper discharge path are disposed.
[0020]
A subsystem 37 for maintaining and recovering the reliability of the head 14 is disposed on the right end side in the movement direction of the carriage 13. The carriage unit 13 is moved to the subsystem 37 side during standby, and the head 14 such as capping means is capped.
[0021]
Next, an outline of the control unit of the ink jet recording apparatus will be described with reference to FIG. The control unit includes a microcomputer (hereinafter referred to as “CPU”) 40 that controls the entire recording apparatus, a ROM 41 that stores necessary fixed information, a RAM 42 that is used as a working memory, and image information. An image memory 43 for storing processed data, a parallel input / output (PIO) port 44, an input buffer 45, a gate array (GA) or parallel input / output (PIO) port 46, a head drive circuit 47 and a driver 48, A timer 49 and the like are provided.
[0022]
Here, the CPU 40 adjusts the driving waveform, the temperature detecting means for detecting the ink ambient temperature using the temperature detecting element 51, the measuring means for measuring the elapsed time from when the power is turned off using the timer 49, and the ink temperature. It also serves as a means for calculating. The ROM 41 stores a correction table 41a used for setting parameters for adjusting the drive waveform. Further, a part of the RAM 42 includes a nonvolatile memory 42a, for example, a battery backup RAM, an EEPROM, and the like.
[0023]
The PIO port 44 includes image information from the host side, data such as paper type data indicating the paper type, various instruction information from an operation panel (not shown), and a paper presence / absence sensor that detects the start and end of the paper. Detection signals, signals from various sensors such as a home position sensor for detecting the home position (reference position) of the carriage 5, and the like, and a necessary signal is sent to the host side and the operation panel side via the PIO port 44. Information is sent out.
[0024]
Further, the head drive circuit 47 provides energy generation means (a piezoelectric element is used in this embodiment) corresponding to each nozzle of the head 14 based on various data and signals given through the PIO port 46. Apply a drive waveform. Further, a detection signal of the temperature detecting element 51 including a thermistor for detecting the ambient temperature of the ink is input via the PIO port 46, and rank information indicating the head rank preset in the head 14 is input to the PIO port 46. To enter through.
[0025]
Here, the temperature detection element 51 is provided on the carriage 13 as shown in FIG. 1 to detect the ambient temperature of the ink. However, the temperature detection element may be attached to the head 14 or the apparatus main body. A temperature detection element may be provided at any one of the locations. In short, it is only necessary to detect the temperature of the environment where the ink is placed. In this specification, “ink ambient temperature” is used to include “environment temperature”.
[0026]
The driver 48 drives and controls the main scanning motor 17 and the sub-scanning motor 27 in accordance with driving data given through the PIO port 46, thereby moving and scanning the carriage 13 in the main scanning direction, and rotating the transport roller 24. Thus, the sheet 3 is conveyed by a predetermined amount.
[0027]
Next, details of a portion of the control unit relating to drive control of the recording head will be described with reference to FIG.
Here, the head 14 has piezoelectric elements which are 32 energy generating elements corresponding to a plurality (32 in this case) of nozzle holes, and one electrode of each piezoelectric element is shared to be a common electrode. The other electrode is individually selected for each piezoelectric element to be a selection electrode.
[0028]
On the other hand, the head drive control unit for controlling the drive of the head includes the main control unit 61 including the CPU 40, the ROM 41, the RAM 42, the timer 49 and the peripheral circuits described above, and the head drive unit 62 for driving the head 14. I have. Since the head driving unit 62 is provided for each color head, the head driving circuit 47 described above is provided with four head driving units 62.
[0029]
The main control unit 61 inputs image information given from the host side of a personal computer or the like, and supplies to the head driving unit 62 a driving timing signal MM that defines timing for generating a driving waveform, and ink for each driving waveform. Outputs serial data (nozzle data) DiA and timing signals (shift clock SCLK, latch signal / LAT) for designating nozzles for ejecting droplets as drive control signals, and waveform parameter signals for designating drive waveform parameters, etc. Output.
[0030]
The waveform generation circuit 63 of the head drive unit 62 can be constituted by, for example, a ROM, a D / A converter or other pulse generation circuit, a waveform transformation circuit such as a calculus circuit, a clip circuit, a clamp circuit, or the like. In addition to the drive timing signal MM for determining the timing for generating and outputting the drive waveform from the main controller 61 to the waveform generation circuit 63, the Vp control signal SVp for selecting the drive voltage (voltage value) Vp of the drive waveform. A waveform parameter signal such as (and / or a tr control signal Str for selecting the rising time constant tr of the drive waveform) is also input.
[0031]
The low-impedance output circuit 64 includes a low-impedance amplifier configured by a buffer amplifier, SEPP (Single Ended Push Pull), or the like. By using the low impedance output circuit 64, the output of the drive voltage waveform becomes a low impedance output with respect to the piezoelectric element, and the waveform is not distorted due to variations in the piezoelectric element and the number of drive channels.
[0032]
Here, an example of the waveform generation circuit 63 and the low impedance output circuit 64 will be described with reference to FIGS.
First, as shown in FIG. 5, the waveform generation circuit 63 receives the drive timing signal MM, generates a drive waveform, and supplies the drive waveform to the low impedance output circuit 64, and the Vp control signal SVp. The drive waveform generator 66 includes a Vp controller 67 that generates and outputs a voltage Vout that determines the voltage Vp of the drive waveform.
[0033]
As shown in FIG. 6, the drive waveform generator 66 and the low impedance output circuit 64 (both form a constant voltage drive circuit) connect the input terminal IN to which the drive timing signal MM is supplied via the buffer B to the transistor Tr1. Are connected to the base of the transistor Tr2 via an inverter I, the power supply voltage Vpp is applied to the collector of the transistor Tr1, and the emitter of the transistor Tr2 is grounded.
[0034]
A series circuit of the charging resistor Ra and the diode D1 is connected to the emitter of the transistor Tr1, and a series circuit of the discharge resistor Rb and the diode D2 is connected to the collector of the transistor Tr2, and the cathode side of the diode D1 and the diode D2 are connected. The anode side is connected, and a capacitor Ck is connected between the connection point a and the ground, and a time constant circuit at the time of charging with the charging resistor Ra and the capacitor Ck, and a time constant circuit at the time of discharging with the discharging resistor Rb and the capacitor Ck Is configured. Further, the voltage Vout from the Vp control unit 67 is applied to the connection point a via the diode Dk.
[0035]
The connection point a is connected between the base of the transistor Tr3 on the input side of the low impedance output circuit 104A composed of the transistors Tr3 to Tr6 and the base of the transistor Tr4, and the emitter of the transistor Tr5 on the output side and the transistor Tr6 A drive waveform SAi obtained from the collector is output to the common electrode of the head 14.
[0036]
In this circuit, when the drive timing signal MM is input to the input terminal IN and the “H” level is input to the buffer B, the buffer B outputs a voltage level lower than the power supply voltage Vpp and the transistor Tr1 is turned on. Since the inverter I becomes “L” and the transistor Tr2 is turned off, charging of the capacitor Ck is started with a charging time constant determined by the charging resistor Ra and the capacitor Ck by the power supply voltage Vpp.
[0037]
At this time, since the voltage Vout is applied to the connection point a via the diode Dk (drop voltage Vd), the charging voltage of the capacitor Ck does not rise to the power supply voltage Vpp, and the voltage (Vout + Vd) level is not increased by the diode Dk. This voltage becomes the maximum value (Vp = Vout + Vd) of the drive voltage Vp of the drive waveform SAi.
[0038]
Further, when the drive timing signal MM is not input to the input terminal IN and the “L” level is input to the buffer B, the output of the buffer B becomes the power supply voltage Vpp and the transistor Tr1 is turned off, while the inverter I Is inverted from the output of the buffer B, so that the transistor Tr1 is turned off and at the same time the transistor Tr2 is turned on, and the capacitor Ck charged to the voltage Vp with a discharge time constant determined by the discharge resistor Rb and the capacitor Ck. Discharging starts.
[0039]
Therefore, the drive voltage Vp of the drive waveform SAi can be variably controlled by changing the voltage Vout applied to the drive waveform generator 66.
[0040]
As shown in FIG. 7, the Vp control unit 67 that generates and outputs a voltage Vout that defines the drive voltage Vp includes a three-terminal regulator 68 and a resistance selection circuit 69. The three-terminal regulator 68 supplies a constant voltage source to the voltage input terminal Vin, so that the resistor R1a connected between the adjustment terminal adj and the voltage output terminal Vout and the resistance of the resistance selection circuit 69 connected between the adjustment terminal adj and the ground. A voltage corresponding to the value R2 is output from the voltage output terminal Vout. For example, LM317T (trade name) manufactured by National Semiconductor or the like can be used. Therefore, the output voltage Vout from the three-terminal regulator 68 is determined by, for example, Vout = 1.25 × (1 + R2 / R1).
[0041]
The resistor selection circuit 69 is formed by connecting a resistor Rs, a parallel circuit of a resistor Rp and resistors R21 to R23 selected by switching transistors Q1 to Q3 in series, for example, SN7406 (trade name) manufactured by Texas Instruments. Etc. can be used. In the resistance selection circuit 69, the Vp control signals SVp1 to SVp3 from the main control unit 61 are input to the bases of the transistors Q1 to Q3, respectively.
[0042]
Therefore, the power supply voltage Vpp is supplied to the three-terminal regulator 68, and the 3-bit Vp control signals SVp1 to SVp3 (waveform parameter setting signals) are supplied from the main control unit 61 to the resistance selection circuit 69. The voltage Vout can be changed at a maximum of eight levels, and the output voltage Vout is input as the voltage Vout of the drive waveform generator 66 described above, thereby setting the drive voltage Vp of the drive waveform SAi to a predetermined value. be able to.
[0043]
The generation of the different voltage Vout is variable using, for example, a voltage dividing circuit in which a resistor and a parallel circuit of a variable resistor and a capacitor are connected in series and the voltage across the capacitor is output as the voltage Vout. The voltage Vout can be changed even by using a D / A converter.
[0044]
Next, the channel selection circuit 65 will be described with reference to FIG. The drive waveform selection circuit 65 includes a 32-bit shift register circuit 71 for inputting the serial clock SCLK and the serial data DiA, and a latch signal / LAT for the register value of the shift register circuit 71 (note that the sign “/” means inversion) )), A 32-bit latch circuit 72, a 32-bit level shifter circuit 73, and an analog switch group 74 whose on / off is controlled by the level shifter circuit 73. The analog switch group 74 includes a pair of analog switches AS1 to AS32 connected to the selection electrodes Do1 to Do32 of each piezoelectric element of the recording head 6.
[0045]
Then, the serial data DiA is taken into the shift register circuit 71 in accordance with the shift clock SCLK, and the serial data DiA taken into the shift register circuit 71 is latched by the latch signal 72 with the latch circuit 72 and inputted to the level shifter circuit 73. The level shifter circuit 73 turns on / off the analog switch ASm (m = 1 to 32) connected to each piezoelectric element according to the content of data. As a result, the drive waveform SAi is applied to the selected piezoelectric element PZT.
[0046]
Next, the drive waveform setting process based on the ink temperature in the ink jet recording apparatus configured as described above will be described with reference to FIGS.
First, the relationship between the ambient temperature (detected temperature) and the change in ink temperature with time will be described. In FIG. 9, the power is turned off at time t0, and the detected temperature at this time is T0 (the ink temperature Tink is substantially equal to the detected temperature T0). I will do it.) Therefore, when the ink ambient temperature rises and the ambient temperature (detection temperature) when the power is turned on (power on) at time t1 is T1, the actual ink temperature Tink has a large ink heat capacity, so the ambient temperature T1. Not follow up.
[0047]
At this time, if the detected temperature T1 detected by the main control unit 61 (CPU 40) is used as it is as temperature information for determining the parameters of the drive waveform to be applied to the head 14, the deviation from the correction amount required by the head to the high temperature side. become. Therefore, in the present invention, the tracking error between the detected temperature and the actual ink temperature is reduced.
[0048]
Here, the correction table 41a will be described with reference to FIG. The ROM 41 stores a correction table 41a used for correcting the drive waveform based on the head rank and temperature information. For example, as shown in the figure, the correction table 41a is a table of drive voltage (parameter) values with respect to the ink temperature Tink for each head rank (three classifications A, B, and C). Note that the minimum step of the temperature axis is sT = 5 ° C.
[0049]
The reason why heads are classified by rank is as follows. In other words, since the ejection characteristics of the head usually vary from head to head, it is necessary to correct the variation with the drive waveform.To determine the correction amount for each head, the head is classified into a plurality of ranks in advance and is set for each head. Has rank information.
[0050]
The drive waveform setting process shown in FIG. 11 will be described with reference to FIG. First, when there is a power-off command, the timer 49 is started, and the ink ambient temperature immediately before the power-off (OFF) is detected. As shown in FIG. After storing in 42a, the power is turned off.
[0051]
Next, as shown in FIG. 12, when there is a power-on (ON) command, the power is turned on (ON), and the ink ambient temperature is detected after the power is turned on and before printing is started. As shown, a detected temperature Tp is calculated, and a difference dt = | Tp−Toff | between the detected temperature Tp and the detected temperature Toff immediately before the power is turned off is calculated.
[0052]
  And the calculated difference dT isIt is a predetermined valueCompared with the minimum step sT of the temperature axis (Tink) of the correction table, it is determined whether dT> sT. At this time dT≦If it is sT, it can be considered that the temperature change is negligibly small and the ink temperature Tink can be regarded as Toff = Toff. Therefore, the detection temperature Toff is determined as the ink temperature Tink as it is, and the correction table based on the determined ink temperature Tink. The drive waveform parameter (here, drive voltage) is set with reference to 41a.
[0053]
On the other hand, when dT> sT, the elapsed time from the power-off is read from the timer 49, and this is used as the elapsed time tp, so that the ink temperature Tink is Tink = Toff + (Tp−Toff) * {1-e ^ ( -A * Tp)} (a is a constant obtained from the ink heat capacity), and the calculated value is determined as the ink temperature Tink (here, calculation = determination). Then, using the determined ink temperature Tink, the correction waveform 41a is referred to and a drive waveform parameter (here, drive voltage) is set.
[0054]
As described above, the ink temperature is determined based on the detection result of the ink ambient temperature when the power is turned off and the elapsed time since the power is turned off, and the drive waveform is adjusted according to the calculated ink temperature. Even if the ambient temperature of the ink changes in the meantime, the head can be driven with an optimal driving waveform, and high image quality can be maintained.
[0055]
In this case, high image quality can be obtained with a simple configuration by calculating the ink temperature using an approximate expression. Further, by adjusting the drive waveform according to the determined ink temperature, high image quality can be obtained with a simple configuration. Instead of changing the parameters of the drive waveform according to the determined ink temperature, a plurality of drive waveforms can be generated and the drive waveform can be selected according to the calculated ink temperature.
[0056]
Next, another embodiment of the present invention will be described with reference to FIG. The structure of the mechanism unit and the control unit of the ink jet recording apparatus is the same as that of the above embodiment, but the CPU 40 of the control unit in this embodiment is a means for adjusting the drive waveform, a temperature detection means for detecting the ink ambient temperature, and the ink It also serves as measuring means for measuring the elapsed time from the start of change in ambient temperature, means for calculating ink temperature, and the like.
[0057]
First, as shown in FIG. 13, when the ink ambient temperature changes after the power is turned on, the detected temperature at which the ink ambient temperature is detected changes as indicated by a broken line, whereas the ink temperature is indicated by a solid line. It changes with a delay with respect to the ink ambient temperature (detected temperature).
[0058]
  Therefore, the ink temperature calculation process in this embodiment shown in FIGS. 14 and 15 will be described with reference to FIG. First, referring to FIG. 14, when power is turned on, timer 49 is started to detect the ambient temperature of ink at time t (1), which is set as detected temperature T (1), and then from time t (1). A predetermined time(Predetermined time)The ink ambient temperature at time t (n) (n ≧ 2) after the lapse is detected, and this is set as the detection temperature T (n), and the time t (time t) of the timer 49 when the detection temperature T (n) is detected. n), the difference between the detected temperature T (n) at time t (n) and the detected temperature T (n-1) at the previous time t (n-1) is dt = | T (n) -T ( n-1) is calculated.
[0059]
  And the calculated dT isIt is a predetermined valueCompared with the minimum step sT of the temperature axis (Tink) of the correction table, it is determined whether dT> sT. At this time dT≦If it is sT, it is considered that the temperature change is negligibly small and the ink ambient temperature does not change, and the ink temperature Tink (n) = T (n) is set, and n is incremented (+1) (n = n + 1). ), The ink ambient temperature at the new time t (n) is detected, and the process of setting this to the detected temperature T (n) is repeated. If dT> sT, the process proceeds to FIG.
[0060]
This will be described in detail with reference to FIG. 13. The timer 49 is started when the power is turned on, the ink ambient temperature is detected at time t (1), and the detected temperature at this time is T (1). . Next, at time t (2) after a certain time has elapsed from time t (1), the ink ambient temperature is detected as described above, and the detected temperature at this time is set to T (2) (n = 2). At this time, there is no change in the ink ambient temperature in the example shown in the figure, and therefore | T (2) −T (1) | = dT <sT, so that the ink temperature Tink (2) = T (2).
[0061]
Next, n = n + 1 is set, and the ink ambient temperature is detected at time t (3), and if the detected temperature at this time is T (3), the ink ambient temperature fluctuates in the detected temperature T (3). Therefore, | T (3) −T (2) | = dT> sT (n = m = 3).
[0062]
Therefore, as described above, when | T (n) −T (n−1) | = dT <sT, n = m is set, and the elapsed time tp () from the time when the ink ambient temperature starts to change. m) is set to tp (m) = t (m) −t (m−1). In the example of FIG. 13, since the ink ambient temperature is changed at the detection time t (3), when the time when the detection temperature starts to change is regarded as t (2), the elapsed time tp (3) from there is tp (3) = t (3) −t (2).
[0063]
Then, the ink temperature Tink is determined based on the elapsed time from the start of the change of the ink ambient temperature, the detection result of the ink ambient temperature, and the detection result of the temperature change start, Tink (m) = T (m−1) + (T (M) −T (m−1)) * {1-e ^ (− a * tp (m)} An approximate expression is used.In the example of FIG. 13, the ink temperature Tink (3) = T (2). + (T (3) −T (2)) * {1-e ^ (− a * tp (3)} (this is expressed as “approximate expression (3)”).
[0064]
Next, the detected temperature after a certain time has elapsed from time t (m + k−1) (k ≧ 1) is read and set as the detected temperature T (m + k) (k ≧ 1). Then, the value t (m + k) of the timer 49 when the detected temperature T (m + k) is detected is read, and the elapsed time tp (m + k) = t (m + k) −t (m−1) is set. Thereafter, the ink temperature Tink is expressed by an approximate expression of Tink (m + k) = T (m−1) + (T (m + k) −T (m + k−1)) * {1−e ^ (− a * tp (m + k)}. Calculated by
[0065]
Then, it is determined whether or not | Tink (m + k) −Tink (m + k−1) | <sT. If | Tink (m + k) −Tink (m + k−1) | <sT, k is incremented (+1). (K = k + 1), returning to the process of reading the detected temperature T (m + k). If | Tink (m + k) −Tink (m + k−1) | <sT, the increase in the ink temperature follows the ink ambient temperature. It is determined that the saturation temperature has been reached, and the ink temperature Tink (m + k) = T (m + k) is determined.
[0066]
For example, in the example shown in FIG. 13, the ink temperature Tink (3) is calculated by reading the third detection temperature T (3) as described above, and after the third detection, the fourth time (k = 1). If the detected temperature of T is (4), then | T (4) −T (3) |> sT. Similarly, the elapsed time tp (4) from when the detected temperature starts to change is tp (4) = t (4) -t (2), and the ink temperature Tink (4) at time t (4) is Tink (4) = T (2) + (T (4) -T (2)) * {1- e ^ (− a * tp (4)} approximate expression (this is expressed as “approximate expression (4)”).
[0067]
In this way, the detection of the ink ambient temperature is repeated n times, and if the ink ambient temperature fluctuates in the m-th detection, assuming that the detected ink ambient temperature is T (m), the m + k-th ink When the detection result is | T (m + k) −T (m + k−1) |> sT at the (m + k) th time, the temperature Tink (m + k) is equal to Tink (m + k) = T (m−1) + ( T (m + k) −T (m + k−1)) * {1−e ^ (− a * tp (m + k)} can be repeatedly obtained (tp (m + k) = t (m + k) −t (m -1)).
[0068]
  In this way, the detection of the ink ambient temperature is repeated a plurality of times, and the elapsed time from the start of the change in the ink ambient temperature is measured from the detection result, and the elapsed time andIn this elapsed timeInk ambient temperature detection result and ink ambient temperature change startIn timeBy calculating and determining the ink temperature based on the detection result, a drive waveform corresponding to the determined ink temperature can be set (including selection), and even if the ink ambient temperature changes during operation. An optimum driving waveform can be given to the head, and high image quality can be obtained.
[0069]
In this case, by calculating the ink temperature using an approximate expression, high image quality can be obtained at low cost even if the ambient temperature of the ink during operation changes. Further, by adjusting the drive waveform according to the calculated ink temperature, high image quality can be obtained with a simple configuration. Instead of changing the parameters of the drive waveform according to the calculated ink temperature, it is possible to generate a plurality of drive waveforms and select the drive waveform according to the calculated ink temperature.
[0070]
Next, an embodiment in which the ink remaining amount is considered in calculating the ink temperature using an approximate expression will be described with reference to FIG.
The ink temperature saturation time (time to reach the saturation temperature) is determined by the structure (shape, dimensions, material) of the ink container (ink cartridge, etc.), the mounting form, and the remaining amount of ink. The saturation time becomes shorter.
[0071]
Here, when the ink thermal time constant when there is no ink consumption in the ink container is a, the thermal time constant a with a certain remaining ink amount is a = b * m (b is the ink container). A constant determined by the structure and the mounting form, m is a variable determined by the remaining amount of ink, and m ≧ 1.
[0072]
The remaining amount of ink can be detected by a well-known technique such as a method of counting the number of ink ejected droplets or a method of optically detecting the liquid level of the ink container. Relationship can be obtained. FIG. 16 shows how ink remaining amount and ink temperature fluctuate when the ambient temperature changes from T0 to T1.
[0073]
Therefore, the ink temperature can be calculated with higher accuracy by changing the thermal time constant a in accordance with the ink remaining amount when calculating the ink temperature.
[0074]
In each of the embodiments described above, the recording apparatus using a piezoelectric element and a head is described. However, as described above, an electrothermal conversion element such as a heating resistor, an electrostatic force between the diaphragm and the counter electrode is used. The present invention can also be applied to recording apparatuses equipped with other types of heads, such as those using. Further, the case where the ink temperature rises is described with an example. When the ink temperature falls, the value of (T (n + 1) −T (1)) only becomes negative, and thus the same calculation is performed. Can do.
[0075]
【The invention's effect】
  As described above, according to the inkjet recording apparatus of the present invention,A temperature detecting means for detecting the ambient temperature of the ink, a measuring means for measuring an elapsed time from when the power is turned off, a detected temperature before turning on after the power is turned on and before starting printing, and a detected temperature immediately before turning off the power When the difference between the detected temperatures is equal to or less than a predetermined value, the detected temperature immediately before the power is turned off is determined as the ink temperature, and when the difference between the detected temperatures exceeds a predetermined value, the detected temperature immediately before the power is turned off. And a means for determining the ink temperature based on the detected temperature and the elapsed time since the power is turned off.Even if the ink ambient temperature changes while the power is off, the ink temperature can be calculated accurately. For example, by setting an optimal drive waveform, high image quality can be recorded.NoCan get.
[0076]
  Here, the inkjet head according to the determined ink temperatureDrop droplets fromBy providing the means for adjusting the drive waveform, it is possible to set an optimum drive waveform according to the ink temperature and to perform recording with high image quality.
[0078]
  According to the inkjet recording apparatus of the present invention,The temperature detection means for detecting the ambient temperature of the ink is compared with two detected temperatures at each time before and after the elapse of a predetermined time after the power is turned on, and when the difference between the detected temperatures is equal to or less than a predetermined value, When the detected temperature at the time is determined as the ink temperature and the difference between the detected temperatures exceeds a predetermined value, the detected temperature at the time after the predetermined time has elapsed, the elapsed time from the same time, and the detection at this elapsed time temperatureBased onAnd a means for determining the ink temperature based onEven if the ink ambient temperature changes during operation, the ink temperature can be calculated accurately. For example, high-quality image recording can be performed by setting an optimal drive waveform.NoCan get.
[0079]
  Here, the inkjet head according to the determined ink temperatureDrop droplets fromBy providing the means for adjusting the drive waveform, it is possible to set an optimum drive waveform according to the ink temperature and to perform recording with high image quality.
[Brief description of the drawings]
FIG. 1 is a schematic perspective explanatory view of a mechanism portion of an ink jet recording apparatus according to the present invention.
FIG. 2 is an explanatory side view of the mechanism part.
FIG. 3 is a block diagram showing a control unit of the recording apparatus
FIG. 4 is a block diagram of a portion related to head drive control of the control unit;
5 is a block diagram of the head drive circuit of FIG. 4;
FIG. 6 is a circuit diagram of a drive waveform generation unit and a low impedance output circuit of the head drive circuit.
FIG. 7 is a block circuit diagram of a Vp control unit of the head drive circuit.
FIG. 8 is a block diagram of a channel selection circuit of the head drive circuit.
FIG. 9 is an explanatory diagram showing an example of the relationship between the ink ambient temperature and the ink temperature.
FIG. 10 is an explanatory diagram for explaining a correction table.
FIG. 11 is a flowchart showing one example of drive waveform setting processing;
12 is an explanatory diagram illustrating an example of a change in ink temperature and a detected temperature used in the description of FIG. 11;
FIG. 13 is an explanatory diagram for explaining the change in the ink ambient temperature after the power is turned on and the ink temperature tracking, and FIGS. 14 and 15;
FIG. 14 is a flowchart of ink temperature calculation processing.
FIG. 15 is a flowchart of ink temperature calculation processing following FIG.
FIG. 16 is an explanatory diagram for explaining the relationship between the remaining amount of ink and the change in ink temperature.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 13 ... Carriage, 14 ... Head, 15 ... Ink cartridge, 49 ... Timer, 51 ... Temperature detection element, 61 ... Main control part, 62 ... Head drive circuit

Claims (4)

In an inkjet recording apparatus equipped with an inkjet head,
Temperature detecting means for detecting the ambient temperature of the ink;
A measuring means for measuring the elapsed time since the power was turned off;
Compare the detected temperature before the start of printing after turning on the power and before the start of printing after the power is turned on, and the detected temperature immediately before the power is turned off when the difference between the detected temperatures is less than a predetermined value. determines that the ink temperature, the when the difference between both the detected temperature exceeds a predetermined value and means for determining the ink temperature on the basis of the elapsed time from the detection temperature及beauty power off when the power-off just before An inkjet recording apparatus characterized by the above. In the ink jet recording apparatus according to claim 1, an ink jet recording apparatus characterized in that it comprises means for adjusting the drive waveform for ejecting droplets from the ink jet head in accordance with the ink temperature and the determined. In an inkjet recording apparatus equipped with an inkjet head,
Temperature detecting means for detecting the ambient temperature of the ink;
After the power is turned on, two detected temperatures at each time before and after the elapse of a predetermined time are compared, and when the difference between the detected temperatures is equal to or less than a predetermined value, the detected temperature at the time after the elapse of the predetermined time is determined as the ink temperature, Means for determining the ink temperature based on the detected temperature at the time after the predetermined time has elapsed, the elapsed time from the same time, and the detected temperature at the elapsed time when the difference between the detected temperatures exceeds a predetermined value ; An ink jet recording apparatus comprising: 4. The ink jet recording apparatus according to claim 3 , further comprising means for adjusting a driving waveform for ejecting droplets from the ink jet head in accordance with the determined ink temperature.

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