JP2001080057A - Ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image quality from deteriorating when an ink temperature does not follow an ink ambient temperature. SOLUTION: The apparatus is equipped with a temperature-detecting element 51 for detecting an ink ambient temperature, a nonvolatile memory 42a for storing a detect temperature when a power source is turned off, a timer 49 for measuring an elapsing time after the power source is turned off, and a means for calculating an ink temperature based on the detect temperature when the power source is turned off which is stored in the nonvolatile memory 42a, and the elapsing time by the timer 49 after the power source is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording apparatus, and more particularly to an ink-jet recording apparatus capable of giving a drive waveform according to an ink ambient temperature.

[0002]

2. Description of the Related 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, a plotter, etc. has a nozzle for discharging ink droplets and a discharge chamber (pressure chamber, pressurizing chamber) communicating with the nozzle. A liquid chamber, a liquid chamber, an ink flow path, etc.) and an energy generating means for generating energy for pressurizing the ink in the discharge chamber. An ink-on-demand type, which pressurizes and ejects ink droplets from nozzle holes, ejects ink droplets only when recording is necessary, is the mainstream.

In such an ink jet head, the amount of ink ejected and the ink droplet ejecting speed are greatly affected by the ambient temperature of the head (also referred to as the ambient temperature of the ink and including the temperature of the head itself) or the temperature of the ink. , The ink ejection amount and ink droplet ejection speed are dot diameter,
It is an important factor in determining dot position accuracy, and image quality may be degraded when ambient temperature or ink temperature changes.

Therefore, conventionally, a method has been adopted in which the ambient temperature of the head is detected and the drive waveform is controlled in accordance with the detected temperature so that the dot diameter and the dot position accuracy are constant.
As described in Japanese Patent Application Laid-Open No. 2-178052, in a liquid ejecting recording apparatus in which a recording head having a temperature detecting element for detecting the temperature of the recording head is detachable, the characteristics of the temperature detecting element are related. Determining means for determining the correction value, and control means for outputting a control signal for controlling the temperature of the recording head in accordance with the correction value determined by the determining means and the detection output of the temperature detecting element, It is known to improve the temperature detection accuracy.

[0005]

However, the head characteristics largely depend on changes in physical properties (such as surface tension and viscosity) due to changes in the temperature of the ink itself. For example, if a device that has been left in a room with a high temperature is moved to a room with a low temperature, it takes time for the temperature of the ink itself to follow the temperature of the head and its surroundings. Then, even though the temperature of the ink itself is still high, the detected temperature becomes low. Therefore, it is determined that the ink temperature is low, and the head is driven at a low temperature setting. Alternatively, if printing starts in the morning immediately after heating is turned on in the morning, regardless of the ink temperature itself,
Since the detected temperature increases, the ink temperature is determined to be high, and the head is driven at a high temperature setting.

As described above, it takes time for the ink temperature to follow the detected ink ambient temperature (detected temperature). Therefore, if printing is started before the ink temperature follows the ink ambient temperature, the image quality is reduced. Will decrease. In this case, it is very difficult to directly detect the temperature of the ink itself.

The present invention has been made in view of the above points, and has as its object to maintain a high image quality by setting an appropriate drive waveform according to the ink temperature.

[0008]

In order to solve the above-mentioned problems, an ink jet recording apparatus according to the present invention measures the ink temperature based on the detection result of the ink ambient temperature when the power is turned off and the elapsed time since the power was turned off. The configuration is to be determined.

Here, it is preferable to provide a means for adjusting a drive waveform given to the ink jet head according to the determined ink temperature. The ink temperature is based on the fluctuation temperature from the detected temperature when the power is turned off to the detected temperature when the ink temperature is determined and e (= 2.718. It is preferable to calculate using an approximate expression including a product with an exponential function. In the case of the calculation using the approximate expression of the ink temperature, it is preferable to change the thermal time constant a used in the approximate expression according to the remaining amount of the ink.

[0010] The ink jet recording apparatus according to the present invention comprises:
The ink temperature is determined based on the detection result of the ink ambient temperature, the elapsed time from the start of the change in the ink ambient temperature, and the detection result of the start of the change in the ink ambient temperature.

Here, it is preferable to provide a means for adjusting a drive waveform applied to the ink jet head according to the determined ink temperature. In addition, the ink temperature is determined by the fluctuation temperature from the detected temperature to the detected temperature when the ink temperature is determined, and e (=
2.718...), And it is preferable to repeatedly calculate using an approximate expression including a product of an elapsed time from the start of the change of the ink ambient temperature to the time of determining the ink temperature and an exponential function. When calculating this ink temperature using an approximate expression, it is preferable to change the thermal time constant a used in the approximate expression according to the remaining amount of ink.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of the mechanism.

This ink jet recording apparatus comprises a carriage movable in the main scanning direction inside the recording apparatus main body 1, a recording head composed of an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. A paper feed cassette (or a paper feed tray) 4 capable of loading a large number of sheets 3 from the front side is detachably attached to a lower portion of the apparatus main body 1. In addition, the manual tray 5 for manually feeding the paper 3 can be opened, and the paper 3 fed from the paper feed cassette 4 or the manual tray 5 is taken in. After recording the image, the sheet is discharged to the sheet discharge tray 6 mounted on the rear side.

The printing mechanism 2 slides the carriage 13 in a main scanning direction (a direction perpendicular to the paper of FIG. 2) by a main guide rod 11 and a sub guide rod 12, which are guide members which are laterally mounted on left and right side plates (not shown). This carriage 1
3 is provided with a head 14 composed of an ink jet head for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet discharge direction facing downward. Above 13, each ink tank (ink cartridge) 15 for supplying each color ink to the head 14 is exchangeably mounted.

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) via a bearing 16, and the front side (downstream side in the paper conveyance direction) is a slave guide rod. 12 are slidably mounted. In order to move and scan the carriage 13 in the main scanning direction, a driving pulley 18 that is rotationally driven by a main scanning motor 17 is used.
A timing belt 20 is stretched between the driven belt 19 and the driven pulley 19, and the timing belt 20 is fixed to the carriage 13.

Although the heads 14 of each color are used here as recording heads, a single head having nozzles for ejecting ink droplets of each color may be used. Furthermore, head 1
The ink jet head used as 4 is an ink jet head that presses ink through a diaphragm that forms a liquid chamber wall by an electromechanical transducer such as a piezoelectric element, or that presses ink by generating bubbles by film boiling caused by a heating resistor. Alternatively, it is possible to use a device that presses ink by displacing the diaphragm with electrostatic force between the diaphragm forming the wall surface of the liquid chamber and an electrode facing the diaphragm. In this embodiment, an ink jet head using a piezoelectric element is used.

On the other hand, the paper 3 set in the paper feed cassette 4
Roller 21 and a friction pad 22 for separating and feeding the paper 3 from the paper feed cassette 4 and a guide member 23 for guiding the paper 3
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 roller 26 that defines the angle at which the paper 3 is sent out from the transport roller 15. Is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.

A print receiving member 29 is provided as 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. I have.

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 which are driven to rotate in order to send out the paper 3 in the paper discharge direction. A delivery roller 33 and a spur 34 for sending out,
Guide members 35 and 36 that form a paper discharge path are provided.

A subsystem 37 for maintaining and restoring the reliability of the head 14 is disposed at the right end of the carriage 13 in the moving direction. During standby, the carriage unit 13 is moved toward the subsystem 37 to cap the head 14 such as capping means.

Next, an outline of a control section of the ink jet recording apparatus will be described with reference to FIG. The control unit includes a microcomputer (hereinafter, referred to as a “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 the like. An image memory 43 for storing the processed data, and a parallel input / output (PI
O) port 44, input buffer 45, gate array (GA) or parallel input / output (PIO) port 46
And a head drive circuit 47, a driver 48, and a timer 49.
Etc. are provided.

Here, the CPU 40 comprises a means for adjusting the drive waveform, a temperature detecting means for detecting the ink ambient temperature using the temperature detecting element 51, a measuring means for measuring the elapsed time from the power-off using the timer 49, It also serves as a means for calculating the ink temperature. A correction table 41 used for setting parameters for adjusting the drive waveform is stored in the ROM 41.
a is stored. A part of the RAM 42 is a non-volatile memory 42a, for example, a battery backup RAM,
EPRAM etc. are included.

In addition to image information from the host side, data such as paper type data indicating the type of paper, various instruction information from an operation panel (not shown), paper for detecting the start and end of the paper are provided in the PIO port 44. A detection signal from the presence / absence sensor, a signal from various sensors such as a home position sensor for detecting the home position (reference position) of the carriage 5, and the like are input to the host and the operation panel through the PIO port 44. Required information is transmitted.

The head drive circuit 47 uses energy generation means (a piezoelectric element in this embodiment) corresponding to each nozzle of the head 14 based on various data and signals provided via the PIO port 46. ) Is applied with a drive waveform or the like. Further, a detection signal of a temperature detecting element 51 such as a thermistor for detecting the ambient temperature of the ink is input via the PIO port 46, and rank information indicating the rank of the head preset for the head 14 is input to the PIO port 46. You have to input via.

Here, the temperature detecting element 51 is provided on the carriage 13 as shown in FIG. 1 so as to detect the ink ambient temperature. However, the temperature detecting element may be attached to the head 14, Alternatively, a temperature detecting element may be attached to any part of the apparatus main body 1. In short, it suffices if the temperature of the environment where the ink is placed can be detected. In this specification, "ink ambient temperature" is used to include "environmental temperature".

The driver 48 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 according to the driving data supplied through the PIO port 46, respectively. 24 is rotated to convey the sheet 3 by a predetermined amount.

Next, details of a portion related to drive control of the recording head in the control section will be described with reference to FIG. Here, the head 14 has 32 piezoelectric elements, which are 32 energy generating elements corresponding to a plurality of nozzle holes (here, 32 nozzle holes), and one electrode of each piezoelectric element is shared to form a common electrode. The other electrode is individually selected for each piezoelectric element and used as a selection electrode.

On the other hand, the head drive control section for controlling the drive of the head includes the CPU 40, ROM 41,
Main control unit 6 including RAM 42, timer 49 and peripheral circuits
1 and a head drive unit 62 for driving the head 14. Since the head driving units 62 are provided for each head of each color, the head driving circuit 47 described above is provided with four head driving units 62.

The main control section 61 receives image information given from the host side of a personal computer or the like and sends a drive timing signal MM for defining a timing for generating a drive waveform to the head drive section 62; Waveform parameters for outputting serial data (nozzle data) DiA for specifying a nozzle for ejecting ink droplets and a timing signal (shift clock SCLK, latch signal / LAT) as a drive control signal and for specifying parameters of a drive waveform for each time Outputs signals, etc.

The waveform generating circuit 63 of the head driving section 62 can be constituted by, for example, a ROM, a D / A converter or another pulse generating circuit and a waveform deforming circuit such as a calculus circuit, a clipping circuit, and a clamp circuit. In addition to the drive timing signal MM for determining the timing for generating and outputting the drive waveform from the main control unit 61, the waveform generation circuit 63 also includes a Vp control signal SVp for selecting a drive voltage (voltage value) Vp of the drive waveform. A waveform parameter signal such as (and / or a tr control signal Str for selecting a rising time constant tr of the drive waveform) is also input.

The low impedance output circuit 64
Buffer amplifier, SEPP (Single Embedded Push)
Pull) and the like. By using the low impedance output circuit 64, the output of the drive voltage waveform becomes a low impedance output to the piezoelectric element, and the waveform is not distorted due to the variation of the piezoelectric element and the difference in the number of drive channels.

Here, an example of the waveform generating 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 a drive timing signal MM, generates a drive waveform, and supplies the generated drive waveform to the low impedance output circuit 64 in accordance with the Vp control signal SVp. And a Vp controller 67 that generates and outputs a voltage Vout that determines the voltage Vp of the drive waveform of the drive waveform generator 66.

The drive waveform generator 66 and the low impedance output circuit 64 (both constitute a constant voltage drive circuit)
As shown in FIG. 6, an input terminal IN to which a drive timing signal MM is supplied is connected to a base of a transistor Tr1 via a buffer B and to a base of a transistor Tr2 via an inverter I, respectively. The power supply voltage Vpp is applied to the collector, and the emitter of the transistor Tr2 is grounded.

A series circuit of a charging resistor Ra and a diode D1 is connected to the emitter of the transistor Tr1, and a series circuit of a discharging resistor Rb and a diode D2 is connected to the collector of the transistor Tr2.
Is connected to the anode side of the diode D2, a capacitor Ck is connected between this 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 is formed by the discharging resistor Rb and the capacitor Ck. Constitutes a time constant circuit at the time of discharge. Further, the voltage Vout from the Vp control unit 67 is applied to the connection point a via the diode Dk.

The connection point a is connected to the transistors Tr3 to Tr3.
A drive waveform that is connected between the base of the transistor Tr4 and the base of the transistor Tr4 on the input side of the low impedance output circuit 104A composed of Tr6, and is obtained between the emitter of the transistor Tr5 on the output side and the collector of the transistor Tr6. SAi is output to the common electrode of the head 14.

In this circuit, the drive timing signal MM is input to the input terminal IN, and "H" is input to the buffer B.
When the level is input, the buffer B outputs a voltage level lower than the power supply voltage Vpp to turn on the transistor Tr1 and the inverter I to "L" to turn off the transistor Tr2. Accordingly, charging of the capacitor Ck is started with a charging time constant determined by the charging resistor Ra and the capacitor Ck.

At this time, the diode Dk is connected to the connection point a.
Since the voltage Vout is applied via the (drop voltage Vd), the charging voltage of the capacitor Ck does not rise to the power supply voltage Vpp, and the voltage (Vout + V
d), and this voltage is applied to the drive waveform SA.
It becomes the maximum value (Vp = Vout + Vd) of the drive voltage Vp of i.

When the drive timing signal MM is not inputted to the input terminal IN and the "L" level is inputted to the buffer B, the output of the buffer B becomes the power supply voltage Vpp, and the transistor Tr1 is turned off. On the other hand, since the output of the inverter I is inverted with respect to the output of the buffer B, the transistor Tr1 is turned off and the transistor Tr2 is turned on at the same time, and the transistor Tr1 is charged to the voltage Vp with the discharge time constant determined by the discharge resistor Rb and the capacitor Ck. The discharge of the capacitor Ck is started.

Therefore, by changing the voltage Vout applied to the drive waveform generator 66, the drive waveform S
The drive voltage Vp of Ai can be variably controlled.

The Vp control section 67 for generating and outputting the voltage Vout defining the drive voltage Vp includes a three-terminal regulator 68 and a resistance selection circuit 69, as shown in FIG.
By supplying a constant voltage source to the voltage input terminal Vin, the three-terminal regulator 68 supplies a resistance R1a connected between the adjustment terminal adj and the voltage output terminal Vout and a resistance R1a 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 can be used. Therefore, the output voltage Vout from the three-terminal regulator 68 is, for example, V
out = 1.25 × (1 + R2 / R1)

The resistor selection circuit 69 includes a resistor Rs and a resistor R
A parallel circuit of p and resistors R21 to R23 selected by the switching transistors Q1 to Q3 is connected in series, for example, Texas Instruments SN7406.
(Product name) or the like. The resistance selection circuit 69 has Vp from the main control unit 61 described above.
Control signals SVp1 to SVp3 are applied to transistors Q1 to Q3.
Each is entered in the base.

Therefore, by supplying the power supply voltage Vpp to the three-terminal regulator 68 and supplying the 3-bit Vp control signals SVp1 to SVp3 (waveform parameter setting signals) from the main control unit 61 to the resistance selection circuit 69,
The output voltage Vout of the three-terminal regulator 68 can be changed at up to eight different levels.
Is input as the voltage Vout of the drive waveform generator 66 described above, the drive voltage Vp of the drive waveform SAi can be set to a predetermined value.

The different voltage Vout is generated, for example, by using 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 between both ends of the capacitor is output as the voltage Vout. Thus, the variable resistance can be changed, and the D / A
The voltage Vout can also be changed by using a converter.

Next, the channel selection circuit 65 will be described with reference to FIG. This drive waveform selection circuit 65
A 32-bit shift register circuit 71 for inputting the serial clock SCLK and the serial data DiA, and the register value of the shift register circuit 71 is latched by a latch signal / LAT.
(Note that the sign “/” means inversion.) A 32-bit latch circuit 72 that latches with “32”, a 32-bit level shifter circuit 73, and an analog switch group 74 whose on / off is controlled by the level shifter circuit 73 Consists of 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.

The serial data DiA is supplied to the shift register circuit 71 in accordance with the shift clock SCLK.
Then, the latch circuit 72 latches the serial data DiA captured by the shift register circuit 71 in response to the latch signal / LAT and inputs the serial data DiA to the level shifter circuit 73.
The level shifter circuit 73 includes an analog switch ASm (m = m) connected to each piezoelectric element according to the content of data.
1 to 32) on / off. Thereby, the driving waveform S
Ai is applied to the selected piezoelectric element PZT.

Next, a process of setting a drive waveform based on the ink temperature in the ink jet recording apparatus having the above-described configuration will be described with reference to FIGS. First, the relationship between the ambient temperature (detected temperature) and the change over time in the ink temperature will be described. Referring to FIG.
nk substantially coincides with the detected temperature T0. ). Therefore, when the ambient temperature of the ink rises and the ambient temperature (detection temperature) when the power is turned on (power is turned on) at time t1 is T1, the actual ink temperature Tink has a large heat capacity of the ink, and therefore the ambient temperature T1 Not following.

At this time, as the temperature information for determining the parameters of the drive waveform given to the head 14, the main controller 6
If the detected temperature T1 detected by the CPU 1 (CPU 40) is used as it is, the correction amount required by the head is shifted to a higher temperature side. Therefore, in the present invention, the following error between the detected temperature and the actual ink temperature is reduced.

Here, the correction table 41a is shown in FIG.
0 will be described. The ROM 41 stores a correction table 41a used to correct a drive waveform based on head rank and temperature information. The correction table 41a is a table in which the values of the drive voltage (parameter) with respect to the ink temperature Tink for each head rank (three classifications of A, B, and C) as shown in FIG. Note that the minimum step on the temperature axis is sT = 5 ° C.

The heads are classified by rank for the following reasons. That is, since the ejection characteristics of the heads usually vary from head to head, it is necessary to correct the variations with the driving waveform.To determine the correction amount for each head, the heads are classified into a plurality of ranks in advance, and the heads are classified into a plurality of ranks. Has rank information.

The drive waveform setting process shown in FIG. 11 will be described with reference to FIG. First, when there is a power-off (off) command, the timer 49 is started to detect the ink ambient temperature immediately before the power-off (OFF), and as shown in FIG. After storing the data in the memory 42a, the power is turned off (off).
Let it.

Next, as shown in FIG. 12, when there is a power on (ON) command, the power is turned on (ON), and after the power is turned on, the ink ambient temperature is detected and printing is started. As shown in the figure, the detected temperature Tp is used as the detected temperature Tp.
Dt = | Tp between power supply and detected temperature Toff immediately before power-off
-Toff | is calculated.

Then, the calculated difference dT is compared with the minimum step sT of the temperature axis (Tink) in the correction table to obtain dT.
> ST. At this time, if dT <sT, the ink temperature Tink = Toff can be considered as a temperature change that is negligibly small, so that the detected temperature Toff is directly determined as the ink temperature Tink, and the determined ink temperature Tink is determined. The parameters of the drive waveform (here, the drive voltage) are set in Tink with reference to the correction table 41a.

On the other hand, when dT> sT, the elapsed time from the power-off is read from the timer 49, and this is set as the elapsed time tp, and the ink temperature Tink is set to Tink = Tink.
off + (Tp-Toff) * {1-e} (-a * Tp)} is calculated using an approximate expression (a is a constant obtained from the heat capacity of the ink), and the calculated value is determined as the ink temperature Tink (here, Calculation = decision). Then, the parameters of the drive waveform (here, the drive voltage) are set with reference to the correction table 41a using the determined ink temperature Tink.

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 ink ambient temperature changes while the power is off, the head can be driven with an optimal drive waveform, and high image quality can be maintained.

In this case, high image quality can be obtained with a simple configuration by calculating the ink temperature using an approximate expression. In addition, 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.

Next, another embodiment of the present invention will be described with reference to FIG.
The third and subsequent steps will also be described. The configuration of the mechanical unit and the control unit of the ink jet recording apparatus is the same as that of the above-described embodiment. However, in this embodiment, the CPU 40 of the control unit adjusts the drive waveform, It also serves as a measuring unit for measuring the elapsed time from the start of the change in the ambient temperature, a unit for calculating the ink temperature, and the like.

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.
The ink temperature changes with a delay with respect to the ink ambient temperature (detection temperature) as shown by the solid line.

Therefore, the ink temperature calculation processing in this embodiment shown in FIGS. 14 and 15 will be described with reference to FIG.
This will be described with reference to FIG. First, referring to FIG. 14, the timer 49 is started when the power is turned on, the ink ambient temperature at time t (1) is detected, and this is set as a detected temperature T (1).
Next, the ink ambient temperature at time t (n) (n ≧ 2) after a predetermined time has elapsed from time t (1) is detected, and this is set as a detected temperature T (n). After reading the time t (n) of the timer 49 when detecting the time n), the detected temperature T (n) at the time t (n) and the previous time t (n)
Difference dt = | of detected temperature T (n-1) at (n-1)
T (n) -T (n-1) is calculated.

Then, the calculated dT is compared with the minimum step sT of the temperature axis (Tink) of the correction table, and dT>
It is determined whether it is sT or not. At this time, if dT <sT,
Assuming that the temperature change is negligibly small and there is no change in the ink ambient temperature, the ink temperature Tink (n) = T
As (n), n is incremented (+1) (n =
(n + 1), a process of detecting the ink ambient temperature at a new time t (n) and setting the detected temperature as the detected temperature T (n) is repeated. Then, if dT> sT, the processing shifts to the processing shown in FIG.

More specifically, this will be described with reference to FIG.
In the case of (1), the ink ambient temperature is detected, and the detected temperature at this time is defined as T (1). Next, at time t (2) after a lapse of a certain time from time t (1), the ink ambient temperature is detected in the same manner 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 of FIG. 7, and therefore | T (2) −T (1) | = dT <
Since sT, the ink temperature Tink (2) = T (2).

Next, when n = n + 1, the ink ambient temperature is detected at time t (3) in the same manner as described above. If the detected temperature at this time is T (3), the detected temperature T (3) is the ink ambient temperature. Is fluctuating, | T (3) −T (2) |
= DT> sT (n = m = 3).

Therefore, as described above, | T (n) -T
When (n−1) | = dT <sT, n = m is set, and the elapsed time tp (m) from the time when the ink ambient temperature starts to change is tp (m) = t (m) − t (m−
Set to 1). In the example of FIG. 13, since the ink ambient temperature changes at the detection time t (3), the elapsed time tp (3) from the time at which the detection temperature starts to change is regarded as t (2). tp (3) = t (3) -t (2).

The ink temperature Tink is calculated based on the elapsed time from the start of the change in the ink ambient temperature, the detection result of the ink ambient temperature, and the detection result of the start of the temperature change.
(M) = T (m-1) + (T (m) -T (m-1)) *
Calculated by an approximate expression of {1-e} (-a * tp (m)}. In the example of FIG. 13, the ink temperature Tink (3) = T
(2) + (T (3) -T (2)) * {1-e} (-a *
tp (3)｝ (this is referred to as “approximation equation (3)”)
Can be requested.

Next, at time t (m + k-1) (k ≧ 1)
Is read after a lapse of a certain time from
(M + k) (k ≧ 1). Then, the detected temperature T (m
+ K) is read, the value t (m + k) of the timer 49 is read, and the elapsed time tp (m + k) = t (m + k) -t
Set to (m-1). After that, the ink temperature Tink is
Tink (m + k) = T (m-1) + (T (m + k) -T
(M + k-1)) * {1-e} (-a * tp (m +
k) Calculated by the approximate expression of｝.

Then, | Tink (m + k) -Tink (m +
k-1) | <sT is determined, and | Tink (m + k)
If −Tink (m + k−1) | <sT, k is incremented (+1) (k = k + 1), and the detected temperature T
Returning to the processing for reading (m + k), | Tink (m + k)
If −Tink (m + k−1) | <sT, it is determined that the rise in the ink temperature has reached the saturation temperature following the ink ambient temperature, and the ink temperature Tink (m + k) = T (m +
Determined in k).

For example, in the example shown in FIG. 13, the ink temperature Tink (3) is calculated by reading the detected temperature T (3) for the third time as described above, and after the third detection, the ink temperature Tink (3) is calculated. = 1, the detected temperature is T (4), and | T
Since (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)}
(This is expressed as “approximation equation (4)”).

In this manner, the detection of the ink ambient temperature is repeated n times, and if the ink ambient temperature fluctuates in the m-th detection, the detected ink ambient temperature is determined by T
(M), the m + k-th ink temperature Tink (m +
k) means that the detection result at the (m + k) -th time is | T (m + k) -T
When (m + k-1) |> sT, as described above,
Tink (m + k) = T (m-1) + (T (m + k) -T
(M + k-1)) * {1-e} (-a * tp (m +
k) It can be repeatedly obtained by the approximate expression of｝ (tp (m + k) = t (m + k) −t (m−1)).

In this manner, the detection of the ink ambient temperature is repeatedly performed a plurality of times, and the elapsed time from the start of the change of the ink ambient temperature is measured based on the detection result. By calculating and determining the ink temperature based on the detection result of the start of the change of the drive voltage, a drive waveform corresponding to the determined ink temperature can be set (including selection), and the ink ambient temperature can be set during operation. Even if it changes, an optimum drive waveform can be given to the head, and high image quality can be obtained.

In this case, by calculating the ink temperature using an approximate expression, high image quality can be obtained at low cost even if the ink ambient temperature during operation changes. In addition, 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, a plurality of drive waveforms may be generated and the drive waveform may be selected according to the calculated ink temperature.

Next, an embodiment will be described with reference to FIG. 16 in which the remaining amount of ink is taken into account in the calculation using the approximate expression of the ink temperature. The saturation time of the ink temperature (the time until the saturation temperature is reached) is determined by the structure (shape, dimensions, and material) of the ink container (such as an ink cartridge), the mounting form, and the remaining amount of ink. The shorter the saturation time, the shorter the saturation time.

Here, assuming that the ink thermal time constant when there is no ink consumption in the ink container is a, the thermal time constant a at a certain remaining amount of ink is a = b * m (b is A constant determined by the structure and mounting form of the container, m is a variable determined by the remaining amount of ink, and m ≧ 1.)

The remaining ink amount can be easily detected by a well-known technique such as a method of counting the number of ink droplets or a method of optically detecting the liquid level of the ink container. The relationship with the variable m can be obtained.
FIG. 16 shows how the remaining ink amount and the ink temperature change when the ambient temperature changes from T0 to T1.

Therefore, the ink temperature can be calculated with higher accuracy by changing the thermal time constant a in accordance with the remaining amount of ink in calculating the ink temperature.

In each of the above embodiments, the recording apparatus having a head using a piezoelectric element has been described. However, as described above, an apparatus using an electrothermal conversion element such as a heating resistor may be used.
The present invention can also be applied to a recording apparatus equipped with another type of head, such as one using electrostatic force between the diaphragm and the counter electrode. Further, the case where the ink temperature rises has been described by way of example. When the ink temperature falls, (T (n + 1) -T
Since the value of (1) only becomes negative, it can be calculated similarly.

[0075]

As described above, according to the ink jet recording apparatus of the present invention, the ink temperature is calculated based on the detection result of the ink ambient temperature when the power is turned off and the elapsed time since the power was turned off. Therefore, even when the ink ambient temperature changes while the power is off, the ink temperature can be accurately calculated, and for example, it is possible to obtain high image quality recording by setting an optimal driving waveform. it can.

Here, by providing a means for adjusting the drive waveform applied to the ink jet head according to the calculated ink temperature, it is possible to set an optimum drive waveform according to the ink temperature, thereby achieving high image quality printing. It can be carried out.

The ink temperature is determined by the fluctuation temperature from the detected temperature when the power is turned off to the detected temperature when the ink temperature is determined and e.
(= 2.718...) And obtain an image quality at low cost by calculating using an approximate expression including a product of an exponential function of an elapsed time from when the power is turned off to when the ink temperature is determined when the power is turned off. Will be able to In the case of the calculation using the approximate expression of the ink temperature, the ink temperature can be calculated with higher accuracy by changing the thermal time constant a according to the remaining amount of the ink.

According to the ink jet recording apparatus of the present invention, the ink temperature is calculated based on the detection result of the ink ambient temperature, the elapsed time from the start of the change in the ink ambient temperature, and the detection result of the start of the change in the ink ambient temperature. Therefore, even when the ink ambient temperature changes during operation, the ink temperature can be accurately calculated, and for example, by setting an optimum drive waveform, it is possible to obtain high image quality printing. .

Here, by providing a means for adjusting the drive waveform given to the ink jet head according to the calculated ink temperature, it is possible to set an optimum drive waveform according to the ink temperature, and to achieve high image quality printing. It can be carried out.

The ink temperature is the fluctuation temperature from the detected temperature to the detected temperature at the time of determining the ink temperature and e (= 2.71).
8) at the bottom and high image quality at low cost by repeatedly calculating using an approximate expression including a product of the elapsed time from the start of the change of the ink ambient temperature to the time of determining the ink temperature and an exponential function. Will be able to do it. When calculating the ink temperature using an approximate expression, it is possible to calculate the ink temperature with higher accuracy by changing the thermal time constant a according to the remaining amount of the ink.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of a mechanism section of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory side view of the mechanism.

FIG. 3 is a block diagram showing a control unit of the recording apparatus.

FIG. 4 is a block diagram of a part related to head drive control of the control unit.

FIG. 5 is a block diagram of the head drive circuit of FIG. 4;

FIG. 6 is a circuit diagram of a drive waveform generator 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 a drive waveform setting process.

FIG. 12 is an explanatory diagram showing an example of a change in ink temperature and a detected temperature used for explaining FIG. 11;

FIG. 13 is an explanatory diagram for explaining the change in the ink ambient temperature and the following of the ink temperature after the power is turned on, and FIGS. 14 and 15;

FIG. 14 is a flowchart of an ink temperature calculation process.

FIG. 15 is a flowchart of the ink temperature calculation process following FIG. 14;

FIG. 16 is an explanatory diagram for explaining a relationship between a remaining amount of ink and a change in ink temperature;

[Explanation of symbols]

13: carriage, 14: head, 15: ink cartridge, 49: timer, 51: temperature detecting element, 61: main control unit, 62: head driving circuit.

Claims (7)

[Claims] 1. An ink jet recording apparatus having an ink jet head, a temperature detecting means for detecting an ambient temperature of ink, a measuring means for measuring an elapsed time from a power-off time, a temperature detected at a power-off time, and the power supply. Means for determining an ink temperature based on an elapsed time from an off-state. 2. The ink jet recording apparatus according to claim 1, further comprising: means for adjusting a drive waveform applied to the ink jet head according to the determined ink temperature. 3. The ink jet recording apparatus according to claim 1, wherein the means for determining the ink temperature comprises a temperature fluctuating from a detected temperature when the power is turned off to a detected temperature when the ink temperature is determined, and e (= 2. 718), and calculates an ink temperature using an approximate expression including a product of an exponential function of an elapsed time from when the power is turned off to when the ink temperature is determined. 4. An ink jet recording apparatus equipped with an ink jet head, a temperature detecting means for detecting an ink ambient temperature, a measuring means for measuring an elapsed time from a start of a change in the ink ambient temperature based on the detected temperature, and the detecting means. Means for determining the ink temperature based on the temperature, the elapsed time from the start of the change in the ink ambient temperature, and the detection result of the start of the change in the ink ambient temperature. 5. The ink jet recording apparatus according to claim 4, further comprising means for adjusting a drive waveform applied to the ink jet head according to the determined ink temperature. 6. The ink jet recording apparatus according to claim 4, wherein the means for determining the ink temperature comprises: e) (= 2.718...) The fluctuation temperature from the detected temperature to the detected temperature at the time of determining the ink temperature. An ink jet recording apparatus, wherein an ink temperature is repeatedly calculated using an approximate expression including a product of an exponential function of an elapsed time from the start of a change in the ink ambient temperature to the time of determining the ink temperature. 7. An ink jet recording apparatus according to claim 3, wherein said means for calculating the ink temperature changes a thermal time constant used in said approximate expression according to the remaining amount of ink. apparatus.