JPH06297718A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To reduce the difference in ink emitting amt. due to the temp. difference between blocks, in a recording apparatus using a recording head whose ink emitting amt. is controlled at every block, by controlling the ink emitting amt. on the basis of the detected temp. of each of the blocks. CONSTITUTION:A recording head can emit many kinds of inks and has large number of emitting orifices with respect to respective color inks of yellow, magenta, cyan and black. Respective emitting heaters corresponding to the number of the respective emitting orifices are arranged on a substrate. The respective emitting orifices are divided into a plurality of blocks to be successively driven. In this case, a temp. sensor 18 is arranged to the central part of the substrate, that is, the area between the heater group and wiring group of cyan and black to detect the average temp. of the recording head. On the basis of the detected temp., an ink emitting amt. is controlled at every block. By this constitution, the difference in ink emitting amt. due to the temp. difference between the respective blocks is reduced.

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 which ejects ink by utilizing thermal energy.

[0002]

2. Description of the Related Art Conventionally, at least three colors (for example, C: cyan, M: center, Y: yellow) are required for recording a color image in an ink jet recording apparatus (hereinafter also referred to as a printer). Accordingly, since four colors of ink, in which Bk: black is added, are required, it is necessary to use recording heads for the number of these colors.

By the way, there is a demand for a color printer of recent years to be used by being incorporated in a so-called notebook personal computer, and for that purpose, it is necessary to reduce the size. Therefore, a small-sized recording head is being provided by integrally forming recording heads corresponding to inks of three or four colors.

On the other hand, in a printer for recording a color image, the reproducibility of the size of the dots formed on the recording paper by the ejected ink droplets, the density stability of the image formed by the set of these dots, and the gradation. Various performances such as reproducibility and color reproducibility are required, and various control methods have been used to cope with this. Particularly, in an ink jet recording apparatus that ejects ink by using thermal energy, the ink ejection amount that affects the above various performances varies due to environmental temperature and self-temperature rise due to ink ejection for recording. An ink ejection amount control method for maintaining performance has been proposed. In this case, when controlling the ejection amount, it is necessary to accurately read the environmental temperature and the self-heating of the recording head by a temperature sensor, the number of recorded dots, and the like.

Further, in a monochrome printer for recording using one color of ink, in order to improve the recording speed, a multi-line head in which a large number of ejection ports are arranged is used,
Higher drive frequencies have been proposed.

[0006]

However, if the number of ejection openings of the recording head is increased or the recording speed is increased,
When an ejection unit that ejects a plurality of ink colors is formed in one recording head, a temperature distribution occurs in the recording head depending on the usage state of the ejection heater, and the ejection amount may fluctuate due to this temperature distribution.

More specifically, when a block of ejection ports for ejecting a plurality of colors of ink is formed in one recording head, the ejection frequency differs depending on each ink color, and a difference in ink temperature may occur between the blocks. is there.

When a so-called full line type recording head in which a large number of ejection openings are arranged corresponding to a predetermined width of the recording paper is used, and when a recording paper having a width shorter than the width of the recording paper is used. During the recording, there is an ejection port that does not eject at all, and even in such a case, a temperature difference (temperature distribution) is generated between the ejection portion and the non-ejection portion.

In such a case, for example, an ink jet recording apparatus in which each ejection port of the recording head is controlled by a constant drive cannot prevent the variation of the ejection amount due to the occurrence of the temperature distribution, resulting in uneven density. In this state, if a full-color image of four colors of cyan, magenta, yellow, and black is recorded, the color balance may be lost, the tint change or the color reproducibility may be deteriorated (increased color difference), and the image quality may be deteriorated. . In addition, there is a problem that density unevenness occurs in a monochrome image such as black, red, blue and green.

In order to solve these problems, it is necessary to have a means for correcting the density unevenness, that is, the discharge amount fluctuation. For example, conventionally, a large number of temperature sensors are mounted in the print head to control the ejection amount of each ejection port according to the outputs of these sensors, or the ejection number is counted for each predetermined block of plural ejection ports, The temperature has been estimated to control the ejection amount for each block, or the print head is kept at a relatively high constant temperature. But,
In the case of such a configuration, another device such as a correction unit for correcting manufacturing variations of a large number of temperature sensors and a counter for counting the number of discharges is required, which causes an increase in cost of the entire device and Inhibits downsizing (increased area required for mounting the sensor, increase in signal lines due to divisional drive, etc.), reduced durability of the recording head, and decreased reliability (bad temperature control). There was a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress variations in ejection amount due to a temperature difference between predetermined blocks of ink ejection ports in a recording head, and to improve density. An object of the present invention is to provide an inkjet recording apparatus capable of performing recording with reduced unevenness.

[0012]

To this end, according to the present invention, a block composed of ejection ports for ejecting ink, the plurality of blocks being capable of controlling the ink ejection amount from the ejection ports for each block In an ink jet recording apparatus that performs recording by ejecting ink onto a recording medium by using a recording head having a plurality of temperature detecting means, the number of which is smaller than the number of blocks, and the temperature detected by the temperature detecting means. A discharge amount control means for controlling the ink discharge amount for each of the plurality of blocks.

More preferably, a recording head having a plurality of blocks, each of which is composed of an ejection port for ejecting ink and in which the amount of ink ejected from the ejection port can be controlled for each block, is used. In an ink jet recording apparatus that performs recording by ejecting ink onto a recording medium, the number of temperature detection units that is smaller than the number of blocks and the number of recording signals indicating ink ejection from the ejection ports are set to the plurality of blocks. Counting means for each of the plurality of blocks, based on the temperature detected by the temperature detecting means and the number of the recording signals for each of the plurality of blocks counted by the counting means And a control means for controlling the operation.

[0014]

According to the above construction, by knowing the number of recording signals for each block, it is possible to estimate the ink temperature change for each block due to ink ejection. Based on the estimated value and the detection output of the temperature detecting means, The ink ejection amount for each block can be controlled. As a result, it is possible to reduce the difference in the ink ejection amount due to the temperature difference between the blocks.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is an exploded perspective view of a recording head unit used in an embodiment of the present invention.

The unit of this example is roughly divided into four parts as shown in FIG. That is, the recording head unit includes the recording head 1, the ink tank portion 4, and the carriage 2.
0 and cover 30.

The recording head 1 has a base plate 13 and a substrate (not shown) bonded near the front end of the base plate 13, and an ejection heater (electrothermal conversion element) for generating thermal energy used for ejection is provided on the substrate. ) And electrode wiring, as well as a temperature detecting element and the like are formed by the same process as the semiconductor manufacturing process. The grooved top plate 10 is bonded to the above-mentioned substrate corresponding to the portion where the discharge heater and the like are arranged, and thus ink paths, discharge ports and the like corresponding to the respective discharge heaters are formed. A front plate is formed vertically and integrally with the front end portion of the top plate 10, and this portion constitutes a discharge port arrangement surface. The base plate 13 is provided with a connector 16 for electrically connecting the circuit formed on the substrate and the apparatus body control circuit. The recording head 1 is capable of ejecting four types of ink, as will be described later, and each ejection port array is arranged so as to form a linear ejection port array 11.

The carriage 20 is slidably provided with a guide shaft 21 (only a part of which is shown in FIG. 1) provided on the main body of the apparatus, and is driven by a drive mechanism (not shown) to guide the guide shaft. It is possible to move along 21.
The recording head 1 is mounted on the carriage 20 so that its connector 16 is inserted into a connector receiver 22 provided on the carriage 20.

The ink tank section 4 corresponds to four kinds of inks of yellow (Y), magenta (M), cyan (C) and black (BK).
It has Y, 4M, 4C and 4BK. this house,
The black ink tank 4BK has other tanks 4Y,
It has a larger ink capacity than 4M and 4C. In these ink tanks, the connection holes 3 provided in each of the ink tanks are connected to the connection pipes 2 of the recording head 1 to form the recording head 1.
It is possible to supply ink to the ink. Each connecting pipe 2 is connected through the supply paths 15Y, 15M, 15C and 15BK,
It is connected to each liquid chamber. Ink tanks 4Y, 4M, 4C
And 4BK include the carriage 20 together with the recording head 1.
Be attached to.

The cover 30 is provided with a member for positioning and fixing the print head 1 and the ink tanks 4Y, 4M, 4C and 4BK when the carriage 20 is mounted, and is used for fixing the print head and the like. A shaft 37 provided on a part of the cover 30 is rotatably supported by a bearing 24 of the carriage 20, so that the cover 30 can be opened / closed by the rotation when the recording head or the like is replaced.

FIG. 2 is a plan view showing details of the substrate of the recording head 1 shown in FIG.

The recording head 1 of this embodiment is capable of ejecting different kinds of ink with one recording head, and 24, 24, 24 and 64 inks of yellow, magenta, cyan and black respectively. Equipped with individual discharge ports. Therefore, as shown in FIG. 2, discharge heaters (electrothermal conversion elements) corresponding to the number of discharge ports are formed on the substrate. The ejection heater group corresponding to each ink type has a space of eight ejection ports for each of yellow, magenta, and cyan. Further, the cyan and black discharge heater groups have a space for 16 discharge ports.

A temperature sensor 18 made of Al is formed in the central portion of the substrate, that is, between the cyan and black heater groups and the wiring groups. The temperature sensor 18, the average temperature of the recording head (hereinafter, also referred to as the head temperature T _H)
Is to detect. The temperature in the vicinity of each ejection port corresponding to each color ink is estimated by counting the number of ejections from these ejection ports.

The maximum driving frequency of the recording head of the present example shown above is f _r = 8.0 kHz, and the driving frequency during normal recording is 5.4 kHz. It also has a resolution of 360 dpi. In this recording head, 64 black ink ejection ports are divided into 8 blocks and driven. That is, one block of ejection port is
Every other 1, 9, 17, 25, 33, 41, 49, 57
The heaters of these ejection ports are simultaneously driven as the second ejection port, and then the second, second, ..., Eighth block including eight ejection ports selected in the same manner are sequentially driven.

The interval for driving each block is 8.5 (μse
c). This is each continuous 1-8,9-1
6, 17-24, 25-32, 33-40, 41-4
For example, when a vertical ruled line is printed by the ink ejected from the 8,49 to 57,58 to 64th ejection ports,
This is a setting to make a vertical straight line visually.
That is, when considering eight consecutive ejection ports, 8 ×
When the carriage moves at a speed of 381 (mm / sec) for 8.5 (μsec) = 68 (μsec),
This is to prevent the visual linearity from being impaired by the inclination of the recorded dot array. In the case of 360 DPI, the inclination of the dot arrangement is a positional deviation of the upper and lower dots, and it is necessary to suppress the resolution to half or less of the resolution: about 35 (μm).

The cyan 24 ejection port is divided into 3 blocks, the magenta 24 ejection port is divided into 3 blocks, and the yellow 24 ejection port is divided into 3 blocks, which are similarly driven.

FIG. 3 is a schematic diagram showing a method for forming a color image in this example.

Color recording is performed as follows using the recording head integrated with multicolor inks shown in FIGS.

That is, in the first scan, the first pass is printed using only 24 ejection openings of black ink, and the recording paper is fed by 24 ejection openings. Next, in the second scan, the first pass is printed using only eight cyan ink ejection ports. At this time, the second pass is black ink 24
Recording is performed using individual discharge ports.

Similarly, after feeding the recording paper by 24 ejection ports, in the third scanning, recording is performed using 16 ejection ports of cyan ink in the first pass. At this time, the third pass prints with 24 ejection ports of black ink, and the second pass prints with 8 ejection ports of cyan ink.

When the recording paper is fed by 24 discharge ports, the fourth
In scanning, recording is performed by using 24 ejection ports of magenta ink. At this time, the 4th pass is 24 ejection ports of black ink, the 3rd pass is 8 ejection ports of cyan ink, and the 2nd pass is cyan. Recording is performed using the 16 discharge ports of.

Further, after feeding the recording paper by 24 ejection ports, in the fifth scan, recording is performed using 16 ejection ports of yellow ink in the first pass. At this time, the fifth pass has 24 ejection ports of black ink, the fourth pass has 8 ejection ports of cyan ink, the third pass has 16 ejection ports of cyan ink, and the second pass has 24 ejection ports of magenta ink. Recording is performed using each discharge port.

Further, after shifting the recording paper by 24 ejection ports, in the sixth scanning, the first pass is recorded by using eight ejection ports of yellow ink. At this time, the sixth pass has 24 ejection ports of black ink, the fifth pass has eight ejection ports of cyan ink, the fourth pass has 16 ejection ports of cyan ink, and the third pass has 24 ejection ports of magenta ink. Second outlet, second
A pass is recorded by using 16 ejection ports of yellow ink.

As described above, color printing for one line (for one pass) can be performed by six scans.

FIG. 4 shows a method for performing monochrome recording, in which recording is performed using 64 black ink ejection ports.

FIG. 5 is a waveform diagram for explaining the divided pulses for driving the recording head used in this example.

In this example, the recording head driving method and the recording method have the following features. A divided pulse driving method is used for driving the recording head. As shown in FIG. 5, V _OP is a driving voltage, P ₁ is a preheat pulse and its width, P ₂ is an interval time and its width, and P ₃ is a main heat. The pulse and its width are shown respectively. T
₁ , T ₂ and T ₃ have widths P ₁ , P ₂ and P _{3 respectively}
Shows the time to decide. V _OP constitutes the electrical energy required to generate thermal energy in the ejection heater, and is determined according to the area of the ejection heater, the resistance value, the film structure and the ink path structure of the recording head.

In the split pulse driving method, the pulses P ₁ , P
_A pulse is given in the order of ₂ and P ₃ . Preheat pulse P ₁
Is a pulse mainly for controlling the ink temperature in the ink passage where the ejection heater is provided. This pulse P ₁ is
Detection output of the temperature sensor 18 of the recording head described above, i.e., to determine the pulse width of the recording start time based on the head temperature T _H, since the start of recording, the counter for counting the number of discharges (hereinafter, the dot counter The pulse width is changed based on the data (also referred to as the data of the temperature rise ΔT of the recording head). Such a method of modulating the pulse width P ₁ is called a PWM driving method.

Of the pulses P ₁ , P ₂ , P ₃ , the pulse P
Reference numeral ₁ denotes a preheat pulse, which mainly controls the ink temperature in the ejection port and changes the ejection amount as described above. The width of the pulse P ₁ needs to satisfy the condition that the pre-foaming phenomenon does not occur due to too much heat energy being applied to the ink. P ₂ is an interval time, and is provided for providing a constant time interval so that the pre-heat pulse P ₁ and the main heat pulse P ₂ do not interfere with each other, and for uniforming the temperature distribution of the ink in the ejection port. It is also possible to control the ejection amount by modulating the interval P ₂ . The pulse P ₃ is a main heat pulse, which causes a bubbling phenomenon in the ink on the ejection heater, and ejects an ink droplet from the ejection port due to the growth of this bubble. These pulse widths are, as mentioned above,
It is determined by the area of the discharge heater, the resistance value, the film structure, the ink path structure of the recording head, the ink physical properties, and the like.

Next, a discharge amount control method using the preheat pulse P ₁ will be briefly described with reference to FIGS. 6, 7 and 8.

FIG. 6 is a diagram showing the relationship between the preheat pulse P ₁ and the ink ejection amount V _D when the head temperature T _H is constant.

As shown in FIG. 6, the pulse width P ₁ is P _1LMT.
Until it reaches P, then after that, the pre-foaming phenomenon disturbs the foaming of the main heat pulse P ₃ and P
_When it exceeds _1MAX , the discharge amount tends to decrease.

Next, FIG. 7 is a diagram showing the relationship between the head temperature T _H and the ejection amount V _{d under} the condition that the preheat pulse P _{1 is} constant. As shown in FIG. 7, the ejection amount V _d is It tends to increase linearly as the head temperature T _H increases.
The coefficient of the region showing each linearity shown in FIGS. 6 and 7 is the preheat pulse dependence coefficient of the ejection amount: K _P = ΔV _DP
/ ΔP ₁ (ng / μs · dot), head temperature dependence coefficient of ejection amount: K _TH = ΔV _DT / ΔT _H (ng / C · dot)
It is decided like.

In the structure of the recording head shown in FIGS. 1 and 2, the above coefficient is

[0046]

## EQU1 ## In the black ink, K _P = 8.25 (ng / μsec · dot) K _TH = 0.7 (ng / μsec · dot) In the cyan, magenta, and yellow inks, K _P = 4.12 ( ng / μsec · dot) K _TH = 0.36 (ng / μsec · dot).

The discharge amount control as shown in FIG. 8 is performed by effectively utilizing these coefficients. That is, by modulating the pulse width P ₁ according to the print head temperature (PWM control), the ejection amount is kept constant even if the environmental temperature changes or the head temperature changes due to self-heating due to printing. You can

As described above, it becomes possible to provide a discharge amount control method capable of keeping the discharge amount of each color ink constant at all times.

The ejection characteristics of the recording head driven using the ejection amount control method as described above are as follows.

In the case of a black ink recording head, the head temperature T _H = 25.0 (° C.) and the pulse voltage V _OP = 25.
When 6 (V), pulse width P ₁ = 1.50 (μsec),
Interval P ₂ = 2.0 (μsec), pulse width P ₃
When a pulse of 3.00 (μsec) is given, optimum driving conditions are established and a stable ink ejection state is obtained. The ink discharge amount at this time is V _d = 80.0 (ng / dot),
The ejection speed is V = 14.0 (m / sec).

In the case of each of the cyan, magenta, and yellow recording heads, the head temperature T _H = 2 for each ink color.
When V _OP = 25.6 (V) at 5.0 (° C), pulse width P
₁ = 1.00 (μsec), interval P ₂ = 2.0
(Μsec) and a pulse width P ₃ = 3.00 (μsec) are given, the optimum driving conditions are obtained, and a stable ink ejection state is obtained. At this time, the ink discharge amount is V _d
= 40.0 (ng / dot), and the discharge speed is V = 14.
It is 0 (m / sec).

FIG. 9 is a schematic perspective view showing an example of an ink jet recording apparatus which uses the recording head shown in FIGS.

In FIG. 9, the recording head 1 has a plurality of ink ejection openings (on the surface facing the recording paper 59) for ejecting the above-described black, cyan, magenta, and yellow inks in the conveyance direction of the recording paper 59. (Not shown). In addition, the recording head 1 is provided with an ink path (not shown) communicating with each of these ejection ports, and each of the ink paths has a heat used for ejecting ink to a substrate forming the recording head 1. An electrothermal conversion element that generates energy is formed. The electrothermal transducing element generates heat by the above-mentioned divided pulse applied to the electrothermal transducing element according to drive data, thereby causing film boiling in the ink, and generating the bubbles due to the film boiling. Ink is ejected from the outlet. For each ink path, a common liquid chamber that communicates with them in common is provided for each ink color, and the ink stored in these is supplied to the ink path according to the ejection operation in each ink path. It

The carriage 20 carries the recording head 1 and ink tanks 4Bk, 4C, 4M and 4Y, and
The pair of guide rails 55, 55 extending parallel to the recording surface of the recording paper 59 are slidably engaged. As a result, the recording head 1 can move along the guide rails 55, 55, and along with this movement, recording is performed by ejecting ink toward the recording surface at a predetermined timing. After the above movement, the recording paper 59 is conveyed by a predetermined amount as shown in FIG. 3, and the above movement is performed again for recording. By repeating such an operation, the recording paper 59 is sequentially
Records characters, images, etc.

A unit for ejection recovery processing is arranged at one end of the movement of the recording head 1. That is, this unit includes a blade 58 for wiping the surface on which the recording head 1 and the ejection port are provided, and a cap used for covering the ejection port surface and absorbing ink.

The control circuit of the ink jet recording apparatus shown in FIG. 9 is formed on a predetermined substrate (not shown), and the CPU in this circuit executes the control processing and data processing shown in FIG.

The ink jet recording apparatus shown in FIG. 9 ejects one row (one pass) of recording for each block of ejection ports corresponding to each ink color in a recording signal of characters, images, etc. sent from a host computer (not shown). It has a counter for individually counting the number, that is, the number of dots formed on the recording paper. It also has a function of counting the number of dots per unit time for each block.

In this example, the temperature rise per unit time in the ink path portion of each ink color corresponding to the number counted by this counter is determined in advance by calculation and experiment, and the relation between this counter value and the temperature rise is determined. Table T
Set the _DOT . In this example, the calculation was performed on the assumption that the temperature rise of the ejection port block of each ink color does not affect the blocks of other colors, but the experimental data also show the influence of the temperature rise of other ink colors. Is known to be negligible. As described above, in the creation of the table, the temperature rises of the four color inks influence each other and become complicated, and other influences are small from the experimental results. , It may be created in consideration of other influences in calculation. The ejection amount control is independently performed for each ink color according to the following sequence with reference to the table set as described above.

A method (sequence) for simultaneously controlling the ejection port blocks of four ink colors using one temperature sensor will be described below.

FIG. 10 is a flow chart showing this sequence.

In step S1, the sensor 18 (see FIG. 2) is used to measure the temperature T _j (j = 1 to 10) every 5 msec.
Is detected to obtain the average temperature T _avg = ΣT _j / Σ _j 10 times, and this is set as the head temperature T _H. Next, step S
In 2, the head temperature _TH is set as the initial temperature of the temperature T _{N (K, C, M, Y)} of the ejection port block of each ink color.

In step S3, the number of dots indicated by the recording signal of each ink color sent from the host computer is set to 50 for the ejection port block of each ink color.
Counting for msec, and let this be N _Ki , N _Ci , N _Mi , and N _Yi .

In step S4, the total number of dots N _K0 , N _C0 for 50 msec for each ink color block is calculated.
Ratio α to N _M0 , N _Y0 (number of dots in the case of full discharge)
_{Find ji} (hereinafter also referred to as recording duty).

[0064]

[ _Mathematical formula-see original _document ] α _Ki = N _Ki / N _K0 α _Ci = N _Ci / N _C0 α _Mi = N _Mi / N _M0 α _Yi = N _Yi / N _{Y0 In} step S5, the above-mentioned dot ratio α _ji is used for the _calculation. The temperature rise ΔT _ji for each ejection port block is obtained by referring to the table, and the head temperature is added to this to obtain the temperature T _ji for each ejection port block.

[0065]

Equation 3] _{T Ki = T H + ΔT Ki} T Ci = T H + ΔT Ci T Mi = T H + ΔT Mi T Yi = T H + ΔT At _Yi step S6, the driving parameters based on the ink color of the temperature T _ji, That is, the pulse width P ₁ (T _ji ) is set to P
Allocate by WM table.

Thereafter, the above sequence is repeated every 50 msec to set the drive parameter (pulse width) according to the recording signal of each color.

FIG. 11 is a diagram showing the relationship between the temperature rise ΔT _ji and the recording ratio α _ji for each ink color.

In the figure, the temperature rise per unit time ΔT _{ji with} respect to the number of recording dots (recording duty) α _ji per unit time under the condition that the ambient temperature is T _R = 25 ° C.
It shows the relationship with.

Even with such a complicated ejection amount control method, when this method is used, the ejection amount can be kept constant even if images of various patterns are recorded, so that the difference in density between the left and right images and the page It is possible to record with excellent gradation reproducibility and color reproducibility without unevenness in inner density or density change.

In this example, the ejection amount control is performed by the PWM control of the pulse P ₁ of the divided pulses.
The same effect can be obtained by controlling the discharge amount by PWM control of the interval P ₂ .

Using the discharge amount control method of this example, the environmental conditions are low, low humidity (15 ° C./10%), high temperature,
The results of the discharge test performed in an environment up to a high humidity environment (35 ° C / 90%) are shown below.

[0072] Black Ink driving conditions pulses P _1: PWM control (T _H = 25 when ℃ P ₁ = 1.50 (μsec) interval P _2: 2.00 (μsec) pulse P _3: 3.00 (μsec ) (However, it is changed according to the individual difference of the _print head), the ejection amount: V _dBk = 80.0 ± 4.0 (ng / d
ot) (between pages, within page), reflection density: O _DBk =
It becomes 1.35 ± 0.05 (between pages, within page).

Cyan, magenta, and yellow driving conditions pulse P₁ : PWM (T_H = P at 25 ℃₁ = 1.00 (μsec) Interval P₂ : 2.00 (μsec) pulse P₃ : 3.00 (μsec) (however, it changes depending on the individual difference of the print head), the ejection amount: V_{dC, M, Y}= 40.0 ± 3.0 (ng /
dot), reflection density: O _DC= 1.20 ± 0.05 (page
Between pages, page), O_DM= 1.20 ± 0.05 (page
Between, page), O_DY= 1.15 ± 0.05 (page
Interval, within the page), showing extremely stable concentration reproducibility.
did.

(Embodiment 2) FIG. 12 is a schematic perspective view showing an ink jet recording apparatus according to a second embodiment of the present invention, in which the present invention is applied to a monochrome printer using a full line type recording head. Is.

The recording head 61 shown in the figure is approximately 280 mm.
4096 discharge ports are arranged over the entire length, and they are fixed to the apparatus during the recording operation (the fixing mechanism is not shown). Temperature sensors are arranged at positions apart from the discharge heater on both sides of the pattern wiring on the substrate of the recording head. The characteristics and structure of the recording head have a resolution of 400DP
I, the total number of discharge ports is 4096, the drive frequency is 4 kHz, and the discharge amount is 40 (pl / dot). When this recording head is driven, 4096 ejection ports (ejection heaters) are used.
It is divided into blocks, and 256 discharge heaters per block are driven and controlled independently for each block.

In such a full-line type recording apparatus, density unevenness similar to the density unevenness (so-called AB density unevenness) that occurs in electrophotography, for example, may occur. For example, if 100 sheets of A4 size paper are vertically fed and then the same size of paper is horizontally fed, the unused ejection ports during vertical feeding recording are suddenly used. And the vertical length causes a temperature distribution in the recording head. As a result, this temperature distribution causes a difference in discharge amount, that is, a density difference, and density unevenness occurs. That is, since the use area of the ejection port changes, it is necessary to perform recording by using the used ejection port and the unused ejection port at the same time. Such a problem is a problem that occurs because all the ejection ports (ejection heaters) of a relatively long recording head are driven under the same driving conditions.

Therefore, in this example, 1. Paper size selected by the user, 2. Paper feed direction, and 3. The drive condition of each discharge heater is switched according to three conditions, that is, the total number of discharge pulses before recording.

That is, a dedicated drive table is provided in advance for each paper size, and the block of each ejection port is divided into a plurality of blocks corresponding to the paper width, and the paper width is detected from the paper size and the paper feed direction. By doing so, the driving condition is set. For example, A6, A5, A4, A3, B5, B4
The discharge heater driving conditions for each block are set from the table in correspondence with various paper sizes and paper feed directions.

Further, the total number of discharged ink droplets (the number of dots) in the previous recording is detected, and the temperature distribution of the recording head is predicted accordingly. Then, based on this printhead temperature distribution, the drive condition for each block set for the paper width is corrected.

As described above, the conditions for the paper width and the like are determined and the driving conditions for each discharge heater are set.
The M control can be performed, and it becomes possible to correct the difference in the ejection amount caused by the temperature distribution of the recording head, which occurs due to the difference in the usage state of the ejection ports.

In this embodiment, the PWM control of the pre-pulse width P ₁ of the divided pulse is performed as in the first embodiment, but the drive voltage V _OP is also changed at the same time to expand the control area. The ejection stability can be further improved.

(Embodiment 3) FIG. 13 is a plan view showing a substrate of a recording head according to a third embodiment of the present invention.

Similar to the first embodiment, it is a substrate of a recording head having a four-color ink integrated structure, and is provided with three temperature sensors 181, 182 and 183, which are less than the number of ink colors, and the ejection amount is determined based on these detection outputs. Take control.

Three temperature sensors 181, 182 and 1
As for the arrangement of 83, one is provided between the ejection port arrays for each ink color, that is, between black and cyan, between cyan and magenta, and between magenta and yellow.

These three sensors 181, 182
183 is used to drive and control the ejection of each ink color independently according to the following sequence.

That is, the sensors 181, 182 and 1
The three head temperatures T _Hi are read by 83 before the start of recording, and 1) the detected temperature T _Hi is determined according to the position and number of the ejection ports used.
The calibration temperature (average temperature that does not depend on the relative position of the temperature sensor and the Si substrate) T _H ′ _X = (X ₁ TH ₁ + X ₂
T _H2 + X ₃ T _H3 / (X ₁ + X ₂ + X ₃ ) is obtained, and the initial drive condition P _1i for each ink color is set by this calibration temperature T ′ _{H X.}

2) The temperature distribution of the recording head is detected from the outputs T _H1 , T _H2 and T _{H3 of the} sensors 183, 182 and 181, and the ejection heater of each ink color block is driven based on this information. _Are independently corrected and controlled (P _1i ).

More specifically, when only 64 ejection ports of black ink are used, the head temperature T _H shows a temperature distribution such that the ejection portion of black ink becomes high. This tendency becomes more remarkable as the print duty becomes higher. Also. During recording, the temperature sensor 183 always shows a high temperature, and the temperature sensors 181 and 182 farther from the black ink ejecting portion show a lower temperature ( _TH1 > _TH2 > _TH3 ).

When the recording head is driven by using the average head temperature T _H measured in this state, the temperature is lower than the actual temperature T _H1 (T _H1 > T _H ) of the discharging ejection port. Since the judgment is made and the control is performed, the control for increasing the discharge amount works. Originally, since the control had to work to reduce the discharge amount, the control diverged. Further, as the pulse width P ₁ becomes longer, the temperature rise due to ejection also becomes larger, so that the temperature difference between the ejection portion and the non-ejection portion of each block becomes larger and larger.

In order to eliminate these vicious circles, for example, if the discharge control is performed only by the above-mentioned calibration temperature T _H ′ _X calculated by weighting the temperatures detected by the temperature sensors 181, 182, 183, as described above. Due to the difference from the actual temperature, the ejection amount of black and yellow ink on both sides of the recording head cannot be kept constant.

On the other hand, as in this example, the calibration temperature T
_H ′ _X and the temperature T _{H1 of} each sensor 183, 182, 181
By constantly monitoring the difference between T _H2 and T _H3 and detecting and controlling the temperature distribution of the print head, it is possible to control the ejection of each ink color simultaneously and independently.

The driving condition of each ink color is, for example, according to the temperature detected by each temperature sensor,

[0093]

[Number 4] _{P 1Bk = P 1Bk0 (T H} ') -ΔP 1BK (α (T
_{H 'X -T H1)) P} 1C = P 1C0 (β (T H1 + T H2) / 2) P 1M = P 1M0 (γ (T H2 + T H3) / 2) P 1Y = P 1Y0 (T H') _{-ΔP 1Y (δ (T H '} X -T
_H3 )).

Further, more accurate control is possible by independently counting and feeding back the recording signals of each ink color. That is, in addition to the above controls 1) and 2), 3)
It is also possible to calculate the self-temperature rise due to printing from the number of dots per unit time of the block of each ink color in the printing signal, and independently control the predicted temperature by correcting the calibration temperature.

The weighting values are the print duty ratios of the respective ink colors, which have been previously obtained through experiments and calculations, the average head temperature T _H ′ _X , the actual ejection port temperature T _Hi (i = Bk,
C, M, Y).

For example, when black ink is _printed at a duty of 100% in this state, the peak temperatures detected in the first line are T _H1MAX = 43 ° C. and T _H2MAX = 30.
C, T _H3MAX = 25 ° C. Therefore, 1) In conventional control,

[0097]

T _H ′ _X = (43 + 30 + 25) / 3 = 31.
0 ° C. (calibration temperature) T _Bk = 48 ° C. (actual temperature) ΔT = 48−31 = 17.0 ° C. Since the driving is performed at a low condition of 17 ° C., the difference in discharge amount increases, which is not preferable. On the other hand, 2) In the control of this embodiment,

[0098]

T _H ′ _X = (43 + 30 + 25) / 3 = 31.
0 ° C. (calibration _{temperature) α (T H1 -T H '} X) = 1.2 · (43-31.0) =
14.4 ° C. (corrected temperature) T _Bk = 48 ° C. (actual temperature) ΔT = 48−31−14.4 = 3.6 ° C. As shown in FIG. (However, α = 1.2 is obtained from calculation and experimental values, and varies depending on factors such as head morphology and material).

In this embodiment, α = 1.2 and β =
The preferable conditions were 1.05, γ = 1.0, and δ = 1.1.

(Others) The present invention is particularly provided with means for generating thermal energy as energy used for ejecting ink (for example, an electrothermal converter or a laser beam) even in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because such a system can achieve high density recording and high definition recording.

Regarding its typical structure and principle, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
Although it can be applied to any of the continuous type, in particular, in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal in a one-to-one correspondence
It is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, the liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable to make this drive signal into a pulse shape because bubbles can be immediately and appropriately grown and contracted, so that liquid (ink) ejection with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, further excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the ink jet from the main body of the apparatus is electrically connected to the main body of the apparatus by being attached to the main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add ejection recovery means of the recording head, preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping unit, a cleaning unit, a pressure or suction unit for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, and a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet system, it is common to control the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change from the solid state of the ink to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as the form of the ink jet recording apparatus of the present invention, in addition to the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmitting / receiving function are provided. It may be a form or the like.

[0109]

As is apparent from the above description, according to the present invention, by knowing the number of recording signals for each block, the ink temperature change for each block due to ink ejection can be estimated. The ink ejection amount for each block can be controlled based on the detection output of the detection means. As a result, it is possible to reduce the difference in the ink ejection amount due to the temperature difference between the blocks.

As a result, it is possible to record a high-quality image with little density unevenness.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a recording head, an ink tank, and a carriage that integrally mounts them, according to an embodiment of the present invention.

FIG. 2 is a plan view showing a substrate forming the recording head shown in FIG.

FIG. 3 is a schematic diagram showing the relationship between printhead scanning and paper feed during color recording using the printhead.

FIG. 4 is a schematic diagram showing scanning of a recording head during monochrome recording using the recording head.

FIG. 5 is a waveform diagram of recording head drive pulses for ejecting ink used in the above-described embodiment.

FIG. 6 is a diagram showing a relationship between a pulse width and an ejection amount when the drive pulse is used.

FIG. 7 is a diagram showing a relationship between a printhead temperature and an ejection amount when the drive pulse is used.

FIG. 8 is a diagram for explaining a discharge amount control method using the drive pulse.

9 is a perspective view showing an example of an inkjet recording apparatus using the recording head shown in FIGS. 1 and 2. FIG.

FIG. 10 is a flowchart showing a procedure of drive pulse width setting processing according to an embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the recording ratio (ejection ratio) and the temperature rise of the recording head in the above embodiment.

FIG. 12 is a perspective view showing an ink jet recording apparatus according to another embodiment of the present invention.

FIG. 13 is a plan view showing a substrate of a recording head according to still another embodiment of the present invention.

[Explanation of symbols]

 1,61 Recording head 4,4Y, 4M, 4C, 4Bk Ink tank 18,181,182,183 Temperature sensor 20 Carriage 59,69 Recording paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/05 2/12 8306-2C B41J 3/04 102 Z 9012-2C 103 B 9012-2C 104 F

Claims (7)

[Claims] 1. A recording medium using a recording head having a plurality of blocks, each of which is composed of an ejection port for ejecting ink, and in which the amount of ink ejected from the ejection port can be controlled for each block. In an inkjet recording apparatus that ejects ink onto a plurality of blocks to perform recording, the number of temperature detection units that is smaller than the number of the plurality of blocks, and the ink ejection amount for each of the plurality of blocks is determined based on the temperature detected by the temperature detection unit. An ink jet recording apparatus comprising: 2. A recording medium using a recording head having a plurality of blocks for ejecting ink, the ink ejection amount from the ejection ports being controllable for each block. In an ink jet recording apparatus for ejecting ink to perform recording, the number of temperature detection units that is smaller than the number of the plurality of blocks and the number of recording signals indicating ink ejection from the ejection ports are counted for each of the plurality of blocks. Counting means for controlling the ink ejection amount for each of the plurality of blocks based on the temperature detected by the temperature detecting means and the number of the recording signals for each of the plurality of blocks counted by the counting means. An ink jet recording apparatus comprising: 3. The ink jet recording apparatus according to claim 1, wherein the plurality of blocks have different types of ejected ink. 4. The ink jet recording apparatus according to claim 1, wherein the plurality of blocks are set corresponding to a size of the recording medium. 5. The number of the temperature detecting means is one less than the number of the plurality of blocks, and the temperature detecting means is arranged between each of the plurality of blocks. The inkjet recording device according to any one of 1. 6. The ink jet recording apparatus according to claim 5, wherein the detection output of the temperature detecting means is weighted according to the arrangement. 7. The recording head according to claim 1, wherein the recording head uses the thermal energy to generate bubbles in the ink, and ejects the ink based on the generation of the bubbles. Inkjet recording device.