JPH09183222A - Ink jet recording device - Google Patents

Abstract

(57) An object of the present invention is to enable an excessive temperature rise due to heat storage of a recording head in an inkjet recording apparatus with a simple configuration, thereby realizing high-speed and high-quality recording. SOLUTION: In the width P2 of a pulse applied to a heating element for generating bubbles in the ink and ejecting the ink by the pressure of the bubbles, the point at which the ink undergoes a phase transition from a liquid phase to a vapor phase B The thermal energy input by the pulse widths P2b and P2b 'after the point directly causes heat accumulation in the recording head. Therefore, the pulse widths P2b and P2b 'are controlled according to the temperature detected by the recording head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus, and more particularly to temperature control of a recording head.

[0002]

2. Description of the Related Art In recent years, OA devices such as personal computers and word processors have become widespread, and as a method for printing out information processed by these devices, a thermal transfer system, a wire dot system, an inkjet system, an LB system.
Various recording methods and recording apparatuses such as the P (laser beam printing method) method have been developed. Further, in these recording devices, speeding up and image quality improvement are one of the major trends.

The problem generally associated with achieving such high speed and high image quality is the problem of heat storage in the recording head. For example, in the thermal transfer method, a pulsed drive signal is applied to the recording head, but if the same pulse is applied when the recording head is accumulating heat and when it is not accumulating, the recording head of the recording head is turned off during the heat accumulation. The temperature does not decrease so much, which causes ink transfer to the recording paper continuously, which may cause image defects called tailing. As a countermeasure against this, in the thermal transfer recording apparatus, a divided pulse as shown in FIGS. 1A to 1F is used as a pulse applied to the recording head, and the pulse number and pulse width of the divided pulse are used according to the temperature of the recording head. The means for controlling the total energy input to the recording head has been taken as a measure against heat accumulation, such as a means for modulating the voltage or a means for modulating the applied voltage.

On the other hand, in the ink jet recording method, since the recording principle is a digital method of whether ink droplets are ejected or not, even if the temperature of the recording head rises, there is a problem such as tailing as in the thermal transfer recording method. 2A does not occur, but as shown in FIG. 2A, the amount of ejected liquid droplets (hereinafter referred to as the ejection amount) changes depending on the temperature of the print head, and therefore, it is necessary to take measures to improve image quality. Become.

However, in the ink jet recording system in which an electric pulse is applied to the heater to rapidly heat the ink to change the liquid phase of the ink to the vapor phase to generate the foaming force, the liquid phase is in the vapor phase. Since the discharge amount is substantially determined by the way of transmitting energy until it changes, the discharge amount is hardly affected by any energy input after the state change to the gas phase. Therefore, in the bubble jet method, it is difficult to control the discharge amount by controlling the total input energy amount according to the temperature rise as in the above-mentioned thermal transfer method. It doesn't.

In the ink jet recording apparatus, one of the conventionally known measures against the variation in the ejection amount caused by the temperature rise is to control the energy transmission method until the state changes to the vapor phase. For example, the divided pulse as shown in FIG. 3A is used, and the width P1 of the preliminary pulse, which is a pulse, and the pause time Toff between the main pulse, which is the first pulse and the second pulse, are controlled to eject the ink. Performs quantity modulation.
2B and 2C show the width P1 of the preliminary pulse described above.
And the ejection amount when the rest time Toff is changed.

When a preliminary pulse is applied with its width P1,
The energy diffuses into the ink during the dwell time Toff, which affects the number of ink molecules that undergo a state change when the energy with foaming of the pulse width P2 is supplied in accordance with the pulse width P1. Can be given. That is, when the temperature of the recording head is increased and the ejection amount is increased, the pulse width P1 is set to be short to reduce the number of molecules involved in the state change of the ink molecules when the main pulse is applied. Can be suppressed.

The control of the pulse width P1 of the preliminary pulse described above controls the amount of input energy, but instead of changing the amount of input energy in this way, the rest time To
The discharge amount can also be controlled by changing ff. FIG. 2C is a diagram showing a change in the ejection amount when the rest time Toff is changed. Even when the pulse widths P1 and P2 are fixed, if the pause time Toff is lengthened, the ejection amount increases. This is the same principle as in the case of the pulse width P1, and the energy due to the application of the preliminary pulse is diffused farther from the heater by increasing the rest time, and as a result, a wider range of ink molecules is generated. A state change can occur when the main pulse is applied, and the ejection amount increases.

In the above description, the pulse applied to the heater is described as two divided pulses, but it is also possible to control the number of ink molecules whose state changes by using more divided pulses. Further, it is apparent that the ejection amount can be controlled by controlling the applied voltage instead of controlling the pulse width. However, as is clear from the above-mentioned ink ejection principle, the ejection amount cannot be modulated even by modulating the pulse width of the main pulse that causes foaming,
This point is very different from the thermal transfer method.

[0010]

However, the above-mentioned conventional measures against temperature rise have the following problems.

As described above, there is a tendency to increase the speed and improve the image quality in any recording apparatus of various recording systems. In order to increase the speed, the driving cycle for driving the recording head is shortened to, for example, 1/2, or the number of recording elements such as heating elements built in one recording head is doubled. However, this also increases the amount of heat generated per unit time.

The ink jet type recording apparatus is no exception, and the amount of heat generation or the amount of heat storage increases with the adoption of the structure for speeding up. Such head temperature fluctuations such as temperature rise can be dealt with by controlling the preliminary pulse width P1 and the rest time Toff as described above.
When the head temperature exceeds a certain value, the pulse width P1 and the pause time Toff cannot be set to zero or less, and there is a limit to the control that makes the pulse width and the like variable. If the temperature is raised in a range beyond the control such as the pulse width modulation, the ejection amount may change according to the temperature rise, and image defects such as tone deviation and density unevenness may appear. As described above, although both high speed and high image quality are required for the inkjet recording apparatus, it is often difficult to achieve both high speed and high image quality at the same time under the present circumstances. .

On the other hand, if the recording head is provided with a cooling device so as to offset the temperature rise of the recording head and control is performed, both high speed and high image quality are compatible, but it is often difficult in terms of cost.

The present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to reduce a larger temperature rise of the recording head due to the speed increase and to achieve high-speed recording without any cost adverse effect. An object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus that can achieve both high-quality recording and high-quality recording.

[0015]

According to the present invention, there is provided:
A recording head that has a heating element, uses the thermal energy generated by the heating element to generate bubbles in the ink, and ejects the ink by the pressure of the bubbles, ejects the ink from the recording head to the recording medium. In an inkjet recording apparatus for recording, a driving unit for applying a driving pulse composed of a plurality of pulses to a heating element, and a unit for modulating a pulse for generating bubbles among the plurality of pulses applied by the driving unit. And a pulse modulation means for performing modulation by adjusting the application end time of the pulse,
It is characterized by having.

More preferably, it further comprises temperature information acquisition means for acquiring the temperature information of the recording head, and the pulse modulation means modulates according to the temperature information acquired by the temperature information acquisition means. .

Further, it is characterized by further comprising an ejection amount setting means for setting the ejection amount of the recording head, and the pulse modulating means modulates in accordance with the ejection amount set by the ejection amount setting means.

With the above arrangement, when a plurality of pulses are applied and ink is ejected, of the pulses that directly generate bubbles, the portion after the ink undergoes the phase transition from the liquid phase to the vapor phase is modulated. As a result, for example, it is possible to eliminate the pulse application to that portion, suppress the temperature rise of the recording head, and largely modulate the ejection amount.

[0019]

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

[First Embodiment] FIG. 4 is a perspective view showing the schematic arrangement of an ink jet recording apparatus according to an embodiment of the present invention.

In FIG. 4, reference numeral 1 denotes a recording sheet made of paper or a plastic sheet. A plurality of recording sheets 1 are stacked in a cassette or the like and are fed one by one to a recording area shown by a feeding roller (not shown). Supplied. In this recording area, an arrow A is formed by a first conveying roller pair 3 and a second conveying roller pair 4 which are arranged at regular intervals and are driven by different stepping motors (not shown).
Conveyed in the direction.

Reference numerals 5a, 5b, 5c and 5d are ink jet type recording heads for recording on the recording sheet 1. These four recording heads are, for example, yellow (Y), magenta (M), cyan (C). ) And black (B
The ink of k) is ejected. Each ink is supplied from an ink cartridge (not shown) and is ejected from the corresponding ink ejection port of the recording head in accordance with an ejection signal. These recording heads and ink cartridges are mounted on the carriage 6, while the carriage motor 2 is mounted on the carriage 6 via the belt 7 and pulleys 8a and 8b.
3 are connected. As a result, the carriage motor 2
By driving 3, the carriage 6 can reciprocally scan along the guide shaft 9.

That is, the recording heads 5a, 5b, 5c and 5d perform recording by ejecting ink onto the recording sheet 1 according to the image signal while moving in the direction of arrow B in the figure. At the same time, it moves to the home position as necessary, and the discharge recovery device 2 eliminates clogging of the discharge port. Further, during the recording operation by the scanning of the recording head, the recording sheet 1 is conveyed by one line in the direction of arrow A by driving the pair of conveying rollers 3 and 4. By repeating the above operation, a predetermined amount of recording can be performed on the recording sheet 1.

FIG. 5 shows a control configuration of the ink jet recording apparatus, for example, a CPU 2 such as a microprocessor.
0a, a ROM 20b storing a control program of the CPU 20a and various data, and a control system 20 including a RAM 20c used as a work area of the CPU 20a and temporarily storing various data such as image data, an interface 21, Driver for driving the operation panel 22, each motor (carriage drive motor 23, paper feed motor drive motor 24, first transport roller pair drive motor 25, second transport roller pair drive motor 26) 27, and recording head driving driver 28
Consists of

The control section 20 inputs / outputs various information (for example, character pitch, character type, etc.) from the operation panel 22 and information such as image signals with the external device 29 via the interface 21. In addition, the control unit 20 uses an O for driving each of the motors 23 to 26 via the interface 21.
It outputs N, OFF signals and image signals for driving the recording head.

When high-speed recording is performed using the ink jet recording head having the above structure, as described above,
The recording head accumulates heat, and the head temperature cannot be adjusted by the control of the pulse width P1 of the preliminary pulse and the control of the pause time Toff which is the pulse interval of the divided pulse, which causes an error in the gradation reproducibility of the halftone recorded image. However, there is a concern that image defects such as uneven density may occur in a recorded image that should have a uniform density.

However, in the present embodiment, the above-mentioned adverse effects are suppressed by controlling the temperature rising rate of the recording head itself. The principle and control method for suppressing the temperature rise will be described below.

FIG. 6A shows the temperature on the heating element when a double pulse consisting of a preliminary pulse and a main pulse is applied to the recording head in a state where the temperature is not raised, and FIG. FIG. 9 is a diagram showing similar temperatures when the same double pulse is applied to the recording head in a heated state.

As is apparent from these figures, in any case, the temperature rise starts with the application of the preliminary pulse, and the rest time T
While off, the thermal energy of the preliminary pulse is sufficiently diffused to improve the thermal efficiency, but the heating element temperature is slightly lowered. However, the temperature rise is continued again by the main pulse that is continuously applied. A certain temperature, that is, B, B'shown in FIGS. 6 (a) and 6 (b)
When the point is reached, the temperature on the heating element begins to rise rapidly. This is because the ink in the vicinity of the heating element changes its state from the liquid phase to the vapor phase at point B in the figure, and the heating element is covered with the ink gas that has transferred to the vapor phase and does not come into contact with the liquid ink. That is, since the heat transfer coefficient of the ink in the case of gas is extremely lower than that in the case of liquid, the heat generating element is substantially thermally insulated. Therefore, the energy (the portion indicated by the pulse width of P2b and P2b 'in the figure) that is continuously applied after the state of the ink has changed is
Almost all the heat is accumulated in the recording head, and the temperature of the heating element rises rapidly. In other words, the pulse widths P2b and P2
Since the energy indicated by b ′ is the energy applied after the ink is foamed, it does not participate in the ink ejection and is one of the main temperature rising factors that affect the temperature rise of the head.

Therefore, in order to suppress the temperature rise, it is theoretically preferable to make P2b and P2b 'as short as possible. However, since the foaming points B and B'are varied due to various difficult factors such as manufacturing variations and surface conditions of the heating elements, and variations in the drive circuit system that drives the recording head, the width cannot be zero. However, how to reduce the temperature becomes a problem in reducing the temperature rise.

When the phenomena shown in FIGS. 6 (a) and 6 (b) are analyzed, the positions of the foaming points B and B'of the ink are earlier in B'shown in FIG. 6 (b). The point is that the temperature of the heating element is approximately 300 ° C. and is almost constant in all cases. That is, in the inkjet method in which the liquid phase ink is changed to the gas phase ink and the ink is ejected by utilizing the foaming pressure generated at this time, the temperature of a part of the liquid phase ink to be foamed is set to the critical foaming temperature (this embodiment). Therefore, it is important to input a sufficient amount of energy to raise the temperature to 300 ° C.), and when the recording head is heated, the input energy can be equivalently reduced by the amount of the temperature increase. .

As described above, the main factor for raising the temperature of the recording head is the energies P2b and Pb2 'which are applied after the liquid phase ink is foamed, so that the recording head is heated and the bubbling points B and B'are increased. Despite the movement, if the same energy is continuously supplied as when there is no temperature rise, P2b '> P
Since it is 2b, the temperature is accelerated. Therefore, by controlling the input energy of the main pulse applied to change the state of the liquid-phase ink to the vapor phase according to the temperature rise of the recording head, strictly speaking, the temperature of the ink near the heating element, It is possible to significantly reduce the temperature rise.

FIG. 7 is a block diagram conceptually showing the structure for carrying out the temperature rise control in this embodiment, and this structure can be specifically constituted by the control unit 20 shown in FIG. .

The temperature information of the recording head, which changes from time to time, is input to the control unit 100 which outputs the energy condition applied to the recording head. According to this input information, the control unit 10
0 outputs the heating element driving condition that determines the optimum main pulse width P2. More specifically, according to the state of the recording head, that is, when the temperature of the recording head rises, the control unit controls the driving condition so that the width P2 of the foaming pulse becomes short according to the temperature information, and the excess pulse P2b causes the recording head to move. The temperature is controlled so that it is always the minimum necessary according to the temperature rise.
As a result, it is possible to effectively suppress a vicious circle in which the temperature rise induces a further temperature rise.

Even in the thermal transfer recording apparatus, the main pulse (final pulse) of the divided pulses when the temperature of the recording head is raised.
A means for controlling the modulation of the signal may be used. The main pulse control performed by this thermal transfer recording apparatus is to reduce the applied energy by the main pulse at the time of temperature rise, thereby recording the density of the recording dot to be recorded by the pulse. ,
Alternatively, it controls the recording dot area. On the other hand, in the above-described inkjet method of the present embodiment, even if the width P2 of the foaming main pulse is modulated, neither the recording dot density nor the recording dot area recorded by the pulse can be modulated. This point is clearly different from the main pulse control of the thermal transfer recording system. In other words, the control of the main pulse width P2 described above is a control means for suppressing the temperature rise that has a relatively long time range, and can be said to be a control technique unique to the inkjet method.

The temperature detecting means of the recording head in this embodiment applies a current to a temperature-sensitive resistance element on a wafer (not shown) on which a heating element is formed, and detects a voltage drop in this temperature-sensitive element to detect the temperature. To know.
The temperature sensitive element is preferably located near the heat generating element in order to detect the ink temperature near the heat generating element more accurately, but there is also a technique for correcting the detection value in consideration of the position where the temperature sensitive element is arranged. Since it is known, the present invention is not limited by the position of the temperature sensitive element. Further, as a technique for detecting the recording head temperature, many publicly known techniques have been disclosed for the purpose of detecting the recording head temperature of a thermal recording system, but the technique is not limited to a specific detection system.

By performing the above-described control according to this embodiment, the temperature rise of the recording head can be significantly suppressed as compared with the conventional pulse application method, but the energy efficiency is 1
Unless it is 00%, the temperature rise cannot be suppressed to zero. Therefore, only by controlling the pulse width P2, the ejection amount of one dot cannot be kept uniform due to the effect of the gradual temperature rise caused by the energy conversion loss. As described above, this is based on the ejection principle of the inkjet method of the present embodiment in which the recording pixel density cannot be modulated by the total input energy amount, unlike the thermal transfer method.
The ejection amount for each dot can be controlled by controlling the pulse interval Toff of 1 or divided pulses.

Accordingly, in the present embodiment, the pulse width P2 control suppresses the temperature rise of the print head to maintain the print head temperature in a temperature range in which the ejection amount can be controlled.
By controlling the length (time) of the interval Toff of one pulse, it is possible to control a uniform ejection amount without being affected by a slight change in the printhead temperature.

As described above, according to the ink jet recording apparatus of the present embodiment, the recording apparatus is provided by increasing the driving frequency of the recording head and increasing the number of heating elements without using a cooling mechanism which is difficult in terms of cost. It is possible to provide an inkjet recording apparatus that achieves both high speed and high image quality.

[Second Embodiment] Next, another embodiment for modulating the recording density as required will be described.

In the first embodiment described above, the temperature rise of the print head is suppressed by suppressing the temperature rise of the print head and by making the ejection amount per dot always equal without being affected by the print head temperature. It has become possible to control to reduce image defects such as density unevenness on the image.

However, with the progress of host devices such as microcomputers, the images to be handled are changing from binary images to multi-valued images, and multi-valued recording is also performed in a recording device which is an output device of images processed on the host device. The demand is increasing. In addition, depending on the diversification of the purpose of use of the output image, a plurality of types of dedicated output media corresponding thereto may be provided, and various recording modes may be set according to the recording medium to be used. In any case, it is preferable that the ejection amount per dot can be controlled according to the purpose.

As described above, in the ink jet recording apparatus, the ejection amount can be controlled by controlling the pulse signal having the preliminary pulse width P1 and the interval Toff between the preliminary pulse and the main pulse, but the control range is so large. The current situation is that it cannot be removed. In order to perform the above-described multi-valued recording and optimum recording according to the medium, control of the pulse width P1 and To
In many cases, control of ff is not always sufficient.

In this embodiment, the base temperature of the recording head is controlled in order to increase the modulation range of the ejection amount. Generally, the ejection amount that can be modulated by the control of the preliminary pulse width P1 or the control of the rest time Toff is about 25%. For example, in the case of a recording head capable of ejecting 80 ng / dot with a single pulse, the ejection amount can be modulated in the range of 80 ng / dot to 100 ng / dot by controlling the pulse width P1 or the pause time Toff.

On the other hand, the variation range of the ejection amount with respect to the temperature of the recording head is about 1% at 1 ° C. For example, in the case of a recording head capable of ejecting 80 ng / dot with a single pulse, when the temperature of the recording head rises by 10 ° C., the ejection amount of 8 ng increases to 88 ng / dot.

The change rate of the ejection amount with respect to the pulse width P1 and the like and the temperature dependence rate of the ejection amount are not exactly the same depending on the configuration of the recording head, and the maximum possible ejection amount is dependent on the size of the recording head and the like. Is limited, and the ejection amount does not increase indefinitely as the printhead temperature rises, but by controlling the printhead temperature,
It is possible to greatly increase the variation range of the discharge amount as described above.

For example, when it is preferable to increase the ejection amount by about 30% when recording on an OHP film as compared with plain paper, the ejection amount cannot be increased by 30% only by controlling the preliminary pulse width P1 or the like, but the recording head. By increasing the temperature, the discharge amount can be increased by 30%. Further, even when printing on the same plain paper, compared to the case of 1-pass printing performed by one scan of the print head,
When printing is performed in a plurality of passes, there is little ink bleeding on the printing medium, so it is necessary to increase the ejection amount in order to achieve the same image density. As described above, not only the above-mentioned difference in the recording medium but also the difference in the recording mode causes the difference in the optimum central ejection amount. In order to cope with this by the temperature of the recording head, the recording head temperature is set to the optimum recording head temperature. Raise the temperature,
Moreover, it is necessary to perform control so that the print head temperature does not further rise after the print head temperature rises to the optimum print head temperature.

From the above, in the present embodiment, as shown in FIG. 8, various ejection amount modulation request factors depending on the multi-value gradation recording, the type of the recording medium, the type of the recording mode such as the one-pass recording mode, and the like are set. It is inputted to the ejection amount request judging means, and the ejection amount request judging means outputs the control conditions of the main pulse width P2 and the pause period Toff which are the driving conditions of the recording element of the recording head. That is, by controlling the main pulse width P2, as described above in the first embodiment, the ejection amount region in which the recording head can eject is offset and
The pause time Toff is controlled to control a finer discharge amount so that a desired discharge amount is obtained under the offset discharge amount.

By controlling the amount of energy supplied to the heating element as described above, it is possible to greatly change the ejection amount range of the recording head. Here, the factors that require modulation of various ejection amounts due to multi-value gradation recording, types of recording media, differences in recording modes, etc., are specifically formed by setting in the host device or setting input by the user. Further, the discharge amount modulation request factor determining means can be specifically configured by the control unit 20 shown in FIG.

In the present embodiment, the pause time Toff is controlled, but the preliminary pulse width P1 may be controlled, or both may be controlled simultaneously. Further, it may have a plurality of preliminary pulse widths P1.

In addition, the main pulse width P is set by using a known sub-heating means using a heating element other than the discharging heating element.
The temperature control by the control of 2 may be supported.

Further, since the constitution and operation and effect other than the ejection amount control means for controlling the ejection amount in accordance with the ejection amount modulation request by the ejection amount modulation request factor are the same as those of the above-mentioned embodiment, detailed description will be given here. The description is omitted.

[Third Embodiment] Next, another embodiment for detecting the temperature of the recording head will be described.

In the above-described embodiment, the temperature of the print head is detected by the temperature detecting element in the print head. On the other hand, in order to utilize the present invention more effectively by making the most of the characteristic of the ink jet method, it is necessary to shorten the pulse widths P2b and P2b 'which are the above-mentioned extra pulses, that is, to detect the recording head temperature more accurately. There is. Therefore, it is necessary to accurately detect the temperature of the ink itself that causes a state change in the vicinity of the printing element. As described above, the temperature of the ink is obtained by performing arithmetic processing on the detection value at the position where the temperature sensor is arranged. However, in addition to the error of the detection value itself, a calculation error may be added.

In this embodiment, the print head temperature is calculated from the print duty by an arithmetic process. That is, with this configuration, the temperature is calculated and estimated from the input energy amount, and thus the ink temperature in the vicinity of the heating element can be accurately calculated. Hereinafter, a configuration for temperature calculation according to the present embodiment will be described in detail with reference to the drawings.

(Temperature Prediction Control) The basic equation for estimating the temperature of the recording head in this embodiment is the following general equation for heat conduction.

[0057]

[Equation 1]

If the recording head is treated as a lumped constant system, the above (1),
The ink temperature of the recording head can be theoretically estimated by calculating the equation (2). However, it is generally difficult to perform the above calculation as it is because of the problem of processing speed.

That is, in the calculation, strictly speaking, all the constituent members have different time constants, and since there are time constants among the members, the number of calculations becomes enormous. In addition, in general, CPUs cannot perform exponential calculation directly,
There is a problem that the calculation time cannot be shortened because it is necessary to perform an approximate calculation or obtain it from a conversion table.

In the present embodiment, such a problem is solved by the following modeling and calculation algorithm.

(1) Modeling The inventors of the present application applied energy to the recording head used in this embodiment by applying a pulse, and sampled data of the temperature rising process of the recording head at that time.
The results shown in FIG. 9 were obtained.

As described above, the recording head is strictly composed of a combination of many members having different heat conduction times, but in the range where the differential value with respect to the elapsed time of the logarithmic-converted temperature rising data is constant, That is, in the range of A, B, and C where the inclinations are constant in FIG. 9, it can be practically treated as a heat conduction model of a single member.

From the above, in the present embodiment, the recording head is treated with two thermal time constants for the model relating to heat conduction (in the above result, it is more accurate to perform modeling with three thermal time constants). Although it is shown that the regression can be performed, the slopes of the ranges B and C in FIG. 9 are approximated to be substantially equal to each other, and in the present embodiment, the recording head is modeled by two thermal time constants with priority given to the calculation efficiency. Is). Specifically, one of the heat conductions is modeled with a time constant that rises to the equilibrium temperature in 0.8 seconds (corresponding to the area A in the above table), and the other heat conduction rises to the equilibrium temperature in 512 seconds. Modeling of those with warming time constants (B and C regions in the above table).

Further, in this embodiment, the recording head is treated as follows and modeled.

The temperature distribution during heat conduction is assumed to be negligible, and all are treated in the lumped constant system.

The heat sources are two: heating for recording and heating of the sub-heater.

FIG. 10 shows an equivalent circuit for heat conduction modeled in this embodiment.

(2) Calculation Algorithm The calculation of the head temperature in this embodiment is performed by expanding the above general equation of heat conduction as follows.

The following equation shows an equation for estimating the temperature rise during heating when nt time has elapsed after turning on the heat source.

[0070]

[Equation 2] a {1-exp [-m * n * t]}… <1> = a {exp [-m * t] -exp [-m * t] + exp [-2 * m * t] -exp [-2 * m * t] + …… + exp [-(n-1) * m * t] -exp [-(n-1) * m * t] + 1-exp [-n * m * t]} = a {1-exp [-m * t]} + a {exp [-m * t] -exp [-2 * m * t]} + a {exp [-2 * m * t] -exp [-3 * m * t]} ……… + a {exp [-(n-1) * m * t] -exp [-n * m * t]} = a {1-exp [-mt ]}… <2-1> + a {exp [-m * (2t-t)]-exp [-m * 2t]}… <2-2> + a {exp [-m * (3t-t) ] -exp [-m * 3t]}… <2-3> ……… + a {exp [-m * (nt-t)]-exp [-m * nt]}… <2-n> or more As a result, the expression <1> is changed to <2-
It can be expressed as 1> + <2-2> + <2-3> + ... + <2-n>. Here, the expression <2-n> is equal to the temperature of the object at time nt when heating is performed from time 0 to t and heating is turned off from time t to nt. Similarly,
The expression <2-3> is the temperature of the object at time nt when heating is performed from time (n-3) t to (n-2) t and heating is turned off from time (n-2) t to nt. , <2-2>
The expression is the temperature of the object at time nt when heating is performed from time (n-2) t to (n-1) t and heating is turned off from time (n-1) t to nt, <2-1> The formulas respectively represent the temperatures of the object at time nt when heating from time (n-1) t to nt.

The above equations <2-1>, <2-2>, ...,
The fact that the sum of <2-n> is equal to the expression <1> means that the temperature of the target object (temperature rising temperature) is the temperature of the target object heated by the energy input per unit time per unit time. The number of times the temperature rises after each lapse is calculated (corresponding to each <2-1> formula, <2-2> formula ... <2-n> formula), and the current object For the temperature, find the sum of how many times the temperature that has risen per unit time in the past is decreasing (<2-1> + <2-2>).
+ ... <corresponding to obtaining <2-n>) indicates that the calculation can be estimated.

In the present embodiment, the calculation of the temperature of the recording head is performed in four ways (heat source 2 × thermal time constant 2) by the above modeling.
For each model.

The necessary calculation intervals and data holding times for the four calculations are shown in the table below.

[0074]

[Table 1]

Further, calculation tables for calculating the head temperature, which are composed of a two-dimensional matrix of applied energy and elapsed time, are shown in FIGS. 11 to 14.

FIG. 11 is a calculation table for a member group in which the heat source is the discharge heater and the time constant is the short range, and FIG.
Is a calculation table for a member group in which the heat source is a discharge heater and the time constant is a long range. In FIG. 13, the heat source is a sub heater,
FIG. 14 shows a calculation table for a member group having a short time constant and FIG. 14 shows a calculation table for a member group having a sub heater as a heat source and a long range time constant.

Is as follows.

As shown in the table above, at 0.05 second intervals,
(1) The member of the thermal time constant represented by the short range
How many times the temperature is raised by driving the heater for discharge (ΔT
mh), (2) How many times the temperature of a member having a thermal time constant represented by a short range is raised by driving the sub heater (ΔT
sh), at 1.0 second intervals, (3) how many times the temperature of the member having the thermal time constant typified by the long range is raised by driving the heater for discharge (ΔTmb), (4) long range The calculation of how many times (ΔTsb) the temperature of the member having the thermal time constant is increased by driving the sub-heater, and by adding ΔTmh, ΔTsh, ΔTmb, and ΔTsb (= ΔTmh + ΔTsh + ΔTmb)
+ ΔTsb) The head temperature at that time can be calculated.

As described above, by modeling the recording head constituted by combining a plurality of members having different heat conduction times with a smaller number of thermal time constants than the actual one, all the heat conduction times are faithfully reproduced. In comparison with the case where the calculation processing is performed for each different member and the thermal time constant between the members, the calculation processing amount can be significantly reduced without significantly lowering the calculation accuracy. Further, by modeling with the time constant as the criterion, it becomes possible to perform the arithmetic processing with a small number of times of processing or without lowering the arithmetic accuracy of T times. For example, using the example above, if you did not model for each time constant,
The required calculation processing interval is set in the area A with a small time constant.
msec is the required calculation interval, and the data retention time of the discretized data is determined in the B and C regions with a large time constant, 512s.
ec is the required data retention time. Ie 50 mse
10240 data for the past 512 seconds are accumulated and processed at intervals of c, which is several hundred times the number of times of arithmetic processing compared with the case of the present embodiment.

As described above, according to the present embodiment, it is possible to obtain all the temperature changes of the recording head by arithmetic processing even in a relatively inexpensive recording apparatus without providing a temperature sensor on the recording head.

As described above, by calculating and estimating the ink temperature in the vicinity of the heating element from the energy input to the recording head, the influence of electrical noise and the temperature sensor can be compared with the case where the head temperature is electrically detected by the temperature sensor. It is possible to eliminate various errors caused by the positional problem of the arrangement, and it is possible to more accurately detect the temperature of the recording ink droplet that causes the state change in the vicinity of the heating element. This makes it possible to more accurately determine the extra pulses P2b and P2b ', and as a result, it is possible to more effectively reduce the occurrence of image defects due to the temperature rise of the recording head. As a result, it is possible to provide an inkjet recording apparatus that achieves both high-speed recording of a recording apparatus and high image quality by increasing the driving frequency of the recording head and increasing the number of heating elements.

Since the configuration other than the temperature calculation means for calculating and estimating the ink temperature near the heating element and the function and effect are the same as those of the above-described embodiment, detailed description thereof will be omitted.

[0083]

As described above, according to the present invention,
When ink is ejected by applying a plurality of pulses, by modulating the portion of the pulse that directly generates bubbles after the ink undergoes the phase transition from the liquid phase to the vapor phase, for example, the pulse application of that portion It is possible to suppress the temperature rise of the recording head and to greatly modulate the ejection amount.

As a result, the occurrence of adverse effects on the image due to the temperature rise of the recording head can be reduced, the driving frequency of the recording head can be increased, and multiple heating elements can be used without increasing the cost by using a cooling means or the like. It is possible to provide an inkjet recording apparatus that can achieve high speed and high image quality.

[Brief description of the drawings]

1A to 1F are schematic waveform diagrams showing an example of an applied pulse applied to drive a recording head of a thermal transfer recording apparatus.

2A to 2C are diagrams illustrating the dependence of the ink ejection amount on the head temperature, double pulse preliminary pulse width, and double pulse dwell time in an inkjet recording head.

FIG. 3 is a schematic waveform diagram showing an example of an applied pulse applied to drive a recording head of a conventional inkjet recording apparatus.

FIG. 4 is a perspective view showing a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention.

5 is a block diagram showing a control configuration in the recording apparatus shown in FIG.

6A and 6B are explanatory views for explaining the principle of the embodiment of the present invention.

FIG. 7 is a block diagram functionally showing the first embodiment of the present invention.

FIG. 8 is a block diagram functionally showing a second embodiment of the present invention.

FIG. 9 is a diagram showing the temperature behavior of the recording head according to the third embodiment of the present invention for each thermal time constant.

FIG. 10 is a diagram showing an equivalent circuit of a printhead model according to the third embodiment.

FIG. 11 is a diagram showing a temperature change calculation table for each heat source and thermal time constant in the third embodiment.

FIG. 12 is a diagram showing a temperature change calculation table for each heat source and thermal time constant in the third embodiment.

FIG. 13 is a diagram showing a temperature change calculation table for each heat source and thermal time constant in the third embodiment.

FIG. 14 is a diagram showing a temperature change calculation table for each heat source and thermal time constant in the third embodiment.

[Explanation of symbols]

 1 Recording Sheet 2 Ejection Recovery Device 3 First Conveying Roller 4 Second Conveying Roller 5 Recording Head 6 Carriage 7 Belt 8a, 8b Pulley 9 Guide Shaft 10 Ink Cartridge 20 Controller 20a CPU 20b ROM 20c RAM

Continuation of the front page (72) Inventor Osamu Iwasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Daigoro Kanematsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (10)

[Claims] 1. A recording head having a heating element, wherein bubbles are generated in the ink by utilizing thermal energy generated by the heating element and the ink is ejected by the pressure of the bubbles, the recording head is transferred to a recording medium. In an inkjet recording apparatus that ejects ink to perform recording, a driving unit for applying a driving pulse composed of a plurality of pulses to a heating element, and a plurality of pulses for generating bubbles among the plurality of pulses applied by the driving unit An inkjet recording apparatus, comprising: a pulse modulating unit that modulates a pulse, the pulse modulating unit performing a modulation by adjusting an application end time of the pulse. 2. A temperature information acquisition unit for acquiring temperature information of a recording head, wherein the pulse modulation unit modulates in accordance with the temperature information acquired by the temperature information acquisition unit. 1. The inkjet recording device according to 1. 3. An ejection amount setting means for setting an ejection amount of a recording head, further comprising: the pulse modulation means for performing modulation in accordance with the ejection amount set by the ejection amount setting means. 1. The inkjet recording device according to 1. 4. The ink jet recording apparatus according to claim 1, wherein the pulse modulator modulates the width of the pulse by adjusting the application end time. 5. The method according to claim 1, further comprising means for modulating at least one of a preliminary pulse applied prior to the pulse for generating the bubble or an interval between the plurality of pulses. The inkjet recording device according to any one of 1. 6. The ejection amount of the recording head is changed by modulation of each of the pulse modulation unit and the unit for modulating at least one of the preliminary pulse and the plurality of pulses, and the change amount is modulated by the pulse modulation unit. The ink jet recording apparatus according to claim 5, wherein the amount of change due to is larger. 7. The ink jet recording apparatus according to claim 2, wherein the temperature information acquisition unit includes a temperature sensor provided in a recording head. 8. The ink jet recording apparatus according to claim 2, wherein the temperature information acquisition unit has a unit for calculating and estimating the temperature of the recording head. 9. The ejection amount setting means sets the ejection amount based on at least one of a gradation of a recording image, a type of a recording medium used for recording, and a recording mode. The inkjet recording device according to item 1. 10. The ink jet recording apparatus according to claim 1, wherein the heating element is an electrothermal conversion element that generates heat energy by applying an electric pulse.