JP3313751B2 - Discharge control method for inkjet recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge control method for an ink jet recording head.

[0002]

2. Description of the Related Art Conventionally, in an ink jet recording apparatus, in order to minimize the occurrence of density fluctuations and density unevenness in a recorded image or the like, particularly, the ejection amount of ink ejected from a recording head (hereinafter referred to as V). _d (pl / dot)
) Has been variously controlled to stabilize it.

[0003] The main methods employed in these controls are:
By adjusting the temperature of the ink (hereinafter referred to as temperature control), it is possible to control the viscosity of the ink, which affects the ejection speed and the ejection amount, and to provide a heating element, and the heat energy generated by the heating element allows the ink to be heated in the ink. In the method in which bubbles are generated and the ink is ejected by the growth of the bubbles, the conditions under which the bubbles are generated and the like are also controlled to stabilize the ejection amount and the like. As a specific configuration for adjusting the ink temperature, a heater for heating the recording head holding the ink (also serving as a dedicated heater or a discharging heater), a temperature sensor for detecting the temperature related to the recording head, Using
There is a configuration in which a temperature detected by a temperature sensor is fed back to a heating amount by a heater. There is also a configuration in which heating by a heater is simply adjusted without feedback of temperature.

[0004] In the above configuration, a heater and a temperature sensor are provided.
There are a case where it is provided near the recording head, for example, on a member constituting the recording head, and a case where it is provided outside the recording head.

[0005] As another method for controlling the discharge amount, or as a method used together with the above method, an electrothermal converter (hereinafter also referred to as a discharge heater) for generating thermal energy in the method of discharging along with the generation of bubbles. ) By controlling the amount of heat generated by changing the pulse width of a single pulse (hereinafter referred to as a heat pulse)
Some stabilize the discharge amount.

The control modes described above are mainly classified into the following four modes. 1) Always perform head temperature control (external / nearby).

[0007] With temperature feedback. 2) The head temperature is adjusted as needed (external / nearby).

[0008] With temperature feedback. 3) Perform high-temperature head temperature control (higher than ambient temperature). With feedback. 4) Pulse width modulation of a single heat pulse.

However, in the first method, since the temperature of the recording head is constantly adjusted, the evaporation of the ink moisture accompanying the heating of the heater is promoted. As a result, thickening and sticking of the ink in the ejection openings in the recording head are induced, and as a result, an increase in the deflection of the ejection direction or non-ejection occurs, or a change in density due to a relative increase in the dye density in the ink. In some cases, the recording quality is degraded due to uneven density.

[0010] Further, as a result of the continuous heating by the heater, a change in the structure of the head and deterioration of members constituting the head are promoted, which also causes a reduction in the reliability and durability of the recording head. Furthermore, this method is generally susceptible to changes in environmental temperature and self-heating (temperature rise due to ejection), which may cause variations in ejection amount and cause density changes and density unevenness.

The second method is a method for adjusting the temperature as needed, and is an improvement of the first method.
For example, in order to perform temperature control after a recording command is input, it is necessary to reach a predetermined temperature in a relatively short time, and a large energy for heating [for example, a heating value (W) of a heater] is required.
Must be given. For this reason, in the temperature control, the width of the temperature ripple may increase and accurate temperature control may not be performed. In such a case, the discharge amount may fluctuate due to the temperature ripple, and density change or density unevenness may occur. Conversely, if an accurate temperature control is to be performed, it is necessary to reduce the applied energy, the time required to reach the target temperature becomes longer, and the waiting time until the start of recording increases.

In the above three methods, in order to reduce the influence of a change in environmental temperature or a change in temperature due to self-heating, the target temperature by temperature control is set higher than the environmental temperature. According to this, it is possible to reduce the fluctuation of the ejection amount at the time of low-duty printing, but at the time of high-duty printing, for example, when the temperature rise due to ejection (self-heating) is large as in full solid printing Cannot avoid the effect of this temperature rise.

As a method of controlling the temperature, the temperature control outside the recording head can generally reduce the influence of the environmental temperature, but has a poor response to the self-heating, and is affected by the self-heating. It can be said that it is easy.

If the temperature is controlled in the vicinity of the recording head (for example, a heater or a temperature sensor is provided on an aluminum plate as a substrate supporting a heater board on which a discharge heater is provided), the response is improved, Although effective for raising the temperature, a temperature ripple may occur due to a large heat capacity of the aluminum plate serving as the substrate, and the discharge amount may fluctuate due to the temperature ripple.

Further, a single pulse of the above method 4 (hereinafter referred to as a single pulse)
The pulse width modulation method using a single pulse) is particularly effective in the above-described bubble-forming ink jet system because the control width of the discharge amount that can absorb the fluctuation of the discharge amount according to the temperature change is small, and the pulse width increases. Accordingly, it is difficult to obtain a desired increase in the discharge amount, and it is more difficult to control the discharge amount accurately than in the case of a plurality of pulses.

As described above, one of the major factors that hinders the conventional ejection control by temperature control is self-heating, which causes the ink in the recording head to accumulate heat with ejection.

For example, when the temperature of the ink changes due to the self-heating of the recording head, the bubble bubbling speed and the refill speed fluctuate. The characteristics may fluctuate and the image may be extremely deteriorated.

In particular, in the case of a full-color image formed of four color inks of cyan, magenta, yellow, and black, if even one of the recording heads discharging these inks has ejection characteristics different from the standard state, for example, The change in color balance due to the difference in the ejection amount causes a change in color and a decrease in color reproducibility (increase in color difference), thereby lowering the overall image quality.

Further, even when an image is recorded in a single color, if the recording head fluctuates in discharge characteristics, choro discharge failure caused by a decrease in refill frequency or an increase in slimness,
Streaks and density fluctuations occur especially in solid printing due to the twist. In addition, if the ejection characteristic causes a shift, the reproducibility of fine lines in an image and the quality of characters deteriorate.

The present applicant has proposed a method of controlling the ejection amount to be constant even when the temperature of the recording head changes due to an environmental temperature or a self-heating, by a divided pulse width modulation that controls the width of a pre-pulse according to the temperature. A (PWM) discharge amount control method (see Japanese Patent Application No. 3-4391) has been proposed.

The present proposal can stably maintain the discharge amount, and is therefore effective in reducing density unevenness due to temperature fluctuation.

[0022]

However, when the head continues to perform high-duty printing or when the environmental temperature is high, a method of controlling the discharge amount by changing the width of a constant modulated energy by a constant temperature change. In some cases, the ejection amount cannot be stably maintained accurately, and density unevenness may occur.

Therefore, an object of the present invention is to stably control the discharge amount even when the head continues to perform high-duty printing or when the environmental temperature becomes high, so that density unevenness does not occur. To provide a discharge amount control method. In particular, it is an object of the present invention to provide an ejection amount control method that takes into account the effect of the ejection opening area of the head.

[0024]

Means for Solving the Problems] To achieve the above object, the present invention is a variation due to temperature change of the amount of ink discharged from the discharge ports of the ink jet recording head, to suppress by modulating the input energy In the method of controlling the ejection of the ink jet recording head, the air is not sufficiently foamed.
A pre-heat pulse to provide energy to the ink,
A method that gives the ink energy to cause foaming
A step of ejecting ink using an in-heat pulse,
The degree of modulation of the preheat pulse width with respect to a change in the temperature of the recording head as the recording head has a larger ejection port area.
And ejecting ink with a small size .

[0025]

According to the above arrangement, when correcting the fluctuation of the ink ejection amount due to the temperature change by the input energy, the foaming is performed.
A pre-press to give the ink energy that does not
Heat pulse and energy to cause foaming
Using a main heat pulse to be applied to the ink, the degree of modulation of the preheat pulse width with respect to the temperature change is reduced for a print head having a larger discharge port area of the print head, and
For ejecting click can be performed better controllability of the ejection amount correction due to a temperature change in consideration of the influence of the discharge port area.

[0026]

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

In the present invention, the waveform of the drive signal, for example, the pulse width is made variable in order to control the discharge amount. In the embodiment described below, however, the drive signal is applied to the heating element in order to perform one discharge. The driving signal to be performed is composed of a plurality of signals. The ejection amount is controlled by modulating the waveform of the signal preceding the driving signal. In the embodiment described below, the drive signal is in the form of a pulse, and this pulse is divided into two pulses to form a plurality of drive signals.

First, with reference to FIGS. 1 to 3, the discharge amount control by the divided pulse will be described.

FIG. 1 is a diagram for explaining divided pulses according to one embodiment of the present invention.

In FIG. 1, V _OP is the drive voltage, P ₁ is the pulse width of the first pulse of the plurality of divided heat pulses (hereinafter referred to as preheat pulse), P ₂ is the interval time, and P ₃ is the second. It is a pulse width of a pulse (hereinafter, referred to as a main heat pulse). T ₁ , T ₂ , and T ₃ indicate times for determining P ₁ , P ₂ , and P ₃ . The drive voltage V _OP is an electric energy required for an electric heat conversion element (heating element) to which the voltage is applied to generate heat energy in ink in an ink liquid path formed by a heater board and a top plate. The value is determined by the area of the electrothermal transducer, the resistance value, the film structure and the liquid path structure of the recording head. The divided pulse width modulation driving method is P
₁ , a pulse is sequentially given with a width of P ₂ , P ₃ , and the preheat pulse is a pulse for mainly controlling the ink temperature in the ink path, and plays an important role in the ejection control of the present invention. ing. The pre-heat pulse width P ₁ is set to a value such foaming phenomenon does not occur in the ink by thermal energy electrothermal transducer is generated by the application.

The interval time is provided to provide a predetermined time interval so that the preheat pulse and the main heat pulse do not interfere with each other and to make the temperature distribution of the ink in the ink path uniform. The main heat pulse is for generating bubbling in the ink in the ink path and discharging the ink from the discharge port, and its width P ₃ is determined by the area of the electrothermal transducer, the resistance value, the film structure and the recording head. It is determined by the structure of the ink liquid path.

For example, the operation of the preheat pulse in the recording head having the structure shown in FIG. 2 will be described.

FIGS. 7A and 7B are a schematic longitudinal sectional view and a schematic front view, respectively, showing an example of the configuration of a recording head to which the present invention can be applied. In the figure, reference numeral 1 denotes an electrothermal converter which generates heat by applying the divided pulse, and the electrothermal converter 1 is disposed on a heater board 9 together with electrode wiring for applying the divided pulse thereto. Is done. The heater board 9 is formed of silicon, and is supported by an aluminum plate 11 forming a substrate of a recording head. Reference numeral 12 denotes a top plate on which a groove for forming an ink path or the like is formed, and a common liquid which supplies ink to the ink path 3 when the top plate 12 and the heater board 9 (the aluminum plate 11) are joined. A chamber 5 is configured. In addition, ejection openings 7 are formed in the top plate 12, and the ink passages 3 communicate with the respective ejection openings 7.

In the recording head shown in the figure, the driving voltage V _OP = 18.0 (V) and the main heat pulse width P ₃
= 4.114 [μsec] and the preheat pulse width P
_{When 1} is changed in the range of 0 to 3.000 [μsec], a relationship between the ejection amount V _d [ng / dot] and the preheat pulse width P ₁ [μsec] as shown in FIG. 3 is obtained.

FIG. 3 is a diagram showing the dependence of the ejection amount on the pre-heat pulse. Hereinafter, the dependence of the ejection characteristics on the pre-heat pulse will be described using the ejection amount as an example. In the figure,
V _O indicates the ejection amount when P ₁ = 0 [μsec], and this value is determined by the head structure shown in FIG.

[0036] As shown in curve a of Figure 3, in accordance with an increase in the pulse width P ₁ of the pre-heat pulse, the ejection amount V _d is increased pulse width P ₁ is a substantially linear resistance from 0 to P _1LMT and the pulse width P ₁ loses completely linearity the change in P _1LMT larger range, the maximum saturation at the pulse width P _1MAX.

[0037] Thus, the range up to the pulse width P _1LMT changes in ejection amount V _d relative to the change in the pulse width P ₁ exhibits almost linearity, facilitates the discharge amount control by changing the pulse width P ₁ It is effective as a range that can be performed.

[0038] When the pulse width is greater than P _1MAX, the ejection amount V _d is smaller than V _MAX. This phenomenon occurs when a preheat pulse having a pulse width in the above range is applied, so that a minute bubbling (a state immediately before film boiling) occurs on the electrothermal transducer, and the next main heat pulse is generated before the bubble disappears. Is applied, and the micro bubbles disturb the bubbling by the main heat pulse, so that the ejection amount is reduced. This region is called a pre-foaming region, and in this region, it becomes difficult to control the discharge amount via a preheat pulse.

If the slope in the relationship diagram between the discharge amount and the pulse width in the range of P ₁ = 0 to P _{1 LMT} [μs] shown in FIG. 3 is defined as the preheat pulse dependence coefficient, the preheat pulse dependence coefficient: K _P K _P = ∂V _dp / ∂P ₁ [ng / μsec · dot] The coefficient K _P is mainly determined by the head structure, driving conditions, physical properties of the ink, and the like. That is, curve b,
c indicates the case of another print head, and it can be seen that the discharge characteristics change when the print head is different. Thus, when the recording head is different, since the upper limit value P _1LMT preheat pulse P ₁ is different, it defines the upper limit value P _1LMT for each recording head, as described below, and the ejection control.

Here, an experiment of a change in the discharge amount was performed by changing the hole area of the discharge port in the head structure. As a result, as shown in FIG. 4 (A), an ejection amount V _d that against the hole area of the discharge port. The environmental temperature T _R at this time is 25 ° C., it is those described pulse width of the preheat pulse P ₁ as a parameter.

[0041] From this figure, as the hole area increases, the discharge amount increases almost in proportion, as the difference between P ₁ is large, it can be seen that the ejection amount difference increases. This hole area as a parameter, that rewriting the change in the ejection amount V _d relative to the pulse width variation of the pre-heat pulse P ₁ is a drawing (B).

[0042] As is apparent from this figure, the pre-heat pulse rate of change with respect to the pulse width of the P ₁ (discharge amount preheat pulse dependence coefficient) of the ejection amount _{V d K P (ng / μsec} ·
dot) increases as the hole area increases.

Another factor that determines the ejection amount of the ink jet recording head is the recording head temperature (ink temperature).
There is. FIG. 5 is a diagram showing the temperature dependence of the discharge amount.
As shown by the curve a in FIG. 5, the environmental temperature T _R of the recording head
Ejection amount V _d relative to the increase in (= head temperature T _H) increases almost linearly. Defining the inclination in FIG temperature dependency coefficient, the temperature dependency _{coefficient: K T K T = ∂V dT} / ∂T H [ng / ℃ · dot] become. The coefficient K _T is mainly determined by the structure of the head, the physical properties of the ink, and the like. Here, the hole area of the discharge port in the head structure and the environmental temperature T _{R of the} head (= head temperature T _H )
It is varied to examine the variation of the ejection amount V _d. FIG. 6 shows the result.

[0044] FIG. 6 (A) are those fixing the driving conditions such as pre-heat pulse P _1, showing the relationship between the discharge amount V _d relative to the hole area the environmental temperature T _R as a parameter. FIG (B) is the ambient temperature T _R a hole area reversed as a parameter
Shows the relationship between the ejection amount V _d relative to the change in (= head temperature T _H).

As is apparent from this figure, the temperature dependence coefficient of the ejection amount _{V d: K T K T =} ∂V d / ∂T H (ng / ℃ · dot) somewhat increases as well area increases It can be seen that it does not depend much on the hole area.

FIG. 7 relates to one embodiment of the present invention and is a diagram for mainly explaining the discharge amount control by pulse width modulation.
The principle of controlling the discharge amount will be described with reference to FIG. Here, the description will be made assuming that the hole area of the discharge port is fixed to a predetermined size.

As shown in the figure, the discharge amount control is constituted by the following three modes. That is, according to the _print head temperature TH, (1) _TH ≦ T _O ... Discharge amount control by temperature control (2) T _O < _TH ≦ _TL ... Discharge amount control by divided pulse width modulation method (3) ) T _L uncontrolled where by _{<T H <T C ... P} 1 = 0, T H is T _C or more is an area that exceeds the foam limit of the ink jet recording head.

[0048] Thus, in the following head temperature T _H is relatively low T _O (e.g. 25 ° C.) performs the ejection amount by temperature control of the recording head described above, with T _O or more relatively high temperatures, the The discharge amount is controlled by changing the pulse width of the preheat pulse described in the drawing (hereinafter, also referred to as PWM control).

As described above, the manner of controlling the ejection amount in accordance with the head temperature is such that in a relatively low temperature region, foaming when heat is applied to the ink becomes unstable due to an increase in ink viscosity. Therefore, the ejection itself may not be performed properly, and therefore, it is difficult to control the ejection amount by pulse width modulation. Therefore, if the head temperature is low the head temperature was predetermined temperature (T _O) beforehand by temperature control, thereby controlling the discharge amount constant amount,
When the head temperature is high, the ejection amount is controlled by modulating the preheat pulse at the time of ejection.

The above-mentioned temperature T _O is the print head temperature targeted by the temperature control. When the print head is at this temperature, in the discharge amount control of this embodiment, the target discharge amount V
_do (here, 30 [ng / dot]) is obtained. The temperature T at which the discharge amount control shown in FIG.
_L can be set as the temperature corresponding to the control limit discharge amount V _LMT shown in FIG. 3 in the relationship shown in FIG.

The mode (1) corresponds to the temperature control area shown in FIG. 7, and is for securing a predetermined discharge amount mainly in a low temperature environment as described above. Is controlled to the target temperature T _O by temperature control. As a result, the ejection amount V _do at the time when the recording head temperature T _H = T _O is obtained.

In this example, in order to minimize the above-mentioned adverse effects of temperature control (thickening, sticking, and temperature control ripple due to evaporation of ink water), a relatively low temperature T _O = 2.
5 ° C. This is because, for example, in a normal use environment, the room temperature is maintained at approximately 20 to 25 ° C., and if the recording head temperature is maintained at approximately this temperature, the above-described adverse effects can be reduced. Further, the pulse width P ₁ of the pre-heat pulse at this time is set to P ₁ = P _1LMT, so that the maximum discharge amount V _LMT is obtained by T _H = 25 ℃. Further, in the control mode of (1), that is, each pulse width and the like at the time of temperature control are P ₁ = 1.87 (μ) as shown in [1] of FIG.
sec), P ₂ = 2.618 (μsec), P ₃ = 4.1
14 (μsec). In addition, this state is a state corresponding to 1 in a table shown in FIG. 9 described later.

The control mode (2) corresponds to the pulse width modulation area shown in FIG. In this area, the recording head temperature is set to T _O due to the self-heating rise due to the ejection and the increase in the environmental temperature.
The above relatively high temperature region (for example, 26 ° C to 44 ° C)
° C.) and is, this temperature is a temperature sensor to change the pre-heat pulse width P ₁ according to the table shown in to Figure 9 detected.

At this time, the temperature step ΔT (° C./step) when changing the preheat pulse width P ₁ is obtained by changing the unit change width of the preheat pulse width to be changed by ΔP ₁ (μs
ec / step),

[0055]

[Outside 1] In becomes calculated the temperature, also the temperature of the head is changed by changing the P ₁ at this value, it is possible to stably control the discharge amount.

FIG. 6 shows each state of the pulse width corresponding to each of the table numbers in FIG. FIG. 10 shows a pulse width modulation sequence at this time. In the case of the _print head of this example, the upper limit P _1LMT of the width of the pulse P ₁ is 0A [Hex] indicated by the table number [1] in FIG. 9, that is, the value indicated by [1] in FIG. This upper limit is set by table pointer information as described later.

Hereinafter, the discharge amount control based on the pulse width modulation shown in FIG. 7 will be described with reference to the sequence of FIG.

The sequence shown in FIG.
This is started by an interruption every sec. First, in step S81, the print head temperature is detected. Next, in step S82, in order to prevent erroneous temperature detection due to heat flux entering the temperature sensor or electrical noise, the past three head temperatures ( _Tn-1 , _Tn-2 , _Tn-3 ) are used. S8
Average value of the temperature T _n detected by _{1 (T n + T n-} 1 + T n-2 +
The T _n-3) / 4 performs processing for the head temperature T _m. In the next step S83 compares the head temperature T _m-1 obtained previous and the average value T _m. Here, the difference T _m −T _m−1 is a predetermined temperature step width ΔT, that is, a pulse width P ₁ , as shown in FIG.
1 unit pulse width ΔP ₁ (0.187 μs) corresponding to the variation width of the pulse width at each stage corresponding to the table number shown in FIG.
c) Within the range of the temperature at which the discharge rate is kept constant when changed (that is, ± ΔT is the temperature range ± 1 ° C. shown in FIG. 9).
(Corresponding to (2 ° C.)), the pulse width P ₁ is left as it is in step S85, and if this difference is larger than + ΔT, the process proceeds to step S86, and the table number referred to in the table of FIG. Raise P ₁ to 1
If the difference is smaller than -ΔT, the process proceeds to step S84, and the table number is set to 1
One of P ₁ to increase the one raising the discharge amount by lowering, always discharge amount is controlled to be a certain amount V _do. In the process, the reason for the change in the pulse width P ₁ varied according to the temperature change was 1 unit pulse width, to prevent the occurrence of density jump to prevent feedback malfunction (temperature sensors erroneous detection, etc.) It is.

[0059] By carrying out control as described above, the target discharge quantity V _do, it is possible to discharge amount control in the range of ± [Delta] V in the temperature range that can be managed by the table of FIG. The state of the change in the ejection amount changes, for example, as indicated by an arrow a in FIG.

If the variation in the discharge amount falls within this range, the density variation occurring during printing of one sheet is suppressed to about ± 0.02 even in the case of, for example, solid printing with a 100% duty. The occurrence of uneven density and streaks that are remarkable in the method do not pose a problem. When the average number of temperature detections is increased, noise and the like are increased, resulting in a smoother change. However, in real-time control, detection accuracy is impaired and accurate control cannot be performed. In addition, when the average number of temperature detections is reduced, the temperature is weakened to noise and the like, and a rapid change occurs. However, in real-time control, the detection accuracy is increased and accurate control is possible.

The control mode (3) corresponds to the non-control area shown in FIG. 7, and this temperature range is outside the normal printing range of the recording head and is not used much.
When the recording head performs recording at, for example, 100% duty, the temperature may rise to this temperature range. In such a case, in this region, P ₁ = 0 (μsec) and only a single main heat pulse is used. To prevent self-heating as much as possible. T _C indicates the operating limit temperature of the head.

In the above example, the table shown in FIG.
0, the head temperature T
Until _H = 46 ° C., V _do = 30 [ng / dot] and Δ
The discharge amount can be controlled in a fluctuation range of V = ± 0.3 [ng / dot].

(Embodiment 1) Now, as shown in FIGS. 7 to 10 described above, control can be performed under limited conditions to some extent, and when discharge control is performed with a predetermined discharge amount using a predetermined head. Experiments have shown that

That is, as shown in FIGS. 4 (B) and 6 (B), the dependence of the ejection amount on the pre-heat pulse (K _P ) and the ejection amount on the temperature (K _T ) using various heads. ), It was found that the ejection amount tended to gradually become saturated as shown in FIGS. 11 (A) and 11 (B). If representing these relationships schematically a formula, relations ejection amount V _d and the pre-heat pulse P ₁ from FIG. 11 (A) is

[0065]

[Outside 2] From FIG. 11B, the relationship between the discharge amount _Vd and the temperature T is as follows.

[0066]

[Outside 3] Becomes Therefore above equation (1) can be expressed as (2), although it is _{rough, V d = K · P 1} m · T n + V do (0 <m, n <1) ... (3).

Then, the preheat pulse dependence coefficient K _P of the discharge amount is K _P = ∂V _d / ∂P ₁ = mKP ₁ ^m-1・ T ⁿ (4), and the temperature dependence coefficient K _T of the discharge amount is K _T = ∂V _d / ∂T = nKP ₁ ^m · T ^n-1 (5) Assuming that ΔP ₁ is a fixed value, the temperature step ΔT at which the preheat pulse P ₁ changes is

[0068]

[Outside 4] Can be expressed as

It should be noted that if it can be expressed as V _d = K ₁ P ₁ ^m + K ₂ T ⁿ + V _do ′,

[0070]

[Outside 5] Becomes

That is, when ΔP ₁ is fixed, it is understood that the temperature step ΔT needs to be increased as the temperature T of the recording head increases and as the preheat pulse P ₁ decreases.

All of these phenomena occur because the discharge amount converges to a certain value as the temperature and the input energy increase. The largest factor that saturates the ejection amount is the ejection opening area of the print head.

[0073] That is, when the ink is ejected by the recording head in a predetermined discharge port area, corresponding to the predetermined discharge port area, the saturation discharge amount is determined, gradually no matter how charged power The increase is attenuated.

Therefore, the control method described with reference to FIGS. 7 to 10 is limited to the case where the discharge amount has not yet reached the saturation region for a predetermined nozzle structure (in this case, the discharge port area). In the case where the discharge amount of the recording head approaches the saturation region due to environmental temperature, self-heating, or the like, it is necessary to perform control as shown in the above equation (6). It is coming.

Therefore, if ΔP ₁ is fixed to some extent, if the temperature step ΔT is controlled so as to increase as the recording head temperature T increases and as the preheat pulse P ₁ decreases, the ejection amount can be increased. Can be stabilized.

An area in which the difference in the degree of control does not occur so much is an area of stable ejection (amount) in the print head. In particular, the area changes depending on the difference in the ejection port area.

FIG. 12 shows a control table for modulating the preheat pulse in this embodiment. As can be seen from this figure (table), the temperature step for decreasing the preheat pulse width is increased when the head temperature increases. Here, the temperature step is 2 ° C. up to a head temperature of 37 ° C., 2.5 ° C. up to 42 ° C., and 3 ° C. above 42 ° C. This makes it possible to control the ejection amount to be constant even when the head temperature increases. Actually, even when printing was performed at a relatively high ambient temperature or at a continuous high-duty printing, the unevenness did not change, and a high-quality image could be obtained.

FIG. 13 shows a heater board of a recording head which can be used in the above embodiment. On the heater board, a temperature sensor, a temperature control heater, a discharge heater, and the like are arranged.

FIG. 13 is a schematic top view of a heater board.
In the figure, temperature sensors 20A and 20B are disposed on the left and right sides of an array of a plurality of discharge heaters 1 on a Si substrate 9, respectively. These discharge heater 1 and temperature sensor 20
A and 20B are similarly arranged in pattern with the temperature control heaters 30A and 30B arranged on the left and right sides of the heater board, and are collectively formed in a semiconductor process. In this example, as for the temperature detected by the temperature sensor, the average value of the temperatures detected by the temperature sensors 20A and 20B is set as the detected temperature.

FIG. 14 shows an ink jet recording apparatus employing the discharge amount control method of the present invention. This device is a full-color serial type printer having replaceable recording heads corresponding to four color inks of black (Bk), cyan (C), magenta (M), and yellow (Y). The head used in this printer has a resolution of 400 dpi, a driving frequency of 4 KHz, and has 128 ejection ports.

In the figure, C denotes four recording head cartridges corresponding to the respective inks of Y, M, C, and Bk. The recording head and an ink tank for storing ink for supplying ink to the recording head are integrally formed. Is formed. Each recording head cartridge C is detachably mounted on the carriage by a configuration (not shown). The carriage 2 is slidably engaged along the guide shaft 11 and is connected to a part of a drive belt 52 that is moved by a main scanning motor (not shown). Thereby, the recording head cartridge C can be moved for scanning along the guide shaft 11. 1
Reference numerals 5, 16, 17, and 18 denote conveying rollers extending substantially in parallel with the guide shaft 11 on the inner side and the lower side in the drawing of the recording area by scanning of the recording head cartridge C. The transport rollers 15, 16 and 17, 18 are driven by a sub-scanning motor (not shown) to transport the recording medium P. The conveyed recording medium P faces the surface of the recording head cartridge C on which the ejection port surface is provided, and forms a recording surface.

A recovery unit is provided facing a movable area of the cartridge C adjacent to a recording area of the recording head cartridge C. In the recovery unit,
Reference numeral 300 denotes a cap unit provided corresponding to each of the plurality of cartridges C having a recording head. The cap unit 300 is slidable in the left and right directions in FIG. When the carriage 2 is at the home position, the carriage 2 is joined to the recording head and capped. In the recovery unit, 401 and 402 are first and second blades as wiping members, respectively, and 403 is a first blade.
In order to clean the blade 401, a blade cleaner made of, for example, an absorber is used.

Further, 500 is a cap unit 300
And a pump unit for absorbing ink and the like from the ejection port of the recording head and the vicinity thereof through the recording head.

FIG. 15 is a block diagram showing a configuration example of a control system in the ink jet recording apparatus.

Here, reference numeral 800 denotes a controller constituting a main control unit, which executes, for example, a CPU 801 in the form of a microcomputer for executing the above-described sequence in FIG. 10, a program corresponding to the procedure, a table shown in FIG.
It has a ROM 803 storing heat pulse voltage values, pulse widths, and other fixed data, and a RAM 805 provided with an area for developing image data and a work area. 8
Reference numeral 10 denotes a host device (which may be a reader unit for image reading) serving as a supply source of image data, and an interface (I / O) for transmitting image data and other commands and status signals.
/ F) 812.

Reference numeral 820 denotes a power switch 822, a copy switch 824 for instructing the start of recording (copying), and a large recovery switch 826 for instructing activation of large recovery.
, Etc., are a group of switches for receiving a command input by an operator. Reference numeral 830 denotes a sensor group for detecting the state of the apparatus, such as a sensor 832 for detecting the position of the carriage 2 such as a home position and a start position, and a sensor 834 including a leaf switch 530 and used for detecting a pump position.

Reference numeral 840 denotes a head driver for driving the electrothermal transducer of the print head according to print data or the like. A part of the head driver is a temperature heater 30A,
It is also used to drive 30B. Further, the temperature detection values from the temperature sensors 20A and 20B are transmitted to the controller 80.
Enter 0. Reference numeral 850 denotes a main scanning motor for moving the carriage 2 in the main scanning direction (the horizontal direction in FIG. 14).
52 is the driver. A sub-scanning motor 860 is used to convey (sub-scan) a recording medium.

The above-described ink jet recording apparatus has recording head cartridges for four colors of ink, cyan, magenta, yellow, and black, and each of these recording head cartridges has an EFPROM 128 for storing information.
Is provided. The information stored in the ROM 128 is
It is read when the power of the ink jet recording apparatus is turned on.
As the ROM data, a table pointer (hereinafter, also referred to as a table number) of a table storing control conditions of the PWM control is read together with the print head ID number, ink color, drive conditions, head shading (HS), and data. As described above, this table pointer is set for each head in accordance with the ejection capacity. In accordance with this table pointer, the main body defining an upper limit value of the width of the preheat pulse P ₁ in the divided pulse width modulation driving method. That is, in the example shown in FIGS. 8 and 9, the table pointer (ID) is set, thereby the maximum width of P ₁ is determined to "0A" (1.87μsec).

Hereinafter, the process of reading the head information stored in the ROM 128 will be briefly described.

First, the head I unique to the recording head
The D number (serial number) is read, and it is checked whether the value of the serial number is, for example, FFFFH. If the serial number is FFFFH, it is determined that there is a head or an error occurs. If the serial number is not FFFFH, the color information of the head is read. Next, it is checked from the color information whether the head is mounted at the correct position specified for each color. If the head is mounted correctly, the next data is read as it is. Is displayed.

Next, it is checked whether the installed recording head cartridge is new by comparing the serial number of the head with the serial number currently stored in the main body. If the head is not a new head, the head information reading process ends. New long if new header information a head (serial number, color information, the pulse width of the main pulse P _3, the PWM control table pointer, the temperature sensor correction value, the head position correction value, date of manufacture, and other information) Is stored in the RAM 805 in the apparatus, and a flag indicating that a new head is mounted is set. Next, the shading information (HS) of the head is read, and the head information reading process ends.

Next, setting of the driving conditions of the recording head will be briefly described.

[0093] Here, the driving conditions are those showing a main pulse P ₃ involved in discharging, when the power supply is turned on as described above, ID number, color information as ROM information of the head,
Table pointer of the pulse P ₃ is read as a head driving condition with table pointer concerning pulse P _1. In accordance with this table pointer, the main body defining a main heat pulse P ₃ width of the divided pulse width modulation driving control described later.

The table P information of the pulse P ₃ is obtained by measuring the ejection characteristics of each head in advance in the head manufacturing process, setting the optimum driving conditions for each head, and storing the information in the ROM 128 of the recording head. deep.

As described above, by reading the table pointer for setting the head drive conditions as the ROM information of the head, it is possible to change the set conditions (drive conditions) on the main body side. Thus, the image quality can be easily stabilized even in the case of the present example using the replaceable recording head.

The table pointer information relating to the preheat pulse is also set in the same manner as the table pointer, and will be described briefly below.

In the head manufacturing process, the discharge amount of each head was measured in advance under standard driving conditions (for example, head temperature: _TH = 2).
Drive voltage in an environment of 5.0 (° C.): V _OP = 18.0 (V)
At the time, P ₁ = 4.87 (μsec) and P ₃ = 4.114
(A pulse of (μsec) is given), and the value is set as a measured ejection amount: _VDM . Next, the standard discharge amount: V _DO = 30.
The difference from 0 [ng / dot] is calculated as V _DO -V _DM, and a table pointer is set based on this. As described above, the upper limit of the preheat pulse is classified according to the amount of ejection depending on the characteristics of each recording head, and this rank is stored in the ROM 128 as table pointer information. The reason why such a setting can be made is that the hole area of the ejection port of the head and the ejection amount have a strong correlation as described above.

[0098] In the table pointer setting for the pre-heat pulse P ₁ described above, the discharge a large amount of recording head, the environmental temperature (head temperature) standard temperature, for example 2
The upper limit of the preheat pulse width P ₁ at 5.0 ° C. is shorter than the upper limit of the standard driving condition (for example, P ₁ = 1.87 μsec) to reduce the discharge amount, and the standard discharge amount V _DO = 30.
0 [ng / dot].

On the other hand, in a recording head with a small discharge amount, the value of the preheat pulse width P ₁ when the environmental temperature is the standard temperature is made longer than the standard driving condition to increase the discharge amount, and the standard discharge amount V _DO = 30. 0.0 [ng / dot].

As described above, the P of the preheat pulse P ₁
The table pointer for performing WM control is set to the RO of the head.
By reading as M information, it is possible to change the setting conditions (driving conditions) of the main body side, it is possible to absorb the variation of the ejection amount of each head, and the image quality can be easily stabilized even in the main body using the replaceable recording head. However, it is possible to improve the yield of the head and reduce the cost of the cartridge head.

As described above with reference to FIGS. 1 to 15, by changing the modulation method of the first pulse of the divided pulse as the driving signal of the heating element according to the temperature of the head, the ejection amount can be reduced. While stabilizing, the temperature of the recording head can be controlled efficiently. Then, the print head control width can be made relatively wide from T _O to T _L , for example, as shown in FIG.

(Embodiment 2) By the way, as described above, when ink is ejected from a recording head having a predetermined ejection opening area, the saturated ejection amount corresponding to the predetermined ejection opening area is determined. Controlled by one table,
The difference in the ejection opening area causes a difference in the ejection amount between the heads. In this case, particularly when full-color printing or the like is performed, the tint changes depending on each head.

Therefore, in the second embodiment, the discharge amount in all heads is controlled to be constant by changing the preheat pulse width when T _H = T _O according to the hole area of the discharge port. Hereinafter, the embodiment will be specifically described with reference to FIGS. FIG. 16 shows that the discharge port area is 320 μm.
In the case of ^2, FIGS. 17 to 20 are each 350,380,4
The case of 10, 440 μm ² is shown.

That is, if the preheat pulse width at the time of the head temperature of 25 ° C. is determined to be 09 _Hex as a standard table, the discharge amount to be controlled varies depending on the hole area of the head. ° C
If the hole area is small, the discharge amount of each head can be made constant by increasing the preheat pulse width at 25 ° C. if the hole area is small.

Further, when the head temperature increases, the discharge amount can be controlled to be constant even at a high temperature by increasing the temperature step for reducing the preheat pulse width as in the first embodiment.

In the case of a head having a small hole area, a small original discharge amount, and a small saturated discharge amount, if the input power is increased to increase the discharge amount, it is necessary to control the position near the saturation region. Therefore, if the discharge amount is excessively increased, control becomes difficult. Conversely, if the preheat pulse width is too large, pre-firing will occur, making it difficult to control.

(Embodiment 3) In Embodiments 1 and 2, the minimum modulation unit of the preheat pulse is fixed (ΔP ₁ = 0.187 μm).
(sec / step), the temperature step ΔT to be modulated is changed depending on the temperature and the discharge port area (hole area). On the other hand, in the present embodiment, the temperature step ΔT is fixed, and the minimum unit ΔP ₁ of the preheat pulse is changed depending on the temperature and the discharge port area. Specifically, ΔP ₁
Control is performed based on a value determined by (μsec / step) = K _T / K _P · ΔT. Here, if ΔT is set to a relatively small value, more precise control becomes possible.

As described above, if the temperature step ΔT for modulating the pre-pulse is kept constant irrespective of the head temperature, there is an advantage that the temperature monitoring in the actual sequence does not become complicated and can be simplified.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which a change in the state of ink is caused by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical structure and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. 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, an electrothermal transducer arranged corresponding to a sheet holding a liquid (ink) or a liquid path, By applying at least one drive signal corresponding to recorded information and giving a sharp temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. As a result, the liquid (ink) corresponding to this drive signal on a one-to-one basis
This is effective because air bubbles inside can be formed. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

The structure of the recording head is not limited to the combination of the discharge port, the liquid path, and the electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above specification. U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is disposed in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. Sho 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

In addition, the form of the ink jet recording apparatus of the present invention is not limited 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 transmission / reception function. It may take a form.

[0113]

As described above, an ejection control method for an ink jet recording head that suppresses a change in the amount of ink ejected from an ejection port of the ink jet recording head due to a temperature change by modulating the input energy. In the step of ejecting ink using a pre-heat pulse for giving energy to the ink that does not cause foaming and a main heat pulse for giving energy to the ink for causing foaming, the ejection port area is large. The smaller the recording head, the smaller the degree of modulation of the preheat pulse width with respect to the temperature change of the recording head, and the more the ink is ejected. It has become possible to achieve stabilization.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pulse waveform of a pulse width modulation driving method of a divided pulse according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a cross section and a front view of a recording head used in an example.

FIG. 3 is a graph showing a relationship between a discharge amount and a pulse width according to the present invention.

Hole area of the discharge port according to the present invention; FIG discharge amount is a graph showing the relationship between the preheat pulse P _1.

FIG. 5 is a graph showing a relationship between a discharge amount and a head temperature according to the present invention.

FIG. 6 is a graph showing a relationship between the area of the ejection port, the ejection amount, and the temperature (environmental temperature) of the print head according to the present invention.

FIG. 7 is an explanatory diagram for explaining a discharge amount control method according to one embodiment of the present invention.

FIG. 8 is a waveform diagram of pulses set in a table according to an embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a head temperature and a preheat pulse modulation control table corresponding thereto according to the embodiment of the present invention.

FIG. 10 is a flowchart of a pulse width modulation sequence according to one embodiment of the present invention.

FIG. 11 is a graph showing the dependence of the ejection amount on the preheat pulse and the ejection amount according to the present invention.

FIG. 12 is a diagram showing a table for controlling a degree of modulation of a preheat pulse according to a temperature according to the embodiment of the present invention.

FIG. 13 is a schematic top view of a heater board used in one embodiment of the present invention.

FIG. 14 is a perspective view of a full-color printer according to one embodiment of the present invention.

FIG. 15 is a block diagram illustrating a control configuration of the printer.

FIG. 16 is a graph showing a relationship between a temperature and a discharge amount with respect to a predetermined discharge port area using a preheat pulse width P ₁ as a parameter in the embodiment of the present invention.

Relates embodiment of Figure 17 the present invention, is a graph showing the pre-heat pulse width P ₁ as parameters the relationship between temperature and the discharge amount for a given ejection opening area.

Relates embodiment of Figure 18 the present invention, is a graph showing the pre-heat pulse width P ₁ as parameters the relationship between temperature and the discharge amount for a given ejection opening area.

Relates embodiment of Figure 19 the present invention, is a graph showing the pre-heat pulse width P ₁ as parameters the relationship between temperature and the discharge amount for a given ejection opening area.

Relates embodiment of Figure 20 the present invention, is a graph showing the pre-heat pulse width P ₁ as parameters the relationship between temperature and the discharge amount for a given ejection opening area.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrothermal transducer (discharge heater) 2 carriage 3 ink liquid path 7 discharge port 9 heater board (Si substrate) 11 aluminum plate 20A, 20B temperature sensor 30A, 30B temperature control heater 801 CPU 803 ROM 805 RAM

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masato Katayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-3-158256 (JP, A) JP-A-3 JP-A-169640 (JP, A) JP-A-3-153369 (JP, A) JP-A-63-149168 (JP, A) JP-A-64-14055 (JP, A) JP-A-2-74351 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/05 B41J 2/01

Claims (6)

(57) [Claims] The method according to claim 1] variation with temperature change of the amount of ink discharged from the discharge ports of the ink jet recording head, in the discharge control method of suppressing the ink jet recording head by modulating the introduced et <br/> energy, foam To give the ink enough energy to produce no ink
Preheat pulse and energy for foaming
Using the main heat pulse that gives energy to the ink.
And the degree of modulation of the preheat pulse width with respect to a change in the temperature of the recording head as the recording head has a larger ejection port area.
A method for controlling the ejection of an ink jet recording head, characterized in that the ink is ejected with a reduced size . 2. The method according to claim 1, wherein the degree of modulation of the preheat pulse width to be modulated is constant, and the width of the temperature change of the recording head when the preheat pulse width is modulated is set to a value corresponding to the area of the discharge port where the ejection port area is large. 2. The ejection control method for an ink jet recording head according to claim 1, wherein the larger the head, the larger the head. 3. The printing head according to claim 1, wherein the area corresponds to an ejection port area of the recording head.
Before information of the preheat pulse width corresponding to the discharge port area from the memory of the recording head when being stored in the memory of each head, the recording head to the apparatus main body is mounted
The main body reads the information of the preheat pulse width ,
3. The ejection control method for an ink jet recording head according to claim 1, wherein a drive signal is controlled in accordance with an ejection port area for each recording head. Wherein the higher the temperature of the ink jet recording head to the temperature change, the relative unit temperature variation pre
2. The method according to claim 1, wherein the degree of modulation of the heat pulse width is reduced. 5. The pre-heat pulser which modulates the temperature of the pre-heat pulse width while modulating the pre-heat pulse width.
5. The ejection control method for an ink jet recording head according to claim 4 , wherein the amount of modulation of the loose width is reduced as the temperature is higher or the preheat width is smaller. 6. The ink jet recording head according to claim 1, wherein a state change of the ink is caused by heat, and the ink is ejected from the ejection port based on the state change to form flying droplets. 7. The ejection control method for an ink jet recording head according to any one of 1 to 6.