JPH0584916A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To obtain appropriate recording density by a method wherein ink temperature is quickly raised to ordinary temperature stably and is kept at the temperature. CONSTITUTION:Ink is heated while energy per unit time to be supplied to a heat insilating heater is gradually decreased to C (4 %), and B (3X) so as to become energy A (2%) per unit time based on a difference between environmental temperature and target temperature.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a recording device for recording on a recording medium such as paper or OHP sheet (hereinafter also referred to as recording paper or simply paper) and a recording head for various recording systems have been proposed. ing. This recording head has
There are a wire dot method, a thermal method, a thermal transfer method, and an inkjet method.

In particular, the ink jet system is a method of jetting ink directly onto a recording sheet, and therefore it is attracting attention as a quiet recording method with low running cost. The recording density of this ink jet recording system has temperature dependency, and the relationship between the recording temperature and the environmental temperature generally decreases as the temperature decreases, as shown in FIG. This is because when the temperature becomes low, the viscosity of the ink becomes large and the ejection amount of the ink decreases. Since an ordinary recording apparatus is set to have an appropriate density at room temperature (for example, 20 ° C.), the recording density becomes lower than the appropriate value in a low temperature environment.

Therefore, the temperature of the recording density is corrected so that an appropriate recording density can be obtained even in a low temperature environment. One method is to warm the ink at low temperature to prevent the viscosity of the ink from increasing.

FIG. 2A is a schematic sectional view of a head cartridge in which a recording head and an ink tank are integrated. Reference numeral 21 is a heater board whose details are shown in FIG. 1B, and a discharge heater 21g is formed on a Si substrate. By applying a voltage to the discharge heater 21g, the ink in the common liquid chamber 23 formed by the heater board 21 and the top plate 22 obtains thermal energy and is discharged as droplets from the discharge port 24 to record. Is done. Ink is supplied from the ink tank 25 to the common liquid chamber 23 through an ink supply pipe 26.

At this time, the heat retaining heater 21d is formed on the heater board 21 together with the discharge heater 21g, and the heat retaining heater 21d is appropriately heated and controlled, whereby the ink in the common liquid chamber can be heated and heated. Reference numeral 21e is a sensor for temperature detection, and the shaded portion indicates the position of the top plate mounted to form the common liquid chamber 23.

FIG. 3 is a graph showing an example of the relationship between the elapsed time and the amount of temperature rise of the ink temperature when the energization of the heat-retaining heater is repeated at regular intervals. In the figure, the curves A, B, C, D and E have energization duty of 2 respectively.
%, 3%, 4%, 5%, 6%. However, the energization duty is the ratio of the pulse energization time and the pulse energization period. As shown in the figure, by selecting the energization duty, the ink temperature is raised to an appropriate temperature,
Can be held.

Therefore, by detecting the environmental temperature and determining the energization duty for raising the temperature of the ink by the temperature difference from the room temperature (target temperature) from FIG. Can be kept warm. At this time, the viscosity of the ink is the same as that at room temperature, so that when recording is performed, it is possible to obtain an appropriate recording density equivalent to that at room temperature.

For example, the temperature at which the proper recording density is achieved is 20 ° C.
3, the energization of the heat retention heater may be controlled at about 3.3% duty when the ambient temperature is 10 ° C. and at about 1.7% duty when the ambient temperature is 15 ° C.

In this way, the ambient temperature is 10 ° C. to 20 ° C.
The duty of energizing the heat-retaining heater at each temperature can be determined as shown in FIG.

Here, the temperature change in FIG. 3 is a temperature change when viewed macroscopically (in this case, on the order of minutes), and when viewed microscopically (in this case, on the order of seconds), during energization. The temperature rises and the temperature decreases from the end of energization to the start of the next energization. That is, there is a change as shown in FIG. 3 as an average of this temperature rise and temperature drop.

In order to change the energization duty depending on the temperature, the pulse interval (or cycle) is always kept constant and the energization pulse width is changed, and the energization pulse width is always kept constant and the pulse interval is kept constant. (Or cycle). For example, the relationship between the temperature and the energization pulse width when the pulse interval is fixed to 6 sec is as shown in FIG. 5, and the relationship between the temperature and the pulse interval when the energization pulse width is fixed as 20 msec is as shown in FIG.

In the above control method, it takes some time from the start of control until the temperature of the ink rises to room temperature.
Therefore, in order to raise the temperature of the ink as soon as possible, the energization control to the heat retention heater is usually started immediately after the recording apparatus is powered on and continued until the power is turned off.
However, during the recording control, the drop in the ink temperature is suppressed to a small extent due to the heat generation of the discharge heater, so that the above control is often interrupted for the purpose of avoiding the complexity of the control.

[0014]

However, the above-mentioned conventional example has the following drawbacks. As can be seen from FIG. 3, it takes some time for the temperature of the ink to rise according to the conventional method until the temperature rises. For example, it takes several tens of minutes to increase the temperature of the ink by 6 degrees as can be seen from the curve A, about 50% after 5 minutes have elapsed from the start of control, and about 65 minutes after 10 minutes have elapsed.
%, The temperature rises only about 80% after 20 minutes. That is, even if the control is started immediately after the power is turned on, if the recording is performed within a short time after the power is turned on, the target proper recording density cannot be obtained.

On the other hand, there is a control system in which the head temperature (ink temperature) is detected, and the heat retention heater is turned on (energized) until the detected temperature reaches normal temperature, and turned on and off at normal temperature. In this method, since the energization duty at the start of control is 100%, the temperature of the ink rises quickly, but the temperature fluctuation (ripple) near room temperature becomes large, and an appropriate recording density cannot be obtained.

Therefore, the present invention has been made to solve the above-mentioned problems, and an ink jet which can obtain a proper recording density by rapidly and stably raising the temperature of the ink to the target temperature. An object is to provide a recording device.

[0017]

In order to achieve the above object, in the ink jet recording apparatus of the present invention, the energy per unit time supplied to the heat retaining heater is the energy per unit time based on the difference between the environmental temperature and the target temperature. The ink is heated while being changed so that

[0018]

According to the above construction, the temperature of the ink can be stably and quickly raised to near the target temperature, so that the recording density can be made appropriate.

[0019]

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

(Embodiment 1) Let us consider the case where the ink temperature is heated to room temperature (20 ° C.) by the conventional method and the environmental temperature is 14 ° C. At this time, from FIG. 3, the energization duty to the heat retention heater is 2%, and the temperature rise of the ink is as shown by the curve A in FIG. As can be seen from FIG. 3, the present embodiment focuses on the fact that the temperature rises faster as the energization duty increases, even when the same 6 ° temperature is raised. In the present embodiment, the following energization control is performed.

Initially, the duty is set to 4% instead of 2% and the temperature is raised by 6 degrees along the curve C. If the current is continued as it is, the temperature will rise more and more. Therefore, after raising the temperature 6 degrees, the duty of the current is changed to 3%. Then, the ink temperature temporarily drops, but soon the temperature rises again along the curve B. When the temperature rise of the ink reaches 6 degrees again, the energization duty is changed to 2% this time. Then, although the ink temperature once drops, the temperature rises again along the curve A, and eventually the ink temperature rises by 6 degrees and the ink temperature is kept substantially constant. The state of the temperature rise of the ink at this time is macroscopically shown by the thick line in FIG. It can be seen from FIG. 7 that the method of the present embodiment raises the ink temperature to the target temperature more quickly than the curve A of the conventional example.

To implement the above control, the following may be performed. First, from FIG. 3, the time during which the temperature rise amount becomes 6 degrees when the energization duty is 4% and 3% in the conventional standby heating is obtained. In the case of 4%, it will be 5 minutes after the start of control, and in the case of 3%, it will be 10 minutes after the start of control. Therefore, the energization duty is 4% from the start of control to 5 minutes, the energization duty is 3% from 5 minutes to 10 minutes from the control start, and the energization duty is 2 from 10 minutes after the start of control. As the percentage changes, the temperature of the ink rises along the thick line in FIG. 7 as described above.

Now, the reason why the ink temperature temporarily drops when the energization duty is gradually lowered in FIG. 7 will be described. Energizing duty 4% in Fig. 7
If the energization duty is changed to 3% when the temperature is increased by 6 degrees, the temperature change from the time of change is the difference between the amount of temperature decrease when energization is stopped at the time of change and the temperature rise due to the duty of 3% from a microscopic point of view. become. Here, the change in the temperature decrease amount is large in the initial stage and gradually decreases. Therefore, the temperature decrease amount becomes larger than the temperature increase amount in the initial stage, and as a result, the ink temperature decreases, and when the magnitude of the temperature decrease amount and the temperature increase amount reverses, the ink temperature increases.

The recording head used in this embodiment has a structure in which the ink is ejected by utilizing the thermal energy from the ejection heater, as in the case described above with reference to FIG. Set the resistance of the heater 21d to 144
Since the driving voltage for heating is Ω ± 20Ω and 24 V, approximately 4 W of electric power can be output.

When the environmental temperature is 11 ° C., it is necessary to raise the temperature of the ink by 9 degrees up to the room temperature of 20 ° C. Therefore, the curves E (6%) and C (5%) in FIG. 3 are raised by 9 degrees. When the time to perform is calculated, it is 5 minutes and 15 minutes after the start of control, respectively.
Therefore, the energization duty is 6% from the start of control to 5 minutes, 4% from 5 minutes to 15 minutes,
After 15 minutes, if it is changed to 3%, it becomes like the bold line in FIG. The ink temperature is raised faster than the conventional curve B. In this way, the energization duty can be determined for each environmental temperature based on the elapsed time from the start of control as shown in FIG. 9, for example.

When the pulse interval is fixed to a constant value t _oms , the pulse width P _ms for setting the energization duty to D% can be calculated by P = t ₀ · D / (100−D). This makes it possible to create a correspondence table of environmental temperature and pulse width. Further, when the pulse width is fixed to a constant value P _{0 ms} , the pulse interval T _ms for setting the energization duty to D% can be calculated by t = P ₀ · (100−D). As a result, a correspondence table of environmental temperature and pulse interval can be created.

Further, when the pulse width is fixed to a constant value P _{0 ms} , the pulse period T _ms for making the energization duty D% can be calculated by T = P ₀ · 100 / D. This makes it possible to create a correspondence table between the environmental temperature and the pulse period.

The configuration for controlling the energization of the heat retention heater will be described with reference to the block diagram of FIG. In the figure, 10 is a CPU, which executes processing such as energization control based on a program stored in the ROM 11. R
The OM 11 stores the program of the CPU 10 and the table shown in FIG. 9 and the like. Reference numeral 12 is a timer for measuring the elapsed time of energization, and 13 is the heat retaining heater 21d described above.
It is a control circuit for controlling the temperature sensor 14 that detects the ambient temperature.

Next, regarding the energization control of the heat retention heater,
This will be described with reference to the flowchart shown in FIG. The timer 12 for measuring the elapsed time is reset in step S1 and the elapsed time is detected in step S2. Step S3
The ambient temperature is detected by the temperature sensor 14 in the ROM, and the ROM is detected based on the ambient temperature and the elapsed time detected in step S4.
The energization duty is determined with reference to the table in FIG.

At step S5, the heat insulation heater 21d is energized with a pulse width or pulse interval corresponding to the determined energization duty. Then, the above steps S2 to S5
Is repeated until the start of recording is detected in step S6.

In the above embodiment, the energizing duty of the heat retaining heater 21d is controlled to control the energy per unit time. However, by converting the energizing duty into energy, the energizing voltage is controlled at a constant period and a constant pulse width. It is also possible to change and implement the above-mentioned control. Further, the voltage can be changed in an analog manner in continuous energization instead of pulse energization.

Regarding the start timing of the energization control, in the conventional method, it takes a long time to raise the temperature of the ink. Therefore, in order to raise the temperature of the ink as soon as possible, it is usual to start the control at an early time after the power is turned on. .. However, in the method of the present embodiment, the temperature of the ink can be raised quickly, so the control start time does not have to be limited to the early time after the power is turned on. For example, in the case of a recording device such as a word processor, control is not started during creation or editing of a document, and energization control is started when a menu for recording execution is called up, or electricity is supplied with a recording execution command. Even if the control is started, there is no problem if the temperature rising rate of the ink is set earlier. When recording on a plurality of pages, the energization control may be performed during a non-recording period such as a page break period.

In this embodiment, the temperature (normal temperature) at which the recording density of the recording apparatus is proper is 20 ° C.
The recording density can be similarly corrected when the temperature is higher than or equal to 0 ° C. and when the temperature is lower than or equal to 20 ° C. The lower limit temperature for correction (10 ° C. in this embodiment) can be freely set.

Further, in the present embodiment, the ink temperature is raised so as not to exceed the target temperature at which the proper recording density is obtained. However, when the change in the ink temperature is increased or decreased, the ink temperature is increased with respect to the target temperature. It can also be changed so that the temperature rises and falls. In this case, the ink temperature is the target temperature increase amount of 150.
It is desirable to change it within the range not exceeding%.

In this embodiment, the temperature rise curve of the ink is slightly jagged as shown in FIG. 7, but the time interval from the start of control is made shorter than 5 minutes to make the energization duty smaller. If changed, the temperature of the ink can be raised infinitely and smoothly. On the contrary, the time interval may be 5 minutes or more if the temperature rise of the ink is a little rough.

(Second Embodiment) Next, a second embodiment for realizing the same ink temperature rise as in the first embodiment will be described. To change the energization duty, the energization pulse period is kept constant and the pulse width is changed. Here, if the pulse period is 6 sec (10 shots per minute), even if the energization duty is changed by changing the pulse width, it will be 50 in 5 minutes.
The emitted pulse will be energized. That is, the elapsed time can be known by counting the number of energizing pulses.

Therefore, when the elapsed time in FIG. 9 is replaced with the number of pulses, the result becomes as shown in FIG. 12, and the above equation may be used to convert the energization duty into the energization pulse width. That is, for each environmental temperature, the same effect as that of the first embodiment can be obtained by changing the energization duty as shown in FIG. 12 depending on the number of energization pulses from the start of control.

When the pulse period is large with respect to the pulse width as in this embodiment, the number of pulses is counted because the change rate of the pulse period is small even when the energization duty is changed with the pulse interval kept constant. By doing so, there is no problem even if the elapsed time is calculated.

FIG. 13 shows a block diagram of energization control of the heat retaining heater in this embodiment. In the figure, the timer 12 of FIG. 10 is replaced with a counter 15 for counting the number of pulses. FIG. 14 shows a flowchart of energization control of the heat retention heater. This figure shows steps S1 and S of FIG.
2. Step S1 in which the elapsed time of S4 is changed to the number of pulses
1, S12, and S14, and detailed description thereof will be omitted.

(Third Embodiment) In the first and second embodiments, the open loop control is performed without detecting the ink temperature to be controlled. In this embodiment, the temperature sensor 2 for detecting the ink temperature is used.
1e (FIG. 2 (B)) is used to perform closed loop control.

Let us consider a case where the target temperature for achieving the proper recording density is 20 ° C. and the ink temperature is raised by 9 ° at 11 ° C. For example, when the control starts, the energization duty is 6%,
When the ink temperature reaches 20 ° C, the energization duty is 1%
When the ink temperature reaches 20 ℃ again, reduce the energization duty by 1%. When this is repeated, the ink temperature changes as shown in FIG. Compared to the conventional ink temperature change curve B, the temperature rises to the target temperature more quickly.

If the energization duty at the start of control is made too large when the target temperature rise amount is too small, the ink temperature rises quickly, so if the timing of changing the energization duty is deviated, the ink temperature exceeds the target. there is a possibility. Therefore, in this embodiment, the initial energization duty for each ink temperature is set as shown in FIG.

As shown in the block diagram of this embodiment in FIG. 17, instead of the temperature sensor 14 for detecting the ambient temperature,
Temperature sensor 21e for detecting the temperature of ink (head)
Have. As shown in FIG. 2B, the temperature sensor 21e is located on the left and right in the vicinity of the discharge heater 21g, and is formed of a diode or aluminum wiring. Further, the ROM 11 stores the table shown in FIG.

In the energization control of this embodiment, as shown in the flowchart of FIG. 18, first, in step S23, the temperature sensor 21e detects the ink temperature, and then in step S2.
In step 4, the energization duty is determined based on FIG. In step S25, the heat insulation heater 21d is energized with a pulse width or pulse interval corresponding to this energization duty. Then, the steps S23 to S25 are the steps S
It is repeated until the start of recording is detected at 26.

In this embodiment, since the ink temperature to be controlled is sensed, the necessary table is shown in FIG.
It has the advantage of being a very simple control. Further, even if there is a deviation between the environmental temperature and the ink temperature, the desired correction can be achieved accurately and stably.

In order to realize the energization duty shown in FIG. 16, it is possible to change the pulse width, the pulse interval, the voltage during pulse energization, the voltage during continuous energization, etc., as in the first embodiment. ..

Further, the more precise the change of the duty is, the higher the accuracy becomes.
It is also possible to consider a method of continuously changing the value without changing it step by step.

It should be noted that any of the embodiments can be applied to all those in which the ejection amount of the recording medium has temperature dependence.
Not only an inkjet method such as an on-demand method or a continuous method that uses thermal energy or mechanical energy from a voltage element or the like, but also a method that melts and ejects a solid ink during recording by a recording head unit may be used.

The heat-retaining heater may heat the ink directly or indirectly, and its kind or installation site is not specified.

The present invention brings excellent effects particularly in a recording head and a recording apparatus of a system utilizing heat energy among the ink jet recording systems.

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

As the constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the straight liquid passage or the direct liquid passage) as disclosed in the above-mentioned specifications, US Pat. No. 4,558,333 and US Pat. No. 4, which disclose a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of 459600 is also included in the present invention. In addition, Japanese Laid-Open Patent Publication No. 123670/1984 discloses a configuration in which a common slit is used as a discharge portion of a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy. The present invention is also effective as a configuration based on JP-A-59-138461, which discloses a configuration that corresponds to the discharge portion.

[0053]

EFFECT OF THE INVENTION Since the ink temperature is quickly and stably maintained up to around room temperature, it is possible to obtain a recording density almost equal to the recording density at room temperature even if recording is performed early after the power is turned on. it can.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between environmental temperature and recording density.

FIG. 2 is a diagram illustrating details of a head cartridge.

FIG. 3 is a graph showing a relationship between an elapsed time and a temperature rise amount of ink when pulse heating control is performed on the heat retention heater.

FIG. 4 is a correspondence table of environmental temperature and energization duty of a conventional example.

FIG. 5 is a correspondence table between the environmental temperature and the energization pulse width in the conventional example.

FIG. 6 is a correspondence table between the environmental temperature and the energization pulse interval in the conventional example.

FIG. 7 is a graph showing the relationship between the elapsed time and the ink temperature rise amount in Example 1.

FIG. 8 is a graph showing the relationship between the elapsed time and the ink temperature rise amount in Example 1.

FIG. 9 is a correspondence table between the environmental temperature and the energization duty of the first embodiment.

FIG. 10 is a block diagram of energization control of the heat retention heater according to the first embodiment.

FIG. 11 is a flow chart of heat retention heater energization control according to the first embodiment.

FIG. 12 is a correspondence table between environmental temperature and energization duty in the second embodiment.

FIG. 13 is a block diagram of heat retention heater energization control according to the second embodiment.

FIG. 14 is a flow chart of heat retention heater energization control according to the second embodiment.

FIG. 15 is a graph showing the relationship between the elapsed time and the ink temperature rise amount in Example 3.

FIG. 16 is a correspondence table between ink temperature and energization duty of the third embodiment.

FIG. 17 is a block diagram of energization control of a heat retention heater according to a third embodiment.

FIG. 18 is a flow chart of heat retention heater energization control according to the third embodiment.

[Explanation of symbols]

 10 CPU 11 ROM 12 Timer 14 Temperature Sensor 15 Counter 21d Insulation Heater 21e Temperature Sensor

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Claims (7)

[Claims] 1. In an ink jet recording apparatus for recording by using a recording head for ejecting ink from an ejection port, a detecting means for detecting an environmental temperature, and heating the ink in the recording head by energy of a drive signal supplied to the recording head. And heating means for supplying the heating signal to the heating means per unit time so that the energy per unit time is based on the difference between the environmental temperature detected by the detecting means and the target temperature of the recording head. An ink jet recording apparatus comprising: a heating control unit that decreases with time. 2. The ink jet recording apparatus according to claim 1, wherein the supply time is detected by a timer that measures an elapsed time from the start of supplying the drive signal. 3. The ink jet recording apparatus according to claim 1, wherein the supply time is detected by a counter that measures the number of pulses from the start of supplying the drive signal. 4. An inkjet recording apparatus for recording using a recording head for ejecting ink from an ejection port,
Based on the head temperature detected by the heating means for heating the ink in the recording head by the energy of the drive signal supplied, the detection means for detecting the temperature of the recording head,
An ink jet recording apparatus comprising: a heating control unit that reduces the energy per unit time of a drive signal supplied to the heating unit as the supply time elapses. 5. The ink jet recording apparatus according to claim 1, wherein the energy per unit time is defined by the pulse width of the drive signal. 6. The ink jet recording apparatus according to claim 1, wherein the energy per unit time is defined by the pulse interval of the drive signal. 7. The recording head is provided for each of a plurality of ejection ports for ejecting ink and corresponding ejection ports, and causes a state change in the ink due to heat to cause ink to be ejected from the ejection port based on the state change. The inkjet recording apparatus according to claim 1, further comprising: a thermal energy generating unit that discharges the droplets to form flying droplets.