JP3278181B2 - Ink jet recording device - Google Patents

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 apparatus for performing recording on a recording medium such as a sheet of paper or an OHP sheet (hereinafter also referred to as recording paper or simply paper) has been proposed in the form of mounting a recording head by various recording methods. Have been. This recording head includes a wire dot type, a thermal type, a thermal transfer type, an ink jet type, and the like.

[0003] In particular, the ink-jet method, which directly ejects ink onto recording paper, has attracted attention as a quiet recording method with low running cost. The recording density of this ink jet recording method has temperature dependency, and the relationship between the recording density and the ambient temperature generally decreases as the temperature decreases, as shown in FIG. This is because when the temperature becomes low, the viscosity of the ink increases, and the ejection amount of the ink decreases. Since a normal recording apparatus is set to have an appropriate density at normal temperature (for example, 20 ° C.), the recording density becomes lower than appropriate in a low-temperature environment.

Therefore, temperature correction of the recording density is performed so that an appropriate recording density can be obtained even in a low temperature environment. As one of the methods, there is a method of preventing the viscosity of the ink from increasing by warming the ink at a low temperature.

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 denotes 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 ports 24 to perform recording. Is performed. The ink supply pipe 2 extends from the ink tank 25 to the common liquid chamber 23.
Ink is supplied through 6.

At this time, by forming a heat retaining heater 21d together with the discharge heater 21g on the heater board 21 and appropriately controlling the heating of the heat retaining heater 21d, it is possible to heat and raise the temperature of the ink in the common liquid chamber. Reference numeral 21e denotes a temperature detecting sensor, and a hatched portion indicates a position of a 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 increase in the ink temperature when pulsed power is repeatedly applied to the heat retaining heater at regular time intervals. In the figure, curves A, B, C, D, and E indicate that the energization duty is 2
%, 3%, 4%, 5% and 6%. However, the energization duty is a ratio between the pulse energization time and the pulse energization cycle. As shown in the figure, by selecting the energization duty, the ink temperature can be raised to an appropriate temperature and maintained.

Therefore, the temperature of the ink is raised to the normal temperature by detecting the environmental temperature, determining the power supply duty for raising the temperature of the ink by the temperature difference from the normal temperature (target temperature) from FIG. It can be kept warm. At this time, since the viscosity of the ink is equal to that at normal temperature, when recording is performed, an appropriate recording density equivalent to that at normal temperature can be obtained.

For example, if the temperature at which the proper recording density is reached is 20 ° C.
3, the energization of the heat retaining heater may be controlled at about 3.3% duty at an environmental temperature of 10 ° C. and at about 1.7% duty at 15 ° C. from FIG.

[0010] In this way, the ambient temperature of 10 ° C to 20 ° C
The energization duty to the heat retention heater at each temperature up to can be determined as shown in FIG.

Here, the temperature change in FIG. 3 is a macroscopic change (in this case, on the order of minutes), and a microscopic change (in this case, on the order of seconds) indicates that the temperature is changed. , And the temperature is repeatedly changed from the end of energization to the start of the next energization. That is, a change as shown in FIG. 3 is obtained as an average of the temperature increase and the temperature decrease.

In order to change the energizing duty depending on the temperature, a method of changing the energizing pulse width while keeping the pulse interval (or cycle) constant, and a method of changing the energizing pulse width while keeping the energizing pulse width constant are described. (Or cycle). For example, the relationship between the temperature and the energizing pulse width when the pulse interval is fixed at 6 sec is as shown in FIG. 5, and the relationship between the temperature and the pulse interval when the energizing pulse width is fixed at 20 msec is as shown in FIG.

In the case of the above control method, it takes a little time from the start of the control until the temperature of the ink rises to the normal temperature. Therefore, in order to raise the temperature of the ink as soon as possible, the energization control to the heat retaining heater is started immediately after the power supply of the printing apparatus is turned on, and usually continued until the power supply is turned off.
However, during the printing control, the decrease in the ink temperature due to the heat generated by the discharge heater is suppressed to a small extent, so that the control is often interrupted for the purpose of avoiding complicated control.

[0014]

In general, the ink jet recording method is based on the problem of discharge failure such as air bubbles and dust in a head cartridge, and ink which becomes thick and unsuitable for recording.
It is necessary to appropriately perform an ejection recovery process for removing ink by forcibly discharging ink. The ejection recovery process is performed by, for example, covering the ejection port with a cap and sucking ink from the ejection port with a pump. At this time, since the ink in the common liquid chamber 23 in FIG. 2 is sucked out from the discharge port 24, new ink is supplied from the ink tank 25 into the common liquid chamber 23 through the ink supply pipe 26. Here, the temperature of the ink to be warmed by the energization control of the heat retaining heater gradually decreases as the ink flows from the common liquid chamber to the ink supply pipe and the ink tank.

Therefore, when the ejection recovery process is performed, the ink of the appropriate temperature in the common liquid chamber is discharged, and the temperature of the ink in the common liquid chamber is lower than the appropriate temperature. Thereafter, the temperature of the new ink in the common liquid chamber is raised to an appropriate temperature by the heat retaining heater.

However, when printing is performed immediately after the ejection recovery processing, the ink has a temperature lower than the appropriate temperature, and thus the recording density is lower than the target appropriate recording density.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an ink jet recording apparatus capable of stably obtaining an appropriate recording density even after an ejection recovery process.

[0018]

In order to achieve the above object, the present invention provides an ink jet recording apparatus for performing recording using a recording head which discharges ink from discharge ports.
Discharge recovery means for performing ink recovery processing by causing ink to flow out of the print head during non-printing, detection means for detecting the environmental temperature at which the print head is placed, and a drive signal for supplying ink in the print head Heating means for heating with the energy of the energy, and when a discharge recovery process is performed by the discharge recovery means, according to the environmental temperature detected by the detection means, a drive signal to be supplied to the heating means per unit time. Determining means for determining the energy to be greater than when the ejection recovery processing is not performed; and a drive signal having a large energy per unit time determined by the determining means for the target temperature and the environmental temperature at which the heating means should raise the temperature. Control means for controlling supply for a predetermined time determined according to the difference.

[0019]

According to the above configuration, after the ink in the common liquid chamber flows out by the discharge recovery processing, the energy per unit time to the heat retaining heater as the heating means is not changed in accordance with the environmental temperature when the discharge recovery processing is not performed. By making the temperature larger than that, the temperature of the new ink lower than the appropriate temperature can be quickly raised to the appropriate temperature, so that the recording density can be stably and appropriately adjusted.

[0020]

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

(Embodiment 1) The temperature drop of the ink due to the ejection recovery process is substantially proportional to the amount of temperature rise by the heat retaining heater.
It is about 10% of the temperature rise amount. For example, if the temperature of the ink is raised by 10 degrees to an appropriate temperature of 20 degrees Celsius in a 10 degrees Celsius environment, the temperature decreases by about 1 degree and the ink temperature becomes about 19 degrees Celsius.

FIG. 7 shows how the temperature of the ink rises when the energization duty to the heat retaining heater is made larger than that in FIG. In the figure, a curve A shows a case where the energization duty is 10%, a curve B shows a case where it is 20%, and a curve C shows a case where it is 30%. The actual change in the ink temperature increases when the pulse is applied, and decreases until the next pulse is applied. In the figure, the average value of the temperature change correlated with the recording density is shown. As described above, by increasing the energization duty to the heat retaining heater, the temperature of the ink can be raised several degrees in about several seconds.

Accordingly, when the temperature is raised to 20 ° C. in an environment of 12 ° C., the temperature drop due to the discharge recovery process is about 0.8 ° C. Therefore, FIG.
If the energization control is performed for 5 seconds, the ink temperature rises to 20 ° C. Thereafter, if the energization duty is returned to about 2.7% of the normal value, the ink temperature is maintained at 20 ° C. before the ejection recovery processing. Similarly, when the temperature is raised to 20 ° C. at an environment of 16 ° C., the temperature drop of the ink is about 0.4 ° C. Therefore, from FIG. ° can be returned.

In this way, by appropriately selecting the energization duty and the energization control time and controlling the energization, the ink can be quickly raised to an appropriate temperature at each environmental temperature. However, in the case of controlling by pulse energization, if the control time is set too short, the number of energization pulses is reduced, and the curve shown in FIG. 7 does not raise the temperature but increases the error. Therefore, the control time should be as long as possible. Is more preferred. For example, when energization control is performed with the energization time kept constant at 5 seconds, the energization duty of the heat retention heater for each environmental temperature is:
It can be determined as shown in FIG.

When the pulse interval is constant at t _{0 ms} ,
The pulse width (pulse energization time) P _ms for setting the energization duty to D% is obtained by P = t ₀ · D (100−D). In the case of FIG.
00 _ms ), the pulse width is determined as shown in FIG. When the pulse width is fixed at P _{0 ms} , the pulse interval t _ms for setting the energization duty to D% can be similarly obtained by t = P ₀ · (100−D) / D.

Therefore, by controlling the energization with the energization duty shown in FIG. 8 after the end of the ejection recovery processing, the ink temperature can be raised in a few seconds at each environmental temperature and the ink temperature can be returned to an appropriate temperature.

The recording head used in the present embodiment has a structure in which ink is ejected by using thermal energy from an ejection heater in the same manner as described with reference to FIG. Set the resistance of heater 21d to 144
Since Ω ± 20Ω and the drive voltage for heating are set to 24V, about 4W of power can be output.

A configuration for controlling the energization of the heat retaining heater will be described with reference to the block diagram of FIG. In FIG. 1, reference numeral 10 denotes a CPU which executes processes such as energization control based on a program stored in a ROM 11. R
In addition to the program of the CPU 10, the OM 11 includes, as shown in FIG.
Are stored. Reference numeral 12 denotes a timer for measuring the elapsed time of energization, and reference numeral 13 denotes a control circuit for controlling the above-described heat retaining heater 21d and the temperature sensor 14 for detecting the environmental temperature.

Next, regarding the energization control of the heat retaining heater,
This will be described with reference to the flowchart shown in FIG. In step S1, the environmental temperature is detected by the temperature sensor 14, and in step S2, the presence or absence of the ejection recovery process is detected. If there is no ejection recovery processing, the energization duty is determined in step S3 with reference to the table of FIG. 3 stored in the ROM 11 based on the detected environmental temperature. In step S4, the heater 21d is energized with a pulse width or a pulse interval corresponding to the determined energization duty. Steps S1 to S4 are repeated until the start of recording is detected in step S5.

On the other hand, if there is an ejection recovery process, step S
In step 6, the timer 12 for measuring the elapsed time is reset, and in step S7, the energization duty having higher energy than usual is determined with reference to the table of FIG. 8 stored in the ROM 11 based on the environmental temperature. In step S8, the heater 21d is energized with a pulse width or a pulse interval corresponding to the determined energization duty. The above steps S7 and S8 are the same as those of the timer 12 in step S9.
Is repeated until 5 seconds have elapsed.

In this embodiment, the ejection recovery process is performed at the time of the user's instruction and at the time of the first printing when the printing is not performed for three days or more.

In the above embodiment, the energy per unit time is controlled by controlling the duty to be supplied to the heat retaining heater 21d. However, by converting the supplied duty to energy, the supplied voltage can be controlled at a constant period and a constant pulse width. It is also possible to realize the above control by changing. In addition, the voltage can be changed in an analog manner in continuous energization instead of pulse energization.

(Embodiment 2) In the first embodiment, it takes about 5 seconds for the ink temperature to return to an appropriate temperature after the discharge recovery processing. Therefore, when printing is performed immediately after the discharge recovery processing,
The start of recording must be interrupted for 5 seconds, and then recording must be performed, which increases the recording time by 5 seconds. Therefore, in the present embodiment, by performing the energization control of the heat retaining heater to compensate for the ink temperature drop due to the ejection recovery processing in a series of the ejection recovery processing, proper recording can be performed even if printing is performed immediately after the ejection recovery processing. It is possible to obtain a concentration.

FIG. 12 shows an example of a flowchart of the ejection recovery process.

In FIG. 12, step S100 is a pumping step, in which a suction force by a pump is applied to a cap covering a discharge port forming surface of a head to suck ink from the discharge ports. In step S200, a suction force is applied to the cap with the cap removed from the head,
This is an idle suction step of sucking ink remaining in the cap, and S300 is a preliminary ejection step of ejecting ink toward the cap. Steps S401 to S406 are an idle suction step, and S500 is a wiping step of wiping the ejection port forming surface of the head with a blade. As can be seen from this, since the control including the time management is complicated in the discharge recovery processing, it is difficult to separately control the energization of the heat retaining heater in parallel with this.

Therefore, in this embodiment, a pulse is supplied to the heat retaining heater in synchronization with the timing in a series of operations of the discharge recovery process.

Since the pump motors driven in steps S401, S403, and S405 are driven at 400 PPS, the time intervals at the start of the forward rotation of the four-degree pump motor shown in FIG. 12 are 767.5 ms (18
7/400 + 0.3 (s)), 725 ms (170/4
+0.3 (s)), which is 725 ms, almost 7 on average.
It may be considered as a 39 ms cycle.

Therefore, the energization pulse width is set so that the decrease in the ink temperature is successfully compensated for by energizing the pulse four times in the period of 739 ms. Since the entire control time is about 3 seconds, the required energization duty can be determined as shown in FIG. 13 from FIG. When this is converted into an energizing pulse width with a period of 739 ms, the result is as shown in FIG.
Therefore, for each environmental temperature, the purpose can be achieved by energizing the warming heater with the pulse width of FIG. 14 for the four timings in the discharge recovery processing flowchart.

When the pulse width in FIG. 14 is compared with the pulse width in the normal heating heater energization control at 6-second intervals in FIG. 5, the pulse widths are almost equal. Therefore, there is almost no problem even if the correction pulse width during the recovery processing is set to the same value in FIG. In this case, the table of the ambient temperature and the pulse width can be shared, so that the table is one.
There are advantages that can be reduced.

The energization control of the heat retaining heater will be described with reference to the flowchart of FIG. Step S
The environment temperature is detected at 11 and the energizing pulse width is determined at step S12. This pulse width is commonly used regardless of the presence or absence of the ejection recovery processing as described above. Step S1
In steps 3 to S15, pulse energization is performed when there is no ejection recovery processing. In step S16, during the ejection recovery process,
From the timing shown by, a pulse current is supplied to the heat retaining heater.

Note that if the pulse width during the recovery process is determined and the normal pulse interval is determined in accordance with the determined pulse width, the flowchart of FIG. 15 can be used in any case. In addition, the number of pulse energization and energization timing during the recovery process are
It is not necessary to limit to FIG. Further, as long as the relationship between the energization duty of the heater and the amount of temperature rise of the ink is known, any kind of heater can be used.

Reference Example In the first and second embodiments, the open-loop control is performed by detecting the environmental temperature instead of directly detecting the temperature of the ink to be controlled. On the other hand, in the reference example, closed loop control is performed using a temperature sensor 21e (FIG. 2B) for detecting the ink temperature. In this case, control is performed using a table as shown in FIG. 8, for example, as in the first embodiment, so that time counting becomes unnecessary. However, since the ink temperature near the temperature sensor 21e rapidly decreases due to the recovery process, the detected ink temperature becomes unstable, and there is a disadvantage that accurate heating control cannot be performed.

As shown in the block diagram of the reference example in FIG. 17, instead of the temperature sensor 14 for detecting the environmental temperature,
Temperature sensor 21e for detecting the temperature of ink (head)
Having. As shown in FIG. 2B, the temperature sensors 21e are located on the left and right in the vicinity of the discharge heater 21g, and are formed of diodes or aluminum wiring. The table shown in FIG. 16 is stored in the ROM 11.

In the energization control of the reference example, as shown in the flowchart of FIG.
This is the same as the control shown in FIG. If the ejection recovery processing is performed in step S22, the temperature of the ink is detected by the temperature sensor 21e in step S26, and it is determined in step S27 whether the ink temperature is equal to or higher than 20 ° C. If the temperature is lower than 20 ° C., the ROM 11 is determined based on the ink temperature in step S28.
The energization duty having higher energy than usual is determined with reference to the table of FIG. In step S29, the heater 21d is energized with a pulse width or a pulse interval corresponding to the determined energization duty. As described above, steps S26 to S29 are repeated until the ink temperature reaches 20 ° C., and the ink temperature can be immediately increased to the normal temperature.

As another closed loop control method, an ink temperature control target temperature (2 in the case of this embodiment) is used.
0 ° C.) and the temperature difference between the temperature of the ink measured by the ink temperature sensor and the heat retention energy applied to the heat retention heater. Further, in this control method, the applied energy to the heat retaining heater is not a steady application, but is continuously changed in accordance with the temperature difference, the applied energy is reduced as the temperature approaches the target temperature, and a steady application is performed when the target temperature is reached.

In the control of the conventional method, when the ink temperature is low and causes a problem, in addition to the discharge recovery processing by the pump of the present embodiment, the following case may be adopted. It is valid. The first is an ejection recovery process in which pressure is applied to the ink from an outlet other than the ejection port to force the ink to be ejected from the ejection port. The second is that the ink ejection port is directed downward to eject the ink using gravity. A third example is an ejection recovery process in which the ink is spontaneously discharged from the outlet, and a third example is an ejection recovery process by preliminary ejection in which the ink is ejected and discarded in the same manner as the normal ink ejection in a recording method that does not generate heat.

It is to be noted that any of the embodiments can be applied to any recording medium whose discharge amount depends on temperature.
In addition to an ink-jet method such as an on-demand method using a thermal energy or mechanical energy using a voltage element or the like and a continuous method, a method in which solid ink is melted and ejected at the time of recording by a recording head unit may be used.

Further, the heat retaining heater may directly or indirectly heat the ink, and its type and installation site are not specified.

The present invention particularly provides an excellent effect in a recording head and a recording apparatus of a system utilizing thermal energy among ink jet recording systems.

The typical configuration 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 can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, liquid (ink)
By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding nucleate boiling to an electrothermal transducer arranged corresponding to the sheet or liquid path in which , Heat energy is generated in the electrothermal transducer, and the film is boiled on the heat-acting surface of the recording head.
As a result, air bubbles in the liquid (ink) can be formed in one-to-one correspondence with the drive signal, which is effective. The growth of this bubble,
The liquid (ink) is discharged through the discharge opening by contraction to form at least one droplet. 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 liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. The drive signal in the form of a pulse is disclosed in U.S. Pat.
Suitable are those described in 345262. If the conditions described in U.S. Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of a discharge port, a liquid path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,558,333 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 459600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication (Kokai) No. 123670/1984 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing pressure waves of thermal energy. The present invention is also effective as a configuration based on JP-A-59-138461 which discloses a configuration corresponding to a discharge unit.

[0052]

According to the present invention, the energy per unit time to the warming heater as the heating means is increased based on the environmental temperature after the outflow of the ink by the ejection recovery process, so that the ink temperature lowered by the outflow of the ink is quickly returned to an appropriate temperature. Thus, recording can be performed at an appropriate recording density even after the ejection recovery processing.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining 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 energization control is performed on a heat retaining heater.

FIG. 4 is a table showing a correspondence between an ambient temperature and an energization duty in a conventional example.

FIG. 5 is a table showing a correspondence between an ambient temperature and an energizing pulse width in a conventional example.

FIG. 6 is a table showing a correspondence between the ambient temperature and the energizing pulse interval in the conventional example.

FIG. 7 is a graph showing a relationship between a control time and an ink heating amount when pulse energization control is performed on a heat retaining heater.

FIG. 8 is a table showing a correspondence between an environmental temperature and an energization duty according to the first embodiment.

FIG. 9 is a table showing a correspondence between an ambient temperature and an energizing pulse width according to the first embodiment.

FIG. 10 is a control block diagram according to the first embodiment.

FIG. 11 is a control flowchart of the first embodiment.

FIG. 12 is a flowchart of a discharge recovery process showing a heating heater energization timing according to the second embodiment.

FIG. 13 is a table showing a correspondence between an environmental temperature and an energization duty according to the second embodiment.

FIG. 14 is a table showing a correspondence between an ambient temperature and an energizing pulse width according to the second embodiment.

FIG. 15 is a control flowchart of the second embodiment.

FIG. 16 is a control block diagram of a reference example.

FIG. 17 is a control flowchart of a reference example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 CPU 11 ROM 12 Timer 14 Temperature sensor 15 Counter 21d Heating heater 21e Temperature sensor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/175 B41J 2/05

Claims (7)

(57) [Claims] 1. An ink jet recording apparatus which performs recording using a recording head which discharges ink from a discharge port, comprising: an ejection recovery means for discharging ink from the recording head to perform an ejection recovery process during non-recording; Detecting means for detecting the set ambient temperature; heating means for heating the ink in the recording head by the energy of the supplied drive signal; and detecting when the ejection recovery processing is performed by the ejection recovery means. Determining means for determining, in accordance with the environmental temperature detected by the means, the energy per unit time of the drive signal to be supplied to the heating means as compared with a case where the ejection recovery processing is not performed; The driving signal having a large energy per unit time should be raised by the heating means.
Control means for controlling supply for a predetermined time determined according to a difference between a target temperature and an environmental temperature . 2. An ink jet recording apparatus according to claim 1, wherein said ejection recovery means sucks ink from said recording head by a suction means. 3. The ink jet recording apparatus according to claim 1, wherein the ejection recovery unit pushes out the ink from the recording head by a pressing unit. 4. An ink jet recording apparatus according to claim 1, wherein said ejection recovery means ejects ink from said recording head by an ejection means. 5. The control unit controls the heating unit to supply a driving signal having a large energy per unit time to the heating unit by increasing a duty of a driving signal supplied to the heating unit in accordance with the environmental temperature. The ink jet recording apparatus according to claim 1, wherein 6. The control means controls the drive signal to be supplied to the heating means in accordance with the environmental temperature to increase the voltage of the drive signal supplied to the heating means so as to supply a drive signal having a large energy per unit time to the heating means. The ink jet recording apparatus according to claim 1, wherein 7. The recording head is provided for each of a plurality of ejection ports for ejecting ink and a corresponding ejection port, and causes a state change due to heat in the ink, and causes the ink to be discharged from the ejection port based on the state change. The ink jet recording apparatus according to any one of claims 1 to 6, further comprising a thermal energy generating unit configured to discharge the liquid to form flying droplets.