JPH1110908A - Ink jet printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the print time as compared with conventional printers by varying the circulation ink supply to an ink jet head depending on the temperature thereof thereby preventing the ink from being pushed out through the ink jet port in the relatively low temperature region of the ink jet head. SOLUTION: The ink jet printer comprises an ink jet head 20 provided with an ink jet port, an ink tank 21 for storing ink, a passage 22 for supplying ink from the ink tank 21 to the ink jet head 20, a passage 23 for circulating the ink from the ink jet head 20 back to the ink tank 21, means 25 for detecting the temperature of the ink jet head 20, a pump 24 for circulating the ink again from the ink tank 21 to the ink jet head 20, and means 27 for controlling ink supply to the ink circulation pump 24 based on the information detected by the temperature detection means 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet printing method and apparatus, and more particularly, to a method of ejecting ink droplets by supplying an electric signal to an electrothermal converter incorporated in an ink-jet head to heat and expand the ink. It is suitable for use in an ink jet printing method and an apparatus for discharging from an outlet.

[0002]

2. Description of the Related Art In general, an ink jet head of an ink jet printing apparatus includes an ink discharge port for discharging ink droplets, an ink path communicating with the ink discharge port, and an ink path for forming an ink droplet facing a part of the ink path. Discharge energy generating means for generating energy.

[0003] The discharge energy generating means uses an electromechanical transducer such as a piezo element, or irradiates an electromagnetic wave such as a laser to generate heat of the ink. Known are those that are ejected from ink ejection ports, and heating elements such as electrothermal transducers.

In particular, an ink jet head that uses an electrothermal transducer as a means for generating discharge energy and discharges ink droplets from ink discharge ports by thermal energy has the following advantages. That is, it is possible to easily arrange a convenient configuration for arranging ink ejection ports for ejecting ink droplets at high density and obtaining a print with high resolution.
In addition, the structure is easy to make compact. Further, the semiconductor device can be manufactured by fully utilizing the advantages of an IC manufacturing technology and a micro-machining technology in which the technical progress and the reliability have been remarkably improved in the recent semiconductor field. By using these technologies, it is easier to increase the length, to increase the dimension, to increase the number of ink ejection ports, and to increase the density, to achieve mass production and to reduce the manufacturing cost.

An ink-jet head which uses an electrothermal transducer as a means for generating discharge energy and has a large number of ink discharge ports manufactured through a semiconductor manufacturing process usually has an ink path corresponding to each ink discharge port. An electrothermal converter is provided for each ink path, and ink is supplied from a common ink chamber communicating with each ink path.

FIG. 9 shows a partially broken structure of such a conventional ink jet head. That is, the inkjet head 101 includes an electrothermal converter 103 formed on a substrate 102 through a semiconductor manufacturing process such as an etching method, a vapor deposition method, or a sputtering method, an electrode 104, an ink path partition wall 105, The main part is constituted by the plate 106.

[0007] Ink is supplied from a not-shown ink tank into the common ink chamber 109 via an ink supply pipe 107 and a connector 108, and is drawn into the ink paths 110 by capillary action. A meniscus is formed at the outlet 111 by surface tension, and is stably held in each ink path 110.

Here, by energizing the electrothermal converters 103 facing the respective ink passages 110, the ink interposed on the electrothermal converters 103 is heated and instantaneously foams to form the ink ejection ports 111. Ink droplets are ejected.

With the above-described configuration, the density of the ink ejection ports 111, that is, the interval, is, for example, 16 high density ink ejection ports 111 per 1 mm, for example, 1 in total.
28 or 256 ink jet heads 101 can be manufactured.

However, an ink jet printing apparatus equipped with an ink jet head 101 of the type shown in FIG. 9 for discharging ink droplets from ink discharge ports using thermal energy has the above-described advantages, Part of the heat energy generated when a pulsed drive voltage is applied to the heat converter 103 is gradually accumulated in the inkjet head 101, and as a result, the temperature of the inkjet head 101 gradually increases, and the ink path 110
As a result, the viscosity of the ink interposed therein decreases, and as a result, the amount of ink ejected from the ink ejection port 111 increases, and the image quality changes.

As a countermeasure against this, the present applicants have disclosed Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 108052/1994, the inkjet head is air-cooled by a blowing means such as a fan to prevent the temperature of the inkjet head from rising, or by circulating and supplying ink to the inkjet head in Japanese Patent Application Laid-Open No. 1-154762. It is proposed to prevent the temperature from rising.

FIG. 10 shows the principle proposed in the above-mentioned Japanese Patent Application Laid-Open No. 1-154762, which circulates and supplies ink to an ink jet head. That is, the ink supply path 20 is provided between the inkjet head 201 and the ink tank 202.
3 and an ink return path 204 are formed.
3. The ink in the ink tank 202 is returned to the ink tank 202 from the ink supply path 203 via the common ink chamber 209 of the inkjet head 201 by the ink return path 204 by the ink circulation pump 205 provided in the middle of Step 3. It is. Further, a temperature detecting means (not shown) is incorporated in the ink jet head 201, and based on the temperature of the ink jet head 201 detected by the temperature detecting means, the ink circulation pump 20
5, the ink supply speed is controlled.

In this case, since a part of the circulating ink is discharged from the ink ejection port 211 of the ink jet head 201, the ink ejection port 21 of the ink jet head 201 is discharged.
The ink discharge port surface 212 opening 1 is brought into contact with a recovery device provided outside the print area, and the ink discharged from the ink discharge port 211 of the inkjet head 201 is collected in a waste ink tank (not shown).

[0014]

The interval between the ink ejection ports of the ink jet head is increased, the number of these ink ejection ports is increased, and the application period of the pulsed drive voltage to the electrothermal transducer is increased. As the printing speed is increased, that is, the driving frequency is increased, and the printing speed is increased, the amount of heat generated by the inkjet head increases.
In the cooling method of the inkjet head by the blowing means proposed in Japanese Patent Application Laid-Open No. 10-80552, the cooling effect is becoming insufficient.

In the cooling method based on the circulation of ink proposed in Japanese Patent Application Laid-Open No. 1-154762, although a greater cooling effect can be obtained than in the previous case, every time the inkjet head is cooled, the inkjet head is changed. After moving out of the print area and against the recovery device, the ink must be circulated. As a result, the time required to reciprocate the ink jet head between the printing area and the recovery device increases, so that the printing time becomes longer and the ink is discharged from the ink discharge port every time the ink is circulated. This causes a problem that the amount of waste ink not used for printing increases, the amount of ink consumption increases, and the running cost increases.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to appropriately control the temperature of an ink-jet head to suppress a change in image quality, to enable printing in a shorter time, and to reduce the consumption of ink to reduce running costs. To provide an ink jet printing method and apparatus therefor.

[0017]

According to a first aspect of the present invention, there is provided an ink jet printing method in which ink discharged from an ink discharge port is supplied from an ink tank to an ink jet head and returned to the ink tank. An inkjet printing method, comprising: detecting a temperature of the inkjet head; and controlling a circulating supply amount of the ink based on the detected temperature of the inkjet head.

According to a second aspect of the present invention, there is provided an ink jet head having an ink discharge port for discharging ink, an ink tank for storing ink, and supplying the ink in the ink tank to the ink jet head. An ink supply path, an ink return path for circulating the ink in the ink jet head into the ink tank, a temperature detecting means for detecting the temperature of the ink jet head, An ink circulation pump for returning the ink from the head into the ink tank again; and a pump control means for controlling a circulation supply amount of the ink by the ink circulation pump based on information detected by the temperature detection means. In an inkjet printing apparatus.

Further, according to a third aspect of the present invention, there is provided an ink jet head having an ink discharge port for discharging ink, an ink tank for storing ink, and supplying the ink in the ink tank to the ink jet head. An ink supply path, an ink return path for circulating the ink in the ink jet head into the ink tank, a temperature detecting means for detecting the temperature of the ink jet head, A plurality of ink circulation pumps for returning the ink from the head to the ink tank again are provided, and the amount of ink circulated and supplied by each of the ink circulation pumps is controlled based on information detected by the temperature detection means of each group. An ink jet printer further comprising a pump control means. In the cement unit.

According to the present invention, the temperature of the ink jet head is detected by the temperature detecting means, and the pump control means controls the operation of the ink circulation pump based on the temperature of the ink jet head detected by the temperature detecting means.

For example, when the temperature of the ink jet head is relatively high, the low temperature ink in the ink tank is supplied to the ink jet head by increasing the circulating supply amount of the ink, and the ink jet head is cooled with high efficiency. . Conversely, when the temperature of the ink jet head is relatively low, by reducing the amount of circulating ink supplied, the low temperature ink in the ink tank is not supplied to the ink jet head much, and the cooling efficiency of the ink jet head is reduced.

As described above, the temperature of the ink jet head is maintained at a predetermined temperature or less by controlling the circulating supply amount of the ink by the pump control means based on the temperature of the ink jet head.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the ink jet printing method of the present invention, the circulating supply amount corresponds to a first circulating supply amount at which ink is not discharged from an ink discharge port corresponding to a low temperature region of the ink jet head, and a high circulating supply amount. It is preferable to have a second circulating supply amount at which ink is discharged from the ink ejection port corresponding to the temperature region, and in this case, the first circulating supply amount and the second circulating supply amount are respectively It may be a fixed value set in advance, or the first circulating supply amount may change continuously according to the temperature of the inkjet head.

It is also effective to further include a step of collecting the ink discharged from the ink discharge port when the ink is supplied to the ink jet head at the second circulation supply amount.

On the other hand, in the ink jet printing apparatus of the present invention, the pump control means includes a first circulating supply amount in which ink is not discharged from the ink ejection port corresponding to the low temperature region of the ink jet head, and a high temperature region of the ink jet head. It is preferable to control the operation of the ink circulation pump to the second circulating supply amount at which ink is discharged from the ink discharge port in response to the first circulating supply amount and the second circulating supply amount. The supply amount may be a fixed value set in advance, or the first circulating supply amount may change continuously according to the temperature of the inkjet head.

It is preferable that the apparatus further comprises recovery means for recovering the ink discharged from the ink discharge port. In this case, the recovery means is provided outside the print area of the ink jet head, and the ink discharge port having the ink discharge port opened is further provided. It may have a capping member that contacts the outlet surface and covers the ink ejection port.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ink jet printing apparatus which can carry out the method of the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a control block of a main part of the ink jet printing apparatus according to this embodiment, and FIG. 2 shows an appearance of the main part. That is, a pair of paper sheets arranged in parallel with the platen roller 12 along the longitudinal direction of the platen roller 12 that holds the printing surface of a print medium (not shown) in the form of a web sheet or cut sheet conveyed by the paper feed motor 11. Guide rail 13, 1
4, a head carriage 15 is slidably mounted. A pair of pulleys 16 and 17 are rotatably arranged on the reciprocating end side of the head carriage 15, and an endless belt 18 is connected to the pulleys 16 and 17 via a connecting member (not shown). Is wrapped around. One pulley 16 is connected to a carriage drive motor 19 that can rotate forward and reverse, and the head carriage 15 is reciprocally scanned along the longitudinal direction of the platen roller 12 as the carriage drive motor 19 rotates forward and backward. ing.

The head carriage 15 in this embodiment has four colors, for example, yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), and cyan (hereinafter referred to as C).
), Four ink jet heads 20Y and 20 corresponding to black (hereinafter referred to as B) inks.
M, 20C, 20B (hereinafter collectively referred to simply as 20
May be written). These four ink jet heads 20 have four ink tanks 21Y, 21M, which store the above-described four color inks, respectively.
21C and 21B (hereinafter, these may be collectively simply referred to as 21) are ink supply pipes 22Y and 22Y, respectively.
22M, 22C, and 22B (hereinafter, these may be collectively referred to simply as 22) and ink return tubes 23Y and 23Y.
3M, 23C, 23B (FIG. 2 shows only the ink return pipe 23Y corresponding to Y for simplification.
These are sometimes collectively referred to as 23) and are connected in the middle of each ink supply pipe 22 with gear pumps 24Y, 24M, 24 as ink circulation pumps.
C, 24B (hereinafter, these may be collectively described simply as 24) are interposed.

It should be noted that a diaphragm pump, a vane pump, a piston pump, a turbine pump, a tube pump, or another known pump capable of changing the discharge flow rate without changing the discharge pressure is preferably employed instead of the gear pump 23 described above. Is possible.

Each ink jet head 20 has a temperature sensor 25 using a thermistor or the like for detecting the temperature T of these ink jet heads 20, and a temperature T of these ink jet heads 20 which is set in advance (hereinafter referred to as an initial temperature). (Referred to as a set temperature) and heaters 26 for heating up to T _B, respectively, and the detection information of each temperature sensor 25 is output to a control unit 27 for controlling ON / OFF of energization to each heater 26. Has become.

Each of the ink tanks 21 has four auxiliary tanks 2 storing ink of each color in order to keep the amount of ink stored in the ink tanks 21 constant.
8 are connected to the respective ink tanks 21.

Further, on the side of the platen roller 12 facing the ink discharge port surface 29 of the ink jet head 20 on the head carriage 15 located at one reciprocating end of the head carriage 15, the direction facing the head carriage 15 is A reciprocating capping table 30 is provided. On the capping table 30, ink ejection ports 44 of the inkjet head 20 (FIGS. 5 and 6) are provided.
(See FIG. 3) is provided. The capping member 31 is provided with an air nozzle 34 communicating with an air pump 33 via an air supply pipe 32, and compressed air blown from the air nozzle 34 toward the ink discharge port surface 29 of the inkjet head 20. Ink absorber 3 using a felt or the like for absorbing ink droplets blown off from ink ejection port surface 29
5 are provided.

The control unit 27 includes a console 3 having a power switch, various switches, and a display function (not shown).
Command from the operator and the temperature sensor 25
The operation of the gear pumps 24, the heaters 26, the air pumps 33, and the like, in addition to the paper feed motor 11 and the carriage drive motor 19, is controlled based on the detection information and the like.

As shown in FIG. 3 showing a more detailed control block of the control unit 27, the control unit 27
And an A / D converter 3 for converting the amplified analog signal into a digital signal.
8, a ROM 39 storing a digital signal corresponding to preset temperature information, a comparator 40 for comparing an output from the ROM 39 with an output from the A / D converter 38, Pump drive circuit 41 that controls the discharge flow rate of gear pump 24 based on the comparison result
With

The ROM39 of the control unit 27, a high-temperature low-circulation temperature T _L than the initial set temperature T _B, further and the low circulation temperature T _L hot high circulating temperature than T _H is stored. Further, the pump drive circuit 41 controls at least one of a current and a voltage for a drive motor (not shown) connected to the gear pump 24 so that the following operation control of the gear pump 24 is achieved. That is,
As shown in FIG. 4 showing the relationship between the temperature T of the ink jet head 20 and the discharge flow rate of the ink from the gear pump 24 in this embodiment, the operation of the gear pump 24 is performed in a temperature region where the ink jet head 20 is lower than the low circulation temperature _TL. there is stopped, it performed circulating supply of ink to the inkjet head 20 Lena, the ink jet head 20 is not more hypoperfusion temperature T _L above, at a temperature region lower than the high circulation temperature T _H is a low discharge flow rate Q _L gear pump 24 is driven at a low circulation mode, the ink jet head 20 is in a high circulation temperature T _H above temperature range, the gear pump 24 is driven at a high circulation mode in which a high discharge flow rate Q _H.

The low discharge flow rate Q _L described above, as shown in FIG. 5 showing the schematic structure of the tip of FIG. 4 and the ink jet head 20 in this state, the common ink chamber 42 of the ink jet head 20 from the ink supply pipe 22 When the ink flows through the ink return pipe 23 through the common ink chamber 4
2. An ink discharge port 44 communicating from the second through an ink path 43
The meniscus shape of the ink formed on the ink ejection port collapses, and the ink path 43 faces the ink ejection port face 29 facing the ink ejection port 44.
Discharge flow rate Q of ink that starts to overflow
_{For R} , the circulation flow rate is smaller. On the other hand, the high discharge flow rate Q _H described above, as shown in FIG. 6 showing the schematic structure of the tip of FIG. 4 and the ink jet head 20 in this state, via the common ink chamber 42 of the ink jet head 20 from the ink supply pipe 22 Return ink tube 2
When the ink flows to the ink discharge port 3, the meniscus shape of the ink formed in the ink discharge port 44 communicating from the common ink chamber 42 via the ink path 43 is broken, and the ink path is formed on the ink discharge port surface 29 facing the ink discharge port 44. to discharge flow rate Q _R of the ink as the ink begins to overflow in 43, since it is often the circulation flow rate than this, is possible to increase the cooling efficiency for the ink jet head 20 than in the previous low discharge flow rate Q _L it can.

Further, in this embodiment, before the printing operation on the printing medium is started, the ink discharge port surface 29 of the ink jet head 20 is cleaned by using the above-described capping member 31, and the ink discharge port surface 29 is cleaned. A head recovery process is performed to remove the attached ink droplets and discharge the ink from the ink discharge port 44 more reliably. In this case, the gear pump 24 is driven in the high circulation mode described above, and the ink in the ink path 43 of each ink jet head 20 is pushed out from the ink discharge port 44 by 9 and the ink droplet I adhering to the ink discharge port surface 29 is removed. Merge. Then, after moving the capping table 30 of the capping member 31 so that the ink absorber 35 provided on the capping member 31 comes into contact with the ink discharge port surface 29 of the inkjet head 20, the air pump 3
The compressed air from 3 is blown out from the air nozzle 34 to the ink discharge port surface 29 of the ink jet head 20, and the ink droplet I attached to the ink discharge port surface 29 is blown off and absorbed by the ink absorber 35.

Thereafter, a printing operation on the print medium is started, and ink droplets of each color are ejected to a predetermined position on the print medium while scanning and moving the head carriage 15 on which the inkjet head 20 is mounted.

As described above, by changing the circulating supply amount of the ink in the ink tank 21 with respect to the ink jet head 20 according to the temperature T of the ink jet head 20, the electrothermal converter (not shown) incorporated in the ink jet head 20 is changed. As a result, it is possible to prevent a problem that the amount of ink ejected from the inkjet head 20 increases and the image quality changes. In a temperature region where the ink jet head 20 is at or above the low circulation temperature T _{L and} lower than the high circulation temperature T _H , the gear pump 24 is driven in the low circulation mode in which the discharge flow rate Q _L is low, and the ink of the ink jet head 20 is discharged. Since the ink did not overflow from the discharge port 44,
It is not necessary to cover the ink discharge port surface 29 of the ink jet head 20 with the capping member 31, so that the time for the head carriage 30 can be eliminated and the printing time can be reduced. In addition, in this case, no ink is discharged from the ink ejection port 44 of the ink jet head 20, so that no ink is consumed during the cooling operation of the ink jet head 20, that is, the amount of waste ink as a whole can be reduced. Can also be reduced.

FIG. 7 shows the flow of the processing in this embodiment. That is, when the operator turns on a power switch (not shown) of the console 36, the ink jet head 20 moves to the home position facing the capping member 31 in step S1, and the ink discharge port surface 29 of the ink jet head 20 is moved. Covered by capping member 31. Next, the heater 26 embedded in the inkjet head 20 in the step S2
, The heating of the inkjet head 20 is performed. Then, based on a detection signal from the temperature sensor 25 incorporated in the ink jet head 20 at step S3, the temperature T of the ink-jet head 20 whether it has reached the initial setting temperature T _B is determined.

In step S3, the ink jet
The temperature T of the pad 20 is the initial set temperature T. _BAnd have not reached
If it is determined, the process returns to step S2 and the heater 26
To the ink jet head 20
Keep heating. In addition, in step S3, the inkjet is performed.
The temperature T of the head 20 is the initial set temperature T_BHas reached
If it is determined, the process proceeds to step S4 and the heater 2
6 is cut off, and the pudding is performed in step S5.
It is determined whether or not to start the work.

[0043] whether the start instruction of the print work at this step S5 is when it is determined not to be output, the temperature T of the ink jet head 20 returns to step S3 has reached the initial setting temperature T _B was again determined, it continues to hold the ink jet head 20 to the initial set temperature T _B. If it is determined in step S5 that a print job start command has been output, the process proceeds to step S6, in which the gear pump 24 is driven in the high circulation mode for a preset time, and the inkjet head 20 is driven.
The ink in the ink path 43 is pushed out from the ink discharge port surface 29, and the temperature T of the ink jet head 20 decreases accordingly, so that the power supply to the heater 26 is restarted in step S7. Then, in step S8, the air pump 33 is driven for a preset time, and compressed air is blown from the air nozzle 34 to the ink discharge port surface 29, and the ink droplet I attached to the ink discharge port surface 29 is removed by the ink absorber. after absorption at 35, again it determines the temperature T of the ink-jet head 20 at step S9 as to whether or not has reached the initial setting temperature T _B.

If it is determined in step S9 that the temperature T of the ink jet head 20 has not reached the initial set temperature T _B , the power supply to the heater 26 is continued,
Temperature T of the ink jet head 20 is initially set temperature T _B
If it is determined that the current has reached the step S11, the flow goes to the step S10, and the energization of the heater 26 is stopped.
After the capping member 31 is retracted from the ink discharge port surface 29 of the inkjet head 20 in the step of
In step 12, the paper feed motor 11 and the carriage drive motor 19 are operated to start the printing operation. Then, in step S13, the inkjet head 20
Is determined whether the temperature T is lower than the low circulation temperature _TL .

In the step S13, during the printing operation, the temperature T of the ink jet head 20 is reduced to the low circulation temperature T _L.
If it is determined that the temperature is lower than the initial temperature T _B and the low circulating temperature T _L , there is no problem even if the printing operation is continued without any problem. And the printing operation on the printing medium is continued as it is. Also, S
In step 13, the temperature T of the inkjet head 20
If it is it is determined that rise above the low circulation temperature T _L, in turn determines whether or not the temperature T of the ink jet head 20 is less than the high circulation temperature T _H in step S15.

The temperature T of the ink-jet head 20 at this step S15 is less than the high circulation temperature T _H, i.e. the temperature T is low circulation temperature T _L of the ink jet head 20
If it is determined that the temperature is between the high circulation temperature _TH and S
Gear pump 24 proceeds to 16 steps are driven by the low circulation mode of the low discharge flow rate Q _L is not pushed the ink from the ink discharge ports 44 of the ink jet head 20, to start the cooling operation for the ink jet head 20.
It is not necessary to perform the cooling operation in the low circulation mode by moving the head carriage 15 to the home position, and there is no problem if the cooling operation is performed in the print area of the inkjet head 20. Subsequent to the step S16, the printing operation for the print medium is continued in the step S14. Then, in step S17, it is determined whether the temperature T of the inkjet head 20 has dropped below the low circulation temperature _TL .

If it is determined in step S17 that the temperature T of the ink jet head 20 has risen to the low circulation temperature _TL or higher, the process proceeds to step S15 where the temperature T of the ink jet head 20 is increased to the high circulation temperature T _L. It is determined whether it is less than _H. If it is determined in step S17 that the temperature T of the ink jet head 20 has fallen below the low circulation temperature _TL , the process proceeds to step S18, where the operation of the gear pump 24 is stopped. The printing operation on the print medium is continued.
Then, it is determined in step S20 whether or not the printing operation has been completed.

If it is determined in step S20 that the printing operation has been completed, the process proceeds to step S21, where the inkjet head 20 moves to the home position facing the capping member 31, and the inkjet head 20 discharges ink. The outlet surface 29 is provided with the capping member 3.
After covering 1, returns to S2 of the step, the energization to the heater 26 is restarted, and holds the inkjet head 20 to the initial set temperature T _B.

[0049] On the other hand, when the temperature T of the ink jet head 20 is determined to be higher than the high circulation temperature T _H is at step S14, the home position to stop the scanning movement of the head carriage 15 proceeds to S22 in step To the ink jet head 20 in step S23.
Is covered with a capping member 31. Then, driven by a time previously set the gear pump 24 at a high circulation mode of the high discharge flow rate Q _H from the ink discharge ports 44 overflows of ink jet head 20 at step S24,, more efficiently inkjet head 20 Cooling. Since there is a possibility that the temperature T of the ink jet head 20 may be excessively lowered with the cooling, the power supply to the heater 26 is restarted in step S25. Then, in step S26, the air pump 33
Is driven for a preset time, and compressed air is blown from the air nozzle 34 onto the ink discharge port surface 29 to absorb the ink droplet I adhering to the ink discharge port surface 29 into the ink absorber 35. temperature T of the ink jet head 20 at step determines whether reaches the initial set temperature T _B.

If it is determined in step S27 that the temperature T of the ink jet head 20 has not reached the initial set temperature T _B , energization of the heater 26 is continued, and the temperature T of the ink jet head 20 is reduced to the initial set temperature T _B. If it is determined that has reached the T _B, the abort energization to the heater 26 proceeds to S28 in step, S
Returning to step 19, the printing operation for the print medium is continued.

In the above-described embodiment, the ink discharge flow rate of the gear pump 24 is changed stepwise in accordance with the temperature T of the ink jet head 20, but the ink discharge flow rate is proportional to the temperature of the ink jet head 20. Of course, it is possible to change.

FIG. 8 shows the relationship between the temperature T of the ink jet head 20 and the discharge flow rate of the gear pump 24 in such another embodiment. That is, when the temperature T of the ink jet head 20 is less than the low circulation temperature T _L is not driving the gear pump 24, at a range temperature T is high circulation temperature T _H of hypoperfusion temperature T _L of the ink jet head 20,
0 circulation flow rate of the ink in proportion to the temperature T of the ink jet head 20 to the discharge flow rate Q _R of the ink in the ink channel 43 starts to overflow from the ink discharge port 44 is continuously changed, the temperature T of the ink-jet head 20 When the temperature is higher than the high circulation temperature T _H , by driving the gear pump 24 at the same high discharge flow rate Q _H as in the previous embodiment, the print image pattern changes every moment during the printing operation. Even if the inkjet head 2
By controlling the cooling efficiency of the inkjet head 20 in accordance with the temperature rise rate of 0, it is possible to reduce image quality deterioration of printed image information.

FIG. 9 is a view for explaining a third embodiment of the ink jet printing apparatus according to the present invention. In this embodiment, a plurality of head units are provided for each head unit. According to the result obtained by comparing the temperature obtained from the unit temperature detecting means with a predetermined temperature set in advance, the ink pressure feeding circulating means provided in the ink circulating path of each head unit independently provided for each head unit is provided. The ink circulation amount in the gear pump is changed stepwise independently for each head unit.

That is, for example, in the case of an ink jet printing apparatus that prints a color image using four head units of cyan, magenta, yellow, and black, the temperature of each head unit is independently printed depending on the color image pattern to be printed. In this embodiment, the head unit cooling operation by ink circulation is independently controlled for each head unit, and each head unit is controlled according to the amount of temperature rise of each head unit. The ink circulation amount for printing of the unit is switched.

The circulating supply of the ink by the driving of the gear pump 24 is performed independently for each ink jet head 20, and the above-mentioned initial set temperature T _B , low circulating temperature _TL , and high circulating temperature. temperature T _H, respectively may be set to a unique value according to the characteristics of each ink.

According to the present invention, there is provided a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging a liquid, particularly in an ink jet system. Thus, an excellent effect can be obtained in an ink jet apparatus of a system that causes a change in the state of a liquid. According to such a method, it is possible to achieve higher density and higher definition of the print.

The typical configuration and principle are described in, for example, US Pat. No. 4,723,129 and US Pat.
It is preferable to use the basic principle disclosed in Japanese Patent Application No. 0796. 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, it is arranged corresponding to the sheet or the flow path holding the liquid. Applying at least one drive signal to the electrothermal transducer that provides a rapid temperature rise exceeding nucleate boiling corresponding to the print information, thereby generating thermal energy in the electrothermal transducer and providing a thermal effect to the inkjet head. This is effective because film boiling occurs on the surface, and consequently, bubbles in the liquid corresponding to this drive signal can be formed one-to-one. By the growth and shrinkage of the bubble, the liquid is discharged through the discharge port 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 the liquid 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. In addition,
US Patent No. 4 of the invention relating to the rate of temperature rise of the heat acting surface
By employing the conditions described in the specification of Japanese Patent No. 313124, more excellent printing can be performed.

The structure of the ink jet head is a combination of a discharge port, a flow path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned specifications. In addition, the present invention includes a configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600, which discloses a configuration in which a heat acting portion is arranged in a bent region. In addition, JP-A-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, and an aperture for absorbing a pressure wave of thermal energy is provided. JP-A-59-138461 which discloses a configuration corresponding to a discharge section
The effects of the present invention are effective even if the configuration is based on the above publication. That is, according to the present invention, printing can be performed reliably and efficiently regardless of the form of the inkjet head.

Further, the present invention can be effectively applied to a full line type ink jet head having a length corresponding to the maximum width of a print medium that can be printed by the ink jet device. Such an ink-jet head may have either a configuration in which the length is satisfied by a combination of a plurality of ink-jet heads, or a configuration as one integrally formed ink-jet head.

In addition, even in the case of the serial type as described above, the ink jet head fixed to the apparatus main body,
Alternatively, a replaceable chip-type inkjet head that can be electrically connected to the apparatus main body or supplied with liquid from the apparatus main body when attached to the apparatus main body, or a tank that stores liquid integrally with the inkjet head itself The present invention is also effective when an ink jet cartridge provided with is provided.

Further, it is preferable to add a discharge recovery means for the ink jet head, a preliminary auxiliary means, and the like as the structure of the ink jet apparatus of the present invention since the effects of the present invention can be further stabilized. Specific examples include capping means for the ink jet head, cleaning means, pressurizing or sucking means, an auxiliary heating element using an electrothermal transducer, another heating element, or a combination thereof. Examples of the heating unit include a preliminary ejection unit that performs ejection different from printing.

The type and number of ink jet heads to be mounted are not limited to those provided only with one ink corresponding to a single color ink, and also correspond to a plurality of inks having different print colors and densities. A plurality may be provided. That is, for example, the print mode of the inkjet apparatus is not limited to the print mode of only the mainstream color such as black, but may be either an integrated inkjet head or a combination of a plurality of inkjet heads. The present invention is also very effective for an apparatus provided with at least one of the full-color print modes using mixed colors. In this case, it is also effective to discharge a processing liquid (printability improving liquid) for adjusting the printability of the ink according to the print medium from the inkjet head to the print medium.

In addition, in the embodiment of the present invention described above, a material which solidifies at or below room temperature and softens or liquefies at room temperature may be used. In general, the temperature is controlled within the range of not more than ° C. and the temperature is controlled so that the viscosity of the liquid is in a stable ejection range. In addition, in order to positively prevent the temperature rise due to thermal energy by using it as the energy of the state change from the solid state to the liquid state, or to prevent the evaporation of the liquid,
What solidifies in a standing state and liquefies by heating may be used. In any case, the liquid is liquefied by the application of the thermal energy according to the print signal, and is liquefied only by the application of the thermal energy, such as the one from which the liquid is ejected and the one which already starts to solidify when reaching the print medium. The present invention can be applied to the case of using a material having a property. The liquid in such a case is disclosed in JP-A-54-56847.
JP-A No. 60-71260 or Japanese Patent Application Laid-Open No. Sho 60-71260, in a state in which the porous sheet is held as a liquid or solid substance in a concave portion or a through hole and faces the electrothermal converter. Is also good. In the present invention,
The most effective one for each of the above-mentioned liquids is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet apparatus according to the present invention is not only used as an image output terminal of an information processing apparatus such as a computer, but also a copying apparatus combined with a reader or the like, and further, a facsimile apparatus having a transmission / reception function. Or a device in the form of a printing device.

[0065]

According to the present invention, the amount of circulating ink supplied to the ink-jet head is changed in accordance with the temperature of the ink-jet head so that the ink is not pushed out from the ink discharge port in a region where the temperature of the ink-jet head is relatively low. Therefore, in this cooled state, it is not necessary to cover the ink ejection port surface of the inkjet head with the capping member, and the printing time can be shorter than before.

Further, since the ink does not overflow from the ink discharge port with the circulating supply of the ink, the amount of waste ink not used in the printing operation can be reduced as compared with the conventional case, and the ink consumption can be suppressed and the running cost can be reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a main part of an embodiment of an inkjet printing apparatus capable of realizing the method of the present invention.

FIG. 2 is a perspective view showing an appearance of a main part in the embodiment shown in FIG.

FIG. 3 is a more detailed block diagram of a control unit in the embodiment shown in FIG.

FIG. 4 is a graph showing the relationship between the temperature of an ink jet head and the circulating discharge flow rate of ink by a gear pump in the embodiment shown in FIG.

FIG. 5 is a conceptual diagram illustrating a state of a tip end portion of the inkjet head in a low circulation mode in the embodiment illustrated in FIG. 1;

FIG. 6 is a conceptual diagram showing a state of a high circulation mode of a tip portion of the inkjet head in the embodiment shown in FIG.

FIG. 7 is a flowchart showing a work procedure in the embodiment shown in FIG.

FIG. 8 is a graph illustrating another example of the relationship between the temperature of the inkjet head and the circulating discharge flow rate of the ink by the gear pump.

FIG. 9 is a perspective view illustrating a broken structure of a conventional inkjet head.

FIG. 10 is a schematic diagram illustrating a schematic structure of a conventional inkjet printing apparatus.

[Explanation of symbols]

11 Paper feed motor 12 Platen roller 13, 14 Guide rail 15 Head carriage 16, 17 Pulley 18 Endless belt 19 Carriage drive motor 20, 20Y, 20M, 20C, 20B Ink jet head 21, 21Y, 21M, 21C, 21B Ink tank 22, 22Y, 22M, 22C, 22B Ink supply pipe 23, 23Y, 23M, 23C, 23B Ink return pipe 24, 24Y, 24M, 24C, 24B Gear pump 25 Temperature sensor 26 Heater 27 Control unit 28 Auxiliary tank 29 Ink ejection port surface 30 Capping Table 31 Capping member 32 Air supply pipe 33 Air pump 34 Air nozzle 35 Ink absorber 36 Console 37 Amplifier 38 A / D converter 39 ROM 40 Comparator 41 Pump drive circuit 42 Common ink chamber 4 Temperature T _B initial set temperature T _L hypoperfusion temperature T _H High circulating temperature Q _L low discharge flow rate Q _H high discharge flow rate Q discharged flow ink from the _R ink ejection port starts overflowing of the ink passage 44 ink discharge ports T inkjet head

Claims (13)

[Claims] 1. An ink jet printing method for supplying ink ejected from an ink ejection port from an ink tank to an ink jet head and returning the ink to the ink tank again, comprising: detecting a temperature of the ink jet head; Controlling the circulating supply amount of the ink based on the temperature of the inkjet head. 2. The circulating supply amount corresponds to a first circulating supply amount at which ink is not discharged from the ink ejection port corresponding to a low-temperature region of the inkjet head, and a high-temperature region of the inkjet head. The ink jet printing method according to claim 1, further comprising a second circulating supply amount at which the ink is discharged from the ink discharge port. 3. The ink-jet printing method according to claim 1, wherein the first circulating supply amount and the second circulating supply amount are respectively predetermined constant values. 4. The ink jet printing method according to claim 1, wherein the first circulating supply amount changes continuously according to the temperature of the ink jet head. 5. The method according to claim 2, further comprising the step of collecting the ink discharged from the ink discharge port when the ink is supplied to the inkjet head at the second circulation supply amount. The inkjet printing method according to any one of claims 1 to 4. 6. An ink jet head having an ink discharge port for discharging ink, an ink tank for storing ink, an ink supply path for supplying ink in the ink tank to the ink jet head, and the ink jet head. An ink return path for circulating the ink in the head into the ink tank; a temperature detecting means for detecting a temperature of the ink jet head; and an ink circulating in the ink tank from the ink jet head to the ink tank again. And a pump control means for controlling the amount of ink circulated by the ink circulating pump based on information detected by the temperature detecting means. 7. An ink jet head having an ink discharge port for discharging ink, an ink tank for storing ink, an ink supply path for supplying ink in the ink tank to the ink jet head, and the ink jet head. An ink return path for circulating the ink in the head into the ink tank; a temperature detecting means for detecting a temperature of the ink jet head; and an ink circulating in the ink tank from the ink jet head to the ink tank again. A plurality of sets of ink circulation pumps, and pump control means for controlling the amount of circulating ink supplied by each set of ink circulation pumps based on information detected by each set of the temperature detection means. An inkjet printing apparatus characterized by the above-mentioned. 8. The ink jet head according to claim 1, wherein said pump control means is adapted to correspond to a low temperature area of said ink jet head and a first circulating supply amount at which ink is not discharged from said ink discharge port, and to correspond to a high temperature area of said ink jet head. 8. The ink jet printing apparatus according to claim 6, wherein an operation of the ink circulation pump is controlled to a second circulation supply amount at which ink is discharged from the ink discharge port. 9. The ink-jet print according to claim 6, wherein the first circulating supply amount and the second circulating supply amount are respectively predetermined constant values. apparatus. 10. The ink jet print according to claim 6, wherein the first circulating supply amount changes continuously according to the temperature of the ink jet head. apparatus. 11. The ink jet printing apparatus according to claim 8, further comprising a recovery unit for recovering ink discharged from the ink discharge port. 12. The ink jet printing apparatus according to claim 11, wherein the recovery unit is provided outside a print area of the ink jet head. 13. The ink jet printer according to claim 11, wherein the recovery unit includes a capping member that covers the ink ejection port by contacting the ink ejection port surface where the ink ejection port opens. Ink jet printing device.