JPH06328730A - Ink jet printer - Google Patents

Abstract

PURPOSE:To carry out suction work even when an ink tank becomes vacant preventing a nozzle communicating with the vacant tank from communicating with outside air at other part than a discharge opening when ink is to be sucked by one suction pump in a state that one ink tank among a plurality of ink tanks is vacant. CONSTITUTION:An ink jet printer comprises one or more ink jet head 1 having a plurality of nozzles for discharging liquid drops, one or more ink tank for supplying ink to the ink jet head 1 through an ink passage 2, and a sucking pump for sucking the ink from all nozzle discharging openings of the ink jet head 1 simultaneously. At sucking by the suctrim pump in a state that one or more of ink tank is vacant, the nozzle which communicates with the vacant tank is prevented from communicating with outside air at other part than the discharging opening. As a result, sucking the work can be carried out even when the tank is vacant and excellent printing can be accomplished regardless of the presence or absence of the ink in the ink tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly to an ink jet printer which records with inks of different colors and densities.

[0002]

2. Description of the Related Art Ink jet printers have been widely used as printers with low noise, low running cost and high recording speed.

In this ink jet printer,
Due to the nature of using liquid ink, an increase in ink viscosity due to evaporation of water in the ink cannot be avoided. Such increase in viscosity causes non-ejection or incomplete ejection due to nozzle clogging, resulting in poor image quality. The following measures have been taken to prevent this.

1) After being left unrecorded for a long time, the increase in the viscosity of the ink reaches deep inside the nozzle and ejection is impossible. Therefore, a purging operation is performed using a suction pump to discharge the ink whose viscosity has increased.

2) In an on-demand printer equipped with a multi-nozzle head, there is a possibility that some nozzles do not eject during a certain period of time during printing. This non-ejection nozzle causes clogging after a lapse of a certain time. Therefore, before this time is reached, ejection is performed from all nozzles regardless of the image to prevent clogging. This measure is called preliminary discharge.

On the other hand, the market of color ink jet printers for recording color images by ejecting inks of different colors through predetermined nozzles is expanding.

Among them, in a small-sized color ink jet printer for personal use, 70% is currently recorded by black ink for character printing and graph ruled lines, and about 30% is recorded by color ink for graphic recording. It is expected to be. Therefore, even if the color ink tank becomes empty, it is presumed that many users will continue to use it as a monochrome printer for a while.

Also in this color ink jet printer, the purging operation and the preliminary ejection in the above 1) and 2) are necessary. For the purging operation, if suction pumps corresponding to nozzles of different colors are prepared, a total of four pumps for yellow, magenta, cyan and black are required. Therefore, a method in which one pump simultaneously sucks ink from all nozzles is widely practiced.

[0009]

However, the above-mentioned conventional example has the following problems.

A conventional ink tank is provided with a communication hole with the outside air for supplying ink. Therefore, when the ink in the tank becomes empty, the nozzle communicates with the outside air through the tank communication hole.

Therefore, even if one ink tank is empty and ink is sucked from all the nozzles at the same time, air is sucked from the nozzles connected to the empty tanks, and ink is not sucked from other nozzles. It will be possible.

Therefore, in a printer which is expected to be used as a monochrome printer even when the color ink tanks become empty, such as the small personal printer described above,
When the individual color tanks are empty, suction is impossible. That is, there is a problem that the purging operation becomes impossible and normal printing cannot be performed thereafter.

Even if the purging operation is possible, since the total amount of ink sucked by the suction pump during one purging operation is a constant value, as the number of empty tanks increases, suction per nozzle is increased. However, there is a problem in that the amount of ink is increased and more ink than the suction amount necessary for maintaining normal printing is wasted.

[0014]

The present invention provides at least the following:
(1) One or more inkjet heads having a plurality of nozzles for ejecting liquid droplets, (2) One or more ink tanks for supplying ink to the inkjet heads through an ink flow path, and (3) the inkjets. In an inkjet printer having one suction pump that simultaneously sucks ink from all nozzle discharge ports of the head, when one or more ink tanks are empty and the suction pump sucks, the nozzles that communicate with the empty tanks are discharge ports. Provided is an inkjet printer, which is characterized in that it does not communicate with the outside air except the above.

The present invention further provides an ink jet printer having (1) empty ink tank detection means and (2) suction ink amount control means for controlling the total ink suction amount based on the detection information from the detection means.

The present invention is particularly effective in an ink jet recording type recording apparatus for recording by forming flying droplets by utilizing thermal energy among the ink jet recording methods.

With regard to its typical structure and principle, for example, US Pat. Nos. 4,723,129 and 4,740 are incorporated.
No. 796, the present invention is preferably carried out using these basic principles. This recording method is applicable to both the so-called on-demand type and the continuous type.

This recording system will be briefly described. A sheet (liquid) holding a liquid (ink) or an electrothermal converter arranged corresponding to a liquid path is converted into a liquid (ink) corresponding to recording information. Heat energy is generated by applying at least one driving signal for giving a rapid temperature rise that causes the film boiling phenomenon beyond the nucleate boiling phenomenon, and causes the film boiling on the heat acting surface of the recording head. . In this way, bubbles can be formed in one-to-one correspondence with the drive signal applied from the liquid (ink) to the electrothermal converter, which is particularly effective for the on-demand recording method. The liquid (ink) is ejected through the ejection holes by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make the driving signal into a pulse shape because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be ejected. This pulse-shaped drive signal is described in US Pat. No. 4,463,359 and US Pat.
Those as described in 45262 are suitable. If the conditions described in US Pat. No. 4,313,124, which is an invention relating to the rate of temperature rise on the heat acting surface, are adopted, more excellent recording can be performed.

The structure of the recording head is a combination of a discharge hole, a liquid flow path, and an electrothermal converter as disclosed in the above-mentioned specifications (straight liquid flow path or right-angled liquid flow path). In addition, as disclosed in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, the present invention includes those having a configuration in which a heat acting portion is arranged in a bending region.

In addition, Japanese Laid-Open Patent Publication No. 123670/1984, which discloses a structure in which a common slit is used as a discharge hole of a plurality of electrothermal converters, and a pressure wave of thermal energy is absorbed. The present invention is also effective in a structure based on Japanese Patent Laid-Open No. 138461/1984, which discloses a structure in which the corresponding opening corresponds to the discharge portion.

Further, as a recording head in which the present invention is effectively used, there is a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. The full line head may be a full line configuration formed by combining a plurality of print heads as disclosed in the above specification, or may be a single full line print head integrally formed.

In addition, by being attached to the apparatus main body, it is possible to electrically connect to the apparatus main body and supply ink from the apparatus main body, which is a replaceable chip type recording head or the recording head itself. The present invention is also effective when a cartridge-type recording head that is specially provided is used.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc. to the recording apparatus of the present invention because the recording apparatus of the present invention can be made more stable. If you list these specifically,
A capping unit, a cleaning unit, a pressure or suction unit, an electrothermal converter or a heating element other than this, or a preheating unit using a combination of these, and a preliminary ejection mode different from recording are provided for the recording head. Adding a means for performing is also effective for stable recording.

Further, the recording mode of the recording apparatus is not limited to the mode in which only the mainstream color such as black is recorded, and either the recording head is integrally formed or a plurality of recording heads are combined. However, the present invention is also extremely effective for an apparatus provided with at least one of a multicolor of different colors or a full color by color mixing.

In the above description, a liquid ink is used, but in the present invention, either an ink that is solid at room temperature or an ink that is in a softened state at room temperature can be used. In the above-mentioned ink jet device, it is common to control the temperature of the ink itself within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature of the ink so that the viscosity of the ink is within a stable ejection range. Any liquid may be used as long as the ink is liquid.

In addition, the excessive temperature rise of the head or ink due to thermal energy is positively prevented by using it as energy for the state change of the ink from the solid state to the liquid state, or the evaporation of the ink is prevented. It is also possible to use an ink that solidifies when left as it is. In any case, liquefaction occurs only when heat energy is applied, such as when ink is liquefied by applying heat energy according to a recording signal and ejected as an ink liquid, or when it reaches the recording medium, it already begins to solidify. The use of an ink having such a property is also applicable to the present invention.

Such an ink is disclosed in JP-A-54-568.
No. 47 or JP-A No. 60-71260, facing the electrothermal converter in the state of being held as a liquid or solid in the recesses or through holes of the porous sheet. It may be in the form.

In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

FIG. 9 is an external perspective view showing an example of an inkjet recording apparatus (IJRA) in which the recording head is mounted as an inkjet head cartridge (IJC).

In the figure, reference numeral 120 is an ink jet head cartridge (IJC) having a nozzle group for ejecting ink so as to face the recording surface of the recording paper fed onto the platen 124. Reference numeral 116 is a carriage HC that holds the IJC 120, and is connected to a part of a drive belt 118 that transmits the driving force of the drive motor 117, and two guide shafts 119A and 11 arranged in parallel with each other.
By making it slidable with 9B, the reciprocating movement over the entire width of the recording paper of the IJC 120 becomes possible.

Reference numeral 126 is a head recovery device, which is IJC1.
It is arranged at one end of the movement path of 20, for example, a position facing the home position. The head recovery device 126 is operated by the driving force of the motor 122 via the transmission mechanism 123, and the IJC 120 is capped. IJC by the cap portion 126A of the head recovery device 126
In association with the capping to 120, ink is sucked by an appropriate suction means provided in the head recovery device 126 or ink is pressure-fed by an appropriate pressure means provided in the ink supply path to the IJC 120, and ink is discharged from the ejection port. Ejection recovery processing such as removing the thickened ink in the nozzle by forcibly discharging is performed. Further, the IJC is protected by capping at the end of recording.

Reference numeral 130 denotes a blade as a wiping member which is disposed on the side surface of the head recovery device 126 and is made of silicon rubber. The blade 130 is held by the blade holding member 130A in a cantilever form, and like the head recovery device 126, the motor 122 and the transmission mechanism 123.
It is possible to engage with the ejection surface of the IJC 120. As a result, the blade 130 is moved to the IJC 12 at an appropriate timing in the recording operation of the IJC 120 or after the ejection recovery process using the head recovery device 126.
It is projected in the movement path of 0 and wipes out dew condensation, wetness or dust on the ejection surface of the IJC 120 as the IJC 120 moves.

According to the present invention, in an ink jet head having a plurality of ink tanks, when one of the plurality of tanks is empty and ink is sucked by one suction pump, The suction operation can be performed even when the tank is empty by preventing the nozzle communicating with the tank from communicating with the outside air except at the discharge port.

In addition to the above means, by providing a suction ink amount control means for adjusting the total ink amount to be sucked by one purging operation according to the number of empty tanks, the suction amount per nozzle is always maintained. It is designed to be kept constant.

[0035]

EXAMPLES Next, the present invention will be specifically described with reference to examples.

(Embodiment 1) FIG. 2 is a diagram showing an example of the ink jet head of the present invention and the vicinity of an ink tank. In the figure, 1 is an ink jet head that ejects ink in accordance with a recording signal, 2 is an ink supply pipe provided in the ink jet head, 3 is an ink supply hole provided in an ink cartridge 4, and 4 is ink of a plurality of colors inside It is an ink cartridge having.

The recording head 1 has the following structure. The recording head 1 has at its front end a group of nozzles for yellow, magenta, cyan, and black on a straight line. Each group has 24 nozzles for yellow, magenta, and cyan and 64 nozzles for black, and has a spacing of 8 nozzles between color nozzles and a spacing of 16 nozzles between cyan and black.
Each of these ejection ports is provided with an ink channel communicating with the ejection port, and a common liquid chamber for supplying ink to these liquid channels is provided behind the portion where the ink channel is disposed. .

In the ink liquid passages corresponding to the respective ejection ports,
An electrothermal converter that generates thermal energy used to eject ink droplets from these ejection ports and electrode wiring for supplying electric power to the electrothermal converter are provided. These electrothermal converters and electrode wirings are formed by a film forming technique on a substrate made of silicon or the like. Further, the ejection port, the ink liquid passage, and the common liquid chamber are formed by stacking a partition wall made of a resin and a glass material, a top plate, etc. on the substrate. Further on the rear side, a drive circuit for driving the electrothermal converter based on a recording signal is provided in the form of a printed circuit board. The silicon substrate and the printed circuit board are fixed on the same aluminum plate.

The ink cartridges 4 are for color (for yellow, for magenta, for cyan) 4a and for black 4a.
b is prepared. The ink cartridge 4 is inserted almost in parallel with the aluminum plate and is also connected to an ink supply pipe protruding in parallel with the aluminum plate. The ink supply pipe projects from a plastic member 5 called a distributor that extends in a direction perpendicular to the silicon substrate, and further communicates with a flow path inside the distributor 5, which flow path communicates with a common liquid chamber. There is.

There are four ink paths in the distributor 5 for yellow, magenta, cyan and black.
There is one, and each common liquid chamber is connected to the ink supply pipe 2. Since the ink cartridges 4 are arranged separately for the left and right with respect to the aluminum plate for the colors (yellow, magenta, cyan) 4a and black 4b, the ink supply pipes 2 are also divided into three and one. To be

FIG. 1 shows a black ink cartridge 4b.
It is sectional drawing which shows the inside. The principle is the same for the color ink cartridge 4a. An ink bag 25 exists inside the ink cartridge, and the bag is filled with ink. Further, two negative pressure plates 26 are contained in the bag, and a compression negative pressure spring 27 is pressed against the inside of the plates. Due to the load of this spring, a negative pressure is applied to the ink, so that the ink does not jump out from the nozzle even if there is an unexpected vibration. The lower end of the ink bag 25 is adhered to the seal mold 28. A seal rubber 29 is press-fitted in the center of the seal mold. The rubber has a hole into which the ink supply pipe 2 is inserted, but when the pipe is not inserted, it is elastically closed, so that ink does not spill.

FIG. 4 is a perspective view showing the whole of an ink jet printer using the above ink jet head and ink cartridge.

The ink jet head 1 and the ink cartridges (4a + 4b) are fixed to the carriage 7. The carriage 7 is supported by the guide A (10) and the guide B (11) and can reciprocate in 14 directions in the figure.
At this time, the ejection surface of the head 1 moves while maintaining a clearance of 1 mm with the recording paper 6. A lead screw 9 is connected to a motor (not shown) to rotate. The carriage 7 reciprocates in synchronization with the rotation of the lead screw.

The recording paper 6 is nipped by a paper feed roller 8 and a pinch roller (not shown) and fed in 15 directions. Further, the recording paper 6 is sandwiched between the paper ejection roller 12 and the spur 16, tension is applied between the paper ejection roller and the paper feed motor, and the recording paper 6 is held flat.

Reference numeral 13 is a purge unit, which will be described in detail with reference to FIG. FIG. 3 is a sectional view of the purge unit. On the side of the purge box 18 facing the head discharge port,
The cap rubber 17 is fixed. At the time of non-recording, the entire unit moves in the 23 direction by means not shown, and the ejection surface of the head comes into close contact with the cap rubber. Thereby, evaporation of water in the ink can be prevented. A cylinder 21 is inserted into the side surface of the purge box 18. The piston 22 can reciprocate in the cylinder. The piston is driven by a stepping mode motor through a mechanism (not shown). By starting from the piston position shown by the solid line in the figure and changing the number of input pulses to the motor, it is possible to accurately stop at four points a, b, c and d. Therefore, four levels of suction amount can be selected. FIG. 7 shows the change over time of the negative pressure in the purge box at this time. When the piston moves backward after the cap rubber has pressed against the head ejection port, air is first sucked, and at time t in FIG. 7, the meniscus formed on the nozzle end surface is destroyed and ink is sucked. If the negative pressure at this time is -p, this negative pressure is maintained until the piston stops thereafter. Points a, b, c, and d in FIG. 7 are points a and b in FIG.
It is a point corresponding to each stroke of b, c, and d. When the piston is stopped at these points, four suction levels can be selected.

Further, a joint 19 is inserted in the purge box 18, and an ink absorber 20 is inserted in the joint. The ink absorber 20 is a silicon tube 24.
Through the inside, it reaches a waste ink tank (not shown). The ink sucked from the nozzle of the head by the piston operation is discarded into the waste ink tank via the ink absorber.

Next, the operation of the apparatus will be described.

When the apparatus is activated, the head ejection port is pressed against the cap rubber. Next, the recording paper 6 is sent to the print start position. While the head is pressed against the purge unit, preliminary ejection of 50 shots for each of black and color is performed. At this time, the temperature of the head substrate is detected by a temperature sensor (not shown) provided on the head. If any of the four tanks is empty, the discharge heater will be in an empty state, and the temperature will rise abnormally. Moreover, if the black tank becomes empty, 64 heaters will become empty, and if one color ink dunk becomes empty, 24 heaters will become empty. The input energy is different and the temperature rise value is different.
Therefore, by detecting the temperature rise value, it is possible to determine whether the empty tank is black or color and how many colors are empty. In the case of the present embodiment, the determination can be made by having the discrimination table of eight kinds of temperature rise values. Since the preliminary ejection is performed once for each carriage 10 scan, it is possible to detect the temperature each time and determine the presence or absence of an empty tank.

The printer of the present embodiment can print characters with black ink even after the color ink is exhausted, but when the black ink is exhausted, the apparatus is automatically stopped and the user waits for replacement of the black ink cartridge. .

Next, when a print signal is input, the carriage scans and discharges at a timing of 360 dots per inch. At that time, 64 black nozzles are used for character printing, and 24 nozzles inside the black nozzles are used for graphic printing. When the printing of one line is completed, the recording paper is fed by 64 dots for character printing and by 24 dots for graphic printing. In the same manner, printing for one page is performed and the sheet is ejected. If printing is continued, new paper is fed. If not, the carriage moves to the front of the purge unit, the unit moves forward, and the head ejection port is capped.

The purging operation is a mode in which the user presses the purging button at any time and a mode in which the purging operation is performed without recording.
There is a mode to automatically purge when left for a day.
In any case, by the method of abnormal temperature rise detection described above,
The presence / absence of an empty tank is detected.
The total suction amount can be controlled to be always constant up to the line, b line when one color tank is empty, c line when two color tanks are empty, and d line when three color tanks are empty.
When the black ink becomes empty, the apparatus automatically stops as described above, and recording can be performed as soon as the replacement of the cartridge is completed.

(Embodiment 2) Next, an example of an ink tank integrated type head will be described with reference to FIG. In this case, four ink tank integrated heads 30 are mounted. As in the first embodiment, the inside of the tank employs a closed bag system. Heads are juxtaposed on the carriage 7 in the order shown. While the carriage moves along the recording paper,
Cyan, magenta, yellow, and black are ejected in this order and printing is performed.

Reference numeral 31 denotes a cap, which has four openings corresponding to the ejection surface of the tank-integrated head. These four openings are connected to one room inside. A hole penetrates through the back side of this room, and the gear pump 32 is connected through the suction tube 34. Further, a drain ink tube 33 is connected to the gear pump.

FIG. 6 shows the internal structure of the gear pump. Three
Reference numeral 8 is a pump gear A, and 39 is a pump gear B, which mesh with each other. Reference numeral 35 is an ink suction port, to which the suction tube 34 of FIG. 5 is connected. Similarly, 36 is an ink discharge port, to which the discharge ink tube 33 is connected. The pump gear A and the pump gear B are put in the hoop casing 37. At that time, the clearance between the tooth tip and the casing is 0.1 mm. When the two gears rotate in the direction of the arrow in FIG. 6, ink flows from the suction port to the discharge port. By driving this gear pump with a DC motor or a stepping motor and controlling the number of rotations of the motor, it becomes easy to select the ink suction amount.

(Embodiment 3) Next, an example of another ink jet head will be described with reference to FIG. In this case, the ink tank and the recording head are of a separable type connected via the ink tube 51. Further, in the first and second embodiments, the negative pressure spring is used to generate the negative pressure in the sealed bag.
In this case, an opening hole communicating with the atmosphere is provided in the tank 40,
A negative pressure is generated by installing the ink tank 20 cm lower than the head. A rubber (not shown) is fitted into the open hole, and since there is a fine hole in the center of the rubber, ink spill does not occur.

In this figure, reference numeral 40 denotes an ink tank, and there are four similar tanks of yellow, magenta, cyan, and black, and ink is supplied to a head (not shown) corresponding to each of them. The ink tank can be inserted and removed in the direction of 52 and can be fixed at a predetermined position by the tank fixing plate 42. At that time, the seal rubber 4 fixed to the tip of the tank
The ink supply pipe 46 penetrates through 5. At the same time, the front end of the tank pushes the valve 43 pressed by the compression valve spring 48 and abutting against the joint 47 downward against the spring force.
A rubber seal bush 44 is fitted inside the valve to close the ink hole 53 when the tank is not attached, but when the tank is installed, the valve 43 moves, the ink hole communicates with the tank, and ink is supplied. It will be possible. Ink is an ink flow path joint 49, a tube joint 50, an ink tube 5.
Go to the head through 1. If the tank is empty, remove the ink tank. As a result, the nozzle of the head does not come into contact with the atmosphere except at the ejection port, and the purging operation described in the first embodiment can be performed.

As described above, the application range of the present invention is wide and can be realized in various kinds of devices.

[0058]

As described above, according to the present invention,
(1) Since the purge operation can be performed even when some of the plurality of ink tanks are empty, good printing can be guaranteed regardless of the presence or absence of ink in the tank. Especially for users who print characters mainly at the center of printing and sometimes print graphics, it is possible to provide a printer that can print good characters in black for a while even after the color ink is exhausted. (2) Empty ink Even if there is a tank, the ink suction amount per nozzle during the purging operation can be made constant, and it is possible to prevent the ink from being wasted more than the suction amount necessary for maintaining good printing, and the printer with low running cost. (3) When the suction ink amount control means is a piston pump driven by a motor, it is sufficient to control the rotation speed of the motor, and the number of parts does not increase. In the case of a head that has a discharge heater and discharges ink droplets by utilizing the growth of bubbles generated by energizing the heater, the head Because you can control the suction amount by detecting a number of empty tank at a Atsushi Nobori, eliminating the need for a special ink remaining amount detecting means.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of a black ink cartridge of the present invention.

FIG. 2 is a perspective view of an example of a recording head and the vicinity of an ink tank according to the present invention.

FIG. 3 is a schematic cross-sectional view showing details of an example of a purge unit of the present invention.

FIG. 4 is a perspective view showing the whole of an inkjet printer equipped with the cartridge of FIG. 1 and the head of FIG.

FIG. 5 is a perspective view of another example of the periphery of the recording head and the ink tank of the present invention.

FIG. 6 is a cross-sectional view showing the internal structure of the gear pump.

FIG. 7 is a graph showing a change in negative pressure with time.

FIG. 8 is a schematic cross-sectional view of an example of the ink tank of the present invention.

FIG. 9 is a schematic perspective view showing an entire example of an inkjet printer of the present invention.

[Explanation of symbols]

 1 head 2 ink supply pipe 3 ink supply port 4 ink cartridge 4a ink cartridge (color) 4b ink cartridge (black) 5 distributor 6 recording paper 7 carriage 8 paper feed roller 9 lead screw 10 guide A 11 guide B 12 discharge roller 13 Purge unit 16 Spur 17 Cap rubber 18 Purge box 19 Joint 20 Ink absorber 21 Cylinder 22 Piston 24 Silicon tube 30 Tank integrated head 31 Cap 32 Gear pump 33 Discharge ink tube 34 Suction tube 35 Ink suction port 36 Ink discharge port 37 Pump casing 38 Pump Gear A 39 Pump Gear B 40 Open Ink Tank 41 Open Hole 42 Tank Fixing Plate 43 Valve 44 Seal Bushing 45 Rubber rubber 46 ink supply pipe 47 joint 48 valve spring 49 ink channel joint 50 tube joint 51 ink tube 53 ink hole 116 carriage 117 drive motor 118 drive belts 119A, 119B guide shaft 120 inkjet head cartridge 122 cleaning motor 123 transmission mechanism 124 platen 126 cap member 130 blade 130A blade holding member

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/165 B41J 3/04 102 N

Claims (6)

[Claims] 1. (1) One or more ink jet heads having a plurality of nozzles for ejecting liquid droplets, (2) One or more ink tanks for supplying ink to the ink jet heads through ink flow paths, And (3) In an inkjet printer having one suction pump that simultaneously sucks ink from all nozzle discharge ports of the inkjet head, when one or more ink tanks are empty, when the suction pump sucks the ink, the empty tank An inkjet printer characterized in that the communicating nozzles do not communicate with the outside air except at the discharge port. 2. The ink jet printer according to claim 1, wherein the ink tank is a sealed type having no communication port with the outside air. 3. A total suction amount of ink is adjusted based on (1) empty ink tank detection means and (2) detection information from the detection means so that the suction ink amount per nozzle is substantially constant. The inkjet printer according to claim 1 or 2, further comprising: suction ink amount control means. 4. The ink jet printer according to claim 3, wherein the suction ink amount control means is a stroke variable piston pump. 5. The ink jet printer according to claim 3, wherein the suction ink amount control means is a gear pump having a motor whose rotation speed is variable. (1) An ink jet head is a head which has a discharge heater inside a nozzle and discharges ink droplets by utilizing bubble growth generated by energizing the heater.
(2) The ink jet printer according to any one of claims 3 to 5, wherein the empty ink tank detection means is a head temperature detection means.