EP0684139B1 - Ink supplying device and ink jet recording apparatus using the same - Google Patents

Description

The present invention relates to an ink jet recording apparatus according to claim 1.

The object of the invention is to provide an ink jet recording apparatus in which the recovery operation can be reduced in frequency and time.

This object is achieved by means of the ink jet recording apparatus according to claim 1. Preferred embodiments of the ink jet recording apparatus according to claim 1 are disclosed in the dependent claims 2 to 5.

In the following the invention is further illustrated by embodiments with reference to the enclosed drawings.

Fig. 1 is a cross-sectional side view showing a facsimile apparatus to which an embodiment of the present invention is applied.

Fig. 2 is a typical view schematically showing a structural example of the ink supply passage of an ink jet recording apparatus according to the present invention.

Fig. 3 is a perspective view showing a structural example of ink supplying means of an ink jet recording apparatus according to the present invention.

Fig. 4 is an exploded perspective view showing an structural example of an ink cartridge installed in an ink jet recording apparatus according to the present invention.

Fig. 1 is a central sectional view showing an embodiment of facsimile apparatus characteristically representing the present invention. The facsimile apparatus of the present embodiment roughly comprises original conveying system A, optical system B, power source unit C, electric circuit board D, recording sheet conveying system E, decurling system F, ink supply system G, and recovery system H.

Next, the ink supply and recovery systems G and H will be described. This unit comprises an ink tank, ink tubes, an ink pump, etc. to keep ink and supply it regularly to a recording head and to remove bubbles generated in the tubes, etc., as well as anything that may clog nozzles.

Fig. 2 is a view illustrating the concept of an embodiment according to the present invention. In Fig. 2, an ink cartridge comprises recording head 38, ink pump 76, ink tank 86, waste ink absorber 96, and air duct 87 which is called breezer.

The initial ink supply to recording head 38 is carried out in a manner given below. In other words, ink pump 76 is actuated in a state where cap 41 is closely contacted with the recording head to circulate ink from ink cartridge 86 in the direction indicated by arrow E, so that the inside of the tubes including the inside of the recording head is filled with ink. At this time, some ink is flown out to cap 41, but it is returned to ink cartridge 86 through waste ink tube 45 and collected to built-in ink absorber 96.

When the initial ink supply is completed, recording head 38 is ready to discharge ink. The ink pump used in the present embodiment, however, is a pump which does not close the flow passage when the pump is at rest. Therefore, the ink supply at the time of discharging is carried out from both front and rear head ink couplers 38d and 38e.

When ink is reduced due to discharging, air should be drawn into the tank in an amount equal to the reduced amount of ink. Breezer 87 functions as an air duct for this purpose. In this breezer 87, check valves capable of being opened by an extremely small difference in pressures are respectively arranged in both directions. Therefore, the valves function if a slight pressure, either negative or positive, is generated in the tank, and operate as air holes substantially. However, the valves are also arranged to control dust intrusion and evaporation.

A reference numeral 92 designates a no-ink detector for detecting no-ink condition in tank 94. The detection is carried out in a manner given below. In other words, since float chamber 90 is open to the atmosphere through breezer 87 which is commonly provided for ink tank 94, the liquid level therein and float 89 which floats thereon indicate the same water level 91a as liquid ink level 91 in ink tank 94. Therefore, at an appropriate location in the lower part of float chamber 90, sensor 88 is arranged for detecting a light interruption. Thus, when liquid level 91 is lowered, i.e., float 89 is lowered following the lowering of water level 91a in the area for detection, the emitting light from the sensor 88 is interrupted, thereby detecting the no-ink condition.

Next, the recovery operation is described. The recovery operation is an action to remove bubbles and cloggings which bender the normal discharging, and is performed in accordance with a recovery sequence, controlled by the recovery system. The recovery operation, however, is exactly the same as the initial ink supply operation. In other words, ink pump 76 is actuated while cap 41 is in contact with recording head 38 to circulate ink in the direction indicated by arrow E, so that bubbles are collected into the ink tank to release them to the outside through the breezer. Also, the contacting condition between projection in cap 41 and nozzle 38a is released to drive the pump for the removal of any clogging in the nozzle. At this time, pressurized ink is flown into float chamber 90. Then, float 89 is raised to closely contact with upper face of float chamber 90 to cover the passage to breezer 87. Therefore, no ink is flown into breezer 87.

Fig. 3 is a perspective view showing the construction of supply and recovery systems G and H, in which the structure of the present embodiment is actually employed. In Fig. 3, a reference numeral 73 designates the base of this unit which also functions as a base for installing ink cartridge 86, which will be described later. Also, a reference numeral 74 designates a member called joint plate which is formed by fixing each of various passage couplers. To this joint plate 74, there are coupled cartridge guide 78 for positioning ink cartridge 86, cartridge joints 79a, 79b, and 79c for connecting tubes to release air, waste ink joint 81 for guiding waste ink produced at the time of recording to waste ink absorber 96 built in ink cartridge 86 through waste ink tank, air joint 80 for connecting the breezer for releasing air with air tube 83, first and second supply tube joints 84 and 85 for connecting first and second ink supply tubes 71 and 72 with ink pump 76 which is driven by pump motor 77. Thus, ink joint 79 connected to ink tank 94 accommodated in ink cartridge 79a provides three functional sections intensively, first ink supply section 79a, second ink supply section 79b, and air passage connecting section 79c, and with its structure, enables first ink supply inlet 95a, second ink supply inlet 75b and air inlet 95c to be coupled altogether, which are operationally related to the function of ink tank 94.

For this purpose, the air passage section leading to the ink tank is formed by joints, thereby making it possible to construct the ink tank with hard resin material to reserve a large quantity of ink without employing ink bags.

Furthermore, by connecting first ink supply inlet 95a and second ink supply inlet 95b, and first ink supply section 79c and second ink supply section 79b, an ink circulation passage is formed to perform ink supply from both of the ink supply regions at the time of recording and to circulate ink from the ink tank through the passage with the pump inbetween, and to circulate ink from the recording head to the ink tank again at the time of initial ink filling and recovery operation.

In other words, since the passage is formed by directly joining the tank and the supply passage, and further the air passage as described earlier, it becomes possible to eliminate, in spite of the ink tank being made of hard plastic resin, such function as a sub-tank which has conventionally been indespensable for a stable ink supply. In the present embodiment, these members are separately fixed to joint board 74, but the structure may also be such that these members are integrally formed with the joint board.

Further, to joint board 74, flow passage board 75 is coupled with flow passage gloove 75a which functions as ink flow passage. In this portion, most of the ink flow passage pipings and connections are installed.

In other words, by fixedly arranging joint section 79 which is annexed to joint board 74 connected to ink tank 94, it becomes possible to provide a structure thereby eliminating the operation related to ink passage 75a in that particular portion.

As a result, a part of ink passage from ink tank 94 to the recording head can be formed only by coupling to the reverse side of joint board 79 the flow passage plate 75 which constitutes a flow passage.

On the other hand, ink tank 94 built in ink cartridge 86 is flexibly accommodated in housings 93a and 93b which constitute the cartridge 86.

By accommodating the ink tank flexibly, it is possible to reliably adjust with ease the coupling condition of the cartridge which should be installed against joint section 79 which is flexibly arranged, and in this way, the installation of cartridge is carried out with assurance.

It is also possible to construct the ink passage from the ink tank without complicated piping arrangements simply by coupling joint board 74 and flow passage plate 75 to form the required flow passage.

As shown in Fig. 4, there are accommodated in ink cartridge 86, the common housings 93a and 93b made of material having a good impact resistance, ink tank 94 made of resin having a good property against fluid and waste ink absorber 96 made of a water absorptive material, having an excellent ink absorptive property such as felt or porous material. The ink supply and air releasing are performed by connecting these members with cartridge 79 on the side of joint plate 74 through joint section 95. Thus, the entire ink cartridge 86 is structured to be detachably installed as a whole on base 73 provided on the side of the apparatus.

Next, the recovery operation which is executed by circulating ink will be described further in detail. In the present embodiment, as shown in Fig. 2, bubble sensor 103 (for example, a transmitting sensor, etc.) is provided to enable detecting bubbles in ink supply tubes. Accordingly, it is possible to perform two different types of recovery operations, i.e., an automatic recovery to be carried out periodically each at a predetermined time, and an occasional recovery to be performed when bubble sensor 103 detects any incidental bubble or bubbles. The occasional recovery becomes possible with the installation of bubble sensor 103, and with this, the incidental non-discharging hitherto experienced can be reduced, thereby making it possible to improve the reliability of the apparatus. Particularly, in consideration of the safety with which all bubbles are removed irrespective of the presence of bubbles, the amount and location thereof, a considerably excessive circulation time and number has been given to perform a sufficient removal of bubbles. In the present embodiment, however, bubble sensors 103a and 103b are provided at either sides of up and down streams of ink flow towards the recording head at the time of circulation. Therefore, if no bubbles are detected by both of the bubble sensors, the recovery action is immediately suspended. Particularly when bubble sensor 103b arranged at the down stream of ink flow at the time of circulation should detect a signal indicating that bubbles have been removed (no bubble presence), the ink pump is stopped after a while (a period required for the detected bubble exhausted to the tank from the current position of the sensor). Consequently, there is no need for providing any excessive circulation time as has been required conventionally, resulting in the termination of the recovery sequence in a shorter period of time. Also, there is an advantage that the reliability of bubble removal improves because the recovery action is terminated after no bubble presence has been detected. In this way, the amount of ink consumed for recovery becomes small, which leads to the prevention of no ink condition at the time of receiving facsimile or of no reception state during the recovery operation.

The present invention provides means for generating heat energy (for example, an electrothermal converter, a laser light, etc.) for the utilization of energy for ink discharging especially for ink jet recording method, and in a recording head and recording apparatus using a method to activate changes in a state of ink by utilizing the aforesaid heat energy, the present invention is particularly effective.

For the typical structure and principle of an invention of the kind, it is preferable to employ the fundamental principle disclosed in the specifications of, for example, U.S. Patents 4723129 and 4740796. This method disclosed in applicable to the so-called on-demand type as well as to the continuous type. Particularly in the case of the on-demand type, by applying at least one driving signal, corresponding to recording information and providing a rapid temperature rise which exceeds nuclear boiling, to an electrothermal converter arranged for sheet or liquid passage holding liquid (ink), heat energy is generated in the electrothermal converter, and film boiling is accordingly generated on the thermal active face of recording head. As a result, bubbles are formed in the liquid (ink) one to one by this driving signal effectively. By the growth and contraction of this bubble, the liquid (ink) is discharged through the discharging port to form at least one droplet. If this driving signal is made to be a pulse type, the growth and contraction of bubble can be effectuated instantaneously and appropriately, and it should be more preferable to employ such system because with it, a discharging of liquid (ink) having an excellent responsibility can be attained. For a driving signal of the pulse type, those disclosed in the specifications of, for example, U.S. Patents 4463359 and 4345262 should be suitable. In this respect, if conditions disclosed in the specification of U.S. Patent 4313124 concerning an invention of the ratio of temperature rise on the aforesaid thermal active face are employed, a further excellent recording can be performed.

For the structure of recording head, those structures, in which a thermal active unit is arranged in a bending region, disclosed in the specifications of U.S. Patents 4558333 and 4459600 are included in the present invention in addition to a combination structure (linear liquid flow passage or right angled liquid flow passage) of discharging ports, liquid passage, and electrothermal converter such as disclosed in each of the above mentioned specifications. Besides, the present invention is still effective for the structures based on the structure disclosed in Japanese Laid-Open Patent Application No. 59-123670 in which common slits against a plurality of electrothermal converters function as discharging ports of the electrothermal converter, and the structure disclosed in Japanese Laid-Open Patent Application No. 59-138461 in which an opening for absorbing the pressure wave of heat energy is used for the discharging port.

Particularly, the present invention is effectively applicable to the recording head of a full line type with a length to cover the width of a maximum recording medium which can be recorded by the recording head. For a recording head such as this, a structure in which a plurality of recording heads as disclosed in the above-mentioned specifications are combined to meet the requirements of such length or a structure in which one recording head, integrally formed, is adopted may be applicable, but the present invention displays the above-mentioned effects more efficiently.

In addition, the present invention is effectively applicable to the installation in the main body of an apparatus either in the case of a recording head of chip type which is freely replaceable to enable the electrical connection with the main body of the apparatus or the ink supply from the main body of the apparatus or in the case of a cartridge type recording head which is integrally mounted in the recording head itself.

It is also desirable to add the recovery means for the recording head, preparative auxiliary means, etc. which constitute a recording apparatus according to the present invention because such addition makes the effects of the present invention more stable. These means are specifically capping means for recording head, wiping means, pressuring or absorbing means, electrothermal converter, or another heating element or preparative heating means by the combination of these elements, and aside from discharging for regular recording, it is also effective to effectuate a preparatory discharging mode for performing a stable recording.

Furthermore, the present invention is extremely effective for a recording apparatus having at least one mode for recoloring with different colors or for full color with mixture of colors by the use of recording heads which are integrally structured into one head or by the combination of plural heads, not to mention the recording mode of principal color such as black, etc. as recording mode for a recording apparatus.

In the embodiment set forth above according to the present invention, the description has been made of the case where liquid ink is used, but the present invention is also applicable to solid ink at room temperature as well as to ink becoming soft at room temperature. In the above-mentioned ink jet apparatus, it is usual to perform temperature control to make viscosity of ink to be in the range of stable discharging by adjusting the temperature of ink itself more to be than 30°C but less than 70°C. Therefore, if only ink becomes fluid at the time of applying recording signals in use, those kinds of ink are also usable. Furthermore, the present invention is applicable to the use of ink having the property that the ink becomes fluid only by heat energy such as the one which can be discharged as liquid ink when it becomes fluid by the application of heat energy in response to recording signals or ink already becoming solidified at the time of reaching recording medium by utilizing positively the temperature rise caused by heat energy as energy to change the state of ink from solid to fluid for prevention or by using ink which is solidified when it is left for the purpose of preventing evaporation. In such case, ink can be held as liquid or solid state in a concave of porous sheet or through holes as described in Japanese Laid-Open Patent Application No. 54-56847 or Japanese Laid-Open Patent Application No. 60-71260, and is placed against the electrothermal converter in such mode. In the present invention, the performance of the above-mentioned film boiling method is most effective when each of the above-mentioned kinds of ink is employed.

Furthermore, the mode of an ink jet recording apparatus according to the present invention is such that in addition to facsimile apparatus having receiving and transmitting functions as in the present embodiment, it can be used as image output terminal for information processing apparatus such as computer, etc, copying apparatus combined with reader, etc. or the like.

In the present embodiment, a recording head is used for the recovery operation by circulation with ink supply tubes arranged at both ends respectively, but the present invention is also applicable to a recording head of such type that it has only one ink supply tube and performs recovery operation by suction from the front face of nozzle as a matter of course. It is also possible to reduce manufacturing cost by forming bubble sensor integrally with the constituents of the head.

Furthermore, in the above-mentioned embodiment, the recording head having at its both ends the supplying tubes and carrying out the recovery operation by the circulation is used, but this invention may be applied to a recording head having one supplying tube and of which recovery operation is carried out by suction from the front face of the nozzle. Also, it is possible to decrease the cost by forming both of the bubble sensor and the recording head in a body.

Further, in accordance with the above-mentioned embodiments, it is possible to provide an ink jet recording apparatus in which by controlling the operation of the ink pump using the means for sensing a bubble in the ink supplying paths, the recovery operation can be reduced in frequency and time to minimum necessary values, the volume of waste ink can be decreased and the number of the recording papers which are recorded with a predetermined amount of ink can be increased, and thus, its running cost can be reduced. Also, in a case where the above-mentioned embodiments are applied to a facsimile machine, since the time necessary to carry out the recovery process is shortened, a long recording enabling time can be achieved, and a probability of disabling facsimile signal reception because the facsimile machine is subject to the recovery process can be made to be small.

Claims (5)

1. An ink jet recording apparatus, wherein at the time of recording ink is supplied from first and second ink supplying paths (71, 72) to an ink jet recording head (38), and at the time of initial filling or recovery ink is circulated through the first ink supplying path (71), the recording head (38) and the second ink supplying path (72), in turn, by a pump driving (76), wherein first and second bubble sensing means (103a, 103b) are provided in respective portions of said first and second ink supplying paths, respectively, to sense a bubble in the respective supplying paths, and when the bubble is sensed by said first and second bubble sensing means, said pump (76) is actuated so that the recovery operation is carried out, said pump being driven until the second bubble sensing means (103b) positioned downstream in the ink circulating direction at the time of said recovery terminates the sensing of the presence of the bubble.
2. An ink jet recording apparatus according to claim 1, wherein said first and second bubble sensing means (103a, 103b) are of a type optically sensing the bubble in the respective ink supplying path (71, 72).
3. An ink jet recording apparatus according to claim 1 or 2, wherein said ink jet recording head (38) is of a full-line type having discharging ports formed across the whole width of the recording area of the recording medium.
4. An ink jet recording apparatus according to one of claims 1 to 3, wherein said recording head (38) is of a type of discharging ink by use of heat energy, and that an electrothermal converter for generating said heat energy is provided.
5. An ink jet recording apparatus according to one of claims 1 to 4, wherein said ink jet recording apparatus is a facsimile machine having a manuscript reading part.

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