Ink jet recording apparatus

Abstract: An ink storage unit (IT) used in an ink jet recording apparatus for recording by ejecting ink comprises a plurality of ink storage chambers (910A), a plurality of movable walls (950) and a mechanism for holding each of the movable walls (950). Each of the ink storage chambers (910A) stores ink. Each of the movable walls (950) is provided in the each ink storage chamber (910A) respectively so as to seal stored ink against air, and each movable wall (950) can move according to a change of amount of ink in each ink storage chamber (910A). The mechanism for holding the movable walls (950) exerts a force opposed to a force which is exerted on the each movable wall (950) according to the change of amount of ink, on each of of the movable walls (950) so as to make the pressure in each ink storage chamber (910A) an appropriate negative pressure.

Description: The present invention relates to an ink jet recording apparatus, and more particularly, to an ink storage unit for storing ink which is supplied to a recording head of the ink jet recording apparatus. An ink jet recording system performs recording in a manner that an ejection-energy-generating element provided at a portion communicating with orifice of a recording head, such as a heating element or a piezoelectric element, operates based on recording signals to eject ink droplets from the orifice, and to attach the ejected ink droplets to a recording medium. This system has such an advantage that high speed recording is possible and operation noises generated by recording are fairly low, and is recently in the wide use in printers. The configuration of an ink supplying system in the above recording system is as follows: Ink which is stored in an ink tank as an ink storage member, is supplied to a recording head via an ink supplying route member such as a tube. The ink supplied to the recording head is temporarily stored in an ink temporary storage portion such as a common liquid chamber, and then is supplied into ink paths in accordance with the ink ejection, the ink paths communicating with orifices correspondingly, an ejection energy generating element being provided in each ink path. A pressure exerted on the ink in the ink supplying system comprising the ink storage member, the ink supplying route member, and the ink paths in the recording head and the like, is always maintained to be lower than the atmospheric pressure (a pressure lower than the atmospheric pressure is hereinafter referred to as a negative pressure). This can prevent ink from leaking out from the orifices of the recording head and an air communication port of the ink storage member, through each of which the ink paths and an inside of the ink storage member communicate with air respectively. An ink supply from the ink storage member to the ink paths, in which ink refilling into the ink paths is included, is mainly performed by the capillary force of the ink paths and the ink supplying tube. In the above ink supplying system, the above described negative pressure in the ink supplying system is generally obtained by making the pressure of the inside of the ink storage member negative. Some configurations for making the pressure of the inside of the ink storage member negative, will be shown below. Fig. 1 is a view showing a head cartridge where the recording head and the ink tank is integrally formed. As shown in Fig. 1, in an ink tank 1000 as the ink storage member, a portion where ink is stored communicates with air via an air communicating port (not shown). Moreover, for instance, as disclosed in the US patent No. 4,771,295, a porous ink absorber 6000 typified by urethane sponge is housed in the ink storage portion. A force to hold ink, which is caused by a capillarity force of the ink absorber 6000 and is regarded as a virtual negative pressure, maintains the negative pressure in the inside of the ink supplying system composed of a series of members from the ink tank 1000 to the ink paths in a recording head unit IJU. With respect to another configuration, as shown in Fig. 2, an ink storage portion 230 is made of flexible materials such as rubber, a plastic film, a laminated aluminum film, etc. in the shape of a bag. The inside of the bag and the whole ink supplying system are maintained at a negative pressure by sealing the inside of the ink storage portion 230 against air. Besides the above configuration for generating the negative pressure, Fig. 3 shows still another configuration of the ink tank. In this configuration, a layer 130 of a liquid is formed on an upper surface of the ink 210 stored in the ink tank 110. The liquid has a specific gravity smaller than that of the ink and will not be mixed with the ink. In this configuration of the ink tank, since the inside of the ink tank communicates with air via an air communicating port 120, the layer 130 of the liquid moves together with the ink liquid surface according to the ink consumption, and hence the layer can always separate the ink from air. In the above described conventional ink storage member, as shown in Fig. 1, where the negative pressure is generated by the porous ink absorber which is provided in the ink tank and is typified by urethane sponge, an effective ink capacity (usable ink capacity) for the ink tank volume can not be obtained because of the existence of the ink absorber. In addition, when the amount of the ink in the ink tank decreases, the negative pressure increases to the contrary, and refilling of the ink into the ink paths accompanying the ink ejection can not be performed well. This may cause defective ejection such as non-ejection. In addition, since amount of ink remaining in the ink tank becomes large because of the negative pressure increasing, use efficiency of ink is difficult to raise. Therefore, in the case where recording is performed by using the above conventional ink tank including the ink absorber so that the enough number of sheets of recorded paper is intended to be obtained, there occurs a problem that the ink tank must be enlarged. Moreover, the urethane sponge of a porous absorber is relatively expensive, and its manufacturing process becomes complicated, and hence it is difficult to provide an ink tank of a low manufacturing cost and with high productivity. In the configuration where the ink storage portion, as shown in Fig. 2, is made of flexible materials such as rubber in the shape of a bag, since the inside of the bag is always sealed and the bag is made of flexible materials, when the amount of the ink in the bag decreases according to the ink ejection and the like, the negative pressure in the bag increases according to deformation of the bag. As a result, because of the same reason as described above, all the ink in the bag can not be exhausted. Moreover, there occurs some problem that the ink tank must be enlarged in order to get the enough number of sheets of paper to be recorded. In the configuration of the ink storage member where the liquid layer is provided in the ink tank as shown in Fig. 3, a desired negative pressure can not be obtained by the ink tank itself. This may not prevent ink from leaking out from orifices of the recording head, and may have adverse effect on the ink ejection by the recording head in the recording apparatus, where the ink tank is mounted on a carriage and the ink in the ink tank trembles markedly by a movement of the carriage while a recording operation, so that the tremble is transmitted to the ink near the orifices. In addition, in the above configuration, the ink tank is usable in the direction shown in Fig. 3. When the ink tank has another attitude or is moved violently, the movable wall, that is, the liquid layer may be destroyed and the ink may leak out via the air communicating port. As for a configuration for solving the above problems in various kinds of the above ink storage member, for example, Japanese Patent Application Laying-Open No. 204355/1985 proposed by the assignee of the present invention discloses the ink storage member. This ink storage member has a movable wall therein. The movable wall is disposed in the ink storage member. A friction force is generated by an O-ring provided between the wall and an internal wall of the ink storage member or by contact between elastic cup-shaped edges of the movable wall and an internal will of the ink storage chamber, with one side face of the movable wall contacting air. This makes it possible to always maintain the constant negative pressure in the inside of the ink storage member by a friction force exerted on the sliding portion of the movable wall. However, the ink storage member using the above movable wall has the following subject to be solved, which is associated with a setting of the friction force. The ink storage member may have various attitudes according to the mount attitude of the recording apparatus on which the ink storage member is mounted. Incidentally, an ink jet recording apparatus of portable type may have various attitudes when transported, and may be subjected to a relatively great external force such as an impact. Consequently, the ink storage member mounted on such an ink jet recording apparatus, which uses the above movable wall, has a configuration that the movable wall must not move against various attitudes or the external force described above, and good ink supply must be always secured. In order to prevent the movable wall from moving easily in the case where a large amount of ink is stored in the ink storage member, it is considered that materials having relatively great friction coefficient may be employed for the movable wall, or that the maximum static friction force is designed to be great by making the contact area between the movable wall and the internal wall of the ink storage member large. However, in this case, the movable wall may have a difficulty in moving according to the ink consumption by ink ejection or the like. As a result, the negative pressure in the ink storage portion increases excessively, so that the ink supply to the recording head may have a difficulty and then the ink ejection by the recording head may be disabled. Besides the above described problem of setting the friction force of the movable wall, in the case where a large amount of ink is stored in the ink storage member, there may occur problems associated with the external force exerted on the ink storage member, a force of inertia produced when the ink storage member which moves together with a recording head, is accelerated or is decelerated during the recording operation and the variation of the pressure on ink in the ink storage member which is caused by a change in environmental temperatures or the like. More specifically, when a large amount of ink is stored, the pressure on ink in the ink storage member fluctuates easily because of the above problems, so that ink may leak out from the orifices of the recording head when the pressure in the ink storage member is high, to the contrary, when the pressure is low, the ink may not be supplied to the recording head. In accordance with the present invention there is provided an ink storage unit for ink jet recording apparatus as set out in claim 1. An embodiment of the present invention provides an ink storage unit which can always supply ink from an ink storage member to a recording head in a good condition and an ink jet recording apparatus provided with the ink storage member. In an embodiment of the present invention, for example, when ink flows from each of a plurality of the sub-chambers following ink ejection by the recording head, the pressure on the ink in each of the ink storage chambers decreases because of the decrease in ink amount in the respective sub-chambers. In this case, each of movable walls moves according to the relationship between a pressure in each of the sub-chambers and the outer atmospheric pressure so that the pressure decrease in each of the sub-chambers is moderated. As a result, the total of the pressure in the ink storage chamber caused by the above movement of the movable walls and other forces exerted on the movable wall, balances force such as a friction force. The force is exerted on the movable walls by movable wall holding means, so that the movable wall rests at a proper position. As a result, even if ink is consumed, the pressure in the each of the sub-chambers is kept constant, for example, a constant negative pressure in the each of the sub-chambers is maintained in a non-ejection state of the recording head. Consequently, it is possible that ink holding function of the ink storage unit is kept better and ink supply is performed according on demand. Since the force exerted on the each of the movable walls is relatively small because of each of the movable walls and the pressure to each of the movable walls being small, the force by the movable wall holding means can become small, and hence the movable walls can move smoothly. The invention will be more readily understood from the following description of exemplary embodiments thereof taken in conjunction with the accompanying drawings, in which: Fig. 1 is a plan view, partly in section, showing a conventional ink storage member; Fig. 2 is a perspective view showing another example of a conventional ink storage member; Fig. 3 is a longitudinal sectional view showing still another example of a conventional ink storage member; Fig. 4A is a plan view, partly in section, showing a recording head cartridge composed of an ink storage unit and a recording head of a first embodiment of the present invention; Fig. 4B is a cross-sectional side view showing a part of the ink storage unit shown in Fig. 4A; Fig. 5 is an exploded perspective view showing the recording head cartridge shown in Fig. 4A; Fig. 6 is a perspective view showing the recording head cartridge shown in Fig. 4A; Fig. 7 is a perspective view showing the recording head cartridge shown in Fig. 4A from which the recording head is removed; Fig. 8 is a plan view for explaining how to mount the recording head cartridge shown in Fig. 4A on the recording apparatus; Fig. 9 is a schematic perspective view showing an ink jet recording apparatus on which the recording head cartridge shown in Fig. 4A can be mounted; Fig. 10 is an exploded perspective view showing another embodiment of the recording head cartridge of the present invention; Fig. 11 is a schematic perspective view showing an example of the ink jet recording apparatus using the recording head cartridge shown in Fig. 10; Fig. 12 is a plan view, partly in section showing the recording head cartridge of another embodiment of present invention; Fig. 13 is a schematic diagram illustrating an embodiment of an apparatus to which the ink jet recording apparatus in accordance with the present invention is equipped; and Fig. 14 is a schematic diagram illustrating an embodiment of a portable printer in accordance with the present invention. FIRST EMBODIMENT Fig. 4A is a plan view showing a recording head cartridge of a first embodiment of the present invention integrally formed together with an ink tank as an ink storage unit and a recording head, and Fig. 4B is a cross sectional view showing a part of the ink storage unit shown in Fig. 4A. Figs. 5 - 9 are views for explaining an recording head cartridge IJC which embodies the present invention, a recording head unit IJU and an ink tank IT, both of them constituting IJC, an ink jet recording apparatus IJRA using the recording head cartridge IJC, and a carriage HC on which the recording head cartridge IJC is mounted in the ink jet recording apparatus IJRA, and for explaining relationships among the above units according to the present invention. Incidentally, in the ink jet recording apparatus, an electric signal supplying means for supplying an electric signal as an ink ejection signal to the recording head is provided. With reference to these drawings, configurations of each unit will be described below. As seen in a later explanation regarding Fig. 5, the recording head cartridge IJC of the first embodiment is composed of the ink tank IT and a recording head unit IJU which are integrally formed, and most part of the recording head cartridge IJC is occupied by the ink tank IT. As seen in Fig. 6, a tip portion of the recording head unit IJU is projected. As described later, the recording head cartridge IJC is fixedly supported by cooperation of a positioning mechanism and an electrical contact portion of the carriage HC provided in the ink jet recording apparatus IJRA (see in fig. 8), and is removably installed on the carriage HC. When ink in the ink tank IT is used up, the recording head cartridge IJC can be exchanged. (I) explanation of the configuration of the recording head unit IJU The recording head unit IJU uses an ink ejection mechanism where, in response to an electric signal, an electrothermal transducer generates thermal energy to produce film boiling in the ink so that the ink ejection is carried out. In Fig. 5, reference numeral 100 denotes a heater board or substrate. The heater board 100 is composed of electrothermal transducers (ejection heaters) arranged in array geometry and electric wiring which is made of aluminum or the like and is used for feeding power to the electrothermal transducers, which are formed on a silicon substrate plate with a film forming technology. Reference numeral 200 denotes a wiring board connecting to the heater board 100, containing wirings to the electric wiring of the heater board 100 (both ends of the wirings, for example, are fixed by wire bonding) and pads 201 which is disposed at an end of the wiring from the heater board 100 for transferring electric signals from the apparatus IJRA. Reference numeral 1300 denotes a top plate with grooves which are provided for forming separation wall for defining individual ink path, a common liquid chamber for temporarily storing ink to be fed to each ink path and so on. In addition, the top plate 1300 is a molded unit with an ink inlet 1500 for pouring ink supplied from the ink tank IT into the common liquid chamber and an orifice plate 400 having a plurality of orifices each of which corresponds to each ink path. Polysulfone is more suitable to materials for integrally molding the top plate 1300, but other molding resinous materials are also available. Reference numeral 300 denotes a supporting plate, which, for example, is made of metal and supports the wiring board 200 with a plane surface of the supporting plate 300 contacting a reversed surface of the wiring board 200. The supporting plate 200 becomes a base plate of the recording head unit IJU. Reference numeral 500 denotes a pressure spring which is in the shape of character M. A central portion of the M character-shaped spring 500 presses a part of the top plate 1300 with a light pressure, the part corresponding to the common liquid chamber, and a projected portion 501 of the spring 500 intensively presses a part of the top plate 1300, a force by the portion 501 exerting on line-like part which corresponds to ink paths, and more preferably to a region adjacent to the orifices. Foot portions of the pressure spring 500 penetrate a holes 3121 formed at the supporting plate 300 and are engaged with a reversed surface of the supporting plate 300, so that the heater board 100 and the top plate 1300 are sandwiched between the supporting plate 300 and the pressure spring 500. In this state, the heater board 100 and the top plate 1300 are fixed to each other by intensively pressing of the pressure spring 500 and the projected portions 501 thereof. Moreover, the supporting plate 300 has positioning holes 312, 1900 and 2000 which engage with positioning projections 1012 and positioning-heat welding projections 1800, 1801 of the ink tank IT, respectively. The supporting plate 300 also has positioning projections 2500 and 2600 for the carriage HC in the apparatus IJRA on the reversed surface of the supporting plate 300. In addition, the supporting plate 300 has a hole 320 through which an ink supplying tube 2200 (described later) penetrates. The ink supplying tube 2200 is provided for supplying ink from the ink tank IT to the recording head unit IJU. The wiring board 200 is attached to the supporting plate 300 with an adhesive or the like. On the supporting plate 300, recess portions 2400 are provided in the vicinity of the positioning projections 2500 and 2600 respectively. In the state that the recording head cartridge IJC has been assembled (see Fig. 6), on three side portions of a tip portion of the recording head unit IJU are formed a plurality of parallel grooves 3000 and 3001 (one side portion is not shown). The recess portions 2400 are positioned at corners of the three side portions to prevent dust, ink or the like from reaching the positioning projections 2500 and 2600. As shown in Fig. 6, a cover 800, on which parallel grooves 3000 are formed, forms an outer wall of the recording head cartridge IJC, and forms a space in which the recording head unit IJU is housed, in cooperation with the ink tank IT. An ink supplying member 600, on which the parallel grooves 3001 are formed, has an ink guiding tube 1600 communicating with the ink supplying tube 2200 in such a manner that one end of the ink guiding tube 1600 is fixed at a portion on the side of the ink supplying tube 2200 like a cantilever. A seal pin 602 is inserted into the ink guiding tube 1600 or the ink supplying tube 2200 so as to secure a capillarity force between the fixed end of the ink guiding tube 1600 and the ink supplying tube 2200. Reference numeral 601 denotes a packing to seal a connection portion of the ink tank IT and the ink supplying tube 2200, and reference numeral 700 denotes a filter provided at the end of the ink supplying tube 2200 facing a side of the ink tank. Since molded, the ink supplying member 600 is inexpensive and has high positioning accuracy. Moreover, the accuracy degradation in the manufacturing process can be prevented, and a pressure-contact state where the ink inlet 1500 is forcibly pressed by the cantilever-like ink guiding tube 1600, is stable during a mass production. In this embodiment, a more complete communication state is secured by pouring a sealing adhesive from the ink supplying member under the pressure-contact state. The ink supplying member 600 is easily fixed to the supporting plate 300 by the method described below. Pins (not shown) on a reversed surface of the ink supplying member 600 are made penetrate the holes 1901 and 1902 of the supporting member 300, and portions of the pins projected beyond the reversed surface of the supporting plate 300 are welded. Since the slightly projected welded portions of the pins are fitted in recess on a side surface (not shown) of the ink tank IT, to which the recording head unit IJU is attached, the positioning of the recording head unit IJU is not interfered by the projected welded portions. (II) explanation of the configuration of the ink tank IT As shown in Figs. 4A and 5, the ink tank IT is formed in the recording head cartridge case 1000. A plurality of separation walls 900 separate the inside of the ink tank IT into a plurality of sub-chambers respectively, and the separation walls 900 are formed of, e.g., resinous materials. A movable wall 950 is provided in each of the chambers, and is made of silicone rubber. The individual movable wall 950 is slidably supported by the both sides separation walls 900 and top and lower covers 1000C of the cartridge case 1000. Consequently, a shape of the section of the movable wall, which is perpendicular to a direction in which the movable wall 950 moves, is specified as follows: When the movable wall 950 is incorporated in the chamber as shown in Fig. 4B, the movable wall 950 is tightly incorporated in a portion which is surrounded with the separation walls 900 and the upper and lower covers 1000C of the recording head cartridge case 1000, and is made in a shape similar with and a little larger than a cross sectional area of the chamber 910 so that the movable wall 950 may press the separation walls 900 and the covers 1000C with an appropriate force caused by the elasticity of the movable wall 950. As a result, the individual movable wall 950, as shown in Fig. 4A, can seal the ink storage chamber 910A against an air chamber 910B which communicates with air via a communicating port 1400 (the each air chamber 910B communicates each other via a hole 900A as shown in Fig. 5), and can cause proper friction forces by the elastic pressure of the movable wall when it moves and it is balanced. With above configuration of the ink tank IT, when ink in the ink tank decreases as the recording head unit consumes ink, the movable wall 950 moves and a volume of the ink storage chamber 910A gradually decreases. Since the friction force is constant, the negative pressure in the ink storage chamber 910A is maintained constant so that good ink supply to the recording head unit IJU is performed and most of ink in the ink tank IT can be used for recording. Moreover, according to the configuration of this embodiment, various forces which include inertia of the movable wall and is exerted on the movable wall 950 is smaller than forces exerted on a movable wall being disclosed in Japanese Patent Application Laid-open No. 204355/1985, wherein a movable wall is applied to a whole ink storage chamber. This makes setting value of the friction force in a moving portion of each movable wall 950 relatively small. Thus, movement of the individual movable wall 950 in accordance with the decrease in an amount of ink in the ink storage chamber 910A can be performed smoothly. In the above configuration, each of tip portions of the ink storage chambers 910A are connected to one ink liquid path 920, which is connected to an ink inlet 1200 shown in Fig. 5 for supplying ink to the recording head unit. The friction force generated between the movable wall 950 and the separation wall 900, depends on both the friction coefficient between silicone rubber forming the movable wall and the separation wall 900 and the pressure force with which the silicone rubber presses the separation wall. And in any attitude of the ink tank, it is necessary that the above pressure force make the movable wall stationary against the atmospheric pressure, the negative pressure in the ink storage chamber, an ink weight and the weight of the movable wall. Moreover, it is also necessary that the above pressure force make the movable wall movable at an ink supplying time when ink is refilled after ink ejection. It is preferable that the negative pressure determined by balancing the above friction force with the above various forces exerted on the movable wall is smaller than a suction force caused by a capillary force generated when ink is refilled after ink ejection so that ink supply is performed smoothly. The above friction force, for example, will be determined as follows: the movable wall 950 completely seal the ink in the ink storage chamber 910A so that the ink in the ink tank may not leak from an air communicating port 1400. In addition, when the recording head cartridge IJC is in a non-ejection state, the movable wall 950 is not allowed to move in any attitude of the recording head cartridge IJC. In this state, it is preferable that a static friction force generated by contact of the movable wall 950 with both the separation walls 900 and the case covers 1000C of the recording head cartridge IJC, is equal to or greater than a total of a weight of the movable wall 950 and an ink weight to be applied thereto. Assuming that the weight of the movable wall 950 is negligible, and 'S' is an area through which the movable wall 950 is in contact with ink, and 'h' is a pressure head of the ink, it is preferable that the static friction force F which prevents the movable wall 950 from moving by the ink weight, is given by the following expression: F > h · S As seen in expression (1), it is apparent that the smaller the pressure head of the ink or the smaller the cross sectional area, the smaller the static friction force required. That is, since the movable wall is divided into many divisions in this embodiment, the static friction force exerted on the individual movable wall becomes small. In order to eject an ink droplet from the orifice of the recording head unit IJU, ink has to be supplied from the ink tank IT to the recording head unit IJU. If the negative pressure in the ink storage chamber 910A, is too high when ink is supplied from the ink tank IT to the recording head unit IJU, ink supply shortage occurs. This makes an ejected ink droplet small in volumes so that density of printed image becomes low, and sometimes makes ink ejection disabled. The negative pressure in the ink storage chamber is limited and depends on configuration of the ink ejection outlet or the ink path in the recording head unit IJU. In general, the negative pressure is preferably within -20gw, more preferably within -15gw. Therefore, it is preferable that the static friction force F required to the movable wall satisfies the following expression: S · h < F < 20gw Incidentally, the negative pressure in the ink storage chamber may gradually increase according to the decrease in ink in the ink storage chamber for some reason. In this case, the negative pressure can be maintained approximately constant by decreasing the friction force exerted on the movable wall according to the movement of the movable wall. This is enabled by, e.g., increasing gradually a cross sectional area of the ink storage chamber. The negative pressure can be also maintained by applying a given force such as an elastic force in a direction where the movable wall moves, instead of the friction force exerted on the movable wall. Moreover, in a recording apparatus of serial type where the recording head, which is integrally formed with the ink tank in the case of this embodiment, is mounted on the carriage to be moved for recording, since recording is usually performed when the moving velocity of the carriage is constant, the movement thereof does not have any effect on the above balance in the movable wall. But, when the carriage accelerates or decelerates, the movable wall and the ink are subjected to an inertia force. For this reason, when the carriage reaches a constant speed, oscillation of the movable wall and the ink caused by the above inertia force must converge promptly. From this point of view, it is preferable that the mass of the movable wall and the pressure head exerted on the movable wall are smaller and the friction force exerted on the movable wall is as large as possible in the friction force range which is determined as described above. In the above configuration, the ink storage chamber can be completely sealed against air during the ink tank movement, so that fine bubbles are prevented from contaminating the ink due to the mixing of air with the ink, and ink viscosity is prevented from being high due to the contact of the ink with air. Fig. 7 shows a configuration of a recording head unit installation surface on the ink tank IT. In Fig. 7, line L 1 passes near a center of arrangement of orifices on an orifice plate 400 (see in Fig. 5) and is perpendicular to the orifice plate 400. In addition, the line L 1 is parallel to either a bottom surface of the ink tank IT or a mount-reference surface of the carriage. Two positioning projections 1012 which are provided on the above installation surface and engagic with the two positioning holes 312 at the supporting plate 300 (see in Fig. 5) are on line L 1 . The height of the positioning projections 1012 is slightly less than the thickness of the supporting plate 300, the positioning projections 1012 perform the positioning of the supporting plate 300 in cooperation with the positioning holes 312. On an extension line of the line L 1 , a finger 2100 is provided which engages a 90-degree engaging surface 4002 of the positioning hook 4001 provided on the carriage HC, and an action force for positioning of the recording head cartridge to the carriage acts in a surface parallel to the above mount reference surface including the line L 1 . As shown later in Fig. 8, the above configuration relationship is effective because positioning accuracy of the recording head cartridge is as precise as positioning accuracy of the orifices of the recording head. Projections 1800 and 1801 of the ink tank IT which are respectively corresponding to holes 1900 and 2000 for fixing the supporting plate 200 to a side surface of the ink tank IT, are longer than the projections 1012. The projections 1800 and 1801 are used for fixing the supporting plate 300 to the side surface of the ink tank IT by penetrating the holes 1900 and 2000 respectively and then by welding projected portions of the projections 1800 and 1801 beyond the surface of the supporting plate 300. Line L 2 is perpendicular to line L 1 and passes on the projection 1801, and line L 3 is perpendicular to line L 1 and passes the projection 1800. Since the center of the ink inlet 1200 is positioned approximately on line L 3 , the connection state of the ink inlet 1200 and the ink supplying tube 2200 is stable and an adverse effect to this connection state caused by an impact of the drop or the like of the recording head cartridge can be reduced. Moreover, since line L 2 does not accord with line L 3 and on the above installation surface, the projections 1800 and 1801 are disposed in the vicinity of the projection 1012 of an orifice side, positioning of the recording head unit IJU to the ink tank IT is reinforced. Incidentally, line L 4 shows a position corresponding to an outer wall of the ink supplying member 600 when the recording head unit IJU is installed to the ink tank IT. Since the projections 1800 and 1801 are disposed on the line L 4 , the projections give a sufficient strength against the weight of the tip portion of the recording head unit IJU and give a sufficient positioning accuracy to a tip configuration thereof. As shown in Fig. 8, reference numeral 2700 is a tip flange of the ink tank IT, and is inserted into a groove on a front plate 4000 of the carriage HC so as to prevent a marked displacement of the ink tank. Reference numeral 2101 is a stopper for the carriage, and is provided corresponding to a bar (not shown) of the carriage HC. At the position where the recording head cartridge IJC is turned to be mounted as described later, the stopper goes under the bar. This can maintain the mount position of the recording head cartridge IJC even though an accidental force, which acts upwards or downwards and makes the recording head cartridge deviate from the mount position, acts on the recording head cartridge. The ink tank IT encloses the recording head unit IJU except for a bottom aperture of the recording head cartridge IJC in cooperation with the cover 800 which covers the recording head unit IJU after the unit IJU is installed to the ink tank IT. When the recording head cartridge is mounted on the carriage HC, the bottom aperture, however, is proximately to the carriage HC so that all slides of the recording head unit is substantially covered. Consequently, heat radiated from the recording head IJH into the enclosed space is available for a heat insulating of the enclosed space, but the temperature of the enclosed space slightly rises after a long-period operation. In this embodiment, on a top surface of the recording head cartridge is provided a slit 1700 which is narrower than the enclosed space in widths and promotes natural heat radiation mainly from the supporting plate, as shown in Figs. 5 and 6. The slit prevents the heat rise and keeps the uniformity of temperature distribution of the whole recording head unit IJU regardless of an environment around the recording head unit. In the recording head cartridge IJC, as shown in Fig. 5, ink goes out of the ink tank IT, passes through the ink inlet 1200, a hole 320 on the supporting plate 300, an ink inlet on the reversed surface of the ink supplying member 600, and comes into the ink supplying member 600 as shown in Fig. 5. After passing through the inside of the ink supplying member, ink goes into the common liquid chamber of the recording head IJH via the ink guide of the ink supplying member 600, appropriate ink supplying tubes and the ink inlet 1500 on the top plate 1300 of the recording head IJH. As connection portions for communicating ink, for example, a packing such as silicone rubber and butyl rubber is disposed and seals the connection portions to secure the ink liquid paths. In this embodiment, as materials of the top plate 1300, such an anti-ink resin as polysulfone, polyether sulfone, polyphenylene oxide or polypropylene is used. The top plate 1300 is integrally formed with the orifice plate 400 by using a metal mold. As described above, the ink supplying member 600, the top plate and orifice plate integral portion and the ink tank 1000 are integrally molded respectively. Thus, the integral molding makes assembly accuracy very high, and is available for improvement in quality in mass production. Moreover, the number of assembly parts can be reduced as compared with that of the conventional ink jet recording apparatus. Consequently, superior desired features can be secured. In this embodiment of the present invention, as shown in Figs. 5 - 7, after assembling is completed, the upper portion 603 of the ink supplying member 600 forms a slit S in cooperation with an end portion 4008 of an upper portion provided with a slot 1700 of the recording head cartridge. A bottom portion 604 of the ink supplying member 600 forms the same slit S (not shown) in cooperation with a thin metal sheet member 4011 (shown in Fig. 7) which is attached with the cover 800 and extends sideward. These slits prompt heat radiation through the slit 1700, and prevents an unnecessary force exerted on the recording head cartridge IJC from being directly exerted on the ink supplying member 600 and the recording head unit IJU. (III) explanation how to mount the recording head cartridge IJC on the carriage HC In Fig. 8, a platen roller 5000 transports a recording medium P such as paper in a direction from back to front of the drawing. The carriage HC can move along the platen roller 5000. The carriage HC comprises a front plate 4000 of 2mm thickness provided in front of the recording head cartridge IJC mounted, an electrical connection supporting plate 4003 which has flexible sheet 4005 provided with a pad 2011 corresponding to a pad 201 on a wiring board 200 of the cartridge IJC and a rubber pad sheet 4007 having an elastic force to press the flexible sheet 4005 onto the each pad 2011 from the back surface of the flexible sheet, and a positioning hook 4001 for fixing the recording head cartridge IJC to a predetermined position. The front plate 4000 has two positioning projected surfaces 4010 in a direction perpendicular to the drawing of Fig. 8 corresponding to the positioning projections 2500 and 2600 of the supporting plate 300, and is subjected to a vertical force toward the projected surface 4010 when the cartridge IJC is mounted. For this reason, a plurality of reinforcing ribs (not shown) are provided on a surface of the front plate 4000 on the side of the platen roller 5000, in a direction of the vertical force. The ribs are slightly projected by about 0.1mm beyond a front surface position L 5 of the recording head unit IJU (shown in two short dashes lines) when the cartridge IJC is mounted, so that the ribs can protect a front surface of the recording head. The supporting plate 4003 is provided with a plurality of the reinforcing ribs 4004 disposed in a direction perpendicular to the above described ribs. The sideward projections of the supporting plate 4003 which are formed with the reinforcing ribs 4004 becomes lower and lower away from the platen roller in order to incline the cartridge IJC when mounted as shown in hatched lines in Fig. 8. Moreover, in a direction perpendicular to Fig. 8, the supporting plate 4003 has two positioning surfaces 4006 on the side of the positioning hook for exerting a force on the cartridge IJC, corresponding to the two positioning projected surfaces 4010, so that the electrical contact is made stable. The above force is oriented a direction opposite to a direction in which the above two positioning projected surfaces 4010 exert a force on the cartridge IJC. The supporting plate forms a pad contact area between the two positioning projected surfaces 4006. The positioning surfaces 4006 uniquely specify a deformation amount of projections on the projection-attached rubber pad sheet 4007 corresponding to the pads 2011. The two positioning surfaces 4006 come in contact with a surface of the wiring board 200 (see Fig. 5) when the cartridge IJC is fixed to a recording enabled position in the carriage HC. In this embodiment, the pads 201 on the side of wiring board 200 are distributed symmetrically with the above described line L 1 , so that the deformation amount of the projections of the rubber pad sheet 4007 is made uniform to stabilize a contact pressure between the pads 2011 and the pads 201. In this embodiment, the pads 2011 are disposed in an arrangement pattern in which there are upper two lines, lower two lines and two rows. The positioning hook 4001 has a slot 4001G which engages with a guide shaft 4009. Positioning of the recording head cartridge IJC for the carriage HC is performed by turning the hook 4001 counterclockwise from a position shown in Fig. 8 and then by moving the hook 4001 to the left parallel with the platen roller 5000 by using a space of the slot 4001G. The hook 4001 can be moved by any device, but it is preferable to use a lever or the like. In any case, when the hook 4001 turns counterclockwise, the recording head cartridge IJC moves toward the platen roller 5000, and moves to a position in which the positioning projections 2500 and 2600 can be in contact with the positioning projected surfaces 4010 of the front plate 4000. Then, a hook engaged surface 4002 closely contacts a surface of a finger 2100, and turns the recording head cartridge IJC horizontally around a contact area formed with the positioning projection 2500 and the positioning surface 4010. Eventually, the pads 201 starts contacting the pads 2011. As a result, when the positioning hook 4001 is held to a predetermined fixed position, the pad 201 completely contacts the pad 2011, and the positioning surface 2500 completely contacts the positioning projected surface 4010, and the engaged surface 4002 contact the surface of the finger 2100, and the wiring board 200 completely contacts the positioning surface 4006 at the same time. Finally, the recording head cartridge IJC has been completely held by the carriage HC. Removal of the recording head cartridge IJC can be performed by using the reverse operation of the hook 4001. (IV) outline of the ink jet recording apparatus IJRA Fig. 9 is a schematic perspective view of the ink jet recording apparatus IJRA in accordance with the present invention. A driving force by a driving motor 5013 is transmitted to a leadscrew 5005 via a transmission gear 5011, 5009, so that the leadscrew 5005 an rotate forwardly or reversely according to a forward or a reverse rotation of a driving motor 5013. The carriage HC can move in both directions indicated by arrows 'a' and 'b' by engaging a pin of the carriage HC (not shown) with a slot 5004 formed on the leadscrew 5005. Reference numeral 5002 is a paper pressure plate which presses a sheet of paper P as a recording medium such as paper onto the platen roller 5000. Reference numerals 5007 and 5008 denote a photo sensor, which detects the home position or the like on the movement of the carriage HC by detecting a lever 5006 of the carriage. Reference numeral 5016 denotes a supporting member of a cap 5022 which caps a front surface of the recording head. Reference numeral 5015 denotes sucking means. The sucking means can make the inside of the cap 5022 a negative pressure to suck ink in the vicinity of the orifices of the recording head through an aperture 5023 in the cap, so that an ejection recovery operation of the recording head is performed. Reference numeral 5017 denotes a cleaning blade and reference numeral 5019 denotes a member for moving the cleaning blade 5017 back and forth. The member 5019 is supported by a supporting plate 5018. It is clear that a well-known cleaning blade is also available for this embodiment. The cleaning blade 5017 and the member 5019 are supported by the apparatus supporting plate 5018. A lever 5021 for starting the suction operation moves according to the movement of a cam 5020 which engages with the carriage HC, so that the lever 5021 controls a change-over of a clutch for changing over the transmission of the driving force of the driving motor. When the carriage HC comes to the home position area, the capping, the cleaning and the ejection recovery operations can be performed at their predetermined positions according to the rotation of the leadscrew 5005. In the case where the configuration is made so that a desired operation may be performed with a predetermined timing, any of the above three operations, however, is applicable to this embodiment. In the above embodiment, an integral configuration of the ink tank and the recording head unit has been explained. It, however, is allowable that the ink tank and the recording head unit are separated and are incorporated as a head cartridge. As shown in Fig. 10, the recording head cartridge IJC can be separated into the ink tank IT and the head unit IJU. When these two portions are integrally incorporated, a projected connector 1200C, Which is provided on a side surface of the ink tank IT and includes an ink communicating portion, is closely connected to a recessed connector (not shown), which is provided on the recording head unit IJU and corresponds to the above projected connector 1200C. This allows ink to be supplied from the ink tank IT to the recording head unit IJU. Moreover, besides the above connectors, a plurality of projected portions 1800B provided on the side surface of the ink tank are closely connected to recessed portions (not shown) which are provided on the recording head unit IJU and correspond to the above projected portions. This enables the ink tank IT to be connected to the recording head IJU securely. The connector 1200C on the ink tank IT and the recessed connector on the recording head unit IJU allow ink to easily flow when connected, and prevents ink from leaking out when disconnected. When ink is used up in the ink tank IT, the ink tank has only to be exchanged by using the separable configuration described above. Incidentally, the recording head cartridge having the above separable configuration is apparently formed by using ink tanks which are described in embodiments shown below. Fig. 11 shows an example of the ink jet recording apparatus with the separable head, cartridge shown in Fig. 10. In this configuration, since portions other than the separable head cartridge are the same as those of the apparatus in Fig. 9, the explanation is omitted According to the present invention, besides the above configurations, various configurations can be made as shown below. Fig. 12 is a plan view partly in section, showing a recording head cartridge of another embodiment. In this embodiment, the inside of an ink tank is divided by a plurality of separation walls 900, and each portion is provided with a movable wall 950. The configuration is similar to that of first embodiment shown in Fig. 4A. It is assumed that an area through which each movable wall 950 contacts ink is 'S', an ink pressure head to each movable wall 950 is 'h', a static friction force at a slide portion of each movable wall 950 is 'F', and the limit on the holding force of an ink tank IT is within -15gw. In Fig. 12 , e.g., it is also assumed that an internal wall of a cartridge case 1000 is divided into 6 portions by the separation wall 900 and an area through which the movable wall 950 contacts ink is 1.5cm 2 , and ink is filled in an ink tank. In this case, when the pressure head of ink which is received by the movable wall 950, is 3gw, the static friction force F of the movable wall is obtained by expression: 4.5gw < F < 20gw The present invention achieves distinct effect when applied to a recording head or a recording apparatus which has means for generating thermal energy such as electrothermal transducers or laser light, and which causes changes in the ink by the thermal energy so as to eject ink. This is because such a system can achieve a high density and high resolution recording. A typical structure and operational principle thereof is disclosed in U.S. patent Nos. 4,723,129 and 4,740,796, and it is preferable to use this basic principle to implement such a system. Although this system can be applied either to on-demand type or continuous type ink jet recording systems, it is particularly suitable for the on-demand type apparatus. This is because the on-demand type apparatus has electrothermal transducers, each disposed on a sheet or liquid passage that retains liquid (ink), and operates as follows: first, one or more drive signals are applied to the electrothermal transducers to cause thermal energy corresponding to recording information; second, the,thermal energy induces sudden temperature rise that exceeds the nucleate boiling so as to cause the film boiling on heating portions of the recording head; and third, bubbles are grown in the liquid (ink) corresponding to the drive signals. By using the growth and collapse of the bubbles, the ink is expelled from at least one of the ink ejection orifices of the head to form one or more ink drops. The drive signal in the form of a pulse is preferable because the growth and collapse of the bubbles can be achieved instantaneously and suitably by this form of drive signal. As a drive signal in the form of a pulse, those described in U.S. patent Nos. 4,463,359 and 4,345,262 are preferable. In addition, it is preferable that the rate of temperature rise of the heating portions described in U.S. patent No. 4,313,124 be adopted to achieve better recording. U.S. patent Nos. 4,558,333 and 4,459,600 disclose the following structure of a recording head, which is incorporated to the present invention: this structure includes heating portions disposed on bent portions in addition to a combination of the ejection orifices, liquid passages and the electrothermal transducers disclosed in the above patents. Moreover, the present invention can be applied to structures disclosed in Japanese Patent Application Laying-open Nos. 123670/1984 and 138461/1984 in order to achieve similar effects. The former discloses a structure in which a slit common to all the thermoelectric transducers is used as ejection orifices of the electrothermal transducers, and the latter discloses a structure in which openings for absorbing pressure waves caused by thermal energy are formed corresponding to the ejection orifices. Thus, irrespective of the type of the recording head, the present invention can achieve recording positively and effectively. The present invention can be also applied to a so-called full-line type recording head whose length equals the maximum length across a recording medium. Such a recording head may consists of a plurality of recording heads combined together, or one integrally arranged recording head. In addition, the present invention can be applied to various serial type recording heads: a recording head fixed to the main assembly of a recording apparatus; a conveniently replaceable chip type recording head which, when loaded on the main assembly of a recording apparatus, is electrically connected to the main assembly, and is supplied with ink therefrom; and a cartridge type recording head integrally including an ink reservoir. It is further preferable to add a recovery system, or a preliminary auxiliary system for a recording head as a constituent of the recording apparatus because they serve to make the effect of the present invention more reliable. As examples of the recovery system, are a capping means and a cleaning means for the recording head, and a pressure or suction means for the recording head. As examples of the preliminary auxiliary system, are a preliminary heating means utilizing electrothermal transducers or a combination of other heater elements and the electrothermal transducers, and a means for carrying out preliminary ejection of ink independently of the ejection for recording. These systems are effective for reliable recording. The number and type of recording heads to be mounted on a recording apparatus can be also changed. For example, only one recording head corresponding to a single color ink, or a plurality of recording heads corresponding to a plurality of inks different in color or concentration can be used. In other words, the present invention can be effectively applied to an apparatus having at least one of the monochromatic, multi-color and full-color modes. Here, the monochromatic mode performs recording by using only one major color such as black. The multi-color mode carries out recording by using different color inks, and the full-color mode performs recording by color mixing. Furthermore, the ink jet recording apparatus of the present invention can be employed not only as an image output terminal of an information processing device such as a computer, but also as an output device of a copying machine including a reader, as an output device of a facsimile apparatus having a transmission and receiving function, and as an output device of an optical disc apparatus for recording and/or reproducing information into and/or from an optical disc. These apparatus requires means for outputting processed information in the form of hard copy. Fig. 13 schematically illustrates one embodiment of a utilizing apparatus in accordance with the present invention to which the ink jet recording system shown in Fig. 9 is equipped as an output means for outputting processed information. In Fig. 13, reference numeral 10000 schematically denotes a utilizing apparatus which can be a work station, a personal or host computer, a word processor, a copying machine, a facsimile machine or an optical disc apparatus. Reference numeral 11000 denotes the ink jet recording apparatus (IJRA) shown in Fig. 9. The ink jet recording apparatus (IJRA) 11000 receives processed information form the utilizing apparatus 10000 and provides a print output as hand copy under the control of the utilizing apparatus 10000. Fig. 14 schematically illustrates another embodiment of a portable printer in accordance with the present invention to which a utilizing apparatus such as a work station, a personal or host computer, a word processor, a copying machine, a facsimile machine or an optical disc apparatus can be coupled. In Fig.14 , reference numeral 10001 schematically denotes such a utilizing apparatus. Reference numeral 12000 schematically denotes a portable printer having the ink jet recording apparatus (IJRA) 11000 shown in Fig. 9 is incorporated thereinto and interface circuits 13000 and 14000 receiving information processed by the utilizing apparatus 11001 and various controlling data for controlling the ink jet recording apparatus 11000, including hand shake and interruption control from the utilizing apparatus 11001. Such control per se is realized by conventional printer control technology.

Claims: An ink storage unit for use in an ink jet recording apparatus for recording by ejecting ink, comprising: an ink storage chamber (910A) for storing ink and for supplying ink along an ink path to an ink jet head; and a movable wall (950) provided in the ink storage chamber and contacting the wall of the ink storage chamber so as to seal the ink stored therein against air, the movable wall being movable in response to a change in the amount of stored ink and the contact between the movable wall and the chamber wall exerting on the movable wall a friction force opposing movement of the movable wall, thereby enabling a negative pressure to be maintained in the chamber, characterized in that the interior of the unit is divided into a plurality of ink chambers (910A) each of which is connected to the same ink path for supplying ink to a single ink jet head and a movable wall (950) is provided in each chamber so as to contact the wall of the chamber and seal the ink stored therein against air, each movable wall (950) being movable in response to a change in the amount of stored ink and the contact between the movable wall and the wall of the associated chamber generating a friction force to oppose the force exerted on the movable wall by a change in the amount of stored ink so as to maintain a negative pressure in the chamber. An ink storage unit according to claim 1, wherein each movable wall is made from a resilient material and is compressed by contact with the wall of the associated chamber. A unit according to claim 1 or 2, wherein each movable wall is made of silicone rubber. A unit according to any one of the preceding claims, wherein the materials and dimensions of each said movable wall are so selected, in accordance with the negative pressure exerted within said ink storage chamber (910A) that movement of said movable wall (950) is smooth and without discontinuities caused by friction. A unit according to any one of the preceding claims, wherein the frictional contact between each movable wall (950) and the wall (900) of the associated chamber is arranged to generate within said chamber a negative pressure smaller than the suction force generated in use of the unit when the recording head is refilled with ink after ink has been supplied from the unit for recording. A unit according to any one of the preceding claims, wherein the contact between the movable wall (950) and the wall (900) of each chamber is arranged to generate a friction force such that the combined force applied by atmospheric pressure and the friction force is equal to or greater than the sum of the weight of the movable wall (950) and the weight of ink to be applied thereto. A unit according to any one of the preceding claims, wherein the walls (900) of the chambers are formed of a resinous material. A unit according to any one of the preceding claims, wherein the cross-sectional area of the ink storage chambers gradually increases. A unit according to any one of the preceding claims and integrally formed with a recording head unit (150). An ink jet recording apparatus comprising: an ink storage unit as claimed in any one of the preceding claims; an ink supplying portion for supplying ink from said ink storage chamber to an ink ejection head (IJC); and a carriage (HC) provided for mounting said ink ejection head and said storage unit. A unit according to claim 9 or an apparatus according to claim 10, wherein said ink ejection head is arranged to use heat energy to generate a bubble to cause ejection of ink. A unit according to any one of claims 1 to 9, wherein said friction force F satisfies a following expression: S . h < F < 20 gw where S is an area through which the movable wall is in contact with the ink in the chamber and h is a pressure head of the ink in the chamber.

Inventors: AONO KENJI, HATTORI YOSHIFUMI, KAWANO KENJI, KITANI MASASHI, KOJIMA MASAMI, SAIKAWA HIDEO, SUZUKI ETSURO, TANNO KOICHI, AONO, KENJI, HATTORI, YOSHIFUMI, KAWANO, KENJI, KITANI, MASASHI, KOJIMA, MASAMI, SAIKAWA, HIDEO, SUZUKI, ETSURO, TANNO, KOICHI, Aono, Kenji, c/o Canon Kabushiki Kaisha, HATTORI, YOSHIFUMI, C/O CANON KABUSHIKI KAISHA, Kawano, Kenji, c/o Canon Kabushiki Kaisha, KITANI, MASASHI, C/O CANON KABUSHIKI KAISHA, KOJIMA, MASAMI, C/O CANON KABUSHIKI KAISHA, SAIKAWA, HIDEO, C/O CANON KABUSHIKI KAISHA, Suzuki, Etsuro, c/o Canon Kabushiki Kaisha, TANNO, KOICHI, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: B41J2
IPC codes: B41J2