Ink jet head, ink tank and ink jet apparatus

Abstract: This invention relates to an ink jet recording apparatus comprises an ink jet head having an ink path communicating with a discharge opening for discharging ink; electrodes arranged in said ink path; a residual ink quantity detection means for detecting residual ink quantity in said ink path in accordance with a resistance value, current value or voltage value from said electrodes; and a correction means for correcting said resistance value, current value or voltage value in accordance with the difference in a resistance of the ink.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an ink jet head, ink tank and ink jet apparatus capable of preventing an erroneous detection due to change of ink component and having an improved ink residual quantity detecting means. Related Background Art Conventional means for detecting residual ink quantity used in ink jet recording apparatus are generally divided into following three groups: (1) Detection means wherein the residual ink detection is performed by detecting the change in resistance turned ON or OFF in accordance with the presence or absence of ink between two electrodes; (2) Detection means wherein the residual ink detection is performed by detecting the analogous change in volume of ink between two electrodes; and (3) Detection means wherein the residual ink detection is resistance residing in an absorbent between two electrodes. However, in conventional ink jet recording apparatuses, when different color inks or different type of inks (for use with plain paper or coated paper or OHP transparency for OHP (overhead projection) (referred "TP" hereinafter)) was used with the same single residual ink detection means, there arose a problem of erroneous detection because the volume resistance of ink varies or changes in accordance with changes in ink components (caused when the kind of dye and/or kind of solvents and/or ratio of composition are different). Generally, the ink tank is constructed in the form of cartridge which is exchanged when the ink is consumed, but when a variation among cartridges exists, there is a fear that the detection accuracy might decrease in the constructuion in which residual quantity detection is effected by comparing the resistance value between the electrodes with the basic or reference value. Such disadvantage is caused by variation of the absorbing member in the cartridge having the absorbing member and making the ink impregnated thereinto for preventing the solution of gas and leakage of ink generated vibration of the ink by shock upon transportation or the like. Recently, the skill for making the recording head and ink tank into cartridge-like construction (cartridge) has been developed, since the recording head can be manufactured cheaply or at low cost by using an electric-thermal converting member as an energy generating element for ink discharge. It is advantageous to impregnate the ink into the absorbing member because the ink head pressure (pressure generated at the discharge opening by a liquid head difference) at the discharge opening of recording head can be stabilized. However, there is fear that the accuracy of detection of the residual ink quantity might decrease when the residual ink quantity is judged by comparison of the resistance value between the electrodes with the uniform reference value, because air bubbles occur upon the ink discharge, in addition to the above variation of absorbing members. US-A-4196625 describes a device for monitoring the supply of electrically conductive recording fluid in a supply container for an ink recording device wherein a circuit arrangement is provided which detects the electrical resistance between electrodes wetted by the recording fluid and triggers a display device when the amount of recording fluid falls below a specific volume. A plurality of electrodes are provided within the recording fluid container, two of which electrodes define therebetween a fluid-specific standard resistance provided by the recording fluid. An object of the present invention is to prevent occurrence of erroneous detection and to provide an ink jet recording head, ink tank and ink jet recording apparatus in which various qualities have been improved. Another object of the present invention is to provide the ink tank and ink jet recording head capable of effecting the residual ink quantity detection of high accuracy and stability with relatively simple construction. In one aspect, the present invention provides an ink jet recording apparatus in accordance with claim 1. The present invention also provides an ink jet head in accordance with claim 17 and an ink tank in accordance with claim 19. An embodiment of the present invention provides an ink jet recording apparatus comprising, an ink jet head having an ink path communicating with a discharge opening for discharging ink; electrodes arranged in said ink path; a residual ink quantity detection means for detecting residual ink quantity in said ink path in accordance with a resistance value, current value or voltage value from said electrodes; and a correction means comprising a correction resistance which is not in contact with the ink for correcting said resistance value, current value or voltage value in accordance with the volume resistance of the ink. An embodiment of the present invention provides an ink jet recording apparatus comprising, an ink tank for storing ink to be supplied to an ink jet head; electrodes arranged in said ink tank; a residual ink quantity detection means for detecting residual ink quantity in said ink tank in accordance with a respective value, current value or voltage value from said electrodes; and a correction means comprising a correction resistance which is not in contact with the ink for correcting said resistance value, current value or voltage value in accordance with the volume resistance of the type of ink. An embodiment of the present invention provides an ink jet head comprising an ink path communicating with an ink discharge opening for discharging ink; electrodes arranged in said ink path, and a correction means comprising a correction resistance which is not in contact with the ink for correcting a resistance value, current value or voltage value sent to a residual ink quantity detection means for detecting residual ink quantity in said ink path, in accordance with the volume resistance of the type of ink. An embodiment of the present invention provides an ink tank comprising an ink storing portion for storing ink to be supplied to an ink jet head, electrodes arranged in said ink storing portion, and a correction means comprising a correction resistance which is not in contact with the ink for correcting a resistance value, current value or voltage value sent to a residual ink quantity detection means for detection residual ink quantity in said ink storing portion, in accordance with the volume resistance of the type of ink. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross section showing one example of an ink jet recording apparatus including an ink jet recording cartridge according to the present invention; Figs. 2 and 4 are graphs showing relation between the residual ink quantity and resistance between electrodes; Figs. 3 and 5 are drawings showing detecting circuits for residual ink quantity; Figs. 6 and 7 are schematic cross section and perspective views showing another embodiment of the ink jet recording cartridge according to the present invention; Fig. 8 is a schematic perspective view showing another embodiment of the ink jet recording cartridge according to still another embodiment of the present invention; Fig. 9 is a schematic cross sectional view showing an ink jet recording cartridge included for illustrative purposes and not falling within the scope of the invention claimed; Fig. 10 is a graph showing relation between the residual ink quantity and resistance between electrodes; Fig. 11 is a schematic perspective view showing still another embodiment of the ink jet recording cartridge according to the present invention; Fig. 12 is a schematic drawing showing an example of ink jet recording apparatus including an ink tank according to the present invention; Fig 13 is a schematic cross section showing still another example of the ink jet recording apparatus including the ink jet recording cartridge; Fig. 14 is a graph showing the relation between the residual ink quantity and resistance between electrodes; Fig. 15 is a still another graph showing relation between the residual ink quantity and resistance between electrodes resulting from variation the ink jet recording cartridge; Fig 16 is a drawing showing still another example of detecting circuit of residual ink quantity; Fig. 17 is a flow chart showing an operational sequence for the detecting circuit shown in Fig. 16; Fig. 18 is a drawing showing still another example of detecting circuit of residual ink quantity; Fig. 19 is a perspective view showing an ink jet recording apparatus according to the present invention. Apparatus embodying the present invention aims to correct for the resistance value change of ink due to difference of color i.e. dye or the like by using correcting means provided on a residual quantity detecting apparatus with respect to resistance value from the electrode for residual quantity detection. In apparatus embodying the invention, even if the ink having different component is used in the same or common head, residual quantity detection can be effected accurately. In apparatus embodying the invention, the proper threshold can be determined for the ink supply source, so highly accurate detection of residual ink quantity can be effected without being affected by variations of the ink tank including an ink absorbing member. Incidently, residual quantity detection can be carried out at the head side or the tank side. In addition, in order to prevent generation of waves on an ink liquid surface due to vibration or shock upon movement of the carriage, it is possible to insert the absorbing member into the head and ink tank. In the correcting circuit, an element having equivalent resistance change can be added for correction. Furthermore, temperature of the printing apparatus and ink monitored can be corrected corresponding to resistance change of the ink due to temperature, which can lead to more accurate residual quantity detection. Embodiment 1 Fig. 1 is a schematic view showing a disposable ink jet recording cartridge. On the cartridge, a recording head tip 1 and an ink tank 9 can be removably mounted. This cartridge is constructed so that the head pressure in the head tank 9 by single can be adjusted so as not to apply water head pressure onto the recording head tip 1 by inserting the absorbing member 6-2 into the ink tank 9. The recording head permits the recording or printing in the downward direction. In Fig. 1, the reference numeral 1 denotes the above-mentioned recording head tip; and 2 denotes an ink discharging portion having the ability for discharging ink and including an ink discharge opening 2a and an ink path provided with energy generating means for generating thermal energy used for discharging ink droplets and communicated with the discharge opening. The reference numeral 3 denotes a liquid chamber for temporally storing ink to be supplied to the ink discharging portion; 4 denotes a flow passage for supplying ink to the liquid chamber; and 5 denotes a filter for removing bubbles and/or dust and the like. The reference numeral 6-1 denotes the above-mentioned absorbent made of porous material or fiber material, and pin-shaped residual ink quantity detection electrodes 7a, 7b and 7c are arranged in the recording head wall to be inserted into the absorbent member 6-1. These elements constitute the recording head tip 1. The reference numeral 9 denotes the above-mentioned ink tank, within which the above-mentioned absorbent 6-2 and ink 10 are accommodated. 9a is a hole formed on the ink tank to be communicated with atmosphere. The ink tank 9 and the recording head tip 1 are removably combined with each other through insertion pins 8 and the like. In order to prevent the leak of the ink, O-ring 13 is provided. It is so designed that, when the ink tank 9 itself is stored, the ink therein does not leak from the ink tank, but, when it is combined with the recording head tip, the ink can flow from the ink tank to the recording head tip via an ink supplying part 13a. Next, an electrical connection between the ink jet recording cartridge and a body of the recording apparatus itself will be explained. Although not shown in Fig. 1, as shown in Fig. 7, the recording head tip has a wiring member 11 (referred to as "lead frame" hereinafter) constituted by a plurality of plate-shaped conductors arranged side by side, and the reference numeral 12a, 12b and 12c (Fig. 3) denote electrodes incorporated into the lead frame 11 to detect the residual ink quantity (described later) and connected to the residual ink quantity detection means having a correction means for correcting the resistance at the main body side in accordance with the difference in the ink composition. The lead frame 11 is embedded in a casing made of, for example, resin, and the electrodes 12 correspond to the residual ink quantity detection electrodes 7, respectively, so that the residual ink quantity detection electrodes 7 are exposed into the absorbent 6-1 to measure the ink resistance value, for example, between the electrodes 7a and 7b thereby detecting the residual ink quantity. Next, the concrete method for detecting the residual ink quantity will be explained. When the amount or quantity of the ink in the ink tank 9 is reduced by consuming the ink in the ink tank 9 during the recording or printing operation and/or the ink recovery operation, the quantity of the ink included in the absorbent 6-1 is also reduced, with the result that small bubbles are introduced into the absorbent to gradually increase the electrical resistance between the electrodes 7a and 7b. Consequently, it is possible to detect the fact that the residual ink quantity reaches its lower limit, by detecting the reduction of the current between the electrodes. By monitoring the value of such current, it is possible to know the relation between the residual ink quantity ℓ and the resistance of the ink R (between the electrodes). In Fig 2, the curves A, B, C and D show the difference in the ink colors (the difference in the dye), and the curves A, B, C, and D and E correspond to black ink (dye density of 3.0%), red ink (dye density of 2.5%), blue ink (dye density of 2.5%), green ink (dye density of 2%) and fresh tint ink (dye density of 2.5%), respectively. As seen from Fig. 2, since the respective volume resistance of the ink varies in accordance with the color thereof, in the case a detection lamp is turned on by activating the residual ink quantity detection means whenever the same resistance value R R is obtained between the electrodes 7a and 7b to detect the residual ink quantity therebetween, there will arise the difference in the residual quantity for each ink A, B, C and D, thus leading the an unfavorable result. In order to activate the residual ink quantity detection means when a certain predetermined residual quantity is reached for any ink A, B, C or D, it is desirable that the detection lamp regarding the residual quantity detection electrodes is turned on when the resistance value R R is obtained, by correcting the curves (Fig. 2) wholly by changing a correction resistance R C in the residual quantity detection circuit at a main body side shown in Fig. 3 to vary the difference in the resistance values between the inks A, B, C and D (for example, when the ink D having a low resistance value is used, by increasing the correction resistance R C to increase an apparent resistance (R = ρ · ℓ/s; here, ρ is specific resistance, ℓ is length, s is area) of the ink D). On the other hand, if the ink A having a high resistance value is used, the detection lamp may be turned on when the resistance value R R is obtained by correcting the curves wholly by decreasing the correction resistance R C to decrease the apparent resistance of the ink A. Further, as to the ink E having the different resistance value, similarly, the correction resistance R C may be changed to obtain the same residual quantity in response to the resistance value R R . In this case, it is desirable to combine the residual quantity detection electrodes so that they are positioned to overlap in the gravity direction (The electrodes may he arranged along the oblique direction). Fig. 4 shows graphs indicating the resistance values measured in the vertical direction and in the horizontal direction. In the apparatus shown in Fig. 1, the resistance between the electrodes 7a and 7b may be detected. However, when the apparatus is arranged in the horizontal direction, the resistance between the electrodes 7b and 7c may be detected. Further, it should be noted that the distance between the electrodes 7 is shifted in the α direction when the distance is long or in the β direction when the distance is short. Each of the electrodes is preferably coated by high anti-corrosive layer such as SUS, gold-plating, platinum and the like. Incidentally, the distance between the electrodes varies in accordance with the structure of the absorbent 6-1 of the head tip, and is preferably about 5 - 30mm. In this case, the resistance of the ink has a value included in a range between a few tens of kΩ. In the printing or recording apparatus for peforming the printing operation by using such ink jet recording cartridge, the following test was carried out. That is to say, after the residual quantity detection lamp has once been turned ON, the ink C was replaced by the ink B. Thereafter, the correction resistance R C was manually varied to obtain a predetermined resistance value (in this example, while the correction resistance was varied manually, it may be varied automatically by using an appropriate means), and the residual quantity detection lamp was turned ON again. In this condition, the residual ink quantities in the two ink tanks was determined. As a result, it was found that there was substantially no difference in the residual quantities of the inks C and B in the ink tanks. However, when the ink is replaced by the different ink, it is desirable that the printing operation is started after the color of the old ink has been completely removed in the apparatus by repeating the recovery sequences regarding the new ink by predetermined times. With the arrangement as mentioned above, it is possible to correctly detect the residual ink quantity by performing the same operation as mentioned above even if the ink tanks are changed on the way of the printing cycles. Further, the residual ink quantity detection circuit adopted to the present invention may be constituted as shown in Fig. 5, since, when the circuit is always being energized, there is the danger of generating the bubbles due to the electrolysis of the ink. In this way, it is possible to perform one measurement for a short time, and also it is possible to completely avoid the generation of the bubbles due to the electrolysis of the ink by reversing the polarity for each measurement. The time required for one measurement is in the order of a few msec. Further, by providing pins for discriminating or detecting the difference in the colors at the cartridge side and by communicating the pins with the main body after mounting the cartridge on the apparatus, the correction resistance may be changed. Embodiment 2 Figs. 6 and 7 are sectional view and perspective view, respectively, of an ink jet recording cartridge (the second embodiment) of the present invention. In this second embodiment, by providing the correction resistance R C in a detection portion at the main body side, the difference in the resistance of the ink due to the difference in the composition of the ink, i.e., the difference in mixture ratio of the solvent is corrected, whereby the resistance output feature of the recording apparatus is standardized. Fig. 6 shows a disposable ink jet recording cartridge. Also on this cartridge, the recording head tip 1 and the ink tank 9 can be removably mounted. Since this cartridge does not include an absorbent in the ink tank, the head pressure of the tank must he maintained by the meniscus at the discharge openings of the discharging portion. Accordingly, this cartridge is used in the recording apparatus which permits the recording in the horizontal direction. The mounting and dismounting of the cartridge can he performed in the same manner as the previously described first embodiment. The features of the cartridge of the second embodiment are the fact that the absorbent is not included also at the recording head tip side and that the plate-like residual ink quantity detection electrodes 7A and 7B are arranged in an ink supplying chamber so as to detect the ink resistance between the electrodes 7A and 7B varied in accordance with a height h of the ink surface as shown in Fig. 7, thereby detecting the residual ink quantity. For example, since the compositions of the optimum inks for the plain paper, coated paper, TP and the like are different from each other, the resistance values of these inks are also different from each other. As for such difference in the resistance value, by changing the correction resitance R C to always maintain the apparent resistance value to the constant value, it is possible to correctly detect the residual ink quantity even if the inks are changed. In the illustrated embodiment, while the correction circuit was provided at the main body side, the correction may be effected by any circuit equivalent to the ink. Further, while the variable correction resistance was used, the correction may be effected by changing over resistors connected in series or in parallel to each other. Next, an ink jet recording apparatus according to a third embodiment of the present invention will be explained. Embodiment 3 Fig. 8 is a perspective view showing the third embodiment of the present invention. In this embodiment, a full color printing can be performed by using four ink jet recording heads. In order to perform the full color printing, although four kinds of inks, i.e., cyan ink, magenta ink, yellow ink and black ink must be used, if four residual quantity detection means suitable to the respective ink colors are incorporated in each of four recording heads, the whole ink jet recording apparatus will be very expensive. Accordingly, in the whole ink jet recording apparatus will be very expensive. Accordingly, in the third embodiment, although the head side may be identical with those of the previous embodiments, the main body side is so designed that the signal values from the respective inks C (cyan), M (magenta), Y (yellow) end K (black) are corrected so that the detection lamp is turned ON when the residual quantities of the inks C, M, Y and K are the same. Since each ink tank can be replaced by a new one independently, the ink in the ink tank can be used at its maximum extent without the erroneous detection, thus permitting the reduction of the running cost of the apparatus. Further, if plurality of recording heads are used, it is possible to prevent the damage of the heads due to the introduction of the bubbles into the discharging portions of the heads caused by the erroneous detection. Fig. 9 is a schematic view of the ink jet recording cartridge of disposable type included for illustrative purposes and not falling within the scope of the invention claimed. In the cartridge shown in Fig. 9, by changing position of the electrode for residual quantity detection of the head side relative to the resistance change of ink resulting from difference of the ink i.e. dye, the resistance correction based on distance is carried out to equalize the resistance output characteristics to the main body of printing apparatus. This arrangement differs from the above Embodiment 1 in the construction that the pin-like electrodes 17a, 17b, 17c, 17d and 17e for ink residual quantity detection are provided on the wall of recording head wall so that they are inserted into the ink absorbing member 6-1 made of porous or fiber like material. Explanation of another element similar to the above Embodiment 1 is omitted by adding same or corresponding numeral for clarification. Next, concrete method of ink residual quantity detection of this cartridge will be explained. In order to achieve the residual quantity detection at predetermined level for each of inks A, B, C and D, the resistance value difference of the inks A, B, C and D are changed by a changing apparatus. For example, in the case using the ink D of low resistance value, the distance between electrodes is selected long to thereby set the apparent resistance R = P ℓ / S (P : resistance ratio, ℓ : length. S : area). Consequently, the curve is entirely corrected to turn on the residual quantity detection when the resistance value is R B . On the other hand, when using the ink A of high resistance value, the distance between electrodes is selected short to set the apparent resistance small. Consequently, the apparent resistance is corrected entirely so that the residual quantity detection will be operated when resistance value is R B . For the ink E of different resistance value variation, the position of electrodes are combined so that residual quantity becomes equal when the resistance is R B . Preferably they are combined in upper-lower relation (oblique positioning is possible) with respect to the gravity direction. The graph obtained by measuring the resistance value in the vertical and horizontal directions relative to the gravity direction is shown in Fig. 10. It is needless to say, the interval of detecting electrode is shifted to α direction or β direction as the distance becomes longer or shorter. In the printing apparatus printing with this cartridge, the ink C is exchanged to ink B after turn on of the ink residual quantity detecting lamp, the electrode position is exchanged from 17a - 17e to 17a - 17d. The lamp is turned on again, and residual ink quantity is detected to reach the result that there is found no difference therebetween. In connection with this, it is preferable to absorb and replace the ink by a constant recover sequence after the ink is replaced by another ink, and carry out printing after the color change has been completely finished. Furthermore, more accurate residual quantity detection become possible by adding the above process even in the course of ink tank exchange in the printing process. Embodiment 4 A fourth embodiment of the present invention will be explained with reference to Figs. 6 and 11. In this embodiment, the resistance value change or variation due to difference of mixing ratio of the soluble agent i.e. difference of composition the ink is corrected by adding a correcting resistance R C at a detecting portion of the head cartridge, so that the resistance output characteristic to the main body of printer becomes equal. In this embodiment, the residual quantity detection is effected by detecting the ink resistance between the electrodes 7A and 7B. However, by making the correcting resistance R C provided on the cartridge changeable relative to resistance value variation due to the ink component, it becomes possible to keep the artificial resistance value constant thereby accurate residual quantity becomes possible as for the ink exchange. In the above embodiment, the simple correcting circuit is added to the head cartridge, but the correction can be made by a circuit equivalent to the ink. Additionally, although variable type correcting resistance is used, it is possible to switch the resistances connected in serial or parallel. Switching can be effected manually or automatically. Embodiment 5 Fig. 12 is a schematic view showing a fifth embodiment of the present invention. In this embodiment, the variation of ink resistance value accompanied by change of dye density of ink is overcome by adding the correcting resistance R C to the tank. The ink jet recording apparatus shown in Fig. 12 is constructed as so-called permanent type having life time as long as the main body of apparatus, in which the recording head 1 mounted on the carriage (not shown) and the ink tank 9 is connected via an ink supplying tube 12. 14 shows detecting circuit for ink residual quantity provided the main body of apparatus. This embodiment is constructed so that the bubble may not be entered into the head by reducing the mounting parts of the head portion, increasing responsibility of the head itself and effecting the residual quantity detection at tank side. With such construction, the bad or poor printing (non-discharge) resulted from bubble entry into the discharge portion due to erroneous detection can be prevented. In the above-mentioned first, second and third embodiments, while the resistance value itself was corrected, the current value or voltage value generated in accordance with the change in the ink resistance value may be effected by correction relative to change. Further, the following alternations or modifications may be adopted: analogous detection or digital detection may be used; the changing of the correction resistance may be effected manually or automatically; the recording head may be a disposable type head or a permanent type head having life time equivalent to the main body of apparatus; the electrodes may be arranged at the tank side or at the head tip side; the ink may be accommodated in the tank with or without the absorbent; the correction is not necessarily performed analogously and stagelessly, and, thus, may be changed digitally or may be changed with the use of any conversion table; and the correction may be used for the detection of the residual ink quantity with the change in the ink resistance due to the difference in temperature of the ink caused by the change in the surrounding conditions. Fig. 13 shows an ink jet recording apparatus onto which and from which a cartridge of disposable type, in which the recording head and ink tank are made integral each other, is mountable. In Fig. 13 reference numeral 101 shows a recording head chip corresponding to a main portion of the ink jet recording head, which head chip discharges the ink under movement opposing to a recording medium 120 corresponding to the recording signal. This constant current circuit to be explained in Fig. 16 later. As mentioned above, since there occurs characteristic variation of among each of cartridges as shown in Fig. 15, if the threshold is determined simply as a point P as shown in Fig 15, there occurs variation of residual ink quantity upon detection by ΔP (about 4 g). This corresponds to 200 sheets (A4 size) with standard letter recording, and 40 to 60 sheets with image recording, which leads to deteriorate responsibility of detecting accuracy. For overcoming the above defect, an area R where the recording becomes impossible is obtained by experiment as shown in Fig. 15, limitation that a point Q located just before recording chip is comprised of a print plate 103 having a base plate (heater board) on which the electric-thermal converting member (discharge heater) as discharge energy generating element and wiring parts therefore, and a line 101 of the discharge opening or liquid path corresponding to the discharge heater. An ink tank 102 has an absorbing member 104 made of porous material and impregnated with predetermined quantity of ink, and pair of electrodes for residual ink quantity are inserted into the absorbing member 104. The ink tank portion 102 and ink head chip are connected each other to construct the head cartridge, 107 is a porous filter provided between the ink tank and head chip and having an outer diameter which does not allow the air bubbles to pass easily. For discharge energy generating element such as electric-thermal converting member disposed in the liquid path line 101 and generating energy for ink discharge and pin-like electrode 105 for residual ink quantity detection inserted into the absorbing member 104, the electrodes for realizing the electric connection therewith are gathered in the form of electrode line 111. The electrode line 111 is connected with a connector 112 of the recording apparatus main body side. Upon recording by the recording apparatus on the recording medium 120 conveyed in the F direction by supply roller pair 116 and discharge roller pair 119, a carriage scanning is carried out with the recording medium 120 being pressed onto a guide 118 by a sheet pressing rail 17 via a roller 121 of the carriage 123 which is scanned along a carriage axis 122. The residual ink quantity detection in the ink tank 102 is basically carried out based on resistance value between the electrodes 105. However, there is fear that the residual ink quantity detection can not be carried out accurately by adopting the circuit construction such as resistance dividing method because the relation between residual ink quantity and resistance between electrodes may vary depending on current supplied between both electrodes, as shown in Fig. 14. Here, the residual ink detection is carried out by using the area is selected as the threshold is adopted. In detail, the point on point Q is initially determined corresponding to an initial value of resistance between the electrodes of cartridge, then no ink is judged when the point reaches to a resistance difference, thereafter sequence of the main body is properly controlled and alarm is displayed for an operator. For that, either data of the initial value or threshold (on the line Q) obtained therefrom is read into the non-volatile memory, and held as an information regarding to the cartridge mounted even when power is OFF. Fig. 16 shows an example of detecting circuit for residual ink quantity for achieving the above treatment or process. In Fig. 16, 100 shows the head cartridge of disposal type shown in Fig. 13, 200 shows a controlling portion of microcomputer type having for example a A/D convertor, 300 shows a non-volatile memory comprised of for example EEPROM or the like, 400 is a voltage converting circuit, and 500 shows a displayer and/or alarming portion for alarming the head cartridge to be exchanged when no residual ink is left. Fig. 17 shows one example of treatment sequence according to the residual ink quantity detection by the controlling portion 200, and operation of the circuit shown in Fig. 16 is explained with reference to Fig. 17. The controlling portion 200 makes a I/O port 1 in a residual ink quantity detecting timing (step 1), and makes a transistor Tr3 ON. As a result, a transistor Tr1 is made ON, and a transistor Tr2 will operate. Here, current Io flown into the transistor is represented by Io = (V Z - V BE )/R 1 where V BE respresents voltage for base-emitter, and V Z is a Zener voltage. The constant current thus obtained flows directly between the both electrodes 5 and 10 in the ink tank of head cartridge. Accordingly, corresponding voltage is generated between the electrodes 5 and 10. After waiting of predetermined time period (for example, one second) which is enough for stabilization thereof (step 5), this voltage is put into a A/D converter inputting terminal of the controlling portion 200 directly or via a voltage converting circuit 400 (step 7). Upon completion of A/D conversion (step 9), the controlling portion 200 makes I/O port and transistors Tr1 - Tr3 OFF (step 11), and judge whether this sequence is started by mounting of new cartridge (step 13). As shown in Fig 15, since the curved condition can be recognized from data in which the ink is consumed, upon mounting of new cartridge, the controlling portion 200 calculates the threshold for no ink judgement suitable for the cartridge by A/D conversion value i.e. initial data (step 15), and write it into the non-volatile memory 300 (step 17). In the succeeding detecting timing of residual quantity, presence/absence of residual ink quantity can be judged by simply comparing the threshold calculated upon mounting of new cartridge and stored in the non-volatile memory 300 with the detected residual quantity (step 19). Thus, in the case no ink residual quantity is detected, an alarm is sent to the operator to exchange the head cartridge (step 21), and effect the sequence to interrupt operation of various parts, or the like. Incidentally, it is possible to store only the initial data upon mounting of new cartridge, and calculate the threshold in the succeeding process from the initial data. As mentioned above, even when resistance variation between the electrodes can not be ignored upon detection of the residual ink quantity in the ink tank portion 102, residual quantity detection of high accuracy become possible by calculating the threshold level from which no ink is judged from the intial value of resistance between electrodes by constant current detection, and comparing the data with the substantial detecting data. In addition, as regard to the change of characteristic resulted from difference of ink and composition, response can be made by adjusting the constant current value. Fig. 18 shows another detecting circuit in which members or means corresponding to those of Fig. 16 have the same numerals. In a head cartridge 100, the function corresponding to the switches (SW1 and SW2) is added for classifying the initial variation of the ink resistance. Actually, this can be effected by cutting the pattern formed on the printing plate by laser in assembling process. In this case, the information of classification is constructed by 2 bits, that is, classify the variation into four ranks,.arbitrary predetermined bit number can be adopted, of course. In this case, the non-volatile memory 300 shown in Fig. 16 for storing the threshold or initial data become unnecessary since the classifying informing is given from the head cartridge, which leads to simple construction of the apparatus and low cost for manufacture. Processing sequence substantially same that of Fig. 17 can be adopted but steps corresponding to steps S15, S17 are not necessary because the non-volatile memory 300 is not included, In the example described with reference to Figs. 13 to 18, the ink jet recording apparatus uses a head cartridge made by combining the recording head tip and the ink tank integrally. However, of course, the head tip and ink tank can be made separately, and the recording head tip need not be disposable. In addition above explanation is made for the liquid jet recording apparatus of serial type in which the recording head is scanned relative to the recording medium to effect recording, the present invention can be applied to so-called multitype recording apparatus in which the discharge opening are arranged over the entire width of the recording medium, very effectively and easily. In other words, the present invention can be applied to the recording apparatus in which problem of variation of ink supplying source such as the ink tank occurs. Fig. 19 is a perspective view showing one example of the ink jet recording apparatus according to the present invention, in which 1000 is a main body of apparatus, 1100 is a power source, and 1200 is an operational panel. The present invention brings about excellent effects particularly in a recording head, recording device of the bubble jet system among the ink jet recording system. As to its representative constitution and principle, for example, one practiced by use of the basic principle disclosed in, for example, U.S. Patents 4,723,129 and 4,740,796 is preferred. This system is applicable to either of the so called on-demand type and the continuous type. Particularly, the case of the on-damand type is effective bacause, by applying at least one driving signal which gives rapid temperature elevation exceeding nucleus boiling corresponding to the recording information on an electricity-heat converters arranged corresponding to the sheets or liquid channels holding liquid (ink), heat energy is generated at the electricity-heat converters to effect film boiling at the heat acting surface of the recording head, and consequently the bubbles within the liquid (ink) can be formed corresponding one by one to the driving signals. By discharging the liquid (ink) through an opening for discharging by growth and shrinkage of the bubble, at least one droplet is formed. By making the driving signals into pulse shapes, growth and shrinkage of the bubble can be effected instantly and adequately to accomplish more preferably discharging of the liquid (ink) particularly excellent in response characteristic. As the driving signals of such pulse shape, those as disclosed in U.S. Patents 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employment of the conditions described in U.S. Patent 4,313,124 of the invention concerning the temperature elevation rate of the above-mentioned heat acting surface. As the constitution of the recording head, in addition to the combination constitutions of discharging orifice, liquid channel, electricity-heat converter (linear liquid channel or right angle liquid channel) as disclosed in the above-mentioned respective specifications, the constitution by use of U.S. Patents 4,558,333 and 4,459,600 disclosing the constitution having the heat acting portion arranged in the flexed region is also included in the present invention. In addition, the present invention can be also effectively made the constitution as disclosed in Japanese Patent Laid-Open Application No. 59-123670 which discloses the constitution using a slit common to a plurality of electricity-heat converters as the discharging portion of the electricity-heat converter or Japanese Patent Laid-Open Application No. 59-138461 which discloses the constitution having the opening for absorbing pressure wave of heat energy correspondent to the discharging portion. Further, as the recording head of the full line type having a length corresponding to the maximum width of recording medium which can be recorded by the recording device, either the constitution which satisfies its length by combination of a plurality of recording heads as disclosed in the above-mentioned specifications or the constitution as one recording head integrally formed may be used, and the present invention can exhibit the effects as described above further effectively. In addition, the present invention is effective for a recording head of the freely exchangeable chip type which enables electrical connection to the main device or supply of ink from the main device by being mounted on the main device, or for the case by use of a recording head of the cartridge type provided integrally on the recording head itself. Also, addition of a restoration means for the recording head, a preliminary auxiliary means, etc. provided as the constitution of the recording device of the present invention is preferable, because the effect of the present invention can be further stabilized. Specific examples of these may include, for the recording head, capping means, cleaning means, pressurization or aspiration means, electricity-heat converters or another heating element or preliminary heating means according to a combination of these, and it is also effective for performing stable recording to perform preliminary mode which performs discharging separate from recording. Further, as the recording mode of the recording device, the present invention is extremely effective for not only the recording mode only of a primary stream color such as black etc., but also a device equipped with at least one of plural different colors or full color by color mixing, whether the recoridng head may be either integrally constituted or combined in plural number. As mentiond heretofor, in the ink jet recording apparatus according to the present invention having correcting means for residual ink quantity, erroneous detection is hard to be generated, and following quality needed for ink jet recording apparatus can be realized without increasing cost. (a) The same or common apparatus can be used for various kinds of ink for normal sheet, count sheet and TP. (b) The same apparatus can be used for different kinds of color inks. (c) It is possible to respond to change of using environment and continuing printing. (d) Injury of the heating element due to erroneous detection, bad printing due to non-discharge can be prevented. In the residual ink quantity detection apparatus detecting the residual ink quantity by resistance of the ink, the ink resistance is corrected at the main body of apparatus, recording head or tank portion, the resistance output characteristic can be kept in constant even if the ink components may vary. Furthermore, accurate residual quantity detection can be effected without exchange of the head even when plural kinds of inks are used. It is also possible to prevent bad printing due to erroneous detection. In detail, from the present invention, the ink jet recording head, ink tank and ink jet recording apparatus capable of effecting stabilized and high accuracy residual ink quantity detection with simple construction can be realized.

Claims: An ink jet recording apparatus comprising an ink jet head (1) for discharging ink, an ink supply (9) for the ink jet head, electrodes (7a,7b,7c) for making contact with the ink, and detecting means for producing a signal representing the quantity of ink in the ink supply based on an electrical signal representing the resistance between the electrodes, correction means comprising a correction resistance (Rc) for correcting the electrical signal for the volume resistance of the kind of ink to be detected, said detecting means being arranged to detect the quantity of ink in the ink supply based on the corrected electrical signal, characterised by the correction resistance not being in contact with the ink. An apparatus according to claim 1, comprising a plurality of ink jet heads (1) each for discharging ink, a respective ink supply (9) for each head and respective electrodes (7a,7b,7c) for making contact with the ink to be discharged by each ink jet head, the detecting means being arranged to produce a respective signal representing the quantity of ink in each ink supply based on an electrical signal representing the resistance between the corresponding electrodes and the correcting means comprises a respective correction resistance for correcting each electrical signal for the volume resistance of the corresponding kind of ink to be detected. An apparatus according to claim 1 or 2, wherein said correction means comprises a variable resistance (Rc) in circuit with the resistance between the electrodes. An ink jet recording apparatus according to any preceding claim, wherein said correction means is provided in the or each ink jet head. An ink jet recording apparatus according to any of claims 1 to 3, wherein said correction means is provided in a body of said ink jet recording apparatus. An ink jet recording apparatus according to any preceding claim, wherein said detecting means includes a circuit for inverting polarity of the electrical signal for detection in each detection. An ink jet recording apparatus according to any preceding claim, wherein the or each ink jet head (1) is provided with an electrothermal conversion element (2) for generating thermal energy to discharge ink. An ink jet recording apparatus according to any preceding claim, wherein the or each ink jet head (1) is formed integrally with an ink tank (9), and is removably mounted on a body of said ink jet recording apparatus. An ink jet recording apparatus according to any preceding claim, wherein, for the or each head, the electrodes are disposed in an ink path (6-1) between said ink supply source (9) and said ink jet head (1). An ink jet recording apparatus according to claim 9, wherein said ink path includes an ink absorbent (6-1). An ink jet recording apparatus according to any of claims 1 to 8, wherein, for the or each head, the electrodes (7A,7B) are disposed in the ink supply source (1). An ink jet recording apparatus according to any of claims 1 to 8, wherein, for the or each head, the electrodes (7a to 7c) are disposed in an ink path in said ink jet head. An ink jet recording apparatus according to any preceding claim, wherein the or each ink jet head (1) is arranged to perform a recording operation by discharging ink downwardly. An ink jet recording apparatus according to any of claims 1 to 12, wherein the or each ink jet head (1) is arranged to perform a recording operation by discharging ink transversely with respect to a vertical direction. An ink jet recording apparatus according to any preceding claim, wherein a plurality of said ink jet heads (1) are provided one for each of a plurality of different colour inks. An ink jet recording apparatus according to any preceding claim, wherein the or each ink jet head (1) is a full-line type ink jet head having a plurality of said discharge openings providing a discharge opening array arranged to extend completely across the recording width of a recording medium. An ink jet recording head (1) mountable upon an ink jet recording apparatus for discharging ink to effect recording on a recording medium, the ink jet head (1) comprising electrodes (7a,7b,7c) for making contact with ink in the ink jet head for enabling an electrical signal representing the resistance between the electrodes to be obtained for allowing a detecting means of the ink jet recording apparatus to produce a signal representing the quantity of ink in the ink jet head, when the head is mounted upon the apparatus, correction means comprising a correction resistance for correcting the electrical signal for the volume resistance of the kind of ink to be discharged by the head, characterised by the correction resistance not being in contact with the ink. An ink jet recording head according to claim 17, wherein the correction means comprises a variable resistance in an electrical circuit with the resistance between the electrodes. An ink tank (9) mountable upon an ink jet recording head for use in an ink jet recording apparatus for supplying ink to the ink jet head for discharge into a recording medium, the tank comprising electrodes (7A,7B) for making contact with ink in the tank for enabling an electrical signal representing the resistance between the electrodes to be obtained for allowing a detecting means of the ink jet recording apparatus to produce a signal representing the quantity of ink in the tank when the tank is mounted upon the ink jet apparatus together with the ink jet head, correction means comprising a correction resistance for correcting the electrical signal for the volume resistance of the kind of ink to be supplied from the ink tank, characterised in that the correction resistance is not in contact with the ink. An ink tank according to claim 19, wherein the correction means comprises a variable resistance in an electrical circuit with the resistance between the electrodes.

Inventors: ARAI ATSUSHI, HIRABAYASHI HIROMITSU, KOITABASHI NORIBUMI, TAJIKA HIROSHI, TAKAYAMAGI YOSHIAKI, ARAI, ATSUSHI, HIRABAYASHI, HIROMITSU, KOITABASHI, NORIBUMI, TAJIKA, HIROSHI, TAKAYAMAGI, YOSHIAKI, ARAI, ATSUSHI, C/O CANON K. K., HIRABAYASHI, HIROMITSU, C/O CANON K. K., KOITABASHI, NORIBUMI, C/O CANON K. K., TAJIKA, HIROSHI, C/O CANON KABUSHIKI KAISHA, TAKAYAMAGI, YOSHIAKI, C/O CANON K. K.
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: B41J2
IPC codes: B41J2