A liquid jet recording appratus

Abstract: A liquid jet recording apparatus including a ink container (102). A pair of electrodes (113A-113B) are provided to be immersed in the ink in the container (102). By applying voltage between the electrodes, and the remainder of the ink is detected by the change of the electric resistance between the electrodes (113A-113B). The voltage application is not continuous that intermittent at the predetermined timing associated with the recording operation (at the tme of carriage reversing) to detect the remainder of the ink. Not during the ink remainder detecting operation, the voltage is not applied to the electrodes.

Description: The present invention relates to a liquid jet recording apparatus. Generally, the liquid jet recording apparatus includes an ink storage such as an ink container containing recording liquid (ink), and when the container becomes short of the liquid or when it becomes empty with the consumption of the liquid, the liquid is supplied. The supply may be accomplished by injecting the liquid or by exchanging a cartridge, when the container is in the form of a cartridge. In order to detect the remaining amount of the ink, a pair of electrodes immersed in the ink is provided in the ink supply system, that is, the ink container or the ink supply passage, wherein a voltage is applied between the electrodes. With the decrease of the ink remaining amount, the electric resistance between the electrodes changes, in response to which the remaining amount of the ink can be detected. However, if the voltage is always applied for detecting the remaining amount, the composition of the ink may be changed by electrolysis with the result that the quality of the record is degraded or that there occurs a liability that the ejection outlets of the recording head are clogged. Therefore, a liquid jet recording apparatus has been suggested in document US-A-4 788 861, in which two inverted square wave signals generated by a squarewave generator and an inverter are applied to electrodes E1 and E3, respectively, such that the voltage between the electrodes alternates to thereby prevent electrolytical decomposition of the recording liquid. However, in practice the output signals of the square wave generator and the inverter can have slightly different residual voltages such that a mean voltage between the electrodes differs from zero. Therefore, the duration of the pulses and, hence, the time period available for the measurement of the remainder has to be limited in order to prevent decomposition. It is therefore an object of the present invention to provide a recording apparatus in which the decomposition of the recording liquid is assuredly prevented without significantly affecting the time period for the measurement of the ink remainder. This object is achieved by a recording apparatus according to claim 1, especially by the feature that said control means selectively establishes a first mode in which said voltage is applied between said electrodes and a second mode in which said voltage is not applied therebetween, said first mode being provided at a predetermined timing during said recording operation, and during said stand-by state only when a remainder detection instruction for effecting a predetermined number of liquid remainder detections is set. Accordingly, electrolysis of the ink can be avoided, since the electric power is only applied during the first mode in which the measurement takes place, wherein the establishment of the first mode can be minimized during the stand-by mode. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a liquid jet recording apparatus according to an embodiment of the present invention. Figure 2 is a perspective view of an example of a recording head (head cartridge) used with the liquid jet recording apparatus of this embodiment. Figure 3 is a sectional view taken along line A-A to illustrate the structure of the ink remainder detecting portion. Figure 4 is a schematic view illustrating the ink supply passage in this embodiment. Figure 5 is a graph of a voltage vs. a remaining amount of the ink under the condition that the current flowing between the detecting electrodes is maintained constant. Figure 6 is a block diagram of an example of a control system for detecting the ink remainder. Figure 7 is a flow chart illustrating an example of the control steps for the remainder detection. Figure 8 is a flow chart showing an example of the process steps during the recording and during the stand-by state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, the preferred embodiments of the invention will be described in detail. Figure 1 shows a liquid jet recording apparatus (ink jet recording apparatus) according to a first embodiment of the present invention. The recording apparatus comprises a head cartridge 14 which includes a recording head chip provided with ink ejection outlets and ejection energy generating elements associated with the respective ejection outlets, and an ink container which is the ink supply source, as a unit. The head cartridge 14 is a fixed on a carriage 14 by a confining member 41, and they are reciprocable in a longitudinal direction along a shaft 21. The ink ejected from the ejection outlet of the recording head chip reaches a recording material 18 which has a recording surface confined by a platen 19 disposed spaced from the ejection outlet with a small clearance, by which an image is formed on the recording material 18. To the ejection energy generating elements (electrothermal transducer elements, for example) of the recording head chip, ejection signals corresponding to image data to be recorded are supplied from a suitable data supply source through a cable 16 and contacts connected therewith. A number of the head cartridge 14 may be one or more (two in the Figure) in accordance with the number of colors to be used. The recording apparatus futher comprises a carriage motor 17 for reciprocating the carriage 15 along the shaft 21, a wire 22 for transmitting the driving force from the motor 17 to the carriage 15, and a feed motor operatively connected with the platen roller 19 to feed the recording medium 18. Figure 2 shows the structure of the head cartridge 14. The head cartridge comprises a recording head chip 111, wiring member (lead frame) including plate like conductor for providing electric connection between the recording head chip 111 and the main assembly of the liquid jet recording apparatus by wiring bonding or the like, ink remainder detecting electrodes 113A and 113B built in the lead frame 112 to detect the ink remainder which will be described in detail hereinafter, an ink passage for supplying ink from the ink container 102 to the recording head chip 111, a partition wall 116 for dividing the ink container 102 and the ink supply passage 114. Designated by a reference numeral 119 is a switch which is on-off-controlled by a controller shown in Figure 6 which will be described hereinafter. Figure 3 shows an example of the detecting electrodes. The lead frame 112 is embedded in a casing 117 made of plastic resin, for example, of the head cartridge which is constituted by the unified ink container 102 and the recording head chip 111. Only the ink remaining amount detecting electrodes 113A and 113B are exposed to the ink supply passage 114 through a conductive portion 118. When the switch 119 is closed, electric power is supplied between the electrodes through a resistance R. As shown in Figure 4, the ink supply passage 114 is provided with an ink supply port 129 formed in the partition wall 116, and the ink supply passage 114 is provided with ribs 120A, 120B and 120C extended alternately from the top and the bottom. The ink introduced into the supply passage 114 through the ink supply port 129 from the ink container 102 is directed to the next section beyond the first rib 120A by an unshown capirally tube, and it is supplied to the recording head chip 111 through the path indicated by an arrow. Upon the recording operation, the ink is ejected through the ejection outlets. When the ink container 102 becomes empty, so that the ink is not introduced into the ink passage 114, the liquid surface level becomes as shown in Figure 4, so tht the ink remainder detecting portion 113A is exposed above the liquid surface level with the result that the electric connection between the detecting portions 113A and 113B is shut. By the absence of the electric current, the reaching of the ink remainder to the limit is detected. Since the electric current flows more or less, as long as the coat of the conductive ink remains between the detecting electrodes. Therefore, where the detecting circuit is so constituted that a constant current flows, there is a relationship as shown in Figure 5 between the voltage V and the ink remainder l . Therefore, it is possible to detect the amount of the ink remainder l . In this embodiment, the remainder detecting operation is performed only at a predetermined timing during the recording operation and the stand-by state, and otherwise, the switch 119 is opened. Figure 6 shows an example of the control system for this embodiment. The control system includes a controller 50 which is the main controlling section and which includes a CPU for executing the process steps which will be described in conjunction with Figures 7 and 8, ROM storing programs executing the process steps and other fixed data, RAM including a working area such as flag and power supply device (not shown) for supplying electric power to the heater or the like. In the Figure, reference V indicates a remainder detection signal from the remainder detector shown in Figure 2, and S is a control signal for closing and opening the switch 119. The remainder detection signal V is inputted only when the switch 119 is closed by which a voltage is applied between the electrodes 113A and 113B. Reference numeral 51 designates a recording head in the head cartridge of a disposable type shown in Figure 2. An ejection recovery device 54 includes a capping device selectively opposed to or engaged with the recording head 51 outside the recording range (Figure 1), for example, at a home position of the recording head 51 or the carriage 15, and it also includes a sucking mechanism communicating with the capping device to suck the ink out of the recording head 51 through the ejection outlets. The control system further includes an alarming device 55 including a display such as LED or a sound generator such as a buzzer or a combination thereof. A main scanning mechanism 56 functions to scanningly move the carriage 15 during the recording operation, and it includes the motor 17 or the like. A subordinate scanning mechanism 57 includes the motor 20 or the like for conveying the recording material. Figure 7 shows an example of the ink remainder detecting process steps in this embodiment, and it is started during the recording operation or during the stand-by state. When this process is started, the switch 119 is closed at step S1, by which a voltage is applied between the electrodes 113A and 113B of the head cartridge 14. At step S3, the discrimination is made as to whether or not the ink remains on the basis of the voltage V between the electrodes (remainder detection signal) V produced by the voltage application. If the result of the discrimination is negative, step S5 is executed by which an alarm indicating the absence of the ink is produced to promote the operator the supply of the ink or exchange of the head cartridge 14, and at step S7, various parts of the apparatus are stopped, and the apparatus waits for the exchange of the head cartridge 14 or the like. On the other hand, if the result of the discrimination at step S3 is affirmative, a step S9 is executed by which the switch 119 is opened to stop the voltage application between the electrodes 113A and 113B to shut the electric current through the ink. Figure 8 shows an example of the process steps executed during the recording operation and the standby state in the liquid jet recording apparatus of this embodiment. At step S11, the discrimination is made as to whether the record instruction signal is produced or not. In response to the discrimination, either of the recording process (step S13) or the stand-by process (step S25). At step S13, the data corresponding to one line to be recorded by one main scan of the recording head 51 is fetched from a predetermined amount (one page, for example) of the image data developed in the RAM in the controller 50, for example, and the data are aligned in a buffer. Then, the ejection energy generating elements on the recording head 51 are selectively actuated in accordance with the image data, while driving the main scanning mechanism 56, to perform the recording on one line. After the recording of one line, the subordinate scanning mechanism 57 is driven to feed the recording material 18 through a predetermined distance. When the one line recording is completed, a step S15 is performed in which the discrimination is made as to whether the one line data are all recorded or not. If not, a step S17 is performed to return the carriage 15 to a predetermined reversing position (the record starting position for the next line or adjacent thereto) to be prepared for the next line printing. At step S19, the remainder detection process shown in Figure 7 is performed. Thereafter, the operation returns to step S13 for performing the next line recording. If the result of the discrimination at step S15 is affirmative, a step S21 is executed to set the carriage 15 to the home position to be prepared for the next recording operation, and the ejection recovery device 54 is opposed to the recording head 51 and to engage the cap thereto. At step S23, a remainder detecting flag, which can be disposed in a predetermined address of the RAM of the controller 50, for example, representing whether the remainder detection is to be performed or not during the stand-by state, and the operation returns to the step S11. During the stand-by state, the discrimination is first made as to whether or not the remainder detection flag is set, at step S25. If it is immediately after the previous recording operation, the result of the discrimination is affirmative. At step S27, the remainder detecting process shown in Figure 7 is performed, and thereafter, at step S29, the remainder detecting flag is reset, and the operation returns to the step S11. If, on the other hand, the result of the discrimination at the step S25 negative, the operation immediately returns to the step S11. As described, the remainder detection is performed only once during the stand-by state in preparation for the next recording operation, whereby the voltage is applied between the electrodes 113A and 113B only during that period, and therefore, the inconveniences attributable to the electrolysis of the ink can be remarkably reduced. At the recording operation, the remainder detection is carried out only at proper timing, and therefore, as compared with the ink remainder is monitored by always applying the voltage, the above inconveniences can be reduced. In addition, the problem arising from the remainder detection performed only during the stand-by state, that is, the ink becomes out during the recording operation with the result of improper recording, can be prevented. In the foregoing embodiment, the remainder detection is performed each time the one line recording, but it may be carried out each of several lines. Where the CPU is not involved during the movement of the carriage to the reverse position, the remaining amount of the ink can be detected during the movement to the reverse position. Further, where the CPU is not involved during the recording operation by the main scanning mechanism 56 and the recording head 51, the remainder detection may be performed during the movement. In these cases, the remainder detection can be started by interruption using a timer. Furthermore, an additional CPU may be provided to perform the above process, so that the processes are performed independently. In the foregoing description, the liquid jet recording apparatus is of such a type that the recording head chip and the ink container constitute a unified head cartridge. However, the present invention is applicable to the case wherein they are separate. Also, the recording head chip is not necessarily disposable. In this case, the ink container may be disposed at any place. It does not need to be a disposable cartridge, but it may be of the type wherein the ink is supplied by injection or the like. In the foregoing description, the ink remainder detection system is used also for discriminating the properness of the ink, but they may be separate means. In addition, the foregoing description has been made with respect to a serial type liquid jet recording apparatus in which the recording head is scanningly moved relative to the recording medium, but the present invention is very effectively and easily usable with a so-called multi-type wherein a number of the ejection outlets are used to cover the entire width of the recording material. As described in the foregoing, in an ink jet recording apparatus wherein the remainder of the ink is detected by applying a voltage between electrodes immersed in the ink, the remainder detecting operation is performed by the application of the voltage only at predetermined timing, and therefore, the problem such as the electrolysis of the ink which results if the voltage is always applies, can be remarkably suppressed. In addition, the remainder detecting operation is performed in association with the recording operation, and therefore, the shortage or lack of the ink is quickly detected, and therefore, the deterioration of the record attributable to the recording operation with the shortage or lack of the ink continued, can be prevented. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims: A recording apparatus for forming an image on a recording material (18) using a recording head (111) having ejection outlets for ejecting recording liquid, comprising: a) liquid supply means (102 ,114, 129) for supplying said recording liquid to said recording head (111) ; b) electrodes (113A, 113B) provided in said liquid supply means (102, 114, 129) and immersed in said recording liquid; and c) control means (50) for applying a voltage between said electrodes (113A, 113B) to detect a remainder of said recording liquid at a predetermined timing during a recording operation of said recording head (111) or during a stand-by state thereof, wherein d) said control means (50) selectively establishes a first mode in which said voltage is applied between said electrodes (113A, 113B) and a second mode in which said voltage is not applied therebetween, said first mode being provided at a predetermined timing during said recording operation, and during said stand-by state only when a remainder detection instruction for effecting a predetermined number of liquid remainder detections is set. A recording apparatus according to claim 1, characterized in that said recording head (111) is reciprocated in predetermined directions relative to said recording material (18) during said recording operation, and that said control means (50) effects the remainder detecting operation by providing said first mode at a predetermined reversing position of the reciprocating movement. A recording apparatus according to claim 1, characterized in that said control means (50) effects the remainder detecting operation by providing said first mode immediately after said recording head (111) reaches a predetermined stop position, after the completion of said recording operation. A recording apparatus according to claim 1, characterized in that said recording head (111) and said liquid supply means (102, 114, 129) are unified into a unit which is detachably mountable to a main assembly of said apparatus. A recording apparatus according to any one of claims 1 to 4 , characterized in that said recording head (111) includes electrothermal transducer elements to eject said recording liquid by thermal energy.

Inventors: KOIZUMI RYOICHI, SAITO ASAO, TAKAYANAGI YOSHIAKI, KOIZUMI, RYOICHI, SAITO, ASAO, TAKAYANAGI, YOSHIAKI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1989
Main classification: B41J2
IPC codes: B41J2