JP2009160881A - Inkjet recording device - Google Patents

Abstract

In a system for determining the amount of ink in an ink tank using an electrode, the remaining amount of ink is detected with high accuracy.
Along with a change in a curve 240 showing a voltage value between electrodes, curves 241 and 243 showing an average value of a plurality of interelectrode voltages measured so far change in the same way. Further, the threshold curve 242 obtained by adding a margin voltage to the average value curve changes in the same manner. This voltage is relatively early in a region where the ink liquid level is in the vicinity of the liquid level where it is determined that there is no remaining amount and the volume of ink connecting between the electrodes fluctuates, and as a result, the detected voltage value curve 240 fluctuates greatly. Since the value exceeds the value of the threshold curve 242, it can be determined that there is no remaining amount. As a result, it is possible to prevent an error in detecting the amount of ink corresponding to the amount of ink consumed due to a delay in determination.
[Selection] Figure 9

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to a configuration for detecting an ink remaining amount in an ink tank using an electrode.

  Various types of printer recording methods are known. However, inkjet recording methods are available for reasons such as non-contact recording on recording media such as paper, easy colorization, and high quietness. In recent years, it has attracted particular attention. In particular, a serial recording type recording apparatus that uses a recording head that discharges ink and scans in a direction orthogonal to the feeding direction of a recording medium such as paper by the recording head is widely used. Such an ink jet recording apparatus uses a recording head having a nozzle for ejecting ink droplets and an ink tank for storing ink to be supplied to the recording head. A discharge energy generating element such as a heater or a piezo element is provided in the nozzle of the recording head, and ink is discharged from the nozzle by generating discharge energy in accordance with an electric signal supplied to the element.

  In the ink jet recording apparatus, when the amount of ink in the ink tank decreases or the ink runs out, ink supply failure to the recording head occurs. As a result, the recording head has a discharge failure such that the discharge amount becomes smaller than the normal amount or does not discharge. In addition, by driving the heater in the absence of ink, the recording head itself can be destroyed. Therefore, the ink jet recording apparatus has conventionally been configured to detect the amount of ink in the ink tank, and performs control such as prompting the user to replace the tank when the detected amount falls below a certain amount.

As a method of detecting such a decrease in the ink amount of the ink tank,
Method 1: A method in which two electrodes are provided in an ink tank, a current is supplied between the electrodes to detect an electrical resistance between the electrodes, and an ink amount is determined to be equal to or less than a predetermined amount accordingly.

  Method 2: An ink tank is formed of a translucent member, an optical sensor is provided in the vicinity of the ink tank, the amount of light passing through the ink tank and the amount of light reflected by the ink tank are measured, and the ink is A method for determining that the amount is less than or equal to a predetermined amount.

Method 3: A method in which the ink volume is mechanically moved by the weight of the ink using a spring or the like, and the presence or absence of ink is determined by the degree of movement.
Etc. are currently in practical use. Among them, the method 1 has advantages such as (1) a complicated mechanism is not required and can be configured at a low cost, and (2) a high degree of freedom in arranging two electrodes regardless of the installation location. It is a widely used method.

  FIG. 1 is a diagram showing an example of this type of detection circuit and a constant current circuit for detection. In FIG. 1, reference numeral 101 denotes a power supply that supplies a constant 5V when the ink amount is detected and is 0V when the ink amount is not detected. A constant voltage of 5V by the power supply 100 is divided by the resistor 102, and the voltage at the point 103 of the circuit is maintained at a constant 3V by using the operational amplifier 108. That is, by connecting the resistor 102 of 200 KΩ between the constant voltage 5 V of the power supply 101 and 3 V of the point 103, the current value flowing therethrough becomes 10 μA of (5V-3V) / 200 KΩ. Thus, a constant current of 10 μA can be passed between the ink amount detection electrode 104 and the GND electrode 105.

  When there is ink between these electrodes 104 and 105, the voltage of the electrode 104 becomes a voltage value of (resistance value of ink) × (current value flowing (10 μA in the example in the figure)). . On the other hand, when there is no ink or when the amount is less than a predetermined amount, the voltage of the electrode 104 shows the same voltage of 3 V as the point 103. The voltage of these electrodes 104 is detected as an analog amount detection signal 106 and is input to the control unit of the printer via an AD port or a voltage comparator. Thereby, it is possible to know whether the voltage value corresponds to the ink amount or whether the voltage value is higher or lower than the predetermined voltage value corresponding to the predetermined ink amount.

  FIGS. 2A and 2B are schematic views showing the configuration of the electrodes and the associated ink tanks in the ink tank mounting portion of the printer. As shown in these drawings, the ink tank 110 is provided with a cylindrical blocking wall 111 at the bottom thereof. Thus, when the ink tank is mounted (FIG. 2B), the electrode 104 of the ink tank mounting portion is disposed so as to be surrounded by the blocking wall 111. As a result, when the amount of ink in the ink tank becomes a certain amount or less, the path of electricity between the electrode 104 and the electrode 105 can be blocked. At the bottom of the ink tank, rubber packing 112 is provided corresponding to the electrodes 104 and 105, respectively. This prevents the ink in the ink tank from leaking outside when the electrode is inserted into the ink tank by mounting the ink tank or when the electrode is not inserted. Reference numeral 113 denotes a base for supporting the ink tank in the mounting portion, 114 denotes a tube for supplying air to the ink tank, and 115 denotes a tube for supplying ink to the recording head. Reference numerals 117 and 118 denote two examples of the amount of ink in the ink tank. In the example shown in the figure, the electrode 104 also functions to send air in accordance with the amount of ink consumed. The electrode 105 functions to supply ink to the recording head. In order to realize these functions, these electrodes are all tubular.

  In the ink amount detection system shown in FIGS. 1, 2A and 2B, when the ink amount in the ink tank falls below the upper surface of the blocking wall 111, it is determined that the ink amount is small (no remaining amount). First, the 5V power supply 101 is turned on. Accordingly, when the ink liquid level is above the upper surface of the blocking wall 111 as in the ink amount 117, a current of 10 μA flows through the resistor 102 and flows between the electrodes 104 and 105 as a medium. At this time, a voltage value corresponding to (resistance value of ink) × (current value of flowing current), which is a voltage lower than the voltage 3 V when current does not flow through ink, becomes the content of the detection signal 106. . On the other hand, when the ink level is below the upper surface of the blocking wall 111 as in the ink amount 118, the ink between the electrodes is blocked by the blocking wall, and no current flows between the electrode 104 and the electrode 105. In that case, the content of the detection signal 106 is the same voltage 3V as the point 103.

  FIG. 3 is a diagram showing another example of ink amount detection, in which an electrode is inserted into a tube that supplies ink to the recording head to detect the ink amount. The electrode 104 side is the ink tank side, and the electrode 105 side is the recording head side. In the example shown in the figure, ink is contained on the recording head side from the boundary 121 and ink is not contained on the ink tank side. Also in this example, when a current is passed between the electrodes 104 and 105 and the space between these electrodes is filled with ink, the voltage of the detection signal 106 is (ink resistance value) × (current flowing). Value). On the other hand, as shown in FIG. 3, when the ink does not fill between the two electrodes, the detection signal 106 shows the same 3V voltage as the point 103.

  FIG. 4 is a diagram showing the contents of the detection signal 106 when ink is consumed during recording or the like using the system shown in FIGS. 1 and 2 described above. Specifically, power is supplied from the power source 101 at intervals of 3 seconds to pass a current between the electrode 104 and the electrode 105, and the voltage value indicated by the detection signal 106 at that time is plotted. In FIG. 4, a curve 130 indicates the voltage value of the detection signal 106 that changes with time. The detection signal 106 shows a predetermined low voltage value until the time 131 when the ink liquid level is above the upper surface of the blocking wall 111 even when ink is consumed. When the ink level reaches the upper part of the blocking wall 111 at time 131, the ink between the electrode 104 and the electrode 105 is blocked and the detection signal 106 indicates 3V. Thereafter, for example, the ink may be connected to the upper surface of the blocking wall 111 for a short time due to the influence of the vibration of the ink tank or the bubbles generated in the ink. In that case, the detection signal 106 indicates the voltage when the ink liquid level is above the upper surface of the blocking wall 111 as at the time points 132 and 133. When the ink liquid level is completely separated from the upper part of the blocking wall 111 and becomes a lower position while repeating such a behavior, the ink between the electrode 104 and the electrode 105 is insulated and the constant voltage 134 (3 V) is obtained. )

  In this manner, when the voltage between the electrodes is higher than the threshold voltage 135, it can be determined that the ink liquid level is lower than the upper part of the blocking wall, that is, the ink amount is small (no remaining amount). Since the voltage value indicated by the detection signal 106 exceeds the threshold voltage 135 at the time 131, it can be determined that there is no remaining amount at this time.

  In the above configuration, the resistance value of the ink between the electrodes varies to some extent depending on the amount of ink, the composition of the ink, and the like. Therefore, the threshold voltage value for determining whether ink is present or not is brought close to the voltage value when there is no ink, that is, the voltage value at the point 103 in FIG. 1, and it is erroneous if the ink amount is still sufficient but there is no remaining amount. I try not to judge. Even in the same type of ink and ink supply system, the absolute value of the voltage value transition of the detection signal 106 may differ depending on the lot. To deal with such cases, when a constant current is passed between the electrodes when the ink amount is in the initial state, the voltage value at that time is used as a reference voltage, and the potential between the electrodes when a constant current is passed between the electrodes is compared. A method of detecting a state in which the remaining amount of ink is reduced is used (see Patent Document 1). That is, in this method, for example, in the system shown in FIG. 1, a constant current is passed between the electrode 104 and the electrode 105 in a state where the ink is in an initial state, that is, in a state where the ink is fully filled. Is stored as a reference value. Then, when detecting the amount of ink, a constant current is passed between the two electrodes, and the voltage value between the two electrodes at that time is compared with the stored reference value to some extent depending on the type of ink. Differences in voltage transition can be predicted.

Japanese Patent No. 2721009

  However, the above-described conventional method for detecting the ink amount has a problem that effective and accurate detection can be performed when the blocking wall 111 and the inner wall of the tube 120 have sufficient water repellency. When the water repellency of the surface of the blocking wall 111 is lowered and begins to have a hydrophilic property, the voltage value indicated by the detection signal 106 becomes a curve 140 shown in FIG. That is, until the time point 141, the same behavior as the curve 130 shown in FIG. However, when the ink liquid level drops to the upper surface of the blocking wall 111, the ink is then partially connected on the side of the blocking wall because of the hydrophilic surface, unlike the curve 130 of FIG. As the liquid level goes down, the partial connection volume decreases, and the voltage value indicated by the detection signal 106 increases accordingly (from time 141 to time 142). Thereafter, bubbles are generated when air is introduced into the ink tank through the electrode 104 as the ink is consumed, so that ink is supplied to the side surface of the blocking wall 111 and the volume of partial connection of the ink may increase. . As a result, the voltage value indicated by the detection signal 106 may drop rapidly (for example, from the time point 142 to the time point 143). Such a behavior is repeated, and at a time point 144, a voltage value at which it can be determined for the first time that the ink liquid level is clearly lower than the blocking wall 111 is obtained. However, in actuality, at or near the time 141, it is necessary to determine that the ink level is lower than the blocking wall and there is no remaining amount, and an ink consumption detection error from the time 141 to the time 144 is detected. Will result. This error is inconvenient when the amount of ink is accurately grasped and the user tries to consume ink without excess or deficiency.

  Further, as shown in FIG. 6, the absolute value of the voltage value transition indicated by the detection signal 106 may vary depending on the lot. In this case, as described above with respect to Patent Document 1, by passing a current between the two electrodes in the initial state of the ink amount and reading the voltage between the two electrodes, the voltage transition due to the type of ink to some extent is achieved. Can predict the difference. However, even a change in behavior due to a decrease in water repellency between electrodes cannot be grasped.

  Furthermore, when a voltage is obtained by supplying a constant current at regular time intervals, such as during recording, the accumulation of charges is stabilized by flowing the current, and the prediction of the voltage transition can be accurately obtained. However, when the interval at which the constant current is applied between the electrodes exceeds a certain value, it may be difficult to predict the voltage transition. This is because it is difficult to predict the voltage value due to the accumulated charges because the discharge proceeds irregularly while no current is flowing. In addition, in a sequence where the ink moves in a relatively large amount, such as a cleaning sequence for the discharge port surface of the recording head or an agitation sequence that prevents sedimentation of the ink components, the amount of charge accumulated in the ink tank is disturbed. It becomes difficult to estimate the voltage value between the electrodes.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an ink jet recording apparatus capable of detecting the remaining amount of ink with high accuracy in a system for determining the amount of ink in an ink tank using electrodes. .

  Therefore, in the present invention, in an ink jet recording apparatus that performs recording on a recording medium using a recording head that ejects ink and an ink tank that stores ink to be supplied to the recording head, a pair of electrodes inserted in the ink tank is interposed between the pair of electrodes. Means for supplying a constant current; voltage detecting means for detecting a voltage value indicating a potential difference between the electrodes when a constant current is supplied between the pair of electrodes; and a plurality of voltages detected by the voltage detecting means in the past A memory means for storing a value, a threshold value is calculated based on a plurality of voltage values stored in the memory means, and a voltage value obtained as a result of detecting the potential difference by the voltage detecting means is calculated. And a control means for determining that the ink amount in the ink tank has fallen below a predetermined amount when the value is equal to or greater than the threshold value.

  According to the above configuration, it is determined whether or not the ink amount is smaller than a predetermined amount using, for example, a threshold value based on an average of a plurality of voltage values measured in the past. As a result, in a region where the volume of ink connecting between electrodes, which is a boundary region where it is determined that the amount of ink is less than a predetermined amount, and the detection voltage value is likely to fluctuate as a result, the ink is more It can be judged that there are few. As a result, it is possible to prevent an error in detecting the amount of ink corresponding to the amount of ink consumed due to a delay in determination.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 7 is a block diagram showing a control unit of the ink jet recording apparatus according to the embodiment of the present invention. With the control configuration shown in FIG. 7, the ink amount of the ink tank according to the embodiment of the present invention is detected. The voltage detection circuit using a pair of electrodes in the ink tank is the same as that shown in FIG. That is, in FIG. 7, the detection signal 106 output from the ink tank 213 regarding the ink amount detection is input to the control unit of the inkjet recording apparatus via the AD port 211. This signal is converted into a digital value and used for an ink amount detection process described later.

  In FIG. 7, reference numeral 200 denotes a CPU that performs all control of the ink jet recording apparatus. That is, the CPU 200 also controls ink amount detection according to the flowchart shown in FIG. Reference numeral 201 denotes a unit that controls communication represented by LAN, IEEE 1394, USB, and the like, and controls data communication between the inkjet recording apparatus and a computer that is a host apparatus. Reference numeral 202 denotes a memory unit composed of a nonvolatile memory such as a ROM or a volatile memory such as a RAM. The memory unit 202 is used as a part for storing processing executed by the CPU 200, a control program, a buffer for temporarily storing images sent from the host device through the communication control unit 201, and a work area. The The voltage value between the past electrodes, which will be described later with respect to the following ink amount detection, is also stored in this memory.

  The ink stored in the ink tank 213 is supplied to the recording head 205 and discharged from a plurality of nozzles of the recording head. Specifically, while the recording head 205 mounted on the carriage scans the recording medium, by driving the heater in the nozzle based on the recording data corresponding to each nozzle at a predetermined timing, the ink is discharged from the nozzle. Discharged. Reference numeral 204 denotes a sensor unit that indicates the scanning position of the recording head 205, and includes a slit film along the search range of the recording head 205 and an optical encoder sensor disposed on the recording head. The sensor unit 204 can relatively represent the position of the recording head by the number of optical encoder sensors crossing the slit. Reference numeral 203 denotes a head control circuit. This circuit 203 gives a memory address of recording data to be read out by the CPU 200 before scanning. Further, when the recording head 205 scans, the recording data corresponding to each nozzle is read from the memory 202 at the scanning position of the recording head 205, and the recording data and its ejection timing are given to the drive circuit of the recording head 205 in a timely manner. Reference numeral 206 denotes a mechatronics control circuit that controls the motor / sensor. The circuit 206 controls a motor for moving the recording medium in the sub-scanning direction, a motor for moving the recording head in the scanning direction, a sensor for detecting the entry and ejection of the recording medium, and the like. Reference numerals 207 and 208 denote motors represented by a stepping motor, a DC motor, and the like, which drive the recording medium and drive the recording head 205 via gears, gears, and belts, respectively. Reference numeral 210 denotes a sensor for detecting the presence / absence of a recording medium. When a recording medium enters the sensor position, a lever or the like is tilted, and this interrupts the photosensor, thereby detecting the presence of the recording medium. Reference numeral 211 denotes an AD port that receives an input of the detection signal 106 indicating the potential difference (voltage value) between the electrodes of the ink tank 213 and converts it into a digital signal. Reference numeral 212 denotes a constant current circuit for causing a constant current to flow between two electrodes of the ink tank based on the control of the CPU 200. In this embodiment, the circuit has the circuit shown in FIG.

  Reference numeral 231 denotes a communication cable that connects a computer serving as a host and the inkjet recording apparatus. A bus 220 connects the CPU 200, the communication control unit 201, the memory 202, the head control circuit 203, the motor / sensor control circuit 206, and the AD port 211. By setting data in the register of each unit from the CPU 200 through the bus 220, the CPU 200 can control all of the ink jet recording apparatus. In addition, a direct memory access function for transferring recording data from the memory 202 to the head control circuit 203 without using the CPU 200 is also possible using this bus. Reference numeral 221 denotes a signal line for sending information about how much the recording head 205 has moved from the optical sensor unit 204. Reference numeral 222 denotes recording data supplied corresponding to each nozzle of the recording head 205 and a signal line for sending the ejection timing. Reference numeral 224 denotes a signal line for causing a constant current to flow between two electrodes in the ink tank 213 under the control of the CPU 200.

  When the ink tank 213 is mounted on the ink jet recording apparatus, the two electrodes are inserted into the ink tank with the structure described above with reference to FIGS. 2 (a) and 2 (b). Reference numeral 225 denotes a supply path for supplying ink from the ink tank 213 to the recording head 205. Reference numerals 227 and 228 denote signal lines for connecting the motor and the motor / sensor control circuit, so that a signal suitable for the phase of the motor, or a rotation / stop signal can be supplied. Reference numeral 230 denotes a signal line that connects the sensor 210 that detects the presence or absence of a recording medium on which an image is to be formed and the motor / sensor control circuit 206, and notifies the CPU 200 whether or not a recording medium exists by using this signal line. To do.

  FIG. 8 is a flowchart showing processing relating to ink amount detection according to an embodiment of the present invention. The ink amount detection process of this embodiment is controlled by the CPU 200.

  This process is started when the recording apparatus is turned on (S10). First, in step S11, variables stored in the memory are initialized. This variable is related to the voltage value between the electrodes measured and stored sequentially up to that point and the number of stored voltage values. A maximum of 128 voltage values are stored, and are represented as variables A0 to A127 below. The number of stored voltage values is represented as variable B. In the initialization in step S11, these variables A0 to A127 and variable B are all set to zero.

  Next, in step S12, as described above, it is determined whether or not a sequence in which the ink flow in the ink tank is relatively large, such as a print head cleaning or an ink tank agitation sequence, is executed. In the cleaning of the recording head, the ink is circulated in the ink supply system from the ink tank to the recording head via the spare tank, so that a relatively large ink flow is generated in the ink tank by the circulating ink. In addition, when the ink to be used uses a pigment as a coloring material, the ink tank is vibrated at a predetermined time interval to stir the ink in the ink tank. This stirring also causes a relatively large ink flow. In these cases, the electric charge between the two electrodes is disturbed by the ink flow, and an unstable voltage value appears. If such a voltage value is transferred to an average value that is a basis for threshold calculation, an appropriate determination cannot be made. Therefore, when the ink flow becomes large, the process proceeds to step S21 so that the voltage value is not measured so as not to be transferred to the average value described below.

  If it is determined in step S12 that the sequence in which the ink flow increases is not executed, in step S13, the ink tank is mounted and the electrode is inserted, and the normal operation is performed by ink ejection from the recording head, such as recording or preliminary ejection. It is determined whether or not the current ink consumption state. In other words, in this embodiment, the ink amount is not detected when the recording head is not in an ink ejection state such as recording or preliminary ejection. On the other hand, if ink is normally consumed for recording or the like, it is determined in step S14 whether or not five seconds or more have passed since the ink amount detection just before that was performed. If 5 seconds or more have not elapsed, ink amount detection is not performed, and if 5 seconds or more have elapsed, ink amount detection from step S15 is performed. In other words, the ink amount is detected at intervals of 5 seconds during the recording operation and preliminary ejection. Also, in this embodiment, the interval of 5 seconds is set so that the frequency of current flow is considered in consideration of the fact that deposits due to electrolysis adhere around the electrode when the current continues to flow while the electrode is immersed in ink. This is to limit the deposition and prevent the deposit.

  In the ink amount detection, first, in step S15, it is determined whether or not 30 seconds or more (predetermined time or more) has passed since the immediately preceding ink amount detection. In this process, as described above, if the interval of applying a constant current between the electrodes exceeds a certain value, the discharge while the current is not flowing proceeds irregularly, so it is difficult to predict the voltage value due to the accumulated charge. It is. In the ink amount detection system of the present embodiment, this fixed time interval is 30 seconds. As described above, when the ink amount cannot be accurately detected, the process proceeds to step S21 as in the case of step S12, and the voltage value is not measured so as not to be included in the average value described below.

  If it is determined in step S15 that 30 seconds or more have not elapsed, the 5V power source 101 shown in FIG. 1 is turned on in step S16, and a constant current is passed between the electrode 104 and the electrode 105. In step S <b> 17, the voltage value indicated by the detection signal 106 is read via the AD port 211 after 100 msec has elapsed since the constant current began to flow between the electrodes. Next, in step S18, the voltage of the power supply 101 is returned to 0 V, and the flow of a constant current between the electrodes is stopped. In step S19, it is determined whether or not the voltage between the two electrodes read in step S17 is greater than a predetermined initial value. In this embodiment, this initial value is 0.8V. When the read interelectrode voltage is an initial value of 0.8 V or less (predetermined value or less), it can be considered that the ink state is very discharged. When a constant current is applied between the electrodes several times in such a state, the voltage between the electrodes rapidly rises to a voltage higher than the initial value. For this reason, when the voltage value is equal to or lower than the initial value, it is necessary to exclude the average value from which the threshold value is calculated in order to increase the accuracy of the threshold value. Therefore, the process proceeds to step S21 so that the measured voltage value is not transferred to the average value described below, as in steps S12 and S15. In this embodiment, the initial value is 0.8 V, which is about 80% of the maximum voltage when the ink is full.

  When it is determined that the voltage value measured in step S19 is greater than or equal to the initial value, in step S20, if the measured voltage value is the kth voltage value, the voltage value is set as the content of the variable Ak-1. At the same time, the average value of the k voltage values measured so far and stored in the memory is calculated. Specifically, the average value of the voltage values is calculated from the number k of the voltage values measured so far, which is the contents of the variable B, and the voltage values between the electrodes which are the contents of the variables A0 to Ak-1, which are the contents of the variables A0 to Ak-1. To do. For example, when the value (k) of the variable B is 20, the average value is obtained by taking the sum of the voltage values that are the contents of the variables A0 to A19 and dividing it by 20 that is the contents of the variable B. Next, in step S22, a predetermined constant voltage margin is added to the obtained average value, and the result is used as a threshold value. In the present embodiment, the margin value is set to 0.4V. This margin is set to a value equal to or greater than a change in voltage mixed as noise in a state where ink is usually completely contained. In step S23, it is determined whether or not the voltage value between the two electrodes read in step S17 is greater than a threshold value.

  If it is equal to or greater than the threshold value, it is defined in step S24 that the ink liquid level is below the upper surface of the blocking wall 111, that is, the ink amount is small (no remaining amount). Accordingly, the user is notified that there is no ink remaining amount via a predetermined user interface. After this process, the process returns to step S11. On the other hand, if it is determined in step S23 that the voltage value between the electrodes is equal to or lower than the threshold value, it is determined in step S25 that the ink liquid level is still above the upper surface of the blocking wall 111. Then, the contents of the variables A0 to A126 are shifted one by one and stored as the contents of the variables A1 to A127, and the contents of the variable A0 are stored as the interelectrode voltage value read in step S14. When the variable B is smaller than 128, the variable B is incremented by one. After the process of step S25, the process proceeds to step S12 and continues. In step S21, the contents of the variable A0 are set to the initial value voltage, the contents of the variables A1 to A127 are all set to 0, and the value of the variable B is set to 1.

  FIG. 9 is a diagram illustrating a change in the interelectrode voltage related to the ink amount detection when the inside of the electrode or the ink tank is poor in water repellency or inherently hydrophilic. Specifically, the figure shows a value obtained by reading the voltage value indicated by the detection signal 106 through the AD port, along with a decrease in the ink amount.

  In FIG. 9, a voltage value curve 240 indicated by a solid line indicates a value indicated by the detection signal 106 indicating a voltage value between the electrodes 104 and 105, and average value curves 241 and 243 indicated by broken lines (both indicate the same broken line). ) Shows the average values obtained by the process shown in FIG. A threshold curve 242 indicated by a broken line indicates a threshold value that changes according to the average value. The time point 244 is a time point when it is determined that the voltage value between the two electrodes 104 and 105 exceeds the threshold line 242 and the ink liquid level is below the upper surface of the blocking wall 111.

  As shown by the voltage value curve 240 in FIG. 9, the ink does not accumulate immediately after the start of recording, and the voltage between the two electrodes is lower than the preset initial value 0.8V. Thereafter, when a current is passed at intervals of 5 seconds, the voltage between the two electrodes begins to rise gradually and becomes larger than the initial value 0.8V. At the same time, the average value curves 241 and 243 also start to rise from the initial values. The threshold voltage 242 obtained by adding a margin voltage of 0.4 V to this average value curve exceeds the measured voltage between two poles, that is, the value of the voltage value curve 240. Judged to have come below the top surface.

  In this way, it is determined whether or not the ink amount is smaller than a predetermined amount using, for example, a threshold value based on an average of a plurality of voltage values measured in the past. As a result, first, in the boundary area where the ink is determined to be less than the predetermined amount, in the area where the volume of the ink connecting the electrodes fluctuates and the detection voltage value obtained as a result is likely to fluctuate, It can be determined that the amount of ink is less than a predetermined amount. As a result, it is possible to prevent an error in detecting the amount of ink corresponding to the amount of ink consumed due to a delay in determination. Second, even if the lot is different and the absolute value of the voltage value change accompanying the change in the ink amount may be different, a threshold value corresponding to the change can be obtained, and accurate ink amount detection can be performed.

  In the above-described embodiment, the average value is calculated using the variables A0 to A127 and the variable B. However, the variable C has a cumulative value, the variable D has a cumulative number, and the average value is the cumulative value C /. Even if the number D is calculated, substantially the same processing can be performed.

It is a figure which shows an example of the detection circuit of the ink amount detection system using an electrode, and the constant current circuit for a detection. (A) And (b) is a schematic diagram which shows the structure of the electrode in the ink tank mounting part of a printer (inkjet recording device), and its related ink tank. FIG. 3 is a diagram showing an example different from FIG. 2 relating to ink amount detection, and showing an example of detecting an ink amount by inserting an electrode into a tube that supplies ink to a recording head. It is a figure which shows the content of the detection signal 106 when ink is consumed with recording etc. using the system shown in FIG. 1, FIG. It is a figure which shows the change of the voltage value between electrodes accompanying consumption of ink when the inside of an ink tank has a hydrophilic property. Similarly, when the inside of the ink tank has a hydrophilic property, it is a diagram showing that the behavior of the voltage value between the electrodes accompanying the consumption of the ink differs depending on the lot. It is a block diagram which shows the control part of the inkjet recording device which concerns on one Embodiment of this invention. It is a flowchart which shows the process which concerns on the ink amount detection which concerns on one Embodiment of this invention. FIG. 6 is a diagram illustrating a change in an interelectrode voltage related to ink amount detection when the inside of an electrode or an ink tank has poor water repellency or inherently hydrophilic properties, according to an embodiment of the present invention.

Explanation of symbols

101 Power supply 104, 105 Electrode 106 Detection signal 200 CPU
202 Memory 205 Recording Head 211 AD Port 212 Constant Current Circuit 213 Ink Tank

Claims (4)

In an inkjet recording apparatus that records on a recording medium using a recording head that ejects ink and an ink tank that stores ink to be supplied to the recording head.
Means for supplying a constant current between a pair of electrodes inserted in the ink tank;
Voltage detecting means for detecting a voltage value indicating a potential difference between the electrodes when a constant current is supplied between the pair of electrodes;
Memory means for storing a plurality of voltage values detected in the past by the voltage detection means;
When a threshold value is calculated based on a plurality of voltage values stored in the memory means, and the voltage value obtained as a result of detecting the potential difference by the voltage detection means is equal to or greater than the calculated threshold value, ink is Control means for determining that the ink amount in the tank has dropped below a predetermined amount;
An ink jet recording apparatus comprising:   2. The ink jet recording according to claim 1, wherein the threshold value is obtained by setting an average value of a plurality of voltage values detected by the voltage detection unit in the past as a reference voltage and adding a constant voltage to the reference voltage. apparatus.   The reference voltage is a sequence in which an interval for supplying a constant current between the electrodes is equal to or longer than a preset time, a sequence in which the ink flows in the ink tank is executed, or a sequence in which the ink in the ink tank is stirred. 3. The ink jet recording apparatus according to claim 2, wherein when the operation is executed, a predetermined initial value voltage is set.   3. The ink jet recording apparatus according to claim 2, wherein the reference voltage is a predetermined initial value voltage when a voltage value when a constant current is supplied between the electrodes is equal to or less than a predetermined value. .

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