JP2007090558A - Inkjet recording device and ink detection method of the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the structure of a detection circuit which detects an ink storage condition in an ink tank by measuring a variation in impedance between electrodes due to the presence of ink when there are a plurality of ink storage portions in an ink supply system and electrodes having physically different shapes are provided in the ink storage sections. <P>SOLUTION: By outputting detection clocks of frequencies set on the basis of electrical characteristics of a plurality of electrodes having physically different shapes to the electrodes, the common use of a main structure of a circuit which make judgment on the presence of ink becomes possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an ink detection method of the apparatus, and more particularly to an improvement in an ink detection system of an ink jet recording apparatus that uses a plurality of ink reservoirs such as ink tanks.

  Conventionally, as a method of measuring the remaining amount of ink in an ink tank used in an ink jet recording apparatus, an electrode pair is arranged in the ink tank, and a change in electrical resistance (impedance) due to the presence or absence of ink between the electrodes is measured. There is something that was made. In such a resistance value measurement method, a method of energizing in a pulse shape has been proposed for the purpose of preventing electrode corrosion and ink characteristic change due to the influence of electrolysis (for example, Patent Document 1, Patent Document). 2).

JP-A-9-76522 JP-A-11-179936

  However, there are a plurality of ink reservoirs for one ink supply system in the ink jet apparatus, and the functions thereof are different, so that the physical shape or the physical shape of the remaining amount detector is different, and the same ink Even in the presence state, the impedance between the remaining amount detection electrodes may be different. In such a case, in the above-described conventional example, it is necessary to configure an electric circuit so as to be compatible with the remaining amount detection unit disposed in each ink storage unit. There was an inconvenience that caused an increase in price. In particular, in an ink jet recording apparatus that uses a plurality of colors of ink for performing color recording, since an ink supply system is provided for each color, an increase in the scale and price of an electric circuit or recording apparatus becomes even more problematic.

  The present invention has been made in view of such a problem, and accurately detects the presence of ink in a plurality of ink reservoirs, simplifies an electric circuit, and reduces the size and price of an ink jet recording apparatus. With the goal.

Therefore, the present invention provides an ink jet recording apparatus comprising a plurality of ink storage units in an ink supply system for a recording head that ejects ink.
A plurality of ink detection means provided in each of the plurality of ink storage portions and having at least a pair of electrodes;
A determination unit that is commonly connected to the plurality of ink detection units and that determines an ink storage state of the ink storage unit based on a signal that varies depending on the presence or absence of ink between the electrodes;
A detection signal generating means for generating a detection signal corresponding to the electrical characteristics of the electrode of each of the plurality of ink detection means and applying the detection signal to the electrode;
It is characterized by comprising.

According to another aspect of the invention, an ink supply system for a recording head that ejects ink includes a plurality of ink storage units, and each of the plurality of ink storage units includes an ink detection unit having at least a pair of electrodes. An ink detection method for detecting an ink storage state of the plurality of ink storage units of a recording apparatus,
Generating a detection signal corresponding to the electrical characteristics of the electrode of each of the plurality of ink detection means and applying the detection signal to the electrode;
Based on a signal that changes depending on the presence or absence of ink between the electrodes by applying the detection signal generated according to the electrical characteristics using a determination unit commonly connected to the plurality of ink detection units, Determining an ink storage state of the ink storage unit provided with an ink detection means having the electrical characteristics;
It is characterized by comprising.

  According to the present invention, since the detection signal corresponding to the characteristics of the ink detection means of each ink reservoir is output, the main configuration of the determination means can be used in common. Therefore, simplification of the ink detection circuit, and consequently, increase in size and price of an ink jet recording apparatus using the ink detection circuit are not caused.

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

  FIG. 1 shows a configuration example of an ink supply system of an ink jet recording apparatus to which the present invention can be applied. In this example, a main ink tank (hereinafter referred to as a main tank) 10 that stores ink and has an ink detection unit 101 is provided as an ink supply source for a recording head 12 that performs recording by discharging ink. The main tank 10 is connected to a pump 142 capable of forward and reverse rotation through a filter 151 provided to remove foreign matters contained in the ink. The pump 142 is connected to a sub ink tank (hereinafter referred to as a sub tank) 11 having an atmosphere communication port 111 and an ink detection unit 112 via an on-off valve 161 in the form of an electromagnetic valve capable of opening and closing the flow path. The sub tank 11 temporarily stores the ink supplied from the main tank 10 and directly supplies the ink to the recording head 12 according to the operation of the ink supply pump 141.

  In the illustrated example, an ink circulation system is formed between the recording head 12 and the sub tank 11. That is, ink is supplied from the sub tank 11 to the recording head 12 by the pump 141, and the supplied ink flows into the flow path in the recording head 12 via the filter 153 for removing foreign matter, and from this flow path. It is distributed to each nozzle 12A. Then, the internal flow path of the recording head 12 returns to the sub tank 11 via the filter 154 for removing foreign matter.

  The recording head 12 is in the form of a line head in which nozzles 12A are arranged over a range of, for example, the entire width of the recording medium in order to perform recording on a recording medium (not shown). Then, the recording medium can be transported in a direction different from the nozzle arrangement direction, and ink can be ejected by driving the nozzles in the process. As the recording head 12, for example, an element having an element that generates thermal energy that causes film boiling in ink as energy used for ejecting ink, or a piezo element that acts on mechanical energy due to volume change is used. What has been used can be used.

  Except during the recording operation, the recording head 12 and the recovery unit 13 can be moved relative to each other to perform capping of the nozzle formation surface of the recording head 12. That is, except during the recording operation, the nozzles of the head 12 are blocked from the outside air by the recovery unit 13 and are kept moist so that the ink inside the nozzles does not dry. In the capping state or in the state where the recovery unit 13 and the recording head 12 are close to each other, the recording head 12 is driven to perform an ink discharge operation (preliminary discharge), or an appropriate pressure is applied to the ink supply system. By applying the ink, the ink is forcibly discharged from the nozzle, whereby a recovery process for making the ink ejection performance good can be performed.

  The recovery unit 13 has an ink detection unit 131 and is connected to the pump 142 via a foreign matter removing filter 152 and a flow path opening / closing valve 162. The ink received in the recovery unit 13 during the recovery process is regular or non-periodic (when the amount of the received ink exceeds a specified value, that is, when the electrode 131 detects that an overflow may occur) ) And the pump 142 is driven (reversed). The collected ink is returned to the main tank 10 and reused. However, when such reuse is impossible, it may be sent to a waste liquid tank (not shown). it can.

  In the above configuration, by driving the pump 141, ink is supplied from the sub tank 11 to the recording head 12, and a recording operation can be performed.

  When the remaining amount of ink in the sub-tank 11 has decreased to a specified amount, the valve 161 is set to an open state and the pump 142 is driven (forward rotation), so that the main tank 10 can transfer ink to the sub-tank 11. Supply is made. At this time, the valve 162 is set to close the flow path, and the flow path to the recovery unit 13 is blocked.

  When collecting the ink received by the recovery unit 13, the ink is returned from the recovery unit 13 to the main tank 10 by setting the valve 162 to the open state of the flow path and driving (reversing) the pump 142. Is done. At this time, the valve 161 is set to close the flow path, and the flow path to the sub tank 11 is blocked.

  In the ink supply system described above, there are a plurality of ink storage portions, that is, the main tank 10, the sub tank 11, and the recovery unit 13, and their functions are different from each other. Accordingly, the purpose of detecting the ink storage amount is different in a series of ink supply controls.

  That is, in the relatively large-capacity main tank 10 serving as an ink supply source, the purpose is to detect a state in which the remaining amount of ink stored is very small (hereinafter referred to as a residual ink trace state). In addition, the sub-tank 11 having a relatively small capacity, which supplies ink to the recording head 12 directly and receives ink from the main tank 10 in a timely manner, has a sufficient amount of remaining ink as well as a small amount of remaining ink. The purpose is to detect (hereinafter referred to as ink filling state). Further, the recovery unit 13 is intended to detect a state where the received ink amount is excessive and overflow may occur (hereinafter, ink receiving amount abnormal state).

  The ink detection unit of each storage unit is configured corresponding to each purpose, and each ink detection unit basically has the following configuration.

  FIG. 2 is a perspective view illustrating a basic configuration example of the remaining amount detection unit. The remaining amount detection unit has a pair of electrodes 200a and 200b, and cables 201a and 201b are drawn out for electrical connection with the detection circuit, respectively. Here, since the pair of electrodes 200a and 200b and the ink 202 therebetween can be regarded as an electrically capacitive load, the presence or absence of ink can be detected by detecting the impedance.

  The remaining amount detection units 101 and 131 disposed in the main tank 10 and the recovery unit 13 have such a basic configuration, but are adapted to each detection purpose (a small amount of ink state and an abnormal ink receiving amount state). The dimensions and arrangement positions of each pair of electrodes are determined. The sub-tank 11 is provided with a pair of electrodes extending to the vicinity of the bottom so as to be suitable for detection of the residual ink trace state, and one of the pair of electrodes is used to detect the ink filling state. An electrode having a predetermined length is provided opposite to the electrode.

  In the case of using the ink remaining amount detection unit as shown in FIG. 2, the pulse current is applied as described above for the purpose of preventing the electrode corrosion and the ink characteristic change due to the influence of electrolysis. A scheme has been proposed.

  FIG. 3 is a conceptual diagram showing the electrical characteristics of the ink remaining amount detection unit shown in FIG. 2, wherein (a) shows the ink amount (cc) when a pulse (detection clock) having a certain frequency is applied. The corresponding change in impedance (Ω), (b) shows the frequency characteristics of the impedance when a certain amount of ink is present between the electrodes. In this embodiment, the ink presence state is basically determined using this characteristic.

On the other hand, when the load is the same, the impedance varies depending on the physical shape of the electrode and the electrical characteristics of the ink. Specifically, when the electrode is mechanically downsized, the impedance increases with respect to the same amount of ink and the same frequency of the detection clock, and when the electrode is mechanically enlarged, the same amount of ink and the same frequency. It can be mentioned that the impedance becomes smaller with respect to the detected clock. This is supported by the following two general formulas.
C = K × S / d (F) (1)
(C: capacitance, K: ink dielectric constant,
S: surface area of electrode in contact with ink, d: distance between electrodes)
Z = 1 / (2 × Π × f × C) (Ω) (2)
(Z: impedance between electrodes, f: pulse frequency of detection circuit, C: capacitance)
Here, the circuit of the ink remaining amount detection unit based on the description in Patent Document 1 will be described.

  FIG. 4 is a block diagram showing a schematic configuration of the circuit. The components are roughly divided into a digital circuit unit 300, an ink tank 310, and an analog circuit unit 320. The digital circuit unit 300 includes a detection clock generation unit 301 and a determination result processing unit 302 that processes the determination result of the ink presence state as functional blocks. The ink tank 310 has an ink detector 311 provided with a pair of electrodes as shown in FIG. The analog circuit unit 320 receives a signal that changes in accordance with the impedance of the ink detection unit 311 and converts the detection signal processing unit 321 into an electrical signal that is optimal for the subsequent circuit, and a threshold voltage that serves as a determination criterion for the presence or absence of ink. And a determination threshold voltage generation unit 323 that compares the signal from the detection signal processing unit 321 with the determination threshold voltage and finally determines the presence or absence of ink.

  Such a configuration is effective when determining the ink presence state of a single ink storage unit (ink tank 310) in the ink supply system. However, when a plurality of (four types in the present example) ink detection units are provided as in the ink supply system of the present embodiment, it is difficult or rather preferable to make the electrode structures of all the detection units physically the same. In some cases, it is necessary to separately prepare a detection circuit as shown in FIG. 4 for loads having different electrical characteristics.

  In the present embodiment, detection clocks having different frequencies are output from the digital circuit unit 300 to a plurality of ink detection units having physically different shapes, while the main configuration of the analog circuit unit 320 is used in common. By doing so, it contributes to simplification of a circuit that performs ink detection for a plurality of ink storage portions, and in turn to the price reduction of an ink jet recording apparatus using the same.

  FIG. 5 shows the configuration of the ink detection circuit according to the present embodiment. Here, portions having the same functions as those in FIG.

  The detection clock generation unit 301 of the digital circuit unit 300 of this example supplies a detection clock having an appropriate frequency to each ink detection unit. For this purpose, in each ink detection unit, the frequency that becomes the impedance value defined from the detection operation characteristic of the analog circuit unit is confirmed in advance, and this is set to detect the appropriate frequency for each detection unit. Clock can be supplied.

  The mode will be described with reference to FIG. In FIG. 6, 5a, 5b, and 5c represent examples of the frequency characteristics of the impedance of the ink detection units disposed in the main tank 10, the sub tank 11, and the recovery unit 13, respectively. Za is an impedance value defined by the detection operation characteristic of the analog circuit unit 320. Furthermore, fm, fs, and fr mean the frequencies of the detection clocks at which the impedance of the ink detection units disposed in the main tank 10, the sub tank 11, and the recovery unit 13 is Za.

  In addition, after checking the detection clock with an appropriate frequency for each ink detection unit in this way, setting and outputting a detection clock with a different frequency for each detection unit as shown in FIG. This can be easily realized by appropriately configuring the logic circuit of the detection clock generator 301, which is a circuit.

  In the analog circuit unit 320 of this example, a selector 324 is interposed between each ink detection unit and the detection signal processing unit 321. The selector 324 has a function of selecting one of the four types of input detection signal output by the tank selection signal generation unit 303 added to the digital circuit unit 300.

  The detection clock generation unit 301 outputs a clock having a frequency corresponding to each detection unit at different timings, for example, in a time division manner, and notifies the tank selection signal generation unit 303 which tank clock is output. . The tank selection signal generation unit 303 outputs a control signal to the selector 324 according to this notification, and the selector 324 outputs one of the four types of detection signal outputs to the detection signal processing unit 321 accordingly. The subsequent detection operation is the same as that described with reference to FIG.

  Then, according to the determination result of the ink presence state of each storage unit by the determination result processing unit 302, the main control unit 400 of the apparatus can perform necessary control. The required control is control for executing recording when there is a sufficient amount of ink in the main tank 10 or the sub tank 11, and ink from the main tank 10 based on detection of a small amount of remaining ink in the sub tank 11 and an ink filling state. Control of supply and supply stop, control of ink return to the main tank 10 based on detection of an abnormal ink reception amount state of the recovery unit 13, ink replenishment based on detection of a small amount of remaining ink in the main tank 10 (new ink tank For example, control of the notification unit 401 to the user who prompts the user to exchange the information.

  The notification unit 401 can include display means for prompting the user to replace the ink tank. As such display means, a message display unit provided on an operation panel or the like of the recording apparatus main body may be used, or display is performed on a setting screen of a printer driver that operates on a computer that constitutes a host device for the recording apparatus. It may be a thing.

  As is clear from the above, in the present embodiment, a detection clock having a frequency corresponding to the characteristics of the ink detection unit of each ink storage unit is output, while the main configuration of the analog circuit unit 320 is used in common. It becomes possible. Therefore, simplification of the ink detection circuit, and consequently, increase in size and price of an ink jet recording apparatus using the ink detection circuit are not caused.

  In the above embodiment, the number of ink detection units or the number of types of ink detection states is four, but this is merely an example, and the present invention is not limited to this. That is, the application of the present invention is effective if there are a plurality of ink detection units or a plurality of types of ink detection states.

  In particular, the present invention is suitable for an ink jet recording apparatus in which a plurality of colors of ink (for example, four colors of black, cyan, magenta, and yellow) are used to form a color image, and an ink supply system is configured for each color. It will be something.

  In the above-described embodiment, the detection clock generation unit is a component of the digital circuit unit, but other configurations may be used as long as they generate clocks of different frequencies.

  Furthermore, as a method of confirming a frequency suitable for each ink detection unit, a state where ink is present and a state where no ink is present is created in advance, and an automatic tuning function is added to the digital circuit unit 300 to automatically find an optimum frequency. The method of making it etc. can be considered. This is effective when the dielectric constant of the ink changes due to environmental changes or the like, and it is necessary to reconfirm and reset the frequency.

  In addition, in the above-described embodiment, the selector is interposed between the ink detection unit and the detection signal processing unit. This is advantageous because it is not necessary to individually wire each ink detection unit to the detection clock generation unit. However, if the individual wiring is not a problem, it is possible to individually supply a detection clock having an appropriate frequency to each ink detection unit.

  In addition, the present invention is applied to a general inkjet recording apparatus, a copying machine, a facsimile having a communication system, an apparatus such as a word processor having a printing unit, or a multifunction recording apparatus combining these apparatuses. can do. The form may be for personal or office use or for industrial purposes.

1 is a schematic diagram illustrating a configuration example of an ink supply system of an ink jet recording apparatus to which the present invention can be applied. FIG. 2 is a perspective view illustrating a basic configuration example of a remaining amount detection unit applied to each ink storage unit of the ink supply system of FIG. 1. (A) And (b) is a conceptual diagram which shows the electrical property of the ink residual amount detection part shown in FIG. It is a block diagram which shows the structure of the conventional ink detection circuit. It is a block diagram which shows the structure of the ink detection circuit which concerns on one Embodiment of this invention. It is explanatory drawing which shows the difference in the electrical property of a some ink detection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main ink tank 101 Main tank ink detection part 11 Sub tank 111 Atmospheric communication port 112 Sub tank ink detection part 12 Recording head 13 Recovery unit 131 Recovery unit ink detection part 141, 142 Pump 151, 152, 153, 154 Filter 161, 162 Flow path on / off valve 200a, 200b Electrode 201a, 201b Electrode connection cable 300 Digital circuit unit 301 Remaining amount detection clock generation unit 302 Judgment result processing unit 303 Tank selection signal generation unit 310 Ink tank 311 Ink remaining amount detection unit 320 Analog Circuit unit 321 Detection signal processing unit 322 Ink presence / absence determination unit 323 Determination threshold voltage generation unit 324 Selector 400 Control unit

Claims (8)

In an ink jet recording apparatus comprising a plurality of ink storage units in an ink supply system for a recording head that ejects ink,
A plurality of ink detection means provided in each of the plurality of ink storage portions and having at least a pair of electrodes;
A determination unit that is commonly connected to the plurality of ink detection units and that determines an ink storage state of the ink storage unit based on a signal that varies depending on the presence or absence of ink between the electrodes;
A detection signal generating means for generating a detection signal corresponding to the electrical characteristics of the electrode of each of the plurality of ink detection means and applying the detection signal to the electrode;
An ink jet recording apparatus comprising:   The determination unit includes a measurement unit that measures an impedance between the electrodes or an electrical signal based on the impedance, a unit that provides threshold information common to the plurality of ink detection units, and the threshold value and a measurement value obtained by the measurement unit. And a means for determining the presence or absence of ink between the electrodes, and the detection signal generation means uses the electrical threshold value of the electrodes so that common threshold information is used for the plurality of ink detection means. 2. The ink jet recording apparatus according to claim 1, wherein clock pulses having different frequencies are generated as the detection signals according to characteristics.   A selector provided between the plurality of ink detection means and the measurement means to select one of the ink detection means and connect to the measurement means; and the detection signal generation means includes the plurality of ink detection means In contrast, it comprises means for outputting the different detection signals in a time-sharing manner and further controlling the selector so that the ink detection means corresponding to the output detection signal is selected. The inkjet recording apparatus according to claim 2.   A main ink tank that serves as an ink supply source, a sub ink tank that temporarily stores ink supplied from the main ink tank and supplies the stored ink to the recording head, and a recovery process of the recording head A recovery unit that receives ink discharged from the recording head is provided as the plurality of ink storage units, and ink for detecting a state in which the remaining amount of ink stored in the main ink tank is very small Detection means is provided, and the sub-tank is provided with ink detection means for detecting a state where the remaining amount of ink stored in the sub-tank is small and a state where the storage amount is sufficient, and the recovery unit Is provided with ink detecting means for detecting a state where the amount of received ink is excessive and overflow may occur. The ink-jet recording apparatus according to any one of claims 1 to 3 and symptoms.   A user who prompts ink replenishment based on a control for executing recording when a sufficient amount of ink is stored in the main ink tank and the sub tank, and detection of a state in which the remaining amount of ink in the main tank is very small Control to perform notification to the main tank, control to perform ink supply and supply stop from the main tank based on detection of a state in which the remaining amount of ink in the sub-tank is small and sufficient, and recovery 5. The ink jet recording apparatus according to claim 4, further comprising control means for executing control for collecting ink from the recovery unit based on detection of a state where ink overflow in the unit may occur. The plurality of ink jet recording apparatuses in which an ink supply system for a recording head that ejects ink includes a plurality of ink storage units, and each of the plurality of ink storage units includes an ink detection unit having at least a pair of electrodes. An ink detection method for detecting an ink storage state of an ink storage unit,
Generating a detection signal corresponding to the electrical characteristics of the electrode of each of the plurality of ink detection means and applying the detection signal to the electrode;
Based on a signal that changes depending on the presence or absence of ink between the electrodes by applying the detection signal generated according to the electrical characteristics using a determination unit commonly connected to the plurality of ink detection units, Determining an ink storage state of the ink storage unit provided with an ink detection means having the electrical characteristics;
An ink detection method comprising the steps of:   The ink detection method according to claim 6, further comprising a measurement step of measuring electrical characteristics of the electrodes included in each of the plurality of ink detection units. The ink detection method according to claim 7, wherein the measuring step is automatically performed under conditions of presence / absence of ink prepared in advance.

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