JP2008207371A - Inkjet image forming device and ink viscosity detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet image forming device which accurately detects the viscosity of ink. <P>SOLUTION: The image forming device detects the viscosity of ink by a viscosity detector 90 by sucking the ink in a subtank 80 into the viscosity detector 90. The result of the viscosity detection is compared with a viscosity value Ns previously set as a stability limit values of printing. If N is less than Ns, the ink in the subtank 80 is not diluted by a diluent. In that case, a dilution pump 95 is driven so as to ensure that the diluent in a diluent tank 92 flows in the direction of an arrow E and the ink flowing into a diluent channel 93 in viscosity detection is returned to the subtank 80. If N is equal to or greater than Ns, the ink is diluted by injecting the diluent in the diluent tank 92 into the ink in the subtank 80. In that case, when the diluent is supplied to the subtank 80 from the diluent tank 92, the diluent is once flowed into the viscosity detector 90 and flowed out. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet image forming apparatus that forms an image by ejecting ink onto a recording medium, and an ink viscosity detection method that detects the viscosity of the ink.

  2. Related Art Inkjet image forming apparatuses (inkjet recording apparatuses) that form images by discharging ink from a recording head (printing head) onto a recording medium are known. In this inkjet image forming apparatus, generally, a high-definition image can be formed using a small recording head in which a plurality of nozzles for ejecting ink are formed at high density. In addition, by arranging a plurality of small recording heads and discharging different color inks from the respective recording heads, a color image can be formed on the recording medium with a relatively inexpensive and small configuration. Inkjet image forming apparatuses have the advantages as described above, and are used in various image output apparatuses such as printers, facsimiles, and copiers regardless of whether they are for business use or home use.

  Among the ink jet type image forming apparatuses as described above, there is a type that reuses ink collected from a print head by a cleaning operation. In an ink jet type image forming apparatus that reuses this ink, the ink collected from the print head is returned to the sub tank and reused. This reused ink may thicken when exposed to the air and volatilizes. Due to this ink thickening, ink ejection from the print head becomes unstable, which causes a reduction in print quality.

In order to stabilize ink ejection from the recording head, the ink jet type image forming apparatus as described above includes an ink viscosity detecting means and an ink viscosity adjusting means for detecting the viscosity of the ink in the sub tank. Some of them are used while adjusting the viscosity of the ink by the ink viscosity adjusting means according to the detected viscosity (for example, see Patent Documents 1 and 2).
JP 2003-063032 A JP-A-2005-001195

  In the ink jet type image forming apparatus as described above, the viscosity of the ink in the sub tank is periodically detected by the ink viscosity detecting means, and if the detected viscosity value is higher than the preset viscosity upper limit value, the ink viscosity A predetermined amount of diluent is injected into the sub tank by the adjusting means, and the viscosity of the ink in the sub tank is maintained within a desired value range.

  Since the detection of the viscosity of the ink in the sub-tank is repeatedly performed, the ink whose viscosity is detected adheres and remains in the ink viscosity detection means (device). The remaining ink may increase in viscosity and cause a detection error at the next viscosity detection.

  In view of the above circumstances, an object of the present invention is to provide an ink jet image forming apparatus and an ink viscosity detection method with improved accuracy of ink viscosity detection.

In order to achieve the above object, an ink jet image forming apparatus of the present invention detects the viscosity of ink stored in an ink tank that supplies ink to a print head by an ink viscosity detecting means, and based on the detected viscosity, In an inkjet image forming apparatus that forms an image by discharging ink from the print head onto a recording medium while supplying a dilution liquid to the ink tank and adjusting the viscosity of the ink in the ink tank.
(1) The ink viscosity detecting means is characterized in that a diluent supplied to the ink tank flows in.

here,
(2) A diluent tank for storing the diluent is provided,
(3) The ink viscosity detecting means is disposed in the middle of a diluent flow path connecting the diluent tank and the ink tank,
(4) The diluent in the diluent tank may be supplied to the ink tank after flowing into and out of the ink viscosity detecting means through the diluent flow path.

further,
(5) You may provide the waste liquid tank which stores the waste liquid connected to the part which connects the said ink viscosity detection means and the said ink tank among the said dilution liquid flow paths.

Furthermore,
(6) A circulating flow path having one end connected to a portion connecting the ink viscosity detecting means and the ink tank in the dilution liquid flow path and the other end connected to the dilution liquid tank is provided. May be.

The ink viscosity detecting method of the present invention for achieving the above object is an ink tank for supplying ink to the print head in an ink jet image forming apparatus that forms an image by discharging ink from the print head onto a recording medium. In the ink viscosity detection method for detecting the viscosity of the ink stored in
(7) The ink remaining in the ink viscosity detecting means is diluted by flowing a diluting liquid for thinning the ink into the ink viscosity detecting means for detecting the viscosity of the ink.

here,
(8) When the ink viscosity detected by the ink viscosity detecting means is not more than a predetermined value, the diluting liquid is allowed to flow into the ink viscosity detecting means without supplying the diluting liquid to the ink tank. Good.

further,
(9) The dilution liquid that has flowed into the ink viscosity detection means may be discarded.

Furthermore,
(10) The diluent that has flowed into the ink viscosity detecting means may be returned to the diluent tank in which the diluent is stored.

  As used herein, “recording” (also referred to as image formation) is not only for forming significant information such as characters and graphics, but also for human beings to be perceived visually, regardless of significance. Regardless of whether or not they are manifested, it includes cases where images, patterns, patterns, etc. are widely formed on a recording medium or the medium is processed.

  The “recording medium” (also referred to as a sheet) is not only paper used in general recording apparatuses but also widely accepts ink such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. This includes what is possible.

  Further, the term “ink” should be broadly interpreted in the same way as the definition of “recording”, and is applied to a recording medium to form an image, a pattern, a pattern, or the like, A liquid that can be used for ink processing (for example, solidification or insolubilization of a colorant in ink applied to a recording medium) is included.

  According to the present invention, since the diluted liquid before being supplied to the ink tank flows into the ink viscosity detecting means, the ink remaining in the ink viscosity detecting means is easily diluted and discharged. For this reason, since the ink viscosity detection means removes the ink viscosity detection error, the accuracy of ink viscosity detection can be improved. As a result, ink ejection from the print head can be stabilized and deterioration in image quality can be prevented.

  The present invention has been realized in an ink jet printer that forms an image by ejecting ink onto a recording medium such as recording paper.

  With reference to FIG. 1, a printer as an example of an ink jet image forming apparatus of the present invention will be described.

  FIG. 1 is a front view schematically showing a printer which is an example of an ink jet image forming apparatus of the present invention.

  The printer 10 is connected to a host PC (personal computer) 12 that sends image information to the printer 10. In the printer 10, four (four) print heads 22 </ b> K, 22 </ b> C, 22 </ b> M, and 22 </ b> Y are arranged side by side in the conveyance direction (arrow A direction) of the recording medium (roll paper in this case). The four print heads 22K, 22C, 22M, and 22Y respectively eject black, cyan, magenta, and yellow inks. These four print heads 22K, 22C, 22M, and 22Y are so-called line heads, and extend in a direction orthogonal to the paper surface of FIG. 1 (a direction orthogonal to the arrow A direction). The lengths of these four print heads 22K, 22C, 22M, and 22Y are slightly longer than the maximum width (the length in the direction perpendicular to the paper surface of FIG. 1) of the recording medium that can be printed by the printer 10. These four print heads 22K, 22C, 22M, and 22Y are fixed and do not move during image formation.

  A recovery unit 40 is incorporated in the printer 10 so that ink can be stably ejected from the four print heads 22K, 22C, 22M, and 22Y. By the recovery unit 40, the ink discharge state from the print heads 22K, 22C, 22M, and 22Y is restored to the initial ink discharge state. The recovery unit 40 includes a capping mechanism 50 that removes ink from the ink discharge port formation (face surfaces) 22Ks, 22Cs, 22Ms, and 22Ys of the four print heads 22K, 22C, 22M, and 22Y during the recovery operation. Yes. The capping mechanism 50 is provided independently for each print head 22K, 22C, 22M, 22Y. In the example of FIG. 1, six colors (that is, six capping mechanisms 50) are shown. The color component is a preliminary mechanism when the print head is added. The capping mechanism 50 includes a known blade, an ink removing member, a blade holding member, a cap, and the like.

  The roll paper P is supplied from the roll paper supply unit 24 and is conveyed in the direction of arrow A by the conveyance mechanism 26 incorporated in the printer 10. The transport mechanism 26 includes a transport belt 26a for loading and transporting the roll paper P, a transport motor 26b for rotating the transport belt 26a, and a roller 26c for applying tension to the transport belt 26a.

  When forming an image on the roll paper P, after the recording start position of the roll paper P being conveyed reaches below the black print head 22K, the print head is based on the recording data (image information). Black ink is selectively ejected from 22K. Similarly, ink of each color is ejected in the order of the print head 22C, the print head 22M, and the print head 22Y to form a color image on the roll paper P. The printer 10 includes main tanks 28K, 28C, 28M, and 28Y for storing ink supplied to the print heads 22K, 22C, 22M, and 22Y, and the print heads 22K, 22C, and 22M, in addition to the components and members described above. , 22Y are provided with various pumps (see FIG. 3 and the like) for supplying ink and performing a recovery operation.

  The electrical system of the printer 10 will be described with reference to FIG.

  FIG. 2 is a block diagram showing an electrical system of the printer of FIG.

  Recording data and commands transmitted from the host PC 12 are received by the CPU 100 via the interface controller 102. The CPU 100 is an arithmetic processing unit that performs overall control such as reception of recording data of the printer 10, recording operation, handling of the roll paper P, and the like. After analyzing the received command, the CPU 100 renders the image data of each color component of the recording data by developing a bitmap on the image memory 106. As an operation process before recording, the capping motor 122 and the head up / down motor 118 are driven via the output port 114 and the motor driving unit 116, and the print heads 22K, 22C, 22M, and 22Y are connected to the capping mechanism 50 (see FIG. 1). ) To move to the recording position (image forming position).

  Subsequently, the roll motor (not shown) that feeds the roll paper P through the output port 114, the motor drive unit 116, the transport motor 120 that transports the roll paper P at a low speed, and the like are driven to drive the roll paper P. -The paper P is conveyed to the recording position. The leading end position of the roll paper P is detected by a leading edge detection sensor (not shown) for determining the timing (recording timing) at which ink starts to be discharged onto the roll paper P conveyed at a constant speed. Thereafter, in synchronism with the conveyance of the roll paper P, the CPU 100 sequentially reads the recording data of the corresponding color from the image memory 106, and prints the read data to the print heads 22K, 22C, 22M, 22Y. Transfer via the circuit 112.

  The operation of the CPU 100 is executed based on a processing program stored in the program ROM 104. The program ROM 104 stores processing programs and tables corresponding to the control flow. A work RAM 108 is used as a working memory. During each operation such as cleaning of the print heads 22K, 22C, 22M, and 22Y, the CPU 100 drives the pump motor 124 via the output port 114 and the motor drive unit 116 to control the pressurization and suction of ink, Viscosity detection is performed via the output port 114.

  Further, the printer 10 is provided with a viscosity detector 90 (which is an example of the ink viscosity detecting means referred to in the present invention) that detects the concentration of ink in the sub tank 80 (see FIG. 3). The viscosity detector 90 is controlled by the viscosity detector control unit 126. The viscosity detector control unit 126 may be configured to drive the viscosity pump 95 (see FIG. 3) and the viscosity detector 90 every predetermined time, or according to an instruction input from the operation panel 110. The viscosity detector 90 may be driven.

  With reference to FIG. 3, the ink supply mechanism incorporated in the printer 10 will be described.

  FIG. 3 is a schematic diagram illustrating an ink supply mechanism incorporated in the printer 10. Although FIG. 3 shows an ink supply mechanism for supplying ink to the print head 22K and for recovering the print head 22K, the ink supply mechanisms having the same configuration are also used for the other print heads 22C, 22M, and 22Y. Is provided. In FIG. 3, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

  The printer 10 (see FIG. 1) incorporates an ink supply mechanism 60 that supplies ink to the print head 22K. The ink supply mechanism 60 includes a main tank (ink cartridge) 28K that can be attached to and detached from the main body of the printer 10, a sub tank 80 disposed between the ink supply paths 62 and 64 that connect the main tank 28K and the print head 22K, A viscosity detector 90 that detects the ink viscosity in the sub tank 80 is configured. The sub tank 80 and the print head 22K are connected by two ink flow paths 64 and 65. A sub tank 80 that stores ink and a diluent tank 92 that stores a diluent for diluting the thickened ink are connected by a diluent channel 93. A viscosity detector 90 that detects the viscosity of the ink stored in the sub tank 80 is disposed (attached) in the middle of the diluent flow path 93.

  Each of the ink flow paths 64 and 65 connects the sub tank 80 and the print head 22K. A pressure pump 63 that is driven when the print head 22K is cleaned is attached to the ink flow path 64. A standby valve 67 that opens and closes the ink flow path 65 at a predetermined timing is attached to the ink flow path 65. The pressurizing pump 63 uses a pump such as a diaphragm pump that can flow ink when not driven, and is driven only so that ink flows in the direction of arrow C in FIG.

  The ink flow path 76 connects the recovery cap 50 and the supply pump 72. The ink discharged from the head nozzle 22Kn at the time of recovery is carried to the sub tank 80 when the supply pump 72 is driven.

  A dilution pump 95 that is driven when detecting the viscosity of the ink and when diluting the ink in the sub-tank 80 is attached to the dilution liquid channel 93. The dilution pump 95 is selectively driven so that ink flows in both directions (arrows D and E directions). In addition, standby valves 96, 97, and 98 that open and close the flow path at a predetermined timing are attached to the diluent flow path 93. These standby valves 96, 97, and 98 are hermetically sealed during standby.

  The sub tank 80 is provided with a well-known liquid level detection sensor 86 for detecting the liquid level of the ink (stored ink) stored in the sub tank 80. When the liquid level detection sensor 86 detects that the ink level in the sub-tank 80 has become below a certain level, the supply valve 73 is opened, the supply pump 72 starts to operate, and ink is sucked from the main tank 28K. 80. On the other hand, when the liquid level detection sensor 86 detects that the ink level in the sub tank 80 has reached a predetermined upper limit level, the supply pump 72 is stopped, the supply valve 73 is sealed, and the ink supply is stopped. Stopped.

  An ink viscosity detection method for detecting the viscosity of the ink in the sub-tank 80 will be described with reference to FIG.

  FIG. 4 is a flowchart showing a procedure until the ink viscosity in the sub tank is detected and diluted.

  This flow is performed when the viscosity pump 95 (see FIG. 3) and the viscosity detector 90 are driven every predetermined time by the above-described viscosity detector control unit 126 (see FIG. 2), or the operation panel 110 (see FIG. 2). This is started when the viscosity pump 95 and the viscosity detector 90 are driven in accordance with an instruction input from (refer to FIG.

  When this flow is started (during the dilution mode), first, the valve 96 disposed in the portion between the sub tank 80 and the viscosity detector 90 in the diluent flow path 93 and the valve 98 communicating with the atmosphere. Is released (S401). In this state, by driving the dilution pump 95 so that the ink moves (flows) in the direction of arrow D (S402), the ink in the sub tank 80 is sucked into the viscosity detector 90, and the viscosity detector 90 The viscosity is detected (S403). When this detection is completed, the dilution pump 95 is stopped (S404). The viscosity detection result N obtained in S403 is compared with a viscosity value Ns set in advance as a printing stability limit value (S405).

  When the viscosity of N is less than Ns in S405, the ink in the sub tank 80 is not diluted with the diluent. In this case, first, the dilution pump 95 is driven so that the diluent in the diluent tank 92 flows in the direction of arrow E (S431). By this operation, the ink that has flowed into the diluent flow path 93 by the viscosity detection is returned to the sub tank 80. After a predetermined time has elapsed, the dilution pump 95 is stopped (S432), and the valves 96 and 98 are sealed (S433).

  When the viscosity of N is equal to or higher than Ns in S405, the dilution is performed by injecting the diluent in the diluent tank 92 into the ink in the sub tank 80. In this case, in order to open the diluent flow path 93 that connects the diluent tank 92 and the sub tank 80, the valve 97 is opened (S411) and the valve 98 is sealed (S412). After the diluent flow path 93 is opened, the dilution pump 95 is driven so that the diluent flows in the direction of arrow E to inject the diluent into the sub tank 80 (S413). The amount of dilution is determined in advance by the value of N, and thereby the driving time of the dilution pump 95 is determined. When the diluent is supplied from the diluent tank 92 to the sub tank 80, the diluent once flows into the viscosity detector 90 and flows out. Therefore, the portion of the viscosity detector 90 where the ink flows is washed with the diluent. After the specified time has elapsed, the valve 98 is opened (S414), the valve 97 is sealed (S415), and the flow path is switched, so that all the diluent in the diluent flow path 93 is pushed into the sub tank 80 with air. Subsequently, the dilution pump 95 is stopped (S416), and the opened valves 96 and 98 are all sealed (S417) to return to the same valve state as before dilution. By the above-described procedure, the inside of the diluent channel 93 can be brought into a state close to that before dilution. That is, the ink remaining after flowing into the viscosity detector 90 when detecting the viscosity of the ink in the sub-tank 80 is easily diluted by the diluting liquid flowing into the viscosity detector 90 and discharged. For this reason, the viscosity detector 90 eliminates an ink viscosity detection error, so that the accuracy of ink viscosity detection can be improved. As a result, ink ejection from the print head can be stabilized and deterioration in image quality can be prevented.

  The method for adjusting the amount of the diluted liquid supplied to the sub-tank performs feedback control in which the supply amount is determined according to the viscosity measured by the viscosity detector and the amount is supplied by the pump. The supply amount can be adjusted by controlling the rotation amount in accordance with the measured viscosity using a tube pump capable of controlling the rotation amount with an encoder or the like.

  A specific example of the viscosity detector will be described with reference to FIGS. 5 and 6.

  FIG. 5 is a schematic diagram showing a rotary viscosity detector. FIG. 6 is a schematic diagram showing a tuning fork vibration type viscosity detector. In these drawings, the same components as those shown in FIG. 3 are denoted by the same reference numerals.

  As shown in FIG. 5, the rotary viscosity detector 130 has a rotating body 134 that is rotated by a motor 132 arranged in a container 136, and ink is allowed to flow into the container 136 from the sub tank 80. The rotation resistance is detected to detect the viscosity of the ink, which is well known.

  The tuning-fork type vibration viscometer 140 is a vibration that causes a pair of leaf springs 141 and 142 having vibrators 146 and 147 attached to their tips to resonate and vibrate in opposite phases at a certain frequency and amplitude by electromagnetic drive units 144 and 145, respectively. The difference in viscous resistance generated between the child and the sample is detected as a change in driving current, which is the driving force, and the viscosity of the sample is continuously obtained using the proportional relationship between the driving current and viscous resistance. is there. The position detection sensor 143 is for knowing that the amplitude is constant. In addition, the temperature sensor 148 in the center part has a feature that viscosity and temperature can be measured simultaneously.

  In any type of viscosity detector, there is a portion into which ink flows, and ink may remain in this portion. Therefore, as described above, the detection error of the ink viscosity can be reduced by flowing the diluent into the portion of the viscosity detector where the ink may remain and removing the residual ink.

  A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 7 is a schematic diagram illustrating the ink supply mechanism of the second embodiment incorporated in the printer 10. FIG. 8 is a flowchart showing a procedure until ink viscosity in the sub tank is detected and diluted in the ink supply mechanism of FIG. In these drawings, the same components as those shown in FIGS. 3 and 4 are denoted by the same reference numerals.

  In the second embodiment, a waste liquid tank 91 and a waste liquid flow path 94 are added to the structure of the first embodiment, and the viscosity detector can be cleaned when dilution is not necessary. The upper end of the waste liquid flow path 94 is connected to a portion of the dilution liquid flow path 93 between the viscosity detector 90 and the valve 96, and the lower end of the waste liquid flow path 94 is connected to the waste liquid tank 91.

  A procedure until the ink viscosity is detected and diluted by such an ink supply mechanism will be described.

  This flow is performed when the viscosity pump 95 (see FIG. 3) and the viscosity detector 90 are driven every predetermined time by the above-described viscosity detector control unit 126 (see FIG. 2), or the operation panel 110 (see FIG. 2). This is started when the viscosity pump 95 and the viscosity detector 90 are driven in accordance with an instruction input from (refer to FIG.

  When this flow is started (during the dilution mode), first, the valve 96 disposed in the portion between the sub tank 80 and the viscosity detector 90 in the diluent flow path 93 and the valve 98 communicating with the atmosphere. Is released (S801). In this state, by driving the dilution pump 95 so that the ink moves (flows) in the direction of arrow D (S802), the ink in the sub tank 80 is sucked into the viscosity detector 90, and the viscosity detector 90 The viscosity is detected (S803). When this detection is completed, the dilution pump 95 is stopped (S804). The viscosity detection result N obtained in S803 is compared with a viscosity value Ns set in advance as a printing stability limit value (S805).

  If N is less than Ns in S805, the ink in the sub tank 80 is not diluted with the diluent. In this case, first, the dilution pump 95 is driven so that the diluent in the diluent tank 92 flows in the direction of arrow E (S831). By this operation, the ink that has flowed into the diluent flow path 93 by the viscosity detection is returned to the sub tank 80. After a predetermined time has elapsed, the dilution pump 95 is stopped (S832), the valves 97 and 99 are opened (S833), and then the valves 96 and 98 are sealed (S834), so that the diluent flow path 93 and the waste liquid flow path. 94 is opened. In this state, the pump 95 is driven so that the diluent flows from the diluent tank 92 into the waste liquid tank 91 (so that the diluent flows in the direction of arrow E) (S835). The viscosity detector 90 is washed by the diluent flowing in the direction of arrow E, and the diluted diluent after washing is discharged to the waste liquid tank 91. After a predetermined time has elapsed, the valve 98 is opened (S836), the valve 97 is sealed (S837), and the flow path is switched, so that all the diluting liquid in the diluting liquid flow path 93 is pushed away into the waste liquid tank 91 with air. By this operation, it is possible to bring the inside of the diluent channel 93 close to the state before dilution. Finally, the pump 95 is stopped (S838), and all open valves are sealed to return to the same valve state as before dilution (S839).

  When the viscosity of N is equal to or higher than Ns in S805, dilution is performed by injecting the diluent in the diluent tank 92 into the ink in the sub tank 80. In this case, in order to open the diluent flow path 93 that connects the diluent tank 92 and the sub tank 80, the valve 97 is opened (S811), and the valve 98 is sealed (S812). After the diluent flow path 93 is opened, the dilution pump 95 is driven so that the diluent flows in the direction of arrow E to inject the diluent into the sub tank 80 (S813). The amount of dilution is determined in advance by the value of N, and thereby the driving time of the dilution pump 95 is determined. When the diluent is supplied from the diluent tank 92 to the sub tank 80, the diluent once flows into the viscosity detector 90 and flows out. Therefore, the portion of the viscosity detector 90 where the ink flows is washed with the diluent. After the lapse of the specified time, the valve 98 is opened (S814), the valve 97 is closed and the flow path is switched, so that all the diluting liquid in the diluting liquid flow path 93 is pushed into the sub tank 80 with air. Subsequently, the dilution pump 95 is stopped (S816), all the opened valves 96 and 98 are sealed (S817), and the same valve state as before dilution is restored. By the above-described procedure, the inside of the diluent channel 93 can be brought into a state close to that before dilution. That is, the ink remaining after flowing into the viscosity detector 90 when detecting the viscosity of the ink in the sub-tank 80 is easily diluted by the diluting liquid flowing into the viscosity detector 90 and discharged. For this reason, the viscosity detector 90 eliminates an ink viscosity detection error, so that the accuracy of ink viscosity detection can be improved. As a result, ink ejection from the print head can be stabilized and deterioration in image quality can be prevented.

  A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 9 is a schematic diagram illustrating an ink supply mechanism of Example 3 incorporated in the printer 10. FIG. 10 is a flowchart showing a procedure for detecting and diluting the ink viscosity in the sub tank in the ink supply mechanism of FIG. In these drawings, the same components as those shown in FIGS. 3 and 4 are denoted by the same reference numerals.

  In the third embodiment, the circulation channel 61 is added to the configuration of the first embodiment so that the ink and the diluted liquid can be used without waste. A valve 99 is attached to the circulation channel 61. One end of the circulation channel 61 is connected to a portion of the diluent channel 93 between the viscosity detector 90 and the valve 96, and the other end is connected to the diluent tank 92.

  A procedure until the ink viscosity is detected and diluted by such an ink supply mechanism will be described.

  This flow is performed when the viscosity pump 95 (see FIG. 3) and the viscosity detector 90 are driven every predetermined time by the above-described viscosity detector control unit 126 (see FIG. 2), or the operation panel 110 (see FIG. 2). This is started when the viscosity pump 95 and the viscosity detector 90 are driven in accordance with an instruction input from (refer to FIG.

  When this flow is started (during the dilution mode), first, the valve 96 disposed in the portion between the sub tank 80 and the viscosity detector 90 in the diluent flow path 93 and the valve 98 communicating with the atmosphere. Is released (S1001). In this state, by driving the dilution pump 95 so that the ink in the sub tank 80 moves (flows) in the direction of arrow D (S1002), the ink in the sub tank 80 is sucked into the viscosity detector 90 to detect the viscosity. The ink viscosity is detected by the device 90 (S1003). When this detection is completed, the dilution pump 95 is stopped (S1004). The viscosity detection result N obtained in S1003 is compared with a viscosity value Ns set in advance as a stability limit value for printing (S1005).

  When the viscosity of N is less than Ns in S1005, the ink in the viscosity detector 90 is not diluted with the diluent. In this case, in order to return the ink used for viscosity detection to the sub-tank 80 as much as possible, the pump 95 is driven so that the ink flows in the direction of arrow E (S1031), and is stopped after a predetermined time (1032). By driving the pump 95, most of the ink in the diluent flow path 93 and the viscosity detector 90 is returned to the sub tank 80, but the ink remains on the walls of the diluent flow path 93 and the viscosity detector 90. This needs to be removed. Therefore, the flow path from the sub tank 80 to the diluent tank 92 is shut off, the valves 97 and 99 are opened (S1033), and the valves 96 and 98 are sealed (S1034), and the diluent tank 92 and the viscosity detector 90 are closed. The flow path for circulating the ink is opened. After the circulation channel is opened, in order to circulate the diluent, the pump 95 is driven so that the diluent flows in the direction of arrow F (S1035). By this driving, the diluted liquid passes through the viscosity detector 90 and the inside of the viscosity detector 90 can be cleaned.

  However, a small amount of ink remaining in the flow path is mixed with the diluent by the circulation operation, and the ink viscosity changes. Therefore, after circulation for a certain time, when the ink and the diluent are mixed, the viscosity of the diluent is detected by the viscosity detector 90 (S1036). The dilution amount at the next dilution is determined according to the viscosity detected here. The relationship between the viscosity of the diluent and the dilution amount is stored in advance in the CPU 100 or the like. Thereafter, the pump 95 is temporarily stopped (S1037), the valve 98 is opened (S1038), the valve 97 is then sealed (S1039), and the pump 95 is driven so that the air from the valve 98 flows in the direction of arrow E. (S1040). As a result, air is sent into the circulation flow path, and all the liquid in the dilution liquid flow path 93 and the circulation flow path 61 is returned to the dilution tank 90. Therefore, the inside of the dilution channel returns to the state before dilution. Finally, the pump 95 is stopped (S1041), and all valves are sealed (S1042).

  On the other hand, when N is a viscosity of Ns or higher in S1005, dilution is performed. The flow of dilution is the same as in the first and second embodiments, and is from S1011 to S1017. The difference from Examples 1 and 2 is the state of the diluted solution. In the case of Examples 1 and 2, since the diluted liquid mixed with the ink is discarded as the waste liquid, the viscosity of the diluted liquid does not change. Therefore, the dilution amount is determined only by the viscosity of the ink in the sub tank 80. On the other hand, in the case of Example 3, since the diluent mixed with the ink returns to the diluent tank 92, the viscosity of the diluent changes with time. Therefore, the amount of dilution is determined by two parameters, the viscosity of the ink in the sub tank 80 and the viscosity of the diluted solution. This flow makes it possible to carry out dilution while maintaining the state before dilution substantially constant, increasing the ink viscosity detection accuracy, and to use ink and diluent without waste.

1 is a front view schematically showing a printer which is an example of an inkjet image forming apparatus of the present invention. FIG. 2 is a block diagram illustrating an electrical system of the printer of FIG. 1. It is a schematic diagram which shows the ink supply mechanism integrated in the printer. It is a flowchart which shows the procedure until it detects and dilutes the ink viscosity in a sub tank. It is a schematic diagram which shows a rotary viscosity detector. It is a schematic diagram which shows a capillary type viscosity detector. It is a schematic diagram which shows the ink supply mechanism of Example 2 incorporated in the printer. FIG. 8 is a flow chart showing a procedure until ink viscosity in a sub tank is detected and diluted in the ink supply mechanism of FIG. 7. It is a schematic diagram which shows the ink supply mechanism of Example 3 incorporated in the printer. FIG. 10 is a flowchart showing a procedure from detection of ink viscosity in a sub tank to dilution in the ink supply mechanism of FIG. 9.

Explanation of symbols

10 Printer 22K, 22C, 22M, 22Y Print head 80 Sub tank 90 Viscosity detector 92 Diluent tank 95 Dilution pump

Claims (8)

The viscosity of the ink stored in the ink tank that supplies the ink to the print head is detected by the ink viscosity detecting means, and the diluted liquid is supplied to the ink tank based on the detected viscosity, and the viscosity of the ink in the ink tank is detected. In an inkjet image forming apparatus that forms an image by discharging ink from the print head to a recording medium while adjusting
The ink-jet image forming apparatus according to claim 1, wherein the ink viscosity detecting means is a unit into which a diluent supplied to the ink tank flows. A diluent tank in which the diluent is stored;
The ink viscosity detecting means is arranged in the middle of a diluent flow path connecting the diluent tank and the ink tank,
2. The inkjet image forming apparatus according to claim 1, wherein the diluent in the diluent tank is supplied to the ink tank after flowing into and out of the ink viscosity detecting means through the diluent flow path. apparatus. 3. The inkjet image forming apparatus according to claim 2, further comprising a waste liquid tank connected to a portion connecting the ink viscosity detecting means and the ink tank in the diluent flow path for storing waste liquid. One end of the diluent flow path is connected to a portion connecting the ink viscosity detecting means and the ink tank, and the other end is provided with a circulation flow path connected to the diluent tank. The inkjet image forming apparatus according to claim 2. In an ink jet type image forming apparatus for forming an image by discharging ink from a print head to a recording medium, an ink viscosity detection method for detecting a viscosity of an ink stored in an ink tank that supplies ink to the print head.
An ink viscosity detecting method comprising diluting ink remaining in the ink viscosity detecting means by flowing a diluting liquid for thinning ink into an ink viscosity detecting means for detecting the viscosity of the ink. 2. The dilution liquid is allowed to flow into the ink viscosity detection means without supplying the dilution liquid to the ink tank when the ink viscosity detected by the ink viscosity detection means is less than a predetermined value. 5. The ink viscosity detection method according to 5. The ink viscosity detection method according to claim 6, wherein the dilution liquid that has flowed into the ink viscosity detection means is discarded. The ink viscosity detection method according to claim 6, wherein the diluent that has flowed into the ink viscosity detector is returned to a diluent tank in which the diluent is stored.

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