Patent Application
20100154706
1. Field of the Invention
The present invention relates to a liquid applying apparatus, and specifically relates to a structure for detecting the amount of a liquid used in the liquid applying apparatus.
2. Description of the Related Art
As a method for detecting the remaining amount of ink or the presence/absence of ink in an inkjet print apparatus, a method is widely known, in which a voltage value at the time of passing a current through the ink is measured by using a pair of electrodes. In such a method, the electric conductivity of the ink easily changes depending on the shapes of the electrodes, the contact state of the electrodes with a liquid, the structure and viscosity of the liquid, a temperature, or the like, and therefore, a technique in which effects of these factors can be suppressed to detect the remaining amount or the like with high precision has been proposed.
Japanese Patent Laid-Open No. H03-270942 (1991) cites the problem that the viscosity of a liquid changes depending on an operation environment temperature and thereby, the flowability of the liquid changes, and for the solution to the problem, a method for changing threshold values used for determining the running-out state of an ink in accordance with the operation environment temperature.
For example, in the liquid applying apparatus as disclosed in Japanese Patent Laid-Open No. 2005-254809, a liquid is filled into a liquid holding portion in the liquid applying mechanism and is circulated therein at the time of using the liquid applying apparatus, and at the time of not using the apparatus, the liquid is drained from the liquid holding portion so that the liquid is returned to the tank. As a structure for detecting the state of filling and returning of the liquid, a liquid sensor is provided in the vicinity of the liquid holding portion. When a pair of electrodes in contact with the liquid in a tube is used as the liquid sensor, there arises the problem that quick detection is difficult especially in the returning operation depending on the state of the viscosity or the like of the liquid according to a change of the environmental conditions. As a result of this, when the operations of filling and returning of the liquid are performed in a continued flow of a printing operation, the print operation may become slow as a whole.
When returning the liquid, a voltage change through time, which is detected between a pair of electrodes, causes a completion of returning the liquid to be detected in, for example, about 20 and several seconds in the case of ink having the viscosity of a normal environment. More specifically, the liquid amount becomes small by the returning of liquid, and thus it takes 20 and several seconds before the detected voltage has a predetermined threshold value or lower. In contrast to this case, when the liquid has a viscosity higher than that of the above described normal environment due to an environmental change, it may take, for example, 60 seconds or more before the detected voltage has a threshold value or lower though actual returning of the liquid is finished at the point of time of a lapse of 20 seconds to 30 seconds. This is because the liquid has high viscosity and thus a voltage higher than the voltage value corresponding to the actual liquid amount occurs between the electrodes due to a bridge of the liquid between the electrodes, inclusion of air bubbles in the liquid and the like. As the cause of the liquid having a high viscosity, decreasing of the ambient temperature, reduction in density due to evaporation, inclusion of microscopic substances such as paper dust and the like are conceivable. As the method for preventing the bridge between the electrodes, increasing the distance between the electrodes is conceivable. However, when an installation place is small like the inside of a tube, if electrodes are disposed to be greatly apart from each other, the resistance value of a liquid becomes large. Therefore, the dynamic range of the conduction state decreases, detection precision becomes low, and the S/N ratio becomes worse. Further, it is conceivable to perform control depending on the ambient temperature by mounting a temperature sensor. However the factor of change in viscosity of a liquid is not only a temperature, and therefore, this coping arrangement may not be sufficient.
To deal with the problem of such a viscosity change, the detecting method disclosed in the aforementioned Japanese Patent Laid-Open No. H03-270942 (1991) provides a thermistor, which operates in response to the change of ambient temperature, in the detecting circuit to change the detection threshold value in accordance with the viscosity change due to an environmental change. Thereby, when the viscosity of a liquid is high, the threshold value is changed so that the detected voltage can be allowed to be equal to or lower than the threshold value at the same timing as the actual completion of returning.
However, the method described in Japanese Patent Laid-Open No. H03-270942 (1991) needs the additional component that is a thermistor and thus has the problem of complicating a structure for detecting a liquid amount correspondingly. Further, as in the case of using the above described temperature sensor, when the viscosity change of the liquid is caused by the factors other than the temperature change, the structure using the thermistor disclosed in Japanese Patent Laid-Open No. 2005-254809 also has the problem of being unable to deal with the viscosity change.
An object of the present invention is to solve the above problems and is to provide a liquid applying apparatus which includes a simple liquid amount detecting structure in a mechanism which fills a liquid in a liquid holding portion and returns the liquid from the liquid holding portion.
In a first aspect of the present invention, there is provided a liquid applying apparatus comprising: an applying roller configured to apply a liquid to a medium; a liquid holding portion configured to contact with said applying roller for holding the liquid to be applied by said applying roller; a tank configured to store the liquid; a path configured to make a communication between said liquid holding portion and said storage unit; a pump configured to cause a flow of the liquid in a flow passage including said liquid holding portion, said storage unit and said path; a pair of electrodes provided in at least one of said liquid holding portion and said path; an output unit configured to output information corresponding to a conduction state between said pair of electrodes; a memory configured to store the information outputted by said output unit at time of a filling operation which uses said pump to fill said liquid holding portion with the liquid supplied from said storage unit through said path; a setting unit configured to set a threshold value used for determining a completion of a returning operation, which uses said pump to return the liquid in said liquid holding portion to said storage unit through said path, based on the information stored in said memory; and a determining unit configured to determine whether or not the returning operation is completed, based on the threshold value set by said setting unit and the information outputted by said output unit at time of the returning operation.
According to the above structure, the threshold value for determining completion of liquid returning can be determined based on the information which is stored in the memory and corresponds to the conduction state between a pair of electrodes at liquid filling, which is stored in the memory. More specifically, the information corresponding to the above described conduction state between the electrodes at the time of the filling corresponds to information on a value based on the viscosity of the liquid at the time of filling. In liquid returning which is performed after the above described filling, the threshold value for determining completion of liquid returning is determined based on the information on the value based on the viscosity of the liquid at the above described time of filling, and therefore, the determined threshold value can be made the value corresponding to the viscosity of the liquid at the time of returning.
As a result, a liquid amount detecting arrangement which performs detection of a liquid amount with high precision at the time of returning operation with a simple structure can be provided.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
When supplying the liquid to fill the liquid holding portion of the liquid applying mechanism 102 with the liquid, the pump 103 is driven, a valve 104 and a valve 106 are opened, and a valve 105 is closed. Thereby, the liquid is sucked out of the tank 108, and reaches the liquid holding portion of the liquid applying mechanism 102 through the tube. Further, by continuing the pump driving in the same state as the above described supply, the supplied liquid returns to the tank 108 in the direction of the arrow B through the liquid holding portion. In this manner, circulation of the liquid is performed.
When the liquid is to be returned, the pump 103 is driven, the valve 104 is closed, and the valves 105 and 106 are opened. Thereby, the air inside the tank 108 is sucked out, the air is fed to the tube 107 and the liquid applying mechanism 102, and thus the liquid in the tube 107 and the liquid holding portion of the liquid applying mechanism 102 is returned to the tank 108.
Here, the valve 106 is a check-valve which is closed at the non-operating time of the liquid applying apparatus. When a liquid applying operation is performed, it is desirable that the liquid holding portion of the liquid applying mechanism 102 is always in the state filled with a liquid. Determination of whether or not the liquid is filled into the liquid holding portion of the liquid applying mechanism 102 is performed by using a configuration including a liquid sensor 101, shown in
At the time of filling operation, the determining circuit 303 reads out a filling threshold value Th0 from a storage memory 304, and makes comparative determination of the filling threshold value Th0 and the voltage value obtained from the A/D converter circuit 302, and thereby, performs determination on whether or not the filling operation is normally performed. Further, the determining circuit receives a voltage value Vh in the filled state from the A/D converter circuit 302 after filling, and writes (stores) the voltage value Vh to the storage memory 304. Meanwhile, at the time of a returning operation, a threshold value calculating circuit 305 as threshold value setting means reads out the voltage value Vh of the filled state from the storage memory 304, calculates (sets) a returning threshold value Th1 by referring to the threshold table (correspondence table) stored in the storage memory 304, and transfers the returning threshold value Th1 to the determining circuit 303. The determining circuit 303 makes comparative determination of the received returning threshold value Th1 and the voltage value obtained from the A/D converter circuit 302 at the time of the returning operation, and thereby, determines whether or not the liquid returning (discharge) operation is completed.
In the case of a filling operation, first in step S401, valve switching is performed. More specifically, the valve 104 and the valve 106 shown in
In step S406, the process waits for a predetermined time which is set in advance within which the liquid is sufficiently filled into the liquid holding portion of the liquid applying mechanism 102 and the tube. During the waiting time, the pump continues to be driven. Subsequently, in step S407, in the state in which the liquid is sufficiently filled, the A/D converter circuit 302 acquires the voltage value at this point of time from the liquid sensor 101 again, converts it into a digital value, and thereafter, outputs the digital value to the determining circuit 303. Thereby, the determining circuit 303 acquires the digital voltage value. The voltage value acquired by the determining circuit 303 here is set as Vh. The determining circuit 303 stores the voltage value Vh in the storage memory. This completes the filling operation.
Meanwhile, in the case of the returning operation, first, in step S501, the threshold value calculating circuit 305 as threshold setting means sets a returning threshold value Th1. Here, the returning threshold value Th1 is not a fixed value which is set in advance, but is set for each returning operation. The method for setting the returning threshold value Th1 will be described later. Next, in step S502, valve switching is performed. The valve 105 and the valve 106 shown in
The calculating method (setting method) of the aforementioned returning threshold value Th1 will be described. For calculation of the returning threshold value Th1, the digital voltage value Vh which is acquired in step S407 and is stored in the memory at the time of the filling operation (immediately preceding filling operation) which is performed prior to the returning operation is used. Hereinafter, this reason will be described.
The voltage value measured by the liquid sensor 101 changes depending on the viscosity of the liquid.
The inventor of the present application pays attention to the fact that the voltage value Vh detected at the filling time changes depending on viscosity, and uses the voltage value as the indicator of the viscosity of the liquid at the time of the returning operation. More specifically, the inventor considers that when the voltage value Vh acquired at the filling time is low, the viscosity is relatively high, and sets the returning threshold value Th1 at the time of the returning operation at a relatively high value.
By determining (setting) the returning threshold vale Th1 by the above method, even when the liquid has relatively high viscosity, the completion of the returning operation can be detected without the time required until the returning operation is completed not becoming longer than necessary.
As above, the threshold value for determining returning completion of a liquid can be decided based on the information which is stored in the memory and corresponds to the conduction state between a pair of electrodes at the time of liquid filling. More specifically, the information corresponding to the conduction state between the above described electrodes at the filling time becomes the information of the value corresponding to the viscosity of the liquid at the filling time. In the liquid returning which is performed after the above described filling time, the threshold value for determining returning completion of the liquid is decided based on the information of the value corresponding to the viscosity of the liquid at the above described filling time, and therefore, the determined threshold value can be set at the value corresponding to the viscosity of the liquid at the time of its returning. Thereby, liquid amount detection with high precision at the time of the returning operation can be performed with the simple construction.
A second embodiment of the present invention differs in the calculating method of the threshold value Th1 from the aforementioned first embodiment, and the other structure and operation are the same as those of the first embodiment.
In the calculating method of the returning threshold value Th1 in the second embodiment, the returning threshold value Th1 is calculated by the following calculation formula by using the voltage value Vh acquired at the time of the filling operation which is performed immediately before the returning operation.
Th1=α×1/Vh
Here, α is a constant. The returning threshold value Th1 is calculated by performing the arithmetic operation of inverse proportion for Vh.
A third embodiment of the present invention likewise differs in the calculating method of the returning threshold Th1 from the first embodiment, and the other structure and operation are the same as those of the first embodiment.
In the calculating method of the returning threshold value Th1 of the third embodiment, the returning threshold value Th1 is calculated by the following calculation formula by using the voltage value Vh which is acquired at the time of the filling operation which is performed immediately before the returning operation.
Th1=α×1/Vh+β
Here, α and β are constants. The returning threshold value Th1 is calculated by performing the arithmetic operation of proportion for Vh.
In the above described first to third embodiments, a pair of electrodes 201 are provided in the tube 107, and the amount and presence/absence of the liquid in the tube are determined in accordance with the conduction state of the electrodes, whereby it is indirectly determined whether or not the liquid returning from the liquid holding portion is completed. However, the method for determining completion of liquid returning is not limited to this. For example, a method may be adopted, in which a pair of electrodes are provided in the liquid holding member, the state of the liquid in the liquid holding portion is directly detected in accordance with the conduction state between the electrodes, and the returning completion is determined. Further, in order to enhance the precision of the determined result, in addition to providing a pair of electrodes in the tube, a pair of electrodes is also provided in the liquid holding member, and the above described determination may be performed by the two pairs of electrodes. Further, in the above described first to third embodiments, as the information corresponding to the conduction state between a pair of electrodes, the information relating to the voltage value corresponding to the conduction state between a pair of electrodes is used, but the information is not limited to this. The information relating to the current value, the resistance value and the like corresponding to the conduction state between a pair of electrodes may be used. In short, the information corresponding to the conduction state between a pair of electrodes relating to the amount and presence/absence of the liquid in the tube and in the liquid holding member can be used.
Further, the liquid supply mechanism is constructed by including a later-described liquid flow path (not illustrated in
The liquid applying apparatus further includes a applying medium supply mechanism 1006 which is constructed of a pickup roller and the like for transferring a applying medium to a nip portion of the applying roller 1001 and the counter roller 1002. Further, in the conveying path of the applying medium, a paper discharge mechanism 1007, which is constructed of a paper discharge roller and the like, and transfers the applying medium coated with a liquid to a paper discharge section (not illustrated), is provided at the rear stream side of the applying roller 1001 and the counter roller 1002. These paper supply mechanism and paper discharge mechanism are also operated by the drive force of the drive motor 1004 which is transmitted through the power transmitting mechanism 1005 in the same way as the applying roller and the like.
The above described liquid is a liquid which promotes cohesion of components (for example, a pigment) in a pigment ink containing a pigment as a coloring material, for example. One example of the components of the liquid is described as follows.
Further, the viscosity of the aforementioned liquid is 5 to 6 cP (centipoises) at 25° C. In application of the present invention, it is natural that the liquid is not limited to the above described one. For example, the liquid containing a component which suppresses curl of the applying medium can be used.
In the case of using water as a liquid, a sliding ability at the abutting portions of the applying roller and the liquid holding member of the present invention becomes favorable by containing the component which reduces surface tension in the aforementioned liquid. In the above described one example of the components of the liquid to be applied, glycerin and the surface active agent are the components which reduce the surface tension of water.
Next, the elements of each of the parts constituting the applying apparatus of which an outline is described above will be described in more detail.
Further, when the liquid holding member 2001 is urged to and abuts on the peripheral surface of the applying roller 1001 by the urging force of a spring member (pressing means) 2006, the liquid holding member 2001 forms a long liquid holding space S extending over the entire liquid applying region by the applying roller 1001. The liquid is supplied into the liquid holding space S through the liquid holding member 2001 from a liquid flow path which will be described later, and the liquid holding member 2001 is constructed as follows. Thereby, in the stopping state of the applying roller 1001, the liquid can be prevented from accidentally leaking outside from the liquid holding space S.
The configuration of the liquid holding member 2001 is shown in
As described above, in the liquid holding member in this embodiment, the abutting member 2009 formed into one piece without a seam abuts on the outer peripheral surface of the applying roller 1001 in a continuous state without a gap by the urging force of the spring member 2006. As a result, the liquid holding space S becomes a space practically closed by the abutting member 2009, one surface of the space forming base member and the outer peripheral surface of the applying roller 1001, and a liquid is held in the space. In the state in which the rotation of the applying roller 1001 stops, the abutting member 2009 and the outer peripheral surface of the applying roller 1001 keep a liquid-tight state, and the liquid can be reliably prevented from leaking outside. Meanwhile, when the applying roller 1001 rotates, the liquid can pass a space between the outer peripheral surface of the applying roller 1001 and the abutting member 2009 in such a manner as to slip through the space, which will be described later. Here, in the stopping state of the applying roller 1001, the outer peripheral surface of it and the abutting member 2009 being in a liquid-tight state means that a liquid is not passed between the inside and the outside of the above described space. In this case, the abutting state of the abutting member 2009 includes the state in which the abutting member 2009 abuts on the above described outer peripheral surface through a liquid film formed by a capillary force, in addition to the state in which the abutting member 2009 directly contacts the outer peripheral surface of the applying roller 1001.
Meanwhile, as shown in
In the above liquid applying apparatus, a applying medium is transferred to between the applying roller 1001 and the counter roller 1002 by the applying medium feeding mechanism 1006, and the applying medium is inserted in between the rollers. With this, the applying medium is transferred to the paper discharge section with the rotation of the applying roller 1001 and the counter roller 1002. During the transfer, the liquid applied on the peripheral surface of the applying roller is transferred onto the applying medium P from the applying roller 1001 as shown in
In
In each of the abovementioned embodiments, the liquid applying apparatus having the liquid applying mechanism is described, and as one mode of such a liquid applying apparatus, an inkjet print apparatus is preferable. Hereinafter, an inkjet print apparatus including the above described liquid applying mechanism will be described.
The inkjet print apparatus 1 is provided with a paper feed tray 2 loaded with a plurality of print media P, and a semicircular separating roller 3 separates the print media P loaded on the paper feed tray one by one to feed the media P to a conveying passage. In the conveying passage, the applying roller 1001 and the counter roller 1002 which constitute the liquid applying means of the above described liquid applying mechanism are arranged, and the print medium P fed from the paper feed tray 2 is fed to between both the rollers 1001 and 1002. The applying roller 1001 rotates in the clockwise direction in
As the inkjet print device, a so-called full line type inkjet print apparatus which performs a print operation by using a long print head in which nozzles for ejecting an ink are arranged along the maximum width of a print medium can be constructed.
Further, the liquid used in the present embodiment is a processing liquid which reacts to ink.
Here, as the processing liquid, there is cited a liquid containing a component which causes a coloring material (dye and pigment) in ink to coagulate, for example. As the component causing the coloring material in the ink to cohere, polyvalent metal salt for causing the pigment in the ink to cohere is cited. Polyvalent metal salt is constructed of polyvalent metal salt ions with two valences or more, and anions which are bound with these polyvalent metal ions. Concrete examples of the polyvalent metal ion include bivalent metal ions such as Ca2+, Cu2+, Ni2+, Mg2+ and Zn2+, trivalent metal ions such as Fe3+ and Al3+, and the like. Further, the anions which are bound with these ions include C1−, NO3−, SO4−, I−, Br−, ClO3−, RCOO− (R is an alkyl group) and the like. Further, polyallylamine and the like which cause a dye in ink to cohere is cited.
In the present embodiment, by using the processing liquid as described above as a liquid, the processing liquid and the pigment which is a coloring material of the ink ejected to the print medium coated with the processing liquid react with each other, and cohesion of the pigment is promoted. By promoting cohesion of the pigment, print density can be enhanced. Further, reduction or prevention of bleeding is enabled. It is a matter of course that the liquid which is used in the inkjet print apparatus is not limited to the above described examples.
Further, when the present invention is applied to detection of the liquid amount in a predetermined liquid (ink) holding section in a liquid circulation supply system in a circulation path relating to supply of the ink, and a cleaning mechanism in an inkjet print apparatus, similar effects also can be obtained.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2008-323734, filed Dec. 19, 2008, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-323734 | Dec 2008 | JP | national |
