Patent Grant
7328983
The present application is based on Japanese Patent Application No. 2005-150535 filed on May 24, 2005, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink-jet printer that ejects droplets of ink onto a recording medium, and a method of controlling an ink-jet printer.
2. Discussion of Related Art
There is known an ink-jet printer including an ink-jet recording head that ejects droplets of ink; an ink tank that stores an ink to be supplied to the recording head via a flexible ink-supply tube; and an air tank that stores air to be supplied to the ink tank. An example of this ink-jet printer is disclosed by Japanese Patent Application Publication No. 2004-58348 or its corresponding U.S. Patent Application Publication No. 2004/0196326A1. This ink-jet printer has such a problem that air enters the flexible ink-supply tube through its wall and, as time elapses, air bubbles grow and increase in the ink-supply tube and eventually lower an ink-ejecting performance of the ink-jet recording head. To solve this problem, the ink-jet printer periodically carries out an air discharging operation in which air is quickly supplied from the air tank to the ink tank so as to discharge forcibly the air bubbles, together with an amount of the ink, from the ink-supply tube into an outside space.
However, in the above-indicated ink-jet printer, each air discharging operation is so performed as to discharge a predetermined amount of ink, irrespective of what amount of air (i.e., air bubbles) may be present in the ink-supply tube, e.g., at a time immediately before each printing or recording operation is started. If the air discharging operation is so performed as to discharge completely the air present in the ink-supply tube even if the total amount of the air may be large, then a large amount of the ink must be discharged together with the air, i.e., the large amount of ink is consumed uselessly. On the other hand, if the air discharging operation is so performed as to discharge only a small amount of the ink, then only an insufficient amount of the air may be discharged, which may lead to lowering the ink-ejecting performance of the ink-jet recording head.
It is therefore an object of the present invention to solve at least one of the above-indicated problems. It is another object of the present invention to provide an ink-jet printer and an ink-jet-printer controlling method each of which assures that a high ink-ejecting performance of the printer is maintained and, when an air discharging operation is carried out, useless consumption of ink is effectively prevented.
The Inventor has carried out extensive studies and found that an amount of air present in an ink-supply passage and an ink inflow passage can be expressed by an exponential function of an elapsed time, t, from a reference time, t=0 (the elapsed time t is a variable). The reference time may be a time when the last air discharging operation is carried out to discharge, through an air-discharge passage, the air present in the ink-supply passage and the ink inflow passage. The present invention has been developed based on this finding.
The above objects may be achieved according to the present invention. According to a first aspect of the present invention, there is provided an ink jet printer, comprising an ink-jet recording head having (a) an ink inflow passage including an ink inlet into which an ink inflows, and (b) an air-discharge passage which allows the ink inflow passage to communicate with an atmosphere; an air-discharge valve which selectively opens and closes the air-discharge passage; an ink tank which stores the ink and which has (c) an ink outlet from which the ink outflows and (d) an air inlet into which an air inflows; a first connector having an ink supply passage which communicates, at one end thereof, with the ink outlet of the ink tank and communicates, at an other end thereof, with the ink inlet of the ink-jet recording head; an air supplying device which supplies the air to the ink tank via the air inlet thereof, an obtaining portion which obtains one of (e) an elapsed time, t, from a reference time and (f) a volume, V, of an air present in the ink supply passage and the ink inflow passage at the elapsed time t, based on an other of the elapsed time t and the volume V of the air, and a following relationship:
V=a·ebt
According to a second aspect of the present invention, there is provided a method of controlling an ink-jet printer including an ink-jet recording head having (a) an ink inflow passage including an ink inlet into which an ink inflows, and (b) an air-discharge passage which allows the ink inflow passage to communicate with an atmosphere; an air-discharge valve which selectively opens and closes the air-discharge passage; an ink tank which stores the ink and which has (c) an ink outlet from which the ink outflows and (d) an air inlet into which an air inflows, a connector having an ink supply passage which communicates, at one end thereof, with the ink outlet of the ink tank and communicates, at an other end thereof; with the ink inlet of the ink-jet recording head; and an air supplying device which supplies the air to the ink tank via the air inlet thereof, the method comprising obtaining one of (e) an elapsed time, t, from a reference time and (f) a volume, V, of an air present in the ink supply passage and the ink inflow passage at the elapsed time t, based on an other of the elapsed time t and the volume V of the air, and a following relationship:
V=a·ebt
In the above-indicated ink-jet printer or the above-indicated ink-jet-printer controlling method, the amount V of the air or the elapsed time t can be accurately obtained, and the air supplying device and/or the air-discharge valve are/is controlled based on the obtained air amount V or the obtained elapsed time t. Therefore, a high ink-ejecting performance of the ink-jet printer can be maintained and, when an air discharging operation is carried out, useless consumption of the ink can be effectively prevented.
In the case where the air supplying device is controlled based on the obtained air amount V or elapsed time t, an operation speed at which the device is operated and/or an operation time period in which the device is kept operated may be determined based the same V, t. In the case where the air-discharge valve is controlled based on the obtained air amount V or elapsed time t, an open-state time period in which the air-discharge valve is kept opened, and/or a timing when the air-discharge valve is opened may be determined based the same V, t. The operation time period of the air supplying device and the open-state time period of the air-discharge valve may be determined to be equal to each other.
The above and optional objects, features, and advantages of the present invention will be better understood by reading the following detailed description of the preferred embodiments of the invention when considered in conjunction with the accompanying drawings, in which:
Hereinafter, there will be described preferred embodiments of the present invention by reference to the drawings.
Each ink-jet recording head 1 is a serial-type recording head that ejects droplets of ink onto the recording sheet while being moved in a main scan direction perpendicular to a sub-scan direction in which the recording sheet is fed by a feeding device, not shown. The four ink-jet heads 1 are configured such that the four heads 1 eject droplets of four different inks, respectively. The four different inks are a cyan ink, a yellow ink, a magenta ink, and a black ink. Thus, the ink-jet printer 101 prints or records a full-color image on a recording sheet.
Hereinafter, each ink-jet head 1 will be described in detail by reference to
The control portion 80 controls the ink-jet head 1 based on commands supplied thereto from the control device 83. The control portion 80 includes a main substrate 82; four auxiliary substrates 81 two of which are provided on one side of the main substrate 82 and the other two of which are provided on the other side of the same 82; and four driver ICs (integrated circuits) 81a that are fixed to respective inner surfaces of the four auxiliary substrates 81 that are opposed to the main substrate 82. The main portion 1a of each ink-jet head 1 includes four actuator units 21. The four driver ICs 81a produce respective drive signals to drive the four actuator units 21. Four heat sine 84 are fixed to respective surfaces of the four driver ICs 81a that are opposed to the main substrate 82.
Four FPCs (flexible printed circuits) 50 each as a power-supply element are connected, at respective one ends thereof, to the four actuator units 21, and are connected, at the respective other ends thereof to the four auxiliary substrates 81, respectively. In addition, the four FPCs 50 are also connected, midway between the four actuator units 21 and the four auxiliary substrates 81, to the four driver ICs 81a, respectively. That is, the four FPCs 50 are electrically connected to the four auxiliary substrates 81 and the four driver ICs 81a, and transmit respective signals outputted from the four auxiliary substrates 81, to the four driver ICs 81a, and supplies the respective drive signals outputted from the four driver ICs 81a, to the four actuator units 21.
The ink-jet head 1 further includes an upper cover 51 that covers the control portion 80; and a lower cover 52 that covers a lower portion of the head 1. The upper cover 51 has an arched ceiling, and covers the control portion 80. The lower cover 52 has a generally rectangular tubular shape with an upper open end and a lower open end, and covers the lower portion of the main substrate 82. The upper and lower covers 51, 52 cooperate with each other to prevent ink scattered in a printing operation, from adhering to, e.g., the control portion 80. In
Next, the reservoir unit 70 will be described by reference to
The reservoir unit 70 is for temporarily storing the ink, and supplies it to the main portion 1a. As shown in
The ink supplied from the ink tank 45 flows into the ink inflow passage 61 via the ink supply tube 65. The ink inflow passage 61 includes the cylindrical space 91a; a through hole 71a that is formed through the thickness of the plate member 71 such that the through hole 71 is aligned with the cylindrical space 91a; and an opening 72a that is formed through the thickness of the plate member 72 such that the opening 72a extends from one end portion of the member 72 that is opposed to the first cylindrical space 91a, to the other end portion of the same 72 that is opposed to the second cylindrical space 92a. In addition, an upper open end of the first cylindrical space 91a constitutes an ink inlet 61a. An opening 73a is formed through the thickness of the plate member 73, and constitutes a reservoir communication opening 61b of the ink inflow passage 61. An air-discharge-valve communication hole 61c is defined by a through hole 71b that is formed through the thickness of the plate member 71 such that the through hole 71b is aligned with the second cylindrical space 92a.
The reservoir 62 is for temporarily storing the ink flowing from the ink inflow passage 61 through the reservoir communication opening 61b thereof, and includes an opening 74a that is formed through the thickness of the plate member 74 such that the opening 74a extends from one end portion of the member 74 that is opposed to the first cylindrical space 91a, to the other end portion of the same 74 that is opposed to the second cylindrical space 92a. A plurality of holes are formed through the thickness of the plate member 75, and constitute a plurality of introduction-passage communication holes 62a through which the reservoir 62 communicates with the plurality of ink introduction passages 63, respectively. The opening 73a has, along a periphery thereof, a stepped portion or surface that supports a filter member 74b that removes dust from the ink.
The ink introduction passages 63 are for supplying the ink stored in the reservoir 62, to the main portion 1a, and are formed in the plate member 76 such that the ink introduction passages 63 are aligned with the introduction-passage communication holes 62a of the plate member 75. The ink introduction passages 63 communicate, at respective one ends thereof, with the introduction-passage communication holes 62a, and communicate, at the respective other ends thereof, with a plurality of ink supply ports 5b (
The air-discharge passage 64 is for discharging, into an ambient space, air produced in the ink supply tube 65 and the ink inflow passage 61, and includes the second cylindrical space 92a, and the air-discharge valve communication hole 61c (hole 71b) formed in the plate member 71 to be aligned with the second cylindrical space 92a. The air-discharge passage 64 communicates with the ink inflow passage 61 via the air-discharge-valve communication hole 61c, and additionally communicates with the air-discharge tube 68.
Next, how the ink flows in the reservoir unit 70 will be described. As indicated by arrows in
As will be described later, when an air discharging operation is carried out in a state in which the air-discharge tube 68 is in communication with the atmosphere, the ink flowing in the ink inflow passage 61 is caused, because of a lower flow resistance, to flow into the air-discharge passage 64 via the air-discharge-valve communication hole 61c, so that the ink is discharged from the air-discharge tube 68 into the ambient space. Thus, air bubbles present in the ink supply tube 65 and the ink inflow passage 61, the ink (i.e., deteriorated ink) whose properties have changed (e.g., its viscosity has increased), and foreign matters that have been captured by the filter 74b are discharged through the air-discharge tube 68.
Next, the main portion 1a of the ink-jet recording head 1 will be described by reference to
As shown in
The flow channel unit 4 has a substantially rectangular-parallelepiped shape extending in the main scan direction. As shown in
As shown in
As shown in
As shown in
A plurality of individual electrodes 35 are formed on the uppermost piezoelectric sheet 41 of each actuator unit 21, such that the individual electrodes 35 correspond to the pressure chambers 10 of the corresponding pressure-chamber group, respectively. A sheet-like common electrode 34 is interposed between the uppermost piezoelectric sheet 41 and the underlying piezoelectric sheet 42, such that the common electrode 34 corresponds to the entirety of the two sheets 41, 42. No electrodes are provided between the two piezoelectric sheets 42, 43 or between the piezoelectric sheets 43, 44.
Each of the individual electrodes 35 has, in its plan view, a substantially rhomboidal shape similar to each pressure chamber 10. More specifically described, one of two acute-angle corners of the rhomboidal individual electrode 35 is extended and is electrically connected to a land 36. The lands 36, connected to the individual electrodes 35, are electrically connected to a plurality of terminals of a corresponding one of the four FPCs 50 (
The common electrode 34 is grounded at a portion thereof, not shown, and is kept at a ground potential. On the other hand, respective electric potentials of the individual electrodes 35 of each actuator unit 21 can be controlled or changed, independent of each other, by a corresponding one of the four driver ICs 81a through respective independent leads of a corresponding one of the four FPCs 50 (
Next, a manner in which each actuator unit 21 is driven or operated will be described. Only the uppermost piezoelectric sheet 41 of each actuator unit 21 is polarized, in advance, in a direction of thickness thereof. Therefore, when an appropriate positive or negative electric voltage is applied to an arbitrary one of the individual electrodes 35, such that an electric field is produced in the same direction as the direction of polarization of a corresponding portion of the uppermost piezoelectric sheet 41 that is sandwiched by the arbitrary individual electrode 35 and the common electrode 34, the corresponding portion deforms owing to piezoelectric effect and thereby functions as an active portion. More specifically described, each of respective portions of the uppermost piezoelectric sheet 41 that are sandwiched by the individual electrodes 35 and the common electrode 34 expands or contracts in the direction of thickness thereof and contracts or expands, owing to transverse piezoelectric effect, in the direction perpendicular to the direction of thickness thereof. On the other hand, none of the other piezoelectric sheets 42, 43, 44 displaces because those sheets 42 through 44 include no portions sandwiched by the individual electrodes 35 and the common electrode 34 and accordingly are inactive portions that cannot be influenced by the electric field.
Thus, each actuator unit 21 has a “uni-morph” structure in which the uppermost piezoelectric sheet 41 distant from the pressure chambers 10 has the active portions and the other three piezoelectric sheets 42, 43, 44 near to the pressure chambers 10 have no active portions. The lower surface of each actuator unit 21 including the four piezoelectric sheets 41 through 44 is fixed to respective upper surfaces of a plurality of partition walls of the cavity plate 22 that define the pressure chambers 10. Therefore, if a strain difference is produced, in the direction perpendicular to the direction of thickness of each actuator unit 21, between each of the active portions of the uppermost piezoelectric sheet 41 and the underlying piezoelectric sheets 42, 43, 44, then the four piezoelectric sheets 41 through 44 are so deformed as to swell into the corresponding pressure chamber 10 (this is a “uni-morph” deformation). Thus, a volume of the pressure chamber 10 is decreased and a pressure of the ink present in the pressure chamber 10 is increased, so that the ink is expelled from the pressure chamber 10 toward the corresponding nozzle 8 and a droplet of the ink is ejected from the nozzle 8. Subsequently, when the electric potential of the individual electrode 35 is returned to the same level as that of the common electrode 34, the four piezoelectric sheets 41 through 44 are returned to their original shapes, so that the volume of the pressure chamber 10 is returned to its original volume and a certain amount of the ink is sucked from the corresponding manifold flow channel 5 into the pressure chamber 10.
Next, each of the four ink tanks 45 will be described by reference to a cross-sectional view thereof shown in
Back to
Next, the switching unit 48 will be described by reference to
As shown in
The flow-passage member 48b has a cylindrical shape, and fits in the inner cylindrical space of the frame member 48a such that the flow-passage member 48b is freely rotatable. The flow-passage member 48b has, in the upper portion thereof shown in
In addition, the flow-passage member 48b has, in the lower portion thereof shown in
Back to
A temperature-and-humidity detector or sensor 90 is for detecting a temperature and a humidity of an ambient air around the ink-jet printer 101, and supplies detection signals representing the detected temperature and humidity, to the control device 83.
Next, the control device 83 will be described by reference to
The air-discharging-operation starting portion 83a starts an air discharging operation when a user inputs a command to start the operation, or when a predetermined time has elapsed since the last air discharging operation was carried out.
The air-amount calculating portion 83b calculates an amount (i.e., a volume) of air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each of the ink-jet recording heads 1. As time elapses, ambient air permeates, little by little, the wall of each ink supply tube 65, and grows into air bubbles some of which move into, and are accumulated in, the corresponding ink inflow passage 61. As described above, the Inventor has found that an amount, V (mL), of air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet head 1 can be expressed, using an elapsed time, t, from an initial time, t=0, as a reference time, by the following equation:
V=a×ebt
The air-amount calculating portion 83b temporarily determines a coefficient b based on the material, wall thickness, and cross-section area of each ink supply tube 65 and pre-selected temperature and humidity of the ambient air. In addition, the air-amount calculating portion 83b corrects the temporarily determined coefficient b based on the actual temperature and humidity of the ambient air, detected by the temperature-and-humidity sensor 90. Here, respective characteristics of the coefficient b with respect to temperature and humidity are explained by reference to
In the present embodiment, a time when the last air discharging operation is carried out is used as the initial time, t=0, and the elapsed time t is measured from the initial time. In addition, 0.014 (mL) is used as the coefficient a, i.e., an amount of air present in the ink supply tube 65 and the ink inflow passage 61 at the initial time, t=0. This value of the coefficient a is experimentally obtained. Thus, the air-amount calculating portion 83b calculates the air amount V as a function of the elapsed time t, i.e., according to the following equation: V=0.014×ebt.
The ink-amount obtaining portion 83c obtains an amount of the ink present in each of the ink tanks 45. More specifically described, the ink-amount obtaining portion 83c counts a total number of droplets of the ink ejected by the nozzles 8 of each ink-jet recording head 1 in all printing operations, and multiplies the counted number by an amount (i.e., a volume) of each ink droplet so as to obtain an ink consumption amount, and adds, to the thus obtained ink consumption amount, a total amount of the ink that is consumed when the air-discharging operations are carried out periodically or regularly, and irregularly when the user intends to recover the each ink-jet head 1 from a failure thereof to eject the ink. The ink-amount obtaining portion 83a calculates an amount (i.e., a volume) of the ink present in each ink tank 45, by subtracting the thus calculated ink consumption amount from an initial ink amount stored by the same 45. However, in addition to, or in place of, the ink-amount obtaining portion 83a, the control device 83 may employ an air-amount obtaining portion that obtains an amount (i.e., a volume) of air present in each ink tank 45, by subtracting the thus calculated ink volume from a volume of the same 45.
The operating-condition determining portion 83d determines, based on the amount (i.e., volume) of air present in the ink supply tube 65 and the ink inflow passage 61, calculated by the air-amount calculating portion 83b, and the ink amount (i.e., volume) obtained by the ink-amount obtaining portion 83c, respective operating conditions of the air pump 47 and the switching unit 48 for the air discharging operation. More specifically described, the respective operating conditions of the air pump 47 and the switching unit 48 are determined such that when the air discharging operation is carried out, the air pressure in the corresponding ink tank 45 is controlled to an appropriate value (i.e., a purging pressure, E) assuring that substantially all the amount (i.e., volume V) of air calculated by the air-amount calculating portion 83b is discharged into the outside space through the air-discharge passage 64. The respective operating conditions of the air pump 47 and the switching unit 48 determined by the operating-condition determining portion 83d include placing the switching unit 48 in its fully or selectively open state, and additionally operating, in a state in which the switching unit 48 is placed in its fully or selectively open state, the air pump 47 at a selected rotation speed (rpm) and for a selected time period, T, and opening the air-discharge valve 49 for the selected time period T. For example, the above-indicated purging pressure E may be directly proportional with the calculated air volume V. To this end, the rotation speed (rpm) of the air pump 47 may be directly proportional with the calculated air volume V. In the last case, the time period T of the air pump 47 may be a predetermined constant value.
Whether the switching unit 48 takes the fully open state or any one of the four selectively open states depends on the number of the ink-jet recording head(s) 1 for which the air discharging operation is carried out. More specifically described, in the case where the air discharging operation is carried out for an arbitrary one of the four ink-jet heads 1, the switching unit 48 is switched, at an appropriate timing, to a corresponding one of the four selectively open states; and in the case where the air discharging operation is carried out for all the four ink-jet heads 1, the switching unit 48 is switched, at an appropriate timing, to the fully open state.
The operation control portion 83e controls, when the air discharging operation is carried out, the air pump 47, the switching unit 48, and the air-discharge valve(s) 49, according to the operating conditions determined by the operating-condition determining portion 83d.
Next, an operation of the control device 83 will be described by reference to a flow chart shown in
Next, an operation of the control device 83 to carry out the air discharging operation at Step S104 of
Subsequently, at Step S203, the switching unit 48 is placed in its fully open state or selectively open state; and at Step S204, the air pump 47 is operated at the rotation speed (rpm) determined at Step S202, for the operation time T also determined at Step S202 and, when the operation of the air pump 47 ends, the appropriate air-discharge valve(s) 49 is or are changed from the closed state thereof to the opened state thereof. Thus, the air is supplied from the air pump 47 to the ink tank(s) 45, and accordingly the air pressure(s) in the ink tank(s) 45 is or are increased up to the purging pressure E, so that appropriate amount(s) of ink(s) flows or flow from the ink outlet(s) 45d of the ink tank(s) 45. The ink(s) flowing from the ink outlet(s) 45d of the ink tank(s) 45 flows or flow, together with the air present in the ink supply tube(s) 65, into the ink inflow passage(s) 61 of the reservoir unit(s) 70. The air and ink(s) flowing in the ink inflow passage(s) 61 flow from the air-discharge valve communicating hole(s) 61c into the air-discharge passage(s) 64, and finally are discharged from the air-discharge tube(s) 68 into the outside space.
At Step S205, after a predetermined time has elapsed, the air-discharge valve(s) is or are closed, and the switching unit 48 is switched to the full or selective atmosphere-communication state. Thus, the air pressure(s) in the ink tank(s) 45 is or are instantaneously returned to the atmospheric pressure, so that the flowing of the ink(s) from the ink tank(s) 45 is instantaneously stopped. Thus, one air discharging operation is finished.
As is apparent from the foregoing description of the ink-jet printer 101 as the first embodiment, the operating-condition determining portion 83d determines, based on the air amount(s) V in the ink supply tube(s) 65 and the ink inflow passage(s) 61, calculated by the air-amount calculating portion 83c, the respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve(s) 49, for the air discharging operation. Therefore, when the air discharging operation is carried out, substantially no ink is consumed uselessly, while the ink-ejecting performance of each ink-jet recording head 1 is maintained.
In addition, the air-discharging-operation starting portion 83a starts the air discharging operations periodically, i.e., at the predetermined regular intervals of time. Therefore, the user need not operate the ink-jet printer 101 to carry out the air discharging operations.
In addition, the air-discharging-operation starting portion 83a starts the air discharging operation when the user inputs the command to carry out the operation. Therefore, the user can operate, at a desired timing, the ink-jet printer 101 to carry out the air discharging operation.
Moreover, the air-amount calculating portion 83b determines the coefficient b based on the material of each ink supply tube 65; the thickness of the wall of the each ink supply tube 65; the area of the cross-sectional area of the inner space of the each ink supply tube 65; and the pre-selected temperature and humidity of ambient air, and corrects the thus determined coefficient b based on the actual temperature and humidity of the ambient air. Therefore, the amount of the air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet recording head 1 can be accurately calculated.
In addition, the single switching unit 48 is commonly used for the plurality of ink-jet recording heads 1. Thus, the ink-jet printer 101 can be produced at low cost.
In addition, the switching unit 48 can be placed in the full or selective atmosphere-communication state in which the unit 48 allows each, or an arbitrary one of, the ink tanks 45 to communicate with the atmosphere. Therefore, the air discharging operation can be quickly stopped by placing the switching unit 48 in the full or selective atmosphere-communication state and thereby allowing all, or an arbitrary one of, the ink tanks 45s to communicate with the atmosphere. Thus, the flowing of the ink(s) from the ink tank(s) 45 can be instantaneously stopped, and the useless consumption of the ink(s) can be effectively prevented.
In a modified form of the first embodiment, the ink-jet printer 101 may be operated such that the air discharging operation is carried out immediately before each printing (or recording) operation is started. In another modified form of the first embodiment, the ink-jet printer 101 may be operated such that if the power of the printer 101 is in an “off” state when the predetermined regular interval of time has just elapsed since the last air discharging operation, then the next air discharging operation is carried out immediately after the power of the printer 101 is turned “on” again.
Next, a second embodiment of the present invention will be described by reference to
The air-growth-time calculating portion 283a calculates, based on the actual temperature and humidity of the ambient air detected by the temperature-and-humidity sensor 90, an air growth time, t1, measured from the last air discharging operation (i.e., an initial time, t=0), during which an amount V of air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet recording head 1 grows, i.e., increases up to a maximum permissible amount, V0, at which the each recording head 1 can exhibit its adequate ink-ejecting performance. More specifically described, the air growth time t1 can be expressed, using the maximum permissible amount V0 (mL), by the following equation:
V0=a×ebtl
Moreover, the air-growth-time calculating portion 283a temporarily determines the coefficient b based on the material of each ink supply tube 65; the thickness of the wall of the each ink supply tube 65; the area of the cross section of the inner space of the each ink supply tube 65; and the pre-selected temperature and humidity of ambient air, and corrects the thus determined coefficient b based on the actual temperature and humidity of the ambient air.
In the present embodiment, a time when the last air discharging operation was carried out is used as the initial time, t=0, and the elapsed time t is measured from the initial time. In addition, 0.014 (mL) is used as the coefficient a, i.e., an amount (mL) of air present in the ink supply tube 65 and the ink inflow passage 61 at the initial time, t=0. This value of the coefficient a is experimentally obtained. Thus, the air-amount calculating portion 83b calculates the air amount V as a function of the elapsed time t, i.e., according to the following equation: V=0.014×ebt. TABLE 1 shows a relationship between air growth time t1 (hour) and ambient-air temperature (° C.) with respect to the ink supply tube 65 through which the black ink is supplied; and a relationship between air growth time t1 (hour) and ambient-air temperature (° C.) with respect to the ink supply tube 65 through which the color ink (i.e., the cyan, yellow, or magenta ink) is supplied.
As shown in TABLE 1, as the ambient-air temperature increases, the speed of growth of the air present in the ink supply tube 65 and the ink inflow passage 61 increases like an exponential function, i.e., the air growth time t1 decreases exponentially.
The air-discharging-operation commanding portion 283b commands starting of an air discharging operation when the air growth time t1 has elapsed from the last air discharging operation.
The operating-condition determining portion 283d determines, based on the ink amount obtained by the ink-amount obtaining portion 83c, respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve(s) 49, for the air discharging operation. More specifically described, the respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve 49 are determined such that when the air discharging operation is carried out, the air pressure in the corresponding ink tank 45 is controlled to an appropriate value (i.e., a purging pressure E) assuring that the maximum permissible amount V0 of air present in the ink supply tube 65 and the ink inflow passage 61 is discharged into the outside space. The respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve 49 determined by the operating-condition determining portion 283d include placing the switching unit 48 in its fully or selectively open state, and additionally operating the air pump 47 at a selected rotation speed (rpm) and for a selected time period T, and opening the air-discharge valve 49 for the selected time period T.
Next, an operation of the control device 283 will be described by reference to a flow chart shown in
As is apparent from the foregoing description of the ink-jet printer as the second embodiment, the air discharging operation is carried out each time the amount V of the air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet recording head 1 reaches the maximum permissible amount V0. Therefore, the amount of the ink uselessly consumed during the air discharging operation can be reduced, while the ink-ejecting performance of the each recording head 1 is maintained.
In addition, the air-growth-time calculating portion 283a determines the coefficient b based on the material of each ink supply tube 65; the thickness of the wall of the each ink supply tube 65; the area of the cross section of the inner space of the each ink supply tube 65; and the pre-selected temperature and humidity of ambient air, and corrects the thus determined coefficient b based on the actual temperature and humidity of the ambient air. Therefore, the air growth time t1 in which the air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet recording head 1 reaches the maximum permissible amount V0 can be accurately calculated.
In a modified form of the second embodiment, the ink-jet printer may be operated such that if the power of the printer is in an off state when the calculated air growth time t1 has elapsed since the last air discharging operation, then the next air discharging operation is carried out in the same manner as described above, when the power of the printer is turned on again within a pre-selected time period following the air growth time t1. However, if the power of the printer is turned on again after the pre-selected time period has elapsed following the air growth time t1, it is preferred that the air discharging operation be carried out with respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve(s) 49 that are so changed or modified as to assure that all amounts of air that are then present in the ink supply tube 65 and the ink inflow passage 61 that are more than the maximum permissible amount V0 can be discharged into the outside space. The above-indicated case in which the power of the ink-jet printer is in the off state is an example of a timing at which the air discharging operation cannot be carried out by the printer.
Next, a third embodiment of the present invention will be described by reference to
The air tank 46 has an air supply port 46a, an air outlet 46b, and an atmosphere-communication port 46c, and stores pressurized air supplied from the air pump 47 through the air supply port 46a. The common air supply tube 67b communicating with the switching unit 48 is connected to the air outlet 46b, and an air-pump communication tube 47a communicating with the air pump 47 is connected to the air supply port 46a. The atmosphere-communication air valve 349 is connected to the atmosphere-communication port 46c of the air tank 46. The pressurized air stored by the air tank 46 is supplied to each of the four ink tanks 45 via the common air supply tube 67b and the corresponding individual air supply tube 67a. The air pump 47 supplies, based on a command supplied from the control device 283, pressurized air to the air tank 46 via the air-pump communication tube 47a. Thus, the air tank 46, the air pump 47, and the air-pump communication tube 47a cooperate with each other to constitute an air supplying device.
The control device 383 has the same construction as that of the control device 83, shown in
In the third embodiment, the switching unit 48 may be switched to its full or selective atmosphere-communication state so that the ink tank(s) 45 is or are communicated with the atmosphere. Alternatively, the ink-jet printer 301 may be operated such that the switching unit 48 is switched to its fully or selectively open state and simultaneously an air pressure in the air tank 46 is made equal to the atmospheric pressure, so that the air pressure(s) in the ink tank(s) 45 is or are made equal to the atmospheric pressure. To this end, the atmosphere-communication air valve 349 is selectively placed, based on a command supplied from the control device 383, in an atmosphere-communication state thereof in which the air valve 349 allows the air tank 46 to communicate with the atmosphere, and a non-communication state thereof in which the air valve 349 does not allow the air tank 46 to communicate with the atmosphere. However, the air tank 46 may be constructed such that as time elapses after the air discharging operation, the air pressure in the air tank 46 naturally or gradually lowers to the atmospheric pressure. In each of the latter two cases, since the switching unit 48 need not be switched to the full or selective atmosphere-communication state, the arrangement of the switching unit 48 can be simplified, and the ink tanks 45 can be easily communicated with the atmosphere.
The upper and lower portions of the flow-passage member 48b of the switching valve 48 may be replaced with two separate members, i.e., an upper flow-passage member and a lower flow-passage member that can be rotated relative to each other while they are air-tightly separated from each other. In this case, in the state in which the upper flow-passage member is placed in the fully or selectively open state thereof, the lower flow-passage member may be placed in the fully or selectively atmosphere-communication state, so as to allow the air tank(s) 46 to communicate with the atmosphere. Thus, the atmosphere-communication air valve 349 may be omitted.
As is apparent from the foregoing description of the ink-jet printer 301 as the third embodiment, the operating-condition determining portion 83d determines, based on the air amount(s) V in the ink supply tube(s) 65 and the ink inflow passage(s) 61, calculated by the air-amount calculating portion 83c, the respective operating conditions of the air pump 47, the switching unit 48, and the air-discharge valve(s) 49, for the air discharging operation. Therefore, when the air discharging operation is carried out, substantially no ink is consumed uselessly, while the ink-ejecting performance of each ink-jet recording head 1 is maintained.
In the third embodiment, the ink-jet printer 301 starts the air discharging operation when it receives the air-discharging-operation starting command inputted by the user into the control device 383, or when the predetermined regular time interval has elapsed since the last air discharging operation. However, the ink-jet printer 301 may be modified, like the second embodiment, such that first the time t1 of growth of the air in the ink supply tube 65 and the ink inflow passage 61 is calculated and, when the calculated air growth time t1 has elapsed, the air discharging operation is carried out.
While the present invention has been described in its preferred embodiments, it is to be understood that the present invention may be embodied in different manners.
For example, in the first embodiment, the air-discharging-operation starting portion 83a starts the air discharging operation either when the ink-jet printer 101 receives the air-discharging-operation starting command from the user, or when the predetermined regular time interval has elapsed since the last air discharging operation. However, the operation starting portion 83a may be modified such that it starts the air discharging operation only when the ink-jet printer 101 receives the air-discharging-operation starting command from the user, or may be modified such that it starts the air discharging operation only when the predetermined regular time interval has elapsed since the last air discharging operation.
In the first embodiment, the coefficient b is determined based on the material of each ink supply tube 65; the thickness of the wall of the each ink supply tube 65; the area of the cross section of the inner space of the each ink supply tube 65; and the temperature and humidity of the ambient air. However, the coefficient b may be determined based on at least one of (a) the material of each ink supply tube 65; (b) the thickness of the wall of the each ink supply tube 65; (c) the area of the cross section of the inner space of the each ink supply tube 65; (d) the temperature of the ambient air; and (e) the humidity of the ambient air.
In the first embodiment, the air-amount calculating portion 83b corrects the coefficient b based on the temperature and humidity of the ambient air detected by the temperature-and-humidity sensor 90. However, the air-amount calculating portion 83b may be modified such that it does not correct the coefficient b.
In the first embodiment, the single switching unit 48 is used commonly for the plurality of ink-jet recording heads 1. However, the ink-jet printer 101 may be modified such that it employs a plurality of switching units 48 for the plurality of ink-jet recording heads 1, respectively.
In each of the first and second embodiments, the control device 83, 283 includes the ink-amount obtaining portion 83c that obtains the amount(s) of the ink(s) present in the ink tank(s) 45, and the operating-condition determining portion 83d, 283d determines, based on the ink amount(s) obtained by the ink-amount obtaining portion 83c, the operating conditions of the air supplying device for the air discharging operation. However, the control device 83, 283 may be modified such that it does not include the ink-amount obtaining portion 83c. In this case, the operating-condition determining portion 83d, 283d determines, without using the ink amount(s) in the ink tank(s) 45, the operating conditions of the air supplying device.
In the second embodiment, the air-growth-time calculating portion 283a calculates, as the air growth time t1, the time period, measured from the last air discharging operation (i.e., an initial time, t=0), during which the amount of air present in the ink supply tube 65 and the ink inflow passage 61 corresponding to each ink-jet recording head 1 grows or increases up to the maximum permissible amount V0 at which the each head 1 can exhibit its adequate ink-ejecting performance. However, the air-growth-time calculating portion 283a may be modified such that it calculates, as the air growth time t1, a time period, measured from the last air discharging operation, during which the amount of air increases up to an amount smaller than the maximum permissible amount V0 by a predetermined amount.
In the third embodiment, the operating-condition determining portion 83d may determine the operating condition of only the air-discharge valve(s) 49, e.g., only a time period T in which the air-discharge valve(s) 49 is or are opened. In the case where the air pump 47 is so operated as to keep the air pressure in the air tank 46, to a predetermined value, the time period T can be selected at a value assuring that the calculated air amount V can be discharged into the outer space via the air-discharge passage(s) 64 opened by the air-discharge valve(s) 49.
It is to be understood that the present invention may be embodied with other changes and improvements that may occur to a person skilled in the art, without departing from the spirit and scope of the invention defined in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-150535 | May 2005 | JP | national |
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| 2004 58348 | Feb 2004 | JP |
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| 20060268076 A1 | Nov 2006 | US |
