Patent Application
20060262172
The present application is based on Japanese Patent Application No. 2005-144538 filed on May 17, 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
An ink-jet recording head having a plurality of ink ejection nozzles and a plurality of pressure chambers communicating with the nozzles, respectively, may have a problem that air bubbles and deteriorated ink remain in the nozzles and/or the pressure chambers and accordingly an ink-ejection performance of the recording head lowers. To solve this problem, it is needed to carry out a purging operation to purge the recording head of the air bubbles and the deteriorated ink. For example, Japanese Patent Application Publication No. 2004-58348 or its corresponding U.S. Patent Application Publication No. 2004/0196326A1 discloses an ink-jet printer that includes an ink-jet recording head; an ink tank that stores ink to be supplied to the recording head; an air tank that stores air having a predetermined pressure; and an air pump that supplies the air to the air tank, and that carries out a purging operation. When the ink-jet printer carries out the purging operation, first, in a state in which an air valve that is provided between the air tank and the ink tank is closed, the air is supplied from the air pump to the air tank, so that the air pressure in the air tank is increased up to the predetermined value. Then, when the air valve is opened, the air in the air tank (i.e., the pressurized air) instantaneously is supplied to the ink tank. Consequently the air pressure in the ink tank is increased up and the ink is quickly supplied to the recording head. Since the ink is quickly supplied to the recording head, the air bubbles and the deteriorated ink remaining in the recording head are forcedly discharged from the nozzles thereof
However, in the above-indicated ink-jet printer, the air pump is operated to increase the air pressure in the air tank, up to the predetermined value, irrespective of what amount of the ink may be present in the ink tank. Therefore, in the case where the amount of the ink present in the ink tank is greater than a reference ink amount assuring that the air pressure in the ink tank becomes equal to a desired pressure immediately after the air valve is opened, the air pressure in the ink tank immediately after the air valve is opened becomes higher than the desired pressure and accordingly an excessive amount of the ink is discharged from the recording head; and in the case where the amount of the ink present in the ink tank is smaller than the reference ink amount, the air pressure in the ink tank immediately after the air valve is opened becomes lower than the desired pressure and accordingly an insufficient amount of the ink is supplied to the recording head and the air bubbles and the deteriorated ink may not be efficiently discharged from the 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 air bubbles and/or ink whose properties have changed (e.g., its viscosity has increased) are discharged in a purging operation while useless consumption of the ink is prevented.
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, including an ink-jet recording head having an ink inlet into which an ink inflows; an ink tank which stores the ink and which has an ink outlet from which the ink outflows and additionally has 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-pressure regulating device which has an air outlet from which the air outflows and additionally has a second connector having an air supply passage which communicates, at one end thereof, with the air outlet and communicates, at an other end thereof, with the air inlet of the ink tank; an amount obtaining portion which obtains at least one of (a) an amount of the ink present in the ink tank and (b) an amount of the air present in the ink tank; and an operation control portion which controls, based on the amount obtained by the amount obtaining portion, an operation of the air-pressure regulating device to regulate a pressure of the air present in the ink tank, to a predetermined value.
According to a second aspect of the present invention, there is provided a method of controlling an ink-jet printer having an ink inlet into which an ink inflows; an ink tank which stores the ink and which has an ink outlet from which the ink outflows and 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; and an air-pressure regulating device including an air outlet from which the air outflows, and a second connector having an air supply passage which communicates, at one end thereof, with the air outlet and communicates, at an other end thereof, with the air inlet of the ink tank. The method comprises obtaining at least one of (a) an amount of the ink present in the ink tank and (b) an amount of the air present in the ink tank, and controlling, based on the obtained amount, an operation of the air-pressure regulating device to regulate a pressure of the air present in the ink tank, to a predetermined value.
In the above-indicated ink-jet printer or the above-indicated ink-jet-printer controlling method, the operating condition of the air-pressure regulating device is determined based on at least one of the amount of the ink present in the ink tank and the amount of the air present in the ink tank. Therefore, irrespective of whether the amount of the ink present in the ink tank is great or small, air bubbles and/or deteriorated ink can be reliably discharged from the ink-jet recording head, while useless consumption of the ink is prevented.
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 head 1 is a serial-type head that ejects droplets of an 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 the recording sheet.
Hereinafter, one of the ink-jet heads 1 each having an identical construction 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 the 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 sinks 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 member 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 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 covering the control portion 80. The lower cover 52 has a generally rectangular tubular shape with upper and lower open ends, 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 plate member 72 that is opposed to the cylindrical space 91a, to the other end portion of the same 72. In addition, an upper open end of the 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.
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 plate member 74 that is opposed to the cylindrical space 91a, to the other end portion of the same 74. 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 introducing the ink stored in the reservoir 62, into 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 (
Next, how the ink flows into the reservoir unit 70 will be described. As indicated by arrows in
Next, the main portion 1a of the ink-jet 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 provided 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 two piezoelectric sheets 43, 44.
Each of the individual electrodes 35 has, in its plan view, a substantially rhomboidal shape similar to that of each pressure chamber 10. More specifically described, one of two acute-angle corners of the each 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 and the respective lands 36.
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 a certain 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 deforms or displaces because those sheets 42 through 44 include no portions sandwiched by the individual electrodes 35 and the common electrode 34 and accordingly they are inactive sheets that cannot be influenced by the electric field.
Thus, each actuator unit 21 has a so-called 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, one of the four ink tanks 45 each having an identical construction 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
Next, the control device 83 will be described by reference to
The ink-amount obtaining portion 83a obtains an amount of the ink present in each of the ink tanks 45. More specifically described, the ink-amount obtaining portion 83a counts a total number of droplets of the ink ejected from the nozzles 8 of each ink-jet recording head 1 in all printing operations, and multiplies the counted number by an amount (or volume) of each ink droplet so as to obtain a consumed amount of the ink, and adds, to the thus obtained consumed amount of the ink, amounts of the ink that are outputted from the each ink-jet head 1 when the purging operations are carried out periodically or regularly, and irregularly when a 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 of the ink present in the each ink tank 45, by subtracting the thus summed consumed amount of the ink, from an initial amount of the ink stored by the same 45. However, in place of, or in addition to the ink-amount obtaining portion 83a, the control device 83 may employ an air-amount obtaining portion that obtains an amount of air present in each of the ink tanks 45. In the latter case, the air-amount obtaining portion may obtain the amount (e.g., volume) of the air present in the each ink tank 45, by subtracting, from a volume of the each ink tank 45, the amount (e.g., volume) of the ink obtained by the ink-amount obtaining portion 83a.
The operation-condition determining portion 83b determines, based on the ink amount obtained by the ink-amount obtaining portion 83a, respective operating conditions of the air pump 47 and the switching unit 48, so that the air pressure(s) in the ink tank(s) 45 is(are) controlled to a predetermined value to carry out the purging operation. The operating conditions determined by the operating-condition determining portion 83b include timings when the switching unit 48 is operated; and at least one operation parameter of the air pump 47 with respect to an operation thereof during a time period from a time when the switching unit 48 takes its closed state to a time when the unit 48 takes the fully open state or an arbitrary one of the four selectively open states.
Whether the switching unit 48 takes the fully open state or an arbitrary one of the four selectively open states depends on the number of the ink-jet recording head(s) 1 for which the purging operation is to be carried out. More specifically described, in the case where the purging 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 purging 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.
Each purging operation includes discharging deteriorated ink through the nozzles 8, and discharging air bubbles produced in the main portion(s) 1a of the ink-jet recording head(s) 1, also through the nozzles 8. The purging operations include the periodic ones that are carried out periodically, and the user-intended ones that are carried out when the user intends to recover the ink-jet head(s) 1 from failure thereof to eject the ink(s).
The operation control portion 83c controls the air pump 47 and the switching unit 48, according to the operating conditions determined by the operating-condition determining portion 83b.
Next, an operation of the control device 83 to carry out the purging operation will be described by reference to a flow chart shown in
More specifically described, providing that a volume of the air pump 47 is expressed as V47 (ml, milliliter); a volume of the air-pump communication tube 47a is expressed as V47a (ml); a volume of the air tank 46 is expressed as V46 (ml); a volume of each individual air-supply tube 67a is expressed as V67a (ml); a volume of the common air-supply tube 67b is expressed as V67b (ml); a volume of the switching unit 48 is expressed as V48 (ml); an air pressure in the air tank 46 is expressed as C (kPa); a volume of an air present in each ink tank 45 that is obtained by subtracting the obtained ink amount from a volume of the each ink tank 45 is expressed as D (ml); and a purging pressure is expressed as E (kPa), the following equation is met according to Boyle's law:
B·C=(B+V67a+D)·E where B=V47+V47a+V46+V67b+V48
That is, providing that an initial air pressure in each ink tank 45 is zero, a product, (air pressure, C)×(volume, B), corresponding to a state before opening of the switching unit 48 is equal to a product, (purging pressure, E)×(volume, B+V67a+D), corresponding to a state after the opening of the unit 48. Therefore, a desired value of the pressure C is so determined as to obtain desired value of the purging pressure E. In addition, a desired rotation amount, A, of the air pump 47 is so determined as to obtain the determined value of the pressure C; and a desired operation time, T, of the air pump 47 is determined based on the desired rotation amount A and a rotation speed, A′, (rpm) of the air pump 47. Operation timings of the switching unit 48 are determined based on the desired operation time T of the air pump 47. Step S102 corresponds to the amount obtaining portion that obtains at least one of (a) the amount of the ink present in each ink tank 45 and (b) the amount of the air present in each ink tank 45.
Then, at Step S103, the switching unit 48 is switched to the closed state, so that the air tank 46 is air-tightly closed. Subsequently, at Step S104, the air pump 47 is operated for the operation time T determined at Step S102, i.e., till the rotation amount of the air pump 47 reaches the desired rotation amount A determined at Step S102. Thus, the air pressure in the air tank 46 is increased up to the determined value of the pressure C. Next, at Step S105, the switching unit 48 is switched to the fully open state or the selectively open state, so that the air tank 46 communicates with one or more ink tanks 45 corresponding to one or more ink-jet recording heads 1 for which the purging operation is to be carried out. Since the air pressure in the air tank 46 is equal to the determined value of the pressure C, the pressurized air stored in the air tank 46 instantaneously flows into the ink tank(s) 45 via the common air-supply tube 67b and the individual air-supply tube(s) 67a. Thus, the air pressure(s) in the ink tank(s) 45 is(are) increased up to the desired value of 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 into the ink inlet(s) 61a of the ink-jet head(s) 1 via the ink supply tube(s) 65. The ink(s) flowing into the ink inlet(s) 61a of the ink-jet head(s) 1 flows or flow from the reservoir unit(s) 70 to the flow-channel unit(s) 4, and finally is(are) forcedly discharged from the nozzles 8. Thus, the air bubbles and/or deteriorated inks that remain in the main portion(s) 1a of the ink-jet head(s) 1 are discharged into an outside space, and thus the ink-ejecting performance(s) of the ink-jet head(s) 1 can be maintained.
At Step S106, after a predetermined time duration has elapsed, the switching unit 48 is switched to the full atmosphere-communication state or the selective atmosphere-communication state. Thus, the air pressure(s) in the ink tank(s) 45 is(are) instantaneously returned to the atmospheric pressure, so that the discharging of the ink(s) from the ink tank(s) 45 is instantaneously stopped. Thus, one purging operation is finished.
As is apparent from the foregoing description of the present ink-jet printer 101, the operating-condition determining portion 83b determines, based on the ink amount(s) obtained by the ink-amount obtaining portion 83a, the respective operating conditions of the air pump 47 and the switching unit 48, such that the air pressure(s) in the ink tank(s) 45 is(are) made equal to the purging pressure E. Therefore, irrespective of what amount(s) of the inks may be present in the ink tanks 45, the air pressures in the ink tanks 45 can be kept at the purging pressure E immediately after the switching unit 48 is switched to the fully open state or the selectively open state. Thus, the air bubbles and the deteriorated inks can be reliably removed from the ink-jet recording heads 1, while useless consumption of the inks is effectively prevented.
In addition, immediately after the switching unit 48 is switched to the fully open state or the selectively open state, the air pressure(s) in the ink tank(s) 45 is(are) made equal to the purging pressure E. Therefore, the inks can be efficiently expelled from the ink tanks 45, and accordingly the useless consumption of the inks is more effectively prevented.
In addition, when the switching unit 48 is switched to the full or selective atmosphere-communication state, the air pressure(s) in the ink tank(s) 45 is(are) immediately made equal to the atmospheric pressure, and the discharging of the ink(s) from the ink-jet recording heads 1 is immediately stopped. Therefore, the useless consumption of the inks is more effectively prevented.
In addition, since the switching unit 48 and the air supplying device (i.e., the air tank 46, the air pump 47, and the air-pump communication tube 47a) are commonly used with the plurality of ink-jet recording heads 1, the cost and size of the ink-jet printer 101 can be reduced.
Moreover, the ink-amount obtaining portion 83a counts the total number of droplets of ink ejected by the nozzles 8 of each ink-jet recording head 1 in all printing operations, and multiplies the counted number by the amount (or volume) of each ink droplet so as to obtain an ink consumption amount, and adds, to the thus obtained ink consumption amount, the total amount of ink that is discharged from the each ink-jet head 1 when the purging operations are carried out periodically or regularly, and irregularly when the user intends to recover the each ink-jet head 1 from its failure to eject ink. The ink-amount obtaining portion 83a calculates the amount of ink stored by the corresponding ink tank 45, by subtracting the thus calculated ink consumption amount from the initial amount of ink stored by the same 45. Therefore, the present ink-jet printer 101 need not employ any devices (e.g., sensors) for actually detecting the amounts of inks stored by the ink tanks 45.
Next, a second embodiment of the present invention will be described by reference to
The four ink valves 69 are provided in the four ink supply tubes 65, respectively, and each of the ink valves 69 opens and closes, based on commands supplied from the control device 283, a corresponding one of the ink supply tubes 65.
The control device 283 controls the ink-jet printer 201 as a whole, e.g., the ink-jet recording heads 1, the air pump 47, the switching unit 48, and the ink valves 69. The control device 283 has a construction substantially identical with that of the control device 83 employed in the first embodiment. However, the operating-condition determining portion 83b additionally determines operation timings of each of the ink valves 69, and the operation control portion 83c additionally controls an operation of the each ink valve 69.
Next, an operation of the control device 283 to carry out a purging operation will be described by reference to a flow chart shown in
More specifically described, providing that a volume of the air pump 47 is expressed as V47 (ml, milliliter); a volume of the air-pump communication tube 47a is expressed as V47a (ml); a volume of the air tank 46 is expressed as V46 (ml); a volume of each individual air-supply tube 67a is expressed as V67a (ml); a volume of the common air-supply tube 67b is expressed as V67b (ml); a volume of the switching unit 48 is expressed as V48 (ml); an air pressure in the air tank 46 is expressed as C (kPa); a volume of an air present in each ink tank 45 that is obtained by subtracting the obtained ink amount from a volume of the each ink tank 45 is expressed as D (ml); and a purging pressure is expressed as E (kPa), the following equation is met according to Boyle's law:
B·C=(B+V67a+D)·E where B=V47+V47a+V46+V67b+V48
Therefore, a desired value of the pressure C is so determined as to obtain a desired value of the purging pressure E. In addition, a desired rotation amount A of the air pump 47 is so determined as to obtain the determined value of the pressure C; and a desired operation time T of the air pump 47 is determined based on the desired rotation amount A and a rotation speed A′(rpm) of the air pump 47. Switching timings of the switching unit 48 are determined based on the operation time T.
Then, at Step S203, the switching unit 48 is switched to the closed state, so that the air tank 46 is air-tightly closed. Subsequently, at Step S204, the air pump 47 is operated for the operation time T determined at Step S202, i.e., till the rotation amount of the air pump 47 reaches the desired rotation amount A determined at Step S202. Thus, the air pressure in the air tank 46 is increased up to the determined value of the pressure C. Next, at Step S205, all, or an arbitrary one, of the four ink valves 69 is closed. Subsequently, at Step S206, the switching unit 48 is switched to the fully open state or the selectively open state, so that the air tank 46 communicates with all, or an arbitrary one, of the four ink tanks 45 corresponding to all, or an arbitrary one, of the four ink-jet recording heads 1 for which the purging operation is to be carried out. Since the air pressure in the air tank 46 is made equal to the determined value of the pressure C, the air stored by the air tank 46 instantaneously flows into the ink tank(s) 45 via the common air-supply tube 67b and the individual air-supply tube(s) 67a. Thus, the air pressure(s) in the ink tank(s) 45 is(are) increased up to the desired value of the purging pressure E. Then, at Step S207, all, or the arbitrary one, of the four ink valves 69 is opened, so that appropriate amount(s) of ink(s) is(are) instantaneously expelled 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 into the ink inlet(s) 61a of the ink-jet head(s) 1 via the ink supply tube(s) 65. The ink(s) flowing in the ink inlet(s) 61a of the ink-jet head(s) 1 flows or flow from the reservoir unit(s) 70 to the flow-channel unit(s) 4, and finally is(are) forcedly discharged from the nozzles 8. Thus, the air bubbles and/or the deteriorated inks that remain in the main portions 1a of the ink-jet heads 1 are discharged into an outside space, and the ink-ejecting performances of the ink-jet heads 1 can be maintained.
At Step S208, after a predetermined time duration has elapsed, 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(are) instantaneously returned to the atmospheric pressure, so that the discharging of the ink(s) from the ink tank(s) 45 is instantaneously stopped. Thus, one purging operation is finished.
As is apparent from the foregoing description of the present ink-jet printer 201, irrespective of what amount(s) of the ink(s) may be present in the ink tank(s) 45, the air pressure(s) in the ink tank(s) 45 can be kept at the purging pressure E immediately after the switching unit 48 is switched to the fully open state or the selectively open state. Thus, the air bubbles and the deteriorated inks can be removed from the ink-jet recording heads 1, while useless consumption of the inks is prevented.
In addition, after the air pressure(s) in the ink tank(s) 45 is(are) made equal to the purging pressure E, the ink valve(s) 69 is(are) opened to allow the ink(s) to flow from the ink tank(s) 45. Thus, the inks can be efficiently expelled from the ink tanks 45.
Next, a third embodiment of the present invention will be described by reference to
The four ink valves 69 are provided in the four ink supply tubes 65, respectively, and each of the ink valves 69 opens and closes, based on commands supplied from the control device 383, a corresponding one of the ink supply tubes 65.
The control device 383 controls the ink-jet printer 301 as a whole, e.g., the ink-jet recording heads 1, the air pump 47, the switching unit 48, and the ink valves 69. The control device 383 has a construction substantially identical with that of the control device 83 employed in the first embodiment. However, the operating-condition determining portion 83b additionally determines operation timings of each of the ink valves 69, and the operation control portion 83c additionally controls an operation of the each ink valve 69.
Next, an operation of the control device 383 to carry out a purging operation will be described by reference to a flow chart shown in
More specifically described, a desired rotation amount, a, of the air pump 47 is so determined that a pressure of an air (volume: D) present in each ink tank 45 that is obtained by subtracting the obtained ink amount from a volume of the each ink tank 45 is made equal to a desired value of the purging pressure E; and a desired operation time, T′, of the air pump 47 is determined based on the desired rotation amount a and a rotation speed, a′, (rpm) of the air pump 47. Switching timings of the switching unit 48 are determined based on the operation time T′.
Then, at Step S303, the switching unit 48 is switched to the fully open state or the selectively open state, so that the air pump 47 communicates with all, or the arbitrary one, of the four ink tanks 45 corresponding to all, or an arbitrary one, of the four ink-jet recording heads 1 for which the purging operation is to be carried out. Subsequently, at Step S304, all, or an arbitrary one, of the four ink valves 69 is closed. Then, at Step S305, the air pump 47 is operated for the operation time T′ determined at Step S302, i.e., till the rotation amount of the air pump 47 reaches the rotation amount a determined at Step S302. Thus, the air pressure(s) in the ink tank(s) 45 is(are) increased up to the desired value of the purging pressure E. Next, at Step S306, all, or the arbitrary one, of the four ink valves 69 are(is) opened, so that appropriate amount(s) of ink(s) instantaneously is(are) expelled 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 into the ink inlet(s) 61a of the ink-jet head(s) 1 via the ink supply tube(s) 65. The ink(s) flowing into the ink inlet(s) 61a of the ink-jet head(s) 1 flows or flow from the reservoir unit(s) 70 to the flow-channel unit(s) 4, and finally is(are) forcedly discharged from the nozzles 8. Thus, the air bubbles and/or the deteriorated inks that remain in the main portions 1a of the ink-jet heads 1 are discharged into an outside space, and the ink-ejecting performances of the ink-jet heads 1 can be maintained.
At Step S307, after a predetermined time duration has elapsed, 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(are) instantaneously returned to the atmospheric pressure, so that the discharging of the ink(s) from the ink tank(s) 45 is instantaneously stopped. Thus, one purging operation is finished.
As is apparent from the foregoing description of the present ink-jet printer 301, irrespective of what amount(s) of the ink(s) may be present in the ink tank(s) 45, the air pressure(s) in the ink tank(s) 45 can be kept at the purging pressure E when the purging operation is carried out. Thus, the air bubbles and the deteriorated inks can be reliably removed from the ink-jet recording heads 1, while useless consumption of the inks is prevented.
In addition, after the air pressure(s) in the ink tank(s) 45 is(are) made equal to the purging pressure E, the ink valve(s) 69 is(are) opened to allow the ink(s) to flow from the ink tank(s) 45. Thus, the inks can be efficiently expelled from the ink tanks 45.
Moreover, since each of the ink tanks 45 functions as an air tank in which air pressure is adjusted, the present ink-jet printer 301 need not employ any exclusive air tanks like the air tank 46 employed in the first or second embodiment.
While the present invention has been described in its preferred embodiments, it is to be understood that the present invention may otherwise be embodied.
For example, in each of the first to third embodiments, the switching unit 48 is switchable to the fall or selective atmosphere-communication state in which the ink tank(s) 45 is(are) communicated with the atmosphere so as to terminate forcibly the purging operation. However, the switching unit 48 may be one that is not switchable to the full or selective atmosphere-communication state. In this case, the ink tank(s) 45 cannot be communicated with the atmosphere, and the purging operation naturally terminates as the air pressure(s) in the ink tank(s) 45 gradually lowers or lower.
In addition, in the first or second embodiment, the ink-jet printer 101, 201 employs the air tank 46 and the switching unit 48. However, the ink-jet printer 101, 201 may be modified not to employ the air tank 46 or the switching unit 48. In this case, it is preferred that the air pump 47 be one that directly supplies a pressurized air having a predetermined pressure, to each of the ink tanks 45.
In each of the first and second embodiments, the air pressure in the air tank 46 is adjusted immediately before the purging operation is carried out. However, the ink-jet printer 101, 201 may be modified to adjust, beforehand, the air pressure in the air tank 46. In this case, the purging operation can be carried out quickly.
In each of the first and second embodiments, the air tank 46 and the air pump 47 cooperate with each other to provide the air supplying device. However, a different sort of air supplying device that can regulate the air pressure supplied to each of the ink tanks 45 may be employed.
In each of the first, second, and third embodiments, when the flow-passage member 48b is rotated in the switching unit 48, the unit 48 can be switched from the fully open state or the selectively open state to the first or second closed state corresponding to the full or selective atmosphere-communication state. However, the switching unit 48 may be modified such that the unit 48 is switchable from the fully open state or the selectively open state to the full or selective atmosphere-communication state that is independent of the first or second closed state, respectively.
In addition, in each of the first, second, and third embodiments, the ink-amount obtaining portion 83a calculates the total consumption amount of the ink ejected from each ink-jet recording head 1 in all printing operations, and the total consumption amount of the ink discharged from the each ink-jet head 1 when the purging operations are carried out periodically or regularly, and irregularly when the user intends to recover the ink-jet head 1 from its failure to eject the ink, and calculates the amount of the ink present in each ink tank 45, by subtracting the sum of the thus determined ink consumption amounts from the initial ink amount stored by the same 45. However, the ink-jet printer 101, 201, 301 may employ ink-amount sensors that actually or directly measure the respective amounts of the inks present in the ink tanks 45.
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 |
|---|---|---|---|
| 2005-144538 | May 2005 | JP | national |
