1. Field of the Invention
This invention relates to an image recording apparatus with a maintenance unit, and more particularly to an image recording apparatus with suction means for sucking in ink on the nozzle plate of the inkjet head.
2. Description of the Related Art
Inkjet image recording apparatuses have been widely used. This type of image recording apparatus has an ink head which includes an ink supply source, an ink chamber, and a plurality of nozzles serving as ink discharge outlets. The image recording apparatus shoots ink in the ink chamber from the individual nozzles, thereby recording an image.
The nozzles are arranged in a column on the nozzle plate. The nozzle plate has a water-shedding finish, thereby preventing the adhesion of ink. Even when a water-shedding finish has been given, the adhesion of ink cannot be prevented completely, which may permit ink to collect on the nozzle plate.
Therefore, to maintain the stable ink jet characteristic, the image recording apparatus has to remove the unnecessary ink on the nozzle plate. For this reason, the image recording apparatus has a maintenance unit for removing the unnecessary ink adhering to the nozzle plate. Such an image recording apparatus has been disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 5-201028.
In this publication, a maintenance unit 1000 as shown in
The maintenance unit 1000 includes a vacuum nozzle 1020, a positioning section 1023, an ink trap section 1026, and a vacuum pump 1027. One end of the vacuum nozzle 1020 is supported by the positioning section 1023 which is capable of moving in the direction in which the nozzles 1013 of the ink jet head are arranged. The other end of the vacuum nozzle 1020 is connected to the vacuum pump 1027 via the ink trap section 1026.
The maintenance unit 1000 causes the positioning section 1023 to scan along the arrangement direction of the nozzles 1013, thereby causing the vacuum nozzle 1020 to face the nozzles squarely one after another. At the same time, the maintenance unit 1000 causes the vacuum pump 1027 to operate, thereby making the pressure of one end of the vacuum nozzle 1020 negative. As a result, the maintenance unit 1000 causes the vacuum nozzle 1020 to suck in the unnecessary ink inside and outside each of the nozzles 1013 one after another.
Generally, in the image recording apparatus, a negative pressure is always applied to the ink chamber 1012 as shown in
The negative pressure is generally set so as to form a meniscus in a specific position in the nozzle. More specifically, the negative pressure is so set that the position where the surface tension of the meniscus balances with the negative pressure comes to the specific position in the nozzle. Since the meniscus is formed by the negative pressure, it is not desirable that ink should be sucked out of the nozzle carelessly.
However, when suction is applied under negative pressure, the ink i in the nozzle 1013 and ink chamber 1012 is sucked into the vacuum nozzle 1020 by suction exceeding the negative pressure in the ink chamber 1012, as shown in
When air has been pulled into the ink chamber 1012, there is a danger that the air will remain in the ink chamber 1012 in air bubbles. Since air bubbles cause pressure loss in the ink chamber 1012, there is a possibility that the inkjet head will lose the desired ink shooting characteristic.
It is an object of the present invention to provide an image recording apparatus with a maintenance mechanism which prevents air from being pulled into the ink chamber.
According to an aspect of the present invention there is provided an image recording apparatus comprising: an inkjet head which includes a nozzle plate where a plurality of nozzles that shoot ink are arranged in a column and an ink chamber which retains ink and is connected to said plurality of nozzles; at least one suction section which has a suction area larger than the nozzles; a suction section driving mechanism which causes the suction area to face the nozzles and moves the suction section relatively in the nozzle arrangement direction; and a positive pressure applying section which applies a positive pressure to the ink chamber, the suction section sucking in ink near the nozzles as moving in the nozzle arrangement direction, while the positive pressure is being applied to the ink chamber.
Hereinafter, referring to the accompanying drawings, embodiments of the present invention will be explained.
First, an embodiment of the present invention will be explained.
The image recording apparatus 1 comprises a paper feed section 10, an image recording section 20, a paper discharge section 50, a maintenance section 60, an ink supply section 70 (see
First, the paper feed section 10 will be explained.
As shown in
Then, the aligned recording medium is transported by the paper feed roller pair 14 to the image recording section 20. Suppose the center of the axis of the recording medium in the transport direction is the Y-axis (from left to right in
Next, the image recording section 20 will be explained.
The image recording section 20 includes a platen section 30 and an ink shooting section 40. First, the platen section will be explained by reference to
[Platen Section]
The platen section 30 is a transport unit which transports the recording medium sent from the paper feed section 10 during image recording. The platen section 30 is composed of a platen belt 31, a plurality of platen belt rollers 32, a platen frame 33, and a platen suction section 34.
With the configuration of the platen belt 31 and the platen belt rollers 32, the recording medium is transported along the Y-axis. A motor is connected to at least one of the plurality of platen belt rollers 32. Being driven by the motor, the platen belt 31 revolves around the platen rollers, thereby transporting the recording medium. A plurality of holes (not shown) are made throughout the platen belt 31.
The platen frame 33 not only supports the platen belt rollers 32 rotatably but also holds the platen suction section 34. The platen frame 33 has a platen frame head facing side 33a which faces the ink shooting section 40. The platen frame head facing side 33a is parallel with the plane extending along the X-axis and Y-axis. In the platen frame head facing side 33a, facing-side holes (not shown) are arranged uniformly all over the area facing the platen belt 31. The platen frame 33 is moved up and down along the Z-axis by a platen lifting and lowering mechanism 33b (see
The platen suction section 34 is a negative pressure generating unit for generating a negative pressure at the platen frame head facing side 33a. The platen suction section 34 is fixed to the side opposite to the side facing the inkjet on the platen frame head facing side 33a. The platen suction section 34, which has a negative pressure generating source (not shown), is configured so as to suck in air from the facing-side holes in the platen frame head facing side 33a by making the pressure at the platen suction section 34 negative, thereby sticking to the recording medium being transported by the platen belt 31.
[Ink Shooting Section]
The ink shooting section 40 shoots ink to the recording medium, thereby forming an image.
The ink shooting section 40 is composed of a plurality of ink head columns 41 and a carriage 42 for holding the ink head columns 41.
The ink head columns 41, each of which has a different color, extend as long as or longer than the maximum width of the recording medium used. In the embodiment, the ink shooting section has a total of four ink head columns 41: a black (K) head column, a cyan (C) head column, a magenta (M) head column, and a yellow (Y) head column. These ink head columns 41 are hung over the carriage 42 as shown in
The ink head columns 41 will be explained in detail by reference to
Each of the ink head columns 41 is so hung over the carriage 42 that, when it is provided in a carriage hole 42B, the head tip is located at a distance of D1 from a surface of the belt 31 along the Z-axis as shown in
As shown in
Next, the ink head unit 43 will be explained in detail.
The ink head unit 43 is composed of at least one inkjet head 44. In the embodiment, the ink head unit 43 is composed of two inkjet heads 44 as shown in
As shown in
The piezoelectric unit 46 is shooting force applying means for exerting forces on the ink to be shot (shooting force). As shown in
Each of the piezoelectric grooves 46a has a groove-forming-face-side opening in the groove forming face 46b. Moreover, each of the piezoelectric grooves 46a extends in a direction (width direction) (the up-and-down direction in
Each of the nozzle electrodes is connected to the control section 90 via a flexible substrate 43d as shown in
The head base plate 44b holds the piezoelectric unit 46 in such a manner that the nozzle plate mounting face 46c protrudes more than the nozzle-side base plate face 44d in the longitudinal direction of the head base plate 44b (in the Z-axis direction in
The head base plate 44b, which is a flat plate made of, for example, aluminum, does the job of a heat sink to cool the piezoelectric unit 46. The head base plate 44b has a piezoelectric unit holding face for holding the piezoelectric unit (the left face in
As shown in
The pitch P is set according to the image recording density. For example, in the embodiment, one inkjet head 44 is set so as to be capable of recording an image of 180 dpi. In this case, the pitch P is set to about 0.14 mm. While in the embodiment, one nozzle 47a is formed for each piezoelectric groove, the number of nozzles 47a is not limited. In the embodiment, each of the inkjet heads 44 shoots ink practically along the Z-axis. The direction in which ink is shot is not limited to the Z-axis and may be arbitrary.
The nozzle plate 47 has a nozzle forming face 47d (the lower face in
The head ink distribution section 48, which is connected to the ink supply section 70 (see
The distributor tube 48a is an ink passage for supplying ink from the ink supply section 70 to the head ink distribution section 48. One end of the distributor tube 48a is connected to the ink supply section 70 and the other end is connected to the small ink container 48b.
The small ink container 48b has a connecting plug to which the other end of the distributor tube 48a is connected. The small ink container 48b holds ink flowing in through the connecting plug. The small ink container 48b is fixed to the ink distribution plate 48c.
The ink distribution plate 48c is fixed to the groove forming face 46b of the piezoelectric unit 46 so as to cover the groove-forming-face-side openings of all the piezoelectric grooves 46a. Therefore, the ink distribution plate 48c is provided between the small ink container 48b and the piezoelectric unit 46 in a direction perpendicular to the groove forming face 46b (from left to right in
The ink chamber 48d is connected to the small ink container 48b and all of the piezoelectric grooves 46a. The ink chamber 48d retains ink from the small ink container 48b and distributes the ink to each piezoelectric groove 46a.
As shown in
Furthermore, as shown in
When the ink head unit 43 is assembled, the nozzle columns of the individual inkjet heads 44 constituting the unit 43 are set so as to be in parallel with one another as shown in
As described above, the ink head column 41 is constructed by arranging the ink head units 43 along the X-axis. In this arrangement, the ink head column 41 has the nozzles of the individual inkjet heads 44 positioned so as to record an image with uniform consistency along the X-axis. Therefore, the ink head columns 41 are arranged with practically a uniform pitch along the X-axis.
In the embodiment, when the ink head columns 41 are mounted on the carriage 42, the face on the side facing the nozzle forming face 47d of the nozzle plate 47 and the recording medium of the nozzle plate cover is made parallel with the X-Y plane. The X-Y plane in the embodiment extends horizontally. However, the direction in which these faces extend is not limited to the horizontal direction and may be inclined with respect to the horizontal plane.
Next, the paper discharge section 50 will be explained.
(Paper Discharge Section)
The paper discharge section 50 is a mechanism for discharging a recording medium on which an image has been recorded by the image recording section 20. The paper discharge section 50 discharges the recording medium sent from the image recording section 20 to a catch tray 54.
Next, the maintenance section 60 will be explained.
(Maintenance Section)
The maintenance section 60 is composed of a plurality of maintenance units 61, a plurality of maintenance ink pans 62, a maintenance suction section frame 63, a transport direction guide frame 64, and four lifting-and-lowering guide frames 65.
The individual maintenance units 61 are provided so as to correspond to the positions of the four ink head columns 41. Specifically, the maintenance units 61 are arranged at specific intervals along the Y-axis as are the ink head columns 41. Each of the maintenance units 61 is composed of a plurality of maintenance suction sections 61A. Specifically, each of the maintenance units 61 is constructed by arranging a plurality of maintenance suction sections 61A along X-axis. In the embodiment, each of the maintenance units 61 has six maintenance suction sections 61A, the same number of ink head units 43 constituting each ink head column 41.
Each of the maintenance units 61 has a base plate 61B which holds six maintenance suction sections 61A. Each of the base plates 61B, which is fixed to the maintenance suction section frame 63, extends along the X-axis. On the base plate 61B, the six maintenance suction sections 61A are arranged in the same manner as the ink head units 43 constituting each ink head column 41. That is, during maintenance explained later, when the maintenance unit 61 is aligned with the ink head column 41, each maintenance suction section 61A is provided in a position facing the corresponding ink head unit 43.
Each of the base plates 61B is connected to a suction pump 66 (see
The maintenance ink pans 62 are ink catchers for preventing ink from scattering during maintenance. There are provided as many maintenance ink pans 62 as there are maintenance units 61. The maintenance ink pans 62 are provided in positions corresponding to the maintenance units 61. Specifically, the individual maintenance ink pans 62 are provided opposite to the ink head columns 41 along the Z-axis, with the maintenance units 61 between the pans and the ink head columns 41. In the embodiment, the maintenance ink pans 62 are provided below the maintenance units 61.
Each of the maintenance ink pans 62 has its dimensions along the X-axis and Y-axis set equal to or larger than those of the maintenance unit 61. Each maintenance pan 62 has its position to the maintenance unit 61 set so as to recover ink drips from the maintenance unit 61. As explained later, the Y-axis dimensions of the maintenance ink pan 62 on the Y-axis are set so that the maintenance ink pan 62 may retreat into a space S between the ink head columns 41 during image recording. Specifically, the dimensions on the Y-axis of the maintenance ink pan 62 are set smaller than the distance D2.
The maintenance ink pan 62 is also fixed to the maintenance suction section frame 63. The arrangement of the maintenance ink pans 62 along Z-axis when being fixed is set so that the maintenance ink pans 62 may retreat into a space S between the ink head columns 41 during image recording. Specifically, on the Z-axis, the maintenance pan 62 is so provided that its lower end (the end on the opposite side to the ink head column) will not be positioned below the tip of the ink head column, when image recording is done.
The maintenance ink pan 62 is connected to a waste fluid tank 67 via a waste fluid tube 61Bb (see
The maintenance suction section frame 63 holds all of the maintenance units 61 as described above. The maintenance suction section frame 63 is supported movably by the transport direction guide frame 64 via a pair of suction section frame driving mechanisms 63a. The pair of suction section frame driving mechanisms 63a support the maintenance suction section frame 63 at both its ends in the Y-axis direction.
The pair of suction section frame driving mechanisms 63a is a maintenance suction section driving mechanism for moving each maintenance suction section 61A along the nozzle column of the corresponding inkjet head 44 via the maintenance suction section frame 63. Specifically, the pair of suction section frame driving mechanisms 63a, which extend along the X-axis, move the maintenance suction section frame 63, which holds the maintenance units 61 that support the maintenance suction sections 61A, along the X-axis. Therefore, when the suction section frame driving mechanisms 63a are driven, each maintenance suction section 61A is moved along the X-axis which is the direction in which the nozzles 47a in each inkjet head 44 are arranged. Therefore, it can be said that the suction section frame driving mechanisms 63a are a mechanism for moving each maintenance suction section 61A in the direction in which the nozzles are arranged. The pair of suction section frame driving mechanisms 63a is configured to move at least the maintenance suction section frame 63 along the nozzle column all over the inkjet head 44.
The transport direction guide frame 64 has a pair of sidewalls 64A along the Y-axis. On both ends of each of the sidewalls 64A, transport direction guide grooves 64Aa, which extend along the Y-axis, are provided.
In addition, the transport direction guide frame 64 has a slide mechanism 64B which provides driving forces along the Y-axis.
The four lifting-and-lowering guide frames 65 are supporting members for supporting the transport direction guide frame 64 in such a manner that the guide frame 64 can move in the Z-axis direction. These lifting-and-lowering guide frames are fixed to the frame (not shown) of the image recording apparatus 1. The lifting-and-lowering guide frames 65 are provided in positions corresponding to the transport direction guide grooves 64Aa. Moreover, each of the lifting-and-lowering guide frames 65 has a lifting-and-lowering guide groove 65a along the Z-axis. The individual lifting-and-lowering guide grooves 65a, which are aligned with the corresponding transport direction guide grooves 64Aa, are connected to the transport direction guide grooves 64Aa by connecting members, such as pins 65b, inserted so as to run through these grooves. This causes the lifting-and-lowering guide frame 65 to support the transport direction guide frame 64 movably along the Y-axis and Z-axis as shown in
The slide mechanism 64B applies driving forces to the transport direction guide frame 64 along the Y-axis, thereby moving the frame 64 along the Y-axis.
As explained above with respect to the platen section 30, when the platen frame 33 moves upward, it presses against the maintenance section 60. Thus, by moving the platen section 30 upward, the transport direction guide frame 64 can be moved upward, since the transport direction guide frame 64 is pressed against by the platen frame head facing side 33a, when the platen frame 33 moves upward. With this configuration, the transport direction guide frame 64 can be moved along the Z-axis according the up-and-down movement of the platen frame 33. Since the transport direction guide frame 64 moves together with the platen frame 33, its dimensions on the Z-axis are set so as not to interfere with the movement of the platen frame 33.
While in the embodiment, the platen frame 33 applies driving forces to the transport direction guide frame on the Z-axis, another independent driving means may apply driving forces.
Hereinafter, the maintenance suction section 61A will be explained in detail by reference to
The maintenance suction section 61A is suction means for cleaning by sucking in ink or dust adhering to each ink head unit 43. As shown in
The suction openings 61Aa are openings of suction inlets when the maintenance suction section 61A applies suction. Therefore, the suction opening 61Aa decides the suction range of the maintenance suction section 61A. The suction openings 61Aa, which are arranged in a column on the suction section head facing side 61Ad, constitute a suction opening column 61Ae. In the embodiment, two suction opening columns 61Ae are arranged symmetrically with 61Ab. Each suction opening column 61Ae is composed of three suction opening sections 61Aa. Each of the suction opening columns 61Ae faces the corresponding inkjet head 44 during maintenance. At this time, the longitudinal direction of the inkjet head 44 basically coincides with the direction in which the suction openings 61Aa are arranged. In other words, the direction in which the suction openings 61Aa are arranged practically coincides with the direction in which the nozzle columns are arranged.
In the above arrangement, each suction opening 61Aa has a larger diameter than that of the nozzle 47a in the (X-axis) direction in which they are arranged. Therefore, the suction area determined by the each suction opening 61Aa is larger than the nozzle 47a. In the embodiment, each suction opening 61Aa has almost the same size as the width of the inkjet head 44 on the X-axis. More specifically, each suction opening 61Aa has almost the same size as that of the nozzle plate cover 47b of the inkjet head 44 in the Y-axis direction.
Furthermore, the ink suction opening 61Aa has a fluid passage 61Af connected to the suction tube 61Ba. Therefore, each suction opening 61Aa is connected to the suction pump 66 via the fluid passage 61Af and suction tube 61Ba. Therefore, when the pressure of the suction pump 66 is made negative, the fluid sucked in by the suction opening 61Aa is sucked in by the suction pump 66 via the fluid passage 61Af. That is, the fluid passage 61Af is a passage for the sucked-in fluid.
More specifically, the fluid passage 61Af has an inlet hole 61Ah open at each suction opening 61Aa as shown in
The inlet hole 61Ah is set within the suction opening 61Aa in such a manner that it does not face the nozzle 47a. In the embodiment, the inlet hole 61Ah is provided at the end of the suction opening 61Aa opposite to guide projecting part 61Ab in the Y-axis direction. More specifically, the inlet hole 61Ah is provided at the outside end with respect to the central part of the maintenance suction section 61A in the Y-axis direction so as to face the nozzle plate cover 47b.
The guide projecting part 61Ab extends practically in the same direction as that in which the suction opening columns 61Ae are arranged. The guide projecting part 61Ab is configured to be capable of being inserted into the guide groove 44e in the ink head unit 43. The guide projecting part 61Ab is set above the maintenance suction section 61A in such a manner that, when it is inserted into the guide groove 44e, the direction in which the suction opening columns 61Ae are arranged is basically in parallel with the nozzle column of each inkjet head 44. At the same time, the guide projecting part 61Ab is so set that, when it is inserted into the guide groove 44e, each inlet hole 61Ah is aligned with the nozzle plate cover 47b of the corresponding inkjet head 44 as described above.
The wiper blade 61Ac is wiping means for wiping the surface facing the recording medium when the inkjet head 44 records an image. There are provided as many wiper blades 61Ac as there are the inkjet heads 44 in the ink head unit 43. In the embodiment, two wiper blades 61Ac are provided in each maintenance suction section 61A. Each wiper blade 61Ac is a little smaller than the nozzle forming face 47d in the Y-axis direction. Each wiper blade 61Ac is placed practically in the same position as that of the nozzle forming face 47d on the X-axis. The wiper blades 61Ac are made of a known elastic member, such as rubber. As shown in
Next, the ink supply section 70 will be explained.
(Ink Supply Section)
As shown in
The ink distributor 71 distributes ink to each ink head unit 43 in the ink head column 41. The ink distributor 71 is provided above the ink head column 41. In the ink distributor 71, ink is retained temporarily. The ink distributor 71 has a distribution ink tube 71a connected to the inkjet head 44 in each ink head unit 43. The ink in the ink distributor 71 is supplied to each inkjet head 44 via the distribution ink tube 71a in a pressurizing process explained later.
The main ink tank 72 is a rigid container, such as a plastic container, capable of being filled with ink. The main ink tank 72 is connected to the ink distributor 71 via the main tank ink tube 72a and to the ink bottle connecting section 73 via the ink supply tube 72b.
Furthermore, the main ink tank 72 is provided with an air release tube 72f connected to the air and a valve (air release valve) 72g in the tube which selectively enables or disables the connection to the air. When the air release valve 72g is opened, the main ink tank 72 is exposed to atmospheric pressure.
To set the inside of the ink distributor 71 at a specific water head pressure when the main ink tank 72 is made open to the air, the main ink tank 72 is provided below the ink head column 41. When the pressure in the ink distributor 71 has been set to the specific water head pressure, the pressure in each ink chamber 48d in each inkjet head 44 becomes negative, forming a desired meniscus in the nozzle 47a. The main ink tank 72 is connected to the air tank 75 via the air tube 72c. A pressurizing valve 72e is provided in the air tube 72c. The pressurizing valve 72e can open and close the air tube 72c.
The air tank 75 is an airtight rigid container, such as a plastic container. The air tank 75 is connected to the pressurizing pump 76 via a pressurizing pump tube 75a. When the pressurizing valve has been closed, the pressurizing pump 76 makes the pressure inside the air tank 75 positive. In the air tank 75, there is provided a pressure sensor 75b, which can detect the pressure in the air tank 75.
The ink bottle connecting section 73 is a connecting section to which the ink bottle 74 retaining ink is installed detachably. A replenish valve 73d is configured to be capable of selectively opening and closing the supply from the ink bottle 74 installed. When the replenish valve 73d opens the supply from the ink bottle 74, the main ink tank 72 is refilled with ink via the ink supply tube 72b.
In the ink supply section 70, the configuration from the air tube 72c to the ink distributor 71 is provided for each ink head column 41. In other words, the air tubes 72c of all the ink head columns 41 are connected to the air tank 75. Therefore, the pressurizing pump 76 is a positive pressure applying section which supplies a positive pressure to all of the ink head columns 41.
Next, the control section 90 will be explained.
(Control Section)
As shown in
(Operation)
The image recording operation of the image recording apparatus 1 configured as described above will be explained.
(Image Recording Operation)
When an image is recorded with the image recording apparatus 1, image data is inputted to the control section 90 via an interface (not shown). Receiving the input image data, the control section 90 carries out an image recording process. At this time, in the maintenance section 60, the maintenance units 61 and maintenance ink pans 62 are set in the retreat position in the space S. In this way, when the maintenance units 61 and maintenance ink pans 62 are placed in the space S, they do not go beyond the tips of the inkjet heads 44 and project into the recording medium. Therefore, the maintenance section 60 is prevented from touching the recording medium improperly in the retreat position during image recording.
In the retreat position, the platen section 30 is placed in the recording medium transport position during image recording. When the platen section 30 and the maintenance section 60 are placed in a specific position, the paper feed section 10 takes a recording medium out of the feeder tray 11 and transports it to the image recording section 20. In the image recording section 20, the ink shooting section 40 shoots ink onto the recording medium transported by the belt 31, thereby forming an image. The recording medium on which an image has been formed is transported to the paper discharge section 50 and is held in the catch tray 54.
When an image is recorded, the control section 90 opens the air release valve 72g and closes the pressurizing valve 72e. As a result, the water head difference between the main ink tank 72 and ink head column 41 causes a negative pressure to be applied to the ink in the ink chamber 48d (see
In the main ink tank 72, an ink level sensor can be provided. The ink level sensor is connected to the control section 90. With this configuration, in the control section 90, when the ink level sensor the information senses that the ink level has dropped below a specific value, the replenish valve 73d opens the supply from the ink bottle 74, thereby replenishing the main ink tank 72 with ink via the ink supply tube 72b. With this configuration, the image recording apparatus 1 supplies ink automatically without troublesome work.
(Maintenance Operation)
Next, the maintenance operation of the image recording apparatus of the embodiment will be explained. This maintenance operation can be carried out with arbitrary timing, such as during the image recording process or at the time when power is applied, under the control of the control section 90. The timing may be set beforehand in the ROM within the control section 90. Alternatively, using input means (not shown) connected to the control section 90, the setting may be stored in the RAM.
In the maintenance operation, a plurality of processes explained below will be carried out.
First, a maintenance section positioning process is carried out.
[Maintenance Section Positioning Process]
In the maintenance section positioning process, the platen section 30 is lowered to a position where the platen section is not pressed against the maintenance section 60 as shown in
Then, the control section 90 gives a driving instruction to the slide mechanism 64B, thereby moving the transport direction guide frame 64. The movement is made along the Y-axis so that the maintenance units 61 may face the ink head columns 41. In other words, the maintenance units 61 are moved in such a manner that their position on the Y-axis practically coincide with the position of the ink head columns 41. As a result of the movement, each maintenance suction section 61A is placed in a position where it faces the corresponding ink head unit 43 as shown in
In this arrangement, each maintenance suction section 61A is placed in a position facing one end of the corresponding inkjet head 44 on the X-axis. More specifically, each maintenance suction section 61A is placed in a position facing more of the outside of the inkjet head 44 than the nozzles 47a. Therefore, with this arrangement, in each maintenance suction section 61A, the suction openings 61Aa do not face the nozzles 47a on the X-axis.
In this way, after the maintenance section positioning process is completed, a purge process is conducted.
[Purge Process]
The purge process will be explained by reference to
In the purge process, the control section 90 provides driving control of the valve and pump in the procedure below. In the purge process, the control section 90 closes the air release valve 72g opened during image recording time S1 (see (1) in
As described above, after the air release valve 72g in each color ink passage is closed, the control section 90 outputs a driving instruction to the pressurizing pump 76 (see (2) in
Then, when the pressure sensor 75b has sensed that the pressure in the air tank 75 has reached a specific value (purge pressure), the pressurizing pump 76 is stopped and at the same time, the pressurizing valve 72e is opened (see (3) in
The purge pressure, that is, the pressure applied to the air tank 75, is set to a value at which ink can be discharged from each nozzle 47a. In other words, the purge pressure is set to a value at which the pressure applied to the nozzle 47a exceeds the surface tension of the meniscus in the nozzle 47a and ink drips from the nozzle plate 47. For example, the purge pressure is set to about 10 to 50 kilopascals (KPa). Since the purge pressure depends on the viscosity of ink and the materials constituting the nozzle 47a or others, it is changed arbitrarily. Applying the purge pressure to each nozzle 47a causes ink to be discharged from each nozzle 47a all at once as shown in
When ink is discharged as described above, foreign matter, such as air bubbles and dust mixed in the ink chamber 48d, is discharged together with the ink from the nozzle 47a.
The discharging of the ink is effected during purge S2 in
To lower the pressure in each ink chamber 48d, the air release valve 72g is opened (see (4) in
When the pressure in the main ink tank 72 has dropped practically to the suction positive pressure, the air release valve 72g is closed. When an attempt is made to lower the pressure in the main ink tank to the suction positive pressure by only one open and close operation of the air release valve 72g, the pressure in the main ink tank 72 changes rapidly. Therefore, when the air release valve is closed, the pressure in each ink chamber 48d changes rapidly. In this case, when the air release valve 72g is closed, a large undershoot occurs according to a rapid change in the pressure. In other words, when the air release valve 72g is closed in response to a rapid change in the pressure, the pressure temporarily takes a value lower than the pressure at the time when the valve is closed. The amount of deflection of the pressure becomes larger as a change in the pressure is larger. Therefore, when the pressure is changed rapidly as described above, there is a possibility that the pressure in the ink chamber 48d will become negative temporarily due to the undershoot. When the pressure become negative temporarily as described above, the fluid level of the ink moves between the nozzle 47a and the piezoelectric groove 46a, which can pull air into the piezoelectric groove 46a.
Therefore, after the purge S2 is completed, the control section 90 of the embodiment opens and closes the air release valve 72g intermittently a plurality of times until the pressure has dropped to the suction positive pressure (see (4) in
As described above, after the pressure in the ink chamber 48d drops to the suction positive pressure and becomes stable, a sucking process is carried out.
[Sucking Process]
In the sucking process, the maintenance suction section 61A sucks in ink adhering to the inkjet head 44. As explained in the maintenance section positioning process, to effect sucking, the suction section 61A is aligned with the inkjet head 44 and pressed against the head 44.
Alignment in height is performed by raising the platen section 30 and pushing up the maintenance suction section 61A from below. After the platen section 30 is raised to a specific position where the maintenance suction section 61A can suck, the movement of the platen section is stopped.
When the maintenance suction section 61A presses against the inkjet head 44, the guide projecting part 61Ab is inserted into the guide groove 44e in the inkjet head 44 and engaged therewith. As a result, in the maintenance suction section 61A, the direction of arrangement of the suction opening columns 61Ae is aligned with the direction of arrangement of the nozzles 47a.
When the alignment of the maintenance suction section 61A with the inkjet head 44 is completed, the suction pump 66 starts driving (see (5) in
As described above, in the maintenance section positioning process, the alignment of the inkjet head 44 with the maintenance suction section 61A and the start of the driving of the suction pump 66 are performed in an area where the nozzle 47a is not provided (see
After the alignment is completed and the negative pressure produced by the suction pump 66 has reached a specific value and become stable, the maintenance suction section 61A starts the sucking S3. In this sucking, the control section 90 gives a driving instruction to the suction section frame driving mechanism 63a of the maintenance suction section 61A. According to the driving instruction, the suction section frame driving mechanism 63a starts to move the maintenance suction section frame 63 together with the maintenance suction section 61A (see (6) in
The recording-medium-side face of the inkjet head 44 is covered with the nozzle plate cover 47b. While the suction section head facing side 61Ad of the maintenance suction section 61A is pressing against the nozzle plate cover 47b and the wiper blade 61Ac is pressing against the nozzle forming face 47d, the maintenance suction section 61A moves in the X-axis direction. As a result, the suction section head facing side 61Ad of the maintenance suction section 61A is separated from the nozzle forming face 47d by the thickness of the nozzle plate cover 47b on the Z-axis.
When pressing against the nozzle forming face 47d as described above, the wiper blade 61Ac is positioned in front of the suction opening column 61Ae in the direction of movement during suction.
The maintenance suction section 61A moves along the X-axis in the sucking S3, thereby sucking in ink (see
The maintenance suction section 61A sucks in the ink in the ink pool. That is, the maintenance suction section does not suck in the ink from the inside of the nozzle 47a where a meniscus is formed as if it pulled off the ink forcibly. In other words, the maintenance suction section 61A of the embodiment sucks in the ink in the ink pool outside the nozzle. This prevents the fluid level of ink from moving unstably between the nozzle 47a and the ink chamber 48d during the suction. That is, the maintenance suction section 61A of the embodiment prevents air from being pulled into the ink chamber 48d as a result of the movement of the fluid level of ink when the ink is sucked in.
The nozzle plate 47 and nozzle plate cover 47b are exposed to ink until the ink is sucked in by the suction section 61A. This allows dust or the like to float to the surface and makes it easier to be sucked in. The maintenance suction section 61A then sucks in the dust floating to the surface together with ink, thereby cleaning the nozzle plate 47 reliably.
During suction, the suction openings 61A are arranged all over the nozzle plate cover 47b along the Y-axis, or in the direction perpendicular to the direction of movement. Therefore, the maintenance suction section 61A moves along the X-axis, thereby sucking in all of the ink pool on the inkjet head 44.
The inlet hole 61Ah is set at a position within the suction opening 61Aa at which the hole does not face the nozzle 47a. As compared with a case where the inlet hole 61Ah faces the nozzle 47a, this setting alleviates the direct effect of the suction applied by the inlet hole 61Ah on the nozzle 47a and allows the ink pool to be sucked in.
Furthermore, as shown in
The suction opening column 61Ae is composed of an arrangement of three suction openings 61Aa. Therefore, as the maintenance suction section 61A moves, the same part of the inkjet head 44 is sucked in by a plurality of suction openings 61Aa. Thus, the ink in the ink pool can be sucked in more reliably. Furthermore, since the suction openings 61Aa are spaced apart in the direction in which they are arranged, the suction opening column 61Ae applies suction to the part to be sucked in of the inkjet head 44 intermittently a plurality of times. In other words, the maintenance suction section 61A causes a change in the negative pressure a plurality of times at the part to be sucked in, without opening and closing the valve or driving control of the suction pump 66. When the negative pressure changes a plurality of times, even highly adhesive ink, such as ink adhering to the less water-repellent nozzle plate cover 47b than the nozzle plate, is sucked in. Therefore, although having a simple configuration, the maintenance suction section 61A sucks in ink more reliably by a change in the negative pressure.
In addition, the wiper blade 61Ac moves in such a manner that the column 61Ae faces the nozzle plate 47, thereby scraping the ink adhering to the nozzle plate 47.
In the sucking S3, the suction positive pressure is always applied to the ink chamber 48d. Thus, as shown in
After all of each inkjet head 44 has been sucked in, the suction section frame driving mechanism 63a ends the driving from one end of the inkjet head 44 to the other end (see (7) in
At the same time, the control section 90 lowers the platen section 30, thereby separating the maintenance section 60 from the inkjet head 44 again as shown in
Then, after the suction pump 66 has ended the driving, the air release valve 72g is opened (see (8) in
After a waiting time T after the pressure in the ink chamber 48d reaches the specific negative pressure under the water head pressure (see S4 beginning at (9) in
In this way, the maintenance operation is completed.
In the configuration, the maintenance suction section 61A sucks in ink, when the ink chamber 48d is under the suction positive pressure. This allows the maintenance suction section 61A to suck in the ink in the ink pool outside the nozzle 47a. Therefore, the image recording apparatus 1 can clean the face of the inkjet head 44 facing the recording medium, while preventing air from being pulled in as a result of the movement of the fluid level of ink.
Before causing the maintenance suction section to suck in ink, the control section 90 controls each valve and pump so as to make the ink chamber 48d have the suction positive pressure. Since the ink pool has been formed at the time of suction, the image recording apparatus 1 prevents air from being pulled in more reliably.
Furthermore, after the sucking process, the control section 90 controls the air release valve 72g and pressurizing valve 72e so as to make the ink chamber 48d have the suction positive pressure. As a result, after the sucking process, an ink pool is formed in the area of the inkjet head 44 facing the recording medium to such an extent that the ink does not drip from the area.
In addition, the control section 90 sets the purge pressure higher than the suction pressure. The control section 90 may set the purge pressure and the suction pressure to the same value. However, when the purge pressure is set higher than the suction pressure, more ink can be caused to flow through the nozzle before suction. Therefore, when there is dust in the ink chamber 48d, the dust is discharged together with the ink more reliably than when less ink flows.
Moreover, when lowering the pressure in the ink chamber 48d to the suction positive pressure, the control section 90 opens and closes the air release valve 72g a plurality of times, thereby lowering the pressure stepwise. This makes it possible to reduce a variation in the pressure caused by undershoot occurring at the time of the closing of the air release valve 72g. As a result, while lowering the pressure in a short time, the image recording apparatus 1 of the embodiment prevents the pressure in the ink chamber from becoming negative due to the undershoot. This suppresses a fluctuation in the fluid level of ink due to the undershoot, thereby preventing air from pulled into the ink chamber.
While in the embodiment, the occurrence of undershoot is prevented by opening and closing the air release valve a plurality of times, the same effect can be produced by changing the degree of opening of the air release valve.
In addition, a plurality of air release tubes 72f and a plurality of air release valves 72g may be provided in the main ink tank 72, thereby controlling the opening the air release tubes. For example, as shown in
The control of the air release valves 72g1, 72g2 is shown in
The air release valve 72g1 is closed after being opened for a specific time. As the valve 72g1 is closed, the air release valve 72g2 is opened. The air release valve 72g2 is opened until the pressure in the ink chamber 48d has reached the pressure set to effect sucking. In general, when the amount of pressure drop per unit time is small, the amount of deflection of the pressure caused by undershoot is small. Therefore, the diameter of the air release tube 72f2 is set to a value at which the pressure in the ink chamber 48d will not become negative at the time of the closing of the valve, even when the air release valve 72g2 is opened for the period.
With the above configuration, while the pressure is being lowering by the opening of the large-diameter air release tube 72f1, the opening of the small-diameter air release tube 72f2 prevents a rapid change in the pressure resulting from undershoot.
While in the above modification, two air release tubes have been used, three or more air release tubes may be used. All of the air release valves may have the same diameter and the opening and closing of the air release valves may be controlled, thereby suppressing undershoot. In this case, too, the pressure can be lowered in a short time, while suppressing undershoot.
In addition, the inlet hole 61Ah is set in a position in the suction opening 61Aa so that it may not face the nozzle 47a during suction. In other words, the inlet hole 61Ah faces an area other than the nozzle 47a of the inkjet head 44. This structure alleviates the direct effect of the suction applied by the inlet hole 61Ah on the nozzle 47a and allows the ink pool to be sucked in. Therefore, the image recording apparatus 1 sucks in surplus ink over a wide area near the nozzle 47a, while preventing the ink in the nozzle 47a from being pulled off and sucked in.
As shown in
If strong suction is not applied to the nozzle 47a, the inlet hole 61Ah may be made in a position facing the nozzle 47a. In the maintenance suction section 61A in
Since the inlet holes 61Ah, 61Ah1 are arranged over a wide area, ink is sucked in more reliably.
Furthermore, in the maintenance suction section 61A of
The suction opening section 61Aa of the embodiment faces the nozzle plate 47 and the nozzle plate cover 47b. Therefore, the maintenance suction section 61A of the embodiment sucks in ink on not only the nozzle plate 47 but also other areas.
In the embodiment, as shown in
The suction opening 61Aa extending to an area beyond the nozzle plate cover 47b of
As shown in
The maintenance suction section 61A of the embodiment is controlled so as to move at a constant speed during suction. This enables the maintenance suction section 61A to suck in ink from each nozzle for the inkjet head 44 as compared with a case where the moving speed changes. The suction pump 66 is driven before the movement is started, which enables the suction section 61A to move after the pressure becomes stable.
In addition, the maintenance suction section 61A can be aligned with the inkjet head 44 in the area where no nozzle is provided. This prevents the nozzle 47a from being exposed to suction even when the suction pump 66 is driven during alignment. Therefore, the maintenance suction section 61A applies suction to each nozzle 47a only when moving in a sucking operation. Thus, the maintenance suction section 61A can apply uniform suction to the entire inkjet head 44.
Furthermore, the maintenance suction section 61A has a plurality of suction openings 61Aa in the direction in which the nozzles 47a are arranged. The maintenance suction section 61A applies a negative pressure intermittently to the parts to be sucked in of the inkjet head 44, thereby sucking in the unnecessary ink more reliably. If the maintenance suction section 61A has a desired function of cleaning the inkjet head 44, it may have only one suction opening 61Aa.
The maintenance suction section 61A has a guide projecting section 61Ab serving as an engaging part inserted in the guide groove 44e in the inkjet head 44. This enables the maintenance suction section 61A to be aligned with the inkjet head 44 securely.
Furthermore, the maintenance suction section 61A has the wiper blade 61Ac serving as wiping means for wiping ink on the inkjet head 44. Using the blade, the maintenance suction section 61A cleans the nozzle forming face 47d reliably. The suction section 61A cleans at least the nozzle plate 47d including the nozzle 46a.
If the maintenance suction section 61A has a desired function of cleaning the inkjet head 44, the wiper blade 61Ac may be eliminated.
While in the embodiment, only one suction opening 61Aa is provided for one inlet hole 61Ah, more than one suction opening 61Aa may be provided for one inlet hole 61Ah. While in the embodiment, the suction opening 61Aa is provided so as to run straight along the Y-axis, its path and shape may be changed arbitrarily. For example, to widen the suction area determined by the suction opening 61Aa, the suction opening 61Aa may be snaked.
Furthermore, while in the embodiment, all of the maintenance suction sections 61A move simultaneously as the maintenance suction section frame 63 moves, an independent driving mechanism may be provided for each maintenance suction section 61A to enable independent movement. In addition, the maintenance suction sections may be moved in units of a suction opening column 61Ae. Moreover, for the suction opening column 61Ae to retreat from the position facing the inkjet head 44 at the time of purge, the maintenance ink pan 62 and the suction opening column 61Ae may be driven independently.
While several embodiments have been explained concretely by reference to the drawings, the present embodiment is not limited to the above embodiments and may be practiced or embodied in still other ways without departing from the spirit or essential character thereof.
According to the present invention, there is provided an image recording apparatus with a maintenance mechanism capable of preventing air from being pulled into the ink chamber.
Number | Date | Country | Kind |
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2003-353312 | Oct 2003 | JP | national |
The present application is a Divisional Application of U.S. application Ser. No. 10/963,876 filed Oct. 12, 2004, now U.S. Pat. No. 7,410,237, which is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-353312, filed Oct. 14, 2003, the entire contents of which are incorporated herein by reference.
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Number | Date | Country | |
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20080278535 A1 | Nov 2008 | US |
Number | Date | Country | |
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Parent | 10963876 | Oct 2004 | US |
Child | 12175338 | US |