Abstract:
For an ink jet printer, a maintenance unit having a simple mechanism that ensures a stable well-closed condition is provided. According to the present invention, rigid contact portions are provided in order to maintain a distance between an ink jet head and a cap in the perpendicular direction when the ink jet head is attached to the cap.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a maintenance unit for an ink jet head that forms images by ejecting ink, and for an ink jet printer.  
         [0003]     2. Related Background Art  
         [0004]     As shown in  FIGS. 4 and 5 , a carriage  101  that holds an ink jet head  100  is supported by a guide rail  102  along which the ink jet head  100  can be moved in the main operating direction, and along which the ink jet head  100  can be moved to a predetermined location at an appropriate acceleration and at a predetermined speed. Depending on the functions of and the specifications for an ink jet printer, a plurality of ink jet heads  100  are prepared, and the positions of the ink jet heads  100  and the distances between them are adjusted to within a predetermined range. A platen  110  is arranged, at a position facing the ink jet head  100 , so that a constant distance from the ink jet head  100  is maintained, regardless of the position of the carriage  101  in the main operating direction. The platen  110  has as a function the support of an ink jet medium  130  to which suction is applied, through an infinite number of holes formed in the platen  110 , to prevent the ink jet medium  130  from floating and to ensure that an appropriate distance is maintained between the ink jet head  100  and the ink jet medium  130 .  
         [0005]     Further, a capping unit  120  and a wiping unit  121  are provided at the end of the platen  110 . The capping unit  120  includes a cap  122  for closing the ink jet head  100  to prevent the ink jet head  100  from drying and to suck up excess ink. As shown in  FIG. 3 , the capping unit  120  is held by cap springs  200 , made of a flexible material, in order to obtain a contact force to be exerted between the cap  122  and the ink jet head  100 , and stabilization of the contact force is aimed at by using flexible strokes of the cap springs  200 . A cap holding mechanism employing the cap springs  200  is characterized in that the function can be maintained even when the distances between the cap  122  and the ink jet head  100  in the main scanning direction and in the direction perpendicular to the sub-scanning direction, and component parallelism are more or less varied. Furthermore, as another advantage, this mechanism has a simple and stable, low cost structure.  
         [0006]     The wiping unit  121  has a wiper  123  for removing foreign substances and ink droplets attached to the ink jet head  100 . When the function of the capping unit  120  and the function of the wiping unit  121  are employed together, the cleaning of the ink jet head  100  and the prevention of clogging, and stable printing are provided by a printer.  
         [0007]     The ink jet medium  130  is sequentially conveyed across the platen  110  by the rotation of a convey roller  111  and of a nip roller  112 , and is moved to an image forming location, while traveling facing the ink jet head  100 . The convey roller  111  has a parameter that determines an appropriate feeding distance in accordance with the operating mode of the ink jet printer or the type of ink jet medium  130 , and is rotated so as to consistently obtain an image quality. The nip roller  112  is used to press the ink jet medium  130  against the convey roller  111  with an appropriate force so that the convey roller  111  can convey the ink jet medium  130 . Some ink jet printers can vary the pressing force applied in accordance with the type of ink jet medium  130 . Further, a heater may be prepared for the platen  110  to accelerate the drying of ink ejected onto the ink jet medium  130 .  
         [0008]     Moreover, at present, there is an ink jet printer having a function that can vary the height of the ink jet head  100  or the carriage  101  to cope with a variety of ink jet media  130 . The conventional ink jet media  130  are mainly paper, and the thicknesses range from about several tens to several hundreds of microns; however, currently, a wide range of material is being employed, such as paper, films, cloth and boards, and the thickness range for ink jet media  130  may extend to several millimeters or several of tens of millimeters. A proposal has been put forward for the production of a printer that, while taking the current situation into account, can adjust the height of a maintenance unit by employing head height information (see, for example, Japanese Patent Unexamined Publication No. 2002-361881).  
         [0009]     Since the capping unit  120  contacts the ink jet head  100  and tightly closes the nozzle opening of the ink jet head  100  and draws in ink using suction, distances between the ink jet head  100  and the cap  122  in the direction perpendicular to the main scanning direction and in the sub-scanning direction should be appropriately maintained. Otherwise, the function of the capping unit  120  will not be maintained, and not only will the image quality be deteriorated, but also the ink jet head  100  will be damaged, and in some cases, a mechanical function fault may disable an ink jet printer. Therefore, the distance between the ink jet head  100  and the cap  122  is a very important factor in the function maintenance of an ink jet printer. Thus, conventionally, parts are specially employed to adjust the distances between the ink jet head  100  and the capping unit  120 , which holds the cap  122 , in the direction perpendicular to the main scanning direction and the sub-scanning direction, or the highly accurate machining of parts is employed to obtain predetermined distances between the ink jet head  100  and the capping unit  120  in the direction perpendicular to the main scanning direction and the sub-scanning direction. However, the use of special parts for the adjustment operation and the provision of very accurately machined parts contribute to increases in manufacturing costs. Further, for an ink jet printer that includes multiple ink jet heads  100 , the number of sets of ink jet heads  100  and caps  122  that must be adjusted is increased, and a satisfactory contact force must be obtained for all the sets. In addition, when multiple sets of ink jet heads  100  and caps  122  are employed, the inclinations and the parallelism of the ink jet heads  100  and the caps  122  greatly affect the contact force exerted between the ink jet heads  100  and the caps  122 . To resolve these problems, the use of very accurately machined parts can not be avoided. Moreover, conventionally, the thickness range of ink jet media  130  is not greatly extended, and ink jet printers are designed on the assumption that for an ink jet head  100  a constant height is adequate. However, recently, as the variety of ink jet media  130  available has increased, a new function for varying the height of an ink jet head  100  is beginning to be added to ink jet printers to permit them to cope with a variety of ink jet media  130  thicknesses. But although this function is being added, the attainment of an adequate capping unit  120  function is difficult for a conventional design based on an ink jet head  100  having a constant height. A mechanism, however, as described in Japanese Patent Unexamined Publication No. 2002-361881, has been proposed that changes the height of a capping unit or a wiping unit, and meshes with the changing of the height of an ink jet head.  
       SUMMARY OF THE INVENTION  
       [0010]     One objective of the present invention is to provide a maintenance unit, for an ink jet printer that has the variable ink jet head height function described above, and an ink jet head and a capping unit, for which neither an adjustment process nor the use of highly accurate machined parts is required during assembly, that ensures a stable, well-closing condition even when there is an increased variance in the distance in the perpendicular direction.  
         [0011]     To achieve this objective, according to the present invention, a maintenance unit for an ink jet head comprises:  
         [0012]     an ink jet head;  
         [0013]     a cap, for performing maintenance for the ink jet head;  
         [0014]     a carriage, for holding the ink jet head;  
         [0015]     a flexible member, for holding the cap; and  
         [0016]     rigid contact portions, for providing a stable distance between the ink jet head and the cap, in the perpendicular direction, when the ink jet head is closely coveted with the cap. Rigid contact portions  204  provide appropriate distances at which a cap  122  can be brought into contact with an ink jet head  100  in the direction perpendicular to the main scanning direction and in the sub-scanning direction. With this arrangement, in a non-contact state, there is a great variance in the distances between the ink jet head  100  and the cap  122  in the direction perpendicular to the main scanning direction and in the sub-scanning direction, whereas in a contact state, the sizes of the rigid contact portions  204  ensure that constant distances are maintained between the ink jet head  100  and the cap  122 . Further, variances in the contact force of a flexible contact portion, that flexibly contacts the ink jet head  100  and the cap  122 , can also be reduced. When multiple ink jet heads  100  and multiple caps  122  are employed, multiple rigid contact portions  204  need only be provided to obtain an accurate parallelism between the ink jet head  100  and the caps  122 . In addition, since the contact force exerted between an ink jet head  100  and a cap  122  depends on the accuracy of the sizes of the rigid contact portions  204 , the number of parts to be managed can be considerably reduced. A carriage  101  and a cap frame  201  are parts which make maintaining accurate distances between the respective parts, the ink jet  100  and the cap  122 , comparatively easy. Therefore, the rigid contact portions  204 , which in this invention are arranged between the ink jet head  100  and the cap  122 , in this invention, may also be located between the carriage  101  and the capping frame  201 .  
         [0017]     When multiple ink jet heads  100  are mounted on the carriage  101  and multiple caps  122  are mounted on the capping unit  120 , the size of the capping frame  201  is increased, so that adjusting the distances, relative only to the cap  122 , in the direction perpendicular to the main scanning direction and in the sub-scanning direction may not be sufficient. In this case, the rigid contact portions  204  are provided for the cap frame  201 , and the distances in the direction perpendicular to the main scanning direction and in the sub-scanning direction must be adjusted collectively by using the cap frame  201 . As another arrangement, instead of arranging the rigid contact portions  204  in the cap  122  or the cap frame  201 , the rigid contact portions  204  can be mounted in the ink jet head  100  or the carriage  101 . According to this system, the same effects can also be obtained, except that the positions of the rigid contact portions  204  are different.  
         [0018]     By providing the rigid contact portion of the invention, tight, stable closing of the ink jet headland the cap is ensured while only a simple structure is used. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a schematic diagram showing a capping unit according to one embodiment of the present invention wherein a cap is open;  
         [0020]      FIG. 2  is a schematic diagram showing the capping unit according to the embodiment wherein the cap is closed;  
         [0021]      FIG. 3  is a schematic diagram showing a conventional capping unit;  
         [0022]      FIG. 4  is a schematic front view of an ink jet printer; and  
         [0023]      FIG. 5  is a schematic side view of the ink jet printer. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     The preferred embodiment of the present invention will now be described while referring to the accompanying drawings.  FIGS. 1 and 2  are diagrams showing a capping unit according to the embodiment of the present invention.  
         [0025]     In the state shown in  FIG. 1 , an ink jet head  100  has not yet been closed by a cap  122 , even though it is facing the cap  122 . In  FIG. 1 , the ink jet head  100  is supported by a carriage  101 , while the cap  122  is supported by cap springs  200  in a cap frame  201 , which is held, its movements limited, by through frame springs  202  on a capping base  203 , so that it can only be moved linearly and perform a swiveling movement in direction perpendicular to the main scanning direction and the sub-scanning direction. The capping base  203  is supported by cams  205 , and the positioning of the capping base  203  is determined by the operating angles of the cams  205 , which can be managed by employing a motor, such as a pulse motor. Movement of the capping base  203 , as well as the cap frame  201 , is limited and it can not be moved relative to the main body of the ink jet printer, only in the direction perpendicular to the main scanning direction and the sub-scanning direction. Rigid contact portions  204  that contact the carriage  101  is located at the ends of the capping base  201 , i.e., at the two places shown in  FIG. 1  and at two other places perpendicular to the paper plane. Since multiple rigid contact portions  204  are thus provided, appropriate distances can be attained in the main scanning direction and in the sub-scanning direction when the ink jet head  100  is closed tightly by the cap  122 . Even if a satisfactory parallelism between the ink jet head and the cap  122  is has not been calculated, the rigid contact portions  204  are sequentially brought into contact, and the cap frame  201  performs a swiveling movement, so that the ink jet head  100  and the cap  122  are parallel. Furthermore, when the carriage  101  is tilted, the appropriate distances between the ink jet head  100  and the cap  122  can be obtained in the close attachment state, when all the rigid contact portions  204  have been brought into contact with the carriage  101 .  
         [0026]     In the state shown in  FIG. 2 , the ink jet head  100  is brought into contact with the cap  122 , and is closed by the cap  122 . To cover the ink jet head  100  with the cap  122 , first, the cams  205  are rotated to move the capping base  203  toward the ink jet head  100 . Then, the ink jet head  100  abuts upon the cap  122 ; but at this time, the ink jet head  100  merely contacts the cap  122 , and a satisfactory contact force has not yet been applied. Next, the carriage  101  and the rigid contact portions  204  on the cap frame  201  contact each other. When all the rigid contact portions  204  on the cap frame  201  have contacted the lower face of the carriage  101 , the accurate distance between the cap  122  and the ink jet head  100  in the direction perpendicular to the main scanning direction and the sub-scanning direction can be obtained, and the designated contact force can be applied. Further, because of the mechanism, an accurate travel distance for the cap frame  201  is not known, and conventionally, the travel distance for the cap  122  would managed by detecting the position of the cap  122  or by using a change in the load imposed on the drive mechanism as a consequence of the contact between the cap  122  and the ink jet head  100 . However, according to the present invention, the need to detect the position of the cap  122  is eliminated, and the cams  205  can be steadily rotated to a predetermined angle. Furthermore, the extra travel distance for the capping base  203  is absorbed by contracting the frame springs  202  after the rigid contact portions  204  have been brought into contact with the carriage  101 .  
         [0027]     In this embodiment, the rigid contact portions  204  are provided on the cap frame  201 . There are other two ways that the rigid contact portions  204  can be arranged, i.e., on the cap  122  and on the cap frame  201 . In a case wherein a large number of caps  122  are to be employed and the size of the cap frame  201  may be increased, the rigid contact portions  204  should be arranged on the cap frame  201 , so that the arrangement of the rigid contact portions  204  relative to the ink jet head  100  can be improved because the two types of springs, i.e., the cap springs  200  and the frame springs  202 , can be employed. In addition, when there are multiple caps  122 , the distances from the ink jet head  100  in the direction perpendicular to the main scanning direction and the sub-scanning direction differ greatly between the caps  122  at both ends, and it is difficult to adjust these distances merely by using the caps  122 .  
         [0028]     In order to obtain the above described structure, the carriage  101  and the cap frame  201  are parts for which the sizes should be managed strictly. As for the carriage  101 , only the distances, between the ink jet head  100  and the lower face portions with which the rigid contact portions  204  are brought into contact with, in the direction perpendicular to the main scanning direction and the sub-scanning direction need be managed. As for the cap frame  201 , only the distances, between the cap  122  attachment portions and the rigid contact portions  204 , in the direction perpendicular to the main scanning direction and the sub-scanning direction need be managed.