Patent Publication Number: US-7218888-B2

Title: Image formation apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image formation apparatus, such as printer, facsimile or copying machine, which forms an image by employing electrophotography. More particularly, it relates to improvements in a cleaning device which is capable of coming into and out of contact with the front surface of a toner image carrier, and which removes remaining toners adherent on the front surface of the toner image carrier during the contact. 
   2. Description of the Related Art 
   In general, an image formation apparatus employing electrophotography includes a photosensitive body which has a photosensitive layer at its outer peripheral surface, a charging device for uniformly charging the outer peripheral surface of the photosensitive body, an exposure device for selectively exposing to light the outer peripheral surface having been uniformly charged by the charging device, thereby to form an electrostatic latent image, a developing device for giving toners being developing agents, to the electrostatic latent image formed by the exposure device, thereby to turn the latent image into a visible image (toner images), a transfer device for transferring the toner images developed by the developing device, onto a sheet of paper or the like recording medium being a subject for transfer, and a cleaning device for removing the toners remaining on the front surface of the photosensitive body after the transfer. 
   Known as the transfer device is one having a toner image carrier (for example, intermediate transfer medium) onto which the toner images formed on the photosensitive body are transferred (primarily transferred), which carries the transferred toner images thereon, and which transfers (secondarily transfers) the toner images onto the sheet of paper or the like recording medium being the subject for transfer. The intermediate transfer medium (toner image carrier) is also furnished with a cleaning device. 
   Usually, the cleaning device of the photosensitive body need not have a construction in which it is brought into and out of contact with the photosensitive body. Since, however, the intermediate transfer medium (toner image carrier) collectively transfers the toner images in, for example, a plurality of colors as have been superimposed, onto the subject for transfer (the sheet of paper or the like recording medium), the cleaning device needs to be brought out of contact with the intermediate transfer medium during the superimposition operation of the toner images, and to be brought into contact after the collective transfer. 
   In such an image formation apparatus, when the cleaning device has come out of contact with the toner image carrier, the toners adhering to the cleaning device scatter and float within the image formation apparatus, thereby to incur various problems that the toners adhere to the intermediate transfer medium or the photosensitive body to degrade a picture quality, that the toners pollute the interior of the apparatus, and so forth. 
   In this regard, there has heretofore been proposed an image formation apparatus which is furnished with a shutoff mechanism for shutting off a toner outflow port when the cleaning device has come out of contact with the front surface of the toner image carrier (refer to, for example, JP-A-2003-295722). 
   The related art technique has had the problem that, even when the shutoff mechanism is quickly actuated, the toners scatter yet. Also, it has had the problem that, since the shutoff mechanism needs to be disposed, the structure of the apparatus becomes complicated. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an image formation apparatus in which toners can be restrained from scattering into the whole apparatus, by a simple construction. 
   In order to accomplish the object, the image formation apparatus of the present invention consists in an image formation apparatus including a toner image carrier which rotates with toner images adhering on its front surface, and a cleaning device capable of coming into and out of contact with the front surface of the toner image carrier, and for removing toners adherent on the front surface of the toner image carrier during the contact, characterized in: 
   that a toner reception portion is disposed on a downstream side than a contact position between the cleaning device and the toner image carrier as viewed in a moving direction of the front surface of the toner image carrier at the contact position, and that the toner reception portion is partitioned into a plurality of chambers. 
   With such a construction, most of the toners which scatter from the cleaning device when the cleaning device has come out of contact with the toner image carrier can be captured by the toner reception portion, and the toners can be restrained from scattering into the whole apparatus. 
   The toner image carrier is rotating, so that wind extending in the moving direction of the front surface of the toner image carrier occurs near the front surface. Since, however, the toner reception portion is disposed on the downstream side in the moving direction of the front surface of the toner image carrier, the toners which come floating in the wind can be captured effectively. 
   Moreover, the toner reception portion is partitioned into the plurality of chambers, which function as toner capture chambers, respectively, so that the toners which come floating in the wind can be captured efficiently. 
   Further, owing to the partition of the toner reception portion into the plurality of chambers, the area of those inwall surfaces of the chambers of the toner reception portion onto which the toners can adhere becomes large, so that the toners can be captured more efficiently. 
   Still further, even when the image formation apparatus is shaken, or the toner reception portion is shaken due to the exchange operation of this toner reception portion, or the like, the toners in the toner reception portion are less liable to move or to spill, owing to the partition of the toner reception portion into the plurality of chambers. 
   Desirably, the apparatus is so constructed that the toner reception portion is partitioned by a partition plate which extends in a direction substantially orthogonal to the moving direction of the front surface of the toner image carrier with respect to the moving direction. 
   With such a construction, the toners which come floating in the wind can be captured efficiently in stages by the plurality of chambers (plurality of toner capture chambers) which are partitioned by the partition plate extending in the direction substantially orthogonal to the moving direction of the image carrier surface (accordingly, the moving direction of the wind). Besides, the toners are liable to impinge against the partition wall extending in the direction substantially orthogonal to the direction of the wind, so that the toners can be captured more efficiently. 
   Desirably, the apparatus is so constructed that an upper end of a rising wall which is located on the most downstream side with respect to the moving direction of the front surface of the toner image carrier, in the toner reception portion, is adjacent to the front surface of the toner image carrier. 
   With such a construction, the toners which are about to pass through the gap between the front surface of the toner image carrier and the toner reception portion are liable to hindered by the rising wall located on the most downstream side, and the toners can be captured more reliably. 
   Desirably, the apparatus is so constructed that a distance between the front surface of the toner image supporter and the upper end of the partition plate, in the toner reception portion, is larger as compared with a distance between the front surface of the toner image supporter and the upper end of the rising wall located on the most downstream side with respect to the moving direction of the front surface of the toner image carrier. 
   With such a construction, the toners can be captured substantially equally into the plurality of chambers partitioned by the partition plate, and the capturable quantity of the toners can be consequently enhanced. More specifically, since the toners are carried floating in the wind, they are more liable to drop on the upstream side of the wind. In this regard, with the construction in which the distance between the front surface of the toner image carrier and the upper end of the partition plate is larger as compared with the distance between the front surface of the toner image carrier and the upper end of the rising wall located on the most downstream side with respect to the moving direction of the front surface of the toner image carrier (accordingly, the direction of the wind), the toners which are carried by the wind are liable to enter the chamber (toner capture chamber) on the downstream side through the gap between the front surface of the toner image carrier and the upper end of the partition wall. It is accordingly permitted to capture the toners substantially equally into the plurality of chambers partitioned by the partition plate. 
   Desirably, the apparatus is so constructed that at least two such partition plates are disposed, and that the upper ends of the partition plates are nearer to the front surface of the toner image carrier on the downstream side in the moving direction of the front surface of the toner image carrier. 
   With such a construction, the toners can be captured efficiently by at least three toner-capture chambers, and they can be captured substantially equally into the plurality of chambers, for the reasons stated above. 
   The apparatus is so constructed that the toner image carrier is constructed of a belt, and that, in a case where a bent portion which changes a traveling direction of the belt is provided on the downstream side in the moving direction of the front surface of the toner image carrier, than the contact position between the cleaning device and the toner image carrier, the toner reception portion extends to under the bent portion. 
   When the bent portion is provided, the toners which slightly remain on the belt surface (in spite of the provision of the cleaning device, some toners remain without being removed) might drop from the bent portion due to slight vibrations in this bent portion, but such toners can also be captured by extending the toner reception portion to under the bent portion. 
   Desirably, the toner reception portion is constructed integrally with a cleaning case on which the cleaning device is mounted. 
   With such a construction, the toner reception portion can be disposed at a high positional precision relative to the contact position between the cleaning device and the toner image carrier, and simultaneously, any toner reception portion need not be disposed separately from the cleaning case. 
   Moreover, assuming that the cleaning case and the toner reception portion be made separate members, the toners might leak out through the gap between both the members, but such is not apprehended owing to the construction of the toner reception portion integral with the cleaning case. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic sectional view showing the internal structure of one embodiment of an image formation apparatus according to the present invention; 
       FIG. 2  is a partial enlarged view of  FIG. 1 ; 
       FIGS. 3A and 3B  are schematic views each showing another embodiment; 
       FIGS. 4A and 4B  are schematic views each showing another embodiment; and 
       FIGS. 5A and 5B  are views for explaining a problem. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Now, embodiments of the present invention will be described with reference to the drawings. 
     FIG. 1  is a schematic sectional view showing the internal structure of one embodiment of an image formation apparatus according to the invention. 
   The image formation apparatus is a color image formation apparatus which can form full-color images on both the sides of a sheet of paper (recording medium) of A3-size, and which includes a case  10 , an image carrier unit  20  accommodated in the case  10 , an exposure unit  30  being an exposure device, a developer  40  being a developing device, an intermediate transfer medium unit  50 , and a fixing unit (fixer)  60  being a fixing device. 
   The case  10  is provided with the unshown frame of the apparatus proper, and the individual units are attached to the frame. 
   The image carrier unit  20  includes a photosensitive body  21  which has a photosensitive layer at its outer peripheral surface, and a corona charger (scorotron charger)  22  which is a charging device for uniformly charging the outer peripheral surface of the photosensitive body  21 . That outer peripheral surface of the photosensitive body  21  which has been uniformly charged by the corona charger  22  is selectively exposed to light by a laser beam L from the exposure unit  30 , thereby to form an electrostatic latent image. The electrostatic latent image is given toners being developing agents, by the developer  40 , thereby to be turned into visible images (toner images). The toner images are primarily transferred onto the intermediate transfer belt  51  of the intermediate transfer medium unit  50  in a primary transfer portion T 1 . Further, the toner images are secondarily transferred onto the sheet of paper being a subject for transfer, in a secondary transfer portion T 2 . 
   The image carrier unit  20  is provided with a cleaning blade  23  which removes the toners remaining on the front surface of the photosensitive unit  21  after the primary transfer, and a waste toner accommodation portion  24  being a waste toner reservoir, which accommodates therein the waste toners removed by the cleaning blade  23 . 
   Provided in the case  10  are a conveyance path  16  along which the sheet of paper formed with the image on one side thereof by the secondary transfer portion T 2  is conveyed toward a sheet-of-paper ejection portion (paper ejection tray portion)  15  located on the upper side of the case  10 , and a return path  17  along which the sheet of paper conveyed toward the sheet-of-paper ejection portion  15  by the conveyance path  16  is switched back and returned toward the secondary transfer portion T 2  so as to form an image also on the other side thereof. 
   Disposed at the lower parts of the case  10  are a paper feed tray  18  which stacks and holds a plurality of sheets of paper, and a paper feed roller  19  which feeds the sheets of paper toward the secondary transfer portion T 2  one by one. 
   The developer  40  is a rotary developer, in which a plurality of developer cartridges each accommodating the toner therein are detachably attached to a rotary member body  41 . In this embodiment, a developer cartridge  42 Y for yellow, a developer cartridge  42 M for magenta, a developer cartridge  42 C for cyan and a developer cartridge  42 K for black are disposed (in the figure, only the developer cartridge  42 Y for yellow is directly depicted). The rotary member body  41  rotates at pitches of 90 degrees in the direction of an arrow, whereby a developing roller  43  is selectively brought into contact with the photosensitive body  21 , and the front surface of the photosensitive body  21  can be selectively developed. 
   The exposure unit  30  projects the laser beam L toward the photosensitive body  21  through an exposure window  31  which is constructed of plate glass or the like. 
   The intermediate transfer medium unit  50  includes a unit frame which is not shown, a driving roller  54 , a driven roller  55 , a primary transfer roller  56 , a guide roller  57  for stabilizing the state of the belt  51  in the primary transfer portion T 1 , and a tension roller  58  which are rotatably supported by the unit frame, and the intermediate transfer belt  51  which is extended over the rollers. Herein, the belt  51  is circulatively driven in the direction of an indicated arrow. The primary transfer portion T 1  is formed between the photosensitive body  21  and the primary transfer roller  56 , while the secondary transfer portion T 2  is formed at the pressure contact part between the driving roller  54  and a secondary transfer roller  10   b  which is disposed on the body side. 
   The secondary transfer roller  10   b  is capable of coming into and out of contact with the driving roller  54  (accordingly, with the intermediate transfer belt  51 ), and the secondary transfer portion T 2  is formed in a case where the roller  10   b  has come into contact with the roller  54 . 
   In the case of obtaining the color image, accordingly, the color image is formed in such a way that the toner images in the plurality of colors are superimposed on the intermediate transfer belt  51  in a state where the secondary transfer roller  10   b  is out of contact with the intermediate transfer belt  51 , and the color image (toner images) is thereafter transferred (secondarily transferred) from on the intermediate transfer belt  51  onto the sheet of paper in such a way that the secondary transfer roller  10   b  comes into contact with the intermediate transfer belt  51 , and that the sheet of paper is fed to the contact part (secondary transfer portion T 2 ). 
   The sheet of paper onto which the toner images have been transferred has the toner images melted and fixed by passing through the gap between the pair of heating rollers  61  of the fixing unit  60 , and it is sent toward the paper ejection tray portion  15 . 
   Numeral  70  designates a cleaning device, which is a device for removing the toners that remain on the front surface of the intermediate transfer belt  51  being the toner image carrier, after the secondary transfer. 
   As shown in  FIG. 2 , the cleaning device  70  has a cleaning case  71 , a seal  72 , and a cleaning blade  73  being a cleaning device. 
   The cleaning device  70  has an in-contact/out-of-contact mechanism not shown, which brings the cleaning blade  73  out of contact with the front surface of the intermediate transfer belt  51  as indicated by solid lines in  FIG. 2 , in the case where the superimposition of the toner images is performed on the intermediate transfer belt  51  being the intermediate transfer medium, and which brings the cleaning blade  73  into contact with the front surface of the intermediate transfer medium  51  as indicated by phantom lines, after the toner images on the intermediate transfer belt  51  have been secondarily transferred onto the sheet of paper or the like. 
   The cleaning blade  73  brings its corner part  73   a  into contact with the front surface of the intermediate transfer belt  51  in a direction counter to the moving direction R of this belt, thereby to remove the remaining toners on the front surface of the intermediate transfer belt  51  so as to scrape them off. 
   After the toners scraped off have stayed on the upper surface  73   b  of the cleaning blade  73 , they drop into the case  71 , and they are conveyed toward a waste toner box not shown, by a screw  74  which is disposed within the case  71 . 
   In the image formation apparatus as described above, the intermediate transfer belt  51  is rotating, so that wind W which extends in the moving direction R of the front surface  51   a  of the intermediate transfer belt  51  occurs near the front surface  51   a.    
   Therefore, the toners t 1  which have stayed on the upper surface  73   b  of the cleaning blade  73  during the contact of this cleaning blade  73  with the front surface  51   a  of the intermediate transfer belt  51  as shown in  FIG. 5A  are blown away by the wind W (blown toners are indicated by sign t 2 ) when the cleaning blade  73  comes out of contact with the intermediate transfer belt  51 , as shown in  FIG. 5B . When the blown toners are let stand, they scatter in the image formation apparatus and incur various problems as stated before. 
   In this embodiment, therefore, as shown in  FIG. 2 , a toner reception portion  75  is disposed on a downstream side than the contact position T between the cleaning blade  73  and the intermediate transfer belt  51  as viewed in the moving direction of the front surface  51   a  of the intermediate transfer belt  51  at the contact position T, and the toner reception portion  75  is partitioned into a plurality of chambers  75 - 1  and  75 - 2 . 
   The toner reception portion  75  is constructed integrally with the cleaning case  71  on which the cleaning blade  73  is mounted. 
   More specifically, the toner reception portion  75  is formed of the bottom plate  71   a  of the case  71 , side plates  71   b  and  71   b  on both the right and left sides of the bottom plate (only the side plate on the deep side is shown in  FIG. 2 ), a rising wall  71   c  which is disposed on the most downstream side with respect to the moving direction R of the front surface of the intermediate transfer belt  51 , and a partition plate  75   a.  Incidentally, these portions are unitarily formed in the shape of a saucer (toner receptacle). 
   The partition plate  75   a  extends in a direction substantially orthogonal to the moving direction R of the front surface  51   a  of the intermediate transfer belt  51  (in a direction substantially orthogonal to the sheet of the drawing of  FIG. 2 ). 
   The upper end  71   c   1  of the rising wall  71   c  is adjacent to the front surface  51   a  of the intermediate transfer belt  51 , and the distance L 2  between the upper end  75   a   1  of the partition plate  75   a  and the front surface  51   a  of the intermediate transfer belt  51  is larger as compared with the distance L 1  between the upper end  71   c   1  of the rising wall  71   c  and the front surface  51   a  of the intermediate transfer belt  51 . 
   According to the image formation apparatus as thus far described, functional effects as stated below are attained.
     (a) The image formation apparatus includes the toner image carrier  51  which rotates with the toner images adhering on its front surface  51   a,  and the cleaning device  73  capable of coming into and out of contact with the front surface  51   a  of the toner image carrier  51 , and for removing the toners adherent on the front surface  51   a  of the toner image carrier  51  during the contact. The toner reception portion  75  is disposed on the downstream side than the contact position T between the cleaning device  73  and the toner image carrier  51  as viewed in the moving direction R of the front surface  51   a  of the toner image carrier  51  at the contact position T, and it is partitioned into the plurality of chambers  75 - 1  and  75 - 2 . Therefore, most of the toners which scatter from the cleaning device  73  (its upper surface  73   b  in this case) when the cleaning device  73  has come out of contact with the toner image carrier  51  can be captured by the toner reception portion  75 , and the toners can be restrained from scattering into the whole apparatus.   

   More specifically, since the toner image carrier  51  is rotating, the wind W extending in the moving direction R of the front surface  51   a  of the toner image carrier  51  occurs near this front surface  51   a.  Since, however, the toner reception portion  75  is disposed on the downstream side in the moving direction R of the front surface  51   a  of the toner image carrier  51 , the toners which come floating in the wind W can be captured effectively. 
   Moreover, the toner reception portion  75  is partitioned into the plurality of chambers  75 - 1  and  75 - 2 , and these chambers  75 - 1  and  75 - 2  function as toner capture chambers, respectively, so that the toners which come floating in the wind W can be captured efficiently. 
   Further, owing to the partition of the toner reception portion  75  into the plurality of chambers, the areas of those inwall surfaces  75   b  of the chambers of the toner reception portion  75  on which the toners can adhere become large, so that the toners can be captured more efficiently. 
   Still further, even when the image formation apparatus is shaken, or the toner reception portion  75  is shaken due to the exchange operation of this toner reception portion  75  (the cleaning device  70  in this case), or the like, the toners in the toner reception portion  75  are less liable to move or to spill, owing to the partition of the toner reception portion  75  into the plurality of chambers.
     (b) The toner reception portion  75  is partitioned by the partition plate  75   a  which extends in the direction substantially orthogonal to the moving direction R of the front surface  51   a  of the toner image carrier, so that the toners which come floating in the wind W can be captured efficiently in stages by the plurality of chambers (plurality of toner capture chambers)  75 - 1  and  75 - 2  which are partitioned by the partition plate  75   a  extending in the direction substantially orthogonal to the moving direction R of the image carrier surface  51   a  (accordingly, the moving direction of the wind). Besides, the toners are liable to impinge against the partition wall  75   a  extending in the direction substantially orthogonal to the direction of the wind W, so that the toners can be captured more efficiently.   (c) The upper end  71   c   1  of the rising wall  71   c  which is located on the most downstream side in the toner reception portion  75  with respect to the moving direction R of the front surface  51   a  of the toner image carrier is adjacent to this front surface  51   a  of the toner image carrier, so that the toners which are about to pass through the gap between the front surface  51   a  of the toner image carrier and the toner reception portion  75  are liable to hindered by the rising wall  71   c  located on the most downstream side, and the toners can be captured more reliably.   (d) The distance L 2  between the front surface  51   a  of the toner image carrier and the upper end  75   a   1  of the partition plate  75   a  is larger as compared with the distance L 1  between the front surface  51   a  of the toner image carrier and the upper end  71   c   1  of the rising wall  71   c  located on the most downstream side in the toner reception portion  75  with respect to the moving direction R of the front surface  51   a  of the toner image carrier, so that the toners can be captured substantially equally into the plurality of chambers  75 - 1  and  75 - 2  partitioned by the partition plate  75   a,  and the capturable quantity of the toners can be consequently enhanced. More specifically, since the toners are carried floating in the wind W, they are more liable to drop on the upstream side of the wind W (the side of the capture chamber  75 - 1 ). In this regard, with the construction in which the distance L 2  between the front surface  51   a  of the toner image carrier and the upper end  75   a   1  of the partition plate  75   a  is larger as compared with the distance L 1  between the front surface  51   a  of the toner image carrier and the upper end  71   c   1  of the rising wall  71   c  located on the most downstream side with respect to the moving direction R of the front surface  51   a  of the toner image carrier (accordingly, the direction of the wind), the toners which are carried by the wind W are liable to enter also the chamber (toner capture chamber)  75 - 2  on the downstream side through the gap (the larger gap L 2 ) between the front surface  51   a  of the toner image carrier and the upper end  75   a   1  of the partition wall  75   a.  It is accordingly permitted to capture the toners substantially equally into the plurality of chambers  75 - 1  and  75 - 2  partitioned by the partition plate  75   a.      (e) The toner reception portion  75  is constructed integrally with the cleaning case  71  on which the cleaning device  73  is mounted, so that the toner reception portion  75  can be disposed at a high positional precision relative to the contact position T between the cleaning device  73  and the toner image carrier  51 , and simultaneously, any toner reception portion need not be disposed separately from the cleaning case  71 .   

   Moreover, assuming that the cleaning case  71  and the toner reception portion  75  be made separate members, the toners might leak out through the gap between both the members, but such is not apprehended owing to the construction of the toner reception portion  75  integral with the cleaning case  71 . 
   Other Embodiments 
     FIGS. 3A and 3B  are schematic views each showing another embodiment. 
   The embodiment shown in  FIG. 3A  consists in a construction in which a toner reception portion  75  is partitioned by four partition plates  75   a,  thereby to define five toner-capture chambers ( 75 - 1  through  75 - 5 ). 
   Even with such a construction, the above functional effects (a), (b) and (e) are attained. Incidentally, toners captured by the toner reception portion  75  are indicated by sign t 3 . 
   Further, since the toner reception portion  75  is partitioned into the large number of chambers (five chambers), the area of those inwall surfaces  75   b  of the chambers of the toner reception portion  75  on which the toners can adhere becomes still larger, so that the toners can be captured more efficiently. 
   The embodiment shown in  FIG. 3B  consists in a construction in which a toner reception portion  75  is partitioned by two partition plates  75   a,  thereby to define three toner-capture chambers ( 75 - 1  through  75 - 3 ). 
   Even with such a construction, the above functional effects (a)–(e) are attained. 
   That is, the number of the partition plates  75   a  for partitioning the toner reception portion  75  can be appropriately set. 
     FIGS. 4A and 4B  are schematic views each showing another embodiment. 
   The embodiment shown in  FIG. 4A  consists in a construction in which a toner reception portion  75  is partitioned by two partition plates  75   a  and  75   a ′, and in which the upper ends of the partition plates  75   a  and  75   a ′ come nearer to the front surface  51   a  of a toner image carrier on a downstream side in the moving direction of the front surface  51   a  of the toner image carrier. 
   Even with such a construction, the above functional effects (a)–(e) are attained. 
   Further, owing to the construction in which the upper ends of the partition plates  75   a  and  75   a ′ come nearer to the front surface  51   a  of the toner image carrier on the downstream side in the moving direction of the front surface  51   a  of the toner image carrier, toners can be captured efficiently in stages by three toner-capture chambers ( 75 - 1  through  3 ), and they can be captured substantially equally into the plurality of chambers ( 75 - 1  through  3 ), for the reasons stated before. 
   The embodiment shown in  FIG. 4B  consists in a construction in which a bent portion B which changes the traveling direction of a belt  51  is provided on a downstream side than the contact position T between the cleaning device  73  and the toner image carrier  51  as viewed in the moving direction of the front surface  51   a  of the toner image carrier, and in which a toner reception portion  75  is extended to under the bent portion B. 
   When the bent portion B is provided, the toners which slightly remain on the belt surface  51   a  (in spite of the provision of the cleaning device  73 , some toners remain without being removed) might drop from the bent portion B due to slight vibrations in this bent portion B (dropping toners are indicated by sign t 4 ), but such toners t 4  can also be captured by extending the toner reception portion  75  to under the bent portion B. 
   Incidentally, even with such a construction, the above functional effects (a)–(e) are attained. 
   Although the embodiments of the present invention have been described above, the invention is not restricted to the foregoing embodiments, but it can be appropriately modified and performed within the scope of the purport of the invention.