Abstract:
An image forming apparatus including: an image bearing member; an optical unit for image exposure of the image bearing member, the optical unit being mountable from a side of the apparatus main body; and an elastic member for pressuring the optical unit downward.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an image forming apparatus using an electrophotographic process, such as a copying machine and a printer.  
           [0003]    2. Related Background Art  
           [0004]    [0004]FIG. 5 is a cross-sectional view of an image forming apparatus. As shown in FIG. 5, in a conventional image forming apparatus  30 , a photosensitive drum  38  is provided inside the apparatus. A charger  35  and a developing unit  36  are provided adjacently around the photosensitive drum  38 . Moreover, a transfer unit  37  and a fixing device  40  are disposed around the photosensitive drum  38 .  
           [0005]    Moreover, a light scanning unit  10  is provided in the vicinity of to the photosensitive drum  38 . Furthermore, a sheet of paper  42 , and feed and transport rollers  43 ,  44 ,  45  capable of successively transporting the sheet of paper  42  are provided below the photosensitive drum  38 . Moreover, an image information controller  33  and a reader unit  32  capable of reading an original are provided above the photosensitive drum  38  in an upper part of the image forming apparatus  30 .  
           [0006]    The light scanning unit  10  provided in the image forming apparatus  30  is for writing on the photosensitive drum  38  using a laser beam. FIG. 6 is a schematic diagram of a side inner part of the light scanning unit  10 .  
           [0007]    As shown in FIG. 6, the light scanning unit  10  has a structure contained in an optical box  20 . That is, the light scanning unit  10  comprises a semiconductor laser as the light source, a collimator lens and a cylinder lens (not shown), a polygon mirror  19 , scanning lenses  21 ,  22 , turn-back mirrors  25 ,  26 ,  27 , a lengthy cylinder lens  29 , and an irradiation window  28  in the optical box  20 .  
           [0008]    Moreover, a laser beam through inside the light scanning unit  10  shown in FIG. 6 is first outputted from the semiconductor laser, collimated by the collimator lens so as to be inputted in the polygon mirror  19 , and deflected by the polygon mirror  19 . Then, the laser beam passes through inside the optical box  20  so as to be reflected successively by the turn-back mirrors  25 ,  26 . Accordingly, the laser beam is reflected so as to pass through the optical parts in the upper and lower two spaces inside the optical box  20 .  
           [0009]    The light scanning unit  10  with the above-mentioned configuration is mounted on a frame provided in the image forming apparatus  30  with a high accuracy.  
           [0010]    The above-mentioned light scanning unit  10  is replaced per unit due to the life of the parts such as exhaustion of the parts in the market. For the unit replacement, the unit can be replaced after detaching the constituent parts such as the reader unit  32  provided in the main body upper part of the image forming apparatus  30 , or the unit can be replaced by sliding and moving from the side of the image forming apparatus  30  without detaching the constituent parts such as the reader unit  32  in the main body upper part.  
           [0011]    In the case of the unit replacement after detaching the constituent parts such as the reader unit  32  in the main body upper part in the former case, since the upper part of the image forming apparatus  30  can be opened, the light scanning unit  10  can be fastened using a screw or the like from above. Thereby, the light scanning unit  10  can be fixed stably.  
           [0012]    In contrast, in the case of the unit replacement without detaching the constituent parts such as the reader unit  32  in the main body upper part in the latter case, as shown in FIG. 6, an auxiliary part  49  is mounted preliminarily on the light scanning unit  10 .  
           [0013]    Then, the light scanning unit  10  is guided to a predetermined position in the main body using a rail (not shown) provided in the main body. After abutting against the auxiliary part  49  with a main body fitting part  50  by the guiding operation, the auxiliary part  49  is forced against the main body fitting part  50  sideways using a fixing member such as a screw  51 . Thereby, the light scanning unit  10  is provided without movement particularly in the horizontal direction.  
           [0014]    However, according to the former method of the two kinds of the detaching and replacing methods for the above-mentioned light scanning unit  10 , since all the constituent parts such as the reader unit  32  are detached, excessive labor and long time are required, and thereby the unit replacement itself is extremely inefficient.  
           [0015]    In contrast, according to the latter method, the light scanning unit  10  is attached/detached while sliding from the side of the main body without detaching the reader unit  32 . In the case of this method, since the light scanning unit  10  can move to a considerably deep part of the main body inside and the reader unit  32  is not detached, it is difficult to fix the light scanning unit  10  from above by a screw or the like.  
           [0016]    Furthermore, the light scanning unit  10  is disposed only by abutting in the lateral direction so as to be stabilized using the gravitational force of the light scanning unit  10 . Therefore, the close contact property of the light scanning unit  10  to the installation part at the time of fixing is low.  
           [0017]    Thereby, an adverse effect is provided to the image quality due to generation of backlash derived from the vibration generated from the light scanning unit  10  itself or the image forming apparatus  30  main body and generation of the error of the installation accuracy itself.  
         SUMMARY OF THE INVENTION  
         [0018]    Accordingly, an object of the present invention is to provide an image forming apparatus capable of mounting an optical unit from sideways.  
           [0019]    Another object of the present invention is to provide an image forming apparatus with a high stability in an optical unit.  
           [0020]    A still another object of the present invention is to provide an image forming apparatus comprising:  
           [0021]    an image bearing member;  
           [0022]    an optical unit for image exposure of the image bearing member, the optical unit being mountable from sideways of the apparatus main body; and  
           [0023]    an elastic member for pressuring the optical unit downward.  
           [0024]    A further object of the present invention will be apparent by the explanation provided below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a side view showing a state before installation of a light scanning unit according to a first embodiment of the present invention.  
         [0026]    [0026]FIG. 2 is a side view showing a state at the time of the installation of the light scanning unit according to the first embodiment of the present invention.  
         [0027]    [0027]FIG. 3 is a perspective view of the light scanning unit according to the first embodiment of the present invention.  
         [0028]    [0028]FIGS. 4A, 4B,  4 C, and  4 D are side views showing light scanning units having various kinds of elastic members according to a second embodiment of the present invention.  
         [0029]    [0029]FIG. 5 is a schematic diagram showing an image forming apparatus.  
         [0030]    [0030]FIG. 6 is a schematic diagram showing a light scanning unit and a photosensitive drum. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Hereinafter, embodiments of the present invention will be explained with reference to the accompanied drawings.  
         [0032]    (First Embodiment)  
         [0033]    First, a light scanning unit (optical unit)  10  inside an image forming apparatus according to a first embodiment of the present invention will be explained. FIGS. 1 and 2 show the light scanning unit and a reference stay in the image forming apparatus, and FIG.  3  is a perspective view of the light scanning unit. The light scanning unit according to the first embodiment is to be attached/detached by moving in the lateral direction with respect to the inside of the image forming apparatus  30  while being contained in the image forming apparatus  30 .  
         [0034]    As shown in FIG. 1, according to the light scanning unit  10  of the first embodiment, elastic members  2 ,  3  are provided integrally each on the both end parts. Moreover, a reference foot  12  and a reference pin  13  are provided in a part on a side opposite to a side on which the elastic members  2 ,  3  are mounted in the light scanning unit  10 .  
         [0035]    The elastic member  2  comprises a spring having a shape with a plate-like metal piece bent halfway. Moreover, one side of the bent parts of the elastic member  2  is fastened to the light scanning unit  10  by a mounting screw  4 . In FIG. 1, the elastic members  2 ,  3  are not pressured from the outside so that a natural state with a large open angle is shown.  
         [0036]    Furthermore, the light scanning unit  10  is provided so as to be mounted on a stay fixed on the image forming apparatus  30 , that is, a main body reference stay  52 . The main body reference stay  52  is for fixing by fitting one end of the light scanning unit  10  in a fitting hole  53  formed in a part thereof. Thereby, a standard installation part for the light scanning unit  10  can be provided.  
         [0037]    Moreover, the main body reference stay  52  is provided with the position accuracy with respect to the photosensitive drum of the image forming apparatus  30  (not shown in FIG. 1) ensured.  
         [0038]    Furthermore, FIG. 2 shows a state with the light scanning unit  10  slid on the main body reference stay  52  and moved to a standard position so that the light scanning unit  10  is installed at the standard installation part.  
         [0039]    As shown in FIG. 2, in the state with one end of the light scanning unit  10  disposed at the standard installation portion on the main body reference stay  52 , the side of the light scanning unit  10  provided with the elastic member  2  is inserted in the fitting hole  53 . At this time, the elastic member  2  is pressured at the end part having the fitting hole  53  so as to be compressed with the open angle reduced.  
         [0040]    According to the compression, the light scanning unit  10  is forced downward continuously so as to be contacted closely with the main body reference stay  52  in FIG. 2. Here, the pressuring force by each elastic member  2  is preferably two times or more as much as the mass of the light scanning unit  10  regarded as equivalent to the pressuring force in order to avoid the influence of the vibration of the light scanning unit  10 .  
         [0041]    In the pressured state, the part below the pressured position is in the vicinity of the reference foot  12  so that stress is not generated largely in the lateral direction with respect to the pressure applied perpendicularly in the vicinity of the reference foot  12 . Thereby, displacement in the lateral direction can hardly be generated as well as the accuracy in the height direction can be ensured by accordance of the reference foot  12  with the accuracy surface of the main body reference stay  52 .  
         [0042]    Moreover, the final position at the time of moving the light scanning unit  10  is determined by coupling the reference pin  13  as a fitting pin with a fitting hole (now shown) provided in the main body reference stay  52 . The light scanning unit  10  is moved while searching the fitting position of the reference pin  13  with one side thereof lifted up.  
         [0043]    That is, specifically, as shown in FIG. 3, the light scanning unit  10  comprises a polygon mirror  19  as a deflecting means, and scanning lenses  21 ,  22  provided in an optical box  20  having a rectangular parallelepiped shape with one corner cut off. Moreover, two of the above-mentioned elastic members  2  and  3  are provided at each of the opposite side parts of the optical box  20 .  
         [0044]    Furthermore, the reference feet  12  are provided on the lower surface of the optical box  20  in the vicinity of the elastic members  2 ,  3 . Moreover, the two reference pins  13  are provided on the lower surface of the optical box  20  in the vicinity of the two elastic members  3 .  
         [0045]    Furthermore, a cylinder lens  18  is provided in the vicinity of the inner side of the part with the cut off shape of the optical box  20  as well as a laser unit  16  as the light source is provided on the outer side thereof.  
         [0046]    The light scanning unit  10  is moved by determining the installation position and positioning by fitting the above-mentioned two reference pins  13  so as to be positioned each at a predetermined hole in the main body reference stay  52 . The positioning operation is executed using the two reference pins  13  without using the elastic members  2  themselves for positioning.  
         [0047]    Moreover, as shown in FIG. 2, according to the first embodiment, an engaging auxiliary member  54  with a fitting hole (not shown) provided on the inner side is used for certain fixation without movement after the installation of the light scanning unit  10  so as to clamp the elastic members  3  having the same configuration as that of the elastic members  2  and the end part of the main body reference stay  52 .  
         [0048]    Thereby, the elastic members  3  and the main body reference stay  52  are clamped so as to be pressured, and engaged by a screw  51  so as to be fixed.  
         [0049]    Moreover, as mentioned above, in general, the lower surface of the light scanning unit  10  is installed on the stay, that is, by the so-called lower surface installation. Furthermore, the light scanning unit  10  is moved in the inside of the image forming apparatus  30  to be installed by the lateral sliding method with respect to the image forming apparatus  30 . It is also possible to provide a guide part for preventing displacement on a part of the main body reference stay  52 , taking the lateral sliding method into consideration.  
         [0050]    Moreover, unlike the light scanning unit  10  of the first embodiment, also in the case of a light scanning unit with the parts such as the turn-back mirror provided partially at the outside, the configuration of the above-mentioned first embodiment can be adopted so as to achieve the same effect as that of the first embodiment.  
         [0051]    As heretofore explained, according to the light scanning unit in the image forming apparatus according to the first embodiment, since the elastic members  2 ,  3  are provided integrally, the elastic members  2 ,  3  can be deformed rationally without disturbing the movement of the light scanning unit  10  in the lateral direction in a simple configuration and they can be fixed certainly in the image forming apparatus as well as the elastic members  2  to be taken out integrally at the time of replacing the light scanning unit  10  can be replaced outside the image forming apparatus, deterioration derived from a long term pressure application can be reduced so that deterioration of the pressuring force due to the elastic deformation of the elastic members  2 , that is, the so-called wear-out (permanent set in fatigue) can be prevented so that a higher reliability can be ensured.  
         [0052]    (Second Embodiment)  
         [0053]    Next, a light scanning unit  10  of an image forming apparatus according to a second embodiment of the present invention will be explained. FIGS. 4A, 4B,  4 C and  4 D are schematic diagrams of the part of the light scanning unit  10  provided with an elastic member according to the second embodiment. Since the other parts and the numerals thereof are same as those of the first embodiment, further explanation is not provided.  
         [0054]    Moreover, although an embodiment with the elastic members  2 ,  3  comprising leaf springs in the light scanning unit  10  has been explained in the first embodiment, other embodiments of the elastic members  2 ,  3  and modified embodiments thereof will be explained in the second embodiment.  
         [0055]    First, FIG. 4A shows an embodiment of the elastic member comprising a coil spring  5  and a contact plate  6  provided integrally with the side part of the light scanning unit  10  of the second embodiment.  
         [0056]    That is, the coil spring  5  is provided in a stepped portion in the side part of the light scanning unit  10  such that the repulsive force is generated in the direction perpendicular to the direction of laterally sliding the light scanning unit  10  as in the first embodiment.  
         [0057]    Moreover, there is provided the contact plate  6  bendable in the direction of compressing the coil spring  5 . Thereby, as in the light scanning unit  10  of the first embodiment, it is contacted partially with the main body reference stay  52  so as to receive the pressuring force in the vertical direction (gravity direction) as in the light scanning unit  10  of the first embodiment. As needed, the elastic members may comprise only the coil spring  5  without providing the contact plate  6  in the elastic members.  
         [0058]    However, since the contact plate  6  is provided at the end part of the light scanning unit  10  so as to be contacted with the end part of the coil spring  5 , at the time of sliding the light scanning unit  10  along the main body reference stay  52  for fitting the part of the elastic member with the fitting hole  53  formed in the main body reference stay  52 , the fitting operation can be executed while being guided by the contact plate  6  so that the coupling of the elastic member with the fitting hole  53  can be facilitated.  
         [0059]    Next, FIG. 4B shows an embodiment of the elastic member comprising a rubber member  7  provided integrally with the side part of the light scanning unit  10  of the second embodiment.  
         [0060]    That is, the elastic member is provided by selectively providing a recess part in the stepped portion at the side part such that the repulsive force is generated in the direction perpendicular to the direction of inserting the light scanning unit  10 , and fitting the rubber member  7  into the recess part. Thereby, the light scanning unit  10  can be moved along the main body reference stay  52  so that the light scanning unit  10  is pressured by the elastic force of the rubber at the time it is placed at a predetermined position so as to be fixed on the main body reference stay  52 .  
         [0061]    Moreover, FIG. 4C shows an embodiment of the elastic member comprising a synthetic resin member  8  provided integrally with the side part of the light scanning unit  10  of the second embodiment.  
         [0062]    The synthetic resin member  8  itself is provided elastically deformably. Therefore, by fitting the elastic member comprising the synthetic resin member  8  in the fitting hole  53  in the main body reference stay  52 , the pressuring force is generated so that the light scanning unit  10  can be engaged thereby.  
         [0063]    The synthetic resin member  8  is mounted on the light scanning unit  10  basically by bonding with a material of another composition or by screwing. In contrast, the optical box  20  configuring the light scanning unit  10  is made of a synthetic resin in most cases. Therefore, the elastic member can be produced also by the so-called two color molding of molding simultaneously with a synthetic resin material of another kind with a high elastic modulus.  
         [0064]    Moreover, FIG. 4D shows an embodiment of the elastic member comprising a bent metal plate provided integrally with the side part of the light scanning unit  10  of the second embodiment.  
         [0065]    That is, the elastic member according to the second embodiment is provided by bending a metal extended plate  14  as an extended part of the lid of the optical box  20  to the inside of the light scanning unit  10  like the elastic members  2 ,  3  of the first embodiment.  
         [0066]    The extended plate  14  is provided integrally with the lid comprising a sheet metal used in general in contact with the optical box  20 . Moreover, the lid attached on the optical box  20  for avoiding the dusts is mounted with a screw, or the like in most cases for ensuring the dust avoiding effect.  
         [0067]    By accordingly using the extended part of the lid mounted on the optical box  20  for avoiding the dusts as the elastic member, since the elastic member need not be provided additionally, the number of parts used for the light scanning unit  10  can be reduced as well as the number of steps of labor can be cut back.  
         [0068]    As heretofore explained, in the second embodiment, embodiments of the elastic member as a coil spring, a rubber, a synthetic resin, or the like other than the plate spring, and addition of a function to the existing part have been described.  
         [0069]    Since the various kinds of the elastic members are mounted integrally with the light scanning unit  10  and used, movement of the light scanning unit  10  in the lateral direction is not disturbed, and they are used in a form deformable according to the movement of the light scanning unit. Therefore, the same effect as in the first embodiment can be obtained. Thereby, the methods of the elastic members may be used partially in a combination.  
         [0070]    Furthermore, it is also possible to use the elastic member only in the one side of the light scanning unit  10  and mount the other side with a screw and an auxiliary part without using the elastic member. The structure depends also on the installation state of the light scanning unit  10  in the main body of the image forming apparatus  30  so that the above-mentioned structures can be selected with reference to the operativity, such as the case capable of easily fastening on one side of the light scanning unit  10 .  
         [0071]    Moreover, since the freedom in the selection of the elastic member can be widened, the direction of attaching/detaching the light scanning unit  10  on/from the main body of the image forming apparatus  30  can be selected optionally. Therefore, depending on the convenience in terms of the configuration of the main body of the image forming apparatus  30  or the shape of the light scanning unit  10 , the direction of sliding and moving with respect to the stay can be determined.  
         [0072]    Furthermore, since freedom of selection of the elastic member for the light scanning unit  10  can be widened by adopting the elastic member of the second embodiment, freedom of the parts layout in the main body can be increased as well as the light scanning unit  10  can be provided in further simple structure and is easily and detachably mountable.  
         [0073]    Although the embodiments of the present invention have been described specifically, the technological scope of the present invention is not limited by the size, the material, the shape and the relative arrangement of the constituent parts mentioned in the embodiments unless specific description thereof is provided.  
         [0074]    Although an embodiment of a copying machine as the image forming apparatus has been provided in the above-mentioned embodiments, it is not limited thereto, and the present invention can be adopted to those comprising a sliding type attachable/detachable light scanning unit such as a printer, a facsimile, a full color copying machine and a monochrome copying machine.  
         [0075]    As heretofore explained, according to the image forming apparatus of the present invention, since the elastic member is provided integrally with at least a part of the light scanning unit provided detachably by moving in a predetermined direction, the light scanning unit in the image forming apparatus can be attached/detached easily at the time of attaching/detaching the same by the sliding method as well as the light scanning unit can be closely contacted and fixed with a predetermined position stably. Thereby, the performance of the light scanning unit can be provided sufficiently so that a good writing image quality can be ensured.  
         [0076]    Although the embodiments of the present invention have been explained, the present invention is not limited thereto, and various modifications can be applied without the technological idea.