Patent Publication Number: US-9902169-B2

Title: Droplets drying device and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-130669 filed on Jun. 30, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a droplets drying device and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided a droplets drying device comprising: a drying mechanism having plural light sources that are arranged in a width direction of a recording medium, and dry droplets ejected onto the recording medium by emitting light toward the droplets; a moving mechanism that moves the drying mechanism in the width direction; a light shield member that is opposed to at least part of the drying mechanism being moved by the moving mechanism, and interrupts light emitted from the light sources disposed in the part, opposed to the light shield member, of the drying mechanism; and a measuring member that is disposed in a light shield region where the light shield member interrupts incoming light, and receives light emitted from each of the light sources and measures a light quantity of the light source as the measuring member is moved relative to the drying mechanism in the width direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a sectional view of a droplets drying device according to a first exemplary embodiment of the present invention; 
         FIG. 2  is another sectional view of the droplets drying device according to the first exemplary embodiment; 
         FIG. 3  is still another sectional view of the droplets drying device according to the first exemplary embodiment; 
         FIG. 4  is a further sectional view of the droplets drying device according to the first exemplary embodiment; 
         FIG. 5  is a plan view of the droplets drying device according to the first exemplary embodiment; 
         FIG. 6A  is a sectional view of a drying unit of the droplets drying device according to the first exemplary embodiment, and  FIG. 6B  is a sectional view of the drying unit and a maintenance unit of the droplets drying device according to the first exemplary embodiment; 
         FIG. 7  is a perspective view of the maintenance unit of the droplets drying device according to the first exemplary embodiment; 
         FIG. 8  is a plan view illustrating how the drying units of the droplets drying devices according to the first exemplary embodiment and droplets ejecting heads are moved; 
         FIG. 9  shows a control system of the droplets drying devices according to the first exemplary embodiment; 
         FIG. 10  is a schematic diagram showing the configuration of an image forming apparatus according to the first exemplary embodiment of the invention; 
         FIG. 11  is a sectional view of a droplets drying device according to a second exemplary embodiment of the invention; 
         FIG. 12  is another sectional view of the droplets drying device according to the second exemplary embodiment; 
         FIGS. 13A and 13B  are further sectional views of the droplets drying device according to the second exemplary embodiment; 
         FIG. 14  shows a control system of the droplets drying devices according to the second exemplary embodiment; and 
         FIG. 15  is a schematic diagram showing the configuration of an image forming apparatus according to a modification of the first or second exemplary embodiment. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
           10 : Image forming apparatus 
           24 : Droplets ejecting head (example droplets ejecting member) 
           28 : Droplets drying device 
           30 : Drying unit (example drying mechanism) 
           42 : Light source 
           48 : Protective member 
           50 : Moving mechanism 
           54 : Controller (example correction unit) 
           64 : Cleaning member 
           66 : Measuring member 
           68 : Body (example light shield member) 
           128 : Droplets drying device 
           154 : Controller (example correction unit) 
           164 : Cleaning member 
           166 : Measuring member 
           168 : Body (example light shield member) 
       
    
     DETAILED DESCRIPTION 
     Exemplary Embodiment 1 
     Droplets drying devices  28  and an image forming apparatus  10  according to a first exemplary embodiment of the present invention will be described below with reference to  FIGS. 1-10 . Arrows H, W, and D in the figures indicate the apparatus top-bottom direction (vertical direction), the apparatus width direction (horizontal direction), and the apparatus depth direction (horizontal direction), respectively. 
     (Overall Configuration) 
     As shown in  FIG. 10 , the image forming apparatus  10  is equipped with an image forming unit  12  for forming an image on a portion of a continuous sheet P (recording medium), a preprocessing unit  14  which houses the continuous sheet P to be supplied to the image forming unit  12 , and a buffer unit  16  which is disposed between the image forming unit  12  and the preprocessing unit  14  and adjusts the rate of conveyance of a portion, to be supplied from the preprocessing unit  14  to the image forming unit  12 , of the continuous sheet P and other things. 
     The image forming apparatus  10  is further equipped with a post-processing unit  18  which houses part of the continuous sheet P put out of the image forming unit  12  and a buffer unit  20  which is disposed between the image forming unit  12  and the post-processing unit  18  and adjusts the rate of conveyance of a portion, to be put out of the image forming unit  12  to the post-processing unit  18 , of the continuous sheet P and other things. 
     A droplets ejecting device  22  for forming an image on a portion, being conveyed along a conveyance path  26 , of the continuous sheet P by ejecting droplets onto it and plural droplets drying devices  28  are disposed inside the image forming unit  12 . 
     The droplets ejecting device  22  is equipped with a droplets ejecting head  24 K which is an example droplets ejecting member for forming a K (black) image by ejecting droplets onto a portion of the continuous sheet P, a droplets ejecting head  24 C which is an example droplets ejecting member for forming a C (cyan) image, a droplets ejecting head  24 M which is an example droplets ejecting member for forming an M (magenta) image, and a droplets ejecting head  24 Y which is an example droplets ejecting member for forming a Y (yellow) image. 
     The droplets ejecting heads  24 K,  24 C,  24 M, and  24 Y are arranged in this order downstream in the conveying direction of the continuous sheet P (hereinafter referred to simply as a “sheet conveying direction” so as to be opposed to a portion of the continuous sheet P. In the following description, characters K, Y, M, and C to be attached to reference numerals will be omitted if the colors K, Y, M, and C need not be discriminated from each other for components concerned. 
     The droplets drying devices  28  for drying droplets ejected onto a portion of the continuous sheet P by the droplets ejecting heads  24  are disposed downstream of the respective droplets ejecting heads  24 K,  24 C,  24 M, and  24 Y in the sheet conveying direction. The droplets drying devices  28  will be described below in detail. 
     (Configuration of Essential Part) 
     Next, the droplets drying devices  28  will be described. As shown in  FIG. 10 , the droplets drying devices  28  are disposed downstream of the respective droplets ejecting heads  24 K,  24 C,  24 M, and  24 Y in the sheet conveying direction. Since the droplets drying devices  28  have the same configuration, only one of them will be described below as a representative one. 
     As shown in  FIG. 1 , the droplets drying device  28  is equipped with a drying unit  30 , a moving mechanism  50  for moving the drying unit  30 , a maintenance unit  52  for maintaining the drying unit  30 , and a controller  54  (see  FIG. 9 ) for controlling the other individual units. 
     [Drying Unit  30 ] 
     The drying unit  30 , which is an example drying mechanism, is disposed at a drying position (see  FIG. 1 ) where it is opposed to a portion of the continuous sheet P or an escape position (see  FIG. 4 ) where it is not. The escape position is spaced from the drying position in the apparatus depth direction. The movement of the drying unit  30  will be described later in detail. 
     As shown in  FIGS. 5 and 6A , the drying unit  30  extends in the apparatus depth direction. The drying unit  30  is equipped with a body member  40 , a board  44  which is mounted with light sources  42 , and a protective member  48  which protects the light sources  42 . 
     [Body Member  40 ] 
     The body member  40 , which is shaped like a rectangular parallelepiped, extends in the apparatus depth direction and has a recess  58  that is open on the side of the continuous sheet P. The body member  40  is formed with a step portion  58 A on the side of the continuous sheet P in such a manner that the width of the recess  58  is increased there. The protective member  48  is attached to the step portion  58 A by a fixing member (not shown). 
     The board  44  is attached, by a fixing member (not shown), to a flat bottom surface  58 B, facing the continuous sheet P, of the recess  58 . 
     [Board  44 ] 
     The board  44  extends in the apparatus depth direction and, as mentioned above, attached to the bottom surface  58 B of the recess  58 . 
     The light sources  42  are mounted on the surface, facing the continuous sheet P, of the board  44 . The plural light sources  42  are surface emission lasers (VCSELs) and are arranged at the same interval in the apparatus depth direction. 
     As shown in  FIG. 9 , drive circuits  60  for controlling drive currents flowing through the respective light sources  42  are formed on the board  44  so as to correspond to the respective light sources  42 . The controller  54  controls the light quantities of the light sources  42  by controlling the drive circuits  60 . The timing etc. of the control of the drive circuits  60  by the controller  54  will be described later in detail together with the operation of the droplets drying device  28 . 
     [Protective Member  48 ] 
     The protective member  48  is a heat-resistant glass plate, extends in the apparatus depth direction, and, as mentioned above, attached to the step portion  58 A of the body member  40 . The protective member  48  protects the light sources  42  and transmits light emitted from the light sources  42 . 
     [Moving Mechanism  50 ] 
     As shown in  FIG. 1 , the moving mechanism  50  is equipped with a rail member  50 A which extends in the apparatus depth direction, a support member  50 B which supports the body member  40 , and a motor  50 C. The rail member  50 A extends in the apparatus depth direction from over the continuous sheet P to the deep side (left side in  FIG. 1 ). 
     The support member  50 B connects the rail member  50 A and the body member  40 . A bottom portion of the support member  50 B is attached to the body member  40 , and its top portion is attached movably to the rail member  50 A. The motor  50 C moves the support member SOB in the apparatus depth direction along the rail member  50 A. 
     With the above configuration, as shown in  FIG. 8 , the controller  54  moves the drying unit  30  between the drying position (drawn by solid lines) where it is opposed to the continuous sheet P and the escape position (drawn by two-dot chain lines) that deviates from the drying position to the deep side in the apparatus depth direction, by controlling the motor  50 C. The timing etc. of the control of the motor  50 C by the controller  54  will be described later in detail together with the operation of the droplets drying device  28 . 
     A moving mechanism (not shown) for moving the droplets ejecting head  24  of each color is also attached to it, and the droplets ejecting head  24  of each color is also moved in the apparatus depth direction like each drying unit  30 . 
     [Maintenance Unit  52 ] 
     The maintenance unit  52  is spaced from the drying unit  30  in both of a case that the drying unit  30  is located at the drying position (see  FIG. 1 ) and a case that the drying unit  30  is located at the escape position (see  FIG. 4 ). As shown in  FIGS. 2 and 3 , the maintenance unit  52  is opposed to the drying unit  30  when the drying unit  30  is being moved between the drying position and the escape position. 
     As shown in  FIG. 1 , the maintenance unit  52  is equipped with a cleaning member  64 , a measuring member  66  for measuring the light quantity of each light source  42 , and a body  68  which is fixed to a frame (not shown; an example of an apparatus body). 
     [Body  68 ] 
     As shown in  FIG. 7 , the body  68 , which is an example light shield member, is shaped like a box having a top opening and is composed of four side plates  68 A and a bottom plate  68 B. The length L 1  in the apparatus depth direction of the body  68  is shorter than the length in the apparatus depth direction of the drying unit  30 . In other words, the body  68  has such a length as to be opposed to part of the plural light sources  42 . 
     As shown in  FIGS. 2 and 6B , when the drying unit  30  is being moved between the drying position and the escape position, the bottom end portion of the drying unit  30  is brought in close proximity to the tips of the respective side plates  68 A in the apparatus top-bottom direction. Light emitted from the light sources  42  opposed to the maintenance unit  52  is interrupted by the body  68 . In the first exemplary embodiment, a region that is surrounded by the side plates  68 A when viewed from above (from the side of the opening of the body  68 ) and where incoming light is thereby interrupted is referred to as a light shield region  80 . Light that goes toward the light shield region  80  does not leak to the outside. 
     [Cleaning Member  64 ] 
     As shown in  FIG. 1 , the cleaning member  64  is disposed in the light shield region  80  and fixed to the body  68 . As shown in  FIG. 7 , the cleaning member  64  is equipped with a rectangular-parallelepiped-shaped seat  70  and a plate-like blade  72  whose base portion is attached to the seat  70  and tip portion is to come into contact with the bottom surface of the protective member  48 . 
     The seat  70  is formed with a slit  70 A which extends in the apparatus width direction. A base portion of the blade  72  is fitted in the slit  70 A. 
     The blade  72  is formed by molding, for example, a rubber material that is elastically deformable, and is oriented so that its thickness direction coincides with the apparatus depth direction. As shown in  FIGS. 2 and 3 , the tip portion of the blade  72  comes into contact with the protective member  48  of the drying unit  30  when the drying unit  30  is being moved between the drying position and the escape position. 
     [Measuring Member  66 ] 
     As shown in  FIGS. 1 and 7 , the measuring member  66  is disposed in the light shield region  80 . As shown in  FIG. 7 , the measuring member  66  is fixed to the top surface of the seat  70  on the deep side of the blade  72  in the apparatus depth direction. 
     The measuring member  66  measures the light quantity of each light source  42 . The controller  54  receives measurement results, for the respective light sources  42 , of the measuring member  66  (see  FIG. 9 ) and corrects their light quantities. Thus, the controller  54  serves as an example correction unit for correcting the light quantity of each light source  42 . How the controller  54  controls the individual units when receiving measurement results of the measuring member  66  will be described below in detail together with the operation of the droplets drying device  28 . 
     (Operation) 
     Next, a description will be made of how the droplets drying devices  28  operate. As shown in  FIGS. 1 and 5 , while the image forming apparatus  10  is not in operation, the drying units  30  are located at the drying positions and the sets of light sources  42  are off. When the image forming apparatus  10  is put into operation and an image forming operation is started, the droplets ejecting heads  24  of the respective colors eject droplets onto a portion of the continuous sheet P being conveyed and form an image there. 
     When droplets are ejected onto the portion of the continuous sheet P by the droplets ejecting heads  24 , the controller  54  controls the sets of drive circuits  60  to cause the sets of light sources  42  to emit light (see  FIG. 6A ), whereby droplets ejected onto the portion of the continuous sheet P are irradiated with light and dried (through evaporation). 
     Upon completion of an image forming operation of one job (i.e., one continuous image forming operation), the ejecting of droplets by the droplets ejecting heads  24  is stopped and the controller  54  controls the sets of drive circuits  60  to turn off the sets of light sources  42 . 
     When the sets of light sources  42  have been turned off, the controller  54  controls the motor  56 C to move the drying units  30  from the drying positions to the escape positions. More specifically, as shown in  FIGS. 2 and 3 , each drying unit  30  is moved in a state that the bottom surface of the protective member  48  is in contact with the tip portion of the blade  72 . As a result, foreign matter such as colorant that is stuck to the bottom surface of the protective member  48  is wiped out by the blade  72 , that is, the protective member  48  is cleaned. Thus, a measurement by the measuring member  66  is made more correct than in a case that no cleaning is performed before a measurement. 
     The controller  54  controls the drive circuits  60  to turn on the light sources  42  in order that come to be opposed to the measuring member  66  with a portion, from which foreign matter has been wiped out, of the protective member  48  interposed between them. More specifically, the controller  54  causes each light source  42  to emit light while the light emitted from it is interrupted by the body  68 . The measuring member  66  receives light emitted from the light source  42  and measures its light quantity. 
     As shown in  FIGS. 2 and 3 , as each drying unit  30  is moved to the escape position, the blade  72  cleans the entire bottom surface of the protective member  48  and the measuring member  66  measures the light quantities of all of the light sources  42 . Upon measuring the light quantities of all of the light sources  42 , the controller  54  receives measurement results of the measuring member  66  and controls the drive circuits  60  to correct the values of drive currents for the respective light sources  42 . More specifically, the controller  54  corrects the values of drive currents for the respective light sources  42  so that they fall within a predetermined range. In other words, the controller  54  corrects the light quantities of the respective light sources  42  so that they fall within a predetermined range. 
     Upon correcting the values of drive currents, the controller  54  controls the motor  50 C to move the drying unit  30  from the escape position to the drying position. As soon as the drying unit  30  reaches the drying position, the controller  54  controls the motor  50 C to move the drying unit  30  to the escape position again (see  FIGS. 1-4 ). 
     The controller  54  controls the drive circuits  60  to cause the light sources  42  that come to be opposed to the measuring member  66  to emit light in order. The measuring member  66  again receives light emitted from each light source  42  and measures its light quantity. During the above course, as in the case of the first movement, the blade  72  comes into contact with the bottom surface of the protective member  48  of the drying unit  30 . 
     When the drying unit  30  has reached the escape position (see  FIG. 4 ), the measuring member  66  has measured the light quantities of all of the light sources  42 . The controller  54  receives measurement results of the measuring member  66  and checks whether or not the light quantities of all of the light sources  42  are within the predetermined range. 
     Upon receiving the measurement results of the measuring member  66 , the controller  54  controls the motor  50 C to move the drying unit  30  from the escape position to the drying position. When the drying unit  30  has been moved to the drying position, the droplets drying device  28  makes preparations for the next image forming operation. 
     (Summary) 
     As described above, the measuring member  66  is disposed in the light shield region  80 . With this measure, the degree of leakage, to outside the body  68  (outside the light shield region  80 ), of light to be measured by the measuring member  66  is made lower than in a case that a measuring member is not disposed in the light shield region  80 . 
     The cleaning member  64  and the measuring member  66  are disposed in the light shield region  80 . With this measure, the degree of size increase of each droplets drying device  28  is made lower than in a case that a cleaning member and a measuring member are disposed in different regions. 
     In each droplets drying device  28 , the cleaning member  64  cleans the protective member  48  and the measuring member  66  measures the light quantities of the respective light sources  42  as the drying unit  30  is moved. With this measure, the power consumption can be made lower than in, for example, a case that the protective member  48  is cleaned and the light quantities of the light sources  42  are measured as both of a drying unit and a maintenance unit are moved. 
     In each droplets drying device  28 , the body  68  has such a size as to be opposed to part of the plural light sources  42 . With this measure, the degree of size increase of the droplets drying device  28  is made lower than in a case that a body has such a size as to be opposed to all light sources. 
     In each droplets drying device  28 , the controller  54  corrects the light quantities of the light sources  42  on the basis of measurement results of the measuring member  66 . As a result, the probability that the light quantities of the light sources  42  deviate from the predetermined range can be made lower than in a case that the light quantities of the light sources  42  are not corrected. 
     In each droplets drying device  28 , the measuring member  66  measures the light quantities of the light sources  42  again by receiving light beams emitted from the light-quantity-corrected light sources  42 . This allows the controller  54  to check whether or not the corrected light quantities of the light sources  42  are within the predetermined range. 
     According to the image forming apparatus  10 , its inside space can be utilized effectively because it is equipped with the droplets drying devices  28 . 
     Exemplary Embodiment 2 
     Droplets drying devices  128  and an image forming apparatus according to a second exemplary embodiment of the invention will be described below with reference to  FIGS. 11-14 . In the second exemplary embodiment, differences from the first exemplary embodiment will be described mainly. 
     As shown in  FIGS. 11 and 12 , each droplets drying device  128  is equipped with a drying unit  30 , a moving mechanism  50 , a maintenance unit  152  to be opposed to the drying unit  30  located at the escape position, and a controller  54  (see  FIG. 14 ). 
     [Maintenance Unit  152 ] 
     The maintenance unit  152  is equipped with a cleaning member  164  for cleaning the protective member  48 , a measuring member  166  for measuring the light quantity of each light source  42 , a body  168 , and a moving mechanism  178  for moving the cleaning member  164 . 
     [Body  168 ] 
     The body  168 , which is an example light shield member, is shaped like a box extending in the apparatus depth direction and having a top opening and is composed of four side plates  168 A and a bottom plate  168 B. 
     As shown in  FIG. 12 , when the drying unit  30  is located at the escape position, the tips of the respective side plates  168 A are in close proximity to the bottom end portion of the drying unit  30  and the side plates  168 A surround the protective member  48  when viewed from above. Light emitted from the light sources  42  of the drying unit  30  located at the escape position is interrupted by the body  168 . A region that is surrounded by the side plates  168 A when viewed from above (from the side of the opening of the body  168 ) and where incoming light is thereby interrupted is referred to as a light shield region  180 . Light that goes toward the light shield region  180  does not leak to the outside. 
     [Cleaning Member  164 ] 
     As shown in  FIGS. 11 and 12 , the cleaning member  164  is disposed in the light shield region  180  and equipped with a rectangular-parallelepiped-shaped seat  170  and a plate-like blade  172  whose base portion is attached to the seat  170  and tip portion is to come into contact with the bottom surface of the protective member  48 . 
     The seat  170  is formed with a slit  70 A (not shown) which extends in the apparatus width direction. A base portion of the blade  172  is fitted in the slit  170 A. 
     The blade  172  is formed by molding, for example, a rubber material that is elastically deformable. As shown in  FIG. 13A , a tip portion of the blade  172  comes into contact with the protective member  48  of the drying unit  30  by moving the cleaning member  164  by the moving mechanism  178 . 
     [Measuring Member  166 ] 
     As shown in  FIG. 11 , the measuring member  166  is disposed in the light shield region  180  and fixed to the top surface of the seat  170  on the deep side of the blade  172  in the apparatus depth direction. The measuring member  166  measures the light quantities of the light source  42  in order that come to be opposed to the measuring member  166  by moving the cleaning member  164  by the moving mechanism  178  as shown in  FIG. 13A . 
     [Moving Mechanism  178 ] 
     As shown in  FIG. 11 , the moving mechanism  178  is equipped with a ball screw  176  which extends in the apparatus depth direction and penetrates through the seat  170  and a motor  174  for rotating the ball screw  176 . The ball screw  176  is rotated in a normal direction or a reverse direction by the controller  154 &#39;s controlling the motor  174 . As a result, the cleaning member  164  is moved between a cleaning start position (see  FIG. 12 ) where cleaning of the protective member  48  is started and a cleaning end position (see  FIG. 13B ) where cleaning of the protective member  48  is finished. 
     (Operation) 
     Next, a description will be made of how the droplets drying devices  128  operate. As shown in  FIG. 11 , while the image forming apparatus is not in operation, the drying units  30  are located at the drying positions and the cleaning members  164  are located at the cleaning start positions. When the image forming apparatus is put into operation and an image forming operation is started, the droplets ejecting heads  24  of the respective colors eject droplets onto a portion of the continuous sheet P being conveyed and form an image there. 
     Upon completion of an image forming operation of one job (i.e., one continuous image forming operation), the ejecting of droplets by the droplets ejecting heads  24  is stopped and the controller  154  controls the sets of drive circuits  60  to turn off the sets of light sources  142 . 
     When the sets of light sources  42  have been turned off, the controller  154  controls the motor  56 C to move the drying units  30  from the drying positions to the escape positions (see  FIGS. 11 and 12 ). At the escape positions, the drying units  30  are opposed to the respective maintenance units  152 . 
     In the state that each drying unit  30  is opposed to the corresponding maintenance unit  152 , the controller  154  controls the motor  174  to move the cleaning member  164  from the cleaning start position to the cleaning end position. As shown in  FIGS. 13A and 13B , as cleaning member  164  is moved, the tip portion of the blade  172  is kept in contact with the bottom surface of the protective member  48 , whereby foreign matter such as colorant that is stuck to the bottom surface of the protective member  48  is wiped out by the blade  172 . 
     The controller  154  then controls the drive circuits  60  to turn on the light sources  42  in order that come to be opposed to the measuring member  166  with a portion, from which foreign matter has been wiped out, of the protective member  48  interposed between them. The measuring member  166  receives light emitted from each light source  42  and measures its light quantity. 
     As shown in  FIG. 13B , as the cleaning member  164  is moved to the cleaning end position, the blade  172  cleans the entire bottom surface of the protective member  48  and the measuring member  166  measures the light quantities of all of the light sources  42 . Upon measuring the light quantities of all of the light sources  42 , the controller  154  receives measurement results of the measuring member  166  and controls the drive circuits  60  to correct the values of drive currents for the respective light sources  42 . More specifically, the controller  154  corrects the values of drive currents for the respective light sources  42  so that they fall within a predetermined range. In other words, the controller  154  corrects the light quantities of the respective light sources  42  so that they fall within a predetermined range. 
     Upon correcting the values of drive currents, the controller  154  controls the motor  174  to move the cleaning member  164  from the cleaning end position to the cleaning start position. As soon as the cleaning member  164  reaches the cleaning start position, the controller  154  controls the motor  174  to move the drying unit  30  to the cleaning end position again (see  FIGS. 13A and 13B ). 
     The controller  54  controls the drive circuits  60  to cause the light sources  42  that come to be opposed to the measuring member  166  to emit light in order. The measuring member  166  again receives light emitted from each light source  42  and measures its light quantity. During the above course, as in the case of the first movement, the blade  172  comes into contact with the bottom surface of the protective member  48  of the drying unit  30 . 
     When the cleaning member  164  has reached the cleaning end position (see  FIG. 13B ), the measuring member  166  has measured the light quantities of all of the light sources  42 . The controller  154  receives measurement results of the measuring member  166  and checks whether or not the light quantities of all of the light sources  42  are within the predetermined range. 
     Subsequently, the controller  154  controls the motor  174  to move the cleaning member  164  from the cleaning end position to the cleaning start position and controls the motor  50 C to move the drying unit  30  from the escape position to the drying position. When the drying unit  30  has been moved to the drying position, the droplets drying device  128  makes preparations for the next image forming operation. 
     The droplets drying device  128  according to the second exemplary embodiment operates in the same manner as the droplets drying device  28  according to the first exemplary embodiment except that the protective member  48  is cleaned and the light quantities of the light sources  42  are measured as the cleaning member  164  is moved, and that the body  168  has such a size as to be opposed to all of the light sources  42 . 
     Although the invention has been described in detail in the form of the particular embodiments, it is apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention. For example, although in the above exemplary embodiments the maintenance timing of the drying units  30  is after completion of one job, it may be some other timing. 
     Although in the above exemplary embodiments each droplets drying device  28  or  128  is disposed downstream of the associated droplets ejecting head  24  of one color in the sheet feeding direction, as shown in  FIG. 15  only one droplets drying device  28  or  128  may be disposed downstream of the droplets ejecting head  24 Y which is disposed most downstream in the sheet feeding direction. 
     Although in the above exemplary embodiments all of the light sources  42  are turned on in order when their light quantities are measured again after their correction, only light-quantity-corrected light sources  42  may be caused to emit light. 
     Although in the second exemplary embodiment the cleaning member  164  is disposed inside the body  168  which is the light shield member, the cleaning member  164  may be disposed outside the body  168 . 
     Although in the second exemplary embodiment the measuring member  166  is attached to the seat  170  of the cleaning member  164 , a measuring member and a cleaning member may be provided separately. In this case, the measuring member and the cleaning member may be moved separately.