Patent Publication Number: US-11644786-B2

Title: Image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus using electrophotography, such as a printer, a copier, a facsimile, or a multifunction peripheral. 
     Description of the Related Art 
     In an image forming apparatus such as a printer, a copier, a facsimile, or a multifunction peripheral in which these are integrally combined, for example, a photosensitive drum, a developing sleeve, a driving roller for rotating an intermediate transfer belt, and the like are provided in an apparatus body as a rotating member. Conventionally, in order to drive these rotating members, a driving unit in which motors and drive gears are integrated is attached to a rear plate of an apparatus body. As an example, for example, there has been proposed a driving unit including two support plates that are arranged at both ends of a drive gear in a rotation axis direction and support a rotation shaft of the drive gear, and the drive gear is arranged in a space sandwiched between the support plates (JP 2007-155072 A). 
     In the driving unit described in JP 2007-155072 A, two support plates are connected to each other via a cover member that closes a gap therebetween. That is, when foreign matter such as dust enters the space where the drive gear is disposed from the outside and adheres to the drive gear, rotational fluctuation occurs in the rotating member driven by the driving unit, and image defects such as periodic band-shaped density unevenness (referred to as banding or the like) may occur in the image formed on the recording material. In addition, when foreign matter adhering to the drive gear is caught in the drive gear, abnormal noise occurs. Therefore, in order to prevent foreign matter from entering from the outside, a cover member that closes a gap between the two support plates is installed. 
     Incidentally, for example, in a case where two support plates are connected using a screw, foreign matter such as metal powder generated by fastening of the screw may adhere to the drive gear. That is, although the support plate is perforated in advance with a fastening hole for fastening a screw, metal powder, which is generated when the support plate is scraped and perforated, may remain in the fastening hole as scraping powder. Conventionally, since a screw is inserted and fastened from the outside toward the inside (space side) of the support plate, the metal powder is pushed inward from the fastening hole by the screw and adheres to the drive gear inside, which is arranged in advance. Alternatively, in a case where the screw is fastened while tapping is performed, metal powder generated by the tapping is pushed inward, and may adhere to the drive gear. The metal powder adhered to the drive gear causes the above-described image defect and abnormal noise similarly to foreign matter such as dust entering from the outside. 
     Therefore, in order to prevent the metal powder generated by the fastening of the screw from adhering to the drive gear, it is conceivable to provide a fastening region in which a fastening hole is formed on the outer peripheries of the two support plates when viewed from the rotation axis direction of the drive gear and to fasten the screw thereto. With such a configuration, the metal powder which may be generated by fastening the screw falls not to the inside (space side) but to the outside of the support plate. Therefore, it is possible to prevent the metal powder from adhering to the drive gear. However, when a fastening region is newly secured in the support plate, the driving unit has to be increased in size, and accordingly, it is difficult to adopt the driving unit because this goes against the recent demand for miniaturization as an image forming apparatus. 
     Therefore, it has been conventionally desired to suppress the occurrence of image defects and abnormal noise due to the adhesion of foreign matter to the drive gear caused by the fastening of the screw in the driving unit without increasing the size of the driving unit, but such a configuration has not been proposed yet. 
     The present invention has been made in view of the above problems, and the present invention provides an image forming apparatus that suppresses occurrence of image defects and abnormal noise due to adhesion of foreign matter to a drive gear, the foreign matter occurring due to fastening of a screw in the driving unit, without increasing the size of the driving unit. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention is an image forming apparatus that forms an image on a recording material, the image forming apparatus including a rotating member, and a driving unit configured to drive the rotating member. The driving unit includes a driving source, a drive gear configured to transmit a driving force of the driving source to the rotating member, a first support member that holds the driving source and includes a first support portion that supports one end portion of a rotation shaft of the drive gear in a rotation axis direction of the drive gear, and a second support member that includes a second support portion that supports another end portion of the rotating shaft and is connected to the first support member by a fastening member. The first support member includes a fastening hole to which the fastening member is fastened, the fastening hole being disposed in a projection plane obtained by projecting the second support portion in a rotation axis direction of the drive gear. The second support member is disposed upstream of the first support member in a fastening direction in which the fastening member is fastened, and includes a mounting portion extending from the second support portion downstream in the fastening direction so as to be in contact with the first support portion in the projection plane, the mounting portion including an attachment hole into which the fastening member is inserted, the attachment hole being disposed at a position overlapping the fastening hole in a contact portion of the mounting portion which is in contact with the first support portion. 
     According to a second aspect of the present invention is an image forming apparatus that forms an image on a recording material, the image forming apparatus including a rotating member, and a driving unit configured to drive the rotating member. The driving unit includes a driving source, a drive gear configured to transmit a driving force of the driving source to the rotating member, a first support member that holds the driving source and includes a first support portion that supports one end portion of a rotation shaft of the drive gear in a rotation axis direction of the drive gear, and a second support member that includes a second support portion that supports another end portion of the rotating shaft and is connected to the first support member by a fastening member. The first support member includes a fastening hole to which the fastening member is fastened and that is disposed in a projection plane obtained by projecting the second support portion in a rotation axis direction of the drive gear. The second support member is disposed upstream of the first support member in a fastening direction in which the fastening member is fastened, and includes a flange portion extending from the second support portion downstream in the fastening direction in the projection plane, the flange portion including an attachment hole into which the fastening member is inserted, the attachment hole being disposed at a position overlapping the fastening hole. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram illustrating a configuration of an image forming apparatus according to a present embodiment. 
         FIG.  2    is a perspective view illustrating a driving unit. 
         FIG.  3    is a view of the driving unit as viewed from a main support member side. 
         FIG.  4    is an exploded perspective view illustrating the driving unit. 
         FIG.  5    is a view of the driving unit as viewed from a sub support member side. 
         FIG.  6    is a cross-sectional view illustrating the driving unit. 
         FIGS.  7 A and  7 B  are views for explaining metal powder generated by fastening of a screw, in which  FIG.  7 A  illustrates a state before inserting the screw into a fastening hole, and  FIG.  7 B  illustrates a state after inserting the screw into the fastening hole. 
         FIG.  8 A  is a view of a conventional driving unit as viewed from a sub support member side, and  FIG.  8 B  is a cross-sectional view illustrating the conventional driving unit. 
         FIGS.  9 A and  9 B  are schematic views illustrating a comparative example, in which  FIG.  9 A  illustrates a case where a screw is fastened from the sub support member side toward the main support member side, and  FIG.  9 B  illustrates a case where a screw is fastened from the main support member side toward the sub support member side. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Image Forming Apparatus 
     An image forming apparatus according to the present embodiment will be described with reference to  FIG.  1   . The image forming apparatus  101  illustrated in  FIG.  1    is an intermediate transfer full-color printer. The image forming apparatus  101  includes image forming units PY, PM, PC, and PK that form yellow, magenta, cyan, and black toner images, respectively. The image forming apparatus  101  forms a toner image on the recording material S according to an image signal from a document reading apparatus  102  provided above the image forming apparatus  101  in the vertical direction or an external device (not illustrated) such as a personal computer. Examples of the recording material S include sheet materials such as paper, a plastic film, and cloth. In the present specification, a side on which a user stands when operating an operation panel (not illustrated) in order to operate the image forming apparatus  101  is referred to as a “front surface”, and the opposite side is referred to as a “back surface”. 
     In the image forming apparatus  101  illustrated in  FIG.  1   , the image forming units PY, PM, PC, and PK are arranged side by side along the moving direction (direction of arrow R 2 ) of the intermediate transfer belt  116 . The intermediate transfer belt  116  is an endless belt member that carries and conveys the toner images primarily transferred from the photosensitive drums  112 Y,  112 M,  112 C, and  112 K of the image forming units PY, PM, PC, and PK. The intermediate transfer belt  116  is stretched around each rotating member of a secondary transfer inner roller  116   a , a tension roller  116   b , a pre-secondary transfer roller  116   c , and a stretching roller  116   d . Then, the intermediate transfer belt  116  is moved in the moving direction by a secondary transfer inner roller  116   a  (rotating member, secondary transfer roller) rotationally driven by a driving unit  90  (see  FIG.  2   ) to be described later. That is, in the present embodiment, the secondary transfer inner roller  116   a  also serves as a driving roller that drives the intermediate transfer belt  116 . 
     The image forming apparatus  101  includes a support frame member  101 A that supports units such as the photosensitive drums  112 Y to  112 K, the secondary transfer inner roller  116   a , the tension roller  116   b , the pre-secondary transfer roller  116   c , and the stretching roller  116   d . The support frame member  101 A includes a plurality of sheet metals such as a front plate provided on the front side of the image forming apparatus  101 , a rear plate provided on the back side and supporting each unit together with the front plate, a stay connecting the front plate and the rear plate, and a support column supporting the front plate, and is covered with an exterior cover (not illustrated) constituting the external appearance of the image forming apparatus  101 . 
     A secondary transfer outer roller  117  is disposed so as to sandwich the secondary transfer inner roller  116   a  and the intermediate transfer belt  116 , and forms a secondary transfer nip portion T 2  for transferring the toner image on the intermediate transfer belt  116  to the recording material S. In the secondary transfer nip portion T 2 , the secondary transfer inner roller  116   a  and the secondary transfer outer roller  117  rotate to nip and convey the recording material S. 
     Under the image forming apparatus  101 , one or a plurality of cassettes  131  in which the recording material S is accommodated are arranged. The recording materials S accommodated in the cassette  131  are supplied one by one from the cassette  131  to the conveyance path  60  in accordance with the image forming timing by the feed roller  151 . The recording material S is conveyed to a registration roller  170  disposed on the conveyance path  60 , skew correction and timing correction are performed by the registration roller  170 , and the recording material S is conveyed toward the secondary transfer nip portion T 2 . The cassette  131  is slidably supported with respect to the support frame member  101 A. The user can refill the cassette  131  with the recording material S by pulling out the cassette  131  to the front side of the image forming apparatus  101 . 
     The four image forming units PY, PM, PC, and PK included in the image forming apparatus  101  have substantially the same configuration except that the colors of the toners used in developing units  114  included therein are different. Therefore, here, the yellow image forming unit PY will be representatively described, and description of the other image forming units PM, PC, and PK will be omitted. 
     In the image forming unit PY, the photosensitive drum  112 Y is disposed as one of the rotating members. The photosensitive drum  112 Y is rotationally driven by the driving unit  90  (see  FIG.  2   ) to be described later. A charging unit  113 , a developing unit  114 , and a primary transfer roller  119  are disposed around the photosensitive drum  112 Y. 
     When the image forming operation is started, first, the surface of the rotating photosensitive drum  112 Y is uniformly charged by the charging unit  113 . Next, the photosensitive drum  112 Y is scanned and exposed by laser light emitted from the exposing unit  110  shared by the image forming units PY to PK. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum  112 Y. The electrostatic latent image on the photosensitive drum  112 Y is developed by toner (developer) in the developing unit  114 , and a toner image is formed on the photosensitive drum  112 Y. The developing unit  114  includes a conveying screw (not illustrated) that circularly conveys the developer in the developer container, a developing sleeve  114   a  (rotating member) that carries the developer and rotates to develop the toner image on the photosensitive drum  112 Y, and the like. The developing sleeve  114   a  is driven by the driving unit  90  (see  FIG.  2   ) to be described later. 
     The toner image formed on the photosensitive drum  112 Y is primarily transferred from the photosensitive drum  112 Y to the intermediate transfer belt  116  at a primary transfer portion formed between the photosensitive drum  112 Y and the primary transfer roller  119  disposed across the intermediate transfer belt  116 . At this time, a primary transfer voltage is applied to the rotating primary transfer roller  119 . Thus, the intermediate transfer belt  116  is rotated while carrying the toner image transferred from the photosensitive drum  112 Y. 
     By sequentially performing the above-described operation in the yellow, magenta, cyan, and black image forming units PY to PK, a toner image can be formed on the intermediate transfer belt  116 . For example, a toner image of a single color can be formed, or a toner image of a desired color can be formed by appropriately superimposing some of the four colors. In accordance with the toner image forming timing, the recording material S supplied from the cassette  131  is conveyed to the secondary transfer nip portion T 2  via the registration roller  170 . Then, for example, when a secondary transfer voltage is applied to the secondary transfer outer roller  117  by a high-voltage power supply (not illustrated), the toner image on the intermediate transfer belt  116  is secondarily transferred to the recording material S when the recording material S passes through the secondary transfer nip portion T 2 . 
     The recording material S to which the toner image has been transferred from the intermediate transfer belt  116  is conveyed to the fixing unit  120 . The fixing unit  120  applies heat and pressure to the recording material S while nipping and conveying the recording material S to fix the toner image on the recording material S. In the case of single-sided printing mode in which a toner image is formed only on one side of the recording material S, the recording material S on which the toner image is fixed by the fixing unit  120  is discharged to a recording material discharge unit  123 . On the other hand, in the case of double-sided printing mode in which toner images are formed on both surfaces of the recording material S, after the toner image is fixed on one surface by the fixing unit  120 , the recording material S is reversed by switchback conveyance, and is conveyed toward the registration roller  170  through a duplex conveyance path  61 . Thereafter, the recording material S undergoes a process similar to that in the case of the single-sided printing mode, a toner image is also formed on the other surface by the fixing unit  120 , and then the recording material S is discharged to the recording material discharge unit  123 . 
     In the case of the present embodiment, the intermediate transfer belt  116 , the secondary transfer inner roller  116   a , the tension roller  116   b , the pre-secondary transfer roller  116   c , the stretching roller  116   d , and the plurality of primary transfer rollers  119  described above form an intermediate transfer unit  300 . 
     Note that, the image forming apparatus  101  can form not only a multicolor image but also a black monochrome image using only the image forming unit PK. In the case of forming a black monochrome image, primary transfer rollers  119  transferring a toner image of a color other than black are separated from the intermediate transfer belt  116  by a primary transfer roller separation mechanism (not illustrated) driven by the driving unit  90  (see  FIG.  2   ) to be described later. 
     Outline of Driving Unit 
     In the image forming apparatus  101  of the present embodiment, a driving unit  90  is provided in order to drive the photosensitive drums  112 Y to  112 K, the secondary transfer inner roller  116   a , the primary transfer roller separating mechanism (not illustrated), and the developing unit  114  (specifically, the developing sleeve  114   a ). An outline of the driving unit  90  will be described with reference to  FIGS.  2  to  4    while referring to  FIG.  1   . 
     As will be described in detail later, the driving unit  90  includes a main support member  20  as a first support member and a sub support member  25  (see  FIG.  4   ) as a second support member which are formed of, for example, a thin sheet metal. In the present embodiment, the driving unit  90  is fixed not inside the support frame member  101 A of the image forming apparatus  101  but outside the support frame member  101 A. Here, the outside of the support frame member  101 A refers to a side surface covered by the above-described exterior cover. Therefore, since the driving unit  90  can be accessed by removing the exterior cover of the image forming apparatus  101 , it is configured to be easier to perform maintenance than a configuration in which the driving unit is fixed to the inside of the support frame member  101 A. 
     As illustrated in  FIGS.  2  and  3   , the driving unit  90  is attached to rear plate  10  of the support frame member  101 A (see  FIG.  1   ). The driving unit  90  is fixed to the rear plate  10  with screws  41  via a plurality of fixing portions  55   a  to  55   h  formed on the outer periphery of the main support member  20  with the sub support member  25  facing the rear plate  10 . Attachment holes for attaching the screws  41  for fastening the main body are formed in the fixing portions  55   a  to  55   h.    
     In the main support member  20 , as illustrated in  FIG.  2   , an outer peripheral wall  15  is provided upright toward the rear plate  10  so as to surround the outer periphery so that foreign matter such as dust does not enter from the outside into the driving unit  90  in which the drive gear (see  FIG.  4   ) is disposed. The fixing portions  55   a  to  55   h  described above are formed by being bent in an L shape with respect to the wall surface of the outer peripheral wall  15  so that a leading edge of the outer peripheral wall  15  comes into contact with the rear plate  10  and can be fixed to the rear plate  10  by the screws  41 . That is, the fixing portions  55   a  to  55   h  are flange portions of the main support member  20 . When it is difficult to continuously provide the outer peripheral wall  15  due to the processing of the sheet metal and an opening is formed, the opening may be closed with a sheet material or the like. 
     As illustrated in  FIGS.  2  and  3   , a plurality of motors  30 CL,  30 K,  30 S, and  30 Ga to  30 Gd are held on one surface side of the main support member  20  as a driving source for driving the rotating member rotatably supported by the rear plate  10 . Here, one motor  30 CL for driving the yellow, magenta, and cyan photosensitive drums  112 Y,  112 M, and  112 C, and one motor  30 K for driving the black photosensitive drum  112 K and the secondary transfer inner roller  116   a  are held. In addition, one motor  30 S for driving the primary transfer roller separation mechanism (not illustrated) described above, and four motors  30 Ga,  30 Gb,  30 Gc, and  30 Gd for individually driving the yellow, magenta, cyan, and black developing units  114  (specifically, the developing sleeve  114   a ) are held. 
     On the other hand, as illustrated in  FIG.  4   , drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd that transmit the driving force of the motors  30 CL,  30 K,  30 S, and  30 Ga to  30 Gd (see  FIG.  3   ) to the rotating member of the support frame member  101 A are provided on other surface of the main support member  20  opposite to the one surface. 
     The drive gear  35 Cla and the drive gear  35 CLb are rotated by driving of the motor  30 CL transmitted by the gear  350   a  that engages with the rotation shaft  30 CLj of the motor  30 CL and rotates. On the other hand, the drive gear  35 CLc is engaged with the gear  350   b  engaged with the drive gear  35 CLb, and is rotated by the drive of the motor  30 CL transmitted via the drive gear  35 CLb and the gear  350   b.    
     In addition, the drive gear  35 Ka is engaged with the drive gear  35 Ke that rotates by being engaged with a drive shaft  30 Kj of the motor  30 K, and rotates by the drive of the motor  30 K transmitted via the drive gear  35 Ke. The drive gear  35 Kb is rotated by driving of the motor  30 K transmitted through the drive gear  35 Kd engaged with the drive shaft  30 Kj of the motor  30 K and the drive gear  35 Kc engaged with the drive gear  35 Kd. 
     Further, the drive gear  35 Sc rotates by driving of the motor  30 S transmitted via the drive gear  35 Sa engaged with the rotation shaft  30 Sj of the motor  30 S and the drive gear  35 Sb engaged with the drive gear  35 Sa. 
     The drive gear  35 Ga directly engages with the rotation shaft  30 Gaj of the motor  30 Ga, so that the drive of the motor  30 Ga is transmitted and the drive gear  35 Ga rotates. The drive gear  35 Gb directly engages with the rotation shaft  30 Gbj of the motor  30 Gb, so that the drive of the motor  30 Gb is transmitted and the drive gear  35 Gb rotates. The drive gear  35 Gc directly engages with the rotation shaft  30 Gcj of the motor  30 Gc, so that the drive of the motor  30 Gc is transmitted and the drive gear  35 Gc rotates. The drive gear  35 Gd directly engages with the rotation shaft  30 Gdj of the motor  30 Gd, so that the drive of the motor  30 Gd is transmitted and the drive gear  35 Gd rotates. 
     Then, the drive gears  35 CLa to  35 CLc transmit the driving force of the motor  30 CL to the yellow, magenta, and cyan photosensitive drums  112 Y,  112 M, and  112 C. More specifically, the drive gear  35 CLa transmits the driving force to the cyan photosensitive drum  112 C, the drive gear  35 CLb transmits the driving force to the magenta photosensitive drum  112 M, and the drive gear  35 CLc transmits the driving force to the yellow photosensitive drum  112 Y. The drive gears  35 Ka and  35 Ke transmit the driving force of the motor  30 K to the black photosensitive drum  112 K. The drive gears  35 Kb to  35 Kd transmit the driving force of the motor  30 K to the secondary transfer inner roller  216   a . Further, the drive gears  35 Sa to  35 Sc are provided to transmit the driving force of the motor  30 S to the primary transfer roller separating mechanism (not illustrated), and the drive gears  35 Ga to  35 Gd are provided to transmit the driving force of the four motors  30 Ga to  30 Gd to the yellow, magenta, cyan, and black developing units  114  (specifically, the developing sleeve  114   a ). Viscous grease is applied to gear tooth surfaces of these drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd in order to secure lubricity or quietness during rotation. 
     The drive gears  35 CLa to  35 CLc include couplings  36   a  to  36   d  that transmit driving to the yellow, magenta, and cyan photosensitive drums  112 Y to  112 C. The drive gear  35 Ka includes a coupling  36   d  that transmits driving to the black photosensitive drum  112 K, and the drive gear  35 Kb includes a coupling  36   e  that transmits driving to the secondary transfer inner roller  216   a . These couplings are respectively exposed from through holes  258   a  to  258   e  provided in a second support portion  25   a  of the sub support member  25 , and can transmit driving force to the respective units. On the other hand, the drive gears  35 CLa to  35 CLc and the drive gears  35 Ka to  35 Ke are disposed in a space surrounded by the main support member  20  and the sub support member  25  for portions having tooth surfaces for transmitting drive. The drive gears  35 Ga to  35 Gd are disposed in a space (that is, in a drive gear storage space formed by the main support member  20  and the sub support member  25 ) covered by the main support member  20  and the sub support member  25 , and are configured to transmit the driving force to the four developing units  114  by providing other gear to which the driving force is transmitted from the drive gears  35 Ga to  35 Gd and a coupling to which the driving force is transmitted from the other gear outside the sub support member  25 . These couplings protrude from through holes provided in the rear plate  10  of the support frame member  101 A to the inside of the support frame member  101 A, so that driving force can be transmitted to the units supported by the support frame member  101 A. 
     The main support member  20  and the sub support member  25  are arranged at both ends of the drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd in the rotation axis direction, and each rotatably supports the rotation shaft of the drive gear. The main support member  20  includes a first support portion  20   a  that supports one end portion of the rotation shaft of the drive gear, and the sub support member  25  includes the second support portion  25   a  that supports another end portion of the rotation shaft of the drive gear. Note that the first support portion  20   a  may be configured to support a portion on one end side of the portion where the teeth of the drive gear are formed, and the second support portion  25   a  may be configured to support a portion on the other end side of the portion where the teeth of the drive gear are formed. As described above, the drive gears  35 CLa to  35 CLc and  35 Ka of the photosensitive drums  112 Y,  112 M,  112 C, and  112 K of the four colors of yellow, magenta, cyan, and black are supported by the main support member  20  and the sub support member  25 . With this configuration, the interaxial distances of the photosensitive drums  112 Y,  112 M,  112 C, and  112 K of the respective colors are less likely to deviate. Therefore, it is possible to suppress the occurrence of color shift when the image formed on each photosensitive drum is superimposed on the intermediate transfer belt  116 . In the present embodiment, any one of the photosensitive drums  112 Y,  112 M,  112 C, and  112 K constitutes a first photosensitive drum, and any one of the remaining photosensitive drums constitutes a second photosensitive drum. In addition, the developing sleeve  114   a  corresponding to the first photosensitive drum constitutes a first developing sleeve, and the developing sleeve  114   a  corresponding to the second photosensitive drum constitutes a second developing sleeve. 
     In the present embodiment, the surfaces of the first support portion  20   a  and the second support portion  25   a  that support the drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd are the same plane, but one or both of the first support portion  20   a  and the second support portion  25   a  may have irregularities, steps, or the like. 
     The main support member  20  and the sub support member  25  are arranged and connected so as to sandwich the drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd. In the case of the present embodiment, the main support member  20  has a larger area than the sub support member  25 , and has higher rigidity than the sub support member  25 . Therefore, in the present embodiment, in order to connect the main support member  20  and the sub support member  25 , the sub support member  25  is fastened to the main support member  20  by the screw  40  (see  FIG.  5    to distinguish it from the screw  41  for fastening the main body) as a fastening member. The sub support member  25  is disposed upstream in the fastening direction (insertion direction, arrow X direction in  FIG.  4   ) in which the screw  40  is fastened to the main support member  20 . 
     In the main support member  20 , an out-of-plane fastening hole  560  and an in-plane fastening hole  570  for fastening the screw  40  are formed in the first support portion  20   a . On the other hand, the sub support member  25  is formed with out-of-plane mounting portions  260   a  to  260   d  and in-plane mounting portions  270   a  to  270   c  for inserting and attaching the screws  40 . The out-of-plane fastening hole  560  and the in-plane fastening hole  570  of the main support member  20 , the out-of-plane mounting portions  260   a  to  260   d  of the sub support member  25 , and the in-plane mounting portions  270   a  to  270   c  will be described later (see  FIGS.  5  and  6   ). 
     Metal Powder 
     Incidentally, when the above-described members such as the main support member  20  and the sub support member  25  are connected using screws, metal powder (foreign matter) generated by fastening of the screws may fall into the driving unit. In a conventional driving unit, falling metal powder adheres to drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd disposed in the driving unit, which causes image defects such as banding and abnormal noise from the drive gear. Here, the metal powder generated by the fastening of the screw will be described with reference to  FIGS.  7 A and  7 B .  FIG.  7 A  illustrates a state before the screw  40  is inserted into the fastening hole  579 , and  FIG.  7 B  illustrates a state after the screw  40  is inserted into the fastening hole  579 . 
     In general, when members are fixed and connected by the screw  40 , there are a case where the screw  40  is inserted into and fastened to the fastening hole  579  which is tapped in advance, and a case where the screw  40  itself is fastened while performing tapping. When the fastening hole  579  is tapped in advance, as illustrated in  FIG.  7 A , metal powder (for example, aluminum powder, iron powder, or the like) generated as scraping powder when tapping is performed may remain in the fastening hole  579 . In this case, as illustrated in  FIG.  7 B , when the screw  40  is inserted into the fastening hole  579  formed in the other member via the attachment hole  279  formed in the one member, the metal powder remaining in the fastening hole  579  is pushed out from the fastening hole  579  by the screw  40  and falls downward in the gravity direction. On the other hand, when the screw  40  itself connects members while performing tapping, a part of metal powder generated as scraping powder when the tapping is performed is pushed out from the fastening hole  579  penetrated by the screw  40  and falls downward in the gravity direction. As described above, in any of the above cases, metal powder (foreign matter) may be generated in the fastening hole  579  when the screw  40  is fastened, and the metal powder is moved by the screw  40  to the downstream in the fastening direction (entry direction) in which the screw  40  is fastened and finally pushed out from the fastening hole  579 . 
     Conventional Example 
     In the conventional driving unit, as described above, the metal powder pushed out from the fastening hole  579  as described above adheres to the drive gear, which causes image defects and abnormal noise.  FIGS.  8 A and  8 B  illustrate a conventional driving unit  90 A.  FIG.  8 A  is a view of the conventional driving unit  90 A as viewed from the sub support member  250  side, and  FIG.  8 B  is a cross-sectional view illustrating the conventional driving unit  90 A. 
     As illustrated in  FIG.  8 A , in the case of the conventional driving unit  90 A, a screw  40  for connecting the sub support member  250  to the main support member  210  is attached to the second support portion  251 . In order to do so, an attachment hole  271  for attaching the screw  40  to the second support portion  251  is formed in the sub support member  250 . 
     On the other hand, as shown in  FIG.  8 B , in the main support member  210 , a mounting portion  222  is extended from the first support portion  211  toward the upstream in the fastening direction (direction of arrow X) of the screw  40  so as to come into contact with the second support portion  251 . In the mounting portion  222 , a fastening hole  571  for fastening the screw  40  is formed at a position overlapping the attachment hole  271  at a contact portion which is in contact with on the second support portion  251 . 
     As can be understood from  FIG.  8 B , in the case of the conventional driving unit  90 A, the distal end (specifically, the distal end of the screw portion) of the screw  40  protrudes from the downstream in the fastening direction of the fastening hole  571 . This is because the downstream end in the fastening direction (fastening portion back side) of the fastening hole  571  is located at a position overlapping the drive gear (drive gear  35 Ka as an example) arranged between the first support portion  211  and the second support portion  251  when viewed from the gravity direction, in a state where the main support member  210  and the sub support member  250  are connected. 
     Therefore, when the metal powder is pushed out from the fastening hole  571  by being moved to the downstream in the fastening direction due to the fastening by the screw  40 , the metal powder falls onto the drive gear  35 Ka and adheres to the gear tooth surface of the drive gear  35 Ka. Then, when the drive gear  35 Ka rotates and meshes, the metal powder is caught therein. Then, rotational fluctuation occurs in the drive gear  35 Ka due to the metal powder, whereby rotational fluctuation also occurs in the black photosensitive drum  112 K (see  FIG.  2   ) driven via the drive gear  35 Ka, and the like, and image defects and abnormal noise as described above occur. 
     Therefore, it is conceivable to change the fastening position between the main support member  210  and the sub support member  250  so that the metal powder pushed out from the fastening hole  571  due to fastening of the screw  40  does not adhere to the drive gear.  FIGS.  9 A and  9 B  illustrate a driving unit  90 B of a comparative example. In the driving unit  90 B illustrated in  FIGS.  9 A and  9 B , only the fastening direction (insertion direction) of the screw  40  is different, and the others are the same.  FIG.  9 A  illustrates a case where the screw  40  is fastened from the sub support member  250  side toward the main support member  210  side (fastening direction is an arrow X direction), and  FIG.  9 B  illustrates a case where the screw  40  is fastened from the main support member  210  side toward the sub support member  250  side (fastening direction is an arrow Y direction). 
     In the comparative example shown in  FIGS.  9 A and  9 B , the main support member  210  and the sub support member  250  are connected by the screw  40  in such a manner that the sub support member  250  covers the main support member  210 . In order to do so, the main support member  210  is formed with a fastening portion  500  bent outward at a position (outside the outer periphery of the first support portion  211 ) deviated from a projection plane of the second support portion  251  obtained by projecting the first support portion  211  in the rotation axis direction of the drive gear (not illustrated). In this case, even if the metal powder is pushed out from the fastening hole  571  due to the fastening by the screw  40 , the metal powder does not enter the inside of the driving unit  90 B and thus does not adhere to the drive gear. 
     However, in the case of the comparative example, since the fastening portion  500  is formed on the outer periphery of the main support member  210  in addition to the fixing portion  55  (see  FIG.  2   ) for fixing the driving unit  90 B to the rear plate  10 , the size of the driving unit  90 B increases. In order to avoid the screw  40  fastened to the fastening portion  500 , it is necessary to form a retraction hole  255  for avoiding the screw  40  in the rear plate  10  in addition to a fastening hole for fastening the screw  41  attached via the fixing portion  55 . That is, it is necessary to secure a space for forming the retraction hole  255  for avoiding the screw  40  in the rear plate  10  and to secure strength, so that the size of the driving unit  90 B increases and the cost increases. 
     When a support member having the fastening hole is formed of a thin sheet metal, the fastening hole  571  is generally formed in a burring shape as illustrated in  FIG.  7 A . In this case, a sufficient distance must be taken from the fastening hole  571  to the bending position of the fastening portion  500  of the main support member  210 . This is because, if the fastening hole  571  formed in the burring shape is close to the bending position, when the fastening portion  500  is formed to be bent, the fastening portion is pulled by bending, and the accuracy of the position is lowered. When it is desired to provide the fastening hole near the bending position, it is necessary to provide a hole called bending relief at the bending root. Therefore, if the fastening hole  571  is provided sufficiently away from the bending position, the size of the driving unit  90 B increases, and if the fastening hole is provided close to the bending position, a hole is formed in the bending root, and metal powder generated due to fastening by the screw  40  can enter the driving unit  90 B from the hole. 
     In order to prevent the metal powder from entering the inside of the driving unit  90 B through the hole formed in the bending root, it is conceivable to fasten the screw  40  from the main support member  210  side toward the sub support member  250  side as illustrated in  FIG.  9 B . However, as in the case of  FIG.  9 A , in order to avoid the screw  40  fastened to the fastening portion  500 , it is necessary to form the retraction hole  255  for avoiding the screw  40  in the rear plate  10 , so that the size of the driving unit  90 B increases and the cost may increase. Further, when an operator detaches the driving unit  90 B, there is a possibility that the screw  40  connecting the main support member  210  and the sub support member  250  is erroneously detached instead of the screw  41  (see  FIG.  3   ) attaching the driving unit  90 B to the rear plate  10  via the fixing portion  55 . That is, it is difficult for the operator to know which screw should be removed in order to remove the driving unit  90 B from the rear plate  10 , and workability at the time of maintenance is deteriorated. 
     Fastening Configuration in Present Embodiment 
     Next, a fastening configuration of the main support member  20  and the sub support member  25  by the screw  40  in the present embodiment in consideration of the problems of the conventional example and the comparative example described above will be described with reference to  FIGS.  4  to  6   . 
     As illustrated in  FIG.  5   , an in-plane fastening hole  570  for fastening the screw  40  is formed in the first support portion  20   a  of the main support member  20 , and in-plane mounting portions  270   a  to  270   c  for inserting and attaching the screw  40  are formed in the sub support member  25 . The in-plane fastening hole  570  of the main support member  20  is formed in a projection plane obtained by projecting the second support portion  25   a  of the sub support member  25  in the rotation axis direction of the drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd (see  FIG.  4   ) in the first support portion  20   a . The projection plane of the second support portion  25   a  is a projection plane obtained by projecting an outer periphery represented by connecting outermost edges of a surface of the second support portion  25   a  supporting the drive gears  35 CLa to  35 CLc,  35 Ka to  35 Ke,  35 Sa to  35 Sc, and  35 Ga to  35 Gd, and is a region indicated by a broken line in  FIGS.  4  and  5   . 
     On the other hand, as shown in  FIG.  6   , the in-plane mounting portion (here, representatively an in-plane mounting portion  270   b ) of sub support member  25  extends from second support portion  25   a  toward the downstream (first support portion  20   a  side) in the fastening direction of screw  40  so as to be in contact with the first support portion  20   a  in the projection plane. In the in-plane mounting portion  270   b , an in-plane attachment hole  27  for inserting and attaching the screw  40  is formed at a position overlapping the in-plane fastening hole  570  of the main support member  20  at the contact portion  220  which is in contact with the first support portion  20   a . As shown in  FIG.  4   , such in-plane mounting portions  270   a  to  270   c  are flange portions formed by cutting a part of the second support portion  25   a  and bending the second support portion toward the main support member  20  side (first support member side). 
     As shown in  FIG.  6   , the main support member  20  is fixed to the rear plate  10  (support frame) of the support frame body  101 A (see  FIG.  1   ) in a state where the sub support member  25  faces the rear plate  10 . In a state where the main support member  20  and the sub support member  25  are connected, the distal end (specifically, the distal end of the screw portion) of the screw  40  protrudes from the downstream in the fastening direction of the in-plane fastening hole  570 . However, in the case of the present embodiment, in a state where the main support member  20  and the sub support member  25  are connected, the downstream end in the fastening direction (fastening portion back side) of the in-plane fastening hole  570  is at a position not overlapping the space  37  sandwiched between the first support portion  20   a  and the second support portion  25   a  when viewed from the gravity direction. That is, the downstream end of the in-plane fastening hole is positioned outside the driving unit  90  so as not to overlap with each drive gear (for example, the drive gear  35 CLb) arranged between the first support portion  20   a  and the second support portion  25   a . Therefore, as described above, even if the metal powder is moved to the downstream in the fastening direction due to the fastening by the screw  40  and pushed out from the in-plane fastening hole  570 , the metal powder does not fall on the drive gear  35 CLb. Therefore, since the metal powder generated by the fastening by the screw  40  cannot adhere to the drive gear  35 CLb, the image defect and the abnormal noise as described above do not occur. Further, in the case of the present embodiment, since it is not necessary to newly secure a space for bringing the main support member  20  in contact with the in-plane mounting portions  270   a  to  270   c  of the sub support member  25  in the gravity direction and fixing the main support member, the present embodiment can be realized without increasing the size of the driving unit  90 . 
     In the case of the present embodiment, as illustrated in  FIGS.  4  and  5   , the main support member  20  is formed with the out-of-plane fastening hole  560  for fastening the screw  40  outside the projection plane of the first support portion  20   a . On the other hand, in the sub support member  25 , the out-of-plane mounting portions  260   a  to  260   d  are extended from second support portion  25   a  toward the downstream (first support portion  20   a  side) in the fastening direction of screw  40  so as to be in contact with first support portion  20   a  outside the projection plane. The out-of-plane mounting portions  260   a  to  260   d  are formed with an out-of-plane attachment hole  261  for inserting and attaching the screw  40 . That is, in the present embodiment, in order to more firmly fix the sub support member  25  to the main support member  20 , the sub support member can also be fixed by the out-of-plane mounting portions  260   a  to  260   d  provided at positions different from the in-plane mounting portions  270   a  to  270   c . The out-of-plane mounting portions  260   a  to  260   d  and the in-plane mounting portions  270   a  to  270   c  are disposed inside the outer periphery of the first support portion  20   a  of the main support member  20  so as to be in contact with the first support portion  20   a.    
     In the present embodiment, relative positioning between the main support member  20  and the sub support member  25  is performed by the in-plane mounting portions  270  provided at three positions, so that positional deviation generated at the time of fastening the screw  40  is suppressed. In the present embodiment, as an example, as illustrated in  FIGS.  4  and  5   , positioning in the left-right direction is performed at one position, and positioning in the up-down direction is performed at two positions. Note that the present invention is not limited thereto, and the in-plane mounting portions  270  may be formed at a total of two positions, that is, one position for positioning up, down, left, and right and one position for rotation stop. Further, if the sub support member  25  can be firmly fixed to the main support member  20 , an in-plane mounting portion  270  may be further provided instead of the out-of-plane mounting portions  260   a  to  260   d . In such a case, since it is not necessary to newly secure a space for fixing the sub support member  25  in the width direction intersecting the gravity direction in the main support member  20 , the driving unit  90  can be further downsized. 
     As shown in  FIG.  6   , since the back side of the fastening portion of the fixing portion  55  for fixing to the rear plate  10  is located on the opposite side of the driving unit  90  in the rear plate  10 , metal powder generated due to fastening by the screw  41  does not adhere to the drive gear. 
     As described above, in the present embodiment, the in-plane mounting portions  270   a  to  270   c  extending from the sub support member  25  are brought into contact with the main support member  20 , and are fastened by the screws  40  from the sub support member  25  side toward the main support member  20  side. In this case, as described above, since the downstream end in the fastening direction (fastening portion back side) of the in-plane fastening hole  570  is located outside the driving unit  90 , metal powder generated due to fastening by the screw  40  cannot adhere to the drive gear, and image defects and abnormal noise as described above do not occur. 
     Other Embodiments 
     In the embodiment described above, the intermediate transfer image forming apparatus  101  in which a toner image is primarily transferred from the photosensitive drums  112 Y to  112 K of the respective colors to the intermediate transfer belt  116 , and then the toner image is secondarily transferred from the intermediate transfer belt  116  to the recording material S has been described as an example, but the present invention is not limited thereto. The above-described embodiment can also be applied to a direct transfer type image forming apparatus that directly transfers a toner image from the photosensitive drums  112 Y to  112 K of the respective colors that carry the toner image and rotate to the recording material S. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-073856, filed Apr. 26, 2021 and Japanese Patent Application No. 2022-036137, filed Mar. 9, 2022, which are hereby incorporated by reference herein in their entirety.