Patent Application
20080240781
This patent specification is based on and claims priority from Japanese Patent Application No. 2007-084767, filed on Mar. 28, 2007 in the Japan Patent Office, the entire contents of which are hereby incorporated by reference herein.
1. Field of the Invention
The present invention relates to an image forming apparatus including a fixing unit, and a fixing unit support method and a fixing unit position adjustment method for the image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus, an image is formed on a recording medium such as a sheet of paper or an OHP (overhead projector) film by charging a drum-like or belt-like rotating photosensitive element; irradiating the photosensitive element with light to form a latent electrostatic image thereon; attaching toner to the latent electrostatic image with a development device to make the latent electrostatic image visible as a toner image; transferring the toner image to the recording medium directly or indirectly via a belt-like intermediate transfer unit; and fixing the toner image on the recording medium.
Such an image forming apparatus includes a frame for reinforcing a body of the image forming apparatus against distortion or twisting. The frame is generally made of steel plate and includes a base member, a pair of opposing side plates set up on the base member, and stays or brackets laid between the side plates. In the frame, detachably attachable components such as a photosensitive device, a charging device, an optical writing device, a development device, a transfer device, a fixing device, an intermediate transfer device, and a recording medium feed device are usually provided in the form of a modular unit or a process cartridge including such units.
The fixing device, which is typically unitized for ease of maintenance, generally fixes an image on a recording medium when the recording medium passes through a fixing nip formed by a fixing member and a pressure member. The fixing nip is set parallel to the transfer rollers, etc., in recording medium feeders and transferring devices that transfer a recording medium to each transfer point and fixing point. When and if the fixing nip is angled with the transfer roller, etc., the transfer directions of a recording medium at the fixing nip and the transfer roller, etc., do not match, resulting in skewing of the recording medium and production of abnormal images transformed in a trapezoidal manner, etc.
As a method of preventing such skewing, pursuing component parts tolerances to perfection is practically difficult in light of cost increase as well as from a technical point of view. Furthermore, since there are a number of parts in an image forming apparatus, the tolerances of individual parts such as a fixing unit and a recording medium feeder are cumulative and directly affect the relative positions of these devices, easily displacing them from their parallel positions. In addition, there are part or unit assembly errors to be considered which are difficult to eliminate completely.
In addition, an assembly jig is required for assembling an image forming apparatus, and naturally, highly accurate design and manufacturing are demanded therefor. However, even with such a highly accurate jig, there is a limit to improvement in the accuracy with which devices are positioned parallel to each other.
Although the situation is as described above, to meet current demand for high definition quality images it is desired that an image forming apparatus has recording medium transfer devices, including a fixing unit; that are positioned parallel to each other with a high degree of precision.
This patent specification describes a novel image forming apparatus that includes a frame having a first side plate and a second side plate opposing the first side plate; a first unit holding member engaged with the first side plate by a combination of a guide groove and a guide protrusion; a second unit holding member attached to the second side plate; a detachable unit located between the first side plate and the second side plate and held by the first unit holding member and the second unit holding member; and a position adjustment member to move the first unit holding member in a longitudinal direction of the guide groove to adjust a position of the detachable unit, the position adjustment member engaging the first unit holding member at a position vertically aligned with a center of gravity G of the detachable unit.
This patent specification further describes a novel fixing unit support method for supporting a fixing unit in an image forming apparatus, including engaging a unit holding member to hold a fixing unit with a frame of a main unit of the image forming apparatus by a combination of a guide groove and a guide protrusion, and providing a position adjustment member having an eccentric cam including a rotary center shaft portion rotatably engaging the frame and an eccentric rotary shaft portion eccentrically positioned relative to the rotary center shaft portion and rotatably engaging the unit holding member at a position vertically aligned with a center of gravity G of the fixing unit.
This patent specification further describes a novel fixing unit position adjustment method for an image forming apparatus, the image forming apparatus including a frame; a unit holding member engaged with the frame by a combination of a guide groove and a guide protrusion to hold a fixing unit; and a position adjustment member having an eccentric cam including a rotary center shaft portion rotatably engaging the frame and an eccentric rotary shaft portion eccentrically positioned relative to the rotary center shaft portion and rotatably engaging the unit holding member at a position vertically aligned with a center of gravity G of the fixing unit, the fixing unit position adjustment method for the image forming apparatus including rotating the position adjustment member and moving the unit holding member in the longitudinal direction of the guide groove to adjust a position of the fixing unit.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
Referring now to the drawings, wherein like reference numerals and reference characters designate identical or corresponding parts throughout the several views thereof, particularly to
A main unit 1 of the color copier, which is the main unit of the image forming apparatus, includes a face cover and a frame 40 covered therewith. The frame 40 serves as the frame of the main unit 1. In the main unit 1, an image forming unit 2 that forms and transfers an image to a recording medium is located in the central part of the main unit 1 and a recording medium storage unit 3 that stores and sequentially feeds recording media to the image forming unit 2 is located below the image forming unit 2. The main unit 1 also includes an internal discharge unit 4 that outputs a recorded recording medium, an image reading unit 5 that reads the image of an original, an operating unit 6 situated in front (indicated by arrow A) of the image reading unit 5, and a duplex unit 7 that reverses the side of a recording medium and returns the recording medium to the image forming unit 2 for duplex printing.
The operating unit 6 includes an input unit (including various keys such as a start key, a numeric keypad, a function setting key, a reset key, a clear/stop key) to control a plurality of functions of the main unit 1 and a display unit (such as a liquid crystal display panel or a liquid crystal touch panel also functioning as an input unit) that displays various pieces of input information and an apparatus status.
In
The color copier also includes a manual feed table 8, a side cover 9, and a front cover 10, all of which can be opened with respect to the main unit 1.
The image forming unit 2 includes four image forming stations in a tandem arrangement along an intermediate transfer unit 17 including an endless intermediate transfer belt 17a. The four image forming stations form yellow (Y), cyan (C), magenta (M), and black (B) images, respectively. Below the four image forming stations, an optical writing device 13 is located.
The four image forming stations have the same configuration and include photosensitive drums 11Y, 11C, 11M, and 11B serving as image bearing members, around which are located charging devices 12Y, 12C, 12M, and 12B, development devices 14Y, 14C, 14M, and 14B, primary transfer rollers 15Y, 15C, 15M, and 15B, and cleaning devices 16Y, 16C, 16M, and 16B, respectively.
The optical writing device 13 faces the four image forming stations and is formed of four light sources using respective laser diodes (LD) corresponding to the four colors; an optical system that collimates a laser beam emitted from the light sources; a polygon scanner (deflector) that includes a polygon mirror (rotating multifaceted mirror) and a polygon motor; and another optical system including scanning and imaging lenses such as an fθ lens provided on each light path for the light sources, correcting lenses, and mirrors. The laser diodes emit beams of light according to image information of each color and the polygon scanner deflects the beams of light and scans the surfaces of the four photosensitive drums 11Y, 11C, 11M, and 11B with the beams of light to write a latent electrostatic image thereon.
In the image forming unit 2, toner bottles 32Y, 32C, 32M, and 32B are located below the internal discharge unit 4 from left to right in
The intermediate transfer belt 17a in the intermediate transfer unit 17 is supported by a drive roller, a driven roller, etc., and rotates in a direction indicated by an arrow shown in
The recording medium storage unit 3, which is situated at the bottom of the main unit 1, includes two paper feed cassettes 3a and 3b storing a recording medium S. The recording medium S is fed from one of the paper feed cassettes 3a and 3b by a paper feed device 19a or 19b and conveyed by a recording medium feeder. Specifically, the recording medium S is fed by conveyance rollers 20a and 20b to a registration roller 21 and the registration roller 21 feeds the recording medium S at an appropriate timing to a secondary transfer nip formed between the secondary transfer roller 22 and the intermediate transfer belt 17a.
According to a first embodiment of the present invention, a fixing unit 35 is located above the secondary transfer roller 22. In the fixing unit 35, a fixing roller 36 and a heat roller 37 support a fixing belt 38 serving as a fixing member. In addition, a pressure roller 39 serving as a pressure member is provided to form a fixing nip with the fixing belt 38.
Above the fixing unit 35, a conveyance roller 23 and a discharge roller 24 that convey and discharge the recording medium S to the internal discharge unit 4, and a switching member 25 that switches the conveyance path for duplex printing are located. Above the conveyance roller 23, the discharge roller 24, and the switching member 25, a reverse roller 26 and a reverse path 27 are located to reverse the conveyance direction of the recording medium S like a switchback. In the case of duplex printing, the recording medium S is temporarily stacked in the reverse path 27 and the conveyance direction thereof is reversed by the reverse roller 26. The recording medium S is then conveyed by conveyance rollers 28 and 29 through a conveyance path for duplex printing and fed to the registration roller 21 again.
The image reading unit 5 is located in the upper part of the main unit 1 and includes a contact glass 5a serving as an original table on which an original is placed, an illumination source 5b that illuminates the original, a first mirror 5c that reflects light reflected from the original, a second mirror 5d, a third mirror 5e, an imaging lens 5f that images the light reflected from the original, and an image sensor 5g such as a CCD (charge-coupled device) that is located at an image location and serves as a reading unit for reading the image of the original.
On the image reading unit 5, there is provided a cover 33 that presses the original placed on the contact glass 5a against the contact glass 5a to keep it in place or an automatic document feeder (ADF) that automatically feeds the original to the contact glass 5a.
A description is now given of a copying process executed by the color copier.
The copying process is started by opening the cover 33 (with respect to the main unit 1) and placing an original on the contact glass 5a in the image reading unit 5. When the ADF is used instead of the cover 33, the original is placed on the original table of the ADF.
By pressing the start switch of the operating unit 6, the image reading unit 5 is instantly driven when the original is placed on the contact glass 5a. When the original is placed on the original table of the ADF, the original reading unit 5 is driven after the original is transferred onto the contact glass 5a. Then, a first traveling body including the light source 5b and the first mirror 5c and a second traveling body including the second mirror 5d and the third mirror 5e begin to travel. The light emitted from the light source 5b is directed to the surface of the original. The first mirror 5c in the first traveling body reflects and directs the light reflected from the original to the second traveling body. The second and third mirrors 5d and 5e in the second traveling body reflect and direct the light through the imaging lens 5f to the image sensor 5g such as a CCD serving as a reading unit, where the image of the original is read. Then, an image forming operation starts in the full color mode or the monochrome mode. The mode is determined depending on the selection including automatic mode at the operating unit 6.
In the image forming unit 2, the charging devices 12Y, 12C, 12M, and 12B uniformly charge the photosensitive drums 11Y, 11C, 11M, and 11B, which are then irradiated with laser beams emitted from the optical writing device 13 including four laser light sources, the deflector, and the four scanning optical systems to form latent electrostatic images thereon.
The latent electrostatic images are developed by attaching toner of different colors thereto by the four development devices 14Y, 14C, 14M, and 14B so that yellow, cyan, magenta, and black toner images are formed on the photosensitive drums 11Y, 11C, 11M, and 11B.
Subsequently, a primary transfer voltage is applied to the primary transfer rollers 15Y, 15C, 15M, and 15B at different timings, thereby transferring the toner images sequentially to the intermediate transfer belt 17a starting from the upstream side and superimposing the toner images one atop another thereon (a process that is herein referred to as primary transfer).
The recording medium S is supplied to the main unit 1 in synchronization with the primary transfer from the recording medium feeder 3a or 3b in the recording medium storage unit 3 by the recording medium feed device 19a and 19b or the manual feed table 8 by a recording medium feed roller 30 and a conveyance roller 31. When the leading edge of the recording medium S reaches the registration roller 21, the recording medium S is held there and detected by a sensor, not shown. Then, the registration roller 21 timely feeds the recording medium S to the secondary transfer nip formed between the secondary transfer roller 22 and the intermediate transfer belt 17a based on a detection signal generated by the sensor.
The images formed on the intermediate transfer belt 17a are conveyed to the secondary transfer nip and transferred to the recording medium S all at one time. The recording medium S is then conveyed to the fixing unit 35 and passes through the fixing nip, where the transferred image is fixed onto the recording medium S by application of heat and pressure. Thereafter, the recording medium S is conveyed by the conveyance roller 23 and discharged by the discharge roller 24 to the internal discharge unit 4. Thus, a color image is formed on the recording medium S.
When the duplex mode is selected at the operating unit 6, the conveyance path of the recording medium S is switched by the switching member 25. The recording medium S of which the image is already fixed on one side is temporarily stacked in the reverse path 27 and the conveyance direction thereof is reversed by the reverse roller 26 like a switchback. The recording medium S is then conveyed by the conveyance rollers 28 and 29 through the conveyance path for duplex printing to the registration roller 21 again in synchronization with the image forming operation.
The registration roller 21 feeds the recording medium S to the secondary transfer nip, where the image formed on the intermediate transfer belt 17a is transferred to the back side of the recording medium S. Then, the recording medium S is conveyed to the fixing unit 35 and the transferred image on the back side thereof is fixed onto the recording medium S by application of heat and pressure. The recording medium S is conveyed by the conveyance roller 23 and discharged by the discharge roller 24 to the internal discharge unit 4. Thus, color images are formed on both sides of the recording medium S.
Toner remaining on the photosensitive drums 11Y, 11C, 11M, and 11B is removed by the cleaning devices 16Y, 16C, 16M, and 16B, respectively. Then, the photosensitive drums 11Y, 11C, 11M, and 11B are simultaneously discharged and charged by the charging devices 12Y, 12C, 12M, and 12B to which a direct-current bias overlapped with an alternating-current component is applied to prepare for the next image formation. Toner remaining on the intermediate transfer belt 17a is also removed by the intermediate transfer belt cleaning device 18 to prepare for the next image formation.
The frame 40 is made of steel plate and includes a base member 41, opposing first and second side plates 42 and 43 set up on the base member 41, and stays or brackets 44 laid between the first and second side plates 42 and 43. The first side plate 42 is the front side plate provided on the operator side (indicated by arrow A) of the main unit 1. The second side plate 43 is the rear side plate provided opposite to the first side plate 42, from where a driving force is transmitted to, for example, the fixing unit 35.
In the frame 40, there are detachably attached the photosensitive drums 11Y, 11C, 11M, and 11B, the charging devices 12Y, 12M, 12C, and 12B, the optical writing device 13, the development devices 14Y, 14C, 14M, and 14B, the primary transfer rollers 15Y, 15C, 15M, and 15B, the cleaning devices 16Y, 16C, 16M, and 16B, the secondary transfer roller 22, the fixing unit 35, the intermediate transfer unit 17, and the recording medium feed device in the form of a modular unit or a process cartridge including the units.
The fixing unit 35 is positioned and held by a front holding member 45 attached to the first side plate 42 and a rear holding member 46 attached to the second side plate 43, and supported between the first and second side plates 42 and 43. In
As illustrated in
An eccentric cam 52 serving as a position adjustment member is inserted into the elongated hole 50 via an eccentric shaft portion 53. As illustrated in
As illustrated in
The eccentric shaft portion 53 is fitted into the elongated hole 50. The front holding member 45 is attached to the first side plate 42 by inserting two upper and lower guide protrusions 61 provided on the first side plate 42 into the respective guide grooves 51. The front holding member 45 is attached to the first side plate 42 by screwing attaching screws 63 into screw holes in the first side plate 42 through four screw elongated holes in the front holding member 45.
The two guide protrusions 61 in this example embodiment are integrally formed with the first side plate 42 by a drawing process such as burring or embossing. The guide protrusions 61 are on a vertical line L that is parallel to a vertical direction of passing the recording medium S through the fixing nip. Therefore, the two guide grooves 51 of the front holding member 45 extend in the direction of the vertical line L. The main reference engagement slot 47, the sub-reference engagement slot 48, and the elongated hole 50 extend in the direction perpendicular to the vertical line L. The four screw elongated holes in the front holding member 45 extend vertically. The vertical line L and the line connecting the center of the center shaft portion 56 and the center of the eccentric shaft portion 53 are at right angles to each other.
Therefore, when the eccentric cam 52 with the handle 55 is rotated, the front holding member 45 is moved in the direction guided by the two upper and lower guide protrusions 61, that is, the direction parallel to the (vertical) direction of the recording medium S passing through the fixing nip. The guide groove 51 has a width substantially equal to the diameter of the guide protrusion 61 so that the guide protrusion 61 engages the guide groove 51 snugly, with substantially no allowance in the width direction of the guide groove 51. Such an arrangement is preferable because it prevents rattling in the direction perpendicular to the vertical line L.
It should be noted that the guide groove 51 (or a elongated hole) and the guide protrusion 61 constitute a combination pair and can be formed on the front holding member 45 and the first side plate 42, respectively, as in the embodiment described above, or vice versa.
In
As illustrated in
As illustrated in
A description is now given of insertion of the fixing unit 35 in the main unit 1 of the image forming apparatus.
The fixing unit 35 is inserted between the front and rear holding members 45 and 46 from the right side of the main unit 1 by opening the side cover 9 illustrated in
Subsequently, the sub-reference protrusions 71 contact curved surfaces 73a (illustrated in
To detach the fixing unit 35 from the main unit 1, the stopper levers 73 are manually rotated upward to release the sub-reference protrusions 71. Then, using the handles 72, the fixing unit 35 is pulled out by guiding the main reference protrusions 70 along the main reference engagement slots 47 and 65 and guiding the sub-reference protrusions 71 along the sub-reference engagement slots 48 and 66.
A description is now given of adjusting a skew or slant of the fixing unit 35.
As illustrated in
A slant of the fixing unit 35 is adjusted by rotating the eccentric cam 52 about the center shaft portion 56 with the handle 55 and referring to the scale 60 with the fixing screw 59 and the attaching screws 63 loosened. The eccentric shaft portion 53 moves upward or downward in the direction of the vertical line L by a distance y1 or y2 as illustrated in
When the aforementioned check indicates that the fixing unit 35 and the registration roller 21 are not parallel and therefore that their relative positions need to be adjusted, the attaching screws 63 and the fixing screw 59 are again loosened and the eccentric cam 52 is rotated to move the front holding member 45. Then, the fixing screw 59 and then the attaching screws 63 are once again tightened. Images are then formed again to check the accuracy with which the fixing unit 35 and the registration roller 21 are positioned parallel to each other. This process is repeated until the fixing unit 35 and the registration roller 21 are correctly positioned parallel to each other. It should be noted that the front holding member 45 moves smoothly in the direction of the vertical line L by moving the eccentric shaft portion 53 in the direction of the vertical line L.
This fixing unit 35 includes a unit body 75 and an induction heating device 76. In the unit body 75, a fixing roller 77 serving as a fixing member and a pressure roller 78 serving as a pressure member form a fixing nip. The image on the recording medium S is fixed while the recording medium S passes through the fixing nip. On the circumferential surface of the fixing roller 77, an induction heating layer is provided. Although the fixing roller 77 is used as a fixing member in the present example, a fixing belt 38 as illustrated in
The center of gravity G of the fixing unit 35 of an electromagnetic induction heating type is also located between the two upper and lower protrusions 61 provided on the first side plate 42 of the frame 40. The guide grooves 51 and the guide protrusions 61 are located on the vertical line L passing through the center of gravity G of the fixing unit 35.
On each of the front and rear surfaces of the unit body 75 of the fixing unit 35, the main reference protrusions 70 and the axial sub-reference protrusions 71 that protrude forward on the front surface and backward on the rear surface, separated by a certain distance. On the top surface of the fixing unit 35, handles 72 are formed upward. By holding the handles 72, the fixing unit 35 is inserted between the front and rear holding members 45 and 46 as described above. Thus, the fixing unit 35 is installed in the main unit 1, supported by the first and second side plates 42 and 43 of the frame 40.
In the fixing unit 35, the unit body 75 and the induction heating device 76 are connected to each other using a connection member 80.
The connection member 80 includes a bent plate 79, a positioning pin 81 protruding from the bent plate 79, and a screw hole 82, and is fixed to the unit body 75 by inserting an attaching screw 83 into the screw hole 82. The leading end of the positioning pin 81 is inserted to a positioning hole 85 (illustrated in
The induction heating device 76 includes an induction coil 93 (refer to
An air intake port 86 is provided on the front of the housing 84 and the positioning hole 85 is located above the air intake port 86. A positioning pin 87 is provided on the rear of the housing 84 at the position corresponding to the positioning hole 85. The positioning pin 87 is inserted into a positioning hole in the rear holding member 46. Thus, the induction heating device 76 is supported pivotably about the positioning pin 81 and the positioning pin 87.
Similar to the front holding member 45 illustrated in
Unlike the front holding member 45 illustrated in
As illustrated in
When the induction heating device 76 is in operation, the cooling fan 90 is driven to feed air to a space between the front holding member 45 and the first side plate 42 through the intake hole 88 in the front holding member 45. The air flows from an intake opening 97 in the first side plate 42 to the air path 94 through the front air intake port 86 in the housing 84 of the induction heating device 76 and cools the induction coil 93. The air heated by the induction coil 93 is discharged from the air path 94 to the exhaust duct 96 by way of a rear air discharge 98 in the housing 84, an exhaust opening 99 in the second side plate 43 and an exhaust hole 100 in the rear holding member 46. Thus, the induction coil 93 of the induction heating device 76 can maintain the thermal efficiency of the fixing roller 77.
It should be noted that although the cooling fan 90 in the example embodiment described above is an intake fan that draws in air to the air path 94 in the induction heating device 76, alternatively, an exhaust fan that exhausts air from the air path 94 can be used, or both an intake fan and an exhaust fan can be used. In addition, although an axial fan is used in the example embodiment, alternatively a sirocco fan as illustrated in
As can be understood by those skilled in the art, numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
Example embodiments being thus described, it will be apparent that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-084767 | Mar 2007 | JP | national |
