Patent Application
20130064579
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2011-197894 filed Sep. 12, 2011.
The present invention relates to image forming apparatuses.
According to an aspect of the invention, there is provided an image forming apparatus including an endless-belt-like image bearing member, an endless-belt-like transport member, a transfer member, a first detection member, a first deviation correcting member, a first correction control section, a second detection member, a second deviation correcting member, and a second correction control section. The endless-belt-like image bearing member rotates while bearing a visible image on a surface thereof. The endless-belt-like transport member is disposed in a transfer region where the visible image on the surface of the image bearing member is transferred onto a medium. Moreover, the endless-belt-like transport member transports the medium while supporting the medium on a surface of the transport member. The transfer member rotatably supports the endless-belt-like transport member and is disposed in the transfer region so as to face the image bearing member with the endless-belt-like transport member interposed therebetween. Transfer voltage used for transferring the visible image on the surface of the image bearing member onto the medium is applied between the transfer member and the image bearing member. The first detection member detects deviation of the endless-belt-like image bearing member in a width direction thereof. The first deviation correcting member extends in the width direction of the endless-belt-like image bearing member and is supported in a tiltable manner relative to the width direction. Moreover, the first deviation correcting member supports the endless-belt-like image bearing member. The first correction control section tilts the first deviation correcting member in a direction for correcting deviation of the image bearing member, if the first detection member detects that the image bearing member is deviated, so as to correct the deviation. The second detection member detects deviation of the endless-belt-like transport member in a width direction thereof. The second deviation correcting member extends in the width direction of the endless-belt-like transport member and is supported in a tiltable manner relative to the width direction. Moreover, the second deviation correcting member supports the endless-belt-like transport member. The second correction control section tilts the second deviation correcting member in a direction for correcting deviation of the transport member, if the second detection member detects that the transport member is deviated, so as to correct the deviation. An amount by which the image bearing member is moved per unit time in the width direction when the first deviation correcting member is tilted is set to be larger than an amount by which the transport member is moved per unit time in the width direction when the second deviation correcting member is tilted.
Exemplary embodiment(s) of the present invention will be described in detail based on the following figures, wherein:
Although exemplary embodiments of the present invention will be described in detail below with reference to the drawings, the present invention is not to be limited to the following exemplary embodiments.
In order to provide an easier understanding of the following description, the front-rear direction will be defined as “X-axis direction” in the drawings, the left-right direction will be defined as “Y-axis direction”, and the up-down direction will be defined as “Z-axis direction”. Moreover, the directions or the sides indicated by arrows X, −X, Y, −Y, Z, and −Z are defined as forward, rearward, rightward, leftward, upward, and downward directions, respectively, or as front, rear, right, left, upper, and lower sides, respectively.
Furthermore, in each of the drawings, a circle with a dot in the center indicates an arrow extending from the far side toward the near side of the plane of the drawing, and a circle with an “x” therein indicates an arrow extending from the near side toward the far side of the plane of the drawing.
In the drawings used for explaining the following description, components other than those for providing an easier understanding of the description are omitted where appropriate.
Referring to
The operating section UI includes a power button, a copy start key, a number-of-copies setting key, and a numerical keypad that serve as an example of an input section, and a display.
The scanner U1 reads a document (not shown) and converts it into image information, and then inputs the image information to the image forming apparatus body U3.
The feeding device U2 includes multiple feed trays TR1 to TR4 as an example of feeders, and a feed path SH1 along which recording paper S serving as an example of a medium accommodated in each of the feed trays TR1 to TR4 is transported toward the image forming apparatus body U3.
Referring to
The controller C processes the received image information to printing information for yellow (Y), magenta (M), cyan (C), and black (K) colors and outputs the information to a laser driving circuit D serving as an example of a driving circuit for a latent-image writing unit. The laser driving circuit D outputs laser driving signals input from the controller C to latent-image forming units ROSy, ROSm, ROSc, and ROSk for the respective colors at a predetermined timing.
Image bearing units Uy, Um, Uc, and Uk for the Y, M, C, and K colors are disposed below the latent-image forming units ROSy, ROSm, ROSc, and ROSk, respectively.
Referring to
In the first exemplary embodiment, the photoconductor drum Pk for the K color, which is frequently used and thus often experiences surface abrasion, is given a larger diameter than the photoconductor drums Py, Pm, and Pc for the remaining colors so as to allow for high-speed rotation and a longer lifespan.
The photoconductor drums Py, Pm, Pc, and Pk are electrostatically charged by the corotron members CCy, CCm, CCc, and CCk, respectively, and electrostatic latent images are subsequently formed on the surfaces thereof by laser beams Ly, Lm, Lc, and Lk output as an example of latent-image write-in light from the latent-image forming units ROSy, ROSm, ROSc, and ROSk. Developing rollers RO provided as an example of developing members in developing units Gy, Gm, Gc, and Gk develop the electrostatic latent images on the surfaces of the photoconductor drums Py, Pm, Pc, and Pk into toner images, as an example of visible images, by using Y, M, C, and K developers.
In first transfer regions Q3, the toner images on the surfaces of the photoconductor drums Py, Pm, Pc, and Pk are sequentially superposed and transferred onto an intermediate transfer belt B, which is an intermediate transfer body serving as an example of an endless-belt-like image bearing member, by first transfer rollers T1y, T1m, T1c, and T1k serving as an example of a first transfer unit, whereby a multi-color image, that is, a color image, is formed on the intermediate transfer belt B. The color image formed on the intermediate transfer belt B is transported to a second transfer region Q4.
In the case of black image data only, the photoconductor drum Pk and the developing unit Gk for the black (K) color are used so that only a black toner image is formed.
After the first transfer process, residual toners on the surfaces of the photoconductor drums Py, Pm, Pc, and Pk are removed therefrom by the photoconductor cleaners CLy, CLm, CLc, and CLk.
The image bearing units Uy, Um, Uc, and Uk and the developing units Gy, Gm, Gc, and Gk constitute toner-image forming members Uy+Gy, Um+Gm, Uc+Gc, and Uk+Gk serving as an example of visible-image forming members.
A toner dispenser U3a serving as an example of a developer supplier is disposed above the image forming apparatus body U3. The toner dispenser U3a has toner cartridges Ky, Km, Kc, and Kk serving as an example of developer containers that are detachably attached thereto. As the developing units Gy to Gk consume toner in an image forming operation, the developing units Gy to Gk are supplied with toner from the respective toner cartridges Ky to Kk.
The intermediate transfer belt B disposed below the photoconductor drums Py to Pk is supported by an intermediate driving roller Rd serving as an example of an intermediate-transfer-body driving member, intermediate tension rollers Rt serving as an example of tension applying members that apply tension to the intermediate transfer belt B, an intermediate steering roller Rw serving as an example of a first deviation correcting member that corrects deviation and meandering of the intermediate transfer belt B, multiple intermediate idler rollers Rf serving as an example of driven members of the intermediate transfer body, and a backup roller T2a serving as an example of an opposing member disposed opposite the second transfer region Q4. The intermediate transfer belt B is supported in a rotatable manner in a direction indicated by an arrow Ya by driving of the intermediate driving roller Rd.
The intermediate driving roller Rd, the intermediate tension rollers Rt, the intermediate steering roller Rw, the intermediate idler rollers Rf, and the backup roller T2a serve as belt support rollers Rd+Rt+Rw+Rf+T2a as an example of intermediate-transfer-body support members according to the first exemplary embodiment. Furthermore, the intermediate transfer belt B, the belt support rollers Rd+Rt+Rw+Rf+T2a, and the first transfer rollers T1y to T1k constitute a belt module BM serving as an example of an intermediate transfer unit. The belt module BM according to the first exemplary embodiment is a replaceable unit that is detachable from the image forming apparatus body U3.
A second transfer unit Ut serving as an example of a transfer transport unit is disposed below the backup roller T2a. The second transfer unit Ut includes a second transfer roller T2b serving as an example of a transfer member and disposed facing the backup roller T2a. The second transfer region Q4 is formed in an area where the second transfer roller T2b faces the intermediate transfer belt B. In the first exemplary embodiment, the second transfer unit Ut has a bias member (not shown) that biases and presses the second transfer roller T2b toward the backup roller T2a. The backup roller T2a is in contact with a contact roller T2c serving as an example of a contact member for applying voltage. The rollers T2a to T2c constitute a second transfer device T2.
A second transfer voltage having the same polarity as the charge polarity of the toners is applied, at a predetermined timing, to the contact roller T2c from the power circuit E controlled by the controller C.
The sheet transport path SH2 is disposed below the belt module BM. The recording paper S fed from the feed path SH1 of the feeding device U2 is transported to the sheet transport path SH2. Then, a registration roller Rr serving as an example of a transport member transports the recording paper S to the second transfer region Q4 via sheet guides SG1 and SG2 serving as an example of medium guide members in accordance with the timing at which the toner images are to be transferred to the second transfer region Q4.
The toner images on the intermediate transfer belt B are transferred onto the recording paper S by the second transfer device T2 as the recording paper S travels through the second transfer region Q4. In the case of a full-color image, the toner images superposed and first-transferred on the surface of the intermediate transfer belt B are collectively second-transferred onto the recording paper S.
After the second transfer process, the intermediate transfer belt B is cleaned by a belt cleaner CLB serving as an example of an intermediate-transfer-body cleaner. The second transfer roller T2b is supported in a contactable and separable manner relative to the intermediate transfer belt B.
The first transfer rollers T1y, T1m, T1c, and T1k, the intermediate transfer belt B, the second transfer device T2, and the belt cleaner CLB constitute a transfer unit T1+B+T2+CLB that transfers the images on the surfaces of the photoconductor drums Py to Pk onto the recording paper S.
The recording paper S having the superposed toner image second-transferred thereon is transported downstream while being supported by a surface of an endless transfer transport belt T2e serving as an example of a transfer transport member disposed below the intermediate transfer belt B.
Multiple suction transport belts BH serving as an example of transport members that transport the recording paper S downstream while supporting the recording paper S on the surfaces thereof are disposed downstream of the transfer transport belt T2e. The recording paper S is transported downstream while the transport speed and the distance between the current recording paper S and the subsequent recording paper S are adjusted by the multiple suction transport belts BH. The suction transport belts BH are each provided with multiple holes (not shown). A fan serving as an example of a suction unit suctions air through the holes so that the recording paper S is transported downstream while being attached to the surfaces of the suction transport belts BH by suction. Since suction transport belts of this type are known in the related art and may be achieved by employing a freely-chosen configuration, such as a configuration discussed in Japanese Unexamined Patent Application Publication No. 2004-347880, a detailed description thereof will be omitted.
The recording paper S transported by the suction transport belts BH is transported to a fixing unit F disposed within the sheet output unit U4. The fixing unit F includes a heating roller Fh serving as an example of a thermal fixing member and a pressing roller Fp serving as an example of a pressure fixing member. A fixing region Q5 is formed in an area where the heating roller Fh and the pressing roller Fp come into contact with each other.
The toner image on the recording paper S is thermally fixed thereon by the fixing unit F as the recording paper S travels through the fixing region Q5. The recording paper S having the toner image fixed thereon in the fixing unit F is output to a sheet output tray TRh serving as an example of a sheet output section.
The paths SH1 and SH2 constitute a sheet transport path SH. The components denoted by reference characters SH, Ra, Rr, SGr, and BH constitute a medium transport unit SU.
Second Transfer Belt
Referring to
A transmission gear G1 serving as an example of a drive transmission member is supported by an axial end of the transport driving roller 2 via a torque limiter (not shown) serving as an example of a transmission limiting member. The transmission gear G1 receives a driving force for rotating the transfer transport belt T2e from a transport driving motor M2 serving as an example of a driving source via an intermediate gear G2 serving as an example of an intermediate transmission member. The torque limiter, the transmission gear G1, the intermediate gear G2, and other gears (not shown) constitute a transmission system G1+G2 according to the first exemplary embodiment.
A front end of a rotation shaft 3a of the transport steering roller 3 is supported by a shaft support member 11. The shaft support member 11 in the first exemplary embodiment is supported by a frame (not shown) of the image forming apparatus body U3 in a rotatable manner about a rotation center 11a at a base end of the shaft support member 11. A terminal end of the shaft support member 11 is provided with a slit-like bias support section 11b that extends inward from the terminal end. The rotation shaft 3a of the transport steering roller 3 is supported by the terminal end of the bias support section 11b in a movable manner along the bias support section 11b. A steering bias spring 12 serving as an example of a bias member that biases the transport steering roller 3 toward the transfer transport belt T2e is supported within the bias support section 11b.
Referring to
Consequently, when the transport steering cam 13 rotates in the forward or reverse direction, the shaft support member 11 rotates about the rotation center 11a, causing the front end of the transport steering roller 3 to move relatively to the rear end thereof. Thus, the front end of the transport steering roller 3 is supported in a movable manner between the initial position shown in
The transport steering roller 3, the shaft support member 11, the transport steering cam 13, and the transport steering motor 14 constitute a transport-belt deviation correcting mechanism 16 serving as an example of a second deviation correcting mechanism. Since a mechanism for tilting the intermediate steering roller Rw of the intermediate transfer belt B is similar to the transport-belt deviation correcting mechanism 16, a detailed description thereof will be omitted.
Referring to
A second movable range L2 within which the transfer transport belt T2e according to the first exemplary embodiment is movable in the width direction relative to the axial direction of the transport steering roller 3 is set to be wider than the first movable range L1. Specifically, in the first exemplary embodiment, the relationship L2>L1 is set such that the transfer transport belt T2e has a wider permissible movable range in the width direction relative to the intermediate transfer belt B. A second detection member SN2 having a second front detection sensor SN2a that can detect a front end of the transfer transport belt T2e in the width direction and a second rear detection sensor SN2b that can detect a rear end thereof is disposed within the second movable range L2.
Referring to
For example, in the first exemplary embodiment, θ1 is set equal to 5°, and θ2 is set equal to 1.25°, and the amount of movement per unit time, that is, steering sensitivity, is set to 0.4 mm for the intermediate transfer belt B and to 0.2 mm for the transfer transport belt T2e. The specific numerical values for the aforementioned angles and the amounts of movement of the belts are not limited to the aforementioned values, and may be changed to freely-chosen values depending on perimeters and rotational speeds of the belts, roller diameters, and cam shapes. In the first exemplary embodiment of the present invention, the relationship θ1≦θ2 may alternatively be set so long as the steering sensitivity of the intermediate transfer belt B is set to be larger than the steering sensitivity of the transfer transport belt T2e.
Controller in First Exemplary Embodiment
Referring to
Signal Output Components Connected to Controller C
The controller C receives output signals from signal output components, such as the operating section UI, the first front detection sensor SN1a, the first rear detection sensor SN1b, the second front detection sensor SN2a, and the second rear detection sensor SN2b.
The operating section UI includes a power button UI1, a display UI2, and an arrow key UI3 and a setting key UI4 serving as examples of input keys.
The first front detection sensor SN1a detects the front end of the intermediate transfer belt B in the width direction.
The first rear detection sensor SN1b detects the rear end of the intermediate transfer belt B in the width direction.
The second front detection sensor SN2a detects the front end of the transfer transport belt T2e in the width direction.
The second rear detection sensor SN2b detects the rear end of the transfer transport belt T2e in the width direction.
Each of the detection sensors SN1a to SN2b in the first exemplary embodiment outputs a detection signal to the controller C at predetermined time intervals of, for example, 0.5 seconds.
Control Components Connected to Controller C
The controller C is connected to a driving-source driving circuit D0, an intermediate-steering-motor driving circuit D1, a transport-steering-motor driving circuit D2, the power circuit E, and other control components (not shown), and outputs actuation control signals thereto.
The driving-source driving circuit D0 rotationally drives the photoconductor drums Py to Pk and the intermediate transfer belt B via a motor M0 serving as an example of a driving source.
The intermediate-steering-motor driving circuit D1 moves the intermediate steering roller Rw between the initial position, the front correction position, and the rear correction position via an intermediate steering motor M1.
The transport-steering-motor driving circuit D2 moves the transport steering roller 3 between the initial position, the front correction position, and the rear correction position via the transport steering motor 14.
The power circuit E includes a development power circuit Ea, a charge power circuit Eb, a transfer power circuit Ec, and a fixation power circuit Ed.
The development power circuit Ea applies development voltage to the developing rollers RO of the developing units Gy to Gk.
The charge power circuit Eb applies charge voltage to the corotron members CCy to CCk so as to charge the surfaces of the photoconductor drums Py to Pk.
The transfer power circuit Ec applies transfer voltage to the first transfer rollers T1y to T1k and the second transfer roller T2b.
The fixation power circuit Ed supplies power for heating the heating roller Fh of the fixing unit F.
Function of Controller C
The controller C has a function of executing processing according to input signals from the signal output components and outputting control signals to the control components. Specifically, the controller C has the following functions.
A job control section C1 serving as an example of an image-forming-operation control section controls the driving and voltage applying timings for the components in the image forming apparatus U in accordance with an input from the operating section UI so as to execute a job as an example of image forming operation.
A motor control section C2 serving as an example of a driving-source control section controls the driving of the motor M0 via the motor driving circuit D0 so as to control the driving of the photoconductor drums Py to Pk.
A power control section C3 includes a development power control section C3A, a charge power control section C3B, a transfer power control section C3C, and a fixation power control section C3D, and controls the operation of the power circuit E so as to control the voltage applied and the power supplied to the components.
The development power control section C3A controls the development power circuit Ea so as to control the development voltage applied to the developing rollers RO of the developing units Gy to Gk.
The charge power control section C3B controls the charge power circuit Eb so as to control the charge voltage applied to the corotron members CCy to CCk.
The transfer power control section C3C controls the transfer power circuit Ec so as to control first transfer voltage applied to the first transfer rollers T1y to T1k and second transfer voltage applied to the second transfer roller T2b.
The fixation power control section C3D controls the fixation power circuit Ed so as to control the temperature of a heater for the heating roller Fh of the fixing unit F. In other words, the fixation power control section C3D controls the fixation temperature.
A first correction control section C4 includes an intermediate-transfer-belt deviation determining section C4A serving as an example of a first deviation determining section, an intermediate-steering-roller tilt-direction determining section C4B serving as an example of a first tilt-direction determining section, an intermediate-steering-roller tilt control section C4C serving as an example of a first tilt control section, and an intermediate-steering-roller position storing section C4D serving as an example of a first position storing section. In a case where the first detection member SN1 detects deviation of the intermediate transfer belt B, the first correction control section C4 tilts the intermediate steering roller Rw in a direction for correcting the deviation of the intermediate transfer belt B so as to correct the deviation.
The intermediate-transfer-belt deviation determining section C4A detects deviation of the intermediate transfer belt B on the basis of a detection result of the first detection member SN1. The intermediate-transfer-belt deviation determining section C4A in the first exemplary embodiment detects whether the intermediate transfer belt B is deviated forward or rearward or whether the intermediate transfer belt B is not deviated on the basis of detection results of the first front detection sensor SN1a and the first rear detection sensor SN1b.
The intermediate-steering-roller tilt-direction determining section C4B determines the tilt direction of the intermediate steering roller Rw on the basis of the determination result of the intermediate-transfer-belt deviation determining section C4A. If it is determined that the intermediate transfer belt B is deviated forward, the intermediate-steering-roller tilt-direction determining section C4B in the first exemplary embodiment determines that the intermediate steering roller Rw should be tilted toward the front correction position. If it is determined that the intermediate transfer belt B is deviated rearward, the intermediate-steering-roller tilt-direction determining section C4B determines that the intermediate steering roller Rw should be tilted toward the rear correction position. If it is determined that the intermediate transfer belt B is not deviated, the intermediate-steering-roller tilt-direction determining section C4B determines that the intermediate steering roller Rw should be moved to the initial position.
The intermediate-steering-roller tilt control section C4C controls the tilting of the intermediate steering roller Rw via the intermediate-steering-motor driving circuit D1. The intermediate-steering-roller tilt control section C4C in the first exemplary embodiment causes the intermediate steering roller Rw to move to the initial position, the front correction position, or the rear correction position on the basis of the determination result of the intermediate-steering-roller tilt-direction determining section C4B.
The intermediate-steering-roller position storing section C4D stores the current position of the intermediate steering roller Rw moved by the intermediate-steering-roller tilt control section C4C.
A second correction control section C5 includes a transfer-transport-belt deviation determining section C5A serving as an example of a second deviation determining section, a transport-steering-roller tilt-direction determining section C5B serving as an example of a second tilt-direction determining section, a transport-steering-roller tilt control section C5C serving as an example of a second tilt control section, and a transport-steering-roller position storing section C5D serving as an example of a second position storing section. In a case where the second detection member SN2 detects deviation of the transfer transport belt T2e, the second correction control section C5 tilts the transport steering roller 3 in a direction for correcting the deviation of the transfer transport belt T2e so as to correct the deviation.
Because the sections C5A to C5D are similar to the aforementioned sections C4A to C4D except for the fact that the intermediate transfer belt B is replaced by the transfer transport belt T2e and the intermediate steering roller Rw is replaced by the transport steering roller 3, detailed descriptions thereof will be omitted for the sake of convenience.
Flowchart of First Exemplary Embodiment
Next, the flow of control performed in the image forming apparatus U according to the first exemplary embodiment will be described with reference to a flowchart.
Flowchart of Deviation Correcting Process
Steps ST in the flowchart in
The flowchart shown in
In step ST1 in
In step ST2, the intermediate steering roller Rw is moved to the initial position. The process then proceeds to step ST3.
In step ST3, it is determined whether or not signals are input from the sensors SN1a and SN1b. If yes, the process proceeds to step ST4. If no, step ST3 is repeated.
In step ST4, it is determined whether or not an end of the intermediate transfer belt B is detected. Specifically, it is detected whether or not one of the sensors SN1a and SN1b has detected an end of the intermediate transfer belt B. If yes, the process proceeds to step ST7. If no, the process proceeds to step ST5.
In step ST5, it is determined whether or not the current position of the intermediate steering roller Rw is the initial position. If no, the process proceeds to step ST6. If yes, the process proceeds to step ST12.
In step ST6, the intermediate steering motor M1 is actuated so as to move the intermediate steering roller Rw to the initial position. The process then proceeds to step ST12.
In step ST7, it is determined whether or not the detected end of the intermediate transfer belt B is the front end. If yes, the process proceeds to step ST8. If no, the process proceeds to step ST10.
In step ST8, it is determined whether or not the current position of the intermediate steering roller Rw is the front correction position. If no, the process proceeds to step ST9. If yes, the process proceeds to step ST12.
In step ST9, the intermediate steering motor M1 is actuated so as to move the intermediate steering roller Rw to the front correction position. The process then proceeds to step ST12.
In step ST10, it is determined whether or not the current position of the intermediate steering roller Rw is the rear correction position. If no, the process proceeds to step ST11. If yes, the process proceeds to step ST12.
In step ST11, the intermediate steering motor M1 is actuated so as to move the intermediate steering roller Rw to the rear correction position. The process then proceeds to step ST12.
In step ST12, it is determined whether or not the job is completed. If no, the process returns to step ST3. If yes, the process returns to step ST1.
Operation of First Exemplary Embodiment
In the image forming apparatus U according to the first exemplary embodiment having the above-described configuration, the toner images formed on the photoconductor drums Py to Pk are superposed and transferred onto the recording paper S in the second transfer region Q4 via the intermediate transfer belt B. The recording paper S having the superposed toner image transferred thereon is transported downstream while being supported on the surface of the transfer transport belt T2e, and is then transported to the suction transport belts BH. Subsequently, the toner image is fixed onto the recording paper S by the fixing unit F before the recording paper S is output to the sheet output tray TRh.
In the first exemplary embodiment, if the intermediate transfer belt B is deviated, the deviation is detected by the first detection member SN1, and the intermediate steering roller Rw is tilted, thereby correcting the deviation. If the transfer transport belt T2e is deviated, the deviation is detected by the second detection member SN2, and the transport steering roller 3 is tilted, thereby correcting the deviation.
In the configuration in which the two belts B and T2e are in contact with each other in the second transfer region Q4, the direction of deviation and the direction for correcting the deviation are sometimes opposite to each other. This may make it difficult to correct the deviation of the belts B and T2e, possibly resulting in instable rotation of the belts B and T2e. If images are transferred onto the intermediate transfer belt B from the photoconductor drums Py to Pk in this state, the image quality may possibly be reduced, such as the occurrence of color misregistration.
In the related art discussed in Japanese Unexamined Patent Application Publication No. 2009-251322, if the deviation is moderate, one of the belts with the larger deviation is corrected for the deviation, while the deviation correcting process is stopped for the other belt. However, while the correcting process is performed for the first belt, the deviation of the second belt increases. This deviation tends to increase especially when the image forming rate is high. Therefore, the correction process is performed by printing a so-called patch image, which is a correction image used for correcting color misregistration in a printed image, resulting in lower productivity.
In the technology discussed in Japanese Unexamined Patent Application Publication No. 2009-251322, if the deviation becomes large, the belts are moved away from each other so as to perform the deviation correcting process individually for the belts. However, with this configuration, image forming operation cannot be performed during the deviation correcting process, resulting in very low productivity.
In particular, in the configuration in which the two belts are in contact with each other in the related art, an already available device and proven numerical values are often used for preventing the deviation of the belts. In addition, the steering sensitivities of the belts are not set to different values but are generally set to the same value.
In contrast, in the first exemplary embodiment, the amount by which the intermediate transfer belt B is moved per unit time in the width direction, that is, the steering sensitivity thereof, is set to be larger than the steering sensitivity of the transfer transport belt T2e. Therefore, the deviation correcting process for the intermediate transfer belt B and the deviation correcting process for the transfer transport belt T2e are performed simultaneously. Moreover, when the belts B and T2e are moving in opposite directions, the intermediate transfer belt B moves predominantly so that the deviation correcting process for the intermediate transfer belt B is prioritized.
With regard to the images transferred onto the intermediate transfer belt B from the photoconductor drums Py to Pk, although deviation and meandering of the intermediate transfer belt B may possibly have an adverse effect on the images, such as color misregistration, expansion and contraction, and skewing, an effect the transfer transport belt T2e has on the transport of the recording paper S is small even if the transfer transport belt T2e is deviated in the width direction. Therefore, in the first exemplary embodiment, the steering sensitivity of the intermediate transfer belt B is set to be larger than that of the transfer transport belt T2e, thereby reducing the occurrence of reduced image quality, such as color misregistration.
Experiments related to the occurrence of color misregistration are performed. The experiments are performed using a remodeled version of Color 1000 Press manufactured by Fuji Xerox Co., Ltd. The types of paper used in the experiments include plain paper with a basis weight of 82 g/m2 as “paper 1” and coated paper with a basis weight of 127 g/m2 as “paper 2”. A first experiment corresponds to a case where the steering sensitivity of the transfer transport belt T2e is set to be smaller than the steering sensitivity of the intermediate transfer belt B, and a second experiment corresponds to a case where the transfer transport belt T2e is set to be larger than the steering sensitivity of the intermediate transfer belt B. In each experiment, a maximum color misregistration value of Y, M, and C images relative to a K image is measured as an amount of color misregistration (μm). The experimental results are shown in
Referring to
Furthermore, in the first exemplary embodiment, although there is a possibility that, when the intermediate transfer belt B is being corrected for deviation, deviation of the transfer transport belt T2e may increase due to clogging of the deviation correcting process for the transfer transport belt T2e, the second movable range L2 is set to be larger than the first movable range L1, meaning that the transfer transport belt T2e is given a larger permissible movable amount. In particular, with regard to the transfer transport belt T2e disposed in the second transfer region Q4 where images are collectively transferred, the permissible movable amount thereof relative to color misregistration may have lower accuracy as compared with that of the intermediate transfer belt B to which images are sequentially transferred from the four photoconductor drums Py to Pk. Thus, the transfer transport belt T2e may have a large permissible movable amount.
Therefore, with the transfer transport belt T2e given a large permissible movable amount, even when the transfer transport belt T2e is largely deviated, the deviation tends to be within the second movable range L2. Thus, the occurrence of breakage or fracturing of the ends of the transfer transport belt T2e caused by excessive deviation of the transfer transport belt T2e is reduced, as compared with a case where the second movable range L2 is smaller.
Furthermore, in the first exemplary embodiment, the transport driving roller 2 of the transfer transport belt T2e is provided with the torque limiter. In a case where a torque limiter is not provided, if the speed varies between the transfer transport belt T2e and the intermediate transfer belt B, the rotational force of the transfer transport belt T2e may be transmitted to the intermediate transfer belt B and affect the behavior of the intermediate transfer belt B, such as deviation thereof, possibly affecting the image quality. In contrast, with the transfer transport belt T2e provided with the torque limiter in the first exemplary embodiment, if a preset driving force, that is, a driving force greater than or equal to torque, is generated in the transport driving roller 2, the transmission of torque is limited so that the rotation of the transfer transport belt T2e is limited. Therefore, the intermediate transfer belt B is less likely to receive an excessive load from the transfer transport belt T2e so that an adverse effect on the rotation of the intermediate transfer belt B is reduced, as compared with a case where a torque limiter is not provided, thereby reducing an adverse effect on the image quality.
Modifications
Although the exemplary embodiments of the present invention have been described in detail above, the present invention is not to be limited to the above exemplary embodiments and permits various modifications within the scope of the invention defined in the claims. Modifications H01 to H08 of the above exemplary embodiments of the present invention will be described below.
In a first modification H01 of the above exemplary embodiments, the image forming apparatus U is not limited to a copier, and may be applied to other types of image forming apparatuses, such as a printer, a facsimile apparatus, or a multifunction apparatus equipped with these multiple functions. Furthermore, the above exemplary embodiments are not limited to a color image forming apparatus, and may be applied to a monochrome image forming apparatus. Furthermore, the above exemplary embodiments are not limited to a so-called tandem-type image forming apparatus provided with the photoconductor drums Py to Pk for the four respective colors, and may be applied to a so-called rotary-type image forming apparatus that performs a developing process by rotating multiple developing units so as to sequentially make them face a single photoconductor drum, or to a so-called retracting-type image forming apparatus in which multiple developing units are supported in a movable manner toward and away from a single photoconductor drum such that a developing process is performed by moving the developing units toward the photoconductor drum.
In a second modification H02, although drum-like photoconductors are described as an example of image bearing members in the above exemplary embodiments, an endless-belt-like photoconductor may be used as an alternative. Specifically, the above exemplary embodiments are applicable to a configuration having an endless-belt-like photoconductor and an endless transfer transport belt or to a configuration having an endless-belt-like photoconductor and an endless intermediate transfer belt.
In a third modification H03, the specific numerical values and materials used in the above exemplary embodiments are changeable in accordance with the design and specifications.
In a fourth modification H04, the number and positions of rollers T2b and 2 to 4 in the above exemplary embodiments are changeable in accordance the design and specifications.
Although the transport steering roller 3 and the transport tension roller 4 are disposed at different positions in the above exemplary embodiments, a fifth modification H05 in which the transport tension roller 4 and the transport steering roller 3 are integrated into a single unit by adding the function of the transport steering roller 3 to the transport tension roller 4 is also possible.
In a sixth modification H06, although the torque limiter is provided in the above exemplary embodiments, the torque limiter may be omitted if the friction coefficient of the belts is low to an extent that the rotational force of the transfer transport belt T2e is hardly transmitted to the intermediate transfer belt B.
In a seventh modification H07, the deviation correcting mechanism used for tilting the steering rollers Rw and 3 in the above exemplary embodiments is not limited to the configuration described in the above exemplary embodiments, and a freely-chosen active steering mechanism known in the related art may be employed so long as the steering sensitivity is within the range defined in the exemplary embodiments of the present invention. For example, various known configurations discussed in Japanese Unexamined Patent Application Publication Nos. 2009-86463, 2010-231112, 2009-251322, and 2007-11107 may be employed.
In an eighth modification H08, although the second movable range L2 is set to be greater than the first movable range L1 in the above exemplary embodiments, the second movable range L2 may be changed in accordance with the limit of deviation of the transfer transport belt T2e. For example, if the transfer transport belt T2e does not experience much deviation, the second movable range L2 may be set to be smaller than the first movable range L1.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-197894 | Sep 2011 | JP | national |
