This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2008-033332 filed on Feb. 14, 2008.
1. Technical Field
The present invention relates to an image-forming device and an image-forming method.
2. Related Art
Methods have been proposed in connection with an image-forming device in which continuous form paper (a sheet extending in a longitudinal direction) is used for preventing damage to a sheet from heat generated by a fixing unit of the device.
An aspect of the present invention provides an image-forming device including a transport unit that transports a recording medium that extends in a longitudinal direction; a tension applying unit that applies tension to the recording medium; an image carrier that holds a toner image; a transfer unit that holds the recording medium between the transfer unit and the image carrier and that transfers the toner image held by the image carrier to the recording medium while tension is applied to the recording medium by the tension applying unit; a fixing unit provided downstream in a transport direction of the recording medium relative to the image carrier, that fixes the toner image transferred to the recording medium on the recording medium; and a retreat unit that causes the recording medium to move away from the fixing unit while tension is not applied to the recording medium by the tension applying unit, wherein rotation of the image carrier is suspended after the toner image is transferred from the image carrier to the recording medium, and after the suspension of rotation of the image carrier, application of tension to the recording medium by the tension applying unit is suspended, and the recording medium is caused to move away from the fixing unit by the retreat unit.
Exemplary embodiments of the present invention will now be described in detail below with reference to the following figures, wherein:
An exemplary embodiment of the present invention will be described.
(Configuration)
Image-forming device 10 includes feeding unit 11 that feeds a sheet extending in the longitudinal direction (hereinafter referred to as “continuous form paper S”) from a sheet source (not shown) into image-forming device 10, image-forming units 12Y, 12M, 12C, and 12K that form a toner image on continuous form paper S, and fixing unit 13 that fixes the toner image on continuous form paper S. The three units are connected in series. Each unit has plural rollers inside it, which are examples of a transport unit that transports continuous form paper S in the direction of arrow A shown in
Feeding unit 11 includes drive roller 111, back tension roller 112, a motor (not shown), which is a rotary drive source of the rollers 111 and 112, and plural rollers that are rotated by continuous form paper S being transported. Drive roller 111 is a member that rotates in the direction of arrow a shown in
Image-forming units 12Y, 12M, 12C, and 12K are units for forming an image using toner of yellow (Y), magenta (M), cyan (C), or black (K). The configurations of image-forming units 12Y, 12M, 12C, and 12K are the same, except that the color of toner is different in each unit. Accordingly, the configuration of only image-forming unit K, which is shown in
Transfer unit 125K includes transfer roller 126K, two transfer guide rollers 127K, sheet separation motor 128K, and a motor (not shown) that causes the rollers 126K and 127K, which are an example of a transfer unit, to rotate. If a transfer bias is applied between transfer roller 126K and photoreceptor drum 121K while continuous form paper S is held between the two units, a toner image is transferred from photoreceptor drum 121K to continuous form paper S. Transfer guide roller 127K is a unit for guiding continuous form paper S so that continuous form paper S is properly transported to between transfer roller 126K and photoreceptor drum 121K. Transfer guide roller 127K is provided upstream or downstream in a transport direction of continuous form paper S relative to transfer roller 126K (in
It is to be noted that in the following description, the components of image-forming unit 12Y, 12M, 12C, and 12K are referred to as “photoreceptor drum 121”, “charging unit 122”, “exposing unit 123”, “developing unit 124”, or “transfer unit 125”, without attaching a symbol “Y”, “M”, “C”, or “K”.
Returning to
Fixing section 133 includes fuser 14 and fuser-facing unit 15, which are provided so that each of the units faces the other unit across a sheet path of continuous form paper S. Fuser 14 is provided at one side of a toner image, and fuser-facing unit 15 is provided at the other side. Fuser 14 is an example of a fixing unit, and fuser-facing unit 15 is an example of a retreat unit Fuser 14 includes plural flash lamps 141 which emit a flash of light at predetermined intervals and reflector plate 142 which opens at the front side of flash lamps 141 (the side near continuous form paper S) and closes at the back side of flash lamps 141 (the side far from continuous form paper S). Flash lamps 141 are arranged at predetermined intervals along a sheet path so that the long side of each flash lamp is parallel to the width direction of continuous form paper S (the direction perpendicular to transport direction A). Reflector plate 142 reflects a flash of light and heat emitted from flash lamp 141 to continuous form paper S.
Fuser-facing unit 15 includes base 150, fixing guide rollers 151 and 152 provided at base 150, guide member 153 provided at base 150, and movement mechanism 15a. Fixing guide roller 151 is provided at the downstream side of transport direction A, and fixing guide roller 152 is provided at the upstream side of transport direction A. Guide member 153 is provided further downstream than fixing guide roller 151. Movement mechanism 15a moves base 150 toward or away from fuser 14, as shown by arrow D of
Clutch 167 is an electromagnetic clutch that transmits rotary torque to a pulley fixed to a rotating shaft only when the clutch is excited. First pulley 154 is fixed to the rotating shaft of motor 162. Rotation of motor 162 is, when clutch 167 is in an on state, transmitted to third belts 160 via first pulley 154, first belt 158, second pulley 155, clutch 167, second belt 159, third pulley 156, and fourth pulleys 163. When rotation is transmitted to third belts 160, third belts 160 rotate in the direction of arrow e shown in
Tension measuring roller 132 is attached to an end of arm 134 so that the roller is able to rotate. Tension measuring roller 132 is pushed by arm 134 toward continuous form paper S (in a downward direction in
Control unit 200 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory), which is housed in feeding unit 11, image-forming unit 12Y, 12M, 12C, or 12K, or fixing unit 13. The CPU retrieves a control program stored in the ROM, loads the program in the RAM, and executes the instructions for the program, thereby controlling components of image-forming device 10 such as drum motor 121m, charging unit 122, developing unit 124, transfer unit 125, fixing unit 133, or transport unit 170. Drum motor 121m is a driving unit for causing photoreceptor drum to rotate. Developing unit 124 includes magnetic motor 124m1 which is a driving unit for causing a magnetic roll provided in a developer storage of developing unit 124 to rotate and stirring motor 124m2 which is a driving unit for causing a stirring roll provided in a developer storage to rotate. Transfer unit 125 includes, in addition to sheet separation motor 128 described above, transfer roller motor 126m which is a driving unit for causing transfer roller 126 to rotate. Fixing unit 133 includes fuser 14 and fuser-facing unit 15, as described above. Transport unit 170 includes drive roller motor 111m which is a driving unit for causing drive roller 111 to rotate, back tension roller motor 112m which is a driving unit for causing back tension roller 112 to rotate, and sub-drive roller motor 131m which is a driving unit for causing sub-drive roller 131 to rotate.
(Operation)
Now, an operation of image-forming device 10 will be described with reference to a timing chart shown in
After an image-forming operation to continuous form paper S such as a transfer operation and a fixing operation is made, control unit 200, while transporting continuous form paper S, switches sheet separation motor 128 from a contact state to a first separation state at time t1. When the switching is performed, transfer roller 126 is caused to move from a first position (the position indicated by a solid line of
Subsequently, at time t3, control unit 200 switches sheet separation motor 128 from a first separation state to a second separation state, and changes a charging bias of charging unit 122 from an on state to an off state, thereby suspending charging against photoreceptor drum 121. As a result, transfer guide rollers 127 move from a first position (the position indicated by a solid line in
Subsequently, at time t4, control unit 200 changes a developing bias of drum motor 121m, magnetic motor 124m1, stirring motor 124m2, and developing unit 124 from an on state to an off state. As a result, rotation of each of photoreceptor drum 121, a magnetic roll, and a stirring roll is suspended, and a developing bias against photoreceptor drum 121 becomes zero. Subsequently, at time t5, control unit 200 switches fuser 14 from an on state to an off state. As a result, power supply to flash lamps 141 is suspended; consequently, emission of a flash of light is suspended.
Subsequently, at tire 6, which is after drum motor 121m is switched to an off state, and rotation of photoreceptor drum 121 is suspended, control unit 200 switches back tension roller motor 113m, drive roller motor 111m, and sub-drive roller motor 131m from an on state to an off state. After the switching is performed, rotation of each of back tension roller 112, drive roller 111, and sub-drive roller 131 gradually slows down. Subsequently, at time 7 immediately subsequent to time 6, control unit 200 switches a RUN mode of sub-drive roller motor 131m from an on state to an off state, and switches clutch 167 from an on state to an off state. The “RUN mode” is a control mode for switching on and off a servo operation of sub-drive roller motor 131m. If a RUN mode is switched from an on state to an off state, rotation of sub-drive roller 131 rapidly slows down and stops in accordance with a servo control.
At time t6, control unit 200 switches back tension roller motor 113m, drive roller motor 111m, and sub-drive roller motor 131m from an on state to an off state; as a result, rotation of back tension roller 112 and drive roller 111 gradually slows down, as indicated by the dashed lines in
Since sub-drive roller 131, which is a transport unit provided downstream in the transport direction, stops transporting continuous form paper S earlier than drive roller 111 (which is a transport unit provided upstream in the transport direction) does, tension of continuous form paper S decreases and accordingly continuous form paper S sags downward by the action of gravity. As a result, if continuous form paper S comes into contact with photoreceptor drum 121 located under the paper in the direction of gravitational force, since rotation of photoreceptor drum 121 is already stopped, the amount of residual toner attached to continuous form paper S, from the surface of photoreceptor drum 121 is less than when photoreceptor drum 121 is rotating.
At time t7, clutch 165 is switched to an off state whereby a transmission function of clutch 165 is disabled. As a result, base 150 is allowed to move freely, and is pulled by elastic force of springs 165, together with continuous form paper S guided by guide member 153, away from fuser 14. As a result, fuser 14, fuser-facing unit 15, and continuous form paper S are moved from the positions shown in
Returning to
Control unit 200 sets variable N to zero (step S1). Subsequently, after confirming that variable N is smaller than four (step S2; YES), control unit 200 determines whether an angle measured by angle sensor 135 of tension measuring roller 132 is equal to or more than 1.5 degrees (step S3). If the measured angle is equal to or more than 1.5 degrees (step S3; YES), which means that tension being applied to continuous form paper S is excessive, control unit 200 switches back tension roller motor 113m and drive roller motor 111m to an on state (step S4). As a result, only the upstream side of continuous form paper S is transported, so that tension applied to continuous form paper S is reduced, and an angle measured by angle sensor 135 becomes closer to zero. Subsequently, control unit 200 determines that an angle measured by angle sensor 135 is within plus or minus 0.75 degrees (step S5). If the measured angle is within plus or minus 0.75 degrees (step S5; YES), which means that a degree of slackness of continuous form paper S is within a predetermined range, control unit 200 switches back tension roller motor 113m and drive roller motor 111m to an off state (step S6). Control unit 200 repeats the above operations until variable N is equal to four.
At step S3, if the angle measured by angle sensor 135 is less than 1.5 degrees (step S3; NO), control unit 200 determines whether the measured angle is less than or equal to minus 1.5 degrees (step S8). If the measured angle is less than or equal to minus 1.5 degrees (step S8; YES), which means that tension being applied to continuous form paper S is insufficient, control unit 200 switches sub-drive roller motor 131m to an on state (step S9). As a result, only the downstream side of continuous form paper S is transported, so that tension applied to continuous form paper S is increased, and an angle measured by angle sensor 135 becomes closer to zero. Subsequently, control unit 200 determines whether an angle measured by angle sensor 135 is within plus or minus 0.75 degrees (step S10), and if the determination is affirmative (step S10; YES), control unit 200 switches sub-drive roller motor 131m to an off state (step S11). Subsequently, control unit 200 increments variable N by one (step S12), and repeats the above operations until variable N is equal to four.
If variable N becomes equal to four (step S2; NO), control unit 200 terminates the slack reduction operation. If at step S5 or step S10, an angle measured by angle sensor 135 is not within plus or minus 0.75 degrees, control unit 200 outputs an error message and thereafter terminates the slack reduction operation (steps S13 and S14).
(Modifications)
The above exemplary embodiment may be modified as described below.
In the above exemplary embodiment, a recording medium may be, instead of paper, a plastic sheet such as an OHP sheet or a cut of cloth, if the recording medium extends in a longitudinal direction.
In the above exemplary embodiment, the position of fixing section 133 may be changed as long as the location is in the downstream side of photoreceptor drum 121 in the transport direction of continuous form paper S.
In the above exemplary embodiment, where rotation of photoreceptor drum 121 is stopped after the whole image-forming operation including a transfer operation and a fixing operation is completed, rotation of photoreceptor drum 121 may be stopped immediately after a transfer operation is completed, because photoreceptor drum 121 completes its role with an end of the transfer operation.
In the above exemplary embodiment, control unit 200, after an image is transferred from photoreceptor drum 121 to continuous form paper S, firstly causes transfer roller 126 to move to the second position, secondly suspends rotation of photoreceptor drum 121, thirdly suspends transportation of continuous form paper S, and fourthly distances continuous form paper S from fuser 14, to reduce contact between continuous form paper S and photoreceptor drum 121, thereby to reduce a degree of contamination on continuous form paper S. However, in the process, control unit 200 may distance continuous form paper S from fuser 14 before suspending transportation of continuous form paper S by transport unit 170. Alternatively, control unit 200 may simultaneously carry out the two operations. To decrease contacts between continuous form paper S and photoreceptor drum 121, thereby to reduce a degree of contamination on continuous form paper S, control unit 200 has merely to suspend rotation of photoreceptor drum 121 after an image is transferred from photoreceptor drum 121 to continuous form paper S, and to stop transportation of continuous form paper S by transport unit 170 and distance continuous form paper S from fuser 14 after the rotation of photoreceptor drum 121 is suspended.
In the above exemplary embodiment, fixing section 133 stops emission of a flash of light before transportation of continuous form paper S is suspended, to reduce the effect of a flash of light to continuous form paper S. However, if the effect of a flash of light is negligible, the emission of a flash of light may be stopped at the same time as the suspension of transportation of continuous form paper S. Alternatively, the emission of a flash of light may be stopped after transportation of continuous form paper S is suspended.
In the above exemplary embodiment, transfer roller 126 is caused to move to the second position before rotation of photoreceptor drum 121 is suspended, to distance continuous form paper S from photoreceptor drum 121. However, transfer roller 126 may be caused to move to the second position at the same time as the suspension of rotation of photoreceptor drum 121. Alternatively, after transfer roller 126 is caused to move to the second position, rotation of photoreceptor drum 121 may be suspended.
In the above exemplary embodiment, where transfer guide rollers 127 are caused to move to the second position after transfer roller 126 is caused to move to the second position transfer guide rollers 127 and transfer roller 126 may be simultaneously caused to move to the second position.
In the above exemplary embodiment, while transportation of continuous form paper S by transport unit 170 is suspended, continuous form paper S is caused to sag over fuser 14, and to move away from fuser 14. However, continuous form paper S may be caused to sag over a sheet path after transportation of continuous form paper S by transport unit 170 is stopped, and thereafter to move away from fuser 14.
In the above exemplary embodiment, where tension is applied to continuous form paper S by drive roller 111, sub-drive roller 131, and back tension roller 112, tension may be applied by a configuration that pushes continuous form paper S in a direction perpendicular to a surface of the paper.
In the above exemplary embodiment, if it is determined that tension being applied to continuous form paper S is excessive at step S3 of
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.
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2008-033332 | Feb 2008 | JP | national |
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Number | Date | Country | |
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20090208267 A1 | Aug 2009 | US |