JP6911455B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In the electrophotographic image forming apparatus, the techniques described in Patent Documents 1 to 3 below are conventionally known with respect to a technique of removing static electricity from a medium after the image is transferred and peeling the medium from the image holder.

In Japanese Patent Application Laid-Open No. 2016-90630 as Patent Document 1, a serrated detack saw (6) is arranged on the downstream side of the transfer region (Q3) to remove static electricity from the sheet (S) in a non-contact manner, and immediately downstream thereof. Described is a configuration in which the conductive hair bundle (19) arranged in the sheet (S) is in contact with or in close contact with the sheet (S) to eliminate static electricity.

In Japanese Unexamined Patent Publication No. 2014-19706 as Patent Document 2, a serrated static elimination needle (21) is arranged on the downstream side of the secondary transfer nip portion (200) and detected by a charge amount detection sensor (24). A configuration is described in which the charged charge of the paper (P) is eliminated by applying a variable static elimination bias to the non-contact static elimination needle (21) according to the charge amount of the paper (P).

In Japanese Patent Application Laid-Open No. 2009-42304 as Patent Document 3, a transfer static elimination needle (11) is arranged on the downstream side of the transfer roller (5), and a pressure roller static elimination needle (14) is attached to the transfer static elimination needle (11). Described is a technique for charging a pressure roller (24) with a pressure roller static eliminator needle (14) by connecting and using the electric charge removed from the recording material (P) with a non-contact transfer static eliminator needle (11). Has been done.

Japanese Unexamined Patent Publication No. 2016-90630 (“0034” to “0051”, FIGS. 3 to 6) Japanese Unexamined Patent Publication No. 2014-19706 (“0033” to “0036”, FIGS. 2 and 3) Japanese Unexamined Patent Publication No. 2009-42304 (“0054” to “0060”, FIG. 4)

In the present invention, as compared with the configuration in which only the non-contact static elimination member is provided on the downstream side of the transfer region and the configuration in which the static elimination member in contact with the medium is added on the immediate downstream side of the non-contact static elimination member, the medium after transfer is used. The technical issue is to reduce insufficient static elimination and excessive static elimination.

In order to solve the technical problem, the image forming apparatus of the invention according to claim 1 is used.
A transfer member that transfers the image held in the image holder to the medium,
A first static elimination member arranged on the downstream side of the transfer member with respect to the transport direction of the medium and statically eliminating the medium.
A second static elimination member arranged on the downstream side of the first static elimination member with respect to the transport direction of the medium and statically eliminating the medium.
A third static eliminator member arranged between the first static eliminator and the second static eliminator with respect to the transport direction of the medium and having the same potential as the first static eliminator.
With the third static eliminator in contact with the first static eliminator,
A conductive member that grounds the first static elimination member, and
The third static eliminator, which is brought into contact with the first static eliminator by folding back the connecting portion formed by the notch.
It is characterized by being equipped with.

The invention according to claim 2 is the image forming apparatus according to claim 1.
The third static elimination member, which is made of a non-woven fabric having conductive fibers.
It is characterized by being equipped with.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2.
The third static elimination member is characterized in that the area of the facing surface facing the medium is smaller than the area of the surface perpendicular to the facing surface.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3.
A conductive member that comes into contact with the first static eliminator and the third static eliminator.
It is characterized by being equipped with.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4.
A conductive member that is grounded with a first static elimination member via a preset resistance element.
It is characterized by being equipped with.

According to the first aspect of the present invention, as compared with the configuration in which only the non-contact static elimination member is provided on the downstream side of the transfer region, or the configuration in which the static elimination member in contact with the medium is added on the immediate downstream side of the non-contact static elimination member. Therefore, it is possible to reduce insufficient static elimination and excessive static elimination of the medium after transfer. Further, according to the invention of claim 1, the third static eliminator member can be brought into contact with the first static eliminator member to have the same potential. Further, according to the invention of claim 1, the third static eliminator member can be brought into contact with the first static eliminator member at the folded connection portion to have the same potential.
According to the second aspect of the present invention, the manufacturing cost can be suppressed as compared with the case where the non-woven fabric is not used.
According to the third aspect of the invention, the static elimination capacity of the third static elimination member can be improved as compared with the case where the area of the facing surface is larger than the area of the surface perpendicular to the facing surface.

According to the invention of claim 4, the first static elimination member and the third static elimination member in contact with the conductive member can have the same potential.
According to the invention of claim 5 , the static elimination ability of the first static elimination member and the third static elimination member can be adjusted by the resistance element.

FIG. 1 is an overall explanatory view of the image forming apparatus of the first embodiment. FIG. 2 is an enlarged view of a main part of the toner image forming apparatus portion of FIG. FIG. 3 is an enlarged view of a portion of the transfer region of Example 1. FIG. 4 is an enlarged view of the transfer region of the first embodiment, and is a cross-sectional view at a position different from that of FIG. 3 in the front-rear direction. FIG. 5 is a cross-sectional view of a main part of the transfer unit of the first embodiment. FIG. 6 is an explanatory view of a portion for electrically connecting the first static elimination member of the first embodiment and the third static elimination member, and FIG. 6A shows a third static elimination member of the first embodiment for the first static elimination. An explanatory view of a main part of a portion in contact with a member, FIG. 6B is an explanatory view of a first alternative form, and FIG. 6C is an explanatory view of a form further different from that of FIG. 6B.

Next, specific examples of embodiments of the present invention (hereinafter referred to as Examples) will be described with reference to the drawings, but the present invention is not limited to the following Examples.
In order to facilitate the understanding of the following description, in the drawings, the front-back direction is the X-axis direction, the left-right direction is the Y-axis direction, and the up-down direction is the Z-axis direction. The directions indicated by Z and −Z or the indicated sides are defined as front, rear, right, left, upward, downward, or front, rear, right, left, upper, and lower, respectively.
In addition, in the figure, the one with "・" in "○" means the arrow from the back of the paper to the front, and the one with "×" in "○" is the front of the paper. It shall mean an arrow pointing from to the back.
In addition, in the explanation using the following drawings, the illustrations other than the members necessary for the explanation are omitted as appropriate for the sake of easy understanding.

FIG. 1 is an overall explanatory view of the image forming apparatus of the first embodiment.
In FIG. 1, the printer U as an example of the image forming apparatus of the first embodiment has a printer main body U1 as an example of the apparatus main body. On the upper surface of the printer main body U1, a first ejection tray TRh is provided as an example of an ejection unit of the first medium. An operation unit UI is provided on the upper surface of the right portion of the printer main body U1. The operation unit UI has a display unit and the like (not shown). The operation unit UI is configured so that the user can perform input operations.
A personal computer PC is electrically connected to the printer U of the first embodiment as an example of an image information transmitting device.

The printer U has a controller C as an example of a control unit. The controller C can receive electrical signals such as image information and control signals transmitted from the personal computer PC. Further, the controller C is configured to be able to output a control signal to the operation unit UI and the electric circuit E. Further, the controller C is electrically connected to the writing circuit DL.
The writing circuit DL outputs a drive signal to the exposure machine ROS as an example of the writing device according to the input information. The exposure machine ROS is configured to be capable of outputting the laser beam L as an example of the writing light according to the input signal.

FIG. 2 is an enlarged view of a main part of the toner image forming apparatus portion of FIG.
In FIGS. 1 and 2, a photoconductor PR as an example of an image holder is arranged on the left side of the exposure machine ROS. The photoconductor PR of Example 1 is rotatably supported in the direction of the arrow about the rotation axis PRa. The photoconductor PR is irradiated with the laser beam L in the writing region Q1.
Around the photoconductor PR, along the rotation direction of the photoconductor PR, a charging roll CR as an example of a charging member, a developing device G, and a photoconductor cleaner CL as an example of a cleaning device for an image holder. Is placed.
In the printer U of the first embodiment, the photoconductor PR, the charging roll CR, the developing device G, and the photoconductor cleaner CL are integrally detachable as a unit. That is, the photoconductor PR, the charging roll CR, the developing device G, and the photoconductor cleaner CL are configured to be detachably attached to and attached to the printer main body U1 as the process unit U2.

A charging voltage is applied to the charging roll CR from the electric circuit E.
The developing apparatus G has a developing container V inside which contains toner as an example of a developing agent. Inside the developing container V, a developing roll Ga as an example of a developer holder is rotatably supported. The developing roll Ga is arranged in the developing region Q2 so as to face the photoconductor PR.
Further, a developing voltage is applied to the developing roll Ga from the power supply circuit E. Further, inside the developing container V, augers Gb and Gc as an example of a developing agent transporting member are rotatably supported.

One end of the replenishment path of the toner replenishment device TH1 as an example of the replenishment device for the developer fixedly supported by the printer U is connected to the developing container V. The other end of the replenishment path of the toner replenishment device TH1 is connected to the discharge port TC3 of the toner cartridge TC as an example of the developer container.
In FIG. 1, the toner cartridge TC has a cartridge body TC1 as an example of a container body that houses toner inside. Inside the cartridge body TC1, a toner transport member TC2 as an example of a developer transport member is rotatably supported. The toner cartridge TC is configured to be removable by inserting and removing it from the printer U in the front-rear direction.
The photoconductor PR, the charging roll CR, the exposure machine ROS, the developing device G, and the like constitute a toner image forming device that forms a toner image on the photoconductor PR.

In FIG. 1, a paper feed tray TR1 to TR4 is provided below the printer U as an example of a medium storage unit. Each paper feed tray TR1 to TR4 accommodates a recording sheet S as an example of a medium.
In FIG. 1, rails RL1 as an example of a container guide member are arranged on both left and right sides of each of the paper feed trays TR1 to TR4. The rail RL1 movably supports both the left and right ends of the paper feed trays TR1 to TR4. Therefore, each of the paper feed trays TR1 to TR4 is supported by a pair of left and right rails RL1 so as to be able to move in and out in the front-rear direction.

In FIG. 1, a paper feed device K is arranged in the upper left portion of each of the paper feed trays TR1 to TR4. The paper feed device K has a pickup roll Rp as an example of a medium take-out member. On the left side of the pickup roll Rp, a handling roll Rs as an example of a handling member is arranged. The handling rolls Rs consist of a feed roll as an example of a medium transporting member and a retard roll as an example of a medium separating member.
A paper feed path SH1 as an example of a medium transport path is arranged on the left side of the paper feed device K. The paper feed path SH1 extends upward. A plurality of transport rolls Ra as an example of the transport members of the medium are arranged in the paper feed path SH1. At the upper end, which is the downstream end of the paper feed path SH1, a register roll Rr as an example of a member for adjusting the transfer timing of the medium is arranged.

Further, a manual feed tray TR0 as an example of the manual feed portion is mounted on the left side portion of the printer U. The left end of the manual feed path SH2 as an example of the manual feed transfer path is connected to the right portion of the manual feed tray TR0. The right end of the manual feed path SH2 is connected to the paper feed path SH1.
In FIG. 1, a transfer roll Rt as an example of a transfer device is arranged above the registration roll Rr. The transfer roll Rt faces and contacts the photoconductor PR in the transfer region Q3. Therefore, the transfer roll Rt of Example 1 rotates in accordance with the rotation of the photoconductor PR. A transfer voltage is applied to the transfer roll Rt from the power supply circuit E.

The photoconductor cleaner CL is arranged on the downstream side of the transfer roll Rt with respect to the rotation direction of the photoconductor PR. The photoconductor cleaner CL has a cleaning blade CL1 as an example of a cleaning member. The cleaning blade CL1 is formed in a plate shape. One end of the cleaning blade CL1 is in contact with the photoconductor PR.
A cleaner container CL2 as an example of the cleaning container is arranged above the cleaning blade CL1. The cleaning blade CL1 is supported by the cleaner container CL2. A space in which the developer can be accommodated is formed inside the cleaner container CL2. Inside the cleaner container CL2, a recovery auger CL3 as an example of a developer transporting member is rotatably supported. Further, a recovery path CL4 as an example of a developer transport path is supported at the front end of the cleaner container CL2. The recovery path CL4 extends from the photoconductor cleaner CL to the developing device G.

In FIG. 1, the fixing device F is supported above the transfer roll Rt. The fixing device F has a heating roll Fh as an example of a heat fixing member and a pressure roll Fp as an example of a pressure fixing member. The heating roll Fh and the pressure roll Fp come into contact with each other in the fixing region Q4. Drive is transmitted to the heating roll Fh from a drive source (not shown) to rotate. Further, electric power for heating a heater (not shown) is supplied to the heating roll Fh from the electric circuit E.
The process unit U2, the transfer roll Rt, and the fixing device F constitute an image recording unit U2 + Rt + F for recording an image on the sheet S.

A sheet guide F1 as an example of a guide portion of the medium is formed on the upper portion of the fixing device F. On the right side of the sheet guide F1, a paper ejection roll R1 as an example of a medium ejection member is arranged. A medium discharge port Ha is formed on the right side of the paper discharge roll R1. A first discharge tray TRh is arranged below the discharge port of the medium.
In FIG. 1, a connecting path SH3 as an example of a medium transport path is arranged above the fixing device F and to the left of the paper ejection roll R1. The connecting path SH3 extends to the left from the discharge port Ha.

On the left side surface of the printer main body U1, a reversing unit U3 as an example of a medium reversing device is supported above the manual feed tray TR0. Inside the reversing unit U3, a reversing path SH4 is formed as an example of a medium transport path. The upper end of the reversing path SH4 is connected to the left end of the connecting path SH3. The lower end of the reversing path SH4 joins the paper feed path SH1 on the upstream side of the register roll Rr.
Further, a second discharge path SH6 as an example of a medium transport path is formed on the upper portion of the reversing unit U3. The right end of the second discharge path SH6 is connected to the connecting path SH3 and branches off from the reversing path SH4. The left end of the second discharge path SH6 extends to the left side surface of the reversing unit U3. A face-up tray TRh1 as an example of the second discharge portion is supported on the left side surface of the reversing unit U3. Therefore, the sheet S that has passed through the second discharge path SH6 is configured to be discharged to the face-up tray TRh1.

(Function of image forming device)
In the printer U of the first embodiment having the above configuration, the image information transmitted from the personal computer PC is input to the controller C. The controller C converts the input image information into information for forming a latent image at a preset time, and outputs the information to the writing circuit DL. The exposure machine ROS outputs the laser beam L based on the signal received by the writing circuit DL. The controller C controls the operation of the operation unit UI, the writing circuit DL, the power supply circuit E, and the like.
In FIGS. 1 and 2, the surface of the photoconductor PR is charged by a charging roll CR to which a charging voltage is applied. An electrostatic latent image is formed on the surface of the photoconductor PR charged by the charging roll CR by being exposed and scanned by the laser beam L of the exposure machine ROS at the writing position Q1. The surface of the photoconductor PR on which the electrostatic latent image is formed passes through the developing region Q2 and the transfer region Q3 in that order.

In the developing region Q2, the developing roll Ga faces the photoconductor PR. The developing roll Ga rotates while holding the developer inside the developing container V on the surface. Therefore, the electrostatic latent image on the surface of the photoconductor PR is developed into a toner image as an example of a visible image by the toner image held on the surface of the developing roll Ga. The developer inside the developing container V is circulated while being stirred by the augers Gb and Gc.
When the developer inside the developing container V is consumed with the development by the developing roll Ga, the developer is replenished from the toner cartridge TC. That is, the toner transport member TC2 is rotationally driven according to the consumption of the developer to transport the toner in the cartridge body TC1 to the discharge port TC3. The toner discharged from the discharge port TC3 is conveyed to the developing container V by a replenishment transfer member (not shown) in the replenishment path of the cartridge toner replenishment device TH1.

Sheets S on which images are recorded are housed in the paper feed trays TR1 to TR4. The sheets S housed in the paper feed trays TR1 to TR4 are taken out by the pickup roll Rp of the paper feed device K. The sheets S taken out by the pickup roll Rp are separated one by one by the handling roll Rs. The sheet S separated by the handling roll Rs is fed into the paper feed path SH1. The sheet S of the paper feed path SH1 is conveyed toward the register roll Rr by the transfer roll Ra.
The sheet S fed from the manual feed tray TR0 is conveyed to the registration roll Rr through the manual feed path SH2. The sheet S transported to the registration roll Rr is transported to the transfer region Q3 by the registration roll Rr at the time when the toner image on the surface of the photoconductor PR moves to the transfer region Q3.

In the transfer region Q3, the transfer roll Rt to which the transfer voltage is applied transfers the toner image on the surface of the photoconductor PR to the sheet S passing through the transfer region Q3.
In FIG. 2, the photoconductor PR after passing through the transfer region Q3 is cleaned by removing the toner adhering to the surface by the cleaning blade CL1. The toner removed by the cleaning blade CL1 is collected in the cleaner container CL2. The toner collected in the cleaner container CL2 is conveyed by the recovery auger CL3. The toner conveyed by the recovery auger CL3 is returned to the inside of the developing container V through the recovery path CL4. That is, the developer recovered by the photoconductor cleaner CL is reused in the developing apparatus G.
The photoconductor PR whose surface has been cleaned by the photoconductor cleaner CL is recharged by the charging roll CR.

The sheet S on which the toner image is transferred in the transfer region Q3 is conveyed to the fixing region Q4 of the fixing device F in a state where the toner image is not fixed.
In the fixing region Q4, the sheet S is sandwiched between the heating roll Fh and the pressure roll Fp, and the toner image is heat-fixed.
The sheet S on which the toner image is fixed by the fixing device F is guided by the sheet guide F1 and conveyed to the paper ejection roll R1. When the sheet S is discharged to the first discharge tray TRh, the sheet S sent to the paper discharge roll R1 is discharged from the discharge port Ha to the first discharge tray TRh.

At the time of double-sided printing, in the sheet S on which the image is recorded on the first surface, the paper ejection roll R1 rotates in the reverse direction with the rear end in the transport direction passing through the sheet guide F1. Therefore, the seat S is conveyed to the reversing path SH4 through the connecting path SH3. The sheet S transported on the reversing path SH4 is transported to the registration roll Rr with the front and back sides reversed. Therefore, the image is retransmitted from the regiroll Rr to the transfer region Q3, and the image of the second surface is recorded.
When the sheet S is discharged to the face-up tray TRh1, the sheet S conveyed through the connection path SH3 by the reverse rotation of the paper discharge roll R1 is carried into the second discharge path SH6. Then, the sheet S conveyed through the second discharge path SH6 is discharged to the face-up tray TRh1.

(Explanation of peeling device)
FIG. 3 is an enlarged view of a portion of the transfer region of Example 1.
FIG. 4 is an enlarged view of the transfer region of the first embodiment, and is a cross-sectional view at a position different from that of FIG. 3 in the front-rear direction.
FIG. 5 is a cross-sectional view of a main part of the transfer unit of the first embodiment.
In FIGS. 1 and 3 to 5, in the printer U of the first embodiment, the transfer unit 1 having the transfer roll Rt is detachably supported with respect to the printer main body U1. The transfer unit 1 has a housing 2 as an example of a frame body. The housing 2 rotatably supports both front and rear ends of the transfer roll Rt.
An upstream guide 3 extending upstream in the transport direction of the seat S is integrally formed in the housing 2. The upstream guide 3 guides the sheet S conveyed from the register roll Rr to the transfer region Q3.

In FIGS. 3 to 5, a vertical wall 4 as an example of a support portion is formed in the housing 2 on the downstream side in the transport direction of the sheet S with respect to the transfer roll Rt.
In FIG. 3, a detack saw 6 as an example of the first static elimination member is supported on the upper surface of the vertical wall 4, that is, the surface on the downstream side in the transport direction of the sheet S. In FIGS. 3 and 6, the detack saw 6 of the first embodiment is composed of a conductive plate extending in the front-rear direction and the left-right direction. The detack saw 6 of the first embodiment is made of a sheet metal made of SUS as an example. The right end of the detack saw 6, that is, the end portion 6a on the side of the sheet S to be conveyed is formed in a sawtooth shape. It should be noted that such a detack saw 6 can adopt various conventionally known configurations, and is described in Patent Document 1, for example, and therefore detailed description thereof will be omitted.

In FIGS. 3 to 5, a downstream cover 11 as an example of the protective member is supported by the housing 2 above the vertical wall 4. The downstream cover 11 has a plate-shaped main body portion 12 extending in parallel with the vertical wall 4 as an example of the support portion.
In FIG. 3, a cloth penetration port 12a as an example of the first conductive passing portion is formed in the central portion of the main body portion 12 in the front-rear direction so as to penetrate the main body portion 12. In FIGS. 4 and 5, the main body 12 has a ground through 12b as an example of the second conductive passing portion penetrating the main body 12 at a position deviated from the cloth through port 12a in the front-rear direction. Is formed.

A downstream guide 17, which is an example of a protective portion and is an example of a guide member, is formed at the right end of the main body portion 12, that is, on the transport path side of the medium. The downstream guide 17 is formed in a downwardly curved shape. As shown in FIG. 3, the downstream guide 17 of the first embodiment is formed so as to be arranged to the right of the right end of the detack saw 6 with the downstream cover 11 mounted on the housing 2. That is, the downstream guide 17 is configured so that the detack saw 6 is not exposed to the outside, the detack saw 6 is protected, and the sheet S can be guided on the right surface of the downstream guide 17, that is, the outer surface.
The downstream guide 17 of the first embodiment has an opening 17a formed at a position corresponding to the tip of the detack saw 6.

FIG. 6 is an explanatory view of a portion for electrically connecting the first static elimination member of the first embodiment and the third static elimination member, and FIG. 6A shows a third static elimination member of the first embodiment for the first static elimination. An explanatory view of a main part of a portion in contact with a member, FIG. 6B is an explanatory view of a first alternative form, and FIG. 6C is an explanatory view of a form further different from that of FIG. 6B.
A static elimination cloth 21 as an example of the third static elimination member is supported on the upper surface of the main body 12, that is, on the downstream side in the transport direction of the medium. The static elimination cloth 21 of Example 1 is made of a non-woven fabric made of conductive fibers. In FIGS. 3 and 6A, the static elimination cloth 21 has a notch 22 in a part of the cloth corresponding to the cloth penetrating portion 12a, and a goodwill-shaped portion as an example of a connection portion in a part of the static elimination cloth 21. 23 is formed, and the goodwill-shaped portion 23 is folded back and passed through the cloth through hole 12a. Therefore, the goodwill-shaped portion 23 that has passed through the cloth through hole 12a is in contact with the detack saw 6. Therefore, the static elimination cloth 21 and the detack saw 6 are set to have the same electric potential.

Further, in the static elimination cloth 21 of the first embodiment, the area of the facing surface 21a facing the sheet S is set to be smaller than the area of the surface perpendicular to the facing surface (the surface supported by the main body 12). So to speak, a sheet-shaped (thin plate-shaped) non-woven fabric is vertically placed so as to protrude from the transport path of the sheet S.
The facing surface 21a of the static elimination cloth 21 of the first embodiment is positioned on the left side of the right end of the downstream guide 17 so as not to come into contact with the sheet S.

In FIGS. 4 and 5, a torsion spring 26 as an example of the conductive member is arranged corresponding to the earth through port 12b. The torsion spring 26 has a contact portion 26a in which a wire rod is spirally wound. The contact portion 26a passes through the ground through hole 12b and comes into contact with the detack saw 6. A spring arm 26b as an example of the connecting portion extends to the left from the contact portion 26a. A supported portion 26c in which a wire rod is spirally wound is formed at the left end of the spring arm 26b. The supported portion 26c is supported by a spring support protrusion 27 as an example of the conduction support portion in a state of penetrating the center. The spring support protrusion 27 is integrally formed on the spring support plate 28 as an example of the conduction support portion protruding to the left from the housing 2.
In the torsion spring 26 of the first embodiment, an elastic force is applied by the spring arm 26b so that the contact portion 26a comes into contact with the detack saw 6 at a preset pressure.

A conductive contact portion 26d extending downward is formed in the supported portion 26c.
A groove 28a extending from the left end to the right side is formed in the lower portion of the spring support plate 28.
In FIG. 5, a resistance support portion 29 is supported behind the spring support plate 28. A groove 29a is formed in the resistance support portion 29 corresponding to the groove 28a.
Further, behind the spring support plate 28, a ground sheet metal 31 as an example of the conductive member is supported. The ground sheet metal 31 is also formed with a clamp portion 31a as an example of the holding portion at a position corresponding to the groove portions 28a and 29a. The ground sheet metal 31 of the first embodiment is made of a conductive metal. Further, the ground sheet metal 31 is grounded, so-called grounded, via a conductive portion (not shown).

A resistance element 32 is supported in each of the groove portions 28a and 29a and the clamp portion 31a. The resistance element 32 has a resistance main body 32a at the center in the front-rear direction and connecting portions 32b and 32c extending from the resistance main body 32a on both front and rear sides. In Example 1, as an example, a resistor of 100 MΩ is used as the resistor main body 32a.
The connecting portion 32b on the front side is supported so as to be sandwiched between the clamp portions 31a. Therefore, the connection portion 32b is connected to the ground.
The connecting portion 32c on the rear side passes through the grooves 28a and 29a and extends rearward. A conductive contact portion 26d is in contact with and supported by the connection portion 32c. The torsion spring 26 is configured so that an elastic force that pushes the connecting portion 32c to the right side acts on the conductive contact portion 26d. Therefore, the conductive contact portion 26d is configured to firmly support the connecting portion 32c with the groove portions 28a and 29a and to make electrical and reliable contact with the groove portions 28a and 29a.

In FIG. 3, a sheet guide 36 as an example of a medium guide member is arranged on the downstream side of the sheet S in the transport direction with respect to the transfer unit 1. A static elimination sheet 37 as an example of the second static elimination member is supported on the surface of the seat guide 36 on the transport path side. The static elimination sheet 37 of Example 1 is made of a non-woven fabric made of conductive fibers, similarly to the static elimination cloth 21. In the static elimination sheet 37, a sheet-shaped non-woven fabric is arranged along the transport path of the sheet S. The static elimination sheet 37 of the first embodiment is arranged at a position where it does not come into contact with the sheet S to be conveyed. Further, the static elimination sheet 37 of the first embodiment is not grounded and is electrically in a so-called float state.

(Action of Example 1)
In the printer U of the first embodiment having the above configuration, the sheet S after transfer is statically eliminated by the detack saw 6, the static elimination cloth 21, and the static elimination sheet 37 arranged on the back surface side until it is conveyed to the fixing region Q4. Will be done.
When the voltage applied to the static eliminator needle is controlled as in the configurations described in Patent Documents 2 and 3, there is a deviation between the voltage detection position and the static eliminator needle. Therefore, the voltage may not be appropriate for the amount of charged toner in the unfixed image on the sheet surface, resulting in insufficient static elimination or excessive static elimination. If the static electricity elimination is insufficient, the paper guides up to the fixing region Q4 may be electrostatically attracted. If the sheet is attracted to the paper guide, a paper jam may occur, or if only the right side in the sheet transport direction is attracted, the sheet will enter the fixing device F in a so-called skewed state, causing paper wrinkles. There is a problem of doing. Paper wrinkles are particularly likely to occur when the rigidity of the sheet S is weak as in the case of thin paper or when the direction of the fibers of the paper (horizontal grain, vertical grain) is vertical, or when vertical streaks are likely to be formed in the sheet S. Further, excessive static elimination weakens the ability to electrically hold the charged toner of the unfixed image. Therefore, the unfixed toner becomes easy to move, which may lead to poor image quality.

Further, in the configurations described in Patent Documents 2 and 3, a configuration in which a voltage is applied to a sensor for detecting a voltage and a static elimination needle is required, and there is a problem that the manufacturing cost tends to increase.
Further, when a static elimination member that comes into contact with the sheet as described in Patent Document 1 is used, excessive static elimination tends to occur. Therefore, image quality may be deteriorated due to excessive static elimination. In particular, when the amount of developer is large or laminated as in the case of a high-density image or an image forming apparatus for multicolor printing, if excessive static elimination occurs, image quality defects such as color loss may occur. It is more likely to occur.

On the other hand, in Example 1, the sheet S that has passed through the transfer region Q3 is discharged from the grounded detack saw 6 by a non-contact discharge. Therefore, excessive static elimination is reduced as compared with the case where a voltage is applied as in Patent Documents 2 and 3. In particular, in the first embodiment, the detack saw 6 is not directly grounded, but is grounded via the resistance element 32. When the voltage is directly grounded, that is, 0 V, excessive static elimination may occur, but in the first embodiment, the excessive static elimination is further suppressed by the resistance value of the resistance element 32.
Further, when the static elimination of the sheet S is insufficient with the detack saw 6, the static elimination cloth 21 on the downstream side performs the static elimination. Therefore, the insufficient static elimination is reduced as compared with the case where the static elimination cloth 21 is not provided. When the detack saw 6 is sufficient for static elimination, discharge is unlikely to occur between the detack saw 6 and the static elimination cloth 21 having the same potential. Therefore, excessive static elimination by the static elimination cloth 21 is also reduced.

Further, when the static elimination cloth 21 is insufficient in static elimination, the static elimination sheet 37 on the downstream side performs static elimination. The static elimination sheet 37 is not grounded and has a lower static elimination capacity than the detack saw 6 and the static elimination cloth 21. Therefore, excessive static elimination in the static elimination sheet 37 is also reduced as compared with the case where the static elimination sheet 37 is grounded.
Therefore, the printer U of the first embodiment has a configuration in which a voltage is supplied to the non-contact static elimination needle as described in Patent Documents 2 and 3, or a configuration having a contact static elimination member as described in Patent Document 1. In comparison with the above, insufficient static elimination and excessive static elimination of the sheet S after transfer are reduced.

Further, the static elimination cloth 21 of the first embodiment is made of a non-woven fabric, not made of sheet metal like the detack saw 6. Therefore, it is easy to control the manufacturing cost.
Further, the static elimination cloth 21 of Example 1 is vertically placed. Therefore, as compared with the case where the static elimination sheet 37 is placed horizontally, the facing surface 21a is sharp and discharge is likely to occur. Therefore, the static elimination performance is higher than that of the horizontal installation.

(Change example)
Although the examples of the present invention have been described in detail above, the present invention is not limited to the above-mentioned examples, and various modifications are made within the scope of the gist of the present invention described in the claims. Is possible. Examples of modifications (H01) to (H07) of the present invention are illustrated below.
(H01) In the above embodiment, a printer as an example of an image forming apparatus has been illustrated, but the present invention is not limited to this, and the present invention can be applied to an image forming apparatus such as a copying machine and a fax machine. Further, the present invention is not limited to a monochromatic image forming apparatus, and can be applied to a multicolor image forming apparatus. Therefore, the photoconductor PR as an example of the image holder has been illustrated, but the present invention is not limited to this. For example, it can be applied to an image forming apparatus having an intermediate transfer belt, an intermediate transfer drum, or the like as an example of an image holder.

(H02) In the above-described embodiment, a configuration in which the static elimination cloth 21 is made of a non-woven fabric has been illustrated, but the present invention is not limited to this. For example, it is possible to use a woven cloth, a conductive resin, or a metal similar to that of the Detack Saw 6.
(H03) In the above-described embodiment, the specific numerical values illustrated can be appropriately changed according to the design, specifications, and the like. Therefore, any resistance value of the resistance element 32 can be used depending on the static elimination performance.
(H04) In the above embodiment, the static elimination cloth 21 is preferably placed vertically, but the length and width of the facing surface 21a of the static elimination cloth 21 can be appropriately changed according to the required static elimination capacity.

(H05) In the above embodiment, the configuration in which the static elimination cloth 21 is brought into contact with the detack saw 6 and the torsion spring 26 is brought into contact with the detack saw 6 is illustrated, but the present invention is not limited thereto. As shown in FIG. 6B, the static eliminator cloth 21 may be in direct contact with the torsion spring 26 without being in contact with the detack saw 6. Further, as shown in FIG. 6C, the torsion spring 26 can be brought into contact with the static eliminator cloth 21 instead of the detack saw 6, and the detack saw 6 can be indirectly contacted with the torsion spring 26 via the static eliminator cloth 21. be. Therefore, it is possible to adopt a configuration in which the detack saw 6 and the static elimination cloth 21 are in direct contact with each other to have the same electric potential, or a configuration in which the electric potential is electrically equalized via a member such as a torsion spring 26.

(H06) In the above embodiment, it is desirable, but not limited to, the torsion spring 26 to apply an elastic force to ensure continuity with the detack saw 6. It can be in any form that can be electrically connected to the detack saw 6 without applying an elastic force. For example, it can be fastened with metal screws, or a conductive tape such as a conductive adhesive or aluminum tape can be used. In addition, it is possible to make arbitrary changes according to the design, specifications, etc., such as providing a plurality of conductive members between the torsion spring 26 and the ground sheet metal 31.
(H07) In the above embodiment, it is desirable to provide the resistance element 32, but it is also possible to provide a configuration in which the resistance element 32 is not provided depending on the required static elimination capacity and the like.

6 ... First static elimination member,
21 ... Third static elimination member,
21a ... Opposing surface,
22 ... notch,
23 ... Connection part,
26 ... Conduction member,
32 ... Resistance element,
37 ... Second static elimination member,
PR ... Image holder,
Rt ... Transfer member,
S ... medium,
U ... Image forming apparatus.

Claims (5)

A transfer member that transfers the image held in the image holder to the medium,
A first static elimination member arranged on the downstream side of the transfer member with respect to the transport direction of the medium and statically eliminating the medium.
A second static elimination member arranged on the downstream side of the first static elimination member with respect to the transport direction of the medium and statically eliminating the medium.
A third static eliminator member arranged between the first static eliminator and the second static eliminator with respect to the transport direction of the medium and having the same potential as the first static eliminator.
With the third static eliminator in contact with the first static eliminator,
A conductive member that grounds the first static elimination member, and
The third static eliminator, which is brought into contact with the first static eliminator by folding back the connecting portion formed by the notch.
An image forming apparatus characterized by being provided with. The third static elimination member, which is made of a non-woven fabric having conductive fibers.
The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. The image forming apparatus according to claim 1 or 2, wherein the third static elimination member has an area of a surface facing the medium smaller than the area of a surface perpendicular to the facing surface. A conductive member that comes into contact with the first static eliminator and the third static eliminator.
The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is provided. A conductive member that is grounded with a first static elimination member via a preset resistance element.
The image forming apparatus according to any one of claims 1 to 4 , wherein the image forming apparatus is provided.

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