JP6953939B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

Conventionally, when transferring an image of a transfer source onto a recording material typified by paper or the like, an image forming apparatus that sandwiches (nip) the recording material in a transfer region between the transfer source member and the transfer member has been known. There is.

For example, in Patent Document 1, when the tip of a recording medium having a thickness of a predetermined value or more pushes the transfer roller, the support of the transfer roller is released by the support releasing means, so that the endless moving body (belt) which is the transfer source is released. A technique for suppressing the fluttering of the belt is disclosed.

Further, for example, in Patent Document 2, after the tip of the paper has passed through the transfer nip, the nip load is controlled to a maximum load larger than the initial load based on the paper transport position, so that the paper can be transferred to the transfer nip. A technique for mitigating an impact caused by an approach is disclosed.

JP-A-2007-10840 Japanese Unexamined Patent Publication No. 2013-72908

However, the vibration of the image holder caused by the passage of the transfer region at the front end and the rear end of the recording material may not be sufficiently suppressed even if the nip load is changed after the passage of the end portion of the recording material. Such vibration of the image holder causes image defects in image transfer from the image holder to the recording material and image formation on the image holder.

Therefore, an object of the present invention is to suppress the vibration of the image holder due to the entry of the recording material into the transfer region, as compared with the case where the nip load is changed after passing through the transfer region at the end of the recording material.

The transfer device according to claim 1 is
At least an image holder whose peripheral surface circulates and holds an image on the peripheral surface,
A transfer member in which at least the peripheral surface circulates and passes through a transfer region between the image holder and the image holder so that the image on the image holder is transferred to the recording material.
A moving mechanism that continuously reduces the relative distance between the transfer member and the image holder before and after passing the tip of the recording material with respect to the transfer region.
Equipped with a,
The surfaces of the transfer member and the image holder are in contact with each other before passing through the tip of the recording material .

The transfer device according to claim 2 is the transfer device according to claim 1.
The moving mechanism moves the position of the transfer member with respect to the image holder .

The transfer device according to claim 3 is the transfer device according to claim 1.
The moving mechanism continuously increases the relative distance before and after passing the rear end of the recording material with respect to the transfer region.

The transfer device according to claim 4 is the transfer device according to claims 1 to 3 .
A detector is provided to detect the end portion of the recording material toward the transfer region before entering the transfer region.
The moving mechanism initiates a change in the relative distance between the transfer member and the image holder when the detector detects the end portion.

The transfer device according to claim 5 is the transfer device according to claims 1 to 4 .
The moving mechanism gradually changes the relative distance between the transfer member and the image holder according to the thickness of the recording material.
The transfer device according to claim 6 is the transfer device according to claims 1 to 5.
The transfer member is a transfer belt.
A transfer roller around which the transfer belt is hung and a pressure welding roller are provided.
The transfer belt comes into contact with the image holder in the section from the transfer roller to the pressure welding roller.

The image forming apparatus according to claim 7 is
At least an image holder whose peripheral surface circulates and holds an image on the peripheral surface,
A former that forms an image on the peripheral surface of the image holder,
A transfer member in which at least the peripheral surface circulates and passes through a transfer region between the image holder and the image holder so that the image on the image holder is transferred to the recording material.
A moving mechanism that continuously reduces the relative distance between the transfer member and the image holder before and after passing the tip of the recording material with respect to the transfer region.
Equipped with a,
The surfaces of the transfer member and the image holder are in contact with each other before passing through the tip of the recording material .

According to the transfer device according to claim 1 and the image forming device according to claim 7, the image holder due to the entry into the transfer region of the recording material is compared with the case where the nip load is changed after passing through the transfer region at the end of the recording material. Vibration can be suppressed.

According to the transfer device according to claim 2, vibration when passing through the tip can be suppressed.

According to the transfer device according to claim 3, vibration when passing through the rear end can be suppressed.

According to the transfer device according to claim 4, both the vibration when passing through the front end and the vibration when passing through the rear end can be suppressed.

According to the transfer device according to claim 5, it is easier to control the start of movement as compared with the case where the detector is not provided.

According to the transfer device according to claim 6, the vibration suppressing effect is higher than that in the case of moving the transfer device at a slow speed regardless of the thickness.

It is a schematic block diagram of the image forming apparatus corresponding to one Embodiment of this invention. It is a figure which conceptually shows the vibration accompanying the impact that the edge of a paper passed through a transfer region. It is a graph which conceptually shows the control for suppressing the vibration by an impact. It is a graph which conceptually shows the distance control on a thick paper. It is a flowchart which shows the control procedure of a nip load.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image forming apparatus corresponding to an embodiment of the present invention.

The image forming apparatus 1 is a so-called direct transfer type monochrome printer.

The image forming apparatus 1 includes a photoconductor drum 10. The photoconductor drum 10 is rotatably supported by the drum support frame 10A, and is driven by the photoconductor motor 16 to rotate in the direction of arrow A. A charger 11, an exposure device 12, and a developer 13 are provided around the photoconductor drum 10. Then, a toner image is formed on the surface of the photoconductor drum 10 through each process of charging by the charger 11, exposure by the exposure device 12, and development by the developer 13, and the toner image is displayed on the photoconductor drum 10. Be retained.

Here, the exposure device 12 exposes the photoconductor drum 10 according to the image data sent from the outside of the image forming apparatus 1, and the image represented by the image data is formed on the photoconductor drum 10 as a toner image. In order to ensure the accuracy of such exposure, the photoconductor drum 10 is driven by the photoconductor motor 16 at a stable rotation speed. In order to realize such a stable rotation speed, the photoconductor motor 16 is supplied with electric power by constant current control. Since the photoconductor motor 16 drives the photoconductor drum 10 by receiving electric power under constant current control, the drive of the photoconductor drum 10 is stable even when the external force on the photoconductor drum 10 changes. There is. The photoconductor drum 10 corresponds to an example of an image holder according to the present invention, and a combination of a charger 11, an exposure device 12, and a developer 13 corresponds to an example of a forming device according to the present invention.

On the other hand, paper P (so-called cut paper), which is a kind of recording material, is conveyed in the direction of arrow X by a paper carrier (not shown), and the transfer region T sandwiched between the photoconductor drum 10 and the transfer device 20 described later is formed. pass. Then, the toner image on the photoconductor drum 10 is transferred onto the paper P while passing through the transfer region T. The image forming apparatus 1 of the present embodiment is an apparatus capable of supporting a plurality of types of paper P, and information indicating the size and thickness of the paper P supplied to the image forming apparatus 1 is input in advance by an input operating means (not shown). It is assumed that it has been done.

The edge of the paper P conveyed to the transfer region T is detected by the paper edge detection sensor 42. The paper edge detection sensor 42 is, for example, an optical sensor or a contact sensor, and detects the passage of the front edge and the rear edge of the paper. The paper edge detection sensor 42 corresponds to an example of the detector according to the present invention.

The remaining toner on the photoconductor drum 10 after the toner image is transferred in the transfer region T is removed from the photoconductor drum 10 by the cleaner 14.

The paper P to which the toner image has been transferred in the transfer region T is further conveyed in the direction of the arrow Y and sent to the fixing device 30. The fixing device 30 includes a heating roller 31 that rotates in the direction of arrow D and a pressure roller 32 that rotates in the direction of arrow E. The heating roller 31 and the pressure roller 32 are in contact with each other to form a fixing region S. The paper P traveling in the direction of the arrow Y rushes into the fixing region S, and is heated and pressurized while passing through the fixing region S, and the toner image on the paper P is fixed on the paper P. As a result of this fixing, an image consisting of a fixing toner image is formed on the paper P. The paper P on which the image is formed is sent out to the outside of the image forming apparatus 1 by a paper transmitter (not shown).

The transfer device 20 corresponds to an embodiment of the transfer device of the present invention, and includes a transfer roller 21, a pressure welding roller 22, a peeling roller 23, and an endless transfer belt 24 hung around the rollers. There is. The transfer roller 21, the pressure welding roller 22, and the release roller 23 are rotatably supported by the transfer device support frame 20A.

The transfer roller 21 is driven by the transfer motor 213 and rotates in the direction of the arrow B to drive the transfer belt 24. The drive by the transfer motor 213 is also performed under constant voltage control. The transfer belt 24 is a resin belt having low elasticity, and is circulated and moved in the direction of arrow C by receiving a driving force by the transfer roller 21. The transfer belt 24 corresponds to an example of the transfer member referred to in the present invention.

The transfer roller 21 is located upstream of the rotation center axis of the photoconductor drum 10 in the paper traveling direction, and presses the transfer belt 24 against the photoconductor drum 10 from the inside of the transfer belt 24. The transfer roller 21 defines the upstream edge of the transfer region T in which the photoconductor drum 10 and the transfer belt 24 are in contact with each other.

Further, the pressure contact roller 22 is located on the downstream side in the paper traveling direction with respect to the rotation center axis of the photoconductor drum 10, and pushes the transfer belt 24 toward the photoconductor drum 10 from the inside of the transfer belt 24. The pressure welding roller 22 defines the downstream edge of the transfer region T.

Further, the peeling roller 23 is a roller having a smaller diameter than the transfer roller 21, and the paper is placed on the transfer belt 24 by sharply bending the traveling direction of the transfer belt 24 by the peeling roller 23. The tip of P is peeled off from the transfer belt 24. The paper P peeled off from the transfer belt 24 is guided by the guide member 41 and proceeds in the direction of the arrow Y, and is sent to the fixing device 30 as described above.

Further, the transfer device 20 includes a cleaner 25. Toner and other stains adhering to the transfer belt 24 are removed from the transfer belt 24 by the cleaner 25.

The transfer roller 21 is connected to a power source (not shown), and a transfer bias is applied to the transfer roller 21 from the power source. Due to the action of the transfer bias, the toner image on the photoconductor drum 10 is transferred onto the paper P while the paper P passes through the transfer region T.

The transfer roller 21 has a rotating shaft 211, and the rotating shaft 211 is rotatably supported by a shaft support frame 212. The shaft support frame 212 is vertically and vertically supported by a transfer device support frame 20A that supports the entire transfer device 20.

Between the shaft support frame 212 and the drum support frame 10A, a push spring 214 for urging the shaft support frame 212 in a direction away from the drum support frame 10A is provided. Further, the transfer device 20 is also provided with an eccentric cam 215 whose rotation axis is rotatably supported by the transfer device support frame 20A. The eccentric cam 215 holds the shaft support frame 212 against the urging force of the push spring 214, and the rotation of the eccentric cam 215 changes the position of the shaft support frame 212. FIG. 1 shows a pressed state in which the transfer roller 21 presses the transfer belt 24 against the photoconductor drum 10 when the shaft support frame 212 is pushed by the eccentric cam 215. When the eccentric cam 215 rotates half a turn around the rotation axis from the state shown in FIG. 1, the shaft support frame 212 is pushed downward by the urging force of the push spring 214, and the transfer roller 21 and the transfer belt 24 are exposed to light. The body drum 10 is separated from the body drum 10. That is, the rotation of the eccentric cam 215 causes the transfer roller 21 and the transfer belt 24 to change the relative distance to the photoconductor drum 10. Due to such a change in the relative distance, the nip load, which is the load at which the paper P is sandwiched (nipped) between the photoconductor drum 10 and the transfer belt 24 in the transfer region T, changes.

The relative distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is also realized by moving the photoconductor drum 10, but due to the difference in the complexity of the peripheral structure, the transfer roller 21 and the transfer belt 24 are exposed to light. It is more realistic to move it with respect to the body drum 10.

The transfer device 20 is provided with a control unit 29 which is a kind of information processing device including a CPU as an arithmetic element and a RAM or ROM as a storage element, and the control unit 29 rotates the eccentric cam 215. The drive of the transfer motor 213 and the like are controlled. The mechanism in which the control unit 29, the shaft support frame 212, the push spring 214, and the eccentric cam 215 are combined corresponds to an example of the moving mechanism referred to in the present invention.

As described above, the paper P rushes into the transfer region T at the time of image formation, but when the relative distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is constant, the paper P rushes into the paper P. An impact force that pushes the photoconductor drum 10 and the transfer roller 21 and the transfer belt 24 open is generated, and such an impact force may cause the photoconductor drum 10 to vibrate in the vertical direction shown in the figure. The vibration may cause an image defect when forming an image on the photoconductor drum 10 or transferring an image from the photoconductor drum 10 onto the paper P. Further, such vibration may occur not only when the paper P rushes into the transfer region T but also when the paper P comes out (passes) from the transfer region T. That is, when the edges of the paper P (each of the front edge and the rear edge) pass through the transfer region T, vibration due to the impact may occur.

FIG. 2 is a diagram conceptually showing the vibration caused by the impact of the end portion of the paper P passing through the transfer region T.

The horizontal axis of FIG. 2 represents the elapsed time, and FIG. 2 shows a graph G1 showing the set value of the nip load and a graph G2 showing the fluctuation of the load (nip load) actually occurring in the transfer region T. ing.

The “transfer nip plunge” line shown in FIG. 2 represents the time when the paper P has plunged into the transfer region T (that is, the tip of the paper P has passed through the transfer region T), and is shown in FIG. The line of "passing through the transfer nip" represents the time when the paper P has passed through the transfer region T and exited (that is, the rear end of the paper P has passed through the transfer region T).

The graph G1 of the nip load shown in FIG. 2 shows that the set value of the nip load is constant before and after the paper P enters the transfer region T. The set value of the nip load is actually the relative distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10, and is the rotation angle of the eccentric cam 215. That is, in the case shown in FIG. 2, the rotation angle of the eccentric cam 215 (see FIG. 1) is constant from the entry into the transfer region T of the paper P to the passage.

When the paper P rushes into the transfer region T while the set value of the nip load is constant in this way, a large load fluctuation ΔF1 occurs immediately after the rushing, as shown in the load fluctuation graph G2. Further, immediately after the paper P is removed from the transfer region T, a large load fluctuation ΔF2 occurs.

These large load fluctuations ΔF1 and ΔF2 represent the vibration of the photoconductor drum 10 due to the above-mentioned impact force.

In order to suppress such large load fluctuations ΔF1 and ΔF2, in the image forming apparatus 1 shown in FIG. 1, when the edge portions (front end and rear end respectively) of the paper P enter the transfer region T, the following As described, the relative distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is controlled.

FIG. 3 is a graph conceptually showing the control for suppressing the vibration due to the impact.

The horizontal axis of FIG. 3 represents the elapsed time, and FIG. 3 shows the graph G3 showing the detection signal of the paper edge detection sensor 42 (see FIG. 1), the graph G4 showing the set value of the nip load, and the fluctuation of the nip load. The graph G5 showing the above is shown.

In the case shown in FIG. 3, when the tip of the paper P is detected as shown by the rising edge of the detection signal graph G3, the nip load set value starts to increase as shown by the nip load graph G4. That is, the eccentric cam 215 starts rotating when the tip of the paper P is detected, and the transfer roller 21 and the transfer belt 24 start to approach the photoconductor drum 10. Such tip detection is performed at a time point before the time point of "transfer nip entry" in which the tip edge of the paper P passes through the transfer region T.

Then, the eccentric cam 215 continues to rotate from before the tip of the paper P enters the transfer region T to after the entry, and the transfer roller 21 and the transfer belt 24 continue to approach the photoconductor drum 10. As a result, the transfer roller 21 and the transfer belt 24 continuously approach the photoconductor drum 10 before and after the tip of the paper P passes through the transfer region T. After that, when the distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 reaches a predetermined distance (that is, the eccentric cam 215 reaches a predetermined angle), the rotation of the eccentric cam 215 stops. The movement of the transfer roller 21 and the transfer belt 24 is also stopped.

As described above, the distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is continuously narrowed before and after the tip of the paper P passes through the transfer region T, so that the load fluctuation graph G5 shows. In addition, load fluctuations caused by plunging the tip of the paper P are suppressed. That is, the tip of the paper P that rushes into the transfer region T is called into the transfer region T so as to be sandwiched between the photoconductor drum 10 and the transfer belt 24 that bring the distances closer to each other, so that the impact of the tip rush is weakened. Further, by continuously bringing the photoconductor drum 10 and the transfer belt 24 closer to each other even after the tip is inserted, the vibration induced by the weakened impact is suppressed, and the above-mentioned load fluctuation is greatly suppressed. become.

On the other hand, when the rear end of the paper P is detected as shown by the falling edge of the detection signal graph G3, the nip load set value starts to decrease as shown by the nip load graph G4. That is, the eccentric cam 215 starts rotating with the detection of the rear end of the paper P, and the transfer roller 21 and the transfer belt 24 start to separate from the photoconductor drum 10. Such detection of the rear end is performed at a time point before the time point of "passing through the transfer nip" at which the rear end of the paper P passes through the transfer region T.

Then, the eccentric cam 215 continues to rotate from before the rear end of the paper P enters the transfer region T to after the entry, and the transfer roller 21 and the transfer belt 24 continue to deviate from the photoconductor drum 10. As a result, the transfer roller 21 and the transfer belt 24 are continuously separated from the photoconductor drum 10 before and after the rear end of the paper P passes through the transfer region T. After that, when the distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 reaches a predetermined distance (that is, the eccentric cam 215 reaches a predetermined angle), the rotation of the eccentric cam 215 stops. The movement of the transfer roller 21 and the transfer belt 24 is also stopped.

As described above, the load fluctuation graph G5 shows that the distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is continuously increased before and after the rear end of the paper P passes through the transfer region T. As described above, the load fluctuation generated when the paper P passes through the rear end is suppressed. That is, the paper P that comes out of the transfer region T is guided to the outside of the transfer region T by the photoconductor drum 10 and the transfer belt 24 that widen the mutual distance, so that the impact due to passing through the rear end is weakened. Further, by continuously separating the photoconductor drum 10 and the transfer belt 24 from each other even after passing through the rear end, the weakened impact is further released and the vibration is suppressed, and the above-mentioned load fluctuation is greatly suppressed. Will be done.

It is desirable that the distance control of the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 before and after passing through the transfer region T at the end of the paper P as described above is controlled according to the rigidity of the paper P. This is because the vibration of the photoconductor drum 10 accompanying the passage of the transfer region T at the end of the paper P is stronger as the rigidity of the paper P is higher. However, if there is no significant difference in the materials of the paper P, the thicker the paper P, the higher the rigidity of the paper P. Therefore, in the present embodiment, the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 The distance control is controlled according to the thickness of the paper P.

FIG. 4 is a graph conceptually showing distance control on thick paper P.

The horizontal axis of FIG. 4 represents the elapsed time, and FIG. 4 shows the graph G3 showing the detection signal of the paper edge detection sensor 42 (see FIG. 1), the graph G6 showing the set value of the nip load, and the fluctuation of the nip load. The graph G7 showing is shown. The detection signal graph G3 shown in FIG. 4 is a graph equivalent to the detection signal graph G3 shown in FIG.

Also in the case shown in FIG. 4, when the tip of the paper P is detected as shown by the rising edge of the detection signal graph G3, the nip load set value is started to increase and set as shown by the nip load graph G6. The increase of the value is continuously continued before and after the tip of the paper P passes through the transfer region T. Further, when the rear end of the paper P is detected as shown by the falling edge of the detection signal graph G3, the nip load set value starts to decrease as shown by the nip load graph G6, and the set value decreases. , The rear edge of the paper P is continuously continued before and after passing through the transfer region T.

However, in the case shown in FIG. 4, the speed of increase / decrease of the set value is slower than in the case shown in FIG. That is, in the present embodiment, the distance variation of the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10 is performed more gently as the rigidity of the paper P increases (that is, as the thickness increases). As a result, as shown in the load fluctuation graph G7, the vibration of the photoconductor drum 10 is suppressed, and the suppressing action against the vibration of the photoconductor drum 10 is constant with respect to the photoconductor drum 10 regardless of the thickness of the paper P. It is higher than the case where the distance between the transfer roller 21 and the transfer belt 24 fluctuates.

FIG. 5 is a flowchart showing a procedure for controlling the distance between the transfer roller 21 and the transfer belt 24 (that is, controlling the nip load) with respect to the photoconductor drum 10.

In the flowchart shown in FIG. 5, it is assumed that two types of thickness paper P are used as an example. Further, in the flowchart shown in FIG. 5, it is assumed that the change in the nip load is synonymous with the change in the distance between the transfer roller 21 and the transfer belt 24 with respect to the photoconductor drum 10.

The control shown in the flowchart of FIG. 5 is executed every time the paper P is conveyed toward the transfer region T, and when this control is started, the thickness of the paper P conveyed this time is determined. (Step S101).

When it is determined that the paper P this time is the thicker of the above-mentioned two types of paper (step S101: Y), the process proceeds to step S102, and the nip load is predetermined. It is set to the first standby load. Then, in step S103, the standby state is set until the tip of the paper P is detected by the paper edge detection sensor 42.

After that, when the tip of the paper P is detected by the paper edge detection sensor 42 (step S103: Y), the nip load is increased (step S104). However, the increase in the nip load in this case is a gradual increase as compared with the case where the thickness of the paper P is thin. Then, the increase of the nip load is continued until the nip load reaches a predetermined load for image transfer (steps S104 and S105). While the nip load continues to increase in this way, the tip of the paper P passes through the transfer region T (see FIG. 1).

When the nip load reaches the image transfer load as a result of the continuous increase of the nip load (step S105: Y), the nip load is fixed to the image transfer load (step S106).

After that, in step S107, the standby state is set until the rear edge of the paper P is detected by the paper edge detection sensor 42.

When the rear edge of the paper P is detected by the paper edge detection sensor 42 (step S107: Y), the nip load is reduced (step S108). This nip load decrease is also a gradual increase as compared with the case where the thickness of the paper P is thin. Then, the nip load continues to decrease until the nip load reaches the first standby load described above (steps S108 and S109). While the nip load continues to decrease in this way, the rear edge of the paper P passes through the transfer region T (see FIG. 1).

When the nip load reaches the first standby load as a result of the continuous reduction of the nip load (step S109: Y), the nip load is fixed to the first standby load (step S110), and the control of FIG. 5 is controlled. finish.

On the other hand, if it is determined in the determination in step S101 that the paper P this time is the thinner of the two types of paper described above (step S101: N), the process proceeds to step S111. , The nip load is set to a predetermined second standby load. Then, in step S112, the state of standby is reached until the tip of the paper P is detected by the paper edge detection sensor 42.

After that, when the tip of the paper P is detected by the paper edge detection sensor 42 (step S112: Y), the nip load is increased (step S113). However, the increase in the nip load in this case is a sharp increase as compared with the case where the thickness of the paper P is thick. Then, the increase of the nip load is continued until the nip load reaches a predetermined load for image transfer (steps S113 and S114). While the nip load continues to increase in this way, the tip of the paper P passes through the transfer region T (see FIG. 1).

When the nip load reaches the image transfer load as a result of the continuous increase of the nip load (step S114: Y), the nip load is fixed to the image transfer load (step S115).

After that, in step S116, the standby state is set until the rear end of the paper P is detected by the paper edge detection sensor 42.

When the rear edge of the paper P is detected by the paper edge detection sensor 42 (step S116: Y), the nip load is reduced (step S117). This decrease in nip load is also a sharp increase as compared with the case where the thickness of the paper P is thick. Then, the nip load continues to decrease until the nip load reaches the second standby load described above (steps S117 and S118). While the nip load continues to decrease in this way, the rear edge of the paper P passes through the transfer region T (see FIG. 1).

When the nip load reaches the second standby load as a result of the continuous reduction of the nip load (step S118: Y), the nip load is fixed to the second standby load (step S119), and the control of FIG. 5 is controlled. finish.

By the control represented by the flowchart described above, the control shown in FIGS. 3 and 4 is realized.

In the flowchart of FIG. 5, control is performed according to the thickness of the paper P. However, when a plurality of types of paper P having different sizes are used, the paper P having a short paper length is shown in FIG. There is a possibility that the change in the nip load as shown in FIG. 4 may not be in time for the passage of the paper P. Therefore, for the paper P having a short paper length, a control mode is conceivable in which the nip load is changed earlier than that of the paper P having a long paper length so that the load change is in time for the passage of the paper P. In the transfer device and the image forming device of the present invention, such a control mode may be adopted.

Further, in the above description, a roll-shaped photoconductor drum is shown as an example of the image-retaining body according to the present invention, but the image-retaining body according to the present invention may be a belt-shaped, for example, an intermediate transfer body. good.

Further, in the above description, the belt-shaped member is exemplified as the transfer member referred to in the present invention, but the transfer member referred to in the present invention may be a roll-shaped member.

Further, in the above description, a monochrome printer is exemplified as an embodiment of the image forming apparatus of the present invention, but the image forming apparatus of the present invention may be a color printer, or may be a copying machine, a facsimile, or a multifunction device. There may be.

Further, in the above description, a direct transfer type apparatus is exemplified as an embodiment of the image forming apparatus of the present invention, but in the image forming apparatus of the present invention, an image is transferred from a photoconductor to a recording material via an intermediate transfer body. It may be an indirect transfer type device to be used. In the case of such an indirect transfer type device, the transfer device of the present invention is applied to a place where an image is secondarily transferred from an intermediate transfer body to a recording material.

Further, the transfer member and the image holder referred to in the present invention may be in contact with each other or may have a gap between them before the recording material enters the transfer region. ..

Further, the present invention has been invented for the purpose of solving the problems described in the "problems to be solved by the invention" column, but the configuration of the present invention is other in a form that does not solve this problems. Diversion to the intended purpose is not hindered, and a form in which the configuration of the present invention is diverted in this way is also an embodiment of the present invention.

1 ... Image forming device (printer), 10 ... Photoreceptor, 11 ... Charger, 12 ... Exposed device,
13 ... Developer, 16 ... Photoreceptor motor, 20 ... Transfer device, 21 ... Transfer roller,
24 ... Transfer belt, 212 ... Shaft support frame, 213 ... Transfer motor,
214 ... Push spring, 215 ... Eccentric cam, 29 ... Control unit, 30 ... Fixing device,
42 …… Paper edge detection sensor

Claims (7)

At least an image holder whose peripheral surface circulates and holds an image on the peripheral surface,
A transfer member in which at least the peripheral surface circulates and passes through a transfer region between the image holder and the image holder so that the image on the image holder is transferred to the recording material.
A moving mechanism that continuously reduces the relative distance between the transfer member and the image holder before and after passing the tip of the recording material with respect to the transfer region.
Equipped with a,
A transfer device characterized in that the transfer member and the image holder are in contact with each other before passing through the tip of the recording material. The transfer device according to claim 1, wherein the moving mechanism moves the position of the transfer member with respect to the image holder. The transfer device according to claim 1, wherein the moving mechanism continuously increases the relative distance before and after passing the rear end of the recording material with respect to the transfer region. A detector is provided for detecting the end portion of the recording material toward the transfer region before entering the transfer region.
Any of claims 1 to 3, wherein the moving mechanism starts a change in the relative distance between the transfer member and the image holder when the detector detects the end portion. The transfer device according to item 1. Any of claims 1 to 4, wherein the moving mechanism gradually changes the relative distance between the transfer member and the image holder according to the thickness of the recording material. The transfer apparatus according to claim 1. The transfer member is a transfer belt.
A transfer roller around which the transfer belt is hung and a pressure welding roller are provided.
The transfer device according to any one of claims 1 to 5, wherein the transfer belt comes into contact with the image holder in a section from the transfer roller to the pressure contact roller. At least an image holder whose peripheral surface circulates and holds an image on the peripheral surface,
A former that forms an image on the peripheral surface of the image holder,
A transfer member in which at least the peripheral surface circulates and passes through a transfer region between the image holder and the image holder so that the image on the image holder is transferred to the recording material.
A moving mechanism that continuously reduces the relative distance between the transfer member and the image holder before and after passing the tip of the recording material with respect to the transfer region.
Equipped with a,
An image forming apparatus characterized in that the transfer member and the image holder are in contact with each other before passing through the tip of the recording material.

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