JP4084517B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, an LED printer, and a plain paper facsimile machine using an electrophotographic process, and particularly supports a transfer roller for transferring a visible image on a photoreceptor onto a transfer material. The present invention relates to an improved structure and a structure of a transfer entrance guide for guiding a transfer material to a transfer position.
[0002]
[Prior art]
In an image forming apparatus using an electrophotographic process, an electrostatic latent image is formed by irradiating a photoconductor uniformly charged in advance with optical image information such as reflected light of an original, and this electrostatic image is formed. A visible image is formed by supplying toner from the developing device to the latent image. Then, the transfer material is supplied from the registration roller to the transfer position in accordance with the timing when the visible image reaches the transfer position by the rotation of the photosensitive member, and the transfer bias voltage from the transfer device such as the transfer roller disposed opposite to the transfer position The visible image on the photoreceptor is electrostatically transferred onto the transfer material by application.
Recently, as a transfer device, a transfer roller system in which a transfer bias is applied to a transfer material via a roller-shaped transfer member, instead of a corona discharge transfer device having a problem such as ozone generation, tends to be frequently used. In an image forming apparatus using a transfer roller as a consumable, transfer is performed several times before the end of the life of the apparatus body in order to cope with the high durability of the apparatus body including related parts involved in image formation. The roller needs to be replaced. This is because the life of the transfer roller subjected to wear is shorter than the life of the apparatus main body.
Incidentally, a transfer inlet guide is disposed along the conveyance path immediately upstream of the nip portion in order to reliably guide the transfer material to the nip portion between the photosensitive member and the transfer roller. If the position of the transfer entrance guide is too far from the nip portion, the guide function is not sufficiently exerted, and the leading edge of the transfer material is guided to the nip portion while contacting the front surface of the nip portion of the transfer roller. This causes a problem that the toner scatters during the transfer. In order to eliminate such problems, if the transfer inlet guide is brought close to the nip portion and the leading edge of the transfer paper is guided directly to the nip portion, screws or hooks for fixing the transfer inlet guide to the apparatus main body are transferred to the transfer roller. Therefore, it is necessary to remove these screws in advance when replacing the transfer roller, which complicates the work.
In order to eliminate such a problem, as shown in FIG. 5, the transfer roller 1 and the transfer inlet guide 2 having the rotation center on the shaft 1a are integrated as a transfer unit, so that the transfer is performed when the transfer roller is replaced. A method has been proposed in which the inlet guide 2 is also removed and replaced. That is, the support structure of the transfer roller 1 shown in FIG. 5 is arranged in the gap between the two fixed guides 4 fixedly erected on the base frame 3 fixed to the apparatus main body and the two fixed guides 4. The transfer bearing member 5 is supported in a vertically movable manner, the elastic member 6 elastically biases the transfer bearing member upward (toward the photosensitive drum 7), and the bearing recess 5a provided in the transfer bearing member 5. And a transfer inlet guide 2 that rotates about a transfer roller shaft 1a that is freely and rotatably supported. The transfer entrance guide 2 includes a guide plate 2a having a longitudinal length substantially equal to the longitudinal direction of the photosensitive drum 7, a side plate 2b formed by bending from both longitudinal ends of the guide plate 2a, and each side plate 2b. It has a hole 2c that is formed so as to penetrate and freely fit into the transfer roller shaft 1a.
Since the guide plate 2a of the transfer entrance guide 2 extends to the vicinity of the transfer nip portion N, the leading end portion of the transfer paper supplied by a resist roller (not shown) can be directly guided to the transfer nip portion. Further, the assembly of the transfer unit and the positioning of the transfer roller 1 and the transfer inlet guide 2 are easy.
However, since the transfer roller 1 and the transfer inlet guide 2 are integrated, there arises a problem that the cost of the transfer unit is increased.
[0003]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to improve the assembly structure of a transfer roller for transferring a visible image on a photoreceptor onto a transfer material and a transfer entrance guide for guiding the transfer material to a transfer position. According to another aspect of the present invention, there is provided an image forming apparatus in which only the transfer roller can be removed without removing the transfer entrance guide in the transfer device in which the transfer entrance guide is extended to the position closest to the transfer nip portion. The purpose is to do.
It is an object of the present invention to facilitate the removal of the transfer roller by automatically projecting from the fixed guide when the photosensitive drum (photosensitive unit) is removed to replace the transfer roller.
A third object of the present invention is to prevent the transfer roller from protruding from the fixed guide when the photosensitive drum (photosensitive unit) is removed when the transfer roller is not replaced.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a process for transferring a visible image formed on an image carrier by an electrophotographic process to a transfer material supplied to a nip portion between the image carrier and a transfer device. An image forming apparatus comprising: a transfer roller that applies a transfer bias to a visible image on the image carrier via a transfer material; a transfer inlet guide that guides the transfer material to the nip portion; A transfer bearing member that detachably and rotatably supports the shaft end portions at both ends of the transfer roller, a fixed guide that supports the transfer bearing member so as to be able to advance and retreat in the vertical direction, and the transfer bearing member is always elastic toward the image carrier. A transfer bearing member main body having a recess for rotatably and detachably supporting each shaft end portion of the transfer roller, and a side from the transfer bearing member main body. Protruding toward The transfer inlet guide has a guide plate that guides the transfer paper on the upper surface, and a hole that is formed in both side walls in the longitudinal direction of the guide plate and loosely fits the rotation shaft, The hole is supported so as to be pivotable in the vertical direction by fitting the hole into the pivot shaft.
According to a second aspect of the present invention, the transfer entrance guide is applied with a force for rotating the guide plate in a direction away from the nip portion about the rotation axis by an elastic biasing force or its own weight. It has a projecting piece for determining the installation angle of the transfer entrance guide, and the projecting piece abuts on the upper surface of the base frame that supports the bottom of the fixed guide.
According to a third aspect of the present invention, there is provided a snap fit for restricting the transfer inlet guide from rotating in a direction away from the nip portion.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIG. 1A is a perspective view showing the overall configuration of a transfer apparatus according to an embodiment of the present invention, FIG. 1B is an exploded perspective view of the main part thereof, FIG. 1C is an exploded view of the main part, and FIG. It is a front view which shows a state.
The transfer device 11 according to the present invention transfers a visible image formed on a photosensitive drum (image carrier) 30 by an electrophotographic process to a nip portion N between the photosensitive drum 30 and the transfer device 11. The present invention is applied to an image forming apparatus provided with a process for transferring to a sheet.
The transfer device 11 includes a transfer roller 12 that applies a transfer bias voltage to a visible image on the photosensitive drum 30 via a transfer material, a transfer inlet guide 13 that guides the transfer material to the nip portion N, and shafts at both ends of the transfer roller 12. A transfer bearing member 15 that detachably and rotatably supports the end portion 12a, a fixed guide 20 that supports the transfer bearing member 15 so as to be able to advance and retreat in the vertical direction, and the transfer bearing member 15 is always elastic toward the photosensitive drum 30. And an elastic member 25 to be urged.
The transfer bearing member 15 has a transfer bearing member main body 16 provided with a recess 16a that rotatably and detachably supports each shaft end portion 12a of the transfer roller 12, and the transfer bearing member main body 16 protrudes laterally inwardly. A rotation shaft 17.
The transfer inlet guide 13 has a guide plate 18 that guides the transfer paper on the upper surface, and a hole 19a that is formed in the longitudinal side wall 19 of the guide plate 18 and loosely fits the rotation shaft 17, and the hole 19a. The transfer entrance guide 13 can be rotated in the vertical direction as a whole by fitting it to the rotation shaft 17.
[0006]
The fixed guide 20 protruding on the base frame 21 having a flat upper surface at a predetermined interval moves the transfer bearing member 15 up and down in the vertical direction (direction to move back and forth toward the photosensitive drum) at its inner edge. Support freely. An inverted U-shaped frame 22 protrudes from the base frame 21 at an outer position corresponding to the gap between the two fixed guides 20, and a protrusion 21 a is formed on the base frame at an inner position of the frame 22. And a lower end portion of a coil spring as the elastic member 25 is locked to the protrusion 21a. The transfer bearing member 15 supported between the fixed guides 20 is close to the inner position of the frame 22, and a protrusion 16 b provided at the lower end of the transfer bearing member main body 16 locks the upper end of the coil spring 25. ing. For this reason, the transfer bearing member 15 is constantly urged upward by the coil spring 25 while being supported between the fixed guides 20 so as to be movable up and down. Further, a protrusion-like stopper 16 c protrudes at a suitable position on the outer surface of the transfer bearing member main body 16, and this stopper 16 c protrudes between the two columns 22 a of the frame body 22. For this reason, the position at which the stopper 16 c contacts the upper side 22 b of the frame body 22 determines the upper limit position of the transfer bearing member 15. In other words, the transfer bearing member 15 cannot move upward beyond the position where the stopper 16c contacts the upper side 22b of the frame.
The shaft end 12a of the transfer roller 12 is rotatably supported in the recess 16a of the transfer bearing member 15 supported between the fixed guides 20.
The transfer inlet guide 13 is centered on the rotation shaft 17 by loosely fitting the rotation shaft 17 projecting horizontally from the inner surface of the transfer bearing member 15 into a hole 19a formed in the longitudinal side wall 19 of the guide plate 18. And turn up and down.
A substantially V-shaped plate-shaped projecting piece 18A having an R-shaped tip is provided obliquely (in the state shown in FIG. 2) from an appropriate position on the lower surface of the guide plate 18 of the transfer inlet guide 13, and the tip of the base-frame 21 It is in contact with the upper surface of. When the transfer roller 12 is pushed downward by setting the photosensitive drum 30 to the mounting position as shown in FIG. 2, the transfer is performed by the cooperation of the rotating shaft 17, the elastic member 25, the projecting piece 18A, and the like. The inlet guide 13 is generally rotated upward (counterclockwise), and in this state, the end 18a of the guide plate 18 is closest to the transfer nip N, and is fed from a registration roller (not shown). The transferred transfer material can be directly supplied to the transfer nip portion N. At this time, the protruding piece 18A is elastically pressed onto the base frame 21 by the force of the elastic member 25 in a state of being retracted to the outside (rightward in FIG. 2) from the axial center position of the transfer roller 12. The posture can be maintained. In this state, the transfer roller having the shaft end seated in the recess 16a cannot be removed upward due to the transfer entrance guide.
This structure is similarly arranged at both ends in the longitudinal direction of the transfer inlet guide 13.
[0007]
FIG. 3 is a view showing a state in which the photosensitive drum 30 is removed from the mounting position. Since the downward pressing force from the photosensitive drum 30 to the transfer roller 12 is released, FIG. 2 shows a compressed state. The elastic member 25 according to the above is opened and expanded. For this reason, the elastic member 25 pushes up the transfer bearing member 15 and the transfer roller 12 upward. Since the stopper 16c provided on the transfer bearing member 15 protrudes to a position in contact with the upper side 22b of the frame 22, the transfer bearing member 15 cannot protrude upward beyond the upper limit position shown in FIG. Further, in the process of shifting from the state of FIG. 2 to the state of FIG. 3, the transfer inlet guide 13 rotatably supported by the rotation shaft 17 of the transfer bearing member 15 rotates clockwise, and the end of the guide plate 18 is rotated. The portion 18 a is separated from the position of the transfer nip portion N. Therefore, in this state, the transfer roller 12 can be separated upward from the recess 16a without being obstructed by the transfer inlet guide 13. Note that the elastic member 25 may be rotated clockwise by the weight of the transfer inlet guide 13 regardless of the upward spring force of the elastic member 25.
In this way, the rotation center of the transfer inlet guide 13 moves up and down as the transfer bearing member 15 moves up and down, and the guide plate 18 moves away from the transfer nip portion around the rotation shaft 17 by the elastic biasing force or its own weight. Then, a force is applied to rotate the transfer roller in a direction in which the transfer roller can be removed, and a protruding piece 18A for determining the installation angle of the transfer inlet guide contacts the upper surface of the base frame 21 that supports the bottom of the fixed guide 20. . Therefore, the transfer entrance guide 13 can be rotated between the position shown in FIG. 2 and the position shown in FIG.
Next, FIG. 4 is a diagram for explaining the configuration of another embodiment of the present invention. The difference of this embodiment from the above embodiment is that the rotation of the transfer inlet guide 13 on the base frame 21 in the clockwise direction is restricted. The snap fit 40 that is an elastic member is disposed. The snap fit 40 protrudes on the base frame in order to restrict the transfer entrance guide 13 from rotating in the clockwise direction (removal direction) from the illustrated sheet passing allowable position regardless of whether or not the photosensitive member 30 is mounted. It is an elastic member provided. As a result of providing the snap fit 40, the transfer roller is prevented from protruding from the fixed guide 20 (the elastic member 25 is expanded) when the photosensitive unit or the like is removed without replacing the transfer roller. For this reason, it is possible to eliminate problems such as the transfer roller protruding against the operator's intention and the subsequent workability being lowered.
Further, the snap fit 40 has, for example, a column part 41 projecting from the upper surface of the base frame 21 and a projecting part 42 projecting laterally from an appropriate position above the column part 41 to support an appropriate position of the transfer inlet guide 13. Since the column part 41 is made of an elastic material such as a leaf spring, resin, rubber, etc. so as to be elastically deformed as a whole, the elastic member 25 is expanded by retracting it in the deformation direction indicated by an arrow by hand. It is also possible to allow the transfer roller to protrude as shown in FIG. That is, the replacement work can be performed without any problem even when the transfer roller is replaced.
[0008]
【The invention's effect】
As described above, according to the present invention, the transfer device has a structure in which the transfer roller for transferring the visible image on the photosensitive member onto the transfer material and the transfer inlet guide for guiding the transfer material to the transfer position are assembled. In the type in which the transfer entrance guide is extended to the position closest to the transfer nip portion, only the transfer roller can be removed without removing the transfer entrance guide. Therefore, it is possible to improve the efficiency of the attaching / detaching work accompanying the replacement of the transfer roller.
In addition, when the photosensitive drum (photosensitive unit) is removed to replace the transfer roller, the transfer roller automatically protrudes from the fixed guide, so that the removal is easy, so that the workability is further improved.
Further, when the transfer roller is not replaced, it is possible to prevent the transfer roller from protruding from the fixed guide when the photosensitive drum (photosensitive unit) is removed, which is convenient in an operation not involving replacement of the transfer roller. In addition, when the replacement is performed, the transfer roller can be protruded by a simple operation.
[Brief description of the drawings]
FIGS. 1A, 1B, and 1C are perspective views showing a configuration of a transfer apparatus according to an embodiment of the present invention. The exploded perspective view of the principal part, The principal part block diagram.
FIG. 2 is a front view showing a main configuration of a transfer apparatus according to the present invention.
3 is an operation explanatory view of the transfer device of FIG.
FIG. 4 is a front view showing a modified embodiment of the transfer apparatus according to the present invention.
FIG. 5 is an explanatory diagram of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Transfer apparatus, 12 Transfer roller, 12a Shaft end part, 13 Transfer entrance guide, 15 Transfer bearing member, 16 Transfer bearing member main body, 17 Rotating shaft, 18 Guide plate, 19 Longitudinal side wall, 19a Hole, 20 Fixed guide, 21 Base frame, frame, 25 elastic member, 30 photosensitive drum (image carrier), 40 snap fit.

Claims (3)

An image forming apparatus comprising a step of transferring a visible image formed on an image carrier by an electrophotographic process to a transfer material supplied to a nip portion between the image carrier and a transfer device,
The transfer device includes a transfer roller that applies a transfer bias to a visible image on the image carrier via a transfer material, a transfer inlet guide that guides the transfer material to the nip portion, and shaft end portions at both ends of the transfer roller. And a transfer bearing member that supports the transfer bearing member rotatably, a fixed guide that supports the transfer bearing member so as to advance and retreat in the vertical direction, and an elastic member that elastically biases the transfer bearing member toward the image carrier at all times.
The transfer bearing member includes a transfer bearing member main body provided with a recess for rotatably and detachably supporting each shaft end portion of the transfer roller, and a rotating shaft protruding sideways from the transfer bearing member main body. ,
The transfer entrance guide has a guide plate that guides the transfer paper on the upper surface, and a hole that is formed in both side walls in the longitudinal direction of the guide plate and loosely fits the rotation shaft. An image forming apparatus, wherein the image forming apparatus is supported so as to be pivotable in the vertical direction by being fitted to the head. The transfer entrance guide is applied with a force by which the guide plate is rotated about the rotation axis in a direction away from the nip portion by an elastic biasing force or its own weight. 2. The image forming apparatus according to claim 1, further comprising a projecting piece for determining, wherein the projecting piece comes into contact with an upper surface of a base frame that supports a bottom portion of the fixed guide. The image forming apparatus according to claim 1, further comprising a snap fit that restricts the transfer entrance guide from rotating in a direction away from the nip portion.

Images