JP2710997B2 - Transfer device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device provided in an electrophotographic image forming apparatus such as a laser printer or a copying machine.

(Prior Art) In an image forming apparatus such as a copying machine, as shown in FIG. 8, as a means for transferring an image (toner image) from a photosensitive drum 100 serving as an image carrier to a transfer paper (transfer material) P, as shown in FIG. A bias voltage is applied to a cylindrical transfer roller 101 made of a conductive material, the transfer roller 101 is brought into contact with the photosensitive drum 100, and the transfer paper P is conveyed to a nip portion that is a contact portion thereof. There is a method of performing transfer.

Then, the transfer roller 101 and the photosensitive drum 100 as described above
A transfer paper guide 102 is provided on the paper supply side of the nip 110 in order to accurately guide and convey the transfer paper P to the nip 110 between the nip 110. The transfer paper guide 102 is generally made of a conductive material such as a metal plate because the transfer paper P tends to generate triboelectric charging, and is grounded via a varistor or a resistor as necessary.

Accordingly, the transfer roller 1 is controlled so that the bias voltage applied to the transfer roller 101 does not leak toward the transfer paper guide 102.
A space distance 1 of about 2 to 3 mm is required between 01 and the end of the transfer paper guide 102.

(Problems to be Solved by the Invention) However, arranging the transfer paper guide 102 around the photosensitive drum 100 or the like with the above spatial distance 1 leads to an increase in the size of the entire apparatus. Also, transfer paper guide
Since it is difficult to bring the leading end of the transfer paper 102 close to the nip 110 between the photosensitive drum 100 and the transfer roller 101, if the transfer paper P has waving or curling, the transfer paper P is accurately moved to the nip 110. There is a problem that the image cannot be guided and conveyed, and the image on the transfer paper P is disturbed.

Further, securing the spatial distance l between the transfer paper guide 102 and the transfer roller 101 also hinders the size of the transfer roller 101 and the photosensitive drum 100 from being reduced, and the apparatus can be reduced in size and cost. There was a disadvantage that it hindered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a transfer device capable of reducing the size and size of an image forming apparatus and forming an appropriate image.

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to a transfer member for transferring an image from an image carrier to a transfer material, wherein the transfer material sent to a transfer position is on the image carrier side In contact with the surface opposite to the surface, a voltage is applied, a transfer member, and a conductive guide member that guides the transfer material in the vicinity of the transfer position, a transfer device having a tip of the guide member An insulating member is provided between the transfer member and the transfer member.

(Operation) According to the present invention, since the insulating member is disposed between the tip of the guide member and the transfer member, even if the guide member is formed of a conductive member such as a metal, the bias voltage from the transfer member can be reduced. The guide member can be brought sufficiently close to the transfer member without worrying about leakage.

Accordingly, the guide member can accurately guide and convey the transfer material to the contact portion between the transfer member and the image carrier, and can reduce the size and size of the image forming apparatus.

(Embodiment) An embodiment of the present invention will be described below using a laser printer as an example with reference to the accompanying drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a view showing a cross section of a main part relating to image formation of a laser printer. In FIG. 1, reference numeral 1 denotes a photosensitive drum serving as an image carrier, and a developing device 2 and a primary charger 3 are provided around the photosensitive drum 1. A cleaning device 4 is provided, and these process devices are incorporated in a cartridge container 5a to constitute a process cartridge 5. The process cartridge 5 is provided detachably with respect to the image forming apparatus main body, thereby facilitating maintenance.

On the other hand, the cartridge container 5a of the process cartridge 5
A transfer charger 6 is disposed on one side of the photosensitive drum 1 protruding outward from the printer, and a fixing unit 7 is disposed on the discharge side of the photosensitive drum 1.

A paper feed roller shaft 8 is disposed on the paper feed side of the photosensitive drum 1 directly below the roller shaft 6a of the transfer charger 6 so as to be rotatable in parallel with the roller shaft 6a. Around the periphery, a paper feed roller 9, idler rollers 10, 10, and swing cams 11, 11 are coaxially fixed. The paper feed roller 9 is fixed to the center of the paper feed roller shaft 8, a pair of idler rollers 10, 10 are fixed to both sides of the paper feed roller 9, and a pair of swing cams are provided at both ends of the paper feed roller shaft 8. 11,11 are fixed. And
The paper feed roller 9 and the swing cam 11 have substantially the same cross-sectional shape, and are eccentrically fixed to the paper feed roller shaft 8.
Portions 9a and 11a protruding outward from the outer periphery of idler roller 10
Are arranged out of phase with respect to the sheet feeding roller shaft 8.

Under the process cartridge 5, the idle rollers 10,10
A conveyance roller 12 rotated by a drive source (not shown) is pressed toward the photosensitive drum 1.
Below 0, one end is supported on the apparatus main body side, and the other end is connected to the separation pad 15 through the pad receiving member 14 by the idler roller 1.
A spring member 13 that presses on 0 and 10 is provided.

Further, in FIG. 1, the transfer paper P
And a paper feed unit comprising a spring member 17 and the like. The loading plate 16 is provided at one end thereof with an engagement protrusion 16a which engages with and disengages from the swing cam 11, and the other end is rotatably supported by a support shaft 18.
The elastic member 17 is elastically urged clockwise in FIG. Therefore,
The transfer paper P placed on the stacking plate 16 is rotated by the rotation of the paper feed roller shaft 8 and the projection 11a of the swing cam 11 and the engagement projection 1 of the stacking plate 16 are rotated.
When the engagement with 6a is released, the loading member 16 is
It is also configured to be pressed by the idler rollers 10, 10.

When the image light L is exposed from a laser scanner (not shown) onto the photosensitive drum 1 uniformly charged by the primary charger 3, an electrostatic latent image is formed on the photosensitive drum 1 and the electrostatic latent image is formed. The electrostatic latent image is directed toward the developing device 2 with the rotation of the photosensitive drum 1, and is developed by a developer (toner) in the developing device 2 to be visualized as a toner image. The toner image on the photosensitive drum 1 is transferred to the transfer paper P via a transfer charger 6.
The residual toner on the photosensitive drum 1 on which the transfer is completed, but the transfer is completed, is cleaned by the cleaning device 4.

On the other hand, the transfer paper P on the stacking plate 16 is
When the engagement between the a and the engagement protrusion 16a of the loading plate 16 is released, the idler rollers 10 and 10 are pressed toward the idler rollers 10 and 10; While being sent to the separation pad 15 side, it is further sent from above the separation pad 15 to the transport roller 12 side. Transport roller 12 and idler roller
The transfer paper P which has reached between 10 and 10 is sent between the photosensitive drum 1 and the transfer charger 6 via the guide 2a attached to the developing device 2 and the transfer paper guide plate 20 with the rotation of the transport roller 12. The toner image on the photosensitive drum 1 is transferred by the transfer charger 6. Then, the transfer paper P on which the transfer is completed is sent to the fixing device 7 and the transferred toner image is fixed as a permanent image.

When the process cartridge 5 is mounted on the apparatus main body, the fixing device 7, the primary charger 6, the transport roller 12, the feed roller shaft 8 and the like rotate about one point.
The photosensitive drum 1 and the primary charger 6 are separated at the time of attachment / detachment to / from the apparatus main body, so that they are prevented from rubbing each other.

Next, a method of positioning and supporting the transfer charger 6 and a method of positioning and supporting the transfer paper guide plate 20 will be described.

First, a method for positioning and supporting the transfer charger 6 will be described.

The transfer charger 6 is a roller type which is pressed against the photosensitive drum 1 and transfers a toner image via a nip 19 formed between the transfer charger 6 and the photosensitive drum 1. A bias voltage is applied to the photosensitive drum 1 via the photosensitive drum 1 to transfer the toner image on the photosensitive drum 1 onto the transfer paper P. The transfer charger (hereinafter, referred to as a transfer roller) 6 is supported by bearings 61, 61 in a pair of transfer roller tables 60, 60 attached to the apparatus body.

That is, as shown in FIG. 3 (only one side is shown in FIG. 3), the roller shafts 6a, 6a projecting from both ends of the transfer roller 6 are formed in the concave portions 60a, 60a in the transfer roller bases 60, 60. Bearings
By being supported on 61, 61, they are supported by transfer roller stands 60, 60 attached to the apparatus main body side.

Here, the concave portion 60a of the transfer roller stand 60 is formed toward the photosensitive drum 1, and the bearing 61 is formed in the concave portion 61a.
a, and a spring member 62 is provided between the bearing 61 and the transfer roller base 60. Since the bearing 61 is pressed toward the photosensitive drum 1, the transfer roller 6 is 6
The nip 19 for transfer is formed between the photosensitive drum 1 and the photosensitive drum 1 through the contact 1.

Therefore, the transfer roller 6 is supported by the transfer roller tables 60, 60 via the bearings 61, 61, and is positioned with respect to the photosensitive drum 1 and the like by being pressed by the photosensitive drum 1. Since at least one side of the bearings 61, 61 is formed of a conductive member, the spring member 62
The transfer bias voltage can be applied from the bearing 61 to the transfer roller 6 through the bearing 61.

As shown in FIG. 3, the transfer roller base 60 is provided with stopper claws 69b and 63 near the opening of the recess 60a.
Even when the process cartridge 5 is taken out of the apparatus main body and the photosensitive drum 1 is not in the apparatus main body, the bearings 61 in the transfer roller base 60 are protruded from the transfer roller base 60 by the stopper claws 60b and 63, or the transfer roller 6 roller shaft 6a
Is prevented from jumping out of the bearing 31. However, since the stopper claw 63 is rotatable by applying a certain force or more, the transfer roller 6 is attached to the bearings 61 in the transfer roller bases 60 from the direction in which the photosensitive drum 1 is disposed. , Is removable.

Next, a method of positioning and supporting the transfer paper guide plate 20 will be described.

The transfer paper guide plate 20 is attached to a guide table 30 which is positioned and supported by the transfer roller 6 and a feed roller shaft disposed below the transfer roller 6, and is formed between the transfer roller 6 and the photosensitive drum 1. This is for accurately guiding and conveying the transfer paper P to the nip portion 19.

First, the guide table 30 will be described.
Is made of an elastically deformable insulating resin, and extends to both ends of the transfer roller 6 along the axial direction of the transfer roller 6 as shown in FIGS. The parts 30a, 30a (see FIG. 5 or FIG. 6) are mounted on the roller shafts 6a, 6a inside the bearings 61, 61 of the transfer roller 6 as shown in FIG. (Only the side is shown), and is disposed in a state of being suspended below the roller shafts 6a, 6a.

Here, the bearing 31 is attached to the support portion 30a of the guide base 30, and both the support portion 30a and the bearing 31 have a shape having an opening upward, and the guide base 30 is connected to the roller shaft 6a, To attach to 6a, support parts via bearings 31, 31
30a, 30a are fitted into the roller shafts 6a, 6a in a pressurized state.

Further, right and left guide portions 30b and 30c extending to the sheet feed roller shaft 8 below the transfer roller 6 are provided on the right end portion and the left end portion side in FIG. 30b, 30c
U-shaped grooves 30d that are opened downward are formed at the lower ends of the guide tables 30 by fitting the U-shaped grooves 30d with the sheet feeding roller shaft 8 as shown in FIG. The guide table 30 is positioned and supported by the transfer roller 6 and the feed roller shaft 8 as a whole. Incidentally, the transfer roller 9 and the idle rollers 10, 10 are attached to the paper feed roller shaft 8 between the left and right guide portions 30b, 30c of the guide table 30.

The transfer paper guide plate 20 is made of a metal thin plate obtained by applying a KN plating or the like to a stainless steel material or an iron material, and as shown in FIG. In a substantially L-shaped state, as shown in FIG.
The transfer guide unit 30 is attached over the entire length of the transfer table 30 and forms a transfer guide unit together with the guide table 30.

The transfer paper guide plate 20 is attached to the guide table 30 as follows.
As shown in FIG. 6, the transfer paper guide plate 20 is formed by a plurality of screws 21 from the lower surface side, and the transfer paper guide plate 20 is formed in an L-shaped cross section to increase its rigidity. This has the effect of preventing bending and warping.

Further, since the transfer paper guide plate 20 constantly rubs against the transfer paper P and generates static electricity due to frictional charging, it is necessary to release the static electricity to the outside. For this purpose, as shown in FIG. 5, several tens to several hundreds of MΩ resistors 2
2 and one end of the resistor 22 is screwed to the first metal plate 2
6, the other end is electrically connected to the transfer paper guide plate 20, the other end is a screw, and the other end of the second metal plate 25 is provided via the second metal plate 25 as shown in FIG. When the U-shaped groove 30d of the right guide support portion 30c of the guide base 30 is fitted to the feed roller shaft 8, the electrical contact 25 is electrically connected to the feed roller shaft 8. So that you can connect to it. That is, since the paper feed roller shaft 8 is grounded via the conductive bearing, the transfer paper guide plate 20 is also grounded via the first and second metal plates 23 and 25, the resistor 22, and the like. It can discharge static electricity to the outside.

Further, at the closest end of the transfer paper guide plate 20 to the photosensitive drum 1 and the transfer roller 6, as shown in FIG. 4, there is a kind of insulating resin between the photosensitive drum 1 and the transfer roller 6. A thin insulating sheet 27 made of Mylar or polycarbonate is provided.
Prevents leaks toward

Thus, the transfer paper guide plate 20 is grounded via the resistor 22 and the like, and the bias voltage applied to the photosensitive drum 1 from the transfer roller 6 is likely to leak to the outside via the transfer paper guide plate 20. However, since the guide table 30 and the insulating sheet 27 made of insulating resin are disposed between the transfer paper guide plate 20 and the charging roller 6, the transfer roller 6 is moved through the transfer paper guide plate 20. There is no fear that the bias voltage leaks. Therefore, the transfer paper guide plate 20 can be disposed close to the transfer roller 6 via the guide table 30 or the like, and the size and size of the entire apparatus can be reduced.

Further, since the leading end of the transfer paper guide plate 20 can be disposed close to the nip portion 19 (for example, 1 mm or less) between the transfer roller 6 and the photosensitive drum 1 via the insulating sheet 27 or the like, curl or The image on the photosensitive drum 1 can be properly transferred to the transfer paper P even if there is waving.

Further, since the transfer paper guide plate 20 is supported by the transfer roller 6 via the guide table 30, the transfer paper guide plate 20 can be accurately moved to the nip portion 19 formed between the transfer roller 6 and the photosensitive drum 1. The transfer paper P can be accurately conveyed to the nip portion 19 by the transfer paper guide plate 20, and the toner image on the photosensitive drum 1 can be properly transferred onto the transfer paper P. it can.

The transfer paper guide plate 20 is a roller shaft of the transfer roller 6.
The transfer roller 6 is supported by the transfer rollers 6a and 6b so as to follow even a slight movement of the transfer roller 6.
It is possible to always maintain an appropriate position and distance with respect to fluctuations in hardness of the steel.

Further, as shown in FIG. 5 and the like, a transfer guide unit in which the transfer paper guide plate 20 and the guide base 30 are integrated with the transfer roller 6 can be compactly mounted. , 60 can be mounted on the bearings 61, 61, so that assembly and maintenance thereof can be facilitated.

Here, the fifth end of the guide table 30 is located on the side of the photosensitive drum 1 (outside the image forming area of the photosensitive drum 1).
As shown in FIG. 6 and FIG. 6, a spacer damper member made of ultra-high-molecular-weight polyethylene, Teflon, POM, or the like does not damage the photosensitive drum 1 even when it comes into contact with the photosensitive drum 1
When the transfer paper guide plate 20 attempts to contact the photosensitive drum 1 due to vibration or impact during operation, or during jam clearance, first, the spacer damper members 26, 26 are attached to the photosensitive drum 1. Transfer paper guide plate 2
0 prevents the photosensitive drum 1 from being damaged.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a transfer belt is used as a transfer charger. The transfer belt 6 is endlessly stretched between a roller (not shown) and a roller 41, and the roller shaft 41 a of the roller 41 is pressed toward the photosensitive drum 1 by a spring member 42 so that the transfer belt 6 Is pressed against the photosensitive drum 1 to perform transfer.

Also in such a case, a guide table 43 made of an insulating resin is disposed between the transfer paper guide plate 40 and the transfer belt 6,
Since the bias voltage from the transfer belt 6 is prevented from leaking toward the transfer paper guide plate 40, the transfer paper guide plate 40
The transfer paper guide plate 40 can be disposed sufficiently close to the transfer belt 6 while the transfer paper guide plate 40 can be disposed sufficiently close to the contact portion between the photosensitive drum 1 and the transfer belt 6.

Therefore, also in this embodiment, the apparatus can be reduced in size and size, and even if the transfer paper P is curled or wavy, proper transfer can be performed on the transfer paper P.

Further, one of the guide tables 43 is pivotally supported by the roller shaft 41a of the roller 41, and the other is guided and supported by the axis of the registration roller 44, so that the transfer paper guide plate 40 supported by the guide table 43 is The transfer paper P can be accurately conveyed to the contact portion 6a by the transfer paper guide plate 20. Therefore, an appropriate image can be transferred onto the transfer paper P by the present apparatus.

(Effects of the Invention) As is apparent from the above description, according to the present invention, since the insulating member is provided between the tip of the guide member and the transfer member, the guide member is made of a conductive member such as a metal. However, the guide member can be brought sufficiently close to the transfer member without worrying about the leakage of the bias voltage from the transfer member, and the guide member allows the contact portion between the transfer member and the image carrier to be accurately positioned. The transfer material can be guided and conveyed, and the size and size of the image forming apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of an image forming apparatus having a transfer device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view around the transfer device of the image forming device, and FIG. FIG. 4 is a view showing a support state of a transfer device of the apparatus, FIG. 4 is an enlarged sectional view around a transfer paper guide plate of the image forming apparatus, and FIG. FIG. 6 is a bottom view of the transfer device (transfer roller) with a transfer guide unit attached thereto, and FIG. 7 is a transfer diagram of an image forming apparatus including the transfer device according to the second embodiment of the present invention. FIG. 8 is a cross-sectional view around the apparatus, and is a view for explaining the prior art. 1 photosensitive drum (image carrier), 6 transfer charger (transfer device), 20, 40 transfer paper guide plate (guide member), 2
7 ... insulating sheet (insulating member), 30, 43 ... guide stand (insulating resin member), P ... transfer paper (transfer material).

Claims (13)

(57) [Claims] 1. A transfer member for transferring an image from an image carrier to a transfer material, wherein a voltage is applied to a transfer material sent to a transfer position, which contacts a surface of the transfer material opposite to the image carrier side. Done,
A transfer device having a transfer member and a conductive guide member for guiding a transfer material in the vicinity of the transfer position, wherein an insulating member is provided between a tip of the guide member and the transfer member. . 2. The transfer apparatus according to claim 1, wherein said guide member is electrically grounded via a resistor. 3. The transfer device according to claim 1, wherein the insulator includes a sheet member. 4. The transfer member according to claim 1, wherein the transfer member is a rotating body, and the insulating member is provided between a tip of the guide member and a peripheral surface of the transfer member. The transfer device as described in the above. 5. The relative positional relationship between the transfer member and the guide member does not substantially change regardless of whether the transfer member moves toward or away from the image carrier. The transfer device according to claim 4, wherein 6. The transfer apparatus according to claim 5, wherein the apparatus includes a support member that supports the guide member, and the support member is supported on a shaft of the transfer member. 7. The transfer device according to claim 6, wherein said support member is an insulator. 8. The transfer device according to claim 6, wherein the guide member, the support member, and the transfer member are integrally detachable from an image forming apparatus main body. 9. The transfer device according to claim 6, wherein the support member is supported by a shaft of a rotating body that supplies a transfer material to the transfer position. 10. The transfer device according to claim 3, wherein the transfer member has a roller shape. 11. The transfer device according to claim 3, wherein the transfer member has a belt shape. 12. The image forming apparatus according to claim 1, wherein the transfer member is provided so as to contact the image carrier.
11. The transfer device according to 11. 13. The transfer device according to claim 1, wherein said image bearing member is an electrophotographic photosensitive member.