JP3502861B2 - Ground structure of transfer belt support roller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a grounding structure of a transfer roller supporting roller for grounding a roller for supporting a transfer roller in a freely movable manner. Conventionally, in an image forming apparatus, there has been a corona transfer method in which a toner image formed on a photoreceptor is transferred onto a sheet using corona discharge by a transfer charger. On the other hand, there has been provided a transfer belt system in which a sheet is conveyed through a photosensitive drum while being conveyed by a transfer belt having a charged surface, and transfer is performed without generating ozone. In this transfer belt method, the endless transfer belt that conveys the sheet is charged, so that the sheet is electrostatically attracted and conveyed. Therefore, there is an advantage that there is no problem that the paper being conveyed is wound around the photosensitive drum. FIG. 6A is a schematic side view of a conventional transfer belt mechanism. Referring to FIG. 1, an endless transfer belt 100 that is pressed against photoconductor drum 2 is wound between a driving roller 101 and a driven roller 102, and the transfer belt 100 has a back side (endless transfer belt). (Inside) is charged via the transfer roller 103 disposed inside the transfer roller. That is, the transfer roller 103 is
In a state where the transfer belt 103 is sandwiched between the transfer belt 103 and the peripheral surface of the transfer belt 103, the transfer belt 103 is in contact with the transfer belt 103 from the back side. Further, before and after the transfer roller 103, supporting rollers 104 and 105 for supporting the transfer belt 100 so that the transfer belt 100 can run freely are arranged. Reference numerals 108 and 109 are a transport roller and a transport guide arranged on the upstream side of the transfer belt 100. 110 is a constant voltage circuit to the transfer roller 103. [0006] Rollers 104 and 101 on the downstream side in the running direction from the transfer roller 103 are used to allow the trailing end 107 of the paper 106 passing therethrough to be smoothly separated from the transfer belt 100 as shown in FIG. Need to be grounded. Further, the roller 105 on the upstream side in the running direction from the transfer roller 103 also needs to be grounded for the following reason. That is, a constant current is supplied to the transfer roller 103 via the constant voltage supply circuit 110.
On the other hand, since the sheet has a hygroscopic property, the sheet may retain a large amount of moisture in such a case. In this case, the resistance value of the sheet 106 decreases, and the current easily flows through the sheet 106. For this reason, the rear end 10 of the sheet 106 being transported is
As shown in FIG. 6B, the transfer guide 7 and the transfer roller 10 are located upstream of the transfer belt 100 in the traveling direction.
9 while the transfer roller 103 is in contact with the paper 10.
6, the transport guide 109 and the transport roller 108 described above.
(Indicated by a dashed arrow in the drawing). [0006] However, the transport further proceeds, and FIG.
As shown in (c), when the rear end 107 of the sheet 106 is separated from the transport guide 109 or the transport roller 108,
Since the path of the electric charge to the transport guide 109 and the transport roller 109 is cut off, the current value supplied from the transfer roller 103 is reduced, resulting in a problem that the transfer performance is changed and the transferred image is disturbed. Therefore, the roller 105
It is necessary to secure the ground and always keep the current path. As described above, it is necessary to ground the rollers 104 and 105 before and after the transfer roller 103. For this reason, conventionally, a ground structure as shown in FIG. 7 has been used. In the figure, the roller 104 will be described as an example. A support shaft 111 of the roller 104 is supported by a side plate 113 via a cylindrical bearing 112. The support shaft 111 penetrates the bearing 112 and the support shaft 111
Ground plate 115 made of a leaf spring
Are elastically contacted with each other, whereby the ground of the roller 104 is achieved. Further, in order to prevent toner from adhering to the bearing 112, the entire bearing 112 is covered by the transfer belt 100. However, the so-called fogging toner, which is placed on the photosensitive drum in a portion where there is no paper, goes around the back side of the transfer belt 100 and sprinkles on the bearing 112, and as a result, In some cases, the support shaft 111 of the roller 104 is locked by the bearing 112. In particular, in the above-described grounding structure, the end 116 of the support shaft 111 of the roller 104 protrudes from the edge 100a of the transfer belt 100 in order to secure grounding. As shown by a white arrow, the toner easily enters the bearing 112 side. Further, the end surface 114 of the rotating spindle 111
The ground plate 115 is in contact with the
Of the support shaft 111 and the ground plate 1
15 may cause toner to enter, and if it does, a ground fault may occur. Accordingly, an object of the present invention is to provide a grounding structure for a transfer belt supporting roller that can prevent the occurrence of rotation lock of the roller while achieving reliable grounding. [0011] In order to achieve the above object, an invention according to claim 1 is to provide a ground for a roller for supporting a transfer belt wound around the transfer belt so that the transfer belt can run freely. In the ground structure of the roller, an electrically conductive bearing having an integral bottomed cylindrical shape fitted to the end of the support shaft and rotatably supporting the support shaft, and a side plate supporting the bearing non-rotatably. And a ground plate supported by the side plate and elastically pressed against the end face of the bearing. In the above construction, since the end of the support shaft is covered with the bag-shaped bearing, the toner does not enter the bearing, and therefore there is no possibility that the bearing is locked. Further, since the ground plate is in contact with the end surface of the stationary bearing, there is no possibility that toner may enter between the ground plate and the end surface of the bearing, and therefore, there is no possibility that a ground fault occurs. Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a schematic side view illustrating a schematic configuration of an image forming unit of the image forming apparatus including a ground structure according to an embodiment of the present invention. Referring to FIG.
1, a charging charger 3, a developing device 4, a transfer belt device 5, and a cleaning device 6 are arranged in this order around the photosensitive drum 2. The image forming section 1 forms an electrostatic latent image by forming an original image on the peripheral surface of the photosensitive drum 2 uniformly charged by the charging charger, and then forms the electrostatic latent image into a toner image by the developing device 4. The transfer belt device 5 transfers the toner image to paper, and the cleaning device 6 collects residual toner. Referring to FIG. 2 and FIG. 3 which is a partially cutaway perspective view of the transfer belt device, the above-described transfer belt device 5 includes an endless transfer belt 10 which is slidably contacted with the photosensitive drum 2.
And a drive roller 11 and a driven roller 12 around which the transfer belt 10 is wound, and the transfer belt 10
Between the transfer roller 13 and the transfer roller 13
And a pair of support rollers 14 and 15 which are arranged on both sides of the transfer belt 10 so that the upper track of the transfer belt 10 can run freely, and auxiliary rollers 16 which support the lower track of the transfer belt 10 so as to run freely. . The transfer belt 10 is made of, for example, polyurethane. The transfer roller 13 is
As shown in FIG. 3, a support shaft 13a having a reduced diameter portion 13c
And an elastic layer 13b made of silicon rubber or the like carried around the support shaft 13a. Referring to FIG. 3, in the transfer belt device 5 described above, each of the rollers 11 to 16
Are supported by a pair of side plates 17 facing each other (only one side is shown in FIG. 3). These support rollers 1
The ground plates 4 and 15 are grounded via a ground plate 31 and a bearing 30, and the ground plates 31 are connected to each other via an extension piece 31f and are collectively connected to a ground wire 34. An upper edge of each side plate 17 is integrally provided with a rib 37 having a predetermined length in the running direction of the transfer belt 10 and having an L-shaped cross section (only one formed on one side plate 17 is shown). Is formed. The rib 37 regulates the movement of the transfer belt 10 in the width direction to prevent the transfer belt 10 from running in a meandering manner. In the present embodiment, description will be made in accordance with the ground structure of the support roller 15. Referring to FIG. 4 which is a schematic perspective view of this ground structure and FIG. 1 which is an exploded perspective view, a support shaft 15a of the support roller 15 is
It is rotatably supported by the receiving portion 32 of the side plate 17 via the above-described bearing 30 made of a conductive resin having a bottomed cylindrical shape (bag shape). The pair of claw portions 31a of the ground plate 31 bite into contact with the end surface 30a of the bearing 30, so that the support roller 15 is grounded. The bearing 30 has a cylindrical shape having one end closed and the other end opened by an opening 30b, and a flange 30c having a larger diameter than other portions is formed at the other end.
Further, a recess 30d is formed in the flange 30c. The receiving portion 32 formed on the side plate 17 is formed of a semi-cylindrical concave portion having a shape adapted to the outer shape of the bearing 30 for receiving the bearing 30. The receiving portion 32 is provided with a positioning surface 32a that abuts against the flange 30c of the bearing 30 to position the bearing 30 in the axial direction, and is fitted with the concave portion 30d of the bearing 30 to rotate the bearing 30. A regulating projection 32b is provided. The ground plate 31 is provided with a screw insertion hole 31 at the lower end 31c of the main piece 31b along the side plate 17.
d. The claw portion 31a extends perpendicularly to an upper end portion 31e which is a free end of the main piece 31b. 31f is an extension piece for integrally connecting a ground plate 31 for grounding the support roller 14. The screw 33 is attached to the mounting hole 34 of the terminal 34 a at one end of the ground wire 34.
b, and through the screw insertion hole 31d of the ground plate 31,
The terminal 34a and the ground plate 31 are fixed by being screwed into the screw holes 35 of the side plate 17 (see FIG. 1).
(See FIG. 4). Earth wire 34
Is connected to the body of the image forming apparatus. Referring to FIG. 4, main plate 31b is bent and deformed in a state where ground plate 31 is attached to side plate 17 and claw portion 31a is brought into contact with end surface 30a of bearing 30, and elastic repulsion due to this deformation is made. The force causes the pawl portion 31a to
Into the end face 30a. FIG. 5 is a partially cutaway plan view of the ground structure. As shown in FIG. 5, the end surface of the flange 30c of the bearing 30 and the stepped surface 15b of the support roller 15 opposed thereto are shown. Although a predetermined gap 36 is formed between them for the sake of assembly accuracy, toner does not enter the gap 36. This is because the intermediate portion of the bearing 30 in the axial direction is covered with the transfer belt 10, and a predetermined distance between the edge 10a of the transfer belt 10 and the gap 36 is secured. The portion covered by the transfer belt 10 is defined as a part of the bearing 30. If the entire bearing 30 is covered by the transfer belt 10, the toner easily adheres to the ground plate 31. This is to prevent this. According to this embodiment having the above configuration, the end of the support shaft 15a is covered with the bag-shaped bearing 30.
There is no possibility that the toner enters the inside of 0, so that there is no possibility that the bearing is locked. In addition, the fixed bearing 30
Since the ground plate 31 is in contact with the end surface 30a, there is no risk of toner entering between the ground plate 31 and the end surface 30a of the bearing 30, and therefore, there is no risk of causing a ground fault. In particular, since the bearing 30 is made of resin and the claw portion 31a of the ground plate 31 can be cut into the bearing, more reliable grounding can be achieved. Note that the present invention is not limited to the above-described embodiment, and various changes can be made within the scope of the present invention. According to the first aspect of the present invention, since a bag-shaped bearing is placed on the end of the support shaft, it is possible to reliably prevent bearing lock due to toner intrusion. Also, since the ground plate is in contact with the end surface of the stationary bearing, no toner enters between the ground plate and the end surface of the bearing.
Reliable earthing can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a ground structure of a transfer belt supporting roller according to an embodiment of the present invention. FIG. 2 is a schematic side view of an image forming unit including the earth structure. FIG. 3 is a partially cutaway perspective view of a transfer belt device including the present earth structure. FIG. 4 is a perspective view of the present earth structure. FIG. 5 is a partially cutaway plan view of the present earth structure. FIG. 6 is a schematic side view of a conventional transfer belt device;
(A) shows a state in which the rear end of the paper being conveyed is about to be separated from the transfer belt. (C) shows a state in which the rear end of the sheet being transported is separated from the transport roller and the transport guide. FIG. 7 is a partially broken plan view of a conventional earth structure. [Description of Signs] 10 Transfer belt 15 Supporting roller 15a Support shaft 17 Side plate 30 Bearing 30a End face 31 Ground plate 31a Claw portion

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Rio Uchida 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Kyocera Mita Co., Ltd. (56) References JP-A-7-287453 (JP, A) Hei 3-111864 (JP, A) JP-A-8-93778 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 550

Claims (1)

(57) [Claim 1] In a grounding structure of a roller for supporting a transfer belt for grounding a roller for supporting a transfer belt wound around the transfer belt so that the transfer belt can run freely, an end of the support shaft may be provided. An integral bottomed cylindrical conductive bearing that is fitted and rotatably supports the support shaft, a side plate that supports this bearing in a non-rotatable manner, and is supported by the side plate. And a ground plate pressed against the transfer belt.