JP3027293B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a driving force transmission system for transmitting a driving force to a pre-transfer roller of an image forming apparatus such as an electrostatic copying machine, a facsimile or a printer.

[0002]

2. Description of the Related Art In a roller transfer type image forming apparatus, in order to eliminate toner contamination on the peripheral surface of the transfer roller and to minimize the occurrence of image unevenness, the peripheral surface of the transfer roller and the surface of the photosensitive drum at the image transfer position. A so-called non-contact type roller transfer system has been proposed in which a small gap is provided between the roller and the roller.

In this method, a gap holding roller having a diameter larger than that of the transfer roller is mounted on each end of a pivot on which the transfer roller is mounted, and the pivot is urged upward by a spring. In some cases, the peripheral surface of the gap holding roller is brought into rolling contact with the surface of the photosensitive drum, thereby forming a constant gap between the peripheral surface of the transfer roller and the surface of the photosensitive drum.

In such an image forming apparatus,
To properly supply paper to the photoconductor drum,
For example, as shown in FIG. 5, the pre-transfer roller 2 may be provided at a position immediately before the photosensitive drum 3 in the paper transport path 9. The pre-transfer roller 2 receives a driving force from the transfer roller 4 via a gear transmission mechanism and rotates in the forward direction with the photosensitive drum 3 to feed paper at the same speed as the peripheral speed of the photosensitive drum 3. It is composed of More specifically, a driving force is applied from a driving gear 13 fixed to a pivot 4a of the transfer roller 4 to a driven gear 10 fixed to a pivot 2a of the pre-transfer roller 2 via a first idle gear 11 and a second idle gear 12. To be transmitted. In addition, 31 is a charger,
32 is a developing device and 33 is a cleaning device.

[0005]

As described above, the transfer roller 4 is vertically movable by a spring separately from the pre-transfer roller 2 so as to form a predetermined gap c with the photosensitive drum 3. They are supported. Therefore, the meshing state of the drive gear 13 fixed to the pivot 4a of the transfer roller 4 with the first idle gear 11 may not be properly formed, and the torque may be increased or decreased due to the occurrence of a tooth bottom contact. May cause uneven rotation.

[0006] In such a case, there is a concern that the feed speed of the sheet with respect to the photosensitive drum 3 fluctuates, causing problems such as image unevenness and jamming. .

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an image forming apparatus in which an appropriate driving force is always transmitted without causing driving unevenness to a pre-transfer roller.

[0008]

According to the present invention, means for solving the above-mentioned problems are constituted as follows. That is, in a non-contact type roller transfer type image forming apparatus in which a pre-transfer roller is provided at a position immediately before the photosensitive drum in a paper conveyance path for guiding a sheet to a photosensitive drum, the pre-transfer roller A driven gear fixed to one end of the pivot of the driven gear, a second idle gear meshed with the driven gear, and a first idle gear meshed with the second idle gear;
A meshing adjustment roller is rotatably provided on the pivot of the first idle gear while being supported by a support frame at a position where a predetermined meshing state is formed with each other. A gap adjusting roller and a drive gear for forming a predetermined gap between the roller and the roller are provided on the pivot of the transfer roller so as to freely rotate, and the gap adjusting roller is provided between the axis of the photosensitive drum and the transfer roller. And a biasing means for biasing the photosensitive drum and the meshing adjustment roller toward the upstream side in the paper feeding direction with respect to a line connecting the shaft center of the photosensitive drum.

[0009]

The gap adjusting roller provided on the pivot axis of the transfer roller so as to freely rotate is biased by an urging means toward the upstream side in the sheet feeding direction from a line connecting the axis of the photosensitive drum and the axis of the transfer roller. The driving gear fixed to the pivot of the transfer roller is always pressed by the photosensitive drum and the meshing adjustment roller provided coaxially with the first idle gear. Thus, the pre-transfer roller is appropriately driven to rotate appropriately.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the image forming apparatus of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a pre-transfer roller 2 of a clamshell type image forming apparatus 1 (see FIG. 4).
Reference numeral 3 denotes a photosensitive drum rotatably supported by the main body of the image forming apparatus 1, and 4 denotes a transfer roller which is in non-contact with the photosensitive drum 3 at an image transfer position. On both sides of the pivot 4a, clearance adjusting rollers 5, 5 are provided rotatably so that the transfer roller 4 can always form a predetermined clearance c with the photosensitive drum 3, and slide on both ends of the photosensitive drum 3. (See FIG. 3).

Reference numeral 6 denotes a support member which is biased and supported upward by springs (biasing means) 8, 8 on a frame member 7 fixed to the main body of the image forming apparatus 1. The paper conveying path 9 is formed on the upper slope of the supporting member 6 so that the pre-transfer roller 2 forms a predetermined gap with the paper conveying path 9 on the upstream side. It is rotatably supported.

Reference numeral 10 denotes a driven gear fixed to one end of the pivot 2a of the pre-transfer roller 2, 12 denotes a second idle gear that meshes with the driven gear 10, 11 denotes a first idle gear that meshes with the second idle gear 12, and 13 denotes a first idle gear. 1st idle gear 11
The transfer gear 4 is fixed to one end of the pivot 4a of the transfer roller 4, and the one gap adjusting roller 5 is provided inside the drive gear.

The pivots 11a and 12a that rotatably support the first idle gear 11 and the second idle gear 12 are fixed to a support member 6 (see FIG. 2). A meshing adjustment roller 17 that appropriately holds the meshing state with the drive gear 13 is fixed.

Numeral 14 designates a bearing for pivotally supporting both ends of the pivot 4a of the transfer roller 4. A spring (biasing means) 1 is slidable up and down in a guide groove 15 formed on both sides of the support member 6.
The gap adjusting rollers 5 and 5 urged upward by the shaft 6 and freely rotatably supported on the pivot 4a are pressed against both ends of the photosensitive drum 3 (see FIG. 3), and one of the rollers is the first. It is pressed against a meshing adjustment roller 17 integral with one idle gear 11.

[0015] The above two directions clearance adjustment rollers 5,5 are urged by a spring 8, 16 is the axis G ₁ and Axis 2a of the axis and the sheet feed direction than a line connecting the photoreceptor drum 3 ( The gap adjustment roller 5 is set toward the upstream side of the arrow P), whereby the one gap adjustment roller 5 is constantly pressed against the photosensitive drum 3 and the meshing adjustment roller 17.

Accordingly, the gap c between the photosensitive drum 3 and the transfer roller 4 is always properly maintained, and even if a gap is generated between the bearing 14 and the guide groove 15, the driving gear 13
The meshing pitch of the first idle gear 11 is always properly maintained, and there is no occurrence of torque fluctuation due to the occurrence of root contact, the pre-transfer roller 2 is appropriately rotated, and the occurrence of image unevenness and jams, etc. Trouble can be avoided,
High quality images can be obtained. In this embodiment, the clearance adjusting rollers 5, 5 are provided by two springs 8, 16.
Is urged to the photoreceptor drum 3, but may be urged by only one spring 8.

As shown in FIG. 4, the image forming apparatus 1 provided with a drive system for the pre-transfer roller 2 comprises an upper half 1a and a lower half 1b which can be opened to one side, and the upper half 1a. A document holding cover 21, contact glasses 22, 23, an automatic document feeder 24, an image reader 25, and an image processing unit 26.
And an image forming unit 29 including the photosensitive drum 3, the developing device 27, the cleaning device 28, and the like. On the other hand, a drive system for the above-described transfer roller 4 and the pre-transfer roller 2 is provided in the lower half 1b, which is set, along with the paper feed cassette 30, the discharge roller 31, and the discharge tray 32.

In such an image forming apparatus 1, the upper half 1
a, the gap c between the photosensitive drum 3 and the transfer roller 4 may be fluctuated. However, the gap between the transfer roller 4 and the photosensitive drum 3
Is properly maintained, and the driving gear 13 integral with the transfer roller 4 and the first idle gear 11 can maintain an appropriate meshing pitch.

[0019]

As described above, according to the image forming apparatus of the present invention, the gap adjusting roller provided rotatably on the pivot of the transfer roller is moved by the urging means to the photosensitive drum,
Since it is pressed against a first idle gear that applies a driving force to the pre-transfer roller and a meshing adjustment roller provided coaxially,
The driving gear fixed to the pivot of the transfer roller always meshes properly with the first idle gear, and the pre-transfer roller is appropriately driven to rotate, thereby preventing image unevenness and jam.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a configuration of a drive system of a pre-transfer roller in an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a partial front view of a main configuration of the image forming apparatus.

FIG. 3 is a front view of the same.

FIG. 4 is an overall configuration diagram of the image forming apparatus.

FIG. 5 is a configuration diagram illustrating an example of a drive system of a pre-transfer roller of a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Pre-transfer roller, 3 ... Photoconductor drum, 4 ... Transfer roller, 5 ... Clearance adjustment roller, 8, 16 ...
Urging means, 9: paper transport path, 10: driven gear, 11: first idle gear, 12: second idle gear, 13: drive gear, 17: meshing adjustment roller.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-134504 (JP, A) JP-A-6-130828 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (1)

(57) [Claims] In a non-contact type roller transfer type image forming apparatus, a pre-transfer roller is provided at a position immediately before the photosensitive drum in a paper transport path for guiding a sheet to the photosensitive drum. The driven gear fixed to one end of the pivot of the roller, the second idle gear meshing with the driven gear, and the first idle gear meshing with the second idle gear are located at positions where a predetermined meshing state is formed with each other. A meshing adjustment roller is rotatably provided on the pivot of the first idle gear while being supported by the support frame, while forming a predetermined gap between the photosensitive drum and the transfer roller at an image transfer position. A gap adjusting roller and a drive gear are provided on the pivot of the transfer roller so as to freely rotate,
Further, the gap adjusting roller is urged toward the upstream side in the paper feeding direction from a line connecting the axis of the photosensitive drum and the axis of the transfer roller, and is pressed against the photosensitive drum and the meshing adjusting roller. An image forming apparatus comprising an urging means for bringing the image forming apparatus into contact with the image forming apparatus.