JPH0624602A - Document conveying device - Google Patents

Abstract

PURPOSE:To enhance transmission efficiency without causing complicated constitution and prevent conveyance stability from being lost due to backlash and spring-back at the time of intermittent driving. CONSTITUTION:In an image forming device provided with a document image reading part and rollers 14, 14' for conveying a document to the document image reading part, gears (14), (14') integrated with a roller shaft are formed into tapered gears, and another tapered gear 25a meshed with the tapered gears (14), (14') is pressure contacted therewith by means of a spring 26.

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 mechanism of a roller for conveying a document in an image reading apparatus using a contact type image sensor, and in particular, it improves transmission efficiency and backlash without complicating the structure. The present invention relates to a document transport mechanism that prevents loss of transport accuracy during intermittent driving due to spring back.

[0002]

2. Description of the Related Art Some original image reading units such as a facsimile machine, a sheet scanner, a laser printer and a copying machine utilize a contact type image sensor, and a timing belt and a gear are used as a driving mechanism of a roller for conveying an original. Etc. are generally used. By the way, the timing belt has no backlash due to its characteristics and is suitable for obtaining precise synchronization, but since it is necessary to apply tension to stretch the belt between sprockets, it improves transmission efficiency. Has a limit. On the other hand, although the transmission efficiency of the transmission mechanism including gears is relatively good, backlash occurs in the meshing portion between the gears, so that there is a disadvantage that accurate feeding cannot be ensured when performing intermittent driving.

In general, in a rotary drive system, twisting (distortion) occurs by rotationally driving a load even if backlash does not occur. This twist varies in magnitude depending on the strength of the rigidity of the members that make up the drive system, but it always occurs, and if the drive system is operated continuously in one direction, it will have a significant effect. However, when so-called intermittent driving including driving stop during operation is performed, springback will occur in the drive system, causing a problem that it will deviate from the original stop position at restart. To do.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, improves transmission efficiency without complicating the structure, and stabilizes conveyance during intermittent driving due to backlash and springback. An object of the present invention is to provide a document transport mechanism that prevents the document from being lost.

[0005]

To achieve the above object, the present invention is an image forming apparatus including a document image reading unit and a roller for feeding a document to the document image reading unit, and a gear integrated with the shaft of the roller. Is a taper gear, and another taper gear meshing with the taper gear is pressed against the taper gear on the roller side by a spring. The original image reading unit and the original image reading unit are provided with rollers for conveying the original. In the image forming apparatus, a hysteresis torque brake utilizing a hysteresis torque generated by a magnetic field between a permanent magnet and a magnetic material is disposed on the shaft of the roller, and the document image reading unit and the document image reading unit are provided. In an image forming apparatus equipped with a roller for conveying a document, the axis of the roller is
It is characterized in that a powder brake, which utilizes the resistance force generated by the solidification of the magnetic powder as a brake for the shaft, is provided.

The present invention will be described in detail below. FIG. 1 is a schematic configuration explanatory view of an electrophotographic image forming apparatus to which the present invention is applied, and its operation is as follows. That is, from the top of the cassette sheet feeding device 1 located at the bottom of the device, the sheet feeding roller 23
The recording paper 2 fed in the pair of registration rollers by
The registration roller pair 3 conveys the image to a latent image carrier composed of the photoconductor drum 4 at a timing. Photoconductor 4
In the process of being driven to rotate in the counterclockwise direction, the surface is charged by the charging charger 5, and the electrostatic latent image is formed on the photoconductor by being irradiated with the laser beam from the laser optical system 6.
This latent image is visualized by toner as it passes through the developing device 7. This visible image is transferred onto the recording paper 2 conveyed to the photoconductor 4 by the transfer charger 8 and is visible on the transferred recording paper. The image is fixed by the fixing device 9. The recording paper discharged from the fixing device is discharged to the paper discharge unit 10 and stored therein. On the other hand, the residual toner on the photoconductor 4 after the transfer of the visible image is removed by the cleaning device. The toner removed from the photoconductor is collected and stored in the toner collecting tank 11.

The operation when reading an image is as follows.
The original 2 fed from the cassette sheet feeding device 1 in the direction of the reading timing roller pair is read by the reading timing roller pair 1.
The sheet is conveyed to the reading sensor 15 (original image reading section) at a timed timing by 4, 14 '. The document that has passed through the reading sensor is discharged to the paper discharge unit 17 by the rotatable branch guide 16 provided on the conveyance path and is stored therein. Further, by attaching the manual paper feeding device 12, a small amount of recording paper or original 13 can be fed to perform the same operation. Reference numeral 22 is a paper feed roller that feeds the manually fed recording paper or original 13 toward the sensor 15.

2 (a) and 2 (b) are a front view and a rear view showing the arrangement of the gear groups constituting the drive system of the image forming apparatus of FIG. 1, and FIG. 2 (a) is the axial center of the registration roller pair 3. In order to drive the gear (3) integrated with and the gears (14), (14 ') integrated with the shaft center of the timing roller pair 14, 14' located on the front side of the reading sensor 15 by the step motor 21. The gear structure of is shown. The driving torque from the stepping motor 21 is transmitted to the gears (14) and (14 ') via the gears G1 and G2. The central axis of the transmission gear 24 connected to the stepping motor 21 via the gear G3 is coaxially integrated with the transmission gear 24 'located on the rear side, and the transmission gear 24' is the shaft of the paper feed rollers 22 and 23. It meshes with gears (22) and (23) integrated with the core.

These gears, especially the reading sensor 1
The stability of the rotational speed of the timing roller pair 14 and 14 ', which is involved in the transportation of the document passing through the sheet 5 and influences the stability of the transportation, is important for stabilizing the image reading accuracy. , 14 'integrated with gear (1
4) and (14 ') show an embodiment for preventing backlash in the meshing portion and for stable driving. In this embodiment, the gear (14) or (14 ')
Is a tapered gear, and a gear 25 is provided which meshes with and drives the gear (14) or (14 ').
The gear 25 is pressed against the gear (14) or (14 ') side by a compression coil spring 26. The gear 25 is a tapered gear portion 2 that meshes with the gear (14) or (14 ').
5a and a coaxial spur gear 25b are integrated. Since the gear 25 is movable in the axial direction, it is pressed by the spring 26 to increase the meshing force between the two tapered gears and prevent the occurrence of backlash.

As described above, according to the first embodiment of the present invention,
Backlash between gear pairs is eliminated, and because it is pressed and rotated by a force slightly stronger than the axial load generated by the tangential load of the gear, it rotates like a normal gear with no backlash. The ruggedness disappears and the rotation of the motor is faithful to the roller pair 14,
It is possible to prevent the misalignment of the document when the document is stationary or restarted by transmitting to 14 '.

FIG. 4 shows a second embodiment of the present invention, in which the shaft end 27 of the timing roller pair 14, 14 'on the side opposite to the shaft end where the gears (14), (14') are integrated. By installing the hysteresis brake 28 in the above, it is possible to prevent the occurrence of minute reverse rotation due to the springback of the drive system. This hysteresis brake 28 has a shaft 27
And a housing 28b (a semi-hard magnet layer is formed on the inner peripheral surface) fixed to the side plate 29 are coaxially opposed to each other at a predetermined interval. It utilizes the hysteresis torque (torque generated by the delay of the phase of the magnetic characteristics) generated between the semi-hard magnetic material and exerts a function as a tricrimitter.

Although not shown, a powder brake may be used instead of the hysteresis brake shown in FIG. As is well known, the powder brake has a shaft (rotor),
Magnetic powder such as iron powder is arranged in a gap between a cylindrical member (stator) arranged around the shaft at a predetermined interval, and the magnetic powder is solidified by a magnetic field to lock the two members. It is configured as follows. In this case as well, similar to the example of FIG. 4, it is possible to prevent the occurrence of minute reverse rotation due to the springback of the drive system. As a result,
It is possible to improve the reading accuracy of the reading sensor and improve the quality of the image formed.

In FIG. 4 and its modified embodiment, the friction load for rotating the shaft 27 is A, and the brake torque of the hysteresis brake or powder brake is B.
Then, the configuration is such that A <B. As described above, according to the second embodiment of the present invention, it is possible to prevent the springback caused by the torsional deformation of the drive system when the intermittent drive is stopped, and to prevent the displacement from the stop position at the time of restarting. It is possible to start reading the original again from the position. It should be noted that the present invention can be generally applied to the case where not only the conveyance stability of the document passing through the contact sensor but also the conveyance stability by the roller for conveying the paper is realized.

[0014]

As described above, according to the present invention, the transmission efficiency is improved without complicating the structure, and the stability of conveyance during intermittent driving is lost due to backlash or spring back. Can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view of an electrophotographic image forming apparatus to which the present invention is applied.

2A and 2B are a front view and a rear view showing an arrangement of gear groups constituting a drive system of the image forming apparatus of FIG.

FIG. 3 is an explanatory diagram of a main part configuration of a first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a main part configuration of a second embodiment of the present invention.

[Explanation of symbols]

1 cassette feeding device, 2 recording paper, 3 registration roller pair, 4 photoconductor drum, 5 charging charger, 6 laser optical system, 7 developing device, 8 transfer charger, 9
Fixing device, 10 paper discharge unit, 14, 14 'timing roller pair, (14), (14') gear, 15 reading sensor, 25 gear, 25a taper gear unit, 25b
Spur gears, 26 springs, 28 hysteresis brakes.

Claims (3)

[Claims] 1. An image forming apparatus comprising a document image reading unit and a roller for feeding a document to the document image reading unit, wherein a gear integrated with a shaft of the roller is a taper gear and the taper gear is provided. An original conveying mechanism characterized in that another taper gear meshing with the roller is pressed against the taper gear on the roller side by a spring. 2. An image forming apparatus including a document image reading unit and a roller for feeding a document to the document image reading unit, wherein the shaft of the roller generates a magnetic field between a permanent magnet and a magnetic material. A document conveying mechanism, which is provided with a hysteresis torque brake that utilizes hysteresis torque. 3. An image forming apparatus comprising a document image reading section and a roller for feeding a document to the document image reading section, wherein a braking force is applied to a shaft of the roller by a coagulation of magnetic powder. An original conveying mechanism characterized by disposing a powder brake used as.