JPH04155352A - Photoreceptor drive mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoreceptor drive mechanism, and more particularly to a drive mechanism for a photoreceptor belt in digital copying machines, laser printers, facsimile machines (FAX), and the like.

Traditionally, electrophotographic recording devices that form images by scanning and exposing a laser beam write data through an optical writing unit consisting of a laser light source, a rotating reflector such as a polygon mirror that rotates at a high speed at a constant speed, and an optical lens. A laser beam is scanned in the main scanning direction, which is the axial direction of the photoreceptor drum, to form a linear electrostatic latent image on the photoreceptor drum. The body drum is rotated and optically scanned again in the main scanning direction, and by repeating this sequentially, an electrostatic latent image corresponding to the original image information is formed. Next, this electrostatic latent image is coated with a developer such as toner. is deposited and developed, sent to a transfer charger to transfer the developed image onto copy paper, and the transferred developed image is peeled off by AC corona discharge and then fixed to record an image. The conventional photoreceptor drum has a gear provided on the end surface of the photoreceptor drum, and is rotationally driven via a timing belt that meshes with the gear. However, in the photoconductor-to-movement system with a speed reduction mechanism using a gear timing belt, the higher the recording density, the more density unevenness (bunching) occurs in the sub-A scan direction (which is the belt drive direction that rotates the drum). ), which is an obstacle to improving image quality. The main cause of this failure is due to the deceleration mechanism. In other words, this is due to machining errors in the rotation transmission elements that constitute the speed reduction mechanism. In the reduction gear, which is one of the elements, eccentric tooth profile errors and changes in contact ratio occur, and in the pulleys of other elements, eccentricity occurs, resulting in pitch unevenness between scanning lines, and the density increases in areas with narrow pitches. Since the density decreases in areas where the pitch is wide, the overall screen appears as density unevenness with a certain period, and the image quality deteriorates.

Furthermore, as a factor other than the speed reducer, there is the influence of load fluctuations occurring between the timing belt and a cleaning device that cleans untransferred toner remaining on the photoreceptor belt. That is, the drive speed of the timing belt is not constant due to load fluctuations, which causes a problem that harmful unevenness occurs on the image.

As a prior art document related to the present invention, there is, for example, JP-A-2-29712 (scanning optical device). This technique was developed in order to eliminate uneven image density caused by the above-mentioned problems with the conventional gear drive system. This is a scanning optical device provided with a moving means that allows a scanning unit to be moved parallel to a flat surface of a photoreceptor.

However, in this method, the scanning optical system itself is driven in the sub-scanning direction, so an inertial load is generated, and as a result, the recording speed cannot be increased, and the disadvantage is that the device becomes larger due to the provision of a moving means. was there.

Purpose The present invention has been made in view of the above-mentioned circumstances, and uses a new reduction mechanism to further reduce load fluctuations without using gears or timing belts that are difficult to improve machining accuracy as in conventional reduction mechanisms. The purpose of this invention is to provide a photoreceptor active mechanism that is capable of obtaining high-quality images without density unevenness (bunching) by using a drive mechanism that is not affected by the effects of turbulence.

In order to achieve the above objects, the present invention provides (1) a photoreceptor drive mechanism of an electrophotographic recording apparatus using a laser as a light source, which includes a photoreceptor made of a seamless belt, a main roller and a nip roller; and a second drive section that is disposed before and after the first drive section and drives with rotation synchronized with the rotation of the first drive section, and the photoreceptor is driven by the first drive section. (2) A planetary roller is provided between the first drive section and the motor that rotationally drives the first drive section. It is characterized by the installation of a traction drive mechanism such as a speed reducer or a magnetic roller type speed reducer. An explanation will be given below based on one embodiment of the present invention.

FIG. 1 is a diagram showing the overall structure of an electrophotographic recording apparatus for explaining the structure of an embodiment of a photoreceptor drive mechanism according to the present invention. In FIG. 1, 1 is an optical writing unit, and 2 is a first drive. Part, 2
a is the main roller, 2b.

2c is a nip roller, 3 is a second drive section, and 3a.

3b, 3c, and 3d are nip rollers, 4a, 4b are driven rollers, 5 is a photoreceptor seamless belt, 6 is a charger, 7 is a developing device, 8 is a paper feeding device, 9 is a fixing device, and 1o is a cleaning device.

In the illustrated electrophotographic recording apparatus, an optical writing unit 1 includes a laser light source, a constant-velocity high-rotation motor, a polygon scanner including a polygon mirror driven by the constant-velocity high-rotation motor, and an fθ lens (on a photoconductor). The main roller 2a scans in the main scanning direction (direction perpendicular to the plane of the paper) by controlling the modulation of the laser beam to a predetermined beam diameter according to the image information. . The photoreceptor is made of a seamless belt and is driven at a constant speed in a sub-scanning direction perpendicular to the laser beam scanning direction. The photoreceptor seamless belt 5 is charged by a charger 6, and is irradiated with an image-modulated laser beam on the main roller 2a to record an electrostatic latent image. The main roller 2a has 2
Nip rollers 2b and 2c are pressed at intervals, and the photoreceptor seamless belt 5 is connected to the main roller 2.
It is sandwiched between nip rollers 2b and 20 in the form of a winding around the main roller 2a, and is transferred under the frictional force that acts on each other due to the rotation of the main roller 2a. By scanning the exposure laser beam between the two nip rollers 2b and 2c, the position of the photoreceptor seamless belt 5 can be kept constant, so that highly accurate scanning can be realized.

In the present invention, in addition to the first drive section 2, two sets of nip rollers 3a, 3b and other nip rollers 3c, 3d and 2 are arranged in opposing pressure contact at the front and back of the first drive section 2.
A pair of driven rows 4a and 4b are arranged, and the photoreceptor seamless belt 5 is formed into a loop shape. The length of the photoreceptor seamless belt 5 is set so as to have a predetermined slack between the photoreceptor seamless belt 3b and the other nip rollers 3c and 3d. A cleaning device 110 is in pressure contact with the upper driven roller 4a and is configured to clean untransferred toner adhering to the photoreceptor seamless belt 5.

Figure 5 is a characteristic diagram showing an example of the results of measuring the relationship between rotational unevenness accuracy of the main roller and load fluctuation, where the horizontal axis shows load fluctuation (g) and the vertical axis shows main roller rotational unevenness (%).
It shows. As is clear from the figure, even if the drive source is the same, the rotational unevenness accuracy changes due to load fluctuations, and it is shown that the smaller the load fluctuation is, the less rotational unevenness becomes, and the rotational accuracy improves.

In the present invention, the writing position by the optical writing unit is on the main roller 2a, and the photosensitive seamless belt 5 is structured to have slack before and after the main roller 2a. In addition, since the arrangement is such that load fluctuations caused by the cleaning device become a load on the second drive unit, the main roller 2a can be driven with high precision without being affected by load fluctuations, reducing image irregularities due to scanning pitch irregularities. It is possible to obtain high-quality image output.

FIG. 2 is a diagram for explaining the drive mechanism of the first drive section, in which 11 is a DC servo motor, 12 is a planetary roller reducer, 13 is a coupler, 14 is a bearing, and 15 is a PLL.
(Phase Locked Loop: Phase Locked Loop
op) control circuit, 16 is a driver, and parts having the same functions as in FIG. 1 are given the same reference numerals. DC servo motor uses PLLII (phase locked loop) control circuit 1
5 and a planetary roller reducer 12 driven by a driver 16 at a high rotation speed and a high precision constant rotation, and which uses a rolling gear transmission, it is possible to smoothly reduce the speed to a predetermined rotation speed.
Rotational precision is one order of magnitude higher than that of conventional gear-driven reducers.

FIG. 3 is a diagram for explaining the drive mechanism of the second drive section, and in FIG. 1, 17 is a stepping motor.

18 is a timing belt, and the nip rollers are given the same symbols 38 to 3d as in FIG. The illustrated stepping motor 17 is set to be driven in synchronization with the rotational speed of the main roller 2a.

The timing belt 18 is paired with a running wheel 17a of the stepping motor 17, and nip rollers 3a, 3b and other nip rollers 3c, 3cl are pressed against each other with a relief in the center.
It is wound around and driven to rotate. A photoreceptor seamless belt 5 is pressed between the pair of nip rollers 3a, 3b and the other nip rollers 3c, 3d, and the photoreceptor seamless belt 5 is movable at the same speed due to mutual frictional force.

Figures 4(a) and 4(b) are diagrams for explaining a reduction gear using magnetic rollers, where figure (a) is a plan view and figure (b) is a plan view.
) is a diagram seen from the axial direction, in which 19 is the DC motor, 1
9a is a motor shaft of the DC motor 19, 20 is a magnet roller, 21 is a main roller, 21a is a main roller shaft,
22 is a bearing.

The illustrated speed reducer is an alternative to the planetary roller type speed reducer shown in FIG. 2, both of which have traction drive mechanisms. That is, both the main roller shaft 21a and the motor 19a are made of ferromagnetic material, and the magnet roller 20 is interposed as an idler between the main roller shaft 21a and the motor shaft 19a. The rotation of the motor 19 is transmitted by the rolling transmission force generated by the attraction force. Reduction ratio main roller shaft 21a and motor shaft 19
It is determined according to the diameter ratio with a. It should be noted that a larger rotational transmission force can be obtained by positioning the magneto row 20 at one position so that it bites into the main roller shaft 21a and the motor shaft 19a.

A rudder/magnet roller type speed reduction mechanism is capable of obtaining a larger transmission force than a planetary type. The reason for this is that while the planetary roller type can generate a transmission torque that is equal to the preload force, the planetary roller type depends on the magnetic force and friction coefficient (therefore, there is a limit to the generated torque).

In the present invention, the photoreceptor seamless belt 5 is slackened before and after the main roller 2a, and the load of the cleaning device 10, which is a large negative shaft load, is placed on the second drive port 3. The rated torque of the first drive unit 2 that moves is sufficiently small to allow wear and tear. Therefore, even if the magnetic roller type is used, the torque for driving the first drive unit can be obtained.

As is clear from the above explanation, the present invention has the following effects.

-(1) Set the writing position by the optical writing unit to the main rotor.
− La top and photoreceptor seamless belt are arranged in the main row.
The structure is such that there is slack at the front and rear of the ribs.
Since the arrangement is such that the load fluctuations caused by the leaning device become a load on the second drive unit, the main roller can perform high-precision rolling motion without being affected by load fluctuations, and the main roller is able to rotate with high precision without being affected by the load fluctuations. Image unevenness 7 can be reduced and high-quality image output can be obtained.

5 (2) Precision can be further improved by using a deceleration mechanism using a traction drive as the drive source for the main roller.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall structure of an electrophotographic recording apparatus for explaining the structure of an embodiment of the photoreceptor drive mechanism of the present invention.
FIG. 2 is a diagram for explaining the drive mechanism of the first drive section,
Fig. 3 is a diagram for explaining the second drive mechanism, Fig. 4 is a diagram for explaining the deceleration mechanism using a magnetic roller, and Part 5 is a diagram for explaining the rotational unevenness accuracy of the main roller in response to load fluctuations. It is a characteristic diagram which shows an example of the result of measuring a relationship. DESCRIPTION OF SYMBOLS 1... Optical writing unit, 2... First drive part, 2a.
...Main roller, 2b, 2c...Nip roller, 3
a. 3b, 3c, 3d = nip roller, 4a, 4b-driven roller, 5... photoreceptor seamless belt. Figure 1!

Claims (1)

[Claims] 1. In a photoconductor drive mechanism of an electrophotographic recording device using a laser as a light source, a photoconductor made of a seamless belt, a first drive part made of a main roller and a nip roller, and the first drive and a second drive part that is arranged before and after the part and driven by a rotation synchronized with the rotation of the first drive part,
A photoconductor drive mechanism, characterized in that the photoconductor is driven with a slack portion provided between a first drive section and a second drive section. 2. A traction drive mechanism such as a planetary roller speed reducer or a magnetic roller speed reducer is interposed between the first drive section and the motor that rotationally drives the first drive section. 1. The photoreceptor drive mechanism according to 1.