JP2000249958A - Optical scanning device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the inexpensive optical scanning device which has small image density irregularity and dot and line-size irregularity by making the scanning speed and scanning time of a laser beam constant by rotating a motor at a high speed in a stable rotation area and then rotating a rotary polygon mirror stably at a low speed by using a speed reducing means. SOLUTION: The motor 3 is rotated at the high speed in the stable rotation area and then the speed reducing mechanism 4 is used to stably rotate the rotary polygon mirror 2 at a low speed. For the speed reducing mechanism 4, gears having different diameters, a magnetic pulley, an idler, a pulley belt, etc., are used. Consequently, the low-speed rotation of the rotary polygon mirror 2 becomes stable. To stabilize the rotation of the motor 3, an inertial mass body 5 is provided on the shaft of the motor 3 or the shaft of the rotary polygon mirror 2. This inertial mass body 5 is made of a disklike member which has a radius nearly equal to or larger than the radius of rotation of the rotary polygon mirror and also has mass equal to or larger than that of the rotary polygon mirror 2. As the disklike member, a plate or casting of iron, aluminum, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device in an image forming apparatus, and more particularly, to a rotating polygon mirror (polygon mirror) which emits laser light whose emission is controlled in accordance with image information.
The present invention relates to an image forming apparatus of a type that forms a latent image on a recording medium by using the method, and relates to rotation control of the rotary polygon mirror when the recording medium has low sensitivity.

[0002]

2. Description of the Related Art FIG. 2 is a schematic diagram of a main part for explaining an example of an image forming apparatus to which the present invention is applied.
Is a semiconductor laser light source whose emission is controlled in accordance with an information signal. For example, a semiconductor laser light source 10 is irradiated with laser light from the laser light source 1, and a recording body on which a latent image corresponding to image information is formed, Reference numeral 20 denotes a recording medium roller for carrying the recording medium 10, and 30 denotes an inking unit including an ink supply tank 31, an ink scraping blade 32, an inking roller 33, and the like. This is a developing section for forming an image. 40 is an intermediate transfer roller, 50 is a recording paper, 60 is a pressure roller, 70 is an infrared heater, and 80 is
Web cleaner 81, cleaning liquid supply tank 82
And a cleaning unit having the same. FIG. 2 shows an example in which the intermediate transfer roller 40 is used. However, the intermediate transfer roller 40 is not always necessary, and the intermediate transfer roller 40 is eliminated, and the ink image formed on the recording body 10 is removed. The recording paper 5 directly without the intermediate transfer member 40
0 may be transferred.

The image forming apparatus shown in FIG. 2 forms an image on a recording paper 50 by a series of operations described below. (At the time of image writing) In a state where the inking unit 30, the intermediate transfer roller 40, the cleaning unit 80, and the like are separated from the recording body roller 20, the light emission of the semiconductor laser 1 is controlled in accordance with an image signal and the semiconductor laser 1 is recorded. An image is written on the recording body 10 by optical scanning in the axial direction of the body 10. As the optical scanning method, a method of writing while moving the laser unit in the main scanning direction by a linear motor or the like while rotating the recording body roller 20 can be applied. However, in the present invention, as described later, the laser beam from the semiconductor laser 1 is reflected by using a rotating polygon mirror (polygon mirror), and the recording body 10 is written by main scanning.

(At the time of printing) The recording paper 50 is fed while the inking unit 30 and the intermediate transfer roller 40 are pressed against the recording medium 10. As the inking unit 30, a plurality of inking rollers 33 whose ink layer thickness is controlled by a blade 32 or the like are used. To supply ink, use blade 32
The ink is dropped from the ink supply tank 31 from above to supply the ink.

[0005] After recording a desired number of sheets, that is, after printing, the intermediate transfer roller 40 and the inking roller 30 are separated from the recording body 10 and the cleaning unit 80 is pressed against the recording body 10 so that the recording body 10 is pressed. Remove the ink remaining on top. After the ink on the recording medium 10 is removed, the recording medium 10 is heated by the infrared heater 70 to erase the latent image during the previous recording (printing). As the cleaning unit 80, the cleaning liquid is impregnated into the web 81 from the cleaning liquid supply tank 82, and the web 81 impregnated with the cleaning liquid is pressed against the recording medium 10 to clean the ink remaining on the recording medium 10. ,Remove.

FIG. 3 is a main part for explaining an example of a case where a laser beam from the laser light source 1 is irradiated on the recording medium 10 to form a latent image on the recording medium 10 in accordance with image information. In the drawing, 1 is a semiconductor laser light source, 2 is a rotary polygon mirror (polygon mirror) for reflecting laser light from the laser light source 1, and 3 is a rotary polygon mirror that rotates the laser light source. 1 to reflect the laser beam from the recording medium 10
A rotary polygon mirror drive motor for optically scanning the upper side in the direction of arrow A and writing image information from the laser light source 1 on the recording body 10.

FIG. 4 is a sectional view of an essential part for explaining an example of a recording body 10 to which the present invention is applied. In the example shown in FIG. 4A, a recording layer 11, a photothermal conversion layer 12, and a substrate 13 are shown. FIG. 4B shows a recording layer 1 in which a light-to-heat conversion material is dispersed.
An example composed of 1 'and the substrate 13 is shown. Recording layer 11, 1
1 'has a heat-sensitive wettability changing function, and when the recording layer is irradiated with a laser beam and heated, the receding contact angle of the heated portion is reduced to be lyophilic and a latent image is formed. .

As shown in FIG. 3, a laser beam modulated by an image information signal is optically scanned on a recording medium using a rotary polygon mirror to form a latent image on the recording medium. Optical scanning devices are often used in laser beam printers that use an electrophotographic method, and form an electrostatic latent image by photoelectric conversion by performing optical scanning on a precharged photoconductor in accordance with image information. Since the photoreceptor has high sensitivity, it is possible to output several to several tens of A4-size printed materials per minute even if a laser having an output of about several mW is used.

[0009]

However, by performing optical scanning on a recording material having a photothermal conversion layer or a recording material having a recording layer in which a photothermal conversion agent is dispersed as shown in FIG. In the case of recording by the method, since the recording medium has extremely low sensitivity, it must be realized by using a high output laser or by increasing the scanning time.

In order to reduce the cost of the apparatus, it is desirable to increase the scanning time without using an expensive high-power laser. However, increasing the scanning time means reducing the scanning speed. For example, in a type in which a rotating polygon mirror is rotated by a motor, the rotating polygon mirror is driven at a low rotation. However, in that case, the inertia action by rotation does not work, so the rotation speed becomes unstable,
Irregularities occur in the rotation of the polygon mirror, leading to fluctuations in the scanning speed and scanning time of the laser beam, resulting in non-uniformity in photothermal conversion, which in turn results in non-uniform image density, non-uniform dot and line sizes (thick and thin), and the like. There is a problem of appearing.

As described above, in an optical scanning device using a rotary polygon mirror, when the rotary polygon mirror is driven at a low rotation speed by a motor, inertial action due to rotation does not work, so that the rotation speed becomes unstable and the polygon mirror becomes unstable. Of the laser beam, resulting in fluctuations in the scanning speed of the laser beam and fluctuations in the scanning time, resulting in non-uniformity in photothermal conversion, resulting in non-uniformity in image density, non-uniformity in dots and line sizes (thick and thin), and the like. Was. In addition, since the number of components increases as the number of components increases, the cost increases.

[0012]

According to a first aspect of the present invention, there is provided a laser light source whose light emission is controlled in accordance with image information, a rotary polygon mirror for scanning laser light from the laser light source, and the rotary polygon mirror. An image for forming a latent image corresponding to image information by irradiating the laser light on the recording medium, comprising: a motor for rotating the recording medium; and a recording medium irradiated with the laser light reflected by the rotating polygon mirror. In the forming apparatus, the recording body is a low-sensitivity recording medium having a photothermal conversion material that converts the laser light applied to the recording body into heat, and the rotating polygon mirror is driven by a motor through a speed reduction mechanism. It is characterized by being rotated, so that the motor is rotated at a high rotation in a stable rotation area, and the rotating polygon mirror is stably rotated at a low speed using a deceleration means, thereby rotating the polygon mirror at a low speed. Stabilize Scanning speed of the laser beam, the scanning time is constant, is obtained to obtain image density unevenness, dot and line size irregularity (Extra-thinning) inexpensive optical scanning device less like.

According to a second aspect of the present invention, in the first aspect of the present invention, the rotating shaft of the motor or the rotary polygon mirror has a disk-shaped mass body having a mass equal to or greater than that of the rotary polygon mirror. Thereby, the rotation of the polygon mirror at low speed is stabilized, the scanning speed and scanning time of the laser beam are kept constant, and an optical scanning device free from image density unevenness, dot and line size unevenness (thickness / thinness), etc. is obtained. It is like that.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a main part of an embodiment of an optical scanning device according to the present invention.
The method in which the optical scanning method shown in FIG. 3 is applied to a case where a latent image is formed on a recording medium having a photothermal conversion material, so that optical writing can be performed by stabilizing the scanning speed even at a low optical scanning speed. It is.

In an optical scanning device using a rotating polygon mirror,
When the rotating polygon mirror is driven at a low speed by a motor, the rotational speed becomes unstable because the inertial action due to the rotation does not work,
Irregularities occur in the rotation of the polygon mirror, which leads to fluctuations in the scanning speed and scanning time of the laser beam, which in turn leads to non-uniformities in photothermal conversion, such as non-uniform image density, non-uniform dot and line sizes (thick and thin), etc. There was a problem that appeared.

According to the present invention, in order to solve this problem, the motor is rotated at a high speed in a stable rotation range, and the speed reduction mechanism 4 is rotated.
Is used to stably rotate the rotating polygon mirror at a low speed. As the reduction mechanism 4, gears having different diameters, magnetic pulleys / idlers, pulleys / belts, and the like were used. This allows
The rotation of the polygon mirror at low speed became stable, the scanning speed and scanning time of the laser beam became constant, and inexpensive optical scanning with less image density unevenness, dot and line size unevenness (thickness / thinness), etc. was obtained. .

In order to stabilize the rotation of the motor,
As the number of components increases or the complexity increases, the cost increases. Therefore, it is also important to reduce the number of components and simplify the components. In order to solve this, an inertial mass body 5 is provided on the axis of the motor 3 or the axis of the rotary polygon mirror 2. The inertial mass 5 preferably has a radius substantially equal to or greater than the radius of rotation of the rotating polygon mirror,
Alternatively, it is assumed that it is constituted by a disk-shaped member having a mass substantially equal to or greater than that of the rotary polygon mirror. In addition, as a disk-shaped member,
A plate, casting, or the like made of metal such as iron, aluminum, copper, and lead is used. Thereby, the rotation of the polygon mirror at low speed is stabilized, the scanning speed and the scanning time of the laser beam become constant,
An optical scanning device free from image density unevenness, dot and line size unevenness (thickness / thinness), etc. was obtained. In addition, since the constituent members are only the disk-shaped members, they can be realized at low cost.

[0018]

According to the first aspect of the present invention, there is provided a laser light source whose light emission is controlled according to image information, a rotary polygon mirror for scanning laser light from the laser light source, and a rotary polygon mirror for rotating the rotary polygon mirror. A motor, and a recording body irradiated with the laser light reflected by the rotating polygon mirror, in the image forming apparatus that forms a latent image according to image information by irradiating the laser light on the recording body, The recording medium is a low-sensitivity recording medium having a light-to-heat conversion material that converts the laser light applied to the recording medium into heat, and the rotating polygon mirror is rotated by the motor through a speed reduction mechanism. The motor can be rotated at a high rotation speed in a stable rotation region, and the rotating polygon mirror can be stably rotated at a low speed by using a deceleration mechanism, whereby the rotation of the polygon mirror at a low speed is stabilized,
The scanning speed and scanning time of the laser beam are constant, and an inexpensive optical scanning device with less image density unevenness, dot and line size unevenness (thickness / thinness), etc. can be obtained.

According to a second aspect of the present invention, in the first aspect of the present invention, the rotating shaft of the motor or the rotary polygon mirror has a disk-shaped mass body having a mass equal to or greater than that of the rotary polygon mirror. By stabilizing the rotation of the polygon mirror at low speed, keeping the scanning speed and scanning time of the laser beam constant,
An optical scanning device free from image density unevenness, dot and line size unevenness (thickness / thinness), etc. can be obtained.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram for explaining an embodiment of an optical scanning device according to the present invention.

FIG. 2 is a main part configuration diagram for explaining an example of an image forming apparatus to which the optical scanning device according to the present invention is applied.

FIG. 3 is a main part configuration diagram for explaining an example in which a conventional optical scanning device is applied to an image forming apparatus to which the present invention is applied.

FIG. 4 is a diagram showing an example of a recording body on which an image is written according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 laser light source 2 rotary polygon mirror 3 motor 4 reduction mechanism 5 inertial mass 10 recording body 20 recording body roller 30 inking unit 40 intermediate transfer roller 50 ... recording paper, 60 ... pressure roller, 70 ... infrared heater, 80 ... cleaning unit.

Claims (2)

[Claims] 1. A laser light source whose emission is controlled according to image information, a rotary polygon mirror for scanning laser light from the laser light source, a motor for rotating the rotary polygon mirror, and the rotary polygon. A recording medium to which a laser beam reflected by a mirror is applied; and an image forming apparatus that forms a latent image corresponding to image information by irradiating the laser beam on the recording medium. An image forming apparatus, comprising: a low-sensitivity recording medium having a light-to-heat conversion material that converts the laser light applied to a body into heat, wherein the rotary polygon mirror is rotated by the motor via a speed reduction mechanism. Optical scanning device. 2. A rotary shaft of the motor or the rotary polygon mirror,
2. The optical scanning device according to claim 1, further comprising a disk-shaped mass body having a mass equal to or greater than that of the rotary polygon mirror. 3.