JPH05197263A - Image forming device - Google Patents

Abstract

PURPOSE:To simplify the adjusting mechanism of an entire device in the case that scanning density is switched as to an image forming device. CONSTITUTION:When recording density is switched, the speed of a photosensitive body is not changed, clock frequency is proportioned the product of the recording density of main and sub scanning, a slit part 19 switching a spot diameter provided on an optical system in accordance with the recording density is actuated, the rotating speed of a polygon mirror 21 is proportioned beam intensity is changed in accordance with the to the recording density in a sub-scanning direction, and light beam intensity is changed in accordance with the recording density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image by imagewise exposing a photosensitive member with a light beam, and more particularly to an image forming apparatus capable of switching scanning density.

[0002]

2. Description of the Related Art Conventionally, lasers and LEDs have been used as image exposure sources.
In an electrophotographic printer using a printer or the like, recording was usually performed at a fixed scanning density. However, in order to support the situation in which one printer is connected to different image input sources (computers, scanners, facsimiles, image files, etc.) and select the recording speed to enhance the usage environment, the scanning density can be switched. There is a demand for a recording apparatus capable of recording and obtaining an image with a desired resolution. Japanese Unexamined Patent Publication No. 2-134258 proposes an invention of an image forming apparatus which meets the above-mentioned requirements. There, a technique is recorded in which the rotation speed of the optical scanning system is switched together with the frequency for modulating the light beam depending on the scanning density.

By the way, when the scanning density is switched, it is necessary to optimally adjust the spot diameter of the laser beam to the set scanning density accordingly. For example, if exposure is performed at 600 dpi with the spot diameter equivalent to 300 dpi,
Even though the scanning line interval is 1/2 of 300 dpi, exposure is performed with the original line width. As a result, a line having twice the optimum thickness appears, and the resolution and halftone reproducibility are not improved. On the contrary, it is 3 with a spot diameter equivalent to 600 dpi.
When an image of 00 dpi is exposed, a gap is generated between adjacent scanning lines. Although it is possible to include a mechanism for switching the spot diameter in the optical system, the exposure energy of the laser light with which the photoconductor is irradiated is not appropriate.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of simplifying the adjusting mechanism of the entire apparatus when the scanning density is switched.

[0005]

To achieve the above object, the first invention of the present invention is, in an image forming apparatus, a recording density setting means for respectively instructing a recording density of an image to be recorded in a main scanning direction and a sub scanning direction, Clock generation means for generating a clock having a frequency proportional to the product of the recording densities in the main scanning direction and the sub scanning direction set by the recording density setting means, and a light beam for emitting a light beam corresponding to image data based on the clock Generating means, a photoconductor that rotates at a constant speed regardless of the recording density, a rotary reflecting mirror that reflects the light beam while rotating and scans the photoconductor, and a sub-scanning direction set by the recording density setting means. A rotary reflecting mirror driving means for driving the rotary reflecting mirror at a rotation speed proportional to the recording density of
Spot diameter setting means for setting the size of the spot formed by the light beam on the photoconductor on the basis of the recording densities in the main scanning and sub-scanning directions set by the recording density setting means; A light beam intensity setting means for setting the light emission intensity of the light beam based on the recording densities in the main scanning direction and the sub scanning direction set by the setting means, and a charger for charging the photoconductor to a uniform potential before the irradiation of the light beam. And a developing device that develops the electrostatic latent image formed on the photoconductor by the irradiation of the light beam with toner.

According to a second aspect of the present invention, in an image forming apparatus, a recording density setting unit for instructing a recording density of an image to be recorded in the main scanning direction and a sub scanning direction, and a main scanning set by the recording density setting unit. Direction, a clock generating means for generating a clock having a frequency proportional to the recording density, a light beam generating means for emitting a light beam corresponding to image data based on the clock, and a sub-scanning direction set by the recording density setting means. Setting of the recording density setting means, a photoconductor that rotates at a speed inversely proportional to the recording density, a rotary reflecting mirror that reflects the light beam while rotating at a constant speed regardless of the recording density, and scans the photoconductor. Based on the recording densities in the main scanning and sub-scanning directions, the spot diameter setting means for setting the size of the spot formed by the light beam on the photoconductor is formed. And a light beam intensity setting means for setting the light emission intensity of the light beam based on the recording densities in the main scanning and sub-scanning directions set by the recording density setting means, and the photosensitive member to a uniform potential before irradiation of the light beam. A charging device for charging and an electrostatic latent image formed on the photoconductor by irradiation of a light beam are formed by toner under the conditions according to the recording density in the main scanning direction and the sub scanning direction set by the recording density setting means. And a developing device for developing.

According to a third aspect of the present invention, in an image forming apparatus, a recording density setting means for instructing a recording density of an image to be recorded in the main scanning direction and a sub scanning direction, respectively, and a clock having a constant frequency regardless of the recording density. Is inversely proportional to the product of a clock generating means for generating a light beam, a light beam generating means for emitting a light beam corresponding to image data based on the clock, and a recording density in the main scanning direction and the sub scanning direction set by the recording density setting means. And a rotary reflecting mirror that reflects the light beam while rotating at a speed that is inversely proportional to the recording density in the main scanning direction set by the recording density setting unit and scans on the photosensitive body. Based on the recording densities in the main scanning and sub scanning directions set by the recording density setting means, the size of the spot formed by the light beam on the photoconductor is set. Spot diameter setting means, the light beam intensity setting means for setting the light emission intensity of the light beam based on the recording densities in the main scanning and sub-scanning directions set by the recording density setting means, and the exposure before the irradiation of the light beam. A charging device for charging the body to a uniform potential and a condition according to the recording densities in the main scanning direction and the sub scanning direction set by the recording density setting means for the electrostatic latent image formed on the photoconductor by irradiation of the light beam. And a developing device for developing with toner underneath.

According to the first aspect of the invention, when the recording density is switched, the speed of the photosensitive member is not changed and the clock frequency is made proportional to the product of the recording densities of the main scanning and the sub scanning, and the spot diameter provided in the optical system. Activate the slit part to switch
By making the rotation speed of the rotary reflecting mirror (polygon mirror) proportional to the recording density in the sub-scanning direction and changing the light beam intensity according to the recording density, optimum recording conditions for each recording density can be obtained.

According to the second aspect of the invention, when the recording density is changed, the speed of the rotary reflecting mirror is not changed, the photosensitive member speed is made inversely proportional to the recording density in the sub-scanning direction, and the clock frequency is recorded in the main scanning direction. In order to obtain the optimum recording condition for each recording density by operating the slit part that switches the spot diameter provided in the optical system in proportion to the above, and changing the light beam intensity and the developing condition according to the recording density. Become.

According to the third aspect of the invention, when the recording density is switched, the speed of the photosensitive member is made inversely proportional to the product of the recording densities of the main scanning and the sub-scanning without changing the clock frequency, and the rotational speed of the rotary reflecting mirror is controlled. Optimum recording conditions for each recording density by operating the slit part that switches the spot diameter provided in the optical system in inverse proportion to the recording density in the scanning direction and changing the light beam intensity and development conditions according to the recording density. Will be obtained.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of an image forming apparatus according to the present invention. In the first embodiment, when switching the recording density, the speed of the photosensitive member is not changed, the clock frequency is proportional to the product of the recording densities of the main scanning and the sub scanning, and the spots provided in the optical system according to the recording density. Optimum recording conditions for each recording density can be obtained by operating the slit part that switches the diameter, making the rotation speed of the polygon mirror proportional to the recording density in the sub-scanning direction, and changing the light beam intensity according to the recording density. It was done like this.

As shown in FIG. 1, this image forming apparatus includes a photoconductor 1 that carries an image and rotates in the direction of arrow A, a photoconductor motor 2 that rotates the photoconductor 1, and a photoconductor 1. A charger 3 for precharging, and an exposure unit 5 for switching the recording density, which is the gist of the present invention, and irradiating image data as a laser onto the photoreceptor 1 to form an electrostatic latent image. A developing roller 7 for developing the electrostatic latent image formed on the photosensitive member 1 with toner, a developing roller motor 9 for rotating the developing roller 7, and a developing roller motor 9 formed on the photosensitive member 1. And a transfer device 11 for transferring the toner image onto a transfer paper or the like.

Then, the exposure section 5 has a recording density setting section 13 for setting the recording densities Nx and Ny of the main scanning and the sub scanning in accordance with the recording density instruction signal inputted prior to the transfer of the image data, and the recording density setting section 13. A clock generator 15 for generating a clock signal having a frequency proportional to the product of Nx and Ny according to the recording densities Nx, Ny in the main scanning direction and the sub-scanning direction from the recording density setting unit 13, and this clock generating unit 1.
The image data input in accordance with the clock signal from No. 5 is used as the recording density Nx, Ny from the recording density setting unit 13.
According to the recording densities Nx and Ny from the recording density setting section 13 and the semiconductor laser driving section 17 for converting into a laser beam having a laser beam intensity corresponding to the output and outputting the laser beam from the laser driving section 17. A slit portion 19 to be adjusted by the slit portion 19 and a rotation for reflecting the laser beam whose beam diameter is adjusted by the slit portion 19 while rotating at a rotation speed proportional to the recording density Ny in the sub-scanning direction from the recording density setting portion 19. The laser beam reflected by the polygon mirror portion 21 is irradiated onto the photoconductor 1 via the fθ lens 23 and the mirror 25 to form an image, and the photosensitive body 1 is exposed. An electrostatic latent image is formed on the body 1.

That is, the photoconductor 1 is rotated at a constant speed regardless of the recording density, and is pre-charged to a uniform potential by the charger 3 before the laser irradiation, and the electrostatic latent image is generated by the laser irradiation. An image is formed, then developed by the developing devices 7 and 9, transferred to a transfer paper by the transfer device 11, and further fixed by means such as a heat roller.

As shown in FIG. 3, the slit portion 19 has an aperture 31 slidably provided with a plurality of kinds of apertures 30, and the recording density setting portion 13.
And a slide motor 33 for sliding the aperture 31 and exchanging the aperture 30 through which the laser beam passes, driven according to the recording densities Nx and Ny. The polygon mirror section 21 is composed of a rotatable polygonal mirror and a polygon motor that rotationally drives the polygonal mirror.

The laser drive unit 17, the slit unit 19, the polygon mirror unit 21, the fθ lens 23, and the mirror 25 are arranged as shown in FIG. 2 when viewed from above.

Specific numerical examples in the first embodiment of the image forming apparatus having the above-mentioned structure are shown below. Recording density Photoreceptor Polygon clock Beam diameter (main) (sub) Linear velocity Rotation speed Frequency (main × sub) 300dpi 300dpi 60mm / s 7087rpm 8.00MH _Z 70x90μm 600dpi 300dpi 60 7087 8.00 60x90 400dpi 400dpi 60 9449 14.22 60x70 600dpi 600dpi 60 14173 32.00 40x50 1200dpi 600dpi 60 14173 64.00 30x50 Next, referring to FIG. 4, a second image forming apparatus according to the present invention is described.
Examples will be described. In this second embodiment,
When switching the recording density, the speed of the polygon mirror is not changed, the photosensitive member speed is made inversely proportional to the recording density in the sub-scanning direction, the clock frequency is made proportional to the recording density in the main-scanning direction, and the optical system is prepared according to the recording density. By operating the slit part for switching the spot diameter, and changing the light beam intensity and the developing condition according to the recording density, the optimum recording condition for each recording density can be obtained.

In order to achieve the above operation, the exposure unit 40 of the image forming apparatus, as shown in FIG. 4, according to the recording density instruction signal inputted prior to the transfer of the image data, the recording density Nx of the main scanning and the sub scanning. , Ny, a clock generator 41 for generating a clock signal having a frequency proportional to the recording density Nx from the recording density setter 13 in the main scanning direction, and the clock generator 15. Image data input according to the clock signal from the recording density setting unit 13
The semiconductor laser driving unit 17 that converts the laser beam into a laser beam having a laser intensity corresponding to y and outputs the laser beam, and the beam diameter of the laser beam from the laser driving unit 17 is set to the recording densities Nx and Ny from the recording density setting unit 13. It has a slit portion 19 which is adjusted accordingly and a polygon mirror portion 43 which reflects the laser beam whose beam diameter has been adjusted by the slit portion 19 while rotating at a constant rotation speed. The laser beam reflected by the fθ lens 23 and the mirror 2
It is irradiated onto the photoconductor 1 via 5 to form an image.

Here, in the second embodiment, the photoconductor 1 is rotated at a speed inversely proportional to the recording density Ny in the sub-scanning direction from the recording density setting section 13, and the developer is used in the developing process. The rotation speed of the developing roller 7 is set so that the supply speed of R is proportional to the rotation speed of the photoconductor 1.
By doing so, the process conditions are optimized. Since other configurations and operations are similar to those of the first embodiment, the same reference numerals are given and description thereof will be omitted.

Specific numerical examples in the second embodiment of the image forming apparatus having the above-mentioned structure are shown below. Recording density Photoreceptor Polygon clock Beam diameter (main) (sub) Linear speed Rotation speed Frequency (main × sub) 300dpi 300dpi 120mm / s 14173rpm 16.00MH _Z 70x90μm 600dpi 300dpi 120 14173 32.00 60x90 400dpi 400dpi 90 14173 21.33 60x70 600dpi 600dpi 60 14173 32.00 40x50 1200dpi 600dpi 60 14173 64.00 30x50 Next, referring to FIG. 5, the third embodiment of the image forming apparatus according to the present invention.
Examples will be described. In this third embodiment,
When switching the recording density, do not change the clock frequency,
A slit that changes the speed of the photoconductor in inverse proportion to the product of the recording densities in main scanning and sub-scanning, the rotation speed of the polygon mirror in inverse proportion to the recording density in the main scanning direction, and switches the spot diameter provided in the optical system according to the recording density. By operating the parts and changing the light beam intensity and the developing condition according to the recording density, the optimum recording condition for each recording density can be obtained.

In order to achieve the above operation, the exposure unit 50 of this image forming apparatus, as shown in FIG. 5, according to the recording density instruction signal inputted prior to the transfer of the image data, the recording density Nx of the main scanning and the sub scanning. , Ny for setting the recording density, a clock generator 51 for generating a clock signal having a constant frequency, and a clock generator 15.
Image data input according to the clock signal of
A semiconductor laser drive unit 17 for converting and outputting a laser beam having a laser beam intensity corresponding to the recording densities Nx and Ny from the recording density setting unit 13 and a laser beam diameter from the laser drive unit 17 are set to the recording density setting unit. Part 1
3 and the slit portion 19 which is adjusted according to the recording densities Nx and Ny, and the laser beam whose beam diameter is adjusted by the slit portion 19 is inversely proportional to the recording density Nx in the main scanning direction from the recording density setting portion 19. It has a polygon mirror portion 53 that reflects while rotating at the above rotation speed, and the laser beam reflected by this polygon mirror portion 53 is irradiated onto the photoconductor 1 via the fθ lens 23 and the mirror 25. To be imaged.

Here, in the third embodiment, the photosensitive member 1 is at a speed inversely proportional to the product of the recording density Nx in the main scanning direction and the recording density Ny in the sub scanning direction from the recording density setting section 13. It is rotating, and in the developing process, the rotation speed of the developing roller is set so that the supply speed of the developer is proportional to the rotation speed of the photoconductor. By doing so, the process conditions are optimized.

The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

Specific numerical examples in the third embodiment of the image forming apparatus having the above-mentioned structure are shown below.

Recording density Photoreceptor Polygon clock Beam diameter (main) (sub) Linear speed Rotation speed Frequency (main × sub) 300dpi 300dpi 240mm / s 28346rpm 32.00MH _Z 70x90μm 600dpi 300dpi 120 14173 32.00 60x90 400dpi 400dpi 135 21260 32.00 60x70 600dpi 600dpi 80 14173 32.00 40x50 1200dpi 600dpi 40 7087 32.00 30x50

[0026]

In the image forming apparatus, by setting the conditions as described above when switching the recording density, it is possible to always form an image under the optimum conditions.

Particularly in the first aspect of the invention, since the condition can be set without changing the speed of the photosensitive member, it is possible to provide an image forming apparatus having a constant recording speed regardless of the recording density. Further, according to the second aspect of the invention, since the recording density can be switched without changing the speed of the rotary reflecting mirror (polygon mirror), it is possible to obtain a high quality halftone image by minimizing the variation of the polygon rotation speed. Further, in the third invention, since the recording density can be switched without changing the clock frequency, the image signal processing can be stably performed regardless of the recording density, and as a result, the final image can be stably obtained. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a plan view of the optical system shown in FIG. 1 viewed from above.

FIG. 3 is a configuration diagram of a slit portion shown in FIG.

FIG. 4 is a configuration diagram of a second embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a configuration diagram of a third embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

1 photoconductor, 3 charger, 5
Exposure unit, 7 developing roller,
9 developing roller motor, 11 transfer device,
13 Recording Density Setting Section, 15, 41, 5
1 clock generator, 17 laser driver,
19 slit section, 21, 43, 53 polygon mirror section, 23 fθ lens, 25 mirror,
30 apertures, 31 apertures,
33 slide motor,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 15/00 102 H04N 1/17 B 7205-5C 1/387 101 4226-5C

Claims (3)

[Claims] 1. A recording density setting unit for setting a recording density of an image to be recorded in the main scanning direction and a sub scanning direction, respectively, and a product of a recording density in the main scanning direction and the sub scanning direction set by the recording density setting unit. A clock generating means for generating a clock of a frequency, a light beam generating means for emitting a light beam corresponding to image data based on the clock from the clock generating means, and a photoconductor rotating at a constant speed regardless of the recording density. A rotary reflecting mirror that reflects the light beam while rotating and scans on the photosensitive member; and a rotation that drives the rotary reflecting mirror at a rotation speed proportional to the recording density in the sub-scanning direction set by the recording density setting unit. Based on the reflecting mirror driving means and the recording densities in the main scanning and sub-scanning directions set by the recording density setting means, the light beam forms an image on the photosensitive member. Spot diameter setting means for setting the size of a spot, based on the recording density in the main scanning and sub-scanning directions set by the recording density setting means, a light beam intensity setting means for setting the emission intensity of the light beam, A charging device for charging the photoconductor to a uniform potential before the irradiation of the light beam, and a developing device for developing the electrostatic latent image formed on the photoconductor by the irradiation of the light beam with toner. Image forming apparatus. 2. A recording density setting means for setting respective recording densities of an image to be recorded in the main scanning direction and the sub scanning direction, and a clock having a frequency proportional to the recording density in the main scanning direction set by the recording density setting means. Clock generating means, a light beam generating means for emitting a light beam corresponding to image data based on the clock from the clock generating means, and a speed inversely proportional to the recording density in the sub-scanning direction set by the recording density setting means. A photoconductor that rotates at a rotation speed, a rotary reflecting mirror that reflects the light beam while rotating at a constant speed regardless of the recording density and scans the photoconductor, and a main scanning direction and a sub-scanning direction set by the recording density setting unit. A spot diameter setting means for setting a size of a spot formed by the light beam on the photoconductor on the basis of the recording density of the recording density; A light beam intensity setting means for setting the emission intensity of the light beam based on the recording densities in the main scanning direction and the sub scanning direction set by the setting means; and a charger for charging the photoconductor to a uniform potential before the irradiation of the light beam. A developing device for developing an electrostatic latent image formed on a photoconductor by irradiation of a light beam with toner under conditions according to the recording densities in the main scanning direction and the sub-scanning direction set by the recording density setting means. An image forming apparatus comprising: 3. A recording density setting means for respectively instructing recording densities of an image to be recorded in the main scanning and sub-scanning directions, a clock generating means for generating a clock having a constant frequency regardless of the recording density, and the clock generating means. Light beam generating means for emitting a light beam corresponding to image data based on the clock, and a photoconductor rotating at a speed inversely proportional to the product of the recording densities in the main scanning direction and the sub scanning direction set by the recording density setting means. A rotary reflecting mirror that reflects the light beam while rotating at a speed inversely proportional to the recording in the main scanning direction set by the recording density setting unit and scans on the photoconductor; and a main setting by the recording density setting unit. Spot diameter setting means for setting the size of the spot formed by forming the light beam on the photoreceptor based on the recording density in the scanning and sub-scanning directions. A light beam intensity setting means for setting the light emission intensity of the light beam based on the recording densities in the main scanning direction and the sub-scanning direction set by the recording density setting means, and charging the photosensitive member to a uniform potential before the light beam irradiation. And the electrostatic latent image formed on the photoconductor by irradiation of the light beam with toner under the conditions according to the recording densities in the main scanning direction and the sub scanning direction set by the recording density setting unit. An image forming apparatus, comprising: