JP2000203084A - Image forming apparatus and positioning method of LED array head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high quality image by fixing an LED array and a photosensitive body to a same fixing member thereby obtaining a focus spot of desired shape constantly on the photosensitive body. SOLUTION: A fixing member, i.e., an upper cover 2, is fixed to open/close freely at the upper part of a body case 1 with a shaft 3 as a fulcrum. The upper cover 2 is fixed with a photosensitive body 4, an LED array head 5, a charger 6, a neutralization LED 7, and the like. The LED array head 5 is unitized while facing an LED array arranged with a large number of LED elements in line and a lens array arranged with a large number of lenses in line each other. Since a constant distance can be kept between the photosensitive body 4 and the LED array head 5, high quality imaging can be carried out continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus using an LED array head and a method for positioning the LED array head.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an image forming apparatus such as a copying machine, a printer, a facsimile or the like using an LED array head as an optical writing means in order to achieve miniaturization and simplification. The LED array head is a combination of an LED array in which a large number of LED elements are arranged in a line and a lens array in which a large number of lenses are arranged in a line. The light emitted from the LED elements is condensed by the lenses constituting the lens array, and is imaged on the surface of the photoconductor with a predetermined spot diameter, so that an electrostatic latent image is formed on the photoconductor. Note that the LED array and the lens array are fixed to a holder or the like, and the positional relationship is fixed.

[0003] It is practically impossible to manufacture a large number of LED elements constituting an LED array so that the characteristics thereof are all the same. Therefore, the amount of light from each LED element varies.

In an image forming apparatus using an LED array head, an image is formed by the same LED element in the sub-scanning direction. Therefore, if the amount of light of each LED element varies, the variation in the amount of light is caused by the variation. Vertical streaks (streaks along the sub-scanning direction) occur. The vertical streak includes a white streak in which an image becomes white due to a small amount of light, and a black streak which becomes blacker than other portions due to a large amount of light.

[0005] For this reason, in an image forming apparatus using an LED array head, an invention for correcting the amount of light of each LED element to be uniform is disclosed in Japanese Patent Laid-Open No. Hei 5-43.
No. 76 and JP-A-5-50653. In the invention described in JP-A-5-4376, trimming is performed by laser light, the resistance value is adjusted, and the light amount is kept constant. According to the invention described in Japanese Patent Application Laid-Open No. 5-50653, correction data for making the light amount of each LED element constant is obtained in advance, and this correction data is obtained by R
Each of the LED elements is stored in the OM, and each LED element is turned on using the correction data during image formation.

Here, even if the light quantity from each LED element becomes uniform, if the positional relationship between the LED array head and the photoconductor changes, the shape of the image spot formed on the surface of the photoconductor changes. As a result, the quality of the formed image deteriorates.

For this reason, Japanese Patent Application Laid-Open No. 2-140762 discloses an invention in which the positional relationship between the LED array head and the photosensitive member is always constant.
According to the invention described in Japanese Patent Application Laid-Open No. 2-140762, a part of the LED array head is brought into contact with a part of a process cartridge exterior enclosing the photosensitive member, thereby forming the LED array head and the photosensitive member. The distance between is kept constant.

[0008]

However, Japanese Patent Laid-Open No. 2-1
In the invention described in Japanese Patent No. 40762, the opening and closing of the main body cover and the attachment and detachment of the process cartridge are repeatedly performed.
The contact portion is worn or deteriorated, and the distance between the LED array head and the photoconductor gradually changes. As a result, the spot diameter formed on the surface of the photoconductor changes, and the quality of the formed image deteriorates.

Here, the life of the LED array head is substantially the same as the life of the main body of the image forming apparatus. Further, in recent years, the life of the photosensitive member has been extended and is approaching the life of the main body of the image forming apparatus. In addition, there is no need to include the photosensitive member in a process cartridge which is a unit of consumable parts.

Accordingly, the present invention is to form a high quality image by always obtaining an image spot of a desired shape on the photoconductor by keeping the distance between the LED array head and the photoconductor constant. It is an object of the present invention to provide an image forming apparatus and a method for positioning an LED array head that can perform the above-described operations.

[0011]

According to the first aspect of the present invention,
An LED array head in which a large number of LED elements whose lighting is controlled in accordance with image data are linearly arranged, and a lens array in which a large number of lenses are linearly arranged, and an LED array head arranged to face the LED array head In the image forming apparatus provided with the photoconductor, the LED array head and the photoconductor are fixedly mounted on the same mounting member.

Here, "the LED array head and the photoreceptor are fixedly mounted" means that once the LED array head and the photoreceptor are once mounted, the cover is opened and closed, and consumable parts are replaced. This means that the distance between the LED array head and the photoreceptor is kept constant even if the above operations are performed.

Therefore, even if the cover provided in the image forming apparatus is opened and closed or a consumable part is replaced, the distance between the LED array head and the photosensitive member is kept constant, and the distance between the LED array head and the photosensitive member is always constant. It is possible to obtain an image spot having a uniform shape, and to continuously perform high-quality image formation.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the photoconductor and the LED array head are assembled integrally and attached to the attachment member.

Therefore, when attaching the LED array head and the photoconductor to the mounting member, it is not necessary to adjust the distance between the LED array head and the photoconductor, and the distance between the LED array head and the photoconductor to the mounting member is eliminated. Mounting work becomes easy. Further, the distance between the LED array head and the photoconductor is kept constant, and an image spot having a constant shape can always be obtained on the photoconductor, and high-quality image formation can be continuously performed. Further, in each image forming apparatus, L
Variations in the distance between the ED array head and the photoconductor are eliminated, and the quality of an image formed by each image forming apparatus becomes uniform.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, a positioning member is attached to a rotation center axis of the photoconductor, and the LED is attached to the positioning member.
By attaching the array head, the photoconductor and the LED array head are integrally assembled.

Accordingly, the distance between the photoconductor and the LED array head is kept constant, and an image spot having a constant shape can always be obtained on the photoconductor, and high quality image formation can be continuously performed. .

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, the photosensitive member and the LE are provided.
An adjustment mechanism for adjusting the distance from the D array head is provided.

Therefore, by adjusting with the adjusting mechanism,
The photoconductor and the LED array head can be adjusted to an optimum distance, the image spot formed on the photoconductor can be formed in an optimum shape, and an even higher quality image can be formed.

According to a fifth aspect of the invention, there is provided a method for positioning an LED array head, comprising: a photoconductor and an LE facing the photoconductor.
In an image forming apparatus, a D array head is fixedly mounted on the same mounting member, and has an adjustment mechanism for adjusting a distance between the photoconductor and the LED array head. Adjustment of the distance to the LED array head was performed while outputting an image.

Therefore, an image spot having a desired shape can be reliably obtained, and high quality image formation can be performed.

The invention according to claim 6 is the invention according to claim 5,
In the positioning method of the ED array head, the distance between the photoconductor and the LED array head is adjusted while outputting an image obtained by repeating one dot lighting and one dot turning off.

Here, "repeat of turning on one dot and turning off one dot" means to turn on every other LED element in the LED array. By performing such lighting to form an image, the formed image has noticeable image unevenness and vertical streaks caused by distortion of an imaged spot and a slight difference in spot diameter.

Therefore, the distance between the photoconductor and the LED array head is adjusted to an optimum distance by adjusting the distance between the photoconductor and the LED array head while observing the appearance of image unevenness and vertical stripes. can do.

The invention according to claim 7 is the invention according to claim 5, wherein
In the positioning method of the ED array head, the distance between the photoconductor and the LED array head is adjusted while outputting an image obtained by repeating one dot lighting and two dots turning off.

Here, "repetition of turning on one dot and turning off two dots" means turning on every third LED element in the LED array. By performing such lighting to form an image, the formed image has noticeable image unevenness and vertical streaks caused by distortion of an imaged spot and a slight difference in spot diameter.

Therefore, the distance between the photoconductor and the LED array head is adjusted to an optimum distance by adjusting the distance between the photoconductor and the LED array head while observing the appearance of image unevenness and vertical stripes. can do.

[0028]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. 1 and 2 are schematic side views showing the entire structure of an LED array printer as an image forming apparatus, FIG. 3 is a block diagram showing an LED array driving unit,
FIG. 4 is a timing chart showing the drive timing of the LED array, and FIG. 5 is a block diagram showing the LED array controller.

As shown in FIG. 1 and FIG. 2, the LED array printer has an upper cover 2 as a mounting member mounted on a main body case 1 so as to be openable and closable about a support shaft 3 as a fulcrum. On the upper cover 2, a photoconductor 4, an LED array head 5, a charging charger 6, an LED 7 for static elimination and the like are fixedly mounted. The LED array head 5 is unitized by opposing an LED array having a large number of LED elements arranged in a line and a lens array having a large number of lenses arranged in a line.

The main unit 1 is provided with a developing unit 8, a transfer roller 9, a cleaning unit 10, a fixing unit 11, a paper feed tray 12, a paper discharge tray 13, and the like. When the upper cover 2 is turned to the closed position shown in FIG. 2, the developing unit 8, the transfer roller 9, and the cleaning unit 10 are arranged at positions close to and facing the outer peripheral surface of the photoconductor 4.

The LED array driving section shown in FIG. 3 has a well-known configuration, and includes a shift register, a latch, an AND gate, and an LED driver. FIG. 4 is a timing chart showing the driving timing. The shift register is reset by the main scanning line synchronization signal (LSYNC), and the CLOCK shifts the one-dot binary image data “0” or “1” from the dot 1 to the dot 1. Input is performed in order, and internally, each dot data is transmitted to each register. When all the n dot data have been sent, the dot data is latched, and when STB is input to the AND gate, only the LED element to which "1" of the image data has been sent is set to STB by the LED driver.
Is lit only for the width of

In the LED array controller shown in FIG. 5, the FIFO for taking in image data from the outside is reset by a main scanning line synchronization signal (LSYNC) from the controller, and takes in image data for one main scanning line. At the same time, the LED array drive unit is reset by LSYNC, and image data is sequentially sent from the FIFO to the LED array drive unit from dot 1 by the clock signal (CLOCK) generated from the oscillator. The strobe pulse generation unit includes, for example, a counter, a comparator, and the like, and outputs a strobe pulse (STB)
After all the dot data are sent to the shift register and latched, they are output to the AND gate of the LED array driving unit. Thereby, the LED element of the image data “1” emits light at the timing of STB.

In such a configuration, the photosensitive member 4 and the LE
Since both the D array head 5 and the D array head 5 are fixedly mounted on the upper cover 2, the upper cover 2 can be opened and closed,
Even if consumable parts such as the developing unit 8 and the cleaning unit 10 are replaced, the distance between the photoconductor 4 and the LED array head 5 is kept constant, and the distance does not change. Therefore, when the LED element emits light, an image spot having a constant shape can be always obtained on the photoreceptor 4, and high quality image formation can be continuously performed.

In the present embodiment, the photosensitive member 4
Although the case where the LED array head 5, the charging charger 6, and the charge removing LED 7 are fixedly mounted on the upper cover 2 has been described as an example, the present invention is not limited to such a structure. The LED array head 5 is fixedly mounted on the same mounting member so that the positional relationship between the photoconductor 4 and the LED array head 5 does not change even when the user opens and closes the cover or replaces a consumable part. I just need.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. 1 to 5 are denoted by the same reference numerals, and description thereof will be omitted (the same applies to the following embodiments). The photoconductor 4 is provided with a rotation center shaft 14 that rotates integrally with the photoconductor 4. Both ends of the rotation center shaft 14 are supported by bearings 15 on the upper cover 2.
It is held by a side plate 16 fixed inside (see FIGS. 1 and 2). A gear 17 is fixed to one end of the rotation center shaft 14, and the gear 17 and a gear 20 fixed to a motor shaft 19 of a motor 18 mesh with each other.

Further, a pair of positioning members 22 are attached to both ends of the rotation center shaft 14 via bearings 21, and a top plate 23 is fixed between these positioning members 22. The top plate 23 extends parallel to the rotation center axis 14, and the LED array head 5 is fixed to the top plate 23. Each of the pair of positioning members 22 is fixed to the side plate 16 by a fixing member 24, and is positioned so that the LED array head 5 does not move in the circumferential direction with respect to the photoconductor 4.

The photoconductor 4, the positioning member 22, the top plate 23, and the LED array head 5 are integrally assembled into a unit before being attached to the upper cover 2, and this unit is attached to the side plate 16 of the upper cover 2. Have been.

In such a configuration, when the LED array head 5 and the photoconductor 4 are mounted on the side plate 16 of the upper cover 2, it is not necessary to adjust the distance between the LED array head 5 and the photoconductor 4. The work of attaching the LED array head 5 and the photoconductor 4 to the side plate 16 becomes easy. Also,
LED array head 5 in each LED array printer
Of the distance between the photoconductor 4 and the
The quality of the image formed by the D array printer becomes uniform.
Further, the distance between the LED array head 5 and the photoconductor 4 is kept constant, so that an image spot having a constant shape on the photoconductor 4 can always be obtained, and high quality image formation can be performed.

Next, a third embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. A pair of positioning members 22 are attached to the rotation center shaft 14 via bearings 21, and an adjusting mechanism 25 is provided between these positioning members 22.
The top plate 23 is attached via the. The LED array head 5 is fixed to the top plate 23.

The adjusting mechanism 25 adjusts the distance between the LED array head 5 and the photoconductor 4, and includes two sliding grooves 25a formed in the positioning member 22 and the top plate 2
3 is formed by a screw rod 25b fixed to both ends and inserted into the slide groove 25a, and a fixing screw 25c screwed into the screw rod 25b to tighten and fix the top plate 23 to the positioning member 22 at an arbitrary position. ing.

In such a configuration, the fixing screw 25c
By loosening the top plate 23, the top plate 23 can be slid along the slide groove 25a in a direction of coming into contact with and separating from the photoconductor 4, and the top plate 23 is fixed at an arbitrary slide position by tightening the fixing screw 25c. can do.
As a result, the LED array head 5 and the photoconductor 4 can be adjusted to an optimum distance, and an image spot formed on the photoconductor 4 can be formed in an optimum shape, so that an even higher quality image can be obtained. Can be formed.

After the photoconductor 4 and the LED array head 5 are fixedly mounted on the upper cover 2 and the upper cover 2 is closed, the fixing screw 25c is loosened or tightened, and the fixing screw 25c is loosened. When top 23
If the user can perform an operation of sliding the photoreceptor 4 toward and away from the photoconductor 4, it is possible to actually output an image and adjust the position by sliding the top plate 23 while viewing the image. By adjusting the distance between the photoreceptor 4 and the LED array head 5 while viewing the output image, it is possible to reliably obtain an image spot having a desired shape, and to form an even higher quality image. Can be performed.

The image output at this time is obtained by repeating one dot lighting and one dot extinguishing in order to make image unevenness and vertical streaks caused by distortion of an imaged spot and a small difference in spot diameter noticeable. The vertical line image obtained by repeating the lighting of one dot and the turning off of two dots depending on the size of one dot is used. Then, while observing the appearance of image unevenness and vertical stripes,
By adjusting the position of L, the L fixed to the top plate 23 is adjusted.
The distance between the ED array head 5 and the photoconductor 4 can be adjusted to an optimum distance.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. A pair of positioning members 22 are mounted on the rotation center shaft 14 via bearings 21 (see FIGS. 6 and 7), and a top plate 23 is mounted between these positioning members 22 via an adjustment mechanism 26. ing. The LED array head 5 is fixed to the top plate 23.

The adjusting mechanism 26 is a mechanism for adjusting the distance between the LED array head 5 and the photoreceptor 4. One adjusting groove 26 a formed on the positioning member 22 and one
3, a pin 26b inserted into the slide groove 26a and inserted into the slide groove 26a, a projection 26c fixed to the outer surface of the positioning member 22, and a female screw 26d formed in the projection 26c. Pin 2 in the direction of urging the
6 b, a projection 26 f fixed to the inner surface of the positioning member 22, and one end fixed to the projection 26 f and the other end contacting the top plate 23, so that the top plate 23 is Spring 2 biasing in the direction away from
6 g.

In such a configuration, the adjusting screw 26e
By tightening or loosening the, the top plate 23 can be slid along the slide groove 26a in the direction of coming into contact with and separating from the photoconductor 4, whereby the LED array head 5 and the photoconductor 4 can be separated from each other. The distance can be adjusted to an optimum value, and the image spot formed on the photoconductor 4 can be formed in a more uniform shape, so that a high-quality image can be formed. Regardless of the position where the adjustment screw 26e is operated, the position of the top plate 23 is always fixed by the urging force of the leaf spring 26g.

In the present embodiment, the photosensitive member 4
Or the LED array head 5 is fixed to the upper cover 2, and after the upper cover 2 is closed, an operation of loosening or tightening the adjustment screw 26e can be performed, so that an image is actually output and the image is output. The position can be adjusted by sliding the top plate 23 while watching. By adjusting the distance between the photoreceptor 4 and the LED array head 5 while viewing the output image, it is possible to reliably obtain an image spot having a desired shape, and to form an even higher quality image. Can be performed.

The image output at this time is obtained by repeating one dot lighting and one dot extinguishing in order to make image unevenness and vertical streaks caused by distortion of an imaged spot and a slight difference in spot diameter noticeable. The vertical line image obtained by repeating the lighting of one dot and the turning off of two dots depending on the size of one dot is used. Then, while observing the appearance of image unevenness and vertical stripes,
By adjusting the position of L, the L fixed to the top plate 23 is adjusted.
The distance between the ED array head 5 and the photoconductor 4 can be adjusted to an optimum distance.

[0049]

According to the first aspect of the present invention, in an image forming apparatus using an LED array head, a photosensitive member and an L
Since the ED array head and the ED array head are fixedly mounted on the same mounting member, even if the cover provided in the image forming apparatus is opened or closed, or a consumable part is replaced, etc. The distance between them can be kept constant, whereby an image spot having a constant shape can always be obtained on the photoreceptor, and high-quality image formation can be continuously performed.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the photoconductor and the LED array head are integrally assembled and fixed to the mounting member. When attaching the head to the mounting member, it is not necessary to adjust the distance between the photoconductor and the LED array head, and the work of mounting the photoconductor and the LED array head to the mounting member can be easily performed, Further, high-quality image formation can be continuously performed while maintaining a constant distance between the photoconductor and the LED array head.
The image quality can be made uniform in all the image forming apparatuses by eliminating variations in the distance from the array head.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, a positioning member is attached to a rotation center axis of the photosensitive member, and the LED array head is attached to the positioning member. And LED
Since the array head is integrally assembled, the distance between the photoreceptor and the LED array head can be kept constant, and an image spot having a constant shape can always be obtained on the photoreceptor. Quality image formation can be continuously performed.

According to the fourth aspect of the present invention,
4. The image forming apparatus according to 2 or 3, wherein the photosensitive member and the LED
An adjustment mechanism is provided to adjust the distance between the array head and the photoreceptor. By adjusting this adjustment mechanism, the photoconductor and the LED array head can be adjusted to the optimal distance, and the photoconductor is formed on the photoconductor. The formed imaging spot can be formed in an optimal shape, and an even higher quality image can be formed.

According to the LED array head positioning method of the present invention, the photosensitive member and the LE by the adjusting mechanism are used.
Since the adjustment of the distance to the D array head is performed while outputting an image, an image spot having a desired shape can be reliably obtained, and high-quality image formation can be performed.

According to the sixth aspect of the present invention, in the method of positioning the LED array head according to the fifth aspect, the adjustment by the adjustment mechanism is performed while outputting an image obtained by repeating one dot on and one dot off. Therefore, the formed image becomes noticeable due to image unevenness and vertical streaks caused by distortion of the imaging spot and slight difference in spot diameter.By observing the appearance of the image unevenness and vertical streaks,
The distance between the photoconductor and the LED array head can be adjusted to an optimum distance.

According to the seventh aspect of the present invention, in the LED array head positioning method according to the fifth aspect, the adjustment by the adjustment mechanism is performed while outputting an image obtained by repeating one dot on and two dots off. Therefore, the formed image becomes noticeable due to image unevenness and vertical streaks caused by distortion of the imaging spot and slight difference in spot diameter.By observing the appearance of the image unevenness and vertical streaks,
The distance between the photoconductor and the LED array head can be adjusted to an optimum distance.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a state in which an upper cover is opened in an LED array printer according to a first embodiment of the present invention.

FIG. 2 is a schematic side view showing a state in which an upper cover in the LED array printer is closed.

FIG. 3 is a block diagram illustrating an LED array driving unit.

FIG. 4 is a timing chart showing the driving timing of the LED array.

FIG. 5 is a block diagram illustrating an LED array control unit.

FIG. 6 is a front view showing a mounting structure of a photoconductor and an LED array head in an LED array printer according to a second embodiment of the present invention.

FIG. 7 is a front view showing a mounting structure of a photoconductor and an LED array head in an LED array printer according to a third embodiment of the present invention.

FIG. 8 is a side view thereof.

FIG. 9 is a front view illustrating a mounting structure of a photoconductor and an LED array head in an LED array printer according to a fourth embodiment of the present invention.

FIG. 10 is a side view thereof.

[Explanation of symbols]

 2 Mounting Member 4 Photoconductor 5 LED Array Head 14 Rotation Center Axis 22 Positioning Member 25, 26 Adjusting Mechanism

Claims (7)

[Claims] 1. An LED array head in which an LED array in which a large number of LED elements whose lighting is controlled according to image data is linearly arranged and a lens array in which a large number of lenses are linearly arranged are unitized. An image forming apparatus comprising a photoreceptor opposed to an array head, wherein the LED array head and the photoreceptor are fixedly mounted on the same mounting member. 2. The image forming apparatus according to claim 1, wherein the photoconductor and the LED array head are assembled integrally and attached to the attachment member. 3. A positioning member is mounted on a rotation center axis of the photoconductor, and the LED array head is mounted on the positioning member.
3. The image forming apparatus according to claim 2, wherein the ED array head is assembled integrally. 4. The image forming apparatus according to claim 1, further comprising an adjusting mechanism for adjusting a distance between the photoconductor and the LED array head. 5. A photoconductor and an LED array head facing the photoconductor are fixedly mounted on the same mounting member, and have an adjustment mechanism for adjusting a distance between the photoconductor and the LED array head. In the image forming apparatus, the adjustment of the distance between the photoconductor and the LED array head by the adjustment mechanism is performed while outputting an image, and the method for positioning an LED array head is provided. 6. The apparatus according to claim 5, wherein the distance between the photoconductor and the LED array head is adjusted while outputting an image obtained by repeating one dot on and one dot off. LED array head positioning method. 7. The apparatus according to claim 5, wherein the distance between the photoconductor and the LED array head is adjusted while outputting an image obtained by repeating one dot on and two dots off. LED array head positioning method.