JP2004302155A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of adjusting the quantity of light for irradiating the surface of a photoreceptor without requiring large-sized complicated constitution. <P>SOLUTION: Twelve LEDs 50 are respectively comparted to either a 1st LED group 51 or a 2nd LED group 52. When it is considered enough that the irradiation amount of the surface of a photoreceptor 21 is about half of that obtained when twelve LEDs 50 all irradiate the surface thereof, the LEDs are controlled so that only six LEDs in the 1st LED group 51 are made to emit light or only six LEDs in the 2nd LED group 52 are made to emit the light by turning on/off switches SW1 and SW2. Therefore, the fatigue of the surface of the photoreceptor occurring because the surface of the photoreceptor is irradiated more than necessary is restrained. In the image forming apparatus where the rotating speed of the photoreceptor at the time of forming an image is decided in accordance with an image forming mode, a problem that the fatigue of the photoreceptor is accelerated because the surface of the photoreceptor is irradiated more than necessary is solved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, and more particularly, to an electrophotographic image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art An electrophotographic image forming apparatus includes a static eliminator. The static eliminator irradiates the surface of the photoreceptor after image transfer to remove unnecessary charges on the surface of the photoreceptor.
Some image forming apparatuses of this type are capable of switching the rotation speed of a photoconductor during printing. In the image forming apparatus, when the photoconductor rotates at a low speed, it is possible to print an image with higher resolution in the sub-scanning direction of the image than at the time of high-speed rotation (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-108406 A
[Problems to be solved by the invention]
By the way, the static eliminator of the image forming apparatus irradiates the surface of the photoconductor with a constant amount of light regardless of the rotation speed of the photoconductor. Accordingly, when the photoconductor rotates at a low speed, the surface of the photoconductor is irradiated more than necessary, and there is a problem that the fatigue of the surface of the photoconductor is accelerated.
In addition, there is also a problem that a large and complicated configuration such as a normal shutter mechanism is required in order to adjust the amount of light applied to the photoconductor surface.
[0005]
The present invention has been made under such a background, and an object of the present invention is to provide an image forming apparatus capable of suppressing fatigue of the surface of a photoconductor when the rotation speed of the photoconductor is switched.
Another object of the present invention is to provide an image forming apparatus capable of adjusting the amount of light applied to the surface of a photoreceptor without requiring a large and complicated structure.
[0006]
Means for Solving the Problems and Effects of the Invention
The invention according to claim 1 is an electrophotographic image forming apparatus comprising: a photoreceptor whose rotation speed can be switched; and a static eliminator for irradiating the photoreceptor surface to remove unnecessary charges on the surface. An image forming apparatus, comprising: a control unit that controls a light amount irradiated by the static eliminator according to a rotation speed of the photoconductor.
[0007]
According to the present invention, it is possible to control the amount of light applied to the surface of the photoconductor in accordance with the rotation speed of the photoconductor. Thereby, it is possible to prevent the surface of the photoconductor from being irradiated more than necessary, and to suppress fatigue of the surface of the photoconductor.
According to a second aspect of the present invention, in the static eliminator, a light emitting element that emits light when a current is supplied is provided at predetermined intervals in an axial direction of the photoconductor, and the light emitting element includes a plurality of light emitting elements. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is divided into element groups, and the control unit controls whether or not to supply a current to the light emitting elements for each of the divided light emitting element groups.
[0008]
According to the present invention, a plurality of light emitting elements that emit light when a current is supplied are divided into several light emitting element groups, and it is controlled whether or not a current is supplied to the light emitting elements for each of the light emitting element groups. Can be. Therefore, the surface of the photoreceptor is evenly irradiated when the time is averaged, so that unnecessary charges on the surface of the photoreceptor can be efficiently removed. Further, unnecessary charges on the surface of the photoconductor can be efficiently removed without requiring a large and complicated structure such as a shutter mechanism.
[0009]
4. The light emitting device according to claim 3, wherein the image forming apparatus is supplied with a current when the photoconductor rotates at the standard rotation speed, which is a certain rotation speed of the photoconductor. The light emitting element standard number is preset, and when the photoconductor rotates at a rotation speed other than the standard rotation speed, the control unit controls the relationship between the rotation speed and the standard rotation speed, and 2. The image forming apparatus according to claim 1, wherein the number of the light emitting elements that supply a current is increased or decreased based on the standard number of the light emitting elements. 3.
[0010]
According to the present invention, a certain rotation speed of the photoconductor and the number of light emitting elements to which current is supplied at that time are set in advance, and when the photoconductor rotates at a speed different from the set rotation speed, The number of light-emitting elements that supply current can be increased or decreased based on the relationship between the preset rotation speed and the actual rotation speed and the preset number of light-emitting elements. That is, when the photoconductor rotates at a speed higher than the standard rotation speed, the number of light emitting elements is increased, and when the photoconductor rotates at a lower speed, the number of light emitting elements is reduced. Thus, even when the photoconductor rotates at a speed different from the preset rotation speed, the photoconductor surface is irradiated with a light amount suitable for removing unnecessary charges on the photoconductor surface. be able to. Thereby, the fatigue of the photoconductor can be suppressed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is an illustrative sectional view showing the structure of a copying machine 1 as an image forming apparatus according to an embodiment of the present invention.
The copying machine 1 includes, for example, an image forming unit 2 including a photoconductor 21, a main charger 22, and a developing device 23. The photoconductor 21 is, for example, a cylindrical body extending in a direction perpendicular to the paper surface of FIG. 1, and is rotated clockwise in FIG. 1 during image formation. During image formation, the surface of the photoconductor 21 is uniformly charged by the discharge of the main charger 22.
[0012]
In this embodiment, the photoconductor 21 is driven to rotate at either high speed or low speed. At low speed, the motor is driven to rotate at about half the speed at high speed. However, the present invention is not limited to this mode. For example, the photoconductor 21 may be driven to rotate at any one of a high speed, a medium speed, and a low speed.
Above the image forming section 2, for example, a laser scanning unit (LSU) 3 is arranged. At the time of image formation, the surface of the photoconductor 21 charged by the main charger 22 is selectively exposed by irradiation light from the laser scanning unit 3 corresponding to a document image. As a result, a so-called electrostatic latent image is formed on the surface of the photoconductor 21. Then, toner is adhered to the surface of the photoreceptor 21 on which the electrostatic latent image is formed by the developing device 23, and a toner image to be transferred to a sheet sent from the sheet cassette 7 to the image forming unit 2 is formed. You. After the transfer to the paper, the surface of the photoconductor 21 is irradiated by the static eliminator 5, and the charge remaining on the surface of the photoconductor 21 is removed.
[0013]
The transfer roller 4 is provided below the photoconductor 21, and is arranged so that the surface thereof faces the surface of the photoconductor 21. The toner image formed on the surface of the photoconductor 21 is transferred when the paper sent from the paper cassette 7 to the image forming unit 2 passes between the photoconductor 21 and the transfer roller 4.
The sheet on which the toner image has been transferred by the image forming unit 2 is guided to the fixing device 6 by a transport belt (not shown). In the fixing device 6, for example, in a process in which the paper passes between the heat roller 61 and the pressure roller 62, a fixing process (heating and pressing) of the toner is performed. Thereafter, the sheet subjected to the fixing process is discharged out of the copying machine 1.
[0014]
The copying machine 1 includes a control unit 10 including a microcomputer and the like, and the control unit 10 controls each unit of the copying machine 1.
The copier 1 includes various print modes. In this embodiment, two types of print modes, a high-speed print mode and a high-quality print mode, are included. When the high-quality print mode is selected, the original image is read while being enlarged twice in the sub-scanning direction, and the enlarged image is formed by the photoconductor 21 that is driven to rotate at a low speed. Thus, an image is printed at twice the resolution of high-speed printing. On the other hand, when the high-speed printing mode is selected, the image is formed on the photosensitive member 21 which is driven to rotate at a high speed. Therefore, the image is printed in about half the time in the high-quality print mode. Which of the high-speed print mode and the high-quality print mode is selected is determined by, for example, an operation of an operation panel (not shown) by an operator.
[0015]
FIG. 2 is a schematic diagram illustrating a surface of the static eliminator 5 as viewed from the photoconductor 21 side.
On the surface of the static eliminator 5 viewed from the photoconductor 21 side, for example, twelve light emitting diodes (LEDs) 50 are provided at predetermined intervals so as to oppose each other in the axial direction of the photoconductor 21. Switches SW1 and SW2 control whether to supply current to LED 50 or not. When a current is supplied to each LED 50, each LED 50 emits light, and the light emission irradiates the surface of the photoconductor 21, thereby removing unnecessary charges on the surface of the photoconductor 21.
[0016]
In this embodiment, the static eliminator 5 is designed so that, for example, when all 12 LEDs 50 emit light in the high-speed printing mode, the surface of the photoconductor 21 is irradiated with a light amount suitable for removing unnecessary charges on the surface of the photoconductor 21. ing. In the control unit 10, the standard rotation speed of the photoconductor 21 is set to high and the standard number of LEDs (standard number of light emitting elements) at the standard rotation speed is set to 12 as the standard specifications of the static eliminator 5. I have.
On the other hand, when all the twelve LEDs 50 emit light in the high-quality print mode, the surface of the photoconductor 21 is irradiated more than necessary, and the fatigue of the surface of the photoconductor 21 is hastened. Therefore, in this embodiment, in order to prevent the surface of the photoconductor 21 from being unnecessarily irradiated in the high-quality printing mode, the number of the LEDs 50 to which the current is supplied in the high-quality printing mode is controlled. ing.
[0017]
Further, in this embodiment, the twelve LEDs 50 are, for example, six first LED groups 51 corresponding to odd numbers as counted from the right end as viewed from the photoconductor 21 side, or six second LEDs corresponding to even numbers as counted from the right end. Each of the groups 52 is classified. By turning on and off the switches SW1 and SW2, whether or not to supply current to all six LEDs for each of the first LED group 51 and the second LED group 52 is controlled.
[0018]
Specifically, when the photoconductor 21 rotates at a low speed, first, the relationship between the low-speed rotation speed and the standard rotation speed set in the control unit 10 is detected. That is, the rotation speed of the photoconductor 21 is detected to be １ ／ (half) of the standard rotation speed.
When the photosensitive member 21 rotates at half the standard rotation speed, the time required for one image formation is about twice as long as the standard rotation speed. Therefore, when the standard number (12) of LEDs 50 emits light at the time when the photoconductor 21 rotates at a low speed, the surface of the photoconductor 21 is irradiated with twice the required irradiation amount. Therefore, in order to prevent the surface of the photoconductor 21 from being unnecessarily irradiated during the low-speed rotation of the photoconductor 21, for example, the number of the LEDs 50 for supplying the current is reduced to half (6) of the standard number of LEDs. It is determined that it is enough.
[0019]
In this embodiment, based on the above determination, for example, by turning on the switch SW1 and turning off the switch SW2, control is performed so that current is supplied to only the six LEDs of the second LED group 52. As a result, the amount of light irradiated on the surface of the photoconductor 21 is about half that in high-speed printing, so that the surface of the photoconductor 21 can be prevented from being irradiated more than necessary. The surface of the photoreceptor 21 is irradiated with a light amount suitable for eliminating unnecessary charges.
[0020]
In the high-quality printing mode, the current may be supplied to only the six LEDs of the first LED group 51 by turning off the switch SW1 and turning on the switch SW2. In addition, by turning on and off the switches SW1 and SW2 alternately in time, the current supply to only the six LEDs of the first LED group 51 and the current supply to only the six LEDs of the second LED group 52 can be performed. You may make it continue repeating. As a result, the surface of the photoconductor 21 is evenly irradiated when the time is averaged, so that unnecessary charges on the surface of the photoconductor 21 can be efficiently removed.
[0021]
As described above, the twelve LEDs 50 provided in the static eliminator 5 are divided into either the first LED group 51 or the second LED group 52, and current is supplied to the LEDs for each of the first LED group 51 and the second LED group 52. Unnecessary charges on the surface of the photoreceptor 21 can be removed without requiring a large and complicated configuration such as a shutter mechanism by controlling whether or not each of them is not.
In addition, the standard specifications of the static eliminator 5 (the standard rotation speed is “high” and the standard number of LEDs at the standard rotational speed is “12”) are set in advance, and when the static eliminator 5 is not in the standard specifications (photosensitive During the low-speed rotation of the body 21, the number (6) of LEDs for supplying current is controlled based on the relationship between the speed and the standard rotation speed (1/2 of the standard rotation speed) and the standard number of LEDs. are doing. Thus, even when the static eliminator 5 is not in the standard specification, the surface of the photoconductor 21 is irradiated with a light amount suitable for removing unnecessary charges of the photoconductor 21. Thereby, fatigue of the photoconductor 21 can be suppressed.
[0022]
Specifically, in this embodiment, if the standard rotation speed is V and the LED standard number is n, for example, when the photoconductor 21 rotates at a speed of αV, a current is supplied to αn LEDs. Based on the characteristics, the control unit 5 controls the number of LEDs that supply current (α is a positive real number). However, it is not necessary to limit to this relationship, and the number of LEDs is controlled so that the light amount becomes suitable for removing unnecessary charges of the photoconductor 21 at times other than the time when the static eliminator 5 is in the standard specification. Any relationship can be used.
[0023]
The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.
In this embodiment, the photoconductor 21 has a high standard rotation speed (in the high-speed print mode) and the standard number of LEDs is 12. However, the present invention is not limited thereto. Alternatively, the configuration may be such that the standard number of LEDs is seven.
[0024]
The configuration is such that the 12 LEDs are divided into either the first LED group 51 or the second LED group 52. However, the configuration is not limited to the two groups. For example, the photoconductor 21 has three types (for example, “high speed”, “ In the case of having a rotation speed of “medium speed” or “low speed”, the configuration may be such that the twelve LEDs are respectively divided into three groups. At this time, it is preferable that the configuration is such that whether or not current is supplied to the LED is controlled for each of the three groups.
[0025]
Therefore, for example, in an image forming apparatus including a photoreceptor having three kinds of rotation speeds of a high speed, a middle speed, and a low speed, the rotation speed is four times the speed at the middle speed and five times the speed at the low speed. When rotating at a rotational speed, each of the twelve LEDs is divided into one of a first LED group including, for example, two LEDs, a second LED group including eight LEDs, and a third LED group including two LEDs. Each may be classified. At this time, current is supplied to the LEDs of the first LED group during low-speed printing, to the LEDs of the first and second LED groups during medium-speed printing, and to the LEDs of the first, second, and third LED groups during high-speed printing. It is preferable that the configuration is simple. When each of the 12 LEDs is divided into any one of the three groups, the rotation speed of the photoconductor 21 is determined by alternately arranging the LEDs in each group in the axial direction of the photoconductor 21. Regardless of this, it is preferable that the 12 LEDs be divided into three groups so that the surface of the photoconductor 21 can be efficiently neutralized.
[0026]
If the rotation speed changes in finer steps, the number of LEDs that supply current may be set in units of one so as to be proportional to the rotation speed. Therefore, for example, in an image forming apparatus including a photoreceptor having three types of rotation speeds of high speed, middle speed, and low speed, for example, 1.1 times of the low speed at the middle speed, and 1.1 times of the low speed at the high speed When rotating at 1.2 times, the configuration may be such that 10 LEDs emit at low speed, 11 LEDs at medium speed, and 12 LEDs at high speed. At this time, if the number of LEDs supplying current is determined as a decimal value from the relationship between the actual rotational speed of the photoconductor and the standard rotational speed and the LED standard number, an integer value approximating the decimal value is determined. The configuration may be such that it is determined that a current is supplied to the LED of that value (number).
[0027]
On the surface of the static eliminator 5 as viewed from the photoconductor 21 side, twelve LEDs are provided at predetermined intervals so as to oppose each other in the axial direction of the photoconductor 21. It is not necessary to limit to the number, and a configuration in which, for example, 16 or 20 LEDs are provided in the static eliminator 5 may be used.
Although the light emitting element is an LED, the light emitting element is not limited to the LED, and may be any light source that can remove unnecessary charges on the surface of the photoconductor 21 by irradiating the surface of the photoconductor 21.
[0028]
Although the copying machine 1 has been described as an embodiment of the present invention, the present invention is not limited to the copying machine but can be applied to other image forming apparatuses such as a printer and a facsimile.
[Brief description of the drawings]
FIG. 1 is an illustrative sectional view showing the structure of a copying machine as an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a surface of the static eliminator as viewed from a photoconductor side.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Copier 10 Control part 2 Image forming part 21 Photoconductor 5 Static eliminator 50 LED
51 First LED group 52 Second LED group

Claims (3)

An electrophotographic image forming apparatus having a photoconductor capable of switching a rotation speed and a static eliminator for irradiating the photoconductor surface to remove unnecessary charges on the surface,
An image forming apparatus comprising: a control unit that controls a light amount irradiated by the charge removing device according to a rotation speed of the photoconductor. In the static eliminator, a light-emitting element that emits light when a current is supplied is provided so as to be spaced at a predetermined interval in the axial direction of the photoconductor,
The light emitting element is divided into a plurality of light emitting element groups,
The image forming apparatus according to claim 1, wherein the control unit controls whether to supply a current to the light emitting element for each of the divided light emitting element groups. The image forming apparatus has a standard rotation speed, which is one rotation speed of the photoconductor, and a light emitting element standard number, which is the number of light emitting elements to which current is supplied when the photoconductor rotates at the standard rotation speed. Is set in advance,
When the photoreceptor rotates at a rotation speed other than the standard rotation speed, the control unit supplies the current based on the relationship between the rotation speed and the standard rotation speed, and the light emitting element standard number. The image forming apparatus according to claim 1, wherein the number of elements is increased or decreased.

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