JP2004054208A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the deviation of the play component of a developing gap caused by the driving of a latent image carrier and a developer carrier and setting the developing gap more accurately. <P>SOLUTION: After driving and rotating a photoreceptor drum 40 and a developing sleeve 65 in advance, the sleeve 65 is brought into contact with the drum 40 by the rotation of a differential screw 113. Then, the screw 113 is rotated in an opposite direction to the rotation before, whereby the sleeve 65 is moved in a direction where it is separated from the drum 40. By controlling the rotating speed of the screw 113, the developing gap Gp is set to a specified value Gp1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and a process cartridge used in the apparatus. More specifically, the present invention relates to a latent image bearing member that carries a latent image on its surface, A developer carrying member that is provided to face the developer carrying the developer on the surface; and supplying the developer carried on the surface of the developer carrying member to the latent image formed on the latent image carrying member to supply the latent image to the latent image. The present invention relates to an image forming apparatus having a developing unit for visualizing an image and a process cartridge used for the image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a facsimile, a copying machine, or the like, a latent image carrier rotatably supported on a housing of an apparatus main body and a casing of a developing unit supported by the housing are rotated. It is known that the so-called development gap, which is the gap between the portion closest to the freely rotatably supported developer carrier, greatly affects the quality of image quality.
[0003]
In recent years, the development gap has been demanded to be narrower and more accurate because of the increasing demand for higher image quality in color images and the like in recent years. Conventionally, the setting of the developing gap is performed by adjusting the installation position of the developer carrier inside the developing unit in a production process with a jig in a static state, and then, the developing unit provided with the developer carrier is mounted on an image forming apparatus. This was done by attaching it to the main body. To give an example of the adjustment range of the developing gap, the adjustment value is very narrow, such as 0.4 ± 0.05 [mm], but the tolerance is 0.05 [mm]. Was what was required.
[0004]
[Problems to be solved by the invention]
However, the conventional method of setting the developing gap has caused various problems as follows.
Setting the developing gap by adjustment with a jig is time-consuming and costly. Further, even if the developer carrier is positioned and provided inside the image forming apparatus main body in consideration of the positional relationship when the developing unit is set in the main body of the image forming apparatus, even if the developing unit is set in the main body of the image forming apparatus, there is an expectation due to deformation or the like. In some cases, a misalignment may occur, and the development gap may deviate from the set value.
Furthermore, since it is not possible to perform individual adjustment of the developing gap after shipment from the factory, the unit is replaced if necessary, which increases the cost. Even if a predetermined developing gap is obtained when the developing unit is set, if the developer carrier or the latent image carrier is driven, the play component affects the displacement of the developing gap. The play component is made up of a tolerance width such as a gap between the spindle of the latent image carrier and the bearing hole and a gap between the spindle of the developer carrier and the bearing hole.
[0005]
Conventionally, an image forming apparatus capable of managing and correcting a developing gap to a predetermined value has been proposed in Japanese Patent Application Laid-Open No. H11-272073. According to this proposal, even after the developer carrier is installed inside the image forming apparatus main body, the developing gap can be detected by the gap detecting means, and the developing gap can be corrected to a predetermined value by the gap correcting means according to the detection result. It is like that. As a result, even if a deviation from the set value in the development gap is found after shipment from the factory, the gap can be corrected after shipment, and the deviation of the development gap resulting from an unexpected positional deviation occurring when the developing unit is set is corrected. be able to.
[0006]
However, Japanese Patent Application Laid-Open No. 11-272073 does not mention that each of the backlash components shifts the developing gap by driving the developer carrier or the latent image carrier, and there is no configuration for dealing with this. Not listed.
[0007]
The present invention has been made in view of the above problems, and has as its object the deviation of the development gap, including the deviation of the play component of the development gap caused by the driving of the developer carrier and the latent image carrier. And a process cartridge used in the image forming apparatus.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 includes a latent image bearing member that carries a latent image on a surface thereof, and a developer provided on a surface of the latent image carrier that faces the latent image carrier. An image comprising: a developer carrier to be carried; and a developing means for supplying a developer carried on the surface of the developer carrier to the latent image formed on the latent image carrier to visualize the latent image. A developing gap setting unit for setting a developing gap, which is an interval between the closest surfaces between the latent image carrier and the developer carrier, to a predetermined interval, the latent image carrier and the developing device; Driving means for driving the developer carrier, and control means for controlling the developing gap setting means so that the latent image carrier and the developer carrier are brought into contact with each other after driving, and thereafter the developing gap is set. It is characterized by having.
An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the developing gap setting means includes a moving member that moves at least one of the latent image carrier and the developer carrier in a distance direction with respect to the other. It is characterized by using.
An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the second aspect, wherein a deceleration mechanism that converts a rotation speed into a very low speed is used as the moving member.
According to a fourth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, a developing gap detecting means for detecting the developing gap, and a developing gap is determined in accordance with a detection result of the developing gap detecting means. And a developing gap correcting means for correcting the value to a value.
An image forming apparatus according to a fifth aspect is the image forming apparatus according to the fourth aspect, wherein an optical sensor having a light emitting element and a light receiving element is used as the developing gap detecting means.
According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect, further comprising an airflow generating unit configured to generate an airflow passing through a light emitting unit surface of the light emitting element and an airflow passing through a light receiving unit surface of the light receiving element. It is characterized by the following.
According to a seventh aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, or sixth aspect, the predetermined value of the developing gap is switchable according to a mode. It is.
The image forming apparatus according to claim 8 is the image forming apparatus according to claim 1, wherein the latent image carrier and the developer carrier are brought into contact after driving, Thereafter, a series of development gap setting operations of setting a development gap are performed after replacement of at least one of the latent image carrier and the developer carrier, or are periodically performed.
10. A process cartridge according to claim 9, wherein a latent image carrier for carrying a latent image on a surface thereof, and a developing means for supplying a developer to the latent image formed on the latent image carrier to visualize the latent image. A charging unit for uniformly charging the latent image carrier, or a cleaning unit for cleaning toner remaining on the latent image carrier after the toner image is transferred from the latent image carrier to a transfer body by the developing unit. In a process cartridge, at least one selected from the group consisting of an integral unit and a detachable unit from the image forming apparatus main body, the process cartridge is provided so as to face the surface of the latent image carrier and carries the developer on the surface. Developer carrier, the developer carrier can be moved until the latent image carrier comes into contact, and the closest surface between the developer carrier and the latent image carrier The development gap The is characterized in the provision of the development gap setting means for setting a predetermined interval.
In these inventions, the latent image carrier and the developer carrier are preliminarily driven, and the play causes a shift in the play component of the development gap, and then the latent image carrier and the developer carrier are brought into contact with each other, The developing gap is set to a predetermined value with the contact position as the point 0. Therefore, even if the latent image carrier and the developer carrier are driven for image formation, there is no shift in the development gap, and image formation can be performed while maintaining the development gap at a predetermined value. Further, since the developing gap is set after the zero point calibration is always performed, the developing gap can be set with high accuracy.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a color printer which is an image forming apparatus of a tandem type intermediate transfer system will be described.
FIG. 1 is a schematic configuration diagram of a color printer to which the present invention can be applied. This color printer comprises a copying apparatus main body 100, a paper feed table 200 on which the copying machine main body 100 is mounted, a scanner 300 mounted on the copying apparatus main body 100, and an automatic document feeder (ADF) 400 mounted thereon. Is done. An intermediate transfer belt 10 as an endless belt-shaped intermediate transfer member is provided at the center of the copying apparatus main body 100.
[0010]
The intermediate transfer belt 10 is wound around three supporting rollers 14, 15, 16 as shown in FIG. In the illustrated example, an intermediate transfer body cleaning device 17 is provided to the left of the second support roller 15 to remove residual toner remaining on the intermediate transfer belt 10 after image transfer. Further, on the intermediate transfer belt 10 stretched between the first support roller 14 and the second support roller 15, four image forming means 18Y, yellow, cyan, magenta, and black are provided along the conveyance direction. The tandem image forming unit 20 is configured by arranging C, M, and B side by side. However, the order of these four colors is an example, and the present invention is not limited to this.
The intermediate transfer belt 10 is configured by laminating a base layer, an elastic layer, and a coat layer in this order. The base layer is made of a material that does not easily stretch, such as a fluororesin or canvas. The elastic layer is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The coat layer is formed by coating the surface of the elastic layer with a material having good smoothness, such as a fluororesin.
[0011]
An exposure device 21 is provided on the tandem image forming section 20, as shown in FIG. On the other hand, on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20, a secondary transfer device 22 as a secondary transfer unit is provided. In the illustrated example, the secondary transfer device 22 is configured by extending a secondary transfer belt 24 as an endless belt between two rollers 23, and pressing the intermediate transfer belt 10 against the third support roller 16. The image on the intermediate transfer belt 10 is secondarily transferred to a sheet as an image holding member. A fixing device 25 for fixing a transferred image on a sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing roller 26 as a fixing member.
[0012]
The secondary transfer device 22 also has a sheet conveying function for conveying the sheet after the image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be provided as the secondary transfer device 22, and in such a case, it is difficult to additionally provide the sheet conveying function. In the illustrated example, a sheet reversing device 28 that reverses the sheet so as to record an image on both sides of the sheet in parallel with the tandem image forming unit 20 described above under the secondary transfer device 22 and the fixing device 25. Is provided.
[0013]
2 and 3 are partially enlarged views of the tandem image forming unit 20 in the printer of the present embodiment. FIG. 3 is a partially enlarged view of one color of the image forming unit. Since the color may be any of yellow, cyan, magenta, and black, no particular description will be given hereafter. As shown in FIGS. 2 and 3, in the tandem image forming unit 20, the image forming units 18Y, 18C, 18M and 18B, which are individual toner image forming units, as shown in FIG. The charging devices 60Y, C, M, and B, the developing units 61Y, C, M, and B, the primary transfer devices 62Y, C, M, and B around the photosensitive drums 40Y, 40, 40, and 50 The cleaning devices 63Y, C, M, and B, and the static eliminators 64Y, C, M, and B are provided. The photosensitive drum 40 has a drum shape in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube such as aluminum, but may have an endless belt shape.
[0014]
The charging device 60 is a charging roller 60 </ b> Y, C, M, or B in the illustrated example. The charging device 60 charges the photosensitive drum 40 by contacting the photosensitive drum 40 and applying a voltage. Of course, charging can also be performed by a non-contact scorotron charger.
[0015]
The developing unit 61 uses a two-component developer composed of a magnetic carrier and a non-magnetic toner. Then, as shown in FIG. 3, a developing sleeve 65 as a developer carrier is provided facing the photoconductor 40 through an opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. Further, the developing case 70 transports the two-component developer while agitating it and adheres to the developer sleeve 65 → a stirrer 66 for exposing the toner of the two-component developer adhered to the developing sleeve 65 to the toner. And a developing unit 67 that transfers to the body drum 40. The stirring unit 66 is positioned lower than the developing unit 67. Further, a doctor blade 73 is provided with the tip approaching the developing sleeve 65. The stirring section 66 is provided with two screws 68, and is separated by a partition plate 69 except for both ends. The two-component developer in the stirring section 66 is transported and circulated while being stirred by the two screws 68, and is supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is pumped up and held by the magnet 72 to form a magnetic brush on the developing sleeve 65. The magnetic brush is cut into an appropriate amount by the doctor blade 73 as the developing sleeve 65 rotates. The cut-off developer is returned to the stirring section 66. On the other hand, the toner in the developer on the developing sleeve 65 is transferred to the photosensitive drum 40 by a developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photosensitive drum 40 is visualized. After the visualization, the developer remaining on the developing sleeve 65 separates from the developing sleeve 65 and returns to the agitating section 66 where there is no magnetic force of the magnet 72.
When the toner concentration in the agitating section 66 is reduced by this repetition, the toner concentration is detected by the toner concentration sensor 71 and the toner is supplied to the agitating section 66.
[0016]
The primary transfer device 62 has a roller shape and is provided by pressing the photosensitive drum 40 with the intermediate transfer belt 10 interposed therebetween. Of course, the primary transfer device may be a non-contact corona charger or the like.
The photoconductor cleaning device 63 includes a cleaning blade 75 made of, for example, polyurethane rubber, whose tip is pressed against the photoconductor drum 40, and a conductive fur brush 76 that contacts the outer circumference of the photoconductor drum 40 and rotates in the direction of the arrow in the drawing. Prepare. Further, a metal electric field roller 77 that rotates in the direction of the arrow in the drawing and applies a bias to the fur brush 76, a scraper 78 whose tip is pressed against the electric field roller 77, and a collecting screw 79 that collects the removed toner are provided. . Then, the toner remaining on the photosensitive drum 40 is removed by the fur brush 76 that rotates in the counter direction with respect to the photosensitive drum 40. The toner attached to the fur brush 76 is removed by applying a bias to the fur brush 76 by an electric field roller 77 rotating in the counter direction. The electric field roller 77 is cleaned by a scraper 78. The toner collected by the photoconductor cleaning device 63 in this manner is brought to one side of the photoconductor cleaning device 63 by the collection screw 79, and is sent to the developing unit 61 by the toner conveying device 80 connecting the photoconductor cleaning device 63 and the developing unit. And used again for development.
The neutralization device 64 is, for example, a lamp, and irradiates light to initialize the surface potential of the photosensitive drum 40.
[0017]
Now, when making a copy using this color electrophotographic apparatus, an original is set on the original table 30 of the automatic original transport apparatus 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.
Then, when a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is conveyed and moved onto the contact glass 32, and then the document is set on the other contact glass 32. At this time, the scanner 300 is immediately driven to travel on the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface to the second traveling body 34, is reflected by the mirror of the second traveling body 34, and passes through the imaging lens 35. The original is read by the reading sensor 36 and read.
[0018]
Then, the photoconductor drums 40Y, C, M, and B are rotated by the individual image forming units 18Y, C, M, and B, and the charging devices 60Y, C are firstly rotated with the rotation of the photoconductor drums 40Y, C, M, and B. , M, and B uniformly charge the surfaces of the photosensitive drums 40Y, C, M, and B, and then use a laser, an LED, or the like from the above-described exposure devices 21Y, C, M, and B according to the contents read by the scanner 300. By irradiating the writing light L, an electrostatic latent image is formed on the photosensitive drums 40Y, 40C, 40M, 40B.
Thereafter, toner is adhered by the developing units 61Y, C, M, and B, and the electrostatic latent image is visualized to form yellow, cyan, magenta, and black on each of the photosensitive drums 40Y, C, M, and B, respectively. Is formed. One of the support rollers 14, 15, 16 is rotationally driven by a drive motor (not shown), the other two support rollers are driven to rotate, the intermediate transfer belt 10 is rotated and conveyed, and the visible image is transferred to the primary transfer device. , The image is sequentially transferred onto the intermediate transfer belt 10. Thereby, a composite color image is formed on the intermediate transfer belt 10. The surfaces of the photoconductor drums 40Y, 40C, 40M, 40B after image transfer are cleaned by removing residual toner with photoconductor cleaning devices 63Y, 63C, 63M, and 63B to be described later. To prepare for the next image formation.
[0019]
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and a sheet is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheet is separated one by one into a sheet feeding path 46, conveyed by a conveying roller 47, guided to a sheet feeding path 48 in the copying machine main body 100, and stopped against a registration roller 49. Alternatively, the sheet feeding roller 50 is rotated to feed out the sheet on the manual feed tray 51, separated one by one by the separation roller 52, and then put into the manual sheet feeding path 53, and similarly hit against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the synthesized color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and the sheet is transferred by the secondary transfer device 22. Record a color image on the sheet. Here, the registration roller 49 is generally often used with being grounded, but it is also possible to apply a bias for removing paper dust from the sheet.
[0020]
The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where the transfer image is fixed by applying heat and pressure by the fixing device 25, and then switched by the switching claw 55 to be discharged. The sheet is discharged at 56 and stacked on a sheet discharge tray 57. Alternatively, the sheet is switched into the sheet reversing device 28 by the switching claw 55, reversed and guided again to the transfer position, the image is recorded on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56. On the other hand, the intermediate transfer belt 10 after the image transfer is cleaned by the intermediate transfer body cleaning device 17 to remove the residual toner remaining on the intermediate transfer belt 10 after the image transfer, so that the tandem image forming unit 20 prepares for the second image formation.
[0021]
FIG. 4 is an explanatory diagram showing an example of a driving mechanism of the developing sleeve 65 and the photosensitive drum 40 in the color printer having the above configuration. The developing sleeve 65 has a sleeve gear 101 at the shaft end, and is arranged to mesh with a sleeve driving gear 102 provided on the main body side. The sleeve driving gear 102 is rotatably supported by a support plate via a ball bearing 103. When the sleeve driving gear 102 is rotationally driven by power from a sleeve driving motor 104, the developing sleeve 65 is rotationally driven via the sleeve gear 101. Is what you do. On the other hand, the photosensitive drum 40 has a shaft 40 a rotatably supported by a support plate via a ball bearing 105, and a distal end thereof is joined to a photosensitive member driving motor 106. The power from the photoconductor driving motor 106 is directly transmitted to the photoconductor shaft 40a, and the photoconductor drum 40 is driven to rotate.
When the developing sleeve 65 and the photosensitive drum 40 rotate for the first time, the developing gap Gp, which is the distance between the closest surface of the developing sleeve 65 and the photosensitive drum 40, is equal to the distance between the ball bearing 103 and the axis of the sleeve driving gear 102. The play between the ball bearing 105 and the photoreceptor shaft 40a and the like is moved in the direction of arrow S in the figure, and the displacement occurs due to this. This backlash shift occurs only when the developing sleeve 65 and the photosensitive drum 40 are first rotated after being set in the apparatus. However, even if the developing unit 61 is set in the apparatus so as to have a predetermined developing gap Gp in advance, there is a gap between the developing sleeve 65 and the photosensitive drum 40 during the actual image formation. Otherwise, the image quality will be degraded. This is because the development gap Gp is an important factor that greatly affects image quality.
[0022]
Hereinafter, features of the present embodiment that can maintain the development gap Gp with high accuracy will be described. FIG. 5 is an explanatory diagram showing features of the present embodiment. As shown in FIG. 5, in the present embodiment, a moving member that moves the developing sleeve 65 toward or away from the photosensitive drum 40 as a developing gap setting unit that sets the developing gap Gp to a predetermined value Gp1. 110, a photoconductor driving motor 106 and a sleeve driving motor 104 as driving means for driving the photoconductor drum 40 and the developing sleeve 65, respectively, and after the photoconductor drum 40 and the developing sleeve 65 are driven, the photoconductor drum 40 And a control device 111 as control means for controlling the moving member so that the developing gap Gp is set to a predetermined value Gp1 after that.
[0023]
FIG. 6 is a diagram showing a specific configuration of the moving member 110 according to the present embodiment. In the present embodiment, as the moving member, a spring 112 for urging the photosensitive drum 40 and the developing sleeve 65 in a direction away from each other, and a small number of rotations in the direction of the distance between the rotating drum 40 and the developing sleeve 65 And a pressing member 114 provided between the spring 112 and the differential screw 113. One end of the spring 112 is supported on a receiving portion 115 provided on the photosensitive drum 40, and the other end is supported on a receiving portion 116 provided on the developing sleeve 65. One end of the differential screw 113 is engaged with the gear 117 gear with a differential screw driving motor, and the other end is abutted against the pressing member 114.
The differential screw 113 is rotated by power from a gear 117 with a motor for driving a differential screw, and uses a reduction mechanism that converts the number of rotations into a small feed in the distance direction between the photosensitive drum 40 and the developing sleeve 65. ing. The principle of this deceleration mechanism is used for a micrometer or the like. By controlling the rotation speed of the differential screw 113, the differential screw 113 is moved in the distance direction between the photosensitive drum 40 and the developing sleeve 65. Feeding can be controlled accurately. Thereby, the developing gap Gp can be set with high accuracy. Here, a stepping motor is used as the differential screw driving motor. The pressing member 114 has one end in contact with the screw end of the differential screw 113, the other in contact with the receiving portion 116 on the side of the developing sleeve 65, and a shaft 114 a pivotally supported by the developing unit 61. Penetrates a cutout portion 114b provided in the portion.
[0024]
In the above configuration, after the photoconductor drive motor 104 and the sleeve drive motor 106 rotate the photoconductor drum 40 and the developing sleeve 65, the control device 111 drives the gear 117 with a differential screw drive motor. The differential screw 113 is rotated. As a result, the differential screw 113 moves in the direction of the distance between the photosensitive drum 40 and the developing sleeve 65 by an amount corresponding to the number of rotations, and the screw end of the differential screw 113 is moved via the pressing member 114 toward the developing sleeve. The receiving portion 116 is pressed to bring the developing sleeve 65 into contact with the photosensitive drum 40. Whether or not the developing sleeve 65 has contacted the photosensitive drum 40 can be detected by, for example, a general detection sensor that detects that the rotational torque of the differential screw 113 has become equal to or more than a certain value. After that, the control device 111 rotates the differential screw 113 in the direction opposite to the previous direction, and moves the differential screw 113 and the pressing member 114 in a direction away from the developing sleeve. Then, the rotation speed is controlled so that the developing gap Gp becomes a predetermined value Gp1 of the preferable developing gap Gp stored in advance in the ROM. As a result, the developing sleeve 65 moves in a direction away from the photosensitive drum 40 under the urging force of the spring 112, and the developing gap Gp is adjusted to the predetermined value Gp1.
[0025]
FIG. 7 is a flowchart illustrating a procedure for setting the developing gap Gp according to the present embodiment. When setting the developing gap Gp, the control device 111 drives the developing sleeve 65 and the photosensitive drum 40 to rotate prior to the setting (step 1). The number of rotations may be at least one revolution or more. In this embodiment, the photosensitive drum 40 is rotated one revolution, and the developing sleeve 65 is driven to rotate at the same speed as during the development for the time that the photosensitive drum 40 makes one revolution. Shall be. Next, the differential screw 113 is rotated by driving the gear 117 with a drive motor for a differential screw to bring the developing sleeve 65 into contact with the photosensitive drum 40 (step 2). When setting the developing gap Gp, this contact position is set to zero point. Next, the rotational speed and the feed amount of the differential screw 113 are controlled by step-rotating the gear with the driving motor for the differential screw so that the developing gap Gp becomes the predetermined value Gp1 stored in the ROM in advance. The developing sleeve 65 is moved in a direction in which the developing sleeve 65 is separated from the photosensitive drum 40 until the gap Gp becomes the predetermined value Gp1. (Step 3).
[0026]
Here, the number of rotations of the developing sleeve 65 and the photosensitive drum 40 performed before the detection of the developing gap Gp is set to one rotation of the photosensitive drum, but the number of rotations is not limited to this. The development sleeve 65 and the photosensitive drum 40 are each moved in a certain direction by the rotation by rotation to obtain a stable development gap Gp, and the rotation may be performed as many times as necessary.
[0027]
Such a series of operations for setting the developing gap Gp is always performed before developing for the first time after the replacement of the developing unit 61 or the photosensitive drum 40, for example, at the time of periodic maintenance of the apparatus main body. Therefore, even when the developing sleeve 65 and the photosensitive drum 40 are reinstalled, it is possible to correct the variation in the developing gap due to the components. In addition, since the developing gap Gp is set after the driving of the developing sleeve 65 and the photosensitive drum 40, it is possible to eliminate a deviation of the developing gap Gp due to a play component or the like. Furthermore, since the developing sleeve 65 and the photosensitive drum 40 are brought into contact with each other after driving, and the zero point calibration is always performed before setting the developing gap, the developing gap can be set with high accuracy.
Further, the above-described series of operations for setting the developing gap Gp may be performed not only immediately after the replacement of the developing unit 61 or the photosensitive drum 40 but also periodically. Even when the developing unit 61 or the photosensitive drum 40 has not been replaced for a long period of time, an unexpected trouble may occur due to the operation of the apparatus, and the developing gap may be shifted. Even in such a case, the accuracy of the developing gap can be maintained by periodically performing the series of operations for setting the developing gap.
[0028]
Further, in this embodiment, a developing gap detecting means for detecting the developing gap and a developing gap correcting means for correcting the developing gap to a predetermined value according to the detection result of the developing gap detecting means may be provided.
FIG. 8 is an enlarged explanatory diagram of the optical sensor 120 as a developing gap detecting unit according to the present embodiment. The optical sensor 120 receives light emitted from the light emitting element 120a by the light receiving element 120b, and obtains a developing gap Gp between the photosensitive drum 40 and the developing sleeve 65 from the amount of the received light. Further, the angle of the light emitting path from the light emitting element 120a can be changed using a mirror or the like. Here, the developing gap correcting means uses the spring 112, the differential screw 113, and the pressing member 114 as the moving member described above.
In the above configuration, a read value from the optical sensor 120 is fed back to the control device 111 after the development gap is set. Then, the rotational speed of the differential screw is controlled again to move the developing sleeve 65 so that the developing gap Gp becomes the predetermined value Gp1 stored in the ROM in advance, and the developing gap Gp is corrected. Here, in order to simplify the apparatus, the developing gap setting unit and the developing gap correcting unit are configured by the same member, but may be configured by using another member.
[0029]
FIG. 9 is a flowchart illustrating a procedure for setting the developing gap Gp according to the present embodiment. The procedure up to step 3 is the same as the procedure described above, and thus the description is omitted.
After setting the developing gap Gp (Step 3), the control device 111 detects the developing gap Gp by the optical sensor 120, and stores the detection result in the ROM (Step 4). Then, the predetermined value Gp1 and the tolerance H of the preset preferable development gap Gp are compared with the detected development gap Gp, and if the development gap Gp is within the tolerance range of the predetermined value Gp1 (Y in step 5). , And the process ends. On the other hand, if the development gap Gp is out of the tolerance range of the predetermined value Gp1, the detection result of the development gap Gp is fed back from the optical sensor 120 to the ROM (N in Step 5). Then, the developing sleeve 65 is moved again by controlling the rotational speed of the differential screw to correct the developing gap Gp (Step 6), and the correction of the gap Gp is completed.
[0030]
Further, in the present embodiment, although not shown, a blower fan may be provided as an airflow generating unit that generates an airflow passing through the light emitting unit and the light receiving unit surface of each of the light emitting element 120a and the light receiving element 120b of the optical sensor 120. . In FIG. 8, the airflow generated by the blower fan flows in one direction from the near side to the back side in the axial direction of the photoconductor. As a result, foreign substances such as dust and toner adhered to the light emitting unit and the light receiving unit surface are removed by an air current, and the performance of detecting the development gap Gp by the optical sensor 120 is maintained by always maintaining a clean state.
It should be noted that instead of passing the airflow flowing in one direction through both surfaces of the light emitting unit and the light receiving unit as in the present embodiment, the airflow flows in two directions and passes through the respective sensor surfaces of the light emitting unit and the light receiving unit. You may comprise.
[0031]
Further, in the present embodiment, the predetermined value of the developing gap may be configured to be switchable depending on the image quality mode. As an example, the predetermined value in the high image quality mode is Gp1, the predetermined value in the normal mode is Gp2, and Gp2 is set wider than Gp1. In the development gap Gp1 in the high image quality mode, the gap Gp1 is narrow and the reproducibility of details is good. However, if foreign matter enters the developing nip, the surface of the photosensitive drum 40 may be damaged, and the image quality may be deteriorated. On the other hand, in the developing gap Gp2 in the normal mode, the reproducibility of details is not as good as in the high image quality mode, and the image quality level is low as a whole. In the present embodiment, the user selects a mode in advance before correcting the development gap Gp, sets a development gap according to the selection result as a predetermined value in the apparatus, and compares and corrects the detected development gap Gp with the detected actual development gap Gp. To do. This allows the user to select the normal mode when it is determined that the user does not need to care about the image quality, and to select the high image quality mode when the user wants to emphasize the image quality.
[0032]
As described above, in the present embodiment, after the developing sleeve 65 and the photosensitive drum 40 are driven in advance, they are brought into contact with each other, and then the developing gap Gp is set. Therefore, even if the photosensitive drum 40 and the developing sleeve 65 are driven for image formation, there is no shift in the developing gap Gp, and it is possible to form an image while maintaining the developing gap Gp at a predetermined value. Further, since the developing gap Gp is set after the developing sleeve 65 is brought into contact with the photosensitive drum 40 and zero point calibration is always performed, the developing gap Gp can be set with high accuracy.
The developing gap setting means includes moving members such as a spring 112 for moving the developing sleeve 65 in a distance direction from the photosensitive drum 40, a differential screw 113, and a pressing member 114. Therefore, the developing gap Gp can be freely adjusted inside the developing unit 61. This is because the moving distance of the developing sleeve 65 with respect to the photosensitive drum 40 can be controlled by controlling the rotation speed of the differential screw 113.
Further, as a moving member, there is provided a differential screw 113 using a speed reduction mechanism for converting the number of rotations into a small feed in the distance direction between the developing sleeve 65 and the photosensitive drum 40. Therefore, the development gap Gp can be set with higher accuracy. This is because the moving distance of the developing sleeve 65 with respect to the photosensitive drum 40 can be adjusted with high accuracy by controlling the rotation speed of the differential screw 113.
Further, an optical sensor 120 including a light emitting element 120a and a light receiving element 120b is used as a developing gap detecting means. Therefore, the developing gap Gp can be measured in the developing unit 61. This is because the optical sensor 120 having the above configuration is smaller than other sensors for detecting the gap Gp.
Further, a blower fan for generating an airflow passing through the light emitting unit and the light receiving unit surface of each of the light emitting element 120a and the light receiving element 120b of the optical sensor 120 is provided. Therefore, erroneous detection of the developing gap Gp can be eliminated, and the developing gap Gp can be accurately and stably detected. This is because foreign matters such as dust and toner attached to the surfaces of the light emitting unit and the light receiving unit can be removed by an air current, and a clean state can always be maintained.
Further, the predetermined value of the developing gap Gp is set to Gp1 in the case of the high image quality mode, and to Gp2 in the case of the normal mode, so that switching is possible. Therefore, it is possible to obtain the optimum image quality required by the user and to avoid the occurrence of a problem caused by unnecessarily narrowing the developing gap Gp.
Further, a series of operations for setting the developing gap Gp is performed immediately after the replacement of the developing unit 61 or the photosensitive drum 40. Therefore, stable image quality can always be obtained. This is because even when the developing sleeve 65 and the photosensitive drum 40 are newly installed, the deviation of the developing gap Gp due to the variation of the components and the deviation of the developing gap Gp due to the driving of the developing sleeve 65 and the photosensitive drum 40 are prevented. This is because the development gap Gp can be maintained at a predetermined value. In addition, a series of operations for setting the development gap Gp are performed periodically. Therefore, even when an unexpected shift occurs, such as a change in the developing gap Gp during the operation of the printer, the developing gap Gp can be periodically corrected to maintain the image quality.
[0033]
In the present embodiment, a developing unit is individually provided for each of the four photoreceptor drums arranged in a row, a single-color toner image is formed on each of the photoconductor drums, and the single-color toner images are sequentially transferred to a sheet to form a composite color image. An example in which the present invention is applied to a so-called tandem type color printer to be formed has been described, but the printer to which the present invention can be applied is not limited to this type of printer. An image forming apparatus that includes at least a developer carrier and a latent image carrier, sets a development gap to a predetermined value, and drives at least one of the developer carrier and the latent image carrier to perform development. Is applicable.
[0034]
Further, at least the photoconductor drum 40 and the moving member 110 are provided, and these are combined with at least one selected from a developing unit, a charging unit, or a cleaning unit which is a part of the image forming unit 18 by a single unit. And a process cartridge detachable from the main body. This makes it possible to collectively and detachably attach to the copier main body 100, thereby improving maintainability and exchangeability. FIG. 10 is an explanatory diagram illustrating an example of such a process cartridge. The process cartridge 90 integrally includes the photoconductor drum 40, the developing unit 61, the photoconductor cleaning device 63, and a moving member 110 that is a developing gap setting unit (not shown). This moving member 110 is, for example, the one shown in FIG. Note that, unlike the example of FIG. 10, the developing unit 61 may be provided on the main body side. In this case, the moving member 110 of the process cartridge can be moved to the developing sleeve 65 of the developing unit 61 on the main body side in a state where the process cartridge is mounted on the main body.
[0035]
【The invention's effect】
According to the image forming apparatus of the first aspect, it is possible to prevent the play of the play component of the developing gap caused by driving the latent image carrier and the developer carrier, and it is possible to set the developing gap with higher accuracy. There is an excellent effect.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.
FIG. 2 is a schematic configuration diagram of a tandem image forming unit in the printer of the embodiment.
FIG. 3 is a schematic configuration diagram of a developing unit according to the embodiment.
FIG. 4 is an explanatory diagram illustrating an example of a drive mechanism of a developing sleeve and a photoconductor of the embodiment.
FIG. 5 is an explanatory diagram illustrating a configuration of a developing unit according to the embodiment.
FIG. 6 is a schematic configuration diagram illustrating a configuration of a developing gap setting unit according to the embodiment.
FIG. 7 is a flowchart illustrating a procedure of setting a developing gap according to the embodiment.
FIG. 8 is an enlarged explanatory view of an optical sensor according to another embodiment.
FIG. 9 is a flowchart illustrating a procedure of setting a developing gap according to another embodiment.
FIG. 10 is an explanatory diagram illustrating a configuration of a process cartridge according to the embodiment.
[Explanation of symbols]
10 Intermediate transfer belt
18C, M, Y, B image forming means
20 Tandem image forming unit
22 Secondary transfer device
25 Fixing device
26 Fixing roller
27 Pressure roller
29 Transfer conveyor belt
40Y, C, M, B photoconductor drum
60Y, C, M, B charging device
61Y, C, M, B developing unit
63Y, C, M, B photoconductor cleaning device
65Y, C, M, B developing sleeve
90 process cartridge
100 Copier body
101 sleeve gear
102 Gear for driving sleeve
103 Ball bearing
104 Sleeve drive motor
105 Ball bearing
106 Photoconductor drive motor
110 Moving member
111 control device
112 spring
113 Differential screw
114 pressing member
115, 116 receiving part
117 Gear with motor for differential screw drive
120 Optical sensor
120a light emitting element
120b light receiving element
200 paper feed table
300 Scanner
400 Automatic Document Feeder

Claims (9)

A latent image bearing member that carries a latent image on the surface,
A developer carrier that is provided to face the latent image carrier surface and carries the developer on the surface;
A developing means for supplying a developer carried on the surface of the developer carrier to the latent image formed on the latent image carrier and developing the latent image to develop the latent image,
Developing gap setting means for setting a developing gap, which is an interval between the closest surfaces between the latent image carrier and the developer carrier, to a predetermined interval;
Driving means for driving the latent image carrier and the developer carrier,
An image forming apparatus comprising: a control unit that controls the developing gap setting unit so that the latent image carrier and the developer carrier are brought into contact with each other after driving, and thereafter a developing gap is set. The image forming apparatus according to claim 1,
An image forming apparatus, wherein a moving member that moves at least one of the latent image carrier and the developer carrier in a distance direction with respect to the other is used as the developing gap setting unit. 3. The image forming apparatus according to claim 2,
An image forming apparatus, wherein a speed reduction mechanism that converts a rotation speed into a very low speed feed is used as the moving member. The image forming apparatus according to claim 1, 2, or 3,
Developing gap detecting means for detecting the developing gap,
An image forming apparatus comprising: a developing gap correcting unit configured to correct a developing gap to a predetermined value according to a detection result of the developing gap detecting unit. The image forming apparatus according to claim 4,
An image forming apparatus using an optical sensor having a light emitting element and a light receiving element as the developing gap detecting means. The image forming apparatus according to claim 5,
An image forming apparatus, further comprising: an airflow generating unit configured to generate an airflow passing through a light emitting unit surface of the light emitting element and an airflow passing through a light receiving unit surface of the light receiving element. The image forming apparatus according to claim 1, 2, 3, 4, 5, or 6,
An image forming apparatus, wherein the predetermined value of the developing gap is switchable depending on a mode. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, or 7,
After driving the latent image carrier and the developer carrier, the two are brought into contact with each other, and then a series of development gap setting operations of setting a development gap are performed, at least one of the latent image carrier and the developer carrier. An image forming apparatus characterized by being implemented after replacement or periodically. A latent image carrier that carries a latent image on the surface,
Developing means for supplying a developer to the latent image formed on the latent image carrier to visualize the latent image, charging means for uniformly charging the latent image carrier, or toner image by the developing means At least one selected from cleaning means for cleaning the toner remaining on the latent image carrier after the latent image carrier has been transferred from the latent image carrier to the transfer member, is integrally attached to and detached from the image forming apparatus main body. In a process cartridge configured to be
A developer carrying member provided to face the surface of the latent image carrying member and carrying a developer on the surface; and the developer carrying member can be moved until the latent image carrying member comes into contact with the developer carrying member. And a developing gap setting means for setting a developing gap, which is an interval between the closest surfaces between the developer carrier and the latent image carrier, to a predetermined interval.

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