Patent Grant
9223243
This application is based on Japanese Patent Application No. 2012-118249 filed with Japan Patent Office on May 24, 2012, the entire content of which is hereby incorporated by reference.
The present invention relates to a charging device that applies a voltage to a charging member, allows the charging member to cause a discharge, and thereby charges a charging target, and to an image forming apparatus including the same.
There has been widely known an image forming apparatus, which uses an electrophotographic method of charging an image carrier by a charging device, exposing the charged image carrier by light corresponding to an image by using an exposure device, thereby forming an electrostatic latent image, visualizing the above-described electrostatic latent image by toner by using a developing device, transferring a toner image thus visualized to a transfer material, fixing the toner image transferred onto the transfer material, and thereby forming an image.
The charging device, which is provided in the image forming apparatus using the above-described electrophotographic method, is required to uniformly charge a surface of the image carrier. When unevenness occurs in a charged state of the surface of the image carrier, the unevenness concerned in the charged state appears as image unevenness, and accordingly, image quality is lowered.
In Japanese Patent Laid-Open Publication No. 2009-25521, as the charging device that charges the surface of the image carrier, there is disclosed a noncontact-type charging device, which applies a voltage to a wire-like charging member, allows the charging member to cause a discharge, and thereby charges the surface of the image carrier.
In the above-described charging device, when dirt such as toner and dust adheres onto the charging member, an abnormal discharge sometimes occurs. When the abnormal discharge occurs, it becomes impossible to uniformly charge the image carrier, and there has been an apprehension that the image unevenness may appear.
In Japanese Patent Laid-Open Publication No. 2009-25521, there is described a cleaning device, which, in the above-described noncontact-type charging device, controls a wire cleaning unit to clean the charging member for each image formation of the number of sheets, which is inputted by a user.
On the other hand, in Japanese Patent Laid-Open Publication No. H08-220846, there is described a contact-type charging device which charges the image carrier by bringing a charging roller into contact therewith, wherein the charging device detects an amount of toner that has adhered onto the charging roller, and controls operations of cleaning means for cleaning the charging roller in response to the detected amount of toner.
In accordance with the charging device including the cleaning device described in Japanese Patent Laid-Open Publication No. 2009-25521, the charging member is cleaned for each image formation of such a predetermined number of the sheets. However, in the case where the dirt of the charging member is much, then sometimes, there has occurred such an event that the dirt cannot be removed from the charging member completely even if the cleaning is performed therefor, resulting in continuation of the image formation while the dirt is being left on the charging member. In this case, there has been a problem that the image unevenness appears since the abnormal discharge occurs and the image carrier is not uniformly charged.
In the above-described noncontact-type charging device, if there is employed such a technology for controlling the operations of the cleaning means in response to the amount of toner that has adhered to the charging member, the technology being described in Japanese Patent Laid-Open Publication No. H08-220846, then wasteful cleaning can be prevented and sudden dirt of the charging member can be coped with rather than in the case of performing the cleaning for each predetermined number of the sheets as described in Japanese Patent Laid-Open Publication No. 2009-25521.
However, even if the cleaning means is configured to be controlled in response to a degree of the dirt of the charging member as described above, the image unevenness caused by the fact that the surface of the image carrier is nonuniformly charged has sometimes occurred.
That is to say, even if it is sensed that the dirt of the charging members is a little, the current case is sometimes such a case where the abnormal discharge occurs in actual. In this case, the charging unevenness occurs, and accordingly, the image unevenness occurs unless the charging member is cleaned.
In general, in one aspect, the present invention relates to an image forming apparatus wherein an image is formed on a sheet. The image forming apparatus comprises a charging device comprising: a charging member to charge an object; an applying unit to apply a voltage to the charging member for generating an electric discharge from the charging member, so that the object is discharged by the charging member; a detecting unit to detect an emission of light of the electric discharge; an output unit to output a detection result by the detecting unit; a cleaning unit to clean the charging member; and a controller to control the cleaning unit to clean the charging member when the detection result is out of a predetermined range.
Preferably, the controller notifies that the charging member should be exchanged when the detection result exceeds a predetermined threshold.
Preferably, the controller controls the charging device to stop the charging operation of the object when the detection result is out of the predetermined range.
Preferably, the output unit outputs a voltage value as the result of the detection.
Preferably, the detecting unit comprises: a receptor to receive the emission of light; and a condensing member to condense the emission of light on the receptor.
Preferably, the detecting unit is moved integrally with the cleaning unit.
Preferably, the detecting unit and the cleaning unit is moved independently of each other.
A description is made below of a first embodiment of the present invention while referring to the drawings.
An image forming apparatus 20 is an image forming apparatus capable of forming a color image on a transfer material (a recording sheet), the image forming apparatus being called a tandem-type image forming apparatus. The image forming apparatus 20 includes: a scanner unit 22; a printer unit 24; a sheet feed unit 32; an operation display unit 23; and the like. Note that, though the description is made below by using an image forming apparatus capable of forming a color image, the present invention is also applicable to an image forming apparatus capable of forming only a monochrome image.
The scanner unit 22 includes: an automatic original feeding device 21; an optical system 22a; a CCD image sensor 22b; and the like.
The printer unit 24 includes: image forming units 40Y, 40M, 40C, 40K which form toner images corresponding to the respective colors of yellow, magenta, cyan and black; an intermediate transfer belt 31 as an image carrier onto which the toner images formed by the respective image forming units are to be transferred; a secondary transfer unit 38 as a transferring unit that transfers the toner images on the intermediate transfer belt 31 onto sheets; a fixing device 34 that fixes the toner images transferred onto the sheets; and the like.
The sheet feed unit 32 includes: sheet feed trays 32a to 32c; and the like. Appropriate sheets are fed at appropriate timing by the sheet feed unit 32.
The operation display unit 23 includes, for example, a touch panel-type screen (a monitor), and a user touches icons and the like, which are to be displayed on the screen, and can thereby perform setting regarding contents of image formation, instruction to start the image formation, and the like.
The above is a summary of the respective units of the image forming apparatus 20. Subsequently, while taking as an example the case of forming a color image on each of the sheets by the image forming apparatus 20, a description is made of a series of operations for such formation of the color image.
When the instruction to start the image formation is made on the operation display unit 23, an original J mounted on an original stage 21a of the automatic original feeding device 21 is conveyed to an original reader. Then, reflected light of light irradiated onto the original from a light source (not shown) is read by the CCD image sensor 22b through the optical system 22a.
Various pieces of image processing are implemented for an image signal, which is read by the CCD image sensor 22b, by an image processing unit (an image processor) to be described later. Then, based on the image signal subjected to the image processing, the image forming units 40Y to 40K form the toner images of the respective colors.
The image forming unit 40Y that forms the toner image of the yellow color includes: a photosensitive drum 41Y as an image carrier, a charging unit (a charging device) 42Y, an exposure unit 45Y, a developing unit 43Y, and a cleaning unit 44Y. In the case of forming the image, the photosensitive drum 41Y is rotated in a direction of an arrow E in
Next, the electrostatic latent image on the photosensitive drum 41Y is developed by the developing unit 43Y, and the toner image of the yellow color is formed on the photosensitive drum 41Y. The formed toner image is electrostatically transferred onto the intermediate transfer belt 31 by applying a transfer voltage to a primary transfer roller 46Y. The toner that remains on the surface of the photosensitive drum 41Y without being completely transferred onto the intermediate transfer belt 31 is removed by the cleaning unit 44Y.
All of the image forming unit 40M that forms the toner image of the magenta color, the image forming unit 40C that forms the image of the cyan color, and the image forming unit 40K that forms the image of the black color have a similar configuration to that of the image forming unit 40Y that forms the image of the yellow color, and accordingly, a detailed description thereof is omitted.
The intermediate transfer belt 31 is an endless belt wound around rollers 37a to 37e, and is rotatably supported. As the intermediate transfer belt 31, a belt made of resin represented by polyimide and a belt in which an elastic layer is provided on a resin raw material are used in general. In the event of performing the image formation, the intermediate transfer belt 31 is rotationally moved in a direction of an arrow F in
In the event of performing color image formation, the transfer voltage is applied to the primary transfer rollers corresponding to the respective colors, whereby, sequentially from the toner image of the yellow color, the toner images of the respective colors are individually transferred electrostatically onto the intermediate transfer belt 31 at timing when the toner images are superimposed on one another.
Meanwhile, the sheets fed by any of the sheet feed trays 32a to 32c are conveyed though a conveying path 33a, and reach a resist roller pair 33c. Conveying-direction skew of the sheets is corrected in such a manner that the sheets are thrust against a nip portion of the resist roller pair 33c. Then, each of the sheets is conveyed to the secondary transfer unit 38 in matching with timing when the color toner images on the intermediate transfer belt 31 are moved to a position opposite to the secondary transfer unit 38.
In the secondary transfer unit 38 as the transferring unit, the color toner images on the intermediate transfer belt 31 are electrostatically transferred onto the sheet (the recording sheet). The sheet onto which the color toner images are transferred is conveyed toward the fixing device (a fixing unit) 34, and the toner images are fixed. Meanwhile, the toner that remains on the intermediate transfer belt 31 without being completely transferred onto the sheet in the secondary transfer unit 38 is removed by an intermediate transfer belt cleaning unit 35.
The fixing device 34 includes: a fixing roller 34a; a pressurizing roller 34b; and the like. A heating unit is provided in the fixing roller 34a. Heat and pressure are applied to the sheet by the fixing roller 34a and the pressurizing roller 34b, whereby the toner images are fixed.
The sheet onto which the toner images are fixed is conveyed through the conveying path 33a, and is discharged to an outside of the image forming apparatus 20.
In the case of forming images on both surfaces of the sheet, the sheet in which the toner images are fixed to the surface by the fixing device 34 is conveyed toward a reversing route 33b by a branch unit 36, and a rearmost end thereof in the conveying direction is reversed. The sheet in which the rearmost end is reversed passes through the reversing route 33b, and is conveyed to the resist roller pair 33c, where the conveying-direction skew thereof is corrected.
Thereafter, color toner images corresponding to an image to be formed on a back surface of the sheet is transferred in the secondary transfer unit 38 as mentioned above, the color toner images on the back surface are fixed by the fixing device 34, and the sheet is discharged to the outside of the image forming apparatus 20.
The above is the description of a series of the operations in the event of forming the color image on the sheet by the image forming apparatus 20. Next, a description is made of a configuration of the charging unit 42.
For the charging unit 42, a corotron-type or scorotron-type charging device is used.
As shown in
A power supply (an applying unit, not shown) is connected to the charging wire 421, and a high voltage is applied thereto when an instruction for the charging is made. When the high voltage is applied to the charging wire 421, a corona discharge is generated, and a surface of the photosensitive drum 41 is charged. The charging wire 421 is made of, for example, tungsten, a wire diameter thereof is 30 μm, and a surface thereof is subjected to gold plating.
The stabilizer 422 is composed of a conductive member, and is arranged so as to surround the charging wire 421. Moreover, a direction of the stabilizer 422 toward the photosensitive drum 41 is opened in order to charge the photosensitive drum 41.
The cleaning unit 423 includes: a cleaning member 423a; a holding member 423b; and a guide rail 423c. As the cleaning member 423a, a member in which abrasive particles are coated on nonwoven fabric is used. In the case of cleaning the charging wire 421, the holding member 423b is moved in a direction of the charging wire 421 by a locking mechanism (not shown), and the cleaning member 423a is turned to a state of being brought into contact with the charging wire 421. This state is defined as a locked state. A voltage is not configured to be applied to the charging wire 421 at the time of the locked state.
When the cleaning unit 423 turns to the locked state, then by drive of a drive unit (a moving unit, not shown), the cleaning unit 323 moves between points A and B of
For the photosensor 425a, a GaAsP photodiode is used. An emission of light by the corona discharge is an emission of light in the ultraviolet range, and accordingly, an element capable of sensing the emission of light in the ultraviolet range is used as the photosensor 425a. Moreover, in order to efficiently sense a discharge emission of light by the photosensor 425a, the light condensing lens 425b that condenses light to the photosensor 425a is provided. Furthermore, the protection plate 425c is provided in order to protect the light condensing lens 425b from a discharge, toner dirt and the like. The protection plate 425c is made of, for example, acrylic resin. The photosensor 425a, the light condensing lens 425b and the protection plate 425c are all held by the holding member 425d.
By the drive of the drive unit (not shown), the photosensor unit 425 is moved between the points A and B of
In the case of sensing the discharge emission of light by the photosensor unit 425, the locked state of the cleaning unit 423 is released, the high voltage is applied to the charging wire 421 to generate the discharge, and then the photosensor unit 425 is moved along the guide rail 423c.
When the cleaning unit 423 and the photosensor unit 425 reach the position denoted by reference symbol A or B in the guide rail 423c, a surface of the protection plate 425c is cleaned by a protection plate cleaning member 426. A plurality of the protection plate cleaning members 426 are individually driven by drive units (not shown). For example, the protection plate cleaning members 426 are reciprocally moved in an arrow direction of
The above is the description of the configuration of the charging unit 42 in this embodiment. In this embodiment, the photodiode is used for the photosensor 425a as mentioned above, and sensing results of the emission of light are outputted as voltage values.
In this embodiment, as shown in
Moreover, there is provided a wire replacement voltage C, and a notice indicating a time for replacement has come is issued in the case where the output voltage of sensing result lowers the wire replacement voltage C a predetermined number of times. Details of these controls will be described later.
Moreover, in
Moreover, in the case where such a variation h−l is larger than a range R during an extremely short period Δt as shown in
Moreover, in this embodiment, Δt is set at 0.1 second; however, this can also be set as appropriate. Furthermore, the above-mentioned determination which takes the upper limit H and the lower limit L as references and the above-mentioned determination which takes as a reference the difference between the maximum value and minimum value of the output voltage may be used in combination with each other.
The CPU 50 plays a role as a control unit (a controller) that controls the operations of the respective units of the image forming apparatus 20. Based on input contents to be transmitted from the respective units of the image forming apparatus 20, the CPU 50 controls the individual operations of the respective units of the image forming apparatus 20.
In the ROM 51, a variety of programs or data are stored. The CPU 50 reads out the programs or the data from the ROM 51, and controls the respective units of the image forming apparatus 20.
The RAM 52 is a place where the programs or the data, which are necessary in the event where the CPU 50 controls the operations of the above-described respective units, are temporarily stored.
The HDD 53 is a place where image data is stored. Data of the original image read by the scanner unit 22 is stored in the HDD 53.
The charging unit 42 described by using
Each of the sensing results by the photosensor 425a is outputted to the CPU 50, and the CPU 50 performs control, which will be described later, based on the sensing result thus outputted. That is to say, the charging unit 42 plays a role as an output part. Moreover, in accordance with an instruction from the CPU 50, the voltage source (an applying unit) 427, the locking mechanism 428 and the drive unit 429 operate individually.
Moreover, a terminal 60 is network-connected to the image forming apparatus 20 through an I/F unit 61. To the terminal 60, information regarding a job in which the image formation is performed is inputted, and the information concerned is transmitted to the CPU 50 in the image forming apparatus 20. Furthermore, from the terminal 60, it is also possible to issue the instruction to start the image formation.
Next, a description is made of the control by the CPU 50 in this embodiment.
During execution of the image formation, the CPU 50 is counting the number of sheets subjected to the image formation (Step S1). Then, in the case where a count n of the number of sheets is less than 10000 (Step S1: Yes), the CPU 50 increases the count n of the number of sheets by 1 (Step S2). Then, the CPU 50 starts the charging by the charging wire 421 (Step S10), and continues the image formation (Step S11). When the image formation is completed, the CPU 50 determines one more time whether or not the count of the number of sheets has reached 10000 (Step S1).
In the case where the image formation is performed as described above and the count n of the number of sheets has reached 10000 (Step S1: No), the CPU 50 sets a wire replacement counter m as m=0 (step S3). Then, the CPU 50 enters a charging wire cleaning mode (Step S4), and performs control to discontinue the charging by the charging wire 421 (Step S5).
Next, the CPU 50 allows the execution of the cleaning of the charging wire 421 (Step S6). Specifically, as described by using
When the cleaning of the charging wire 421 is completed, the CPU 50 causes the photosensor unit 425 to sense the discharge emission of light from the charging wire 421 and to output the sensing result (Step S7). Specifically, the CPU 50 controls the locking mechanism 428 to release the locked state of the cleaning unit 423, and allows the voltage source 427 to apply the high voltage for the charging to the charging wire 421, and then allows the drive unit 429 to move the cleaning unit 423 along the guide rail 423c. At this time, the photosensor unit 425 also moves integrally with the cleaning unit 423, and accordingly, the discharge emission of light from the charging wire 421 is sensed over the length direction of the charging wire 421 by the photosensor 425a in the photosensor unit 425. The sensing result is outputted to the CPU 50. Moreover, the locked state of the cleaning unit 423 is released, and accordingly, the cleaning of the charging wire 421 is not performed.
When the discharge emission of light from the charging wire 421 is sensed and the sensing result is outputted, the CPU 50 performs a variety of controls corresponding to the sensing result of the discharge emission of light. In the case where a sensing voltage of the discharge emission of light is within a predetermined range (Step S8: Yes), the CPU 50 determines that the cleaning of the charging wire 421 is sufficient. Then, the CPU 50 resets the count n of the number of sheets as n=1 (Step S9), and performs control to execute the charging of the photosensitive drum 41 by the charging wire 421 (Step S10). Then, the CPU 50 performs the image formation for subsequent sheets (Step S11).
Meanwhile, in the case where the sensing voltage of the discharge emission of light is out of the predetermined range (Step S8: No), the CPU 50 determines whether or not the sensing voltage concerned is lower than a wire replacement voltage (Step S12). In the case where the sensing voltage is lower than the wire replacement voltage C (Step S12: Yes), the CPU 50 increases the wire replacement counter m by 1 (Step S13). Then, the CPU 50 determines whether or not the wire replacement counter m is less than a predetermined value M (Step S14). In the case where the wire replacement counter m is less than the predetermined value M (Step S14: Yes), the CPU 50 enters the wire cleaning mode (Step S4), and follows the procedure of Step S5 to Step S7. That is to say, the CPU 50 allows the execution of the cleaning of the charging wire 421 one more time, allows the sensing of the discharge emission of light from the charging wire 421, and allows output of a sensing result.
Then, in Step S8, the CPU 50 determines one more time whether or not the sensing voltage of the discharge emission of light is within the predetermined range. In the case where the sensing voltage of the discharge emission of light is out of the predetermined range one more time (Step S8: No), the CPU 50 repeatedly executes the procedure of Step S12 to Step S14. When the wire replacement counter m is less than the predetermined value M in Step S14, the CPU 50 returns to Step S4, where the cleaning of the charging wire 421 is further performed.
When the sensing voltage of the discharge emission of light is settled within the predetermined range in Step S8 (Step S8: Yes), the image formation for the subsequent sheets is performed.
Meanwhile, in the case where the wire replacement counter m has reached the predetermined value M in Step S14 (Step S14: No), that is, in the case where the sensing result of the discharge emission of light falls down M times below the wire replacement voltage C, the CPU 50 issues a wire replacement signal (Step S15). In such a way, for example, the CPU 50 discontinues the execution of the job, and displays contents to advise the replacement of the charging wire 421 on the operation display unit 23.
In such a manner as described above, after the charging wire 421 is periodically cleaned, the charging wire 421 is further cleaned in the case where it is necessary to further clean the charging wire 421 based on the determination for the sensing result of the discharge emission of light. Hence, the image formation is prevented from being executed while the state where the abnormal discharge occurs is being left, and it becomes possible to form a good image free from unevenness.
Moreover, when the sensing result of the discharge emission of light falls down below the wire replacement voltage C the predetermined number of times in the case where the charging wire 421 is periodically cleaned, the CPU 50 notifies the user that it is a time to replace the charging wire 421. In such a way, the user can easily get to know the time to replace the charging wire 421.
The discharge emission of light for actually charging the photosensitive drum 41 is sensed, and the above-described control is performed based on the sensing result thereof. Hence, in comparison with the conventional technology, it becomes possible to more surely prevent the charging by the abnormal discharge, and to get to know the time to replace the charging wire 421.
Moreover, the cleaning unit 423 and the photosensor unit 425 are composed integrally with each other, whereby cost reduction is achieved.
In this embodiment, in Step S8 of
Moreover, in this embodiment, the notice to indicate that it is a time to replace the charging wire 421 is issued in the case where the sensing result of the discharge emission of light falls down below the wire replacement voltage C the predetermined number of times. However, this predetermined number of times can be set as appropriate, and may be once or a plurality of times.
Subsequently, a description is made of a second embodiment of the present invention. In comparison with the first embodiment, this embodiment is different therefrom in control procedure by the CPU 50, and except for this, has a similar configuration to that of the first embodiment. Hence, with regard to portions which duplicate the above-mentioned portions, a detailed description thereof is omitted.
In the flowchart shown in
Upon entering the sensing mode, the CPU 50 proceeds to Step S7, and senses the discharge emission of light from the charging wire 421. Specifically, the CPU 50 releases the locked state of the cleaning unit 423, and applies a voltage to the charging wire 421. Then, the CPU 50 moves the cleaning unit 423 and the photosensor unit 425, which are composed integrally with each other, along the guide rail 423c.
Here, in the control procedure shown in
When the discharge emission of light from the charging wire 421 is sensed and the sensing result is outputted in Step S7, the CPU 50 performs a variety of controls corresponding to the sensing result of the discharge emission of light (Step S8). In the case where the sensing voltage of the discharge emission of light is within the predetermined range (Step S8: Yes), the CPU 50 performs control to execute the charging of the photosensitive drum 41 by the charging wire 421 (Step S10). Then, the CPU 50 performs the image formation for subsequent sheets (Step S11).
Meanwhile, in the case where the sensing voltage of the discharge emission of light is out of the predetermined range (Step S8: No), the CPU 50 executes the procedure of Step S12 to Step S14. That is to say, the CPU 50 determines whether or not the sensing voltage concerned is lower than the wire replacement voltage, and increases the wire replacement counter m by 1 in the case where the sensing voltage is lower than the wire replacement voltage C. Then, the CPU 50 determines whether or not the wire replacement counter m is less than the predetermined value M. In the case where the wire replacement counter m has reached the predetermined value M (Step S14: No), the CPU 50 issues the wire replacement signal (Step S15).
In the case where the wire replacement counter m has not reached the predetermined value M (Step S14: Yes), the CPU 50 proceeds to the procedure of Step S4 to Step S8. That is to say, the CPU 50 allows the execution of the cleaning of the charging wire 421, and allows the sensing of the discharge emission of light after the completion of the cleaning. When the outputted sensing voltage of the discharge emission of light is settled within the predetermined range (Step S8: Yes), the CPU 50 starts the charging by the charging wire 421 (Step S10), proceeds to the image formation for the subsequent sheets (Step S11).
As described above, in the case where the number of sheets subjected to the image formation is 1000 or more to less than 10000, the discharge emission of light from the charging wire 421 is sensed for each image formation for one sheet, and the cleaning of the charging wire 421 is executed in the case where the abnormal discharge is sensed.
In the case where the count n of the number of sheets has reached 10000 in Step S1′ (Step S1′: “3”), the CPU 50 resets the count n of the number of sheets as n=1 (Step S18). Then, the CPU 50 sets the wire replacement counter m as m=0 (Step S3), and executes the procedure of Step S4 to Step S8. That is to say, the CPU 50 allows the execution of the cleaning of the charging wire 421, and allows the sensing of the discharge emission of light after the completion of the cleaning.
When the sensing voltage of the discharge emission of light is settled within the predetermined range (Step S8: Yes), the CPU 50 performs control to execute the charging of the photosensitive drum 41 by the charging wire 421 (Step S10). Then, the CPU 50 performs the image formation for subsequent sheets (Step S11). When the sensing voltage of the discharge emission of light is out of the predetermined range (Step S8: No), the CPU 50 allows the execution of the procedure of Step S12 to Step S14 one more time. If the wire replacement counter m increased by 1 has not reached the predetermined value M (Step S14): Yes), then the CPU 50 proceeds to the procedure of Step S4 to Step S8. That is to say, the CPU 50 allows the cleaning of the charging wire 421 and the sensing of the discharge emission of light one more time.
As described above, the CPU 50 allows the execution of the cleaning of the charging wire 421 until the sensing result of the discharge emission of light is settled within the predetermined range.
In accordance with this control procedure, in the case where the number of sheets subjected to the image formation has reached 10000, the cleaning of the charging wire 421 is performed, and the count of the number of sheets is reset. That is to say, the cleaning of the charging wire 421 is periodically performed for each image formation for 10000 sheets. In accordance with the control procedure of
Moreover, in the case where the count n of the number of sheets has not reached 1000 in Step S1 (Step S1′: “1”), the CPU 50 increases the count n of the number of sheets by 1 (Step S2), and proceeds to the image formation for the subsequent sheets without allowing the sensing of the discharge emission of light. This procedure is based on a thought that a possibility that the charging wire 421 may get dirty and the abnormal discharge may occur is small during a period while the image formation is not performed much. By this control procedure, it is possible to enhance the productivity during this period. However, the sensing of the discharge emission of light may be executed for each image formation of one sheet even in the case where the number of sheets subjected to the image formation has not reached 1000.
In accordance with this embodiment, the discharge emission of light is sensed for each image formation of one sheet, the sensing result thereof is outputted to the CPU 50, and the CPU 50 controls the operations of the cleaning unit 423 based on the sensing result. Hence, even in the case where the charging wire 421 gets dirty suddenly and the abnormal discharge occurs, the charging wire 421 can be cleaned soon by the cleaning unit 423. In such a way, it becomes possible to prevent the occurrence of the image unevenness caused by a sudden abnormal discharge.
Moreover, it is determined whether or not it is a time to replace the charging wire 421 for each image formation of one sheet, and accordingly, the user can be notified soon that the current state is a state where the charging wire 421 should be replaced when the state concerned occurs. Hence, it becomes possible to more surely prevent an image failure and the like, which are caused by the fact the charging wire 421 is used while the state where the charging wire 421 should be replaced is being left.
Furthermore, the discharge emission of light for actually charging the photosensitive drum 41 is sensed, and the above-described control is performed based on the sensing result thereof. Accordingly, it becomes possible to surely prevent the charging by the abnormal discharge, and to issue a notice on the time to replace the charging wire 421.
Subsequently, a description is made of a third embodiment of the present invention. A detailed description of configurations in this embodiment, which duplicate those in the first or second embodiment, is omitted.
With regard to a control procedure by a CPU 50 in this embodiment, a similar procedure to the procedure shown in
In this embodiment, the cleaning unit 423 and the photosensor unit 425 are driven independently of each other. Hence, when it is timing to sense the discharge emission of light, the photosensor unit 425 can be moved instantaneously, and accordingly, it becomes possible to perform the sensing of the discharge emission of light smoothly.
Subsequently, a description is made of a fourth embodiment of the present invention. A detailed description of configurations in this embodiment, which duplicate the above-mentioned configurations, is omitted.
In the case of sensing the discharge emission of light, which comes from the charging wire 421, with the configuration as described above, the photosensor unit 425 is moved along the guide rail 425e by a drive unit (not shown). The photosensor 425a senses the discharge emission of light, which comes from the charging wire 421, and transmits through the stabilizer 422a composed of the optically transparent substance.
As the stabilizer 422a, for example, one in which ITO is coated on a surface of a glass substrate can be used. Besides this, materials which have conductivity and optical transparency can be used.
With regard to a control procedure by a CPU 50 in this embodiment, a similar procedure to the procedure shown in
In this embodiment, the cleaning unit 423 and the photosensor unit 425 are driven independently of each other. Hence, when it is timing to sense the discharge emission of light, the photosensor unit 425 can be moved instantaneously, and accordingly, it becomes possible to perform the sensing of the discharge emission of light smoothly.
Moreover, the photosensor unit 425 is provided apart by the stabilizer 422a, and accordingly, the light condensing lens 425b is hardly affected by the discharge and the toner dirt. Hence, the protection plate 425c is not provided in this embodiment. In such a way, it becomes possible to reduce the cost.
Subsequently, a description is made of a fifth embodiment of the present invention.
Moreover, as a charging unit 42 in this embodiment, the configuration shown in any of
In this embodiment, in the case where the sensing result of the discharge emission of light is not within the predetermined range, the CPU 50 performs control to forcibly discontinue the image formation.
In the flowchart shown in
In such a way, it becomes possible to prevent the occurrence of the image unevenness caused by the charging of the photosensitive drum 41 owing to the abnormal discharge. The discharge emission of light for actually charging the photosensitive drum 41 is sensed, and accordingly, it becomes possible to more surely prevent the charging by the abnormal discharge.
In the flowchart shown in
However, as shown in
Subsequently, a description is made of a sixth embodiment of the present invention.
Moreover, as a charging unit 42 in this embodiment, the configuration shown in any of
In this embodiment, in the case where the sensing result of the discharge emission of light is not within the predetermined range, the CPU 50 performs control to change operation conditions and the like related to the image formation.
In the flowchart shown in
As the conditions to be changed in Step S20, an exposure amount, a developing bias and the like are mentioned. For example, in the case where a sensing result that a spot with a small charging amount occurs on the photosensitive drum 41 is obtained in Step S8, then an exposure condition is changed so as to reduce an exposure amount on the spot concerned, or alternatively, a developing condition is changed so as to increase a developing bias on the spot concerned. Moreover, besides the above-described conditions, such image processing as compensating charging unevenness may be implemented for image data.
In such a way, it becomes possible to prevent the occurrence of the image unevenness caused by the charging of the photosensitive drum 41 owing to the abnormal discharge. The discharge emission of light for actually charging the photosensitive drum 41 is sensed, and accordingly, it becomes possible to more surely prevent the charging by the abnormal discharge.
Though the description is also made in the fifth embodiment, after the cleaning of the charging wire 421 is executed in Step S6, the CPU 50 may proceed to Step S7, and may allow the sensing of the discharge emission of light, and may allow the output of the sensing result.
Subsequently, a description is made of a seventh embodiment of the present invention.
Moreover, as a charging unit 42 in this embodiment, the configuration shown in any of
This embodiment is characterized in that the sensing result of the discharge emission of light is displayed on the operation display unit 23 and the like, and the user is allowed to decide the next operation.
In the flowchart shown in
Then, the CPU 50 receives input by the user (Step S22). When the input from the user is made after waiting for the input concerned (Step S22: Yes), the CPU 50 determines whether or not the input instructs the discontinuation of the image formation (Step S23). In the case where the input by the user instructs the discontinuation of the image formation (Step S23: Yes), the CPU 50 ends the processing.
Meanwhile, in the case where the input by the user does not instruct the discontinuation of the image formation (Step S23: No), the CPU 50 subsequently determines whether or not the input by the user instructs the replacement of the charging wire 421 (Step S24). In the case where the input by the user instructs the replacement of the charging wire 421 (Step S24: Yes), the CPU 50 issues the wire replacement signal (Step S15), and ends the processing.
In the case where the input by the user does not instruct the replacement of the charging wire 421 (Step S24: No), the CPU 50 allows operations according to the input by the user (Step S25). As the operations according to the input by the user, for example, there are mentioned: the continuation of the image formation without adding anything; the continuation of the image formation after cleaning the charging wire 421; another display of the sensing result after cleaning the charging wire 421; and the like.
In such a way, it becomes possible to prevent the occurrence of the image unevenness caused by the charging of the photosensitive drum 41 owing to the abnormal discharge. The discharge emission of light for actually charging the photosensitive drum 41 is sensed, and accordingly, it becomes possible to more surely prevent the charging by the abnormal discharge. Moreover, there is an advantage that it is easy for the user to grasp the sensing result of the discharge emission of light and it is possible to execute the operations desired by the user.
Though the description is also made in the fifth embodiment, after the cleaning of the charging wire 421 is executed in Step S6, the CPU 50 may proceed to Step S7, and may allow the sensing of the discharge emission of light, and may allow the output of the sensing result.
Moreover, though the sensing result of the discharge emission of light is displayed on the operation display unit 23 and the like in this embodiment, it is not necessarily necessary to display the sensing result on the operation display unit 23. A notice on the sensing result may be configured to be issued by other methods such as voice notification, or only options for the sensing result may be configured to be displayed without issuing the notice concerned.
Although the present invention has been fully described byway of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be constructed as being included therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-118249 | May 2012 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20090060535 | Hamaya | Mar 2009 | A1 |
| 20100278553 | Burry et al. | Nov 2010 | A1 |
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| Entry |
|---|
| Machine translation of Yamaguchi, JP 2005092117 A, publication date: Apr. 7, 2005. |
| Machine translation of Kishi, JP JP 02048691 A, publication date: Feb. 19, 1990. |
| Japanese Notification of Reasons for Refusal corresponding to Application No. 2012-118249; Date of Mailing: Feb. 24, 2015, with English translation. |
| Japanese Office Action “Notice of Reasons for Refusal” regarding Patent Application No. 2012-118249; Mailing Date: Jul. 22, 2014. |
| Number | Date | Country | |
|---|---|---|---|
| 20130315615 A1 | Nov 2013 | US |
