JP2014164294A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately performing adjustment of imaging conditions on the basis of a detection result of surface potential detection means for detecting a surface potential of an image carrier.SOLUTION: An image forming apparatus adjusts imaging conditions on the basis of a surface potential of a photoreceptor drum 1Y (image carrier) on the downstream side of a developing position when the intensity of exposure light L from an exposure device 7Y is at a first value and at a second value, while the drive of a developing roller 51 (developer carrier) is stopped and the developing roller 51 is applied with a developing bias equivalent to a developing bias during a developing step.

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a composite machine thereof, and particularly detects a surface potential in an image carrier such as a photosensitive drum or a photosensitive belt. The present invention relates to an image forming apparatus that adjusts image forming conditions based on the detection result.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, the surface potential of an image carrier such as a photosensitive drum or a photosensitive belt is detected and detected for the purpose of stably forming a good image. A technique for adjusting the image forming condition based on the result is known (for example, see Patent Document 1).

  Specifically, in an image forming apparatus such as Patent Document 1, a potential sensor (surface potential detection means) that detects a surface potential of a photosensitive drum (image carrier) rotates the photosensitive drum with respect to an exposure position by the exposure device. It is located at a position downstream in the direction and upstream of the developing position by the developing device in the rotation direction of the photosensitive drum. Then, based on the detection result detected by the potential sensor, image forming conditions such as a developing bias, a charging bias, and an exposure portion potential (amount of exposure light) are adjusted.

  On the other hand, in Patent Document 2, a surface potential sensor (surface potential detecting means) is installed at a position downstream of the developing position of the developing device in the rotation direction of the photosensitive drum, and the photosensitive drum is detected by the surface potential sensor. A technique for detecting the surface potential (latent image potential) is disclosed. Specifically, the surface potential (latent image potential) of the photosensitive drum is measured by the surface potential sensor in a state where a developing bias different from that in the developing step is applied to the developing roller (developer carrier) so that the developing step is not performed. Detected.

In the technique of Patent Document 1 or the like, since the potential sensor (surface potential detection means) is installed at a position close to the exposure position, the surface potential (latent image potential) of the photosensitive drum is not sufficiently stabilized (photosensitive member). The surface potential is detected by the potential sensor and the image forming conditions are determined based on the detection result before the transit time of the charge in the charge transport layer is sufficiently secured. Could not be done accurately. In particular, such a problem is a problem that cannot be ignored in a downsized and high-speed image forming apparatus in which a small-diameter photosensitive drum is driven to rotate at a high speed.
On the other hand, since the technique of Patent Document 2 has a potential sensor installed at a position downstream of the developing device (developing position) in the rotation direction of the photosensitive drum (image carrier), the above-described problems are avoided. The deterrent effect can be expected.

  However, as a result of repeated research, the inventor of the present application has conducted research on the surface of the photosensitive drum by a potential sensor in a state in which a developing bias different from that in the developing step is applied to the developing roller (developer carrier) as in Patent Document 2. When the potential is detected, or when the surface potential of the photosensitive drum is detected by the potential sensor without applying the developing bias to the developing roller, the surface potential of the photosensitive drum is the actual image forming time (image formation). If the surface potential is detected by a potential sensor and the imaging conditions are determined based on the detection results, it will be known that the imaging conditions cannot be adjusted accurately. did.

  The present invention has been made to solve the above-described problems, and it is possible to accurately adjust the image forming conditions based on the detection result of the surface potential detecting means for detecting the surface potential of the image carrier. An object of the present invention is to provide an image forming apparatus.

  An image forming apparatus according to a first aspect of the present invention includes an image carrier that travels in a predetermined direction, a charging device that charges a surface of the image carrier, and the image carrier that is charged by the charging device. An exposure apparatus that irradiates the surface of the image with exposure light to form a latent image on the image carrier, and a developer carrier that houses the developer and faces or abuts the image carrier. A developing device that develops a latent image formed on the image carrier by the exposure device in a state where a predetermined developing bias is applied to the developer carrier, and forms a toner image; And a surface potential detecting means for detecting a surface potential of the image carrier on the downstream side in the running direction of the image carrier, and driving and stopping of the developer carrier independently of the running of the image carrier. So that you can And adjusting the image forming conditions to be performed during non-image formation, controlling the drive means to drive the image carrier and stop driving the developer carrier, and In a state where a developing bias having the same value as the predetermined developing bias or a value close to the predetermined developing bias is applied to the developer carrying member, the amount of exposure light applied to the surface of the image carrier by the exposure device is set to the first value. A first detection result detected by the surface potential detection means, and a second value different from the first value for the amount of exposure light applied to the surface of the image carrier by the exposure device. Based on the second detection result detected by the surface potential detection means, the charging bias applied to the charging device, the developing bias applied to the developer carrying member, and the exposure device irradiates Amount of the exposure light, and adjusts at least one of.

  In the present invention, the light amount of the exposure light of the exposure apparatus is set to the first value in a state where the driving of the developer carrying member is stopped and a developing bias equivalent to the developing bias in the developing process is applied to the developer carrying member. The image forming conditions are adjusted on the basis of the surface potential of the image carrier on the downstream side of the developing position when the value is set to the second value. Thus, it is possible to provide an image forming apparatus in which the image forming conditions are accurately adjusted based on the detection result of the surface potential detecting means for detecting the surface potential of the image carrier.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus. FIG. It is the schematic which shows the principal part of an image creation part. 6 is a graph showing a change in the surface potential of the photosensitive drum when a developing bias is applied and a change in the surface potential of the photosensitive drum when no developing bias is applied. The relationship between the amount of exposure light when a developing bias is applied and the surface potential of the photosensitive drum and the relationship between the amount of exposure light when no developing bias is applied and the surface potential of the photosensitive drum are shown. It is a graph. 6 is a flowchart illustrating control for performing image adjustment and adjustment of image forming conditions during non-image formation.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
As shown in FIG. 1, an intermediate transfer belt device 15 is installed in the center of the image forming apparatus main body 100. Further, process cartridges 6Y, 6M, 6C, 6K corresponding to the respective colors (yellow, magenta, cyan, black) are arranged in parallel so as to face the intermediate transfer belt 8 (intermediate transfer member) of the intermediate transfer belt device 15. Yes.

  Referring to FIG. 2, a process cartridge 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging device 4Y (charging unit) disposed around the photosensitive drum 1Y, and a developing device 5Y ( The developing unit), the cleaning device 2Y (photoconductor cleaning device), the charge eliminating unit (not shown), and the like are configured to be detachable (replaceable) from the image forming apparatus main body 100 as one unit. . Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y. That is, the process cartridge 6Y forms an image forming unit together with a primary transfer roller 9Y as a transfer device (primary transfer device).

  The other three process cartridges 6M, 6C, and 6K (image forming unit) have substantially the same configuration as the process cartridge 6Y (image forming unit) corresponding to yellow except that the color of the toner used is different. Therefore, an image corresponding to each toner color is formed. Hereinafter, description of the other three process cartridges 6M, 6C, and 6K (image forming unit) will be omitted as appropriate, and only the process cartridge 6Y (image forming unit) corresponding to yellow will be described.

Referring to FIG. 2 (and FIG. 3), the photosensitive drum 1Y (image carrier) is rotationally driven by the main motor 91 in the clockwise direction. Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging device 4Y (charging roller) (this is a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position (exposure position) of the exposure light L emitted from the exposure device 7Y (optical writing head), and the electrostatic scan corresponding to yellow is performed by exposure scanning at this position. A latent image is formed (this is an exposure process).

Thereafter, the surface of the photosensitive drum 1Y reaches a position (development position) facing the developing device 5Y (developing device main portion 50), and the electrostatic latent image is developed at this position to form a yellow toner image. (Development process).
Thereafter, the surface of the photosensitive drum 1Y passes through a position opposed to the surface potential sensor 81 (surface potential detecting means) and then reaches a position opposed to the intermediate transfer belt 8 and the primary transfer roller 9Y. The toner image on the photosensitive drum 1Y is transferred onto an intermediate transfer belt 8 (a transfer target) as an intermediate transfer member (this is a primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning device 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is collected in the cleaning device 2Y by the cleaning blade 2a (cleaning). Process.)
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes (image forming steps) performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the same manner as the process cartridge 6Y (image forming unit) for yellow in the other process cartridges 6M, 6C, and 6K (image forming unit). That is, exposure light based on image information is emitted from the exposure device disposed above the image forming unit onto the photosensitive drums of the process cartridges 6M, 6C, and 6K.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, referring to FIG. 1, the intermediate transfer belt device 15 includes an intermediate transfer belt 8 as an intermediate transfer member (a transfer target), a primary transfer roller 9Y (four transfer devices (primary transfer devices)) 2), a driving roller, a driven roller, and the like. The intermediate transfer belt 8 is stretched and supported by a driving roller, a driven roller, and a primary transfer roller, and is endlessly moved in the arrow direction (counterclockwise direction) in FIG. 1 by the rotational driving of the driving roller.

A primary transfer roller 9Y as a primary transfer device sandwiches the intermediate transfer belt 8 with the photosensitive drum 1Y to form a primary transfer nip. A transfer voltage (transfer bias) opposite to the polarity of the toner is applied to the primary transfer roller 9Y.
Then, the intermediate transfer belt 8 as a transfer target travels in the direction of the arrow, and sequentially passes through the primary transfer nip of each primary transfer roller (9Y). In this way, the toner images of the respective colors on the respective photosensitive drums (1Y) are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19 as a secondary transfer device. At this position, the driving roller (secondary transfer counter roller) sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 as a secondary transfer device to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip (secondary transfer step). . At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 16 (intermediate transfer cleaning blade). At this position, the untransferred toner on the intermediate transfer belt 8 is mechanically removed by an intermediate transfer cleaning blade (intermediate transfer cleaning device 16) that is in pressure contact with the intermediate transfer belt 8. The intermediate transfer cleaning blade is a substantially plate-like member made of an elastic material such as urethane rubber, and is in contact with the intermediate transfer belt 8 with a predetermined contact pressure and contact angle.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

Here, referring to FIG. 1, the recording medium P conveyed to the position of the secondary transfer nip is fed from a sheet feeding unit 26 disposed below the apparatus main body 100 to a sheet feeding roller 27 and a registration roller pair 28. (A pair of timing rollers) or the like.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20 (fixing nip). At this position, the color image (toner image) transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 (fixing member) and the pressure roller 22 (pressure member). (This is a fixing process.)
Thereafter, the recording medium P is discharged out of the apparatus by a pair of paper discharge rollers. The recording medium P discharged out of the apparatus by the pair of paper discharge rollers is sequentially stacked on the stack unit (main body cover 110) as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the image forming unit in the image forming apparatus will be described in detail with reference to FIGS.
As shown in FIG. 2, the process cartridge 6Y includes a photosensitive drum 1Y (image carrier), a charging device 4Y (charging roller), a developing device 5Y, a cleaning device 2Y, and the like.
A photoconductive drum 1Y as an image carrier is a negatively charged organic photoconductor, and receives a driving force from a main motor 91 (see FIG. 3) installed on the apparatus main body 100 side to receive the timepiece of FIG. It is rotationally driven in the direction. Although not shown, the photosensitive drum 1Y includes an undercoat layer as an insulating layer, a charge generation layer (CGL) and a charge transport layer (CTL) as a photosensitive layer, a protective layer on a conductive support as a base layer. (Surface layer) are sequentially laminated.
Specifically, when the surface of the photosensitive drum 1Y is charged to a negative potential by the charging device 4Y, positive charges (holes) and electrons are generated as carriers in the CGL by exposure of the exposure light L during the exposure process. Among these, electrons move to the base layer side having a high potential, and positive charges which are carriers having a polarity opposite to the charged polarity on the surface of the photoconductor move to the photoconductor surface side having a low potential. The positive charge that has reached the surface of the photoconductor is neutralized by combining with electrons on the surface of the photoconductor, so that a region without charge (a region having a low potential) is formed and an electrostatic latent image is formed. A toner image is formed on the photosensitive drum 1Y by attaching toner to the electrostatic latent image by the developing device 5Y. In order to attach the toner to the electrostatic latent image, a developing power source 95 (power source) is formed so as to form an electric field so that the toner receives an electrostatic force from the developing roller 51 (developer carrier) toward the photosensitive drum 1Y. The developing bias (voltage) is applied to the developing roller 51.

The charging device 4Y is a charging roller having elasticity in which a medium-resistance foamed urethane layer in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed is formed on a cored bar. The material of the middle resistance layer of the charging device 4Y (charging roller) is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. A rubber material in which a conductive material such as metal oxide is dispersed, or a foamed material of these materials can also be used. Then, a predetermined charging bias (voltage) is applied from the charging power source 96 (power source) to the core of the charging device 4Y (charging roller) to charge the surface of the photosensitive drum 1Y with a predetermined charging potential. Yes.
In this embodiment, the charging roller 4Y is configured to contact the photosensitive drum 1Y. However, the charging roller 4Y may be configured not to contact the photosensitive drum 1Y.

  The cleaning device 2Y is provided with a cleaning blade 2a that is in sliding contact with the photosensitive drum 1Y, and mechanically removes and collects untransferred toner on the photosensitive drum 1Y. The cleaning blade 2a is a substantially plate-like member formed of an elastic material such as urethane rubber, and is in contact with the photosensitive drum 1Y with a predetermined contact pressure and contact angle.

  The developing device 5Y is arranged such that a developing roller 51 as a developer carrying member is opposed to the photosensitive drum 1Y with a small gap therebetween, and a developing region is formed between both members 1Y and 51. Is done. In the developing device 5Y, toner (nonmagnetic or magnetic one-component developer) as a developer is accommodated. The developing device 5Y develops the electrostatic latent image formed on the photosensitive drum 1Y (forms a toner image).

Hereinafter, the developing device 5Y will be described in detail with reference to FIGS.
Referring to FIG. 2, developing device 5Y in the present embodiment is a non-contact one-component developing type developing device, and mainly develops an electrostatic latent image formed on photosensitive drum 1Y. The main part 50 and a toner container 60 as a developer container in which toner (one-component developer) to be supplied to the developing device main part 50 is accommodated.
The developing device 5Y is detachably (replaceable) with respect to the apparatus main body 100 together with the other image forming members 1Y, 2Y, 4Y as a process cartridge 6Y, but with respect to the developing device main part 50 (process cartridge 6Y). Thus, the toner container 60 can be replaced separately. That is, the toner container 60 is detachably (replaceable) at an upper position with respect to the developing device main part 50 (process cartridge 6Y) mounted on the apparatus main body 100. Then, the main body cover 110 (see FIG. 1) is opened and closed around a hinge (not shown) to separate the toner container 60 from the developing device main part 50 and replace only the toner container 60, or the toner container. For example, the developing device main part 50 (process cartridge 6Y) in which 60 is mounted is replaced.
The toner container 60 is replaced at a timing when the toner stored in the toner container 60 runs out, and the developing device main unit 50 (process cartridge 6Y) is replaced by its constituent parts (for example, the developing roller 51, the photosensitive drum 1Y, etc.). Is performed at the timing when the toner reaches the end of its life and the internal toner runs out. Therefore, the toner container 60 may be replaced independently, but the developing device main unit 50 (process cartridge 6Y) is replaced together with the toner container 60 (with the toner container 60 mounted). It will be.

  The developing device main unit 50 includes a developing roller 51 as a developer carrying member, a supply roller 53 as a developer supply member, a doctor blade 52 as a developer regulating member, transport screws 54 and 55 as a plurality of transport members, A partition member 56 that separates the first conveyance path B1 by the first conveyance screw 54 and the second conveyance path B2 by the second conveyance screw 55, a main-side supply port 57 for supplying toner from the toner container 60, and the like. ing.

The developing roller 51 supplies toner (developer) to the electrostatic latent image formed on the photosensitive drum 1Y so as to face the photosensitive drum 1Y. As the developing roller 51, a roller having a roller portion (roller main portion) made of an iron-based material or an aluminum-based material on a rotating shaft portion (core metal) formed of a conductive metal material such as stainless steel is used. be able to.
The supply roller 53 is disposed below the two conveying screws 54 and 55, and is in sliding contact with the developing roller 51 to supply toner to the developing roller 51. In the supply roller 53, a foamed polyurethane layer having conductivity is laminated on a cored bar. The supply roller 53 also has a function of removing, from the developing roller 51, toner on the developing roller 51 that has not been subjected to the developing process in a region (developing position) facing the photosensitive drum 1Y.
The doctor blade 52 (developer regulating member) is disposed so that the tip thereof contacts the outer peripheral surface of the developing roller 51 at a predetermined pressure and angle, and the amount of the developer carried on the developing roller 51 is determined. regulate. As the doctor blade 52, a thin plate member made of a metal material such as stainless steel can be used.

  Here, a predetermined voltage is applied to the developing roller 51, the supply roller 53, and the doctor blade 52 from a developing power source 95 (power source), and the movement of the toner on the developing roller 51 is promoted. In this embodiment, an alternating voltage is applied as a developing bias to the developing roller 51 so that the toner reciprocates between the developing roller 51 and the photosensitive drum 1Y at the developing position. A voltage can also be applied as a developing bias.

The two conveying screws 54 and 55 (conveying members) are mounted in the apparatus main body 100 and convey the toner stored in the developing device main part 50 in the axial direction (the direction perpendicular to the paper surface of FIG. 2). To form a circulation path.
The first conveying screw 54 as the first conveying member is disposed at a position (upward position) facing the supply roller 53, and conveys the toner horizontally in the axial direction (longitudinal direction) (FIG. 2). The toner is supplied onto the supply roller 53 while being conveyed from the front side to the back side in the direction perpendicular to the paper surface.

The second conveying screw 55 as the second conveying member is disposed at a position (an upper position) facing the first conveying screw 54 via the partition member 56, and the toner is axially (longitudinal direction). ) Horizontally (conveyance from the back side to the front side in the direction perpendicular to the paper surface of FIG. 2). Then, the second transport screw 55 has a first relay unit disposed on the upstream side of the first transport path B1 for the toner circulated from the downstream side of the first transport path B1 by the first transport screw 54 via the second relay unit. Transport through.
The two conveying screws 54 and 55 are arranged so that the rotation axis is substantially horizontal, like the developing roller 51 and the photosensitive drum 1Y. Moreover, as for the two conveyance screws 54 and 55, as for all, the screw part is helically wound by the axial part.

The conveyance path (first conveyance path B1) by the first conveyance screw 54 and the conveyance path (second conveyance path B2) by the second conveyance screw 55 are separated from each other by a partition member 56 (wall portion).
Although illustration is omitted, the downstream side of the second conveyance path B2 by the second conveyance screw 55 and the upstream side of the first conveyance path B1 by the first conveyance screw 54 communicate with each other via the first relay unit. . The toner that has reached the downstream side of the second transport path B2 by the second transport screw 55 falls by its own weight at the first relay section and reaches the upstream side of the first transport path B1.
Further, the downstream side of the first conveyance path B1 by the first conveyance screw 54 and the upstream side of the second conveyance path B2 by the second conveyance screw 55 are communicated with each other via the second relay unit. Then, the toner that has not been supplied onto the supply roller 53 in the first conveyance path B1 stays in the vicinity of the second relay unit and rises, and is conveyed to the upstream side of the second conveyance path B2 via the second relay unit. (Supplied).
In addition, in order to improve the toner transportability in the second relay unit (the transfer of toner against the direction of gravity from the first transport path B1 to the second transport path B2), the downstream of the first transport screw 54. A paddle-shaped part or a screw part formed in the reverse direction of the screw winding direction can also be provided at the position on the side (the position corresponding to the second relay part).

Referring to FIG. 2, the developing device main portion 50 is formed with a main portion-side supply port 57 communicating with the container-side supply port 63 of the toner container 60 at an upper position. The main portion side supply port 57 is for supplying toner (developer) from the toner container 60 to the developing device main portion 50.
Although not shown, gears are provided on the shaft portions of the developing roller 51, the supply roller 53, the first conveying screw 54, and the second conveying screw 55, and a gear train including an idler gear is formed. ing. Then, a driving force is input to these gear trains from the developing motor 92 (driving means), and the developing roller 51, the supply roller 53, the first conveying screw 54, and the second conveying screw 55 rotate in the direction of the arrow in FIG. Driven.
The developing motor 92 is provided separately from the main motor 91 that rotationally drives the photosensitive drum 1Y, and is configured so that the developing device 5Y can be driven independently. That is, the main motor 91 and the developing motor 92 functioning as driving means can drive and stop driving of the developing roller 51 (developer carrier) independently of the running (rotation) of the photosensitive drum 1Y. It will be configured to be able to.

Here, the toner container 60 as a developer container includes an agitator 61, a container side conveying screw 62 as a container side conveying member, a container side supply port 63, and the like.
The agitator 61 is formed by attaching a thin plate-like flexible member to the rotating shaft portion. The agitator 61 rotates in the counterclockwise direction of FIG. 2 to thereby store the toner accommodated in the accommodating portion C of the toner container 60. Is transported toward the transport path by the container-side transport screw 62.
The container-side transport screw 62 (container-side transport member) transports the toner contained in the container toward the container-side supply port 63 toward one end in the longitudinal direction while being attached to the apparatus main body 100.
The container-side supply port 63 is formed on one end side in the longitudinal direction in the transport path by the container-side transport screw 62. The toner discharged from the container side replenishing port 63 is replenished to the upstream side of the second transport path B2 of the developing device main portion 50 through its main portion side replenishing port 57 by its own weight fall.

The developing device 5Y configured as described above operates as follows.
First, the toner replenished from the toner container 60 into the second transport path B2 through the replenishing ports 57 and 63 is stirred and mixed by the second transport screw 55 together with the toner circulating in the main part 50 of the developing device. , Supplied to the first transport path B1. A part of the toner transported to the first transport path B1 is supplied to and supported by the supply roller 53 while being transported to the first transport screw 54. The toner carried on the supply roller 53 is frictionally charged at the pressure contact portion with the developing roller 51 and then moved onto the developing roller 51 and carried thereon. Thereafter, the toner carried on the developing roller 51 is made thin and uniform at the position of the doctor blade 52, and then reaches the position (developing position) facing the photosensitive drum 1Y. At this position, the toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field (developing electric field) formed at the developing position.

Hereinafter, a characteristic configuration of the image forming apparatus 100 according to the present embodiment will be described in detail.
As shown in FIGS. 2 and 3, the image forming apparatus 100 according to the present embodiment is downstream in the rotation direction (downstream in the running direction) of the photosensitive drum 1Y with respect to the developing device 5Y (developing position). Surface as surface potential detection means for detecting the surface potential of the photosensitive drum 1Y on the upstream side in the rotation direction (upstream in the running direction) of the photosensitive drum 1Y with respect to the primary transfer roller 9Y (transfer position) as the transfer device. A potential sensor 81 is installed. As the surface potential sensor 81 (surface potential detection means), known ones disclosed in Patent Documents 1 and 2 can be used.

  Then, during non-image formation (during warm-up, standby, etc.), the surface potential on the photosensitive drum 1Y (mainly the exposure potential (latent image potential)) is detected by the surface potential sensor 81. Based on the detection result, the control unit 90 determines the image forming conditions during the image forming process (at the time of image formation). Specifically, the image forming conditions adjusted and controlled by the control unit 90 based on the detection result of the surface potential sensor 81 are the charging bias (VC) applied from the charging power source 96 to the charging device 4Y and the developing power source 95 for developing. The developing bias (VB) applied to the roller 51 and the amount of exposure light (LDP) irradiated from the exposure device 7Y. At this time, the latent image formed on the photosensitive drum 1Y by the exposure device 7Y is a solid image so that the development potential is maximized.

  Thus, in the present embodiment, since the surface potential sensor 81 is installed at a position sufficiently away from the exposure position (on the downstream side of the development position), the surface potential (latent image) of the photosensitive drum 1Y. After the potential is stabilized to some extent, the surface potential can be detected by the surface potential sensor 81. That is, in the photosensitive layer of the photosensitive drum 1Y, a sufficient time (transit time) for the positive charge generated by exposure to move to the surface of the photosensitive member and combine with the negative charge can be secured. Thereby, the image forming condition adjusted based on the detection result of the surface potential sensor 81 becomes highly accurate.

In this embodiment, in the adjustment of the image forming conditions performed during non-image formation, the main motor 91 and the developing motor 92 (the rotation of the developing roller 51 is stopped by rotating the photosensitive drum 1Y to stop the rotation). The exposure unit 7Y irradiates the surface of the photosensitive drum 1Y with a developing bias having the same value as or a value approximate to a predetermined developing bias applied during the developing process. The first detection result (X1) detected by the surface potential sensor 81 when the light amount of the exposure light L is set to the first value, and the light amount of the exposure light L irradiated on the surface of the photosensitive drum 1Y by the exposure device 7Y. Is applied to the charging device 4Y based on the second detection result (X2) detected by the surface potential sensor 81 when the value is a second value different from the first value. Charging bias (VC), a developing bias applied to the developing roller 51 (VB), the light quantity of the exposure light L is irradiated from the exposure device 7Y (LDP), and adjusting at least one of.
Specifically, when there is no difference between the first detection result (X1) and the second detection result (X2), the charging bias (VC) applied to the charging device based on the detection result (X1 or X2). ), The value of the developing bias (VB) applied to the developing roller 51 and the amount of light (LDP) of the exposure light irradiated from the exposure device 7Y, respectively. On the other hand, when there is a difference between the first detection result (X1) and the second detection result (X2), a correction value (Δ) is obtained based on the difference, and the correction value (Δ) is obtained. Accordingly, the values of the charging bias (VC) applied to the charging device, the developing bias (VB) applied to the developing roller 51, and the amount of exposure light (LDP) irradiated from the exposure device 7Y are corrected and determined.

  As described above, the surface potential detection is performed in a state where a developing bias equivalent to that in the developing step is applied to the developing roller 51, because the surface potential sensor 81 is sensitive to the developing roller 51 without applying the developing bias. When the surface potential of the body drum 1Y is detected or a developing bias (for example, the polarity is reversed) different from that at the developing step is applied to the developing roller 51, the surface potential sensor 81 is applied. When the surface potential of the photosensitive drum 1Y is detected by the above, the surface potential of the photosensitive drum 1Y is different from that in the actual image forming process (image formation), and the surface potential is detected by the surface potential sensor 81. This is because if the image forming condition is determined based on the detection result, the image forming condition cannot be adjusted accurately.

  More specifically, the degree of acceleration of the charge generated in the photosensitive layer varies depending on the magnitude of the electric field formed at the development position by the development bias, and the surface potential of the photosensitive drum 1Y at the development position varies. Therefore, at the position downstream of the development position, the surface potential in a state where the charge generated in the photosensitive layer is accelerated by the application of the development bias as in the actual image forming process is detected, and based on the detection result. By determining the image forming condition (development potential), it is possible to adjust to the image forming condition that is accurately adapted to the actual image forming process.

FIG. 4 is a graph showing a change in the surface potential of the photosensitive drum 1Y when a developing bias is applied to the developing roller 51 (a graph indicated by a solid line), and when a developing bias is not applied to the developing roller 51. And a graph showing a change in surface potential of the photosensitive drum 1Y (shown by a broken line).
As shown in FIG. 4, it can be seen that there is a difference in the speed at which the photoreceptor surface potential is lowered when the developing bias is applied and when it is not applied. If the surface potential at the developing position is detected without applying the developing bias, the transition of the surface potential indicated by the broken line graph is confirmed. In such a case, when the exposure-development time T2 is long (for example, T2 = 100 ms), the surface potential at the development position is detected without applying the development bias, and the image forming conditions are set. Even if the adjustment is made, it is difficult to cause a major problem with the image quality. However, when the exposure-development time T1 is short (for example, T1 = 50 msec), the image quality is adjusted by detecting the surface potential at the development position without applying the development bias and adjusting the image formation conditions. Will cause a major problem. That is, if the image forming condition is adjusted based on the detection result in a state where the surface potential difference of the photosensitive drum 1Y is large, the developing potential is controlled to be lower than the optimum value, and the toner adheres. The image quality deteriorates due to a decrease in the amount.

In the present embodiment, as described above, when the surface potential is detected by the surface potential sensor 81 with the developing bias applied to the developing roller 51, the rotational driving of the developing roller 51 is stopped. This is because the surface potential sensor 81 is installed on the downstream side of the developing position, so that if the developing roller 51 is driven to rotate, toner is supplied from the developing roller 51 onto the photosensitive drum 1Y, and the photosensitive roller 1Y This is because the surface potential (latent image potential VL) of the body drum 1Y cannot be accurately detected.
Specifically, when the image forming conditions are adjusted during non-image formation, the photosensitive drum 1Y is kept at a predetermined distance (in this embodiment, about 50 mm) with the developing roller 51 applied with the developing bias stopped. After running, the surface potential sensor 81 detects the surface potential (VL) of the photosensitive drum 1Y. As described above, the surface potential is detected after the driving of the developing roller 51 to which the developing bias is applied is stopped and the driving of the photosensitive drum 1Y is started for a predetermined distance (or a predetermined time). This is because a slight amount of toner is initially supplied from the developing roller 51 to the photosensitive drum 1Y even when the driving of the developing roller 51 is stopped.

In the present embodiment, as described above, the first detection result (X1) detected by the surface potential sensor 81 when the light amount of the exposure light L is the first value, and the light amount of the exposure light L. The image forming condition is adjusted based on the second detection result (X2) detected by the surface potential sensor 81 when is set to a second value different from the first value.
This is because it is possible to set an optimum development potential in the image forming process by detecting the surface potential of the latent image formed by the exposure light of different light amounts and obtaining the development potential based on the detection result. .

Specifically, in the present embodiment, the light amount of the exposure light L applied to the surface of the photosensitive drum 1Y by the exposure device 7Y is adjusted to the first value (before adjusting the image forming conditions described above during non-image formation. LDP 1) based on the toner image developed by the developing device 5Y on the latent image formed on the photosensitive drum 1Y, a charging bias (VC) applied to the charging device 4Y, a developing bias (VB) applied to the developing roller 51, Image adjustment is performed to temporarily determine the value of the amount of exposure light L (LDP) irradiated from the exposure device 7Y. Then, the second value (LDP2) of the exposure light L when the image forming condition is adjusted is the light amount of the exposure light L that is temporarily determined when the image adjustment is performed.
That is, when performing the image formation condition adjustment control described above, the exposure amount used when the image adjustment (process control) is performed (the exposure amount during the normal image formation step is set to be larger). ) Is used as the first value (LDP1), and the exposure amount temporarily determined as a result is used as the second value (LDP2).

Further, when the image forming conditions are adjusted during non-image formation, the developing bias applied to the developing roller 51 in a state where the driving is stopped is set as a developing bias temporarily determined when the above-described image adjustment is performed. That is, when the above-described adjustment of the image forming conditions is performed, as a result of the image adjustment (process control) being performed, a development bias that is provisionally approximated (development bias during a normal image forming process) is approximated. ) Is used.
In the image adjustment (process control), the latent image formed with an exposure amount larger than the exposure amount in the normal image forming process is developed (visualized) by the developing device 5Y, and the image portion This is performed by detecting the surface potential and the surface potential of the non-image portion with the surface potential sensor 81.

FIG. 5 is a graph (shown by a solid line) showing the relationship between the amount of exposure light (LDP) and the surface potential (VL) of the photosensitive drum 1Y when a developing bias is applied to the developing roller 51. A graph (shown by a broken line) showing the relationship between the amount of exposure light (LDP) and the surface potential (VL) of the photosensitive drum 1Y when no developing bias is applied to the developing roller 51; It is.
In the actual image forming process, in order to reduce toner consumption and realize fine dot reproduction, when forming a latent image on the photosensitive drum 1Y, a light amount that is weaker than the light amount at the time of image adjustment is used. Used. However, by using this weak light amount, the latent image potential (VL) cannot be sufficiently lowered, and the development potential determined at the time of image adjustment cannot be secured. For this reason, in order to secure the developing potential even when a weak light quantity is used, the difference in the detected surface potential (M1 in FIG. 5 is about 30 V) is determined as a charging bias (VC) determined at the time of image adjustment. Correction is made in addition to the developing bias (VB) and the exposure amount (VDP).
Here, as shown in FIG. 5, the exposure amount (LDP) is higher when the surface potential is detected with the developing bias applied than when the surface potential is detected with no developing bias applied. It can be seen that the surface potential on the photosensitive drum 1Y tends to decrease in a large region. This is because the region where the exposure amount is strong is easily affected by the developing bias, and the movement of charges in the photosensitive layer is promoted. Specifically, as shown in FIG. 5, when the surface potential is detected without applying the developing bias, the surface potential difference M2 between the image adjustment and the image forming process is about 10V. When the surface potential is detected with the developing bias applied, the surface potential difference M2 between the image adjustment and the image forming process is about 30V. Therefore, when surface potential detection is performed with a development bias applied, it is particularly important to adjust and correct the imaging conditions based on the surface potential detection results obtained using exposure light of different sizes. become.

FIG. 6 is a flowchart showing control for performing image adjustment and adjustment of image forming conditions during non-image formation, and summarizes the control described so far.
As shown in FIG. 6, first, the exposure amount is set to LDP1 (which is a relatively large value), image adjustment (process control) is started (step S1), and provisional image forming conditions (charging bias VC). , Development bias VB, exposure amount LDP2) are determined (step S2). Note that LDP2 at this time is determined by αVC + β.
Thereafter, the driving of the developing roller 51 is stopped (step S3), and the developing bias VB temporarily determined in step S2 is applied to the developing roller 51 (step S4). Then, the latent image potential formed with the exposure amount LDP1 used in step S1 as the first value is detected by the surface potential sensor 81 as the first detection result (X1), and the exposure temporarily determined in step S2 The latent image potential formed with the amount LDP2 (<LDP1) as the second value is detected by the surface potential sensor 81 as the second detection result (X2) (step S5). The charging bias VC used at this time is provisionally determined in step S2.
Then, it is determined whether or not there is a difference between the first detection result (X1) and the second detection result (X2) detected in step S5 (step S6). As a result, if it is determined that there is no difference, the image forming conditions (VC, VB, LDP2) provisionally determined in step S2 are formally determined and used as the final image forming conditions (step S7). Then, an actual image forming process is performed according to the formally determined image forming conditions.
On the other hand, if it is determined in step S6 that there is a difference, a correction value (Δ) is calculated from the difference (step S8) and corrected based on the correction value (Δ). Image conditions (VC ′, VB ′, LDP2 ′) are determined (step S9). Then, an actual image forming process is performed according to the corrected image forming conditions.

Here, as an example of the correction performed in step S9, the case described above with reference to FIG. 5 (the case where the surface potential difference M2 between the image adjustment process and the image forming process is 30 V) is used. explain.
Assume that the image forming conditions provisionally determined in step S2 are VC = 740V, VB = 590V, and LDP2 = 70%. After that, when it is determined in steps S6 and S8 that the difference (surface potential difference M2) is 30V, VC ′ = 740V + 30V = 770V, VB ′ = 590V + 30V = 620V, LDP2 ′ = 70% + ( α × 30 + β) = 75% is determined.
By performing the correction in this way, it is possible to secure the development potential determined at the time of image adjustment and to output a stable and high-quality image.

  As described above, in the present embodiment, the developing roller 51 (developer carrier) is stopped and exposure is performed in a state where a developing bias equivalent to the developing bias in the developing process is applied to the developing roller 51. Based on the surface potential of the photosensitive drum 1Y (image carrier) on the downstream side of the development position when the light amount of the exposure light L of the apparatus 7Y is the first value and the second value. The image conditions are adjusted. Thereby, based on the detection result of the surface potential sensor 81 (surface potential detecting means) that detects the surface potential of the photosensitive drum 1Y, the image forming conditions can be adjusted accurately.

In the present embodiment, the photosensitive drum 1Y (image carrier), the developing device 5Y (developing device main part 50), the charging device 4Y, and the cleaning device 2Y are integrated as a process cartridge 6Y. The present invention was applied to cases where However, the application of the present invention is not limited to this, and all or a part of these apparatuses 1Y, 2Y, 3Y, and 5Y are each configured as a unit that is detachably attached to the image forming apparatus main body 100. Of course, the present invention can be applied even if it is.
In the present embodiment, the surface potential sensor 81 can be a component of the process cartridge 6Y.
In these cases, the same effects as in the present embodiment can be obtained.
In the present application, “process cartridge” means a charging device (charging unit) for charging an image carrier, a developing device (developing unit) for developing a latent image formed on the image carrier, and an image carrier. It is defined as a unit in which at least one of the cleaning devices (cleaning unit) for cleaning the top and the image carrier are integrated and installed detachably with respect to the image forming apparatus main body.

In this embodiment, the image forming apparatus 100 is provided with the non-contact one-component developing type developing device 5Y configured such that the developing roller 51 is opposed to the photosensitive drum 1Y with a gap. The present invention was applied. On the other hand, the present invention can also be applied to the image forming apparatus 100 provided with the developing device 5Y of the contact one-component developing system configured such that the developing roller 51 is in contact with the photosensitive drum 1Y. it can. Furthermore, a developing device of a two-component developing system (a developing device containing a two-component developer composed of a toner and a carrier) configured such that the developing roller faces the photosensitive drum with a gap therebetween. The present invention can also be applied to the image forming apparatus 100 in which () is installed.
Further, in the present embodiment, the present invention is applied to the color image forming apparatus 100 in which the toner image is transferred to the intermediate transfer belt 8 as a transfer target by a plurality of image forming units. On the other hand, the present invention can naturally be applied to a monochrome image forming apparatus in which a toner image is transferred to a recording medium as a transfer medium by an image forming unit.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1Y photosensitive drum (image carrier),
4Y charging device,
5Y developing device,
6Y, 6M, 6C, 6K process cartridge (imaging part),
7Y exposure equipment,
9Y primary transfer roller (transfer device),
51 Developing roller (developer carrier)
81 surface potential sensor (surface potential detection means),
100 Image forming apparatus main body (apparatus main body).

JP 2004-78088 A Japanese Patent No. 2815886

Claims (6)

An image carrier that travels in a predetermined direction;
A charging device for charging the surface of the image carrier;
An exposure device that irradiates the surface of the image carrier charged by the charging device with exposure light to form a latent image on the image carrier;
A developer is contained in the developer, and has a developer carrier that faces or abuts the image carrier, and the image carrier is supported by the exposure device with a predetermined developing bias applied to the developer carrier. A developing device for developing a latent image formed on the body to form a toner image;
Surface potential detection means for detecting the surface potential of the image carrier on the downstream side in the running direction of the image carrier with respect to the developing device;
Drive means configured to be able to drive and stop driving the developer carrier independently of the travel of the image carrier;
With
In the adjustment of image forming conditions to be performed at the time of non-image formation, the driving means is controlled to run the image carrier and stop the driving of the developer carrier, and the predetermined developing bias is applied to the developer carrier. Detected by the surface potential detection means when the exposure light amount irradiated to the surface of the image carrier by the exposure device is set to a first value with a developing bias having the same value as or a value close to the same applied. Detected by the surface potential detecting means when the first detection result and the amount of exposure light applied to the surface of the image carrier by the exposure device are set to a second value different from the first value. Based on the second detection result, the charging bias applied to the charging device, the developing bias applied to the developer carrier, and the amount of exposure light irradiated from the exposure device are at least Image forming apparatus characterized by adjusting one. When there is no difference between the first detection result and the second detection result, based on the detection result, a charging bias applied to the charging device, a developing bias applied to the developer carrier, and the exposure device Determine the value of the amount of exposure light irradiated from
When there is a difference between the first detection result and the second detection result, a correction value is obtained based on the difference, and a charging bias applied to the charging device based on the correction value, the developer 2. The image forming apparatus according to claim 1, wherein the values of the developing bias applied to the carrier and the amount of exposure light irradiated from the exposure device are corrected and determined. A latent image formed on the image carrier with the first light amount of the exposure light applied to the surface of the image carrier by the exposure device before adjusting the image forming conditions during non-image formation. Based on the toner image developed by the developing device, the values of the charging bias applied to the charging device, the developing bias applied to the developer carrying member, and the amount of exposure light emitted from the exposure device are respectively tentatively determined. Make image adjustments
The second value at the time of adjusting the image forming condition is a light amount of the exposure light that is provisionally determined at the time of performing the image adjustment. Image forming apparatus.   The developing bias applied to the developer carrying member in a stopped state when the image forming conditions are adjusted during non-image formation is a development bias that is temporarily determined when the image adjustment is performed. The image forming apparatus according to claim 4.   When the image forming conditions are adjusted at the time of non-image formation, the surface detecting means is provided after the image carrier travels a predetermined distance in a state where the developer carrier to which the developing bias is applied is stopped. The image forming apparatus according to claim 1, wherein the surface potential of the image carrier is detected by. A transfer device for transferring a toner image formed on the image carrier to a transfer target;
6. The surface potential detection unit detects a surface potential of the image carrier on the upstream side in the traveling direction of the image carrier with respect to the transfer device. Image forming apparatus.

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