JP2014178356A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which is capable of suppressing the degradation of image quality caused by the unevenness of a developer layer thickness by suppressing the deviation in the longitudinal direction of the amount of developer passing through between a developer carrier and a developer regulation member and to provide a process cartridge including the developing device and an image forming apparatus.SOLUTION: The developing device includes a developing container 50 storing the developer, developer conveyance members 53 and 54 stirring and conveying the developer, a developer carrier 51 including a non-magnetic sleeve 511 including magnetic field generation means 55 forming a magnetic pole and scooping and carrying the developer onto and on the surface of the sleeve 511 by a magnetic force, to convey the developer to an area facing a latent image carrier 1, and a developer regulation member 52 regulating the layer thickness of the developer. The developer regulation member 52 is attached to the developing container, so that the top end side of the developer regulation member faces the surface of the sleeve. The longitudinal central portion fc of the developer regulation member is curved so as to more project toward the upstream side in the rotational direction of the sleeve than the longitudinal both ends fs of the developer regulation member.

Description

  The present invention relates to a developing device for developing an electrostatic latent image on an image carrier, a process cartridge having the developing device, a copier, a printer, a facsimile, a plotter having the developing device or the process cartridge, or at least one of these. The present invention relates to an image forming apparatus such as a multi-function machine equipped with two.

  2. Description of the Related Art Conventionally, a two-component developing type developing device carries a two-component developer composed of toner and carrier on a developer carrying member, conveys it to a developing area facing the image carrying member, and forms a static image formed on the image carrying member. It is a device that develops and visualizes an electrostatic latent image. After the development process is completed and the toner is consumed in the development area, the developer is collected, mixed with the replenished toner, stirred, and again used for development.

A developer used in such a two-component developing system developing device needs to maintain a constant toner concentration and charge amount in order to obtain a stable toner image. The toner density is adjusted by the amount of toner consumed in the development and the amount of replenished toner, and the charge amount is given by frictional charging when the carrier and the toner are mixed, and these functions are provided near the developer carrier. Prepared.
The developer supply device, for example, arranges a plurality of conveying screws as developer agitating and conveying members in a developer container, and at least one of them is opposed to the developer carrying member as a supply screw, and the developer carrying member And supply of the developer are simultaneously advanced between the toner and the supply screw.
As the developer carrying member disposed opposite to the vicinity of the developer supply device, a rotatable non-magnetic developing sleeve containing a magnetic field generating means in which magnets for forming a plurality of magnetic poles are fixedly arranged is widely used. This developing sleeve carries the developer agitated by the conveying screw of the developer supply device with a magnetic force on the developing sleeve by the magnetic force of the internal magnetic field generating means, and further, the developer is supported by a developer regulating member (doctor blade). It is regulated to a constant layer thickness and conveyed to a development area facing an image carrier such as a photoconductor.

Here, the developer carried on the developing sleeve is regulated to have a constant volume by passing through a gap portion (doctor gap) between the surface of the developing sleeve and the developer regulating member (doctor blade).
The weight per unit area of the developer (film layer) that has passed through the doctor gap is called the pumping amount (or transport amount), and is known to have a large effect on the image density. If the pumping amount is too large relative to the gap between the developing areas where the developing sleeve and the photoconductor face each other, the developer is compressed in the developing area and the developer itself melts and adheres due to frictional heat generated by the shear stress at that time. The trouble of doing occurs.

On the other hand, if the amount of pumping is small, sufficient toner cannot be supplied to the photoreceptor surface of the image carrier, which causes problems such as image density reduction and density unevenness. Therefore, in order to stably obtain a high-quality image, it is important to secure a pumping amount within an appropriate range in the longitudinal direction of the developing sleeve, and to convey it to a developing region (opposing portion) facing the image carrier. .
Therefore, it is common to set the doctor gap formed by the developer regulating member to be uniform with respect to the longitudinal direction of the developer carrier so that the amount of developer drawn up is uniform with respect to the longitudinal direction of the developer carrier. is there.

However, with the conventional configuration of the developing device, when the speed of the image forming apparatus in the market and the demand for higher image quality are increased, the rotation speed of the developer carrier and the magnetic force of the magnetic field generating means inside the developer carrier increase. The developer pressure applied to the developer regulating member is increased, and a deflection occurs in the central portion in the longitudinal direction of the developer regulating member. And the phenomenon that the doctor gap in a longitudinal direction center part becomes large compared with the doctor gap of a longitudinal direction edge part generate | occur | produces. As a result, there is a problem that unevenness occurs in the developer layer thickness in the longitudinal direction, leading to a decrease in image quality.
In order to solve the problem in the developing device having such a conventional configuration, Patent Document 1 discloses that the longitudinal end of the front end surface of the developer regulating member is supported by the developing device casing and opposed to the developing sleeve. Discloses a developing device having a convex shape with a difference in straightness of 0.02 to 0.08 mm with respect to both ends.

In such a configuration, when the front end surface at the center in the longitudinal direction of the developer regulating member is pressed during driving, the doctor gap at the center in the longitudinal direction is enlarged and displaced so that the deviation from the doctor gap at both ends is absorbed. . However, with the recent increase in the speed of image forming apparatuses, it is necessary to increase the number of rotations of the developer carrying member, and accordingly, the extent to which the developer presses the central portion of the developer regulating member has increased. .
For this reason, in the configuration of Patent Document 1 described above, the doctor gap at the center of the developer regulating member becomes larger than the end due to an increase in pressing force from the developer accompanying an increase in the rotation speed of the developer carrier.
That is, in the technique of Patent Document 1, the central portion of the developer regulating member is displaced so as to absorb the deviation of the doctor gap in the longitudinal direction caused by the increase in the amount of developer pumped with the increase in the rotation speed of the developer carrier. The deviation in the longitudinal direction of the amount of developer passing through the doctor gap cannot be suppressed, so that the image quality is deteriorated due to unevenness of the developer layer thickness.

  The present invention has been made in view of the above-described problems of the prior art, and suppresses a deviation in the longitudinal direction of the amount of developer passing through the gap (doctor gap) between the developer carrier and the developer regulating member. An object of the present invention is to provide a developing device capable of suppressing deterioration in image quality due to uneven developer layer thickness, a process cartridge containing such a developing device, and an image forming apparatus.

The present invention has the following configuration in order to achieve the above object.
A developing device according to the present invention includes a developing container that contains a two-component developer composed of toner and a carrier, a developer conveying member that agitates and conveys the two-component developer, and a rotating support that is rotatably supported by the developing container. A non-magnetic sleeve containing a magnetic field generating means for forming a magnetic pole, and a two-component developer agitated and conveyed by the developer conveying member is pumped and carried on the sleeve surface by a magnetic force to carry a latent image carrier. In the developing device, the developer carrying member conveyed to the opposite area of the sheet, and the developer regulating member that regulates the layer thickness of the two-component developer, the developer regulating member is disposed on the surface of the sleeve. The developer regulating member is attached to the developer container so that the front end side of the developer regulating member faces in the longitudinal direction, and the central portion in the longitudinal direction of the developer regulating member is upstream in the rotational direction of the sleeve as compared with both longitudinal ends. Characterized in that curved to protrude toward the.

  According to the present invention, in the initial state before the developer pressure is applied, the flatness at which the deviation in the plane perpendicular direction between the longitudinal center portion and both end portions on the front end side of the developer regulating member is 0.1 to 0.6 mm. It is formed in a curved shape so as to form When the developer pressure is applied to the leading end side of the developer regulating member, a displacement that cancels the deviation in the plane orthogonal direction occurs, so that the doctor gap between the leading edge of the main plate portion and the surface of the developer carrying member can be made equal. It is characterized in that the thickness of the developer carried on the developer carrying member can be adjusted to be constant in the longitudinal direction, image unevenness can be eliminated, and image quality can be improved.

1 is an overall configuration diagram of an image forming apparatus including a developing device and a process cartridge according to an embodiment of the present invention. FIG. 2 is a side sectional view of a process cartridge that accommodates the developing device of FIG. 1. 2A and 2B are diagrams illustrating the developing device of FIG. 1, in which FIG. 1A is a longitudinal sectional view, and FIG. It is a figure explaining the movement of the developer to the supply screw and collection | recovery screw of the developing device of FIG. It is a figure explaining the movement of the developer to the magnetic force line of the developing roller of the developing device of FIG. 1, and a supply screw and a recovery screw. FIG. 2 is a plan view of a doctor blade provided on a developing roller of the developing device in FIG. 1. FIG. 2 is a schematic perspective view for explaining a curved state of a doctor blade that is opposed to a developing roller of the developing device of FIG. 1. It is explanatory drawing of the relative position of the developing roller and doctor blade used with the developing device of FIG. It is a figure explaining the curved state of the front-end | tip edge of the doctor blade provided with the developing roller of the developing device of FIG. FIG. 2 is an exploded perspective view before assembling a doctor blade to a developing roller mounted on a developer container used in the developing device of FIG. 1, (a) is an overall view, and (b) is a partially cutaway enlarged view. FIG. 2 is a perspective view after assembling a doctor blade to a developing roller mounted on a developer container used in the developing device of FIG. 1, (a) is an overall view, and (b) is a partially cutaway enlarged view. FIG. 7 is a diagram illustrating the relationship between the flatness of a doctor blade provided on the developing roller of the developing device of FIG. 1 and the pumping amount deviation FCRρ. 2A and 2B are front views of an example of a doctor blade flatness detecting device used in the developing device of FIG. 1, in which FIG. 1A shows an end data detection state, and FIG. 2B shows a center data detection state; It is a schematic perspective view explaining the curved state of the doctor blade used with the image development apparatus which is 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments and modifications, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description thereof is omitted.

First, with reference to FIGS. 1 to 12, a developing device as a first embodiment of the present invention, a process cartridge that houses the developing device, and an overall configuration of an image forming apparatus including these will be described. The image forming apparatus 100 here is a color copying machine.
The color copying machine (hereinafter referred to as an image forming apparatus) 100 is a so-called tandem type image forming apparatus, and is formed along a lower portion of an intermediate transfer belt 8 provided in the intermediate transfer unit 10 with yellow (Y) and magenta (M ), Image forming portions 6Y, 6M, 6C, and 6K (hereinafter also referred to as 6Y to 6K) corresponding to four colors of cyan (C) and black (K).

  Each of the image forming units 6Y to 6K includes a photosensitive drum 1 as an image carrier and a scanner 300 including an automatic document feeder 400 that automatically feeds a transfer material P onto the photosensitive member 1. Image formation is performed by a printer unit (image forming unit) 500 in accordance with an image signal from another image signal input device. In the printer unit 500, a four-color toner image corresponding to a document image is transferred to the supplied transfer material P, and after the fixing process, the transfer material P on which the four-color toner image is fixed is sent to the stack unit 30. Since the image forming units 6Y to 6K disposed in the apparatus main body 101 have substantially the same configuration except that the color of the toner used in the image forming process is different, the image forming unit 6 and the photosensitive drum 1 in FIG. The alphabet (Y, M, C, K) of the reference numerals with the primary transfer roller 9 is omitted.

  As shown in FIG. 2, the image forming unit 6 includes a photosensitive drum 1 as an image carrier, a charging unit 4, a developing device 5, a cleaning unit 2, and the like disposed around the photosensitive drum 1. Yes. An image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1. The photosensitive drum 1, the charging unit 4, the developing device 5, and the cleaning unit 2 constituting the image forming unit 6 are configured to be detachable from the apparatus main body 101, and are replaced with new ones when their lifetimes are reached. Is done. In this embodiment, the photosensitive drum 1, the charging unit 4, the developing unit 5, and the cleaning unit 2 that constitute the image forming unit 6 are each a single unit, but these units are integrated (two-point difference line shown in FIG. 2). The process cartridge may be detachable from the apparatus main body 101. In that case, maintainability of the image forming unit 6 is improved.

  The photosensitive drum 1 is rotationally driven in a clockwise direction in FIG. 2 by a driving unit (not shown), and the surface thereof is uniformly charged at the position of the charging unit 4 (charging process). Thereafter, the surface of the photosensitive drum 1 reaches an irradiation position of a laser beam L irradiated from an exposure unit (not shown), and an electrostatic latent image is formed by exposure scanning at this position (exposure process). Thereafter, the surface of the photosensitive drum 1 reaches a position facing a developing device 5 (which will be described in detail later), and the electrostatic latent image is developed at this position to form a desired toner image (developing step). ). Thereafter, the surface of the photosensitive drum 1 reaches a position facing the intermediate transfer belt 8 and the primary transfer roller 9 (a region facing the latent image carrier), and the toner image on the photosensitive drum 1 is intermediate transferred at this position. Transferred to the belt 8 (primary transfer process).

  At this time, a small amount of untransferred toner remains on the photosensitive drum 1. Thereafter, the surface of the photosensitive drum 1 reaches a position facing the cleaning unit 2, and untransferred toner remaining on the photosensitive drum 1 is collected by the cleaning blade 2a at this position (cleaning step). Finally, the surface of the photosensitive drum 1 reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position. Thereby, a series of image forming processes performed on the photosensitive drum 1 is completed.

The image forming process described above is performed in each of the four image forming units 6Y, 6M, 6C, and 6K. That is, a laser beam L (see FIG. 2) based on image information is irradiated toward each photosensitive drum 1 from an exposure unit (not shown) disposed below the image forming unit 6. Specifically, the exposure unit irradiates the photosensitive drum 1 through a plurality of optical elements while irradiating the laser beam L from the light source and scanning the laser beam L with a polygon mirror that is rotationally driven. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums 1 through the development process are superimposed and transferred onto the intermediate transfer belt 8, whereby a color image is formed on the intermediate transfer belt 8.
Four primary transfer rollers 9Y, 9M, 9C, and 9K (see FIG. 1) sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form primary transfer nips. ing. A transfer bias having a polarity opposite to the polarity of the toner is applied to each primary transfer roller 9.

  The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nip of each primary transfer roller 9. As a result, the respective color toner images on the respective photosensitive drums 1 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 superimposed and transferred reaches a position facing the secondary transfer roller 19. At this position, the secondary transfer backup roller 12 and the secondary transfer roller 19 sandwich the intermediate transfer belt 8 to form a secondary transfer nip. The color toner image formed on the intermediate transfer belt 8 is secondarily transferred onto the transfer material P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the transfer material P remains on the intermediate transfer belt 8, and the untransferred toner is removed by a cleaning unit (not shown) to return to the initial state. Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

  As shown in FIG. 1, the transfer material P transported to the position of the secondary transfer nip passes from a paper feed unit 26 disposed below the apparatus main body 101 via a paper feed roller 27, a registration roller pair 28, and the like. It is what was conveyed. A large number of transfer materials P are stored in the paper supply unit 26, and when the paper supply roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost transfer material P faces the registration roller pair 28. Separated. The transfer material P conveyed to the registration roller pair 28 is temporarily stopped at the nip position of the registration roller pair 28 that has stopped rotating. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the transfer material P is conveyed toward the secondary transfer nip so that a desired color image is formed on the transfer material P. Transcribed.

  The transfer material P on which the color image is transferred at the secondary transfer nip position is conveyed to the fixing unit 20, and the color image transferred to the surface is fixed by heat and pressure by the fixing roller and the pressure roller. The transfer material P on which the image is fixed is discharged by a pair of paper discharge rollers 29 and sequentially stacked on the stack unit 30 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

  As shown in FIG. 1, toner bottle units 31Y, 31M, 31C, and 31K are provided above the intermediate transfer unit 10, and each toner bottle is connected to each developing device via a toner supply unit (not shown). ing. When toner replenishment is required, the toner bottle is rotated and replenished via a toner replenishment port 56 (see FIG. 3B) described later.

Next, the configuration and operation of the developing device will be described in detail.
As shown in FIG. 3A, the developing device 5 includes a developing roller 51 as a developer carrying member facing the photosensitive drum 1 and a doctor blade as a developer regulating member installed below the developing roller 51. 52, a developer accommodating case member 50 as a developing container for accommodating a two-component developer composed of a carrier and toner, and a first conveying path 59 and a second conveying path 58 formed in the developer accommodating case member 50, A supply screw 53 serving as a first transport member housed in the first transport path 59 and a recovery screw 54 serving as a second transport member housed in the second transport path 58 are provided.

Here, the developing roller 51 and the recovery screw 54 of the supply screw 53 are rotatably supported by the developer containing case member 50 (developing container).
The supply screw 53 is disposed to face the developing roller 51 and supplies the developer to the developing roller 51 while mixing and stirring the developer. The collection screw 54 is disposed above the supply screw 53 so as to face the developing roller 51 and collects the developer separated from the developing roller 51.

  As shown in FIG. 3A, the developing roller 51 includes a columnar magnet 55 fixed inside, a rotatable nonmagnetic sleeve 511 that rotates around the magnet, and the like. The magnet 55 of the developing roller 51 has five magnetic poles, P1 to P5. When the sleeve 511 rotates around the magnet 55 on which five magnetic poles are formed, the developer moves on the developing roller 51 along with the rotation. In addition, the radial line attached | subjected to the developing roller 51 of Fig.3 (a) shows the position where each magnetic force of P1 pole-P5 pole becomes a peak. Here, a developer is used in which the normal direction peak magnetic flux density of the magnetic pole (magnetic field generating means) of the developer pumping pole P5 is 60 mT or more and 95 mT or less, and is in the vicinity of the portion facing the image material regulating member. As a result, the developer can hold an appropriate pumping amount on the developing roller 51 by the pumping pole P5, and is regulated to a layer thickness corresponding to the doctor gap as the developing sleeve 511 rotates.

The developer containing case member 50 is filled with a fixed amount of a developer in which a toner mainly composed of a polyester resin and a carrier that is a magnetic fine particle are uniformly mixed at a toner concentration of 7 Wt%. The supply screw 53 and the collection screw 54 arranged in parallel are rotated at 600 to 800 rpm to simultaneously stir and transport the toner after replenishment, thereby uniformly mixing the toner and the carrier and applying the charge.
As shown in FIG. 3B, the toner is replenished from a toner replenishing port 56 (see FIGS. 10A and 11A) provided on the upstream side of the collection screw 54 in the transport direction.
The uniformly mixed developer is supplied to the outer peripheral portion of the sleeve by the magnetic force P4 and P5 of the magnet 55 (see FIG. 3A) contained in the developing roller 51 from the supply screw 53 provided in parallel to the developing roller 51. It is conveyed to the surface.

  As shown in FIG. 3, when the developing roller 51 rotates as shown by an arrow in the drawing, it is carried to a developing region formed by the photosensitive drum 1 and the developing roller 51, thereby forming a developing electric field by a high voltage power source (not shown). The toner develops the latent image on the photosensitive drum 1. The developer after development is collected in the second conveyance path 58 as the developing roller 51 rotates, and the separation developer 57 that partitions the first conveyance path 59 and the second conveyance path 58 is used. It is recovered by the recovery screw 54.

FIG. 4 is a diagram showing a developer conveying member that stirs and conveys the two-component developer of the developing device 5 of the present embodiment, and is viewed from the direction of arrow A in FIG. 3A after the developing roller 51 is removed. The plan view shows the flow of the developer between the supply screw 53 and the recovery screw 54.
In the communication ports U1 and U2 which are developer delivery areas at the screw end, the upper and lower transport paths communicate vertically. The developer is conveyed from the upper stage to the lower stage at the communication port U2, and from the lower stage to the upper stage at the communication port U1.
As for the shape of the screw at the communication port, a paddle or a reverse-wound screw is provided, and the conveying ability in the direction perpendicular to the conveying direction is given.

FIG. 5 is a cross-sectional view of the developing device 5 in a direction orthogonal to the developer transport direction.
As shown in FIG. 5, the developing device 5 has a vertical biaxial conveyance configuration with a collection screw 54 and a supply screw 53 (first stirring shaft), and a doctor blade 52 (developer regulating member is a developer regulating member) below the developing roller 51. Will be described later in detail).
Within the developing device 5, the developer (see black dots in the figure) is affected by the magnetic force of the magnet and moves from the supply screw 53 disposed below onto the developing sleeve 511, which is a non-magnetic sleeve, to develop the developing sleeve. 511 is carried and conveyed. With the rotation of the developing sleeve 511, the amount of developer is regulated by a doctor blade 52) that is horizontally below the axis center. The developer is circulated on the developing sleeve 511, contacts the photosensitive drum 1 in the developing region, and is peeled off from the developing sleeve 511 by the reaction of magnetic force and the separation plate 57. The peeled developer moves downward along the separation plate 57 and is conveyed in one direction while being agitated by the recovery screw 54 (second agitation shaft) in the second conveyance path 58 (second partition chamber). The

The developer that has reached the end of the collection screw 54 falls to the first conveyance path 59 through the communication hole U2 (see FIG. 4), and is collected by the supply screw 53 (first stirring shaft) (second stirring shaft). ) Is moved in the opposite direction to the developing sleeve 511. Excess developer is pushed up to the second conveyance path 58 (second partition chamber) from the communication hole U1 located in the direction opposite to the communication hole U2, and is again stirred by the recovery screw 54 (second stirring shaft).
As described above, the developing device 5 is a lower doctor two-axis unidirectional circulation system in which the doctor blade 52 is disposed on the lower side and the developer is circulated only in one direction using a biaxial stirring shaft. In FIG. 5, the developer regulating member 2 is schematically illustrated in a generally used flat plate shape.

Next, the doctor blade 52 that is a developer regulating member that regulates the layer thickness of the two-component developer will be described in detail.
As shown in FIG. 6, the doctor blade 52 here is press-molded by bending a metal plate member once. The doctor blade 52 includes a main plate portion 521 on the leading end side that is long in the longitudinal direction of the developing roller 51, a bent portion 522 that follows the rear side of the main plate portion 521, and end fastening portions 523 that are located at both ends in the longitudinal direction. It is integrally molded.
Since the doctor blade 52 bends and forms a bent portion 522 with respect to the main plate portion 521 that is long in the longitudinal direction of the developing roller, the bending portion 522 reinforces the shape rigidity of the long flat plate-like main plate portion 521 that forms the main part of the developer regulating member. it can.

  A main plate portion 521 on the distal end side of the doctor blade 52 (developer regulating member) is attached to the developing container so as to face the surface of the developing sleeve 511 in the longitudinal direction of the sleeve. Here, as shown in FIGS. 10 (a), 10 (b), 11 (a), and 11 (b), the end fastening portions 523, which are both ends in the longitudinal direction, are connected to the developer containing case member 50 (developing device housing). Body) side fastening bracket 501. Here, the left and right fastening brackets 501 are formed with nut holes 502 (see FIG. 10B) on the fastening surfaces on which the end fastening portions 523 are overlapped. After overlapping the end fastening portion 523 on the fastening bracket 501, the bolt B <b> 1 inserted into the bolt hole 524 on the end fastening portion 523 side is fastened to the nut hole 502, so that the left and right end portions of the doctor blade 52 The fastening part 523 is fastened. The doctor blade 52 can be arranged in parallel along the longitudinal direction of the developing roller 51 by being fastened to the fastening bracket 501.

Here, the doctor blade 52 arranges the leading edge 525 of the main plate portion 521 so as to face the surface of the developing roller 51 (developer carrier).
As shown in FIGS. 7 and 9, the main plate portion 521 of the doctor blade 52 has a deviation ρ1 in the flatness in the longitudinal direction of the developing roller. With respect to the left and right end fastening portions 523 (both ends), the main plate portion 521 (developer regulating member) has a central portion fc in the longitudinal direction having a flatness of 0.1 to 0.6 mm with respect to both ends fs. Forms a curved shape. Here, the central bending direction of the longitudinal central portion fc is set on the side close to the nonmagnetic sleeve 511. At this time, as shown in FIGS. 8 and 9, the longitudinal center portion fc of the doctor blade 52 (developer regulating member) protrudes toward the upstream side in the rotational direction of the sleeve 511 as compared to the longitudinal end portions fs. It is curved.
That is, in the initial state before the developer pressure is applied as described later, as shown in FIGS. 7 and 9, the longitudinal center portion fc and both end portions fs of the main plate portion 521 of the main plate portion 521 (developer regulating member) are provided. It is formed in a curved shape so as to have a flatness where the deviation ρ1 in the plane orthogonal direction is 0.1 to 0.6 mm.

Next, a method for measuring the flatness of the main plate 521 used here will be described.
As shown in FIGS. 13 (a) and 13 (b), a block gauge 202 (any two parallel surfaces facing each other) is placed on the regular plate 201, and the end of the doctor blade 52 (developing doctor) is placed thereon. Put the fastening part 523 on. The upper surfaces of the block gauges 202 at both ends are (in theory) parallel surfaces, and this surface is set to a zero point by the dial gauge 203.
From this state, the probe of the dial gauge 203 is moved against the warped surface (lower surface) of the doctor blade 52 while moving ds in the longitudinal direction, and the difference from the zero point is read. The reason why the doctor blade 52 is measured from the lower surface of the figure is that a magnetic plate or a diffusion plate (not shown) is attached on the upper surface side (limited to two-component development), and the portion that contacts the upper surface of the block gauge 202 is flat. This is because there are many cases that are not.

Here, considering the definition of general flatness, the flatness of the doctor blade 52 is the maximum value when the dial gauge 203 is scanned over the entire length direction. However, when the end fastening portion 523 (both ends) of the doctor blade 52 is used as a reference, the flatness deviations are set for the three regions of the main plate portion 521 in the longitudinal direction center portion fc and the left and right end portions fs. It is important.
This is because a curved shape aimed at the main plate portion 521 cannot be formed unless the flatness is different between the longitudinal center portion fc of the main plate portion 521 corresponding to the development region and the left and right end portions fs.

For example, when it is desired to have a smooth curved shape that protrudes beyond the left and right ends fs at 0.6 mm in the longitudinal center fc of the main plate 521, the flatness near the left and right ends fs is set to about 0.3 mm. It is good to set.
Note that the doctor blade 52 of the present embodiment has a flatness of about 0.6 mm. For this reason, the inclination of the end fastening portion 523 itself is extremely small, and fastening (assembly) with the bolt B1 as shown in FIGS. 10 and 11 is possible. At this time, the region near both ends fs tends to return to a straight shape, but since the influence on the longitudinal central portion fc is small, the longitudinal central portion fc can maintain a curved state.

Next, as shown in FIGS. 7 to 9, in the doctor blade 52, the protruding surface side of the longitudinal central portion fc forms a surface on which developer pressure is applied, and is downward in the drawing, that is, upstream in the rotational direction of the sleeve. It is formed so that it protrudes toward.
Further, here, as shown in FIG. 8, the front end edge 525 of the central portion fc in the longitudinal direction of the main plate portion 521 is disposed to face the surface of the developing roller 51. At this time, the main plate portion 521 is arranged so as to extend along a reference line L0 (this line is an inclined line along the inclination of the doctor blade 52 shown in FIG. 5) extending in the radial direction from the center point O of the developing roller 51.

  And if it arrange | positions so that the center part fc of the main board part 521 may extend along the reference line L0 as shown in FIG. 8, the edge part fastening part 523 (both ends) will leave | separate upwards in the figure from the reference line L0. At this time, the leading edge 525 of the central portion fc of the doctor blade 52 is separated by a gap g1 (doctor gap) from the surface of the developing roller 51 along the reference line L0. Further, the leading edge 525 of both edge portions fs of the doctor blade 52 is separated from the surface of the developing roller 51 by a gap g2 (doctor gap).

At this time, as shown in FIG. 8, the end fastening portion 523 (one of fs) is formed by bending the flatness, which is the deviation ρ1 in the plane orthogonal direction of the main plate portion 521, to be 0.1 to 0.6 mm. Part), the distal end edge 525 of the longitudinal central part fc is approached by a doctor gap narrowed by a difference dg (= g2−g1). That is, the longitudinal center portion fc is disposed closer to the surface of the developing sleeve 511 than both longitudinal ends.
In the actual assembly process, the doctor gap g1 at the center portion fc and the doctor gap g2 at both end portions fs are measured and adjusted with a thickness gauge.

In the developing device 5 having the doctor blade 52 having such a configuration, as shown in FIG. 5, the developer is held on the developing roller 51 (developer carrier) by the pumping pole P5, and the developing sleeve 511 is rotated. In association with rotation, the developing roller 51 regulates the layer thickness according to the doctor gap.
That is, here, the wider the doctor gap, the larger the amount of developer drawn up, and conversely, the narrower the doctor gap, the smaller the amount of developer drawn up. Here, the longitudinally central portion fc of the doctor blade 52 shown in FIGS. 8 and 9 has a convex shape protruding toward the upstream side in the rotational direction of the sleeve (the lower surface in FIGS. 8 and 9), which is the surface on which the developer pressure is applied. . Here, a deviation is given in the straightness in the longitudinal direction, that is, in the vertical direction perpendicular to the longitudinal direction (the direction perpendicular to the surface of the main plate portion 521 in FIG. 7). In this case, the doctor gap at the longitudinal center fc is set narrower in advance than the doctor gap at the left and right ends fs by a difference dg (= g2−g1).

As a result, the center portion fs in the longitudinal direction is displaced in a direction in which the difference dg of the doctor gap is canceled (disappeared) in a state where the developer pressure is applied. That is, the developing sleeve is displaced downstream in the rotation direction by the pressing force of the two-component developer pumped up on the surface of the developer carrying member.
For this reason, it can be set as the doctor gap substantially the same as the doctor gap of the right-and-left both ends fs also in the longitudinal direction center part fs. That is, the doctor gap can be made substantially constant over the longitudinal direction of the developing roller.
Thus, by using the curved doctor blade 52 (developer regulating member) of FIG. 7, the surface of the central portion fc to which the developer pressure is applied when the developing roller 51 rotates is compared with the both end portions fs. Displacement in a direction away from Therefore, the doctor gap at the central portion fc is widened. As a result, the doctor gap can be made equal in the longitudinal direction of the developing roller, and a uniform pumping amount can be obtained in the longitudinal direction of the developing roller. For this reason, the thickness of the developer carried on the developing roller 51 can be adjusted to be constant in the longitudinal direction, image unevenness can be eliminated, and image quality can be improved.

Here, FIG. 12 shows the Center (fc part) flatness [mm] and FCR pumping amount deviation [mg / cm ^ ² ] (development roller longitudinal direction) measured by the inventor based on the doctor blade 52 of FIG. The experimental results and data of the pumping amount deviation in Here, the abbreviation for FCR: Front, Center, and Rear. The developing device is mounted with the longitudinal direction as the front-rear direction of the image forming apparatus. The doctor blade 52 here is a pressed product of a metal plate, and a material or a thickness that makes it easy to ensure rigidity as the doctor blade 52 by forming the bent portion 522 by one-time bending is appropriately adopted. The

From the flatness of FIG. 12 and the FCR pumping amount deviation data, the FCR pumping amount deviation tends to decrease when the flatness [mm] with respect to both ends fs of the longitudinal central portion fc is in the range of about 0.10 to 0.60. Met. In other words, when the flatness [mm] with respect to both ends fs of the central portion fc in the longitudinal direction is set in a range of about 0.10 or more and 0.60 or less, the developer layer thickness in the longitudinal direction of the developing roller is made close to uniform. be able to. In addition, when the flatness [mm] with respect to both ends fs of the central portion fc in the longitudinal direction is in the range of about 0.28 or more and 0.51 or less, the FCR pumping amount deviation falls within a value in the vicinity of 1 [mg / cm ^ ² ], The layer thickness of the developer in the longitudinal direction of the developing roller can be made almost constant.

<Modification 1>
In the first embodiment described above, the leading edge 525 of the main plate portion 521 of the doctor blade 52 (developer regulating member) is linear when viewed from a direction perpendicular to the surface portion of the main plate portion 521 in FIG. is there. And when it sees from the direction along the surface part of the main board part (refer to Drawing 9), tip edge 525 is curving.

In the first modification, instead of this, a doctor blade 52a as shown in FIG. 14 may be used.
Since this doctor blade 52a is different from the doctor blade 52 used in the above-described embodiment, only the shape of the leading edge 525a of the main plate portion 521a is different, and the other configurations are the same, and therefore, the description of the overlapping configuration is omitted. Further, since the configuration of the image forming apparatus other than the developing device is the same, the description of the overlapping configuration is omitted.
Here, as shown in FIG. 14, the end face (tip edge in plan view) 525a of the main plate portion 521a of the doctor blade 52a is viewed from a direction perpendicular to the surface portion of the main plate portion 521a. The center portion fc in the longitudinal direction is protruded toward the developing sleeve 511 (direction d1 in FIG. 14) rather than the left and right end portions fs. And when it sees from the direction along the surface part of the main board part, the front-end | tip edge 525a is curving similarly to the doctor blade 52 of 1st Embodiment mentioned above. Note that an end surface (tip edge in plan view) 525a on the front end side of the longitudinal central portion fc protrudes 0.02 to 0.08 mm toward the developing roller 51 (d1 direction) from both left and right end portions fs.

  As described above, the end surface (tip edge in plan view) 525a of the doctor blade 52a (developer regulating member) facing the developing sleeve 511 has a longitudinal center portion fc of 0.02 to 0 with respect to both end portions fs. 0.08 mm straightness difference. In addition, the central portion in the longitudinal direction of the end surface has a convex shape protruding toward the developing sleeve 511, and a curved shape is provided between the central portion fc in the longitudinal direction and both end portions fs.

  That is, the doctor blade 52a has a configuration in which the central portion fc in the longitudinal direction has both a convex shape and a curved shape (the central portion fc of the doctor blade 52 has). Therefore, when the developer conveyed along with the driving of the developing sleeve 511 contacts the longitudinal center fc of the main plate portion 521a and applies a pressing force, the longitudinal center fs cancels (disappears) the doctor gap difference dg. Displace in the direction. For this reason, it is possible to make the doctor gap substantially the same as the doctor gap of the left and right ends fs even in the longitudinal center fs, and to make the doctor gap substantially constant over the longitudinal direction of the developing roller.

Even in the case where there is a concern that the doctor gap in the central portion in the longitudinal direction further expands as the image forming speed of the image forming apparatus increases, in the first modification, the longitudinal central portion fc further has a convex shape. I have. As described above, since the doctor gap of the central portion fc in the longitudinal direction is set to be significantly narrow in advance compared to the left and right end portions fs, the developer pumping amount can be made substantially uniform in the longitudinal direction. Therefore, image unevenness can be prevented and image quality can be improved.
Although a color copying machine has been described as an image forming apparatus, the present invention can also be applied to a monochrome copying machine. The present invention can also be applied to image processing apparatuses such as printers and facsimile machines.

DESCRIPTION OF SYMBOLS 50 Developer housing case member 501 Developing device housing side 51 Developer carrier 511 Sleeve 52 Developer restricting member 521 Main plate portion 525 Main plate portion leading edge 53, 54 Developer conveying member 55 Magnetic field generating means fc Central portion fs Both end portions

JP 2007-121964 A

Claims (12)

A developer container containing a two-component developer comprising a toner and a carrier;
A developer conveying member for stirring and conveying the two-component developer;
A non-magnetic sleeve rotatably supported by the developer container and including magnetic field generating means for forming a plurality of magnetic poles; and the two-component developer agitated and transported to the developer transport member by the magnetic force A developer carrier that is pumped up and carried to a region opposite to the latent image carrier;
In a developing device comprising a developer regulating member that regulates the layer thickness of the two-component developer,
The developer regulating member is
The developer regulating member is attached to the developing container so that the front end side of the developer regulating member faces the longitudinal direction with respect to the surface of the sleeve, and the central portion in the longitudinal direction of the developer regulating member is compared with both longitudinal end portions. The developing device is curved so as to protrude toward the upstream side in the rotational direction of the sleeve.   2. The developing device according to claim 1, wherein the developer regulating member is disposed closer to the surface of the sleeve than the both ends in the longitudinal direction due to the curvature. .   The central portion in the longitudinal direction of the developer regulating member is configured to be displaced downstream in the rotational direction by a pressing force by a two-component developer pumped up on the surface of the developer carrying member. 3. The developing device according to 1 or 2.   The gap between the longitudinal center portion of the developer regulating member and the surface of the sleeve and the gap between both longitudinal ends of the developer regulating member and the surface of the sleeve are displaced in the longitudinal direction by displacement downstream in the rotational direction. The developing device according to claim 3, wherein the developing device is set to be substantially uniform over the entire area.   5. The central portion in the longitudinal direction of the developer regulating member is curved so as to have a flatness of 0.1 to 0.6 mm with respect to both ends in the longitudinal direction. The developing device according to one.   6. The developer regulating member according to claim 1, wherein the developer regulating member has a configuration in which a main plate portion and a bent portion are formed long in a longitudinal direction by bending a metal plate member once. Development device.   7. The magnetic field generation unit according to claim 1, wherein a normal direction peak magnetic flux density of a magnetic pole in the vicinity of a portion facing the developer regulating member is 60 mT or more and 95 mT or less. Development device.   The end surface on the tip side facing the sleeve in the developer regulating member has a difference in straightness of 0.02 to 0.08 mm in the longitudinal center with respect to both ends, and the longitudinal center of the end surface The developing device according to claim 1, further comprising a convex shape protruding toward the sleeve.   The end surface on the tip side facing the sleeve in the developer regulating member has a difference in straightness of 0.02 to 0.08 mm in the longitudinal center with respect to both ends, and the longitudinal center of the end surface 8. The development according to claim 1, further comprising a convex shape protruding toward the sleeve and a curved shape between the central portion in the longitudinal direction and the both end portions. apparatus.   A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the developing device according to claim 1.   An image forming apparatus comprising the process cartridge according to claim 10.

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