JP7146512B2 - developing device - Google Patents

Description

The present invention relates to a developing device provided with a regulating blade made of resin.

The developing device includes a developing frame, a rotatable developer carrier that carries developer for developing an electrostatic latent image formed on the image carrier, and a developer carried on the developer carrier. A regulating blade is provided as a developer regulating member for regulating the amount of developer. The regulating blade is arranged across a direction parallel to the axis of rotation of the developer carrier, facing the developer carrier with a predetermined gap (hereinafter referred to as an SB gap) between the developer carrier and the developer carrier. be. The SB gap is the shortest distance between the developer carrier and the regulating blade. By adjusting the size of the SB gap, the amount of developer conveyed to the developing area where the developer carrier faces the image carrier is adjusted.

The developing device described in Patent Document 1 includes a resin developer regulating member molded from resin and a resin developing frame body molded from resin.

JP 2015-34929 A

Corresponding to the increase in the width of the sheet on which the image is to be formed, the maximum image in the image area in which the image can be formed on the image carrier in the direction parallel to the rotation axis of the developer carrier (rotational axis direction). The length of the area of the developing frame corresponding to the area (maximum image area of the developing frame) increases.

When the developing frame is resin-molded by injection molding, the developing frame is a resin-molded product having a gate portion that serves as an entrance for the resin to flow into the molded product through the gate when the melted resin is poured into the molded product. provided in When resin-molding a developing frame with a large length in the longitudinal direction, the distance over which the melted resin flows becomes long. , is generally provided in the maximum image area of the resin-made developing frame.

Further, when the developing frame is resin-molded by injection molding, a large molding pressure is applied to the gate portion when the melted resin flows into the gate portion through the gate, so residual stress is generated in the gate portion. It will be. Residual stress from the gate portion provided on the resin development frame is applied to the development frame over time, and deforms the resin development frame over time. As a result, when the resin regulation blade is fixed to the resin development frame, the size of the SB gap changes over time due to the residual stress from the gate portion provided on the development frame. there is a risk of

The present invention has been made in view of the above problems. An object of the present invention is to solve the problem that, in a state in which a resin regulating blade is fixed to a resin development frame, the size of the SB gap decreases over time due to residual stress from a gate portion provided in the development frame. An object of the present invention is to provide a developing device capable of suppressing temporal fluctuations.

In order to achieve the above object, a developing device according to one aspect of the present invention has the following configuration. That is, the developing device includes a developing rotator that carries and conveys developer to a position where an electrostatic image formed on an image carrier is developed; a resin regulating blade including a regulating portion for regulating the amount of developer carried on the developing rotator at a position closest to the developing rotator; an attachment portion for mounting the regulating blade; a resin-made developing frame body having a first chamber to which the developer is supplied and a second chamber separated from the first chamber by a partition wall; a first conveying screw arranged to convey the developer in a first direction; and a second conveying screw arranged in the second chamber to convey the developer in a second direction opposite to the first direction. a screw, wherein the regulating blade is attached to the attachment portion using an adhesive ; the development frame is provided with a gate portion ; a portion corresponding to the maximum image area of the image carrier with respect to the direction of the rotational axis of the developing device, wherein the portion of the developing device is defined by a first plane including the rotational axis of the developing rotational member and the rotational axis of the image carrier , partitioning into a part having the regulating portion and a part not having the regulating portion, and dividing the part having the regulating portion into a plane including the rotation axis of the first conveying screw and perpendicular to the first plane; When the first part and the second part are divided by the second plane, the first part does not have the mounting portion and has the gate portion of the developing frame. and the second part has the mounting portion and does not have the gate portion of the developing frame . Further, in order to achieve the above object, a developing device according to another aspect of the present invention has the following configuration. That is, the developing device includes a developing rotator that carries and conveys developer to a position where an electrostatic image formed on an image carrier is developed; a resin regulating blade including a regulating portion for regulating the amount of developer carried on the developing rotator at a position closest to the developing rotator; an attachment portion for mounting the regulating blade; a resin-made developing frame body having a first chamber to which the developer is supplied and a second chamber separated from the first chamber by a partition wall; a first conveying screw arranged to convey the developer in a first direction; and a second conveying screw arranged in the second chamber to convey the developer in a second direction opposite to the first direction. a screw, wherein the regulating portion is vertically below the rotation axis of the developing rotor; the developing device frame is provided with a gate ; a portion corresponding to the maximum image area of the image carrier with respect to the direction of the rotational axis of the developing device, wherein the portion of the developing device is defined by a first plane including the rotational axis of the developing rotational member and the rotational axis of the image carrier , partitioning into a part having the regulating portion and a part not having the regulating portion, and dividing the part having the regulating portion into a plane including the rotation axis of the first conveying screw and perpendicular to the first plane; When the first part and the second part are divided by the second plane, the first part does not have the mounting portion and has the gate portion of the developing frame. and the second part has the mounting portion and does not have the gate portion of the developing frame .

According to the present invention, in a state in which the resin regulating blade is fixed to the resin development frame, the size of the SB gap decreases over time due to the residual stress from the gate portion provided in the development frame. can be suppressed.

1 is a cross-sectional view showing the configuration of an image forming apparatus; FIG. 2 is a perspective view showing the structure of a developing device; FIG. 2 is a perspective view showing the structure of a developing device; FIG. 3 is a cross-sectional view showing the configuration of a developing device; FIG. FIG. 3 is a perspective view showing the configuration of a resin doctor blade (single body); FIG. 3 is a perspective view showing the configuration of a resin-made development frame (single body); FIG. 4 is a schematic diagram for explaining the rigidity of a resin doctor blade (single body); FIG. 3 is a schematic diagram for explaining the rigidity of a resin-made development frame (single body); FIG. 3 is a schematic diagram for explaining the straightness of a resin doctor blade (single body). FIG. 4 is a perspective view for explaining deformation of a resin doctor blade caused by temperature change; FIG. 4 is a cross-sectional view for explaining deformation of a resin doctor blade caused by agent pressure; 1 is a perspective view showing the configuration of a developing device according to a first embodiment; FIG. 2 is a cross-sectional view showing the configuration of the developing device according to the first embodiment; FIG. 2 is a bottom view showing the configuration of the developing device according to the first embodiment; FIG. FIG. 3 is a perspective view showing the configuration of a developing device according to a comparative example; FIG. 3 is a cross-sectional view showing the configuration of a developing device according to a comparative example;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the following embodiments do not limit the present invention according to the claims, and all combinations of features described in the first embodiment are not essential to the solution of the present invention. Not exclusively. The present invention can be implemented in various applications such as printers, various printing machines, copiers, facsimiles, and multi-function machines.

[First Embodiment]
(Configuration of image forming apparatus)
First, the configuration of the image forming apparatus according to the first embodiment of the present invention will be described with reference to the cross-sectional view of FIG. As shown in FIG. 1, an image forming apparatus 60 includes an endless intermediate transfer belt (ITB) 61 as an intermediate transfer body, and an upstream roller along the rotation direction of the intermediate transfer belt 61 (the direction of arrow C in FIG. 1). Four image forming units 600 are provided from the side to the downstream side. Each of the image forming units 600 forms a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (Bk).

The image forming section 600 includes a rotatable photosensitive drum 1 as an image carrier. Further, the image forming unit 600 includes a charging roller 2 as charging means, a developing device 3 as developing means, a primary transfer roller 4 as primary transfer means, and a primary transfer roller 4 as primary transfer means. , a photoreceptor cleaner 5 as a photoreceptor cleaning means.

Each of the developing devices 3 is detachable from the image forming device 60 . Each developing device 3 has a developing container 50 containing a two-component developer (hereinafter simply referred to as developer) containing non-magnetic toner (hereinafter simply referred to as toner) and magnetic carrier. In addition, toner cartridges containing toner of each color of Y, M, C, and Bk are detachable from the image forming apparatus 60 . The respective color toners of Y, M, C, and Bk are supplied to the developing containers 50 through the toner conveying paths. Details of the developing device 3 will be described later with reference to FIGS. 2 to 4, and details of the developer container 50 will be described later with reference to FIG.

The intermediate transfer belt 61 is stretched by a tension roller 6, a driven roller 7a, a primary transfer roller 4, a driven roller 7b, and a secondary transfer inner roller 66, and is driven to be conveyed in the direction of arrow C in FIG. The inner secondary transfer roller 66 also serves as a drive roller for driving the intermediate transfer belt 61 . As the inner secondary transfer roller 66 rotates, the intermediate transfer belt 61 rotates in the direction of arrow C in FIG.

The intermediate transfer belt 61 is pressed by the primary transfer roller 4 from the back side of the intermediate transfer belt 61 . Further, by bringing the intermediate transfer belt 61 into contact with the photosensitive drum 1 , a primary transfer nip portion as a primary transfer portion is formed between the photosensitive drum 1 and the intermediate transfer belt 61 .

An intermediate transfer body cleaner 8 as belt cleaning means is in contact with the tension roller 6 via the intermediate transfer belt 61 . Further, a secondary transfer outer roller 67 as a secondary transfer means is arranged at a position facing the secondary transfer inner roller 66 with the intermediate transfer belt 61 interposed therebetween. The intermediate transfer belt 61 is sandwiched between a secondary transfer inner roller 66 and a secondary transfer outer roller 67 . As a result, a secondary transfer nip portion as a secondary transfer portion is formed between the secondary transfer outer roller 67 and the intermediate transfer belt 61 . At the secondary transfer nip portion, the toner image is attracted to the surface of the sheet S (paper, film, etc.) by applying a predetermined pressure and transfer bias (electrostatic load bias).

Sheets S are stacked and stored in a sheet storage unit 62 (for example, a feeding cassette, a feeding deck, or the like). The feeding unit 63 feeds the sheet S in time with the image forming timing by using, for example, a friction separation method using a feeding roller or the like. The sheet S sent out by the feeding means 63 is conveyed to the registration rollers 65 arranged in the middle of the conveying path 64 . After skew correction and timing correction are performed by the registration rollers 65, the sheet S is conveyed to the secondary transfer nip portion. The arrival timing of the sheet S and the arrival timing of the toner image at the secondary transfer nip coincide with each other, and the secondary transfer is performed.

A fixing device 9 is disposed downstream of the secondary transfer nip portion in the sheet S conveying direction. The fixing device 9 applies a predetermined amount of pressure and heat to the sheet S conveyed to the fixing device 9 , thereby melting and fixing the toner image on the surface of the sheet S. FIG. The sheet S on which the image has been fixed in this way is discharged to the discharge tray 601 as it is by forward rotation of the discharge roller 69 .

In the case of double-sided image formation, the ejection roller 69 rotates forward to convey the sheet S until the trailing edge of the sheet S passes through the switching flapper 602, and then rotates the ejection roller 69 in the reverse direction. As a result, the sheet S is conveyed to the double-sided conveying path 603 with the leading and trailing edges exchanged. After that, the sheet is conveyed again to the conveying path 64 by the re-feeding roller 604 in time with the next image forming timing.

(Image forming process)
During image formation, the photosensitive drum 1 is rotationally driven by a motor. The charging roller 2 uniformly charges the surface of the photosensitive drum 1 which is driven to rotate. The exposure device 68 forms an electrostatic latent image (electrostatic image) on the surface of the photosensitive drum 1 charged by the charging roller 2 based on the image information signal input to the image forming device 60 . The photoreceptor drum 1 can form electrostatic latent images of a plurality of sizes.

The developing device 3 has a rotatable developing sleeve 70 as a developer carrier that carries developer (development rotary member that carries and carries developer). The developing device 3 develops the electrostatic latent image formed on the surface of the photoreceptor drum 1 using the developer carried on the surface of the developing sleeve 70 . As a result, the toner adheres to the exposed portion on the surface of the photoreceptor drum 1 to form a visible image. A transfer bias (electrostatic load bias) is applied to the primary transfer roller 4 , and the toner image formed on the surface of the photosensitive drum 1 is transferred onto the intermediate transfer belt 61 . A small amount of toner (transfer residual toner) remaining on the surface of the photoreceptor drum 1 after the primary transfer is collected by the photoreceptor cleaner 5 and prepared for the next image forming process.

The image forming processes of the respective colors, which are processed in parallel by the image forming units 600 of the respective colors of Y, M, C, and Bk, are sequentially superimposed on the toner images of the upstream colors primarily transferred onto the intermediate transfer belt 61 . done. As a result, a full-color toner image is formed on the intermediate transfer belt 61, and the toner image is conveyed to the secondary transfer nip portion. A transfer bias is applied to the secondary transfer outer roller 67, and the toner image formed on the intermediate transfer belt 61 is transferred to the sheet S conveyed to the secondary transfer nip portion. A small amount of toner (residual toner) remaining on the intermediate transfer belt 61 after the sheet S has passed through the secondary transfer nip portion is collected by the intermediate transfer member cleaner 8 . The fixing device 9 fixes the toner image transferred onto the sheet S. As shown in FIG. The recording material S that has undergone fixing processing by the fixing device 9 is discharged to a discharge tray 601 .

A series of image forming processes as described above is completed, and preparations are made for the next image forming operation.

(Structure of developing device)
A general configuration of the developing device will be described with reference to the perspective view of FIG. 2, the perspective view of FIG. 3, and the cross-sectional view of FIG. FIG. 4 is a sectional view of the developing device 3 along section H in FIG.

The developing device 3 includes a resin-made developing frame body (hereinafter simply referred to as the developing frame body 30) molded from resin, and a resin-made cover formed separately from the developing frame body 30 and molded from resin. A developer container 50 configured by a frame (hereinafter simply referred to as a cover frame 40) is provided. 2 and 4 show the state in which the cover frame 40 is attached to the developing frame 30, and FIG. 3 shows the cover frame 40 attached to the developing frame 30. FIG. It shows the state without The details of the structure of the development frame 30 (single body) will be described later with reference to FIG.

The developer container 50 is provided with an opening at a position corresponding to a developing region where the developing sleeve 70 faces the photosensitive drum 1 . The developing sleeve 70 is rotatably arranged with respect to the developing container 50 so that a part of the developing sleeve 70 is exposed to the opening of the developing container 50 . Bearings 71 that are bearing members are provided at both ends of the developing sleeve 70 .

The interior of the developing container 50 is partitioned into a developing chamber 31 as a first chamber and a stirring chamber 32 as a second chamber by a vertically extending partition wall 38 . The developing chamber 31 and the stirring chamber 32 are connected at both ends in the longitudinal direction via two communicating portions 39 of the partition wall 38 . Therefore, the developer can be communicated between the developing chamber 31 and the stirring chamber 32 through the communicating portion 39 . The developing chamber 31 and the stirring chamber 32 are arranged side by side in the horizontal direction.

Inside the developing sleeve 70 is fixed a magnet roll as magnetic field generating means that has a plurality of magnetic poles along the rotation direction of the developing sleeve 70 and generates a magnetic field for carrying the developer on the surface of the developing sleeve 70 . are arranged as follows. The developer in the developing chamber 31 is pumped up under the influence of the magnetic field generated by the magnetic poles of the magnet roll and supplied to the developing sleeve 70 . Since the developer is supplied from the developing chamber 31 to the developing sleeve 70 in this manner, the developing chamber 31 is also called a supply chamber.

A first conveying screw 33 serving as conveying means for agitating and conveying the developer in the developing chamber 31 is arranged in the developing chamber 31 so as to face the developing sleeve 70 . The first conveying screw 33 includes a rotating shaft 33a as a rotatable shaft portion and a spiral blade portion 33b as a developer conveying portion provided along the outer periphery of the rotating shaft 33a. rotatably supported. A bearing member is provided at each of both ends of the rotary shaft 33a.

Further, in the stirring chamber 32 , a second conveying screw 34 is arranged as a conveying means for agitating the developer in the stirring chamber 32 and conveying the same in the opposite direction to the first conveying screw 33 . The second conveying screw 34 includes a rotating shaft 34a as a rotatable shaft portion and a helical blade portion 34b as a developer conveying portion provided along the outer circumference of the rotating shaft 34a. rotatably supported. A bearing member is provided at each of both ends of the rotating shaft 34a. By rotationally driving the first conveying screw 33 and the second conveying screw 34, a circulation path through which the developer circulates is formed between the developing chamber 31 and the stirring chamber 32 via the communicating portion 39. .

In the developer container 50, a regulating blade (hereinafter referred to as a doctor blade 36) as a developer regulating member for regulating the amount of developer carried on the surface of the developing sleeve 70 (also referred to as the developer coat amount) is provided for the developer. It is attached facing the surface of the sleeve 70 in a non-contact manner. The doctor blade 36 has a coat amount regulating surface 36 r as a regulating portion that regulates the amount of developer carried on the surface of the developing sleeve 70 . The doctor blade 36 is a resin doctor blade molded from resin. The configuration of the doctor blade 36 (single body) will be described later with reference to FIG.

The doctor blade 36 has a predetermined gap (hereinafter referred to as SB gap G) with the developing sleeve 70 in the longitudinal direction of the developing sleeve 70 (that is, the direction parallel to the rotation axis of the development sleeve 70 (rotational axis direction)). ), facing the developing sleeve 70 . In the present invention, the SB gap G is the shortest distance between the maximum image area of the developing sleeve 70 and the maximum image area of the doctor blade 36 . Incidentally, the maximum image area of the developing sleeve 70 is the developing sleeve corresponding to the maximum image area among the image areas in which an image can be formed on the surface of the photosensitive drum 1 in the direction parallel to the rotation axis of the developing sleeve 70. 70 area. Further, the maximum image area of the doctor blade 36 is the doctor blade corresponding to the maximum image area among the image areas in which an image can be formed on the surface of the photosensitive drum 1 in the direction parallel to the rotation axis of the developing sleeve 70. 36 areas. In the first embodiment, the photosensitive drum 1 is capable of forming electrostatic latent images of a plurality of sizes. An image area corresponding to a large size (for example, A3 size) shall be indicated. On the other hand, in the modification in which the photosensitive drum 1 can form an electrostatic latent image of only one size, the maximum image area is the size of the image area of that one size that can be formed on the photosensitive drum 1. shall be read as indicating that

The doctor blade 36 is arranged substantially facing the peak position of the magnetic flux density of the magnetic poles of the magnet roll. The developer supplied to the developing sleeve 70 is affected by the magnetic field generated by the magnetic poles of the magnet roll. Further, the developer that is regulated and scraped by the doctor blade 36 tends to stay in the upstream portion of the SB gap G. As a result, a developer pool is formed upstream of the doctor blade 36 in the rotational direction of the developing sleeve 70 . Part of the developer in the developer pool is conveyed so as to pass through the SB gap G as the developing sleeve 70 rotates. At this time, the layer thickness of the developer passing through the SB gap G is regulated by the coating amount regulating surface 36r of the doctor blade 36. FIG. In this manner, a thin layer of developer is formed on the surface of the developing sleeve 70 .

A predetermined amount of developer carried on the surface of the developing sleeve 70 is conveyed to the developing area as the developing sleeve 70 rotates. Therefore, by adjusting the size of the SB gap G, the amount of developer transported to the development area is adjusted. In the first embodiment, the target size of the SB gap G (so-called target value of the SB gap G) when adjusting the size of the SB gap G is set to about 300 μm.

The developer conveyed to the developing area magnetically rises in the developing area to form magnetic spikes. The toner in the developer is supplied to the photoreceptor drum 1 by the contact of the magnetic brush with the photoreceptor drum 1 . Then, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed as a toner image. The developer on the surface of the developing sleeve 70 after passing through the developing region and supplying the toner to the photosensitive drum 1 (hereinafter referred to as the developer after the developing process) is formed between the same magnetic poles of the magnet roll. It is peeled off from the surface of the developing sleeve 70 by the repelling magnetic field. The developer stripped off from the surface of the developing sleeve 70 after the developing process drops into the developing chamber 31 and is collected into the developing chamber 31 .

As shown in FIG. 4, the developing device frame 30 is provided with a developer guide portion 35 for guiding the developer to be transported toward the SB gap G. As shown in FIG. The developer guide portion 35 and the developing frame 30 are formed integrally, and the developer guide portion 35 and the doctor blade 36 are formed separately. The developer guide portion 35 is formed inside the developing frame 30 and arranged upstream of the coat amount regulating surface 36 r of the doctor blade 36 in the rotation direction of the developing sleeve 70 . By stabilizing the flow of the developer by the developer guide portion 35 and arranging the developer so as to have a predetermined developer density, the coating amount regulation surface 36r of the doctor blade 36 is in the closest proximity to the surface of the developing sleeve 70. A developer weight can be specified.

Further, as shown in FIG. 4 , the cover frame 40 is formed separately from the developing frame 30 and attached to the developing frame 30 . Further, the cover frame 40 partially covers the opening of the developing sleeve 30 so that the outer peripheral surface of the developing sleeve 70 is partially covered over the entire longitudinal direction of the developing sleeve 70 . At this time, the cover frame 40 partially covers the opening of the developing frame 30 so that the developing region of the developing sleeve 70 facing the photosensitive drum 1 is exposed. In the first embodiment, the cover frame 40 is fixed to the developing frame 30 by ultrasonic bonding. , welding, or the like. Regarding the cover frame body 40, as shown in FIG. 4, the cover frame body 40 may be composed of one part (resin molded product), or the cover frame body 40 may be composed of a plurality of parts (resin molded product). A molded product) may be used.

(Structure of resin doctor blade)
The configuration of the doctor blade 36 (single body) will be described with reference to the perspective view of FIG.

During the image forming operation (developing operation), developer pressure (hereinafter referred to as developer pressure) generated by the developer flow is applied to the doctor blade 36 . The lower the rigidity of the doctor blade 36, the more easily the doctor blade 36 is deformed when the agent pressure is applied to the doctor blade 36 during the image forming operation, and the size of the SB gap G tends to fluctuate more easily. During the image forming operation, the agent pressure is applied in the lateral direction of the doctor blade 36 (in the direction of arrow M in FIG. 5). Therefore, in order to suppress the variation in the size of the SB gap G during the image forming operation, the rigidity of the doctor blade 36 in the widthwise direction is increased so that the deformation of the doctor blade 36 in the widthwise direction is suppressed. It is desirable to

As shown in FIG. 5, in the first embodiment, the doctor blade 36 is shaped like a plate from the viewpoint of mass productivity and cost. Further, as shown in FIG. 5, in the first embodiment, the cross-sectional area of the _side surface 36t of the doctor blade 36 is reduced, and the length t2 of the doctor blade 36 in the thickness direction is It is smaller _than the length t1 in the lateral direction. As a result, the doctor blade 36 (single body) is easily deformed in a direction (arrow M direction in FIG. 5) perpendicular to the longitudinal direction of the doctor blade 36 (arrow N direction in FIG. 5). Therefore, in the first embodiment, in order to correct the straightness of the coating amount regulation surface 36r, the doctor blade 36 is bent in the direction of arrow M in FIG. It is fixed to the blade attachment portion 41 of 30 . Details of straightness correction of the doctor blade 36 will be described later with reference to FIG.

(Structure of Resin Development Frame)
The configuration of the development frame 30 (single body) will be described with reference to the perspective view of FIG. FIG. 6 shows a state in which the cover frame 40 is not attached to the developing frame 30 .

The developing frame 30 has a developing chamber 31 and a stirring chamber 32 partitioned from the developing chamber 31 by a partition wall 38 . The partition wall 38 is made of resin and may be formed separately from the developing frame 30 or may be formed integrally with the developing frame 30 .

The development frame 30 has a sleeve support portion 42 for rotatably supporting the development sleeve 70 by supporting bearings 71 provided at both ends of the development sleeve 70 . The development frame 30 also has a blade mounting portion 41 integrally formed with the sleeve support portion 42 and for mounting the doctor blade 36 thereon. FIG. 6 shows a virtual state in which the doctor blade 36 is lifted from the blade mounting portion 41. As shown in FIG.

In the first embodiment, in a state where the doctor blade 36 is attached to the blade attachment portion 41, the adhesive A applied to the blade attachment surface 41s of the blade attachment portion 41 is cured, thereby causing the blade attachment portion 41 to The doctor blade 36 is fixed at the end.

(Rigidity of resin doctor blade)
The rigidity of the doctor blade 36 (single body) will be described with reference to the schematic diagram of FIG. The rigidity of the doctor blade 36 (single body) is measured in a state where the doctor blade 36 is not fixed to the blade mounting portion 41 of the developing frame 30 .

As shown in FIG. 7, a concentrated load F1 is applied in the lateral direction of the doctor blade 36 to the central portion 36z of the doctor blade 36 in the longitudinal direction of the doctor blade 36. As shown in FIG. At this time, the rigidity of the doctor blade 36 (single body) is measured based on the deflection amount of the doctor blade 36 in the lateral direction at the central portion 36z of the doctor blade 36 .

For example, assume that a concentrated load F1 of 300 gf is applied in the lateral direction of the doctor blade 36 to the central portion 36z of the doctor blade 36 in the longitudinal direction of the doctor blade 36 . At this time, the amount of deflection of the doctor blade 36 in the lateral direction at the central portion 36z of the doctor blade 36 is 700 μm or more. At this time, the amount of deformation of the central portion 36z of the doctor blade 36 on the cross section is 5 μm or less.

(Rigidity of Resin Development Frame)
The rigidity of the development frame 30 (single body) will be described with reference to the schematic diagram of FIG. The rigidity of the development frame 30 (single body) is measured in a state where the doctor blade 36 is not fixed to the blade mounting portion 41 of the development frame 30 .

As shown in FIG. 8 , a concentrated load F1 is applied in the lateral direction of the blade mounting portion 41 to the central portion 41z of the blade mounting portion 41 in the longitudinal direction of the blade mounting portion 41 . At this time, the rigidity of the development frame 30 (single body) is measured based on the bending amount of the blade mounting portion 41 in the lateral direction at the central portion 41z of the blade mounting portion 41 .

For example, assume that a concentrated load F1 of 300 gf is applied in the lateral direction of the blade mounting portion 41 to the central portion 41z of the blade mounting portion 41 in the longitudinal direction of the blade mounting portion 41 . At this time, the bending amount in the lateral direction of the blade mounting portion 41 at the central portion 41z of the blade mounting portion 41 is 60 μm or less.

Assume that the central portion 36z of the doctor blade 36 and the central portion 41z of the blade mounting portion 41 of the developing frame 30 are each applied with the same concentrated load F1. At this time, the amount of bending of the central portion 36z of the doctor blade 36 is ten times or more the amount of bending of the central portion 41z of the blade mounting portion 41 . Therefore, the rigidity of the developing frame 30 (single body) is ten times higher than that of the doctor blade 36 (single body). Therefore, when the doctor blade 36 is attached to the blade mounting portion 41 of the developing frame 30 and the doctor blade 36 is fixed to the blade mounting portion 41 of the developing frame 30, the rigidity of the doctor blade 36 is reduced. The stiffness of the body 30 becomes dominant. Further, when the doctor blade 36 is fixed to the developing frame 30 over the entire maximum image area, the doctor blade 36 is fixed to the developing frame 30 more than when only both ends in the longitudinal direction of the doctor blade 36 are fixed. The rigidity of the doctor blade 36 in the folded state is increased.

Further, the rigidity of the developing frame 30 (single body) is larger than the rigidity of the cover frame 40 (single body). Therefore, when the cover frame 40 is attached to the developing frame 30 and the cover frame 40 is fixed to the developing frame 30 , the rigidity of the developing frame 30 is higher than that of the cover frame 40 . become dominant.

(Straightness correction of resin doctor blade)
The image is formed on the surface of the photosensitive drum 1 in the direction parallel to the rotation axis of the developing sleeve 70 in response to the increase in the width of the sheet S, such as the width of the sheet S on which the image is to be formed is A3 size. The length of the maximum image area out of the image areas that can be formed is increased. Therefore, the length of the maximum image area of the doctor blade 36 increases as the width of the sheet S on which the image is formed increases. When a doctor blade having a large length in the longitudinal direction is molded from resin, it is difficult to ensure the straightness of the coated amount regulating surface of the resin doctor blade molded from resin. This is because, when molding a doctor blade with a large length in the longitudinal direction, when the thermally expanded resin thermally contracts, depending on the position in the longitudinal direction of the doctor blade, the progress of thermal contraction advances and lags. This is because there are likely to be places where the

Therefore, in the resin doctor blade, as the length of the doctor blade in the longitudinal direction increases, the SB gap tends to vary in the longitudinal direction of the developer carrier due to the straightness of the coat amount regulating surface of the doctor blade. There is a tendency. If the SB gap is different in the longitudinal direction of the developer carrier, there is a possibility that the amount of developer carried on the surface of the developer carrier may be uneven in the longitudinal direction of the developer carrier.

For example, a resin doctor blade whose length in the longitudinal direction corresponds to A3 size (hereinafter referred to as a resin doctor blade corresponding to A3 size) was manufactured with the accuracy of a general resin molded product. In this case, the straightness of the coating amount regulating surface is about 300 μm to 500 μm. Further, even if a resin doctor blade corresponding to A3 size is manufactured with high precision using a high-precision resin material, the straightness of the coating amount control surface is about 100 μm to 200 μm.

In the first embodiment, the size of the SB gap G is set to approximately 300 μm, and the tolerance of the SB gap G (that is, the tolerance of the SB gap G to the target value) is set to ±10% or less. Therefore, in the first embodiment, the adjustment value of the SB gap G is 300 μm±30 μm, which means that the maximum allowable tolerance for the SB gap G is 60 μm. For this reason, even if a resin doctor blade corresponding to A3 size is manufactured with the accuracy of a general resin molded product, even if it is manufactured with high precision using a high-precision resin material, the straightness of the coating amount control surface The tolerance of the SB gap G is exceeded by the degree of accuracy alone.

In a developing device equipped with a resin doctor blade, regardless of the straightness of the coating amount regulating surface, the SB gap G is sufficient for the rotation of the developer carrier while the doctor blade is fixed to the mounting portion of the developing frame. It is desirable to keep the distance within a predetermined range over the direction parallel to the axis. Therefore, in the first embodiment, the straightness of the coating amount regulating surface is corrected. As a result, even if a doctor blade made of resin having a coating amount regulation surface with low straightness is used, the SB gap G does not affect the rotation of the developing sleeve 70 when the doctor blade is fixed to the mounting portion of the developing frame. To be within a predetermined range over the direction parallel to the axis.

Here, the straightness of the coat amount regulating surface 36r of the doctor blade 36 will be described with reference to the schematic diagram of FIG. The straightness of the coating amount regulation surface 36r is defined as the difference between the maximum value and the minimum value of the outer shape of the coating amount regulation surface 36r when a predetermined position of the coating amount regulation surface 36r in the longitudinal direction of the coating amount regulation surface 36r is used as a reference. It is expressed by the absolute value of the difference. For example, the central portion of the coat amount regulating surface 36r in the longitudinal direction of the coat amount regulating surface 36r is defined as the origin of an orthogonal coordinate system, a predetermined straight line passing through the origin is the X axis, and a predetermined straight line is drawn from the origin perpendicular to the X axis. Let the straight line be the Y-axis. In this orthogonal coordinate system, the straightness of the coat amount control surface 36r is represented by the absolute value of the difference between the maximum value and the minimum value of the Y coordinate of the outer shape of the coat amount control surface 36r.

As shown in FIG. 9, in the doctor blade (single body) made of resin, the central portion of the coating amount regulation surface 36r of the doctor blade 36 is greatly bent in the longitudinal direction of the doctor blade 36. As shown in FIG. Therefore, it is necessary to correct the straightness of the doctor blade 36 by reducing the difference in the positions of the tip portions 36e (36e1 to 36e5) of the doctor blade 36 shown in FIG. Considering the allowable tolerance of the SB gap G and the mounting accuracy of the doctor blade 36 to the developing frame 30, the straightness of the coating amount regulation surface 36r of the doctor blade 36 must be corrected to 50 μm or less. In view of the fact that the accuracy of the straightness of the metal doctor blade is 20 μm or less by secondary cutting, it is more preferable to set the straightness of the coating amount regulation surface 36r of the resin doctor blade 36 to 20 μm or less. It is to correct. In the first embodiment, the set value for correcting the straightness of the coating amount regulation surface 36r of the doctor blade 36 is set to approximately 20 μm to 50 μm in consideration of a realistic mass production process.

Therefore, in the first embodiment, a force (also called a straightness correction force) for bending at least a part of the maximum image area of the doctor blade 36 is applied to the doctor blade 36, and the maximum image area of the doctor blade 36 is Flex at least a portion. As a result, the straightness of the coating amount regulation surface 36r of the doctor blade 36 is corrected to 50 μm or less.

In the example of FIG. 9, the outer shapes of the tip portions 36e1 and 36e5 of the doctor blade 36 are used as a reference, and the tip portions 36e2, 36e3 and 36e4 are adjusted so that the outer shapes of the tip portions 36e2, 36e3 and 36e4 match the reference. to apply a straightness correction force in the direction of arrow I in FIG. As a result, the shape of the coat amount regulating surface 36r of the doctor blade 36 is corrected from the coat amount regulating surface 36r1 to the coat amount regulating surface 36r2, so the straightness of the coat amount regulating surface 36r of the doctor blade 36 is corrected to 50 μm or less. can do. In the example of FIG. 9, the tip portions 36e1 and 36e5 (both ends in the longitudinal direction of the coating amount regulation surface 36r) are used as a reference for matching the outer shape of the tip portion 36e of the doctor blade 36. 36e3 (longitudinal central portion of the coating amount regulation surface 36r) may have an outer shape. In that case, the outer shape of the tip portion 36e3 of the doctor blade 36 is used as a reference, and a straightness correction force is applied to the doctor blade 36 so that the outer shape of the tip portions 36e1, 36e2, 36e4, and 36e5 are aligned with the reference. do.

In this way, in order to correct the straightness of the doctor blade 36, the doctor blade (a single ) must be less rigid.

(SB gap adjustment method)
The SB gap G is adjusted by moving the doctor blade 36 with respect to the developing frame 30 so that the relative position of the doctor blade 36 attached to the blade attachment portion 41 with respect to the developing sleeve 70 supported by the sleeve support portion 42 is adjusted. By moving 36 positions. At a predetermined position of the blade attachment portion 41 determined by adjusting the SB gap G, the doctor blade 36 having at least a portion of the maximum image area of the doctor blade 36 deflected is preliminarily covered over the entire maximum image area of the blade attachment surface 41s. It is fixed by the adhesive A applied over the entire surface. The maximum image area of the blade attachment surface 41s is the blade corresponding to the maximum image area among the image areas in which an image can be formed on the surface of the photosensitive drum 1 in the direction parallel to the rotation axis of the developing sleeve 70. It is the area of the mounting surface 41s. At this time, of the maximum image area of the doctor blade 36 , the area bent to correct the straightness of the coating amount regulation surface 36 r is fixed to the blade mounting portion 41 . If the area receiving the force for bending at least a part of the maximum image area of the doctor blade 36 is fixed to the blade mounting portion 41 by the adhesive A, the adhesive is applied to a portion of the blade mounting surface 41s. It is assumed that A does not have to be applied. Therefore, the adhesive A applied over the entire maximum image area of the blade mounting surface 41s means that the following conditions are satisfied. In the area corresponding to the maximum image area of the doctor blade 36, the adhesive is applied in an area of 95% or more of the maximum image area of the blade mounting surface 41s, including the area bent to correct the straightness of the coat amount control surface 36r. A is applied.

This prevents the area of the maximum image area of the doctor blade 36, which is bent in order to correct the straightness of the coating amount regulation surface 36r, from the bent state to return to the original state before bending. can be suppressed. By doing so, the doctor blade 36 is fixed to the blade attachment portion 41 in a state in which the straightness of the coating amount regulation surface 36r is corrected to 50 μm or less.

Incidentally, in the first embodiment, the size of the SB gap G is measured (calculated) by the method described below. The size of the SB gap G was measured by mounting the developing sleeve 70 on the sleeve supporting portion 42 of the developing frame 30, the doctor blade 36 on the blade mounting portion 41 of the developing frame 30, and the cover frame. 40 is fixed to the developing frame 30 .

In measuring the size of the SB gap G, a light source (for example, an LED array, a light guide, etc.) is inserted into the developing chamber 31 along the longitudinal direction of the developing chamber 31 . A light source inserted into the developing chamber 31 irradiates the SB gap G from within the developing chamber 31 with light. Further, cameras for capturing images of light rays emitted from the SB gap G to the outside of the developing frame 30 are arranged at five locations corresponding to the tip portions 36e (36e1 to 36e5) of the doctor blade 36, respectively.

The cameras arranged at these five locations pick up images of light beams emitted from the SB gap G to the outside of the development frame 30 in order to measure the positions of the tip portions 36e (36e1 to 36e5) of the doctor blade 36, respectively. At this time, the camera reads the position where the developing sleeve 70 is closest to the doctor blade 36 on the surface of the developing sleeve 70 and the tip portion 36e (36e1 to 36e5) of the doctor blade 36. FIG. Subsequently, the size of the SB gap G is calculated by converting the pixel value from the image data generated by reading with the camera into a distance. If the calculated size of the SB gap G is not within the predetermined range, the SB gap G is adjusted. When the calculated size of the SB gap G falls within a predetermined range, the doctor blade 36 with at least a portion of the maximum image area of the doctor blade 36 bent is fixed to the blade mounting portion 41 of the developing frame 30. Determine as position.

In the first embodiment, it is determined whether the SB gap G is within a predetermined range over the direction parallel to the rotation axis of the developing sleeve 70 by the method described below. First, the maximum image area of the doctor blade 36 is divided into four or more at equal intervals, and the SB gap is formed at each divided portion of the doctor blade 36 (including both ends and the center of the maximum image area of the doctor blade 36). Measure G at 5 or more points. Then, the maximum value of the SB gap G, the minimum value of the SB gap G, and the median value of the SB gap G are extracted from samples of the measured values of the SB gap G measured at five or more locations.

At this time, the absolute value of the difference between the maximum value of the SB gap G and the median value of the SB gap G is 10% or less of the median value of the SB gap G, and the minimum value of the SB gap G and the median value of the SB gap G The absolute value of the difference should be 10% or less of the median value of the SB gap G. In this case, it is assumed that the tolerance of the SB gap G is ±10% or less, and that the SB gap G is within a predetermined range in the direction parallel to the rotation axis of the developing sleeve 70 . For example, when the median value of the SB gap G is 300 μm from samples of measured values of the SB gap G measured at five or more locations, the maximum value of the SB gap G is 330 μm or less and the minimum value of the SB gap G is 270 μm. Anything above that is fine. That is, in this case, the adjustment value of the SB gap G is 300 .mu.m.+-.30 .mu.m, and the tolerance of the SB gap G is allowed up to 60 .mu.m.

(linear expansion coefficient)
Next, the deformation of the doctor blade 36 and the developing frame 30 caused by the temperature change due to the heat generated during the image forming operation will be described with reference to the perspective view of FIG. The heat generated during the developing operation includes, for example, heat generated when the rotation shaft of the developing sleeve 70 and the bearing 71 rotate, heat generated when the rotation shaft 33a of the first conveying screw 33 and its bearing member rotate, and the SB gap G heat generated when the developer passes through the The temperature around the developing device 3 changes due to the heat generated during the image forming operation, and the temperatures of the doctor blade 36, the developing frame 30 and the cover frame 40 also change.

As shown in FIG. 10, the elongation amount of the doctor blade 36 due to temperature change is H [μm], and the elongation amount of the blade mounting surface 41s of the blade mounting portion 41 of the developing frame 30 due to temperature change is I [μm]. It is also assumed that the linear expansion coefficient α1 of the resin forming the doctor blade 36 and the linear expansion coefficient α2 of the resin forming the developing frame 30 are different. In this case, the amount of deformation of the developing frame 30 and the doctor blade 36 due to temperature changes is different due to the difference in the coefficient of linear expansion. 10 will be deformed in the direction of arrow J. The deformation of the doctor blade 36 in the direction of arrow J in FIG. 10 is hereinafter referred to as deformation of the doctor blade 36 in the warp direction. Deformation of the doctor blade 36 in the direction of warp leads to variation in the size of the SB gap G. In order to suppress variations in the size of the SB gap G caused by heat, the coefficient of linear expansion α2 of the resin forming the sleeve support portion 42 and the blade mounting portion 41 of the development frame 30 (single body) and the doctor blade 36 Each of the coefficients of linear expansion α1 of the resin constituting the (single substance) is related. That is, if the coefficient of linear expansion α1 of the resin forming the doctor blade 36 and the coefficient of linear expansion α2 of the resin forming the developing device frame 30 are different, the amount of deformation due to temperature changes will differ due to the difference in these coefficients of linear expansion. .

In general, resin materials have a larger coefficient of linear expansion than metal materials. When the doctor blade 36 is made of resin, the doctor blade 36 is warped and deformed due to the temperature change due to the heat generated during the image forming operation, and the central portion of the doctor blade 36 in the longitudinal direction tends to bend. As a result, in the developing device in which the resin doctor blade 36 is fixed to the resin developing frame, the size of the SB gap G tends to fluctuate with temperature changes during the image forming operation.

(Structure of Developing Device According to First Embodiment)
In the first embodiment, at least part of the maximum image area of the doctor blade 36 is bent in order to correct the straightness of the coating amount regulation surface 36r to 50 μm or less. Then, the doctor blade 36 with at least a portion of the maximum image area of the doctor blade 36 bent is fixed to the blade mounting portion 41 of the developing frame 30 with an adhesive A over the entire maximum image area of the doctor blade 36. adopts a method to

At this time, if there is a large difference between the coefficient of linear expansion α2 of the resin forming the developing device frame 30 and the coefficient of linear expansion α1 of the resin forming the doctor blade 36, the following problems occur when the temperature changes. be. That is, when the temperature changes, the deformation amount (expansion amount) of the doctor blade 36 due to the temperature change differs from the deformation amount (expansion amount) of the developing frame 30 due to the temperature change. As a result, even if the SB gap G is adjusted with high precision when determining the position where the doctor blade 36 is to be attached to the blade attachment surface 41s of the developing frame 30, the SB gap G may be shortened due to temperature changes during the image forming operation. It will change the size.

In the first embodiment, since the doctor blade 36 is fixed to the blade mounting surface 41s over the entire maximum image area, fluctuations in the size of the SB gap G caused by temperature changes during the image forming operation are suppressed. There is a need to. The fluctuation amount of the SB gap G caused by heat generally needs to be suppressed to ±20 μm or less in order to suppress unevenness in the amount of developer carried on the surface of the developing sleeve 70 in the longitudinal direction of the developing sleeve 70 .

The difference between the linear expansion coefficient α1 of the resin forming the doctor blade 36 and the linear expansion coefficient α2 of the resin forming the developing device frame 30 having the sleeve supporting portion 42 and the blade mounting portion 41 is hereinafter referred to as the linear expansion coefficient difference α2−. Let us call it α1. A change in the maximum amount of deflection of the doctor blade 36 due to the linear expansion coefficient difference α2-α1 will be described using Table 1. In a state in which the doctor blade 36 is fixed to the blade mounting portion 41 of the developing frame 30 over the entire maximum image area of the doctor blade 36, a temperature change from normal temperature (23° C.) to high temperature (40° C.) is applied. The maximum amount of deflection of the doctor blade 36 when applied was measured.

The coefficient of linear expansion of the resin forming the developing frame 30 having the sleeve supporting portion 42 and the blade mounting portion 41 is α2 [m/°C], and the coefficient of linear expansion of the resin forming the doctor blade 36 is α1 [m/°C]. do. Table 1 shows the results of measuring the maximum amount of deflection of the doctor blade 36 while changing the parameter of the linear expansion coefficient difference α2-α1. In Table 1, when the absolute value of the maximum amount of deflection of the doctor blade 36 is 20 μm or less, the maximum amount of deflection is indicated as “◯”, and when the absolute value of the maximum amount of deflection of the doctor blade 36 is greater than 20 μm, the maximum The amount of deflection is shown as "x".

As can be seen from Table 1, in order to suppress the fluctuation amount of the SB gap G caused by heat to ±20 μm or less, it is necessary to satisfy the following relational expression (Equation 1) for the linear expansion coefficient difference α2−α1. There is
(Formula 1)
−0.45×10 ⁻⁵ [m/°C]≦α2−α1≦0.55×10 ⁻⁵ [m/°C]

Therefore, the development frame 30 is configured such that the linear expansion coefficient difference α2−α1 is −0.45×10 ⁻⁵ [m/° C.] or more and 0.55×10 ⁻⁵ [m/° C.] or less. The resin and the resin constituting the doctor blade 36 may be selected. When the same resin is selected as the resin forming the developing device frame 30 and the resin forming the doctor blade 36, the linear expansion coefficient difference α2-α1 becomes zero.

When the adhesive A is applied to the doctor blade 36 and the developing frame 30, the linear expansion coefficients of the doctor blade 36 and the developing frame 30 to which the adhesive A is applied vary. However, the volume of the adhesive A applied to the doctor blade 36 and the developing frame 30 is very small, and the effect of temperature change on the dimensional variation of the adhesive A in the thickness direction is negligible. Therefore, when the adhesive A is applied to the doctor blade 36 and the developing frame 30, the deformation of the doctor blade 36 in the warp direction caused by the variation of the linear expansion coefficient difference α2-α1 is at a negligible level. is.

Similarly, since the cover frame 40 is fixed to the developing frame 30, if the amounts of deformation of the developing frame 30 and the cover frame 40 due to temperature changes are different, the deformation of the cover frame 40 in the warping direction This leads to variations in the size of the SB gap G. The coefficient of linear expansion of the resin forming the developing frame 30 having the sleeve supporting portion 42 and the blade mounting portion 41 is α2 [m/°C], and the coefficient of linear expansion of the resin forming the cover frame 40 is α3 [m/°C]. and Then, the difference between the linear expansion coefficient α3 of the resin forming the cover frame 40 and the linear expansion coefficient α2 of the resin forming the developing device frame 30 having the sleeve support portion 42 and the blade mounting portion 41 is hereinafter referred to as the linear expansion coefficient Let us call it the difference α3-α2. At this time, as in Table 1, the linear expansion coefficient difference α3-α2 must satisfy the following relational expression (Equation 2).
(Formula 2)
−0.45×10 ⁻⁵ [m/°C]≦α3−α2≦0.55×10 ⁻⁵ [m/°C]

Therefore, the development frame 30 is configured such that the linear expansion coefficient difference α3-α2 is −0.45×10 ⁻⁵ [m/° C.] or more and 0.55×10 ⁻⁵ [m/° C.] or less. The resin and the resin forming the cover frame 40 may be selected. When the same resin is selected for the developing frame 30 and the cover frame 40, the linear expansion coefficient difference α3-α2 becomes zero.

(agent pressure)
Next, the deformation of the doctor blade 36 due to the agent pressure generated by the flow of the developer being applied to the doctor blade 36 during the image forming operation will be described with reference to the cross-sectional view of FIG. 11 . FIG. 11 is a cross-sectional view of the developing device 3 taken along a cross section perpendicular to the axis of rotation of the developing sleeve 70 (cross section H in FIG. 2). 11 shows the configuration of the vicinity of the doctor blade 36 fixed with the adhesive A to the blade mounting portion 41 of the developing frame 30. As shown in FIG.

As shown in FIG. 11, a line connecting the closest position of the doctor blade 36 to the developing sleeve 70 on the coat amount regulating surface 36r and the center of rotation of the developing sleeve 70 is defined as the X axis. At this time, the doctor blade 36 is long in the X-axis direction and has high rigidity in the cross section in the X-axis direction. Further, as shown in FIG. 11, the ratio of the cross-sectional area T1 of the doctor blade 36 to the cross-sectional area T2 of the wall portion 30a of the developing device frame 30 located near the developer guide portion 35 is small. .

As described above, in the first embodiment, the rigidity of the developing frame 30 (single body) is ten times or more higher than the rigidity of the doctor blade 36 (single body). Therefore, when the doctor blade 36 is fixed to the blade mounting portion 41 of the developing frame 30 , the rigidity of the developing frame 30 is dominant with respect to the doctor blade 36 . As a result, during the image forming operation, the amount of displacement (maximum deflection) of the coating amount regulation surface 36r of the doctor blade 36 when the doctor blade 36 receives the agent pressure is equal to the amount of displacement (maximum deflection) of the developing frame 30. ) is effectively equivalent to

During the image forming operation, the developer pumped up from the first conveying screw 33 passes through the developer guide portion 35 and is conveyed to the surface of the developing sleeve 70 . Thereafter, even when the doctor blade 36 defines the layer thickness of the developer to the size of the SB gap G, the doctor blade 36 receives developer pressure from various directions. As shown in FIG. 11, when the direction perpendicular to the X-axis direction (the direction defining the SB gap G) is defined as the Y-axis direction, the developer pressure in the Y-axis direction is applied to the blade mounting surface 41s of the developing frame 30. perpendicular to That is, the agent pressure in the Y-axis direction is a force in the direction of peeling off the doctor blade 36 from the blade mounting surface 41s. Therefore, the bonding force of the adhesive A must be sufficiently large against the agent pressure in the Y-axis direction. Therefore, in the first embodiment, the adhesion of the adhesive A to the blade mounting surface 41s is considered in consideration of the adhesive force of the adhesive A and the force that tends to separate the doctor blade 36 from the blade mounting surface 41s due to the pressure of the agent. The area and coating thickness are optimized.

As described above, in the first embodiment, the resin doctor blade 36 is attached to the blade attachment portion 41 of the resin development frame 30 with the adhesive A over the entire maximum image area of the doctor blade 36. It is fixed. Further, in the first embodiment, when the resin doctor blade 36 is fixed to the blade mounting portion 41 of the resin development frame 30, the straightness of the doctor blade 36 (single body) is corrected. In addition, a doctor blade 36 made of resin having low rigidity is used. Therefore, in the developing device 3 in which the resin-made doctor blade 36 having low rigidity is fixed to the resin-made developing frame 30, the rigidity of the resin-made developing frame 30 (single body) is increased to increase the rigidity of the resin-made developing frame 30. There is a need to increase the stiffness of the doctor blade 36 in its fixed state. This is because, by increasing the rigidity of the doctor blade 36 fixed to the developing frame 30, fluctuations in the SB gap G are suppressed during the image forming operation, and the SB gap G is maintained at a predetermined value during the image forming operation. This is to keep it within range.

In order to increase the rigidity of the resin-made development frame 30 (single body), it is conceivable to increase the basic thickness of the development frame 30 . However, in a resin molded product with a basic thickness greater than a predetermined value, when the resin thermally expands during molding and thermally shrinks, the inside of the resin molded product is The extent to which a difference in progress of heat shrinkage occurs between the outer side and the outer side tends to increase. In other words, a resin molded product having a thickness larger than a predetermined value tends to have uneven molding shrinkage compared to a resin molded product having a thickness less than or equal to the predetermined value. This is because the resin that has thermally expanded during molding gradually cools from the outside of the resin molded product, which is the part that is in contact with the mold, toward the inside of the resin molded product, which is the part that is not in contact with the mold. This is because contraction proceeds. Therefore, when the basic thickness of the resin molded product is larger than a predetermined value, sink marks tend to occur more easily in the resin molded product than when the basic thickness of the resin molded product is equal to or less than the predetermined value. It is in.

In addition, as the thickness of the resin molded product increases, the cooling time and cycle time during molding increase, which is disadvantageous from the viewpoint of mass production. Therefore, there is a limit to how much the basic thickness of the developing frame 30 can be increased for the purpose of increasing the rigidity of the resin-made developing frame 30 (single body). Therefore, in the first embodiment, the basic thickness of the developing frame 30 is set to 1.0 mm or more and 3.0 mm or less so as not to be disadvantageous in terms of mass production. Also, in order to prevent uneven molding shrinkage, it is generally preferable to make the basic thickness of the developing frame 30 uniform.

The length of the maximum image area of the developing frame 30 increases as the width of the sheet S on which the image is formed increases, such as when the width of the sheet S is A3 size. It should be noted that the maximum image area of the developing frame 30 is the development corresponding to the maximum image area among the image areas in which an image can be formed on the surface of the photosensitive drum 1 in the direction parallel to the rotation axis of the developing sleeve 70. It means the area of the frame 30 .

When the developing device frame 30 is resin-molded by injection molding, the gate portion 80 serving as an inlet for the resin to flow into the molded product through the gate when the melted resin is poured into the molded product is a resin molded product. It is provided on the frame 30 . When the developing frame 30 having a large length in the longitudinal direction is resin-molded, the distance over which the melted resin flows becomes long. The portion 80 is generally provided in the maximum image area of the developing frame 30 made of resin. In addition, when the appearance of the resin-made developing device frame 30 is generally seen, the gate portion 80 is generally a mark that serves as an entrance through which the melted resin flows into the molded product (a so-called gate portion). traces).

Further, when the developing device frame 30 is resin-molded by injection molding, a large molding pressure is applied to the gate portion 80 when the melted resin flows into the gate portion 80 through the gate. will occur. Residual stress from the gate portion 80 provided in the resin-made developing frame 30 is applied to the developing frame 30 over time, and deforms the resin-made developing frame 30 over time. As a result, when the resin doctor blade 36 is fixed to the resin development frame 30, the residual stress from the gate portion 80 provided in the development frame 30 causes the SB gap G to increase. There is a possibility that it may change over time.

The residual stress applied to the development frame 30 has a component applied to the development frame 30 along the direction intersecting the rotation axis of the development sleeve 70 . In addition, the direction intersecting the rotation axis of the developing sleeve 70 is not limited to the direction perpendicular to the rotation axis of the development sleeve 70, but the angle ( However, including directions with acute angles). When the component of the residual stress applied to the developing device frame 30 along the direction intersecting the rotational axis of the developing sleeve 70 is applied to the developing device frame 30 over time, the stress along the direction intersecting the rotational axis of the developing sleeve 70 becomes , the developing frame 30 to which the doctor blade 36 is fixed is distorted. Therefore, the residual stress from the gate portion 80 (the component of the residual stress applied to the developing frame 30 along the direction intersecting the rotation axis of the developing sleeve 70) contributes to the variation in the size of the SB gap G. Resulting in.

As described above, it is required to prevent the SB gap G from fluctuating during the image forming operation while the doctor blade 36 made of resin having low rigidity is fixed to the developing frame 30 made of resin. Therefore, in a state in which the doctor blade 36 made of resin with low rigidity is fixed to the development frame 30 made of resin, the residual stress from the gate portion 80 provided in the maximum image area of the development frame 30 is applied to the development frame over time. It is desirable to suppress variations in the size of the SB gap G that accompany contact with the body 30 . Therefore, when the doctor blade 36 made of resin with low rigidity is fixed to the developing frame 30 made of resin, the variation in the size of the SB gap G caused by the residual stress from the gate portion 80 is suppressed. Similarly, the position of the gate portion 80 is designed with respect to the maximum image area of the developing frame 30 .

In the first embodiment, when the doctor blade 36 made of resin with low rigidity is fixed to the developing device frame 30 made of resin, the residual stress from the gate portion 80 causes the variation in the size of the SB gap G. A gate portion 80 is provided for the maximum image area of the developing frame 30 so as to suppress the . Details are described below.

The configuration of the developing device according to the first embodiment will be described with reference to the perspective view of FIG. 12, the cross-sectional view of FIG. 13, and the bottom view of FIG. FIG. 12 shows the maximum image area of the developing device frame 310 provided in the developing device 300 according to the first embodiment. FIG. 13 is a cross-sectional view of the developing device 300 taken along the cross section H (maximum image area of the developing frame 310) in FIG. FIG. 14 is a bottom view of the developing device 300 when the developing device 300 attached to the image forming apparatus 60 is viewed from below in the vertical direction. In each of FIGS. 12, 13, and 14, the same reference numerals as in FIGS. 2, 3, and 4 indicate the same configuration. In the configuration of the developing device 300 (the configuration of the developing device frame 310), the differences from the configuration of the developing device 3 (the configuration of the developing device frame 30) described above with reference to FIGS. 2, 3, and 4 will be mainly described. .

In the first embodiment, as shown in FIGS. 13 and 14, the gate portion 80 is not provided at the bottom of the developing frame 310 in the maximum image area within the area P of the developing frame 310 . On the other hand, a gate portion 80 is provided at the bottom of the developing frame 310 in the maximum image area within the area Q of the developing frame 310 . The bottom portion of the developing frame 310 described in the first embodiment is the most vertical portion of the developing frame 310 when the developing sleeve 70 is at the position where the electrostatic image formed on the photosensitive drum 1 is developed. It is not limited to the outer wall portion positioned downward (for example, the outer wall portion positioned at the bottom of the partition wall 38). At the bottom of the developing frame 310, there are not only the outer wall portion positioned at the U-shaped bottom surface of the developing chamber 31 and the outer wall portion positioned at the U-shaped bottom surface of the stirring chamber 32, but also the U of the developing chamber 31. The outer wall portion located on the side wall surface of the letter shape and the outer wall portion located on the side wall surface of the U-shape of the stirring chamber 32 are also included.

When the developing device 300 is viewed in a cross section perpendicular to the rotation axis of the developing sleeve 70, a straight line L passing through the rotation center of the developing sleeve 70 and the closest position N, and the rotation of the first conveying screw 33 with respect to the straight line L The developing frame 310 is partitioned into a plurality of areas by a perpendicular line M passing through the center. The closest position N is the position where the developing sleeve 70 comes closest to the photosensitive drum 1 . That is, as shown in FIG. 13, the straight line L is a straight line passing through the rotation center of the developing sleeve 70 and the rotation center of the photosensitive drum 1 . Of the plurality of divided regions of the developing frame 310 at this time, the divided region of the developing frame 310 in which the blade mounting portion 41 is arranged is the region P of the developing frame 310 . In other words, the region P of the developing device frame 310 is a region that occupies 0 to 90 degrees upstream of the closest position N with respect to the rotational direction of the developing sleeve 70 . Further, among the plurality of divided regions of the developing frame 310 at this time, the divided region of the developing frame 310 where the blade mounting portion 41 is not arranged is the region Q of the developing frame 310 . In other words, the area Q of the developing frame 310 is an area occupied from 90 degrees to 180 degrees upstream of the closest position N with respect to the rotational direction of the developing sleeve 70 .

As described above, in the first embodiment, the gate portion 80 is provided for the bottom portion of the developing frame 310 in the maximum image area within the area Q of the developing frame 310 (inside the partitioned area [Q]). On the other hand, the position where the gate portion 80 is provided with respect to the maximum image area of the developing frame 310 is sufficiently away from the maximum image area of the blade mounting portion 41 . Therefore, the extent to which the residual stress from the gate portion 80 provided at the bottom of the developing frame 310 in the maximum image area in the region Q of the developing frame 310 contributes to the variation in the size of the SB gap G is sufficiently small. It is. On the other hand, in the first embodiment, the gate portion 80 is not provided at the bottom portion of the developing frame 310 in the maximum image area within the area P of the developing frame 310 (inside the partitioned area [P]). Therefore, it is necessary to consider the effect of the residual stress generated by providing the gate portion 80 at the bottom of the developing frame 310 in the maximum image area in the region P of the developing frame 310 contributing to the variation in the size of the SB gap G. There is no

Therefore, in the first embodiment, the residual stress from the gate portion 80 is applied to the developing frame 310 over time while the doctor blade 36 made of resin having low rigidity is fixed to the developing frame 310 made of resin. The variation in the size of the SB gap G accompanying this can be suppressed.

(Comparative example)
Next, the configuration of a developing device according to a comparative example will be described with reference to the cross-sectional view of FIG. 15 and the bottom view of FIG. FIG. 15 is a cross-sectional view of the developing device 500 taken along the cross section H (maximum image area of the developing frame 510) in FIG. FIG. 16 is a bottom view of the developing device 500 when the developing device 500 attached to the image forming apparatus 60 is viewed from below in the vertical direction. In each of FIGS. 15 and 16, the same reference numerals as in FIGS. 13 and 14 indicate the same configuration. A region P shown in FIG. 15 indicates the same region as the region P shown in FIG. A region Q shown in FIG. 15 indicates the same region as the region Q shown in FIG. The configuration of the developing device 500 (the configuration of the developing device frame 510) according to the comparative example is the configuration of the developing device 300 (the configuration of the developing device frame 310) according to the first embodiment described above with reference to FIGS. We will focus on the differences. Note that the bottom portion of the developing frame 510 described in the comparative example has the same definition as that of the bottom portion of the developing frame 310 described in the first embodiment, and the description will be continued below.

In the comparative example, as shown in FIGS. 15 and 16, the gate portion 80 is not provided at the bottom portion of the developing frame 510 in the maximum image area within the area Q of the developing frame 510 . On the other hand, a gate portion 80 is provided at the bottom of the developing frame 510 in the maximum image area within the region P of the developing frame 510 .

Thus, in the comparative example, the gate portion 80 is provided for the bottom portion of the developing frame 510 in the maximum image area within the area P of the developing frame 510 . On the other hand, the position where the gate portion 80 is provided with respect to the maximum image area of the developing frame 510 is relatively closer to the maximum image area of the blade mounting portion 41 than in the first embodiment. Therefore, the extent to which the residual stress from the gate portion 80 provided at the bottom of the developing frame 510 in the maximum image area in the region P of the developing frame 510 contributes to the variation in the size of the SB gap G is determined by the first It becomes relatively larger than the embodiment. In particular, when the doctor blade 36 made of resin with low rigidity is fixed to the developing frame 510 made of resin, the extent to which the size of the SB gap G fluctuates is likely to increase. This is because, in this state, the magnitude of the SB gap G fluctuates due to the residual stress from the gate portion 80 provided at the bottom of the developing frame 510 in the maximum image area in the region P of the developing frame 510. is likely to be large. As a result, the residual stress from the gate portion 80 provided at the bottom of the developing frame 510 in the maximum image area in the area P of the developing frame 510 is applied to the developing frame 510 over time, and the stress shown in FIG. Warping deformation occurs in the doctor blade 36 in the direction of arrow J shown in . Then, the central portion of the doctor blade 36 in the longitudinal direction bends, and the size of the SB gap G fluctuates.

On the other hand, in the first embodiment, the residual stress from the gate portion 80 provided at the bottom of the developing frame 310 in the maximum image area within the area Q of the developing frame 310 contributes to the variation in the size of the SB gap G. The extent to which it does is sufficiently small. Therefore, the residual stress from the gate portion 80 provided at the bottom of the developing frame 310 in the maximum image area in the area Q of the developing frame 310 is applied to the developing frame 310 over time. Warp deformation does not occur in the doctor blade 36 in the indicated arrow J direction.

According to the first embodiment described above, when the doctor blade 36 made of resin having low rigidity is fixed to the developing device frame 310 made of resin, the residual stress from the gate portion 80 causes the SB gap G The position of the gate portion 80 is designed so that the variation in the size of is suppressed. Specifically, as shown in FIGS. 13 and 14, the gate portion 80 is not provided at the bottom of the developing frame 310 in the maximum image area in the region P of the developing frame 310, and the developing frame 310 A gate portion 80 is provided at the bottom portion of the developing frame 310 in the maximum image area within the area Q of (1). As a result, in the first embodiment, when the resin doctor blade 36 having low rigidity is fixed to the resin development frame 310, the residual stress from the gate portion 80 causes the SB gap G to increase. It is possible to suppress the fluctuation of the height.

In the first embodiment, as shown in FIG. 14, two gates 80 are provided at the bottom of the developing frame 310 in the maximum image area within the area Q of the developing frame 310 with a space therebetween. . By providing a plurality of gate portions 80 on the developing device frame 310 in this way, when the melted resin flows into the gate portions 80 through the gates, the flow rate is proportional to the number of the gate portions 80 provided on the developing device frame 310 . As a result, the amount of resin flowing into each gate portion 80 is dispersed. When the number of gate portions 80 provided on the developing frame 310 is plural, the number of gate portions 80 provided on the developing frame 310 is greater than that when the number of gate portions 80 provided on the developing frame 310 is one. The molding pressure applied per 80 is reduced. As a result, compared to when the number of gate portions 80 provided on the developing frame 310 is only one, when the number of gate portions 80 provided on the developing frame 310 is plural, the number of gate portions 80 increases. Residual stress generated from around one of the portions 80 is reduced.

That is, by providing a plurality of gate portions 80 at the bottom portion of the developing frame 310 in the maximum image area within the region Q of the developing frame 310, the residual stress from the gate portions 80 contributes to the variation in the size of the SB gap G. can be further reduced. Therefore, the number of the gate portions 80 provided at the bottom of the developing frame 310 in the maximum image area in the region Q of the developing frame 310 is better than the number of the gate portions 80 being one. contributes to variations in the size of the SB gap G can be further reduced. Therefore, the number of the gate portions 80 provided at the bottom of the developing frame 310 in the maximum image area in the area Q of the developing frame 310 is better than the number of the gate portions 80 being one. is advantageous from the viewpoint of the influence that contributes to the variation of the size of the SB gap G.

Further, in the first embodiment, as shown in FIG. A gate portion 80 having a thickness is provided. When the melted resin flows into the gate portion 80 through the gate, the resin flows per unit area of the gate portion 80 in proportion to the size of the cross-sectional area of the gate portion 80 provided in the development frame 310. will be distributed. When the cross-sectional area of the gate portion 80 provided on the developing device frame 310 is larger than the predetermined value, the cross-sectional area of the gate portion 80 provided on the developing device frame 310 is larger than the predetermined value. However, the molding pressure applied to each gate portion 80 is reduced. As a result, compared to when the cross-sectional area of the gate portion 80 provided on the developing device frame 310 is equal to or smaller than the predetermined value, the cross-sectional area of the gate portion 80 provided on the developing device frame 310 is larger than the predetermined value. In this case, the residual stress generated from each gate portion 80 becomes smaller.

That is, the gate portion 80 having a thickness larger than the basic thickness of the developing frame 310 is provided at the bottom of the developing frame 310 in the maximum image area within the area Q of the developing frame 310 . As a result, it is possible to further reduce the influence of the residual stress from the gate portion 80 that contributes to the variation in the size of the SB gap G. FIG. Therefore, it is advantageous to make the thickness of the gate portion 80 provided at the bottom of the developing frame 310 in the maximum image area in the area Q of the developing frame 310 larger than the basic thickness of the developing frame 310 . This is because, by making the thickness of the gate portion 80 provided at the bottom portion of the region Q of the developing frame 310 larger than the basic thickness of the developing frame 310, the residual stress from the gate portion 80 causes the SB gap. This is because the influence that contributes to the variation in the magnitude of G can be further reduced.

(Other embodiments)
The present invention is not limited to the above embodiments, and various modifications (including organic combinations of each embodiment) are possible based on the gist of the present invention, and they are excluded from the scope of the present invention. is not.

In the above embodiment, as shown in FIG. 1, the image forming apparatus 60 configured to use the intermediate transfer belt 61 as an image carrier has been described as an example, but the present invention is not limited to this. It is also possible to apply the present invention to an image forming apparatus having a structure in which recording materials are brought into direct contact with the photosensitive drum 1 in order for transfer. In that case, the photosensitive drum 1 constitutes a rotatable image carrier that carries a toner image.

Further, in the above-described embodiment, as shown in FIG. 2, the developing device 3 is exemplified with a configuration in which the developing sleeve 70 rotates counterclockwise and the doctor blade 36 is arranged below the developing sleeve 70. , but is not limited to this. It is also possible to apply the present invention to a developing device 3 (developing device 300 ) in which the developing sleeve 70 rotates clockwise and the doctor blade 36 is arranged above the developing sleeve 70 .

Further, in the above embodiment, as shown in FIG. 2, the developing device 3 (developing device 300) in which the developing chamber 31 and the stirring chamber 32 are arranged side by side with respect to the horizontal direction has been described as an example. However, it is not limited to this. The present invention can also be applied to a developing device 300 in which the developing chamber 31 and the stirring chamber 32 are arranged vertically in the direction of gravity.

Further, in the above embodiment, the developing device 300 is explained as one unit, but the image forming section 600 (see FIG. 1) including the developing device 3 is integrated into a unit, and the image forming device 60 is attachable and detachable. A similar effect can be obtained even in the form of a cartridge. Further, as long as the image forming apparatus 60 includes the developing device 300 or the process cartridge, the present invention can be applied regardless of whether it is a monochrome machine or a color machine.

31 Developing Chamber 32 Stirring Chamber 33 First Conveying Screw 34 Second Conveying Screw 36 Doctor Blade 38 Partition Wall 41 Blade Mounting Portion 70 Developing Sleeve 80 Gate Portion 300 Developing Device 310 Developing Frame

Claims (12)

A developing device,
a developing rotary member that carries and conveys the developer to a position where the electrostatic image formed on the image carrier is developed;
a resin regulating blade disposed facing the developing rotator and including a regulating portion for regulating the amount of developer carried on the developing rotator at a position closest to the developing rotator;
a mounting portion for mounting the regulating blade; a first chamber in which the developer is supplied to the developing rotary member; and a second chamber separated from the first chamber by a partition wall, wherein the developer a resin-made developing frame housing a
a first conveying screw disposed in the first chamber for conveying the developer in a first direction;
a second conveying screw disposed in the second chamber for conveying the developer in a second direction opposite to the first direction;
with
The regulating blade is attached to the attachment portion using an adhesive,
The developing frame is provided with a gate,
The developing device has a portion corresponding to the maximum image area of the image carrier with respect to the rotation axis direction of the developing rotary member,
dividing the portion of the developing device into a part having the regulating portion and a part not having the regulating portion by a first plane including the rotation axis of the developing rotor and the rotation axis of the image carrier;
and,
When the part having the regulating portion is divided into a first part and a second part by a second plane including the rotation axis of the first conveying screw and perpendicular to the first plane,
The first part does not have the mounting portion and has a gate portion of the developing frame ,
The developing device, wherein the second part has the mounting portion and does not have the gate portion of the developing device frame . 2. The developing device according to claim 1, wherein in the second part, the regulation blade is attached over the entire area of the attachment portion using an adhesive. The developing frame is provided with a plurality of gate portions,
The first part has all of the plurality of gate portions of the development frame ,
3. The developing device according to claim 1, wherein the second part has none of the plurality of gate portions of the developing device frame . 4. The developing device according to any one of claims 1 to 3, wherein the regulating portion is positioned vertically below a rotation axis of the developing rotor. 5. The image forming apparatus according to any one of claims 1 to 4, wherein the length in the rotation axis direction of the developing rotor in the portion corresponding to the maximum image area is a length corresponding to A3 size. developing device. further comprising a resin cover frame separated from the development frame,
6. The developing device according to claim 1, wherein the cover frame covers the first chamber and the second chamber. The developing device according to any one of Claims 1 to 6, wherein the regulating blade has a rigidity that allows it to bend. A developing device,
a developing rotary member that carries and conveys the developer to a position where the electrostatic image formed on the image carrier is developed;
a resin regulating blade disposed facing the developing rotator and including a regulating portion for regulating the amount of developer carried on the developing rotator at a position closest to the developing rotator;
a mounting portion for mounting the regulating blade; a first chamber in which the developer is supplied to the developing rotary member; and a second chamber separated from the first chamber by a partition wall, wherein the developer a resin-made developing frame housing a
a first conveying screw disposed in the first chamber for conveying the developer in a first direction;
a second conveying screw disposed in the second chamber for conveying the developer in a second direction opposite to the first direction;
with
the regulating portion is vertically below the rotation axis of the developing rotor;
The developing frame is provided with a gate,
The developing device has a portion corresponding to the maximum image area of the image carrier with respect to the rotation axis direction of the developing rotary member,
dividing the portion of the developing device into a part having the regulating portion and a part not having the regulating portion by a first plane including the rotation axis of the developing rotor and the rotation axis of the image carrier;
and,
When the part having the regulating portion is divided into a first part and a second part by a second plane including the rotation axis of the first conveying screw and perpendicular to the first plane,
The first part does not have the mounting portion and has a gate portion of the developing frame ,
The developing device, wherein the second part has the mounting portion and does not have the gate portion of the developing frame . The developing frame is provided with a plurality of gate portions,
The first part has all of the plurality of gate portions of the development frame ,
9. The developing device according to claim 8, wherein the second part has none of the plurality of gate portions of the developing frame . 10. The developing device according to claim 8, wherein the length in the direction of the rotation axis of the developing rotor in the portion corresponding to the maximum image area is a length corresponding to A3 size. further comprising a resin cover frame separated from the development frame,
11. The developing device according to claim 8, wherein the cover frame covers the first chamber and the second chamber. The developing device according to any one of claims 8 to 11, wherein the regulating blade has a rigidity that allows it to bend.

Images