JP6904784B2 - Developing equipment and image forming equipment - Google Patents

Description

The present invention relates to an image forming apparatus using an electrophotographic method.

In an image forming apparatus that uses an electrostatic recording method or an electrophotographic recording method such as a copier or a printer, magnetic toner is supported on the surface of a developing sleeve in which a magnet roller is arranged as a developing agent carrier to increase elasticity. There is a configuration in which the amount of toner is regulated by the regulation blade that has. At that time, if the amount of toner is excessively regulated, the toner on the developing sleeve becomes insufficient and the density becomes low. Therefore, in the image forming region, it is common to have a so-called abdominal pad configuration in which the middle portion of the regulating blade is brought into contact with the developing sleeve and the tip is set to a free end to provide a toner intake portion. At that time, a larger amount of toner can be supplied onto the developing sleeve by increasing the length from the contact portion between the regulating blade and the developing sleeve to the tip of the regulating blade and making the intake portion larger.

Further, in a developing unit (developing apparatus) provided with a developing agent carrier, in order to prevent toner from leaking from gaps between the members, toner is trapped at the end in the longitudinal direction by a sealing member composed of a magnet. The configuration is known. However, since the sealing member of the magnet is expensive, as a cheaper sealing method, an elastic sealing member in which a fiber material such as felt or Teflon (registered trademark) pile is provided on the surface of a base material made of a foam member such as a sponge. Is widely used. At that time, a so-called abutting configuration is widely known in which the side surface of the regulation blade and the side surface of the elastic sealing member are pressed against each other to close the gap. However, in order to press-contact the regulation blade and the elastic seal member, it is necessary to provide a member that pushes the elastic member from the outside, which complicates the configuration. On the other hand, among the regulation blades, a so-called overlap configuration in which the surface behind the surface in contact with the developing sleeve is brought into contact with the surface of the elastic sealing member is widely known. However, when the amount of toner supplied is increased by enlarging the intake portion as described above, the toner to be inserted into the elastic seal member at any time is trapped through the gap between the regulation blade and the developing sleeve when the overlap configuration is adopted. It may not be cut off. As a result, toner leakage may occur.

On the other hand, there is known a developing device in which the tips of the restricting blades are gradually retracted at both ends in the longitudinal direction to bring the developing sleeve into edge contact with both ends in the longitudinal direction (Patent Document 1). Further, in order to reduce the amount of toner inserted between the elastic sealing member and the developing sleeve, a method is known in which the end of the magnetic field generation region is provided inside the sealing member in the magnetic contact developing method (Patent Document 2). ..

Japanese Unexamined Patent Publication No. 5-307321 Japanese Unexamined Patent Publication No. 2014-122983

However, when using a conventional developing device, there are the following problems. For example, when the regulating blade is brought into edge contact with the developing sleeve, the contact area between the regulating blade and the developing sleeve is reduced as compared with the case of abdominal pad, so that the contact pressure per area of the regulating blade and the developing sleeve is increased. Further, in the portion where the regulation blade and the elastic seal member overlap, the regulation blade is pushed by the elastic seal member, so that the contact pressure between the regulation blade and the developing sleeve becomes large. Therefore, when the regulation blade is brought into edge contact with the developing sleeve at the portion where the regulation blade and the elastic seal member overlap, an excessive contact pressure acts between the regulation blade and the development sleeve. Therefore, the toner sticks between the regulation blade and the developing sleeve, and a gap is formed between the regulation blade and the developing sleeve, which may cause toner leakage.

Further, when the tip of the regulation blade is retracted to make the toner taking-in portion smaller, among the toner deposited on the surface of the developing sleeve, the toner adhered more firmly becomes easy to selectively carry around. This is even more pronounced at the longitudinal end where circulation is poor. On the other hand, as in Patent Document 1, when the portion where the tip of the regulating blade is retracted is brought into edge contact with the developing sleeve, the toner on the developing sleeve can be peeled off. However, when the portion where the tip of the regulation blade is retracted is also used as an abdominal pad, the toner cannot be sufficiently peeled off, the toner on the developing sleeve sticks, and toner leakage may occur.

In addition, the method of providing the end portion of the magnetic field generation region inside the sealing member is not preferable in the magnetic non-contact developing method. This is because by providing the end of the magnetic field generation region inside the sealing member, the magnetic force of the developing electrode facing the photosensitive drum at the end in the longitudinal direction is also weakened, and the force for holding the toner in the developing sleeve is weakened. In that case, as described in the text of Patent Document 2, in the magnetic non-contact developing method, there is a possibility that toner may fly from the developing sleeve to the photosensitive drum, that is, so-called fog.

An object of the present invention is to provide a technique capable of suppressing sticking and leakage of a developer at the longitudinal end of a developing unit.

In order to achieve the above object, the developing apparatus according to the present invention is
A container that houses the magnetic developer and has an opening for supplying the magnetic developer,
A developer carrier rotatably provided in the container at the opening and carrying the magnetic developer, and a developer carrier.
A magnetic field generating member provided inside the developer carrier and generating a predetermined magnetic field,
A regulatory member that comes into contact with the developer carrier and regulates the layer thickness of the magnetic developer supported on the developer carrier.
A sealing member that seals a gap between an end portion of the developer carrier in the rotation axis direction and an end portion in the longitudinal direction of the opening.
In a developing device equipped with
An overlapping portion in which the developer carrier, the regulating member, the sealing member, and the container are sequentially arranged so as to be in contact with each other in a direction orthogonal to the rotation axis direction at the end portion of the opening in the longitudinal direction. Have,
The magnetic field generating member has a first region having a predetermined size in the direction of the rotation axis, and a range from one end connected to the first region to the outer end of the overlap portion in the direction of the rotation axis. the magnitude have a, a second region including a minimum portion of the minima,
The restricting member includes a fixed end fixed to the container, a free end opposite to the fixed end, and an abutting portion that abuts the developer carrier between the fixed end and the free end. The end portion in the rotation axis direction has a short portion in which the length between the contact portion and the free end is shorter than the central portion in the rotation axis direction.
Wherein in the rotation axis direction and the position of the short and small portions and a position of the second region and wherein the overlap with Rukoto.
In order to achieve the above object, the image forming apparatus according to the present invention is
An image carrier that carries a latent image and
With the above developing device
With
The developing apparatus develops the latent image to transfer the developer image formed on the image carrier to the recording material, thereby forming an image on the recording material.

According to the present invention, it is possible to suppress sticking and leakage of the developer at the longitudinal end of the developing unit.

Schematic diagram showing the end configuration of the developing unit according to the first embodiment. Schematic cross-sectional view showing the configuration of the image forming apparatus according to the first embodiment. Schematic perspective view showing the configuration of the developing unit according to the first embodiment. Schematic diagram showing the end configuration of the developing unit according to the first embodiment. Schematic diagram showing the end configuration of the developing unit according to the first embodiment. Schematic cross-sectional view showing the configuration of the developing unit according to the first embodiment. Schematic diagram showing the end configuration of the developing unit according to the second embodiment. Schematic diagram showing the end configuration of the developing unit according to the third embodiment. Schematic diagram showing the end configuration of the developing unit according to the fourth embodiment. Schematic diagram showing the end configuration of the developing unit according to the fifth embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplarily based on examples with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

[Example 1]
The present invention relates to a developing apparatus, a developing cartridge, a process cartridge, and an image forming apparatus using the same. The developing apparatus has a developing sleeve in which a magnet roller is arranged inside as a developing agent carrier that carries a developing agent on the surface, and an electrostatic latent structure formed on a photosensitive drum (image carrier) by the developing sleeve. This is a device that visualizes an image (electrostatic image) using a developing agent. The developing cartridge is a cartridge in which the developing apparatus is integrated into a cartridge and is detachably attached to the image forming apparatus main body. Further, the process cartridge is a cartridge in which the photosensitive drum and the developing device acting on the photosensitive drum are integrated into a cartridge and detachably attached to the image forming apparatus main body. Further, the image forming apparatus forms an image on a recording medium (recording material) such as a sheet material by using an electrophotographic image forming method. Examples of the image forming apparatus to which the present invention is applicable include an electrophotographic copying machine, an electrophotographic printer (LED printer, laser beam printer, etc.), a facsimile machine, a word processor, and the like.

(Configuration of image forming apparatus)
The configuration of the image forming apparatus 100 in the first embodiment will be described with reference to FIG. 2, and the image forming process in the first embodiment will be described. FIG. 2 is a schematic cross-sectional view showing a schematic configuration of the image forming apparatus 100 according to the first embodiment.

The image forming apparatus 100 is provided with a process cartridge 110 in which a photosensitive drum 111 (image carrier), a charging roller 112 (charging means), a cleaning unit 113, and a developing unit 114 are integrated, and which is detachably attached to the apparatus main body. A part of the image forming operation is executed with the process cartridge 110 mounted on the main body of the apparatus. Here, the apparatus main body is a component of the apparatus configuration of the image forming apparatus excluding the process cartridge 100.

The photosensitive drum 111 is uniformly charged to a predetermined polarity and potential by the charging roller 112 while rotating in the direction of arrow R1. Then, the laser beam transmitted from the exposure unit 120 is exposed on the photosensitive drum 111, and an electrostatic latent image is formed. The developing sleeve 1 (developer carrier) provided on the developing unit 114 is close to the photosensitive drum 111 with a predetermined clearance, and the developing sleeve 1 and the photosensitive drum 111 are brought into contact with each other by a bias application power source (not shown). A development bias is applied between them. Due to this development bias, toner moves from the development sleeve 1 to the surface of the photosensitive drum 111 to visualize the electrostatic latent image and form a toner image (developer image). The transfer roller 130 is composed of a conductive core metal and a urethane foam layer, and is in contact with the photosensitive drum 111 in a state where the recording material P does not intervene. The toner image formed on the photosensitive drum 111 is transferred onto the recording material P by the bias applied to the transfer roller 130. The toner image transferred onto the recording material P is fixed to the recording material P by being pressurized and heated by the fixing unit 140, and becomes a final image. Further, among the toner images formed on the photosensitive drum 111, a part of the toner remaining without being transferred to the recording material P is conveyed to the cleaning unit 113 and scraped from the surface of the photosensitive drum 111.

(Structure of development unit)
The configuration of the developing unit 114 as the developing apparatus in the first embodiment will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a schematic perspective view showing the configuration of the developing unit 114 in the first embodiment. In addition, in FIG. 3, in order to explain the arrangement of each member, a part of the members located on the front surface will be partially cut and depicted. As shown in the figure, the developing unit 114 includes a developing sleeve 1 (developer carrier), a regulating blade 2, a magnet roller 3 (magnetic field generating member), a blowout prevention sheet 4, an end seal 5 (seal member), and a developing unit 114. A frame body 6 (developer container) is provided. The developing sleeve 1 and the magnet roller 3 are coaxial, and when the notation simply referred to as the axial direction is used hereafter, it means the axial direction of the developing sleeve 1 and the magnet roller 3.

The developing sleeve 1 is a hollow aluminum cylinder coated with a resin layer containing conductive particles, receives power from a drive gear (not shown), and is rotatably arranged in the direction of arrow R2. The regulation blade 2 is composed of a rubber flat plate 21 having minute irregularities on the surface and a SUS sheet metal 22. The rubber flat plate 21 has a cantilevered structure in which one end is supported by the SUS sheet metal 22 in a direction orthogonal to the axial direction, and the surface of the rubber flat plate 21 on the free end side is brought into contact with the developing sleeve 1 to bring the developing sleeve into contact with the developing sleeve 1. The amount of toner on 1 is regulated to be substantially constant. The SUS sheet metal 22 is attached to the frame body 6 by a screw (not shown). The magnet roller 3 is a roller composed of a magnet attached to and fixed to the developing unit 114. The magnet roller 3 is arranged inside the developing sleeve 1 to generate a magnetic field for supporting toner on the surface of the developing sleeve 1.

The blowout prevention sheet 4 is a flexible sheet member, and by being in close contact with the developing sleeve 1, toner leakage from the frame body 6 is prevented. The end seal 5 is an elastic member in which the contact surface with the developing sleeve 1 is subjected to a fine flocking treatment, and is brought into close contact with the developing sleeve 1, the regulating blade 2, the blowout prevention sheet 4, and the frame body 6. Prevents toner from leaking from both ends of the frame 6 in the axial direction. Magnetic toner is contained in the frame body 6, and toner is supplied to the developing sleeve 1 at the developing opening 7 separated by the regulating blade 2, the blowout prevention sheet 4, and the end seal 5. In FIG. 3, the back side of the developing opening 7 as the opening serves as the toner accommodating portion in the frame body 6 as the developing agent container.

That is, the blowout prevention sheet 4 and the end seal 5 are regulated by the regulation blade 2 so that only the toner carried on the developing sleeve 1 moves from the inside to the outside of the frame 6 through the developing opening 7. It is a sealing member of. The regulation blade 2 is arranged between the peripheral surface of the developing sleeve 1 rotatably arranged in the developing opening 7 and the frame body 6, and is supported on the peripheral surface of the developing sleeve 1 from the developing opening 7. The layer thickness of the toner moving to the outside of the frame body 6 is regulated to a predetermined thickness. The blowout prevention sheet 4 is arranged between the peripheral surface of the developing sleeve 1 and the frame body 6 on the side opposite to the side on which the regulation blade 2 is arranged, and prevents toner from leaking to the outside of the frame body 6 from between the two. To prevent. The end seal 5 prevents toner from leaking to the outside of the frame 6 through the gap between the developing sleeve 1, the frame 6, and the regulation blade 2 at both ends of the developing sleeve 1 in the axial direction. At the end in the longitudinal direction (axial direction) of the developing opening 7 of the container 6 in which the end seal 5 is arranged, the developing sleeve 1, the regulating blade 2, the end seal 5, and the container 6 are the rotating shafts of the developing sleeve 1. Overlapping portions are formed so as to be sequentially in contact with each other in a direction orthogonal to the direction.

4 and 5 are schematic views showing the end configuration of the developing unit 114 in the first embodiment. In addition, in FIG. 5 with respect to FIG. 4, in order to explain the regulation blade 2 in detail, the developing sleeve 1 and the magnet roller 3 are omitted. Further, among the members, since the left and right sides in the axial direction are substantially symmetrical except for the drive gear (not shown), only one end portion is shown, and the other side is omitted. At that time, in FIGS. 4 and 5, the left side shows the outside in the axial direction, and the right side shows the inside in the axial direction. The vertical break lines F1, F2, and F3 indicate the positions in the axial direction. Regarding the dimensional relationship of each member in the axial direction, the rubber flat plate 21 of the regulation blade 2 overlaps with the end seal 5 at both ends in the axial direction, and the end portion in the axial direction of the rubber flat plate 21 is the end seal 5. It is located in the middle. Similarly, the magnet roller 3 is also arranged so as to overlap the end seal 5.

The rubber flat plate 21 of the regulation blade 2 has, as a regulation member, a fixed end on the side fixed to the frame 6 in a direction orthogonal to the axial direction, and a free end on the side opposite to the fixed end. There is. The structure has a contact portion 24 that comes into contact with the developing sleeve 1 between the fixed end and the free end. That is, the tip side (free end side) of the rubber flat plate 21 from the contact portion 24 with the developing sleeve 1 extends like a cross section with respect to the peripheral surface of the developing sleeve 1, and the tip portion of the contact portion 24. A space (toner intake portion) having a substantially wedge-shaped cross section is formed between the surface and the peripheral surface of the developing sleeve. In the following, the length of the rubber plate, that is, the free end of the rubber flat plate 21 in the direction orthogonal to the axial direction, and the fixed end of the rubber flat plate 21, that is, the SUS sheet metal 22 that serves as a fulcrum when the rubber flat plate 21 is deformed. The explanation will be given with the distance between the contact portion and the contact portion as the free length L.
The rubber flat plate 21 has short and small portions 23 at both ends in the axial direction, the free length L of which is shorter than that of the central portion in the axial direction. In other words, the rubber flat plate 21 has short and small portions 23 at both ends in which the length from the contact portion 24 to the free end is shorter at both ends than in the central portion in the axial direction. As a result, the force at which the rubber flat plate 21 and the developing sleeve 1 abut at the abutting portion 24 at the overlapping portion that overlaps with the end seal 5 is as compared with the case where the free length L is the same as the axial central portion. , Become smaller. In this way, it is possible to prevent the force of contact between the rubber flat plate 21 and the developing sleeve 1 from increasing in the overlapping portion, and the contact portion 24 in which the rubber flat plate 21 and the developing sleeve 1 come into contact with each other with a substantially uniform force over the entire axial direction. And said.
On the other hand, since the free length L of the rubber flat plate 21, that is, the length from the contact portion 24 to the free end is shortened at both ends, the size of the intake portion is also reduced. In the present embodiment, the region from the end F1 of the rubber flat plate 21 to the central end F3 of the short and small portion corresponds to the second region in the present invention, and F3 of one end including the axial central portion. The region from to F3 (not shown) at the other end corresponds to the first region in the present invention. The short and small portions 23 are formed up to the overlapping portion, and the length between the contact portion 24 and the free end is constant, at least in the region overlapping the overlapping portion.

If the rubber flat plate 21 does not have the short and small portions and the intake portion is large even in the region where the rubber flat plate 21, the end seal 5, and the developing sleeve 1 overlap each other in the axial dimensional relationship, the sealing property may be deteriorated. There is sex. That is, in the rubber flat plate 21, a gap (capture portion) is formed between the rubber flat plate 21 and the peripheral surface of the developing sleeve 1 on the tip side of the contact portion 24, and the end portion of the rubber flat plate 21 overlaps with the end seal 5. The sealed area by the seal 5 will be eroded. In that case, the toner that is inserted into the elastic sealing member 5 from the gap between the regulation blade 2 and the developing sleeve 1 at any time cannot be trapped, and toner leakage may occur.
Therefore, by providing short and small portions 23 at both ends of the rubber flat plate 21 in the axial direction to make the gap between the tip side of the rubber flat plate 21 from the contact portion 24 and the peripheral surface of the developing sleeve 1 as small as possible, the end seal is provided. It is preferable to reduce the gap that erodes the sealed area by 5.

The short and small portion 23 has a flat portion 23a in which the free length L does not change in the axial direction and an inclined portion 23b in which the free length L continuously changes, and the flat end portion 23a is located at the most end portion in the axial direction. is doing. That is, the short and small portion 23 is located between the contact portion 24 and the free end so that the position of the free end changes in a direction inclined with respect to the long method direction from the central portion side toward the overlapping portion. The length changes. Further, the tip of the rubber flat plate 21 is gentle at the vertical breaking line F3 which is the boundary between the long axial center portion and the inclined portion 23b having a free length L and the vertical breaking line F2 which is the boundary between the inclined portion 23b and the flat portion 23a. It is connected by an arc.

Further, as described above, the regulation blade 2 has a so-called abdominal pad configuration in which the developing sleeve 1 and the contact portion 24 are in surface contact with each other over the entire axial direction including the short and small portions 23. The contact portion 24 is formed so as to have a constant width in the circumferential direction with respect to the peripheral surface of the developing sleeve 1 over the entire area in the axial direction. If the regulation blade 2 is brought into edge contact with the developing sleeve 1 at a portion where the regulation blade 2 overlaps with the end seal 5, the contact pressure between the regulation blade 2 and the development sleeve 1 becomes large as described above. Therefore, the toner is fixed between the regulation blade 2 and the developing sleeve 1, and a gap is formed between the regulation blade 2 and the developing sleeve 1, so that the toner easily leaks. Therefore, it is preferable that the regulation blade 2 is provided as an abdominal pad even in a portion where the regulation blade 2 overlaps the end seal 5.

(Structure of magnet roller)
The magnetic pole arrangement and the distribution of the magnetic flux density of the magnet roller 3 in the first embodiment will be described with reference to FIGS. 6 and 1. FIG. 6 is a schematic cross-sectional view showing a cross-sectional configuration of the developing unit 114 in the center of the axial direction in the first embodiment. At the center of the axial direction, the magnet roller 3 has four magnetic poles arranged along its circumferential direction, and the magnetic flux density in the normal direction is high at the developing pole S1, the regulating pole N1, the supply pole S2, and the collecting pole N2. Each shows a peak value. The magnet roller 3 is fixed in the illustrated state (that is, the arrangement of the magnetic poles is always the same as the illustration), and the developing sleeve 1 is moved with the rotation of the photosensitive drum 111 (in the R1 direction). It rotates around the magnet roller 3 (in the R2 direction).

Each magnetic pole is formed at each position so as to generate a magnetic field (magnetic field) that exerts the following actions on the toner of the present embodiment, which is a magnetic developer. The developing electrode S1 is provided near the closest position between the developing sleeve 1 and the photosensitive drum 111, and supports toner on the developing sleeve 1 during development. The regulating electrode N1 is provided near the contact position between the developing sleeve 1 and the regulating blade 2 to regulate the layer thickness of the toner on the developing sleeve 1. The supply electrode S2 is provided at a position facing the developing opening 7, and carries and conveys the toner in the frame 6 on the developing sleeve 1. The collecting electrode N2 is provided near the contact position between the developing sleeve 1 and the blowing prevention sheet 4 to prevent toner from leaking from the gap between the developing sleeve 1 and the blowing prevention sheet 4.

The polarities of the magnetic poles at the center in the axial direction are as follows: the developing pole S1 and the supply pole S2 are the S poles, the regulating pole N1 and the collecting pole N2 are the N poles, and the N poles and the S poles are alternately arranged in the circumferential direction. ing. The magnetic developer in this embodiment includes both a one-component magnetic toner and a two-component developer composed of a magnetic carrier and a toner (pigment). Hereinafter, when the development pole S1, the regulation pole N1, the supply pole S2, and the collection pole N2 are referred to, the magnetic flux densities of the four magnetic poles at the center in the axial direction indicate the circumferential position showing the peak value.

Further, FIG. 1 is a schematic diagram and a graph showing the magnetic flux density of the magnet roller 3 at the end of the developing unit 114. The graph shows the magnetic flux density in the normal direction for each of the four locations in the circumferential direction, and the axial position is made to correspond to the horizontal axis of the graph based on the vertical break lines F1, F3, and F4. ing. Since the magnetic flux density in the normal direction and the positional relationship in the axial direction are substantially symmetrical on the left and right in the axial direction, only one end is shown, and the other side is omitted.

The magnetic flux density was measured by the following method using a Gauss meter (manufactured by FW Bell). First, a jig that can rotate the magnet roller 3 on an axis that overlaps the rotation center of the developing sleeve 1 is prepared, and the measurement terminal of the Gauss meter is fixedly installed at a position that overlaps the outer diameter of the developing sleeve 1. At that time, the magnetic flux density in the normal direction is measured by directing the measurement terminal to the center of rotation of the mag roller 3. Next, the magnet roller 3 is rotated to adjust to a predetermined circumferential position, and then the measurement terminal is moved in the axial direction to measure the magnetic flux density at the predetermined axial position. Then, by performing this operation for each magnetic pole, the axial distribution of the normal magnetic flux density of each magnetic pole is measured.

The vertical break line F4 is a line indicating the end position of the magnet roller 3 in the axial direction. The developing pole S1, the regulating pole N1, and the collecting pole N2 are magnetized to the end of the magnet roller 3, and the method is performed from the vicinity of the vertical break line F4, which is the end position of the magnet roller 3, toward the outside in the axial direction. The magnetic flux density in the linear direction gradually decreases. At that time, it is preferable to arrange the magnet roller 3 so that the developing electrode S1 has a predetermined magnetic flux density to the outside of the developing opening 7, that is, to the longitudinal position where the end seal 5 is provided. As a result, it is possible to suppress the flying of toner from the developing sleeve 1 to the photosensitive drum 111, that is, fog.

On the other hand, the supply electrode S2 of the magnet roller 3 has a first region having a predetermined magnitude of the magnetic flux density in the normal direction located at the center in the axial direction and a minimum magnetic flux density in the normal direction. It includes a second region having a change point C (minimum portion). The second region is provided at both ends of the first region, and the change point C (minimum portion) is located in the range from one end connected to the first region to the outer end in the axial direction of the overlapping portion overlapping the end seal 5. do. With such a configuration, in the second region, the magnitude of the magnetic flux density decreases from the axial central portion side connected to the first region to the change point C, but again as it goes further outward from the change point C. The magnetic flux density increases. Then, the magnetic flux density decreases again at the point where the magnetic flux density reaches the maximum value, and becomes the minimum value (zero) at the end in the axial direction. As a result, a magnetic force acts on both sides in the axial direction around the change point C. Therefore, the toner on the surface of the developing sleeve 1 supported at the axial position where the change point C is located is peeled off to both sides in the axial direction. Therefore, the change point C is arranged at the axial position corresponding to the short portion 23, that is, between the vertical break line F1 and the vertical break line F3. As a result, it becomes difficult for toner to stay between the regulating blade 2 and the developing sleeve 1 in the overlapping portion, and toner leakage due to toner sticking between the regulating blade 2 and the developing sleeve 1 can be suppressed. In addition, as described above, the short and small portions 23 promote the traveling of the toner, whereas the toner is stripped off on both sides in the axial direction at the supply electrode S2 to suppress the sticking of the toner.

As a method of forming the change point C, for example, there is a method of changing the strength of magnetization in the axial direction. That is, it is preferable to weaken the strength of magnetization slightly inside the most end portion and the central portion in the axial direction of the magnet roller 3.

Further, as another method, for example, there is a method in which only the supply electrode S2 is not magnetized to the end end of the magnet roller 3. In that case, in the supply pole S2, the magnetic flux density in the normal direction gradually decreases from the vicinity of the magnetized boundary portion toward the axial end portion, and at the outermost end portion of the magnet roller 3, the magnetic pole of the supply pole S2 The influence of is eliminated. On the other hand, on both sides of the supply pole S2 in the circumferential direction, there are a regulation pole N1 and a collection pole N2 having opposite polarities. Therefore, due to the influence of the regulation pole N1 and the collection pole N2, the supply pole S2 is reversed to the polarities of the regulation pole N1 and the collection pole N2 at the axialmost end portion of the magnet roller 3. At that time, the position where the S pole and the N pole are just inverted becomes the above-mentioned change point C (in the axial magnetic flux density distribution in the phase of the supply pole S2 on the peripheral surface of the developing sleeve, the polarity of the supply pole S2 becomes Invert with the change point C in between). Therefore, when this method is used, the magnetic flux density in the normal direction at the change point C becomes zero.

The larger the inclination in which the magnetic flux density in the normal direction changes in the axial direction, the stronger the magnetic force for stripping the toner carried on the surface of the developing sleeve 1 from both sides in the axial direction. Therefore, as a method for forming the change point C, of the above two methods, the method in which only the supply electrode S2 is not magnetized to the outermost end of the magnet roller 3 is easier to strip the toner. That is, after the magnitude of the magnetic flux density decreases to the minimum value, it does not increase again and continues to the overlapping portion.
Further, in this embodiment, only the supply electrode S2 has a configuration having a minimum value of the magnetic flux density, but as long as the toner holding power that does not cause fog, edge toner leakage, toner adhesion of the photosensitive drum, etc. is guaranteed. Other configurations may be adopted. For example, it may be configured to have a minimum value at another pole, a plurality of poles, or all poles.

[Other Examples]
In Example 1, the case where the short and small portion 23 is composed of the flat portion 23a and the inclined portion 23b is shown. On the other hand, for example, as shown in the schematic view of FIG. 7, the short and small portion 23 may be composed of only the flat portion 23a (Example 2). On the contrary, as shown in the schematic view of FIG. 8, the short and small portion 23 may be composed of only the inclined portion 23b (Example 3). Further, as shown in the schematic view of FIG. 9, the short portion 23 may be bent (Example 4). Even in such a case, the toner sticking in the short portion 23 is suppressed by providing the change point C at which the magnetic flux density in the normal direction of the supply pole S2 is minimized at the axial position corresponding to the short portion 23. can do.
Further, as shown in the schematic view of FIG. 10, the change point C may be arranged in the overlapping portion, that is, between the vertical break line F1 and the vertical break line F5 (Example 5). Here, the vertical break line F5 indicates the position of the inner end portion of the end seal 5 in the axial direction. With such a configuration, the toner deposited on the surface of the developing sleeve 1 is removed from the end seal 5 and the developing sleeve 1 by stripping the toner on both sides in the axial direction at the supply electrode S2 as in the first embodiment. It is possible to prevent the toner from getting stuck in the space and sticking to the toner. The device configuration not described here in Examples 2 to 5 is the same as that in the first embodiment, and the description thereof will be omitted.

1 ... Development sleeve (developer carrier), 2 ... Regulatory blade, 21 ... Rubber flat plate (regulatory member), 23 ... Short and small part, 23a ... Flat part, 23b ... Inclined part, 3 ... Magnet roller (magnetic field generating member), 5 ... End seal (seal member), 6 ... Frame (developer container), 114 ... Development unit (developer), 100 ... Image forming device

Claims (8)

A container that houses the magnetic developer and has an opening for supplying the magnetic developer,
A developer carrier rotatably provided in the container at the opening and carrying the magnetic developer, and a developer carrier.
A magnetic field generating member provided inside the developer carrier and generating a predetermined magnetic field,
A regulatory member that comes into contact with the developer carrier and regulates the layer thickness of the magnetic developer supported on the developer carrier.
A sealing member that seals a gap between an end portion of the developer carrier in the rotation axis direction and an end portion in the longitudinal direction of the opening.
In a developing device equipped with
An overlapping portion in which the developer carrier, the regulating member, the sealing member, and the container are sequentially arranged so as to be in contact with each other in a direction orthogonal to the rotation axis direction at the end portion of the opening in the longitudinal direction. Have,
The magnetic field generating member has a first region in which the magnitude of the magnetic flux density is a predetermined magnitude in the rotation axis direction, and from one end connected to the first region to the outer end of the overlap portion in the rotation axis direction. a second region including a minimum portion of the size becomes minimum in the range of, for possess,
The restricting member includes a fixed end fixed to the container, a free end opposite to the fixed end, and an abutting portion that comes into contact with the developer carrier between the fixed end and the free end. The end portion in the rotation axis direction has a short portion in which the length between the contact portion and the free end is shorter than the central portion in the rotation axis direction.
A developing device in which the position of the short and small section in the rotation axis direction and the position of the second region and wherein the overlap with Rukoto. The first aspect of claim 1, wherein the second region decreases from the side of the first region toward the side of the overlapping portion, and then increases again after the size decreases to the minimum size. Developer. In the second region, from the side of the first region toward the side of the overlapping portion, the size is reduced from the predetermined size to the minimum size, and then the minimum size is the longitudinal length. The developing apparatus according to claim 1, wherein the developing apparatus continues to the end in the direction. The magnetic field generating member has at least one magnetic pole in the circumferential direction of the surface having a magnetic flux density at the center in the central portion in the rotation axis direction in the region of the surface of the developer carrier facing the inside of the container. The developing apparatus according to any one of claims 1 to 3, wherein the developing apparatus has the first region and the second region at least at the position in the circumferential direction having the magnetic pole. The developing apparatus according to any one of claims 1 to 4, wherein the regulating member has a constant length between the abutting portion and the free end in the overlapping portion. The developing apparatus according to any one of claims 1 to 5, wherein the contact portion is formed over the entire area of the regulating member in the direction of the rotation axis. The minimum portion is formed by the contact portion and the free end so that the position of the free end changes in a direction inclined with respect to the rotation axis direction from the central portion side toward the overlapping portion. The developing apparatus according to any one of claims 1 to 6 , wherein the length between the two is changed. An image carrier that carries a latent image and
The developing apparatus according to any one of claims 1 to 7.
With
An image forming apparatus, characterized in that the developing apparatus develops the latent image to transfer an image of a developer formed on the image carrier to a recording material, thereby forming an image on the recording material.

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