JP4699124B2 - Developing apparatus and developing method - Google Patents

Description

The present invention relates to a current image apparatus and developing method.

  The electrophotographic system is widely used in image forming apparatuses such as copiers, printers, and facsimiles because images having good image quality can be easily formed. In general, an image forming apparatus using an electrophotographic method irradiates light based on image information onto a charged surface of a photosensitive drum that is uniformly charged with a charging unit that uniformly charges the surface of the photosensitive drum containing a photoconductive substance. An exposure means for forming an electrostatic latent image, a developing means for supplying a toner to the electrostatic latent image on the surface of the photosensitive drum to visualize it, and a toner image carried on the surface of the photosensitive drum on the surface of the recording medium. And a fixing unit for fixing the toner image on the recording medium to the recording medium by heating, pressurizing, or the like.

  Here, the developing means is generally provided so as to be in contact with or close to the photosensitive drum, and a developing roller that carries a developer layer on the surface thereof and supplies toner to the electrostatic latent image, and the developing roller surface A doctor blade, which is a plate-like member that is provided in contact with the developer roller and regulates the layer thickness of the developer layer on the surface of the developing roller, and a developer that charges the toner by its rotational drive and includes the charged toner. A developing device is used that includes a stirring roller that is fed to the periphery of the printer, a developing roller, a doctor blade, and a developing tank that contains a stirring roller and contains a developer. When the developer is a two-component developer, the developer layer on the surface of the developing roller is an aggregate due to the electric attraction between the toner and the carrier, and a magnetic member includes a magnetic member included in the developing roller. A large number of so-called magnetic brushes are made and formed.

  In such a developing device, a plate member made of aluminum is frequently used for the doctor blade. The doctor blade is generally screwed to the developing tank at both ends. In that case, the development of the doctor blade is caused by the fact that the screwing position of the developer tank and the screwing position of the doctor blade do not exactly match and stress is applied from both ends toward the center by the screw. In many cases, bending occurs such that the central portion in the roller axial direction is separated from the developing roller. As a result, at the center of the doctor blade, the distance between the doctor blade and the developing roller surface (hereinafter referred to as “doctor gap”) is wider than the doctor gap at both ends of the doctor blade. There arises a problem that the regulated amount of the developer layer changes. Although it is technically possible to further increase the accuracy of the screwing positions of the developing tank and doctor blade, it is extremely difficult to deal with them on an industrial scale.

  On the other hand, with the remarkable development of electrophotographic image forming technology, there is a very large demand for higher image quality. In order to achieve high image quality, it is necessary not only to increase the image density, but also to accurately and precisely reproduce minute changes in the document to form a high-definition image. For this purpose, the toner supply amount to the electrostatic latent image is adjusted as appropriate, and if the document has minute changes, the toner supply amount is appropriately reduced to reduce the amount of fine toner such as a solid image or a general print image. In the case of a document having no change, it is necessary to return the toner supply amount to the normal amount. Since the toner supply amount is almost proportional to the layer thickness of the developer layer, the toner supply amount is generally adjusted by adjusting the doctor gap to regulate the layer thickness of the developer layer carried on the developing roller. Is done. Such an adjustment is performed on the premise that the doctor blade and the developing roller are in exactly parallel positions.

In order to form a high-definition image, it is necessary to narrow the doctor gap from about 400 μm to about 200 μm and to adjust the developer conveyance amount to ²⁰ to 70 mg / cm ² that can satisfactorily reproduce a document with minute changes. . However, as described above, when the doctor gap is narrower than the center part at both ends, and the doctor gap is further narrowed to form a high-definition image, the doctor gap at both ends becomes narrower than necessary. In some cases, the developer conveyance amount becomes extremely small, and image defects such as image defects may occur. In addition, the frictional stress applied to the developer when passing through the doctor gap, particularly the doctor gaps at both ends, is increased, and the developer is deteriorated, resulting in poor charging of the toner, thereby reducing the image density. . Furthermore, in the current situation where high image quality and high-speed image formation are required, if the doctor gap becomes too narrow, the frictional stress applied to the doctor blade also increases, the wear of the doctor blade, the developer on the doctor blade There is also a problem that the durability of the doctor blade is lowered due to adhesion of the dentist.

  Conventionally, a groove extending in the axial direction of the developing roller is formed on the surface of the developing roller in order to increase the developer conveyance amount of the developing roller. For example, a developing roller has been proposed in which a plurality of grooves extending in the axial direction of the developing roller are formed on the surface of the developing roller, and a region other than the region where the groove on the surface of the developing roller is formed is roughened (for example, Patent Document 1). Further, a developing roller has been proposed in which grooves having a depth of 0.5 μm or more and smaller than the particle size of the magnetic toner are formed on the surface (see, for example, Patent Document 2). Further, there has been proposed a developing roller in which irregularities extending in the axial direction of the developing roller are regularly and alternately formed on the surface of the developing roller (see, for example, Patent Document 3). However, all the grooves formed on the surface of the conventional developing roller have the same shape and the same size, and although the developer conveying ability of the developing roller can be increased, there is a drawback that it cannot cope with high definition. In such a conventional developing roller, in order to cope with high definition, it is conceivable to narrow the width of the groove and reduce the developer conveying ability on the surface of the developing roller. However, the width of the groove has a threshold value at which the developer conveyance capacity decreases rapidly, and it takes a complicated process and high cost to form the groove so that the threshold value is not exceeded. It is difficult.

Japanese Utility Model Publication No. 5-25459 JP-A-6-236113 Japanese Patent Laid-Open No. 11-52709

The object of the present invention is that when the doctor blade is bent and the doctor gaps at the center and both ends in the developing roller axial direction are different , the developer conveying capacity at the center and both ends hardly changes, and the development Provided are a developing device including a developing roller and a developing method capable of adjusting a developer conveyance amount to a level corresponding to high image quality without causing deterioration of the agent and a decrease in the durability of the doctor blade. That is.

The present invention relates to a developing roller that is provided so as to be in contact with or close to the photosensitive drum and supplies developer to the electrostatic latent image on the surface of the photosensitive drum, in a region other than both ends in the axial direction of the developing roller. A developing roller in which a groove is formed;
A stirring roller that frictionally mixes the developer and supplies it to the periphery of the developing roller;
A doctor blade that regulates the layer thickness of the developer layer that is provided in contact with or close to the surface of the developing roller and carried on the surface of the developing roller;
In a developing device including a developing roller, a stirring roller, a doctor blade, and a developing tank containing a developer,
The groove has a groove opening provided on the surface of the developing roller, and a bottom provided nearer to the axial center of the developing roller than the groove opening, and is formed to extend in the axial direction of the developing roller. Further, by changing only the groove shape in the cross section perpendicular to the axis of the developing roller without changing the width dimension in the circumferential direction of the developing roller at the groove opening part and the depth dimension from the groove opening part to the bottom part , the developing roller In the axial direction of the groove, the developer transport capability at both ends of the groove is higher than the developer transport capability at the center of the groove,
The doctor blade is a developing device characterized in that a central portion thereof is bent so as to be separated from the developing roller.

Furthermore, the developing roller of the present invention is
The groove formed on the surface of the developing roller is formed so that the developer conveying capability increases stepwise from the central portion of the groove toward both ends in the axial direction of the developing roller.

Furthermore, the developing roller of the present invention is
The groove shape in a cross section perpendicular to the axis of the developing roller is a square shape, a trapezoidal shape, a V shape, or a semicircular shape.

Furthermore, the developing roller of the present invention is
In the region where the groove on the surface of the developing roller is formed, the surface of the developing roller excluding the inner wall surface and the bottom of the plurality of grooves is roughened.

Furthermore, the developing roller of the present invention is
The roughening treatment is performed so that the ten-point average roughness Rz = 40 to 100 μm.

Furthermore, the developing device of the present invention provides:
The photosensitive drum and the developing roller rotate in the same direction, and the peripheral speed ratio between the photosensitive drum and the developing roller is 1.0 or more.

Furthermore, the developing device of the present invention provides:
The photosensitive drum and the developing roller rotate in opposite directions, and the peripheral speed ratio between the photosensitive drum and the developing roller is 2.0 or more.

Furthermore, the developing device of the present invention provides:
The developer is a two-component developer containing a toner and a carrier.
In the present invention, the developer is supported on a developing roller provided in the developing device, and the amount of the developer is regulated by a doctor blade provided in the developing device, and then the toner contained in the developer is removed from the surface of the photosensitive drum. In the developing method for supplying and developing the electrostatic latent image of
Mizoguchi portion provided in the developing roller surface, and has a bottom portion than the groove opening is provided in the axial center side of the developing roller, and a groove formed so as to extend in the axial direction of the developing roller, Mizoguchi portion By changing only the groove shape in the cross section perpendicular to the axis of the developing roller without changing the width dimension in the circumferential direction of the developing roller and the depth dimension from the groove opening to the bottom , the axial direction of the developing roller, The developer is carried in a groove formed such that the developer conveying ability at both ends of the groove is higher than the developer conveying ability at the center of the groove,
In the developing method, the amount of the developer is regulated by a doctor blade that is bent so that a central portion thereof is separated from the developing roller.
In the present invention, the groove is
In the axial direction of the developing roller, the developer conveying capacity at both ends of the groove is 60 to 90 mg / cm ² , and the developer conveying capacity at the center of the groove is 20 to 70 mg / cm ^2. And
Further, the invention is characterized in that the width dimension in the circumferential direction of the developing roller at the groove opening portion of the groove is in the range of 2 to 5 times the particle diameter of the carrier contained in the developer.
Further, the invention is characterized in that the depth dimension from the groove opening portion to the bottom portion of the groove is in the range of 1 to 3 times the particle diameter of the carrier contained in the developer.
In the present invention, the distance between the center positions of adjacent grooves in the circumferential direction of the developing roller is in the range of 20 to 30 times the particle diameter of the carrier contained in the developer. .

According to the present invention, there is provided a developing roller that is provided so as to be in contact with or close to the photosensitive drum and supplies developer to the electrostatic latent image on the surface of the photosensitive drum, and a region other than both ends in the axial direction of the developing roller. A developing roller in which a groove is formed, a stirring roller that frictionally mixes the developer and supplies the developer to the periphery of the developing roller, and a development roller that is provided on and in contact with the developing roller surface and is carried on the developing roller surface In the developing device including a doctor blade that regulates the layer thickness of the agent layer, a developing roller, a stirring roller, a doctor blade, and a developing tank that stores the developer, the groove is provided in the surface of the developing roller. parts, and has a bottom portion than the groove opening is provided in the axial center side of the said developing roller, and is formed so as to extend in the axial direction of the developing roller, further, the axis of the developing roller By changing only the groove shape in a cross section perpendicular to, the axial direction of the developing roller, the developing agent conveying capacity of the central portion of the groove, towards the developer conveying capacity of the two ends of the groove is increased There is provided a developing device in which the doctor blade is bent so that the central portion thereof is separated from the developing roller. In the present invention, since grooves are formed in a region excluding both end portions in the developing roller axial direction on the surface of the developing roller, the developer scatters into the developing device and thus into the image forming device, resulting in image quality degradation, and the surface of the photosensitive drum. Damage can be prevented more reliably. Further, on the surface of the developing roller of the present invention, by changing only the groove shape in the cross section perpendicular to the axis of the developing roller, grooves having different developer conveying capabilities are formed at both ends and the center of the groove. Although the doctor gap, which is the distance between the developing roller and the doctor blade, is different between the both ends and the center of the developing roller in the axial direction, a developer layer consisting of substantially the same amount of developer (a spike magnetic brush) Is carried.

That is, in the present invention, although the doctor gap at both ends than at the central portion of the developing roller axial direction short, since the groove as the developer conveying capacity towards the end portions than at the central portion of the groove becomes higher Ru is formed Further, it is possible to make the developer conveying ability in the developing roller axial direction uniform. By adopting such a configuration, the doctor gap is narrowed in order to obtain a developer conveying capability suitable for finely reproducing minute changes in the document, for example, the doctor gap becomes narrower than necessary at both ends. However, the developer conveyance capacity at both ends does not extremely decrease, and excessive stress is not applied to the developer, so image defects such as image loss and image density decrease due to developer deterioration Is significantly prevented. As a result, it is possible to stably form a high-definition and high-density image without image defects. In addition, a developing device in which the durability of the doctor blade is hardly deteriorated can be obtained.

  According to the present invention, in the developing roller axial direction, the groove is formed so that the developer conveying capability increases stepwise or continuously from the center to both ends of the groove, thereby being influenced by the doctor gap. Therefore, it is possible to further uniform the developer conveying ability in the axial direction of the developing roller, and it is possible to form a higher definition image without image defects.

  According to the present invention, by selecting a groove shape in a cross section perpendicular to the axis of the developing roller from a square shape, a trapezoidal shape, a V shape, and a semicircular shape, the developer conveying ability of the groove can be arbitrarily adjusted, It becomes easy to cope with high definition.

According to the present invention, in the region where the groove on the surface of the developing roller is provided, the surface of the developing roller except for the inner wall surface and the bottom of the groove is roughened (preferably the ten-point average roughness Rz is 40 to 100 μm). By performing the (roughening process), the developer transport amount set in each groove is more reliably reproduced, so that a high-definition image is stably formed over a long period of time.

  According to the present invention, the photosensitive drum and the developing roller are rotationally driven in the same direction so that the rotational peripheral speed of the developing roller is 1.0 times or more the rotational peripheral speed of the photosensitive drum, or the photosensitive drum and the developing roller Is rotated in the opposite direction, and the rotational peripheral speed of the developing roller is set to 2.0 or more of the rotational peripheral speed of the photosensitive drum, whereby the developer is more smoothly supplied to the electrostatic latent image on the surface of the photosensitive drum. it can. That is, this configuration also contributes to higher image definition.

According to the present invention, the developer used in the developing device of the present invention is preferably a two-component developer containing a toner and a carrier, and a two-component developer containing a negatively chargeable nonmagnetic toner and a positively chargeable magnetic carrier. Is particularly preferred. By using such a developer, and further using a negatively charged photosensitive drum, it is possible to easily and stably carry out high-definition images, and to reduce costs.
Digitalization becomes easy.
According to the present invention, the doctor gap at both ends is narrower than the central portion in the developing roller axial direction, and the developer conveying capability at both ends of the groove is 60 to 90 mg / cm ² suitable for high density image formation . The groove is formed so that the developer carrying capacity at the center is 20 to 70 mg / cm ² suitable for high-definition image formation, and the developer carrying capacity at both ends is relatively higher than the center of the groove. Thus, a high-definition image free from image defects can be stably obtained over a long period of time.
According to the present invention, when a two-component developer containing toner and a carrier is used, the width dimension in the circumferential direction of the developing roller at the groove opening is selected from a range of 2 to 5 times the carrier particle diameter. Then, the developer can smoothly enter the groove, and the developer conveying ability of the groove can be easily set to the designed value.
According to the present invention, when a two-component developer containing a toner and a carrier is used, the depth dimension from the groove opening to the bottom of the groove is selected from a range of 1 to 3 times the carrier particle diameter. The entry of the agent into the groove and the replacement from the groove proceed smoothly, and it becomes easy to make the developer carrying capacity of the groove as designed.
According to the present invention, when a two-component developer including toner and carrier is used, the dimension between the center positions of adjacent grooves in the circumferential direction of the developing roller is selected from a range of 20 to 30 times the carrier particles. By doing so, the developer conveying ability set for each groove is accurately reproduced, and high definition of the image can be realized with certainty.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a developing device 1 according to a first embodiment of the present invention. FIG. 2 is a side view schematically showing a configuration of a main part of the developing device 1. That is, it is a side view of the developing roller 3 and the doctor blade 4 of the developing device 1 as seen from a direction perpendicular to the axis of the developing roller 3. FIG. 3 is a cross-sectional view of the rectangular groove 15 extending in the developing roller axial direction in a direction perpendicular to the developing roller 3 axis.

  The developing device 1 includes a developing tank 2 for storing a developer, a developing roller 3 accommodated in the developing tank 2, a doctor blade 4, a first stirring roller 5 and a second stirring roller 6, and a wall surface of the developing tank 2. And a toner sensor 7 to be mounted.

  The developer tank 2 is a member for storing the developer as described above, and the opening 9 for exposing a part of the developing roller 3 to a portion facing the photoconductive drum 8 and the second stirring roller 6 are provided above. A toner supply port 10 for supplying toner to the developing tank wall is formed. A toner storage container (toner hopper) (not shown) is provided outside the toner replenishing port 10, and toner is replenished according to the toner concentration and / or toner consumption amount in the developing tank 2 as will be described later.

  The developing roller 3 is provided so that a part of the developing roller 3 is exposed to the outside of the developing tank 2 in the opening 9 of the developing tank 2 and is opposed to and close to the photosensitive drum 8. This is a cylindrical member that forms a region and is rotatably driven in the direction of the arrow 13 (counterclockwise direction) by driving means (not shown). The developing roller 3 includes a magnet member 11 composed of a plurality of magnetic poles (N1, N2, N3, S1, S2, S3, S4) and a developing sleeve 12 formed on the surface of the magnet member 11 therein. Is done. Furthermore, at least one, preferably two or more grooves 15 are formed on the surface of the developing sleeve 12.

  The magnet member 11 carries a spike-like magnetic brush (not shown) as a developer layer on the groove 15 formed on the surface of the developing sleeve 12 by the magnetic force.

  A groove 15 having a groove portion 15x and a bottom portion 15y (not shown) closer to the axial center of the developing roller 3 than the groove portion 15x is formed on the surface of the developing sleeve 12 so as to extend in the developing roller axial direction. The groove 15 includes a central portion 15a and both end portions 15b having different developer conveying capabilities. Further, as will be described in detail later, the doctor blade 4 is fixed to the wall surface of the developing tank 2 by screws 16 a and 16 b, and the shape of the central portion of the doctor blade 4 in the developing roller axial direction is separated from the developing roller 3. Therefore, the groove 15 is formed so that the developer conveying capability of the both end portions 15b is higher than that of the central portion 15a.

  Although not shown in the drawings, the central portion 15a and both end portions 15b of the groove 15 are grooves having a rectangular groove shape in a cross section perpendicular to the axis of the developing roller 3 (hereinafter simply referred to as “groove shape” unless otherwise specified). is there. In the rectangular groove 15, the width dimension W in the circumferential direction of the developing roller at the groove opening 15 x (hereinafter simply referred to as “width dimension W” unless otherwise specified) and the depth dimension D from the groove opening 15 x to the bottom 15 y (hereinafter referred to as “width dimension W”). Unless otherwise specified, it is simply referred to as “depth dimension D”), and the groove volume per unit length is formed so that both end portions 15b are larger than the center portion 15a. It can be set so that the developer conveying capability is larger than that of the central portion 15a. The “length” here is a length in the developing roller axial direction.

By appropriately changing at least one of the width dimension W, the depth dimension D, and the groove shape, the central portion 15a and both end portions 15b having a desired developer conveying capability are formed. As the depth dimension D increases, not only does the developer conveyance capacity increase due to the increase in the groove volume, but also because the bottom of the groove is closer to the magnet member 11, the developer conveyance capacity. Will increase. In the present embodiment, the central portion 15a has a width dimension W: 0.1 to 0.4 mm, a depth dimension D: 0.1 to 0.25 mm, a groove pitch: 1.6 to 3.2 mm, and a developer. Conveyance amount: formed to about 20 to 70 mg / cm ² . Both end portions 15b are formed to have a width dimension W: 0.3 mm, a depth dimension D: 0.3 mm, a groove pitch: about 1.3 to 2.6 mm, and a developer transport amount: about 60 to 90 mg / cm ^2. . The developer transport amount at both ends 15b is set to be higher than the developer transport amount at the center portion 15a. In the present embodiment, the developing roller 3 is formed so that the outer circumference of the developing sleeve 12 in a cross section perpendicular to the axis of the developing roller 3 is 8 cm. FIG. 4 shows the maximum vertical magnetic flux density distribution of the main pole (N1) with respect to the straight line connecting the rotation center point (axial center) of the developing roller 3 and the rotation center point (axial center) of the photosensitive drum 8. Movement when a straight line connecting the position indicating the magnetic flux and the rotation center point of the developing roller 3 (= normally, a center line that bisects the magnetic flux density distribution in the vertical direction) is moved to the left and right in the circumferential direction of the developing roller 3 It is a graph which shows the change of developer conveyance amount (mg / cm < ² >) with respect to distance (cm). In this graph, the position where the straight line connecting the rotation center point of the developing roller 3 and the rotation center point of the photosensitive drum 8 coincides with the straight line connecting the position showing the maximum magnetic flux and the rotation center point of the developing roller 3. “0”. In the graph of FIG. 4, the X-axis value is not a direct movement distance but a value on the measurement jig when the measurement jig is used. Further, in FIG. 4, the ▪ mark is a measured value of the developer transport amount at the central portion 15a, and the ♦ mark is a measured value of the developer transport amount at both ends 15b. From this graph, no matter where the groove 15 is formed on the surface of the developing roller 3, the central portion 15a and both end portions 15b have the developer transport amount (about ²⁰ to 70 mg / cm ^{2 and} about 60 to 90 mg / cm ^2). ).

  In this way, the groove 15 is set to have a higher developer conveyance amount at the both end portions 15b than at the central portion 15a. Therefore, before being restricted by the doctor blade 4, the developer conveyance amount per unit length of both end portions 15b is larger than the developer conveyance amount per unit length of the central portion 15a. When the restriction by the doctor blade 4 is applied in such a state, the doctor gap at the both end portions 15b is narrower than that at the central portion 15a. For this reason, without considering the bending of the doctor blade 4, simply adjusting the doctor gap by moving the doctor blade 4 close to the developing roller 3 or away from the developing roller 3 allows the high-definition image or the high-density image to be displayed. A developer amount suitable for formation can be carried on the surface of the developing roller 3.

  Although at least one groove 15 is formed on the surface of the developing sleeve 12 as described above, it is preferable that the formation region be a region excluding both end portions in the developing roller axial direction. As a result, it is possible to more reliably prevent the developer from scattering into the developing apparatus 1 and thus into the image forming apparatus, the accompanying deterioration in image quality, and the surface of the photosensitive drum 8 from being damaged.

  Further, it is preferable that the surface of the developing sleeve 12 where the groove 15 is formed is subjected to a roughening process except for the inner wall surface and the bottom of the groove 15. As a result, the developer conveyance amount is further quantified, so that a high-definition and high-density image can be stably formed over a long period of time. Further, by excluding the inner wall surface and bottom of the groove 15 from the roughening treatment, the amount of developer entering the groove 15 is determined only by the width dimension W, depth dimension D and shape of the groove. The setting of the developer transport amount of 15 can be facilitated, and the image to be formed can be further refined.

  Further, the surface roughening treatment method is not particularly limited, and any known method can be adopted. Further, although the degree of roughening is not particularly limited, the roughening treatment is preferably performed so that the ten-point average roughness Rz is in the range of 40 to 100 μm. If it is less than 40 μm, the coefficient of friction on the surface of the developing sleeve 12 becomes small, and the developer conveyance amount may decrease. If it exceeds 100 μm, the friction coefficient on the surface of the developing sleeve 12 becomes too large and the developer conveyance amount becomes excessive, and the development stress due to clogging in the portion between the developing sleeve 12 and the doctor blade 4 increases. There is a possibility that poor conveyance of the agent, deterioration, etc. may occur and good image formation cannot be performed.

  When the developer is a two-component developer including toner and carrier, the width dimension W in the circumferential direction of the developing roller at the groove opening portion of the groove 15 is selected from a range of 2 to 5 times the carrier particle diameter. It is preferable to do this. If it is less than 2 times, the entry of the developer into the groove is limited, and the developer transport amount becomes insufficient, so that an image having a high image density may not be obtained. On the other hand, if it exceeds 5 times, the developer conveyance amount becomes too large, and the developer is clogged between the developing roller 3 and the doctor blade 4 and the accompanying development stress increases. May occur.

  The depth D from the groove opening to the bottom of the groove 15 is preferably selected from a range of 1 to 3 times the carrier particle diameter. If it is less than 1 time, the developer conveyance amount becomes insufficient and an image with a high image density may not be obtained. On the other hand, if it exceeds three times, the replacement of the developer in the groove does not proceed smoothly, and there is a risk that image quality defects such as ghosts may occur. Further, the mechanical strength of the developing sleeve 12 becomes insufficient, and the durability and productivity of the developing roller 3 may be reduced.

  Further, when a plurality of grooves 15 are formed in the circumferential direction of the developing roller, the distance between the center positions in the circumferential direction of the developing roller between adjacent grooves 15 is in the range of 20 to 30 times the carrier particle diameter. It is preferable to select. If the ratio is less than 20 times, the developer conveyance amount becomes excessive, and the developer is clogged between the developing roller 3 and the doctor blade 4 and the development stress is increased accordingly. There is a fear. On the other hand, if it exceeds 30 times, the number of grooves decreases, the developer transport amount becomes insufficient, and an image having a sufficient image density may not be obtained.

  Although the developing sleeve 12 can be formed using a material commonly used in this field, it is preferable to use a conductive material. Examples of the conductive material include a metal composition, a resin composition obtained by adding a conductive material to a resin, and a rubber composition obtained by adding a conductive material to a rubber material. The resin composition may be a foam, and the rubber composition may be vulcanized.

  Since a DC superimposed AC voltage is applied between the developing roller 3 and the photosensitive drum 8 and an alternating electric field is generated in the developing region, only toner having a charge from the magnetic brush-shaped developer layer on the surface of the developing roller 3 is generated. Is attached to the electrostatic latent image on the surface of the photosensitive drum 8, whereby the developing operation is executed.

  The photosensitive drum 8 facing the developing roller 3 is provided so as to be rotatable in the direction of the arrow 14 (clockwise direction). As shown in the figure, the rotation direction around the axis of the developing roller 3 and the rotation direction around the axis of the photosensitive drum 8 are preferably opposite to each other. As a result, in the development region where the developing roller 3 and the photosensitive drum 8 are close to each other, the developing roller 3 and the photosensitive drum 8 are provided so as to rotate in the same overflow rotation direction. At this time, the rotational peripheral speed of the developing roller 3 is preferably set to 1.0 times or more, more preferably 1.5 times or more the rotational peripheral speed of the photosensitive drum 8. As a result, the developer is supplied without difficulty to the latent image portion on the surface of the photosensitive drum 8, and a high-definition image can be stably formed. If the rotational peripheral speed of the developing roller 3 is significantly lower than 1.5 times the rotational peripheral speed of the photosensitive drum 8, the amount of toner supplied to the electrostatic latent image on the surface of the photosensitive drum 8 is excessively reduced, which is sufficient. An image having an image density may not be formed. The rotation direction and the peripheral speed ratio are not limited to the above, and for example, the rotation direction around the axis of the photosensitive drum 8 and the rotation direction around the axis of the developing roller 3 are the same direction and are opposite in the development region. Even if the peripheral speed ratio between the photosensitive drum and the developing roller is set to 2.0 or more, the toner is supplied to the latent image portion on the surface of the photosensitive drum 8 without difficulty. Therefore, high-definition images can be formed stably.

  The doctor blade 4 is a plate-like member that regulates the layer thickness of the developer layer (the spike-shaped magnetic brush) carried in the groove 15 formed on the surface of the developing roller 3, and the tip edge thereof is against the surface of the developing roller 3. Provided with a predetermined interval (doctor gap). The doctor blade 4 is fixed and clamped to the wall surface of the developing tank 2 by screws 16a and 16b in the vicinity of the opening 9 of the developing tank 2. When fixing the doctor blade 4 to the developing tank 2 with the screws 16a and 16b, the dimensions of the developing tank 2 and the doctor blade 4 are not completely matched, or the screwing positions of the developing tank 2 and the doctor blade 4 are not completely matched. In many cases, the doctor blade 4 cannot be provided in parallel to the developing roller 3 because the stress from both ends by the screws 16a and 16b is larger than the necessary amount. In the present embodiment, the doctor blade 4 is bent, and the doctor blade 4 is bent in such a shape that the central portion in the developing roller axial direction is separated from the developing roller 3. Accordingly, the doctor gap, which is the distance between the developing roller 3 and the doctor blade 4, is larger at the central portion in the axial direction of the developing roller 3 than at both ends. Moreover, in this Embodiment, although the plate-shaped member made from aluminum is used for the doctor blade 4, it is not limited to it, For example, the plate-shaped member which consists of stainless steel etc. can be used.

  The first stirring roller 5 is provided on the opposite side of the developing roller 3 from the photosensitive drum 8 so as to face and separate from the developing roller 3, and in the axial direction in conjunction with the developing roller 3 by a driving means (not shown). It is the cylindrical member provided so that rotation drive is possible. The toner and the carrier are slid by the rotation (stirring) of the first agitating roller 5, and the contact friction at that time gives the toner a sufficient charge necessary for developing the electrostatic latent image on the surface of the photosensitive drum 8. . The first stirring roller 5 sufficiently charges the toner as described above, and feeds the developer containing the sufficiently charged toner around the developing roller 3.

  The second stirring roller 6 is provided on the opposite side to the developing roller 3 with respect to the first stirring roller 5 so as to face and separate from the first stirring roller 5, and is further provided in a cylindrical shape that can be rotationally driven by a driving means (not shown). It is a member. The toner supplied into the developing tank 2 from the toner replenishing port 10 formed on the developing tank wall above the second stirring roller 6 by the rotation (stirring) of the second stirring roller 6 and the developer in the developing tank 2. The toner is preliminarily charged by mixing, and the developer is fed around the first stirring roller 5.

  The toner sensor 7 is mounted on the bottom surface of the developing tank below the first stirring roller 5, and is provided so that the sensor surface is exposed inside the developing tank 2. When the developing device 1 is incorporated in an electrophotographic image forming apparatus (not shown), the toner sensor 7 is electrically connected to a CPU (not shown) that controls various operations of the image forming apparatus. Then, the toner concentration in the developing tank 2 is detected by the toner sensor 7, and the detection result is delivered to the CPU. The CPU determines whether toner can be supplied to the developing tank 2 based on the detection result. When it is determined that the toner needs to be replenished, a control signal is sent to replenish the toner into the developing tank 2 from a toner storage container (not shown) via the toner replenishing port 10.

  The two-component developer used in the developing device 1 of the present invention includes a toner and a carrier. As the toner and carrier, any of those conventionally used in electrophotography can be used. However, a two-component developer containing a negatively chargeable nonmagnetic toner and a positively chargeable magnetic carrier is used, and a negatively charged photosensitive drum is further used. It is preferable to use it. As a result, it is possible to easily and stably implement high-definition images, and it is easy to reduce costs and digitize images.

  According to the developing device 1, the developer replenished from the toner replenishing port 10 of the developing tank 2 is charged by the rotation of the first stirring roller 5 and the second stirring roller 6 and supplied to the periphery of the developing roller 3. In the groove 15 on the surface of the developing roller 3, developer layers having different amounts of developer are carried in the developing roller axial direction. By restricting the developer layer with a doctor blade 4 having a different doctor gap in the developing roller axial direction, the developer transport amount on the surface of the developing roller 3 is made uniform. Toner is supplied to the electrostatic latent image and the electrostatic latent image is developed.

  In the present embodiment, the groove 15 formed on the surface of the developing roller 3 has a rectangular shape in a cross section perpendicular to the axis of the developing roller 3, but the groove shape is not limited to a rectangular shape, and is V-shaped. It can be formed in various groove shapes such as a trapezoidal shape, a trapezoidal shape, and a semicircular shape.

  In the present embodiment, only the groove 15 is formed on the surface of the developing roller 3. However, the present invention is not limited to this, and a groove having the same developer conveyance amount in the axial direction of the developing roller may be formed together with the groove 15. it can.

  FIG. 5 is a top view showing a configuration of grooves 21, 22, and 23 formed on the surfaces of developing rollers 20a, 20b, and 20c according to another embodiment of the present invention. The grooves 20, 21, and 22 are all assumed to have a square groove shape and an equal depth dimension.

  The groove 21 is formed such that the width dimension of both end portions 21y in the developing roller axial direction is larger than that of the central portion 21x. As a result, the developer transport amount per unit length of the both end portions 21y can be increased more than that of the central portion 21x.

  The groove 22 is formed such that the width dimension increases stepwise from the central portion 22x in the developing roller axial direction toward both end portions 22y. As a result, the developer transport amount can be increased stepwise from the central portion 22x toward both end portions 22y.

  The groove 23 is formed so that the width dimension continuously increases from the central portion 23x in the axial direction of the developing roller toward both end portions 23y. As a result, it is possible to meticulously cope with a continuous change in the doctor gap when the doctor blade is bent, and the developer conveyance amount can be continuously increased.

  Since the developer layers carried in the grooves 21, 22, and 23 are subjected to layer thickness regulation by the doctor blade in a bent state, the developer conveyance amount on the surface of the developing roller can be made more uniform, and image defects are generated. Therefore, it is possible to cope with higher density and higher definition of the image.

  FIG. 6 is a side view showing a configuration of grooves 24a, 24b, and 24c formed on the surface of the developing roller according to another embodiment of the present invention. The grooves 24a, 24b, and 24c are assumed to have a square groove shape and equal width dimensions.

  The groove 25 is formed so that the depth dimension of both end portions 25y in the developing roller axial direction is larger than that of the central portion 25x. As a result, the developer transport amount per unit length of the both end portions 25y can be increased more than that of the central portion 25x.

  The groove 26 is formed so that the depth dimension increases stepwise from the central portion 26x in the developing roller axial direction toward both end portions 26y. As a result, the developer conveyance amount can be increased stepwise from the central portion 26x toward both end portions 26y.

  The groove 27 is formed so that the depth dimension continuously increases from the central portion 27x in the axial direction of the developing roller toward both end portions 27y. As a result, it is possible to meticulously cope with a continuous change in the doctor gap when the doctor blade is bent, and the developer conveyance amount can be continuously increased.

  Since the developer layer carried in the grooves 25, 26, and 27 is subjected to layer thickness regulation by the doctor blade in a bent state, the developer conveyance amount on the surface of the developing roller is made more uniform, and image defects are generated. Therefore, it is possible to cope with higher density and higher definition of the image.

  The developing device 1 of the present invention can be suitably used as a developing means in an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile that has been conventionally used.

1 is a cross-sectional view schematically showing a configuration of a developing device according to a first embodiment of the present invention. It is a side view which shows typically the structure of the principal part of the developing device shown in FIG. FIG. 6 is a cross-sectional view of a rectangular groove extending in the developing roller axial direction in a direction perpendicular to the developing roller axis. It is a graph which shows the change of the developer conveyance amount of the groove | channel on the basis of a main pole (N1). It is a top view which shows typically the structure of the groove | channel formed in the surface of the developing roller which is other embodiment of this invention. It is a side view which shows typically the structure of the groove | channel formed in the surface of the developing roller which is other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing device 2 Developing tank 3 Developing roller 4 Doctor blade 5 1st stirring roller 6 2nd stirring roller 7 Toner sensor 8 Photosensitive drum 9 Opening part 10 Toner replenishing port 11 Magnetic generating member 12 Developing sleeve 13, 14 Arrow 15, 21, 22, 23, 25, 26, 27 grooves

Claims (13)

A developing roller that is provided so as to be in contact with or close to the photosensitive drum and supplies developer to the electrostatic latent image on the surface of the photosensitive drum, and grooves are formed in regions other than both ends in the axial direction of the developing roller. A developing roller,
A stirring roller that frictionally mixes the developer and supplies it to the periphery of the developing roller;
A doctor blade that regulates the layer thickness of the developer layer that is provided in contact with or close to the surface of the developing roller and carried on the surface of the developing roller;
In a developing device including a developing roller, a stirring roller, a doctor blade, and a developing tank containing a developer,
The groove has a groove opening provided on the surface of the developing roller, and a bottom provided nearer to the axial center of the developing roller than the groove opening, and is formed to extend in the axial direction of the developing roller. Further, by changing only the groove shape in the cross section perpendicular to the axis of the developing roller without changing the width dimension in the circumferential direction of the developing roller at the groove opening part and the depth dimension from the groove opening part to the bottom part , the developing roller In the axial direction of the groove, the developer transport capability at both ends of the groove is higher than the developer transport capability at the center of the groove,
The developing device, wherein the doctor blade is bent so that a central portion thereof is separated from the developing roller. The groove is
2. The developing device according to claim 1, wherein the developer conveying capability is increased stepwise from a central portion of the groove toward both ends in the axial direction of the developing roller. The groove shape of the groove in a cross section perpendicular to the axis of the developing roller is
The developing device according to claim 1, wherein the developing device is rectangular, trapezoidal, V-shaped, or semicircular. In the region where the groove on the surface of the developing roller is formed,
The developing device according to claim 1, wherein the surface of the developing roller excluding the inner wall surfaces and bottom portions of the plurality of grooves is subjected to a roughening process. The roughening process is
The developing device according to claim 4, wherein the ten-point average roughness Rz is 40 to 100 μm.   6. The developing according to claim 1, wherein the photosensitive drum and the developing roller rotate in the same direction, and a peripheral speed ratio between the photosensitive drum and the developing roller is 1.0 or more. apparatus.   6. The development according to claim 1, wherein the photosensitive drum and the developing roller rotate in opposite directions, and a peripheral speed ratio between the photosensitive drum and the developing roller is 2.0 or more. apparatus. Developer is
The developing device according to claim 1, wherein the developing device is a two-component developer including a toner and a carrier. After the developer is carried on a developing roller provided in the developing device and the amount of the developer is regulated by a doctor blade provided in the developing device, the toner contained in the developer is transferred to the electrostatic latent image on the surface of the photosensitive drum. In the development method of supplying to the development and developing
Mizoguchi portion provided in the developing roller surface, and has a bottom portion than the groove opening is provided in the axial center side of the developing roller, and a groove formed so as to extend in the axial direction of the developing roller, Mizoguchi portion By changing only the groove shape in the cross section perpendicular to the axis of the developing roller without changing the width dimension in the circumferential direction of the developing roller and the depth dimension from the groove opening to the bottom , the axial direction of the developing roller, The developer is carried in a groove formed such that the developer conveying ability at both ends of the groove is higher than the developer conveying ability at the center of the groove,
A developing method characterized in that the amount of the developer is regulated by a doctor blade that is bent so that a central portion is separated from the developing roller. The groove is
In the axial direction of the developing roller, the developer conveying capacity at both ends of the groove is 60 to 90 mg / cm ² , and the developer conveying capacity at the center of the groove is 20 to 70 mg / cm ^2. The developing method according to claim 9.   11. The development according to claim 9, wherein a width dimension in a circumferential direction of the developing roller at a groove opening portion of the groove is in a range of 2 to 5 times a particle diameter of a carrier contained in the developer. Method.   The depth dimension from the groove opening part to the bottom part of the groove is in the range of 1 to 3 times the particle diameter of the carrier contained in the developer. The developing method as described.   The distance between the center positions of grooves adjacent to each other in the circumferential direction of the developing roller is in the range of 20 to 30 times the particle diameter of the carrier contained in the developer. The developing method according to any one of the above.

Images