JP2008026572A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that can prevent replenished toner from reaching a developing sleeve directly in a low-charged state or uncharged state, then, prevent image density unevenness, toner scattering, etc., and to provide a developing unit and an image forming apparatus. <P>SOLUTION: The developing device includes: a toner-replenishment-side agitating screw 11 as an agitating means for agitating and dispersing a two-component developer consisting of toner and a carrier in a developer container and conveying it to a predetermined position; a toner replenishing device 30 as a toner replenishing means for replenishing toner consumed for development; and a mono pump as an air replenishing means for replenishing air, wherein an air blast nozzle 32 connected to the mono pump is disposed upstream of the toner replenishment hole 20 to which the toner is replenished, in the conveying direction of the two-component developer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device in an electrophotographic image forming apparatus.

  2. Description of the Related Art In recent years, along with market demands for image forming apparatuses using electrophotographic technology such as copiers and printers and for personalization, the developing apparatuses have been downsized. Further, in response to such a request, when the toner runs out, the disposable developing device that is replaced with the developing device, or a latent image carrier (on which an electrostatic latent image of the original image is formed) in addition to the developing device. A so-called process cartridge in which a photosensitive member) and a cleaning unit for removing toner remaining on the photosensitive member are integrated is also widely used.

  In one of the electrophotographic image forming methods, the so-called two-component development method, generally, the developer is a carrier (iron powder having a diameter of 30 to 200 microns), toner (a fine resin powder in which a pigment having a diameter of 10 microns is dispersed). It consists of two kinds. By mixing and stirring both, the toner is charged by friction with the carrier. When this triboelectric charge is non-uniform or insufficient, problems such as image quality deterioration and increase in scattered toner occur.

  One of the reasons why this triboelectric charge becomes uneven and insufficient is as follows. As the machine speed increases, the developer agitating and conveying member rotates at a high speed, and the toner is fine particles. Therefore, a part of the replenished toner is scattered or floated without being agitated well with the developer. Move up and down. When such toner is transported to the developing roller and transported to the developing area, uncharged, reversely charged, and weakly charged poorly charged toner causes non-image area background contamination, density unevenness, and toner scattering.

  It is thought that the problem of the top slip of the replenished toner is caused by the fact that the replenished toner cannot be mixed well because the flow characteristics and surface characteristics of the replenished toner are different from the already filled developer. The surface characteristics of the developer depend on the history, and it is very difficult to always make the parameters such as the fluidity of the replenishment toner and the developer equal.

  Further, depending on the screw shape, the carrier and the toner may not be sufficiently stirred. Although this involves the friction phenomenon between the powder surface and the screw, both measurement and numerical simulation are difficult, and many rely on the experience of conventional designers.

  In order to eliminate such a problem, in the conventional developing device, the number of fins attached downstream of the screw in the replenishment side stirring chamber is made larger than that in the upstream side, so that the agent level in the replenishment side stirring chamber is increased between upstream and downstream. The structure to change is proposed (for example, refer patent document 1). Since this is a countermeasure only for the screw shape, the mixing of the replenishing toner and the developer stays in the region within the fin rotation radius, which is insufficient as a countermeasure against the upper slip generated on the surface of the agent.

  On the other hand, there is one that transports developer and toner using air (see, for example, Patent Documents 2, 3, and 4). These have an air supply means in the toner replenishing device provided outside the developing unit, and increase the fluidity by air to improve the conveyance efficiency, reduce the cost, improve the reliability, improve the design margin, etc. Has an effect. However, even in these inventions, when supplying the replenishment toner to the developer, it cannot be said that the agitation is sufficiently improved even by the replenishment toner that contains a large amount of air and has increased fluidity.

Further, in order to prevent a decrease in the charge amount of the toner and a decrease in the fluidity as the developer, a dry gas (for example, nitrogen gas) is supplied into the developer according to the humidity of the developer in the developer. Some of them maintain a constant humidity (see, for example, Patent Document 5).
JP 2004-272017 A JP-A-11-272075 JP 2005-141271 A JP 2005-250508 A JP-A-6-19293

  As described above, the conventional developing device has insufficient points to prevent the replenishment toner from slipping and to uniformly disperse the toner.

  The present invention has been made to solve the conventional problems, and can prevent the replenished toner from reaching the developing sleeve directly in a low-charged state or an uncharged state, thereby preventing image density unevenness and toner scattering. An object is to provide a developing device, a developing unit, and an image forming apparatus.

  In order to solve the above-mentioned problems, the present invention creates a state in which mixing of developer and replenishment toner is promoted at a toner replenishment location by effectively mixing air into the developer, and a new replenishment toner is always used as a developer. And quickly agitate sufficiently.

  The developing device according to claim 1, wherein the two-component developer composed of toner and carrier is stirred and dispersed by rotation of two screws provided in the developer container and conveyed to a predetermined position. A toner replenishing unit that replenishes toner consumed by development, and an air supply unit that supplies air to the upstream side in the transport direction by the agitation unit with respect to a location where the toner is replenished by the toner replenishing unit; The air supply means supplies the air at a timing earlier than the timing at which the toner is replenished by a certain time.

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the position of the tip of the air inlet of the air supply means is variable with respect to the conveying direction of the two-component developer.

  According to a third aspect of the present invention, there is provided the developing device according to the first aspect, wherein the air supply means has a plurality of air inlets.

  According to a fourth aspect of the present invention, there is provided the developing device according to the first aspect, wherein the toner replenishing unit replenishes toner toward an air ejection surface formed at an interface of the two-component developer by air injection of the air supply unit. have.

  According to a fifth aspect of the present invention, there is provided the developing device according to the first aspect, wherein the tip of the air inlet of the air supply means is provided on the axial wall surface of the screw of the stirring means.

  A developing device according to a sixth aspect of the present invention is the developing device according to the first aspect, wherein the screw of the stirring means rotates in a forward and reverse direction according to a predetermined condition.

  A developing device according to a seventh aspect is the developing device according to the first aspect, wherein a part of the blade shape of the screw of the stirring means in the region close to the location is at least parallel to the axial direction of the screw and has two components It has a configuration having a shape having a region perpendicular to the developer conveyance direction.

  A developing unit according to an eighth aspect includes: the developing device according to any one of the first to seventh aspects; a latent image carrier; a charging device; and a cleaning device for the latent image carrier. At least two or more are integrally formed.

  An image forming apparatus according to a ninth aspect includes the developing unit according to the eighth aspect.

  The present invention includes an air supply unit that supplies air to the upstream side in the conveyance direction by the stirring unit, and the timing at which the air supply unit supplies the air is higher than the timing at which the toner is supplied to a predetermined location by the toner supply unit. The developing device has the effect of preventing the replenished toner from reaching the developing sleeve directly in a low or uncharged state and preventing unevenness in image density, toner scattering, etc. Can be provided.

  Hereinafter, an image forming apparatus to which a developing device of the present invention is applied will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a color image forming apparatus as an embodiment of the present invention. More specifically, this is a tandem indirect transfer type electrophotographic copying apparatus (hereinafter also referred to as “color copying apparatus”).

  In FIG. 1, a color copying apparatus includes a copying apparatus main body 100, a paper feed table 200 on which the copying apparatus main body 100 is placed, a scanner 300 attached to the copying apparatus main body 100, and an automatic document transport attached on the scanner 300. Device (ADF) 400.

  In the center of the copying apparatus main body 100, an endless belt-like intermediate transfer body 110 extending in the lateral direction is provided. Here, the intermediate transfer member 110 is wound around three support rollers 114, 115, and 116 so as to be able to rotate and convey clockwise in the figure. An intermediate transfer member cleaning device 117 is provided on the left side of the support roller 115 among the three support rollers 114, 115, 116. This removes residual toner remaining on the intermediate transfer body 110 after image transfer.

  Of the three support rollers 114, 115, 116, the intermediate transfer body 110 stretched between the support rollers 114 and 115 is black, yellow, and yellow along the transport direction (belt movement direction). , Magenta, and cyan image forming means 118 are arranged side by side to constitute a tandem image forming unit 120. An exposure device 121 is provided immediately above the tandem image forming unit 120.

  Further, a secondary transfer device 122 is provided on the side opposite to the tandem image forming unit 120 with the intermediate transfer member 110 interposed therebetween. This is formed by suspending a secondary transfer belt 124 formed of an endless belt between two rollers 123 and pressing the support roller 116 via the intermediate transfer body 110 to arrange an image on the intermediate transfer body 110. Is transferred to a sheet.

  Next to the secondary transfer device 122, a fixing device 125 for fixing the image transferred to the sheet is provided. Here, the pressure roller 127 is pressed against the fixing belt 126 formed of an endless belt. The secondary transfer device 122 also has a sheet conveying function for conveying the image-transferred sheet to the fixing device 125. A sheet reversing device 128 for reversing the sheet for recording images on both sides of the sheet is provided below the secondary transfer device 122 and the fixing device 125 in parallel with the tandem image forming unit 120.

  When copying using the above-described color copying apparatus, a document is set on the document table 130 of the ADF 400. Alternatively, the ADF 400 is opened, a document is set on the contact glass 132 of the scanner 300, the ADF 400 is closed, and the document is pressed. Next, when a start key (not shown) is operated, the scanner 300 is driven after the document set on the document table 130 is conveyed onto the contact glass 132 or immediately, and the first traveling body 133 and the second traveling body 134 are driven. To run. Next, the first traveling body 133 emits light from the light source, and reflected light reflected from the document surface is further reflected toward the second traveling body 134 and reflected by the mirror of the second traveling body 134 to form the imaging lens 135. And enters the reading sensor 136 to read the content of the document.

  Further, when a start key (not shown) is operated, one of the paper feed rollers 142 of the paper feed table 200 is selected and rotated, and a sheet is fed out from one of paper feed cassettes 144 provided in multiple stages in the paper bank 143. The paper is separated one by one by the separation roller 145 and put into the paper feed path 146, transported by the transport roller 147, guided to the paper feed path 148 of the copying apparatus main body 100, and abutted against the registration roller 149 and stopped. Next, the registration roller 149 is rotated in synchronization with the composite color image on the intermediate transfer member 110, and the sheet is fed between the intermediate transfer member 110 and the secondary transfer device 122. The sheet is transferred by the secondary transfer device 122 and transferred. Record a color image on top. The image-transferred sheet is conveyed from the secondary transfer device 122 to the fixing device 125, and heat and pressure are applied by the fixing device 125 to fix the transferred image. Then, the sheet is switched by the switching claw 155 and discharged by the discharge roller 156. And stacked on the paper discharge tray 157. Alternatively, the sheet is switched by the switching claw 155 and is put into the sheet reversing device 128, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged to the discharge tray 157 by the discharge roller 156.

  On the other hand, the intermediate transfer body cleaning device 117 removes residual toner remaining on the intermediate transfer body 110 after image transfer, and prepares for the next image formation by the tandem image forming unit 120. In the tandem image forming unit 120, each image forming unit 118 includes a charging device, a developing device, a primary transfer device, a photoconductor cleaning device, a static elimination device, and the like around the drum-shaped photoconductor 1. Yes. Here, the photosensitive member 1, the charging device, the developing device, the primary transfer device, the photosensitive member cleaning device, or the charge eliminating device (for example, at least two or more of the photosensitive member 1, the charging device, the developing device, and the photosensitive member cleaning device). Are integrated as a developing unit (so-called process cartridge).

  FIG. 2 is a sectional view showing the developing device. FIG. 3 is a cross-sectional view showing the configuration inside the developer container in the developing device.

  In FIG. 2, the developing device 61 includes, in a developer container, a toner replenishment side stirring screw 11 as a developer stirring means, a developer carrier side stirring screw 12, and a developer carrier (developing roller) 13. A toner supply port (not shown) (corresponding to 20 in FIG. 3) is provided on the outer wall of the container of the first developer stirring chamber 14, and toner is supplied from a toner supply device (corresponding to 30 in FIG. 3). I am doing so. Hereinafter, the first developer stirring chamber is referred to as a supply side stirring chamber 14. The toner replenishing side agitation screw 11 agitates and conveys the toner replenished from the toner replenishing device and the developer (two-component developer having magnetic particles and toner) in the developer container. Further, the agitation screw 12 in the second developer agitation chamber 15 (developer carrier side) agitates and conveys the developer in the developer container. Hereinafter, the second developer stirring chamber is referred to as a development side stirring chamber 15.

  Further, as shown in FIG. 3, the replenishment side stirring chamber 14 and the development side stirring chamber 15 in the developer container 65 are partitioned by a partition plate 80, and the developer is delivered to both ends of the developer container 65. There is an opening for. Further, for example, the replenishing toner is injected by dropping from above at the position of the toner replenishing port 20.

[First embodiment]
FIG. 4 is a schematic diagram showing how toner is supplied from the toner supply device 30 to the supply side stirring chamber 14. This is the developer container 65 viewed from the viewpoint direction A (shown in FIG. 3). The direction of gravity is from top to bottom in the figure.

  As shown in FIG. 4, the toner replenishing device 30 conveys replenished toner from a toner storage device (not shown) by a replenishing toner conveying screw 31, and enters the replenishing side stirring chamber 14 from the opening (left side in the figure) by gravity. Drop and replenish. A region where the replenishment toner falls into the developer in the replenishment side stirring chamber 14 is referred to as a toner replenishment port 20.

  An air outlet (nozzle) 32 is inserted below the replenishment side stirring chamber 14 at a position not in contact with the replenishment side stirring screw 11 and upstream of the toner replenishment port 20 with respect to the developer transport direction. . The air ejection port 32 is connected to a volume change type pump (hereinafter referred to as “mono pump”) using a single-shaft eccentric screw (not shown), and air can be inserted at an arbitrary timing and an arbitrary time. The mono pump is compatible with high pressure loss systems and can be used in powder fields. For example, when a pressure of 5 k (Pa) is applied for 0.3 (s) by using a monopump, a powder region having a small bulk density is generated in the vicinity of the air insertion port in the developer in the replenishing side stirring chamber 14. . This region has a very high mixing property, and the replenishment toner can be appropriately mixed into the developer using this region.

  Direct observation of how the toner replenished in the developer is dispersed is impossible with visible light. Therefore, this effect is achieved by applying the X-ray visualization technique using the metal tracer described in Japanese Patent Application No. 2005-075247 (reference number: 200403529) and Japanese Patent Application No. 2005-269535 (reference number: 200505037) by the same applicant. Validate.

Here, glass beads “GBL100” defined in “JIS-Z8901” simulating a developer was used as the powder. Further, tungsten powder having the same average diameter was used as the metal tracer. The characteristics of both are shown in FIG. In the X-ray visualization technology described in Japanese Patent Application No. 2005-075247, the difference between the agent (for example, glass beads) and the metal tracer (for example, tungsten powder) due to the difference in specific gravity is almost no in such a screw conveyance system. Prove that it doesn't matter. The state of mixing is evaluated by injecting a metal tracer in the same state as the supply of replenishing toner, and visualizing and observing the behavior of the metal tracer.
FIG. 6 is a cross-sectional view showing the shapes of the replenishment side agitation screw 11 and the replenishment side agitation chamber 14 used for evaluating the mixing properties of the glass beads and the metal tracer.

  Here, the screw pitch is 25 mm, the screw shaft diameter is 6 mm, the screw diameter is 18 mm, and the stirring chamber width is 20 mm.

  FIG. 7 is a view showing an X-ray transmission image of the replenishment side stirring chamber 14 before and after mixing of the metal tracer. FIG. 8 is a diagram showing a pressure generation profile of the monopump.

  FIG. 7A is a visualized image before the tracer is mixed, and X-ray transmission images of the tracer injection device 40 and the screw 11 are shown. Here, the arrow indicates the conveyance direction of the glass beads simulating the developer. FIG. 7 (b) shows a metal tracer pass line in the case where there is no air outlet at the bottom of the replenishment side stirring chamber 14. FIG. 7C shows a pass line of a metal tracer in the case where an air outlet is provided at the lower part of the replenishment side stirring chamber 14. In both (b) and (c), the rotational speed of the screw is 24 rpm. The aforementioned pass line image is created by the method described in Japanese Patent Application No. 2005-269535. The pass line is an image obtained by integrating the tracer image at each time over time. The observation region in FIG. 7 corresponds to the observation range indicated by the dotted line in FIG. 3, and the direction in which gravity acts is the direction perpendicular to the paper surface. In FIG. 8, the x-axis indicates time (seconds), and the y-axis indicates the pressure difference on the intake side from the atmosphere.

  Here, the behavior of the pass lines in FIG. 7B and FIG. 7C will be compared. There are two major differences. 1) Pass line is greatly diffused with air insertion. 2) With air insertion, immediately after turning on the tracer, it moves slightly in the direction opposite to the transport direction as shown by the circle in FIG. 7 (c). The agent density (bulk density) in the vicinity of the tracer inlet is lowered by air insertion, and the tracer easily reaches the center of the agent. This is considered to move in the direction opposite to the conveying direction due to the positional relationship with the screw blades. Further, regarding the diffusion of the pass line, which is the effect of 1), the diffusion coefficient indicating the magnitude of the system diffusion was quantitatively measured by the following image measurement technique (procedure 1 to procedure 6).

  In the procedure 1, the background is removed from the X-ray transmission image by the method described in Japanese Patent Application No. 2005-269535, and a visualized image having only a tracer image is prepared.

  In step 2, a plurality of states in which the center of gravity of the tracer image area is located on the central axis of the screw are selected from the visualized images. Specifically, the background is removed from the visualized image (with background) at two times (time = t1, t2 (t2> t1)) shown in FIGS. 9A and 9B, and FIGS. The visualized image (without background) shown in d) is acquired.

  In step 3, the metal tracer of the image selected in step 2 is assumed to be an ellipsoid, and the pixel density distribution is measured for each pixel (hereinafter referred to as “pixel”) in the major axis direction. Here, FIG. 11A shows a pixel density measurement line in the major axis direction of the metal tracer at time = t1, and FIG. 11B shows a pixel density measurement line in the major axis direction of the metal tracer at time = t2. Is shown.

  The metal tracer performs a spiral motion about the central axis of the screw. Since the X-ray image is a two-dimensional projection plane, the positional relationship between the projection plane and the tracer needs to be the same in order to relatively compare changes in the tracer area. This time, the tracer image located on the central axis of the screw was used for measurement. Here, FIG. 10 shows the correspondence between the metal tracers 51 and 52 and the tracer images 53 and 54 on the screw central axis of the X-ray projection plane. Furthermore, (1) the size of the tracer region is sufficiently small with respect to the rotational radius of the spiral motion, and (2) the elliptical long axis direction of the tracer is located in parallel with the rotational direction of the spiral motion (tangential direction of the rotational circle). The range that satisfies what must be done is considered to be a range where there is no problem in observation.

In step 4, the density value is multiplied by a certain coefficient so that the area surrounding the pixel density distribution at each time and the x-axis becomes the area “1”. This operation is hereinafter referred to as “standardization”.
Although the tracer area is diffused, the overall mass (pixel density = a value obtained by integrating the density over the area) does not change. On the other hand, the volume V of the tracer ellipsoid is represented by “V = 4π (abc) / 3” (a, b, and c indicate the lengths of the ellipsoid in the x, y, and z axis directions). Here, the major axis direction is the x direction. In the X-ray transmission image, the pixel density “u” and the density “d” and transmission distance “D” of the transmissive substance located in the X-ray transmission direction have an exponential relationship. Thus, when the transmission distance is very small, it can be approximated by a linear expression such as “d = ku (k: coefficient)”.

  Then, if the concentration distribution in the x direction of the major axis is u (x), the y direction is u (y), and the z direction is u (z), then “m” as the mass of the tracer ellipsoid is given by equation (1). Indicated.

  For the sake of simplicity, tracer diffusion is performed by extending in the major axis direction, and assuming that there is no change in length or density in the other two directions, the above equation (1) can be approximated by the following equation (2). (K ′: constant).

  As described above, since the total mass of the tracer does not change, the mass m takes a constant value at each time.

  This expression (3) represents the area surrounded by u (x) indicating the concentration distribution in the x direction and the x axis. This value does not depend on time, and always takes a constant value as shown in Expression (4).

  Hereinafter, in order to approximate the distribution of u (x) with a normal distribution, a graph showing the equation (5) will be considered.

In step 5, the concentration distribution in the major axis direction of the tracer obtained in step 4 is assumed to be a normal distribution, and an appropriate variance is obtained by the least square method. Here, Equation (6) is shown as a probability density function equation of a general normal distribution. However, U is a density relative value, x is a pixel position, and σ ² is variance.

  An example of the result obtained by this is shown in FIG. In FIG. 12, the x-axis of the graph is a pixel distance (pixel) when the center of gravity position on the tracer long axis is the origin (x = 0), and the y-axis is a normalized pixel density relative value. The pixel distance can be converted to an actual spatial distance (mm) by multiplying the correction coefficient “c”. Here, c = 0.166.

In step 6, a preferable air ejection timing is obtained. Equation (7) is shown as a general one-dimensional diffusion equation. However, U is a density relative value, x is a pixel position, t is time, and κ ² is a diffusion coefficient.

  Here, the temporal intensity distribution of the point source having the intensity “1” placed at the origin (x = 0) at t = 0 is expressed by Expression (8). This is a special solution in which the boundary condition of the diffusion equation is a normal distribution type.

Here, κ ² is a diffusion coefficient, and the larger the value, the larger the diffusion of the system. Equation (8) is equivalent to Equation (6). That is, assuming that the metal tracer changes along a normal distribution, the magnitude of this change can be expressed by the diffusion coefficient of the diffusion equation. Comparing both equations, σ ² = 2κ ² t. Therefore, in the normal distribution curve of FIG. 12, assuming that σ ² at time = t1, t2 obtained by least square method approximation is σ ₁ ² , σ ₂ ² , the diffusion coefficient κ ² is given by equation (9).

Thereby, the diffusion term κ ² of the diffusion equation indicating the magnitude of the system diffusion can be obtained.
For the derivation of the diffusion coefficient, measurement data obtained by performing visualization 10 times under the same conditions were used. Further, when the area surrounded by the pixel density distribution measured in the procedure 3 and the x-axis (see formula (3)) is significantly different (here, 20% or more), it is determined as abnormal data and excluded from the measurement.

As a result of this measurement, κ ² = 0.23 (mm ² / s) in the case of “without air insertion”, κ ² = 1.23 (mm ² / s) in the case of “with air insertion”, The result that diffusion was increased by 5 times or more was obtained, and the significance exceeding the sufficient error range was measured.

The air insertion timing was 0.5 (s) after the toner replenishment timing. 0.0 Timing of air inserted from the toner supply (s), 1.0 average value of the diffusion coefficient kappa ² in (s), respectively ^{0.225 (mm 2 /s),0.5(mm 2 / s} ) Met. These values may be related to the air profile (monopump pressure generation profile) and the positional relationship between the air outlet 32 and the toner replenishing port 20, respectively, but at least the timing of air insertion is toner replenishment. However, it is desirable to delay for a certain time. Here, the air insertion timing control may be performed by the controller of the color copying apparatus on the air supply unit based on information from the toner supply device 30 (for example, a signal indicating the toner supply timing). .

  Further, if the amount of air jetted is too large, the developer surface may suddenly boil, and the agent balance may change greatly. When such a change in the agent balance is detected, it is desirable that the toner replenishing side agitation screw 11 and the developer carrier agitation screw 12 are appropriately set so as to be able to reversely rotate and have a function of restoring the agent balance. For example, a drive motor (not shown) as drive means for driving the toner replenishment side agitation screw 11 and developer carrier side agitation screw 12, and a microcomputer (color copying apparatus) as drive control means for controlling the drive of the drive motor The microcomputer may rotate the drive motor in the forward direction or the reverse direction based on a predetermined condition.

  According to the color copying apparatus as the first example of the embodiment of the present invention, the two-component developer composed of the toner and the carrier is stirred and dispersed in the developer container and conveyed to a predetermined position. Toner replenishment side agitating screw 11 and developer carrier side agitating screw 12 as the agitating means, toner replenishing device 30 as the toner replenishing means for replenishing the toner consumed by the development, and toner as a location where the toner is replenished By providing an air outlet 32 (corresponding to the air inlet) connected to a monopump serving as an air supply means for supplying air to the replenishment port 20 upstream in the developer conveying direction. A powder region having a small bulk density is generated near the air insertion opening in the developer. This area has a very high mixing property, and it is possible to appropriately mix the replenishment toner into the developer by using this area. As a result, the toner is prevented from slipping and the image quality is deteriorated and the scattered toner is prevented. An effect is obtained. In addition, since the timing of supplying air from the air ejection port 32 is a predetermined time earlier than the timing of newly supplying toner to the toner replenishing port 20, an appropriate replenishment timing for intermittent air insertion is defined. As a result, the above-described effects can be further improved. This configuration corresponds to an embodiment of claim 1.

Further, according to the present embodiment, for example, a drive motor (not shown) as drive means for driving the toner replenishment side stirring screw 11 and the developer carrier side stirring screw 12 and drive control for controlling the drive of the drive motor. A microcomputer is provided as a means, and as a predetermined condition, for example, when the air ejection amount is larger than a preset value, the developer motor surface is increased by rotating the drive motor in the forward direction or the reverse direction. It is possible to avoid the problem of sudden boiling and a large change in the agent balance. That is, it is possible to suppress side effects associated with the intermittent air insertion described above. This configuration corresponds to an embodiment of claim 6.
[Second Embodiment]
FIG. 13 is a cross-sectional view showing a configuration inside the developer container in the developing device 61. As in FIG. 3, this is a view looking down in parallel to gravity.

  In FIG. 13, the air jet 32a is installed so that the lower wall surface may be contacted with respect to the screw. Further, the front end portion of the air ejection port 32a (corresponding to the front end portion of the air injection port) is arbitrary in a region downstream of the toner supply port 20 in parallel with the central axis of the toner supply side stirring screw 11. It is configured to be able to move its location. The other air jet 32b is installed in the direction perpendicular to the air jet 32a so that the end of the jet coincides with the wall surface of the developer container. Here, the fluidity of the replenished toner may vary greatly depending on the humidity and temperature in the atmosphere. In such a case, the area where the toner drops onto the actual developer varies depending on the positional relationship with the toner supply port. Therefore, the stirring efficiency can be kept constant by dynamically changing the position of the air outlet 32a according to the fluidity of the replenishing toner. On the other hand, the air jet port 32b similarly maintains an appropriate bulk density of the mixing efficiency on the developer side by ejecting air from the vertical direction, particularly when the fluidity is significantly changed due to the deterioration of the developer. It becomes possible.

  According to the color copying apparatus as the second embodiment of the present invention, the air outlet 32a connected to the monopump as the air supply means and the air outlet 32a are arranged in the central axis direction (for example, developer Moving means (for example, a driving mechanism such as a rack and pinion) that moves in the transport direction), a moving driving means that drives the moving means (for example, a driving motor such as a stepping motor), and a movement that controls the moving driving means Control means (for example, the microcomputer), and the fluidity of the toner to be replenished is controlled by the humidity in the atmosphere by allowing the tip of the air jet port 32a to move in the transport direction of the two-component developer. Even when the temperature varies greatly depending on the temperature, it is possible to maintain an appropriate bulk density for the developer near the toner supply port. This configuration corresponds to an embodiment of the second aspect.

  In addition, according to the present embodiment, the plurality of air ejection ports 32a and 32b are provided in order to perform air insertion from different directions with respect to the toner replenishing port 20, so that the fluidity of the replenished toner is in the atmosphere. Even when it varies greatly depending on humidity and temperature, it is possible to maintain an appropriate bulk density for the developer near the toner supply port. This configuration corresponds to an embodiment of the third aspect.

[Third embodiment]
FIG. 14 is a cross-sectional view showing a configuration inside the developer container in the developing device 61. FIG. 15 is a cross-sectional view showing the developing device 61. 14 is a side view of the developer container 65, and FIG. 15 is an overhead view of the developer container 65.

  14 and 15, the toner replenishing port 20 is positioned on the extended line of the central axis of the air ejection port 32, and the central axis of the air ejection port 32 does not intersect the axis of the toner replenishing side stirring screw 11. Is set.

  According to such a color copying apparatus as the third embodiment of the present invention, the toner replenishing device 30 as the toner replenishing means 2 is supplied by air injection from the air outlet 32 connected to the monopump as the air supplying means. New toner is supplied on the air ejection surface formed at the component developer interface, and the ejection surface of the air fed into the developer coincides with the toner supply port 20. Therefore, the mixing efficiency in this region is maximized, and the influence of the ejection surface on the other developer regions can be reduced. As a result, the occurrence of inconveniences such as imbalance and scattering of the agent balance is suppressed. Is possible. This configuration corresponds to an embodiment of the fourth aspect.

[Fourth embodiment]
FIG. 16 is a cross-sectional view showing the configuration inside the developer container in the developing device 61.

  In FIG. 16, the shaft of the toner supply side stirring screw 11 is hollow in the vicinity of the toner supply port 20, and the air outlet 32 is connected to the hollow portion, and is provided on the shaft of the toner supply side stirring screw 11. Air is jetted into the developer from the opening 32 '. Since the toner replenishing side agitating screw 11 is rotating, the jetted air increases the bulk density evenly with respect to the developer present in the rotating direction. That is, the mixing efficiency can be improved.

  According to such a color copying apparatus as the fourth embodiment of the present invention, the opening 32 'of the air outlet 32 connected to the monopump as the air supply means (corresponding to the tip of the air inlet). ) Is provided on the shaft wall surface of the toner replenishing side agitating screw 11 as the agitating means, so that the mixing efficiency of the developer near the toner replenishing port is improved evenly as the toner replenishing side agitating screw 11 rotates. It becomes possible. This configuration corresponds to an embodiment of the fifth aspect.

[Fifth embodiment]
FIG. 17 is a cross-sectional view showing a configuration inside the developer container in the developing device 61.

  In FIG. 17, a plate-like protrusion (rectangular plate) 11 a extending in the radial direction is formed on the outer peripheral surface of the central axis of the toner supply side stirring screw 11. That is, the toner replenishment side agitation screw 11 is characterized in that the replenishment toner is supplied in a region where a part of the wing shape is at least parallel to the transport axis (center axis) direction and to the developer transport direction. It has a shape with a region that is vertical. As described above, the two-component development issues are as follows: 1) the promotion of mixing of newly supplied toner into the developer expressed by the guideline of diffusion coefficient, and 2) the point of frictional charging by stirring the carrier and toner. However, according to the present embodiment, a developing device using a screw suitable for the problems 1) and 2) can be obtained.

  Here, in order to confirm the effect of the present example, the diffusion coefficient and the conveyance speed were evaluated for the five types of screws shown in FIGS. In addition, the diffusion coefficient at the time of using the said 5 types of screw is shown in below-mentioned Fig.20 (a), and the conveyance speed is shown in below-mentioned FIG.20 (b).

  Each screw shown in FIG. 18 has the following parameters. FIG. 18A shows a standard screw (Normal), and the screw pitch width is D = 25.0 mm. FIG. 18B shows a wide screw (Broad) and a screw pitch width: D = 37.5 mm. The screw has a screw pitch width 1.5 times that of Normal. FIG. 18C shows a wide screw (large) (Sbroad) and a screw pitch width: D = 57.5 mm. The screw pitch width of this Sbroad is 2.3 times that of Normal. FIG. 18D shows a double screw (Double), and the screw pitch width is D = 25 mm. The screw pitch width of this Double is the same as that of Normal. FIG. 18E shows a protrusion-equipped screw (Prot) in which a rectangular plate (protrusion) is installed with a phase difference of 180 degrees, and the screw pitch width is D = 25 mm. The screw pitch width of this Prot is the same as Normal. FIG. 18 shows a toner supply port 20 as a tracer supply location.

  According to the diffusion coefficient in FIG. 20A and the conveying speed in FIG. 20B, the diffusion coefficient is large for the wide screw (medium) (Broad), the wide screw (large) (Sbroad), and the screw with protrusion (Prot). In addition, the conveyance speed is large for a double screw. The reason is as follows.

  When the screw pitch becomes large like the wide screw (medium) and (large), the moving speed of the screw (screw pitch × rotational speed) increases in proportion to the screw pitch. Despite this, the reason why the conveying speed of the agent does not increase in accordance with the moving speed of the screw is considered to be because the friction between the screw surface and the agent changes. That is, when the screw pitch is increased, the inclination angle of the blade with respect to the developer conveyance direction is increased, and thus the force pushing the powder on the screw blade surface in the conveyance direction is decreased. For example, as shown in FIG. 21, consider a minute powder region in contact with the screw blade surface. Here, when the drag force received from the blade surface is “N” and the angle formed by the blade surface with respect to the transport direction is “α”, the force “Nh” received in the transport direction is expressed by Expression (10).

  Here, assuming that the screw pitch width is “D” and the shape of each screw is considered as a sine function (A: screw diameter) of the formula (11) passing through the origin, the inclination of the screw at the origin is represented by the formula (12). Become.

That is, the inclination of each screw at the central axis is 4.52 (= Double, Prot) for the standard screw (Normal), 3.02 for Broad, and 1.97 for Sroad. The screw moving speed (mm / s) is 10.0 (= Double, Prot) for Normal, 15.0 for Broad, and 23.0 for Sbroad. Here, the slip coefficient is defined as “powder moving speed / screw moving speed”. FIG. 22 shows a comparison between the relative slip coefficient when the normal slip coefficient is “1” and the relative value when the normal is set to “1” with respect to the inclination in the central axis of the normal.
In FIG. 22, it can be seen that Normal, Broad, and Sbroad are substantially correlated. That is, when the screw pitch increases (when the inclination of the central axis decreases), the slip ratio tends to decrease (slip increases). On the other hand, this tendency does not apply to Double and Prot having the same screw pitch as that of Normal. This is because in Double, since the wings are doubled, the area affected by the drag from the wings is doubled, so the conveying speed is increased. In Prot, it is considered that the influence of the drag in the transport direction is dispersed because the wing shape is added which gives a drag in the direction perpendicular to the transport direction of the developer.

Furthermore, the behavior (pass line) of the metal tracer after replenishment when the above-mentioned five types of screws are used by the method described in Japanese Patent Application Nos. 2005-075247 and 2005-269535 by the same applicant. What was visualized is shown in FIG.
When the pass line in FIG. 19 is observed, a metal tracer simulating a large amount of newly supplied toner is moving in the direction perpendicular to the developer conveyance direction in the wide screw (Sroad) and the screw with protrusion (Prot). I understand. These are advantageous screws from the viewpoint of promoting frictional charging. In addition, both have a large diffusion coefficient as a guide for the degree of mixing. However, as shown in FIG. 22, Sbroad has a problem that the slip coefficient is very small and the conveyance efficiency is very poor.

  Therefore, that is, a region where a part of the blade shape (for example, 11a in FIG. 17) is parallel to the transport axis (center axis) direction and perpendicular to the developer transport direction at the supply location of the new replenishment toner. According to Prot having a shape having a developing device, a developing device using a screw suitable for the problems 1) and 2) described above can be obtained.

  According to the color copying apparatus as the fifth embodiment of the present invention, the air supply means is not provided, and the two-component developer composed of the toner and the carrier is stirred and dispersed in the developer container to be in a predetermined position. A toner replenishment side agitating screw 11 and a developer carrier side agitating screw 12 as the agitating means for conveying, and a toner replenishing device 30 as a toner replenishing means for replenishing the toner consumed by the development are provided, and the toner replenishing side agitating screw 11 is a structure using a screw with a protrusion (Prot). With this configuration, a part of the blade shape of the protruding screw in a region close to the toner supply port 20 is at least parallel to the central axis direction of the protruding screw and perpendicular to the transport direction of the two-component developer. Therefore, it is possible to realize an appropriate screw shape with respect to the problems of the two-component development (problems of the above 1) and 2), the acceleration of mixing, and the tribocharging.

[Sixth embodiment]
FIG. 23 is a cross-sectional view showing a configuration inside the developer container in the developing device 61.

  In FIG. 23, an air outlet 32 is inserted in a lower portion of the replenishment side stirring chamber 14 at a position not in contact with the replenishment side stirring screw 11 and upstream of the toner replenishment port 20 with respect to the developer transport direction. . As described above, the mixing efficiency and the stirring efficiency are improved by the projection screw (Prot). However, the mixing efficiency can be further improved by ejecting air.

  According to such a color copying apparatus as the sixth embodiment of the present invention, the air jet 32 using a protrusion-equipped screw (Prot) as the replenishing-side stirring screw 11 and connected to the monopump as the air supply means. By providing this, a part of the wing shape of the protruding screw is parallel to at least the central axis direction of the protruding screw in a region close to a location where the toner is newly supplied (for example, the toner supply port 20). And a shape that has a region that is perpendicular to the transport direction of the two-component developer, and defines an appropriate screw shape for two-component development issues (1) and (2) above, mixing acceleration, and tribocharging is doing. With this configuration, the mixing efficiency is further improved as compared with the fifth embodiment. This configuration corresponds to an embodiment of claim 7.

  Furthermore, according to the first to sixth embodiments described above, it is possible to provide a process cartridge as a developing unit provided with a developing device having effects peculiar to each embodiment, and a color copying apparatus as an image forming apparatus. Can do. This configuration corresponds to one embodiment of claims 8 and 9.

The diffusion coefficient measurement method used this time is uncertain (95% inclusiveness) as a relative value of 18.7%, which is relatively large, but the tendency due to the screw shape shown in FIG. 20 is significant. This is the range that can be discussed. The method for deriving uncertainty is described below.
Here, considering the conversion factor, the Gaussian distribution approximated to the tracer pixel distribution at the diffusion coefficient κ ² (mm ² / s), the conversion factor α (mm ² / pix ² ), and the times t ₁ and t ₂ (s). If the variances σ ₁ ² , σ ₂ ² and the error ε (mm ² / s) associated with the measurement of the diffusion coefficient are satisfied, Equation (13) is established.

In addition, since the diffusion coefficient is obtained by capturing the diffusion of the tracer particle region, the actual behavior of the powder and the tracer are different. In this way, the difference in the diffusion coefficient caused by the measurement principle itself is expressed as δκ ^2, and this error factor is also considered. That is, error factors related to δκ ² , Δσ ² , Δt, and α are considered.

  FIG. 24 is a diagram showing each error factor and its propagation path. This error factor is a list of typical error factors, and there are some details that are still under study. For example, the traceability of the tracer described later.

  In general uncertainty analysis, accuracy and precision are calculated from error factors, and evaluated by multiplying the sensitivity coefficient for unit conversion and taking the sum of squares. Recorded. Whether the error factor is counted as accuracy or precision has little effect on the uncertainty of the final result in this case. The sensitivity coefficient is obtained by differentiating the equation (13) with a parameter for error evaluation. Here, if the accuracy with the unit of the factor “i” is “Bi”, the sensitivity coefficient is “θi”, and the overall accuracy is “B”, Expression (14) is established.

Hereinafter, the result of the uncertainty analysis using the standard diffusion coefficient measurement values (shown in FIG. 25) will be briefly described.
(1) The error video signal rate error of 1 ms propagating to Δt is counted as accuracy.
(2) Since the error imaging system propagating to Δσ ² and the error due to image analysis are very complicated, the evaluation was performed as follows. The same tracer image is taken at the center of the field of view and around the field of view, and σ ² is calculated for each. As shown in FIG. 26, an error of 18% occurred in σ ² due to the effects of light attenuation and distortion in the periphery. This value is included in the accuracy. In this case, the sensitivity coefficient is “1”.
(3) The error conversion coefficient α propagated to the conversion coefficient α represents κ ² (pix ² / s) obtained by pix, which is a unit of length on the image, by κ ² (mm ² / s). Is a coefficient multiplied by. Although omitted during calculation, the accuracy of α was 0.00027 (mm ² / pix ² ) when the reference scale and physical length measurement errors were 0.5 pix and 0.1 mm, respectively.
(4) as an error propagating in error Derutakappa ² propagating in δκ ^2, there is a follow-up property and the three-dimensional properties of the tracer issues into powder field tracer particles. Regarding the former, it was confirmed that the moving speed of the powder particles in the metal tracer transport direction (corresponding to the developer transport direction) and the tracer moving speed were almost the same. is there. Therefore, this time, 5% = 0.155 (pix ² / s) is counted as the accuracy estimated on the maintenance side.

  FIG. 27 shows each sensitivity coefficient.

If the overall accuracy is “B”, the uncertainty (95% inclusiveness) is
^{B = (BΔt 2 + BΔσ 2} + Bα 2 + Bκ 2) 1/2 = 0.045
The relative value was 18.7%.

This appears to be a fairly large uncertainty, but the largest error factor was the fitting error propagating to Δσ ² . Although the center of the field of view was compared with the periphery for value counting, the actual measurement often uses two points near the center, and it seems that such a large uncertainty will not occur, but this part will be improved in the future. I think that the accuracy can be improved effectively by adding.

1 is a cross-sectional view of a color copying apparatus as an embodiment of the present invention. 1 is a cross-sectional view of a developing device as an embodiment of the present invention. It is sectional drawing of the developer container in the image development apparatus as one Embodiment of this invention. FIG. 5 is a schematic diagram illustrating a toner replenishing method according to an embodiment (first example) of the invention. It is a figure which shows the characteristic of the glass bead and tungsten powder for verifying dispersion | distribution of the replenishment toner as one Embodiment (1st Example) of this invention. It is sectional drawing which shows the shape of the supply side stirring screw and supply side stirring chamber as one form (1st Example) of this invention. It is a figure which shows the X-ray visualization image of the replenishment side stirring chamber before and behind mixing of the metal tracer as one Embodiment (1st Example) of this invention. It is a figure which shows the pressure generation profile of the monopump as one form (1st Example) of embodiment of this invention. The figure which shows the X-ray visualization image ((a), (b) has a background, (c), (d) has no background) of the metal tracer as one embodiment (first example) of the present invention. is there. It is a figure which shows the positional relationship of the X-ray projection surface and metal tracer as one form (1st Example) of embodiment of this invention. It is a figure which shows the pixel density | concentration measurement straight line of the major axis direction of the metal tracer as one form (1st Example) of this invention. It is a figure which shows the pixel density value (normal distribution curve which approximated pixel distribution) at the time of making the origin into the origin the gravity center position in the center axis | shaft of the supply side stirring screw as one form (1st Example) of embodiment of this invention. is there. It is sectional drawing of the image development apparatus as one Embodiment (2nd Example) of this invention. FIG. 10 is a schematic diagram illustrating a toner replenishing method according to an embodiment (third example) of the invention. It is sectional drawing of the developing device as one Embodiment (3rd Example) of this invention. FIG. 10 is a schematic diagram illustrating a toner replenishing method according to an embodiment (fourth example) of the invention. FIG. 10 is a schematic diagram illustrating a toner replenishing method according to an embodiment (fifth example) of the invention. It is a side view of five kinds of screws for evaluation of a diffusion coefficient and a conveyance speed as an embodiment of the present invention (fifth example). It is a figure which shows the X-ray visualization image of the pass line of a metal tracer at the time of using 5 types of screws in FIG. It is a figure which shows the diffusion coefficient and conveyance speed at the time of using 5 types of screws in FIG. It is a figure which shows the force which the micro blade surface of the screw as one form (5th Example) of this invention exerts on a micropowder area | region. It is a figure which shows the slip coefficient and inclination of each screw when the slip coefficient of the standard screw as one mode of implementation of the present invention (fifth example) and the inclination at the central axis are 1. FIG. 10 is a schematic diagram illustrating a toner replenishing method according to an embodiment (sixth example) of the present invention. It is a figure which shows the error factor and propagation path in the measurement of the diffusion coefficient of the metal tracer as one embodiment of the present invention. It is a figure which shows the measured value of the diffusion coefficient of the metal tracer at the time of using the standard screw as one Embodiment of this invention. It is a figure which shows the error propagated to (DELTA) (sigma) ² at the time of image | photographing the tracer image as one Embodiment of this invention in the visual field center and periphery. Derutakappa ² as one embodiment of the present invention, Δσ ^2, Δt, is a diagram illustrating the sensitivity coefficient alpha.

Explanation of symbols

1: Image carrier (photosensitive member)
11: Toner supply side stirring screw 12: Developer carrier side stirring screw 13: Developing roller 14: Supply side stirring chamber 15: Development side stirring chamber 16: Development sleeve 20: Toner supply port 50: Doctor blade 30: Toner supply device 31 : Replenishing toner conveying screw 32, 32a, 32b: Air outlet 40: Tracer injection device 41: Screw image 51: First tracer 52: Second tracer 61: Developing device 65: Developer container 80: Partition plate

Claims (9)

Agitating means that agitates and disperses the two-component developer composed of toner and carrier by rotation of two screws disposed in the developer container and conveys the toner to a predetermined position, and replenishes the toner consumed by the development. Toner supply means, and air supply means for supplying air to the upstream side in the transport direction by the agitation means to a location where toner is supplied by the toner supply means,
The developing device according to claim 1, wherein the air supply means supplies air at a certain time earlier than the timing at which toner is supplied to the location. The developing device according to claim 1,
The developing device characterized in that the position of the tip of the air inlet of the air supply means is variable with respect to the transport direction of the two-component developer. The developing device according to claim 1,
A developing device comprising a plurality of air inlets of the air supply means. The developing device according to claim 1,
The developing device according to claim 1, wherein the toner replenishing unit replenishes toner toward an air ejection surface formed at an interface of the two-component developer by injecting air from the air supply unit. The developing device according to claim 1,
2. A developing device according to claim 1, wherein a tip of an air inlet of the air supply means is provided on a shaft wall surface of the screw of the stirring means. The developing device according to claim 1,
The developing device according to claim 1, wherein the screw of the stirring means rotates in the forward and reverse directions according to a predetermined condition. The developing device according to claim 1,
A shape in which a part of the blade shape of the screw of the stirring means in a region close to the portion has a region that is at least parallel to the axial direction of the screw and perpendicular to the conveying direction of the two-component developer. A developing device characterized by the above.   8. The developing device according to claim 1, at least two of the latent image carrier, the charging device, and the cleaning device for the latent image carrier are integrally formed. Development unit.   An image forming apparatus comprising the developing unit according to claim 8.

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