JP2010266575A - Screw, developing device, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a screw capable of improving mixability of two or more kinds of powder in a rotary shaft direction; a developing device provided with the screw; an image forming apparatus including the developing device; and a process cartridge. <P>SOLUTION: The screw has a rotary shaft supported to be rotatable, and a spiral blade protrusively provided spirally on a circumferential surface of the rotary shaft, and conveys the powder in the rotary shaft direction while stirring the powder by the spiral blade with rotation of its own, wherein the spiral blade waves within one pitch of the spiral blade. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a screw as stirring and conveying means for conveying powder and the like while stirring, a developing device provided with the screw, an image forming apparatus and a process cartridge provided with the developing device.

As a developing device using a two-component developer including a toner and a carrier, a developer supply conveyance path having a developer supply screw for supplying the developer to the development roller while conveying the developer parallel to the axis of the development roller, and a developer supply A device including a developer agitating / conveying path having a developer agitating screw that conveys the developer while agitating the developer in a direction opposite to the screw is known (for example, Patent Document 1).
The developer supply screw and the developer agitating screw have a rotatable rotating shaft and a spiral blade projecting spirally on the peripheral surface thereof, and are driven to rotate by a driving means. The developer is conveyed in the rotation axis direction. The most downstream part in the transport direction of the developer supply transport path and the most upstream part of the developer stirring transport path, and the most downstream part in the transport direction of the developer stirring transport path and the most upstream part of the developer supply transport path, respectively. The developer is circulated and conveyed through the developer agitation conveyance path and the developer supply conveyance path. In such a developing device, a toner replenishing port is provided above the upstream portion in the transport direction of the developer agitation transport path in order to replenish the toner consumed in the development.

  If the developer in the developer agitating / conveying path to which toner is replenished from the toner replenishing port cannot be sufficiently mixed in the direction of the rotation axis by the developer agitating screw, the toner replenished from the toner replenishing port will enter the developer. It becomes difficult to be dispersed in the direction of the rotation axis. As a result, the developer in the developer agitating / conveying path is partially conveyed in the rotation axis direction while the toner concentration is high, and a toner density deviation occurs in the developer in the developer agitating / conveying path in the rotation axis direction. . When the developer is fed from the developer stirring / conveying path to the developer supply / conveying path and supplied to the developing roller with the toner density deviation occurring, there is a problem that density unevenness occurs in the developed image.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a screw capable of improving the mixing property of two or more kinds of powders in the rotation axis direction, a developing device provided with the screw, and the development described above. An image forming apparatus including the apparatus and a process cartridge are provided.

In order to achieve the above-mentioned object, the invention of claim 1 has a rotating shaft that is rotatably supported, and a spiral blade that protrudes in a spiral manner on the peripheral surface of the rotating shaft. Accordingly, in the screw that conveys the powder in the direction of the rotation axis while stirring the powder by the spiral blade, the spiral blade is wavy within one pitch of the spiral blade.
Further, the invention of claim 2 has a rotating shaft that is rotatably supported, and a spiral blade that protrudes in a spiral manner on the peripheral surface of the rotating shaft, and the spiral blade as it rotates. In the screw that conveys the powder in the direction of the rotation axis while stirring the powder, the angle formed by the ridgeline of the spiral blade and the virtual plane orthogonal to the rotation axis changes within one pitch of the spiral blade. It is characterized by being.
According to a third aspect of the present invention, in the developing device of the first aspect, at least the angle formed by the ridgeline of the spiral blade and the virtual plane orthogonal to the rotation axis changes within the one pitch. It is characterized by this.
According to a fourth aspect of the present invention, in the developing device according to the first or second aspect, at least a size of an angle formed by a root of the spiral blade and a virtual plane orthogonal to the rotation axis changes within the one pitch. It is characterized by that.
Further, the invention of claim 5 is to carry a developer conveying member that conveys a developer containing toner and a carrier, and a developer conveyed by the developer conveying member on its endlessly moving surface, As a developer conveying member in a developing device having a developer carrying body that develops a latent image carried on the latent image carrying body by transporting it to a region facing the latent image carrying body as its surface moves The screw according to claim 1, 2, 3 or 4 is used.
According to a sixth aspect of the present invention, there is provided a latent image carrier that carries a latent image, a developing means that develops the latent image on the latent image carrier, and a visible image developed on the latent image carrier. In a process cartridge in which at least the latent image carrier and the developing means are held as a unit on a common holding body and are integrally attached to and detached from the main body of the image forming apparatus. A developing device according to claim 5 is used as the developing means.
According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier. The developing device is used.

According to the first aspect of the present invention, the side surface of the spiral blade is wavy within one pitch of the spiral blade, so that the spiral blade is close to perpendicular or parallel to the rotation axis. The closer the spiral blade is to the rotation axis, the greater the powder conveyance force in the direction of the rotation axis, and the closer the spiral blade is to the rotation axis, the smaller the powder conveyance force in the direction of the rotation axis. Become. Therefore, the conveying force of the powder in the direction of the rotation axis by the spiral blade is different within one pitch because the spiral blade is undulating within the one pitch. As the conveying force increases, the powder becomes easier to be conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder becomes less likely to be conveyed in the direction of the rotation axis. A speed difference occurs in the conveyance speed of the powder to be produced. The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is conveyed in the direction of the rotation axis per unit time is different within the one pitch, so that the powder is easily mixed in the direction of the rotation axis. Therefore, when two or more kinds of powders are stirred and conveyed, the powders can be dispersed in the direction of the rotation axis within the one pitch than when the side surfaces of the spiral blades are not wavy.
In the invention of claim 2, the size of the angle formed by the ridge line of the spiral blade and the virtual plane orthogonal to the rotation axis is changed within one pitch of the spiral blade. The smaller the angle formed, the closer the spiral blade is to the rotation axis, and the larger the angle formed, the closer the spiral blade is to the rotation axis. The closer the spiral blade is to the rotation axis, the greater the powder conveyance force in the direction of the rotation axis, and the closer the spiral blade is to the rotation axis, the smaller the powder conveyance force in the direction of the rotation axis. Become. Therefore, by changing the size of the angle formed by the ridgeline of the spiral blade and the virtual plane perpendicular to the rotation axis within the one pitch, the conveying force of the powder in the rotation axis direction by the spiral blade is within one pitch. It is different. As the conveying force increases, the powder becomes easier to be conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder becomes less likely to be conveyed in the direction of the rotation axis. A speed difference occurs in the conveyance speed of the powder to be produced. The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is conveyed in the direction of the rotation axis per unit time is different within the one pitch, so that the powder is easily mixed in the direction of the rotation axis. Therefore, when two or more kinds of powders are stirred and conveyed, the powder is larger than the case where the angle formed by the ridgeline of the spiral blade and the virtual plane orthogonal to the rotation axis is not changed within the one pitch. Can be dispersed in the direction of the rotation axis.

  As described above, according to the first to seventh aspects of the present invention, there is an excellent effect that the powder mixing property in the rotation axis direction can be improved.

The schematic diagram of the screw with which the conveyance surface of the blade | wing to which this invention is applied, the ridgeline part, and the root are wavy. Schematic diagram of normal screw. (A) Explanatory drawing of the dispersibility of the powder axial direction in case there is little dispersion | distribution in the distribution of the conveying speed of the powder axial direction by a screw. (B) Explanatory drawing of the axial dispersibility of a powder in case the dispersion | distribution of the conveyance speed of the powder in the axial direction by a screw is large. The schematic diagram of the screw which the conveyance surface of a blade | wing is undulating. A schematic diagram of a screw having a blade having a large lead angle portion and a small lead angle portion and having a large lead angle portion and a small lead angle portion that are not smoothly connected. Schematic diagram of a screw where the ridgeline of the blade is undulating but the root of the blade is not undulating. Schematic diagram of a screw whose ridgeline is not wavy but whose root is wavy. FIG. 4 is a diagram illustrating an outline of a copying machine according to a second embodiment. Sectional drawing which shows the structure of a developing device. Sectional drawing parallel to the axial direction of a developing device. The graph which showed the relationship between the time after toner replenishment, and toner density. The graph which showed the distance until replenishment toner is taken in in a developing agent. Schematic diagram of a screw with a notch in the normal screw blade. Schematic diagram of a screw with a paddle on a normal screw. Configuration diagram for tandem indirect transfer color copiers. FIG. 2 is a schematic configuration diagram of an image forming unit.

[Embodiment 1]
The present invention has a rotating shaft that is rotatably supported, and a spiral blade that is spirally projected on the peripheral surface of the rotating shaft, and rotates while stirring the powder by the spiral blade as it rotates. An embodiment in which the present invention is applied to an axially conveyed screw will be described. In addition, unless otherwise specified, the screw in the present embodiment has a rotating shaft that is rotatably supported and a spiral blade that protrudes in a spiral manner on the peripheral surface of the rotating shaft. It is a screw that conveys powder in the direction of the rotation axis while stirring the powder with a spiral blade.

  First, a conventional screw (hereinafter referred to as a normal screw) is shown in FIG. 2 as a comparison with the screw of the present invention. The normal screw shown in FIG. 2 has a rotating shaft 50 provided with a spiral blade 51 for stirring and conveying powder in the direction of the rotating shaft. The arrow shown in FIG. 2 represents the velocity vector of the powder in contact with the normal screw blade 51 in the rotation axis direction. In this normal screw, the lead angle θ (angle formed by the outer periphery of the blade and the rotation shaft 50) is always constant in the rotation axis direction, and the powder is conveyed at substantially the same speed in the rotation axis direction. Even if the powder is conveyed with such a normal screw, the powder is not so mixed in the direction of the rotation axis.

  With reference to FIG. 3, the dispersibility of the powder in the rotation axis direction by a screw will be described. Here, the concept in the case of stirring and conveying two types of powder, powder A and powder B, with a screw will be described. FIG. 3A is a diagram in the case where there is little variation in the distribution of the conveying speed of the powder in the rotation axis direction due to the screw (when the conveying speed distribution is sharp). Further, the blackness in the figure is darker as the proportion of the powder A is larger. When the distribution of the conveying speed of the powder in the rotation axis direction by the screw as shown in FIG. 3A is small, the powder A and the powder B are not so much in the rotation axis direction that is the conveying direction of the powder. It is transported without mixing. For this reason, the portion where the ratio of the powder A is large (the portion where the color is dark) is almost transported in the direction of the rotation axis as it is. As described above, the normal screw as shown in FIG. 2 is such that the powder is conveyed at substantially the same speed in the rotation axis direction and the distribution of the conveyance speed in the rotation axis direction of the powder is less varied. Although the dispersibility in the axial direction is not as extreme as in FIG. 3A, it is close to the state shown in FIG.

  On the other hand, if the conveying speed of the powder in the rotation axis direction by the screw varies as shown in FIG. 3B, the portion where the ratio of the powder A shown in FIG. The powder becomes uniform in the process of being conveyed in the direction of the rotation axis by the screw.

  A screw having the features of the present invention is shown in FIGS. FIG. 1 shows a screw in which a conveying surface 51a, a ridge line portion 51b, and a root 51c of a blade 51 are undulated. FIG. 4 shows a screw in which the conveying surface 51a of the blade 51 is undulating. The screw shown in FIGS. 1 and 4 is different from the normal screw shown in FIG. 2 in that the lead angle θ is not constant within one pitch of the blades 51. The screw shown in FIG. 1 has a portion where the lead angle θ continuously changes from 1 degree to 55 degrees at a quarter rotation period. The screw shown in FIG. 4 is a screw in which a portion where the lead angle θ continuously changes from 1 degree to 55 degrees exists in a ½ rotation cycle.

  The angle of the lead angle θ decreases as the blade 51 approaches the vertical axis with respect to the rotation shaft 50, and the angle of the lead angle θ increases as the blade 51 approaches the rotation shaft 50 in parallel. Further, the smaller the lead angle θ is, the larger the powder conveying force in the direction of the rotation axis by the blade 51 is. The larger the lead angle θ is, the more the powder is conveyed in the direction of the rotation axis by the blade 51. Becomes smaller. Therefore, by changing the lead angle θ of the blade 51 within one pitch, the conveying force of the powder in the direction of the rotation axis by the blade 51 is different within one pitch. As the conveying force increases, the powder is more easily conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder is less likely to be conveyed in the direction of the rotation axis. A difference in speed occurs in the conveying speed of the powder.

  In FIG. 4, the velocity vector in the rotation axis direction of the powder in contact with the screw is indicated by an arrow. However, in the portion where the lead angle θ of the screw is small, the conveying speed of the powder is slow and the powder tends to accumulate, It can be seen that the powder conveyance speed increases at the portion where the lead angle θ is large. That is, the screw shown in FIGS. 1 and 4 has a portion where the conveying speed of the powder in the rotation axis direction by the screw is fast and a slow portion, and there is a variation in the conveying speed of the powder in the rotation axis direction by the screw. growing.

  The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is transported in the rotation axis direction per unit time is different within one pitch, so that the powder is easily mixed in the rotation axis direction. Therefore, when two or more kinds of powder are stirred and conveyed, the powder can be dispersed in the direction of the rotation axis as compared with the case where the lead angle θ of the blade 51 is not changed within one pitch.

  Further, since the portion 51 having a large lead angle θ and the portion having a small lead angle θ are alternately provided on the screw blade 51, a portion having a large lead angle θ is fast transferred to a portion having a small lead angle θ where powder is accumulated. The powder conveyed at a speed flows in, and this also improves the dispersibility of the powder in the rotation axis direction.

  Therefore, when the screw having the undulation of the conveying surface 51a, the ridge line portion 51b and the root 51c of the blade 51 shown in FIG. 1, or the screw having the undulating of the conveying surface 51a of the blade 51 shown in FIG. When used, the dispersibility in the rotational axis direction of the powder is close to the state as shown in FIG.

  In the screw shown in FIGS. 1 and 4, the blades 51 spirally wound around the rotation shaft 50 have a periodic shape, but the cycle in which the magnitude of the lead angle θ is random. Even in the case of the shape of the blade 51 having no property, the same effect can be obtained.

  Further, the blade 51 shown in FIG. 5 has a portion having a large lead angle θ and a portion having a small lead angle θ, and a portion having a large lead angle θ and a portion having a small lead angle θ are not smoothly connected to each other, FIG. The ridgeline of the blade 51 shown in FIG. 6 is undulated but the root 51c of the blade 51 is not undulated, and the ridgeline of the blade 51 shown in FIG. The screw which is struck is the same as the screw in which the conveyance surface 51a of the blade 51 shown in FIG. 1, the ridge 51b and the root 51c is undulated, and the screw in which the conveyance surface 51a of the blade 51 shown in FIG. In addition, for the reasons described above, the conveying speed of the powder in the direction of the rotation axis of the screw varies, and the dispersibility of the powder in the direction of the rotation axis can be improved. Further, although not shown in the drawing, the ridge line and the root 51c of the blade 51 are not undulated, and even the screw having only the conveying surface 51a of the blade 51 is undulated for the reason described above, the conveying speed of the powder in the rotation axis direction by the screw is increased. Variations occur and the dispersibility of the powder in the rotation axis direction can be improved.

  That is, if the angle formed by the conveying surface 51a of the screw blade 51 and the rotation shaft 50 increases or decreases in the rotation axis direction, a speed difference occurs in the powder conveyance speed in the rotation axis direction by the screw, and the rotation of the powder. The dispersibility in the axial direction can be improved.

  Moreover, it can be said that the screw shown in FIG.1, FIG.4, FIG.5, FIG.6 and FIG. 7 has swung the blade | wing 51 within one pitch of the spiral blade | wing 51. The dispersibility in the rotation axis direction will be described.

  By undulating the blades 51 within one pitch, an angle formed by the conveyance surface 51a of the blade 51 fixed to the rotation shaft and a virtual plane orthogonal to the rotation shaft 50 is determined for each portion of the conveyance surface 51a within one pitch. Can be different. The smaller the angle formed, the closer the transport surface 51a is to the rotation axis 50, and the greater the angle formed, the closer the transport surface 51a is to the rotation axis 50. The blade 51 has a larger powder conveyance force in the direction of the rotation axis as the conveyance surface 51 a becomes closer to the rotation axis 50, and becomes closer to the rotation axis direction as the conveyance surface 51 a becomes closer to the rotation axis 50. The conveying power of the powder becomes smaller. Therefore, by causing the blades 51 to swell in the direction of the rotation axis within one pitch, the conveying force of the powder in the direction of the rotation axis by the blades 51 differs for each portion of the conveyance surface 51a within one pitch. As the conveying force increases, the powder is more easily conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder is less likely to be conveyed in the direction of the rotation axis. A difference in speed occurs in the conveying speed of the powder. The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is transported in the rotation axis direction per unit time is different within one pitch, so that the powder is easily mixed in the rotation axis direction. Therefore, when two or more kinds of powders are stirred and conveyed, the powders can be dispersed in the direction of the rotation axis as compared with the case where the blades 51 are not swung in the direction of the rotation axis within one pitch.

  Here, when the specific gravity of the powder A and the powder B is different, the powder A and the powder B are separated into two layers. Therefore, it is necessary to disperse the powder in the direction orthogonal to the rotation shaft 50 by the screw, in addition to dispersing the powder in the rotation axis direction by the screw. At this time, conventionally, a paddle having a surface parallel to the rotation axis is provided on the rotation axis of the screw, as in the screw described in JP-A-11-119529, and the powder is used as a rotation axis by the paddle. It is dispersed in the orthogonal direction. However, such a paddle has almost no conveying force to convey the powder in the direction of the rotation axis, so that it is difficult to obtain the effect of varying the conveyance speed of the powder in the direction of the rotation axis as described above. It hardly contributes to the improvement of dispersibility in the rotation axis direction. In addition, providing the paddles slows the powder conveyance speed.

  1, 4, 5, 6, and 7, the lead angle θ of the blade 51 is changed, and the conveying surface 51 a of the blade 51 is close to the paddle, that is, the powder is rotated on the rotating shaft 50. There is a portion that is easy to disperse in a direction orthogonal to the. In this portion, an effect of dispersing the same powder as the paddle in the direction orthogonal to the rotation shaft 50 can be obtained. In addition, since no paddle is provided, it is possible to suppress a decrease in the conveying speed of the powder in the direction of the rotation axis, compared to the case where a paddle is provided. Therefore, in the screws shown in FIGS. 1, 4, 5, 6, and 7, the powder in the rotation axis direction and the direction orthogonal to the rotation axis 50 is suppressed while suppressing a decrease in the conveying speed of the powder in the rotation axis direction. The agitation of the body can be achieved at the same time, and the improvement of the dispersibility in the direction of the rotation axis of the powder and the improvement of the dispersibility in the direction perpendicular to the rotation axis 50 of the powder can be achieved.

  There is an electrophotographic copying apparatus using a screw as means for stirring and conveying two types of powders having different specific gravities.

[Embodiment 2]
Hereinafter, a developer as a developer agitating / conveying member used in an electrophotographic copying apparatus (hereinafter referred to as a copying machine) that is an image forming apparatus according to the present invention and used in a developing apparatus that contains a developer composed of toner and a carrier. An embodiment applied to a conveying screw will be described below with reference to the drawings. The present invention is not limited to this example.

  FIG. 8 is a diagram showing an outline of the copying machine according to the embodiment of the present invention. The copying machine includes a reading unit 1, an image processing unit 6, an image forming unit 12, a system control unit 18, and an operation unit 19. The reading unit 1 includes a lamp 2, a CCD 3, an amplifier 4, and A / D conversion. The image processing unit 6 includes a shading correction unit 8, a filter 9, a γ correction unit 10, and a gradation processing unit 11. The image forming unit 12 includes a writing unit 13, and a photoconductor. A drum 30, a charging charger 15, a developing sleeve 16, a paper feed tray 17, and a temperature / humidity detection unit 20 that detects temperature / humidity are included. The reading unit 1, the image processing unit 6, and the image forming unit 12 are connected to the operation unit 19. It operates under the control of the system control unit 18 according to the above instructions.

  In the copying machine shown in FIG. 8, the light emitted from the lamp 2 in the reading unit 1 is reflected by the original surface, converted into an electric signal by the CCD 3, and adjusted in amplitude by the amplifier 4. The digital image data quantized by the A / D converter 5 is obtained. The generated digital image data is input to the image processing unit 6, subjected to the shading correction unit 8, the filter 9, the γ correction unit 10, the gradation processing unit 11, and the like in this order and sent to the image forming unit 12.

  The digital image data input to the image forming unit 12 is converted into laser light 14 in accordance with the data value in the writing unit 13 and irradiated to the photosensitive member charged by the charging charger 15, and an electrostatic latent image is formed on the surface of the photosensitive member. Form. The developing sleeve 16 adheres toner to the surface of the photoreceptor in accordance with the formed electrostatic latent image. The toner adhering to the surface of the photoconductor is transferred onto the paper surface sent from the paper feed tray 17, passes through the fixing unit, and is output as a copy document.

  FIG. 9 is a cross-sectional view showing the configuration of the developing device 40 in the copying machine shown in FIG. The developing device 40 includes a developing case 42 that is disposed on the side of the photosensitive drum 30 and has an opening formed toward the photosensitive drum 30. Note that at least the photosensitive drum 30 and the developing device 40 can be configured as a process cartridge that is held in a common holding body as a unit and can be integrally attached to and detached from the copying machine main body. As described above, since the photosensitive drum 30 and the developing device 40 can be integrally attached and detached as a process cartridge, the maintainability of the photosensitive drum 30 and the developing device 40 can be improved. Part of the developing sleeve 16 as a developer carrying member that carries a two-component developer (hereinafter referred to as developer) composed of toner and a magnetic powder carrier is exposed from the opening of the developing case 42 of the developing device 40. It is arranged as follows. The developing sleeve 16 has a cylindrical shape made of a non-magnetic material, and has a magnet roller as a magnetic field generating means fixed inside. The developing sleeve 16 can freely rotate around the magnet roller.

  On the opposite side of the developing sleeve 16 from the portion facing the photosensitive drum 30, a developer accommodating portion 41 for accommodating a developer is formed by a developing case 42. The developer accommodating portion 41 is provided with developer agitating and conveying screws 44 and 45 for conveying the developer in the developer accommodating portion while stirring.

  In FIG. 9, there is a partition between the developer agitating and conveying screws 44, 45, but there is no partition on the front side and the back side of the developer accommodating portion 41 in the drawing, and the developer can move. It is like that. In addition, a doctor blade 43 that regulates the amount of developer carried on the developing sleeve 16 and conveyed to a portion facing the photosensitive drum 30 is provided. Further, a toner hopper 46 for containing replenishing toner is provided above the developer stirring and conveying screw 45 in the developer containing portion 41.

  In the developing device 40 having the above-described configuration, the developer agitating and conveying screws 44 and 45 rotate to convey the developer accommodated in the developer accommodating portion 41 to the vicinity of the developing sleeve 16 while being agitated. At this time, the developer is triboelectrically charged by the stirring action. The developer conveyed to the vicinity of the developing sleeve 16 is carried on the surface of the developing sleeve 16 by a magnetic force generated by a magnet roller inside the developing sleeve 16. Thereafter, the developer whose layer thickness is regulated by the doctor blade 43 is transported to a position closest to the photosensitive drum 30, and the toner is electrically attached to the electrostatic latent image.

  In this developing device 40, the toner concentration in the developer container 41 is detected in order to obtain a high quality image by always maintaining the mixing ratio of the toner with respect to the magnetic carrier in the developer to be developed at an appropriate value. It is necessary to maintain this at a predetermined value. If it is detected that the toner concentration is lowered, the toner replenishment control unit 48 that performs toner replenishment control to replenish the replenishment toner from the toner hopper 46 to obtain an appropriate toner concentration is controlled. Therefore, a toner concentration sensor 27 is installed as a toner concentration detection device that detects the toner concentration of the developer in the developer accommodating portion 41 based on the magnetic permeability of the developer. Based on the toner concentration TC of the developer detected by the toner concentration sensor 27 and the temperature / humidity from the temperature / humidity detection unit 20 that detects the temperature / humidity, the toner replenishment control unit 48 sets the toner concentration of the developer as described later. Is adjusted and controlled.

  First, a conventional screw (hereinafter referred to as a normal screw) is shown in FIG. 2 as a comparison with the screw of the present invention. The screw shown in FIG. 2 is provided with a spiral blade 51 that stirs and conveys the developer in the direction of the rotation axis that is the developer conveyance direction. The arrow shown in FIG. 2 represents the velocity vector of the powder in contact with the normal screw blade 51 in the rotation axis direction. In this normal screw, the lead angle θ (angle formed by the blade outer periphery and the rotation shaft 50) is always constant in the rotation axis direction, and the developer is conveyed at substantially the same speed in the rotation axis direction. Even if the developer is transported with such a normal screw, the developer is not so mixed in the direction of the rotation axis.

  The dispersibility of the developer in the rotation axis direction by the screw will be described with reference to FIG. FIG. 3A is a diagram in the case where there is little variation in the distribution of the conveyance speed of the developer in the rotation axis direction due to the screw (when the conveyance speed distribution is sharp). Further, the blackness in the figure indicates that the higher the toner density (the toner density is the ratio of the toner weight to the developer weight), the darker the color. When the distribution of the conveying speed of the powder in the direction of the rotation axis of the powder by the screw as shown in FIG. 3A is small, the portion where the toner concentration is high and the portion where the toner concentration is low are conveyed without being mixed very much. . For this reason, a portion having a high toner density (a portion having a dark color) is almost always conveyed in the direction of the rotation axis. As described above, the normal screw as shown in FIG. 2 is such that the developer is conveyed at substantially the same speed in the direction of the rotation axis, and there is little variation in the distribution of the conveyance speed of the developer in the direction of the rotation axis. Although the dispersibility in the axial direction is not as extreme as in FIG. 3A, it is close to the state shown in FIG.

  On the other hand, if the developer conveyance speed in the direction of the rotation axis of the screw varies as shown in FIG. 3B, even if there is a portion where the toner concentration is high as shown in FIG. As shown, as the developer is conveyed in the direction of the rotation axis by the screw, the developer is mixed and the toner density becomes uniform.

  A screw having the features of the present invention is shown in FIGS. FIG. 1 shows a screw in which a conveying surface 51a, a ridge line portion 51b, and a root 51c of a blade 51 are undulated. FIG. 4 shows a screw in which the conveying surface 51a of the blade 51 is undulating. Unlike the normal screw shown in FIG. 2, the lead angle θ of the screws shown in FIGS. 1 and 4 is not constant within one pitch. The screw shown in FIG. 1 has a portion where the lead angle θ continuously changes from 1 degree to 55 degrees at a quarter rotation period. The screw shown in FIG. 4 is a screw in which a portion where the lead angle θ continuously changes from 1 degree to 55 degrees exists in a ½ rotation cycle.

  The angle of the lead angle θ decreases as the blade 51 approaches the vertical axis with respect to the rotation shaft 50, and the angle of the lead angle θ increases as the blade 51 approaches the rotation shaft 50 in parallel. Further, as the lead angle θ decreases, the developer conveying force in the direction of the rotation axis by the blade 51 increases, and as the lead angle θ increases, the developer conveyance force in the direction of the rotation axis by the blade 51. Becomes smaller. Therefore, by changing the lead angle θ of the blade 51 within one pitch, the developer conveying force in the direction of the rotation axis by the blade 51 is different within one pitch. The developer is more easily conveyed in the direction of the rotation axis as the conveyance force is increased, and the developer is less likely to be conveyed in the direction of the rotation axis as the conveyance force is decreased. Therefore, the developer 51 is conveyed in the rotation axis direction by the blades 51 within one pitch. There is a speed difference in the developer transport speed.

  In FIG. 4, the velocity vector in the rotation axis direction of the developer in contact with the screw is indicated by an arrow. However, in the portion where the lead angle θ of the screw is small, the developer conveyance speed becomes slow and the developer tends to accumulate, and the lead In the portion where the angle θ is large, the developer conveyance speed is increased. That is, the screw shown in FIGS. 1 and 4 includes a portion where the developer conveyance speed in the rotation axis direction by the screw is fast and a portion where the developer conveyance speed in the rotation axis direction by the screw varies. growing.

  As the transport speed increases, the distance that the developer is transported in the direction of the rotation axis per unit time becomes longer. As the transport speed decreases, the distance that the developer is transported in the direction of the rotation axis decreases. As described above, the developer transport distance in the rotation axis direction per unit time is different within one pitch, so that the developer is easily mixed in the rotation axis direction. Therefore, when the developer composed of the toner and the carrier is agitated and conveyed, the toner and the carrier are dispersed in the direction of the rotation axis in the developer as compared with the case where the lead angle θ of the blade 51 is not changed within one pitch. be able to.

  Further, since the portions having a large lead angle θ and the portions having a small lead angle θ are alternately provided on the screw blade 51, the portions having a large lead angle θ are quickly conveyed to the portions having a small lead angle θ where the developer is accumulated. The developer conveyed at a speed flows in and the developer is agitated. This also improves the dispersibility of the developer in the direction of the rotation axis.

  When the screw having the undulation of the conveying surface 51a, the ridge line portion 51b and the root 51c of the blade 51 shown in FIG. 1, or the screw having the undulating of the conveying surface 51a of the blade 51 shown in FIG. 4 was used. In this case, the dispersibility of the developer in the rotation axis direction is close to the state shown in FIG.

  In the screw shown in FIGS. 1 and 4, the blades 51 spirally wound around the rotation shaft 50 have a periodic shape, but the cycle in which the magnitude of the lead angle θ is random. Even in the case of the shape of the blade 51 having no property, the same effect as described above can be obtained.

  Further, the blade 51 shown in FIG. 5 has a portion having a large lead angle θ and a portion having a small lead angle θ, and a portion having a large lead angle θ and a portion having a small lead angle θ are not smoothly connected to each other, FIG. The ridgeline of the blade 51 shown in FIG. 6 is undulated but the root 51c of the blade 51 is not undulated, and the ridgeline of the blade 51 shown in FIG. The screw which is struck is the same as the screw in which the conveyance surface 51a of the blade 51 shown in FIG. 1, the ridge 51b and the root 51c is undulated, and the screw in which the conveyance surface 51a of the blade 51 shown in FIG. In addition, for the reasons described above, the transport speed of the developer in the direction of the rotation axis by the screw varies, and the dispersibility of the developer in the direction of the rotation axis can be improved. Further, although not shown in the drawing, the ridge line and the root 51c of the blade 51 are not undulated and even the screw having only the conveying surface 51a of the blade 51 is undulated for the reason described above, the developer conveying speed in the rotation axis direction by the screw is increased. Variations occur, and the dispersibility of the developer in the direction of the rotation axis can be improved.

  That is, if the angle formed between the conveying surface 51a of the screw blade 51 and the rotating shaft 50 increases or decreases in the rotating shaft direction, a speed difference occurs in the developer conveying speed in the rotating shaft direction by the screw, and the rotation of the developer. The dispersibility in the axial direction can be improved.

  The screw shown in FIGS. 1, 4, 5, 6, and 7 can be said to have the blades 51 undulating within one pitch of the spiral blades 51. The dispersibility in the rotation axis direction will be described.

  By undulating the blades 51 within one pitch, an angle formed by the conveyance surface 51a of the blade 51 fixed to the rotation shaft and a virtual plane orthogonal to the rotation shaft 50 is determined for each portion of the conveyance surface 51a within one pitch. Can be different. The smaller the angle formed, the closer the transport surface 51a is to the rotation axis 50, and the greater the angle formed, the closer the transport surface 51a is to the rotation axis 50. The blade 51 has a greater developer conveying force in the direction of the rotation axis as the conveyance surface 51 a becomes closer to the rotation axis 50, and in the rotation axis direction as the conveyance surface 51 a becomes closer to the rotation axis 50 in parallel. The developer transport force of the developer becomes smaller. Therefore, by causing the blades 51 to swell in the direction of the rotation axis within one pitch, the developer conveying force in the direction of the rotation axis by the blades 51 differs for each portion of the conveyance surface 51a within one pitch. The developer is more easily conveyed in the direction of the rotation axis as the conveyance force is increased, and the developer is less likely to be conveyed in the direction of the rotation axis as the conveyance force is decreased. Therefore, the developer 51 is conveyed in the rotation axis direction by the blades 51 within one pitch. There is a speed difference in the developer transport speed. As the transport speed increases, the distance that the developer is transported in the direction of the rotation axis per unit time becomes longer. As the transport speed decreases, the distance that the developer is transported in the direction of the rotation axis decreases. As described above, the developer transport distance in the rotation axis direction per unit time is different within one pitch, so that the developer is easily mixed in the rotation axis direction. Therefore, when the developer composed of toner and carrier is agitated and conveyed, the toner and carrier are dispersed in the developer in the direction of the rotation axis rather than the case where the blades 51 are not swung in the rotation axis direction within one pitch. be able to.

  In the present embodiment, as the developer transport screw 45, at least one of the transport surface 51a, the ridge line portion 51b, and the root 51c of the spiral blade 51 of the developer transport screw extends from one end side to the other end side in the rotation axis direction. 1, 4, 5, 6, and 7, and the like that are undulated within one pitch of the spiral blade 51 are used.

  Here, the toner replenished from the toner hopper 46 to the developer accommodating portion 41 provided with the developer conveying screw 45 falls on the upper surface of the developer accommodated in the developer accommodating portion 41. If the developer bulk of the developer accommodating portion 41 near the toner replenishment location is high and the developer transport screw 45 is covered with the developer, the toner is lighter than the developer, so that the toner is within the rotation trajectory of the developer transport screw 45. It is difficult to enter and floats on the upper surface of the developer above the developer transport screw 45. The toner floating on the upper surface of the developer gradually moves downstream in the transport direction without being sufficiently agitated with the developer. The toner is not sufficiently agitated and reaches the most downstream portion in the transport direction with the charge amount being low, and is transferred to the developer storage portion 41 provided with the developer transport screw 44, from the developer storage portion 41 to the developing roller. If the toner is supplied to the toner and used for development, a toner density deviation occurs in the developer used for development, and an abnormal image is generated. Therefore, it is necessary to take in the toner that floats on the upper surface of the developer.

  Conventionally, a paddle having a surface parallel to the rotation axis is provided on the rotation axis of the screw, and the toner floating on the upper surface of the developer is taken into the developer by the paddle, and the developer is dispersed in a direction orthogonal to the rotation axis. Yes. However, such a paddle has almost no conveying force to convey the powder in the direction of the rotation axis, so that it is difficult to obtain the effect of varying the conveyance speed of the powder in the direction of the rotation axis as described above. It hardly contributes to the improvement of dispersibility in the rotation axis direction. Also, the developer transport speed is slowed by providing the paddle.

  1, 4, 5, 6, and 7, the lead angle θ of the blade 51 changes, and the conveying surface 51 a of the blade 51 is close to the paddle, that is, floats on the upper surface of the developer. There is a portion where the toner is taken into the developer and the developer is easily dispersed in a direction perpendicular to the rotation axis 50. In that portion, the same effect as that of the paddle can be obtained by taking the toner floating on the upper surface of the developer into the developer and dispersing the developer in a direction perpendicular to the rotation shaft 50. Further, since the paddle is not provided, it is possible to suppress a decrease in the conveyance speed of the developer in the direction of the rotation axis as compared with the case where the paddle is provided. Therefore, in the screw shown in FIG. 1, FIG. 4, FIG. 5, FIG. 6 and FIG. 7, the toner floating on the upper surface of the developer is taken into the developer while suppressing a decrease in the conveying speed of the developer in the rotation axis direction. It is possible to achieve both stirring of the developer in the direction of the rotation axis and the direction orthogonal to the rotation axis 50, and to improve the dispersibility in the direction of the rotation axis of the developer and the dispersibility in the direction orthogonal to the rotation axis 50 of the developer. be able to.

Next, the improvement effect in the case of using the wavy screw will be described.
FIG. 11 shows a toner replenishment at one end of the developer accommodating portion 41 in the direction of the rotation axis of the developer conveying screw after replenishing toner from the toner hopper 46 to the developer accommodating portion 41 accommodating the developer in the developing device 40. From the position P1 to the toner density detection position P2 provided with the toner density sensor on the other end side (250 [mm]), the developer at the toner density detection position P2 after the developer is transported by the developer transport screw 45 This is the result of detecting the toner density. The rough locations of the toner supply position P1 and the toner density detection position P2 are shown in FIG.

In FIG. 11, the measurement was performed using the following three screws.
1) Screw in which the conveying surface 51a, the ridge line portion 51b, and the root 51c of the blade 51 are undulating (see FIG. 1).
2) A normal screw in which none of the conveying surface 51a, the ridge line portion 51b, and the root 51c of the blade 51 is wavy (see FIG. 2).
3) A screw in which notches 52 of 2 [mm] (from the tip of the blade 51 to the vicinity of the center) are inserted into the screw blade 51 at two locations for each round of the screw (one pitch of the blade 51) with respect to the normal screw. (See Figure 13)

  In the graph of FIG. 11, as the replenished toner arrives at the toner density detection position P2 earlier and the toner density fluctuation of the developer due to the replenished toner is smaller, the developer transportability by the developer transport screw, the replenishment toner A desirable state for dispersibility is shown.

  As can be seen from FIG. 11, when the normal screw is used, the arrival time from the toner replenishment position P1 to the toner density detection position P2 is the earliest, and the developer transport speed is the fastest. Is big. Next, when a screw having a notch 52 in a normal screw is used, the toner concentration fluctuation of the developer is small and the effect of dispersing the toner in the developer in the direction of the rotation axis is great, but the toner is supplied from the toner replenishment position P1. The arrival time to the density detection position P2 is the latest, and the developer transport speed is greatly reduced as compared with the case where a normal screw is used. On the other hand, when the wavy screw is used, the toner density fluctuation of the developer is small, and the effect of dispersing the toner in the developer in the rotation axis direction is great. Also, the arrival time from the toner replenishment position P1 to the toner density detection position P2 is slightly slower than that of the normal screw, but is not as slow as when using a screw having a notch 52 in the normal screw, and the developer transport. The speed is not so much lower than the normal screw. This is because the wavy screw has almost the same distance (pitch speed) as the developer traveling in one rotation as compared with the normal screw, so that the developer transport speed does not drop much compared to the case where the normal screw is used.

  In the case where the paddle is attached to the normal screw, the effect of taking the toner floating on the developer into the developer is great, but there is almost no dispersibility in the rotation axis direction by the paddle. Therefore, when the experiment of FIG. 11 was performed using a screw with a paddle attached to the normal screw, the result of the normal screw shown in FIG. 2 was almost the same. In other words, the purpose of improving both the incorporation of the replenishment toner into the developer and the dispersibility in the direction of the rotation axis cannot be achieved with the configuration in which the paddle is attached to the normal screw.

  FIG. 12 shows the distance until the replenished toner is taken into the developer. In FIG. 12, after replenishing toner from the toner hopper 46 to the developer accommodating portion 41 containing the developer in the developing device 40, toner replenishment at one end side of the developer conveying screw rotating shaft direction of the developer accommodating portion 41. The distance from the position P1 to the toner density detection position P2 where the toner density sensor on the other end is provided until the replenished toner that has been visually observed is completely taken into the developer. It is.

In FIG. 12, the distance until the replenished toner is taken into the developer was measured using the following four screws.
1) Screw in which the conveying surface 51a, the ridge line portion 51b, and the root 51c of the blade 51 are undulating (see FIG. 1).
2) A normal screw in which none of the conveying surface 51a, the ridge line portion 51b, and the root 51c of the blade 51 is wavy (see FIG. 2).
3) A screw provided with a paddle 53 for each round of the screw (every pitch of the blades 51) with respect to the normal screw (see FIG. 14).
4) Notches 52 of 2 [mm] (from the tip of the blade 51 to the vicinity of the center) were inserted into the screw blade 51 at two locations for each screw revolution (one pitch of the blade 51) with respect to the normal screw. Screw (see Fig. 13)

  As can be seen from FIG. 12, the distance until the replenishment toner is taken into the developer is the longest for the notched screw, followed by the normal screw, the wavy screw, and the screw with paddle. Thus, it can be seen that the notch screw has a slower toner uptake rate into the developer than the normal screw, and the wavy screw has a faster toner uptake rate into the developer than the normal screw.

  Further, when the amount of the replenishment toner is increased, the distance until the replenishment toner is taken into the developer becomes longer.

  In the corrugated screw, the amount of supply toner floating on the upper surface of the developer at the portion where the lead angle θ of the blade 51 of the screw is large is taken into the developer. That is, when the lead angle θ is increased, the screw blades 51 are configured to be close to paddles, and the amount of supply toner floating on the upper surface of the developer is taken into the developer. For this reason, the wavy screw blade 51 has a larger lead angle θ than the normal screw, so that the wavy screw has a faster mixing of the replenishment toner and the developer floating on the upper surface of the developer than the normal screw. The effect is obtained.

  11 and 12, the screw having the undulation of the conveying surface 51a, the ridge line portion 51b, and the root 51c of the blade 51 causes the supply of the replenishment toner floating on the upper surface of the developer to the developer and the development. It can be seen that the screw can achieve both improvement in the dispersibility in the rotation axis direction of the toner in the agent.

  Therefore, by using the wavy screw, the toner concentration of the developer supplied to the developing roller can be made uniform, the toner concentration fluctuation can be reduced, and the occurrence of an abnormal image can be suppressed.

  Further, the present invention can also be applied to a tandem indirect transfer type color copying machine shown in FIG. 15, and the same effects as described above can be obtained. FIG. 15 is a block diagram of a tandem indirect transfer type color copying machine embodying the present invention. This image forming apparatus is mainly composed of a copying machine main body 200, a paper feed table 300 on which the copying machine main body is mounted, a scanner 400 mounted on the copying apparatus main body, and an automatic document feeder (ADF) 500 mounted thereon. Yes.

  The copying machine main body 200 is provided with an intermediate transfer belt 210 that is an endless belt-like intermediate transfer member at the center. In the example of FIG. 15, the intermediate transfer belt 210 is wound around three support rollers 214, 215, and 216 so as to be able to rotate and convey in the clockwise direction in the drawing. In the illustrated example, an intermediate transfer member cleaning device 217 that removes residual toner remaining on the intermediate transfer belt 210 after image transfer is provided on the left side of the support roller 215 among the three support rollers. Further, on the intermediate transfer belt 210 stretched between the support roller 214 and the support roller 215, four image forming units 218 of black, yellow, magenta, and cyan are arranged side by side along the conveyance direction. Thus, the tandem image forming unit 220 is configured. An exposure device 221 is provided above the tandem image forming unit 220 as shown in FIG.

  On the other hand, a secondary transfer device 222 is provided on the opposite side of the intermediate transfer belt 210 from the tandem image forming unit 220. In the illustrated example, the secondary transfer device 222 is configured such that a secondary transfer belt 224 that is an endless belt is stretched between two rollers 223 a and 223 b, and is pressed against the support roller 216 via the intermediate transfer belt 210. The image on the intermediate transfer belt 210 is transferred to a sheet.

  A fixing device 225 for fixing the transferred image on the sheet is provided on the left side of the secondary transfer device 222 in the drawing. The fixing device 225 is configured by pressing a pressure roller 227 against a fixing belt 226 that is an endless belt.

  The secondary transfer device 222 described above is also provided with a sheet transport function for transporting the sheet after image transfer to the fixing device 225. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device 222. In such a case, it is difficult to provide this sheet conveyance function together.

  In the illustrated example, the sheet is disposed below the secondary transfer device 222 and the fixing device 225 in parallel with the tandem image forming unit 220 described above, and the sheet is reversed to record images on both sides of the sheet. A sheet reversing device 228 is provided.

Next, the individual image forming units 218 of the tandem image forming unit 220 will be described.
FIG. 16 is a schematic configuration diagram of the image forming unit 218. The image forming unit 218 includes a photosensitive drum 240 as an image carrier, a charging device 260 as a charging unit, a developing device 261 as a developing unit, and a temperature / humidity for detecting temperature / humidity around the photosensitive drum 240. A detection unit 282 and the like are provided.

  Among the parts constituting the image forming unit 218, the charging device 260 has a roller shape, and charges the photosensitive drum 240 by applying a voltage in contact with the photosensitive drum 240. Of course, charging can be performed by a non-contact scorotron charger. The developing device 261 uses a two-component developer containing a magnetic carrier and non-magnetic toner, and includes a developer container 266.

  The developer accommodating portion 266 conveys the two-component developer with stirring and supplies and adheres the two-component developer to the developing sleeve 265. The developer accommodating portion 266 and two parallel developer agitating screws 267 and 268 are provided, and the space between the two developer agitating screws 267 and 268 is partitioned by a partition plate 269 except for both ends in the rotation axis direction. It has been. Further, a toner density sensor 271 is attached to the developing case 270. Based on the toner concentration TC of the developer detected by the toner concentration sensor 271 and the temperature / humidity from the temperature / humidity detection unit 282 that detects the temperature / humidity, the toner replenishment control unit 280 determines the toner concentration of the developer as will be described later. Is adjusted and controlled.

  The developer accommodating portion 266 is configured to transfer the toner of the two-component developer attached to the developing sleeve 265 to the photosensitive drum 240 and to carry the developer facing the photosensitive drum 240 through the opening of the developing case 270. A developing sleeve 265 as a body is provided. Further, a doctor blade 273 is provided that is held with a gap spaced apart from the surface of the developing sleeve 265 by a certain distance.

  When making a copy using this color electrophotographic copying machine, a document is set on the document table 530 of the automatic document feeder 500. Alternatively, the automatic document feeder 500 is opened, a document is set on the contact glass 532 of the scanner 400, and the automatic document feeder 500 is closed and pressed.

  When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 500, the document is transported and moved onto the contact glass 532, and then the document is set on the other contact glass 532. At that time, the scanner 400 is immediately driven, and the first traveling body 433 and the second traveling body 434 travel. Then, the first traveling body 433 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 434 and reflects by the mirror of the second traveling body 434 and passes through the imaging lens 435. The document is placed in the reading sensor 436 and the original content is read.

  When a start switch (not shown) is pressed, one of the support rollers 214, 215, and 216 is rotationally driven by a drive motor (not shown), the other two support rollers are driven to rotate, and the intermediate transfer belt 210 is rotated and conveyed. To do. At the same time, the photosensitive drums 240 are rotated by the individual image forming units 218 to form black, yellow, magenta, and cyan monochrome images on the respective photosensitive drums 240, respectively. Then, along with the conveyance of the intermediate transfer belt 210, these single color images are sequentially transferred to form a composite color image on the intermediate transfer belt 210.

  On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 342 of the paper feed table 300 is selectively rotated, the sheet is fed out from one of the paper feed cassettes 344 provided in multiple stages in the paper bank 343, and the separation roller 345. Are separated one by one into the paper feed path 346, transported by the transport roller 347, guided to the paper feed path 248 in the copying apparatus main body 200, and abutted against the registration roller 249 to stop.

  Alternatively, the sheet feeding roller 250 is rotated to feed out the sheets on the manual feed tray 251, separated one by one by the separation roller 252, put into the manual sheet feeding path 253, and abutted against the registration roller 249 and stopped.

  Then, the registration roller 249 is rotated in synchronization with the composite color image on the intermediate transfer belt 210, the sheet is fed between the intermediate transfer belt 210 and the secondary transfer device 222, and is transferred by the secondary transfer device 222. A color image is recorded on the sheet.

  The sheet after the image transfer is conveyed by the secondary transfer device 222 and sent to the fixing device 225. The fixing device 225 applies heat and pressure to fix the transferred image, and then is switched by the switching claw 255 and discharged. The paper is discharged at 256 and stacked on the paper discharge tray 257. Alternatively, it is switched by the switching claw 255 and put into the sheet reversing device 228, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 257 by the discharge roller 256.

  On the other hand, the intermediate transfer belt 210 after image transfer is removed by the intermediate transfer body cleaning device 217 to remove residual toner remaining on the intermediate transfer belt 210 after image transfer, and prepares for the image formation by the tandem image forming unit 220 again.

As mentioned above, according to this embodiment, it has the rotating shaft 50 supported rotatably, and the blade | wing 51 which is the spiral blade protruded helically on the surrounding surface of the rotating shaft 50, and is self-rotating. Along with this, in the screw that conveys the powder in the direction of the rotation axis by the blade 51 while stirring the powder, the conveying surface 51a of the blade 51 is undulated within one pitch of the blade 51. Since the blades 51 are wavy within one pitch of the blades 51, the blades 51 a are close to vertical or parallel to the rotation shaft 50. The closer the blades 51 are perpendicular to the rotation shaft 50, the greater the powder conveyance force in the rotation axis direction, and the closer the blades 51a are parallel to the rotation shaft 50, the powder conveyance force in the rotation axis direction. Becomes smaller. Therefore, the conveying force of the powder in the direction of the rotation axis by the blades 51 varies within one pitch because the side surfaces of the blades 51 are wavy within the one pitch. As the conveying force increases, the powder becomes easier to be conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder becomes less likely to be conveyed in the direction of the rotation axis. A speed difference occurs in the conveyance speed of the powder to be produced. The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is conveyed in the direction of the rotation axis per unit time is different within the one pitch, so that the powder is easily mixed in the direction of the rotation axis. Therefore, when two or more kinds of powders are stirred and conveyed, the powders can be dispersed in the direction of the rotation axis within the above-mentioned one pitch as compared with the case where the conveying surface 51a of the blade 51 is not wavy.
Moreover, according to this embodiment, it has the rotating shaft 50 supported rotatably, and the blade | wing 51 which is the spiral blade projected on the surrounding surface of the rotating shaft 50 helically, and can rotate itself. Along with this, in the screw that conveys the powder in the direction of the rotation axis while stirring the powder by the blade 51, the size of the angle formed by the ridgeline of the blade 51 and the virtual plane orthogonal to the rotation shaft 50 changes within one pitch of the blade 51. is doing. The smaller the angle formed, the closer the blade 51 is to the rotating shaft 50, and the larger the angle formed, the closer the blade 51 is parallel to the rotating shaft 50. The closer the blades 51 are perpendicular to the rotation shaft 50, the greater the powder conveyance force in the rotation axis direction, and the closer the blades 51 are parallel to the rotation shaft, the more powder conveyance force in the rotation axis direction is. Get smaller. Therefore, by changing the size of the angle formed by the ridge line of the blade 51 and the virtual plane orthogonal to the rotation axis 50 within the one pitch, the conveying force of the powder in the rotation axis direction by the blade 51 is one pitch. Different within. As the conveying force increases, the powder becomes easier to be conveyed in the direction of the rotation axis, and as the conveying force decreases, the powder becomes less likely to be conveyed in the direction of the rotation axis. A speed difference occurs in the conveyance speed of the powder to be produced. The distance that the powder is transported in the direction of the rotation axis per unit time increases as the transport speed increases, and the distance that the powder is transported in the direction of the rotation axis per unit time decreases as the transport speed decreases. As described above, the distance that the powder is conveyed in the direction of the rotation axis per unit time is different within the one pitch, so that the powder is easily mixed in the direction of the rotation axis. Therefore, when two or more kinds of powders are agitated and conveyed, the powder is larger than the case where the angle formed by the ridge line of the blade 51 and the virtual plane orthogonal to the rotation axis 50 is not changed within the one pitch. The body can be dispersed in the direction of the axis of rotation.
Further, according to the present embodiment, the size of the angle formed by at least the ridgeline of the blade 51 of the screw on which the conveying surface 51 a of the blade 51 is wavy within one pitch of the blade 51 and the virtual plane orthogonal to the rotation axis 50. Is changing within the above pitch, the ridge line portion 51b of the blade 51 is also wavy. Since the angle of the blade 51 with respect to the rotation shaft 50 gradually changes in the screw in which the ridge line portion 51b of the blade 51 is wavy, the developer conveyance speed also changes momentarily and can be dispersed in the rotation axis direction due to the speed difference. In the portion where the ridge line portion 51b of the blade 51 undulates and the blade 51 lies on the rotation shaft 50, the toner floating on the upper surface of the developer is more concentrated in the developer than the screw where the ridge line portion 51 of the blade 51 is not undulated. The power to capture is increased. Therefore, the replenishment toner can be taken in and dispersed in the developer faster than the conventional screw in which the ridge line portion 51b of the blade 51 is not wavy. Further, since the rotating shaft 50 has a conveying force in the rotating shaft direction than the paddle 53 provided in parallel with the rotating shaft direction, the developer is transported in the rotating shaft direction more than the configuration in which the paddle 53 is provided on the rotating shaft 50. A decrease in speed can be suppressed.
In addition, according to the present embodiment, the angle formed by at least the root 51c of the blade 51 of the screw on which the conveying surface 51a of the blade 51 is wavy within one pitch of the blade 51 and the virtual plane orthogonal to the rotation shaft 50 is large. Is changing within the one pitch, the root 51c of the blade 51 is also wavy. Since the root 51c of the blade 51 is wavy, the angle of the blade 51 with respect to the rotating shaft 50 of the screw in which the root 51c of the blade 51 is waved gradually changes. Can disperse the powder in the direction of the rotation axis. Where the root 51c of the blade 51 undulates and the blade 51 lies on the rotation shaft 50, the toner floating on the upper surface of the developer is taken into the developer more than the screw where the root 51c of the blade 51 is not undulated. Strength becomes stronger. For this reason, the replenished toner can be taken into and dispersed in the developer faster than a screw in which the root 51c of the conventional blade 51 is not wavy. Further, since the rotating shaft 50 has a conveying force in the rotating shaft direction than the paddle 53 provided in parallel with the rotating shaft direction, the developer is transported in the rotating shaft direction more than the configuration in which the paddle 53 is provided on the rotating shaft 50. A decrease in speed can be suppressed.
In addition, according to the present embodiment, while carrying the developer transport member that transports the developer containing toner and carrier, and the developer transported by the developer transport member on its endlessly moving surface, In a developing device having a developer carrying member that develops a latent image carried on the latent image carrier by transporting it to a region opposite to the latent image carrier as its surface moves, the developer carrying member By using the screw of the present invention, it is possible to make the toner density of the developer supplied to the developer carrying member uniform, to reduce the fluctuation of the image density, and to suppress the occurrence of an abnormal image.
According to the present embodiment, the latent image carrier that carries the latent image, the developing means that develops the latent image on the latent image carrier, and the visible image developed on the latent image carrier are transferred. In the process cartridge that is held in a common holder as a unit, at least the latent image carrier and the developing means in the image forming apparatus including the transfer means for transferring to the image forming apparatus main body, As a means, by using the developing device provided with the screw of the present invention, the toner density of the developer supplied to the developer carrying member can be made uniform, the fluctuation of the image density can be reduced, and an abnormal image is generated. Can be suppressed.
Further, according to the present embodiment, in the image forming apparatus including the latent image carrier that carries the latent image and the developing unit that develops the latent image on the latent image carrier, the screw of the present invention is used as the developing unit. By using the developing device provided with, the toner density of the developer supplied to the developer carrying member can be made uniform, the fluctuation in image density can be reduced, and the occurrence of abnormal images can be suppressed.

DESCRIPTION OF SYMBOLS 1 Reading part 2 Lamp 4 Amplifier 5 Converter 6 Image processing part 8 Shading correction part 9 Filter 10 Correction part 11 Gradation processing part 12 Image formation part 13 Writing part 14 Laser beam 15 Charging charger 16 Developing sleeve 17 Paper feed tray 18 System Control unit 19 Operation unit 20 Temperature / humidity detection unit 27 Toner density sensor 30 Photosensitive drum 40 Developing device 41 Developer container 42 Developing case 43 Doctor blade 44 Developer stirring and conveying screw 45 Developer stirring and conveying screw 46 Toner hopper 48 Toner supply control Part 50 Rotating shaft 51 Blade 51a Conveying surface 51b Edge line part 51c Root 52 Notch 53 Paddle 200 Copying device main body 210 Intermediate transfer belt 214 Support roller 215 Support roller 216 Support roller 217 Intermediate transfer member cleaning device 21 8 Image forming unit 220 Tandem image forming unit 221 Exposure device 222 Secondary transfer device 223a Roller 224 Secondary transfer belt 225 Fixing device 226 Fixing belt 227 Pressure roller 228 Sheet reversing device 240 Photosensitive drum 248 Feed path 249 Registration roller 250 Feed roller 251 Manual feed tray 252 Separating roller 253 Feed path 255 Switching claw 256 Discharge roller 257 Discharge tray 260 Charging device 261 Developing device 265 Developing sleeve 266 Developer container 267 Developer stirring screw 269 Partition plate 270 Developing case 271 Toner Density sensor 273 Doctor blade 280 Toner replenishment control unit 282 Temperature / humidity detection unit 300 Paper feed table 342 Paper feed roller 343 Paper bank 344 Paper feed cassette 345 Separating roller 34 Feeding path 347 transport rollers 400 scanner 433 first carriage 434 second traveling body 435 imaging lens 436 sensor 500 automatic document feeder 530 platen 532 contact glass

JP 2007-334287 A

Claims (7)

A rotating shaft that is rotatably supported;
A spiral blade projecting spirally on the peripheral surface of the rotating shaft,
In a screw that conveys the powder in the direction of the rotation axis while stirring the powder by the spiral blade with its rotation,
2. A developing device according to claim 1, wherein the spiral blade is undulated within one pitch of the spiral blade. A rotating shaft that is rotatably supported;
A spiral blade projecting spirally on the peripheral surface of the rotating shaft,
In the screw that conveys in the direction of the rotation axis while stirring the powder by the spiral blade with its rotation,
The developing device according to claim 1, wherein an angle formed by a ridge line of the spiral blade and a virtual plane orthogonal to the rotation axis is changed within one pitch of the spiral blade. The developing device according to claim 1.
A developing device characterized in that at least an angle formed by a ridgeline of the spiral blade and a virtual plane orthogonal to the rotation axis changes within the one pitch. The developing device according to claim 1 or 2,
A developing device characterized in that at least an angle formed by a root of the spiral blade and a virtual plane orthogonal to the rotation axis changes within the one pitch. A developer conveying member that conveys a developer containing toner and a carrier, and the developer conveyed by the developer conveying member is carried on the surface that moves endlessly while the latent image is moved along with its own surface movement. In a developing device having a developer carrier that is transported to a region facing the carrier and develops a latent image carried on the latent image carrier,
A developing device using the screw according to claim 1, 2, 3, or 4 as the developer conveying member. A latent image carrier that carries a latent image; a developing unit that develops the latent image on the latent image carrier; and a transfer unit that transfers a visible image developed on the latent image carrier to a transfer member. In a process cartridge that is held in a common holding body as a unit and at least the latent image carrier and the developing unit in the image forming apparatus provided, and is integrally attached to and detached from the image forming apparatus main body,
A process cartridge using the developing device according to claim 5 as the developing means. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier.
An image forming apparatus using the developing device according to claim 5 as the developing means.

Images