JP2012242638A - Cleaning device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an amount of developer within a predetermined range in the upstream side in the developer conveyance direction when conveying the developer by a conveyance screw.SOLUTION: A conveyance screw 9 comprises a first conveyance screw 9a and a second conveyance screw 9b which rotate in the same axis in the longitudinal direction of a developer storage part. The first conveyance screw is provided in a developer discharge port side and the second conveyance screw is provided in the opposite side of the developer discharge port. The first conveyance screw is drive-controlled at a predetermined speed so as to convey a collected developer to the discharge port, and the second conveyance screw is controlled to drive itself forward and backward depending on a detection result by detection means.

Description

  The present invention relates to a cleaning device that conveys a developer in a developer container and discharges the developer from a discharge port, and an image forming apparatus using the same.

  In an electrophotographic image forming apparatus, a developer image is formed on a photosensitive drum that is an image carrier, and the developer image is transferred to a recording medium to form an image. At this time, the developer cannot be completely transferred from the photosensitive drum to the recording medium, and a slight amount of developer remains on the image carrier. The residual developer is removed and collected by a cleaning device.

  As the cleaning device, for example, a cleaning blade is pressed against the longitudinal circumferential surface of the photosensitive drum, the developer remaining on the photosensitive drum is scraped off by this blade, and the developer is disposed along the longitudinal direction of the photosensitive drum. Collect in storage. A conveyance screw that can rotate around an axis substantially parallel to the rotation axis of the photosensitive drum is provided in the developer accommodating portion, and the developer collected in the developer accommodating portion is moved from one side to the other side in the longitudinal direction. The developer is conveyed and discharged from a developer discharge port provided on the other side to a developer reservoir.

  In the cleaning device that transports the collected developer with the transport screw in this way, the developer is not transported uniformly in the longitudinal direction of the transport screw, but rather on the upstream side in the developer transport direction (hereinafter simply referred to as “upstream”). And the downstream side (hereinafter simply referred to as “downstream side”).

  For example, there is one in which the blade screw pitch on the downstream side is configured larger than that on the upstream side (Patent Document 1). Or there exists what made the downstream blade screw outer diameter larger than the upstream side (patent document 2). In these cases, when the developer is transported by the transport screw, the developer is more easily deposited on the downstream side than on the upstream side. Therefore, the developer transporting force on the downstream side is configured to increase the developer clogging. It is made so that it does not occur.

JP 2006-251114 A JP 05-072952

  In recent years, image forming apparatuses using a developer have come to use a method in which an abrasive is contained in the developer and fine foreign matters on the surface of the photosensitive drum are removed by the polishing effect. Yes. In particular, in an image forming apparatus provided with a cleaning device that transports the developer collected from the photosensitive drum from one side to the other side in the longitudinal direction of the photosensitive drum by the transport screw, the recovered developer is transported by the transport screw. The surface of the photosensitive drum can be polished with the collected developer by bringing it into contact with the photosensitive drum.

  However, when rotating the conveying screw having a uniform conveying force in the longitudinal direction to convey the developer from one side of the longitudinal direction to the other side and discharge it from the discharge port, the developer from the upstream side on the downstream side in the longitudinal direction Is transported and stays, but does not stay upstream. Therefore, in the longitudinal direction of the photosensitive drum, a polishing effect by the abrasive is obtained on the downstream side, but the polishing effect by the abrasive is reduced on the upstream side. As a result, an image defect may occur in which the image is whitened on the upstream side where the polishing effect is small.

  Therefore, in order to obtain a polishing effect by the developer, it is conceivable that the developer conveying force by the conveying screw is different between the upstream side and the downstream side. However, in the configurations shown in Patent Documents 1 and 2, since the developer transport force on the downstream side is larger, it is possible to prevent the developer from clogging on the downstream side, but the collected developer is used on the upstream side. It is difficult to retain effectively.

  It is also conceivable to make the recovered developer uniform in the longitudinal direction of the photosensitive drum by controlling the rotation speed of the conveying screw or by partially reversing the direction of the spiral of the conveying screw. However, even in this case, in the cleaning device that transports the developer from one side of the photosensitive drum to the other side in the longitudinal direction, the developer amount can be adjusted in the entire longitudinal direction, but only the upstream side is adjusted. Difficult to do.

  The present invention has been made in view of the above points, and an object thereof is to provide a developer amount in a predetermined range on the upstream side in the developer conveyance direction when the developer in the developer accommodating portion is conveyed by a conveyance screw. The present invention provides a cleaning device and an image forming apparatus using the same.

  A typical configuration according to the present invention for achieving the above object is that the developer recovered from the image carrier is accommodated in the developer accommodating portion, and the developer in the developer accommodating portion is conveyed to the discharge port by the conveying member. In the cleaning device that discharges the developer, a longitudinal developer container that stores the collected developer, a developer discharge port provided at one end in the longitudinal direction of the developer container, and the development A transport member that transports the developer collected in the developer container along the longitudinal direction of the image carrier toward the developer discharge port, and detects the amount of developer stored in the developer container. Detecting means, and the conveying member has a first conveying screw and a second conveying screw that rotate in the longitudinal direction of the developer accommodating portion, and the first conveying screw is on the developer discharge port side. Arranged in the second conveying screw Is disposed on the opposite side of the developer discharge port across the first conveyance screw, and the first conveyance screw is driven and controlled at a predetermined speed so as to convey the developer to the discharge port. The screw is forward / reversely driven and controlled according to the detection result of the detection means.

  In the present invention, the developer in the developer container is transported by the second transport screw on the upstream side in the transport direction. Since the rotation direction of the second conveying screw is controlled in accordance with the detection result of the detecting means, the amount of developer can be finely controlled even upstream of the developer accommodating portion where the developer is difficult to stay.

1 is a schematic explanatory diagram of an electrophotographic image forming apparatus. It is a schematic explanatory view of a cleaning device. It is a perspective explanatory view of a cleaning device. It is a configuration explanatory view of the cleaning device. It is explanatory drawing of the connection structure of a conveyance screw. It is explanatory drawing of the connection structure of a conveyance screw. It is explanatory drawing of the blade | wing shape of a conveyance screw. It is explanatory drawing of the blade | wing of a conveyance screw. It is a related figure which shows threshold value A and B and the drive of a 2nd conveyance screw. It is a related figure which shows drive of threshold value A, B, C and a 2nd conveyance screw. It is a flowchart which shows the drive operation of the 2nd conveyance screw which set threshold-value A, B, C. It is a related figure which shows drive of threshold value A, B, D and a 2nd conveyance screw. It is a flowchart which shows the drive operation of the 2nd conveyance screw in consideration of apparatus environment. It is explanatory drawing which shows the shape of the conveyance screw used in experiment. 6 is a graph showing the results of Experiment 1. 10 is a graph showing the results of Experiment 2.

  Next, an embodiment for carrying out the present invention will be specifically described with reference to the drawings.

[First Embodiment]
<Overall configuration of image forming apparatus>
FIG. 1 is a schematic cross-sectional explanatory diagram of an image forming apparatus including a cleaning device according to the present embodiment. The image forming apparatus according to the present embodiment is used as an electrophotographic copying machine, a printer, or the like.

  First, the overall configuration of the image forming apparatus A of the present embodiment will be described together with the image forming operation. During image formation, a charging bias is applied by the charging roller 2 to the photosensitive drum 1 serving as an image carrier that rotates in the direction of arrow A in FIG. 1, and the surface of the photosensitive drum 1 is uniformly charged. The photosensitive drum 1 is irradiated with laser light 3 corresponding to an image signal from an exposure unit (not shown), and an electrostatic latent image is formed on the photosensitive drum. The electrostatic latent image is developed by the developing device 4 to form a developer image with the developer.

  The recording medium 6 is conveyed to a transfer unit by a conveying means (not shown) so as to synchronize with the formation of the developer image. This transfer portion is constituted by a nip portion between the photosensitive drum 1 and the transfer roller 5, and when the recording medium 6 is conveyed to the nip portion, a transfer bias is applied to the transfer roller 5 to the photosensitive drum 1. The formed developer image is transferred to a recording medium. The recording medium onto which the developer image has been transferred is conveyed to a fixing device (not shown), heated and pressurized to fix the developer image on the recording medium, and then discharged to a discharge unit.

  On the other hand, the developer on the photosensitive drum 1 is not completely transferred to the recording medium in the transfer portion, and a minute developer remains on the photosensitive drum 1. The residual developer is removed and collected by the cleaning device B, and the next developer image is formed on the photosensitive drum 1.

<Cleaning device>
As shown in FIGS. 1 and 2, the cleaning device of the present embodiment has a strip-shaped rubber member 7b having an appropriate elasticity and hardness, such as polyurethane or chloroprene rubber elastomer, at the end of a support member 7a made of sheet metal. The attached cleaning blade 7 is attached to the developer accommodating portion 8.

  The rubber member 7 b has substantially the same length as the length of the photosensitive drum 1 in the longitudinal direction, and is in pressure contact with the peripheral surface of the photosensitive drum 1. The developer remaining on the photosensitive drum 1 is scraped off by the rubber member 7b, and the collected developer is accommodated in the developer accommodating portion 8.

  The developer accommodating portion 8 has a duct shape arranged along the longitudinal direction of the photosensitive drum 1, and a conveyance screw 9 that is a conveyance member for conveying the toner collected inside is rotatably arranged. The conveying screw 9 conveys the developer collected from the photosensitive drum 1 along the longitudinal direction of the photosensitive drum 1 from one side in the longitudinal direction in the developer accommodating portion 8 to the other side. As shown in FIG. 3, a discharge port 8 a for discharging the collected developer to the collection box 10 is provided at one end portion in the longitudinal direction of the developer container 8.

  As a result, the developer remaining on the photosensitive drum 1 is scraped off by the cleaning blade 7 and collected in the developer accommodating portion 8. The developer collected in the developer accommodating portion 8 is conveyed by the conveying screw 9 along the longitudinal direction of the photosensitive drum 1 to the discharge port 8a, and is discharged from the discharge port 8a to the collection box 10.

  Note that the developer of the present embodiment contains an abrasive, and the developer collected in the developer container 8 rubs against the surface of the rotating photoconductor drum 1 to rub against the surface of the photoconductor drum 1. It is intended to remove the attached fine foreign matter. Therefore, in the present embodiment, the developer accommodating portion 8 is disposed above the photosensitive drum 1 so that the collected developer is easily brought into contact with the photosensitive drum 1.

  In the present embodiment, the conveying screw 9 is configured and the drive thereof is controlled so that the developer collected in the developer accommodating portion 8 is effectively polished on the surface of the photosensitive drum 1. It is configured to do. The configuration of the conveying screw 9 and the drive control of the conveying screw 9 will be described later.

<Developer>
Here, the developer used in this embodiment will be described. The developer is generally magnetic resin particles, and the base of the magnetic resin particles is mainly composed of a binder resin, and contains a charge control agent and magnetic powder inside. An external additive blended for the purpose of improving performances such as charging stability, lubricity imparting, abrasiveness imparting, and scattering prevention adheres around the base material.

  The recovered developer contains an abrasive such as cerium oxide, silicon carbide, or strontium titanate that polishes the photosensitive drum 1, and the voltage from the charging roller is in contact with the charging roller 2 of the photosensitive drum. There is an effect of preventing image defects by removing discharge products and the like attached by discharge due to application.

  Here, the external addition amount of strontium titanate externally added as abrasive particles is preferably 0.1 to 25 parts by weight, more preferably 2.0 to 3.0 parts by weight with respect to 100 parts by weight of the toner particles. . When the amount is less than 0.1 parts by weight, the polishing effect is not sufficiently exhibited. When the amount is more than 25 parts by weight, the cohesiveness is increased, the developability is reduced, the polishing effect is too strong, and the photoconductor is excessively shaved. This is because scratches are generated.

  As the abrasive, strontium titanate was used, but similar abrasives include silicon oxide, aluminum oxide, titanium oxide, zinc oxide, zirconia, chromium oxide, cerium oxide, tungsten oxide, antimony oxide, copper oxide, Tin oxide, tellurium oxide, manganese oxide, boron oxide, barium titanate, aluminum titanate, magnesium titanate, calcium titanate and other oxides, silicon carbide, tungsten carbide, boron carbide, titanium carbide and other carbides, silicon nitride, A nitride such as titanium nitride or boron nitride, or other organic particles may also be used.

  As the abrasive added to the toner, cubic type particles are preferable because of high polishing effect. The cubic type particles have an average particle size of 30 to 300 nm, more preferably 40 to 250 nm. When the average particle size is less than 30 nm, the polishing effect of the particles in the cleaner portion is insufficient. On the other hand, if the thickness exceeds 300 nm, the polishing effect is too strong, and scratches are generated on the photosensitive drum 1, which is not suitable.

  In the present embodiment, as described above, in addition to the magnetic recovery developer containing an external additive such as an abrasive, powder particles in general can be used as a recovery target.

<Conveying screw>
Next, the configuration of the conveying screw 9 according to this embodiment will be described. FIG. 3 is a perspective view illustrating a configuration of the cleaning device B according to the present embodiment, and FIG. 4 is a schematic diagram of the cleaning device B.

  If the collected developer stays in the developer accommodating portion 8 to some extent and does not slide on the photosensitive drum, the polishing effect of the photosensitive drum 1 by the abrasive contained in the collected developer is reduced and image defects are likely to occur. Become. This insufficient retention of the collected developer tends to occur on the upstream side (hereinafter referred to as “upstream side”) of the transport screw 9 in the developer transport direction. Therefore, in the present embodiment, the conveying screw 9 is divided into the first conveying screw 9a and the second conveying screw 9b, and can be rotated independently of each other, and the developer is controlled by controlling the driving of the second conveying screw 9b on the upstream side. The retention of the developer in the storage unit 8 is controlled.

  A conveying screw 9 that conveys the developer along the longitudinal direction of the photosensitive drum 1 is provided in the developer accommodating portion 8. As shown in FIG. 4, the transport screw 9 includes a first transport screw 9 a and a second transport screw 9 b that rotate on the same axis in the longitudinal direction of the developer accommodating portion 8, and the first transport screw 9 9a is disposed on the developer discharge port side, and the second transport screw 9b is disposed on the opposite side of the developer discharge port with the first transport screw 9a interposed therebetween.

(Material)
Examples of the material of the conveying screw 9 include resin materials such as a molding material, an acrylic resin, a polyester resin, a polyvinyl acetal resin, and an epoxy resin. Rubber materials such as polyurethane, styrene-butadiene copolymer, chloroprene, butadiene rubber, ethylene-propylene-diene rubber, chlorosulfonated polyethylene rubber, fluorine rubber, silicone rubber, acrylic rubber, nitrile rubber, chloroprene rubber and other elastomers May be used.

(Consolidated structure)
As shown in FIG. 5, the conveying screw 9 of the present embodiment includes a shaft end 9 a 1 of the first conveying screw 9 a and a shaft end 9 b 1 of the second conveying screw 9 b that are rotatably connected to each other via a connecting member 11. Both screws 9a and 9b are supported so as to be rotatable on the same axis.

  The connecting member 11 may be made of the same material as the conveying screws 9a and 9b, or may be a metal material such as copper, aluminum, tin, iron, or nickel. A member having a smaller friction coefficient than the material of the conveying screws 9a and 9b may be used. The shape of the connecting member 11 is preferably cylindrical or spherical so as not to hinder the slidability of the transport screws 9a and 9b to be connected. Moreover, the connection member 11 should just be connected so that the mutual rotation of the conveyance screws 9a and 9b may not be hindered, and a configuration in which the developer is difficult to adhere inside is preferable.

  The length C of the connecting member 11 in FIG. 5 is 5 to 50 mm, preferably 20 to 30 mm. When it is smaller than 5 mm, the connection between the first conveying screw 9a and the second conveying screw 9b becomes weak, the axis of the conveying screw is not fixed, and a certain operation is not performed, and the connecting portion may be detached. On the other hand, if it is larger than 50 mm, the friction of the sliding portion becomes large and the operation of the conveying screw is hindered.

  Furthermore, in order to improve the slidability of the connection part of the 1st conveyance screw 9a and the 2nd conveyance screw 9b, you may apply | coat the substance which raises slidability, such as grease and molybdenum disulfide, to the inside or the surface of the connection member 11. .

  As shown in FIG. 5, by connecting the both conveying screws 9 a and 9 b using the connecting member 11, the connecting portion between the first conveying screw 9 a and the second conveying screw 9 b is not uneven, and therefore the connecting portion Developer adhesion or the like is less likely to occur.

  As shown in FIG. 5, it is preferable that the connecting portion between the first conveying screw 9a and the second conveying screw 9b does not cause unevenness. As shown in FIG. 4, the connection part may protrude a little from the screw shaft.

  Moreover, you may make it the connection structure of the 1st conveying screw 9a and the 2nd conveying screw 9b show in FIG. That is, the shaft diameter of the second conveying screw 9b is made larger than that of the first conveying screw 9a, and the end of the first conveying screw 9a is inserted into the fitting hole formed in the second conveying screw 9b so as to be rotatable. Concatenated. By doing in this way, both conveyance screw 9a, 9b can be connected, without using a connection member.

  As shown in FIG. 3, the conveying screw 9 that is rotatably connected on the same axis as described above has the first conveying screw 9a connected to the first drive source 12a via a gear, The conveying screw 9b is also connected to the second drive source 12b through a gear.

  Therefore, the 1st conveyance screw 9a and the 2nd conveyance screw 9b are comprised so that rotation speed and a rotation direction can be rotated independently. Each of the conveying screws 9a and 9b is provided with spiral blades 9a2 and 9b2 on the rotation shaft, and the developer in the developer accommodating portion 8 is directed toward the discharge port 8a by rotating the blades 9a2 and 9b2. Are transported.

  Further, since the first conveying screw 9a and the second conveying screw 9b are configured to rotate on the same axis, the amount of developer in the longitudinal direction in the developer accommodating portion 8 is uniform in the same space as one conveying screw. It becomes possible to keep it. However, the first conveying screw 9a and the second conveying screw 9b do not necessarily have to rotate on the same axis as long as the developer can be sequentially conveyed to the downstream side.

(Length of second conveying screw)
As described above, when the developer in the developer accommodating portion 8 is conveyed, the retention of the developer in the developer accommodating portion 8 is controlled by controlling the driving of the second conveying screw 9b on the upstream side. Therefore, the length of the second conveying screw 9b located on the upstream side in the entire conveying screw 9 is desirably in the range of 1/5 or more and 1/2 or less of the longitudinal length of the photosensitive drum 1. . If the length is shorter than 1/5, the amount of the collected developer conveyed by the second conveying screw 9b is small and the developer amount cannot be adjusted. On the other hand, if it is longer than 1/2, it is difficult to adjust the developer amount on the upstream side.

(Feather shape)
The blade shape of the conveying screw 9 of the present embodiment is preferably circular, but may be cut or uneven. FIG. 7 shows an example of a conveying blade shape. 7A and 7B show a case where the shape of a part of the conveying blade is changed to improve the retention of the developer. By cutting a part of the circular blade, the developer transportability is suppressed, and the developer stays more. Moreover, as shown to FIG. 7C, you may take the structure which provided the processus | protrusion to the axis | shaft between a blade | wing, and provided the processus | protrusion to the conveyance blade as shown to FIG. 7D.

  When the collected developer is accumulated in the developer accommodating portion 8, the collected developer is easily fixed to the blades and shafts of the screw. By attaching protrusions as described above to the shafts and blades, it is possible to prevent the developer from sticking and to prevent the conveyance of the developer. In addition, the outer diameter of the conveying blade is unified in the longitudinal direction in this embodiment, but some of the conveying blade outer diameters may be different as shown in FIG. 7E. Although FIG. 7E shows the case where two types of outer diameter blades are alternately arranged, two or more types of blade outer diameters may be used, and the arrangement is not limited to this. You can choose freely.

(Blade pitch)
FIG. 8 is an enlarged view of the conveying screw. The interval a indicates the interval between the blades on the conveying screw, and is expressed as a blade pitch width in this embodiment. Further, the interval b indicates the outer diameter of the blade on the screw, and is expressed as the blade outer diameter in this embodiment.

  The pitch width of the blades is 5 to 30 mm, preferably 10 to 20 mm. If the pitch width is smaller than 5 mm, the developer conveying force increases and the developer stays worse. In addition, since the blades are too dense, the developer is aggregated and fixed. When the pitch width is larger than 30 mm, the developer transportability is reduced, and the developer stays up. However, when a large amount of the developer is fed, a countermeasure cannot be taken and a cleaning failure is caused.

  Further, the outer diameter of the blade of the conveying screw 9 may be 20 to 80%, preferably 30 to 50% of the area S2 occupied by the outer diameter of the developer with respect to the cross-sectional area S1 shown in FIG. Good. If the area of the outer diameter of the blade is more than 80% of the cross-sectional area of the developer accommodating portion 8, the transport amount of the recovered developer increases, and sufficient retention of the recovered developer targeted in this embodiment cannot be expected. On the other hand, if it is less than 20%, the collected developer stays too much, causing aggregation and fixation in the developer container, leading to poor cleaning.

<Driving screw drive control>
Next, the drive control of the transport screw 9 will be described focusing on the drive control of the second transport screw 9b.

  In the present embodiment, a detection means for detecting the amount of developer collected in the developer accommodating portion 8 is provided, and the amount of developer in the developer accommodating portion 8 according to the detection result by the detecting means. Is controlled so as to be within a predetermined range.

(Developer amount detection means)
As a detecting means for detecting the amount of developer in the developer accommodating portion 8, in the present embodiment, as shown in FIG. 4, the driving torque of the second drive source 12b for driving the second conveying screw 9b is detected by the torque detecting portion 13. The developer amount detected in the developer container 8 is detected based on the detected value, and in particular, the developer amount upstream in the transport direction is detected.

  Specifically, the torque applied to the drive system of the second conveying screw 9b, for example, a gear is converted into a voltage value and detected. That is, when the developer amount is large, the torque is large, and when the developer amount is small, the torque is small. Then, the number of rotations of the drive source, the direction of rotation, and the like are controlled by the fluctuation of the torque value to control the drive of the second conveying screw 9b.

  The configuration of the developer amount detecting means may not be the torque detection. For example, when a developer having magnetic force such as a magnetic developer is used, the developer amount may be detected using a magnetic permeability sensor. The magnetic permeability sensor measures the amount of developer in contact with the magnetic permeability sensor from the number of lines of magnetic force passing through the built-in electromagnetic core, and thereby detects the amount of developer in the developer container 8.

  In accordance with the detection result by the developer amount detection means, the control unit 14 including a CPU or the like controls the rotation direction and rotation speed of the second drive source 12b.

(Drive control)
In the case where an abrasive is contained in the developer to suppress the occurrence of image flow, it is necessary to maintain a constant amount of the developer collected on the photosensitive drum in order to maintain the polishing effect. In this embodiment, the rotation direction and the rotation speed of the first conveying screw 9a and the second conveying screw 9b can be independently driven and controlled. As a result, by controlling the driving of the second conveying screw 9b located on the upstream side in accordance with the developer amount so that the upstream developer amount is in a predetermined range, the upstream of the photosensitive drum that is difficult to stay. The amount of developer on the side is controlled to maintain the polishing effect.

  In describing the drive control of the conveying screw 9 of the present embodiment, when the first conveying screw 9a and the second conveying screw 9b are rotated forward, the developer is conveyed in the direction of the arrow X1 in FIG. It will be described as transporting in the direction of arrow X2 in FIG.

  In the present embodiment, the first conveying screw 9a on the downstream side always rotates forward at a constant predetermined speed to convey the developer to the discharge port 8a. On the other hand, the second conveying screw 9b on the upstream side is rotated at the same speed as the first conveying screw 9a, but the rotation direction is driven to rotate forward or reverse depending on the developer amount. Thereby, the amount of developer in the developer accommodating portion 8 is set within a predetermined range.

  Specifically, when the lower threshold value (lower limit setting value) of the predetermined range is A and the upper threshold value (upper limit setting value) is B, as shown in FIG. Until the side threshold value B is detected, the second conveying screw 9b is reversely rotated. As a result, the collected developer is transported in the direction of arrow X2 (see FIG. 3) opposite to the discharge port 8a, and stays on the upstream side of the developer accommodating portion 8 until the upper limit of the predetermined range is reached.

  Thereafter, when the torque detector 13 detects the upper threshold B, the second conveying screw 9b is rotated forward to convey the collected developer in the direction toward the discharge port 8a. As a result, the upstream collected developer is conveyed and discharged in the direction of arrow X1 (see FIG. 3), and does not stay above the upper threshold B within a predetermined range.

  When the upstream developer is discharged and the torque detector 13 detects the lower threshold A, the second conveying screw 9b is rotated in the reverse direction to convey the collected developer in the direction opposite to the discharge port 8a. To stay in. Thus, the upstream collected developer does not become lower than the lower threshold A within a predetermined range.

  As described above, the rotation direction of the second conveying screw 9b is repeatedly switched from the start to the end of the print job so that the collected developer amount is in the predetermined range A to B. The determination of the torque value is averaged with that detected a plurality of times within a certain range, and the change of the rotation direction of the second conveying screw 9b is determined when the next job command is received after determining the threshold value. It may be changed. Further, as the determination of the predetermined value, the number of sheets to be passed can be managed, and detection may be performed when the set number of sheets to be passed is printed.

  In the present embodiment, the lower threshold value A is a value that makes it meaningless to provide a threshold value because the developer amount does not reach the developer amount that causes the transportability of the transport screw when the developer amount is less than that. Further, the upper threshold value B is a value that hinders conveyance because the developer in the developer accommodating portion 8 becomes excessive when the amount of the developer is more than that. Accordingly, the respective threshold values are set so as to fall within a range from the time when the developer transportability occurs to the time before the developer stays too much to be fixed.

  By switching the rotation direction of the second conveying screw 9b as described above, the amount of developer in the developer accommodating portion 8, particularly the upstream amount of developer that is difficult to stay, is within a predetermined range, and the collected developer. Thus, the polishing effect of the photosensitive drum 1 is reliably maintained.

[Second Embodiment]
In the first embodiment described above, the second conveying screw 9b is rotated at a constant rotational speed. However, if a developer amount larger than the upper threshold B is retained, the second rotational speed is higher than usual. The developer may be discharged by rotating the two conveying screw 9b forward.

  For example, when the out-of-range threshold C larger than the above-described upper threshold B is set as the developer amount and the torque detection unit 13 detects the out-of-range threshold (out-of-range set value) C, the second conveying screw 9b. Is rotated at a rotational speed faster than the rotational speed of the first transport screw 9a to transport the recovered developer toward the discharge port 8a.

  FIG. 10 is a diagram showing the relationship between the threshold value when the threshold values A, B, and C (A <B <C) are provided, the rotational direction and the rotational speed of the second conveying screw 9b. In the transport system having a distance in the longitudinal direction as in the present embodiment, it is difficult to cope with a large amount of developer that is fed into a part. Therefore, when the developer amount reaches the out-of-range threshold C that exceeds the upper threshold B of the predetermined range, the rotation speed of the second conveying screw 9b is made higher than that of the first conveying screw 9a until the upper threshold B is reached. Drive forward to reduce developer clogging. At this time, the ratio of the rotational speed of the second transport screw 9b is set to 1.1 to 1.5 times, preferably 1.1 to 1.3 times the rotational speed of the first transport screw 9a.

  FIG. 11 is a flowchart showing the drive control procedure shown in FIG. The torque detector 13 receives the print job (S1), detects the rotation of the photosensitive drum (S2), detects the developer amount (S3), and collects the developer amount (screw drive torque) at that time. To control the rotation direction and rotation speed of the second conveying screw 9b (S4 to S7).

  As described above, when the collected developer amount stays above the upper threshold B, the developer is discharged by rotating the second conveying screw 9b at a speed higher than the normal speed, thereby reliably clogging the developer. Can be reduced.

[Third Embodiment]
In the first embodiment described above, the rotation amount of the second conveying screw 9b is switched between the lower threshold A and the upper threshold B within a predetermined range, but the lower threshold A and the upper threshold B are used. Control may be performed by setting an in-range threshold value (in-range set value) D (A <D <B) located between.

  For example, as shown in FIG. 12, first, the second developer screw 9b is reversely rotated until the torque detector 13 detects the in-range threshold value D, and the recovered developer is conveyed in the X2 direction opposite to the discharge port side. Then, the developer is retained on the upstream side. And if the torque detection part 13 detects the said threshold value D, until it detects the upper side threshold value B from that time, the drive of the 2nd conveyance screw 9b will be stopped. That is, first, the second conveying screw 9b is reversely rotated to positively retain the developer upstream, and thereafter the rotation is stopped to slow the staying speed.

  Thereafter, when the torque detector 13 detects the upper threshold value B, the second conveying screw 9b is rotated forward to convey the upstream developer in the X1 direction and discharged from the discharge port. When the developer is discharged and decreases and the torque detector 13 detects the threshold value D, the second conveying screw 9b is stopped and the developer is retained on the upstream side. By repeating this, the amount of developer in the developer accommodating portion 8 is kept constant.

  By setting the in-range threshold D as described above and controlling the second conveying screw 9b to stop rotating based on the value, the upstream developer amount can be adjusted gently. . In the above description, when the threshold value D is detected, the rotation of the second conveying screw 9b is stopped. However, the rotation speed is made slower than normal and the rotation is reversed or forward without stopping. It is possible to adjust the upstream developer amount gradually.

[Fourth Embodiment]
In the first embodiment described above, the rotational direction or rotational speed of the second conveying screw 9b is switched in accordance with the amount of developer in the developer accommodating portion 8. However, in consideration of the installation environment of the apparatus, Also good.

  In a high-temperature and high-humidity environment, the influence of foreign matter adhering to the surface of the photosensitive drum appears more remarkably. Therefore, improvement of the polishing effect by the developer is required in a high temperature and high humidity environment. Therefore, a temperature / humidity sensor for detecting the environmental temperature and humidity in the image forming apparatus is installed, and the temperature and humidity in the apparatus are set to a high temperature that is higher than the set temperature and humidity (for example, temperature 30 ° C. or higher, humidity 80% or higher). In the case of a high humidity environment, the threshold value of the developer amount by the torque detector 13 is set to a higher value than in the normal environment (for example, the temperature is less than 30 ° C. and the humidity is less than 80%). Reset the values of the thresholds C and D) to 20-30% higher. As a result, the polishing effect by the developer can be improved.

  It should be noted that the temperature and humidity set as the high temperature and high humidity, and the threshold level to be increased when the high temperature and high humidity become high may be set according to the setting table.

  FIG. 13 is a flowchart showing the above procedure. Compared to the flowchart of FIG. 11, this flowchart increases the procedure of detecting the temperature and humidity between steps S1 and S2 (S8) and resetting the threshold level depending on the environment (S9).

  By setting the threshold value in consideration of the apparatus environment as described above, it is possible to effectively prevent the influence of foreign matters adhering to the surface of the photosensitive drum.

〔Experimental result〕
Next, the results of an actual developer conveyance experiment using the cleaning device according to the above-described embodiment will be described.

<Experiment 1>
The apparatus used in Experiment 1 performed conveyance control in which the threshold values A, B, and C described in the second embodiment were set by the image forming apparatus and the cleaning apparatus described in the first embodiment.

  The developer having the abrasive used in Experiment 1 is a magnetic one-component developer having an average particle diameter of 7 μm produced by a pulverization method. Specifically, with respect to 100 parts by weight of the developer particles, 1.0 part by weight of hydrophobic silica (volume average particle size 10 nm) hydrophobized on the surface of the silica base with a silane coupling agent and silicone oil is oxidized. Externally added 0.8 weight of titanium (volume average particle size 50 nm). In order to improve the polishing properties, strontium titanate (volume average particle size 1.5 μm) as polishing particles with 3.0 parts by weight added thereto was used.

  As the conveying screw, a spiral screw having a blade outer diameter of φ14, a core metal diameter of φ6, and a blade pitch width of 10 mm as shown in FIG. 14 was used for each of the first and second conveying screws.

  The connection method shown in FIG. 6 in which the length of the first conveying screw 9a is 350 mm, the length of the second conveying screw 9b is 100 mm, and the end of the first conveying screw 9a is inserted into the end of the second conveying screw 9b. The length of the connecting portion was 20 mm. Both the first conveying screw 9a and the second conveying screw 9b have a developer conveying speed of 118 mm / sec, and the conveying speed of the second conveying screw 9b when the developer amount increases and the conveying speed is switched is 154 mm / sec. .

The developer accommodating portion 8 has a cross-sectional area of 350 mm ² and a longitudinal length of 450 mm and a volume of 157 cm ³ . The collected developer was sent to the developer accommodating portion 8 at a loading amount of 0.6 mg per A4 horizontal sheet, and the effect was confirmed from the change in the accumulated amount of collected developer at the drive end 15 mm of the second conveying screw 9b.

  As a means for detecting the recovered developer amount, a torque detection configuration in which the torque applied to the drive gear of the second conveying screw 9b is converted into a voltage value was used.

Monitoring was performed at the same time as the job command, the threshold was judged, and the rotation direction and rotation speed of the second conveying screw 9b were controlled. At this time, the recovery developer amount detecting the lower side threshold A and 0.2 g / cm ^3, was set upper threshold B 0.45 g / cm ^3, a range threshold C to 0.6 g / cm ^3. Then, switching is performed when the collected developer amount detection means determines the threshold value five times in succession in 100 msec, and the switching timing is when the next job command is received after the threshold value is determined.

  FIG. 15 shows an effect obtained when the above-described drive control is performed on a conventional example of conveyance performed without changing the rotation speed with a single conveyance screw.

When compared with the conventional example described as “no control”, the developer amount was kept at about 0.4 g / cm ³ when the above control was performed, and the effect was confirmed. Compared to the conventional example, the developer recovery amount was large and the polishing effect on the photosensitive drum was sufficient, and no image defect was observed at the driving side end.

<Experiment 2>
In Experiment 2, using the image forming apparatus shown in Experiment 1, another threshold value D is provided between the lower threshold value A and the upper threshold value B (A <D <B). An experiment was performed to control the drive of the second conveying screw described in the embodiment.

Threshold A, B, as the D, and the lower side threshold A 0.2g / cm ^3, a range within the threshold D and 0.27 g / cm ^3, the upper side threshold B and 0.45 g / cm ^3, a range threshold C The effect of Experiment 1 and Experiment 2 was compared by setting to 0.6 g / cm ³ . The result is shown in FIG. From this result, it can be seen that if the in-range threshold value D is provided and the second conveying screw 9b is driven and controlled, the amount of staying developer can be controlled more smoothly.

<Experiment 3>
In Experiment 3, using the image forming apparatus shown in Experiment 1, transport control was performed in consideration of the apparatus environment described in the fourth embodiment.

As the environmental temperature and humidity, when a temperature of 30 ° C. or higher and a humidity of 80% or higher are detected, it is assumed that the environment is in a high temperature and high humidity environment, and each threshold level is reduced by 80% in cases other than the high temperature and high humidity environment. Specifically, in a high temperature and high humidity environment, the lower threshold A is 0.16 g / cm ³ , the in-range threshold D is 0.21 g / cm ³ , the upper threshold B is 0.36 g / cm ³ , and the out-of-range threshold C Was set to 0.48 g / cm ³ to confirm the effect.

As a result, even in a high-temperature and high-humidity environment where the collected developer particles have increased cohesiveness, the collected developer amount is maintained at 0.3 g / cm ³ , and no image defect occurs at the end of the second conveying screw 9b, No cleaning failure occurred.

DESCRIPTION OF SYMBOLS A ... Image forming apparatus B ... Cleaning apparatus 1 ... Photosensitive drum 2 ... Charging roller 3 ... Laser beam 4 ... Developing apparatus 5 ... Transfer roller 6 ... Recording medium 7 ... Cleaning blade 7a ... Support member 7b ... Rubber member 8 ... Developer Accommodating portion 8a ... discharge port 9 ... conveying screw 9a ... first conveying screw 9a1, 9b1 ... shaft end 9a2, 9b2 ... blade 9b ... second conveying screw 10 ... recovery box 11 ... connecting member 12a ... first drive source 12b ... first Two drive sources 13 ... Torque detection unit 14 ... Control unit

Claims (8)

In the cleaning device for storing the developer recovered from the image carrier in the developer storage portion, and transporting and discharging the developer in the developer storage portion to the discharge port by the transport member.
A longitudinal developer container for accommodating the collected developer;
A developer discharge port provided at one end in the longitudinal direction of the developer accommodating portion;
A conveying member that conveys the developer accommodated in the developer accommodating portion along the longitudinal direction of the image carrier toward the developer discharge port;
Detecting means for detecting the amount of developer accommodated in the developer accommodating portion;
Have
The conveying member includes a first conveying screw and a second conveying screw that rotate in a longitudinal direction of the developer accommodating portion, and the first conveying screw is disposed on the developer discharge port side, and the second conveying screw The screw is disposed on the opposite side of the developer discharge port across the first conveying screw,
The first conveying screw is driven and controlled at a predetermined speed so as to convey the developer to the discharge port,
The cleaning device according to claim 1, wherein the second conveying screw is forward / reversely driven and controlled in accordance with a detection result of the detection unit.   When the lower threshold of the predetermined range of the developer amount is A and the upper threshold is B, the second conveying screw discharges the developer until the detecting means detects the upper threshold B. When the detection means detects the upper threshold value B, the second conveying screw rotates forward so as to convey the developer in the direction toward the discharge port. 2. The cleaning device according to claim 1, wherein when the detection unit detects a lower threshold A, the second conveying screw is driven to rotate reversely so as to convey the developer in a direction opposite to the discharge port.   When the out-of-range threshold value C larger than the upper threshold value B is set and the detection means detects the out-of-range threshold value C, the second conveying screw is rotated faster than the rotating velocity of the first conveying screw. The cleaning device according to claim 2, wherein the cleaning device is driven so as to convey the developer in a direction toward the discharge port.   When an in-range threshold value D is set between the lower threshold value A and the upper threshold value B, and the detecting means detects the in-range threshold value D, the detecting means detects the upper threshold value B. The cleaning device according to claim 2 or 3, wherein the driving of the second conveying screw is stopped until it is done.   The developer amount threshold detected by the detection unit is switched to a value higher than the temperature and humidity when the environmental temperature and humidity of the apparatus are equal to or higher than the set temperature and humidity. 5. The cleaning device according to any one of 4 above.   The length in the longitudinal direction of the second conveying screw is not less than 1/5 and not more than 1/2 of the length in the longitudinal direction of the image carrier. The cleaning device described.   The cleaning apparatus according to claim 1, wherein a developer containing an abrasive is conveyed. In an image forming apparatus for forming an image by transferring a developer image formed on an image carrier to a recording medium,
3. A developer conveying device that collects the developer remaining on the image carrier after transferring the developer image from the image carrier to the recording medium, conveys the collected developer, and discharges the developer from a discharge port. An image forming apparatus comprising the cleaning device according to claim 7.

Images