JP4892374B2 - Developer supply device and image forming apparatus - Google Patents

Description

The present invention relates to a developer replenishing device and an image forming apparatus that replenish toner or a developer composed of toner and a carrier.

JP 2006-119668 A

  In the image forming apparatus of the above-described type, a suction type single-shaft eccentric screw pump is used for the purpose of supplying powdery toner or a powdery two-component developer having a toner and a carrier. Patent Document 1 and the like. Such a suction type single-shaft eccentric screw pump is generally called a MONO pump, and when the rotor rotates, a gap defined between the outer peripheral surface of the rotor and the inner peripheral surface of the through hole of the stator is formed. It moves so that the powder enclosed in the gap is transferred. Generally, the rotor is made of a rigid body such as metal or resin, and the stator is made of an elastic material such as rubber or soft resin.

  In conventional suction type single-shaft eccentric screw pumps, the amount of replenishment when driven by multiple rotations, for example, the total amount of replenishment when driven by 5 revolutions, is small. At the time of printing an image to be consumed, a change in the toner density of the developer due to the amount of toner replenishment was not observed. In other words, the driving time of the suction type single-shaft eccentric screw pump and the replenishment amount were in a substantially proportional relationship.

  By the way, when the consumed amount is a small amount and replenished in small amounts according to the amount, it is preferable that the suction type single-shaft eccentric screw pump is driven intermittently for a short time. However, when the suction type single-shaft eccentric screw pump is intermittently driven for a short time, the amount of replenishment varies each time, and the drive time and the amount of replenishment may not be proportional. If more toner than expected is supplied, the developer agitation performance is constant, and the dispersibility of the toner may deteriorate.

SUMMARY OF THE INVENTION In view of the above-described conventional circumstances, an object of the present invention is to provide a developer replenishing device and an image forming apparatus that can suppress a variation in the amount of developer replenishment per one replenishment drive and reduce a change in toner density. And

In order to solve the above-mentioned problems, the present invention is formed in a screw shape in which a rigid material such as metal is eccentric, and a rotor that is driven to rotate, and a screw-shaped hole is formed on the inside made of a rubber material. And a developer that replenishes the developing device with the developer stored in the required amount of developer storage using a suction-type single-shaft eccentric screw pump that includes a stator that encloses and contacts the rotor. In the replenishing device, the rotor is driven to rotate by a stepping motor, and a replenishment unit of the suction type single-axis eccentric screw pump is set so that the rotation speed of the rotor is constant and the rotation time is constant. adjust the number replenishing unit of the screw pump, with replenishing amount of the developer is required to drive the rotor, drive the rotor in the supply unit of the A rotation angle, proposes a developer supply apparatus characterized by an integral multiple of 360 °.

In the developer supply device of the present invention, it is effective to calculate the amount of developer consumed by development and control the amount of developer supplied to the developer device.
Furthermore, in the developer replenishing device of the present invention, it is effective to calculate the cumulative replenishment amount by counting the number of replenishment units and manage the remaining amount of developer in the developer storage unit.

Furthermore, in order to solve the above problems, the present invention replenishes the developing device with toner or a developer composed of toner and carrier using the developer replenishing device according to any one of claims 1 to 3. An image forming apparatus characterized by the above is proposed.

  In the image forming apparatus of the present invention, the toner used has a weight average particle diameter of 3 to 8 μm and a ratio (D4 / D1) of the weight average particle diameter (D4) to the number average particle diameter (D1) is 1. When it is in the range of .00 to 1.40, it is effective.

According to the present invention, the developer to be replenished per replenishment unit has a rotor driving rotation angle that is an integral multiple of 360 °, thereby eliminating variations in the replenishment amount due to differences in the rotor driving rotation angle . Toner density fluctuation can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic external configuration diagram of an image forming apparatus according to the present invention, and FIG. 2 is a vertical sectional explanatory view showing an example of a developer replenishing device of the image forming apparatus.

  FIG. 1 is a schematic view showing a color laser printer which is an example of an image forming apparatus according to the present invention. This color laser printer has a configuration in which an image forming unit 3 is disposed substantially at the center of the apparatus main body 1 and a paper feeding unit 2 is disposed below the image forming unit 3. The image forming unit 3 is provided with an intermediate transfer belt 7 as an image carrier formed of a flexible endless belt that is wound around a plurality of rollers 4, 5, 6 and rotates clockwise. Yes. Four image forming units 8Y, 8C, 8M, and 8BK are arranged opposite to each other on the upper belt running side between the rollers 4 and 5 of the intermediate transfer belt 7 as image forming units.

  The four image forming units 8 are provided with a photosensitive drum as a latent image carrier in contact with the intermediate transfer belt 7 and an apparatus for executing an electrophotographic process such as charging, developing, and cleaning. The four image forming units 8Y, 8C, 8M, and 8BK have the same structure, but the color of the toner to be developed is divided into four colors of yellow, cyan, magenta, and black. An optical writing unit 9 is disposed above the image forming unit 8 as optical writing means for irradiating the surface of each photosensitive drum with light-modulated laser light.

  In the image forming apparatus configured as described above, when an image forming operation is started, a toner image is formed on the photosensitive drum 10 of each image forming unit 8 based on an electrophotographic process, and the toner image is transferred to the intermediate transfer belt. 7 is sequentially superposed and transferred by a transfer means (not shown), and thus a full-color toner image is carried on the surface of the intermediate transfer belt 7. On the other hand, a transfer material made of paper, a resin sheet, or the like is fed from the paper feeding unit 2, and is fed in synchronization with the toner image to the secondary transfer device 11 facing the roller 6 via the registration roller 25. Is done. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the secondary transfer device 11, whereby the full-color toner image on the surface of the intermediate transfer belt is collectively collected on the transfer material. Transcribed. When the transfer material on which the toner image has been transferred passes through the fixing device 12, the toner image is melted and fixed on the transfer material by the heat and pressure. Thus, the transfer material on which the image is fixed is discharged to a paper discharge unit 13 outside the image forming apparatus main body 1. Note that any one of the image forming units 8 can be used to form a single-color image or a two-color or three-color image.

FIG. 2 is an explanatory cross-sectional view showing an outline of a toner replenishing device that replenishes the developing device 14 with a developer, and in this embodiment, toner.
In FIG. 2, reference numeral 20 denotes a toner storage container as a developer storage section. As shown in FIGS. 2 and 3, the toner storage container 20 has a bag container 21 and a cap member 22 having a single toner discharge section. It consists of and. A description of the specific configuration of the toner container 20 is omitted because it is not the gist of the present invention.

  The toner container 20 set in the image forming apparatus main body 1 communicates with the developing device 14 via a toner transfer tube 35 as a toner replenishment path, and a connecting member connected to the base member 22 in the toner replenishment path. And a suction type uniaxial eccentric screw pump 30 for transferring the toner in the container to the developing device 14 by suction force. The suction type uniaxial eccentric screw pump 30 and the nozzle 23 transfer the toner. It is connected by a tube 35 for use. Reference numeral 24 denotes a shutter that closes the discharge port when the nozzle 23 is removed from the toner container 20.

  In the developing device 14, screws 15 and 16 having spiral fins called conveyance augers inside the casing rotate in the directions of arrows A and B, and a developer containing a mixture of toner and carrier is contained in this portion. Yes. The transport auger is formed so that, for example, the screw 15 transports the developer from the front side to the back side in the figure, and the screw 16 transports the developer from the back side to the front side. By providing a portion without the partition 17, the developer is stirred while circulating. A part of the circulating developer is sucked and attracted by the magnetic force by the developing roller 19, and the uniform thickness is regulated by the doctor blade 18. Then, the electrostatic latent image on the photoreceptor is brought into contact with the photoreceptor. The toner is developed with toner to form a toner image. Here, only the toner adheres to the photosensitive member, and the toner is replenished from the toner replenishing port 38 in order to keep the amount of toner in the circulating developer in the developing device constant.

  The suction-type single-shaft eccentric screw pump 30 is a powder pump generally called a Mohno pump, and includes two main parts, a rotor 31 and a stator 32. The rotor 31 is formed in a screw shape in which a material having rigidity such as metal is eccentric, and is connected to a drive shaft 36 driven by a stepping motor 37. The stator 32 is made of a rubber material and has two screw-shaped holes formed inside. The stator 32 wraps and includes the rotor 31, contacts the rotor 31 and is held by a housing 33 made of a resin material or the like. ing. The suction type uniaxial eccentric screw pump 30 generates a strong self-priming force (suction pressure) by the rotation of the rotor 31, and can suck toner from the toner container 20 through the nozzle 23. The toner transfer tube 35 is made of, for example, a flexible tube having an inner diameter of about 4 to 7 mm, and has excellent toner resistance such as a rubber material such as polyurethane, nitrile, EPDM, or silicone, or a plastic material such as polyethylene or nylon. It is composed of

  In the toner replenishing device having such a configuration, when the amount of consumed toner is small, the suction type uniaxial eccentric screw pump 30 is intermittently driven little by little. At this time, the amount of toner to be replenished varies even during the same driving time. I explained earlier that there is a problem of doing.

  The cause of such a problem will be described with reference to FIG. 3A and 3B show the relationship between the rotor 31 and the stator 32 at the rotation angle of the rotor, where FIG. 3A is a view in the rotor longitudinal direction, and FIG. 3B is a vertical sectional view with respect to the rotor axis.

  In FIG. 3, it can be seen that the cross-sectional area of the space between the rotor 31 and the stator 32 is not uniform in the longitudinal direction of the rotor 31, and the shape of the space is changed. Therefore, for example, when the rotor 31 is moved by 1/3, it can be seen that the space volume to be moved for each time is different. Therefore, it was found that when the control is performed without being aware of the rotation angle of the rotor 31, the toner replenishment amount varies and the toner replenishment amount varies.

  FIG. 4 is a graph showing the toner replenishment amount when the rotor 31 is rotated 216 °, 288 °, 432 °, and 504 ° using a stepping motor. The vertical axis represents the toner replenishment amount, and the horizontal axis represents the number of replenishments. ing.

As apparent from FIG. 4, it is clear that the replenishment amount fluctuates when the rotation angle of the rotor 31 is 216 °, 288 °, 432 °, and 504 °.
Therefore, in the replenishment system of the present invention, a replenishment unit is set in which the rotation speed of the rotor 31 of the suction type single-shaft eccentric screw pump 30 is constant and the rotation time is constant, and the rotation angle of the rotor 31 in the replenishment unit is an integer of 360 °. It is set to double. That is, the rotation angle of the rotor 31 is set to 360 ° × n (n is an integer).

As described above, when the rotation angle of the rotor 31 is set to 360 °, the toner replenishment amount can be accurately replenished with small fluctuations as indicated by the triangular marks in FIG.
Next, a specific example of drive control of the suction type single-shaft eccentric screw pump 30 will be described.

  The driving of the suction type single-shaft eccentric screw pump 30 in the present embodiment has a control specification such that the stepping motor 37 rotates 200 (msec) at a driving speed of 300 (rpm) per replenishment unit. The suction type uniaxial eccentric screw pump 30 does not stabilize the suction pressure generated in the pump until a certain driving time is reached. Further, the suction pressure generated in the pump is not stable even when it is not higher than a certain drive rotation speed. Therefore, the suction type single-shaft eccentric screw pump 30 in the present embodiment has a driving speed of 300 (rpm) and a driving time of 200 (msec) per replenishment unit. That is, the rotation angle of the rotor 31 in one supply unit is set to 360 °. Also, an experiment is performed with toner and a device that uses the replenishment amount per replenishment unit, and the value is input to the control unit of the main body.

  The toner supply is executed after the number of supply units corresponding to the supply amount is calculated. Therefore, the smaller the replenishment amount of one replenishment unit, the higher the accuracy of replenishment becomes possible, and therefore, n is preferably set to 1. Further, since the approximate amount of toner replenished is determined from the cumulative number of replenishments in the replenishment unit, the amount of toner remaining in the toner storage container 20 can be calculated and applied to the remaining toner management of the toner storage container 20. can do.

  The toner replenishing device by the replenishment system configured as described above can reduce the replenishment amount per replenishment unit and finely replenish the developer, thereby improving the dispersibility of the toner and further reducing the toner density fluctuation. Can do. Further, when the suction type single-shaft eccentric screw pump is driven by a normal motor or clutch, the rise and fall times vary for each part of the motor or clutch or for each drive of the motor or clutch. At this time, the rotation angle cannot be accurately controlled and the replenishment amount varies. However, since the stepping motor 37 is used in this embodiment, the rotation angle can be accurately controlled, so that only the target rotation angle is driven. Thus, it is possible to eliminate variations in the replenishment amount and stabilize the toner density.

  By the way, the toner replenishment control includes a replenishment control system for measuring and replenishing the toner density of the developer such as a magnetic permeability sensor, and a replenishment control system for replenishing the toner by calculating the toner consumption from the image area and the number of pixels to be formed There is. In the former replenishment control system, the control is such that the toner is consumed and the toner density is lowered and then the toner is replenished to increase the toner density, so a time lag is inevitably caused. Therefore, in this toner replenishing device that can replenish without any variation in the replenishment amount, the latter replenishment control method can be used to greatly reduce the time from toner consumption to replenishment, and to reduce fluctuations in developer toner density. can do.

Next, the toner suitably used in the image forming apparatus of the present invention will be described.
In order to reproduce minute dots of 600 dpi or more, the toner preferably has a weight average particle diameter of 3 to 8 μm. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent.

When the weight average particle diameter (D4) is less than 3 μm, phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur.
When the weight average particle diameter (D4) exceeds 8 μm, it is difficult to suppress scattering of characters and lines.

Moreover, it is preferable that ratio (D4 / D1) of a weight average particle diameter (D4) and a number average particle diameter (D1) exists in the range of 1.00-1.40.
The closer (D4 / D1) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

Next, a method for measuring the particle size distribution of toner particles will be described.
Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.

  First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the weight and number of toner particles or toner using a 100 μm aperture as an aperture. Calculate weight distribution and number distribution. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

  The above has described the case of transporting and supplying new toners used in image forming apparatuses such as copying machines, among other powders. However, in order to meet various environmental problems and various demands for resource recycling in recent years, they are collected. Various toner recycling mechanisms for returning the residual toner to the developing device and recycling it as a developer have been proposed. It goes without saying that the replenishment system, developer replenishing device, and image forming apparatus of the present invention are intended for these recycled toners.

  Further, the developer of the present invention is not limited to a new toner or recycled toner, but may be a developer in which a toner and a carrier are already mixed. At this time, if a developer having a high toner concentration is added, the dispersibility of the toner is increased and the toner concentration fluctuation can be reduced. Furthermore, the present invention is also effective in trickle development in which the developer is replenished and discharged little by little, and the toner density fluctuation can be reduced.

1 is a schematic diagram illustrating an embodiment of an image forming apparatus according to the present invention. 2 is a schematic vertical sectional view showing a toner supply device of the image forming apparatus. FIG. The relationship between the rotor and the stator at the rotation angle of the rotor is shown, (a) is a view in the rotor longitudinal direction, and (b) is a vertical sectional view with respect to the axis of the rotor. 6 is a graph in which the vertical axis represents the amount of toner replenishment and the horizontal axis represents the number of replenishments when the rotor is rotated 216 °, 288 °, 360 °, 432 °, and 504 °.

Explanation of symbols

14 Developing Device 30 Suction Type Uniaxial Eccentric Screw Pump 31 Rotor 32 Stator 37 Stepping Motor

Claims (5)

A rigid material such as metal is formed into an eccentric screw shape, and a rotor that is driven to rotate, and a screw-shaped hole made from a rubber material is formed on the inside. In a developer replenishing device for replenishing a developing device with a developer stored in a required amount of developer storing portion using a suction type single-shaft eccentric screw pump having a stator,
The rotor is driven to rotate by a stepping motor, and the replenishment unit of the suction type single-shaft eccentric screw pump is set such that the rotation speed of the rotor is constant and the rotation time is constant,
Adjusting the replenishment unit number of the suction type single-shaft eccentric screw pump, replenishing the requested amount of developer by driving the rotor ,
The developer replenishing device characterized in that the driving rotation angle of the rotor in the replenishment unit at that time is an integral multiple of 360 °. The developer replenishing device according to claim 1 , wherein the developer replenishing device calculates the amount of developer consumed by development and controls the amount of developer replenished to the developing device. 2. The developer replenishing apparatus according to claim 1 , wherein a cumulative replenishment amount is calculated by counting the number of replenishment units, and the remaining amount of developer in the developer storage unit is managed. . An image forming apparatus, wherein the developer replenishing device according to any one of claims 1 to 3 is used to replenish toner or a developer composed of toner and a carrier to the developing device. 5. The image forming apparatus according to claim 4 , wherein the toner used has a weight average particle diameter of 3 to 8 μm and a ratio (D4 / D1) of the weight average particle diameter (D4) to the number average particle diameter (D1). An image forming apparatus having a range of 1.00 to 1.40.

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