JP2021071533A - Image forming apparatus - Google Patents

Abstract

To optimize the interval of execution of a vibration mode for vibrating a toner receiving member of a developing device.SOLUTION: A developing device has a developer container, a developing sleeve, a supply sleeve that supplies a toner to the developing sleeve, a toner receiving member that is arranged below the developing sleeve and the supply sleeve, and a vibration mechanism that vibrates the toner receiving member. A temperature and humidity sensor detects information on the absolute amount of moisture inside the developer container. The control unit executes a vibration mode for shaking off a toner accumulated on the toner receiving member with the vibration of vibration means. When the temperature or the relative humidity inside the developer container is the same, if a result of detection made by the temperature and humidity sensor is a first value, the control unit sets the interval of execution of the recovery mode to a first time in which the supply sleeve is driven, and if the result of detection is a second value larger than the first value, sets the interval of execution of the recovery mode to a second time shorter than the first time in which the supply sleeve is driven.SELECTED DRAWING: Figure 9

Description

The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, and a multifunction device having a plurality of these functions.

Conventionally, as a developer used in an image forming apparatus using an electrophotographic method, a two-component developer containing a non-magnetic toner (hereinafter referred to as toner) and a magnetic carrier (hereinafter referred to as carrier) has become widespread. ing. A hybrid development method is known as a development method for developing an electrostatic latent image formed on a photosensitive drum, which is an example of an image carrier, using this two-component developer. In the hybrid development method, a developing sleeve that develops a photosensitive drum by supporting and rotating toner and a supply sleeve that supplies toner to the developing sleeve by supporting and rotating a developer in a developing container are used. Be done.

In the hybrid development method, toner may scatter from the facing portion between the supply sleeve and the developing sleeve and its surroundings, and the toner scattered in the developing container rides on the airflow in the developing container and faces the regulating blade and the developing sleeve. May deposit on the inner wall of the developing container. When the accumulated toner aggregates and adheres to the developing sleeve, the aggregated toner is supplied onto the photosensitive drum, which may cause image defects. Therefore, there has been proposed a developing device in which a toner receiving member is provided in a portion where toner is deposited and the toner receiving member can be vibrated by vibrating means (see Patent Document 1). The image forming apparatus provided with this developing apparatus executes a vibration mode in which the toner receiving member is vibrated at the time of non-image forming for each fixed number of prints, sifts off the accumulated toner, and collects the accumulated toner by the developer carried on the supply sleeve. I am trying to do it.

Japanese Unexamined Patent Publication No. 2012-208469

However, in the image forming apparatus including the developing apparatus described in Patent Document 1 described above, the vibration mode is executed to vibrate the toner receiving member at the time of non-image formation for each fixed number of prints, so that the vibration interval is appropriate. It may not be. That is, the amount of toner scattered in the developing container is the amount of toner supplied to the positions facing the supply sleeve and the developing sleeve, the strength of the airflow around the supply sleeve and the developing sleeve, and the charge per unit mass of toner. It depends on the amount (hereinafter referred to as the toner charge amount) and the like. Of these, if the amount of toner charged is small, the toner is likely to scatter, and the toner is deposited on the toner receiving member more quickly. The amount of toner charged depends on, for example, the absolute amount of water in the environment inside the developing device. In an environment where the absolute water content is large, the toner charge amount tends to decrease, so that the toner is easily released from the carrier and the amount of toner scattered increases.

Here, when the toner charge amount becomes small due to printing being performed in an environment having a large absolute water content, the toner is deposited faster. At this time, in the configuration in which the vibration mode is executed for each fixed number of prints described above, the interval at which the toner receiving member is vibrated is too long with respect to the speed at which the toner is deposited, and the toner sieving may not catch up. In this case, toner accumulation and aggregation proceed on the inner wall of the developing container, and the aggregated toner adheres to the developing sleeve to supply the aggregated toner to the photosensitive drum, which may cause image defects. .. On the other hand, when the toner charge amount becomes large due to printing being performed in an environment where the absolute water content is small, the toner deposition becomes slow. At this time, in the configuration in which the vibration mode is executed for each fixed number of prints described above, the interval at which the toner receiving member is vibrated is too short with respect to the speed at which the toner is deposited, and the image formation is interrupted each time. There is a risk that productivity will decrease.

An object of the present invention is to provide an image forming apparatus capable of optimizing the execution interval of a vibration mode for vibrating a toner receiving member of a developing apparatus.

The image forming apparatus of the present invention supports an image carrier on which an electrostatic latent image is formed, a developing container containing a developing agent containing a non-magnetic toner and a magnetic carrier, and rotates the image. A developing sleeve capable of developing an electrostatic latent image on the image carrier in a region facing the carrier and a developing agent inside the developing container can be supported and rotated to supply toner to the developing sleeve. A developing apparatus having a supply sleeve, a toner receiving member arranged below at least one of the developing sleeve and the supplying sleeve, and a vibrating means for vibrating the toner receiving member, and the developing container. A detection means that detects information on the absolute water content inside the processor, and a control unit that can execute a vibration mode that sifts off the toner accumulated on the toner receiving member by the vibration of the vibration means by controlling the vibration means. The control unit includes, and the temperature inside the developing container or relative to the case where the detection result of the detection means has a first value and the case where the detection result has a second value larger than the first value. When the humidity is the same, when the detection result is the first value, the execution interval of the vibration mode is set to the first time when one of the developing sleeve and the supply sleeve is driven. When the detection result is the second value, the execution interval of the vibration mode is set to a second time shorter than the first time when one of the sleeves is driven.

According to the present invention, it is possible to optimize the execution interval of the vibration mode that vibrates the toner receiving member of the developing device.

FIG. 6 is a schematic configuration sectional view of an image forming apparatus according to an embodiment. The control block diagram of the image forming apparatus which concerns on embodiment. FIG. 6 is a schematic configuration sectional view of the developing apparatus according to the embodiment. Schematic vertical cross-sectional view of the developing apparatus according to the embodiment. A vibration motor and a vibration weight of the developing apparatus according to the embodiment, (a) is a side view, and (b) is a front view. Schematic vertical cross-sectional view of the developing apparatus according to the embodiment when the recovery mode is executed. The graph which shows the relationship between the absolute moisture content of the developer used in the developing apparatus which concerns on embodiment, and the toner charge amount. The graph which shows the relationship between the toner charge amount and the toner accumulation amount of the developer used in the developing apparatus which concerns on embodiment. The flowchart which shows the execution procedure of the collection mode by the image forming apparatus which concerns on embodiment. The graph which shows the relationship between the absolute water content of the developer used in the developing apparatus which concerns on embodiment, and the deposition coefficient.

The image forming apparatus according to the embodiment will be described with reference to FIGS. 1 to 10. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG.

[Image forming device]
The image forming apparatus 1 shown in FIG. 1 is an electrophotographic full-color printer having four color (yellow, magenta, cyan, black) image forming portions PY, PM, PC, and PK in the apparatus main body. In the present embodiment, the image forming unit PY, PM, PC, and PK are arranged along the rotation direction of the intermediate transfer belt 7, which will be described later, in an intermediate transfer tandem system. The image forming apparatus 1 records a toner image (image) according to an image signal from a host device such as a personal computer or the like, which is not shown and is communicatively connected to the document reading apparatus (not shown) connected to the apparatus main body. Form in S. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

The process of forming the toner image will be described. First, the image forming unit PY, PM, PC, and PK will be described. However, the image forming portions PY, PM, PC, and PK are configured to be substantially the same except that the toner colors are different from yellow, magenta, cyan, and black. Therefore, in the following, the yellow image forming unit PY will be described as an example, and the other image forming units PM, PC, and PK will be omitted.

The image forming unit PY is mainly composed of a photosensitive drum 2, a charging device 3, an exposure device 4, a developing device 5, and the like. The surface of the photosensitive drum 2 as an example of the rotationally driven image carrier is uniformly charged in advance by the charging device 3, and then electrostatically latent by the exposure device 4 driven based on the signal of the image information. An image is formed. That is, an electrostatic latent image is formed on the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is developed by the developing device 5 with toner and visualized as a toner image. Further, the toner in the developer consumed in image formation is replenished together with the carrier from a toner cartridge (not shown).

After that, a predetermined pressing force and a primary transfer bias are applied by the primary transfer rollers 6 arranged to face each other with the photosensitive drum 2 and the intermediate transfer belt 7 sandwiched between them, and the toner image formed on the photosensitive drum 2 is displayed on the intermediate transfer belt 7. Primary transfer to. A small amount of transfer residual toner remaining on the photosensitive drum 2 after the primary transfer is removed by the cleaning device 8 to prepare for the next image forming process again.

The intermediate transfer belt 7 is stretched by a tension roller 10, a secondary transfer inner roller 11, and a drive roller 12. The intermediate transfer belt 7 is driven by the drive roller 12 so as to move in the direction of arrow R1 in the drawing. The image forming process of each color processed by the above-mentioned image forming unit PY, PM, PC, and PK is performed at the timing of sequentially superimposing on the toner image of the color upstream in the moving direction that is primarily transferred onto the intermediate transfer belt 7. .. As a result, a full-color toner image is finally formed on the intermediate transfer belt 7 and conveyed to the secondary transfer unit T2. The secondary transfer portion T2 is a transfer nip portion formed by a portion of the intermediate transfer belt 7 stretched on the secondary transfer inner roller 11 and the secondary transfer outer roller 13. The transfer residual toner after passing through the secondary transfer unit T2 is removed from the intermediate transfer belt 7 by the transfer cleaner device 14.

For the process of forming the toner image sent to the secondary transfer unit T2, the transfer process of the recording material S to the secondary transfer unit T2 is executed at the same timing. In the transfer process, the recording material S is fed from a sheet cassette (not shown) or the like, and is fed to the secondary transfer unit T2 in accordance with the image formation timing. In the secondary transfer unit T2, a secondary transfer voltage is applied to the secondary transfer inner roller 11.

As described above, the toner image is secondarily transferred from the intermediate transfer belt 7 to the recording material S in the secondary transfer unit T2 by the image forming process and the transport process. After that, the recording material S is conveyed to the fixing device 15, and the toner image is melted and fixed on the recording material S by being heated and pressurized by the fixing device 15. The recording material S on which the toner image is fixed is discharged to the discharge tray by the discharge roller.

[Control unit]
The image forming apparatus 1 includes a control unit 20 for performing various controls such as the above-mentioned image forming operation. The operation of each part of the image forming apparatus 1 is controlled by the control unit 20 provided in the image forming apparatus 1. A series of image forming operations is controlled by the operation unit on the upper surface of the apparatus main body or the control unit 20 according to each input signal via the network.

As shown in FIG. 2, the control unit 20 includes a CPU (Central Processing Unit) 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, and the like as arithmetic control means. The CPU 21 controls each part of the image forming apparatus 1 while reading a program corresponding to the control procedure stored in the ROM 22. Work data and input data are stored in the RAM 23, and the CPU 21 controls by referring to the data stored in the RAM 23 based on the above-mentioned program or the like. The control unit 20 processes image information in the image processing unit 24 to generate drive signals for each unit, controls the operation of each unit in the image formation control unit 25, and controls the toner supply to the developing device 5 in the replenishment control unit 26. Do. The toner concentration sensor 58, the optical sensor 80, and the temperature / humidity sensor 81 are connected to the control unit 20. The toner concentration sensor 58 and the optical sensor 80 will be described later. The temperature / humidity sensor 81 is provided, for example, on a part of the wall portion of the stirring chamber 53 on the downstream side in the toner transport direction in order to detect information on the temperature and humidity inside the developing apparatus 5 as an example of the detecting means. (See Fig. 3).

The control unit 20 calculates the absolute water content inside the developing device 5 based on the information on the temperature and humidity inside the developing device 5, which is the detection result of the temperature / humidity sensor 81. That is, the temperature / humidity sensor 81 detects information regarding the absolute water content inside the developing container 50. In this embodiment, the control unit 20 calculates information on volume absolute humidity as information on absolute water content. Further, in the present embodiment, the control unit 20 describes the case where the information regarding the volume absolute humidity is calculated as the information regarding the absolute water content, but the present invention is not limited to this, and the weight absolute humidity is related as the information regarding the absolute water content. The information may be calculated.

[Two-component developer]
Next, the developer used in this embodiment will be described. In this embodiment, a two-component developer containing non-magnetic toner particles (toners) and magnetic carrier particles (carriers) is used as the developer. The toner is colored resin particles containing a binder resin, a colorant, and other additives as needed, and an external agent such as colloidal silica fine powder is externally added to the surface thereof. The toner used in this embodiment is a negatively charged polyester resin, and has a volume average particle size of about 7.0 μm. The carrier used in the present embodiment is made of, for example, magnetic metal particles such as iron, nickel, and cobalt whose surface has been oxidized, and has a volume average particle size of about 50 μm.

[Developer]
Next, the developing apparatus 5 will be described in detail with reference to FIGS. 3 to 6. As shown in FIGS. 3 and 4, the developing apparatus 5 includes a developing container 50, a developing sleeve 60, a supply sleeve 61, and a collection mechanism 70 (see FIG. 4).

The developing container 50 contains a developing agent containing a non-magnetic toner and a magnetic carrier. The substantially central portion of the developing container 50 is partitioned by a partition wall 51 so that the developing chamber 52 and the stirring chamber 53 are adjacent to each other in the horizontal direction. The developer is housed in the developing chamber 52 and the stirring chamber 53. In the developing chamber 52 and the stirring chamber 53, a first transport screw 54 and a second transport screw 55 that are rotatable for stirring and circulating the developer are arranged, respectively. The first transport screw 54 is arranged at the bottom of the developing chamber 52 so as to face substantially parallel to the axial direction of the supply sleeve 61, and the second transport screw 55 is located at the bottom of the stirring chamber 53 as the first transport screw. It is arranged substantially parallel to 54. The developer is conveyed by rotating the first transfer screw 54 and the second transfer screw 55. The transport path for transporting the developer in the developing chamber 52 is designated as the developing transport path 52p, and the transport path for transporting the developer in the stirring chamber 53 is designated as the stirring transport path 53p. The developer conveyed by the rotation of the first transfer screw 54 and the second transfer screw 55 circulates in the developing chamber 52 and the stirring chamber 53 through the communication portions 56 and 57 which are the openings at both ends of the partition wall 51.

In the stirring chamber 53, a toner concentration sensor 58 is arranged so as to face the second transfer screw 55. As the toner concentration sensor 58, for example, a magnetic permeability sensor that detects the magnetic permeability of the developer in the developing container 50 is used. The control unit 20 replenishes the toner from the toner cartridge to the stirring chamber 53 via the toner replenishment port 59 based on the detection result of the toner concentration sensor 58.

As shown in FIG. 4, a developing sleeve 60 is provided between the photosensitive drum 2 and diagonally above the supply sleeve 61 when viewed from the direction of the rotation axis of the supply sleeve 61. The supply sleeve 61 and the developing sleeve 60 are arranged so as to face each other in the facing portion Ar2 with the rotation axes substantially parallel to each other. The developing sleeve 60 faces the photosensitive drum 2 on the opening side of the developing container 50. The developing sleeve 60 and the supply sleeve 61 are each rotatably provided around a rotation axis. The developing sleeve 60 and the supply sleeve 61 are rotationally driven counterclockwise in FIG. 4 by a driving unit 9 (see FIG. 2) provided in the main body of the apparatus. That is, the developing sleeve 60 and the supply sleeve 61 rotate in opposite directions at the facing portion Ar2, and the rotation speed is made variable by the driving unit 9.

The supply sleeve 61 is made of a non-magnetic sleeve that rotates counterclockwise in FIG. 4, and is rotatably provided around a non-rotating magnet roller 61a that is a magnetic field generating means provided on the inner peripheral side. The magnet roller 61a has a plurality of magnetic poles, and has a developing pole S1 and magnetic poles S3, N2, N1, and S2 for carrying the developing agent. Of these, the magnetic poles S2 and S3 having the same poles are installed adjacent to each other inside the developing container 50, and a repulsive magnetic field is formed between the poles. The supply sleeve 61 can supply toner to the developing sleeve 60 by supporting and rotating the developer inside the developing container 50.

The developing sleeve 60 is made of a non-magnetic sleeve that rotates in the counterclockwise direction in FIG. 4, and is rotatably provided around a non-rotating magnet 60a having one magnetic pole provided on the inner peripheral side. The developing sleeve 60 can develop an electrostatic latent image on the photosensitive drum 2 in the developing region Ar1 which is a region facing the photosensitive drum 2 by supporting and rotating the toner. The supply sleeve 61 and the developing sleeve 60 face each other with a predetermined gap in the facing portion Ar2. The magnetic pole N3 of the magnet 60a in the developing sleeve 60 has a different polarity from the opposing developing pole S1.

A regulation blade 62 is attached to the developing container 50 in the longitudinal direction facing the supply sleeve 61. The regulation blade 62 is positioned upstream of the facing portion Ar2 between the developing sleeve 60 and the supply sleeve 61 in the rotation direction of the supply sleeve 61 (counterclockwise rotation direction in FIG. 4). A slight gap is formed between the tip of the regulation blade 62 and the surface of the supply sleeve 61.

[Toner supply and demand]
A developing voltage (hereinafter referred to as a developing bias) in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeve 60. A supply voltage (hereinafter, referred to as a supply bias) in which a DC voltage and an AC voltage are superimposed is applied to the supply sleeve 61. These voltages are applied to the developing sleeve 60 and the supply sleeve 61 from the bias power supply 82 (see FIG. 2) as an example of the voltage application unit via the bias control circuit. That is, the bias power supply 82 applies a voltage including a DC component and an AC component between the developing sleeve 60 and the supply sleeve 61.

The developer in the developing chamber 52 is conveyed to the supply sleeve 61 by the first transfer screw 54, and forms spiked magnetic ears by the magnetic field generated on the supply sleeve 61. The magnetic spikes on the supply sleeve 61 are layer-thickly regulated by the regulation blade 62, and then conveyed to the facing portion Ar2 between the supply sleeve 61 and the developing sleeve 60 by the rotation of the supply sleeve 61. An electric field is generated in the facing portion Ar2 between the supply sleeve 61 and the developing sleeve 60 due to the potential difference ΔV between the DC voltage of the supply bias applied to the supply sleeve 61 and the DC voltage of the developing bias applied to the developing sleeve 60. The generated electric field forms a toner thin layer on the developing sleeve 60.

The toner layer thickness on the developing sleeve 60 changes, for example, due to the difference in rotation speed between the supply sleeve 61 and the developing sleeve 60. This is because the amount of toner supplied by the supply sleeve 61 and the amount of toner supplied by the developing sleeve 60 change due to the difference in rotation speed. The thickness of the toner layer formed on the developing sleeve 60 can be expressed by the amount of toner supplied per unit area on the developing sleeve 60. From this, as the rotation speed of the supply sleeve 61 is increased with respect to the rotation speed of the development sleeve 60, the toner layer formed on the development sleeve 60 becomes thicker. Generally, the relationship between the rotation speeds of the developing sleeve 60 and the supply sleeve 61 is expressed by the ratio of the rotation speeds when the rotation speed of the developing sleeve 60 is used as the denominator and the rotation speed of the supply sleeve 61 is used as the numerator. This rotation speed ratio is selected so as to form a necessary and sufficient toner layer for developing the latent image on the photosensitive drum 2, and is set to 1.6 in the present embodiment. Therefore, the faster the rotation speed of the supply sleeve 61 or the slower the rotation speed of the developing sleeve 60, the thicker the toner layer on the developing sleeve 60. Further, the toner layer thickness on the developing sleeve 60 can also be controlled by the potential difference ΔV between the DC voltage of the supply bias and the DC voltage of the developing bias. By increasing the potential difference ΔV, the toner layer on the developing sleeve 60 becomes thicker. Generally, the range of the potential difference ΔV at the time of development is about 100V to 350V.

The toner thin layer formed on the developing sleeve 60 by contact with the magnetic spikes on the supply sleeve 61 is formed on the facing portion (hereinafter referred to as the developing region Ar1) between the photosensitive drum 2 and the developing sleeve 60 by the rotation of the developing sleeve 60. Be transported. Since the development bias is applied to the developing sleeve 60, toner flies from the developing sleeve 60 to the photosensitive drum 2 due to the potential difference between the developing sleeve 60 and the photosensitive drum 2, and the electrostatic latent image on the photosensitive drum 2 is developed.

The toner remaining unused for development is again conveyed to the facing portion Ar2 between the developing sleeve 60 and the supply sleeve 61, and is rubbed and collected by the magnetic spikes on the supply sleeve 61. The magnetic spikes fall from the supply sleeve 61 into the developing chamber 52 at the stripping portion where the repulsive magnetic field of the magnet roller 61a is formed, and are mixed with the developing agent circulating in the developing container 50. After that, a predetermined amount of toner is replenished from the toner replenishment port 59 based on the detection result of the toner concentration sensor 58, circulates in the stirring chamber 53 and the developing chamber 52, and mixed with the developing agent circulating in the developing container 50. Toner. The mixed developer is resupplied onto the supply sleeve 61.

[The Resolution and Collection Corporation]
Next, the recovery mechanism 70 for recovering the accumulated toner will be described in detail with reference to FIGS. 4 to 6. As shown in FIG. 4, a recovery mechanism 70 is provided in the vicinity of the developing sleeve 60 of the developing container 50. The recovery mechanism 70 is arranged substantially parallel to the developing sleeve 60, and constitutes a wall portion that is inclined downward from below the developing sleeve 60 toward the supply sleeve 61 when viewed from the rotation axis direction of the developing sleeve 60. The collection mechanism 70 has a toner receiving member 71 and a vibration mechanism 72 which is an example of a vibrating means for vibrating the toner receiving member 71.

The toner receiving member 71 is provided along the longitudinal direction on the upper surface of the collection mechanism 70 to receive the toner on which the scattered toner is deposited. That is, the toner receiving member 71 is arranged so as to face the lower side of at least one of the developing sleeve 60 and the supply sleeve 61. The toner receiving member 71 is a metal plate material, and is supported by a bottom portion 74 made of synthetic resin via a coil spring 73 made of a compression coil spring. The coil spring 73 is mounted on a pedestal 75 integrally formed with the bottom portion 74.

The vibration mechanism 72 is fixedly provided on the back surface of the toner receiving member 71. The vibration mechanism 72 includes a motor holder 76, a vibration motor 77, and a vibration weight 78. A vibration motor 77 is fixed to the back surface of the toner receiving member 71 via a motor holder 76. A circuit board and electronic components (not shown) for controlling the drive of the vibration motor 77 are mounted in the motor holder 76.

5 (a) and 5 (b) are schematic views of the vibration motor 77 and the vibration weight 78 of the vibration mechanism 72. As shown in FIGS. 5A and 5B, the vibration weight 78 of the vibration mechanism 72 has a so-called D-cut shape having a flat surface portion 78a along the central axis on a part of the peripheral side surface of the cylindrical shape. There is. That is, the vibration weight 78 has a shape asymmetrical with respect to the rotation shaft 77a of the vibration motor 77 fitted at a position overlapping the central axis. When the rotation shaft 77a of the vibration motor 77 rotates at a rotation speed equal to or higher than a predetermined rotation speed, the centrifugal force acting on the flat surface portion 78a is smaller than the other parts of the vibration weight 78. An eccentric and non-uniform centrifugal force is applied. The vibration motor 77 vibrates when this centrifugal force is transmitted to the rotating shaft 77a. The shape of the vibration weight 78 is not limited to the D-cut shape, and may be any shape whose center of gravity deviates from the central axis with respect to the rotation axis 77a.

FIG. 6 is a schematic side view showing the operation of the toner receiving member 71 while the developing apparatus 5 is being driven. By rotating the rotating shaft 77a of the vibration motor 77 at a high speed of, for example, about 10000 rpm, the vibration weight 78 also rotates at a high speed together with the rotating shaft 77a. The rotation direction of the rotation shaft 77a of the vibration motor 77 is a counterclockwise direction in FIG. At this time, since an eccentric and non-uniform centrifugal force is applied to the vibration weight 78, the vibration motor 77 and the motor holder 76 vibrate via the rotating shaft 77a. Along with this vibration, the toner receiving member 71 to which the motor holder 76 is fixed also vibrates. Due to the vibration of the toner receiving member 71, the toner T deposited on the toner receiving member 71 is separated from the surface of the toner receiving member 71 and is sifted toward the inclined downward side.

As a result, the supply sleeve 61 and the developing sleeve 60 in the developing apparatus 5 rotate at high speed, and even when the amount of toner floating is large, the accumulation of toner on the toner receiving member 71 can be suppressed. Due to the vibration of the toner receiving member 71, the toner T deposited on the toner receiving member 71 slides downward (in the direction of the white arrow in FIG. 6) along the inclination of the toner receiving member 71, and the toner falling surface 79 and the supply sleeve 61 It falls into the area Ar3 sandwiched between the two. In the present embodiment, since the toner receiving member 71 is arranged so that the toner dropping surface 79 is substantially vertical, the toner T in the region Ar3 is likely to fall freely.

In the present embodiment, the control unit 20 controls the vibration mechanism 72 at the time of non-image formation, thereby sifting off the toner accumulated on the toner receiving member 71 by the vibration of the vibration mechanism 72. It is feasible. In the present embodiment, the non-image forming time means that the toner image is not formed on the photosensitive drum 2, for example, between the papers during the image forming job, during the forward rotation, and during the backward rotation. , When the image formation job is not executed.

Further, in the present embodiment, in order to return the toner T that has fallen into the region Ar3 to the developing chamber 52, the supply sleeve 61 is rotated in the direction opposite to that at the time of image formation (clockwise in FIG. 6) during non-image formation. .. By rotating the supply sleeve 61 in the opposite direction, the toner T that has fallen and accumulated in the region Ar3 travels to the surface of the supply sleeve 61, passes through the gap between the supply sleeve 61 and the regulation blade 62, and passes through the gap between the supply sleeve 61 and the regulation blade 62, and passes through the gap between the supply sleeve 61 and the regulation blade 62. Forced back to.

[Toner replenishment control]
The toner replenishment control for the developing device 5 will be described. The image forming apparatus 1 performs automatic toner replenishment control (ATR: Auto Toner Replenisher) for replenishing the developing apparatus 5 with an amount of toner corresponding to the amount consumed by the development. In this embodiment, the following type of ATR control is adopted in order to stabilize the density of the output image. The control unit 20 of the toner hopper replenishment screw provided between the toner cartridge and the toner replenishment port 59 according to the image ratio at the time of image formation, the detection result of the toner density sensor 58, the detection result of the density of the patch image, and the like. Toner is replenished to the developing container 50 by controlling the number of rotations. That is, based on the image ratio at the time of image formation, the amount of toner replenished corresponding to the predicted toner consumption is obtained. Further, based on the detection result of the toner concentration sensor 58, the toner replenishment amount based on the above image ratio is corrected. Further, the target value of the detection result of the toner density sensor 58 is corrected by using the density detection result of the patch image formed at a predetermined frequency. In the present embodiment, instead of replenishing an arbitrary replenishment amount at any time, replenishment is suppressed up to a preset one-time replenishment amount (for example, one rotation of a toner hopper replenishment screw), and each replenishment amount is reduced. Rotate the supply screw once. Thereby, a stable supply amount can be obtained.

Further, the image processing unit 24 of the control unit 20 calculates the toner consumption due to image formation based on the image information received from the personal computer connected via the image reading device, the network, or the like. In the present embodiment, the toner consumption is obtained from the image ratio based on the video count value (image signal value) integrated based on the image information, and is integrated for each image output. The replenishment control unit 26 of the control unit 20 obtains the amount of toner corresponding to the toner consumption as the toner replenishment amount, but the T / D detected by the toner concentration sensor 58 deviates from the target value of the T / D. In that case, the amount of toner replenished is corrected so as to reduce the deviation. Then, when the required replenishment amount exceeds the replenishment amount for one rotation of the replenishment screw of the toner hopper, the replenishment control unit 26 rotates the replenishment screw by the required number of rotations to replenish the toner to the developing device 5. ..

The replenishment control unit 26 transmits a patch image, which is an example of a control toner image of a predetermined size (for example, 15 mm square) of a predetermined latent image contrast, at a predetermined frequency (for example, for each number of image outputs). And this is transferred to the intermediate transfer belt 7. The image density (reflection density) of this patch image is measured on the intermediate transfer belt 7 by an optical sensor 80 (see FIGS. 1 and 2) as an example of the density detecting means.

Then, the measured image density is compared with the reference image density, and the target value of T / D is changed so as to reduce the deviation of the image density (patch detection control). As a result, it is possible to predict the toner charge amount from the toner amount used for forming the patch image and deal with the fluctuation of the image density caused by the fluctuation of the toner charge amount due to the deterioration of the carrier or the like.

[Toner scattering]
Here, the scattering of toner will be described. The main cause of toner scattering is the transfer of toner by the electric field performed at the opposite portion Ar2 between the supply sleeve 61 and the developing sleeve 60, and the air flow generated by the rotation of the supply sleeve 61 and the developing sleeve 60. Here, the scattering of the toner due to the electric field and the scattering of the toner due to the air flow will be described.

First, the scattering of toner due to an electric field will be described. The developer is supported by a magnet roller 61a arranged inside the supply sleeve 61, forms magnetic spikes on the supply sleeve 61, and is conveyed to the opposite portion Ar2 between the supply sleeve 61 and the developing sleeve 60. A supply bias and a development bias are applied to the supply sleeve 61 and the development sleeve 60, respectively, and an electric field is generated at the opposite portion Ar2 due to the potential difference between the supply bias and the development bias. In the developer conveyed to the opposing portion Ar2, the toner is released from the carrier by the electric field. The released toner follows the electric field generated by the DC voltage and AC voltage between the supply bias and the development bias, and flies from the supply sleeve 61 toward the development sleeve 60 while reciprocating between the supply sleeve 61 and the development sleeve 60. To do. Of the toners that have followed the electric field, those that have moved out of the range affected by the electric field are scattered in the developing apparatus 5. Further, since the released toner having a low toner charge amount tends to be difficult to follow the electric field, among the released toner, the toner floating at a position away from the carrier and the developing sleeve 60 is contained in the developing apparatus 5. It will be scattered. Therefore, the more toner has a lower toner charge amount, the larger the amount of scattered toner.

Next, the scattering of toner due to the air flow will be described. The supply sleeve 61 and the developing sleeve 60 are rotated so as to advance in opposite directions at the facing portion Ar2. Therefore, the airflow generated by the rotation of the supply sleeve 61 and the developing sleeve 60 travels along the supply sleeve 61 and then changes direction so as to travel along the developing sleeve 60 at the portion Ar2 facing the developing sleeve 60. At this time, since a rotational force acts on the airflow, an airflow vortex is generated in a portion downstream of the development sleeve 60 in the rotational direction from the opposite portion Ar2 of the supply sleeve 61 and the developing sleeve 60. When the toner that reciprocates between the supply sleeve 61 and the developing sleeve 60 following the electric field generated by the supply bias and the developing bias enters the airflow vortex, it moves out of the range affected by the electric field and enters the developing apparatus 5. It may scatter. Therefore, toner tends to scatter around the facing portion Ar2 where the supply sleeve 61 and the developing sleeve 60 face each other.

[Absolute Moisture Amount, Toner Charge Amount and Toner Accumulation Amount]
Here, the accumulated amount of toner is easily affected by the scattering of toner, and may be particularly sensitive to the absolute amount of water in the developing apparatus 5. The reason will be explained below. First, FIG. 7 shows the relationship between the absolute water content of the developer used in the present embodiment and the toner charge amount. As shown in FIG. 7, it is known that the toner charge amount changes according to the absolute water content. Further, FIG. 8 shows the relationship between the amount of toner charged and the amount of toner deposited on the toner receiving member 71 when the supply sleeve 61 and the developing sleeve 60 are driven. Here, the image forming operation was performed for a predetermined time, and the amount of toner deposited was measured from the integrated value of the adhesion area and the density of the toner adhering to the toner receiving member 71 at that time. As shown in FIG. 8, the smaller the toner charge amount, the larger the toner accumulation amount. This is because the smaller the toner charge amount, the smaller the Coulomb force acting on the toner and the carrier, so that the toner easily flies from the carrier. Therefore, when the absolute water content is large, the toner charge amount tends to be small, so that the toner scattering amount is large. Since the amount of toner deposited in the developing apparatus 5 tends to increase with the amount of toner scattered, the amount of toner adhering to the toner receiving member 71 increases when the absolute amount of water is large. Therefore, it is necessary to shorten the vibration interval of the toner receiving member 71 as the absolute water content increases.

[Recovery mode execution interval]
When the control unit 20 operates the vibration mechanism 72 to execute the recovery mode of sieving the toner of the toner receiving member 71, the recovery mode can be executed at intervals of, for example, a fixed number of prints. However, when the toner charge amount becomes small, for example, when the absolute water content in the environment inside the developing device 5 becomes large, the toner is deposited quickly. At this time, in the configuration in which the vibration mode is executed for each fixed number of prints, the interval for operating the vibration mechanism 72 is longer than the interval for vibrating the toner receiving member 71 for the toner to be deposited, and the execution frequency is low. Become. For this reason, toner accumulation and aggregation proceed on the inner wall of the developing apparatus 5, the aggregated toner adheres to the developing sleeve 60, and the aggregated toner is supplied onto the photosensitive drum 2, which may cause image defects. .. On the other hand, when the toner charge amount becomes large due to a small absolute water content in the environment inside the developing device 5, the toner deposition becomes slow. At this time, in the configuration in which the vibration mode is executed for each fixed number of prints described above, the interval at which the toner receiving member 71 is vibrated becomes shorter than the speed at which the toner is deposited, and the execution frequency increases, so that the productivity decreases. There is a risk of doing so. Therefore, in the present embodiment, the execution interval of the recovery mode in which the toner receiving member 71 is vibrated to recover the accumulated toner is optimized based on the absolute water content of the environment inside the developing device 5 which correlates with the toner charge amount. ing. As a result, toner deposition can be suppressed without reducing productivity more than necessary.

The execution procedure of the recovery mode in the present embodiment will be described in detail with reference to the flowchart shown in FIG. When the control unit 20 receives the image formation job information, the temperature / humidity sensor 81 detects the temperature / humidity in the developing container 50, and calculates the absolute water content inside the developing device 5 based on the detected information (step). S1). The temperature / humidity in the developing container 50 may be detected by the temperature / humidity sensor 81 at all times, at predetermined time intervals, or at a predetermined number of image formations. You may.

The control unit 20 acquires the deposition coefficient R by referring to the table in the image formation control unit 25 based on the calculated absolute water content (step S2). Here, as shown in FIG. 10, the deposition coefficient R corresponds to the amount of toner deposited on the toner receiving member 71, and is set so that the larger the absolute water content, the larger the value. That is, the deposition coefficient R is a coefficient that weights the speed at which the toner is deposited according to the calculated absolute water content.

The control unit 20 acquires the drive time t of the supply sleeve 61 when the image forming job is executed (step S3). The control unit 20 calculates the deposition index P = R × t based on the deposition coefficient R and the drive time t (step S4), integrates the deposition index P, and calculates the integrated deposition index P1 = ΣP (step). S5). The cumulative deposition index P1 is a numerical value indicating the degree of toner deposition on the toner receiving member 71.

The control unit 20 determines whether or not the integrated deposition index P1 exceeds the threshold value P0 (step S6). Here, the threshold value P0 is based on the integrated deposition index P1 when the toner deposited on the toner receiving member 71 adheres to the developing sleeve 60 and an image defect occurs, and the integrated deposition index P1 when an image defect occurs is set to 0. The value is multiplied by eight. In this embodiment, the threshold value P0 = 1200 is set. By determining the degree of toner accumulation on the toner receiving member 71 with the threshold value P0, the recovery mode can be executed before the image defect occurs. When the control unit 20 determines that the integrated deposition index P1 does not exceed the threshold value P0 (NO in step S6), the control unit 20 ends the process. The temperature / humidity sensor 81 detects the temperature / humidity in the developing container 50 again (step S1).

When the control unit 20 determines that the integrated deposition index P1 exceeds the threshold value P0 (YES in step S6), for example, the control unit 20 executes a collection mode between the papers during the image formation job (step S7). That is, the control unit 20 executes the recovery mode when the cumulative deposition index P1 which is the cumulative value of the deposition index P regarding the calculated absolute water content exceeds the threshold value P0 after the execution of the previous recovery mode. In the present embodiment, the control unit 20 executes the collection mode between the papers, but the present invention is not limited to this, and the control unit 20 executes the recovery mode during the pre-rotation before image formation and after the post-rotation after image formation. You may do it. After executing the recovery mode, the control unit 20 resets the cumulative deposition index P1 (step S8) and ends the process.

Here, since the control unit 20 executes the recovery mode when the cumulative accumulation index P1 which is the cumulative value of the accumulation index P regarding the calculated absolute water content exceeds the threshold value P0, the case where the absolute water content is large Exceeds the threshold P0 earlier than when is small. That is, the control unit 20 determines the temperature or relative humidity inside the developing container 50 depending on whether the detection result of the temperature / humidity sensor 81 is the first value or the detection result is the second value larger than the first value. When are the same, the judgment is made as follows. In this case, when the detection result of the temperature / humidity sensor 81 is the first value, the control unit 20 sets the execution interval of the recovery mode to the first time when the supply sleeve 61 is driven. In this case, when the absolute water content is a second value larger than the first value, the control unit 20 sets the execution interval of the recovery mode to be a second time shorter than the first time when the supply sleeve 61 is driven. To. The case where the temperature or the relative humidity is the same is not limited to the case where the temperature or the relative humidity is the same, and includes the case where the temperature or the relative humidity is substantially the same. In addition, the case where the temperature or relative humidity is the same is not limited to the case where the same temperature or relative humidity is maintained, and the case where the same temperature or relative humidity is reached again even if the temperature or relative humidity is once different. Also includes. Further, the case where the temperature or the relative humidity is the same is not limited to the case where the temperature or the relative humidity is the same at the time of executing one image forming job, and for example, it is the same between different image forming jobs at different times and places. Including cases.

As described above, according to the image forming apparatus 1 of the present embodiment, in the control unit 20, the integrated deposition index P1 regarding the absolute water content detected by the temperature / humidity sensor 81 exceeds the threshold value P0 after the execution of the previous recovery mode. If so, the recovery mode is executed. Further, when the absolute water content detected by the temperature / humidity sensor 81 is a second value larger than the first value, the control unit 20 sets the execution interval of the recovery mode shorter than the first time when the supply sleeve 61 is driven. I try to be the second hour. As a result, it is possible to prevent the collection mode from being executed too long or too short as compared with the case where the collection mode is executed for each fixed number of images formed, and the collection mode execution interval is based on the cumulative deposition index P1. Can be optimized. Further, even when the temperature and humidity environment fluctuates, it is possible to suppress the adhesion of the toner deposited on the toner receiving member 71 to the developing sleeve 60 while suppressing the decrease in productivity, and it is possible to suppress image defects.

That is, according to the image forming apparatus 1 of the present embodiment, the execution interval for executing the recovery mode is changed according to the calculated absolute water content. For example, when the absolute water content is large, the control unit 20 can execute the recovery mode before the amount of accumulated toner exceeds the permissible amount, and the toner accumulated on the toner receiving member 71 is transferred to the developing sleeve 60. Adhesion can be suppressed and image defects can be suppressed. Further, when the absolute water content is small, the execution interval of the recovery mode can be set long, so that image defects can be effectively suppressed while suppressing a decrease in productivity.

Further, according to the image forming apparatus 1 of the present embodiment, the control unit 20 weights the deposition coefficient R from the absolute water content to set the execution interval of the recovery mode according to the absolute water content. I am changing. Specifically, the larger the absolute water content, the greater the weighting. Therefore, the amount of toner scattered does not simply increase in proportion to the absolute water content, but the larger the absolute water content, the more it can be dealt with that the increase exceeds the proportional increase. As a result, the execution interval of the recovery mode is more accurately compared to the case where the execution interval of the recovery mode is changed in proportion to the absolute water content without weighting the absolute water content. Can be optimized.

[Comparative evaluation]
Image evaluation and productivity were compared between the above-described example according to the image forming apparatus 1 of the present embodiment and Comparative Example 1 and Comparative Example 2. Here, image formation is performed at a plurality of image formation speeds, the recovery mode is executed based on the absolute water content in the example, and in Comparative Example 1 and Comparative Example 2, for each fixed number of prints (hereinafter, cumulative number of sheets). The recovery mode was executed.

The cumulative number of deposited sheets in Comparative Example 1 was 100, and the cumulative number of deposited sheets in Comparative Example 2 was 500. The image used for image formation had an image ratio of 30%, endurance printing of 10,000 sheets was performed, and the presence or absence of image defects at that time and the number of executions of the collection mode were compared. Durable printing of 10,000 sheets was performed in the following five environments. The deposition coefficient R under each environment was R = 5 in environment 1, R = 3 in environment 2, R = 2 in environment 3 and environment 4, and R = 1 in environment 5. These environmental conditions are shown in Table 1.
(1) Environment 1 (temperature 30 ° C., relative humidity 80%, absolute water content 24.3 g / m ³ )
(2) Environment 2 (temperature 30 ° C., relative humidity 65%, absolute water content 19.7 g / m ³ )
(3) Environment 3 (temperature 30 ° C., relative humidity 50%, absolute water content 15.2 g / m ³ )
(4) Environment 4 (temperature 23 ° C., relative humidity 75%, absolute water content 15.4 g / m ³ )
(5) Environment 5 (temperature 23 ° C., relative humidity 50%, absolute water content 10.3 g / m ³ )

The image formation speed was 25 sheets / minute. The rotation speed of the photosensitive drum 2 of the developing device 5 is 125 mm / s, the ratio of the rotating speed of the photosensitive drum 2 to the rotating speed of the developing sleeve 60 is 1.5, and the rotating speed of the developing sleeve 60 is 187.5 mm / s. And said. Further, the ratio of the rotation speed of the developing sleeve 60 to the rotation speed of the supply sleeve 61 was set to 1.6, and the rotation speed of the supply sleeve 61 was set to 300 mm / s. The rotation direction of the developing sleeve 60 is a with rotation that is the same direction as the photosensitive drum 2 in the developing region Ar1, and the rotation direction of the supply sleeve 61 is a counter rotation that is opposite to the developing sleeve 60 at the portion Ar2 facing the developing sleeve 60. And said. The length of the toner receiving member 71 in the longitudinal direction was 315 mm, the length of the toner receiving member 71 in the lateral direction was 25 mm, the rotation speed of the vibration motor 77 in the recovery mode was 10000 rpm, and the driving time was 10 seconds.

The results of the implementation are shown in Table 2. Regarding the image evaluation in Table 1, 10 images formed after the durability of 10,000 images were visually inspected, and it was confirmed whether or not an image defect due to agglomerates of toner accumulated on the toner receiving member 71 was observed. When no image defect due to agglomerates was observed on the image, it was evaluated as “◯”, and when it was observed, it was evaluated as “x”.

As shown in Table 2, in Examples, better results could be obtained as compared with Comparative Example 1 and Comparative Example 2. On the other hand, in Comparative Example 1, no image defect occurred, but the recovery mode was executed more than necessary, so that the productivity was lowered as compared with the Example. In Comparative Example 2, the productivity was good, but image defects were confirmed. Therefore, according to the present embodiment, since the execution interval of the recovery mode can be changed according to the absolute water content, the recovery mode can be executed before the amount of accumulated toner exceeds the permissible amount, and productivity is required. It was confirmed that toner deposition could be suppressed without dropping the toner.

Further, for example, when environment 1 and environment 3 are compared, the temperature is the same and the absolute water content is different. In this case, in the present embodiment, since the deposition coefficient R = 2 and the threshold value P0 = 1200 in the environment 3, the execution interval of the recovery mode is every 600 seconds, which is the first time when the supply sleeve 61 is driven. This is every 250 images formed. Further, in the present embodiment, since the deposition coefficient R = 5 and the threshold value P0 = 1200 in the environment 1, the execution interval of the recovery mode is every 240 seconds, which is the second time when the supply sleeve 61 is driven. This is every 100 images formed. Therefore, the detection result of the temperature and humidity sensor 81 in the case is 15.2 g / ^{m 3} (first value), and if it is greater than 24.3 g / ^{m 3} (second value) of the developer container 50 It is assumed that the internal temperature is the same. In this case, it was confirmed that the control unit 20 shortens the execution interval of the recovery mode to 240 seconds, which is the second time shorter than 600 seconds, which is the first time when the supply sleeve 61 is driven.

Further, for example, when the environment 3 and the environment 5 are compared, the relative humidity is the same and the absolute water content is different. In this case, in the present embodiment, since the deposition coefficient R = 1 and the threshold value P0 = 1200 in the environment 5, the execution interval of the recovery mode is every 1200 seconds, which is the first time when the supply sleeve 61 is driven. This is every 500 images formed. Further, in the present embodiment, since the deposition coefficient R = 2 and the threshold value P0 = 1200 in the environment 3, the execution interval of the recovery mode is every 600 seconds, which is the second time when the supply sleeve 61 is driven. This is every 250 images formed. Therefore, the detection result of the temperature / humidity sensor 81 is 10.3 g / m ³ (first value) and 15.2 g / m ³ (second value), which is larger than that, in the developing container 50. It is assumed that the relative humidity inside is the same. In this case, it was confirmed that the control unit 20 shortens the execution interval of the recovery mode to 600 seconds, which is the second time shorter than 1200 seconds, which is the first time when the supply sleeve 61 is driven.

1 ... image forming device, 2 ... photosensitive drum (image carrier), 5 ... developing device, 20 ... control unit, 50 ... developing container, 60 ... developing sleeve, 61 ... supply sleeve, 71 ... toner receiving member, 72 ... vibration Mechanism (vibration means), 81 ... Temperature / humidity sensor (detection means).

Claims (2)

An image carrier on which an electrostatic latent image is formed, and
An electrostatic latent image on the image carrier can be developed in a developing container containing a developing agent containing a non-magnetic toner and a magnetic carrier and a region facing the image carrier by supporting and rotating the toner. A developing sleeve, a supply sleeve capable of supplying toner to the developing sleeve by supporting and rotating the developing agent inside the developing container, and facing below at least one of the developing sleeve and the supply sleeve. A developing apparatus having a toner receiving member arranged therein and a vibrating means for vibrating the toner receiving member.
A detection means for detecting information on the absolute water content inside the developing container, and
A control unit capable of executing a vibration mode in which the toner deposited on the toner receiving member is eliminated by the vibration of the vibration means by controlling the vibration means is provided.
The control unit has the same temperature or relative humidity inside the developing container when the detection result of the detection means has a first value and when the detection result has a second value larger than the first value. At one time, when the detection result is the first value, the execution interval of the vibration mode is set to the first time when one of the developing sleeve and the supply sleeve is driven, and the detection result is the said. When it is the second value, the execution interval of the vibration mode is set to the second time shorter than the first time when the one sleeve is driven.
An image forming apparatus characterized in that. The information regarding the absolute water content is information regarding the volume absolute humidity.
The image forming apparatus according to claim 1.

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