JP2005241675A - Developing device, image forming apparatus, and method for controlling developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the operation of a motor for driving an agitation member within a toner storage container in a developing device in a stationary state (at stationary output) in the earliest possible time while preventing the occurrence of a step out and heat generation at the start of operation (agitation) when a load is liable to be increased by toner aggregation. <P>SOLUTION: The driving conditions of the motor 30 are so switched that the output torque (rotating speed) of the motor 30 attains the torque (lower speed) higher than the output torque (rotating speed) in a stationary period (a processing period of S 6 and S 7) thereafter in the initial period (a processing period of S 3 and S 4) before the detection (S 4) of the rotation for one pitch component that results in the passage of agitation blades 22a to 22d formed at the agitation member 22 after the start of rotation of the agitation member 22 through the entire agitation region [the entire periphery (360°) region] by the agitation member 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device having a mechanism for stirring toner by a stirring member that rotates in a toner container, an image forming apparatus including the developing device, and a control method for the developing device.

An electrophotographic image forming apparatus (printer, copying machine, facsimile machine, etc.) includes a developing device that develops an electrostatic latent image formed on a photoreceptor as a toner image. Some developing devices include a toner replenishing means for replenishing toner from the toner replenishing tank to the developing tank.
Such a developing device includes a developing tank that contains toner and a means for detecting the remaining amount of toner in the developing tank (for example, when a two-component developer is used, a toner concentration detecting means based on detecting the permeability of the developer. The toner replenishing means includes a toner replenishing tank for storing toner to be replenished to the developing tank, and a toner replenishing roller having a surface layer formed of an elastic member such as a sponge. When the toner remaining amount in the developing tank falls below a predetermined remaining amount, the toner replenishing roller rotates to replenish toner from the toner replenishing tank to the developing tank.
Furthermore, an agitating member for agitating the toner by rotating is provided inside a toner replenishing tank (an example of a toner accommodating container) in which toner for replenishment is accommodated. This is provided to loosen the toner because the toner aggregates when it is stored in the toner replenishing tank for a long time, which may be a detrimental effect of toner replenishment to the developing tank. Usually, the toner supply roller and the stirring member are driven in conjunction with each other. In other words, the stirring member rotates during toner supply, and the rotation of the stirring member also stops when toner supply is stopped. The stirring member is formed with stirring blades for efficiently stirring the toner.
Here, when the toner is agglomerated, the resistance of the toner is large, and a large load is applied to the motor that rotationally drives the stirring member. In addition, when the motor is a motor whose rotational speed is controlled by adjusting the frequency of the drive signal (hereinafter referred to as a frequency control motor) such as a stepping motor, the motor is rotated at a high speed with a large load (resistance) applied to the stirring member. Attempting to do so causes a problem that step-out occurs and normal motor control cannot be performed. In general, with a frequency control motor, a large output torque is obtained when rotating at low speed with a low driving frequency, and step-out is unlikely to occur, but it is relatively small when driven at high frequency and rotated at high speed. Only output torque can be obtained, and step out is likely to occur. Further, even if the drive frequency is rapidly increased to a high frequency, the step-out is likely to occur.
Also, in a motor controlled by drive voltage, drive current, or PWM duty, the higher the drive signal level (voltage, current, PWM duty), the greater the output torque depending on the load (resistance on the stirring member) However, if the high load state continues for a long time, the problem arises that the motor generates heat until it reaches an abnormally high temperature. In particular, when a load greater than the output torque is applied and the motor is locked, heat generation of the motor becomes more prominent. Such heat generation causes a motor failure.
Conventionally, Patent Document 1 discloses a configuration in which a torque limiter is provided between an agitator (corresponding to a stirring member) and its rotating shaft so that an excessive load is not applied to the motor. Thus, even if a high load is applied to the motor due to toner aggregation, it is possible to prevent the motor from stepping out or generating heat.
Japanese Patent Laid-Open No. 2004-26883 discloses that at the time of toner replenishment, a frequency control motor that drives the stirring member is first driven at a low frequency, and if the toner replenishment is not completed, the frequency is increased stepwise. It is shown. As a result, it is possible to prevent a step-out due to a sudden increase in drive frequency.
On the other hand, in Patent Document 3, the driving speed of the toner replenishing motor is controlled in accordance with the toner density (toner remaining amount) (toner density = low → higher motor speed, toner density = high → slower motor speed). )It is shown.
JP-A-4-323678 JP-A-4-471 JP-A-5-107916

However, in the technique disclosed in Patent Document 1, a relatively low torque that does not cause a step-out when the limit torque of the torque limiter is rotated at the rotational speed at the time of steady stirring of the stirring member driving motor (frequency control motor). There is a problem that the motor is idling frequently due to toner aggregation.
Further, in the technique disclosed in Patent Document 2, when toner is agglomerated, if the driving frequency of the frequency control motor is increased before the stirring member substantially passes through the entire stirring region, step-out easily occurs. If the timing for increasing the toner is late, the toner replenishment speed becomes slow.
Furthermore, in the technique disclosed in Patent Document 3, the motor driving speed becomes the fastest at the start of toner replenishment (that is, at the start of toner stirring), which tends to cause the toner to agglomerate when stirring is stopped. For this reason, when a frequency control motor is used, the motor (frequency drive motor) is driven under the driving condition that causes the lowest torque and the out-of-step when toner is agglomerated. There was a point. On the other hand, when a motor controlled by voltage, current, etc. is used, the high output state is continued until the toner concentration increases, so that the motor generates heat.
Accordingly, the present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a motor that drives the stirring member in the toner container at the start of operation (stirring) that tends to be a high load due to toner aggregation. To provide a developing device capable of operating in a steady state (steady output) as early as possible while preventing occurrence of step-out and heat generation, an image forming apparatus including the developing device, and a control method for the developing device. It is in.

In order to achieve the above object, the present invention provides a developing device comprising a stirring member that stirs toner by rotating in a toner container and a motor that rotationally drives the stirring member. An all-region passage detecting means for detecting that the stirring blade formed on the stirring member after the start substantially passes through the entire stirring region by the stirring member; and the all-region passage detecting means from the start of rotation of the stirring member. First motor control means for switching the driving conditions of the motor so that the output torque of the motor in the initial operation period until it is detected that substantially has passed through the entire region is higher than the output torque in the subsequent steady period; , And a developing device characterized by comprising the above. Here, as an example of “substantially passing through the entire stirring region”, when the four stirring blades are formed uniformly in the rotation direction, the stirring blades are “It has substantially passed through the entire stirring region (the entire circumferential region of 360 °)”.
Here, it can be considered that the first motor control means switches the output torque of the motor by switching the set rotational speed for the motor as the driving condition of the motor. This is a configuration in the case where the motor is the frequency control motor (low speed (ie, low frequency) = high torque) in which the rotational speed control is performed by adjusting the frequency of the drive signal.
On the other hand, when a motor controlled by a drive voltage, a drive current, or a PWM duty is used, the motor drive conditions include the power level of the drive signal (drive voltage, drive current, PWM duty) as the motor. Should be set.
With such a configuration, since the agitation member is driven at a high torque at the start of toner agitation, which is often in a state where toner is agglomerated due to the agitation stop, the toner can be loosened effectively. Here, the driving period at high torque is the minimum period necessary to loosen the agglomerated toner, that is, the initial motion in which the stirring blade formed on the stirring member substantially passes through the entire stirring region by the stirring member. It is only a period. For this reason, when the frequency control motor is used as the motor, the stirring operation in the steady state (steady output) can be performed at the earliest stage while preventing the motor from stepping out during the initial operation period. Further, when a motor controlled by voltage, current, or the like is used as the motor, the initial operation period is relatively short, so that the stirring operation in the steady state can be performed at the earliest stage while preventing the motor from generating heat. Become.
Generally, the rated output (hereinafter referred to as the continuous rated output) that can be driven continuously (continuously) is set as the operable condition of the motor. Is also possible. Accordingly, if the output torque of the motor in the initial operation period is set to an output exceeding the continuous rated output, a developing device that can more effectively loosen the agglomerated toner against the load than in the prior art. It becomes possible to do.

A toner remaining amount detecting means for detecting a remaining amount of toner in a developing tank for temporarily storing toner used for development; and a rotation speed of the stirring member when the remaining amount detected by the remaining toner amount detecting means is reduced. A replenishing roller that is driven at a proportional rotational speed and replenishes toner from the toner container to the developing tank, and the first motor control means determines the rotational speed of the motor during the steady period as the remaining toner amount. A setting based on the remaining amount detected by the detecting means is conceivable. This is a configuration in which the motor is the frequency control motor.
As described above, the toner is often agglomerated due to the agitation stop, and at the start of toner agitation (that is, the initial movement period), the agitation member is driven at high torque (low speed) to prevent the motor from stepping out. Is done. On the other hand, with the above-described configuration, after the necessary minimum toner loosening (substantially passing through the entire stirring region of the stirring blade) is performed, that is, after the motor is not subjected to a large load, the toner remaining Since the agitating member and the replenishing roller are rotationally driven at a speed corresponding to the amount, quick toner replenishment is possible.
Further, if the first motor control means switches the driving condition of the motor stepwise from the condition in the initial operation period to the condition in the steady period, the motor step-out due to a sudden increase in driving frequency (speed) is detected. Can be prevented.

In addition, when the elapsed time from the previous rotation stop of the stirring member to the current rotation start is shorter than a predetermined time, the motor in the steady period from the beginning of the motor instead of the control by the first motor control means It is also conceivable to include second motor control means for setting the drive conditions.
When the elapsed time from the previous stop of rotation of the stirring member to the start of the current rotation is short, the toner in the toner container is usually not agglomerated. It is not performed, and the stirring operation in the steady state becomes possible earlier.
Further, if the motor has a permanent magnet on the mover, for example, a stepping motor or a timing motor (also called a synchronous motor), the frequency of the drive signal and the rotational speed are proportional. There is no need to provide a servo circuit for motor control, and output torque (rotation speed) can be accurately controlled with a simple open loop configuration.
By the way, the intermolecular force of the toner becomes stronger in inverse proportion to the particle diameter, and as will be described later, the intermolecular force of the toner becomes stronger remarkably when the toner particle diameter is 7 μm or less. Since the toner is more likely to aggregate as the intermolecular force of the toner is stronger, the developing device is particularly suitable when the particle size of the toner is about 7 μm or less.

Further, the present invention may be an image forming apparatus characterized by comprising the developing device.
Similarly, the present invention may be understood as a control method for executing processing in the developing device.
That is, in a control method of a developing device that includes a stirring member that stirs toner by rotating in a toner container, and a motor that rotationally drives the stirring member, the stirring member after the rotation of the stirring member is started. The all-passage detection step of detecting that the stirring blade formed in the stirring member substantially passes through the entire stirring region by the stirring member, and the entire region passing substantially through the all-region passage detection step from the start of rotation of the stirring member. A motor control step of switching the driving conditions of the motor so that the output torque of the motor in the initial operation period until it is detected is higher than the output torque in the subsequent steady period. This is a control method of the developing device.

According to the present invention, after the start of rotation of the stirring member, the output torque of the motor in the initial motion period until it is detected that the stirring blade formed on the stirring member has substantially passed through the entire stirring region by the stirring member is Since the motor drive conditions are switched so that the output torque is higher than the output torque in the subsequent steady period, the toner is often in an agglomerated state due to the agitation stop, and at the start of toner agitation (the initial operation period), the effect is high. The toner can be loosened. In addition, since the driving period at high torque is only the minimum period necessary to loosen the agglomerated toner, that is, the initial movement period during which the stirring blades substantially pass through the entire stirring area, Stirring operation in a steady state can be performed at the earliest stage while preventing heat generation.
A toner remaining amount detecting means for detecting a remaining amount of toner in a developing tank for temporarily storing toner used for development; and a rotation speed of the stirring member when the remaining amount detected by the remaining toner amount detecting means is reduced. A replenishing roller that is driven at a proportional rotational speed and replenishes toner from the toner container to the developing tank, and the first motor control means determines the rotational speed of the motor during the steady period as the remaining toner amount. A setting based on the remaining amount detected by the detecting means is conceivable. This is a configuration in which the motor is the frequency control motor.
As described above, the toner is often agglomerated due to the agitation stop, and at the start of toner agitation (that is, the initial movement period), the agitation member is driven at high torque (low speed) to prevent the motor from stepping out. Is done. On the other hand, with the above-described configuration, after the necessary minimum toner loosening (substantially passing through the entire stirring region of the stirring blade) is performed, that is, after the motor is not subjected to a large load, the toner remaining Since the agitating member and the replenishing roller are rotationally driven at a speed corresponding to the amount, quick toner replenishment is possible.
Furthermore, if the driving condition of the motor is switched stepwise from the condition in the initial operation period to the condition in the steady period, it is possible to prevent the motor from stepping out due to a sudden increase in driving frequency (speed).
In addition, when the elapsed time from the previous stop of rotation of the stirring member to the start of the current rotation is short, that is, when it is considered that the toner is not aggregated, the motor in the steady period from the start of the motor If the driving conditions are set, unnecessary switching control of the motor is not performed, and the stirring operation in the steady state can be performed earlier.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
1 is a side sectional view showing the configuration of the developing device X according to the embodiment of the present invention, FIG. 2 is a flowchart showing a control procedure of toner replenishment and stirring by the developing device X, and FIG. FIG. 4 is a graph showing the relationship between the toner particle size and the intermolecular force of the toner.

First, a schematic configuration of a copying machine 1 as an example of an image forming apparatus including a developing device X according to an embodiment of the present invention will be described with reference to FIG.
An upper part of the copying machine 1 is a document reading unit 110. This is because a plurality of documents set on a document setting tray on the upper surface of the automatic document conveying device 112 are automatically formed by a glass plate one by one by an automatic document conveying device 112 provided in the document reading unit 110. This is a device for feeding on the original platen 111.
The reading optical system of the document reading unit 110 that scans and reads an image of a document placed on the document table 111 or fed onto the document table 11 by the automatic document feeder 112 is the document table 111. The first scanning unit 113, the second scanning unit 114, the optical lens 115 that forms an image of reflected light from the original on the CCD line sensor 116, the CCD line sensor 116 that is a photoelectric conversion element, and the like. It is configured. The first scanning unit 113 includes an exposure lamp unit 113a that exposes the document surface, a first mirror 113b that reflects a reflected light image from the document in a predetermined direction, and the like. Further, the second scanning unit 114 includes second and third mirrors 114 a and 114 b that guide reflected light from the original reflected from the first mirror to the CCD line sensor 116.
Then, the document image read by the document reading unit 110 is sent as image data to an image data input unit (not shown), and predetermined image processing is performed on the image data. The image forming unit 210 is temporarily stored in the memory of the image forming unit, and the image data in the memory is read after the image processing is completed or in response to a predetermined output instruction from the outside, and is arranged below the document reading unit. Is transferred to the writing unit 227.

The writing unit 227 includes a semiconductor laser light source (not shown) that emits laser light according to the contents of image data transferred from the image processing unit or from an external device, and a polygon mirror that deflects the laser light at an equal angular velocity. (Not shown) includes an f-θ lens (not shown) for correcting laser light deflected at a constant angular velocity so as to be deflected at a constant velocity on the photosensitive drum 2. In this embodiment, a laser writing unit is used as the writing unit 227. However, a solid scanning optical writing head unit using a light emitting element array such as an LED or an EL may be used. As the photosensitive drum 2, for example, a photoconductive layer such as amorphous silicon (a-Si), selenium (Se), or an organic photo semiconductor (OPC) is formed on the outer peripheral surface of a conductive base (metal drum) made of aluminum or the like. Is formed in a thin film shape, but is not particularly limited.
Further, the image forming unit 210 forms a toner on an electrostatic latent image formed on the photosensitive drum 2 around the photosensitive drum 2, a charger 223 for charging the photosensitive drum 2 to a predetermined potential. A developing device X for visualizing the toner image, a transfer device 225 for transferring a toner image formed on the surface of the photosensitive drum 2 to a recording sheet (paper), a static eliminator 229 for discharging the photosensitive drum 2, A cleaning device 226 for collecting excess toner on the photosensitive drum is also provided. The recording sheet onto which the image has been transferred by the image forming unit 210 is then sent to the fixing unit 217 to fix the image on the recording sheet.
In addition to the fixing unit 217, on the discharge side of the image forming unit 210, there is a switchback path 221 that reverses the direction (front and back) of the recording sheet in order to form an image again on the back surface of the recording sheet. A stapling process is performed on the formed recording sheet and a post-processing device 260 having an elevating tray 261 is provided. The recording sheet on which the toner image has been fixed by the fixing unit 217 is guided to the post-processing device 260 by the paper discharge roller 219 through the switchback path 221 as necessary, where predetermined post-processing is performed. After that, it is discharged onto the lifting tray 261.
The copying machine 1 is connected to a sheet tray 251 and a switchback path 221 provided below the image forming unit 210 as a sheet feeding unit that supplies the recording sheet to the image forming unit 210. In addition to a double-sided unit 255 and a multi-stage sheet feeding unit 270 having a plurality of sheet feeding trays 252 and 253 for temporarily retracting a recording sheet when forming an image on both sides of the image forming apparatus, a hand is provided protruding from the side of the copying machine 1. A manual sheet feeding device 300 that provides a difference tray 254 is provided. Further, a transport unit 250 is provided for transporting the recording sheets set on the trays 251, 252, 253, and 254 to a transfer position by the transfer device 225 of the image forming unit 210. The duplex unit 255 can be replaced with a normal paper cassette, and the duplex unit 255 can be replaced with a normal paper cassette.

Next, the configuration of the developing device X will be described using the sectional side view of FIG.
The developing device X is mainly composed of a developing unit 10, a toner replenishing unit 20, and another control unit 40.
The developing unit 10 includes a developing roller 12 that rotates to face the rotating photosensitive drum 2 on which an electrostatic latent image is formed, a developing tank 11 that temporarily stores a developer containing toner used for development, and a developing tank. 11, screw roller-like stirring rollers 13, 14, and 15 that stir the developer inside. When the developing roller 12 rotates, the developer is conveyed from the developing tank 11 to the photosensitive drum 2, thereby developing the electrostatic latent image on the photosensitive drum 2.
The developer in the developing tank 11 is stirred and charged by the rotation of the developing roller 12 and the stirring rollers 13 to 15. A developing bias voltage is applied to the developing roller 11 in order to provide a potential difference from the photosensitive drum 2.
Further, the developing unit 10 detects a toner concentration sensor 16 (of the toner remaining amount detecting means) that detects a toner remaining amount in a two-component developer (developer including toner and carrier) in the developing tank 11 as a toner concentration. Example). The toner concentration sensor 16 is a magnetic permeability sensor that detects the magnetic permeability of the developer, and the toner concentration in the developer is detected based on the detected value.

In addition, the toner replenishing unit 20 provided in the developing device X agitates the toner by rotating inside the toner replenishing tank 21 (an example of the toner container) that contains the toner replenished to the developing tank 11. A stirring member 22 and a toner replenishing roller 23 for replenishing toner in the toner replenishing tank 21 into the developing tank 11 through a replenishing port 24 are provided. The toner supply roller 23 is a roller whose surface layer is formed of an elastic member such as a sponge.
The stirring member 22 is formed with stirring blades 22a, 22b, 22c and 22d for efficiently stirring the toner. In the example shown in FIG. 1, four stirring blades 22a to 22d are formed at an equal angle in the rotation direction of the stirring member 22. However, the present invention is not limited to this, and one or more other sheets (for example, A stirring member formed with 3 or 6 stirring blades is also conceivable.
The stirring member 22 and the toner replenishing roller 23 are rotationally driven by a motor 30 via a coupling mechanism such as a gear (not shown).
Since the toner replenishing roller 23 is driven to rotate by the motor 30 which is a common drive source with the stirring member 22, it is driven at a rotational speed (including the same rotational speed) proportional to the rotational speed of the stirring member 22. Is done.
The toner replenishing device 20 compares the magnetic permeability detection value (toner concentration) detected by the toner concentration sensor 16 with a reference value V _ref for determining toner replenishment, and the magnetic permeability detection value is equal to or greater than the reference value V _ref. The toner supply roller 23 is rotated when the toner density is low (that is, the remaining amount of toner is low), and the toner supply roller 23 is stopped when V _ref −β (β> 0) or less. Let As a result, when the detected density (detected remaining amount) by the toner density sensor 16 (toner remaining amount detecting means) decreases (permeability increases), the stirring member 22 and the toner replenishing roller 23 are proportional to each other. Driven at a rotational speed, the toner is intermittently supplied from the toner supply tank 21 (toner container) to the developing tank 11.
Operation control (starting, stopping, rotation driving control of the motor 30 based on toner density (magnetic permeability detection value), etc.) of the developing device X including the toner supply unit 20 is performed by the control unit 40. The control unit 40 includes a CPU, a ROM that stores a program executed by the CPU, and other peripheral devices, and the CPU executes each process described later by executing the control program stored in the ROM. Further, the control unit 40 includes a clock transmitter (not shown), and thereby has a function of aging time.
The control unit 40 is connected to a data storage unit 41 which is a storage unit such as an SRAM for storing various data used for executing the control program.

Next, a procedure for controlling toner replenishment and agitation by the developing device X will be described with reference to a flowchart shown in FIG. This process is implemented by the control unit 40 executing a control program. In the following, S1, S2,... Represent processing procedure (step) numbers. In the initial state before the start of this process, the motor 30 is stopped, and therefore, the toner supply roller 23 and the stirring member 22 are also stopped.
<Step S1>
First, the control unit 40 monitors based on the detection value of the toner density sensor 16 until the remaining amount of toner in the developing tank 11 is equal to or less than a predetermined remaining amount (S1). Specifically, the magnetic permeability detection value (toner concentration) detected by the toner concentration sensor 16 is compared with the reference value V _ref for determining toner replenishment, and the magnetic permeability detection value is equal to or higher than the reference value V _ref . In this case, it is determined that the toner remaining amount is equal to or less than the predetermined remaining amount.
<Step S2>
When it is detected that the toner remaining amount is equal to or less than the predetermined remaining amount (low), the control unit 40 determines the difference from the previous stop time based on the difference between the previous stop time of the motor 30 and the current time. The elapsed time is calculated, and it is determined whether or not this is equal to or shorter than the predetermined elapsed time (S2). The previous stop time of the motor 30 is information that the control unit 40 stores in the data storage unit 41 when the motor 30 is stopped in the process of step S9 described later.
<Step S3>
Here, when it is determined that it is not less than the predetermined elapsed time, that is, when there is a high possibility that toner is aggregated in the toner replenishing tank 21, the motor 30 will be described later. It is rotated at a torque higher than the output torque in the steady period (S3).
In the developing device X, a motor (frequency control motor) such as a stepping motor whose speed is controlled by the frequency of the drive signal is used as the motor 30. Therefore, the control unit 40 outputs a drive signal having a relatively low frequency corresponding to a set rotational speed lower than a set rotational speed in a steady period, which will be described later, as a drive signal output to the motor 30 (that is, relatively low). Outputs the set rotation speed). As a result, the rotation is performed at a torque higher than the output torque in a steady period to be described later.
The stepping motor used as the motor 30 has a permanent magnet on the mover, and the frequency of the drive signal is proportional to the rotational speed, so there is no need to provide a servo circuit for motor control. The output torque (rotation speed) can be accurately controlled with a simple open loop configuration.
When a motor controlled by a drive voltage, a drive current, or a PWM duty is used as the motor 30, the power level (drive voltage or drive current) of the drive signal in a steady period to be described later is sent to the motor 30. If a drive signal with a power level higher than (PWM duty) is output to the motor 30, the motor is driven with an output torque higher than the steady period.

<Step S4>
Next, the control unit 40 determines whether or not the stirring member 22 has been rotated by one pitch (S4), and the motor driving condition at an output torque higher than the steady period until the stirring member 22 has been rotated by one pitch. To maintain.
Here, the rotation by one pitch means that the stirring blades 22a to 22d are adjacent to each other at the time of stop (22b for 22a, 22c for 22b, 22c for 22c, 22d for 22d, 22a) means that the stirring member 22 shown in FIG. 1 is rotated by 90 °.
When the stirring member 22 is rotated by one pitch, the stirring blades 22a to 22d formed on the stirring member 22 after the start of the rotation of the stirring member 22 are moved to the entire stirring region (all circumference ( 360 °) region).
As a means for detecting rotation by one pitch (an example of the whole area passage detecting means), for example, a rotary potentiometer is provided on the rotating shaft of the stirring member 22 and the number of output pulses is counted by the control unit 40. Conceivable. Alternatively, when the frequency control motor is used, since the frequency of the drive signal is known, the time during which the pulse output of the drive signal corresponding to one pitch is made is counted, and the stirring member 22 is indirectly measured by the measured time. May be detected by rotating approximately one pitch. In addition, a limit switch that is turned on every time the rotation shaft of the stirring member 22 rotates by one pitch is provided, and it is conceivable to detect that the rotation has been performed by one pitch depending on the ON / OFF state of the limit switch.
In this way, after the stirring member 22 starts rotating, it is detected that the stirring member 22 has been rotated by one pitch (that is, the stirring blades 22a to 22d formed on the stirring member 22 are (Until it is detected that substantially all of the agitation region (all-around region) has been substantially passed by the agitating member 22) is referred to as "initial movement period", and the subsequent period during which the motor 30 is rotating is referred to as "steady period" To do.

<Step S5>
Next, when it is detected that the agitating member 22 has been rotated by one pitch, the control unit 40 determines the rotation speed of the motor 30 during the steady period by detecting the density of the toner density sensor 16 (that is, the toner). It is set based on the remaining amount detected by the remaining amount detecting means (S5).
Specifically, when the shortage of the remaining toner amount with respect to the target remaining amount is large (toner density is low), the shortage amount with respect to the target remaining amount is small (the toner concentration is close to the target concentration) so as to be relatively fast. ), The rotational speed of the motor 30 in the steady period is set so as to be relatively low. For example, the data storage unit 41 stores in advance a conversion table for converting the toner concentration (that is, the detected value of the magnetic permeability) into the rotation speed of the motor 30, and according to the conversion table in the steady period. This can be realized by setting the rotation speed of the motor 30 or by setting it according to a predetermined conversion formula.
<Step S6>
Next, the control unit 40 gradually increases the rotational speed (driving condition) of the motor 30 from the current rotational speed to the rotational speed (set rotational speed) set in step S6. Switch (S6). Thereby, when the motor 30 is the frequency control motor, it is possible to prevent the motor 30 from stepping out due to a sudden increase in the driving frequency (speed).
In this way, the control that causes the control unit 40 to transit from step S3 → S4 → S5 → S6 is an example of the control by the first motor control means. That is, by the process of steps S 3 → S 4 → S 5, the initial motion period from when the stirring member 21 starts to rotate until it is detected that the stirring blades 22 a to 22 d have substantially passed through the entire stirring region by the stirring member 22 ( The output torque (rotational speed) of the motor 30 in the processing period (S3, S4) is higher (lower speed) than the output torque (rotational speed) in the subsequent steady period (processing period of S6, S7). The driving condition of the motor 30 is switched. Furthermore, the driving condition of the motor 30 is switched stepwise from the condition in the initial operation period to the condition in the steady period by the process of step S6.
As described above, in the developing device X, the output torque of the motor 30 is switched by switching the set rotational speed (that is, the frequency of the motor drive signal) for the motor 30 as the drive condition of the motor 30.

By the processing of steps S3 to S6 described above, the stirring operation in the steady state (steady output) can be performed at the earliest stage while preventing the motor from stepping out during the initial operation period.
In general, when the rotation of the stirring member 22 is started, the toner is often agglomerated because the stirring is stopped until then. In such a state, the stirring member 22 is driven with a high torque, so that the toner can be loosened effectively.
The driving period with high torque is the minimum period required to loosen the agglomerated toner, that is, the one pitch portion in which the stirring blades 22a to 22d substantially pass through the entire stirring region by the stirring member 22. It is only the period of rotation (the initial movement period). For this reason, when the frequency control motor is used as the motor 30, it is possible to prevent the motor 30 from stepping out during the initial operation period. Further, when a motor controlled by voltage, current, or the like is used as the motor, the initial operation period is relatively short, so that the stirring operation in the steady state can be performed at the earliest stage while preventing the motor from generating heat. Become.
Furthermore, if the output torque of the motor 30 (set torque (speed) in step S3) in the initial operation period is set to an output exceeding the continuous rated output, the agglomerated toner is more resistant to the load than before. It can be loosened more effectively.

On the other hand, in step S2, the control unit 40 determines that the elapsed time from the previous stop of the motor 30 (that is, the previous rotation stop of the stirring member) to the start of the current rotation is shorter than the predetermined time. In this case, instead of the control (an example of the control by the first motor control means) that makes the transition from step S3 to S4 to S5, the process proceeds from step S2 to step S5 as it is. Thus, the driving condition of the motor 30 in the steady period is set from the beginning of the starting of the motor 30 (an example of processing of the second motor control means).
Thus, when the elapsed time from the previous stop of rotation of the agitating member 22 to the start of the current rotation is short, the toner in the toner replenishing tank 21 is normally in a non-aggregated state. Unnecessary switching control of the 30 driving conditions is not performed, and the stirring operation in the steady state can be performed earlier.

<Step S7>
Next, the controller 40 determines whether the remaining amount of toner in the developing tank 11 is sufficient based on the detection value of the toner density sensor 16 (S7). Specifically, when the detected magnetic permeability value (toner concentration) detected by the toner concentration sensor 16 becomes V _ref −β (β> 0) or less, it is determined that the remaining amount of toner is sufficient.
<Steps S8 and S9>
If it is determined that the remaining amount of toner is not sufficient, the process returns to step S5 and the above-described processing is repeated. On the other hand, if it is determined that the remaining amount of toner is sufficient, the control unit 40 stops the rotation of the motor 30 (S8), and the data storage unit 41 uses the current time as the stop time. (S9), the process returns to S1 to repeat the above-described processing.

By the way, the intermolecular force of the toner increases in inverse proportion to the particle size.
FIG. 4 is a graph showing the relationship between the toner particle size and the intermolecular force of the toner. Here, in both FIGS. 4A and 4B, the horizontal axis is the toner particle size (μm).
The vertical axis in FIG. 4A is a value obtained by normalizing the intermolecular force Fd of the toner particle diameter d with reference to the intermolecular force F ₇ when the toner particle diameter d = 7 μm.
The vertical axis of FIG. 4B shows the slope (ΔFd / Δd) of the intermolecular force Fd of the toner with respect to the toner particle diameter d, and the slope (ΔF ₇ / Δd) when the toner particle diameter d = 7 μm. Values normalized to the standard.
As can be seen from the graphs of FIGS. 4A and 4B, the intermolecular force of the toner increases rapidly when the toner particle size is 7 μm or less. Since the toner is more likely to aggregate as the intermolecular force of the toner is stronger, the developing device X is particularly suitable when the particle size of the toner is about 7 μm or less.

  The present invention can be applied to a developing device used for electrophotographic image formation.

FIG. 3 is a side sectional view showing the configuration of the developing device X according to the embodiment of the present invention. 6 is a flowchart showing a control procedure of toner replenishment and stirring by the developing device X. FIG. 3 is a front sectional view illustrating a configuration of an image forming apparatus including the developing device X. 6 is a graph showing the relationship between the toner particle size and the intermolecular force of the toner.

Explanation of symbols

X: Development device 1 ... Image forming device 2 ... Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 10 ... Developing part 11 ... Developing tank 12 ... Developing rollers 13, 14, 15 ... Stirring roller 16 ... Toner density sensor (toner remaining amount detecting means)
20 ... Toner replenishing section 21 ... Toner replenishing tank (toner container)
22 ... stirring members 22a to 22d ... stirring blade 23 ... toner supply roller 24 ... supply port 30 ... motor 40 ... control unit 41 ... data storage unit 110 ... image reading unit 210 ... image forming unit 270 ... multi-stage sheet feeding unit 300 ... manual feed Sheet feeding device

Claims (9)

In a developing device comprising a stirring member that stirs toner by rotating in a toner container, and a motor that rotationally drives the stirring member.
All-area passage detection means for detecting that the stirring blades formed on the stirring member after the start of rotation of the stirring member have substantially passed through the entire stirring area by the stirring member;
The output torque of the motor in the initial operation period from the start of rotation of the stirring member until it is detected by the all-area passage detection means that it has substantially passed the entire area is higher than the output torque in the subsequent steady period. First motor control means for switching the driving conditions of the motor so that
A developing device comprising:   2. The developing device according to claim 1, wherein the first motor control unit switches the output torque of the motor by switching a set rotation speed for the motor as a driving condition of the motor. Toner remaining amount detecting means for detecting the remaining amount of toner in a developing tank for temporarily storing toner used for development;
A replenishing roller that is driven at a rotation speed proportional to the rotation speed of the agitating member when the remaining amount detected by the toner remaining amount detecting means decreases, and replenishes toner from the toner container to the developing tank;
The developing device according to claim 2, wherein the first motor control unit sets a rotation speed of the motor in the steady period based on a remaining amount detected by the remaining toner amount detecting unit.   4. The developing device according to claim 2, wherein the first motor control unit switches the driving condition of the motor stepwise from a condition in the initial operation period to a condition in the steady period. 5.   When the elapsed time from the previous stop of rotation of the stirring member to the start of the current rotation is shorter than a predetermined time, the motor is driven in the steady period from the beginning of the motor instead of the control by the first motor control means. The developing device according to claim 1, further comprising second motor control means for setting conditions.   The developing device according to claim 1, wherein the motor has a permanent magnet on a mover.   The developing device according to claim 1, wherein the toner has a particle size of about 7 μm or less.   An image forming apparatus comprising the developing device according to claim 1. In a control method for a developing device, comprising: a stirring member that stirs toner by rotating in a toner container; and a motor that rotationally drives the stirring member.
An all-region passage detection step for detecting that the stirring blade formed on the stirring member after the start of rotation of the stirring member substantially passes through the entire stirring region by the stirring member;
The output torque of the motor in the initial operation period from the start of rotation of the stirring member until it is detected that the entire area has been substantially passed by the all-area passage detection step is higher than the output torque in the subsequent steady period. A motor control step of switching the driving conditions of the motor so that
A control method for a developing device, comprising:

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