JP5672986B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that develops an electrostatic latent image on an image carrier, a copying machine including the developing device, a printer, a facsimile, a plotter, and an image forming apparatus such as a multifunction peripheral including at least one of them. About.

In a developing device including a developing unit that visualizes an electrostatic latent image on an image carrier and a developer stirring unit provided at a location away from the developing unit, between the developing unit and the developer stirring unit A powder pump that is configured to circulate the developer and that causes the developer in the developer agitation unit to enter the path for conveying the developer from the developer agitation unit to the development unit. What is provided with (air pump) is known.
However, the developer conveyance by air is affected by the bulk density of the developer, and the conveyance amount changes when the bulk density changes depending on the toner concentration and the deterioration state of the developer.
When the transport amount to the developing unit decreases, the developer capacity in the developing unit decreases, so that sufficient developer cannot be supplied to the developing roller, and defects such as density unevenness occur at the screw pitch on the image.
For this reason, when air conveyance is used for supplying the developer to the developing unit, it is important to keep the conveyance amount constant.

In view of this, a method for detecting the volume of the developer in the developer stirring section and controlling the transport amount has been proposed.
For example, in Patent Document 1, detection means for detecting the powder level is provided in the developer stirring unit, and the ratio of the developer amount between the developer stirring unit and the developing unit is adjusted to be appropriate.
However, since the powder level is raised and lowered by the rotation of the stirring blade during stirring, accurate control is difficult.
Further, it cannot be used when the total amount of the developer in the developing device fluctuates, such as when the deteriorated developer is discharged to the outside.
In addition, as shown in FIG. 10B, there is a method in which a flow meter for measuring the flow rate of air is installed between the air pump and the conveying means to control the amount of air being conveyed to be constant. .
In this method, control is performed so that the amount of air during conveyance is constant, but a part of the developer may flow into the flow meter from the conveyance path immediately after the conveyance is stopped. The principle of a hot-wire air flow meter that is generally used is that an element heated by flowing a current is provided in a tube, and the amount of heat cooled by the air flowing in the tube is converted into the amount of air flowing.

  However, the method of detecting and controlling the air flow rate has a problem that the amount of flowing current changes when dust or developer adheres to the element, and the accurate flow rate cannot be measured.

  The present invention has been made in view of such circumstances, and provides a developing device capable of making the amount of developer transported by air substantially constant regardless of changes in the bulk density of the developer and preventing problems such as density unevenness. Is its main purpose.

To achieve the above object, the present invention provides a developing unit that visualizes an electrostatic latent image on an image carrier as a toner image, and a developer that is provided outside the developing unit and is discharged from the developing unit. A developer agitation unit that agitates and mixes toner to be replenished in accordance with a change in toner density in the development unit; and a developer conveyance unit having a conveyance path for conveying the developer from the developer agitation unit to the development unit; An air supply means for supplying air to the developer conveying means, and in the developing device for conveying the developer by air from the developer agitating unit to the developing unit, conveying for detecting the developer conveying pressure by air It has a pressure detection means, and when the detection value by the said conveyance pressure detection means is higher than a reference value, the supply amount of the air by the said air supply means is increased .

According to a second aspect of the present invention, there is provided a developing unit that visualizes an electrostatic latent image on an image carrier as a toner image, a developer that is provided outside the developing unit and is discharged from the developing unit, and the developing unit. A developer agitating unit for agitating and mixing the toner to be replenished in accordance with a change in toner density, a developer conveying means having a conveyance path for conveying the developer from the developer agitating unit to the developing unit, and the developing An air supply means for supplying air to the developer transport means, and a transport pressure detecting means for detecting the pressure of the developer transport by air in the developing device for transporting the developer from the developer agitating section to the developing section by air. When the detection value by the conveyance pressure detection means is lower than a reference value, the air supply amount by the air supply means is reduced .
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the transport pressure detecting means is provided between the developer transport means and the air supply means. To do.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, a valve is provided between the transport pressure detecting unit and the air supply unit. The air supply amount is adjusted by adjusting the open / close state .

A fifth aspect of the present invention is an image forming apparatus including the developing device according to any one of the first to fourth aspects.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, when the detected value by the transport pressure detecting means continues to be higher or lower than a predetermined value, it is determined that the development is abnormal and the development is performed. The drive of the apparatus is stopped .

  According to the present invention, the amount of developer transported by air can be made substantially constant regardless of the change in the bulk density of the developer transported from the developer stirring unit to the developing unit, and problems such as density unevenness can be prevented.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. It is a general | schematic perspective view of a developing device. It is sectional drawing of a image development part. It is sectional drawing of a developing agent stirring part. FIG. 6 is a characteristic diagram illustrating a relationship between a developer bulk density and a developer conveyance amount. FIG. 6 is a characteristic diagram illustrating a relationship between a developer bulk density and an air pressure during developer conveyance. It is a flowchart which shows control operation. It is a characteristic view which shows the relationship between an air pressure and air discharge amount. FIG. 6 is a characteristic diagram illustrating a relationship between an air flow rate during developer conveyance and a developer conveyance amount. It is a schematic diagram which shows the difference in the measuring method of an air flow rate. FIG. 6 is a characteristic diagram illustrating a relationship between a developer conveyance state and air pressure. It is a schematic diagram which shows the control structure based on the air pressure in 2nd Embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
The first embodiment will be described with reference to FIGS. First, an outline of a configuration of an image forming apparatus including a developing device (developing system) according to the present embodiment will be described with reference to FIG.
Image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the lower surface of the intermediate transfer belt 8 as an unfixed image carrier in the intermediate transfer unit 10. ing. These image forming units 6Y, 6M, 6C, and 6K have the same structure except that the color of the toner used in the image forming process is different.
Each image forming unit 6 includes a photosensitive drum 1 as an image carrier, a charging unit (not shown) disposed around the photosensitive drum 1, a developing device 5, a cleaning unit (not shown), and the like.

An image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1.
The photosensitive drum 1 is rotationally driven in the clockwise direction in the figure by a driving unit (not shown), and the surface is uniformly charged at the position of the charging means (charging process).
Thereafter, the surface of the photosensitive drum 1 reaches an irradiation position of a laser beam emitted from an exposure unit (not shown), and an electrostatic latent image is formed by exposure scanning at this position (exposure process).
Thereafter, the surface of the photosensitive drum 1 reaches a position facing the developing device 5, and the electrostatic latent image is developed at this position to form a desired toner image (developing process).
Thereafter, the surface of the photosensitive drum 1 reaches a position facing the intermediate transfer belt 8 and the primary transfer bias roller 9, and the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 8 at this position. (Primary transfer process).
Thereafter, the surface of the photosensitive drum 1 reaches a position facing the cleaning unit, and untransferred toner remaining on the photosensitive drum 1 is collected at this position (cleaning step). After cleaning, the surface of the photosensitive drum 1 is initialized with the potential of a neutralizing roller (not shown). Thus, a series of image forming processes performed on the photosensitive drum 1 is completed.

  The above-described image forming process is performed by each of the four image forming units 6Y, 6M, 6C, and 6K as shown in FIG. That is, a laser beam based on image information from an exposure unit (optical writing device) (not shown) disposed below the image forming unit is applied to the photosensitive drums of the image forming units 6Y, 6M, 6C, and 6K. Irradiated toward. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

The four primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. The primary transfer bias rollers 9Y, 9M, 9C, and 9K are applied with a transfer bias having a polarity opposite to the polarity of the toner.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19 as a secondary transfer unit. The color toner image formed on the intermediate transfer belt 8 is transferred onto a transfer sheet S as a recording medium conveyed to the secondary transfer nip position.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.
A plurality of transfer sheets S are stored in a paper supply unit 26 disposed in the lower part of the apparatus main body 100 and are separated and fed one by one by a paper supply roller 27. The fed transfer sheet S is temporarily stopped by the registration roller pair 28, and after the oblique shift is corrected, it is conveyed toward the secondary transfer nip by the registration roller pair 28 at a predetermined timing. As described above, a desired color image is transferred onto the transfer sheet S at the secondary transfer nip.

The transfer sheet S on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing unit 20, where the color image transferred on the surface is fixed by heat and pressure generated by the fixing roller and the pressure roller. The
After the fixing, the transfer paper S is discharged as an output image to the paper discharge unit 30 formed on the upper surface of the apparatus main body by the paper discharge roller pair 29 and stacked. Thus, a series of image forming processes in the image forming apparatus is completed.
In FIG. 1, the code | symbol 32 has shown the reading part.

Next, the configuration of the developing device (developing system) 5 containing a two-component developer composed of toner and carrier will be described in detail.
FIG. 2 shows the overall configuration of the developing device 5. In FIG. 1, only the developing unit of the developing device 5 is shown.
The developing device 5 includes a developing unit 12 and a developer stirring unit 40 that stirs and mixes the developer and toner, and the developing unit 12 is disposed independently above the developer stirring unit 40. It has become.

The developing unit 12 is a unit for developing the electrostatic latent image on the photosensitive drum 1 with a developer (toner) to form a toner image. The toner image formed on the photosensitive drum 1 provided facing the developing unit 12 is transferred to the recording medium as described above, and fixed and fixed on the recording medium by the fixing unit, and the image is output.
As shown in FIG. 3, the developing unit 12 supplies a developer to the photosensitive drum 1 so as to be close to and opposed to the photosensitive drum 1, and develops a developer carrying member (developing) that visualizes the latent image. Roller) 11.
Inside the developing unit 12, the developer (toner and carrier) is transported in parallel to the axis of the developer carrier 11 while the developer is supplied to the developer carrier 11 and a transport member such as a screw to be collected is collected. Is arranged (described later), and the developer is circulated and conveyed through the downstream agitation site while agitating and conveying the developer. Next, the circulation of the developer will be described.

Since the toner in the two components is consumed by the development, the developer (toner and carrier) having a decreased toner concentration passes through the developer transfer pipe 33 for recovery as shown in FIG. It is transferred to. The developer agitating unit 40 has a vertically long cylindrical shape, and is provided with an agitating means described later. The agitating means is driven by a motor 45.
Connected to the upper side of the developer stirring section 40 is a toner supply pipe 21 for supplying a shortage of toner consumed by development. A toner container 22 containing supply toner is connected to the toner supply pipe 21.
When an insufficient toner concentration is detected, a screw (not shown) serving as a conveying means provided in the toner supply tube 21 is driven by the motor 34 and the supply toner in the toner container 22 is supplied to the developer stirring unit 40. .
The amount of developer replenished by the toner replenishing tube 21 is determined by the control means 70 (see FIG. 4) according to the detection result of the toner concentration sensor attached to the vicinity of the recovery screw of the developing unit 12.

In the developer agitation unit 40, the replenishment toner supplied from the toner container 22 via the toner replenishment pipe 21 and the developer returned via the developer transfer pipe 33 are agitated and mixed to be dispersed and converted into toner. Is charged.
A fixed amount of the developer after stirring is discharged downward by the rotary feeder 50. The developer discharged from the rotary feeder 50 is generated by an air pump 60 as an air supply means, and is supplied to the developer stirring unit 40 and the supply position (opening) 15 in the developing unit 12 together with the air flow sent through the tube 35. In between, the developer passes through the tube 31 as a transport path for transporting the developer to the developing unit 12.
An end (supply port) of the tube 31 is connected to an opening 15 located at the left end in the longitudinal direction of the developing unit 12.

The amount of developer transported to the developing unit 12 is determined by the rotational speed of the rotary feeder 50 and the flow rate of the air pump 60. Since conveyance of the developer by the developer transfer pipe 33 is performed using gravity, an air pump is not necessary.
The developer transfer pipe 33 and the tube 31 as the developer transport path are formed of flexible tubes such as silicon. The tube 31, the rotary feeder 50, and the like constitute a developer conveying means.

FIG. 3 is a cross-sectional view of the developing unit 12. The developer carrying member 11 disposed in close proximity to the photosensitive drum 1 includes a non-magnetic cylindrical developing sleeve constituting the outer peripheral portion, and magnetic field generating means (a plurality of magnetic poles magnetized on the inner side). A developing roller composed of a magnet roller or a plurality of magnets), and the developing sleeve is driven to rotate around a fixed (non-rotating) magnet. The latent image on the photosensitive drum 1 is developed with toner in the developer while being held on the surface to form a toner image.
Reference numeral 13 denotes a collection screw for collecting and transporting the developer used for development, and the collected developer is directed from the opening 16 (see FIG. 2) provided at the most downstream toward the developer transfer pipe 33. Sent out. Reference numeral 14 denotes a supply screw that supplies the developer after stirring to the sleeve, and reference numeral 25 denotes a doctor blade that regulates the layer thickness of the developer on the surface of the developing sleeve.

FIG. 4 is a cross-sectional view of the developer agitating unit, developer conveying means, and air supply means.
It is an Example at the time of using a screw and a rotating plate-shaped stirring blade as a stirring member. A vertically extending screw 43 that is directly connected to the rotating shaft 45 a of the motor 45 is disposed at a cylindrical shaft center portion of a vertically long cylindrical container 41 that constitutes the developer stirring unit 40. A rotating blade 44 for stirring is attached to the rotating shaft 45a through a cylindrical shaft 46 with a loose fitting that can rotate.
A first drive gear G1 is fixed to the rotation shaft 45a of the motor 45. The first drive gear G1 is meshed with the first intermediate gear G2. The first intermediate gear G2 is fixed to an intermediate shaft 47 that is supported between the frame (not shown) and the upper surface of the container 41. A second intermediate gear G3 is fixed to the intermediate shaft 47 below the first intermediate gear G2. A second drive gear G4 fixed to the upper end of the cylindrical shaft 46 is engaged with the second intermediate gear G3. The second drive gear G4 is loosely fitted to the rotary shaft 45a so as to be freely rotatable, and is free to rotate with respect to the first drive gear G1, and is integrated with the rotary blade 44 via the cylindrical shaft 46. It has become.

When the motor 45 is rotated, the screw 43 directly connected to the motor 45 is rotated. At the same time, the power is transmitted in the order of the first drive gear G 1, the first intermediate gear G 2, the second intermediate gear G 3, and the second drive gear G 4, and the rotating blades 44 are rotated in a rotation direction different from that of the screw 43. .
The screw 43 conveys the developer in the container 41 from the bottom to the top by the rotation. The rotary blade 44 rotates around the screw 43 along the inner peripheral surface of the container 41.
The inlet of the excess developer discharge portion 42 is opened at the side of the container 41, and the connection port 41 a for the outlet of the developer transfer pipe 33 and the connection port 41 b for the outlet of the toner supply pipe 21 are formed at the upper part of the container 41. Is provided.
The replenishment toner enters from the upper connection port 41b of the container through the toner replenishment pipe 21, and the collected developer from the developing unit 12 enters from the upper connection port 41a of the container through the developer transfer pipe 33.

While stirring with the stirring blade 44, it conveys from the bottom to the top with the screw 43, produces convection, and stirs three-dimensionally. In this way, the replenishment toner stored in the toner container 22 and the developer remaining in the development conveyed from the recovery screw in the developing unit 12 are agitated and mixed to adjust the toner density and charge amount to an appropriate level.
The developer after stirring is delivered to the rotary feeder 50 from an outlet 48 formed in the lower part of the developer stirring unit 40.
As shown in FIG. 2, the rotary feeder 50 communicated with the developer stirring unit 40 is located at the developer discharge position from the developer stirring unit 40.
As shown in FIG. 4, the rotary feeder 50 includes a rotor 51 having a plurality of blades around an axis. The developer is disposed upstream of the rotor 51 by rotating the rotor 51 by a motor 55. The developer agitated by the agitation unit 40 functions to be discharged to the lower discharge unit 54 by a certain amount.
The rotary feeder 50 is a feeding unit that conveys the developer from the developer stirring unit 40.

A pressure gauge 61 is provided in the path (tube 35) between the air pump 60 and the discharge unit 54 as a transport pressure detecting means for measuring the air pressure.
The pressure gauge 61 is used to detect the pressure of air flowing through the conveyance path. If the developer is provided in the developer conveyance path, the developer enters the pressure gauge 61 and causes a failure. Therefore, the developer is provided at a position upstream from the developer conveyance path 31. A valve 62 for adjusting the air supply flow rate is provided between the air pump 60 and the pressure gauge 61.
The pressure detected by the pressure gauge 61 is fed back to the control means 70 that controls the solenoid 65 that opens and closes the valve 62.
The open / close state of the valve 62 is adjusted based on the pressure detected by the pressure gauge 61, and the developer supply amount to the developing unit 12 is controlled to be constant.

The developer conveyance amount is determined by the air flow rate and the rotational speed of the rotary feeder 50. However, even if the input air flow rate and the rotational speed of the rotary feeder 50 are the same, as shown in FIG. The developer conveyance amount varies depending on the bulk density.
This is because the air flow rate during developer conveyance is smaller than the input air amount. During the developer conveyance, a load for conveying the developer is applied, and the pressure of the conveyance air rises.
When the air pressure rises, as shown in FIG. 8, the air flow rate decreases, so that the air flow rate during conveyance is smaller than the input air flow rate measured in the unloaded state. Since the amount of conveyance load varies depending on the bulk density of the developer, the air flow rate during conveyance varies depending on the bulk density, and the conveyance amount of the developer varies.

As shown in FIG. 10B, a flow meter 63 for measuring the flow rate of air may be installed between the air pump 60 and the conveying means so that the amount of air being conveyed may be controlled to be constant. However, a part of the developer may flow into the flow meter 63 from the conveyance path 31 immediately after the conveyance is stopped.
The principle of a hot-wire air flow meter that is generally used is that an element heated by flowing a current is provided in a tube, and the amount of heat cooled by the air flowing in the tube is converted into the amount of air flowing. Accordingly, when dust or developer adheres to the element, the amount of current flowing changes, and an accurate flow rate cannot be measured.
As a result of intensive studies by the present inventors, it has been found that the air pressure changes depending on the bulk density of the developer being conveyed, as shown in FIG. Therefore, as shown in FIG. 10A, the air pressure during the conveyance is detected, the conveyance amount is estimated, and the conveyance amount is controlled to be constant. The dotted line in FIG. 10A means that the air pump 60 is feedback-controlled by the control means 70 based on the measured value by the pressure gauge (same in other drawings).

A method for controlling the developer conveyance amount will be described with reference to the flowchart of FIG.
Check in advance the pressure-air flow characteristic curve of the air pump used.
The dotted line in FIG. 8 represents the relationship between the discharge air flow rate and the pressure of the diaphragm type air pump 60 used in this embodiment. If the air flow rate under no load (pressure 0) and the air pressure during conveyance are known, the air flow rate during conveyance can be obtained.
Before the developing device starts to be driven, the amount of input air is calculated from the open / closed state of the valve 62, and this is recorded as the input air amount L1. Note that the valve 62 is used in a slightly closed state. This is because if the valve 62 is used in a fully opened state, the air supply amount cannot be increased any further.
When the developer air conveyance starts, the pressure gauge 61 is used to monitor the air pressure during the developer conveyance.

After the developer circulation operation is sufficiently stabilized, the conveyance air amount L2 is calculated from the characteristic curve of the air pump shown in FIG. 8 based on the detected pressure value P and the input air amount L1.
Since the developer transport amount is determined by the transport air amount, the developer transport amount M corresponding to the transport air amount L2 is calculated from the relationship between the transport air amount and the developer transport amount in FIG.
When the pressure is higher than the reference value Ps, it means that the bulk density of the developer to be transported is high and the transport amount is reduced from the reference amount. When the transport amount is reduced, the agent capacity of the developing unit is reduced, and there is a possibility that problems such as uneven image density occur.
Therefore, the amount L2 of the conveyance air is calculated from the pressure, and when the developer conveyance amount is less than the reference amount, it is determined that the developer supply amount to the developing unit 12 is insufficient, the valve 62 is opened, and the conveyance is performed. The air supply amount L1 is increased to L1 ′ so that the air flow rate inside becomes Ls.
On the other hand, when it is determined that the pressure is low and the developer conveyance amount is larger than the target value, the valve 62 is closed to reduce the air supply amount to the developing unit 12. When the valve 62 is opened and closed to change the amount of input air, the recorded input air flow rate L1 is rewritten and updated to L1 ′.

By such control, the supply amount to the developing unit 12 can be made constant. The image formation start timing is preferably after the supply amount to the developing unit 12 becomes constant.
Further, during image formation, the output of the pressure gauge 61 is detected every time an image is formed, and the air flow rate supplied by opening and closing the valve 62 is adjusted. As a result, the supply amount to the developing unit 12 can be kept stable even during image formation even if the bulk density of the developer changes due to fluctuations in toner density.
In addition, moderate air exists in the path during conveyance, but if an agent is clogged in the conveyance path 31 due to some trouble, the load increases and the pressure rises more than twice that during normal conveyance. If the transport path 31 is clogged with the agent, the supply of the developer to the developing unit 12 stops and image formation cannot be performed.

Further, when the developer is accumulated in the rotary feeder 50 and is locked, since the developer does not fall into the discharge portion 54, almost only air is supplied and the pressure becomes almost zero. In this case as well, image formation cannot be performed because the developer is not supplied to the developing unit 12.
When the pressure greatly deviates from the normal use range, not only such a problem occurs, but also the developer may overflow from the developing unit 12 or the developer stirring unit 40 if the pressure is kept moving as it is.
Therefore, as shown in FIG. 11, the range of pressure used for normal conveyance is determined, and when the pressure is out of the range, it is determined that there is an abnormality and the drive of the developing device is stopped. Displayed on an operation panel (not shown) to inform the user.

A second embodiment will be described with reference to FIG. Note that the same parts as those of the above-described embodiment are denoted by the same reference numerals, and unless otherwise specified, the description of the configuration and functions already described is omitted, and only the main parts are described.
In the above embodiment, the valve 62 is used. However, the present embodiment is characterized in that the control is performed without using the valve 62.
Measuring the air pressure during conveyance is the same as in the first embodiment, but in this embodiment, the air flow rate is adjusted by adjusting the voltage of the air pump 60 instead of the valve.
The motor (not shown) of the air pump 60 is connected to a power source capable of adjusting the applied voltage, and adjusting the voltage changes the rotational speed of the motor that drives the air pump 60 and changes the amount of air discharged.
Based on the measured air pressure, the air flow rate is calculated. When the air flow rate is low, the voltage applied to the air pump 60 is increased to increase the amount of input air supplied to the developing device.
Conversely, when the air flow rate is reduced, the voltage applied to the air pump 60 is lowered. If the relationship between the voltage applied to the motor that drives the air pump 60 and the discharge air amount is known, the air flow rate can be controlled.

  When the transport amount is not controlled, the developer bulk density changes depending on the deterioration, temperature, and humidity of the developer, and the supply amount of the developer changes under the influence.In the present invention, however, the pressure during the developer transport is changed. Since the amount of air is adjusted, the transport amount of the developer can be kept constant regardless of the state of the developer. If the developer transport amount is constant, the developer capacity of the developing unit 12 does not fluctuate and stable image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum as an image carrier 5 Developing device 12 Developing part 31 Conveyance path 40 Developer stirring part 60 Air pump as air supply means 61 Pressure gauge 62 as conveyance pressure detection means 62 Valve

JP 2010-139564 A

Claims (6)

A developing unit that visualizes the electrostatic latent image on the image carrier as a toner image, and a developer that is provided outside the developing unit and replenished according to changes in the developer discharged from the developing unit and the toner density of the developing unit A developer agitating unit for agitating and mixing the toner to be developed, a developer conveying unit having a conveying path for conveying the developer from the developer agitating unit to the developing unit, and an air for supplying air to the developer conveying unit A developing device that transports the developer by air from the developer agitating unit to the developing unit,
It has a conveyance pressure detection means for detecting the pressure of developer conveyance by air, and when the detection value by the conveyance pressure detection means is higher than a reference value, the supply amount of air by the air supply means is increased. Development device. A developing unit that visualizes the electrostatic latent image on the image carrier as a toner image, and a developer that is provided outside the developing unit and replenished according to changes in the developer discharged from the developing unit and the toner density of the developing unit A developer agitating unit for agitating and mixing the toner to be developed, a developer conveying unit having a conveying path for conveying the developer from the developer agitating unit to the developing unit, and an air for supplying air to the developer conveying unit A developing device that transports the developer by air from the developer agitating unit to the developing unit,
It has a conveyance pressure detection means for detecting the pressure of developer conveyance by air, and when the detection value by the conveyance pressure detection means is lower than a reference value, the amount of air supplied by the air supply means is reduced. Development device. The developing device according to claim 1 or 2,
2. A developing device according to claim 1, wherein said conveying pressure detecting means is provided between said developer conveying means and said air supply means . In the developing device according to any one of claims 1 to 3 ,
A developing device , wherein a valve is provided between the conveyance pressure detecting means and the air supply means, and an air supply amount is adjusted by adjusting an open / close state of the valve . An image forming apparatus comprising the developing device according to claim 1. The image forming apparatus according to claim 5.
An image forming apparatus, wherein when the detected value by the conveying pressure detecting means continues to be higher or lower than a predetermined value, it is determined as abnormal and the driving of the developing device is stopped .

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