JP2009098294A - Developing device, toner supply method therefor, and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of constantly obtaining a stable amount of supplied toner in the supply of toner to a developing tank from a toner hopper, to provide an image forming apparatus with the developing device, and to provide a toner supply method for the developing device. <P>SOLUTION: The developing device includes: the developing tank 21 storing two-component developer; the toner hopper 7 for supplying toner to the inside of the developing tank 21; and a toner cartridge 30 for supplying toner to the inside of the toner hopper 7. The toner hopper 7 has: a toner introducing port R through which toner supplied from the toner cartridge 30 is introduced to the inside of the hopper; a toner support port Q through which the toner inside the hopper is supplied to the developing tank 21; a toner agitating roller 75 disposed below and near the toner introducing port R and used to agitate the toner inside, thereby making a toner interface flat; a toner interface detecting sensor 76 disposed near the toner agitating roller 75 and used to detect the toner interface; and a toner supply roller 73 disposed inside and near the toner supply port Q and used to supply toner to the inside of the developing tank 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, a toner replenishing method thereof, and an image forming apparatus including the same.

An image forming apparatus using an electrostatic electrophotographic method generally includes apparatuses for performing various processes such as charging, exposure, development, transfer, peeling, cleaning, static elimination, and fixing, and an image is formed on a transfer material (recording medium). An image based on data is formed.
In the image forming process in the image forming apparatus, for example, the surface of the rotationally driven photoconductor is uniformly charged by a charging device, and the charged photoconductor surface is irradiated with laser light to form an electrostatic latent image. Subsequently, the electrostatic latent image on the photoconductor is developed by the developing device, and a toner image is formed on the surface of the photoconductor. Subsequently, the toner image on the photosensitive member is transferred onto the transfer material by the transfer device, and then the toner image is fixed on the transfer material by being heated by the fixing device. Further, the transfer residual toner remaining on the surface of the photoreceptor is removed by a cleaning device and collected in a predetermined recovery unit, and the remaining charge is removed from the surface of the photoreceptor after cleaning by the static eliminator. Prepare for formation.

As a developer for developing the electrostatic latent image on the photoreceptor, a one-component developer composed of only toner or a two-component developer composed of toner and carrier is generally used.
In the case of using a one-component developer, since the one-component developer does not contain a carrier, the developing device has an advantage that it does not require a stirring mechanism for uniformly mixing the toner and the carrier and is simplified. There is a drawback that the charge amount of the toner is difficult to stabilize.
When a two-component developer is used, the developing device requires a stirring mechanism for uniformly mixing the toner and the carrier, and the structure is complicated. However, the developing device is excellent in charging stability and adaptability to a high-speed machine, and high-speed image. Widely used in forming apparatuses and color image forming apparatuses.

  In order to maintain image quality, a developing device for a two-component developer needs to maintain the toner concentration in the developing tank at an appropriate concentration, and therefore generally detects the magnetic permeability of the developer as an index of the toner concentration. When the magnetic permeability detection value (detection signal level) exceeds a reference value for toner replenishment determination (hereinafter referred to as a magnetic permeability reference value), the toner is supplied to the developing tank assuming that the toner concentration is below a predetermined value. It is comprised so that.

A general developing device includes a toner hopper that is detachably attached to the developing tank in order to supply toner into the developing tank. The toner hopper includes a toner replenishing port for replenishing toner accommodated in the developing tank, a toner replenishing roller disposed in the vicinity of the inside of the toner replenishing port, and a pumping roller for pumping the internal toner to the toner replenishing roller. When the toner replenishing roller rotates, the toner adhering to the toner replenishing roller drops into the developing tank through the toner replenishing port and is replenished.
At this time, by comparing the output value of a toner concentration sensor (for example, a magnetic permeability sensor) disposed in the developing tank with a predetermined threshold value, it is detected whether the toner concentration is within a reference concentration range, and When the output value is larger than a predetermined threshold value, the toner supply roller is rotated so that the toner is supplied into the developing tank so that the output value reaches the threshold value.
In order to control the toner density more accurately, a method for controlling the toner density based on the toner consumption calculated from the image data has also been proposed (see, for example, Patent Document 1).
JP 2004-70067 A

  However, it has been found that the above-described developing device has a problem that the toner density in the developing tank is not stabilized within the reference density range. In general, the amount of toner replenished from the toner hopper to the developing tank was thought to be proportional to the number of rotations of the toner replenishing roller. However, as a result of studies by the present inventors, if the height of the toner interface in the toner hopper fluctuates, It has been found that the amount of toner replenishment varies with respect to the number of rotations of the replenishment roller, that is, the amount of toner replenishment per rotation of the toner replenishment roller varies. This is because when the height of the toner interface in the toner hopper fluctuates, the amount of toner pumped up to the toner replenishing roller by the scooping roller varies, and the density (pressure) of the toner around the toner replenishing roller varies accordingly. It is thought that.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing device capable of always obtaining a stable toner replenishment amount in toner replenishment from the toner hopper to the developing tank, and an image forming apparatus having the same. Another object of the present invention is to provide a toner replenishing method for a developing device.

  Thus, according to the present invention, a developing tank that contains a two-component developer containing toner and a magnetic carrier, a toner hopper that contains toner and replenishes the toner into the developing tank, and contains toner inside. And a toner cartridge for replenishing toner into the toner hopper, wherein the toner hopper replenishes toner to be replenished from the toner cartridge and replenishes toner inside the developer tank. A toner replenishing port, a toner agitating roller disposed in the vicinity of the lower portion of the toner introducing port to agitate the toner inside to flatten the toner interface, and a toner agitating roller disposed in the vicinity of the toner agitating roller to Toner replenishment for replenishing toner in the developing tank, located near the inside of the toner replenishing port The toner cartridge is disposed so as to be rotatably supported by the holder and communicated with the toner supply port. The holder has a toner supply port communicating with the toner introduction port of the toner hopper. A toner bottle having a bottle opening, and a drive control unit for driving and controlling the toner bottle, the toner agitation roller, and the toner replenishing roller, and a toner interface in the toner hopper is lower than a predetermined height. A developing device is provided in which the drive controller rotates the toner bottle in accordance with a signal from the toner interface detection sensor when the toner is detected, and supplies the toner into the toner hopper from the bottle opening.

  According to another aspect of the present invention, there is provided a toner replenishing method of the developing device, the step of detecting the toner concentration in the developing tank by the toner concentration detection sensor, The control unit determines whether the density detection signal is within a reference density range, and if the density detection signal from the toner density detection sensor is outside the reference density range, the control unit A toner replenishing method is provided that includes rotating the toner replenishing roller to replenish toner from the toner hopper into the developing tank by driving a three-drive system.

  According to still another aspect of the present invention, a photosensitive drum on which an electrostatic latent image is formed, a charging device that charges the surface of the photosensitive drum, and a charged surface of the photosensitive drum An exposure device for forming an electrostatic latent image, the developing device for forming a toner image by attaching toner to the electrostatic latent image on the surface of the photosensitive drum, and a toner image on the surface of the photosensitive drum. There is provided an image forming apparatus including a transfer device that transfers the toner image, a cleaning device that cleans the surface of the photosensitive drum, and a fixing device that fixes a toner image on a recording medium.

  According to the developing device and the toner replenishing method of the present invention, the toner interface in the toner hopper can be maintained as a generally flat surface by stirring the toner, and the amount of toner in the toner hopper can be detected with high accuracy. Therefore, when the toner amount in the toner hopper decreases and the toner interface becomes lower than the predetermined height, the toner is replenished from the toner cartridge into the toner hopper, and the height of the toner interface can be kept constant. As a result, the toner replenishment amount replenished to the developing tank by the rotation of the toner replenishing roller can be stabilized, and variation in the toner density in the developing tank can be suppressed and stabilized within the reference density range.

  According to the image forming apparatus of the present invention, since it is possible to stabilize the toner density variation in the developing tank within the reference density range, there is no density unevenness, and an image having a uniform image density is transferred. Can be formed into a material.

(Description of developing device and toner supply method using the same)
The developing device of the present invention includes a developing tank that contains a two-component developer containing toner and a magnetic carrier, a toner hopper that contains toner inside and replenishes the toner into the developing tank, and contains toner inside. And a toner cartridge that replenishes toner into the toner hopper, wherein the toner hopper replenishes toner to be replenished from the toner cartridge, and replenishes toner inside the developer tank. A toner replenishing port, a toner agitation roller disposed near the toner introduction port to agitate the toner inside to flatten the toner interface, and a toner agitation roller disposed near the toner agitation roller to detect the toner interface A toner interface detecting sensor, and a toner replenishing roller disposed near the inside of the toner replenishing port to replenish toner in the developing tank The toner cartridge includes a holder having a toner supply port that communicates with a toner introduction port of the toner hopper, and a bottle opening that is rotatably held by the holder and arranged to communicate with the toner supply port A toner bottle and a toner bottle driving mechanism for rotating the toner bottle, and further comprising a drive control unit that drives and controls the toner bottle, the toner agitation roller, and the toner replenishing roller. The drive control unit rotates the toner bottle according to a signal from the toner interface detection sensor when the toner interface becomes lower than a predetermined height, and supplies the toner into the toner hopper from the bottle opening. Features.
Here, the “toner interface” means the surface layer of the toner exposed in the space in the toner hopper.

The developing device of the present invention is not limited to the above-described configuration, and the following configurations can be appropriately combined.
In this developing apparatus, the height of the rotation shaft of the toner stirring roller is the same as or lower than the height of the rotation shaft of the toner replenishing roller, and the predetermined height of the toner interface is equal to that of the rotation shaft of the toner stirring roller. You may comprise so that it may be the same as height.
In this way, the toner interface around the toner supply roller can be adjusted to be close to the height of the rotation shaft of the toner supply roller, so that the pressure applied to the toner around the toner supply roller can be relieved, and toner aggregation can occur. Can be prevented. That is, if the toner interface around the toner replenishing roller is at a position higher than the rotation axis of the toner replenishing roller, the pressure applied to the toner around the toner replenishing roller becomes high and the toner tends to aggregate, thus preventing this. Can do.

In the developing device, the drive control unit includes a first drive system that rotationally drives the toner bottle, a second drive system that rotationally drives the toner stirring roller, and a third drive system that rotationally drives the toner supply roller. And a control unit that controls the first drive system, the second drive system, and the third drive system, and the control unit is configured to control the toner when the toner interface in the toner hopper becomes lower than a predetermined height. The first drive system and the second drive system may be driven by a signal from the interface detection sensor.
In this way, the toner bottle and the toner agitation roller can be synchronously controlled when toner needs to be replenished into the toner hopper, and the toner interface can be flattened simultaneously with the replenishment of toner into the toner hopper. The toner interface can be kept horizontal. As a result, the detection accuracy of the toner interface detection sensor is increased. Further, when unnecessary, the toner bottle and the toner agitation roller are stopped from rotating so that the stress on the toner can be suppressed. Further, when toner replenishment in the developing tank is necessary, the toner conveying roller can be driven and controlled independently of the toner bottle and the toner stirring roller.

In the developing device, the control unit may drive the second drive system in synchronization with the drive of the third drive system.
In this way, the toner agitation roller can be rotated to keep the toner interface horizontal when toner needs to be replenished into the developing tank, and the toner can be developed with a stable replenishment amount by the rotating toner replenishment roller. The tank can be replenished.

In the developing device, the toner hopper further includes a toner scooping roller between the toner stirring roller and the toner replenishing roller, and a height of the rotating shaft of the toner scooping roller is equal to a height of the rotating shaft of the toner replenishing roller. It may be configured to be the same or lower.
In this way, it is possible to further reduce the pressure applied to the toner around the toner supply roller and more effectively prevent toner aggregation.

In the developing device, the toner hopper may further include a transport roller between the toner supply roller and the toner scooping roller.
In this way, it is possible to reliably and smoothly supply the toner from the toner drawing roller to the toner supply roller.

The developing device may further include a second toner interface detection sensor that detects a toner interface at a position below the toner interface detection sensor.
When the toner in the toner cartridge runs out and toner is no longer supplied to the toner hopper, the amount of toner in the toner hopper is remarkably reduced. The toner density in the layer cannot be maintained at the reference density. By providing the second toner interface detection sensor, it is possible to detect that the amount of toner in the toner hopper is extremely low, and to stop driving the developing unit before the toner density in the developing layer cannot be maintained at the reference density. it can.
As a result, it is possible to prevent the toner image having a reduced image density from being formed on the recording medium. In addition, the detection signal from the second toner interface detection sensor can prompt the user to replace the toner cartridge, stop the driving of the toner replenishing roller, the toner agitation roller, etc. to save power, and remove the toner in the toner hopper. It is possible to prevent excessive stirring and stress.

The developing device further includes a toner concentration detection sensor that detects the concentration of toner in the developing tank and outputs a concentration detection signal to the control unit, and the control unit receives a density detection signal from the toner concentration detection sensor. The third drive system may be driven when the value indicates that the density is lower than the reference density.
In this way, when the toner in the developing tank is consumed and the toner density becomes lower than the reference density, the toner supply roller immediately rotates and the toner in the toner hopper is supplied into the developing tank. The toner density can be maintained at the reference density with high accuracy. Even if the toner is supplied to the developing tank, it takes a certain amount of time (15 seconds or less) until the toner density is averaged, and the image density during this period is somewhat lower (thinner) than the standard. It is preferable that toner is replenished early so that the image density does not become lower than the reference by setting the value slightly higher.

In such toner replenishment, the control unit determines whether the toner density detection sensor detects the toner density in the developing tank and whether the density detection signal from the toner density detection sensor is within the reference density range. And when the density detection signal from the toner density detection sensor indicates that the density is lower than the reference density, the control unit drives the third drive system to rotate the toner replenishment roller and from the toner hopper to the developing tank. And a step of replenishing toner into the toner.
Further, the controller drives the first drive system and the second drive system by a signal from the toner interface detection sensor when the toner interface in the toner hopper becomes lower than a predetermined height, and rotates the toner bottle to rotate the toner hopper. A step of replenishing the toner and rotating the toner stirring roller to stir and flatten the toner in the toner hopper may be further included. In this way, the toner interface in the toner hopper can be kept flat, and the toner interface can be detected with high accuracy by the toner interface detection sensor.

The two-component developer tends to increase chargeability under a low humidity environment (humidity 30% or less), and tends to decrease chargeability under a high humidity environment (humidity 70% or more). Therefore, the toner density detection by the toner density detection sensor tends to show a higher density than the actual density in a low humidity environment, so the toner replenishment timing tends to be delayed and the image density tends to become lower. Since toner density detection by the toner density detection sensor tends to indicate a lower density than actual, the toner replenishment timing is advanced and the image density tends to increase. In this specification, the image density means the density of a toner image formed on a recording medium by an image forming apparatus provided with the developing device.
Therefore, the developing device further includes a humidity sensor that detects humidity in the developing tank and outputs a humidity detection signal to the control unit, the control unit based on the humidity detection signal from the humidity sensor. The third drive system may be driven when the reference density is corrected and the density detection signal from the toner density detection sensor indicates that it is lower than the corrected reference density.

In this way, it is possible to correct in the direction of increasing the reference density of the toner density detection sensor in a low humidity environment, and to correct in the direction of decreasing the reference density of the toner density detection sensor in a high humidity environment. Thus, it is possible to suppress a deviation in toner replenishment timing and maintain the toner density in the developing tank at a desired density with higher accuracy.
In such toner replenishment, the humidity in the developing tank is detected by the humidity detection sensor, and the control unit corrects the reference density based on the humidity detection signal from the humidity sensor, and the density from the toner density detection sensor. When the detection signal indicates that it is lower than the corrected reference density, the control unit can execute the toner supply method further including a step of driving the third drive system.

The developing devices having various configurations described above can be used as developing devices for electrophotographic image forming apparatuses (for example, electrophotographic copying machines, printers, facsimiles).
That is, this image forming apparatus forms a latent image on the surface of the photosensitive drum on which the electrostatic latent image is formed, a charging device that charges the surface of the photosensitive drum, and the charged surface of the photosensitive drum. An exposure device, the above-described developing device that forms a toner image by attaching toner to the electrostatic latent image on the surface of the photosensitive drum, a transfer device that transfers the toner image on the surface of the photosensitive drum to a recording medium, and a photosensitive member At least a cleaning device for cleaning the surface of the body drum and a fixing device for fixing the toner image on the recording medium are provided.

In addition to the above-described configuration, the image forming apparatus includes a paper feed unit including a paper feed cassette that supplies the recording medium (recording sheet) to the photosensitive member, and a paper discharge tray that discharges the recording medium on which the toner image is formed. In addition, a document reading device for reading a document, a document transport device for automatically transporting a document to a document scanning device, a manual feed tray for supplying an arbitrary recording medium to a photosensitive member, A large-capacity paper feed unit that accommodates a large-capacity recording medium, a post-processing device that performs post-processing (for example, Z-folding processing, stapling processing, etc.) on the recording medium on which an image is formed may be provided.
Hereinafter, a developing device and an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
FIG. 1 is a schematic sectional view showing an image forming apparatus A including a developing device X according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view showing the developing device X.
First, the configuration of the image forming apparatus A will be described with reference to FIG.
The image forming apparatus A receives an image read by an image reading apparatus (not shown) and data from a device externally connected to the image forming apparatus A (for example, a host device such as a personal computer). This is a printer that records and outputs as an image.
The image forming apparatus A includes a photosensitive drum 3, a charging unit 5, an optical scanning unit 11, a developing device X, a transfer unit 6, and a cleaning unit which are sequentially arranged around the photosensitive drum 3 and perform each function of the image forming process. 4 and the charge removal lamp 12 and the like, each of which forms an image forming unit.

The charging unit 5 uniformly charges the surface of the photosensitive drum 3.
The optical scanning unit 11 scans an optical image on the uniformly charged photosensitive drum 3 to write an electrostatic latent image.
The developing unit 1 described later provided in the developing device X supplies toner to the electrostatic latent image written by the optical scanning unit 11 to visualize (develop) it.
The transfer unit 6 transfers the toner image visualized on the photosensitive drum 3 onto a recording sheet.
The cleaning unit 4 removes the toner remaining on the photosensitive drum 3 so that a new image can be recorded on the photosensitive drum 3.
The static elimination lamp 12 removes electric charges on the surface of the photosensitive drum 3.

  In addition, a supply tray 10 provided in the main body of the image forming apparatus A is disposed below the image forming apparatus A. The supply tray 10 is a recording material storage tray that stores recording sheets. The recording sheets stored in the supply tray 10 are separated one by one by the pickup roller 16 and the like, conveyed to the registration roller 14, and timed with the image formed on the photosensitive drum 3 by the registration roller 14. The toner is sequentially supplied between the transfer unit 6 and the photosensitive drum 3. Then, the image recorded and reproduced on the photosensitive drum 3 is transferred onto the recording sheet. The supply of the recording sheet to the supply tray 10 is performed by pulling the supply tray 10 to the front side (front side of the drawing) of the image forming apparatus A.

On the lower surface of the image forming apparatus A, a desk device having a multi-stage recording sheet supply tray (not shown) prepared as a peripheral device and a sheet receiving port 13 are provided. The sheet receiving port 13 is for receiving recording sheets sent from a large-capacity recording material supply device or the like that can accommodate a large amount of recording sheets and sequentially supplying the recording sheets toward the image forming unit.
A fixing device 8 is disposed in the upper part of the image forming apparatus A. The fixing device 8 includes a fixing roller 81 and a pressure roller 82. The fixing device 8 sequentially receives recording sheets on which an image has been transferred, and is transferred onto the recording sheet by heat and pressure by the fixing roller 81 and the pressure roller 82. The developed image is fixed. As a result, an image is recorded on the recording sheet.

Further, a conveying roller 17, a switching gate 9, a reversing roller 18 and a stacking tray 15 are arranged above the fixing device 8, and the recording sheet on which an image is recorded is further conveyed upward by the conveying roller 17 and switched. The paper passes through the gate 9 and is discharged to the stacking tray 15 by the reverse roller 18.
In addition, another discharge port is provided on the side wall of the casing of the image forming apparatus A on the opposite side of the reversing roller 18 across the switching gate 9. The paper discharge port is for feeding a recording sheet on which an image is formed to a recording material re-feeding conveyance device or a post-processing device (not shown) that is selectively mounted for double-sided image formation or post-processing.

When double-sided image formation or post-processing is specified at the time of image formation, the recording sheet is once discharged toward the stacking tray 15 by the reversing roller 18 and stopped after the sheet trailing edge is held. The reverse roller 18 is reversely rotated. Then, the sheet is reversely conveyed in the reverse direction, that is, in the direction in which the recording material refeeding conveyance apparatus and the post-processing apparatus that are selectively mounted for double-sided image formation and post-processing are mounted. At this time, the switching gate 9 is switched from the solid line state in FIG. 1 to the broken line state.
When performing double-sided image formation, the reversely conveyed sheet passes through a recording material re-feed conveyance device (not shown) and is supplied again to the image forming apparatus A from a paper feed port provided in the lower portion of the side wall of the casing. When post-processing is performed, the recording material re-conveying device is transported to a post-processing device via a relay transport device (not shown) by another switching gate, and post-processing is performed. Note that FIG. 1 illustrates a case where the recording material refeeding and conveying apparatus and the post-processing apparatus are not mounted.

In the upper and lower space portions of the optical scanning unit 11, a control unit 110 for accommodating a circuit board for controlling an image forming process, an interface board for receiving image data from an external device, and the like, the various interface boards, and the image A power supply device 111 and the like for supplying electric power to each part to be formed are arranged.
Hereinafter, various embodiments of the developing device X applied to the image forming apparatus A will be described.

<Developer Embodiment 1>
The developing device X of Embodiment 1 shown in FIG. 2 accommodates a two-component developer (hereinafter sometimes abbreviated as a developer) composed of toner and a carrier, and supplies the toner to the photosensitive drum 3. .
The developing device X includes a developing unit 1, a toner replenishing unit 2, and a drive control unit (not shown).

The developing unit 1 includes a developing tank 21 that contains a developer provided close to the photosensitive drum 3, and a developing roller 24 that is rotatably provided in the developing tank 21 so as to face the photosensitive drum 3. Further, a stirring rotary blade 22 and a toner stirring roller 23 for stirring the developer in the developing tank 21 are provided.
The developing tank 21 has a first opening at a position close to the photosensitive drum 3, a second opening on the opposite side of the first opening, and a developing roller 24 near the first opening. Is disposed, and the stirring rotary blade 22 is disposed in the vicinity of the second opening.

The developing unit 1 configured as described above conveys the developer from the developing tank 21 to the photosensitive drum 3 side as the developing roller 24 rotates, thereby developing the electrostatic latent image on the photosensitive drum 3. To do.
The developer in the developing tank 21 is stirred and charged by the rotation of the developing roller 24, the stirring rotary blade 22 and the toner stirring roller 23. Further, a developing bias voltage is applied to the developing roller 24 in order to provide a potential difference from the photosensitive drum 3.

Further, the developing unit 1 further includes a toner concentration detection sensor 25 that detects the toner concentration of the two-component developer including the toner and carrier in the developing tank 21, and detects the toner concentration in the developer based on the detected value. It is configured.
A magnetic permeability sensor is used as the toner concentration detection sensor 25, and is disposed in the vicinity of the toner stirring roller 23 on the bottom wall of the developing tank 21.

Further, the toner replenishing unit 2 of the developing device X includes a toner hopper 7 that accommodates toner to be replenished to the developing tank 21 and a toner cartridge 30 that accommodates toner to be supplied to the toner hopper 7.
The toner hopper 7 has a casing 74 for containing toner, a toner introduction port R formed in the casing 74 for introducing the toner replenished from the toner cartridge 30, and a replenishment toner to the developing tank 21. A toner replenishing port Q formed in the casing 74, a toner agitating roller 75 which is disposed in the vicinity of the lower portion of the toner introducing port R and agitates the toner inside to flatten the toner interface, and in the vicinity of the toner agitating roller 75. A toner interface detection sensor 76 that is disposed to detect the toner interface, a toner supply roller 73 that is disposed near the inside of the toner supply port Q and supplies toner to the developing tank 21, and conveys the toner to the toner supply roller 73. A transport roller 72 and a toner pump roller 71 that pumps toner to the transport roller 72 are provided.

In the casing 74, the toner supply port Q is disposed on the developing wall 1 side of the bottom wall, and the toner introduction port R is disposed on the opposite side of the upper wall from the toner supply port Q. A toner replenishing roller 73 is disposed in the vicinity, and a toner stirring roller 75 is disposed in the vicinity of the toner introduction port R. Further, a conveyance roller 72 is disposed near the toner supply roller 73 between the toner supply roller 73 and the toner stirring roller 75, and a toner scooping roller 71 is disposed near the toner stirring roller 75.
In addition, on the bottom wall of the casing 74, the portions immediately below the toner stirring roller 75, the toner scooping roller 71, and the conveying roller 72 are formed in a circular arc concave shape along the rotation trajectory of each roller, and the toner replenishing port Q is provided. The formed part is formed in a square groove shape at a position lower than the part directly below the conveying roller 72.

As the toner replenishing roller 73, a sponge roller having a rotating shaft passing through the axis of a cylindrical porous member is used. The diameter of the toner supply roller 73 is about 10 to 50 mm, and the diameter of the rotating shaft is about 4 to 10 mm.
As the transport roller 72, a spiral roller having a spiral blade provided on a rotation shaft is used. The spiral blade is configured such that the spiral winding direction is reversed from one end to the middle and from the other end to the middle of the rotation shaft, and the toner on both ends is conveyed to the center by rotating the spiral roller. The diameter of the transport roller 72 is about 10 to 50 mm, and the diameter of the rotating shaft is about 4 to 10 mm.

  The toner pumping roller 71 is configured to have pumping blades protruding in a direction orthogonal to the axial direction from the rotating shaft. If the toner pumping roller 71 has a function of feeding the toner in the casing 74 to the conveying roller 72 while stirring, the other Is not particularly limited in configuration. In order to efficiently convey and agitate the toner, it is preferable that a plurality of pumping blades (two in FIG. 2) are provided, and the pumping blades are made of resin (for example, PET resin) and have flexibility. Also good. Further, an opening through which the toner can flow is formed between the front end and the base end of the pumping blade so that an appropriate amount of toner can be transported to the transport roller 72, or a notch is formed in a part of the pumping blade. Good. The diameter of the toner drawing roller 71 is about 10 to 100 mm, and the diameter of the rotating shaft is about 4 to 10 mm.

The toner agitation roller 75 is configured to have an agitation blade protruding in a direction orthogonal to the axial direction from the rotation axis, and if the toner agitation roller 75 has a function of agitating the toner in the casing 74 and flattening the toner interface, The configuration is not particularly limited. In order to efficiently flatten the toner interface, a plurality of stirring blades (six in FIG. 2) may be provided, and the stirring blades may be made of resin (for example, PET resin) and have flexibility. In order to further flatten the toner interface more efficiently, an opening through which the toner can flow may be formed between the tip and the base end of the stirring blade, or a notch may be formed in a part of the stirring blade. The diameter of the toner stirring roller 75 is about 10 to 100 mm, and the diameter of the rotating shaft is about 4 to 10 mm.
A flexible metal piece 75a (for example, an aluminum piece), which will be described later, is fixed to the tip of some stirring blades.

The toner replenishing roller 73, the conveying roller 72, the toner scooping roller 71, and the toner stirring roller 75 configured as described above maintain the toner amount in the casing 74 at a constant amount, and the toner in the casing 74 at a constant amount. In order to stably supply to the developing unit 1, the following height positional relationship is set.
The height of the rotation shaft of the toner stirring roller 75 is the same as or lower than the height of the rotation shaft of the toner supply roller 73. Further, the height of the rotation shaft of the toner pumping roller 71 is the same as or lower than the height of the rotation shaft of the toner supply roller 73. Further, the height of the rotation shaft of the transport roller 72 is higher than the height of the rotation shaft of the toner transport roller 73.

A magnetic permeability sensor is used as the toner interface detection sensor 76 (hereinafter also referred to as the interface sensor 76), and the wall surface of the casing 74 on the toner stirring roller 75 side is closer to the rotating shaft of the toner stirring roller 75. It is attached at a high position and a position through which the metal piece 75a passes.
The toner interface detection sensor 76 detects the height of the toner interface in the casing 74. Specifically, the toner interface detection sensor 76 detects the distance when the tip of the metal piece 75a rotating together with the toner stirring roller 75 is closest. Thus, the height (toner amount) of the toner interface is detected.

That is, the degree of bending of the rotating metal piece 75a differs depending on the height of the toner interface in the casing 74 when passing in front of the interface sensor 76, and when the toner interface is higher than the interface sensor 76, it bends due to the resistance of the toner. Increases, the distance from the interface sensor 76 increases. When the toner interface gradually falls, the deflection decreases, so the distance also decreases. When the toner interface becomes lower than the interface sensor 76, the toner resistance applied to the metal piece 75a disappears and the bending does not occur, so the distance between the metal piece 75a and the interface sensor 76 becomes the smallest.
As described above, the rotation locus of the tip of the metal piece 75a changes depending on the height (toner amount) of the toner interface, and a permeability detection signal having a value corresponding to the change of the rotation locus of the metal piece 75a is a permeability sensor. The interface sensor 76 outputs. When the stirring blade of the toner stirring roller 75 is made of a resin having flexibility, the change in the rotation locus of the metal piece 75a becomes larger because the stirring blade is also bent.

  The toner cartridge 30 includes a holder 31 having a toner supply port 31a that communicates with the toner introduction port R of the toner hopper 7, and a bottle opening that is rotatably held by the holder 31 and arranged to communicate with the toner supply port 31a. A toner container 32 having a cylindrical container having a toner container, and the toner accommodated therein is supplied to the toner hopper 7 through the bottle opening, the toner supply port 31a, and the toner introduction port R as the toner bottle 32 rotates. It is comprised so that.

  The drive control unit drives and controls the toner bottle 32, the toner agitation roller 75, the toner scooping roller 71, the transport roller 72, and the toner supply roller 73, and the toner interface in the toner hopper 7 becomes lower than a predetermined height. The toner bottle 32 is rotated by a signal from the toner interface detection sensor 76 at that time, and the toner is supplied into the toner hopper 7 from the bottle opening. Here, the predetermined height of the toner interface means the same height as the rotation shaft of the toner stirring roller 75.

More specifically, the drive control unit includes a first drive system that rotationally drives the toner bottle 32, a second drive system that rotationally drives the toner stirring roller 75, a toner supply roller 73, a transport roller 72, and a toner pumping roller 71. And a control unit that controls the first drive system, the second drive system, and the third drive system. The control unit 40 may further control the drive of the developing roller 24, the toner stirring roller 23, and the stirring rotary blade 22 of the developing unit 1.
The first drive system includes a motor and a gear mechanism that transmits the rotational force of the motor to the toner bottle 32. Specifically, some of the gears of the motor and the gear mechanism are provided outside the developing device X, and the other gears of the gear mechanism are integrally attached to the shaft end of the toner bottle 32.
The toner cartridge 30 is detachably mounted in the image forming apparatus main body, and the gear on the toner bottle 32 side and the gear on the motor side mesh with each other when mounted.

The second drive system includes a motor and a transmission mechanism that transmits the rotational force of the motor to the toner stirring roller 75. This transmission mechanism can use a plurality of gears or a plurality of pulleys and a belt wound around them.
The third drive system includes a motor and a transmission mechanism that synchronously transmits the rotational force of the motor to the toner supply roller 73, the conveyance roller 72, and the toner scooping roller 71. This transmission mechanism can use a plurality of gears or a plurality of pulleys and a belt wound around them.

The control unit drives the first drive system and the second drive system by a signal from the toner interface detection sensor 76 when the toner interface in the toner hopper 7 becomes lower than a predetermined height.
Further, the control unit may drive the second drive system synchronously with the drive of the third drive system, that is, drive the first, second, and third drive systems synchronously, In this case, the first to third drive systems can be configured with one motor and a transmission mechanism.
Further, the control unit may drive the third drive system when the density detection signal from the toner density detection sensor 25 indicates that the density is lower than the reference density.

As described above, the operation control of the developing device X including the toner replenishing unit 2, that is, the start and stop, the rotational drive control of the toner replenishing roller 73 based on the toner concentration (magnetic permeability detection value), and the like are performed by the control unit.
FIG. 3 is a block diagram illustrating a part of the configuration of the control unit 40.
The control unit 40 includes a CPU 41, a ROM 42 and a RAM 43 that store programs executed thereby, and other peripheral devices. Input / output devices such as a toner concentration detection sensor 25, a toner interface detection sensor 76, and first to third drive systems. Are connected, and the CPU 41 executes each process described later by executing a program stored in the ROM 42.

The CPU 41 controls each input / output device according to a program written in advance in the ROM 42, and writes data input / output during this time in a predetermined memory area of the RAM 43. The toner concentration detection sensor 25 outputs a signal corresponding to the magnetic permeability of the developer stored in the developing tank 21 to the CPU 41.
The CPU 41 supplies drive data to the third drive system based on the signal output from the toner concentration detection sensor 25. This drive data is information that specifies the drive frequency that defines the rotational speed of the motor. The third drive system drives the motor based on the drive data supplied from the CPU 41. The motor is a pulse motor as an example, and supplies rotation to the toner supply roller 73. In this case, the third drive system drives the motor with a drive pulse having a duty ratio corresponding to the drive frequency specified by the drive data.

As shown in FIGS. 2 and 3, in the developing unit 1, the toner concentration detection sensor 25, which is a magnetic permeability sensor, detects the magnetic permeability of the toner in the developing tank 21 as the toner concentration.
When the toner concentration in the developing tank 21 is lower than the reference concentration, the magnetic permeability detection value detected by the toner concentration detection sensor 25 exceeds the supply reference value Vref for toner supply determination. The controller 40 determines that the magnetic permeability detection value has exceeded the supply reference value Vref, and then the control unit 40 drives the third drive system so that the toner supply roller 73 rotates for a predetermined number of rotations or for a predetermined time. Then, toner is supplied into the developing tank 21.
The number of rotations or the rotation time of the toner replenishing roller 73 can be determined based on a comparison result between the magnetic permeability detection value by the toner concentration detection sensor 25 and the replenishment reference value (toner concentration reference value). At this time, for example, the number of rotations or the rotation time can be determined according to the difference or ratio between the magnetic permeability detection value and the replenishment reference value, or the rate of increase of the magnetic permeability detection value within a unit time.

The toner cartridge 30 is driven and controlled by a drive control unit based on information (toner interface height) detected by the toner interface detection sensor 76. When the toner interface height is lower than the toner interface detection sensor 76, the toner bottle 32 rotates for a predetermined number of rotations or for a predetermined time, and supplies toner into the toner hopper 7.
At this time, the number of rotations or the rotation time of the toner bottle 32 can be determined based on a comparison result between a value detected by the toner interface detection sensor 76 and a preset permeability reference value (toner interface height reference value). it can.

The toner agitation roller 75 is rotated while at least one of the toner bottle 32 and the toner supply roller 73 is rotating, thereby flattening (leveling) the toner interface of the toner in the casing 74. As a result, the detection accuracy of the toner interface detection sensor 76 is enhanced, so that the amount of toner in the toner hopper 7 can be detected with high accuracy, and the height of the toner interface can be maintained constant.
As a result, the replenishment amount of toner replenished to the developing tank 21 by the rotation of the toner replenishing roller 73 is stabilized, and variations in toner density and image density in the developing tank 21 can be suppressed. Further, the height of the rotation shafts of the toner drawing roller 71 and the toner agitation roller 75 is set at the same level as or lower than the rotation shaft of the toner supply roller 73, so that the toner around the toner supply roller 73 is provided. Stress (pressure caused by the weight of the toner) can be relieved, and toner aggregation can be prevented. The toner agitation roller 75 is stopped while the toner bottle 32 and the toner replenishing roller 73 are stopped, thereby minimizing the stress on the toner.

Next, a toner replenishing method of the developing device X of Embodiment 1 will be described.
In the toner supply method of the developing device X, when the toner is supplied from the toner hopper 7 to the developing unit 1, the toner concentration in the developing tank 21 is detected as shown in the flowcharts of FIGS. A step of detecting by the sensor 25; a step of determining by the control unit 40 whether or not the density detection signal from the toner density detection sensor 25 is within a reference density range; and a density detection from the toner density detection sensor 25. The controller 40 drives the third drive system to rotate the toner supply roller 73 to supply toner from the toner hopper 7 into the developing tank 21 when the signal indicates that it is lower than the reference density. .

More specifically, in a state where the developing device 1 is driven (step 1), the toner concentration detection sensor 25 detects the toner concentration of the toner in the developing tank 21 (step 2), and outputs a detection signal including a permeability detection value. Output to the control unit 40. The control unit 40 compares the magnetic permeability detection value with the replenishment reference value (reference concentration) (step 3). If the magnetic permeability detection value is larger than the replenishment reference value, it is determined that the toner concentration is lower than the reference concentration, and the toner The third drive system is driven and controlled to rotate the supply roller 73 (step 4). As a result, a predetermined amount of toner is supplied from the toner hopper 7 to the developing tank 21. The toner supply roller 73 stops after rotating for a predetermined number of rotations or for a predetermined time as described above.
On the other hand, when the magnetic permeability detection value is equal to or less than the replenishment reference value, the control unit 40 determines that the toner concentration satisfies the reference concentration, maintains the stopped state of the third drive system, and returns to Step 2.
After step 4, the state of the developing unit 1 is determined (step 5), and while the developing device 1 is in the driving state, the toner concentration of the toner in the developing tank 21 is monitored and the toner concentration is maintained at the reference concentration. The

  In the toner replenishing method of the developing device X, when toner is replenished from the toner hopper 7 to the developing unit 1, the toner interface in the toner hopper 7 is lower than a predetermined height as shown in the flowcharts of FIGS. The controller 40 drives the first drive system and the second drive system in response to a signal from the toner interface detection sensor 76 when the toner is detected, and rotates the toner bottle 32 to replenish the toner into the toner hopper 7. The method further includes the step of rotating the stirring roller 75 to stir the toner in the toner hopper 7 and flatten it.

More specifically, the toner interface detection sensor 76 detects the height of the toner interface of the toner in the casing 74 (step 1), and outputs a detection signal including a magnetic permeability detection value to the control unit 40. The control unit 40 compares the magnetic permeability detection value with the replenishment reference value (toner interface height reference value) (step 2). If the magnetic permeability detection value is greater than the replenishment reference value, the height of the toner interface is the reference height. The first drive system is driven and controlled to rotate the toner bottle 32 (step 3). As a result, a predetermined amount of toner is supplied from the toner bottle 32 to the toner hopper 7. The toner bottle 32 stops after rotating a predetermined number of rotations or a predetermined time as described above.
On the other hand, if the magnetic permeability detection value is less than or equal to the replenishment reference value, the controller 40 determines that the toner interface height is greater than or equal to the reference height, and maintains the stopped state of the first drive system (step 7).

During and after Step 3, the state of the toner bottle 32 is determined (Step 4), and if the toner bottle 32 is rotating, the control unit 40 causes the second drive system to rotate the toner stirring roller 75. Is controlled (step 6). As a result, the toner interface in the toner hopper 7 supplied with toner from the toner cartridge 30 is maintained flat (substantially horizontal).
On the other hand, if it is determined in step 4 that the toner bottle 32 is stopped, the state of the toner replenishing roller 73 is determined (step 5). The second drive system is driven and controlled to rotate 75 (step 6), and if the toner supply roller 73 is stopped, the control unit 40 controls the second drive system to stop the toner agitation roller 75 (step 7). ).
As described above, while the toner interface is lower than the predetermined height and the toner stirring roller 75 is rotating, the toner is replenished from the toner bottle 32 into the toner hopper 7, and the height of the toner interface becomes the reference height. Maintained. That is, the amount of toner in the toner hopper 7 is maintained at a substantially constant amount.
As a result, the amount of toner replenished to the developing tank 21 by the rotation of the toner replenishing roller 73 can be stabilized, and variations in toner density and image density can be suppressed.

<Second Embodiment of Developing Apparatus>
The developing device (not shown) of the second embodiment is the same as that of the first embodiment except that the toner hopper further includes a second toner interface detection sensor that detects a toner interface at a position below the toner interface detection sensor. It is the composition. A magnetic permeability sensor is also used as the second toner interface detection sensor.

  The difference between the second embodiment and the first embodiment will be mainly described in detail with reference to FIG. 2. In this developing device, the toner interface in the toner hopper 7 is lowered below a predetermined height by the toner interface detection sensor 76 in the upper position. Then, the toner bottle 32 rotates and the toner hopper 7 is replenished with toner. However, when the amount of toner in the toner bottle 32 decreases and the toner replenishment amount to the toner hopper 7 decreases remarkably, The toner interface falls below the rotation axis of the toner interface detection sensor 76 and the toner stirring roller 75. During this time, the height of the toner interface is also detected by the second toner interface detection sensor, and the detection signal (magnetic permeability detection value) is output to the control unit 40.

 The controller 40 compares the magnetic permeability detection value from the second toner interface detection sensor with a preset second reference value (second toner interface height reference value). When the toner interface further falls and reaches a predetermined height, the control unit 40 determines that the magnetic permeability detection value from the second toner interface detection sensor has become larger than the second reference value. At this time, the amount of toner in the toner hopper 7 is remarkably reduced, and it is becoming difficult to stably replenish the toner from the toner replenishing roller 73 to the developing unit 1 with a constant amount. At this point, the control unit 40 controls the developing unit 1 being driven to stop. That is, the control unit 40 stops the developing roller 24, the toner stirring roller 23, and the stirring rotary blade 22 that are being driven. In addition, the control unit 40 stops driving each roller in the toner hopper 7 and the toner bottle 32, and further stops conveying the recording medium to the developing device X so as to stop the new image formation by the image forming apparatus A. Control may be performed.

As described above, the control unit 40 compares the magnetic permeability detection value from the second toner interface detection sensor with the second reference value, and the control unit 40 controls the developing unit 1 according to the result. 5 may be included between steps 2 and 3, between steps 3 and 4, between steps 4 and 5, between steps 4 and 6, between steps 5 and 6, or between steps 6 and 2.
When the amount of toner replenished by the toner cartridge 30 decreases, the amount of toner in the toner hopper 7 decreases, and it becomes difficult to stably replenish the toner in the developing tank 21 with a constant amount, the toner in the developing tank 21 However, according to the second embodiment, the second toner interface detection sensor and the control unit 40 avoid the image formation in which the image quality is deteriorated. be able to.
Since the second toner interface detection sensor is not provided in the developing device X of the first embodiment, for example, when the toner concentration in the developing tank 21 falls below the reference concentration for a predetermined time or more, the control unit 40 performs development. The unit 1, the toner hopper 7, the toner bottle 32, the recording medium conveyance drive system, and the like may be stopped.

<Embodiment 3 of the developing device>
The developing device (not shown) of Embodiment 3 further includes a humidity sensor that detects humidity in the developing tank and outputs a humidity detection signal to the control unit, and the control unit uses the humidity detection signal from the humidity sensor. The reference density is corrected based on this, and the third drive system is driven when the density detection signal from the toner density detection sensor indicates that the density is lower than the corrected reference density. (See FIG. 2).
In this case, a humidity correction value B corresponding to the output of the humidity sensor is set and input to the control unit in advance. The humidity correction value B for the humidity is, for example, B = −15 when the humidity is 0 to 10%, B = −10 when the humidity is 10 to 20%, B = −5 when the humidity is 20 to 30%, and 30 to 60%. For example, B = 0 when the humidity is 60% to 70%, B = 5 when the humidity is 70% to 80%, B = 10 when the humidity is 70% to 80%, and B = 15 when the humidity is 80% to 100%. The numerical value of the humidity correction value B means 0.02 V / number of values.

The operation of the developing device according to the third embodiment will be described with reference to the flowcharts of FIGS. 2 and 6. First, the humidity in the developing tank 21 is detected by the humidity sensor (step 1), and the humidity detection signal is output from the humidity sensor. It is output to the control unit 40. The control unit 40 determines the humidity correction value B according to the output (humidity detection signal) of the humidity sensor, and adds the humidity correction value B to the toner reference density A to determine the correction reference density C (step 2). .
Then, it is determined whether the developing unit 1 is in a driving state (step 3). When the developing unit 1 is in a driving state, as described in the first embodiment, a density detection signal (magnetic permeability) from the toner density detection sensor 25 of the developing tank 21 is determined. Since the detection value is input to the control unit 40, the control unit 40 compares the toner density in the developing tank 21 with the correction reference density C (step 4). The comparison by the control unit 40 in step 3 is not performed when the developing unit 1 is in a stopped state.

If the toner density is lower than the corrected reference density C in step 4, the control unit 40 rotates the toner supply roller 73 (step 5), thereby supplying an appropriate amount of toner into the developing tank 21. On the other hand, if the toner density is not less than the correction reference density C in step 5, the process returns to step 3.
According to such a developing device and a toner replenishing method, correction is performed in the direction of increasing the reference density of the toner density detection sensor in a low humidity environment, and correction is performed in the direction of decreasing the reference density of the toner density detection sensor in a high humidity environment. Therefore, it is possible to correct a deviation in timing of toner replenishment due to a change in humidity, and to maintain the toner concentration in the developing tank at a desired concentration with higher accuracy.

<Other embodiments>
1. In the first and second embodiments, a method in which the toner concentration detection sensor 25 detects the toner concentration in the developing tank 21 is employed. In the third embodiment, the toner concentration detection sensor 25 and the humidity sensor are used in combination, depending on the humidity environment. The method of detecting the toner density after correcting the toner reference density is used, but a method of calculating the toner amount consumed based on the image information to obtain the toner density may be adopted.

2. In the first to third embodiments, the toner hopper 7 has the conveyance roller 72 and the toner scooping roller 71. However, either one or both of the conveyance roller 72 and the toner scooping roller 71 can be omitted.
When the conveyance roller 72 is omitted, the bottom wall of the casing 74 between the toner pumping roller 71 and the toner supply roller 73 is formed in a slope shape, and the toner pumped up by the toner pumping roller 71 moves to the toner supply roller 73 side. It is preferable to be configured to flow.
When the toner pumping roller 71 is omitted, the toner stirring roller 75 is disposed close to the conveying roller 72.
When the conveyance roller 72 and the toner scooping roller 71 are omitted, the toner stirring roller 75 is disposed close to the toner supply roller 73. Also in this case, the bottom wall of the casing 74 between the toner stirring roller 75 and the toner supply roller 73 is formed in a slope shape so that the toner pumped up by the toner stirring roller 75 flows toward the toner supply roller 73 side. It is preferable to configure.
In these cases, the toner cartridge 30 is positioned above the toner stirring roller 75.

1 is a schematic cross-sectional view illustrating an image forming apparatus including a developing device according to Embodiment 1 of the present invention. 1 is a schematic cross-sectional view illustrating a developing device according to a first embodiment. FIG. 2 is a block diagram illustrating a part of a configuration of a control unit in the developing device of Embodiment 1. 6 is a first flowchart illustrating a toner replenishing method by the developing device according to the first exemplary embodiment. 6 is a second flowchart illustrating a toner replenishing method by the developing device according to the first exemplary embodiment. 10 is a flowchart illustrating a toner replenishing method by the developing device according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing part 2 Toner replenishing part 3 Photoconductor drum 7 Toner hopper 21 Developing tank 22 Agitating rotary blade 23 Toner agitating roller 24 Developing roller 25 Toner density detection sensor 30 Toner cartridge 31 Holder 31a Toner supply port 32 Toner bottle 40 Control part 71 Toner pump Roller 72 Conveying roller 73 Toner supply roller 74 Casing 75 Toner stirring roller 75a Metal piece 76 Toner interface detection sensor A Image forming apparatus Q Toner supply port R Toner introduction port

Claims (13)

A developing tank containing a two-component developer containing toner and a magnetic carrier; a toner hopper containing toner inside and replenishing the toner into the developing tank; and containing toner inside and supplying the toner into the toner hopper A toner cartridge to be replenished,
The toner hopper includes a toner introduction port for introducing toner replenished from the toner cartridge, a toner replenishment port for replenishing toner inside the developer tank, and a position near the lower side of the toner introduction port. A toner agitation roller arranged to agitate the toner inside to flatten the toner interface, a toner interface detection sensor arranged in the vicinity of the toner agitation roller to detect the toner interface, and an area near the inside of the toner supply port. A toner replenishing roller disposed to replenish toner in the developing tank;
The toner cartridge includes a holder having a toner supply port communicating with a toner introduction port of the toner hopper, and a toner bottle having a bottle opening rotatably held by the holder and arranged to communicate with the toner supply port And
And a drive control unit for driving and controlling the toner bottle, the toner stirring roller, and the toner supply roller,
In response to a signal from the toner interface detection sensor when the toner interface in the toner hopper becomes lower than a predetermined height, the drive control unit rotates the toner bottle and supplies the toner into the toner hopper from the bottle opening. A developing device.   The height of the rotating shaft of the toner stirring roller is the same as or lower than the rotating shaft of the toner replenishing roller, and the predetermined height of the toner interface is the same as the height of the rotating shaft of the toner stirring roller. The developing device according to claim 2. The drive control unit includes: a first drive system that rotationally drives the toner bottle; a second drive system that rotationally drives the toner agitation roller; a third drive system that rotationally drives the toner supply roller; and the first drive system. A control unit that controls the drive system, the second drive system, and the third drive system;
The control unit drives the first drive system and the second drive system according to a signal from the toner interface detection sensor when the toner interface in the toner hopper becomes lower than a predetermined height. Development device.   The developing device according to claim 3, wherein the control unit drives the second drive system in synchronization with the drive of the third drive system. The toner hopper further includes a toner scooping roller between the toner stirring roller and the toner replenishing roller;
The developing device according to claim 1, wherein a height of a rotation shaft of the toner drawing roller is equal to or lower than a height of a rotation shaft of the toner supply roller.   The developing device according to claim 5, wherein the toner hopper further includes a conveyance roller between the toner supply roller and the toner scooping roller.   The developing device according to claim 1, wherein the toner hopper further includes a second toner interface detection sensor that detects a toner interface at a position below the toner interface detection sensor. A toner concentration detection sensor that detects the concentration of toner in the developing tank and outputs a concentration detection signal to the control unit;
The developing device according to claim 3, wherein the control unit drives the third drive system when a density detection signal from the toner density detection sensor indicates that the density is lower than a reference density. A humidity sensor that detects humidity in the developing tank and outputs a humidity detection signal to the control unit;
The control unit corrects the reference density based on a humidity detection signal from the humidity sensor and indicates that the density detection signal from the toner density detection sensor is lower than the corrected reference density. The developing device according to claim 8, wherein the system is driven. A toner replenishing method for a developing device according to claim 8,
Detecting the toner concentration in the developing tank by the toner concentration detection sensor;
Determining in the controller whether or not a density detection signal from a toner density detection sensor is within a reference density range;
When the density detection signal from the toner density detection sensor indicates that the density is lower than the reference density, the controller drives the third drive system to rotate the toner replenishing roller and move the toner hopper into the developing tank. And a toner replenishing method.   In response to a signal from the toner interface detection sensor when the toner interface in the toner hopper becomes lower than a predetermined height, the controller drives the first drive system and the second drive system to rotate the toner bottle. The toner replenishing method according to claim 10, further comprising a step of replenishing the toner into the toner hopper and rotating the toner stirring roller to stir and flatten the toner in the toner hopper. The developing device is a toner replenishing method further comprising a humidity sensor that detects humidity in the developing tank and outputs a humidity detection signal to the control unit,
Detecting the humidity in the developing tank with the humidity detection sensor;
When the control unit corrects the reference density based on a humidity detection signal from a humidity sensor and indicates that the density detection signal from the toner density detection sensor is lower than the corrected reference density, the control unit The toner replenishing method according to claim 10, further comprising a step of driving a third drive system.   A photosensitive drum on which an electrostatic latent image is formed; a charging device that charges the surface of the photosensitive drum; an exposure device that forms an electrostatic latent image on the charged surface of the photosensitive drum; 10. A developing device according to claim 1, wherein a toner image is formed by adhering toner to an electrostatic latent image on the surface of a photosensitive drum, and a toner image on the surface of the photosensitive drum is recorded on a recording medium. An image forming apparatus comprising: a transfer device that transfers the toner image; a cleaning device that cleans the surface of the photosensitive drum; and a fixing device that fixes the toner image to a recording medium.

Images