JP2012163628A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation of an amount of developer in a developing container by appropriately discharging the developer in the developing container with a simple configuration in an image forming device having a configuration for discharging developer in the developing container from a discharge port arranged at a wall surface of the developing container with overflow.SOLUTION: The image forming device includes a developing device having a developing container storing two-component developer containing toner and carrier, conveyance means for conveying the two-component developer, and control means for controlling so that, when an amount of toner consumption for one or a plurality of images exceeds a prescribed threshold, the conveyance speed of the developer conveyance means is made faster than when not exceeding the threshold.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic system. In particular, the present invention relates to an image forming apparatus including a developing device that uses a two-component developer composed of toner and a carrier.

  Conventionally, image forming apparatuses that employ electrophotographic methods and electrostatic recording methods, particularly color image forming devices that form full-color or multi-color images by electrophotographic methods, have almost all developing devices in terms of color development and color mixing. A two-component developer (hereinafter, developer) in which toner and carrier are mixed is used.

  In the two-component development method, the toner is consumed while the carrier is not consumed, so that the toner is stirred in the developing container for a long time. Therefore, due to durability, external additives and toner adhere to the carrier surface and deteriorate. As a result, there is a problem that the tribo (friction charge amount) imparting ability of the carrier is lowered, the toner tribo (friction charge amount) is lowered, and image defects such as fogging occur. Therefore, as a study of long-life development, development of a developer that extends the durable life and development of a process that does not deteriorate the developer are being carried out. However, the current developer life is when a standard image is output on A4 paper. The actual number is 30,000 to 50,000.

  In response to the above problems, there has been proposed an apparatus that suppresses the deterioration of the carrier in the developing container by discharging the developer in the developing container from the discharge port and supplying a new developer. This is a so-called trickle system in which the developer is discharged and collected by overflowing the discharge port provided on the wall surface of the developing device.

  In such a trickle-type developing device, supply of a new developer or carrier and discharge of the developer in the developer container are sequentially repeated, whereby the deteriorated developer in the developer container is newly supplied toner. And it will be replaced by carriers. For this reason, the ability of the carrier in the developing container to give a tribo is maintained, so that it is possible to suppress a reduction in image quality and to extend the frequency of changing the developer.

  Here, the above configuration will be described in more detail. In the above configuration, when the state where the developer is replenished frequently in the developing container continues, the amount of the developer in the developing container increases and the level of the developer increases. On the other hand, even when there is little or no developer replenishment in the developer container, the developer overflows from the discharge port and is discharged. The level of the developer is lowered.

  Therefore, in the trickle type developing device, the amount of developer in the developing container varies. However, if the amount of the developer in the developer container is too large, the developer is not sufficiently stirred, and the tribo to the toner is lowered, causing problems such as image unevenness and fogging, and problems such as overflow of the developer from the developer container. Will occur. On the other hand, if the amount of developer in the developing container is too small, image defects such as density unevenness and white spots in which part of the image portion is white will occur due to an insufficient amount of developer that forms an electrostatic latent image. Therefore, it is necessary to maintain the developer amount in the developing container within an appropriate range.

  In Patent Document 1, the amount of developer in the developing container is estimated by a toner concentration sensor, and when the estimated amount of developer is small, a discharge screw provided downstream of a supply screw that supplies toner to the developing sleeve. The structure which raises the rotational speed of this and reduces a rotational speed when there are many is disclosed. Thereby, the discharge amount of the developer in the developing container is adjusted.

JP 2010-122418 A

  However, in the configuration proposed in Patent Document 1, since the amount of developer in the developer container is estimated based on the output change of the toner density sensor and the result of the pressure sensor, the detection accuracy of the sensor and the developer around the sensor are estimated. Therefore, it is difficult to estimate the developer amount stably and accurately. Therefore, the amount of developer in the developing container may fluctuate greatly.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that stably suppresses fluctuations in the developer amount in a developing container.

  In order to solve the above problems, the image forming apparatus of the present invention has the following configuration.

An image carrier that forms an electrostatic latent image, a developer container that contains a two-component developer containing toner and a carrier, and a developer carrier that carries and transports the two-component developer and uses the electrostatic latent image as a toner image A developer conveying means that conveys and circulates the two-component developer accommodated in the developing container and that is accommodated in the developing container; and a discharge port that discharges the two-component developer accommodated in the developing container and accommodated in the developing container. A developing device comprising: a detecting device that detects information relating to a toner consumption amount of an output image; and a replenishing device that replenishes the developer based on the information relating to the toner consumption amount,
And a control unit that controls the developer conveying unit so that the conveying speed of the developer conveying unit is faster when the toner consumption amount of one or more sheets detected by the detecting unit exceeds a predetermined threshold. It is characterized by that.

  According to the present invention, fluctuations in the developer amount in the developing container can be stably suppressed. Thereby, it is possible to suppress image defects such as overflow of the developer from the developing container, image unevenness and fogging, and white spots in the image portion, and to stably obtain a high-quality image.

1 is a schematic diagram of an image forming apparatus according to the first embodiment. 1 is a schematic view of a developing device according to the first embodiment. 1 is a block diagram illustrating a system configuration of an image forming apparatus to which the first embodiment is applied. 5 is a table showing the relationship between the replenishment amount and consumption amount for toner and carrier. FIG. 2 is a cross-sectional view in the longitudinal direction of the developing device according to the first embodiment. FIG. 6 is a diagram illustrating developer discharge characteristics at various conveyance speeds in the developing device according to the first embodiment. FIG. 5 is a flowchart illustrating a method for controlling the rotation speed of the conveying screw in the first embodiment. FIG. 3 is a diagram illustrating developer discharge characteristics in Example 1. FIG. 6 is a diagram illustrating an average stay time of toner. It is the figure which showed the measuring method of the angle of repose. FIG. 10 is a diagram illustrating developer discharge characteristics at an initial stage of each conveyance speed and during idling in Example 2. FIG. 10 is a flowchart illustrating a method for controlling the rotation speed of the conveying screw in the second embodiment. FIG. 6 is a diagram illustrating developer discharge characteristics in Example 2. FIG. 10 is a diagram illustrating the discharge characteristics of an initial developer at various conveyance speeds in Example 3. FIG. 10 is a view showing the discharge characteristics of a 170-minute idling developer in Example 3. FIG. 10 is a flowchart illustrating a method for controlling the rotation speed of the conveying screw in the third embodiment. 10 is a control table for controlling the rotation speed of the conveying screw in the third embodiment.

Example 1
The image forming apparatus of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a schematic view of an image forming apparatus according to this embodiment. In the image forming apparatus 100, a photosensitive drum 1 as an image carrier is rotatably provided. First, the surface of the photosensitive drum is uniformly charged by a primary charger 2. Thereafter, an electrostatic latent image is formed on the photosensitive drum by exposing the surface of the photosensitive drum 1 with a laser light emitting element 3 as an exposure unit. This electrostatic latent image is developed by the developing device 4 to form a toner image. Thereafter, the toner image is transferred to the transfer paper 7 by the transfer charger 5, and further fixed on the transfer paper by the fixing device 8 to obtain a fixed image. Further, the transfer residual toner on the photosensitive drum is removed by the cleaning device 9 and the potential on the photosensitive drum is erased by the pre-exposure lamp 10. Thereafter, the photosensitive drum 1 forms an image again by the above-described image forming process.

Next, the developing device 4 will be described in detail.
FIG. 2 is a schematic view of the developing device of this embodiment. The developing device 4 includes a developing container 20, and a two-component developer (hereinafter referred to as a developer) containing toner and a carrier as a developer is accommodated in the developing container 20. Further, the developing device 4 includes a developing sleeve 24 that is a developer carrying member, and a blade 25 that regulates the layer thickness of the developer carried and conveyed on the developing sleeve 24. The developing container 20 has an opening at a position facing the photosensitive drum 1, and the developing sleeve 24 is rotatably provided so as to partially expose the opening. The developing sleeve 24 is made of a nonmagnetic material such as aluminum or stainless steel, and a magnet roller 50 as a magnetic field means is installed in a non-rotating state. The developing sleeve 24 rotates in the direction indicated by the arrow (counterclockwise) during development, and carries and transports the developer whose layer thickness is regulated by the blade 25.

  The developing container 20 includes a developing chamber 21a for supplying a developer to the developing sleeve 24 by a partition wall 23 extending in a direction perpendicular to the paper surface, and a stirring chamber 21b for collecting and stirring the developer from the developing sleeve 24. And a circulation path for circulating the developer. In this embodiment, the vertical stirring type is provided with the developing chamber 21a and the stirring chamber 21b above and below in the vertical direction. However, the present invention is not limited to this. good. Further, in the developing chamber 21a and the agitating chamber 21b, first and second conveying screws 22a and 22b are arranged as conveying means for agitating and conveying the developer, respectively.

  A hopper 31 that contains a replenishment developer in which toner and a carrier are mixed is disposed above the developing device 4. The hopper 31 constituting the toner replenishing means includes a replenishing screw 32 that is a screw-shaped replenishing member at a lower portion, and one end of the replenishing screw 32 extends to a developer replenishing port 30 provided in the developing device 4. . The developer supply amount is determined by the rotation speed of the supply screw 32. The rotation speed of the supply screw 32 is obtained by developing the reference latent image on the photosensitive drum 1 shown in FIG. Control is performed based on the detection result of the patch detection sensor 11 that detects the density of the toner image. The toner density detection method may be an optical detection method or a detection method using an ultrasonic sensor.

  Here, from a short-term viewpoint, the developer may be replenished so that the same amount of toner is included with respect to the amount of toner consumed in the output image and the control patch image. Therefore, the required replenishment amount varies depending on the mixing ratio of the developer toner and the carrier. That is, the higher the carrier mixing ratio, the more the required replenishment amount increases and the cost increases. However, since a large amount of new carriers are replenished, there is an advantage that a stable charge amount can be always given to the toner. On the other hand, the lower the carrier mixing ratio, the lower the required replenishment amount and the lower the running cost. On the other hand, the ratio of deteriorated carriers contained in the developer in the developer container increases, so the charging of toner becomes unstable. Therefore, there is a disadvantage that it is difficult to stabilize the image quality over a long period of time. In this embodiment, the mixing ratio of toner and carrier in the developer is 9: 1. However, it is not limited to this ratio, and an appropriate mixing ratio may be set. As described above, the toner consumed by the image formation is replenished to the developer container 20 through the developer replenishment port 30 from the hopper 31 by the developer in the hopper being transported by the rotation of the replenishment screw 32. .

  A discharge port 40 is provided on the wall surface of the developing device 4, and the deteriorated developer is discharged from the discharge port 40 and collected into the collection container 42. When the developer level in the developer container rises due to replenishment of the developer or the like, the developer is discharged so as to overflow from the discharge port 40 as the level of the developer rises. The discharged developer is transported to a recovered developer storage (not shown) by a recovery screw 41 that is a recovery member.

  Hereinafter, the video count value will be described in detail. FIG. 3 is a block diagram showing the system configuration of the image forming apparatus to which this embodiment is applied. In FIG. 3, reference numeral 213 denotes an external input interface (external input I / F), and RGB image data from an external device (not shown) such as a document scanner or a computer (information processing apparatus) via the external input interface 213 as necessary. Input color image data. A LOG conversion unit 204 converts luminance data of RGB image data input based on a lookup control table (LUT) configured by data stored in the ROM 210 into CMY density data (CMY image data). Convert. A masking / UCR unit 205 extracts black (Bk) component data from the CMY image data, and performs a matrix operation on the CMKY image data in order to correct the color turbidity of the recording color material. A lookup control table unit (LUT unit) 206 is a CMYK image input using a gamma lookup control table (γ lookup control table) in order to match the image data with the ideal gradation characteristics of the printer unit. Density correction is performed for each color of data. The γ lookup control table is created based on the data developed on the RAM 211, and the contents of the control table are set by the CPU 209. A pulse width modulation unit 207 outputs a pulse signal having a pulse width corresponding to the color density level of the image data (image signal) input from the LUT unit 206. Based on the pulse signal, the laser driver 102 drives the laser light emitting element 3 and irradiates the photosensitive drum 1 to form an electrostatic latent image.

  The video signal counting unit 214 integrates the color density level (0 to 255 level) for each 600 dpi pixel of the image data input to the LUT unit 206 for one image. This integrated image data value is called a video count value. This video count value becomes the maximum value 1023 when all the output images are at 255 level. When there is a limitation in the circuit configuration, the video count value can be obtained by similarly calculating the image signal from the laser driver 102 using the laser signal count unit 215 instead of the video signal count unit 214. Is possible. In this embodiment, the toner consumption amount is calculated from the video count value of the image output by the detection means including the external input I / F 213, the LOG conversion unit 204, the masking UCR unit 205, the LUT unit 206, and the video signal count unit 214. Detected.

  The video count value signal is input to the printer controller, and the rotational speeds of the sleeve driving means 301 and the screw driving means 302 are controlled based on the signal.

  FIG. 4 is a table showing the relationship between the replenishment amount and consumption amount for toner and carrier. The video count value is determined by the image to be output. Further, since the same amount of toner as the toner consumption is replenished, the amount of developer to be replenished is determined, and this replenished carrier amount corresponds to the increase in the capacity of the developer in the developing container. Here, the video count value and the toner consumption amount of the image are substantially proportional, and the video count value and the replenished carrier amount are also substantially proportional.

  In this embodiment, the rotational speed of the conveying screw is controlled based on the video count value of the output image. However, this may be controlled based on the printing rate. The printing rate referred to here is “video count value of output image / maximum video count value of paper size of output image”.

  FIG. 5 is a longitudinal sectional view of the developing device of this embodiment. The first conveying screw 22a is arranged in the developing chamber 21a substantially parallel along the axial direction of the developing sleeve 24, and rotates to convey the developer in the developing chamber 21a in one direction along the axial direction. To do. The second conveying screw 22b is disposed in the agitating chamber 21b substantially in parallel with the first conveying screw 22a, and conveys the developer in the agitating chamber 21b in the direction opposite to the first conveying screw 22a. In this manner, the developer is allowed to pass between the developing chamber 21a and the stirring chamber 21b through the openings (that is, communication portions) 26 and 27 at both ends of the partition wall 23 by the first and second conveying screws 22a and 22b. Circulated.

  In this embodiment, the rotation driving of the developing sleeve 24 and the rotation driving of the first and second conveying screws 22a and 22b include a sleeve driving unit 301 and a screw driving unit 302, which are driving units, respectively. It can be controlled by any rotational drive.

Next, the developer discharge characteristics of the developing device 4 of this embodiment will be described.
As shown in the figure, the position of the discharge port 40 is located on the side surface of the developing chamber 21a, on the upstream side in the developer transport direction from the position of the developer supply port 30, and in the middle in the developer transport direction of the developing chamber 21a. It is provided so as to be located downstream of the point (intermediate point). This is to prevent the replenished new developer from being discharged immediately. However, it may be formed on the downstream side in the developer conveying direction from the position of the developer supply port 30 or in the stirring chamber 21b.

  The developer discharge characteristics are determined by the size and position of the discharge port 40, and the conveying capacity determined by the size of the blades of the first and second conveying screws 22a and 22b as developer conveying means, the rotational speed of the screw, and the like. Is. For example, the developer discharge characteristic is increased when the conveying capability of the conveying screws 22a and 22b is increased.

  In the present embodiment, the discharge port 40 is a rectangular hole of 15 mm long × 10 mm wide (substantially parallel to the developer transport direction). In addition, the lower end of the discharge port 40 is located 5 mm above the center of the shaft of the first conveying screw 22 a and 5 mm upstream from the end of the partition wall 23 on the communication portion 27 side. On the other hand, the first conveying screw 22a and the second conveying screw 22b have the same configuration, and a stirring blade having a pitch of 30 mm and an outer diameter of 28 mm in the axial direction on a rotating shaft having an axial diameter of 8 mm, that is, The screw blades which are spiral wings are evenly provided. The driving means for the first and second conveying screws 22a and 22b is a common motor (not shown), and the conveying speed (rotational speed) is variable between 300 rpm and 700 rpm.

  Here, the present inventors conducted the following experiment in order to examine the developer discharge characteristics of the developing device 4 of this embodiment.

  That is, a predetermined amount of developer is put in the developer container 20 and closed with a lid so that the developer is not discharged from the discharge port 40 for 1 minute, and the developing sleeve 24 and the first and second conveying screws 22a and 22b are closed. Rotate idly. Further, the amount of developer put into the developing container 20 at this time is set to a developer amount in increments of 20 g from 320 g to 600 g. Here, the reason why the lid is closed for 1 minute and the discharge port is closed is to stabilize the surface of the developer in the developer container. Thereafter, the discharge port is opened without covering the developer so that the developer is discharged from the discharge port, and the developing sleeve 24 and the first and second conveying screws 22a and 22b are idled for another minute. During this 1 minute, the weight of the developer overflowing from the discharge port 40 was measured. However, in the experiment, the rotation speed of the developing sleeve 24 was fixed at a rotation speed at the time of image formation, 350 rpm in this embodiment, and the first and second conveying screws 22a and 22b were measured at a rotation speed of 300 rpm and 500 rpm, respectively. . In this experiment, the measurement was performed without supplying the developer. Further, the weight ratio of toner in the developer in the developing container 20 (referred to as “T / D ratio”) having a T / D ratio = 8% was used. Although the T / D ratio varies between about 6% and 12% when an actual image forming apparatus is used, the experiment was conducted using a developer having a T / D ratio of 8% as a representative. The experimental results are shown in FIG.

  FIG. 6 is a graph showing developer discharge characteristics according to the conveying screw speed and the developer amount in the developer container. The horizontal axis represents the developer amount (g) in the developing container 20, and the vertical axis represents the developer weight (mg) discharged from the discharge port 40 per unit time. In addition, two conveying speeds of 300 and 500 rpm were used as the conveying speed of the conveying screw. Here, the unit time is the rotation time of the developing sleeve 24 and the first and second conveying screws 22a and 22b that the image forming apparatus 100 needs per one side of the A3 sheet. That is, the unit of the vertical axis (mg / A3 single side) is the developer discharged from the discharge port in 1.5 seconds because the printing speed of the image forming apparatus used in the experiment is 40 sheets / minute in terms of A3. The weight (mg) is shown.

  As shown in FIG. 6, the developer discharge characteristic, which is the weight of the developer discharged from the discharge port 40 per unit time according to the amount of developer in the developer container, is the first and second conveying screws 22 a, It greatly depends on the rotational speed of 22b. That is, when the rotation speed is fast (500 rpm), compared to when it is slow (300 rpm), if the developer amount is the same, the developer discharge amount in the developer container 20 is large and the discharge characteristics are large. Further, even if the amount of developer in the developing container 20 is small, the developer is discharged. These are because when the rotation speed of the conveying screw is high, the developer can be pumped into the developing chamber more than when it is slow.

The mechanism by which the developer discharge characteristic depends on the rotation speed of the conveying screw can also be explained below. First, the conveyance capability of the conveyance screw with respect to the developer in the developing container 20 is generally expressed by the following formula. That is, the conveying capacity is defined as the volume obtained by integrating one pitch of the blade of the screw for one rotation of the screw multiplied by the screw conveying speed and the developer conveying efficiency.
“Conveyance capacity” = π * {(outer diameter of screw blade) ^ 2- (screw shaft diameter) ^ 2} * (screw pitch interval) * (screw rotation speed) * (developer conveyance efficiency)
It is expressed. Here, the developer conveyance efficiency was calculated as 80% for the screw of this example. From the above formula for calculating the conveying capacity, the conveying capacity increases as the rotational speed of the screw increases, and when the conveying capacity increases, the amount of developer flowing in the vicinity of the outlet 40 increases per unit time. This is because the amount of developer discharged is increased.

  Next, the stability (balance) of the developer amount in the developing container will be described. The amount of developer in the developing container is stabilized when the amount of developer replenished and the amount of developer discharged are balanced.

  Here, the developer replenishment amount is such that the developer is replenished so as to include the same amount of toner as consumed in the output image and the control patch image, as described above. For example, in this embodiment, when the output image is an image of 255 levels on the entire A3 single side (the above-mentioned video count value is 1023), the toner consumption at this time is very high at about 900 mg. Therefore, since the mixing ratio of the toner and the carrier is 9 to 1, a large amount of the developer is replenished with 900 mg of toner and 100 mg of carrier and a total of 1000 mg.

  On the other hand, when the output image is an all-zero-level image on one side of A3 (the video count value is 0), the toner consumption amount is about 8 mg corresponding to the fog toner amount. However, in this embodiment, since the image density stability control (the control method is not shown) is performed using the patch detection sensor 11 that detects the density of the patch image on the photosensitive drum, a small amount of toner (A3 one side) 1mg) is consumed. Therefore, when the output image is an image of 0 level on the entire A3 one side, the total toner consumption at this time is as small as about 9 mg. Therefore, it is necessary to replenish the developer so as to contain the same amount of toner, and the amount is 9 to 1 in the mixing ratio of the toner and the carrier. Replenish the agent.

  Here, from the discharge characteristics shown in FIG. 6, as the developer amount in the developer container 20 increases, the developer discharge amount from the discharge port 40 also increases. When the rotation speed of the first and second conveying screws 22a and 22b is 300 rpm, when the developer amount increases to 580 g, 100 mg of developer per A3 single-sided output time is discharged from the discharge port. Therefore, if the image of the video count value 1023 is continuously output, when the amount of developer in the developer container 20 increases to 580 g, “replenished developer amount (1000 mg)” and “consumed toner amount”. (The sum of (900 mg) and the developer discharged from the discharge port (100 mg)), and the increase in the developer amount stops.

  Conversely, if the amount of developer in the developer container decreases, the discharge from the discharge port 40 also decreases. When the rotation speed of the first and second conveying screws 22a and 22b is 300 rpm, when the developer amount is reduced to 460 g, only 1 mg of developer is discharged from the discharge port per A3 single-sided output time. Therefore, if images with a video count value of 0 are continuously output, when the amount of developer in the developer container 20 decreases to 460 g, “replenished developer amount (10 mg)” and “consumed”. The sum of the toner amount (9 mg) and the developer discharged from the discharge port (1 mg) balances, and the decrease in the developer amount in the developing container stops.

  As described above, the fluctuation range of the developer amount in the developing container 20 is 460 g to 580 g when the rotation speeds of the first and second conveying screws 22a and 22b are 300 rpm. Similarly, when the rotational speeds of the first and second conveying screws 22a and 22b are increased to 500 rpm, they are 400 g to 520 g.

Here, the method for controlling the rotational speeds of the first and second conveying screws of the present invention will be described in detail.
As described above, when the amount of toner consumed in the output image is large, the amount of developer in the developing container 20 “increases” and balances. Further, when the toner consumption of the output image is small, the amount of developer in the developing container 20 is “decreased” and balanced. Therefore, in this embodiment, the control shown in FIG. 7 can be performed to suppress the variation in the developer amount. That is, by controlling the rotation speeds of the first and second conveying screws 22a and 22b to two rotation speeds of 300 rpm and 500 rpm, the lower limit of the developer amount at the rotation speed of 300 rpm is 460 g and 500 rpm. The fluctuation of the developer amount is suppressed to 520 g which is the upper limit of the developer amount at the rotation speed of ˜. That is, when the toner consumption amount of the output image is large, the rotation speed of the conveyance screw is increased, and when the toner consumption amount of the output image is small, the rotation amount of the conveyance screw is decreased. It is configured to suppress the fluctuations.

  FIG. 7 is a flowchart showing a method for controlling the rotational speed of the conveying screw of this embodiment, which will be described in detail below.

  When an image is input from the outside (step S1), the video signal count unit 214 measures the video count value of the output image (step S2). When the video count value is 0 to 196, the printer control unit 300 controls the rotation speed of the conveyance screw to 300 rpm, and when the video count value is 197 to 1023, the rotation speed of the conveyance screw is controlled to 500 rpm (step S3). ). Thereafter, an image forming process operation is executed (step S4). Thus, in this embodiment, the video count value 196 is set as a threshold value, and when this threshold value is exceeded, 500 rpm is set, and when it is not exceeded, 300 rpm is set. By setting the above threshold value, the development in the developer container is between 460 g which is the lower limit of the developer amount at the rotation speed of 300 rpm and 520 g which is the upper limit of the developer amount at the rotation speed of 500 rpm. This is desirable because fluctuations in dosage can be suppressed. However, the threshold value is not limited to this video count value 196, and even if it is 200 or 300, fluctuations in the developer amount can be suppressed. Furthermore, the speed of the conveying screw is controlled in accordance with the toner consumption amount of one image to be output, and the amount of developer in the developer container is smaller than that in the configuration in which the agent level in the developer container is detected. It can be said that the responsiveness to increase / decrease is high and the fluctuation of the developer amount can be suppressed more stably.

  FIG. 8 is a diagram showing developer discharge characteristics of the image forming apparatus of this embodiment. The discharge characteristics of this example are the curves (curves indicated by A, B, C, and D) shown as “Example 1”. That is, the discharge characteristic curve is a combination of the discharge characteristic curve when the rotation speeds of the first and second conveying screws 22a and 22b are 300 rpm and the discharge characteristic curve when the rotation speed is 500 rpm.

  Here, when the image of the video count value 1023 having the maximum toner consumption amount is continuously output when the developer amount is 480 g and stable (balanced), the rotation speed of the conveying screw is 500 rpm. At this time, the replenished carrier amount corresponding to the increase in the developer amount is 100 mg from FIG. As described above, when the image of the video count value 1023 is continuously output, the developer amount increases to 520 g (position D) where the replenished carrier amount 100 mg and the discharged developer amount are balanced at the conveyance screw rotation speed of 500 rpm. I will do it.

  When the image of the video count value 0 (solid white) with the minimum toner consumption is continuously output after the developer amount is balanced at 520 g, the conveyance screw rotation speed is switched to 300 rpm by the printer control unit 300. . At this time, the replenished carrier amount corresponding to the increase in the developer amount in the developing container is 1 mg. Therefore, the developer amount is reduced to 460 g (position B) where the carrier amount 1 mg replenished at the conveying screw rotation speed of 300 rpm and the discharged developer amount are balanced.

  Thereby, when the conveying screw speed is not controlled, the fluctuation range of the developer amount is 120 g, whereas in this embodiment, the fluctuation range of the developer amount can be set to 460 g to 520 g and 60 g. . In addition, since only a change in the speeds of the first and second conveying screws is required and no new members or spaces are required, the developing device can be made compact.

  In this embodiment, the control of the rotational speeds of the first and second conveying screws is the same. However, the present invention is not limited to this, and the first and second conveying screws may be controlled separately. What is necessary is just to control the conveyance speed of the other or both developer conveyance members.

  In this embodiment, the rotational speed of the conveying screw is controlled by two types of 300 rpm and 500 rpm. However, the rotational speed of the conveying screw may be finely divided according to the video count value and controlled by three or more rotational speeds. In that case, it is possible to suppress the variation of the developer as compared with the case of two types of rotation speeds.

  Further, the developer conveying means is not limited to a screw-shaped conveying screw, and may be a saw coil conveying that conveys by driving a conveying coil or a saw member. Further, the developer conveying means is not limited to having two conveying screws as developer conveying members, and may be configured to have one or three or more.

  Further, as a toner consumption amount, instead of the video count value, the laser signal count value counted by the laser signal count unit 215 and the toner density of the toner image may be measured by an optical sensor.

  In this embodiment, the rotational speed of the conveying screw is controlled based on the video count value of one image output immediately after the video count value measurement by the video signal count unit 214, but the present invention is not limited to this. The rotational speed of the conveying screw may be controlled in accordance with the average value of the video count values of the images for a plurality of images output to. You may control according to the average value of the video count value for a predetermined number of sheets. However, even in such a case, it is considered that it is desirable to use about 1 to 100 sheets in order to finely control the developer discharge amount.

  In addition, as a control of the rotation speed of the conveying screw, the rotation speed of the conveying screw may be controlled according to the toner consumption amount for each continuous print number of images to be output continuously instead of every predetermined number of sheets.

(Example 2)
In the first embodiment, every time video count value information of an image to be output to the printer control unit 300 is sent from the video signal counting unit 214 or the laser signal counting unit 215, the first and second conveying screws 22a and 22b rotate. Control was made to enable switching of the speed.

  On the other hand, in this embodiment, the developer is deteriorated due to the change in the developer amount in the developing container by controlling the rotation speed of the first and second conveying screws 22a and 22b in accordance with the degree of developer deterioration. Even suppress. Here, the degree of developer deterioration referred to in the present embodiment means that the developer is rubbed with a developing sleeve, a conveying screw, or a blade, so that the external additive of the toner is peeled off or the toner or the external additive on the carrier surface. To the extent that the developer deteriorates and the fluidity changes. In this embodiment, the degree of developer deterioration is estimated from the average printing rate of the output image. When the output of an image with a low printing rate continues, the developer deteriorates and the fluidity changes, but even in this case, the lower limit of the developer amount in the developer container is suppressed and the developer amount is reduced. Reduce fluctuations. As a result, overflow of the developer from the developing container, white spots in the image area and unevenness of the trace of the conveying screw of the developing device that occur when the amount of the developer in the developing container is too small appear in the image, resulting in image unevenness. Such image defects can be suppressed.

  Hereinafter, it will be described in detail with reference to the drawings. However, in this embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment, and description thereof is omitted.

  FIG. 9 is a graph showing the relationship between the average staying time of toner and the printing rate in this embodiment. The average staying time of the toner is an average of the staying time of the developing container after the toner is replenished in different developing containers for each toner. Further, the printing rate mentioned here is “video count value of output image / maximum video count value of paper size of output image”. In FIG. 9, the horizontal axis represents the printing rate (%), the vertical axis represents the average toner residence time (minutes), the developer amount in the developing container is 500 g, and the toner concentration (T / D ratio) is 8%. FIG. 6 is a diagram illustrating an average staying time of toner in a developing container when it is assumed to be constant. The developing sleeve rotation time per A3 single sheet, which is the maximum paper size, is 1.5 seconds (including 0.1 seconds between papers), and the toner consumption on the photosensitive drum at a printing rate of 100% is 0.62 mg / cm Under the constant condition of ^ 2, the average stay time after printing 100K images of each A3 single-sided printing rate is calculated. If the average stay time is long, the number of times of rubbing by the developing sleeve, the transport screw, and the blade increases. In this embodiment, the rotation speed of the transport screw is controlled using the average stay time of the toner as the developer deterioration degree. ing. However, the present invention is not limited to this, and when the driving time of the developing sleeve is directly measured, the longer the driving time, the more the deterioration proceeds, and the toner consumption amount is the toner replacement amount, and the developer deterioration degree is the developing sleeve rotation time / toner. You may obtain | require as consumption.

  If the paper size is the same, the amount of toner that is developed on the photosensitive drum 1 and consumed from the developing container of an image having a low printing rate is smaller than that of an image having a high printing rate. Furthermore, a small amount of toner is consumed means that a small amount of toner is replenished. The probability that one toner particle in the developing container is used for development and exits from the container becomes lower as the printing rate is lower. Accordingly, the toner staying in the developing container has a longer average staying time in the developing container as the printing rate is lower under the condition that the paper size and the toner density (T / D ratio) in the container are constant.

  Further, if the toner stays in the developing container for a long time, the toner is more likely to be agitated by the conveying screw or rubbed when passing through the blade. When the toner is rubbed, the external additive is peeled off or embedded in the toner surface, and the fluidity of the developer changes. That is, the flowability of the developer and the degree of developer deterioration can be predicted by obtaining the average printing rate of the output image.

  In order to clarify the relationship between the average residence time of the toner and the flowability of the developer, the present inventors conducted the following experiment. That is, in the developing device 4 of the image forming apparatus 100 to which the present invention can be applied, an initial developer, a 170-minute idling developer in which the developing sleeve and the conveying screw are idly rotated for 170 minutes, are prepared, The angle of repose was measured as an index. That is, developers with different average toner residence times were prepared and the difference in fluidity was measured. In the image forming apparatus according to the present embodiment, the repose angle of the initial developer (developer with an average stay time of 0 minutes) is 30 degrees, and the repose angle of the 170-minute idle developer (the developer with an average stay time of 170 minutes). Was 42 degrees. In other words, it was found that the idling developer is less fluid due to toner deterioration due to rubbing around the conveying screw and blade.

  Here, the angle of repose is measured at a temperature of 23 ° C. and a humidity of 50%. As shown in FIG. 10, the developer placed on the sieve (710 μm opening, wire diameter φ450 μm) 400 drops by vibration, It passes through a funnel (toner ejection hole φ5 mm) 401 under the sieve. Thereafter, the developer is piled up on the measurement control table (φ80 mm circle) 402 placed underneath. When the developer accumulates, the angle θ shown in FIG. 10 gradually increases, and when the developer accumulates above a certain level, the developer slips and the angle θ becomes a constant value. The angle θ at that time is the angle of repose.

  When the flowability of the developer changes, it is considered that the discharge characteristic of the developer also changes. Therefore, an experiment similar to that performed in Example 1 was also performed in this example.

  That is, the developer amount in units of 20 g from 320 g to 600 g is put into the developing container 20, and the developer sleeve is stabilized by rotating the developing sleeve 24 and the first and second conveying screws 22a and 22b for 1 minute. Thereafter, the developer overflowing from the discharge port 40 was measured while the developing sleeve 24 and the first and second conveying screws 22a and 22b were rotated for another minute.

  However, the rotation speed of the developing sleeve 24 was fixed at 350 rpm, and the rotation speeds of the first and second conveying screws 22a and 22b were measured at 300 rpm and 500 rpm, respectively. Further, in this example, an experiment was conducted with two types of developers, ie, a fluid initial developer (indicated as “initial”) and a 170-minute idling developer (indicated as “idling”). The experimental results are shown in FIG.

  FIG. 11 is a diagram showing developer discharge characteristics at the initial stage and idling time in this embodiment. The horizontal axis represents the developer amount (g) in the developing container, and the vertical axis represents the developer amount (mg) discharged from the discharge port 40 per unit time (A3 single side).

  In both the initial developer and the 170-minute idling developer, the developer discharge characteristics greatly depend on the rotation speeds of the first and second conveying screws 22a and 22b. In this embodiment, the discharge amount of the idling developer for 170 minutes was larger than that of the initial developer at the same conveying screw rotation speed. This is because the deteriorated developer has a smaller bulk density and the surface of the developer container rises than the undegraded developer, so that the developer is overflowed from the wall of the discharge port 40 of the developer container. This is probably because the discharge is easier in the configuration of discharging. In such a developing device in which the discharge characteristics are increased as compared with the case where the developer is not deteriorated, the developer container is controlled by controlling the rotation speed of the conveying screw described below. The fluctuation of the developer amount in the inside can be suppressed.

  FIG. 12 is a flowchart showing a method for controlling the rotational speed of the conveying screw in this embodiment. This will be described below.

  The image to be output is input (step S101), and the video count value of the image output by the video signal count unit 214 is measured (step S102). Further, the average value of the printing rate for 1000 sheets already output is obtained from the video count value for 1000 sheets already output and the paper size (step S103). Here, when the average value of the printing rate for 1000 sheets already output is 0% to 20% and the developer deterioration degree is high, the rotation speed of the conveying screw is set to 300 rpm, and the printing rate is larger than 20%. When the degree is low, the screw rotation speed is controlled to 500 rpm (step S104). Under this setting, an image forming process operation is executed (step S105). Thereafter, the process proceeds to the next image forming process. Thus, the printing rate of 20% is set as a threshold value, and when this threshold value is exceeded, 500 rpm is set, and when it does not exceed 300 rpm, the developer amount in the developing container is determined using these two rotation speeds. Variation can be suppressed. If the printing rate is 20% or more, the average staying time of the toner, that is, the state of the deterioration of the developer is not high. Therefore, the rotation speed of the conveying screw is set to 500 rpm, and the developer discharge amount is increased. On the other hand, in a state where the deterioration rate of the toner having a printing rate of 20% or less is high, the developer amount fluctuation can be suppressed by setting the rpm to 300 rpm so that the developer discharge amount does not increase excessively. However, the threshold value is not limited to 20%, and fluctuations in the developer amount can be suppressed even when the threshold value is 30% or 40%.

  The developer discharge characteristic of the image forming apparatus of the present embodiment is as shown in “curve of embodiment 2” in FIG. That is, the discharge characteristic in the region between the discharge characteristic curve when the rotation speed of the conveyance screw in the initial developer is 500 rpm and the discharge characteristic curve when the rotation speed of the conveyance screw in the 170-minute idle rotation developer is 300 rpm. Will have. In other words, even when image output with a low printing rate continues and the developer deteriorates, the lower limit value of the developer amount in the developer container can be reduced by setting the rotation speed of the 300 rpm conveyance screw with a smaller discharge amount and smaller discharge characteristics. 360 g is used to suppress a decrease to 340 g, which is the lower limit of the developer amount of 500 rpm of the idling developer. Also, as the upper limit of the developer amount, in order to avoid an excessive increase up to 560 g at the initial 300 rpm, when the image output at a high printing rate continues, by setting the rotation speed to 500 rpm with a larger discharge amount and greater discharge characteristics, It is suppressed to 520 g. That is, even when the developer is deteriorated, the amount of the developer can be varied within the range of 360 g to 520 g.

  In this embodiment, the average value of the printing rates for 1000 sheets that have already been output is obtained. However, the present invention is not limited to this. However, in consideration of the change in fluidity due to the deterioration of the developer, it is desirable to set the average printing rate of about 100 to 10,000 sheets, which is a sheet suitable to some extent for measuring the degree of deterioration of the developer. Conceivable.

(Example 3)
In this embodiment, the conveying screw is more optimally combined by combining the embodiment 1 and the embodiment 2 in accordance with both information of “average value of printing rate for 1000 sheets already output” and “video count value”. To control the rotation speed. In the present embodiment, a developer composed of toner having fluidity different from those in the first and second embodiments is used. Specifically, the amount of wax contained in the toner is increased. Therefore, the change in fluidity when the developer is deteriorated is slightly different from the above-described embodiment.

  Hereinafter, description will be given based on the drawings. However, in this embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment, and description thereof is omitted.

  The developer discharge characteristics of the developing device 4 of this embodiment are as shown in FIGS. Here, FIG. 14 is a diagram showing the developer discharge characteristics of the initial developer, and FIG. 15 is a diagram showing the developer discharge characteristics of the 170-minute idling developer. A little different, when the rotation speed of the conveying screw is 500 rpm, the developer discharge amount is slightly increased even if the developer amount is the same. 14 and 15, the horizontal axis represents the developer amount (g) in the developing container, and the vertical axis represents the weight (mg) of the developer discharged from the discharge port 40 per unit time.

  First, for comparison, in accordance with the control method of the first embodiment, every time video count value information is transmitted to the printer control unit, that is, every time an image is output, the rotation speed of the conveying screw is set to 300, 500, 700 rpm. Consider the case where control is switched to.

  Here, immediately after a large number of copies of an image having a video count value 1023 are continuously output, the fluidity of the developer characteristics increases due to the continuous output of an image with a high printing rate, and the discharge characteristics are as shown in FIG. Therefore, the rotation speed of the conveying screw is 700 rpm and the developer amount is 420 g. Here, when the video count value of the output image suddenly becomes 0, the printer control unit 300 switches the rotation speed of the conveying screw to 300 rpm. At this time, since it is below 460 g, which is the lower limit of the developer amount fluctuation at the rotation speed of the conveying screw of 300 rpm, the surface of the developer in the developing container is lowered too much and white spots and unevenness of the conveying screw mark appear in the image. There is a risk of such image defects. This is because even if the developer amount is the same, if 300 rpm compared to 700 rpm, the force of pumping up the developer amount into the developing chamber 21a is weak, and the surface of the developer will drop too much. Therefore, in a state where the developer whose discharge characteristics are as shown in FIG. 14 is not deteriorated, it is desirable to use the rotation speeds of 300 rpm and 500 rpm and not the rotation speed of 700 rpm. That is, control is performed using a minimum speed of 300 rpm and a maximum speed of 500 rpm as the rotation speed of the conveying screw.

  On the other hand, immediately after a large number of copies of an image with a video count value of 0 are output continuously, the developer characteristics decrease in fluidity due to continuous output of an image with a low printing rate, and the discharge characteristics are as shown in FIG. At this time, the discharge characteristic of the developer is considerably similar to that of the developer before deterioration even if the rotation speed of the conveying screw is different. For this reason, the control that uses 300 rpm and 500 rpm and does not use the rotation speed of 700 rpm does not sufficiently suppress the fluctuation range of the developer. In other words, by using a rotation speed of 700 rpm in addition to 300 rpm and 500 rpm, it is possible to further suppress the fluctuation range of the developer amount. That is, control is performed using a minimum speed of 300 rpm and a maximum speed of 700 rpm.

  From the above, it can be understood that the optimum rotation speed of the conveying screw differs between the developer in the initial state and the developer that has deteriorated because the discharge characteristics change. Therefore, a method for controlling the rotational speed of the conveying screw that reduces these problems will be described. That is, in this embodiment, in order to obtain the rotation speed of the conveyance screw that is optimal for the developer discharge characteristic that varies depending on the degree of developer deterioration, the conveyance screw is based on the average printing rate and toner consumption shown in FIG. A control table is used to determine the rotation speed. Thereby, in the present embodiment, the above-described problems can be reduced as much as possible in both the initial developer and the deteriorated developer. That is, it is possible to suppress image defects such as white spots and unevenness of the conveying screw trace in the image, and it is possible to suppress the fluctuation range of the developer even when the developer is deteriorated. Hereinafter, the control method will be described in detail.

  FIG. 16 is a flowchart of the method for controlling the conveying screw in this embodiment. First, an image is input from the outside (step S201), and the video signal count unit 214 measures the video count value of the output image (step S202). Further, an average value of the printing rates for the past 1000 sheets already output is obtained (step S203). Further, the video count value for one sheet to be output is obtained (step S204). Next, the rotation speed of the conveying screw is controlled based on a control table described later (step S205).

  FIG. 17 is a control table for controlling the rotation speed of the conveying screw in this embodiment. The horizontal axis represents the average printing rate for the past 1000 sheets obtained in step S203, and the vertical axis represents the rotation speed of the conveying screw. From the video count value obtained in step S204, the one having the closest video count value is selected from the five broken lines, and the rotation speed of the conveying screw having the average printing rate obtained in step S203 is obtained.

  The control table shown here shows the maximum speed used by the transport screw as the average print rate for the past 1000 sheets increases, in order to obtain the optimum rotation speed of the transport screw for the developer discharge characteristics that change depending on the degree of developer deterioration. A control table with a reduced minimum speed is used. As shown in FIG. 17, when the average printing rate is 0%, the rotation speed of the conveying screw is controlled at 300 to 700 rpm. On the other hand, when the average printing rate is 100%, the rotation speed of the conveying screw is controlled at a speed of 300 to 500 rpm. By such control, it is possible to suppress image defects such as white spots and unevenness of a conveying screw mark in the image, and it is possible to suppress the fluctuation range of the developer even when the developer is deteriorated.

  The determination of the rotation speed of the conveying screw will also be described. When the average printing rate for the past 1000 sheets is 0% and 100%, the maximum and minimum speeds are set as described above, and the developer discharge characteristics when the average printing rate is 30% and 60% are also measured. And have decided. Even in the cases of 30% and 60%, the lower limit of the rotation speed of the conveying screw is set to 300 rpm, and the upper limit of the rotating speed is an image where the surface of the developer in the developing container is lowered too much and white spots and unevenness of the conveying screw mark are imaged. The maximum developer amount at the upper limit of the rotation speed is substantially the same and slightly larger than the minimum rotation speed at 300 rpm, i.e., the rotation speed at which no image defect occurs. ing. Here, the reason for controlling the maximum speed without changing the minimum speed before and after deterioration is that the discharge characteristics before and after deterioration can be made closer, which is more desirable. .

  In this embodiment, the minimum speed is set to 300 rpm and the maximum speed is changed by the average printing rate. However, the present invention is not limited to this, and both the maximum speed and the minimum speed may be changed by the average printing rate.

  Further, the developer table is not limited to the control table described above, and when the developer discharge characteristics differ depending on the position of the discharge port, the developer characteristics, etc., the maximum speed and minimum speed used by the screw rotation speed are higher as the average printing rate is higher. A control table that increases the width may be used.

  In addition, although the one having the closest video count value among the five polygonal lines is selected from the video count value, the present invention is not limited to this, and a control table using more or fewer polygonal lines may be used.

  In this embodiment, the change in the fluidity due to the deterioration of the developer is taken into consideration by the average value of the printing rate for 1000 sheets already output. However, the present invention is not limited to this. Even if it calculates | requires using, since the deterioration degree of a developer can be considered, it is good.

(Other examples)
In this embodiment, a developer having characteristics different from those of the developers used in Embodiments 1 to 3 is used, and the position and shape of the discharge port are changed, so that the developing device having discharge characteristics different from those of Embodiments 1 to 3 is used. It is characterized by being. Specifically, when the developer is deteriorated, the developing device has a smaller developer discharge characteristic than when the developer is not deteriorated.

  In such a developing device, it is necessary to make the control of the conveying screw for suppressing the fluctuation of the developer amount different from that in the second embodiment. Hereinafter, the control of the conveying screw will be described in detail. Since the configuration and the like of the image forming apparatus in the present embodiment are the same as those in the first and second embodiments, description thereof will be omitted.

  In Example 2, a printing rate of 20% is set as a threshold value, and when this threshold value is exceeded, 500 rpm is set, and when it does not exceed 300 rpm, the developer amount in the developing container is determined using these two rotation speeds. It was set as the structure which suppresses the fluctuation | variation of. In this embodiment, it is the same that the printing rate of 20% is set as a threshold value, but if this threshold value is exceeded, 300 rpm is set, and if it does not exceed 500 rpm, these two rotation speeds are used. The variation of the developer amount in the developing container is suppressed. This is because, in this embodiment, since the developer discharge characteristics are smaller than when the developer is not deteriorated when the developer is deteriorated, when the developer deterioration has progressed, it is not 300 rpm. This is because the change in the developer amount in the developer container can be suppressed by switching to 500 rpm, which has a higher discharge characteristic.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing device 20 Developing container 21a Developing chamber 21b Agitation chamber 22a First conveying screw 22b Second conveying screw 24 Developing sleeve 25 Blade 30 Supply port 31 Hopper 40 Discharge port 42 Collection container 50 Magnet roller 100 Image forming apparatus

Claims (12)

An image carrier for forming an electrostatic latent image;
A developer container containing a two-component developer containing toner and a carrier; a developer carrier that carries and conveys the two-component developer to form an electrostatic latent image as a toner image; and a developer container provided in the developer container. A developing device comprising developer conveying means for conveying and circulating the two-component developer accommodated; and a discharge port provided in the developer container for discharging the two-component developer accommodated in the developer container;
Detecting means for detecting information relating to toner consumption of the output image;
In an image forming apparatus comprising: a replenishing unit that replenishes the developer with a developer based on information on the toner consumption amount;
And a control unit that controls the developer conveying unit so that the conveying speed of the developer conveying unit is faster when the toner consumption amount of one or more sheets detected by the detecting unit exceeds a predetermined threshold. An image forming apparatus.   The control unit can switch the transport unit to a plurality of transport speeds, and changes the maximum speed and the minimum speed of the developer transport means according to the degree of developer deterioration in the developer container. The image forming apparatus according to claim 1.   When the developing device has a larger discharge characteristic of the two-component developer discharged from the discharge port than when the developer is not deteriorated when the developer is deteriorated, the control means determines the deterioration of the developer in the developer container. 3. The image forming apparatus according to claim 2, wherein when the degree is high, the difference between the maximum speed and the minimum speed of the developer conveying unit is made larger than when the degree of developer deterioration is low.   4. The image according to claim 3, wherein the control unit increases the maximum conveyance speed of the developer conveyance unit when the developer deterioration degree is high compared to when the developer deterioration degree is low. Forming equipment.   The image forming apparatus according to claim 1, wherein the detection unit detects a video count value of an output image.   6. The developer deterioration degree is an average printing rate for a predetermined number of sheets obtained from a toner consumption detected by the detection unit and a paper size to be output. The image forming apparatus described in 1.   The image forming apparatus according to claim 2, wherein the developer deterioration degree is obtained from a toner consumption amount detected by the detection unit and a driving time of the developer conveyance unit. . An image carrier for forming an electrostatic latent image;
A developer container containing a two-component developer containing toner and a carrier; a developer carrier that carries and conveys the two-component developer to form an electrostatic latent image as a toner image; and a developer container provided in the developer container. A developing device comprising developer conveying means for conveying and circulating the two-component developer accommodated; and a discharge port provided in the developer container for discharging the two-component developer accommodated in the developer container;
Detecting means for detecting information on the degree of developer deterioration in the developing container;
An image forming apparatus having replenishing means for replenishing the developer container with a two-component developer;
An image forming apparatus comprising: a control unit configured to switch and control a conveyance speed of the developer conveyance unit based on a degree of developer deterioration in the developer container detected by the detection unit.   When the developing device has a larger discharge characteristic of the two-component developer discharged from the discharge port than when the developer is not deteriorated when the developer is deteriorated, the control means determines the deterioration of the developer in the developer container. The image forming apparatus according to claim 8, wherein when the degree exceeds a predetermined threshold, the transport speed of the developer transport unit is made faster than when the degree does not exceed the predetermined threshold.   The developer container is separated by a partition into a developing chamber for supplying the developer to the developer carrying member and an agitating chamber for stirring the developer, and the developer conveying means is provided in the developing chamber and the agitating chamber, respectively. 10. The image according to claim 1, wherein the control unit controls a conveyance speed of one, the other, or both of the developer conveyance members. Forming equipment.   The image forming apparatus according to claim 10, wherein the discharge port is located on a side surface of the developing chamber and downstream of an intermediate point in a developer transport direction of the developing chamber.   The control means controls the developer conveying means by a control table in which a conveying speed of the developer conveying means is determined based on a developer discharge characteristic of a two-component developer discharged from the discharge port. The image forming apparatus according to any one of claims 1 to 11.

Images