JPH04333079A - Developing device and image forming device - Google Patents

Abstract

PURPOSE:To compensate variation in output value of a toner density sensor. CONSTITUTION:A control means 2 is provided to operate the developing part to agitate developer when electrical power source is connected after the image forming device is not activated and let stand. When the output value of a magnetic sensor 1 is greater than a specified toner concentration control value, the toner is replenished by the toner replenishing part to the developing part until the specified toner concentration control value is reached by the output value of the magnetic sensor 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device and an image forming apparatus for image forming apparatuses such as copying machines and printers.

0002

2. Description of the Related Art In image forming apparatuses such as copying machines and printers, an image bearing member made of a photoreceptor is generally rotated by a motor during image forming operation, uniformly charged by a charger, and then exposed to an image by an exposure means. This is performed to form an electrostatic latent image, and this electrostatic latent image is developed by a developing device into a developed image. Then, this developed image is transferred to transfer paper and fixed by a fixing device, residual toner on the photoconductor is removed by a cleaning device, and the photoconductor is neutralized by a static eliminator, thereby making it possible to form the next image. ing.

[0003] The above-mentioned developing device also includes a developing section that develops an electrostatic latent image on a photoreceptor with a two-component developer consisting of toner and carrier, a toner replenishing section that supplies toner to the developing section, and a toner replenishing section that supplies toner to the developing section. a toner concentration sensor consisting of a developing bias voltage power source that applies a developing bias voltage to the developer; and a magnetic sensor that is embedded in the developer and detects the mixing ratio of toner and carrier in the developer by detecting its magnetic permeability. The toner concentration control section samples the output value of the magnetic sensor at a predetermined timing, and controls the toner replenishment section so that the toner concentration of the developer becomes a predetermined toner concentration control value based on the output value. Controls toner supply. In addition, if the output value of the magnetic sensor does not reach the predetermined toner concentration control value even after toner replenishment is performed, it is detected that the toner in the toner replenishment unit has run out (toner end), and the display unit displays the toner end. It is carried out.

0004

[Problems to be Solved by the Invention] In the above-mentioned image forming apparatus, the output value of the toner density sensor after operation changes due to variations in the temperature dependence of the toner density sensor, the distribution state of the developer, the amount of charge (Q/M), etc. There is often a difference between the output value of the toner concentration sensor after the toner concentration sensor has been left inactive, even if the toner concentration of the developer is the same. In other words, the sampled output value of the toner density sensor during the last image formation immediately before the power is turned off after running all day, and the sampled output value of the toner density sensor when the power is turned off, left overnight, and then restarted the next day. There is often a difference between the output value sampled by the toner density sensor during image formation. Therefore, when operating first thing in the morning (first day of the day), the output value of the toner concentration sensor becomes too high than the toner concentration control value, and the toner concentration is determined to be too low, resulting in false detection of toner end or excessive toner replenishment. This may cause disadvantages such as background staining, toner scattering, etc.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device and an image forming device that can overcome the above drawbacks and compensate for fluctuations in the output value of a toner density sensor.

[0006]

[Means for Solving the Problem] In order to achieve the above object, the invention of claim 1 provides a developing section that stirs a developer made of toner and a carrier and develops a latent image on an image bearing member with this developer. , a toner replenishing section that replenishes toner to the developing section, and a magnetic sensor that detects the mixing ratio of the toner and carrier of the developer, and the toner of the developer based on the output value of the magnetic sensor. In a developing device of an image forming apparatus in which toner replenishment of the toner replenishing section is controlled so that the density becomes a predetermined value, as shown in FIG. is operated to stir the developer, and when the output value of the magnetic sensor 1 is higher than a predetermined toner concentration control value, the toner replenishing section is operated until the output value of the magnetic sensor 1 reaches a predetermined toner concentration control value. In the developing device according to claim 1, as shown in FIG. A third aspect of the invention is one in which the toner replenishment is performed intermittently, and as shown in FIG. is the magnetic sensor 1
Even if the output value of does not reach a predetermined toner concentration control value, the toner replenishing section is made to stop toner replenishment and developer agitation in the developing section is terminated, and the invention according to claim 4,
An image carrier on which an image is formed, a drive source for rotating the image carrier, a latent image forming means for forming a latent image on the image carrier, and a developer made of toner and carrier that is stirred and produced. A developing section that develops a latent image on an image carrier with a developer, a toner replenishing section that supplies toner to the developing section, a developing bias power supply that applies a developing bias voltage to the developing section, and a toner and carrier of the developer. a developing device having a magnetic sensor that detects a mixing ratio of the toner, and in which toner replenishment of the toner replenishing section is controlled so that the toner concentration of the developer becomes a predetermined value based on the output value of the magnetic sensor; As shown in FIG. 4, an image forming apparatus includes a transfer device that transfers the developed image to a transfer body, a cleaning device that cleans the image bearing member after the developed image transfer, and a static eliminator that neutralizes the static electricity from the image bearing member. When the power is turned on after being left inactive, the developing section is operated to stir the developer, and when the output value of the magnetic sensor 5 is higher than a predetermined toner concentration control value, the output value of the magnetic sensor 5 reaches a predetermined value. The toner replenishing section replenishes toner to the developing section until the toner concentration control value is reached, and when the toner replenishment has elapsed for a predetermined time, the output value of the magnetic sensor 5 does not reach the predetermined toner concentration control value. control means 6 for causing the toner replenishing section to stop toner replenishment and ending developer agitation in the developing section; and the driving source, the developing bias power source, the cleaning device, and the static eliminator when stirring the developer in the developing section. and a control means 7 for operating the device, and the invention according to claim 5 includes:
a developing section that stirs a developer consisting of toner and carrier and uses the developer to develop a latent image on an image bearing member; a toner replenishing section that supplies toner to the developing section; and a toner and carrier of the developer. and a magnetic sensor that detects the mixing ratio of the developer, and when the power is turned on after being left inactive, the developing section is operated to agitate the developer, and the toner concentration of the developer is determined based on the output value of the magnetic sensor. In a developing device of an image forming apparatus in which toner replenishment of the toner replenishing section is controlled such that the toner replenishment portion becomes a predetermined value, when the output value of the magnetic sensor 8 is higher than a predetermined toner concentration control value, a predetermined toner concentration increase occurs. According to claim 6, the toner replenishing unit is provided with a control means 9 for causing the developing unit to replenish toner to the toner replenishing unit.
In the developing device according to claim 5, in the developing device, the output value of the magnetic sensor 8 before and after the toner replenishment is compared, and if the output value after the toner replenishment is not higher than the output value before the toner replenishment is performed. According to a seventh aspect of the present invention, in the developing device according to claim 6, the toner end detecting means performs the comparison a plurality of times to perform toner replenishment. The toner end is displayed (11) when the output value after toner replenishment is not higher than the previous output value for a predetermined number of times.

[0007]

[Operation] In the invention of claim 1, the control means 2 operates the developing section to stir the developer when the power is turned on after the image forming apparatus is left inactive, and the output value of the magnetic sensor 1 controls the predetermined toner concentration. When the output value of the magnetic sensor 1 reaches a predetermined toner concentration control value, the toner replenishing section replenishes toner to the developing section.

In the second aspect of the invention, the control means 3 operates the developing section to stir the developer when the power is turned on after the image forming apparatus is left inactive, so that the output value of the magnetic sensor 1 adjusts to a predetermined toner concentration control level. When the output value of the magnetic sensor 1 reaches a predetermined toner concentration control value, the toner replenishing section intermittently supplies toner to the developing section.

In the third aspect of the invention, the control means 4 operates the developing section to stir the developer when the power is turned on after the image forming apparatus has been left inactive, so that the output value of the magnetic sensor 1 is adjusted to a predetermined toner concentration control level. When the output value of the magnetic sensor 1 reaches a predetermined toner concentration control value, the toner replenishing section replenishes toner to the developing section. However, the control means 4 causes the toner replenishing section to stop toner replenishment even if the output value of the magnetic sensor 1 does not reach the predetermined toner density control value when the toner replenishment has elapsed for a predetermined time, and the developing section performs the development. Finish stirring the agent.

In the fourth aspect of the invention, when the control means 6 operates the developing section to stir the developer when the power is turned on after being left inactive, and when the output value of the magnetic sensor 5 is higher than a predetermined toner concentration control value, The toner replenishing section replenishes toner to the developing section until the output value of the magnetic sensor 5 reaches a predetermined toner density control value, and when the toner replenishment has elapsed for a predetermined time, the output value of the magnetic sensor 5 reaches the predetermined toner density control value. Even if the toner concentration control value is not reached, the toner replenishing section is made to stop toner replenishment, and developer agitation in the developing section is ended. Further, the control means 7 operates the driving source, the developing bias power source, the cleaning device, and the static eliminator when stirring the developer in the developing section.

In the fifth aspect of the invention, when the output value of the magnetic sensor 8 is higher than a predetermined toner concentration control value, the control means 9 causes the toner replenishing section to replenish toner by a predetermined increase in toner concentration to the developing section. .

In the sixth aspect of the invention, when the output value of the magnetic sensor 8 is higher than a predetermined toner concentration control value, the control means 9 causes the toner replenishing section to replenish toner by a predetermined increase in toner concentration to the developing section. . Furthermore, the toner end detection means 10 compares the output value of the magnetic sensor 8 before and after toner replenishment, and displays the toner end if the output value after toner replenishment is not higher than the output value before toner replenishment. conduct.

In the seventh aspect of the invention, when the output value of the magnetic sensor 8 is higher than a predetermined toner concentration control value, the control means 9 causes the toner replenishing section to replenish toner by a predetermined increase in toner concentration to the developing section. . Furthermore, the toner end detection means 11 compares the output value of the magnetic sensor 8 before and after toner replenishment multiple times, and if the output value after toner replenishment is not higher than the output value before toner replenishment is performed, a predetermined number of times. As a result, toner end is displayed.

[0014]

Embodiment FIG. 8 shows a first example of a copying machine to which the present invention is applied. This copying machine is an example in which the present invention is applied to a color copying machine having a plurality of developing devices. A photosensitive drum 21 serving as an image carrier is rotationally driven by a main motor (not shown) during a copying operation, is uniformly charged by a charging charger 22, and then subjected to image exposure by an exposure device 23 to form an electrostatic latent image. In the exposure device 23, the document mounting table 24
The upper document is illuminated by the illumination device 25, and the reflected light is irradiated onto the photosensitive drum 21 via the mirrors 26 to 28, the lens 29, the mirror 30, and the filter device 31. By moving it, optical scanning is performed and color components corresponding to the color separation filter of the filter device 31 in the document are exposed on the photoreceptor drum 21 to form an electrostatic latent image. The color filter device 31 has red, green, and blue color separation filters and an ND filter, and these filters connect the mirror 30 and the photosensitive drum 21.
By selectively inserting the electrostatic latent images between the red, green, blue, and black color components, electrostatic latent images are selectively formed. Note that the ND filter may not be used when forming the electrostatic latent image of the black component. After the electrostatic latent image is formed on the photosensitive drum 21, unnecessary portions are neutralized by the eraser 20.

When an electrostatic latent image of a black component is formed on the photoreceptor drum 21, this electrostatic latent image of a black component is processed by a black developing device 32 using a two-component developer containing a black toner and a carrier. It is developed into a black image, and transferred to the transfer drum 33.
The image is transferred by the transfer charger 34 to the transfer paper that is held wrapped around the image. The transfer paper is fed by a paper feeder 35 and transferred to the photosensitive drum 2 by a registration roller 36.
It is sent out at a time when the tip aligns with the visible image on 1.
It is wound around and held on the transfer drum 33. After the black developed image is transferred, the photosensitive drum 21 is neutralized by a pre-cleaning static eliminating charger 37, and residual toner is removed by a magnetic brush cleaning device 38, making it possible to form the next image. Through such operations, a developed image of the black component is formed and transferred.

Further, in the same way as the formation and transfer of a developed image of the black component, the formation and transfer of developed images of the other three color components are performed. However, the electrostatic latent images of each color component of red, green, and blue formed on the photoreceptor drum 21 are processed by the developing devices 39 to 39 for each color.
At step 41, the image is developed with a two-component developer containing toner of each color of cyan, magenta, and yellow and a carrier to form a developed image of each color, which is transferred to a transfer paper on a transfer drum 33.

In the copy mode for monochrome copying, a developed image of a black component is formed and transferred, or a developed image of another one color component is formed and transferred, and then the transfer paper on the transfer drum 33 is transferred to a separate charger. 42 and separation claws 43 , the transfer drum 33 is separated from the transfer drum 33 and transported by a transport device 44 . The developed image is fixed on this transfer paper by a fixing device 45,
A single color copy is delivered to the tray 46. In a color copy mode in which two or more color components are combined, the formation and transfer of developed images of each color component are performed sequentially for two or more color components, and the developed images of two or more color components are transferred to the transfer paper on the transfer drum 33. The transfer paper on the transfer drum 33 is separated from the transfer drum 33 by a separation charger 42 and a separation claw 43 and is transported by a transport device 44. The developed image is fixed on this transfer paper by a fixing device 45, and the paper is discharged to a tray 46 as a color copy.

The copying operation described above is performed continuously for the set number of copies by turning on the print switch. The fixing device 45 is, for example, one that fixes the developed image on the transfer paper by applying heat and pressure when the transfer paper from the conveying device 44 passes between fixing rollers 45a and 45b. The rollers 45a and 45b are heated by a heater. The fixing temperature of the fixing device 45 is detected by a temperature detection element consisting of a thermistor, and based on the temperature detection signal from the thermistor, the fixing temperature control unit controls the power supply from the power supply to the heater so that the fixing temperature becomes a set temperature close to 200°C. Control.

FIG. 9 shows the structure of the black developing device 32. As shown in FIG. The black developing device 32 includes a developing section 32a and a toner replenishing section 32b.
It is made up of. In the developing section 32a, a paddle 47, a developing sleeve 48, an agitator 49, etc. are rotationally driven by a developing motor via a toner supply clutch, and a magnetic roller is provided inside the developing sleeve 48. The developer in the developing container 50 is stirred by the paddle 47 and conveyed by the developing sleeve 48, and then transferred to the doctor 51.
After being scraped off to a certain amount by the developer sleeve 48 and the photoreceptor drum 21, the black electrostatic latent image on the photoreceptor drum 21 is visualized. Thereafter, the developer is returned to the developer container 50 through the development gap, separated from the developer sleeve 48 by the paddle 47, stirred, and passes through the toner concentration sensor 52. Developing sleeve 4
The developer scraped off from 8 by the doctor 51 returns into the developer container 50 via the separator 53 and is stirred by the paddle 47.

In the toner replenishing section 32b, when the toner replenishing clutch is turned on, an agitator (not shown) in the toner hopper 32 is rotated by the developing motor, and the toner in the toner hopper 32 is sent to the toner replenishing roller 55. When the toner replenishment clutch is turned on, the toner replenishment roller 55 is rotationally driven by the developing motor, and the toner is scraped off from the toner replenishment roller 55 by a seal 56 made of urethane foam or the like that is bitten into the toner replenishment roller 55, and the toner is removed from the developer container. Fall within 50. This fallen toner is agitated with the developer by an agitator 49. A developing bias voltage is applied to the developing sleeve 48 from a developing bias power source, and a differential transformer type magnetic sensor is used as the toner concentration sensor 52. By detecting the magnetic permeability of the developer within its detection range, the toner concentration sensor 52 detects the developer. Detects the mixing ratio of toner and carrier.

FIG. 10 shows the control system of this embodiment. The toner concentration detection means 57 is constructed using the above-mentioned toner concentration sensor 52, and magnetically detects the mixing ratio of the toner and magnetic carrier of the two-component developer in the developing section 32a. The analog output signal of this toner concentration detection means 57 is sampled and A/D converted by a central control unit (CPU) 58 having a sample storage function. The control system in which each part of this embodiment is controlled by the CPU 58 includes an operation section 59 having a print switch, a numeric keypad, a sheet count display means, etc., a clock means 60, which are connected to the CPU 38, and a main motor that drives the photoreceptor drum 21, etc. 61, a cleaning motor 64 for driving the developing motor 62, the toner supply clutch 63, the cleaning device 38, and a cleaning bias for applying a bias to the magnetic brush roller of the cleaning device 38 to remove toner from the photosensitive drum 21; A driver 67 is connected to the CPU 58 for driving a power source 65, the pre-cleaning static elimination charger 37, a developing bias power source 66 for applying a developing bias voltage to the developing sleeve 48 in the developing device 32, and the like. The CPU 58 takes in input signals from the numeric keys, etc. of the operating section 59, and controls the sheet number display means, etc. of the operating section 59. Further, the CPU 58 takes in an input signal from the toner concentration detection means 57 and sends it to the main motor 61 via the driver 67.
, development motor 62, toner replenishment clutch 63, cleaning motor 64, cleaning bias power supply 65, pre-cleaning static elimination charger 37, development bias power supply 66
control etc.

By the way, since the charging ability of the carrier of the developer changes between the initial stage and the time that passes thereafter, even if the toner concentration is constant, the toner on the photoreceptor drum 21 changes due to the difference in the amount of charge of the carrier over time. The amount of adhesion changes. Generally, a developed image is formed on the photoreceptor drum 21 under certain image forming conditions, and the density of the developed image is detected by a reflective photosensor and fed back to the toner replenishing section, thereby increasing the density of the copied image. We use a method that does not change over time. However, in this method, the control value of toner density is often varied using a reflective photosensor. In this embodiment, the toner hopper 32 is filled with toner, and when the toner and carrier mixture ratio (toner concentration) detected by the toner concentration sensor 52 is small and the developer is insufficient, toner is replenished. When the clutch is turned on, the toner supply roller 55 is driven to rotate, and the toner hopper 3
The toner in 2 is supplied to the developing section 32a.

FIG. 11 shows the toner density control flow of the CPU 58. The CPU 58 checks the print signal from the print switch, and when the print switch is turned on, controls each section 61, 62, 63, . . . of this copying machine via the driver 67 to start the copying operation as described above. Each time a copying operation is performed, the toner density signal Dx from the toner density detection means 57 is sampled once and compared with the toner density control value D0. And C
PU58 operates toner replenishment clutch 63 when Dx>D0.
for a predetermined time (within the time required for one copying operation)
is turned on via the driver 67 to replenish toner. Further, when Dx>D0, the CPU 58 turns off the toner replenishment clutch 63 via the driver 67,
Do not replenish toner. After the CPU 58 continuously performs such an operation for the number of sheets set by the operation unit 59, the CPU 58 terminates the operation by turning off each unit 61, 62, 63, . . . via the driver 67. The toner concentration of the developer in the developing section 32a is stabilized at the toner concentration control value D0 by toner replenishment according to the toner concentration signal Dx from the toner concentration detection means 57 described above.

FIG. 12 shows a normal toner end detection flow for explaining this copying machine. In this toner end detection flow, the CPU 58 clears the counter C0 to 0 at the initial stage when the power is turned on, and each unit 61, 62,
63 .
2, the toner concentration signal Dx from the toner concentration detection means 57 is sampled. Next, the CPU 58 compares the toner density signal Dx sampled this time with the toner density control value D0+a (value of a predetermined number of bits), and compares the toner density signal Dx sampled this time with
If not D0+a), repeat the above operation. Also,
When Dx>(D0+a), the CPU 58 recognizes that the toner density is higher than the expected value, adds 1 to counter C0, stores the value in counter C, and stores this value in counter C.
By determining whether the value of has become, for example, 10 or more, it is determined whether this state has continued for more than one copying operation (for example, 10 times) (for 10 copies). When the value of the counter C does not reach 10, the CPU 58 returns to the step of performing the above-described copying operation, but when the value of the counter C reaches 10 or more, the toner replenishing section 32b in the developing device 32 performs the toner replenishing operation. Despite the execution, the toner hopper 54 to the developing unit 32
It is determined that toner has not been replenished in the toner hopper 54 (that is, the toner is in an end state where there is no toner in the toner hopper 54), and the display of the operation unit 59 displays toner end to prompt the user to replenish toner in the toner hopper 54. prompt.

Normally, the amount of toner consumed in one copying operation (copying operation for one sheet of transfer paper) can be replenished by one toner replenishing operation of the toner replenishing section 32b. As long as the replenishment amount is set and there is toner in the toner hopper 54, the toner concentration signal Dx from the toner concentration detection means 57 will not significantly exceed the toner concentration control value D0. If the above a is too large, the toner concentration of the developer in the developing section 322a will drop too much when the toner end is displayed based on the toner end judgment, and on the other hand, if the a is too small, the toner end may be falsely detected. There is sex. Therefore, it is necessary to set a to an appropriate value so that these problems do not occur.

[0026] In addition, normally, if the document area ratio (the area ratio of the image area to the entire document) is about 60% or less, the toner replenishment amount of the toner replenishing section 32b is often designed to be able to follow the same. , all solid originals (original area ratio is 10)
0% original), the toner replenishment amount of the toner replenishing section 32b cannot follow the toner consumption due to development in the developing section 32a. In other words, the toner replenishing ability of the toner replenishing section 32b is not guaranteed for such a document with a high document area ratio. This is because if the amount of toner replenished at one time by the toner replenishing section 32b is too large, the agitation of the developer in the developing section 32a will not keep up and the charging of the toner will become insufficient, causing background stains and causing toner to leak into the developing device. In reality, it is difficult to replenish a large amount of toner all at once because this may easily cause problems such as toner scattering outside the toner.

In the processing flow of FIG. 12, Dx>(D
0+a) 10 or more times in a row, the toner density is recognized to be higher than the expected value.For documents with a high document area ratio as described above, the toner hopper 5
Even if there is toner in the toner 4, the toner replenishment in the toner replenishing section 32b does not follow the toner consumption due to development in the developing section 32a, so Dx>(D0+a). have. In other words, if the number of 10 times is small, it will be easier to falsely detect toner end, and conversely, if the number of 10 times is large, it will be difficult to falsely detect toner end, but the toner density will drop when the toner is actually end. Therefore, the above 10 times is a reasonable value in this embodiment. In other image forming apparatuses, the number of times of ten times described above may be set to another number of times that is appropriate for the apparatus.

[0028] If the toner end detection is performed as described above,
In particular, there is no need for a dedicated toner end detection sensor for directly detecting that the toner in the toner hopper 54 has run out, and the number of parts can be reduced, resulting in a cost advantage.

However, with only the above-described configuration of this embodiment, the following problems occur. first,
The amount of charge on the toner tends to increase when the developing device 32 is continuously operating, and tends to decrease when the developing device 32 is not operating and is left alone. Furthermore, the degree of aggregation of the developer in the developing section 32a differs between when the developing device 32 is in operation and when it is left standing. Furthermore, during a copying operation, the temperature inside the copying machine rises and the temperature of the toner concentration sensor 52 rises. The output value of this toner concentration sensor 52 tends to fluctuate somewhat due to changes in temperature.

Due to these factors, the toner concentration sensor 52
The output value sampled after the end of the continuous copying operation and the output value sampled after leaving it for one day, for example, are completely different from the developing unit 32 between the two samplings.
Although there is no toner balance (consumption and replenishment) of the developer in a, it often changes. In reality, the output value of the toner density sensor 52 sampled after being left for one day is considerably higher than the output value of the toner density sensor 52 sampled after the continuous copying operation has ended. In this state, when the output value of the toner concentration sensor 52 is considerably high, the toner concentration sensor 52 detects the toner concentration as being lower than the toner concentration control value D0, and the toner end detection described above means that the toner concentration sensor 52 detects the toner concentration as being lower than the toner concentration control value D0. It is easy to falsely detect the end. In other words, if the output value D' of the toner density sensor 52 sampled after being left for one day becomes D'≫(D0+a), the toner density sensor In some cases, the toner density cannot be recovered so that the output value of 52 becomes equal to or less than (D0+a). Since toner is consumed during development in the copying operation, the toner density of the developer does not increase rapidly even when toner is replenished, and by the time the output value of the toner density sensor 52 falls below (D0+a), the original area has The higher the rate, the more times the toner needs to be replenished.

Therefore, in this copying machine, the CPU 58 is as shown in FIG.
Execute the toner end detection flow shown in 3. CPU5
8, when the power is turned on, the above-mentioned fixing device 45 is first activated.
, a temperature detection signal from a temperature detection element consisting of a thermistor for detecting the fixing temperature is checked to determine whether the fixing temperature f of the fixing device 45 is 50° C. or lower. C
If the fixing temperature f is below 50°C, the PU58 determines that this copying machine has been left in a non-operating state with the power turned off for a long time before starting the current operation, and from now on, It is called. Here, when the power of this copying machine is turned off after the continuous copying operation is completed, the heater of the fixing device 45 is also turned off, and the fixing temperature of the fixing device 45 decreases. The fixing temperature of the fixing device 45 is controlled to a set temperature of nearly 200° C. by the fixing temperature control section when the copying machine is in operation, and eventually decreases to room temperature when the copying machine is left alone. Therefore, the CPU 58 determines whether the present copying machine has been left unattended based on the fixing temperature of the fixing device 45. Of course, the CPU 58 may use a timer or the like to detect whether the copying machine has been left unattended by counting the time since the power was turned off.

First thing in the morning, the developer in the developing section 32a has aggregated, the amount of charge has decreased, and the temperature of the toner concentration sensor 52 has also decreased. Further, in this copying machine, there is usually a warm-up time for heating the fixing device 45 and the like after the power is turned on and before copying operation is possible.

Therefore, the CPU 58 uses the warm-up time to control the developing motor 62 via the driver 67.
By rotating the main motor 61, the developing device 32 and the photoreceptor drum 21 are operated, increasing the amount of charge of the toner and reducing aggregation of the developer. In this case, the CPU 58 includes the developing bias power supply 66, the eraser 20
, the pre-cleaning static elimination charger 37, the cleaning motor 64, and the cleaning bias power supply 65 are connected to the driver 6.
Turn it on via 7. The mode in which the developing device 32 and the like are operated in this manner first thing in the morning will hereinafter be referred to as the first morning agitation mode. In the first stirring mode that morning, the CPU 58 samples the toner concentration signal Dx from the toner concentration detection means 57 and compares it with the toner concentration control value D0, and determines that Dx>D.
0, the toner replenishment clutch 63 is turned on for 4 seconds via the driver 67 and the toner replenishment roller 55 is turned on.
Toner is replenished by rotating the . Then, C
The PU 58 stops toner replenishment by turning off the toner replenishment clutch 63 for 2 seconds via the driver 67 and stopping the toner replenishment roller 55, and samples the toner concentration signal Dy from the toner concentration detection means 57 to determine the toner concentration. Compare with control value D0. And CPU5
8, if Dy≦D0, the process returns to the step of turning on the toner replenishment clutch 63 for 4 seconds and repeats the above operation, and when Dy≦D0, the developing motor 62 is turned off via the driver 67, thereby turning on the developing section 32a. and stop the main motor 61 and developing bias power supply 6.
6, Eraser 20, Pre-cleaning static elimination charger 37
, the cleaning motor 64 and the cleaning bias power supply 65 are turned off via the driver 67. Also, CPU
58 stops the developing section 32a by immediately turning off the developing motor 62 via the driver 67 when Dx>D0 is not found in the above comparison, and also stops the developing section 32a.
Also, the developing bias power source 66, eraser 20, pre-cleaning charger 37, cleaning motor 64, and cleaning bias power source 65 are turned off via the driver 67.

In this way, in the morning stirring mode, toner is replenished to return the toner concentration signal from the toner concentration detection means 57 to the toner concentration control value D0, thereby preventing erroneous detection of toner end. Furthermore, if toner is continuously replenished in the first-morning agitation mode, toner replenishment efficiency may deteriorate due to insufficient charging of toner or toner scattering. Therefore, as described above, the occurrence of this problem is prevented by performing toner replenishment intermittently, such as for 4 seconds and stopping for 2 seconds.

As described above, according to the present copying machine, when the power is turned on after being left inactive, the developing section 32a is operated to stir the developer, and the output value of the toner concentration sensor 52 consisting of a magnetic sensor is controlled to control the toner concentration. When the output value of the magnetic sensor 52 is higher than the toner concentration control value D0, the toner replenishing section 32b replenishes toner to the developing section 32a until the output value of the magnetic sensor 52 reaches the toner concentration control value D0, so that fluctuations in the output value of the toner concentration sensor can be compensated for. , When the power is turned on after being left inactive, the output value of the toner concentration sensor becomes too high than the toner concentration control value D0, resulting in erroneous detection of toner end, excessive toner replenishment, background staining, and toner scattering. It is possible to prevent problems such as Furthermore, since toner replenishment is performed intermittently in the first morning agitation mode, it is possible to prevent toner from being insufficiently charged or from scattering, thereby increasing toner replenishment efficiency.

By the way, in the copying machine described above, if the first morning agitation mode takes a long time, temporarily the developing section 32a
Even if the toner concentration of the developer in the developer has not recovered to the toner concentration control value D0, the first morning agitation mode may be terminated at the same time as a predetermined time elapses. If this is done, the warm-up time will be shortened and it will be easier to use, and the user will not care if the warm-up time is too long. Therefore, if the output value of the toner concentration sensor is brought close to the toner concentration control value D0 in the morning stirring mode, even if only within the allowable time, the possibility of erroneous ener end detection is reduced.

The second embodiment of the present invention has been developed with attention to this point, and FIG. 14 shows the toner end detection flow of the CPU in this second embodiment. This second embodiment is different from the CPU 5 in the first embodiment.
8 is an example in which the toner end detection flow shown in FIG. 14 is executed instead of the toner end detection flow shown in FIG. 13. In this toner end detection flow, when the fixing temperature f is 50° C. or less, the CPU 58 clears the timer t to 0, and then rotates the developing motor 62 and the main motor 61 via the driver 67 to turn on the developing bias power supply 6.
6, Eraser 20, Pre-cleaning static elimination charger 37
, the cleaning motor 64 and the cleaning bias power supply 65 are turned on. Thereafter, the CPU 58 turns on the timer t to start measuring time, and when the timer t does not reach the allowable time t0, the CPU 58 turns on the toner concentration detection means 57 described above.
The process proceeds to the step of sampling the toner density signal Dx from the . However, the CPU 58 determines that the timer t is the allowable time t.
When it reaches 0, the developing unit 32a is stopped by turning off the developing motor 62, and the main motor 61, developing bias power source 66, eraser 20, pre-cleaning static elimination charger 37, cleaning motor 64, and cleaning bias power source 65 are switched to the driver 67. Turn it off via .

[0038] Also, in the morning stirring mode, the developing section 32a
If the photoreceptor drum 21 is stopped while the developer is being stirred, the developer is always rubbed against the same part of the photoreceptor drum 21, and toner and carrier tend to stick to the photoreceptor drum 21, causing the photoreceptor to This may cause adverse effects such as deterioration of the body drum 21 or generation of band-shaped toner streaks on copied images during copying operations. In addition, the developer on the developing sleeve 48 is affected by the stoppage of the photoreceptor drum 21 and lacks smooth flow, and the developer accumulates in the wedge-shaped space formed between the developing sleeve 48 and the photoreceptor drum 21, and eventually There is a possibility that the developer may overflow or the driving of the developing sleeve 48 and the photosensitive drum 21 may be locked.

Therefore, the developing section 32 is set in the stirring mode first thing in the morning.
When the developer is being stirred in step a, the CPU 58 turns on/off the main motor 61 and the developing motor 62 at the same time as the developing unit 3 through the driver 67 as described above.
2a and the photosensitive drum 21 are operated simultaneously. In this case, the CPU 58 turns off the charger 22 and turns on the developing bias power supply 66, the eraser 20, and the pre-cleaning charger 37 via the driver 67 so that toner is less likely to adhere to the photosensitive drum 21. In addition, in order to clean residual toner on the photoreceptor drum 21 that causes background smearing, the CPU 58 operates a cleaning motor 64,
The cleaning device 38 is operated by turning on the cleaning bias power supply 65 via the driver 67.

As described above, according to the second embodiment, when the predetermined time has elapsed since toner replenishment, the magnetic sensor 52
Even if the output value does not reach the predetermined toner concentration control value D0, the toner replenishing section 32b is made to stop toner replenishment and the developing section 32
Since the stirring of the developer in step (a) is completed, the warm-up time is shortened, making it easier to use, and the possibility of erroneous ener-end detection is also reduced. In addition, the developing section 32 is operated in the stirring mode first thing in the morning.
Since the main motor 61, developing bias power supply 66, cleaning device 38, and static eliminators 20 and 37 are operated when stirring the developer in step a, the developer is not always rubbed against the same part of the photoreceptor drum 21, and the photosensitive drum 21 is not exposed to light. body drum 21
This prevents toner and carrier from sticking to the photoreceptor drum 21 and prevents the photosensitive drum 21 from deteriorating and from forming band-like toner streaks on the copied image during copying operations. Furthermore, the developer on the developing sleeve 48 is no longer affected by the stoppage of the photoreceptor drum 21 and lacks smooth flow, and the developer flows into the wedge-shaped space formed between the developing sleeve 48 and the photoreceptor drum 21. It also eliminates the possibility of accumulation and overflowing or locking of the driving of the developing sleeve 48 and photoreceptor drum 21.

In the copying machine described above, when the output value of the toner concentration sensor 52 is extremely high first thing in the morning, if toner is replenished in the first morning stirring mode until the output value of the toner concentration sensor 52 reaches the toner concentration control value D0. There is a possibility that the toner density increases too much, resulting in the density of the copied image being too high, the background of the copy being smudged, or the toner scattering. Therefore, it is conceivable to avoid toner replenishment to the point where such a problem occurs. Since it is uniquely determined by how many bits the output value of the toner concentration sensor 52 decreases by what percentage the toner concentration increases.
It is only necessary to limit the increase in toner concentration due to toner replenishment to an extent that does not cause the above-mentioned problems.

The third embodiment of the present invention was created based on this idea, and FIG. 15 shows the flow of toner end detection by the CPU in this third embodiment. In this third embodiment, in the first copying machine, the CPU
58 is shown in FIG. 15 instead of the toner end detection flow in FIG. 13.
The toner end detection flow is executed. In this toner end detection flow, the CPU 58 detects that when the output value Dy of the toner concentration detection means 57 becomes lower than the initial output value Dx of the toner concentration detection means 57 by some bits,
For example, when the bit decreases by 5 bits, toner replenishment is terminated. That is, the CPU 58 converts the sampled toner density signal Dy from the toner density detection means 57 into the toner density control value D.
Instead of comparing with 0, compare Dx-Dy with 5 and Dx-
If Dy is 5 or more, turn the toner replenishment clutch 63 4se.
Returning to the step of turning on only c, toner replenishment is performed intermittently as described above. However, the CPU 58
When Dy is no longer 5 or more, the developing motor 62 is stopped via the driver 67 to finish toner replenishment,
Then, the main motor 61 , the developing bias power supply 66 , the eraser 20 , the pre-cleaning charger 37 , the cleaning motor 64 , and the cleaning bias power supply 65 are turned off via the driver 67 . As a result, the toner concentration does not rise above the allowable limit value, and the increase in toner concentration can be kept below the allowable limit value, thereby preventing the above-mentioned problems.

Furthermore, it is possible that there is actually no toner in the toner hopper 54 first thing in the morning, and in this state, a copying machine that implements the toner end detection flow as shown in FIG. The toner end is detected only when it is time to make a copy. However, for copying machines that use the first-morning agitation mode mentioned above, it is possible to detect toner end earlier in the first-morning agitation mode, and in this way, toner can be replenished before the density of the copied image becomes thinner. The portion 32b can be replenished with toner. In other words, if the toner end is detected in the toner end detection flow shown in FIG. 12 while performing a copying operation, the density of the copied image inevitably becomes low. However, if the toner end is detected in the morning agitation mode, such problems can be alleviated.

The fourth embodiment of the present invention has been developed with attention to such points, and FIG. 15 shows a part of the processing flow of the CPU in this fourth embodiment. In this fourth embodiment, in the third embodiment described above, the CPU 58 checks the temperature detection signal from the temperature detection element consisting of a thermistor for detecting the fixing temperature of the fixing device 45, and detects the fixing temperature of the fixing device 45. It is determined whether or not the fixing temperature f of 45 is 50° C. or lower, and if the fixing temperature f is 50° C. or lower, it is determined that it is first thing in the morning, and the developing device is rotated by rotating the developing motor 62 and the main motor 61. 32 and the photosensitive drum 21, and the developing bias power supply 66, the eraser 20, and the pre-cleaning static elimination charger 3.
7. Turn on the cleaning motor 64 and cleaning bias power supply 65 via the driver 67. And C
The PU 58 samples the toner concentration signal Dx from the toner concentration detection means 57 and compares it with the toner concentration control value D0. Since Dx>D0, the PU 58 clears the counter C0 to 0 and then activates the toner replenishment clutch via the driver 67. 6
3 is turned on for 4 seconds to rotate the toner replenishing roller 55 to replenish toner. Then the CPU
58 is a toner supply clutch 63 via a driver 67
is turned off for 2 seconds to stop the toner replenishment roller 55 to stop toner replenishment, and the toner density signal Dy from the toner density detection means 57 is sampled and compared with the first toner density signal Dx. And CPU5
8, if Dx-Dy≦0, returns to the step of clearing the counter C0 to 0 and repeats the above operation, and Dx
When −Dy≦0, 1 is added to counter C0 and the value is stored in counter C, and this is done by determining whether the value of counter C has reached multiple times, for example, 5 times or more. Determine whether the condition has occurred five or more times in a row.

Here, when there is no toner in the toner hopper 54, toner is not replenished even if the toner supply roller 55 is rotated, so when Dx-Dy≦0, there is no toner in the toner hopper 54. It can be determined that However, if Dy and Dx are compared only once, it may not be possible to accurately compare Dy and Dx due to various variations, so if Dy and Dx are compared only once, Dx- It is dangerous to judge that the toner has run out when Dy≦0. Therefore, in this example, when Dx-Dy≦0 occurs five times in a row, it is detected as toner end, thereby preventing erroneous detection of toner end.

That is, when the value of the counter C does not reach 5, the CPU 58 activates the toner supply clutch 63 for 4 seconds.
Returning to the step of turning on only C, when the value of the counter C becomes 5 or more, it is determined that the toner has run out, and the operation section 59 displays the toner end to prompt the user to replenish the toner supply section 32b with toner. In this case, Dx-D
It is not necessary to determine whether y is less than or equal to 0, and Dx-Dy may be compared with a natural number that is not very large, such as 1 or 2. In other words, if toner replenishment is actually performed, Dx-Dy will become a larger value, so the natural number may be set within an error range.

[0047]

[Effect of the invention] As described above, according to the invention of claim 1,
When the power is turned on after the image forming apparatus has been left inactive, the developing section is operated to stir the developer, and when the output value of the magnetic sensor for detecting toner concentration is higher than a predetermined toner concentration control value, the magnetic sensor is activated. Equipped with a control means that causes the toner replenishing section to replenish toner to the developing section until the output value reaches a predetermined toner concentration control value, it is possible to compensate for fluctuations in the output value of the magnetic sensor, and the power supply can be removed even after being left inactive. Prevents problems such as erroneous detection of toner end, excessive toner replenishment, background staining, and toner scattering due to the output value of the magnetic sensor becoming too high than the toner concentration control value at the time of loading. be able to.

Further, according to the invention of claim 2, claim 1
In the developing device described above, since the control means causes the toner replenishing section to replenish toner intermittently, it is possible to prevent insufficient charging of toner and scattering of toner, thereby increasing toner replenishment efficiency. can.

According to the third aspect of the invention, in the developing device according to the first aspect, the control means causes the output value of the magnetic sensor to reach a predetermined toner density control value when toner replenishment has elapsed for a predetermined time. Even if the toner is not reached, the toner replenishing section stops toner replenishment and developer agitation in the developing section is completed, so the warm-up time is shortened, making it easier to use, and reducing the possibility of erroneous ener end detection.

According to the fourth aspect of the present invention, when the power is turned on after being left inactive, the developing section is operated to stir the developer, the driving source for rotating the image carrier, the developing bias power source,
Since the cleaning device and the control means for operating the static eliminator are provided, the developer is not always rubbed against the same part of the image bearing member, and toner and carrier are not stuck to the image bearing member. It is possible to prevent the deterioration of the image quality and the occurrence of band-like toner streaks in the copied image during copying operations. Furthermore, the developer no longer flows smoothly due to the influence of the stoppage of the image carrier, and the developer no longer accumulates in the space between the developing device and the image carrier and overflows from there. This also eliminates the possibility that the drive of the carrier may become locked.

According to the fifth aspect of the present invention, when the output value of the magnetic sensor is higher than a predetermined toner concentration control value, the control means causes the developing section to replenish toner by a predetermined increase in toner concentration. As a result, the toner end can be detected early in the morning, and the toner replenishing section can be replenished with toner before the density of the copied image becomes low.

According to the invention of claim 6, in the developing device of claim 5, the output values of the magnetic sensor before and after toner replenishment are compared, and the output value after toner replenishment is higher than the output value before toner replenishment. Equipped with a toner end detection means that displays toner end when the toner is not high, it is possible to detect toner end early in the morning, and replenish toner in the toner replenishing unit before the density of the copied image becomes thin. It can be performed.

According to the seventh aspect of the present invention, in the developing device according to the sixth aspect, the toner end detection means performs the comparison a plurality of times to determine that the output value after toner replenishment is higher than the output value before toner replenishment. Since toner end is displayed when the toner is not high for a predetermined number of times, it is possible to detect toner end earlier in the morning.
It is possible to reliably replenish toner in a toner replenishing section before the density of a copied image becomes low.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the invention of claim 1.

FIG. 2 is a block diagram showing the invention according to claim 2.

FIG. 3 is a block diagram showing the invention according to claim 3.

FIG. 4 is a block diagram showing the invention according to claim 4.

FIG. 5 is a block diagram showing the invention according to claim 5.

FIG. 6 is a block diagram showing the invention according to claim 6.

FIG. 7 is a block diagram showing the invention according to claim 7.

FIG. 8 is a sectional view showing a first example of a copying machine to which the present invention is applied.

FIG. 9 is a sectional view showing the configuration of a developing device in the copying machine.

FIG. 10 is a block diagram showing a control system of the copying machine.

FIG. 11 is a flowchart showing a part of the processing flow of the CPU in the copying machine.

FIG. 12 is a flowchart showing a processing flow for explaining the copying machine.

FIG. 13 is a flowchart showing another part of the processing flow of the CPU in the copying machine.

FIG. 14 is a flowchart showing part of the processing flow of a CPU in a second example of a copying machine to which the present invention is applied.

FIG. 15 is a flowchart showing part of the processing flow of a CPU in a third example of a copying machine to which the present invention is applied.

FIG. 16 is a flowchart showing part of the processing flow of a CPU in a fourth example of a copying machine to which the present invention is applied.

[Explanation of symbols]

1, 5, 8 Magnetic sensor

Claims (7)

[Claims] 1. A developing section that stirs a developer made of toner and carrier and uses the developer to develop a latent image on an image bearing member; a toner replenishing section that supplies toner to the developing section; and a toner replenishing section that supplies toner to the developing section. a magnetic sensor that detects a mixing ratio of toner and carrier; and based on the output value of the magnetic sensor, toner replenishment of the toner replenishing unit is controlled so that the toner concentration of the developer becomes a predetermined value. In a developing device of an image forming apparatus, when the power is turned on after the image forming apparatus is left inactive, the developing section is operated to agitate the developer and the output value of the magnetic sensor is lower than a predetermined toner concentration control value. A developing device comprising: a control means for causing the toner replenishing section to replenish toner to the developing section until the output value of the magnetic sensor reaches a predetermined toner concentration control value when the output value of the magnetic sensor reaches a predetermined toner concentration control value. 2. The developing device according to claim 1, wherein said control means causes said toner replenishing section to replenish toner intermittently. 3. The developing device according to claim 1, wherein when the toner replenishment has elapsed a predetermined time, the control means controls the toner density control value even if the output value of the magnetic sensor does not reach a predetermined toner concentration control value. A developing device characterized by causing a toner replenishing section to stop toner replenishment and to terminate developer agitation in the developing section. 4. An image carrier on which an image is formed, a drive source for rotating the image carrier, a latent image forming means for forming a latent image on the image carrier, and a developer comprising toner and carrier. a developing section that agitates the developer and develops the latent image on the image carrier with the developer; a toner replenishing section that supplies toner to the developing section; a developing bias power source that applies a developing bias voltage to the developing section; and the developer. The developer has a magnetic sensor that detects a mixing ratio of toner and carrier, and based on the output value of the magnetic sensor, toner replenishment of the toner replenishing section is controlled so that the toner concentration of the developer becomes a predetermined value. An image forming apparatus comprising: a developing device, a transfer device that transfers the developed image to a transfer body, a cleaning device that cleans the image bearing member after the developed image transfer, and a static eliminator that neutralizes the image bearing member, When the power is turned on after being left inactive, the developing section is operated to stir the developer, and when the output value of the magnetic sensor is higher than a predetermined toner concentration control value, the output value of the magnetic sensor is set to a predetermined toner concentration control value. The toner replenishing section replenishes the toner to the developing section until the toner concentration reaches the predetermined toner concentration control value, and when the toner replenishment has elapsed for a predetermined time, the toner is supplied to the developing section even if the output value of the magnetic sensor does not reach the predetermined toner concentration control value. control means for causing a replenishment section to stop toner replenishment and to end agitation of developer in the development section; and control for operating the drive source, the development bias power supply, the cleaning device, and the static eliminator when agitating the developer in the development section; An image forming apparatus comprising: means. 5. A developing section that stirs a developer composed of toner and carrier and uses the developer to develop a latent image on an image bearing member; a toner replenishing section that supplies toner to the developing section; and a toner replenishing section that supplies toner to the developing section; a magnetic sensor that detects the mixing ratio of toner and carrier, and when the power is turned on after being left inactive, the developing section is operated to agitate the developer, and the developer is stirred based on the output value of the magnetic sensor. In a developing device of an image forming apparatus in which toner replenishment of the toner replenishing unit is controlled so that the toner concentration of the developer becomes a predetermined value, when the output value of the magnetic sensor is higher than a predetermined toner concentration control value, A developing device comprising a control means for causing the developing section to replenish toner by an amount corresponding to an increase in toner concentration. 6. In the developing device according to claim 5, when the output value of the magnetic sensor before and after the toner replenishment is compared, and the output value after the toner replenishment is not higher than the output value before the toner replenishment is performed. A developing device comprising a toner end detection means for displaying toner end. 7. The developing device according to claim 6, wherein the toner end detection means performs the comparison a plurality of times, and when the output value after toner replenishment is not higher than the output value before toner replenishment, the predetermined condition is determined. A developing device characterized by displaying an indication of toner end depending on the number of times the toner has been used.