JPH0218588A - Developing device - Google Patents

Abstract

PURPOSE:To replenish toner corresponding to actual toner density by varying the output set value of a toner density detection sensor for toner supply according to the conveying speed of a developer. CONSTITUTION:The output set value of the toner density detection sensor 82 is varied according to the conveying speeds of developer conveying machines 71 and 72 and the start period of the toner replenishment is so adjusted as to supply the toner when a developer passes a supply opening 81. Speed variation is performed when development is performed or not performed or at the time of image density adjustment. The output set value of the sensor 82 is switched by varying a comparative reference voltage. In another way, comparison data corresponding to various conveying speeds for the sensor output are stored in a ROM in a table and the toner supply corresponding to the conveying speed may be carried out according to the stored data. Consequently, uniform toner density is obtained and an image of high quality is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine or a laser beam printer, and particularly relates to a developing device using a two-component developer. It is something.

(Prior Art) This type of developing device is designed so that the l/toner concentration of the developer, that is, the amount of toner with respect to the carrier, is uniform.
The developer is stirred and conveyed in a circulation path so that the developer is suitably charged by FJ triboelectricity, and a portion of the developer is used for development along the way.

Further, it is desired that the latent image density after development is constant with respect to a specific set density. However, this causes a decrease in toner density and a decrease in image density.

To solve this problem, a conventional method has been to detect the toner concentration with a sensor and replenish the toner to the developer being circulated when the detected concentration is below a predetermined value (
JP-A-62-28780).

(Problems to be Solved by the Invention) Incidentally, as image forming apparatuses have become more sophisticated in recent years, the speed at which the developer is conveyed has also been changed according to the control mode.

However, with sensors that detect toner concentration as changes in magnetic permeability in response to carriers in the developer, it has been found that even if the toner concentration is the same, the output changes depending on the developer transport speed, and the image density It was found that this was the cause of the non-uniformity.

Therefore, in the present invention, even if the toner conveyance speed is changed in accordance with the control mode, it may be changed based on the actual speed regardless of the output fluctuation of the toner concentration detection sensor, and the The set value of the output of the concentration detection sensor may be switched based on information stored in advance.

(Function) The toner concentration of the developer being stirred and conveyed through the circulation path is detected by a concentration detection sensor. This detection output is given to the control means.

The control means activates the toner replenishment means to replenish toner when the detection output is less than a set value that is changed depending on the developer transport speed at that time. As a result, even if the developer conveyance speed is changed according to the control mode, toner can be replenished according to the actual toner concentration, regardless of the resulting fluctuation in the output of the l/toner concentration detection sensor. .

By setting the control modes for when the developer is in use and when it is not in use so that the transport speed when the developer is not in use is slower than when it is in use, the agitation, transport, and replenishment of developer can be controlled more easily than when the developer is in use. It is an object of the present invention to provide a developing device that can perform toner replenishment even when not in use and can replenish toner according to insufficient density.

(Another Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides for developing a two-component developer while stirring and conveying it in a circulation path, and also detects the toner concentration detected by a sensor. In a developing device that is equipped with a toner replenishing means that operates when the toner is less than a predetermined value, and whose conveying speed can be changed according to the control mode, the set value of the output of a toner concentration detection sensor that should perform toner replenishment is set according to the conveying speed. The invention is characterized in that it is equipped with a control means for changing.

The control mode for changing the conveyance speed is a development control mode and a non-development control mode, and the control mode for changing the conveyance speed is a control mode for changing the development speed to control image density adjustment. Sometimes.

Also, toner replenishment should be performed] - The set value of the output of the toner concentration detection sensor changes the comparison reference voltage.While preventing toner deterioration due to excessive stirring, the toner concentration is adjusted according to the actual toner concentration regardless of the difference in conveyance speed. It is possible to solve problems such as poor agitation of the replenished toner and poor toner concentration due to replenishment of toner.

In addition, by changing the developing speed, the amount of toner supplied to the developing section per unit time can be changed, and the electrostatic latent image can be developed without causing errors in determining the toner concentration due to changes in the conveying speed. Image density can be adjusted.

Furthermore, if the set value of the output of the toner concentration detection sensor for which toner replenishment is to be performed is switched by changing the comparison reference voltage, this can be reliably achieved with a simple configuration.

Furthermore, if this switching is done based on information stored in advance, various speed changes can be easily and accurately handled by using an appropriately set table or the like.

(Embodiment) FIG. 1 shows a simplified internal structure of a blue color copying machine 1 showing an embodiment of the present invention, and is equipped with four types of developing devices. The original written on the original glass 2 is exposed to a CCD line sensor 5 by an exposure lamp 3 and a lens array 4, and is colored R (let), G (green), and B (blue).
It is read as a color signal of three primary colors. The color signals of this PCB are converted into Y (yellow), M (
The signal is converted into a 3-value or 4-value signal obtained by adding 13k (blur, ri) to C (soan) or dirt, and is transmitted to the laser optical system 6 as an output J signal. The copying machine of this embodiment does not have image memory for three colors, and the image reader unit 7 scans each time when creating an image for each color.
Based on this, signals to Y, M, C or Y, M, C 113 are sequentially transmitted to the Rayleigh optical system 6c.

The laser optical system [3 is equipped with a scanning polygon mirror 8, an rθ lens 9, a refraction mirror 10, etc., and is capable of forming images for each color added to the Y, M, C or Y, M, C1Ilk (7) signals. Exposure is performed by irradiating a laser beam onto the photosensitive tram 11. Photosensitive paper cassette I/21a, 211
It is stored in a loaded state in I, and the supply ♀J (roller 22a
, 22h, etc., are fed into the apparatus one by one. Then, when the leading edge contacts the resostar 1m + - roller 23, the recording material 56 is stopped once to ensure subsequent timing, and at the same time, the toe correction is performed.

24 is a paper sensor used for this purpose.

A transfer tram 25 is provided at the transfer portion of the photosensitive tram 1.11 and is driven to rotate in the direction of the arrow. Inside the transfer drum 25, a suction charger 26, a transfer charger 27, and a separation charger 28 are arranged along the circumferential direction. Further, a transfer charger 29 is provided in the photosensitive 1-ram 11 opposite to the transfer charger 27, and a separate charger 2B
A separation charger 30 is disposed on the outer side of the transfer 1 ram 25, facing the transfer 1 ram 25.

Due to the exposure by the Rayleigh optical system 6, the photosensitive layer l, 1]
The electrostatic latent image formed on ``2'' is visualized as a 1~ner image by any one of the developing devices 16-19.

On the other hand, the recording material ram 11 fed from the sister i cola 23 is rotated in the direction of the arrow. The surface of the photosensitive I/ram 11 is provided with an organic photosensitive material that is laminated as a unit on a conductive substrate, and a material that exhibits particularly high sensitivity near a laser emission wavelength of 780 nm is used. Further, in this embodiment, the photosensitive tram 11 is negatively charged by a charger 12. Around the photosensitive drum 11 are a drum J, a cleaner 13, )/ner collection roll 14, an eraser lamp 15,
In addition to the charger 12, the four types of developing devices are also provided. The first developer 16 supplies yellow toner, the second developer 17 supplies magenta toner, the third developer 18 supplies cyan toner, and the fourth developer 19 supplies blank i・These toners are negatively charged.

Further, toner replenishment is carried out based on the replenishment signal, and the toner of each color stored in the toner hoppers 20a to 20d is sent to each developing device 16, 17, 18, and 19 through a pipe 8 (not shown) at an appropriate time.
This is done by transporting via.

Recording materials 56 such as plain paper and 011P film are fed to the feeder 56.
is gripped by the gripper 31 and transferred to the transfer tram 25.
As the transfer tram 2 rotates, the suction charger 26
5 and is wound onto the transfer drum 25 as the transfer drum 25 rotates. Then, while the recording material 56 passes between the transfer chargers 27 and 29, the toner image on the photosensitive drum 11 is transferred to the recording material 56. Note that in full color mode F, the recording material 56 is rotated four times by the transfer drum 25.

The recording material 56 for which the transfer process has been completed is transferred to the separation charter 28.
．． 30 , the toner is separated from the transfer drum 25 by a sorting claw 32 , and fed to a heat fixing device 40 by a transport heald 33 . The transferred recording material 564;1 is heated and pressurized each time it passes through the thermal fixing device 40, the image is fixed on the recording material 564;

As shown in FIGS. 2 and 3, each of the developing devices 16 to 19 mixes and stirs a two-component developer consisting of a mixture of toner and carrier, and connects a forward conveyance section 61 and a reverse conveyance section 62. A developer transport section 63 that repeatedly transports the developer in the direction of the arrow in FIG. The forward conveyance section 61 of the section 63 is provided with a toner storage section 66 for replenishing toner.

Each of the conveyance sections 61 and 62 has a gutter-like conveyance path formed adjacently by the bottom of the casing 67, and has a partition wall 70 between them.
partitioned by. However, there are communicating portions 70a and 70 at two locations on the left and right sides of this partition wall 70 in FIG.
b, and communicates with the conveying sections 61 and 62.

The forward conveyance section 61 is provided with a forward agitation conveyance roller 71 that agitates and conveys the developer from the left side to the right side in FIG. Reverse stirring conveyance roller 7 that conveys while stirring to the left side
2 is provided. Gorera stirring conveyance roller 71.72
The developer is transferred from the conveyance section 61, 62 to the communication section 70a.
, 70b while being circulated and stirred.

When the reverse direction agitation conveyance roller 72 faces the brush that conveys the developer conveyed through the reverse direction conveyance section 62 to the developing section 65, the magnetic poles (S) of the same polarity of the magnet member 75 are lined up next to each other at that part. Due to the formation of a repulsive magnetic field, the developer is separated from the developing sleeve 74, incorporated into the developer being conveyed through the reverse direction conveyance section 62, and is again circulated and conveyed.

On the other hand, a toner storage section 66 for replenishing toner is partitioned from the forward transport section 61 by a partition wall 80, and the toner pumper 2
Toner is replenished from 0a to 20d.

A toner replenishment port 81 is formed in a portion of the partition wall 80 on the downstream side of the forward conveyance section 61, and toner concentration detection sensors 82a to 82 are provided at appropriate positions upstream of the replenishment port 81.
d faces the conveyance section 61 from the toner storage section 66 side of each of the developing devices 16 to 19. Sensors 82a-82
The sensor surface d is smooth and substantially flush with the inner surface of the conveyance section 61.

The sensors 82a to 82d detect changes in the toner concentration contained in the developer as changes in magnetic permeability, and output the detected values to the CPU 201 shown in FIG. 5 as a control section. This CPU 201 has operation controls 1 to 73 for the copying machine.

The developing section 65 is made of a non-magnetic conductive material (for example, aluminum) and includes a developing roller 76 which has a magnetic section +A'15 built into a developing sleeve 74 that receives a bias voltage, and is attracted and held on the surface of the developing roller 76 to form a magnetic brush state. A height regulating member 77 is provided to regulate the height of the developer. Here, the developing sleeve 74 is supplied with the developer conveyed by the reverse agitation conveyance roller 72 through the reverse direction conveyance path 62 by scooping up the developer by the bucket 73, absorbs the developer onto the surface thereof, and conveys it to the photosensitive drum 11 side. . The conveyed developer forms a magnetic brush along the lines of magnetic force formed by the different magnetic poles of the magnetic member 75, and passes through the portion facing the photosensitive drum 4, forming an image on the surface of the drum. When the electrostatic latent image is rubbed, toner is attracted and transferred by a potential stronger than that of the developing sleeve 74 of the electrostatic latent image, and the electrostatic latent image is visualized.

The developer on the developing sleeve 74 after the above-mentioned development is
After that, it is transported and the bucket 730 rotates.

By the way, as the carrier material for the developer, an appropriate material is selected and used, such as magnetic iron powder, ferrite, those coated with a resin, or a material in which magnetic powder is dispersed in a resin material. In this example, magnetic ferrite (
A carrier coated with an acrylic resin and having an average particle diameter of φ-30 μm to 40 μm is used. On the other hand, the toner used is a hese made of polyester resin and has an average particle size of about φ-10 μm to 15 μm. The optimum mixing ratio of these carrier materials with toner is 7ωt%~
It is 10ωt%.

Inside the toner storage portion 66, there is a toner receiving port 66a above the toner storage portion 66.
A replenishment roller 83 is provided to collect the toner input through the replenishment port 81 and to prevent the toner from being sent out from the replenishment port 81.

As shown in FIG. 4, in each of the developing devices 16 to 19, the rotation of a dedicated developing motor 84a to 84d is transmitted to the rotating shaft 72a of the reverse stirring and conveying roller 72 via gears 85 and 86. The rotation of the rotating shaft 72a is controlled by gears 87, 88.
The rotation axis 71.1 of the forward stirring conveyor roller 71 via 89
L is transmitted. Further, the gear 86 is connected to the rotating shaft 83.3 of the supply roller 83 via a gear 90.93. When the motors 84a to 84d are driven by dirt, the stirring conveyance rollers 71, 72 and the replenishment t-1 roller 83 are simultaneously driven.

Furthermore, a gear 87 is connected to the rotating shaft 74a of the developing sleeve 74 by one of the sleeve flances 94a to 94d, and a gear 95.96.
．． They are connected via 97. Therefore, motor 84a
Even if ~84d is driven φ3, its rotation is due to the clutch 94a.
~94d is on or not, the developing sleeve 74
is driven or not.

When the developing devices 16 to 19 are not in use, they are driven to replenish toner, but once the developing sleeve 74 is stopped, toner is not supplied to the photosensitive tram 11, that is, development is not performed. This is to ensure that.

Replenishment motors 98a to 98d are installed in each of the toner poppers 20a to 20d. Supply motor 98a
The toner concentration must be detected in the corresponding developing device 16 so that the toner is delivered.

This timing adjustment is performed by adjusting the operation timing of the operation controller replenishment motors 98F] to 98d by the CPυ201, that is, the toner replenishment start timing. For this purpose, the CPU 201 is connected to the toner concentration detection sensors 82a to B2d via comparison circuits 202d to 202d, and driver circuits 203a to 203d for the developing motors 84a to 84d and replenishment motors 98a to 98.
8d tribar circuits 204a to 204d are connected. Further, the CPU 201 is connected to the ROM 205 as well as other inputs and outputs for controlling the operation of the copying machine 1.

Further, in this embodiment, each of the developing units 16 to 19 is sequentially selected and used to develop a full-color image, but even when not in use, they continue to be driven to agitate and transport toner and replenish 1-toner. I am working hard to make this possible. This makes it possible to eliminate the effects on image quality caused by a delay in the rise of toner concentration due to toner replenishment or insufficient stirring.

However, excessive agitation may cause the toner to melt onto the carrier surface.
When the toner concentration detection output from the toner bomber 2a is less than a predetermined value, tv+ is applied, and the toner from the toner bomber 2a is supplied to the toner storage section 66 of the developing device 16. At this time, in the toner storage section 66, the supplied toner is transferred to the toner replenishing port 81 by rotating the replenishing +λ shaft 83.
forward ffi] to the II sending section 71 for replenishment. Similarly, the other replenishment motors 98F1 to 98d are operated in response to the detection of toner concentration in the corresponding developing devices 17 to 19, and timely feed out the toner in the hoppers 2011 to 200d to remove the toner in the developing devices 17 to 19. The toner is supplied to the storage section 66 so that the toner is replenished.

As shown in FIG. 2, the toner supply port 81 is provided downstream of the toner concentration detection sensor 82 by a distance of 1 4ij+l. 1 at the toner concentration detection sensor 82.
In order to replenish the developer at ΔI- in FIG. 7, where the toner concentration is detected to be below a predetermined value, the developer at ΔL or the toner indicated by ΔL' in FIG. Mouth 81
When the developer reaches the position , the developer is deposited from the toner replenishing port 81 into the forward transport section 71 and deteriorates, such as causing charging failure. To prevent this, the developing motors 84a to 84d are
) Using the C speed control motor, the developing units 16 to 19 are controlled to be driven at a lower speed when they are not in use than when they are in use.

This control is performed by issuing a speed reduction signal when the developing sleeve clutches 94a to 94d are turned off at the end of development, and continuing for a certain period of time t1, as shown in FIG. Of course, the time L1 is determined regardless of the auto-soya of the main body of the copying machine.

The conveyance speed of the developer in the image forming devices 16 to 19 differs between when they are in use and when they are not in use. Due to this angle, the timing at which the developer whose concentration is detected by the toner concentration detection sensors 82a to 82d reaches the toner supply port also changes. For this reason, the toner replenishment start timing is also changed at the same time as the conveyance speed is changed.

Also, when the conveyance speed changes, the sensor 82 for toner concentration changes.
The output level of a to 82d changes. For example, the relationship between the rotational speed and sensor output of the forward stirring conveyance roller 71 is as shown in FIG. The number is 10Or,
When p and m are used, the relationship between the toner concentration and the sensor output is as shown in FIG. In order to cope with this, the comparison circuit 2
02a to 202d, as shown in FIG. 6, the reference voltage V I+ for the sensor output at high speed and the reference voltage V for the sensor output at low speed are switched and connected. This switching is performed automatically by relay contact 206.

Toner replenishment is performed even while developing units 16 to 19 are in use.
This is done every time it is detected that the l.color density is below a predetermined value, but when multi-copying is performed, a slowdown signal is also output when the developer is not in use between each copy, as shown in Figure 11. It is also possible to replenish toner while preventing excessive stirring. However, in order to ensure that this low-speed transport does not impair the stability of high-speed transport necessary for copying,
This is done with a margin of time t2 and t3 shown in the figure before and after.

Furthermore, in the above case, toner replenishment corresponding to the actual toner concentration was made possible by switching the comparison reference voltage for the output of the toner concentration detection sensor in response to changes in the conveyance speed. It is also possible to prepare a table of comparison data for the conveyance speed and store it in the ROM in advance, and toner replenishment according to the conveyance speed may be performed based on this data.

(Effects of the Invention) According to the present invention, in a developing device that circulates and conveys a two-component developer and performs development on the way, toner is replenished when the toner concentration detected by the concentration detection sensor is below a predetermined value. Even if the conveyance speed is changed according to the control mode, the setting value of the output of the density detection sensor for replenishing toner is changed according to the conveyance speed, so the output of the density detection sensor will fluctuate according to the conveyance speed. Regardless of the toner concentration, toner can be replenished according to the actual toner concentration, and 1
〜Natural density is not detected when toner is replenished based on the detection of the density of the developed image formed on the photosensitive sensor, which is an inconvenient problem in which the image density is not constant due to excess or deficiency in the density. The developed area represents the toner concentration of the developer in a specific area in the reverse direction conveyance unit that supplied toner to that area, so if the developed area is below a predetermined value, it will be detected as soon as it is detected. Toner must be replenished to the developer in the specific area. Therefore, in this case as well, the toner replenishment start timing may be adjusted so that the toner is replenished at the time when the developer present in the specific portion passes through the toner replenishment port, as described above.

Further, the toner replenishment method described above is suitable not only for full-color copying machines but also for any machine that has two or more developing units and is selectively used.

Further, the developing device can easily adjust the developed density by changing the developing speed. In this case, since the conveyance speed of the developer changes, the start timing of toner replenishment may be changed in accordance with the conveyance speed, as in the case described above.

The problem is resolved.

With variable speed control that continues driving at a lower conveyance speed than when in use when not in use, the developing device By replenishing and stirring toner using the time when the developing unit is not in use, it is possible to prevent the image quality from being affected by insufficient rise in toner density or insufficient stirring due to toner replenishment. If toner replenishment and agitation are performed in the idle developing device when the developing device is selectively used, opportunities for toner replenishment and agitation will increase, reducing the need for toner replenishment while the developing device is in use.
It is possible to prevent the influence of temporary non-uniform toner density due to toner replenishment while the developing device is in use.

Moreover, it is possible to avoid the problem that the developer is deteriorated due to excessive stirring caused by low-speed conveyance when the developing device is not in use.

Furthermore, when the developing speed of the developing device is changed, the density of the developed image can be easily adjusted without causing toner replenishment to deviate from the actual 1.toner density due to the resulting change in the general feed speed. be able to.

In addition, a toner concentration detection sensor ("°
If the output setting value is changed by changing the comparison reference voltage, this can be reliably achieved with a simple configuration.

Also, this switching is described in 1. If this is done based on the above information, it is possible to easily respond to various speed changes and target G'M by using an appropriately set table or the like.

[Brief explanation of the drawing]

The first part is a schematic diagram showing the internal structure of a full-color copying machine according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the developing device taken along a horizontal plane, and FIG. 3 is a cross-sectional view taken along a vertical plane of the developing device. Figure 4 is a perspective view showing the drive mechanism of the developer, Figure 5 is a block wiring diagram of the control circuit, Figure 6 is a detailed diagram of the comparison circuit, and Figure 7 is from the developer toner concentration detection position to the toner replenishment position.・An explanatory diagram showing the moving state of FIG. 11 is a chart showing a modified example of the drive control state of the developing device. 16 to 19- 61.62 71.72 82a to 82d 98a to 98d 202a to 202d Vl, Vll Developing device first order, reverse transport section order in each direction, reverse each stirring transport roller developing sleeve 1 henna 1 replenishment port - toner concentration Detection senna supply roller Developing sleeve clutch supply motor Cr'l+ Comparison circuit [10M Reference power supply

Claims (5)

[Claims] (1) The two-component developer is stirred and transported in the circulation path and subjected to development midway through the process. A toner replenishing means is provided that operates when the toner concentration detected by the sensor is below a predetermined value, and the transport speed is set in a control mode. What is claimed is: 1. A developing device that can be changed according to a conveying speed, the developing device comprising: a control means that changes a set value of an output of a toner concentration detection sensor that should perform toner replenishment according to a conveying speed. (2) The developing device according to claim 1, wherein the control modes for changing the conveyance speed are a development control mode and a non-development control mode. (3) The developing device according to claim 1, wherein the control mode for changing the conveyance speed is a control mode for changing the developing speed for controlling image density adjustment. (4) The developing device according to claim (1), wherein the set value of the output of the toner concentration detection sensor for performing toner replenishment is switched by changing a comparison reference voltage. (5) The developing device according to claim (1), wherein the set value of the output of the toner concentration detection sensor for performing toner replenishment is switched based on information stored in advance.