JPH0667527A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a vivid multicolor image without causing color mixture and also to eliminate an influence on an environment by controlling a condition for sticking toner which is contained in developer constituting a magnetic brush on a developer carrier onto a toner carrier. CONSTITUTION:The device is provided with a sensor 80 for detecting the concentration of toner on the toner carrier 68 and a CPU for controlling the condition for sticking the toner contained in the developer constituting the magnetic brush on the developer carrier 66 based on the detection signal by the sensor 80. Then, by controlling the condition for sticking the toner contained in the developer constituting the magnetic brush on the developer carrier 66, the quantity of the toner lying on the toner carrier 68 can be always maintained constant. That is, by comparing the output of the toner concentration detecting sensor 80 with a previously set value, the rotating speed ratio, or a potential difference is controlled, and the toner weight on the toner carrier 68 is set within the extent of 0.5-1.5mg/cm<2>, so that the fluctuation of image density caused by the deterioration etc., of the developer can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device generally used in an image forming apparatus, and more particularly, it is used as a printer for computers, facsimiles, CADs, etc., and the charging, exposing and developing steps are repeated a plurality of times. The present invention relates to a developing device used in a multicolor image forming apparatus in which visible images of a plurality of colors are formed on an electrostatic latent image carrier, and more specifically, a toner is attached to the toner carrier using a magnetic roll, The present invention relates to a developing device that has a control electrode that is arranged in the vicinity of a toner carrier and is separated from the toner carrier, thereby forming a toner cloud in a developing region to develop an electrostatic latent image.

[0002]

2. Description of the Related Art In recent years, a large number of image information processed in offices and the like are developed images of different colors or formed by synthesizing different information on one sheet, and a plurality of developing devices are housed. Image forming apparatuses are on the market.

By the way, there are various types of multicolor image forming apparatuses using electrophotography. As one of them, toner images of respective colors are sequentially formed on the photoconductor drum, and the toners of respective colors formed on the photoconductor are sequentially transferred onto the recording paper held around the transfer drum. There is a method of forming a multicolor image. In this case, a charging unit, an exposing unit, a plurality of developing units corresponding to respective colors, a transferring unit and a cleaning device are arranged around the photosensitive drum, and charging, exposing and developing are performed for each rotation of the photosensitive drum. Repeat the steps of transfer and cleaning. As a result, a toner image of each color is sequentially superposed and transferred onto the recording paper for each rotation of the photosensitive drum to form a multicolor image.

As another method of the above-mentioned multicolor image forming apparatus, toner images of respective colors are sequentially formed on the photosensitive drum for each rotation, and the toner images of the respective colors formed on the photosensitive drum are formed. It is also known to form a multicolor image by transferring a toner image onto a recording sheet in a single transfer process.

However, in any of the above-described multicolor image forming apparatuses, a toner image of one color is formed on the photosensitive drum every one rotation thereof, so that a multicolor image is formed. , The photoconductor drum must be rotated by the number of required colors. Therefore, there is a problem that it takes a long time to obtain a final multicolor image, and the image formation cannot be speeded up. In the former method,
A transfer drum for sequentially transferring the toner images formed on the photoconductor drum is required, which causes a problem that the device becomes large. Further, in the former method, the toner images formed on the photoconductor drum are sequentially transferred onto the recording paper held on the transfer drum. There is a problem in that color misregistration and positional misalignment may occur, and it is necessary to ensure accuracy.

Therefore, as a solution to these problems, as disclosed in Japanese Patent Laid-Open No. 63-273883,
A plurality of recording units including a charging device, an exposure optical system, and a developing device are arranged around the photosensitive drum, and a toner image of each color is formed on the photosensitive drum while the photosensitive drum makes one rotation.
A multicolor image forming apparatus has also been proposed which transfers the toner images of the respective colors onto a recording sheet in a single transfer process.

However, in the case of the multicolor image forming apparatus according to this proposal, a plurality of toner images are formed on the photoconductor drum during one rotation of the photoconductor drum, and the transfer process is only required once. , If the development is repeated multiple times while the photosensitive drum makes one rotation, the toner image already formed on the photosensitive drum is disturbed at the time of the subsequent development, or the toner adheres to the developing roll of the developing device at the subsequent stage and is mixed. However, there is a problem that color mixing occurs.

In order to solve this problem, an apparatus which forms only toner on a toner carrier and develops an electrostatic latent image on a photosensitive drum by a toner layer formed on the toner carrier, Various types have already been released. This developing method has been conventionally used in the development of non-magnetic one-component toner. In the method of developing the electrostatic latent image on the photoconductor drum by the toner layer formed on the toner carrier, since the toner on the toner carrier and the photoconductor drum are not in contact with each other, the toner on the photoconductor drum is not contacted. Disturbance does not easily occur in the toner image already developed, and high quality multicolor image can be obtained,
It has advantages such as the possibility of developing toners of a plurality of colors on the photosensitive drum in a superimposed manner.

In such a non-contact one-component developing method, the toner applied to the toner carrier is carried by the Coulomb force of the developing electric field formed between the toner carrier and the photosensitive drum. It is necessary to remove it from the surface of the body and move it to the photosensitive drum side.

However, the adhesion of the toner to the toner carrier is considerably larger than the Coulomb force due to the developing electric field formed between the toner carrier and the photoconductor drum, and the toner is separated from the toner carrier and the photoconductor drum is separated. It is difficult to move it to the side.

Therefore, in reality, for example, Japanese Patent Publication Sho 63
As disclosed in Japanese Patent Laid-Open No. 31776, a method is proposed in which an AC electric field is applied between a toner carrier and a photosensitive drum to facilitate separation of toner from the surface of the toner carrier and development. Has been done. In addition, JP-A-56-116
In the method disclosed in JP-A-060, a porous electrode is arranged between a toner carrier and a photosensitive drum, and an AC voltage is applied to the porous electrode to separate the toner from the toner carrier. There is also proposed a method in which a toner cloud is generated to develop the toner on the photosensitive drum.

According to these methods, the toner can be separated from the toner carrier even if the charge amount of the toner is relatively high. However, in the former method, the toner carrier and the photosensitive drum are relatively spaced apart from each other. Since an AC electric field is applied between and, it is necessary to increase the AC electric field, and this AC electric field may disturb the toner image already developed on the photosensitive drum. There is.

On the other hand, in the latter method, the toner can be separated from the toner carrier even when the toner charge amount is relatively high, and a relatively low AC electric field can be used. There is little risk of disturbing the toner image already developed on the top, and there is a possibility that toners of a plurality of colors can be superposed and developed on the photosensitive drum.

However, in the case of the one-component developing method using the above-mentioned toner carrier, since the toner is frictionally charged, the charge amount of the toner is low and there is a problem in long-term maintenance of image quality. The toner on the toner carrier may be changed by the blade member for controlling the toner layer on the toner carrier and for frictionally charging the toner while controlling the toner layer on the toner carrier by a slight change in the toner characteristics. There is a problem that the image is partially clogged and an image defect is likely to occur, and it cannot be said that the reliability is necessarily high.

In order to solve these problems, the advantages of the one-component developing method using a toner carrier and the advantages of the conventional two-component developing method are successfully combined to obtain the desired characteristics of both. A developing device has been proposed.

That is, in JP-A-59-121077, a two-component developer is advanced to a toner carrier using a developer carrier, and the toner is transferred onto the toner carrier to form a toner layer. A developing device is shown.

In the developing method according to this proposal, a toner layer can be stably formed and conveyed on the toner carrier, but since a two-component developer is used, frictional charging of the carrier and toner is performed. As a result, the charge amount of the toner becomes relatively high, and it becomes difficult to separate the toner from the toner carrier in the developing process, and a strong AC electric field must be applied between the toner carrier and the photosensitive drum. Therefore, the AC electric field disturbs the toner image developed on the photosensitive drum before that, so that it is not possible to uniformly develop the toners of a plurality of colors.

Therefore, there has been proposed a method in which an auxiliary electrode made of a wire is provided between the toner carrier and the photosensitive drum, and a weak AC electric field is applied to the auxiliary electrode so as not to disturb the developed toner. (JP-A-3-113474).

FIG. 11 is a schematic configuration diagram showing an actual application of the developing device disclosed in Japanese Patent Laid-Open No. 3-113474.

The developing device 120 is provided with a toner carrier 101 which faces the electrostatic latent image carrier 105 in a housing 115 which houses a two-component developer and which conveys non-magnetic toner by adhering the non-magnetic toner to the surface thereof. A developer carrier 102 that is disposed close to the toner carrier 101 and that conveys a two-component developer while adsorbing the two-component developer on the surface, and a developer carrier 102 that is disposed substantially parallel to the developer carrier 102 and agitates the two-component developer. It has developer agitating members 106 and 107 which are conveyed while. Further, a control electrode 104 for controlling the flight of the non-magnetic toner is disposed in the vicinity of the toner carrier 101 in the gap between the electrostatic latent image carrier 105 and the toner carrier 101.

After the electrostatic latent image carrier 105 is uniformly charged,
It is a photoreceptor capable of forming an electrostatic latent image due to a difference in charging potential on the surface by irradiation with laser light or the like.

The developer carrying member 102 has a plurality of magnetic poles fixed in position inside, and forms a magnetic brush on the surface of which a magnetic carrier with non-magnetic toner is formed in a spike shape.

The developer agitating members 106 and 107 convey the developer in opposite directions, and are separated from each other by a partition wall 108 and communicate with each other at both ends thereof.
The developer is conveyed while being stirred in 110 and circulated in a fixed direction.

The control electrode 109 is, as shown in FIG.
The housing 115 is supported by a frame body 116 attached to the opening facing the electrostatic latent image carrier 105, and comprises a plurality of thin wires stretched so as to be substantially parallel to the axis of the toner carrier 101. It is a thing. The wire 109 extends over the entire length of the toner carrier 101 in the axial direction when the frame 116 is attached to the housing 115.
A predetermined gap is maintained with the surface of the toner carrier 101.

In such a developing device, the developer is agitated by the developer agitating members 106 and 107, and a predetermined charge is applied to the nonmagnetic toner by frictional charging between the nonmagnetic toner and the magnetic carrier, so that the developer carrying member is carried. Is supplied to 102. The developer forms a magnetic brush on the developer carrier 102, is conveyed by the rotation of the surface of the developer carrier 102, and is rubbed against the surface of the toner carrier 101. An oscillating electric field is formed between the developer carrier 102 and the toner carrier 101 by the bias power sources 112 and 113.
The toner attached to the magnetic carrier is the toner carrier 1
No. 01 is transferred to form a thin layer of toner.

The thin layer of toner formed on the toner carrier 101 is conveyed to the developing area in the vicinity of the electrostatic latent image carrier 105 by the rotation of the toner carrier 101. The control electrode 104 provided in the vicinity of the toner carrier 101 has
A DC superimposed AC voltage is applied from the bias power source 111, and the toner is clouded by the oscillating electric field generated in the developing area and adheres to the electrostatic latent image for development.

Such a developing device can be used, for example, in a multicolor image forming apparatus using a plurality of developing devices containing toners of different colors.

Particularly, it is said that the electrostatic latent image carrier can be developed without disturbing toner images of a plurality of colors by repeating the charging, exposing and developing processes a plurality of times during one rotation of the electrostatic latent image carrier. There are advantages.

[0029]

However, the above-mentioned prior art has the following problems. That is, in the case of the developing device according to the above proposal, the developer is agitated by the developer agitating members 106 and 107 so that the nonmagnetic toner and the magnetic carrier are frictionally charged so that a predetermined charge is applied to the nonmagnetic toner. According to the charge amount of the developer, the developer carrier 102 changes from the toner carrier 1 to the toner carrier 1.
The toner transfer amount to 01 is almost determined. Therefore, the charge amount of the non-magnetic toner changes due to the deterioration of the magnetic carrier or the non-magnetic toner due to environmental changes or changes over time, and a difference occurs in the amount of toner transferred from the developer carrying member 102 to the toner carrying member 101. As described above, when the amount of toner on the toner carrier 101 is different, the amount of toner clouded by the control electrode 104 is different, and the amount of toner in the developing area is changed, so that the electrostatic latent image is changed. There is a problem that the image density on the carrier 105 changes.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art. The purpose of the present invention is to obtain a clear developed image of a multicolor image without color mixture. Of course, it is an object of the present invention to provide a developing device capable of obtaining a stable developed image without being affected by the environment and the like.

[0031]

The above-mentioned technical problems are as follows.
In the developing device according to the present invention, a developer carrier that carries a two-component developer having a non-magnetic toner and a magnetic carrier and conveys it as a magnetic brush in the circumferential direction, the developer carrier and the electrostatic latent image A toner carrier arranged to face the formed electrostatic latent image carrier at different positions in close proximity to each other; a means for regulating the amount of developer on the developer carrier; and the developer carrier. A means for forming an electric field between the developer carrier and the toner carrier to electrostatically attach the toner in the developer constituting the upper magnetic brush to the toner carrier; and the electrostatic latent image carrier. A control electrode arranged in a gap from the toner carrier to control the flight of toner,
The control electrode is arranged in the vicinity of the toner carrier so as to be separated therefrom, and a toner cloud is formed by an alternating voltage applied to the control electrode, and a development image is formed on the electrostatic latent image carrier by the toner cloud. In the apparatus, a toner density detecting means for detecting the density of the toner carried on the toner carrying body, and a developer forming a magnetic brush on the developer carrying body based on a detection signal of the toner density detecting means. And a control means for controlling the conditions for adhering the toner inside the toner carrier onto the toner carrier.

The control means controls, for example, at least one of the number of revolutions of the developer carrier, the voltage applied to the developer carrier, the number of revolutions of the toner carrier, and the voltage applied to the toner carrier. Is composed of.

[0033]

In the present invention, the toner density detecting means for detecting the density of the toner carried on the toner carrying body, and the magnetic brush on the developer carrying body based on the detection signal of the toner density detecting means. And a control unit for controlling the conditions for adhering the toner in the developing agent onto the toner carrier. Therefore, the toner density detecting means detects the density of the toner carried on the toner carrying body, and the control means forms the magnetic brush on the developer carrying body based on the detection signal of the toner density detecting means. By controlling the conditions for adhering the toner in the developer onto the toner carrier, the amount of toner carried on the toner carrier can always be kept constant and stable without being affected by the environment, etc. It is possible to provide a developing device capable of obtaining a developed image.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows a multicolor image forming apparatus to which an embodiment of the developing device according to the present invention can be applied.

The multicolor image forming apparatus is roughly composed of an image forming section 1 located at the upper part and a sheet feeding section 2 located at the lower part.

In the image forming section 1, 3 is a translucent belt-shaped photoreceptor, and this translucent belt-shaped photoreceptor 3 is
Drive roller 4a and a plurality of idler rollers 4b to 4e
It is hung around and arranged vertically. The belt-shaped photoreceptor 3 is rotationally driven in the direction of arrow A by the drive roller 4a. Around the belt-shaped photoconductor 3, a first image recording unit 5, a second image recording unit 6, a third image recording unit 7, a fourth image recording unit 8, and an optical sensor 10 for registration adjustment.
a, a pre-transfer corotron 9, a development density sensor 10b, a light guide section 11 for guiding the light of a discharge lamp 16 described later, a transfer section 12, a pre-cleaning corotron 1.
3, a cleaning device 14 and a ground strip 15 are arranged respectively. The components forming each of these image recording units and the like are arranged along the surface of the belt-shaped photoconductor 3 which is held substantially vertically. Further, inside the lower end portion of the belt-shaped photoreceptor 3, the belt-shaped photoreceptor 3 is provided before and after the transfer section 12.
A static elimination lamp 16 for irradiating the inside from the inside is arranged.

The transfer section 12 is a transfer corotron 12a.
Also, the peeling corotron 12b is provided, and is arranged at the lowermost end of the vertically long belt-shaped photosensitive member 3 so that the sheet conveying direction is substantially horizontal. Further, adjacent to the transfer section 12, a sheet conveying device 17 and a conveying roller 18 are provided on the sheet introducing side, and a conveying belt 20 for conveying the recording sheet after transfer to the fixing device 19 is provided on the sheet discharging side. There is.

The first image recording section 5 includes a first charger 21, a laser light source (not shown), a rotary polygon mirror 22a irradiated with laser light, and a motor 22b for rotationally driving the rotary polygon mirror 22a. , Lenses 22c and 22d, mirror 22e,
The first exposure device 22, the first potential sensor 23, the first developing device 24, and the like, which are configured by 22f and the like, are provided. Also, the second
The image recording unit 6 includes a second charger 25, a second exposure device 26 including a light emitting diode array, a second potential sensor 27, a second developing device 28, and the like. Similarly, in the third and fourth image recording units 7 and 8, the third and fourth chargers 29 and 33, the third and fourth exposure devices 30 and 34, the third and fourth potential sensors 3 are also included.
1, 35, third and fourth developing machines 32, 36 and the like are provided.

The first, second, third, and fourth image recording units 5, 6, 7, and 8 are formed on the belt-shaped photoconductor 3 by toners of black, red, green, and blue, for example. Each color image is formed. In addition, each potential sensor 23,
Reference numerals 27, 31, 35 detect the surface potential of the belt-shaped photoconductor 3 in each of the image recording units 5, 6, 7, 8 and control each by a control circuit (not shown) so that the surface potential is set to a predetermined potential. The chargers 21, 25, 29, 33 are controlled. Further, the final development density is detected by the development density sensor 10b,
Each image recording unit 5, 6, 7, so that an appropriate density can be obtained.
The developing conditions in No. 8 are adjusted. The development density sensor 10b is configured by arranging color sensor elements corresponding to each color in a direction perpendicular to the moving direction of the photoconductor 3. Each of the developing machines 24, 28, 32, 36 is provided with a developing roll 24a, 28a, 32a, 36a and a backup roll 24b, 28b, 32b, 36b. The second, third, and fourth developing units 28, 32, and 36 must not cause the toner image formed on the photoconductor 3 by the preceding developing unit to be disturbed, and thus the non-contact type developing device. Is adopted.

Further, the paper feeding section 2 includes an intermediate tray 41 having paper feeding devices 37, 38, 39 and 40, respectively.
The paper feed trays 42 and 43, the large capacity tray 44, the paper reversing unit 45, and the like are arranged. The intermediate tray 41 has a switching claw device 46 including a plurality of switching claws 46a, 46b, 46c.
Is provided. In addition, 47 and 48 are transport rolls, 4
9 is a reverse roll.

Next, a circuit configuration for forming an image in the above-mentioned multicolor image forming apparatus will be described with reference to FIG.

Image signals from the image input device 51, the computer 52, the communication device 54 and the like communicating via the communication line 53 are supplied to the multicolor image forming device 50 via the image processing device 55. It The image signal supplied to the image processing device 55 is separated by the color separation circuit 56 into first to fourth color component signals, for example, four color component signals of black, red, green and blue, and the first color component signal. Is supplied to the first exposure device 22 of the first recording section 5 without being substantially delayed, and the second to fourth color components are respectively supplied to the second exposure device 22 via the first to third delay circuits 57 to 59. ~ Second of the fourth recording unit 6, 7, 8
~ Supplied to the fourth exposure device 26, 30, 34. In addition,
Delay time T1 in the first to third delay circuits 57 to 59,
T2 and T3 correspond to the distances of the exposure positions of the belt-shaped photoreceptor 3 by the second to fourth exposure devices 26, 30, and 34 from the exposure position of the first exposure device 22.

Further, the first to fourth chargers 21, 25, 29, 33 of the recording sections 5 to 8 and the first to fourth exposure devices 22, 2 are arranged.
6, 30, 34, first to fourth developing machines 24, 28, 32,
The operation of 36 is controlled by the control device 61 that operates based on an instruction from the control panel 60.

First, regarding the image forming mode, red and black 2
A case of forming a color image will be described as an example.

In this case, the control device 61 controls the first and second image recording units 5 based on the instruction from the operation panel 60.
Only 6 is operable, and the third and fourth image recording units 7 and 8 are inoperable. This operation / non-operation switching is performed by, for example, the first and second chargers 21, 25, the first and second exposure devices 22, 26, the first and second developing devices 24,
This is performed by applying a predetermined operating voltage or bias voltage to only 28.

The belt-shaped photosensitive member 3 which is rotationally driven in the direction of the arrow A by the driving roller 4a, firstly includes the first image recording unit 5
In FIG. 4, the first charger 21 uniformly charges the toner as shown in FIG. As a result, the surface potential of the photoconductor 3 becomes, for example, Vp (where Vp is a negative value). Next, in the first exposure device 22, the surface of the photoconductor 3 is exposed by the light Lk from the laser modulated by the signal corresponding to the black of the image, and the potential of the exposed portion becomes, for example, VR (however, VR Is a negative value) (see (b) of the same figure).
Next, this exposed portion advances to the first developing portion 24, where it is developed with the black toner Tk (see FIG. 7C).
Even after this development, the surface potential of the black image portion remains low. Next, the black developing portion advances to the second image recording portion 6,
Recharged by the second charger 25, the surface potential of the photoconductor 3 rises to near VP (see (d) in the figure). Next, in the second exposure device 26, the light LR from the light-emitting diode array modulated by the signal corresponding to the red color of the image is emitted.
As a result, the surface of the photoconductor 3 is exposed, and the potential of the exposed portion drops to VR (see (e) in the same figure). Next, this exposed portion advances to the second developing portion 28, where the red toner TR
Is developed (see (f) in the figure). After this red development, the surface potential of the red image portion remains low.

The belt-shaped photosensitive member 3 further advances to the third and fourth
Although it passes through the image recording units 7 and 8, since the image recording units 7 and 8 are inoperative, the toner images of the respective colors are not affected.

Next, the toner image is adjusted in charge by the pre-transfer corotron 9 and the discharging lamp 16 to be in a state suitable for transfer.

When the toner images of the respective colors reach the transfer unit 12, in synchronization therewith, the recording paper is conveyed from any of the trays 41 to 44 of the paper feeding unit 2 by any of the paper feeding devices 37 to 40. The sheet is fed to the image forming unit 1 side along B, is further conveyed by the sheet conveying device 17 and the conveying roller 18, and comes into contact with the surface of the belt-shaped photoreceptor 3.

In the transfer section 12, the toner image of each color is transferred from the surface of the belt-shaped photoconductor 3 to the recording paper by the electric field from the transfer corotron 12a. The recording paper after the transfer is separated from the belt-shaped photoconductor 3 by the separating corotron 12b and is conveyed to the fixing device 19 by the conveying belt 20 to fix the toner image on the recording paper.

The recording paper after fixing advances, for example, in the direction of arrow C, and is directly discharged outside the apparatus by the conveying roller 47 with the image surface facing upward. When the paper is discharged with the image surface facing down, the conveying rollers 48 and 49 are used to temporarily move the arrows D and E.
Then, the conveyance rollers 48 and 49 reverse the rotation of the conveyance rollers 47, and the conveyance rollers 47 eject the sheets to the outside of the machine.

The toner remaining on the belt-shaped photosensitive member 3 after the transfer is removed by the cleaning device 14 after the charge state is adjusted by the charge eliminating lamp 16 and the pre-cleaning corotron 13. Further, the electric charge remaining on the photoconductor 3 is discharged through the ground strip 15 to prepare for the next image forming cycle.

In the case of double-sided copying, the recording paper after fixing advances in the direction of arrow D, is conveyed by the conveying roller 48 to the paper reversing unit 45 of the paper feeding unit 2, and is temporarily moved by the reversing roller 49 in the direction of arrow E. After being conveyed, the rotation of the reversing roller 49 is reversed, the conveying direction of the recording paper is reversed in the direction of arrow F, and the recording paper is stored in the intermediate tray 41 with the image surface facing upward. At this time, by changing the postures of the switching claws 46a, 46b, 46c of the switching claw device 46 according to the size of the recording paper, the recording paper is stored in the intermediate tray from the proper position. This recording paper is sent to the transfer unit 12 of the image forming unit 1 again by the paper feeding device 37, and the image on the back surface of the recording paper is formed this time. In the case of double-sided printing, it goes without saying that a toner image is formed by the image forming unit 1 on each side.

Further, in the case of making two copies by superposing on one side, the recording paper may be directly conveyed from the conveying roller 48 to the intermediate tray 41.

Next, a developing device according to an embodiment of the present invention will be described.

FIG. 1 shows an example of the structure of a non-contact type developing device. This developing device includes the first to fourth developing machines 24,
It is applicable to any of 28, 32, and 36, but in particular, the belt-shaped photoreceptor 3 on which a toner image is already formed.
It is suitable for the second and subsequent developing machines that develop the toner image by superposing on the second developing machine. Here, the case of application to the second developing machine 28 will be described as an example.

As shown in FIG. 1, the second developing device 28 is arranged so as to face the belt-shaped photosensitive member 3 as an electrostatic latent image carrier. The second developing device 28 carries a developer that magnetically attracts the two-component developer into a housing 65 that contains the two-component developer including a non-magnetic toner and a magnetic carrier to form a magnetic brush on the surface. Body 66,
The developer control member 67 for controlling the amount of the developer adsorbed on the developer carrier 66, and the developer carrier 66 and the belt-shaped photoconductor 3 are arranged so as to be close to each other at different positions. , And a cylindrical toner carrier 68 that rotates by adhering non-magnetic toner. A control electrode 69 for controlling the flight of the non-magnetic toner is provided at a position where the toner carrier 68 and the belt-shaped photoconductor 3 face each other.

Further, the housing 6 of the second developing machine 28
5, a first developer stirring chamber 70 is provided adjacent to the developer carrying member 66, and a second developer stirring chamber 70 is partitioned by the first developer stirring chamber 70 and a partition 71. A chamber 72 is provided. The first developer agitating chamber 70 and the second developer agitating chamber 72 communicate with each other at both ends in the axial direction of the developer carrier 66, and the first developer agitating chamber 70 and the second developer agitating chamber 72 respectively agitate and convey the developer. The screw auger 73 and the second screw auger 74 are provided. These two screw augers 73,74
Has a rotation direction set so as to convey the developer in mutually opposite directions, and the developer circulates in the first developer stirring chamber 70 and the second developer stirring chamber 72. .
As a result, the distribution of the non-magnetic toner in the developer is kept constant, and the frictional charging with the magnetic carrier causes −5 to −5.
A charge of −25 μc / g is applied. The stirred developer is supplied to the developer carrier 66 by the first screw auger 73.

The developer carrying member 66 is such that a rotatable cylindrical sleeve is arranged on the outer periphery of a magnet whose position is fixed, and the two-component developer is magnetically attracted to the surface of the sleeve. The sleeve can be rotated and the developer can be conveyed while forming the magnetic brush. The developer carrying member 66 has a DC power supply AC voltage (frequency 2 to 12 KHz, V _{PP 2} Kv or less,
Vdc-100V to -600V is preferable. ) Has been applied. The toner having an electric charge is transferred to the toner carrier 68 by Coulomb force, and is transferred to the surface of the toner carrier 68.
A thin layer of toner is formed with a charge of 10 to -30 μc / g.

As the toner carrier 68, a cylinder of aluminum whose surface is anodized, a cylinder of phenol resin, or a metal resin having a synthetic resin layer formed thereon is used. ~ -400
A DC voltage of V is applied. In addition, the toner carrier 6
A DC superimposed AC voltage may be applied to 8.

The toner carrier 68 and the belt-shaped photoconductor 3 are arranged so as to face each other with a distance of 200 μm to 500 μm held therebetween. The rotation direction is set so that the movements of the surfaces of are in the same direction. The movements of both surfaces may be set in opposite directions.

The control electrode 69 is composed of a conductive wire, is linearly arranged in a plurality of rows in the axial direction of the toner carrier 68, and is provided so that a part of the peripheral surface of the toner carrier 68 is exposed. It is supported at both ends of the opening of the housing 65, and is arranged close to the toner carrier 68. A DC bias AC voltage (frequency 2 to 12 KHz, V _PP 200) is applied to the control electrode 69 from the developing bias power source 77.
-1000V or less and _VDC- 100V-400V are preferable. ) Is applied and a toner cloud is generated in the electric field. The clouded toner flies in the electric field, adheres to the electrostatic latent image on the belt-shaped photoconductor 3, and is developed. The control electrode 69 is not limited to a wire and may be a thin metal plate having an opening larger than the average particle size of a plurality of toner particles.

By the way, in this embodiment, the toner concentration detecting means for detecting the toner concentration on the toner carrier is located downstream of the facing portion of the toner carrier and the developer carrier in the rotational direction of the toner carrier. Further, it is provided on the upstream side of the control electrode and close to the toner carrier.

As the sensor of the toner concentration detecting means, there are both a reflection type sensor for reading specular reflection light and a diffusion type sensor for reading diffused light. The sensitivity of the reflection type sensor is black>blue>green> brown. The order is> red, and the diffusion type sensor has the order of red>brown>green>blue> black, and the diffusion type sensor has a characteristic that blue and black have almost no sensitivity. Therefore, in this embodiment, a reflection type sensor is adopted to enable detection of all colors. Red is the most difficult to detect with reflected light, so it is possible to use blue light, which is a complementary color, as a light emitting source to increase the sensitivity of red, but in general, a blue LED has a small output and a sensor. Can not be used for. Therefore, in this embodiment, 900 nm infrared light is used as the light source for the sensor because long-wavelength light is easily obtained as an output.

The toner concentration detecting sensor 80 is shown in FIG.
As shown in FIG. 3, the light emitting element 81 and the light receiving element 82 are provided, and the light from the light emitting element 81 is applied to the toner layer on the toner carrier 68, and the reflected light is detected by the light receiving element 82 and converted into an electric signal. It is designed to be converted and amplified. At this time, the ratio of the reflected light amount V _{CL on the} clean surface without toner to the reflected light amount V _IM when the toner layer is formed has a characteristic as shown in FIG. 6 with respect to the weight (density) of the toner layer. Then
The change in toner weight (concentration) can be known.

Further, the toner concentration detecting sensor 80
As shown in FIG. 7, a light shielding plate 83 is provided in front of the light emitting element 81 and the light receiving element 82, and light from the light emitting element 81 is transmitted through the pinhole 84 provided in the light shielding plate 83.
8 and the reflected light from the toner carrier 68 is received by the light receiving element 82 through the pinhole 85. It is desirable that the pinholes 84 and 85 have a diameter of about 1.0 mm in view of the amount of light and directivity. With this configuration, the directivity is improved and the sensor sensitivity can be improved. In this case, the directivity is further improved by setting the distance between the light emitting element 81 and the light shielding plate 83 to about 2 mm and widening the distance between the light receiving element 82 and the light shielding plate 83 to the same or larger.

Further, the toner concentration detecting sensor 80
Can improve the detection sensitivity by setting the toner carrier 68 closer to the position where the fields of view of the light emitting element 81 and the light receiving element 82 through the pinholes 84 and 85 match, and the light emitting element 81 and the light receiving element 82 can be improved. By narrowing the angle formed by and, the degree of detection of diffused light is reduced and higher sensitivity can be achieved. By reducing the angle formed by the light emitting element 81 and the light receiving element 82, it is possible to increase the sensitivity without receiving diffused light or diffusely reflected light. The angle formed by the light emitting element 81 and the light receiving element 82 is preferably 30 ° or less.

FIG. 8 is a timing chart showing the control operation of the multicolor image forming apparatus. The toner on the toner carrier 68 can be removed by reversing the bias applied to the developer carrier 66 after PRINTJOB is completed, and at this time, the toner on the toner carrier 68 is not detected by the toner concentration detection sensor 80. The amount of reflected light on a clean surface can be detected. Further, the amount of reflected light when the toner layer is formed is detected by detecting the surface of the toner carrier 68 in PRINTJOB.

FIG. 9 shows the relationship between the toner weight on the toner carrier 68 and the image density. It can be seen that the toner weight and the image density have a substantially proportional relationship, and the toner weight on the toner carrier 68 and the toner density also have a substantially proportional relationship. From this relationship and the sensor sensitivity shown in FIG. 6, the image density can be controlled by the output of the toner density detection sensor 80. As shown in FIG. 5, the output of the toner concentration detection sensor 80 is input to a CPU 90 as a control means, and the CPU 90 has the developer carrier 66.
At least one of the number of rotations, the voltage applied to the developer carrier 66, the number of rotations of the toner carrier 68, and the voltage applied to the toner carrier 68.

With the above construction, the developing device according to this embodiment can always perform stable development without being affected by the environment and the like. That is, in the housing 65 of the developing device, as shown in FIG. 1, the developer is stirred and conveyed by the first and second screw augers 73 and 74, and the stirred developer is
The first screw auger 73 allows the developer carrying member 66.
Is supplied to. This developer is attracted to the surface of the developer carrier 66 by magnetic force to form a magnetic brush. The developer adhering to the surface of the developer carrying member 66 has an optimum developer amount of, for example, 1.5 to 5 depending on the developer regulating member 67.
After the layer thickness is controlled to 3.0 mm, the developer carrier 66 is conveyed in the direction of the arrow as the developer carrier 66 rotates. Then, when the developer carrying member 66 is rotated to a position facing the toner carrying member 68, the toner in the developer attached to the surface of the developer carrying member 66 is separated between the developer carrying member 66 and the toner carrying member 68. The bias voltage applied to the toner carrier 68 causes the electrostatic field formed in the direction from the developer carrier 66 to the toner carrier 68 to transfer to the toner carrier 68 and adhere to the surface of the toner carrier 68. , On the surface of the toner carrier 68,
A toner layer having a constant layer thickness is formed.

The toner adhering to the surface of the toner carrier 68 is conveyed to the developing position facing the belt-shaped photoconductor 3 as the toner carrier 68 rotates. At this developing position, the control electrode 69 located between the toner carrier 68 and the belt-shaped photosensitive member 3 is supplied with a bias power supply 77 to generate a DC superimposed AC voltage (frequency 2 to 12 KHz, V _PP 2
It is preferably from 0 to 1000 V or less and from _VDC- 100 V to -400 V. ) Is being applied. Therefore, the toner adhering to the surface of the toner carrier 68 easily moves to the belt-shaped photoconductor 3 side by the oscillating electric field formed between the control electrode 69 and the belt-shaped photoconductor 3, and the belt-shaped photoconductor 3 is moved. The electrostatic latent image formed on the surface of 3 is developed. The distance between the toner carrier 68 and the belt-shaped photoconductor 3 is 200 μm or more.
It is set to 500 μm.

At this time, when the charge amount of the non-magnetic toner changes due to the deterioration of the magnetic carrier or the non-magnetic toner due to environmental changes or changes over time, there is a difference in the toner amount transferred from the developer carrying member 66 to the toner carrying member 68. Occurs. in this way,
When a difference occurs in the amount of toner on the toner carrier 68, a difference occurs in the amount of toner clouded by the control electrode 69,
A change in the amount of toner in the developing area causes a change in image density on the belt-shaped photoconductor 3.

By the way, in this embodiment, FIG. 1 and FIG.
As shown in, the toner amount on the toner carrier 68 is detected by the toner concentration detection sensor 80, and the CPU 90 determines whether the toner concentration detected by the toner concentration detection sensor 80 is within a predetermined range. It Then, when the toner density on the toner carrier 68 is equal to or lower than a predetermined value, the ratio of the number of revolutions of the developer carrier 66 and the toner carrier 68 is increased, and as shown in FIG. Increase the amount of toner on body 68.

The developer carrier 66 and the toner carrier 6
It is also possible to increase the amount of toner on the toner carrier 68 by increasing the difference in bias voltage applied to 8 as shown in FIG. It is also possible to increase the charge amount of toner by increasing the number of rotations of the first and second screw augers 73 and 74, and increase the amount of toner on the toner carrier 68.

As described above, in the above embodiment, the toner concentration detecting sensor 80 for detecting the concentration of the toner carried on the toner carrier 68 and the developing signal based on the detection signal of the toner concentration detecting sensor 80. Agent carrier 66
CPU 9 for controlling conditions for adhering the toner in the developer constituting the upper magnetic brush onto the toner carrier 68.
It is configured to include 0. Therefore, the toner density detection sensor 80 detects the density of the toner carried on the toner carrier 68, and based on the detection signal of the toner density sensor 80, the CPU 90 causes the magnetic brush on the developer carrier 66 to be detected. By controlling the conditions for adhering the toner in the developer constituting the toner carrier 68 onto the toner carrier 68, the amount of toner carried on the toner carrier 68 can be constantly maintained at a constant level. It is possible to provide a developing device capable of obtaining a stable developed image without being affected.

That is, as described above, by comparing the output of the toner concentration detection sensor 80 with a preset value, the above-described rotation speed ratio or potential difference is controlled, and the toner weight on the toner carrier 68 is reduced to 0. 5 mg / cm ^{2 to} 1.5 m
By setting it in the range of g / cm ² , it becomes possible to prevent the change of the image density due to the deterioration of the developer.

[0078]

EFFECT OF THE INVENTION The present invention has the above-mentioned constitution and operation, and of course, it is possible to obtain a developed image of a clear multicolor image without color mixture, and it is stable without being affected by the environment or the like. It is possible to provide a developing device capable of obtaining a developed image.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a developing device according to the present invention.

FIG. 2 is a block diagram showing a multicolor image forming apparatus to which the developing device according to the present invention is applied.

FIG. 3 is a block diagram showing a control unit of the multicolor image forming apparatus.

FIGS. 4A to 4F are potential explanatory diagrams showing image forming steps of a multicolor image forming apparatus, respectively.

FIG. 5 is a main part configuration diagram showing an embodiment of a developing device according to the present invention.

FIG. 6 is a graph showing the relationship between toner concentration and Log (V _IM / V _CL ).

FIG. 7 is a configuration diagram showing a main part of a toner concentration detection sensor.

FIG. 8 is a timing chart showing the relationship between the image forming operation of the multicolor image forming apparatus and the operation of the detection member.

FIG. 9 is a graph showing the relationship between toner weight and image density.

FIG. 10 is a graph showing a method of controlling development density.

FIG. 11 is a block diagram showing a conventional developing device.

FIG. 12 is a perspective view showing a control electrode of the developing device.

[Explanation of symbols]

3 belt-shaped photoconductor, 28 second developing machine, 66 developer carrier, 68 toner carrier, 69 control electrode, 80
Toner density detection sensor.

Claims (2)

[Claims] 1. A device having a non-magnetic toner and a magnetic carrier.
A developer carrier that carries a component developer and conveys it as a magnetic brush in the circumferential direction and an electrostatic latent image carrier that forms an electrostatic latent image with the developer carrier closely face each other at different positions. The toner carrier arranged as described above, means for regulating the amount of the developer on the developer carrier, and the toner in the developer constituting the magnetic brush on the developer carrier to the toner carrier. Means for forming an electric field that electrostatically adheres between the developer bearing member and the toner bearing member, and control for controlling the toner flight, which is arranged in the gap between the electrostatic latent image bearing member and the toner bearing member An electrode, the control electrode is disposed separately in the vicinity of the toner carrier, a toner cloud is formed by an alternating voltage applied to the control electrode, and the toner cloud develops on the electrostatic latent image carrier. Image forming device In a developer forming a magnetic brush on the developer carrier based on a toner concentration detecting means for detecting the concentration of the toner carried on the toner carrier, and a detection signal of the toner concentration detecting means. And a control means for controlling the conditions for adhering the toner of claim 1 onto the toner carrier. 2. The control means controls the number of revolutions of the developer carrier, the applied voltage of the developer carrier, the number of revolutions of the toner carrier,
The developing device according to claim 1, wherein at least one of the voltages applied to the toner carrier is controlled.