JPH0667547A - Developing device - Google Patents

Abstract

PURPOSE:To stably attain multicolor developing of high image quality by one pass and to prevent the occurrence of irregularities in an image by providing a vibration impressing means for vibrating a control electrode in order to form toner cloud by an alternating voltage. CONSTITUTION:Inside a positioning groove 81 as one part of a wire supporting body 80, a piezoelectric vibrator 84 as the vibration impressing means is arranged in contact with the control electrode 69. By impressing a high frequency alternating voltage(1 to 50kHz) on the piezoelectric vibrator 84 so as to be vibrated at the high frequency, the vibration is transmitted to the control electrode 69, and electrostatically charged toner sticking on the surface of a toner carrier 68 is separated from the surface of the toner carrier 68 by the vibration of the control electrode 69, and also, the generation of the toner cloud is promoted. Then, the need of peeling the toner sticking on the surface of the toner carrier 68 by a high alternating electrical field is eliminated, and the toner cloud can be formed by impressing comparatively lower alternating electrical field(1000V/mm to 4000V/mm) in between the control electrode 69 and the toner carrier 68.

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. The present invention relates to a developing device used in a multicolor electrophotographic apparatus in which a visible image of a plurality of colors is formed on an electrostatic latent image carrier, and more specifically, a toner is formed on a toner carrier by using a developer carrier. The present invention relates to a developing device that has a control electrode that is attached to and is placed in the vicinity of a toner carrier and is spaced apart therefrom, 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 provided. Image forming apparatuses are on the market.

By the way, as a multicolor image forming apparatus using the electrophotographic technique, there is a system as shown below.

(1) Toner images of the respective colors are sequentially formed on the photosensitive drum, and the toner images of the respective colors formed on the photosensitive drum are sequentially transferred onto the recording paper so as to be transferred.
What forms a multicolor image.

(2) Toner images of the respective colors are sequentially formed on the photosensitive drum, the toner images of the respective colors formed on the photosensitive drum are sequentially transferred onto the intermediate transfer member, and then the intermediate transfer member is transferred. A multicolor image is formed by transferring a plurality of toner images transferred on top of one another onto a recording sheet in a single transfer process.

(3) A plurality of image forming units each including a photoconductor drum and a charger, an exposure unit, a developing unit, a transfer unit, and a cleaning device arranged around the photoconductor drum are arranged corresponding to each color, and the image forming unit is arranged on the recording paper. A multicolor image is formed by sequentially superimposing and transferring the toner images on the respective photosensitive drums.

However, in the multicolor image forming apparatus of the above method (1), the photosensitive drum must be rotated by the number of required colors, and it takes a long time to obtain a final multicolor image. . In addition, since the toner images of the respective colors are sequentially superimposed and transferred onto the recording paper, a highly accurate paper conveyance technique is required to convey the recording paper to the transfer portion at the same position for each color in order to prevent color misregistration.

In the multicolor image forming apparatus of the type (2), the problem of color misregistration can be solved by using the intermediate transfer member, but after the toner image of the required color is transferred to the intermediate transfer member, further recording paper is used. Therefore, the time required to obtain the final multicolor image is somewhat longer than that in the method (1).

Further, in the multicolor image forming apparatus of the type (3), since an image forming unit corresponding to each color is required, the apparatus becomes large and the cost becomes high.

Therefore, as a solution to these problems, as disclosed in Japanese Patent Laid-Open No. 63-273883,
A plurality of recording units consisting of a charger, an exposure optical system and a developing unit are arranged around one photosensitive drum, and toner images of each color are formed on the photosensitive drum while the photosensitive drum makes one rotation. A multicolor image forming apparatus has 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 completed only 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 easily occurs.

In order to solve this problem, a developing device for forming only toner on a toner carrier and developing an electrostatic latent image on a photosensitive drum by a toner layer formed on the toner carrier is known. , 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. In addition, the toner image already developed is less likely to be disturbed, a high-quality multicolor image can be obtained, and there is a possibility that toners of a plurality of colors can be superposed and developed on the photosensitive drum.

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 force 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 photosensitive drum, and the toner is separated from the toner carrier and the photosensitive 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, but in the former method, the toner carrier and the photosensitive drum are relatively large in the space. 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 if 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 toner carrier, since the toner is frictionally charged only, 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.

Therefore, as a solution to 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 desirable 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 on a toner carrier and conveyed, 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, a method has been proposed 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-1-304477 and JP-A-3-113474).

The developing device according to this proposal has a developer carrier for carrying a two-component developer having a non-magnetic toner and a magnetic carrier and conveying it as a magnetic brush in the circumferential direction; A toner carrier arranged so as to closely face and face the electrostatic latent image carrier on which a latent image is formed, a means for regulating the amount of developer on the developer carrier, and a developer carrier. A means for forming a DC superimposed AC electric field between the developer carrier and the toner carrier, which electrostatically attaches the toner in the developer constituting the magnetic brush on the body to the toner carrier, A control electrode arranged in a gap between the image carrier and the toner carrier to control the flight of the toner particles is provided, and the control electrode is separately arranged near the toner carrier and is applied to the control electrode. By alternating voltage and DC voltage Te is to form a toner cloud that is configured to form a developed image on the latent electrostatic image bearing member by the toner cloud.

That is, a uniform and stable thin toner layer is formed on a toner carrier by a two-component developing method, and an electrode structure composed of several wires and a toner arranged between the photoconductor and the toner carrier. By applying an alternating electric field between the carrier, the toner released from the toner carrier around the electrode structure is formed into a toner cloud that does not contact the photoreceptor, and a DC electric field between the photoreceptor and the toner carrier is formed. To develop on the photoconductor.

The amount and height of the toner cloud are greatly influenced by the amount of toner to be conveyed and the strength of the alternating electric field,
Keeping this constant is a very important point in stabilizing the image quality.

The above-mentioned electrode wire is adapted to adapt to the toner carrier by the average electrostatic force associated with the AC voltage and maintain a constant gap with the toner carrier.

The strength of the alternating electric field for obtaining a sufficient amount and height of the toner cloud is a peak, and usually 200 V to 1000 V (4000 V / mm to 200 V in a gap of 50 μm).
It is very high (00 V / mm), and in order to prevent discharge between the toner carrier and the electrode wire, the surface of the toner carrier is usually covered with a high resistance layer such as alumite or resin.

[0028]

However, the above-mentioned prior art has the following problems. That is, in the case of the developing device according to the above-mentioned proposal, if the high resistance layer covering the surface of the toner carrier is worn due to rubbing with the toner after long-term use, or the high resistance layer has defects or unevenness. However, there arises a problem that unevenness of an electric field occurs between the electrode wire and the toner carrier to cause image unevenness, or dielectric breakdown of the high resistance layer occurs to cause an image defect. Therefore, it has been desired to form the toner cloud with a lower electric field.

Further, since the electrode wire is in the cloud of toner flying in the alternating electric field of high frequency during development, fine powder of toner may be fixed to the electrode wire during the development process for a long time, or If coarse toner particles, carriers or foreign substances larger than the gap between the electrode wire and the toner carrier enter and accumulate, the toner supply in this part will decrease and the electric field will weaken and the generation of toner cloud will be significantly hindered. Therefore, there is a problem that the image density is lowered.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art. The object of the present invention is to stably perform multi-color development with good image quality in one pass. It is an object of the present invention to provide a developing device capable of forming a toner cloud with a low electric field and causing no image unevenness even when used for a long time.

[0031]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is a developing method in which a two-component developer having a non-magnetic toner and a magnetic carrier is carried and conveyed as a magnetic brush in the circumferential direction. An agent carrier, a toner carrier arranged so as to closely face and oppose the developer carrier and the electrostatic latent image carrier on which the electrostatic latent image is formed, and the developer carrier Means for controlling the amount of developer above,
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 magnetic brush on the developer carrier to the toner carrier; A control electrode arranged in a gap between the latent image carrier and the toner carrier to control the flight of toner is provided, and the control electrode is arranged in the vicinity of the toner carrier so as to be separated therefrom, and is applied to the control electrode. In a developing device that forms a toner cloud by an alternating voltage and forms a developed image on the electrostatic latent image carrier by the toner cloud, a vibration applying unit that vibrates the control electrode is arranged.

The vibration frequency of the vibration applying means is
For example, it is set to a value that is 1 KHz or more and 50 KHz or less and is not an integral multiple of the natural frequency of the control electrode.

Further, the vibration applying means is driven, for example, only during the developing operation.

[0034]

In the present invention, since the vibration applying means for vibrating the control electrode is arranged, the toner carried around the toner carrier is vibrated by vibrating the control electrode by the vibration applying means. Can be separated from the surface of the toner carrier. Therefore, the alternating voltage applied to the control electrode for forming the toner cloud may be a low voltage, and the high resistance layer or the like covering the surface of the toner carrier does not cause dielectric breakdown or the like to cause an image defect.

Further, in the present invention, since the vibration applying means for vibrating the control electrode is arranged, the control electrode is vibrated by the vibration applying means so that the fine powder of toner is fixed to the control electrode. In addition, it is possible to prevent coarse particles of toner, carriers, and foreign matter that are larger than the gap between the control electrode and the toner carrier from entering and accumulating, and thus preventing a decrease in image density. be able to.

[0036]

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 divided into 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 photosensitive member, and this translucent belt-shaped photosensitive member 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, is first of all the first image recording section 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 of about -400 V (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 that is modulated by the signal corresponding to the black of the image, and the potential of the exposed portion is, for example, VR, about -100V. (However, VR is a negative value) (see (b) in the 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 and is recharged by the second charger 25, and the surface potential of the photoconductor 3 has a VP of about -50.
It rises to near 0 V (see (d) of the same figure). Then the second
In the exposure device 26, by the light LR from the light emitting diode array modulated by the signal corresponding to the red color of the image,
The surface of the photoconductor 3 is exposed, and the potential of the exposed portion drops to VR of about -100 V (see (e) in the same figure). Next, this exposed portion advances to the second developing portion 28 where it is developed with the red toner TR (see FIG. 7F). 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
After passing through the image recording units 7 and 8, the surface of the photoconductor 3 is charged to about −550V by the third charger 29 and the image unit is exposed to about −140V by the third exposure device 30 in the same manner as described above. , And the third developing unit 32 reverses the development. Subsequently, the surface of the photoconductor 3 is changed by the fourth charger 33.
The image portion is charged to about −600V, the image portion is exposed to about −180V by the fourth exposure device 34, and the fourth developing portion 36 reverse-develos the image portion.

Depending on the performance of the charger, the potential of the exposed portion of the former stage is low, so it is necessary to make it higher than the charged potential of the former stage in order to make the potential of the photosensitive member uniform by recharging.
The recharge potential of the photoconductor rises as the charging, exposing, and developing steps are repeated.

Next, the charge of the toner image is adjusted by the pre-transfer corotron 9 and the charge eliminating 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 one of the trays 41 to 44 of the paper feeding unit 2 by 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 to the paper reversing unit 45 of the paper feeding unit 2 by the conveying roller 48, and once in the direction of arrow E by the reversing roller 49. 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 copying twice 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. 5 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. 5, 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 circumference 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. This developer carrying member 66 is supplied with a bias DC voltage from a bias power supply 75 and a DC superimposed AC voltage (AC peak-to-peak voltage of 50 to 500).
V, frequency 2 to 12 KHz is preferable, and DC voltage is -1
00-600V is preferable. ) Has been applied. As described above, the toner obtains a triboelectric charge of −5 to −25 μq / g due to the frictional interaction between the toner and the carrier, and by the direct current superimposed alternating electric field applied between the developer carrier 66 and the toner carrier 68, -10 on the surface of the toner carrier 68
Toner having an electrostatic charge of .about.20 .mu.c / g is electrostatically deposited so as to form a thin layer.

As the toner carrier 68, a cylinder of aluminum whose surface is anodized, a cylinder made 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 400 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 (AC peak-to-peak voltage of 50 to 2 is applied to the control electrode 69 from the developing bias power source 77.
50 V and a frequency of 2 to 12 KHz are preferable, and a DC voltage of −100 to −400 V is preferable. ) Is applied and a toner cloud is generated in the electric field. The toner carrier 68
As described above, the surface of -10 to -20 μc / g
The toner having the electrostatic charge of is electrostatically attached. The toner is separated from the surface of the toner carrier 68 by the alternating electric field formed by the DC superimposed AC voltage applied to the control electrode 69, and forms a toner cloud around the control electrode 69. The clouded toner flies in an alternating electric field, adheres to the electrostatic latent image on the belt-shaped photoconductor 3, and is developed.

By the way, in this embodiment, a vibration applying means for vibrating the control electrode is provided.

That is, the control electrode 69 is, for example,
The control electrodes 69 are made of a tungsten wire having a diameter of 30 to 200 μm, and are arranged between the belt-shaped photosensitive member 3 and the toner carrier 68 in parallel with the toner carrier 68 and apart from each other in the vicinity of the toner carrier 68. There is. Further, as shown in FIG. 1, the control electrodes 69 are positioned at intervals of 0.5 mm to 1.0 mm by the positioning grooves 81 of the wire support 80 arranged at both ends of the control electrodes 69. It is adjusted and stretched by the engaged coil spring 83 so as to be parallel to the toner carrier 68.

Further, the wire 69 and the toner carrier 6
The gap between the toner carrier 8 and the toner carrier 8 is kept substantially constant during the developing operation by adapting to the toner carrier 68 by the average electrostatic force associated with the alternating voltage applied between the wire 69 and the toner carrier 68.

Further, as shown in FIG. 1, a piezoelectric vibrating element 84 as a vibration applying means is arranged in contact with the control electrode 69 inside the positioning groove 81 at a part of the wire support 80. ing. Moreover, in the piezoelectric vibrating element 84, the vibrating direction of the control electrode 69 is such that the toner carrier 68
And the belt-shaped photosensitive member 3 are arranged so as to be orthogonal to the facing direction, that is, the direction along the tangential direction of the toner carrier 68.

Then, by applying a high frequency AC voltage (frequency of 1 KHz to 50 KHz) to the piezoelectric vibrating element 84, the piezoelectric vibrating element 84 is moved to the toner carrier 68.
The control electrode 69 is finely vibrated at a high frequency along the tangential direction of the control electrode 69.
The toner is attached to the surface of the toner carrier 68 by electrostatic force to mechanically separate the toner from the surface of the toner carrier 68 by the vibration of the control electrode 69, and further promotes the generation of the toner cloud. Therefore, the toner carrier 6
8 It is not necessary to peel off the toner adhering to the surface by electrostatic force with a high alternating electric field, and a relatively low alternating electric field between the control electrode 69 and the toner carrier 68 (1000 V / m
m to 4000 V / mm) can be applied to form a toner cloud.

Further, due to the vibration of the wire 69, the toner adheres to the control electrode 69 even if it is used for a long time, or
In order to prevent the accumulation, the toner is prevented from adhering to the control electrode 69, and the toner and the foreign matter are prevented from accumulating between the control electrode 69 and the toner carrier 68.

If the frequency of the high frequency AC voltage applied to the piezoelectric vibrating element 84 is an integral multiple of the natural frequency of the wire 69, the vibration of the wire 69 resonates with the vibration of the diaphragm and the amplitude increases, and The vibration of 69 makes a knot. If the vibration of the wire 69 causes a knot, the vibration of the knot part becomes too weak, and the effect of preventing toner sticking and accumulation cannot be obtained. Therefore, it is desirable that the frequency of the high frequency AC voltage applied to the piezoelectric vibrating element 84 is not an integral multiple of the natural frequency of the wire.

If the amplitude of the wire 69 is too large, the wire 69 may come into contact with the toner carrier 68 and damage the wire 69, and the toner cloud may become too large and toner may be scattered. Therefore, the amplitude of the wire 69 is appropriately set so as not to become too large.

As described above, in the above embodiment, since the piezoelectric vibrating element 84 for vibrating the control electrode 69 made of a wire is arranged, the piezoelectric vibrating element 84 is arranged.
By vibrating the control electrode 69 by the toner carrier 6 around the toner carrier 68,
8 surfaces can be separated. Therefore, the alternating voltage applied to the control electrode 69 for forming the toner cloud may be a low voltage, and the high resistance layer or the like covering the surface of the toner carrier 68 does not cause dielectric breakdown or the like to cause an image defect. .

Further, in the present invention, the control electrode 69
Since the piezoelectric vibrating element 84 that vibrates the piezoelectric vibrating element 84 is arranged, the piezoelectric vibrating element 84 causes the control electrode 69 to move.
By vibrating, the fine powder of toner is fixed to the control electrode 69, and the coarse powder of the toner, the carrier and the foreign matters larger than the gap between the control electrode 69 and the toner carrier 68 enter and deposit. It is possible to prevent the deterioration of the image density.

[0077]

According to the present invention, which has the above-described structure and operation, it is possible to form a toner cloud with a low electric field and to perform multicolor development with good image quality in one pass stably. It is possible to provide a developing device that does not cause image unevenness even when used for a long time.

[Brief description of drawings]

FIG. 1 is a front view of essential parts showing an embodiment of a developing device according to the present invention.

FIG. 2 is a configuration diagram showing an image forming apparatus to which the developing device according to the present invention can be applied.

FIG. 3 is a block diagram showing a control circuit.

4 (a) to 4 (l) are potential explanatory diagrams showing image forming steps, respectively.

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

[Explanation of symbols]

3 belt-shaped photoconductor, 28 second developing machine, 66 developer carrier, 68 toner carrier, 69 control electrode, 84
Piezoelectric vibration element.

Claims (3)

[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 the developing apparatus being characterized in that it disposed a vibration applying means for vibrating the control electrode. 2. The vibration frequency of the vibration applying means is 1 KH.
The developing device according to claim 1, wherein the developing device has a frequency of z or more and 50 KHz or less and is not an integral multiple of the natural frequency of the control electrode. 3. The developing device according to claim 1, wherein the vibration applying unit is driven only during a developing operation.