JPH02238471A - Image forming device - Google Patents

Abstract

PURPOSE:To form a proper, a multicolor or a multiple image in simple constitution by obtaining such developing means as that each developing means holds and conveys a developer and is provided with a developer carrier which develops a latent image on an image carrier in a developing part facing the image carrier. CONSTITUTION:The developing means 6 positioned on the top upstream side of the image carrier 1 in its moving direction houses a developer which is a two-component developer having toner particles and magnetic particles and the other developing means 8 houses a developer which is a two-component developer having single- component toner particles and magnetic particles. The developing means 6 and 8 carry and convey the developers and are provided with the developer carriers 32 and 52 which develop a latent image on the image carrier 1 in the developing part facing the image carrier 1. Then, the developing means 8 which houses the single- component toner particles and the magnetic particles is provided with a magnetic particles binding member 54 which regulates the supply of the magnetic particles in the developer to the developing part. The single-component toner particles are film-coated onto the developer carriers 32 and 52 and supplied to the developing part. Hereby, color mixture caused in plural developing means is eliminated in further simple constitution and a clear image can be formed.

Description

[Detailed Description of the Invention] - No. 1 The invention relates to an image forming apparatus using an electrophotographic method or an electrostatic recording method, and in particular, a color electrophotographic copying device using two or more colors, or a color electrophotographic copying device that performs multiple development using a plurality of developing means. This article relates to an image forming device used in various other multicolor electrophotographic copying devices. As is well known, an image forming apparatus, such as a two-color electrophotographic copying apparatus that reproduces document image information using electrophotography, is equipped with two image carriers, ie, photosensitive drums. , a device configured to overlay and transfer developed images of different tones formed on the surface of each of these photoreceptor drums onto a transfer material conveyed from outside the apparatus by a transfer material conveyance system, and one photoreceptor drum. Set up. A device configured to form a developed image for one color on the surface of the photosensitive drum during one rotation of the photosensitive drum, and to form a developed image for two colors during two rotations and transfer it to a transfer material. be. The former device has two photoreceptor drums, which increases the size of the device and also causes an increase in cost. On the other hand, the latter device has one photoreceptor drum.
Although the device itself can be made more compact compared to the former device because it only requires two rotations, it has the disadvantage that the copying speed is slow because a developed image for two colors cannot be formed unless the photoreceptor drum rotates twice. ．． Therefore, by eliminating the drawbacks of each of the above-mentioned two methods and adopting the advantages of both methods, one photoreceptor drum is used as a two-color electrophotographic copying device.
Apparatuses have been proposed in which images are developed using two color developers simultaneously or sequentially during rotation. This device has a problem in that the developer from the upstream developing means in the direction of movement of the photosensitive drum is mixed into the developing section of the downstream developing means. Therefore, the color tone of the toner particles in the developing means on the lower side was selected to be darker than that in the developing means on the upstream side, so that even if there was mixing, it would not be noticeable. The friction band 'fL charge amount (tripo) of the toner particles in the developing means on the side is set to be larger than that of the toner particles in the developing means on the lower side, and the developing section on the downstream side is developed on the upstream side. The toner particles on the upstream side are prevented from being peeled off from the surface of the photoreceptor drum, and furthermore, the developing means on the downstream side holds the developer without contacting the photoreceptor drum. Efforts have been made to avoid color mixing by using an electric field to fly the toner. In addition, when a two-component developer having toner particles and magnetic carrier particles is used as the developer in the upstream developing means, the developer attached to the photoreceptor drum for development may contain The contained magnetic carrier particles have weak adhesion to the photoreceptor drum and are likely to fall due to gravity, so there is a risk that they may be mixed in at the downstream developing section due to magnetic attraction in the downstream developing means. be. the result,
The mixed carrier particles cause problems such as variations in the toner tripod in the downstream developing means and uneven application of the toner onto the developer carrier. In addition, different types of development may occur, such as when the upstream development section uses a two-component developer and a magnetic brush development method, while the downstream development section uses a one-component developer and a non-contact development method. If this method is adopted, a major problem arises in that different kinds of developers are mixed in the downstream developing means. For this reason, a magnetic suction roller is used between the two developing means to prevent the carrier particles from moving downstream, and the downstream developing means is provided with a means for removing the carrier particles that have entered the downstream side. Some effort is needed. However, various measures such as L-missing have not been a complete solution to the problem of developer contamination, and
This makes the equipment complicated. Problems such as increasing the size also arise. Accordingly, an object of the present invention is to develop a system for developing a two-color electrophotographic copying apparatus, for example, in which images are developed simultaneously or sequentially by a plurality of developing means while one image carrier rotates. An object of the present invention is to provide an image forming apparatus that solves the above-mentioned defects and problems, has a simple configuration, and is capable of forming good multicolor or multiple images. The objects of the present invention are completely achieved by the configuration described below. In summary, the present invention provides a plurality of developing means located near an image carrier and arranged in parallel in the direction of movement thereof, each developing means containing a developer of a different tone, and each developing means storing a developer of a different tone. In an image forming apparatus configured to visualize an Ns image on an image carrier, in the developing means E located at the most upstream side in the moving direction of the image carrier, the stored developer is mixed with toner particles and magnetic particles. The developer contained in the other development L stage is a two-component developer having one-component toner particles and magnetic particles, and each developing means has:
A developer carrier is provided that carries and conveys a developer and visualizes a latent image on the image carrier in a developing section facing the image carrier, and accommodates lIO & separation toner particles and magnetic particles. The developing means is provided with a magnetic particle restraining member for restricting the magnetic particles in the developer from being supplied to the developing section, and the developing section is provided with a thin layer of l-component toner particles on the developer carrier. An image forming apparatus characterized in that it is supplied by
It is. Preferably, the thickness of the developer layer in the developing section of the upstream developing means is larger than the gap between the image carrier and the developer carrier, and the thickness of the developer layer in the developing section of the downstream developing means is preferably larger than the gap between the image carrier and the developer carrier. and the developer carrier. Furthermore, the same magnetic grains f can be used for each developing means.
笈▲1 Hereinafter, one embodiment of the wooden invention will be explained in detail with reference to the drawings. FIG. 2 shows a schematic configuration of an image forming apparatus according to the present invention, and particularly illustrates a two-color electrophotographic copying apparatus. As is clear from FIG. 2, the apparatus of the present invention includes an optical system that exposes given original image information, a copying system that receives and copies the original image exposed by the optical system, and It consists of an image signal controller 2 which is an adjustment means for adjusting the drive of the optical system. The optical system is exposed
The copying system consists of a laser optical system 3, and a plane mirror 20 disposed near the copying system. A cleaning device 18, a static elimination lamp l9, a corona Mitt device 4, 2l, a developing device 6, 8 as a developing means, a paper feed cassette 10, a paper feed roller 11,
It consists of a pair of registration rollers 12, a guide member 13, a transfer corona discharger 9, a sheet conveying system 14, a fixing device 15, and a pair of discharge rollers 16. The laser optical system 3 described above emits light according to a first image pattern, which will be described in detail later, based on a drive command signal output from the image signal controller 12. The surface of the photosensitive drum 1 is irradiated with a light beam 7 corresponding to the second image pattern. The photoreceptor drum 1, which has a photoreceptor such as an OPC formed on its outer periphery, is supported by a shaft means (not shown) so that it can rotate only in the direction of arrow a (clockwise) in FIG. The cleaning device 18 scrapes and collects the developer remaining on the photoreceptor of the photoreceptor drum 1. The charge eliminating lamp 19 is disposed on the downstream side of the cleaning device 18 in the rotational direction of the photoconductor drum (1), and is adapted to eliminate charges remaining on the photoconductor I- of the photoconductor drum 1. There is. #i The corona discharger 4 is disposed on the downstream side of the static elimination lamp 19 in the rotational direction of the photoreceptor drum l. The residual developer is removed by the cleaning illumination step 8 described above, and the static elimination lamp 1 is removed.
This is to uniformly charge the photoreceptor after the residual charge has been removed by step 9. In the section from the position where the corona waste electric device 4 is disposed to the position where the developing device 6 is disposed on the lower side of the rotational direction of the photoconductor drum 1, the peripheral edge of the photoconductor drum 1 is as follows: This is a space, and the above-mentioned laser optical system 3 is installed in the space.
a plane mirror 20 that receives the first laser beam 5 irradiated from the plane, reflects it, and sends it onto the surface of the photosensitive drum 1;
is installed. The above-mentioned developing device 6 is located close to the surface of the photoreceptor drum l on the rotational direction f side of the photoreceptor drum l with respect to the arrangement position of the front mirror 20, and the developing device 6 is further connected to the photoreceptor of the developer 6. A corona discharger 21 is disposed on the downstream side of the body drum l in the rotational direction. The corona discharger 2l uniformly re-charges the surface of the photosensitive drum l after the development is completed by the developing device 6. Further, on the downstream side of the corona discharger 21, there is a developing device 8 facing the developing device 6 with an interval that allows the second laser beam irradiated from the laser optical system 3 to pass through. They are arranged respectively. The details of the configurations of the developing devices 6 and 8 described above will be described later. The guide member l3 is disposed close to the surface of the photoreceptor drum l on the downstream side in the rotational direction of the photoreceptor drum l than the position where the developing device 8 is provided, and guides the transfer material one by one. A transfer material such as a transfer paper supplied from the paper feed cassette IO is received through a feeding roller l1 to be sent out and a pair of registration rollers l2 rotating in synchronization with the rotation of the photoconductor drum l, and the transfer material is transferred to the photoconductor. drum l
It is configured to guide you to the surface. The transfer corona discharger 9 is located on the downstream side in the rotational direction of the photosensitive drum 1 from the position where the guide member l3 is provided.
The developed image on the photoreceptor drum L is guided by the guide member l3 to the outer peripheral surface of the photoreceptor drum l, and the developed image on the photoreceptor drum l is transferred to the transfer material adsorbed to the outer peripheral surface. It is transcribed sequentially. Said sheet conveyance system l4
is located on the downstream side in the rotational direction of the photoreceptor drum l than the placement position of the transfer corona discharger 9, and is arranged with the starting end side in the conveying direction facing the outer circumferential surface of the photoreceptor drum l. It receives the transfer material separated from the outer peripheral surface of the photosensitive drum 1 by a separation static eliminator (not shown) and conveys it to the fixing device 15. The fixing device l5
is disposed close to the terminal end side of the sheet conveyance system l4 in the conveyance direction, and is configured to fix the developed image transferred from the photosensitive drum l to the transfer material by the transfer corona discharger 9 to the transfer material. It is configured. The discharge port-ra pair l6 is disposed on the left side of the apparatus main body 100, as shown in FIG. It is designed to be discharged. As is well known, the image forming apparatus configured as described above is under the control of an electronic circuit control means (not shown), such as a microcomputer, which is built into a control unit (not shown) as a whole. This is what has been written. In one embodiment according to the present invention, the microcomputer subtracts the DC component of the developing bias voltage applied to the developing device from the latent image potential of that area when the photosensitive drum l is irradiated with laser light. Based on the potential of the latent image on the subsequent photoreceptor drum l, the developing devices 6 and 8 each perform development based on characteristic curve data indicating the relationship between the development density of the darkened image stored in advance and the potential of the latent image. It functions as a means to set the developing bias potential applied during development. Figure 1 is an enlarged view of the main parts of the configuration of Figure 2.
Identical parts 9 are given the same reference numerals. Here, the developing device 6 is a normal two-component developing device, but the most preferable configuration is shown in this embodiment. The developing device 6 includes an image carrier,
That is, it has a developing sleeve 32 as a developer carrier that is close to or in contact with the photosensitive drum l. The developing sleeve 32 is made of aluminum, SUS 3 1 6, for example.
It is made of non-magnetic materials such as Also, the developing sleeve 3
2, the right half circumferential surface is inserted into the container 27 through a horizontally elongated opening formed in the lower left wall of the developing container 27 in the longitudinal direction of the container, and the left half circumferential surface is exposed outside the container and rotatably supported on a bearing. It is rotatably driven in the direction of arrow b. Incidentally, the surface of the developing sleeve 32 has an unevenness of 0.5 to 30 gm, which is advantageous for conveying the developer. A fixed permanent magnet (magnet) 3l serving as a fixed magnetic field generating means is disposed within the developing sleeve 32, and even when the developing sleeve 32 is rotationally driven, this magnet 31 is fixedly maintained in the illustrated position and orientation. ．． This magnet 31 is N1
Pole magnetic pole 31a. S1 pole magnetic pole 3lb. Nz magnetic pole 3
1c. It has 4 magnetic poles: Sz pole and 3ld magnetic pole. Note that an electromagnet may be used as the magnet 3l instead of a permanent magnet. A non-magnetic blade 34 serving as a developer regulating member is disposed on the upper edge side of the opening of the developer supply device in which the developing sleeve 32 is disposed, along the length of the upper edge of the opening. The non-magnetic blade 3
4 has its base fixed to the side wall of the container, and its tip side protrudes to the outside of the container 27 beyond the upper edge of the opening. This non-magnetic blade is formed by bending, for example, SUS316 so that its cross section is in the shape of a square. Further, a magnetic particle limiting member 35 whose front end surface serves as a developer guide surface 351 is provided adjacent to the non-magnetic blade 34 . The developer has red non-magnetic toner particles 28 and magnetic particles 33 as magnetic carrier particles, the toner particles 28 are replenished from a toner storage container 40, and the magnetic particles 33 are replenished from a magnetic particle storage container 4L. Ru. The magnetic particles 33 are made of ferrite particles (f & large magnetization 60 e
(m u /g) coated with a resin may be used. or. In order to prevent the leakage of magnetic particles 33 or non-magnetic toner particles 28 from the developer container l27 side portion in which the developer sleeve 32 is disposed, a magnetic material 37 is disposed inside the lower part of the developer container, facing the developer sleeve 32. ．． iQ is done. The magnetic material 37 is, for example, a plated iron plate. As a result, the magnetic field between the magnetic body 37 and the Sz polarity magnetic pole 31d provides a sealing effect that recovers the magnetic particles 33 and prevents leakage. Furthermore, a toner supply member 39 is provided within the developer container 27 in order to supply toner to the magnetic particle brush portion formed by the fixed magnetic pole 3l within the developer sleeve 32.

The toner supply member 39 has a rubber sheet affixed to a rotatably supported plate, and serves to convey toner by sweeping the lower surface of the developer container in the direction of arrow C. Toner supply member 39
Toner is supplied to the toner storage container 40 by a toner conveying member 38 rotating in the direction of arrow d. A sealing member 42 is provided at the lower portion of the developer container 27 to seal off toner that accumulates there. The sealing member 42 has elasticity, is bent along the rotational direction of the developing sleeve 32, and elastically presses the surface side of the sleeve 32. This sealing member 42 has an end on the downstream side in the rotational direction of the sleeve in a contact area with the sleeve so as to allow the developer to enter the inside of the container. A scattering prevention electrode plate 43 is disposed at the lower edge of the opening of the developer container 27 to prevent floating developer generated during the development process from scattering by applying a voltage of the same polarity as the developer to cause the floating developer to adhere to the photoreceptor side. Ru.

In addition, from the developing bias power supply 44, one bit of support such as a rectangular wave is supplied.
A developing bias voltage in which a component is superimposed on a DC component is applied between the photosensitive drum 1 and the developing sleeve 32. Next, the configuration on the exit side of the developer container formed by the developer guide surface 351 of the developer limiting member 35 and the magnetic pole 3l facing the developer guide surface 351 will be explained. The developer conveyed by the developing sleeve 32 passes between the sleeve 32 and the developer guide 351.
The magnetic particles are retained in the stool-shaped space formed between the particles and subjected to the stirring and mixing action of the magnetic particles under appropriate packing conditions.
This significantly improves the attachment of tripo to the 1-ner particles. Furthermore, by installing a magnetic body 341 on the non-magnetic blade 34 side of the developer limiting member 35, the magnetic pole 31
A strong concentrated magnetic field is generated between a and a. The effect of stirring and loosening the magnetic particles is improved. Next, another developing device 8 will be explained. In the developing device 8,
An opening of the developing container 50 is provided facing the photosensitive drum l, and a developing sleeve 52 is disposed there with a part thereof facing the opening (the developing sleeve 32 in the developing device 6 (It can have a similar configuration). Also, the above g
A magnetic particle restraining member 54 is disposed above the L image sleeve 52, and its abdomen is placed above the developing sleeve 52.
It is in contact with the circumferential surface of the This magnetic particle restraining member 54 is composed of a rubber plate and a thin metal plate, and is designed to make elastic contact. The structure of the magnetic particle restraining member 54 is not limited to the structure shown in FIG. 1, but may be, for example, the structure shown in the embodiment shown in FIG. In FIG. 3, the magnetic particle restraining member 54 is a non-magnetic elastic blade, and is disposed along the longitudinal direction on the upper edge side of the opening of the developer supply container in which the developing sleeve 52 is disposed, and one end is connected to the developer container. It is fixed to the side wall, and the developing sleeve 5 is attached to the tip side.
It is in contact with the oka surface of 2. A magnetic member 70 is fixed to a portion having a certain area including the free end. Here, the magnetic member 70 has a function of increasing the effect of strengthening the magnetic field component in the tangential direction of the developing sleeve and strengthening the binding force of the magnetic particles 57. In this embodiment, the non-magnetic elastic blade 54 has a thickness of 0.5 mm. 5-3 mm, hardness 30°~90″'
urethane rubber was used, and as the magnetic member 70, an iron plate with a thickness of 0.5 to 2 mm was used. Also, the contact pressure is 20
~200 g/cm (development, force per unit length in the longitudinal direction of the sleeve). Note that the above magnetic material is not an essential requirement. In the wooden embodiment, the distance from the free end of the non-magnetic elastic blade 54 to the magnetic member 70 is 5 mm so that the magnetic field between the magnetic pole N3 of the magnet 51 and the magnetic member 70 acts effectively to restrain the magnetic particles. Hereinafter, < is preferably 3 mm or less. If this sentence is larger than 5 mm, the Bi member 70
Since the magnetic field between the magnetic pole N3 and the magnetic pole N3 acts in a direction that makes it easier for the magnetic particles to pass through the point 7l, the non-magnetic elastic blade 54
This will increase the burden of mechanical restraint. Therefore, the setting conditions for the non-magnetic elastic blade 54 become narrower. In this embodiment, the tip of the elastic member 54 and the developing sleeve 52
The relationship between the gap dI' and the particle diameter r of the magnetic particles 57 is r
> d 1 is preferable. That is, the condition for the non-magnetic elastic blade 54 to contact the sleeve is preferably such that the contact surface of the non-magnetic elastic blade 54 contacts the belly within a range including its free end. In addition, according to the configuration of the above-described embodiment, when the non-magnetic elastic blade 54 contacts or presses the developing sleeve 52, leakage of magnetic particles can be almost completely prevented.
The reason for this is that not only the restraining force due to the magnetic field between the magnetic member 70 and the magnetic pole N] but also the mechanical restraining force due to the non-magnetic elastic blade 54 acts. However, in this case, the contact pressure and tip shape of the non-magnetic elastic blade 54 are adjusted so that the developer coating layer that is to be applied onto the developing sleeve 52 after passing through the blade 54 is not scraped off by the non-magnetic elastic blade 54. Is it necessary to set the required conditions? For example, the contact pressure and d. Generally, it is set only by the non-magnetic elastic blade 54, but according to the invention, the action of the magnetic force generated between the magnetic member 70 and the magnetic pole N is added. As a result, the non-magnetic elastic blade 54 is uniformly drawn toward the surface of the developing sleeve 52 in its longitudinal direction, so that the mechanical setting conditions regarding the non-magnetic elastic blade 54 are loosened accordingly. Referring back to FIG. 1, a magnetic particle circulation regulating member 55 is provided on the upper side of the inner end of the L magnetic particle restraining member 54. Note that due to the rear force of the opening, the developer container 5
Toner feeding members 59 and 60 are provided at the bottom of the printer. Inside the developer container 50, a toner feeding member 59,
A magnetic brush is formed by a blue one-component non-magnetic toner 58 and a layer of magnetic particles 57 (which may be the same as the magnetic particles 33 used in the developer 6) restrained by the developing sleeve 52. and is being accommodated. The toner feeding members 59 and 60 are moved in the direction of the arrow (
Clockwise e. f), and by its rotation, the one-component non-magnetic toner ~58 is transferred to the magnetic particles 57.
The non-magnetic toner 58 is transferred to the layer of the magnetic particles 57 to form a layer of the magnetic particles 57. The developing sleeve 52 has magnetic poles N3 and S3 inside.
A magnet roll 51 having a diameter is fixed. The developing sleeve 52 is moved in the direction of arrow g (counterclockwise).
When the magnet roll 51 rotates, the magnetic particles 57 to which the non-magnetic toner 58 attached, which is restrained by the magnetic pole N1 of the magnet roll 51, cooperate with the magnetic force of the magnet roll 51.
is conveyed toward the outside of the developing device 8. The magnetic particle restraining member 54 and the magnetic particle circulation regulating member 55 are configured to prevent the two-component system from being transported to the outside of the developing device 8 by the rotation of the developing sleeve 52 and the magnetic force of the magnet roll 51. In the developer, magnetic particles 5
7 is caused to fall under its own weight in the direction of arrow h in FIG. 1 by colliding with the layer of magnetic particles 57. And non-magnetic toner 58
The one passes through the opening as it is without falling under its own weight, and at that time, it is carried out as a thin layer of the required thickness on the surface of the developing sleeve 52, and is transferred to the developing section facing the outer periphery of the photoreceptor drum l. Sent to. In addition, in the above embodiment, the regulating member 55 is not always necessary depending on the conditions. The magnetic particles 57 that have fallen under their own weight come into contact with nearby non-magnetic toner 58 and adhere thereto, and then are attracted onto the developing sleeve 52 again by the magnetic force of the magnet roll 51 described above to form a magnetic brush. do. Developing bias'? The t source 56 applies a developing bias voltage in which an alternating current component such as a rectangular wave is superimposed on a direct current component to the developing sleeve 52, so that an electrostatic latent image is formed by the second laser beam 7. photoreceptor drum 1
A thin layer of non-magnetic toner 58 on the developing sleeve 52 is supplied to a developing section opposite to the developing section, and the electrostatic latent image is developed by jumping. Note that in the above embodiment, the developing bias power supplies 44 and 56
may be used in common. Furthermore, seal members 62 and 63 having the same functions as the aforementioned seal member 42 and scattering prevention plate 43 are provided at the lower edge of the opening of the developer container 50, respectively. Also, Magne 2 Troll 5L N4. The S+ pole functions to efficiently collect and convey onto the developing sleeve 52 the magnetic particles 57 that have passed through the restraining member 54 or the magnetic particles 33 that have adhered to the photosensitive drum l from the developing unit 6 side. There is. In this example, the finer the magnetic particles, the better the image quality, which is particularly advantageous in avoiding ground blur and sleeve ghost. This is because as the particle size becomes finer, the specific surface area increases, and the degree of contact with the object to be contacted also increases, so that sufficient tripo is applied to the developer between the developing sleeve 52 and the magnetic particles. It is. On the other hand, if the magnetic particles are made coarser, soil burrs will occur. However, when the particle size is made smaller, the magnetic binding force caused by the magnetic field becomes smaller, making it easier for the magnetic particles to leak out of the developer container. Therefore, the particle size distribution of the magnetic particles should be as fine as possible without leaking out of the container, and accurate classification is required. For example, by a known method, ferrite-based magnetic particles coated with silicone-based resin can be made into JIS-zeao magnetic particles.
Classify using a standard sieve specified by JIS-
The particle size distribution was measured using a particle size distribution test method based on H2fiOl, and the above magnetic particles were classified into 5 stages between 145 and 400 mesh, and the quality of image formation was compared between these mixed appropriately. As a result, the following results were obtained. This was confirmed. ℃ 4 to deal with leakage of magnetic particles
The particle size component of 00 mesh (particle size 37 gm) or less should be 20% by weight or less, and in order to sufficiently prevent leakage, 10
It is preferable to keep it below % of heavy acid. 145 mesh (grain size 105
pm) or higher particle size components are classified and removed as much as possible. It is preferable that the particle size component of 200 mesh (particle size 74 m) is 30% by weight or less. For further improvement, use 250 mesh (
It is preferable that the particle size component (particle size 63 pm) is 30% by weight or less. Q) Regarding yellowtail, the average particle size is 350 to 200.
In the mesh (particle size 44 to 74 pm) range, there was almost no occurrence even in the case of relatively large magnetic particles. This is because the non-magnetic developer on the developing sleeve is rubbed by the elastic member, so even if the sliding friction by the magnetic particles alone is insufficient to apply the tripod, such as causing ground force blur,
In order to generate ground yellowtail (6f).

Note that each magnetic particle may be made of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more types of magnetic particles. As described above, in the developing device 8, each part of the non-magnetic developer has a sufficient amount of charge on the developing sleeve 52, and a uniform thin layer can be formed stably over a long period of time.
Therefore, this thin developer layer makes it possible to develop the latent image on the Hs image bearing surface to one brightness and with good resolution. Furthermore, since non-magnetic developers can produce vivid colors, high-quality color copies (single color, multicolor, natural color) with excellent color reproducibility can be obtained. Next, the developing device 8 will be explained in more detail. As the developer sleeve 52, the surface of an aluminum sleeve with a diameter of 20 mm was subjected to amorphous sandblasting treatment with 7 random abrasive grains as in the case of the developer 6, and the magnet 5
It is magnetized with 4 poles, N pole and S pole, and the N3 pole is about 750
As shown in Figure 3, the sleeve was placed at a position where the angle α made with the vertical line m passing through the center O of the sleeve was 95°. Furthermore, when the above magnet was set to 1000 Gauss, the circulation in the h direction in Figure 1 was approximately doubled. In addition, as magnetic particles, 74 to 44 g m (
200 to 350 mesh), ferrite particles whose surface is coated with a mixed resin of acrylic and fluorine (I
emu/g) and styrene/g as a non-magnetic developer.
When using a blue toner in which 0.7% of colloidal silica was externally added to toner powder with an average particle size of 12 gm, consisting of 100 parts of butadiene copolymer resin and 5 parts of copper cap cyanine pigment, the developing sleeve Coating FJ is approximately 30 to 50 μm, and the tripo charge amount of one toner on the developing sleeve measured by the blow-off method is -14 pots.
/ g was obtained. As is already well known, the image forming process in the image forming apparatus described above is based on the disappearance of the surface potential on the photoreceptor drum 1 corresponding to an original image formed on the photoreceptor drum 1 by irradiation with laser light or the like. This is done using the so-called reversal development method, in which toner is applied to the area. In carrying out such a reversal development method, the photoreceptor drum 1-F is uniformly charged to about -600 V by the corona discharger 4, and the photoreceptor drum 1-F is uniformly charged to approximately -600V by the corona discharger 4, and the photoreceptor drum 1-F is uniformly charged to approximately -600V by the corona discharger 4. The potential of the first image pattern in the original image information formed by the laser beam 5 of 1 is set to -150V, and the outer surface of the photosensitive drum 1 and the outer surface of the developing sleeve 32 are opposed to each other. Set the gap to approximately 350 l. and,
Based on a drive command signal from a microcomputer (not shown) built in the control unit (not shown) mentioned above, the developing bias applied to the developing sleeve 32 from the developing bias power supply 44 is controlled at a frequency of 1.
．． 6KHZ. 71 The peak-to-peak value of the pressure waveform is 1.
When the voltage is 3KV and the center value is set to -450V, a good developed image without uneven development or fog can be obtained when the non-magnetic toner 28 charged with negative polarity is supplied from the developer 6. Then, the photoreceptor drum 1}.
The charging potential for uniformly charging is set to about -700V, and the potential of the second image pattern in the document image information is set to -250V by the second laser beam 7 emitted from the laser optical system 3. In addition, the facing gap between the outer circumferential surface of the photoreceptor drum l and the outer circumferential surface of the developing sleeve 52 is set to about 200 μL. Based on a drive command signal from a microcomputer (not shown) built in the control unit (not shown) described above, the developing bias power supply 56 applies a developing bias to the developing sleeve 52 at a frequency of 2. 0KHZ.
The peak-to-peak value of the voltage waveform is 1. When the voltage is OKV and the center value is set to -600V, when the non-magnetic toner 58 charged with negative polarity is supplied from the developer 8,
There is almost no color mixture in the developed image of the first image pattern developed by the developing device 6, and a good developed image can be obtained. The alternating current TE. applied to the developing sleeve 52 of the developing device 8. The TL field is preferably applied at a potential that does not significantly exceed the image area voltage of the photosensitive drum 1F. The reason for this is to minimize color mixing caused by toner once attached to the photosensitive drum l returning to the developing sleeve 52. The non-magnetic developer layer formed on the developing sleeve 52 is
To maintain a non-contact state with respect to the photosensitive drum 1 and to enable superimposed development in a developing device 8 without disturbing the developed image formed on the photosensitive drum 1 in the developing device 6. Note that this strongly depends on the alternating electric field formation. Further, in the structure of the developing device 6, as described above, it is important to form a wedge-shaped space between the sleeve 32 and the developer guiding surface near the opening in order to improve the tripod application to the toner. This makes it easier to increase the tripo value of the toner in the first developed image, which is necessary to prevent color mixing when overlapping development is performed on the photoreceptor drum l. According to the experiment, 1f, developer 8
When the developer used in the above was used in the developer 6, the tripo charge amount of the toner when used in the developer 8 was -14 pcou1/
g, while in developer 6 it was -27p-c
The value of o u l / g has been obtained. In fact, in order to prevent color mixing, it is desirable to have a tripo value of this level. Also, the characteristics of the magnetic particles set in the developing units 6 and 8 should be adopted and shared when actually used. By that,
Even if the magnetic particles 33 of the developing device 6 are mixed into the magnetic particles 37 of the developing device 8 via the photosensitive drum 1, there is an advantage that the characteristics of triboelectricity imparted to the toner are not changed. This allows stable, high-quality images to be obtained over a long period of time. Further, the magnetic particles 33 attached to the photoreceptor drum 1 from the developing device 6 are finally transferred to the photoreceptor drum 1 in the developing device 8.
It can be almost completely removed from the surface of the magnetic particles, and clear color images can be obtained without adhesion of magnetic particles. Although non-magnetic toner particles were used as the toner particles in the above embodiments, magnetic toner particles may also be used as long as they have weaker magnetism than the magnetic particles 33 and 57 and can be tripo-charged. In addition, in the above embodiment, the method of supplying the developer was described by taking as an example a disposable type developer in which the developer container is integrated with the developer container. The present invention can also be applied when using a replaceable replenishment cartridge. Also,
A separate device may be provided to maintain a constant mixing ratio of non-magnetic toner particles and magnetic particles in the developer container. Furthermore, as the developing method of the developing device 8, a non-contact developing method using an alternating W bias electric field is preferable, but as long as it does not disturb the developed image formed on the photoreceptor drum l in the developing section of the developing device 6. Other developing methods may also be used. Further, although the waveform of the developing bias is a mating electric field for the developing device 8, it is also possible to replace it with a DC electric field. Furthermore, in this embodiment, the process of performing multiple color overlapping development during one rotation of the photoreceptor drum 1 has been described, but the process in which multiple color overlapping development is performed by rotating the photoreceptor drum 1 for each color is also applicable. can also be applied. The developing bias may be a DC electric field regardless of the periodic displacement electric field. It is preferable that the non-magnetic blade be made of a material whose triboelectric series is distant from the developer so as to impart a predetermined charging polarity to the developer. Further, the surface of the non-magnetic elastic blade facing the developing sleeve may be roughened to provide unevenness on the surface to further improve the ability to attach the toner. Furthermore, the magnet 51 disposed within the developing sleeve 52 is not limited to the four-pole arrangement shown in the embodiment.
It may be configured with only two magnetic poles as long as it does not significantly affect the collection of magnetic particles according to the present invention. Furthermore, conductive powder such as carbon may be mixed into the elastic member to maintain it at the same potential as the sleeve. Since the present invention is as detailed above, it is possible to avoid color mixing in multiple developing means with a simple configuration, form a clear image, and exhibit high speed. We can provide an image forming device that can perform

[Brief explanation of drawings]

FIG. 1 is a sectional view of the main parts of a multicolor image forming apparatus showing an embodiment of the present invention. Figure 2 is a schematic diagram of the entire system. FIG. 3 is a sectional view showing another embodiment. l: Photosensitive drum (image carrier) 2. Image signal controller 3: Laser optical system 4: Corona discharger 6: Developing device (developing means) 8. Developing device (hand-held development) 32. 52: Developing sleeve (developer carrier) 54: Magnetic particle restraining member 55: Magnetic particle circulation regulating member No.

Claims (1)

[Claims] 1) A plurality of developing means are located in the vicinity of the image carrier and arranged in parallel in the direction of movement thereof, each of the developing means contains a developer of a different tone, and each developing means is used to develop the image on the image carrier. In an image forming apparatus configured to visualize a latent image, the developing means located at the most upstream side in the moving direction of the image carrier contains a two-component developer containing toner particles and magnetic particles. In the other developing means, the stored developer is a two-component developer having one-component toner particles and magnetic particles, and each developing means supports and transports the developer, and is connected to the image carrier. In the developing means, which is equipped with a developer carrier that visualizes the latent image on the image carrier in opposing developing sections and accommodates one-component toner particles and magnetic particles, the magnetic particles in the developer are An image forming apparatus characterized in that a magnetic particle restraining member is provided to restrict supply of toner particles to a developing section, and one-component toner particles are supplied to the developing section by coating a thin layer on a developer carrier.