JP3605785B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and relates to an electrophotographic image forming apparatus that forms an image by arranging a charging unit, an image exposing unit, a developing unit, and the like around an image forming body.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as one type of an electrophotographic image forming apparatus, a charging unit, an image exposing unit, and a developing unit are arranged around an image forming unit, and charging of the image forming unit by the charging unit and image exposing unit by the image exposing unit are performed. An image forming apparatus is used which forms a latent image on an image forming body by the above method and forms an image on the latent image by contact reversal development by a developing unit.
[0003]
On the other hand, in order to effectively use the toner, after the image is formed, the transfer residual toner remaining on the image forming body is cleaned by a cleaning unit, and the cleaning toner is transported to a developing unit using a screw pipe or the like, and is re-used in the developing process. The used toner recycling method is generally used. However, since the mechanism of the toner recycling method for transporting the cleaning toner using the screw pipe is complicated, a roller-shaped member is used as the toner recycling means, and the transfer residual toner in the image area on the image carrier is once formed. The toner on the cleaning means in the non-image area is again discharged (attached) to the image forming body and carried to the developing means, and the developing means removes the toner on the image forming body from the developing means. Methods for collecting and reusing them inside have been proposed in JP-A-8-166750, JP-A-8-152832, JP-A-8-6454, JP-A-6-51672, and the like.
[0004]
[Problems to be solved by the invention]
However, in the toner recycling unit using the roller member according to the above proposal, the transfer residual toner on the image forming body has a strong adhesive force to the image forming body, and the transfer residual toner to the toner recycling unit is not collected well. Also, the toner is not sufficiently discharged to the image forming body from the toner recycling unit because of strong adhesion to the toner recycling unit.
[0005]
For this reason, the present inventors use an image forming section (image forming area) on the image forming body by using toner recycle means using a magnetic brush made of magnetic particles formed on a magnetic particle conveying body (sleeve) instead of the roller member. 1), the transfer residual toner is once collected from the image forming body by the toner recycling means by the magnetic brush, and the toner on the toner recycling means is discharged (attached) to the image forming body again in the non-image area (non-image forming area) and developed. We are studying a method of collecting the toner on the image forming body inside the developing unit and reusing it by the developing unit, but if the toner concentration in the magnetic brush of the toner recycling unit becomes high, A problem arises in that the ability to collect transfer residual toner (cleaning ability) is reduced, and cleaning failure occurs.
[0006]
Also, about 10% of the toner image formed on the image is usually collected by the magnetic brush as the transfer residual toner. However, if the amount of the transfer residual toner on the image forming body due to the amount of the toner developed by the developing means is large, the magnetic brush is removed. , The recovery ability (cleaning ability) is reduced, and a cleaning failure occurs.
[0007]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and changes the collecting ability in accordance with the toner concentration in the magnetic brush of the toner recycling means and the amount of toner developed by the developing means. The purpose of the present invention is to provide an image forming apparatus that retains the characteristics.
[0008]
[Means for Solving the Problems]
The object is to collect the residual toner in the image forming area on the image forming body, and then discharge the residual toner on the image forming body in the non-image forming area to remove the latent image on the image forming body. With a two-component developer composed of toner particles and carrier particles In an image forming apparatus having a toner recycling unit that recovers to a developing unit for developing, the toner recycling unit is formed on a magnetic particle transport body facing the image forming body. Having the same particle size and composition as the carrier particles The first aspect of the present invention is achieved by an image forming apparatus which is a magnetic brush made of magnetic particles, and changes a collection condition of the toner recycling means according to a toner concentration in the magnetic brush (first invention).
[0009]
Further, the object is to collect the transfer residual toner in the image forming area on the image forming body, and then discharge the residual toner on the image forming body in the non-image forming area, thereby forming the latent image on the image forming body. With a two-component developer composed of toner particles and carrier particles In an image forming apparatus having a toner recycling unit that recovers to a developing unit for developing, the toner recycling unit is formed on a magnetic particle transport body facing the image forming body. Having the same particle size and composition as the carrier particles A second aspect of the present invention is achieved by an image forming apparatus which is a magnetic brush made of magnetic particles, and changes a collection condition of the toner recycling unit according to an amount of toner developed by the developing unit. .
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. Note that the description of the present application does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.
[0012]
An image forming process of an image forming apparatus according to an embodiment of the present invention and configurations and functions of respective mechanisms will be described with reference to FIGS. 1 to 4. FIG. 1 is a sectional view of a laser printer showing an embodiment of an image forming apparatus common to the present invention, FIG. 2 is an enlarged view of a toner recycling unit, and FIG. FIG. 4 is a diagram showing a method of collecting untransferred toner to the developing means.
[0013]
1 to 4, the photosensitive drum 10 as an image forming body is driven and rotated at a peripheral speed (linear speed) of 150 mm / sec, for example, in a direction indicated by an arrow in FIG. 1, and a scorotron charging as a corona charging device is performed. After the peripheral surface is uniformly charged by corona discharge of the same polarity as toner (minus polarity in the present embodiment) by the imager 11, image exposure based on an image signal is performed by an exposure optical system 12 as image exposure means. Done. The exposure optical system 12 rotationally scans a laser beam emitted from a laser light source (not shown) by a rotary polygon mirror 12b, and forms a latent image on the photosensitive drum 10 via an fθ lens 12c, a reflection mirror 12d, and the like.
[0014]
A developing device 13 is provided as a developing unit that develops with a two-component developer composed of toner particles and carrier particles, and a developing sleeve that carries the developer to develop a latent image formed on the photosensitive drum 10 131. In the development, a DC voltage having the same polarity as the toner (in this embodiment, a negative polarity) and a DC bias superimposed on the DC voltage are applied between the developing sleeve 131 as a developer conveying member and the photosensitive drum 10. Is applied by reversal development of the contact. As the toner used for the developer, a spherical toner having a high recovery efficiency of the transfer residual toner described later is preferably used.
[0015]
In the present invention, a mixture of the developer and the magnetic particles due to a trouble is also considered, and it is preferable to use the same carrier particles of the developer in the developing unit and the same magnetic particles in the toner recycling unit described later.
[0016]
From this viewpoint, it is preferable to use the following developer including carrier particles and toner particles as the developer having carrier particles that can be commonly used with magnetic particles.
[0017]
In general, when the average particle size of the magnetic carrier particles is large, the state of the ears of the developing magnetic brush formed on the developing sleeve 131 as the developer carrying member becomes coarse, so that the electrostatic bias is given while applying the vibration by the electric field of the developing bias. Even when the latent image is developed, there is a problem that unevenness is likely to appear in the toner image, and the toner density in the ears becomes low, so that high density development is not performed. This problem can be solved by reducing the average particle size of the magnetic carrier particles. As a result of experiments, it has been found that the above problem does not occur when the weight average particle size is 100 μm or less. However, if the particle size of the magnetic carrier is too small, the magnetic carrier adheres to the surface of the photoconductor drum 10 together with the toner particles, or the magnetic carrier is easily scattered. These phenomena are related to the strength of the magnetic field acting on the carrier and the resulting strength of the magnetization of the carrier. Generally, when the weight average particle diameter of the magnetic carrier becomes 40 μm or less, the above tendency gradually starts to appear. , 30 μm or less. Therefore, in the developing device 13, as the magnetic carrier of the developer, those having a weight average particle diameter of preferably 100 μm or less and 40 μm or more are suitably used. When the magnetic carrier is spherical, the stirring property of the toner particles and the carrier particles and the transportability of the developer are improved, and the charge controllability of the toner is further improved. Is preferred because it hardly causes aggregation.
[0018]
Such phenomena and conditions are the same in the toner recycling means.
[0019]
The magnetic carrier as described above is made of a metal such as iron, chromium, nickel, or cobalt, or a compound or alloy thereof, such as triiron tetroxide or γ-ferric oxide, as in a conventional magnetic carrier. Spherical particles of ferromagnetic substances such as chromium dioxide, chromium dioxide, manganese oxide, ferrite, and manganese-copper alloy, or the surface of these magnetic particles is made of styrene resin, vinyl resin, ethylene resin, rosin modified resin , A resin such as an acrylic resin, a polyamide resin, an epoxy resin, a polyester resin, a silicone resin, a fluororesin, or a spherical resin particle containing magnetic fine particles dispersed therein. The obtained particles are obtained by selecting the particle size using a conventionally known average particle size selection means.
[0020]
Forming the carrier particles into a spherical shape by using a resin or the like as described above, in addition to the effects described above, makes the developer layer formed on the developer transport carrier uniform, and also allows the developer transport carrier to have a uniform shape. An effect that a high bias voltage can be applied is also provided. That is, the fact that the carrier particles are spheroidized by a resin or the like means that (1) the carrier particles are generally easily magnetized and adsorbed in the long axis direction, but the spheroidization loses the directionality, so that the developer layer is uniformly formed. It is formed and locally prevents low-resistance regions and layer thickness unevenness. (2) With the increase in the resistance of the carrier particles, the edge portion seen in the conventional carrier particles disappears, and the electric field does not concentrate on the edge portion. As a result, a high bias voltage is applied to the developer carrier. Even so, there is an effect that the electrostatic latent image is not disturbed by the discharge to the electrode member or the surface of the photosensitive drum 10 or the bias voltage does not break down. The fact that this high bias voltage can be applied means that the above-described effects in development under an oscillating electric field can be sufficiently exerted. The above-described wax is also used for spheroidizing the carrier particles having the above-mentioned effects. However, from the viewpoint of the durability of the carrier, the use of the above-described resin is preferable. Has a resistivity of 10 ⁸ Ωcm or more, especially 10 ^Thirteen It is preferable to form magnetic particles having an insulating property of Ωcm or more. The resistivity is 0.50 cm ² After tapping in a container having a cross section of 1 kg / cm on the packed particles ² This value is obtained by reading a current value when a voltage that generates an electric field of 1000 V / cm between the load and the bottom electrode is applied. When the resistivity is low, the developer transport carrier When a bias voltage is applied, electric charges are injected into the carrier particles, so that the carrier particles easily adhere to the surface of the photosensitive drum 10 or breakdown of the bias voltage easily occurs.
[0021]
In summary, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least three times or less, have no protrusions such as needles or edges, and have a resistivity of 10%. ⁸ Ωcm or more, preferably 10 ^Thirteen It is an appropriate condition that it is Ωcm or more. Then, such magnetic carrier particles are used to increase the resistance of spherical magnetic particles by forming an oxide film or the like, and in the case of magnetic fine particle dispersion carriers, use magnetic fine particles as much as possible, and after forming the dispersed resin particles, It is produced by subjecting it to a spheroidizing treatment or obtaining dispersed resin particles by a spray drying method. The magnetic susceptibility of the carrier particles is preferably 30 to 70 emu / g in order to stably adsorb to the developing sleeve 131 having a fixed magnet therein.
[0022]
Such phenomena and conditions are the same in the toner recycling means.
[0023]
Next, the toner particles will be described.
[0024]
As the average particle size of the toner increases, the roughness of the image becomes conspicuous. Normally, for development having a resolving power of fine lines arranged at a pitch of about 10 lines / mm, a toner having an average particle diameter of about 10 μm is not a problem. However, when a fine particle toner having an average particle diameter of 1 to 5 μm is used, The resolving power is remarkably improved, and a clear high-quality image with faithful reproduction of shading is provided. For the above reasons, the average particle diameter of the toner is 10 μm or less, preferably 1 to 5 μm. Further, the charge amount of the toner particles is preferably 3 to 30 μC / g (particularly preferably 10 to 20 μC / g) because the toner particles follow the electric field and are collected and discharged by the toner recycling means. In particular, when the particle size is small, a high charge amount is required. Such phenomena and conditions are the same in the toner recycling means.
[0025]
The toner as described above is obtained by the same method as the conventional toner. That is, a toner obtained by selecting spherical or amorphous non-magnetic or magnetic toner particles in a conventional toner by an average particle size selecting means can be used. Among them, it is preferable that the toner particles are particles containing magnetic fine particles, and it is particularly preferable that the amount of the magnetic fine particles does not exceed 60 wt%, particularly does not exceed 30 wt%. When the toner particles contain magnetic fine particles, the uniformity of the magnetic brush is further improved because the toner particles are affected by the magnetic force contained in the developer carrier, and the fogging is further improved. The generation is prevented, and the scattering of toner particles hardly occurs. However, if the amount of the magnetic material contained is too large, the magnetic force between the carrier particles and the carrier particles becomes too large, so that a sufficient development density cannot be obtained. , And it becomes difficult to control the triboelectric charging, and the toner particles are easily damaged.
[0026]
As for the toner shape, the spherical toner has higher fluidity than the irregular toner, has a low adhesive force to the image forming body, and has a high transfer rate, so that the transfer residual toner can be easily collected from the image forming body and discharged. If it is easy and preferable, a cleaning blade used for cleaning transfer material residual toner can use a toner having a small particle diameter that has been worn out and cannot be used.
[0027]
Summarizing the above, in the developing device 13, preferable toner particles use the resin described above for the carrier particles and further use fine particles of a magnetic substance, and add a coloring component such as carbon and a charge control agent and the like as necessary. The toner particles have an average particle diameter of 10 μm or less, particularly preferably 1 to 5 μm, which can be produced by a method similar to a conventionally known method for producing toner particles.
[0028]
In the toner recycling means, magnetic particles similar to the above-described carrier particles are preferably used. In the developing device 13, the spherical carrier particles and the toner particles as described above are different from those in the conventional two-component developer. A developer mixed in the same ratio is preferably used, and if necessary, a fluidizing agent for improving the fluid sliding of the particles, a cleaning agent for cleaning the surface of the image carrier, and the like are also mixed. You. As a fluidizing agent, colloidal silica, silicon varnish, metal soap, nonionic surfactant, or the like can be used. As a cleaning agent, a surfactant such as a fatty acid metal salt, organic group-substituted silicon, or fluorine can be used. Can be.
[0029]
The recording paper P, which is a transfer material, is sent out by a feed roller 15a from a paper feed cassette 15, which is a transfer material storage means, is fed by a feed roller 15b, and is conveyed to a timing roller 15c.
[0030]
The recording paper P is synchronized with the toner image formed on the photosensitive drum 10 by the driving of the timing roller 15c, and the transfer belt 14a stretched around the driving roller 14d, the driven roller 14e, and the tension roller 14i. Is supplied to a nip portion (transfer area) 14b formed between the photosensitive drum 10 and the transfer belt 14a by a transfer belt device 14 as a transfer unit provided with the photosensitive drum, and the photosensitive drum is sandwiched between the transfer belt 14a. The image on the peripheral surface of the photoreceptor drum 10 is collectively formed on the recording paper P by a transfer unit 14c provided opposite to the transfer drum 10 and applied with a transfer voltage having a polarity opposite to that of the toner (positive polarity in this embodiment). Is transferred to
[0031]
If a corona transfer device directly facing the image forming member is used as the transfer means, the toner polarity in the absence of the transfer material or the toner outside the transfer material is inverted by corona discharge with respect to the toner outside the transfer material. (To be described as a positive polarity in the present embodiment), the toner remaining after transfer on the image forming body is collected by a toner recycling unit to which a recycle bias of a polarity opposite to the toner described later (a positive polarity in the present embodiment) is applied. Make it difficult. With the above-described transfer belt and transfer roller, the toner outside the transfer material is transferred to the transfer unit side with the negative polarity without reversing the polarity, and the load on the toner recycling unit is reduced. It is preferably used.
[0032]
The recording paper P separated from the transfer belt device 14 by the separator 14h as a transfer material separating means is conveyed to a fixing device 17 having a heating fixing roller 17a having a heater inside at least one of the rollers and a pressure roller 17b. Then, heat and pressure are applied between the heating fixing roller 17a and the pressure roller 17b to fix the toner adhered on the recording paper P, and the recording paper P is discharged to the outside of the apparatus by the discharge roller 18.
[0033]
The toner remaining in the untransferred toner area on the peripheral surface of the photosensitive drum 10 after the transfer of the image forming area where the toner image is to be formed is subjected to light elimination by a light eliminator 16 as a charge eliminator. After the potential level of the toner is reduced to substantially zero, the toner is rotated in the same direction as the photosensitive drum 10 and has a sleeve 110 which is a magnetic particle carrier on which a magnetic brush made of magnetic particles is formed on the outer peripheral surface. In the toner recycling apparatus 100, the DC bias E1 has a polarity opposite to that of the toner indicated by the solid line in FIG. 2 due to a recycling bias in which an alternating current (AC) bias AC1 is superimposed on the direct current (DC) bias E1 as necessary (in the present embodiment). (Positive polarity) to the sleeve 110 of the toner recycling unit to which a toner collection bias of 300 to 1500 V is applied. It is collected in a magnetic brush on the outer peripheral surface of the sleeve 110 I. In order to completely recover the transfer residual toner in the transfer residual toner region, the toner recovery bias application region is formed slightly longer on both sides than the image forming region. The AC bias AC1 has a frequency of 1 to 10 kHz and a voltage of V _pp A 500 to 2000 V sin wave or rectangular wave is used. Note that S1 is a first toner concentration detecting device as first toner concentration detecting means for measuring the toner concentration of the magnetic brush for changing the toner collecting condition of the toner recycling device 100 described later.
[0034]
The potential level of the photosensitive drum 10 is reduced to substantially zero by the light neutralization of the light neutralizer 16, the electrostatic attraction force of the transfer residual toner to the photosensitive drum 10 is weakened, the transfer residual toner is easily moved, and the transfer residual Transfer of the toner to the magnetic brush on the sleeve 110 to which a toner collection bias of the opposite polarity (positive polarity) to the toner is applied is facilitated, and the collection efficiency is improved.
[0035]
As the magnetic particles forming the magnetic brush of the toner recycling device 100, when a two-component developer is used as a developer used in the developing device 13 in order to improve the collection and discharge of the transfer residual toner, the carrier described above is used. Magnetic particles having the same particle diameter and a weight average particle diameter of 40 to 100 μm are used, and the composition is the same as that of the carrier particles used in the developing means described above. Further, by selecting the magnetic particles having the same diameter as the carrier particles, no problem occurs because the magnetic particles do not adhere to the photosensitive drum 10 even if they enter the developing unit 13. For the same reason, it is preferable to select the same resistivity and magnetic susceptibility. Of course, in order to prevent the toner recycling device 100 from adhering to the photosensitive drum 10, the magnetic particles may be selected to have a larger particle size, resistivity, or magnetic susceptibility than the carrier particles.
[0036]
Next, in the non-image forming area between the image forming areas after passing the transfer residual toner area, the DC bias E1 of the recycling bias is set to the same polarity as the toner shown by the dotted line in FIG. The toner is switched to the toner discharge bias to which −300 to −1500 V is applied, and the collected toner adhered to the magnetic brush on the sleeve 110 is discharged (adhered) to the photosensitive drum 10. The toner discharge bias application area is between the toner recovery bias application areas, and is set to be slightly shorter than between the image formation areas (non-image formation areas). At this time, the photosensitive drum 10 is subjected to light elimination by the light eliminator 16. The potential level of the photoconductor drum 10 is made substantially zero by the light neutralization, so that the discharged toner adheres to the photoconductor drum 10 easily.
[0037]
As shown in FIG. 4A, a toner layer is formed on the photosensitive drum 10 whose potential level has been set to substantially zero. The attached toner is attached to the photosensitive drum 10 with a negative polarity due to the toner discharge bias, and the potential level of the toner layer is approximately -50V.
[0038]
Subsequently, the surface potential of the photosensitive drum 10 is -750 V by a scorotron charger 11 serving as a charging unit on the photosensitive drum 10 to which the discharged toner is attached, by a DC voltage having the same polarity as the toner (in this embodiment, a negative polarity). 4B, the potential level on the surface of the photosensitive drum 10 is charged to, for example, about -650 V, and the potential level of the toner layer adhering thereto is reset as shown in FIG. The voltage rises slightly to about -100 V due to charging.
[0039]
In this state, the discharged toner that has been recharged and adhered to the photosensitive drum 10 reaches the developing device 13, and as shown in FIG. 4C, has the same polarity as the toner lower than the photosensitive member potential (minus in this embodiment). The developer is rubbed with the developer on the developing sleeve 131 of the developing device 13 to which a cleaning developing bias (polarity) of −100 to −650 V is applied, and is cleaned (collected) from the photosensitive drum 10 to the developing device 13. At this time, even if all of the toner is not collected, the toner is not used for the next image forming area, so that there is no problem in the image. Further, the toner is attracted to the developing sleeve 131 by setting the developing bias for cleaning to the same or a lower value as the developing bias used for reversal development at the time of image formation.
[0040]
The photosensitive drum 10 from which the residual toner has been removed by the toner recycling device 100, the scorotron charger 11 and the developing device 13 is uniformly charged again by the scorotron charger 11, and enters the next image forming cycle.
[0041]
In the above description, when the toner is removed and discharged by the magnetic brush of the sleeve 110, the photoconductor potential has irregularities unless the light is removed by the light remover 16 as the charge removing means. Is not reduced. For this reason, photoremoval is performed to smooth the photoreceptor potential, thereby enabling uniform and high recovery or discharge. This also facilitates toner collection by the developing means. Further, since the toner is attracted to the photosensitive drum 10 by electrostatic electric force and does not stain the charging unit at the time of recharging, a charging roller can be used as the charging unit.
[0042]
Further, in order to facilitate the recovery of the toner discharged by the toner recycling means from the photosensitive drum 10 to the developing device 13, the developing method of the developing device 13 may be a magnetic toner or a toner other than the contact development using the two-component magnetic brush. One-component contact development using non-magnetic toner is used. Further, the one-component and two-component toners used in the developer are preferably spherical polymerized toners capable of high image quality. Since the spherical toner has a small adhesive force to the photoreceptor drum 10 and the magnetic particles and easily moves electrostatically, the spherical toner has a higher collection efficiency and a higher discharge efficiency as compared with the pulverized toner (irregular toner). Conventionally, when cleaning with a general rubber blade, it is possible to use a spherical toner that is more likely to be rubbed out than a blade as a preferable toner in the present invention.
[0043]
According to FIG. 2, a toner recycling device 100 as a toner recycling means is opposed to a rotating photosensitive drum 10 and is made of, for example, aluminum or stainless steel as a magnetic particle carrier rotated in the same direction as the photosensitive drum 10. , A magnetic body 111 having N and S poles provided inside the sleeve 110, and a magnetic brush made of magnetic particles formed on the outer peripheral surface of the sleeve 110 by the magnet body 111. It consists of. The toner recycling device 100 includes a regulating plate 121 provided opposite to the magnet S2 as a regulating member for regulating an amount of magnetic particles forming the magnetic brush, and a back surface of the regulating plate 121 (the photosensitive drum 10). A box-shaped holding member 122 is provided integrally with the regulating plate 121 so as to be in close contact with the surface (opposite to the opposite side) to form a box body 120. The retaining portion SP2 of the magnetic particles is formed above the holding member 122 constituting the box 120 (inside the box 120). Further, an opening SP1 is formed on the back of the sleeve 110 between the position of the cleaning unit CL for collecting and discharging the transfer residual toner and the staying portion SP2 on the downstream side in the rotation direction of the sleeve 110. Due to the rotation of the magnetic brush, foreign matter in the magnetic brush and foreign matter from an opening SP3 described later drop into the space of the opening SP1. This prevents foreign matter from staying in the magnetic brush. Foreign matter collected at the bottom of the toner recycling device 100 is collected by a collecting screw 123 into a collecting container (not shown).
[0044]
The stagnant portion SP2 is a reservoir for forming a uniform magnetic particle layer. The stagnant portion SP2 preferably has such an amount that the transfer material toner can be collected (stored) and that can be discharged by several rotations of the sleeve 110. The magnetic particles held in the part SP2 are such that the transfer amount of the transfer material toner in the image forming area is about 2 to 10 times the magnetic particle passing amount per rotation of the sleeve 110 passing through the regulating plate 121, and the non-image forming area. To discharge the collected toner, and the amount of magnetic particles held in the stagnant portion SP2 is preferably about 20 to 200 g. If the amount of magnetic particles is increased, the recovery capacity will increase, but the discharge time will be long.In order to reduce the non-image forming area as much as possible and to increase the copying speed, it is difficult to discharge in the non-image forming area which should be set as short as possible. Let it. When the amount of the magnetic particles is reduced, the discharge time is shortened, but the toner concentration is increased even with a small amount of collected toner, so that the collecting ability is reduced and the durability of the image forming body is lost due to filming.
[0045]
As described above, an appropriate amount of magnetic particles is stored in the stagnant portion, a uniform magnetic particle layer is formed, and the balance between the collecting ability and the discharging ability is maintained.
[0046]
In addition, by providing a stagnant portion SP2 in the box 120 formed by the regulating plate 121 and the holding member 122, a dashed line in FIG. The circulation path of the magnetic particles shown is formed. The circulation path is formed under the magnetic field of the magnets N2 and N3, and magnetic particles fall from the surface of the sleeve 110 due to the repelling magnetic field, so that a favorable circulation path is formed. Further, an opening SP3 of the holding member 122 is provided on the side of the box 120 opposite to the regulating plate 121. The magnetic particles on the sleeve 110 do not fall off due to the magnetic force of the magnet S3 corresponding to the apex position of the holding member 122 of the opening SP3, and only the non-magnetic foreign matter passes through the opening SP3 from the circulation path through which the magnetic particles rotate. Fall outside.
[0047]
By the above, foreign matter such as paper powder mixed with the magnetic particles in the stagnant portion is removed satisfactorily, the clogging of the magnetic particles in the regulating member of the toner recycling means is prevented, and a stable magnetic particle layer and a good magnetic brush are formed. Is done. In addition, deterioration of the chargeability and fluidity of the magnetic particles due to entry of foreign matter is prevented.
[0048]
In order for toner collection and discharge by the magnetic brush to be performed satisfactorily, at the time of collection, it is better to rub the photosensitive drum 10 to which the transfer residual toner adheres with a dense magnetic brush. Soft rubbing of the photoconductor drum 10 with a brush enhances the discharging ability. For this reason, the magnetic brush formed on the sleeve 110 is rotated in the same direction as the photosensitive drum 10 at a rubbing speed of 0.7 to 1.2 times the speed of the photosensitive drum 10 with respect to the photosensitive drum 10. That is, the toner is collected and discharged so as to wrap the toner on the photosensitive drum 10. When the rubbing speed is less than 0.7 times, the toner is not removed from the photosensitive drum 10. If it exceeds 1.2 times, scattering of toner and magnetic particles is likely to occur.
[0049]
Further, the filling rate of the magnetic particles in the magnetic brush at the magnetic brush rubbing part for collecting and discharging the toner is set to 0.05 to 0.30 (5 to 30%), so that the toner adhering to the magnetic particles can be reduced. The magnetic particles can easily move along the spikes from the surface of the sleeve 110 (the lower layer of the magnetic brush) to the surface of the photosensitive drum 10 (the upper layer of the magnetic brush). When the filling rate is less than 0.05 (5%), the ability as a magnetic brush is lost, and the toner on the photosensitive drum 10 cannot be removed. On the other hand, if it exceeds 0.30 (30%), the magnetic particles become too dense, so that it is difficult for the toner to move in the magnetic particles, and the collection and discharge are not performed well. If the amount of the magnetic particles in the magnetic brush is too large, it takes time to discharge the toner adhering to the magnetic particles, so that the non-image forming area needs to be long, and the next image formation is delayed.
[0050]
The composition of the magnetic particles forming the magnetic brush of the toner recycling device 100 is the same as the composition of the carrier particles used in the above-described developing means, but the particle size of the magnetic particles is determined by collecting and discharging the transfer residual toner. Is used, magnetic particles having a weight average particle size of 40 to 100 μm are used. When the particle size is small and the weight average particle size is less than 40 μm, the magnetic brush ears become dense, the rubbing force is weak, and the toner does not easily move to the lower layer of the magnetic brush, and the collection is not performed well. In addition, there is a problem that the toner easily adheres to the photosensitive drum 10. On the other hand, if the particle size is large and the weight average particle size exceeds 100 μm, the magnetic brush ears are rough and the magnetic particles do not sufficiently rub against the toner.
[0051]
Further, the transport amount of the magnetic particles of the magnetic brush is set to 10 to 100 mg / cm. ² As a magnetic brush. In this range, ears having an appropriate density and height are formed on the sleeve 110 such that the toner is drawn into the lower layer while having a sliding force or the toner is drawn out from the lower layer. 10mg / cm with small transport amount ² If the particle size is less than the range, the magnetic brush ears are rough and the magnetic particles do not sufficiently rub against the toner. In addition, the transport amount is large and 100 mg / cm ² Is exceeded, the brushes of the magnetic brush become dense, the rubbing force is weak, and the toner does not easily move to the lower layer of the magnetic brush, and the toner is not collected well. In addition, there is a problem that the toner easily adheres to the photosensitive drum 10.
[0052]
As described above, the weight average particle diameter of the magnetic particles is 40 to 100 μm, and the transport amount of the magnetic particles of the magnetic brush is 10 to 100 mg / cm. ² As described above, the magnetic brush is rotated in the same direction as the photosensitive drum 10 at a speed of 0.7 to 1.2 times the rotation speed of the photosensitive drum 10, and the magnetic brush It is preferable to set the filling rate to 0.05 to 0.3 in order to make the density and strength of the spikes of the magnetic brush appropriate and to properly collect and discharge the transfer residual toner.
[0053]
The magnetic susceptibility of the magnetic particles is preferably 30 to 70 emu / g. When the magnetic susceptibility is small and less than 30 emu / g, the brush of the magnetic brush becomes dense, the rubbing force is weak, and the toner does not easily move to the lower layer of the magnetic brush, and the collection is not performed well. Further, the toner easily adheres to the photosensitive drum 10. When the magnetic susceptibility is large and exceeds 70 emu / g, the magnetic brush ears are rough and the magnetic particles do not sufficiently rub against the toner. The resistivity of the magnetic particles is 10 ⁸ It is preferable to have an insulating property of Ω · cm or more. When an alternating current is applied, an electric field is formed without causing a discharge between the photosensitive drum 10 and the magnetic particles, so that the toner can be collected and discharged. The resistivity is 0.50 cm ² After tapping in a container having a cross section of 1 kg / cm on the packed particles ² And a current value obtained by applying a voltage that generates an electric field of 1000 V / cm between the load and the bottom electrode is read.
[0054]
As described above, a magnetic brush is formed in which the recovery and discharge of the transfer residual toner by the toner recycling unit are performed in a well-balanced manner.
[0055]
The first invention according to claim 1 or 4 will be described with reference to FIGS. 5 to 9 and FIG. FIG. 5 is a view showing a first toner concentration detecting means for measuring the toner concentration of the magnetic brush, and FIG. 6 is a diagram showing a second toner for measuring the toner concentration of the magnetic brush by measuring the concentration of the discharged toner. FIG. 7 is a diagram illustrating a density detecting unit, FIG. 7 is a diagram illustrating a third toner concentration detecting unit that measures the toner concentration of the magnetic particles in the staying part, and FIG. 8 is a diagram illustrating the third toner density detecting unit in FIG. FIG. 9 is a circuit diagram of the third toner concentration detecting means of FIG.
[0056]
According to FIG. 2 or FIG. 5, the toner recycling device 100 as a toner recycling unit is opposed to the rotating photosensitive drum 10 and serves as a magnetic particle carrier rotated in the same direction as the photosensitive drum 10 in the cleaning unit CL. For example, a cylindrical sleeve 110 made of an aluminum material or a stainless steel material, a magnet body 111 having N and S poles provided inside the sleeve 110, and formed on the outer peripheral surface of the sleeve 110 by the magnet body 111 And a magnetic brush made of magnetic particles. The untransferred toner is rotated in the same direction as the photoconductor drum 10 and enters a toner recycling device 100 as a toner recycling unit having a sleeve 110 which is a magnetic particle carrier on which a magnetic brush made of magnetic particles is formed on the outer peripheral surface. Due to the recycle bias in which an alternating current (AC) bias AC1 is superimposed on the direct current (DC) bias E1 as needed, the direct current bias E1 has a polarity (in the present embodiment, a positive polarity) of 300- The toner is collected by the magnetic brush on the outer peripheral surface of the sleeve 110 by the sleeve 110 of the toner recycling unit to which the toner collection bias of 1500 V is applied. The AC bias AC1 has a frequency of 1 to 10 kHz and a voltage of V _pp A 500 to 2000 V sin wave or rectangular wave is used.
[0057]
The magnetic particles forming the magnetic brush of the toner recycling device 100 may include the above-described carrier particles when a two-component developer is used as a developer used in the developing unit in order to improve the collection and discharge of the transfer residual toner. Magnetic particles having the same particle diameter as above and having a weight average particle diameter of 40 to 100 μm are used, and the composition is the same as that of the carrier particles used in the developing means described above. Further, by selecting the magnetic particles having the same or larger diameter than the carrier particles, no problem occurs because the magnetic particles do not adhere to the photosensitive drum 10 even if they enter the developing means. For the same reason, it is preferable to select one having the same or higher resistivity and magnetic susceptibility. By the control described below, the toner concentration of the magnetic brush at the time of collecting the transfer residual toner is preferably controlled to be 2 to 5%, which is lower than the developer concentration of the developing unit, which is usually 5 to 8%.
[0058]
As shown in FIG. 2, a first toner concentration detecting device S1 as first toner concentration detecting means is provided to face the magnetic brush of the sleeve 110. The first toner concentration detecting device S1 is a reflection-type detecting device that measures the toner concentration of the magnetic brush that has collected the transfer residual toner and changes the collecting (cleaning) conditions of the toner recycling device 100. .
[0059]
As shown in FIG. 5, DS1 is a light receiving element including a phototransistor and a photodiode, and DS2 is a light emitting element such as an LED. A small-diameter aperture member DS3 and a condensing lens DS4 are provided on the front surface of the light emitting element DS2, and the light flux from the light emitting element DS2 forms a spot-like image on the peripheral surface of the sleeve 110 at the position of the toner attached to the magnetic brush. The light receiving element DS1 receives the amount of reflected light, and the first toner concentration detecting device S1 is configured to measure the toner concentration of the magnetic brush. The collection (cleaning) conditions are changed through a control unit (not shown) in accordance with the toner concentration.
[0060]
The condition is changed by changing the DC bias E1 of the toner collecting bias within the range of 300 to 1500 V of the polarity opposite to that of the toner (positive polarity in the present embodiment), or changing the frequency of the AC bias AC1 using a sine wave or a square wave. In the range of 1 to 10 kHz, or change the voltage of the AC bias AC1 to V _pp When the voltage is changed within the range of 500 to 2000 V, or when a rectangular wave is used as the AC bias AC1, the DC component is changed by changing the duty ratio of the rectangular wave, or the rotational speed of the sleeve 110 is changed. Done. The setting by changing the condition is performed for each copy, for each print, or for each predetermined number of copies such as, for example, 10, 50 or the like.
[0061]
Further, as shown by a dotted line in FIG. 2, instead of the first toner concentration detecting device S1, the first toner concentration detecting device S1 is located close to the outlet side of the discharged toner of the toner recycling device 100 and opposed to the photosensitive drum 10, and A second toner density detecting device S2 is provided as a second toner density detecting device, which is a reflection type detecting device similar to the density detecting device S1, and is discharged from the toner recycling device 100 by the second toner density detecting device S2. It is also possible to change the collection (cleaning) conditions of the toner recycling apparatus 100 by measuring the density of the discharged toner on the photosensitive drum 10.
[0062]
As shown in FIG. 6, DS1 is a light receiving element including a phototransistor and a photodiode, and DS2 is a light emitting element such as an LED. A small-diameter aperture member DS3 and a condensing lens DS4 are provided on the front surface of the light emitting element DS2, and the light flux from the light emitting element DS2 is spot-like at the position of the attached toner (discharged toner) on the peripheral surface of the photosensitive drum 10. An image is formed, and the light receiving element DS1 receives the reflected light amount, and the second toner concentration detecting device S2 is configured to measure the toner concentration of the discharged toner. The second toner concentration detecting device S2 measures the toner concentration. The collection (cleaning) conditions are changed through a control unit (not shown) in accordance with the toner concentration of the discharged toner.
[0063]
The condition is changed by changing the DC bias E1 of the toner collecting bias within the range of 300 to 1500 V of the polarity opposite to that of the toner (positive polarity in the present embodiment), or changing the frequency of the AC bias AC1 using a sine wave or a square wave. In the range of 1 to 10 kHz, or change the voltage of the AC bias AC1 to V _pp When the voltage is changed within the range of 500 to 2000 V, or when a rectangular wave is used as the AC bias AC1, the DC component is changed by changing the duty ratio of the rectangular wave, or the rotational speed of the sleeve 110 is changed. Done. The setting by changing the condition is performed for each copy, for each print, or for each predetermined number of copies such as, for example, 10, 50 or the like. The toner collecting ability can be improved by increasing the DC bias E1, decreasing the frequency of the AC bias AC1, or increasing the voltage of the AC bias AC1. When the reverse setting is performed, the collecting capacity can be set low.
[0064]
As shown by a dotted line in FIG. 2, instead of the first and second toner concentration detecting devices S1 and S2, a third toner concentration detecting device S3 as a third toner concentration detecting means is provided below the staying portion SP2. And embedded in the holding member 122. The third toner concentration detection device S3 is a contact-type detection device, which measures the toner concentration by contacting the magnetic particles flowing in the stagnant portion SP2 and changes the collection (cleaning) conditions of the toner recycling device 100. To do.
[0065]
The measurement by the toner concentration detecting device S3 is a method using a change in the resonance frequency of the LC resonance circuit due to a change in the magnetic permeability of the inductance of the coil described below with reference to FIGS.
[0066]
As shown in FIG. 9, the resonance circuit includes an inductance coil L and a capacitor C. ₁ , C ₂ , A transistor Q, and a resistor R, a typical Colpitts oscillation circuit, and the inductance coil L is a plane coil. When a voltage V is applied to this circuit, an oscillation signal is output from the source of the transistor Q. The resonance circuit is not limited to the Colpitts oscillation circuit. Further, as the toner concentration detecting device S3, generally used methods such as L detection by coil inductance and capacitance detection by a capacitor are used.
[0067]
As shown in FIG. 7 or FIG. 8, the planar coil 41 is a printed circuit board spirally arranged on a surface of a planar board (printed circuit board, PC) 42 from a central coil electrode 43 to a peripheral coil electrode 44. is there. As the flat substrate 42, an insulating resin, for example, glass epoxy or the like is used. The copper foil is spirally pattern-etched on the flat substrate 42 to form the flat coil 41. Alternatively, a conductive layer is formed on the planar substrate 42 by evaporating aluminum or copper. The planar coil 41 has a line width of about 50 to 100 μm and a pitch of about 100 to 200 μm. This surface becomes the detection coil surface. Note that a thin copper wire may be spirally wound and arranged on the flat substrate 42, and this may be used as the flat coil 41.
[0068]
Electrical components such as capacitors C1 and C2, a transistor Q, and a resistor R of an oscillation circuit are mounted on the back surface of the flat substrate 42 opposite to the surface on which the flat coil 41 is formed. The central coil electrode 43 and the peripheral coil electrodes 44 formed at both ends of the planar coil 41 are both through holes, and the planar coil 41 is connected to the electrical components via the electrodes 43 and 44, Further, it is connected to a power supply of voltage V and outputs a detection signal to the outside. The collecting (cleaning) conditions are changed through a control unit (not shown) in accordance with the toner concentration of the magnetic brush measured by the third toner concentration detecting device S3.
[0069]
The condition is changed by changing the DC bias E1 of the toner collecting bias within the range of 300 to 1500 V of the polarity opposite to that of the toner (positive polarity in the present embodiment), or changing the frequency of the AC bias AC1 using a sine wave or a square wave. In the range of 1 to 10 kHz, or change the voltage of the AC bias AC1 to V _pp When the voltage is changed within the range of 500 to 2000 V, or when a rectangular wave is used as the AC bias AC1, the DC component is changed by changing the duty ratio of the rectangular wave, or the rotational speed of the sleeve 110 is changed. Done. The setting by changing the condition is performed for each copy, for each print, or for each predetermined number of copies such as, for example, 10, 50 or the like.
[0070]
As described above, the collecting ability is changed in accordance with the toner concentration in the magnetic brush of the toner recycling unit and the toner concentration of the discharged toner on the image forming body, and the proper collecting performance (cleaning performance) by the toner recycling unit is maintained. You.
[0071]
A second invention according to claim 2 or 4 will be described with reference to FIG. 10, FIG. 2, and FIG. 7 to FIG. FIG. 10 is a diagram illustrating a case where the amount of toner developed by the developing unit is detected.
[0072]
According to FIG. 2 or FIG. 10, the toner recycling device 100 as a toner recycling unit is opposed to the rotating photosensitive drum 10 and serves as a magnetic particle transporter rotated in the same direction as the photosensitive drum 10 in the cleaning unit CL. For example, a cylindrical sleeve 110 made of an aluminum material or a stainless steel material, a magnet body 111 having N and S poles provided inside the sleeve 110, and formed on the outer peripheral surface of the sleeve 110 by the magnet body 111 And a magnetic brush made of magnetic particles. The transfer residual toner in the image forming area where the toner image is formed is rotated in the same direction as the photoreceptor drum 10, and is a sleeve 110 which is a magnetic particle carrier in which a magnetic brush made of magnetic particles is formed on the outer peripheral surface. In the toner recycle device 100 as a toner recycle unit having a toner, a DC bias E1 is superimposed with an alternating current (AC) bias AC1 as necessary, so that the direct current bias E1 and the toner indicated by the solid line in FIG. The toner is collected by the magnetic brush on the outer peripheral surface of the sleeve 110 by the sleeve 110 of the toner recycling unit to which a toner collection bias of 300 to 1500 V of the opposite polarity (positive polarity in this embodiment) is applied.
[0073]
Next, in the non-image forming area between the image forming areas after passing through the transfer residual toner area, the DC bias E1 of the recycle bias is changed to the negative polarity (in the present embodiment) of the same polarity as the toner indicated by the dotted line in FIG. Switching to a toner discharge bias to which 300 to -1500 V is applied, the collected toner adhering to the magnetic brush on the sleeve 110 is discharged (adhered) onto the photosensitive drum 10, and the discharged toner recharged by the scorotron charger 11 is discharged. The developer is cleaned (recovered) by a developing sleeve 131 of a developing device 13 which is a developing unit. The AC bias AC1 of the toner recycling device 100 has a frequency of 1 to 10 kHz and a voltage of V _pp A 500 to 2000 V sin wave or rectangular wave is used. By the control described later, it is preferable that the toner concentration of the magnetic brush at the time of collecting the transfer residual toner is controlled to 2 to 5%, which is lower than the developer concentration of the developing unit which is usually 5 to 8%.
[0074]
The details of the developing device 13 as the developing means shown in FIG. 10 will be described below.
[0075]
The developing sleeve 131, which is a developer conveying member, rotates the photosensitive drum 10 while keeping a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 by abutting rollers (not shown) provided at both ends of the developing sleeve 131 (FIG. 10 is rotated in the same direction (clockwise rotation in FIG. 10).
[0076]
The fixed magnet 132 is included in a developing sleeve 131 having a diameter of 15 mm to 35 mm, has N and S magnetic poles, is fixed concentrically with the developing sleeve 131, and applies a magnetic force to a nonmagnetic sleeve peripheral surface.
[0077]
The layer thickness regulating plate 133 serving as a developer layer forming unit is formed of an elastic magnetic rubber blade provided to face the fixed magnet 132, and regulates the layer thickness of the two-component developer on the peripheral surface of the developing sleeve 131. .
[0078]
The collection and supply roller 135, which is a developer collection and supply unit, is formed of a foamed roller member such as urethane rubber, and removes (collects) the two-component developer from the developing sleeve 131, or sets the two-component developer on the developing sleeve 131. Supply.
[0079]
The stirring screws 136 and 137 rotate at a constant speed in directions opposite to each other, and stir and mix the toner and the carrier in the developing device 13 to form a two-component developer containing a predetermined toner component evenly.
[0080]
The fourth toner concentration detecting device S4 as the fourth toner concentration detecting device having the same configuration as the third toner concentration detecting device S3 described with reference to FIGS. , Is removed (recovered) by the recovery and supply roller 135 from the developing sleeve 131, and is contacted with the two-component developer by the flow of the two-component developer sent to the stirring screw 136 to measure the developer toner concentration. Then, the amount of toner developed by the developing device 13 as a developing unit is detected, and the collection (cleaning) conditions of the toner recycling device 100 are changed.
[0081]
In the case of a two-component developer, the amount of toner in the developing device 13 and the amount of toner supplied to the developing device 13 are regarded as those used in the toner image as described above. As another detection method, a control unit (not shown) measures a value obtained by integrating the number of dots of image data formed by the exposure optical system 12 to change the collection (cleaning) condition of the toner recycling apparatus 100. A solid black image is formed on the photoreceptor drum 10 by the developing unit 13 and the density of the solid black image is determined by the first and second toner density detection described in FIG. 5 or 6 of the first invention. The measurement is performed by a reflection type detection device having the same configuration as the devices S1 and S2, and the transfer residual toner collected by the toner recycling device 100 is estimated to be 10%. How such as changing the conditions used.
[0082]
The condition is changed by changing the DC bias E1 of the toner collecting bias within the range of 300 to 1500 V of the polarity opposite to that of the toner (positive polarity in the present embodiment), or changing the frequency of the AC bias AC1 using a sine wave or a square wave. In the range of 1 to 10 kHz, or change the voltage of the AC bias AC1 to V _pp When the voltage is changed within the range of 500 to 2000 V, or when a rectangular wave is used as the AC bias AC1, the DC component is changed by changing the duty ratio of the rectangular wave, or the rotational speed of the sleeve 110 is changed. Done. The setting by changing the condition is performed for each copy, for each print, or for each predetermined number of copies such as, for example, 10, 50 or the like.
[0083]
As described above, the collecting ability is changed according to the amount of toner developed by the developing means, and the proper collecting property (cleaning property) by the toner recycling means is maintained.
[0085]
As described in the first and second aspects of the present invention, the recovery of the toner recycling device 100 as a toner recycling unit through a control unit (not shown) by the detection of the first to fourth toner density detection units. (Cleaning) conditions are changed, and the toner concentration of the magnetic brush formed on the sleeve 110 of the toner recycling device 100 is lower than the developer concentration of the developing unit, which is usually 5 to 8% by the above-described control. When the toner recycle device 100 is not improved in cleaning performance and the toner concentration in the magnetic brush exceeds 5%, it is regarded as a trouble and the control is performed through the control unit. The conditions of the toner recycling device 100 are changed by the forced collection control described below without stopping the image formation or without performing the image formation. .
[0086]
The condition of the forced recovery is changed by setting the DC bias E1 of the toner recovery bias to a value higher in absolute value than the set value within the range of 300 to 1500 V of the polarity opposite to the toner (positive polarity in the present embodiment), for example, the set value of 500 V To 1000 V, the frequency of the AC bias AC1 in which a sine wave or a rectangular wave is used is changed to a value lower than a set value within a range of 1 to 10 kHz, for example, the set value of 8 kHz is changed to 5 kHz, or the AC bias AC1 is changed. Voltage to V _pp A value higher than the set value within a range of 500 to 2000 V, for example, V _pp Set value of 1000V to V _pp If the voltage is changed to 1500 V or a rectangular wave is used as the AC bias AC1, the duty ratio of the rectangular wave is changed to change the DC component to a value higher in absolute value than the set value, or to 0. The rotation speed of the sleeve 110, which has been set to a linear speed of 7 to 1.2 times, is changed to a high speed of 1.2 to 2.0 times higher than a set value.
[0087]
As described above, the collecting ability is changed in accordance with the toner concentration in the magnetic brush of the toner recycling unit and the transfer residual toner on the image forming body due to the amount of toner developed by the developing unit. (Cleanability) is maintained.
[0088]
【The invention's effect】
According to the present invention, the collecting ability is changed according to the toner concentration in the magnetic brush of the toner recycling unit and the amount of toner developed by the developing unit, and the proper collecting property (cleaning property) by the toner recycling unit is maintained. You.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a laser printer showing an embodiment of an image forming apparatus common to the present invention.
FIG. 2 is an enlarged view of a toner recycling unit.
FIG. 3 is a diagram illustrating an operation range of a recycling bias of a toner recycling unit.
FIG. 4 is a diagram illustrating a method of collecting transfer residual toner to a developing unit.
FIG. 5 is a diagram illustrating a first toner concentration detecting unit that measures the toner concentration of the magnetic brush.
FIG. 6 is a diagram illustrating a second toner density detecting unit that measures the toner density of the magnetic brush by measuring the density of the discharged toner.
FIG. 7 is a diagram showing a third toner concentration detecting means for measuring the toner concentration of the magnetic particles in the staying portion.
FIG. 8 is a perspective view of a third toner concentration detecting unit of FIG. 7;
FIG. 9 is a circuit diagram of a third toner density detecting unit of FIG. 7;
FIG. 10 is a diagram illustrating a case where the amount of toner developed by a developing unit is detected.
[Explanation of symbols]
10 Photoconductor drum
11 Scorotron charger
12 Exposure optical system
13 Developing device
100 Toner recycling device
110 sleeve
122 Holding member
131 developing sleeve
AC1 AC bias
E1 DC bias
S1 First toner concentration detecting device
S2 Second toner density detection device
S3 Third toner concentration detecting device
S4 Fourth toner density detecting device
SP2 Staying part

Claims (4)

After once collecting the transfer residual toner in the image forming area on the image forming body, it is discharged onto the image forming body in the non-image forming area, and the latent image on the image forming body is composed of toner particles and carrier particles. An image forming apparatus having a toner recycling unit that collects the toner into a developing unit that develops with a two-component developer ,
The toner recycling unit is a magnetic brush formed of magnetic particles having the same particle diameter and composition as the carrier particles, formed on a magnetic particle carrier opposed to the image forming body,
An image forming apparatus, wherein a collection condition of the toner recycling unit is changed according to a toner concentration in the magnetic brush. After once collecting the transfer residual toner in the image forming area on the image forming body, it is discharged onto the image forming body in the non-image forming area, and the latent image on the image forming body is composed of toner particles and carrier particles. An image forming apparatus having a toner recycling unit that collects the toner into a developing unit that develops with a two-component developer ,
The toner recycling unit is a magnetic brush formed of magnetic particles having the same particle diameter and composition as the carrier particles, formed on a magnetic particle carrier opposed to the image forming body,
An image forming apparatus, wherein a collection condition of the toner recycling unit is changed according to an amount of toner developed by the developing unit. 2. The image forming body according to claim 1, wherein the magnetic brush rubs the image forming body while moving in the same direction as the image forming body at a speed of 0.7 to 1.2 times a moving speed of the image forming body. Or the image forming apparatus according to 2. The image forming apparatus according to claim 1, wherein a toner concentration in the toner recycling unit is controlled to be lower than a toner concentration of a developer in the developing unit.

Images