JP2644489B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device of a two-component developing system for performing development using magnetic carrier particles and toner particles.

The present invention is a developing device applicable to various types of display devices for image recording, printers, and facsimile electrophotographic devices.

(Background technology)

In electrophotography using a two-component developer, toner particles as a visual material and magnetic carrier particles are mixed,
The two-component composition is supplied onto a developing sleeve in which a magnet is arranged to form a magnetic brush made of the composition, and the magnetic brush is rubbed or rubbed on an electrophotographic photosensitive plate having an electrostatic latent image. The toner images are formed on the photosensitive plate by bringing them close to each other.

The toner particles are charged in a direction opposite to the charge polarity of the electrostatic latent image on the photosensitive plate due to friction with the magnetic particles, and the toner particles on the magnetic brush adhere to the electrostatic latent image by an electric field, and the electrostatic latent image is charged. Image development takes place. The magnetic particles are attracted by the magnet in the sleeve and collected in the developing container.

By the way, the mixing ratio between the toner particles and the magnetic particles is related to the application of the charge to the toner particles, and as a result, greatly affects the copy image quality. For this reason, in a two-component developing device, a control device (hereinafter referred to as an ATR) which automatically detects the toner concentration so as to maintain the toner concentration in the developer within a predetermined range, and maintains the toner concentration according to the output of 3. ).

[Problems to be solved]

However, when the ATR device obtains a toner replenishment signal from the toner concentration detection device and supplies replenishment toner to increase the toner concentration of the developer in the container, it takes time for the developer to reach the development area. Delay occurs. Therefore, even after the supply signal is generated, an image having a low copy density continues for a while. Conversely, when the toner supply is performed and the toner density becomes sufficiently high, and the toner supply signal is stopped, the toner density remains high for a while.

In order to alleviate the above-mentioned problems, a device that performs high-precision detection and controls the toner density setting range to be narrow is required. However, the ATR device becomes complicated and large as a developing device, and costs increase. However, the above-mentioned problems have not been completely solved.

[Object of the invention]

The present invention provides a solution to the above-described problems without image deterioration, that is, adhesion of a carrier to a photoreceptor, light density and white spots due to application of an excessively charged charge to toner, magnetic brush marks, background fog, and the like. No defects such as inverted fog, Dmax
It is an object of the present invention to provide an image having sufficient gradation and good gradation γ.

It is another object of the present invention to provide a developing device that can perform development without having an accurate ATR device, and that can immediately supply or stop supply of replenished toner in response to toner concentration detection.

[Summary of the Invention]

To achieve the above object, the present invention provides a developer container containing a two-component developer containing magnetic particles and toner particles, a developer carrier provided at an opening of the developer container and carrying a developer. Detecting means for detecting the toner concentration in the developer container, developer amount control means for controlling the amount of developer carried on the developer carrier based on the detection output of the detecting means,
Is a developing device.

〔Example〕

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention. The latent image carrier 1 is an insulating drum for electrostatic recording or α-
It is a photosensitive drum or a photosensitive belt having a photoconductive insulating material layer such as Se, Cds, ZnO ₂ , OPC, α-Si. The latent image carrier 1 is rotated in the direction of arrow a by a driving device (not shown).
Reference numeral 22 denotes a developing sleeve which is close to or in contact with the latent image carrier 1, and is made of a specific magnetic material such as aluminum or SUS316. The developing sleeve 22 has a horizontally long opening formed in the longitudinal direction of the container on the lower left wall of the developing container 36, with a substantially right half circumferential surface protruding into the container 36, and a left substantially half circumferential surface being exposed outside the container to be rotatably supported. It is provided horizontally and is driven to rotate in the direction of arrow b.

Reference numeral 23 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means inserted into the developing sleeve 22 and positioned and held in the position and orientation shown in the figure. It is fixed and held as it is in the posture. The magnet 23 has three magnetic poles: an N-pole 23a, an S-pole 23b, and an N-pole 23c. The magnet 23 may be provided with an electromagnet instead of the permanent magnet.

Reference numeral 24 designates a base fixed to the side wall of the container on the lower edge side of the developer supply opening in which the developing sleeve 2 is disposed. A non-magnetic blade as a developer regulating member
For example, SuS316 is bent into a cross-section road shape.

27 is a magnetic particle having a particle size of 20 to 100 μm, preferably 3 to 100 μm.
0 to 80 μm and the resistance value is 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm
Ferrite particles (maximum magnetization of 30 to 100 emu / g) coated with a resin may be used as described above.

 37 is a non-magnetic toner.

Reference numeral 60 denotes an auxiliary regulating plate made of a thin elastic metal plate, for example, a phosphor bronze plate having a thickness of 0.1 to 0.5 mm, provided on the downstream side in the rotation direction of the sleeve 22 of the nonmagnetic blade 24. . A cylindrical eccentric cam 61 provided substantially in parallel to the axial direction of the sleeve 22 is in contact with the distal end portion 601 of the auxiliary regulating plate 60.

Reference numeral 62 denotes a toner concentration detection sensor which supplies toner by repeating rotation (rotation in the direction of arrow C) and stop of the toner auxiliary roller 63 in accordance with the output of the sensor 62. Reference numerals 64 and 65 denote sealing members that regulate application of the toner on the toner supply roller.

Reference numeral 66 denotes a stirring member which rotates in the direction of arrow d, and mixes and stirs the developer and the replenishment toner separated from the sleeve 22 by the scraper 67.

 38 is a toner storage container.

The developer regulated by the non-magnetic blade 24 is further regulated by the auxiliary regulating plate 60 and transported to the developing area. The developer after development is supplied to a known toner concentration detection sensor 62.
As a result, the toner concentration in the developer is detected. When the toner concentration is low, the supply roller 63 starts rotating and supplies toner. However, there is a time delay before the developer containing the replenished toner is conveyed to the development area and used for development, and when a large amount of replenished toner is supplied suddenly, the tribo is not sufficiently provided. Therefore, a rising phenomenon appears in the copy density for replenishment little by little. Therefore, as shown in FIG. 2, the gap between the distal end portion 601 of the auxiliary regulating plate 60 and the developing sleeve 22 is widened to increase the amount of developer applied on the sleeve 22. As a result, the supply amount of the developer to the developing area increases, and the copy image density can be improved immediately after the toner density is detected. Conversely, when the toner concentration becomes sufficiently high and the toner supply is stopped, the developer having the higher toner concentration still exists in the developing container, and the toner concentration does not immediately decrease. Therefore, as shown in FIG. 3, the gap between the distal end portion 601 of the auxiliary regulating plate 60 and the developing sleeve 22 is narrowed to reduce the amount of the developer applied on the sleeve 22. As a result, the supply amount of the developer to the developing area can be reduced, and the density of the copy image can be suppressed immediately after the toner density is detected.

Further, it is preferable that the operation of the eccentric cam 61 be continuously changed according to the toner density. That is, as the toner density decreases in accordance with the output of the sensor 62, the developer application amount is gradually increased, and as the toner density increases, the developer application amount is gradually decreased. Variations in copy density during toner replenishment can be reduced.

FIG. 4 shows copy density curves of the embodiment (solid line) and the conventional comparative example (dashed line) when the developing device shown in FIG. 1 is used. Arrows ON / OFF indicate toner supply signals.

In the embodiment of FIG.
A stainless steel sleeve with a diameter of 0.5 mm was used, and the surface of the sleeve was knurled with a groove having a depth of about 0.5 mm in the axial direction.

The maximum value of the surface magnetic flux density of the 23a and 23c poles was about 650 gauss and that of the 23b pole was 850 gauss when the magnet 23 was magnetized in three poles.

The blade 24 was made of non-magnetic stainless steel having a thickness of 1.5 mm, and was provided downstream of the 23a pole with respect to the sleeve rotation direction.

Ferrite with a particle size of 70 to 90μ (maximum magnetization 56em) coated with a resin mixture of acrylic and fluorine on the surface
u / g and a resistance value of 10 ⁷ to 10 ⁸ Ωcm).

As the non-magnetic toner, a toner powder having an average particle size of 13 μm mainly composed of 90 parts of styrene resin and 7 parts of polypropylene and 4 parts of carbon black was used.

The gap between the photosensitive drum 1 and the sleeve 22 is about 1 mm
The distance between 22 and blade 24 was 0.8 mm. The gap between the tip 601 of the auxiliary regulating plate 60 and the sleeve 22 is continuously up to 0.8 m according to the output of the sensor 62 by the control of the eccentric cam 61.
m, set to 0.5 mm at minimum.

The latent image potential of the photosensitive drum was set to -650 V for the image portion and +150 V for the non-image portion, and a DC voltage of -200 V was applied to the developing sleeve 22 as a developing bias.

As shown in FIG. 4, the copy in the case where the application amount increase / decrease control according to the present invention is added to this control is more than the control in which only the supply (ON) and stop (OFF) of the replenishment toner indicated by the broken line arrow is performed. It can be seen that the change in the concentration is small.

FIG. 5 is a sectional view of a developing device according to another embodiment of the present invention. FIG. 5 shows a developing device that mixes and stirs magnetic particles and toner particles on a developing sleeve, unlike the embodiment of FIG. Hereinafter, a case where the present invention is applied to this device will be described. The latent image carrier 1 is an insulating drum for electrostatic recording or α
-Se, Cds, is ZnO _2, OPC, photosensitive drum or photosensitive belt having a photoconductive insulating material layer, such as alpha-Si. Latent image carrier 1
Is rotated in the direction of arrow a by a driving device (not shown). Reference numeral 22 denotes a developing sleeve which is close to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or SUS316. The developing sleeve 22 is a developing container
A substantially right peripheral surface is projected into the container 36 into a horizontally long opening formed in the container longitudinal direction on the lower left wall of the container 36, and a substantially left peripheral surface is exposed to the outside of the container so as to be rotatably supported and laterally provided. Arrow b
It is driven to rotate in the direction.

Reference numeral 23 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means inserted into the developing sleeve 22 and positioned and held in the position and orientation shown in the figure. It is fixed and held as it is in the posture. The magnet 23 has four magnetic poles, an N-pole 23a, an S-pole 23b, an N-pole 23c, and an S-pole 23d. The magnet 23 may be provided with an electromagnet instead of the permanent magnet.

Reference numeral 24 designates a base fixed to the side wall of the container on the upper edge side of the developer supply opening where the developing sleeve 2 is disposed, and the front end side protrudes outside the container 36 from the position of the upper edge of the opening to extend along the length of the upper edge of the opening. A non-magnetic blade as a developer regulating member
For example, SuS316 is bent into a cross-section road shape.

Reference numeral 26 denotes a magnetic particle limiting member whose upper surface is in contact with the lower surface of the non-magnetic blade 24 and whose front end surface is a developer guide surface 261.

27 is a magnetic particle having a particle size of 30 to 100 μm, preferably 4 to
0 to 70 μm and the resistance value is 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm
As described above, a ferrite particle (maximum magnetization of 60 emu / g) coated with a resin can be used.

 37 is a non-magnetic developer toner.

Numeral 31 is a magnetic material disposed on the inner surface of the lower portion of the developing container so as to face the developing sleeve 22 in order to prevent the leakage of the magnetic particles 27 or the non-magnetic toner particles 37 from the lower portion of the developing container 36 on which the developing sleeve 22 is disposed. There is, for example, an iron plate that is plated. A magnetic field between the magnetic body 31 and the S-polarity magnetic pole 23d provides a sealing effect of recovering the magnetic particles 27 and preventing leakage.

Reference numeral 39 denotes a toner supply member for supplying toner to the brush portion of the magnetic particles formed by the fixed magnetic poles 23 in the developing sleeve 22.A rubber sheet is attached to a rotatably bearing sheet metal, and the toner is swept down the lower surface of the developing container. Transport. The toner is supplied to the toner supply member 39 by a toner conveying member in a toner storage container 38 (not shown).

38 and 35 are a toner storage container and a magnetic particle storage container, respectively.

Numeral 40 denotes a sealing member for sealing the toner accumulated in the lower portion of the developing container 36, which has elasticity and is bent in the rotation direction of the sleeve 22 to elastically press the surface side of the sleeve 22. The seal member 40 has an end on the downstream side in the sleeve rotation direction in a contact area with the sleeve so as to allow the developer to enter the inside of the container.

Reference numeral 30 denotes an anti-scattering electrode plate for applying a voltage of the same polarity as that of the floating developer generated in the developing step to adhere to the photoreceptor side to prevent scattering.

The S magnetic pole 23d is magnetic sealing magnetic field generating means for forming a magnetic field from one side to the other with the magnetic member 31. One part of the S magnetic pole 23d faces the magnetic member 31. Magnetic member 31
Is located below the developing device at the substantial end of the developer accommodating portion of the developer container. At the periphery of the container, the movement of the collected magnetic carrier particles causes the developer on the sleeve surface to move downward into the developer. Take in the toner particles located at Therefore, stable recovery of magnetic particles has the effect of stabilizing the developing ability.

The magnetic member 31 has a “ku” or “L” shape, and a material having weak magnetism by deforming a non-permanent magnetic or non-magnetic material such as iron or the like can be applied. When a magnet is used as the magnetic member 31, the plane 66
There must be S polarity different poles from the magnetic N of the magnet N _2.

That is, since the magnetic member 31 prevents the loss of the magnetic particles while restraining the magnetic particles and facilitates the collection of the magnetic particles, it is possible to prevent the toner particles in the developer container from leaking from the container.

Further, by arranging the magnetic pole 23d as described above, another preferable effect can be obtained in relation to the magnetic pole 23a.
That is, the magnetic brush is not formed in a coarse state (compared to a state in which the magnetic brush is simply stagnated) in the magnetic brush 21 due to the above-described relationship between the bottom of the storage portion of the container 36 and the magnetic pole 23d. Does not become excessive. Excessive incorporation causes insufficient charging of the toner and causes fogging.

This configuration is also effective when magnetic particles and non-magnetic or weak magnetic toner are mixed in the developer container.

According to the experiment, the distance between the developing sleeve and the magnetic member 31 2.
At 5 mm, the magnetic carrier particles were completely recovered, no leakage of toner particles was observed, and stable development was achieved.
The presence of the surface 66 in this region means that the magnetic force of the magnetic pole 23d is
It is considered that the magnetic field sealing effect is increased because 6 is appropriately dispersed and the magnetic force in this region can be substantially increased.

The distance d ₂ between the end portion of the non-magnetic blade 24 and the developing sleeve 22 surface is 50～800Myuemu, preferably 150 to 500. If this distance is less than 50 μm, the magnetic particles described later are clogged in the meantime, and the developer layer tends to be uneven, and the developer required for good development cannot be applied, and the density of the developed image is low and uneven. There is a disadvantage that can only be obtained. On the other hand, if the thickness is larger than 800 μm, the amount of the developer applied on the developing sleeve 22 increases, so that the predetermined developer layer thickness cannot be regulated, the magnetic particles adhere to the latent image carrier and the developer circulation described later increases. However, there is a disadvantage that the development regulation by the developer limiting member 26 is weakened, and the toner is insufficiently fogged to easily fog.

Angle θ is −5 to 35 °, preferably 0 to 25 °.
In the case of −5, the developer thin layer formed by the magnetic force, the mirror force, the cohesive force, and the like acting on the developer becomes sparse and has many irregularities. As the amount increases, it is difficult to obtain a predetermined amount of the developer.

Even if the magnetic particle layer is driven to rotate in the direction of arrow b, the magnetic particle layer moves slowly as it separates from the sleeve surface due to the balance between the magnetic force and the restraining force based on gravity and the conveying force in the moving direction of the sleeve 2. In other words, a stationary layer that can move to some extent but hardly moves is formed above the magnetic particle layer. Of course, some fall under the influence of gravity.

Therefore, by appropriately selecting the arrangement positions of the magnetic poles 23a and 23d and the fluidity and magnetic characteristics of the magnetic particles 27, the magnetic particle layer is conveyed toward the magnetic pole 23a closer to the sleeve to form a moving layer.
Due to the movement of the magnetic particles, the magnetic particle layer (first layer) takes in the toner from the toner layer (second layer), and the toner is frictionally charged by the rubbing with the magnetic particles or the sleeve, and the sleeve 2 rotates as the sleeve 2 rotates. It is conveyed to a development area and subjected to development.

The movement of the magnetic particle layer is determined by the fluidity and magnetic force of the developer. When the toner content in the magnetic particles is low, the magnetic transport force of the developer is improved, and the moving speed of the magnetic particle layer in the container is increased. The reason is that if the amount of toner interposed between the magnetic particles is small, the magnetic brush can be easily formed,
This is because the amount of the developer applied thereon increases, and the developer collected in the developing container again after the development stops moving the magnetic particle layer. Therefore, the toner from the toner layer is easily taken in, and the toner concentration in the magnetic particle layer increases.

Conversely, when the toner content of the magnetic particle layer is high, the magnetic transport force of the developer decreases, and the moving speed of the magnetic particle layer in the container decreases. This is because it is difficult to form a magnetic brush due to the large amount of toner interposed between the magnetic particles, and the amount of developer applied on the sleeve decreases,
This is because the moving speed of the magnetic particle layer in the container does not increase even if it is collected in the container. Therefore, it becomes difficult to take in the toner from the toner layer into the magnetic particle layer, and the toner concentration in the magnetic particle layer does not increase any more. Therefore, a certain amount of toner content is naturally maintained.

Next, the magnetic particle layers in the vicinity of the non-magnetic blade 24, which is a developer application amount regulating member, and in the vicinity of the limiting member 26 will be described. The limiting member does not only mechanically prevent unnecessary entry of the replenishment toner into the developer regulating portion. As described above, the member 26 has a magnetic pole in the regulation region surrounded by the sleeve.
Magnetic particles conveyed with the rotation of the sleeve by N ₁ pole is packed along the guide surface 261 of the limiting member 26 density is increased. In this area, the magnetic particles that are transported and enter and the magnetic particles that flow out of the blade are dynamically replaced. It is in a substantial packing state. For this reason, the toner is applied to the toner from the magnetic particles or the sleeve, and the toner having a small amount of the toner applied to the magnetic particles or the sleeve adhered to the sleeve with a small force is separated from the magnetic particles or the sleeve. In other words, the electrification improvement of the toner selection is performed. Therefore, the toner to which the tribo application is sufficiently given can be used for development. In addition, the non-uniform state during the transfer of the magnetic particles is also averaged in the space, and the uniform and stable application of the magnetic particle layer is achieved. Therefore limited members
The guide surface 261 is indispensable, and the inclination of the slope and the volume of the space greatly affect the packing state of the magnetic particles in the space.

On the other hand, the magnetic pole fixed to this area
23a rearranges the packing-state magnetic particles along the lines of magnetic force. The packing state in the space is unstable with respect to the application of tribo, and a constant packing state is always required for stabilization. This is to form a magnetic brush with magnetic particles that have been conveyed almost tangentially on the sleeve with a force that is perpendicular to that direction. And the uniformity and stabilization of the application of the tribo and the application of the magnetic particle layer are further promoted. At this time, if the developer concentrated by the peripheral configuration is subjected to a large pressure, there is a problem that the developer is clogged too much.
It is considered that the portion where the maximum magnetic force is generated faces the guide surface 261, thereby preventing excessive pressure concentration in the regulation region, and maintaining the concentration of the developer and the stable high-density magnetic particle existence ratio. .

Due to the above-described regulation region, a stable amount of magnetic particles and sufficiently charged toner particles can be formed as a thin developer layer on the surface of the developing sleeve. Therefore, the development effect in the development region 102 becomes stable. And an alternating electric field forming means for forming an alternating electric field in the developing unit for transferring at least the toner particles carried on the surface of the developing member among the developer conveyed to the developing unit to the electrostatic latent image carrier. In the developing unit, the volume ratio of the magnetic particles of the developer conveyed to the developing unit with respect to the volume of the space defined by the electrostatic latent image carrier and the developer carrying member is
It was confirmed that a great effect was obtained for the developing method and the apparatus of 1.5% to 30%.

FIG. 5 shows a case where a magnetic body 50 is installed on the non-magnetic blade side of the developer limiting member 26. In this case, it is not preferable to provide the magnetic body 50 at a position facing the magnetic pole 23a. This is because if they are opposed to each other, a strong concentrated magnetic field is generated between them and the magnetic pole 23a, and the effect of stirring and loosening the magnetic particles by the magnetic pole 23a is reduced. However, providing a magnetic material in the restricting portion and magnetically restricting the magnetic particles with the sleeve internal magnet 23 increases the tolerance of the gap between the restricting member and the sleeve, and is effective. Further, not only the tolerance, but also the length of the gap between the regulating member and the sleeve itself can be increased, and can be increased by about 70 to 100 μm as compared with the case of using only the non-magnetic blade. Further, the angle θ can be increased by about 3 to 7 ° as compared with the case where only the non-magnetic blade is used. Also, when comparing the magnetic particles or the toner adhered on the sleeve, the charge amount of the toner adhered on the sleeve is smaller than that charged on the magnetic particles. The reason is that the magnetic particles are also conveyed together with the movement of the sleeve, so that the toner on the sleeve is less likely to be rubbed by the magnetic particles. In order to raise the toner on the sleeve to a predetermined value, it is necessary to actively rub the toner on the sleeve. That is, it is necessary to have magnetic particles that cause a relative speed deviation in the vicinity of the sleeve surface against the movement of the sleeve.

However, it is impossible to simply lower the transportability of the magnetic particles in view of the above-described effect of taking in the toner. Further, as described above, it is also possible to arrange a magnetic body in the regulating portion so as to face the magnetic pole 23a in the sleeve as described above to generate a concentrated magnetic field and improve the sliding force of the magnetic particles on the sleeve, as described above. The effect of disposing the maximum magnetic force generating portion of the magnetic pole in the space created by the regulating member 26 is reduced.

Therefore, in the present embodiment, the magnetic body 50 is provided downstream of the magnetic pole 23a with respect to the sleeve rotation direction, and the magnetic field lines on the blade side of the magnetic pole 23a are concentrated substantially in the tangential direction of the sleeve surface. As a result, only the magnetic particles near the sleeve surface form a magnetic brush along the sleeve surface,
The toner on the sleeve was rubbed, and the tribo-application of the toner on the sleeve could be increased.

The magnetic flux density of the magnetic pole 23a is 600G or more, preferably 700G.
The above is preferred. This is because the application state of the developer tends to be more stable with respect to the change in the toner content of the magnetic particle layer as the magnetic flux density of the cut magnetic pole increases. Particularly, in the developing device of the present invention which does not have an automatic toner replenishing device for maintaining the toner content, the magnetic flux density is preferably 800 G or more.

However, since the transport force of the developer increases with an increase in the magnetic force of 23a, the amount of the developer applied on the sleeve increases,
It is necessary to select within an appropriate range according to the design specifications. According to the present inventors, a good result can be obtained by considering about 800 to 1200 G in view of other developing device configurations.

In FIG. 5, the magnetic pole 23c is a developing magnetic pole. The developing magnetic pole is preferably located substantially in the developing section, and preferably has a magnetic flux density of 800 G or more in order to prevent the magnetic particles from adhering to the latent image.

It goes without saying that the present invention includes any combination of the above-described configurations.

In any case, the present invention can provide a high image quality which cannot be obtained by the conventional developing method and apparatus, and has an excellent effect that the developing apparatus can be made a small disposable type.

The toner supply member 9 is provided in the developing container 36, and rotates or drives in the direction of arrow d in proximity to or in contact with the magnetic particle layer to supply the toner 37 to the magnetic particle layer.

A toner storage container 38 for storing toner is disposed adjacent to the developing container 36 in a substantially horizontal direction, and a toner conveying member 10 for sending toner into the developing container 36 is provided in the toner storage container. .

The S magnetic pole 23b is a carrier magnetic pole provided to prevent the developer layer uniformly coated on the non-magnetic blade 4 from being disturbed due to the large gap between the cut magnetic pole 23a and the developing magnetic pole 23c. Since the S magnetic pole 23b does not disturb the developer layer, the strength of the magnetic pole is preferably equal to or slightly lower than that of the developing magnetic pole 23c. When a developing sleeve having a diameter of 20φ is used, if the distance between the cut magnetic pole and the developing magnetic pole is within 100 ° of the central angle of the sleeve, the developer layer on the sleeve has little disturbance.
When ゜ is exceeded, the developer layer is largely disturbed, and it is preferable to provide a transport pole in the middle.

The S magnetic pole 23d is a recovery magnetic pole for recovering the developer after the development, and is disposed on the upstream side in the developing sleeve moving direction from the tip of the magnetic seal. If the magnetic pole 23d is located downstream of the tip of the magnetic seal, magnetic particles are formed by the magnetic pole 23d near the toner intake port at the bottom of the developing container, making it extremely easy to take in the toner, and the triboelectric charging is not sufficiently performed. It is easy to cause fog.

Here, the volume ratio of the magnetic particles in the developing section will be described. "Developing part" means the photosensitive drum 1 from the sleeve 22
Where toner is transferred or supplied. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present therein relative to the volume of the developing section. In the above-mentioned developing device, it is extremely preferable that this volume ratio has an important effect, and it is extremely preferable that this ratio be 1.5 to 30%, particularly 2.6 to 26%.

If it is less than 1.5%, a decrease in the density of the developed image is observed, a sleeve ghost is generated, a remarkable density difference occurs between a portion where the spike 51 is present and a portion where the spike 51 is not formed, This is not preferable in that the thickness of the developed developer image becomes non-uniform as a whole.

If it exceeds 30%, the degree of closing the sleeve surface increases, which is not preferable in that fogging occurs.

In particular, the above-mentioned conditions mentioned as the preferred developing method for the present invention are such that the image quality does not monotonously deteriorate or increase as the volume ratio increases or decreases.
Sufficient image density is obtained in the range of
Is exceeded, the image quality is degraded, and further, when the image quality is in the range of the above numerical value, neither sleeve ghost nor fogging occurs. The former is considered to be due to the negative characteristics, and the latter is thought to be caused by the fact that the amount of magnetic particles becomes large and the surface of the sleeve 22 cannot be opened, and the amount of toner supplied from the surface of the sleeve 22 is greatly reduced. Can be

If it is less than 1.5%, the reproducibility of the line image is inferior and the image quality density is remarkably reduced. On the other hand, if it exceeds 30%, there is a problem that the magnetic particles damage the surface of the photosensitive drum, and there is a problem of transfer and fixation that occurs because they adhere as a part of the image.

When the presence of magnetic particles is close to 1.5%, when reproducing a large-area uniform high-density image (solid black), "Arabi"
In some cases (particular environment or the like), there is a case where a partial development unevenness referred to as “development unevenness” occurs. This value is more preferable because the volume ratio of the magnetic particles to the developing part is 2.6% or more, and when the magnetic particles are close to 30%, the spikes of the magnetic particles are reduced. There is a case where toner supply from the sleeve surface is delayed around the contact portion (when the developing speed is high, etc.), and there is a possibility that scale-like density unevenness occurs when solid black is reproduced. As a certain range for preventing this, the above volume ratio of the magnetic particles is more preferably 26% or less.

If the volume ratio is in the range of 1.5 to 30% (in the embodiment, 4%)
%, As shown in FIG. 6, the spikes 51 are formed on the surface of the sleeve 22 in a sparse state to a desirable extent, and the toner on both the sleeve 22 and the spikes is sufficiently released to the photosensitive drum 1. Since the toner 100 on the sleeve also flies and transfers with an alternating electric field, almost all the toner can be consumed for development. Percentage)
And a high image density. Preferably, a small but intense spike vibration is caused, which loosens the magnetic particles and the toner 100 adhering to the sleeve 22. In any case, it is possible to prevent the occurrence of uneven sweep and ghost images as in the case of a magnetic brush. Further, the vibration of the spikes increases the frictional contact between the magnetic particles 27 and the toner 28, so that the frictional charging of the toner 28 can be improved and the occurrence of fog can be prevented. The high developing efficiency is suitable for downsizing of the developing device. The magnetic pole in FIG. 5 is different from the developing pole 23c in FIG. 5 as the S pole 23b, but either may be used in this example.

The volume ratio of the magnetic particles 27 present in the developing section is (M /
h) × (1 / ρ) × [(C / (T + C)], where M is the coating amount (g / cm) of the developer (mixture... ² ), h is the height (cm) of the developing space, ρ is the true density of magnetic particles g / cm ³ , C / (T
+ C) is the weight percentage of magnetic particles in the developer on the sleeve.

The ratio of the toner to the magnetic particles in the developing section defined above is preferably 4 to 40% by weight. When the alternating electric field is strong (the change rate is large or Vpp is large) as in the above embodiment, the spikes separate from the sleeve 22 or its base, and the separated magnetic particles 27 move between the sleeve 22 and the photosensitive drum 1. Reciprocate in the space. Since the energy of the reciprocating motion is large, the effect of the above-described vibration is further promoted.

The above behavior was confirmed by photographing at 8000 frames / sec with a high-speed camera (manufactured by Hitachi, Ltd.). Even when the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced to increase the contact pressure between the photosensitive drum 1 and the spikes and reduce the vibration, the gap is large at the entrance and exit sides of the developing unit. Vibration occurs, and the above-described effects are achieved.

Conversely, it is preferable to increase the gap between the photosensitive drum 1 and the sleeve 22 so that the ears do not contact the photosensitive drum 1 in a state where no magnetic field is applied, but it is preferable that the ears be in contact with the photosensitive drum 1 when the magnetic field is applied.

In FIG. 5, the surface of an aluminum sleeve having a diameter of 20 mm is used as the sleeve 22 and the surface of the aluminum sleeve is subjected to irregular sand blasting with alundum abrasive grains. The one shown in the following was used.

A non-magnetic stainless steel having a thickness of 1.2 mm was used as the blade 24, and ferrite (maximum magnetization 60 emu / g) having a particle diameter of 60 to 50 μm whose surface was coated with a silicone resin was used as the magnetic particles.

As the non-magnetic toner, a blue toner obtained by externally adding 0.8% of colloidal silica to a toner powder having an average particle diameter of 11 μm composed of 100 parts of a styrene / butadiene copolymer resin and 5 parts of a copper phthalocyanine pigment was used. A toner coating layer having a coating thickness of about 10 to 30 μm is obtained on the surface,
Further, a magnetic particle layer of 100 to 500 μ was obtained as an upper layer.
The toner adheres to the surface of each magnetic particle.

The magnetic particles are raised by the magnetic field by the magnetic pole 23b in the sleeve 22 in and around the developing section, and have a maximum length of about 0.8 to 1.
A 3mm brush was formed.

This developing device is incorporated in a PC-10 type copying machine manufactured by Canon Inc., and a photosensitive drum 3 (made of organic photosensitive material) and a sleeve 22 are mounted.
Was 350 to 450 μm. The peripheral speed difference between the photosensitive drum and the developing sleeve is almost zero. The developing sleeve had an outer diameter of 20 mm, and the photosensitive drum had an outer diameter of 60 mm. The photosensitive drum used was an OPC drum and had a charged latent image potential of -700V. Development was performed using a bias power supply 4 having a DC voltage of -300 V superimposed on an AC voltage having a frequency of 1700 Hz and a peak-to-peak value of 1400 V.

The numbers in Table 1 are the same as the numbers of the measurement points shown in FIG. 7, and for the examples and comparative examples of Nos. 1 to 35, the above-described developing unit configuration, the state of the developer during copy durability, and the image quality evaluation This is a summary of

Θ in Table 1 is an angle formed between the blade 24 and the magnetic pole 23a shown in FIG. SBGap is the gap length between the blade 24 and the sleeve 22. The D ₁ amount is the weight of the starting agent supplied on the sleeve 22 initially.

The magnetic force is the maximum magnetic flux density on the sleeve surface of the magnetic pole 23a.

High, medium, and low toner consumption indicate the density of the original used during copy durability. "Large" is close to solid black, "Medium" is the average value that is usually used, and "Small" is almost solid white. Show something close to.

In the developing device having the above-described configuration, the toner density, the amount of the applied developer, and the image quality on the developing sleeve after A4,000 sheets of durability were evaluated.

The starting material (D ₁ agent), the magnetic particles C to toner T
Was mixed at a ratio of 25: 3 into a 35-75 g (± 2 g) container, and the sleeve was rotated to form a magnetic particle layer (first layer) on the sleeve.

Then, the supplied toner agent (D ₂ agent) were charged onto a magnetic particle layer to form a toner layer (second layer).

Fig. 7 Measurement points Is the amount of developer applied M (mg / cm ² ) on the developing sleeve after the operation of the developing device, obtained by changing the configuration of various developing devices as shown in Examples and Comparative Examples in Table 1. Toner density a And

In FIG. 7 and Table 1, the developer application amount M on the developing sleeve is Is The magnetic particle layer on the developing sleeve in the developing container (first
Movement speed of the layer increases. This is because, as described above, the formation of the magnetic brush is facilitated by reducing the interposition of the toner between the magnetic particles, and the magnetic transport force is improved. Layer (first
This is because the moving speed of the layer increases. This excessive increase in the moving speed makes it easy to take in excessive toner from the replenishment toner layer (second layer) in contact with the magnetic particle layer (first layer). Eventually, the toner concentration of the magnetic particle layer increases, the toner tribo application is reduced, and image fogging occurs during operation of the developing device.

Also, when the amount of the developer applied on the developing sleeve increases, the transportability of the developer on the sleeve also decreases, and the developer is conveyed in a narrow space between the photosensitive drum and the developing sleeve and a narrow space such as a developing container inlet. It becomes easy to stay. This is particularly likely to occur when the toner concentration is high or when ferrite-based spherical magnetic particles are used as in this embodiment.

M is In this case, traces of the shape of the magnetic brush easily appear on the image copy. This is because the density of the brush is low because the application amount M is small.

Also, if the amount of the developer applied to the sleeve is small, the moving speed of the magnetic particle layer (first layer) decreases, and it becomes difficult to take in the replenishment toner into the magnetic particle layer. For this reason, the toner concentration in the magnetic particle layer decreases, and an excessive state of toner tribo application occurs. Therefore, it is difficult for the toner to separate from the magnetic particles or the sleeve, and the density on the image is reduced.

When the toner density a is less than 6.2, the image density is reduced, but the magnetic particles are more likely to adhere to the photoreceptor or a solid image is liable to cause white spots. This is because the magnetic particles used have a resistance value of 10 ⁷ or more, so when the toner concentration decreases, the magnetic particles tend to accumulate the charge induced by the latent image electric field from the sleeve side, and the coulomb between this charge and the latent image charge This is because magnetic particles tend to adhere to the photosensitive drum or neutralize latent image charges by force.

In addition, when a> 15, the occurrence of image fogging on the image becomes more conspicuous. This is to supply toner beyond the tribo-imparting ability of the magnetic particles used.

As described above, the area surrounded by the four curves in FIG. It is believed that the fact that the quality of the reproduced image is extremely critical is evident from the fact that there is a significant decrease in image quality under set conditions deviating from this region.

Further, a preferable setting in terms of image quality stabilization is 7.4a13.8 according to the many embodiments shown in FIG. 2 and Table 1. It is.

As described above, according to the present embodiment, fog, ghost images, uneven sweep, and development can be performed with high image density and high development efficiency.

As the material of the sleeve 22, in addition to aluminum, a conductor such as brass or stainless steel, a paper cylinder, or a synthetic resin cylinder can be used. In addition, when the surfaces of these cylinders are subjected to conductive treatment or are made of a conductor, they can also function as developing electrodes. Furthermore, a conductive elastic body, for example, a conductive sponge may be wound around the peripheral surface using a core roll.

With respect to the magnetic pole 23b of the developing unit, the magnetic pole is arranged at the center of the developing unit in the embodiment, but may be shifted from the center, or the developing unit may be arranged between the magnetic poles. FIG. 8 shows another embodiment.

Silica particles may be added to the toner to enhance the fluidity, or abrasive particles may be externally added for polishing the surface of the photosensitive drum 3 serving as a latent image holding member in a transfer type image forming method. A toner obtained by adding a small amount of magnetic particles to a toner may be used. That is, magnetic toners can be used as long as they are significantly weaker than magnetic particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the developer layer remaining on the sleeve 22 without being subjected to the development from the surface of the sleeve 22 rotated back into the container 21 is once scraped off by a scraper means (not shown). The scraped sleeve surface may be brought into contact with the magnetic particle layer to perform re-coating of the developer.

The embodiment shown in FIG. 5 may be provided with a mechanism for detecting the concentration of the magnetic particles and the toner and automatically replenishing the toner according to the output, similarly to the embodiment shown in FIG. .

The developing device of the present invention can be used as a single-use type developing device in which the container 21, the sleeve 22, the blade 24 and the like are integrated, or as a normal developing device fixed to an image forming apparatus.

〔The invention's effect〕

According to the present invention, a highly accurate ATR device is not required,
By properly setting the configuration of the developing device and the application conditions of the developer, the ATR device can be removed. Also, the combination with the conventional ATR apparatus of the present invention minimized the density fluctuation during copying.

[Brief description of the drawings]

1 is an explanatory view of an embodiment of the developing device according to the present invention, FIGS. 2 and 3 are explanatory views of the operation of FIG. 1, and FIG. 4 is an explanatory view of a durability density curve according to the embodiment of FIG. FIG. 5 is an explanatory view of another embodiment of the developing device according to the present invention, FIG. 6 is an enlarged explanatory view of a main part of a preferred developing structure of FIG. 5, and FIG. 7 is a toner according to the embodiment of FIG. FIG. 8 is a graph of a curve showing the relationship between the density and the amount of developer applied. FIG. 8 is an explanatory view of another embodiment of the developing device according to the present invention. 1 photosensitive drum 22 developing sleeve 23 magnet 27 magnetic particles 38 toner particles 36 developing container

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Taka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahide Kinoshita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-58-173762 (JP, A) JP-A-59-113464 (JP, A)

Claims (1)

(57) [Claims] 1. A developer container for containing a two-component developer containing magnetic particles and toner particles, a developer carrying member provided at an opening of the developer container and carrying the developer, and a developer container. A developing device comprising: a detecting unit configured to detect a toner concentration in the image forming apparatus; and a developer amount controlling unit configured to control an amount of a developer carried on a developer carrier based on a detection output of the detecting unit.