JPH0473794B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a dry developing device used in a copying process such as electrophotography.

Prior Art Dry developing methods that have already been put into practical use include a two-component developing method using a powder developer made of a mixture of toner and a magnetic carrier, and a one-component developing method using a powder developer consisting only of magnetic toner. It can be broadly divided into methods. In the two-component development method, the toner itself has good development and transfer characteristics, but there are problems with deterioration of the carrier and stability of the mixture ratio of toner and carrier. In the one-component development method,
In recent years, many copying machines have adopted this method because there are no problems associated with using a carrier. However, there is a difficult problem in that the toner requires conductivity during development and insulation during transfer, which are mutually contradictory conditions. Currently, the copying process is not very burdensome;
Using insulating magnetic toner with good transfer characteristics,
Various measures are being taken to improve development characteristics. Here, a method of developing a toner layer using a charged magnetic toner in a thin layer and a method of developing the toner layer as a layer of a certain thickness will be compared and considered.

In the thick layer method, when there are no differences in the physical properties or surface conditions of the toner particles, the toner can be well charged by friction with the developing sleeve, but the toner in the upper layer is hardly charged by friction, resulting in poor development. . However, if the toner has a certain distribution of physical properties or surface conditions, the toner in the upper layer will be triboelectrically charged between the toner particles. That is, when there is a difference in the triboelectrification series of toners, stable charging characteristics can be obtained and good development can be achieved. on the other hand,
In the case of the thin layer method, good development can be achieved if there is a difference in the triboelectrification series between the toner and the developing sleeve, but since the toner layer is thin, the developed image density is inherently low. .

By the way, stable development is actually possible when a development experiment is conducted using a thick layer method. The reason for this is that the amount of magnetic powder exposed on the toner surface and the exposed amount of additives such as dyes and carbon black vary depending on the dispersibility, classification, post-processing process, etc. during toner manufacturing, so the triboelectrification sequence between toner particles differs. This is because frictional electrification occurs between the toner particles due to the difference in the toner particles. However, as the ratio of oppositely charged toner (individual toner particles are originally negatively charged due to frictional charging with the developing sleeve) in the developer increases, the probability of contact between the oppositely charged toner and the developing sleeve increases, and the original negative electrode The charge polarity is transferred to . When only the oppositely charged toner was separated by development, it was found that the magnetic powder content was high. Since such toner has poor charge retention properties, charge leakage is likely to occur during conveyance on the outer circumferential surface of the developing sleeve, and it is also thought that charge polarity may easily shift.

However, even with such a thick layer method, the developing gap and the height regulating gap are narrow, requiring high precision, and the toner tends to clog the height regulating gap. Furthermore, the development mechanism depends on the toner in a stochastic manner, making it difficult to reproducibly produce such toner. Furthermore, since the toner concentration is 100%, there are drawbacks such as large fluctuations in the amount of toner in the development area.

In order to eliminate these drawbacks, it has been proposed to mix a magnetic carrier into the toner layer on the outer peripheral surface of the developing sleeve (Japanese Patent Laid-Open No. 147837/1983). FIG. 1 shows the basic structure of a developing device conventionally used in a one-component developing method. 1 is a cylindrical developing sleeve, 2 is a magnetic roller having S and N poles sequentially magnetized on its outer periphery, 3 is a height regulating member, 4 is a toner tank, and 5 is a photosensitive drum. Based on the rotation of the magnetic roller 2 in the direction of arrow a or the rotation of the developing sleeve 1 in the direction of arrow b, the toner is circulated and conveyed in the direction of arrow b on the outer peripheral surface of the developing sleeve 1, and the toner is rotated in the direction of arrow c. The electrostatic latent image previously formed on the surface of the body drum 5 is developed by rubbing. In this case, the amount of toner reaching the development area A is regulated by the height regulating plate 3 .

By the way, in such a developing device, when development is performed by mixing a magnetic carrier into the toner layer on the outer circumferential surface of the developing sleeve 1, some of the carriers suddenly reach the upstream side B of the height regulating plate in the developer conveying direction. After that, the toner conveying force acts on the arrow d.
As shown in , a phenomenon in which the toner diffused into the toner tank 4 was observed. That is, as copying progresses, the amount of carrier transported to the developing area A decreases, toner density fluctuates (increases), or the frictional charging between the toner and carrier becomes insufficient, resulting in a high-quality copied image. It is not possible to obtain . This also means that the toner density cannot be set to a predetermined value. Further, when uneven density of toner occurs in the axial direction of the developing sleeve 1, the toner and carrier are not easily affected by the force of movement in the axial direction, so that the uneven density is difficult to eliminate.

Purpose Therefore, the object of the present invention is to stabilize the toner concentration, achieve sufficient frictional electrification between the toner and the carrier, and to provide a method suitable for one-component development in which a small amount of starter carrier is mixed. It is an object of the present invention to provide a dry developing device that can effectively eliminate density unevenness in the axial direction.

Summary In order to achieve the above object, a dry developing device according to the present invention has a magnetic roller inside and circulates and conveys a powder developer made of a mixture of toner and magnetic carrier on the outer peripheral surface in one direction. a developing sleeve, a brush height regulating member provided on the upstream side of the developing region in the developer transport direction, a front regulating member provided on the upstream side of the brush height regulating member so as to face the outer circumferential surface of the developing sleeve, and a brush height regulating member. and a toner replenishment section installed on the upstream side of the front regulation member; and a toner replenishment section installed on the upstream side of the front regulation member; The interval is large enough to allow most of the developer whose layer thickness is regulated by the height regulating member to pass through, and is also large enough to prevent the carrier from flowing out in the cavity, so that the developer that has passed through the developing area The present invention is characterized in that the developer is configured such that the developer is conveyed from the sleeve to the empty chamber without substantially diffusing, and that development is performed using a developer consisting of a mixture of the toner and a magnetic carrier.

That is, by temporarily accumulating the developer transported to the developing area in the empty chamber, the carrier is prevented from being diffused into the toner replenishing section. Thus, due to the existence of the vacancy, a certain amount of carriers are present in the vacancy. When the empty chamber is above the developing sleeve, the dead weight of the developer in the empty chamber acts between the developing sleeve and the front regulating member, so that the toner from the toner replenishing section is transferred to the developing sleeve. The toner is replenished until the toner conveying force by the toner balances with the self-weight. In addition, if the empty chamber exists below the developing sleeve, the sum of the amount of developer held on the developing sleeve and the amount of developer existing in the empty chamber is constant, so toner is consumed by development. When this occurs, a gap is created in the empty chamber by the volume of the consumed toner. Therefore, the empty chamber is replenished with the same amount of toner as the consumed toner amount due to the toner feeding force of the developing sleeve. In other words, an amount of toner corresponding to the amount of toner consumed in the development area is supplied into the empty chamber. Therefore, a constant toner density can always be maintained in the development area. At the same time, the frictional electrification between the toner and the carrier becomes sufficient, and the developer is stirred within this cavity, thereby quickly eliminating density unevenness in the axial direction.

Embodiment FIGS. 2 and 3 show a first embodiment of a dry developing device according to the present invention.

First, the outline of the copying apparatus will be explained according to FIG. 2. The photosensitive drum 10 can be driven to rotate at a constant speed in the direction of arrow c, and around it are a charging charger 11, an image exposure means 12, and the present invention. A developing device 20, a transfer charger 13, a residual toner cleaning blade 14, and a residual charge eraser lamp 15 are installed. Also, the copy paper is conveyed from the right to the left as shown by the two-dot chain line.
After the transfer, the image is discharged from the copying apparatus via a fixing device (not shown).

The developing device 20 coaxially houses a magnetic roller 22 with S and N poles sequentially magnetized on the outer periphery inside a developing sleeve 21 formed in a cylindrical shape from a conductive non-magnetic material.
A height regulating plate 23 is provided, and the developer is distributed based on the rotation of the magnetic roller 22 in the direction of arrow a and/or the rotation of the developing sleeve 21 in the direction of arrow b.
The developing sleeve 21 is circulated and transported in the direction of arrow b on the outer peripheral surface thereof. Further, a developer front regulation plate 24 is installed upstream of the height regulation plate 23 . The front regulating plate 24 is formed integrally with the housing member of the toner replenishing tank 25, and its tip faces the outer circumferential surface of the developing sleeve 21. And the hot height regulation plate 23
A cavity 26 is formed between the front regulation plate 24 and the front regulation plate 24, and above this cavity 26 is a cover 2 that can be opened and closed.
7, and is open only towards the outer peripheral surface of the developing sleeve 21.

On the other hand, the lower part of the toner supply tank 25 is provided with a front regulation plate 24.
A toner replenishing section 28 is opened on the upstream side of the toner replenishing section 28. A replenishing tank bottom forming plate 29 is installed at the bottom of the toner replenishing section 28, and a perforated scraper 30 is provided on the outer circumferential surface of the developing sleeve 21 in a so-called forward direction. It is installed so that it comes into pressure contact with the Furthermore, developer spill prevention plates 31 and 32 are installed at the lower end of the toner supply tank 25 and below the development area A.

In the above configuration, the present inventors have developed a development area A.
The gap d ₁ in , the gap between the height regulating plate 23 and the front regulating plate 24 and the outer circumferential surface of the developing sleeve 21
Various development experiments were conducted by changing the conditions such as d ₂ and d ₃ or the type of toner and carrier, and good results were obtained in each case. Here, some experimental examples will be described.

[Experiment example] Gap d ₁ : 0.60mm Gap d ₂ : 0.40mm Gap d ₃ : 1.20mm Magnetic roller Magnetic force: 750G Number of poles: 8 Number of rotations: 800rpm (direction of arrow a) Developing sleeve Outer diameter: 31mm Number of rotations: 80rpm (Direction of arrow b) Process speed (peripheral speed of photoconductor drum): 130 mm/sec. Carrier: F-182 manufactured by Nippon Teppou Co., Ltd. Average particle size: 65 to 70 μm Supply amount: 40 g Toner: Charged magnetic toner Magnetic powder content : 40wt% Electrostatic latent image potential: +400V (highest potential) Developing bias: DC +100V AC 600Hz 500Vrms In this experimental example, 60,000 copies were made, but there was hardly any consumption of the carrier on the outer peripheral surface of the developing sleeve 21. There was no deterioration of the carrier itself.

[Experiment example] Magnetic roller: Fixed Developing sleeve: 80 rpm (direction of arrow b) Carrier: F-182 manufactured by Nippon Tetsuko Co., Ltd. Average particle size: 65 to 70 μm Supply amount: 40 g Toner: Charged magnetic toner Magnetic powder content: 15 wt % Other conditions are the same as [Experiment example] In addition, in this experiment example, as a color toner to replace the above-mentioned toner, the degree of magnetic powder was changed for sepia, and a prototype containing 5 to 10 wt% of TiO ₂ + pigment was also used for green. I tried both, but I was able to get good copies of the images.

[Experiment example] Gap d ₁ : 0.50 mm Gap d ₂ : 0.30 mm Gap d ₃ : 1.00 mm Carrier: Fuji Electrochemical Co., Ltd. X-012 Average particle size: 45 μm Supply amount: 80 g Toner: Non-magnetic toner Electrostatic latent image Potential: +400V (highest potential) Developing bias: DC +150V Here, we will explain the movement of the carrier and toner, and the mechanism of development.

The carrier is first supplied to the empty chamber 26 by opening the cover 27, and is placed on the outer peripheral surface of the developing sleeve 21 by operating the developing device. On this occasion,
A certain amount of toner may be mixed in the carrier in advance. The toner is then stored in the replenishment tank 25 and supplied to the outer peripheral surface of the developing sleeve 21 from the replenishment section 28 . The toner is circulated and conveyed in the direction of arrow b on the outer peripheral surface of the developing sleeve 21 based on the rotation of the magnetic roller 22 in the direction of arrow a or the rotation of the developing sleeve 21 in the direction of arrow b, and as it passes through the empty chamber 26. The toner is stirred and mixed with the carrier, and the toner is negatively charged by frictional charging with the developing sleeve 21 or frictional charging with the carrier. In practice, development is performed in a state where the toner and carrier are sufficiently mixed, and the electrostatic latent image formed with positive polarity on the photoreceptor drum 10 is developed in the development area A.

The toner after development is further conveyed in the direction of arrow b along with the carrier, and is replenished with new toner through the hole of the perforated scraper 30 at the toner replenishing section 28, where it once accumulates in the empty chamber 26 and is stirred and mixed. It reaches the development area A again.

In this case, the amount of developer conveyed to the development area A is regulated by the gap _d2 of the height regulating plate 23;
Since the gap d ₃ of the front regulation plate 24 is set larger than the gap d ₂ , all the carriers reach the vacant room 26 through the gap d ₃ . Here, the carrier and toner regulated by the height regulating plate 23 accumulate in the empty chamber 26 and are also stirred and mixed in the axial direction of the developing sleeve 21, but these carriers in particular are only stirred within the empty chamber 26. Therefore, the toner is not dispersed from the toner replenishing section 28 into the toner replenishing tank 25.
The toner density in the development area A is determined by the amount of carrier accumulated in the empty chamber 26. By the way, as mentioned above, due to the existence of the vacant room 26, the vacant room 26
There is a certain amount of carriers. On the other hand, since the dead weight of the developer in the empty chamber 26 is acting between the developing sleeve and the front regulating member 24, the toner from the toner replenishing section is kept in balance with the toner conveying force of the developing sleeve 21. Until, that is,
Empty room 2 until the amount corresponds to the amount consumed in development area A.
Supplied within 6 days. Therefore, a constant toner density can be maintained in the development area A at all times. Further, by adjusting the amount of carrier supplied into the empty chamber 26 in advance, it is possible to arbitrarily and accurately set the toner concentration.

In this case, gap _d3 needs to allow more developer to pass through than gap _d2 . In other words, the gap _d3 needs to be large enough to allow all of the toner including the carrier to pass through, and the front regulation plate 24 partitions the empty chamber 26 and the toner supply tank 25.
To prevent the carriers accumulated in the tank 6 from diffusing into the supply tank 25. If the gap _d3 is narrower and less developer passes than the gap _d2 , the carrier will accumulate at the front regulating plate 24, making it impossible to achieve the object of the present invention. Further, when the developer passes through the empty chamber 26, not only is sufficient frictional charging between the toner and the carrier, but also the unevenness of toner concentration in the axial direction is effectively eliminated.

Note that, in order to increase the developer conveyance force by the developing sleeve 21, minute irregularities may be formed on the outer circumferential surface of the developing sleeve 21 by blasting or the like.

On the other hand, as carriers, iron powder carriers, ferrite carriers, resin-coated carriers thereof, and binder carriers in which fine powder carriers are bound with resin are used. A magnetic toner or a non-magnetic toner can be used as the toner, and the higher the content of magnetic powder, the worse the fixing properties, and if it exceeds 40 wt%, the toner density in the development area A tends to decrease. Therefore, it is appropriate that the content be 40wt% or less. As described above, when the toner contains magnetic powder, it is difficult to cause machine stains due to scattering even if the toner is not sufficiently frictionally charged with the carrier, but it is difficult to produce color compared to non-magnetic toner. That is, in order to cancel the color of the magnetic powder, it is necessary to add TiO ₂ etc. and further add dyes and pigments to adjust the color, and the addition of TiO ₂ etc. has a negative effect on the mutual frictional electrification between toner particles. This is because. However, in the case of magnetic toner, the image quality can be improved by applying an AC developing bias.

When using non-magnetic toner, it is not possible to utilize the frictional electrification between toner particles, and if the frictional electrification with the carrier is not sufficiently performed, the toner is likely to scatter, and when using magnetic toner, In comparison, it is necessary to keep the toner density (in the development area) low. Therefore, it is preferable that the front regulation plate 24 is made of a magnetic material and a so-called carrier curtain is formed at the installation portion of the front regulation plate 24 to suppress the amount of toner replenishment from the toner supply unit 28 . In addition, to ensure more sufficient frictional charging between the toner and the carrier, it is necessary to
The amount of carriers accumulated in this empty chamber 26 may be increased by increasing the distance in the circumferential direction.

Next, the function of the carrier for toner will be explained.

First, the carrier has a function of ensuring triboelectric charging of the toner. Concomitantly, the frictionally charged toner is electrostatically attracted to the developing sleeve 21, and the toner is conveyed to the developing area A while retaining the toner charge. If the toner and carrier are mixed, the toner can obtain sufficient charge due to friction with the carrier, but if the carrier is not present and the toner layer is thick, the uppermost layer cannot retain sufficient charge. In addition, the carrier has a function of increasing magnetic permeability and improving conveying force. In other words, the presence of the carrier increases the substantial magnetic field strength in the development area A, which is effective in removing fog with magnetic toner. Furthermore, by increasing the dielectric constant in the development area A, the actual electric field strength increases, or the actual volume of the developer increases.In other words, even if the toner layer is not made thinner, the actual toner concentration can be increased with a thick layer. It can be lowered.

For example, in the case of charged magnetic toner, there is a reversely charged toner having a carrier function among such toners, and during development, the oppositely charged toner having a carrier function causes the developing sleeve 21 to undergo bias development by an applied bias voltage. I do. in this way,
If the oppositely charged toner is attracted to the circumferential surface of the developing sleeve 21, a normal bias voltage will not be applied between the photosensitive drums 10, so it is necessary to scrape it off with a scraper and return it to the dry developing device 20. When carriers are mixed together as in the present invention, the carriers are bias-developed on the developing sleeve 21, but since the carrier conveying force due to the magnetic force of the magnetic roller 22 is greater than the suction force due to the bias, the carriers are not applied to the developing sleeve 21. without sticking
The carrier is smoothly conveyed over the developing sleeve 21 by the magnetic roller 22. Therefore, in this embodiment, a perforated scraper 30 is provided downstream of the developing area A to quickly scrape the developer onto the developing sleeve 21.
Although I tried to scrape it off, it is not necessarily necessary. However, if a perforated scraper 30 is provided, it is possible to improve the stirring and mixing efficiency.

Here, the characteristics (charging properties) required of the magnetic toner will be explained.

Magnetic toner has frictional electrification with the carrier, developing sleeve, etc., and when the magnetic toner is used alone for development, the amount of adhesion on the toner polarity side, which is charged due to friction with the carrier, is greater than the amount of adhesion on the opposite polarity side. It is necessary to have twice or more the characteristics. That is, the fourth
As shown in the figure, in the case of negatively charged toner with a large adhesion amount on the positive potential side, this means that there is a relationship of tan θ ₁ /tan θ ₂ ≧2. This means that the magnetic toner itself has chargeability, and although the charged magnetic toner is triboelectrically charged with the carrier, developing sleeve, etc., it is also triboelectrically charged between the toner particles, so by comparing the developability of magnetic toner alone, It has polarity selectivity in the amount of adhesion. By giving the magnetic toner such a chargeability characteristic, it becomes possible to use it at a high toner mixing ratio.

However, when tanθ ₁ /tanθ ₂ is smaller than 2, the toner mixing ratio cannot be increased.
This is because, in this case, there are a large number of toners that are oppositely charged, so it is difficult to triboelectrically charge all of them with the carrier and make the polarities of the toners uniform. Therefore, in this case, the amount of supplied toner having sufficient charge decreases, making it impossible to obtain sufficient image density.

The reason why the cover 27 can be opened and closed is not only for initially setting a predetermined amount of carriers, but also for removing or replenishing carriers when the carriers deteriorate or are consumed for some reason. Of course, if a carrier replenishment/removal section is provided separately, the height regulating plate 23, front regulating plate 24, and cover 27 may be integrally molded with resin, as shown in FIG. If the corners 26a and 26b are rounded, the flow (circulation) of the developer within the empty chamber 26 becomes smoother, and excessive intrusion of toner from the toner supply tank 25 can be more reliably prevented. However, in reality, in each of the above experimental examples, there was no occurrence of blocking due to excessive penetration of toner, which would cause problems. In addition, in order to prevent excessive intrusion of toner, if the magnetic roller is fixed, the magnetic roller 2
It is also effective to have the front regulating plate 24 as one of the two magnetic poles facing each other. In this case, due to the action of the magnetic field, the developer swells up at the tip of the front regulating plate 24 facing the magnetic pole, which not only makes it possible to increase the gap _d3 , but also prevents excessive toner from entering from the replenishing section 28. is prevented.

On the other hand, in FIG. 6, the vacant space 26 is
A second embodiment is shown below. In this second embodiment, a height regulating plate 23 and a front regulating plate 24 are provided below the developing sleeve 21, and the empty space 26 is provided with a saucer-type cartridge 35 that can be taken in and out in the axial direction of the developing sleeve 21. It is configured. Therefore, the initial setting and replacement of the carrier are performed by taking the cartridge 35 in and out. The developer is circulated and conveyed in the direction of arrow b' on the outer peripheral surface of the developing sleeve 21 based on the rotation of the magnetic roller 22 in the direction of arrow a' and/or the rotation of the developing sleeve 21 in the direction of arrow b'. Photosensitive drum 10 is indicated by an arrow
It is said that it can be rotated in the c′ direction. Further, the toner replenishing section 28 is formed of a partition plate 33 and a front regulating plate 24, and is provided with a toner stirring member 34 that can be rotated in the direction of arrow e. Toner supply tank 25
Although not shown, extends to the right so that the toner pressure (self-weight) in the supply tank 25 does not directly act on the developing sleeve 21 . Even in this case, since the sum of the amount of developer held on the developing sleeve 21 and the amount of developer present in the empty chamber 26 is constant, when the toner is consumed by development, the amount of the consumed toner is A gap will be created in the empty room by the volume. Therefore, the toner feeding force of the developing sleeve 21 replenishes the vacant chamber with the same amount of toner as the consumed toner amount, and a constant toner density can be maintained in the developing area A at all times.

Effects As is clear from the above explanation, according to the present invention, a space is formed between the height regulating member and the front regulating member provided on the upstream side thereof, and the distance between the front regulating member and the sleeve is increased. However, since it is large enough to allow most of the developer whose layer thickness is regulated by the height regulating member to pass through, and is also large enough to prevent the carrier from flowing out within the cavity, the developer transported to the developing area is The toner particles accumulate in the empty chamber and are stirred and mixed, thereby preventing the carrier from being dispersed into the toner replenishing tank. Thus, due to the existence of the vacancy, a certain amount of carriers are present in the vacancy. If the empty space is above the developing sleeve,
Since the dead weight of the developer in the chamber acts between the developing sleeve and the front regulating member, toner is replenished from the toner replenishing section until the toner conveying force of the developing sleeve balances the dead weight. Furthermore, if the empty chamber exists below the developing sleeve, the sum of the amount of developer held on the developing sleeve and the amount of developer existing in the empty chamber is constant;
When toner is consumed by development, a gap is created in the empty chamber by the volume of the consumed toner. Therefore, the empty chamber is replenished with the same amount of toner as the consumed toner amount due to the toner feeding force of the developing sleeve. In other words, an amount of toner corresponding to the amount of toner consumed in the development area is supplied into the empty chamber. Therefore, a constant toner density can always be maintained in the development area. In other words, by adjusting the amount of carrier in advance, it is possible to arbitrarily and accurately set the toner concentration. Further, when the developer passes through the cavity, sufficient frictional electrification occurs between the toner and the carrier, and the carrier present in the cavity quickly eliminates uneven toner concentration in the axial direction of the developing sleeve. A so-called filter effect can be expected.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional dry developing device, FIG. 2 is a sectional view showing a first embodiment of the dry developing device according to the present invention, FIG. 3 is a sectional view of the main part of FIG. 2, and FIG. The figure is a graph showing the charging characteristics of toner.
FIG. 6 is a sectional view showing a modification of the embodiment. FIG. 6 is a sectional view showing a second embodiment. DESCRIPTION OF SYMBOLS 10... Photoreceptor drum, 20... Dry developing device, 21... Developing sleeve, 22... Magnetic roller, 23... Height regulation plate, 24... Front regulation plate, 2
5...Toner supply tank, 26...Empty room, 28...Toner supply section, 35...Cartridge, A...Development area.

Claims (1)

[Claims] 1. A developing sleeve that has a magnetic roller inside and that circulates and conveys a powder developer made of a mixture of toner and magnetic carrier on its outer peripheral surface in one direction, and is provided on the upstream side of the developing area in the developer conveying direction. A brush height regulating member, a front regulating member provided on the upstream side of the brush height regulating member so as to face the outer circumferential surface of the developing sleeve, and an opening toward the outer circumferential surface of the developing sleeve between the brush height regulating member and the front regulating member. and a toner replenishment section installed upstream of the front regulation member, and the distance between the front regulation member and the sleeve is such that the developer whose layer thickness is regulated by the height regulation member is almost completely removed. It is of a size that allows the carrier to pass through the sleeve and is also large enough to prevent the carrier from flowing out within the cavity, so that the developer that has passed through the development area is conveyed from the sleeve to the cavity without substantially diffusing. A dry type developing device, characterized in that it is configured as follows, and that development is performed using a developer made of a mixture of the toner and a magnetic carrier.