JP4187617B2 - Development device, image forming device - Google Patents

Description

  The present invention relates to a developing device that performs development on a photoreceptor rotated by a developer contained in a developing container, and an image forming apparatus including the developing device.

An electrophotographic image forming apparatus includes a developing device that develops an image on a rotating photosensitive member on which an electrostatic latent image is formed by supplying a developer contained in a developing container with a developing roller.
The developing device is disposed in close proximity to the photosensitive member on which the developing container rotates so that the opening faces the developing container, and outside air flows into the developing container through the opening from the gap between the photosensitive member and the developing container. In many cases, suction means such as a suction fan for sucking air is provided in order to obtain a negative pressure. This is to prevent the developer in the developing container from flowing out of the gap between the developing container and the photoreceptor and scattering.
For example, in Patent Document 1, in a two-component developing device having a developing roller, a hollow shaft is disposed in the axial direction in the vicinity of the developing roller, and the openings formed at both ends of the hollow shaft. A developing device provided with a suction device is shown.
Patent Document 2 discloses a developing device in which suction ports are brought close to both end portions of a magnet roller provided in a developing container, and a developer scattered from the magnet roller is sucked from the suction port by a suction fan. Yes.
Further, Patent Document 3 includes a magnetic roll for supplying the developer to the photosensitive drum and collecting the residual developer in a housing (corresponding to the developing container) containing the developer, and the axial direction of the magnetic roll. A developing device is shown in which slits are provided so as to face each other, and the scattered developer is sucked by a suction duct through the slits.
Japanese Utility Model Publication No. 5-90512 Japanese Patent Laid-Open No. 10-274883 JP 2000-39768 A

However, since the rotation of the photoconductor causes an air flow toward the downstream side in the rotation direction of the photoconductor in the vicinity of the surface of the photoconductor, the opening of the development container can be maintained even if the pressure inside the developer container is negative due to air suction. There is a problem in that the developer flows out and scatters due to the air flow caused by the rotation of the photoconductor from the gap between the edge and the photoconductor on the downstream side in the rotation direction of the photoconductor.
On the other hand, the above-mentioned patent documents do not show a specific configuration for preventing the developer from flowing out (scattering) against the air flow caused by the rotation of the photosensitive member.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the development seat from flowing out (scattering) from the developing container against the air flow caused by the rotation of the photosensitive member. It is an object of the present invention to provide a developing device having a typical configuration and an image forming apparatus including the developing device.

In order to achieve the above object, the present invention provides a developing container in which an opening is opposed to a rotating photosensitive member and accommodates a developer, and a gap between the photosensitive member and the developing container through the opening. And a suction unit that sucks air so that outside air flows into the developer container. The photosensitive device in the opening serves as a flow path of air from the opening to the suction unit in the developer container. A central air inlet and both air inlets that are formed in the developing container in the vicinity of both ends and near the center of the developing container in the direction of rotation of the photoconductor, and communicate with the suction means. The developing container and the magnet roller disposed in the developing container are disposed at the most in the flow path from the edge to the central inlet and the inlets at both ends. There is a flow path with a minimum cross-sectional area that is an adjacent part, and the flow path length from the edge to the central inlet is shorter than the flow path from the edge to the inlets at both ends. The developing device is characterized by being formed .

In general, the rotation of the photosensitive member, wherein the rotation axis direction of the photosensitive member, with the pressure near the center is high, the flow of air to the vicinity of both end portions generated from the vicinity of the central portion, which causes Thus, the scattering of the developer near the both end portions becomes remarkable.
On the other hand, according to the above configuration, it is possible to prevent the pressure in the vicinity of the center from increasing due to the air flow path (flow) in the vicinity of the center as much as possible, and to the suction means near the both ends. Since a flow path (flow) of air is formed, it is possible to prevent the developer from scattering from the vicinity of both ends.

Also, the present invention may be one that captures an image forming apparatus having a pre Kigen image device.

According to the present invention, before Symbol flow path of air in the vicinity of the center by (stream) can be prevented as much as possible that the higher the pressure in the vicinity of the central portion, further, the air toward the suction means in the vicinity of the end portions Since the flow path (flow) is formed, it is possible to prevent the developer from scattering from the vicinity of both end portions to the outside .

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a cross-sectional view showing an overall configuration of an image forming apparatus Z provided with a developing device X according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a schematic configuration of the developing device X, and FIG. FIG. 4 is a plan sectional view of a portion of the developing container on the side close to the photosensitive drum, and FIG. 4 shows a gap between the developing container and the photosensitive drum when the gap between the parallel plates is approximated. FIG. 5 is a graph showing the flow velocity distribution. FIG. 5 is a graph showing the relationship between the distance h between the downstream gaps between the photosensitive drum and the developing container and the scattering flow rate Qo to the outside of the developing container. FIG. FIG. 7 is a graph showing the relationship between the flow rate per unit length of the air in the axial direction of the photosensitive drum Qf and the scattering flow rate Qo to the outside of the developing container, and FIG. 7 shows the relationship between the ambient wind speed and the thermal resistance in the aluminum member Graph, Fig. 8 shows toner particle size and toner empty Is a graph showing the relationship between the relative values of the resistor / toner mass.

First, the overall configuration of an image forming apparatus Z provided with a developing device X according to an embodiment of the present invention will be described with reference to FIG.
The image forming apparatus Z has a copier mode (copy mode), a printer mode, and a FAX mode as print modes. An operation input from an operation unit (not shown) or a print job from an external host device such as a personal computer. The print mode corresponding to the reception is selected by the control unit described later.
As shown in FIG. 1, the image forming apparatus Z is roughly divided into a document reading unit 10, a paper feeding unit 20, a printing unit 30, and a paper discharge unit 40, and the document reading unit 10 is arranged above the paper feeding unit 20. A paper discharge unit 40 is provided at an intermediate position between the document reading unit 10 and the paper supply unit 20.
Hereinafter, the copier mode will be described from the above processing modes.
After the user places a document on the platen glass 11 of the document reading unit 10 (scanner unit), the sheet (recording paper) is placed on the sheet feeding cassette 21 of the sheet feeding unit 20 or the manual feed tray 23 provided on the side of the apparatus. After copying and inputting the condition input keys (number of prints / printing magnification, etc.) on the operation panel (not shown) arranged on the front of the exterior of the device, the copy operation is started by operating the start key on the operation panel. The
When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22a rotates to feed (feed) the paper into the apparatus, and the fed paper reaches the registration roller 31 (roller pair) and is captured. The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image formation start portion) of the image formed on the photosensitive drum 32, and the leading edge of the paper is uniformly pressed against the registration roller 31. Thus, the leading edge position of the paper is corrected.

On the other hand, in the document reading unit 10, the copy lamp 12a (light source) is turned on, and the exposure starts when the copy lamp unit 12 moves in the direction of the arrow. Irradiation light applied to the document by the copy lamp 12a becomes reflected light (reflected light from the document) including image information of the document, and the reflected light is transmitted from the first mirror 12b provided in the copy lamp unit 12 to the second light. Reading is performed by inputting to the CCD 16 from the mirror 13, the third mirror 14, and the optical lens 15.
The image information read in this way is converted into an electrical signal by a CCD circuit (not shown), and the image information signal is subjected to image processing under a set condition, and the laser scanner unit. 33 as print data.

On the other hand, a part of the peripheral surface of the photosensitive drum 32 is charged to a predetermined charging potential in the entire axial direction by the charging unit 34 (charging means), and the entire peripheral surface is predetermined by rotating the photosensitive drum 32. Charged to charged potential. The surface of the charged photoconductor 32 moves to the next process by the rotation of the photoconductor drum 32.
Next, in the laser scanner unit 33 (exposure means), the laser beam emitted from the semiconductor laser is deflected by the polygon mirror (rotating polygon mirror) having a plurality of reflecting surfaces in the rotation direction and various optical systems, while being deflected. The drum 32 is irradiated. As a result, the laser beam is scanned on the photosensitive drum 32 charged by the charging unit 34, and an electrostatic latent image is formed on the photosensitive drum 32.
Thereafter, toner (an example of a developer) in the developing tank 61 is supplied onto the surface of the rotating photosensitive drum 32 by a magnet roller 62 (developing means) in the developing tank 61 provided in the developing device X, and an electrostatic latent image is obtained. The toner is visualized (developed) in accordance with the potential gap on the photosensitive drum 32 by this toner.
In addition, paper (recording paper) to be imaged is conveyed in the direction of the photosensitive drum 32 by the registration roller 31 in time, and the toner on the photosensitive drum 32 is transferred by the transfer unit 36 (corona charger (transfer means)). Is transferred to the paper. The toner remaining on the photosensitive drum 32 is scraped off by the cleaning blade 37 a of the drum unit and collected by the cleaner unit 37.
The surface of the photosensitive drum 32 from which the toner has been removed by the cleaning blade 37a is neutralized as necessary by a neutralization device 39 (a neutralization unit) while moving to the charging unit 34.

On the other hand, the sheet on which the toner has been transferred passes between the heating roller 38a and the pressure roller 38b of the fixing device 38 (fixing step), and heat and pressure are applied, so that the unfixed toner on the sheet is transferred to the sheet. Then, the sheet is melted and fixed to the sheet discharge tray 42 by the sheet discharge roller 41. The heating roller 38a is heated by a heater 38c provided therein.
In addition, when it is detected by a predetermined sensor that a document is placed on the document tray 19 included in the document reading unit 10, the paper feed roller 51 rotates when a predetermined start key operation is performed. Then, the document placed on the document tray 19 is sent into the document reading unit 10 and is transported through a predetermined transport path Rt1. A registration roller 53 is provided on the conveyance path Rt1, and the original is captured by the registration roller 53 and positioned at the leading end of the original, and then conveyed to the original reading position at a predetermined timing. Then, the document being conveyed is exposed while the copy lamp unit 12 is stopped at a predetermined stop position (document reading position). The process of reading the document image by the reflected light from the document obtained by this exposure is as described above.
The document whose image has been read in this way is discharged to the document discharge unit 18.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of the developing device X according to the embodiment of the present invention.
The developing device X includes a developing container 61 that is disposed in close proximity to a rotating photosensitive drum 32 (an example of the photosensitive member) with an opening 61a facing it, and a magnet that supplies toner to the surface of the photosensitive drum 32. The outside air passes through the opening 61 a from the gap between the roller 62, the paddle 63 that stirs and conveys the toner in the developer container 61 and supplies the toner to the magnet roller 62, and the photosensitive drum 32 and the developer container 61. In order to flow into the container 61, an exhaust fan 64 a that sucks air in the container and discharges it to the outside of the developer container 61 is provided in order to maintain the inside of the developer container 61 at a negative pressure.
Under the developing container 61, an exhaust duct 64b is provided over substantially the entire axial direction of the photosensitive drum 32 (also the axial direction of the magnet roller 62). Air that has flowed into the developing container 61 through the opening 61a from the gap with the developing container 61 passes around the magnet roller 62, and passes through the intake ports 61c and 61d provided on the lower side of the developing container 61. After passing through the exhaust duct 64b, the exhaust fan 64a discharges the developing device X. The air thus discharged is discharged after being removed by a predetermined filter (not shown) in the flow path in the developing container 61. The exhaust fan 64a and the exhaust duct 64b constitute an example of the suction means, and are hereinafter referred to as suction means 64.

In the developing device X, the distance (the height of the gap 61e) between the edge 61e of the opening 61a of the developing container 61 on the downstream side in the rotational direction of the photosensitive drum 32 and the photosensitive drum 32 is 2 mm or less. It is configured. The reason is described below.
As described above, the rotation of the photosensitive drum 32 causes an air flow toward the downstream side in the rotation direction of the photosensitive drum 32 (hereinafter referred to as the developing downstream side) in the vicinity of the surface of the photosensitive drum 32. . In the developing device X, the opening 61a of the developing container 61 is disposed in close proximity to the rotating photosensitive drum 32, so that the edge 61e of the opening 61a of the developing container 61 on the downstream side of the development The air flow in the gap 61e with the photosensitive drum 32 rotating at a peripheral speed U (m / s) during development is such that one of the two parallel plates is fixed and the other is the speed U (m / s). ) Can be approximated to the air flow between both flat plates when moving in parallel. That is, the fixed-side flat plate corresponds to the edge portion 61e, and the moving-side flat plate corresponds to the photosensitive drum 32.
Here, the circumferential speed during development of the photosensitive drum 32 is U (m / s), the position in the gap h direction in the gap 61b (corresponding to the distance from the fixed plate) is y, and the inside and outside of the developing container 61 are outside. A differential pressure (corresponding to a differential pressure (pressure loss) between the upstream side and the downstream side in the moving direction of the moving plate in the parallel plate) is ΔP, and the edge portion 61e and the photoconductive drum 32 in the circumferential speed direction of the photoconductive drum 32. Is the length of the portion (the gap 61b portion) facing each other (corresponding to the length of the moving plate in the parallel plate in the moving direction) L (m), the air in the gap 61b (corresponding to between the parallel plates) The flow rate distribution u (y) (m / s) of the air and the air flow rate Q (m ³ / s) flowing into the developing container 61 from the gap 61b of the interval h due to the air suction of the suction means 64 are as follows: (1) and (2 It can be approximated by the equation. Here, y is the position of the edge 61e surface (fixed flat plate side) 0 (zero) and the surface of the photosensitive drum 32 surface (moving flat plate side) is h, and the direction of air flow velocity u (y) Is a negative direction of movement of the photosensitive drum 32, and μ is a viscosity coefficient of air.
u (y) = [ΔP / (2 μL)] (h−y) · y−U · y / h (1)
Q = [ΔP / (12 μL)] h ³ −U · h / 2 (2)
The flow rate represented by the second term “U · h / 2” in the equation (2) is the air flow rate flowing out of the developing container 61. Therefore, by reducing the distance h of the gap 61b, the flow rate of air flowing out of the developing container 61, that is, the amount of toner scattering can be reduced.
FIG. 4 is a graph showing the flow velocity distribution of the equation (1), that is, the flow velocity in the gap 61b when the gap 61b between the developing container 61 and the photosensitive drum 32 is approximated as a gap between parallel plates. It is a graph showing distribution, the vertical axis is y, and the horizontal axis is the flow velocity u (y).
A portion where the air flow rate is a negative flow rate (shaded portion) indicates that the air flows out of the developing container 61.

On the other hand, the flow path resistance of the gap 61b, which is the outside air inlet, is small with respect to the flow path resistance of the entire flow path, so that the influence on the overall flow rate reduction is small.
Here, if A = ΔP / (2 μL) and y in the equation (2) where u (y) = 0, then y is
yo = A · h / [A + U / h] (3)
It becomes. Further, Qo is expressed by the following equation (4), where Qo is the air flow rate in the region y = yo to h, that is, the outflow air flow rate to the outside of the developing container 61 (hereinafter referred to as the amount of scattered air). .
Qo = A · [(h / 2) (h ² −yo ² ) − (1/3) (h ³ −yo ³ )]
- {U / (2h)} (h 2 -yo 2) ... (4)
Here, the air suction flow rate (hereinafter referred to as fan air volume) QF (m ³ / s) of the exhaust fan 64a is set to 2.0 × 10 ⁻³ , 4.0 × 10 ⁻³ , 6.0 × 10 ⁻³ and FIG. 5A is a graph in which h is plotted on the horizontal axis and the scattered air volume Qo is plotted on the vertical axis when the speed is changed to 8.0 × 10 ⁻³ (m ³ / s). Here, in FIG. 5, for convenience, QF is expressed in units of (L / s). A value obtained by multiplying the air flow rate Q obtained by the equation (2) by the development width is the fan airflow rate QF.
As can be seen from FIG. 5A, the amount of scattered air Qo also changes in accordance with the change in QF.
Therefore, the graph of FIG. 5B is obtained by performing the process of removing the influence of the change in the fan airflow rate QF on the graph of FIG.
The graph of FIG. 5 (b) is a value (QF · QF) ^1/2 that is obtained by multiplying the scattered air volume Qo on the vertical axis by (the 1/2 of the fan air volume QF) with respect to the graph of FIG. 5 (a). It is the converted graph. According to the relationship after the conversion, data is plotted at substantially the same point for each interval h of the gap 61b regardless of the change in the fan airflow rate QF. When this is approximated by a broken line (the wavy line in FIG. 5B), the inflection point is a point of h = 2 mm. This is because when h ≦ 2 mm, the increase rate of the scattered air volume Qo relative to the fan air volume QF is very small, and when h> 2 mm, the increase rate of the air scatter air volume Qo relative to the fan air volume QF is large. That is.
From the above, if h is 2 mm or less, the increase in the scattering flow rate Qo can be suppressed regardless of other conditions. As a result, the scattering of toner can be suppressed, and as a result, there is no image adhesion with scattered toner. Good image formation can be performed.

It is also possible to grasp the conditions for preventing toner scattering from another viewpoint.
That is, an interval (height of the gap 61b) between the edge 61e of the opening 61a of the developing container 61 on the downstream side in the rotation direction of the photosensitive drum 32 and the photosensitive drum 32 is h, and the photosensitive drum 32 and With the magnet roller 62 (developing roller) provided in the developing device X being stopped, the photosensitive drum 32 of the air flowing into the developing container 61 from the gap 61b of the interval h by air suction of the suction means 64. When the flow rate per unit length in the rotation axis direction (depth direction in FIG. 2) is Qf (m ³ / s / m) and the peripheral speed of the photosensitive drum 32 during development is U (m / s). , (Qf / U / h) ≧ 2.0 may be satisfied.
The reason for the configuration will be described below.

In the same manner as described above, the air flow in the gap 61b is approximated to the air flow between the parallel plates.
When the first term of the equation (2) is converted as A = ΔP / (2 μL), the following equation (5) is obtained.
[ΔP / (12 μL)] = Qf / h3 = A / 6 (5)
Further, in order to normalize the equation (4) with respect to the peripheral speed U of the photosensitive drum 32, both sides of the equation (4) are divided by U, and the equation (4) is converted using the flow rate Qf per unit length. Then, the following equation (6) is obtained.
Qo / U = [Qf / h3 / U] ・
^{[(H / 2) (h 2} -yo 2) - (1/3) (h 3 -yo 3) ]
- {1 / (2h)} (h 2 -yo 2) ... (6)
Here, when the interval h of the gap 61b is changed to 0.5, 1, 2, 4, and 8 (mm), the equation (6) is expressed by Qf / U on the horizontal axis and Qo / U on the vertical axis. FIG. 6 (a) shows a graph.
As can be seen from FIG. 6A, Qo / U also changes in response to changes in h.
Therefore, the graph of FIG. 6B is obtained by performing processing for removing the influence of the change in the interval h of the gap 61b on the graph of FIG.
The graph of FIG. 6B is the same as the graph of FIG. 6A, with Qo / U on the vertical axis and Qf / U on the horizontal axis divided by h (Qo / U / h), (Qf / U / h).
The expression of the graph of FIG. 6B is expressed by the following expression (7).
[Qo / U / h] = 0.053 · [Qf / U / h] ^−0.75 (7)
According to the relationship after conversion, data is plotted at substantially the same point for each value of (Qf / U / h) regardless of the change in the interval h. When this is approximated by a broken line (the wavy line in FIG. 6B), the inflection point becomes a point of (Qf / U / h) ≈2. This is because, when (Qf / U / h) ≧ 2, the increase rate of the scattered air volume Qo with respect to the condition setting of Qf, U, h is very small, and when (Qf / U / h) <2, Qf, U, h That is, the increasing rate of the scattered air volume Qo with respect to the condition setting is increased.
From the above, if it is configured to satisfy (Qf / U / h) ≧ 2.0, the increase in the scattering flow rate Qo can be suppressed regardless of other conditions, and as a result, toner scattering can be suppressed. Therefore, it is possible to form an image with good image quality without adhesion of scattered toner.

Further, in the developing device X, the fan air volume is QF (m ³ / s), and the air from the opening 61a in the developing container 61 to the suction means 64 (that is, to the intake ports 61c and 61d). (QF / S) ≧ 0.75, where S (m ² ) is the average cross-sectional area of the channel.
For example, the cross-sectional area of the channel 65 (see FIG. 2) having the smallest cross-sectional area among the air channels from the opening 61a to the intake ports 61c and 61d in the developing container 61 is defined as S _min (m ² ). If (QF / _Smin ) ≧ 0.75 is satisfied, (QF / S) ≧ 0.75 is satisfied.
In the developing device X shown in FIG. 2, part fraction and the magnet roller 62 and the developer container 61 is closest is the flow path 65 of the smallest cross-sectional area. The reason for this configuration is as follows.

When the development is performed continuously by rotating the magnet roller 62, the temperature in the developing container 61 rises due to frictional heat between the magnet roller 62 and the toner, and the rotational torque of the magnet roller 62 increases. This may cause problems such as toner aggregation, solidification, and fusing.
In the developing device X, the air flow is generated by the suction means 64, whereby the inside of the developing container 61 is forcibly air-cooled. However, in forced air-cooling, the heat radiation surface is increased as the air velocity of the cooling air increases. This reduces the thermal resistance from the air to the surrounding air, resulting in more efficient cooling.
FIG. 7 is a graph showing the relationship between ambient wind speed (horizontal axis) and thermal resistance in aluminum, which is often used as a material for the magnet roller 62.
As shown in FIG. 7, when the relationship between the wind speed and the thermal resistance is approximated by a broken line, a point at which the wind speed is about 0.75 (m / s) is an inflection point. This inflection point is slightly different depending on the material of the heat radiating surface (here, the surface of the magnet roller 62), but the inflection point is approximately 0.75 (m / s) in the case of a metal material.
Therefore, if the configuration is such that (QF / S) ≧ 0.75, the inside of the developing container 61 can be effectively cooled while preventing toner scattering.

FIG. 3 is a plan sectional view of a portion of the developing container 61 on the side close to the photosensitive drum 32.
As shown in FIG. 3, the air inlet 61d is located near both ends of the bottom surface of the developing container 61 in the direction of the rotation axis of the photosensitive drum 32 (also referred to as the rotation direction of the magnet roller 62, hereinafter referred to as the width direction). The intake port 61c is provided in the vicinity of the central portion in the width direction of the inclined surface formed from the bottom surface to the side surface of the developing container 61.
As a result, an air flow path from the opening 61a to the suction means 64 (that is, the exhaust duct 64b) in the developing container 61 serves as an air flow path in the vicinity of both ends and the center in the rotation axis direction of the photosensitive drum 32. A flow path is formed to flow from the vicinity to the suction means 64 side.
In general, in the gap 61b portion, due to the rotation of the photosensitive drum 32, the pressure in the central portion increases in the width direction, and an air flow from the central portion to the both end portions occurs. This causes toner scattering at both ends.
On the other hand, according to the configuration shown in FIG. 3, it is possible to prevent the pressure in the vicinity of the central portion from being increased as much as possible due to the air flow path (flow) toward the intake port 61 c in the vicinity of the central portion. Further, the air flowing near the both end portions can be prevented from being scattered from the vicinity of both end portions to the outside by the air flow path (flow) toward the intake port 61d near the both end portions.
Here, by providing the intake port 61c in the vicinity of the central part slightly above the intake port 61d in the vicinity of the both end parts, the center of the air flow path to the intake port 61d in the vicinity of the both end parts is provided. The reason why the length of the flow path reaching the intake port 61c in the vicinity of the portion is shorter is that the air flow in the flow path in the vicinity of the central portion is slightly stronger (faster), and the gap 61b and the intake air are increased. section between the mouth 61c, and the section between the clearance 61b and the suction port 61 d in order to prevent the higher pressure.

Incidentally, the effectiveness (air resistance) R that the toner receives due to the flow of air is proportional to the square of the toner particle diameter D (R∝D ² ). The greater the effectiveness R, the easier the toner will scatter. In contrast, as the mass m of one toner particle is larger, the toner is less likely to be scattered. Therefore, when R / m is used as an index representing the ease of toner scattering, it can be said that the smaller the R / m is, the less toner is scattered.
FIG. 8 is a graph (solid line) representing the relationship between the toner particle size D (μm) and the relative value of R / m, and the broken line approximation is represented by a wavy line.
As shown in FIG. 8, R / m becomes an inflection point when the toner particle diameter D is 8 μm. Therefore, it can be seen that the toner particle size (developer particle size) D ≦ 8 μm is preferable because the scattering of the toner can be suppressed.

  The present invention is applicable to a developing device that performs development on a photoreceptor.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus Z including a developing device X according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a schematic configuration of the developing device X. FIG. 3 is a plan sectional view of a portion of a developing container provided in the developing device X on a side close to a photosensitive drum. 6 is a graph showing a flow velocity distribution in a gap when the gap between the developing container and the photosensitive drum is approximated as a gap between parallel plates. 6 is a graph showing the relationship between the gap h between the photosensitive drum and the developing container and the scattering flow rate Qo to the outside of the developing container. 7 is a graph showing the relationship between the flow rate per unit length of air flowing into the developing container in the axial direction of the photosensitive drum Qf and the scattering flow rate Qo to the outside of the developing container when the apparatus is stopped. The graph showing the relationship between the surrounding wind speed and thermal resistance in an aluminum member. 6 is a graph showing a relationship between a toner particle diameter D and a relative value of air resistance / toner mass of toner.

Explanation of symbols

X ... developing device Z ... image forming apparatus 10 ... image reading unit 18 ... document discharging unit 20 ... paper feeding unit 30 ... printing unit 31, 53 ... registration roller 32 ... photosensitive drum (photosensitive material)
33 ... Laser scanning unit 34 ... Charging unit 36 ... Transfer unit 38 ... Fixing device 39 ... Static elimination device 40 ... Discharge unit 61 ... Developer container 61a ... Opening 61b ... Gap between the downstream edge of the opening and the photosensitive drum 61c, 61d ... intake port 61e ... downstream edge of opening 62 ... magnet roller (developing roller)
63 ... Paddle 64 ... Suction means 64a ... Exhaust fan 64b ... Exhaust duct 65 ... Air flow path with the smallest cross-sectional area

Claims (2)

A developing container in which the opening is opposed to the rotating photosensitive member and the developer is accommodated, and air so that outside air flows into the developing container through the opening from the gap between the photosensitive member and the developing container. A developing device comprising suction means for sucking
As an air flow path from the opening to the suction means in the developing container , both ends of the developing container in the direction of the photosensitive member rotation axis from the edge on the downstream side of the rotating direction of the photosensitive member in the opening A flow passage formed in the vicinity of the central portion and the central portion and connected to the suction means side to flow to the central portion inlet port and the both end portion intake ports. There is a flow path with a minimum cross-sectional area, which is a portion where the developing container and the magnet roller disposed in the developing container are closest to each other, and the flow from the edge portion to the central intake port. 2. A developing device according to claim 1, wherein a path length is shorter than a flow path length from the edge to the air inlets at both ends . An image forming apparatus comprising the developing device according to claim 1 .

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