JPH1063081A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of immediately dispersing supplied toner in a developer, for imparting a proper charge quantity, without exerting excessive force to the developer and having a high ability for uniformizing the concn. of the toner in the developer in a developer storage part. SOLUTION: A developer carrying path for circulating the developer is provided in the developer storage part for storing a two-component developer of mixture of toner and carrier. A developer carrying member 14 having a feeding screw like blade body 20 is provided in the developer carrying path and a mesh-like screen member 22 is fitted between the blade bodies 20. The developer carrying member 14 is rotated so that the developer is carried and passes through the mesh-like screen member 22 several times, to be stirred and properly electrified by the friction between the toner and carriers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus (image recording apparatus) such as a printer, and more particularly to a developing device that forms a monochromatic or multicolor image using a two-component developer in which a toner and a carrier are mixed.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an electrostatic latent image formed on an electrostatic latent image carrier is visualized by a developing means, and this visible image (visible image) is recorded on a recording sheet. It is configured to transfer and copy an image. that time,
As a developing device for visualizing the electrostatic latent image formed on the electrostatic latent image carrier, there are a developing device using a one-component developer and a developing device using a two-component developer composed of a toner and a carrier. A developing device using a component developer has a mixing ratio of toner and carrier in the developer, that is, toner.
Although it is necessary to adjust the density, and it is necessary to equip a developer agitating mechanism, there is a problem that the apparatus becomes large, but from the viewpoint of usefulness such as image quality characteristics, many have been proposed and widely used. I have.

In the above-described developing apparatus using a two-component developer, in order to obtain a stable image, toner is replenished into the developer in accordance with the amount of consumed toner, and toner density and developer It is necessary to make the amount uniform in the longitudinal direction of the developing device and to impart a sufficient charge amount to the toner. Therefore, as a method of circulating and transporting the developer in the longitudinal direction of the developing device while agitating the replenishing toner and the developer, a conventional two-component developing device employs a feed screw type developing device in which the developer is transported by the rotation thereof. A method in which a plurality of developer transport members are provided and the developer transport directions are set to be opposite to each other, or as disclosed in Japanese Utility Model Laid-Open Publication No. There has been proposed a method in which a fixed displacement plate is provided, and stirring and circulating conveyance are performed by the rotation of the fixed displacement plate.

However, since the feed screw-shaped developer conveying member simply circulates and conveys the developer in the longitudinal direction of the developing device, it has a low ability to equalize the toner density and has a low actual opening speed. In the method disclosed in JP-A-53-32029, the ability to agitate the developer in the longitudinal direction is further reduced as compared with the feed screw-shaped developer conveying member. Further, the toner replenished in the developer is not in a state of being individually dispersed, but in a state where toner particles are aggregated. For this reason, it is extremely difficult to impart an appropriate charge amount to the replenishing toner, and the aggregated toner or the low-charged toner is transferred from the developer accommodating portion onto the developer carrying member, causing toner scattering and ground fog. Is liable to occur.

[0005] Here, toner scattering is a phenomenon in which aggregated toner is scattered from a developer carrier onto an electrostatic latent image carrier or into an image forming apparatus. If toner scattering occurs on the electrostatic latent image, serious dirt on the image occurs, and if it occurs in the image forming apparatus, performance degradation around the contaminated site is caused. In particular, ground fog and toner scattering occur remarkably when the toner consumption per unit time is large and the supply toner amount is large, that is, when the image area ratio is high. Therefore, there is a problem that it is difficult to cope with image formation with a high area ratio.

In order to solve such a problem, it is necessary to disperse the toner in the developer immediately after replenishment, and a method for solving this problem has been proposed. A method for enhancing the developer agitation force, a method for improving the developer dispersing effect by improving the shape of the developer conveying member and the developer agitating roller, and a method for bringing the thin blade into contact with the toner supply roller. And a method of installing a mesh filter.

The method of dispersing the replenishing toner in the developer will be further described. The method of enhancing the developer stirring force can be realized by increasing the rotation speed of the developer conveying member. Since a strong compressive force or frictional force acts on the developer, there is a problem that the deterioration of the developer is accelerated.

As a method of improving the shape of the developer conveying member, Japanese Utility Model Laid-Open Publication No. 50-5645 discloses a method of providing a developer stirring roller having a coil spring wound thereon, and stirring the developer. A method of stirring the toner and the carrier by moving the roller in a direction other than the rotation direction of the roller has been proposed. JP-A-6-167876 discloses a method of providing a plurality of blade members perpendicular to a feed screw-shaped developer conveying member to generate a turbulent flow of the developer to assist mixing and stirring. Has been proposed.

In Japanese Patent Application Laid-Open No. Hei 7-134499, the toner replenishing section comprises a toner replenishing roller, a thin-layer blade in contact with the roller, and a toner supplying roller. Forming a thin layer in which toner is individually dispersed on a toner replenishing roller by the thin layer blade, and charging the toner at the same time;
There has been proposed a method of replenishing toner by bringing the toner on the toner replenishment roller into contact with the developer on the developer.

As disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-20064, a method using a mesh filter is not necessarily aimed at assisting the mixing and stirring of the toner and the carrier. A method has been proposed in which a mesh filter having a size larger than at least the carrier diameter is provided at a position in the developer circulation path where the developer is not buried in the developer to remove foreign matter mixed in the developer. Japanese Patent Publication No. 61-55110 discloses a developing device in which a mesh screen member is provided along the longitudinal direction of a developing device, and toner is discharged from the mesh to supply toner. A method has been proposed in which a developer flow is caused to act on a toner discharge surface of a toner member.

[0011]

However, in the method disclosed in Japanese Utility Model Laid-Open Publication No. Sho 50-5645, the ability to move the developer in the axial direction of the developer stirring roller is provided by a feed screw type developer conveying member. Therefore, there is a problem that the ability to make the toner density uniform in the longitudinal direction of the developing device is low and density unevenness is likely to occur. Also,
In order to enhance the uniformity, it is necessary to increase the wire diameter of the coil spring, which makes it extremely difficult to immediately disperse the replenishment toner in the developer.

In the method disclosed in Japanese Patent Application Laid-Open No. 6-167876, since the probability that the supplied aggregated toner contacts the vertical blade member is low, it is extremely difficult to immediately disperse the supplied toner in the developer. Have difficulty. Further, in order to increase the contact probability, it is necessary to increase the width or increase the number of the vertical blade members.In these cases, however, the replenishment toner is likely to be captured at the site of the vertical blade members. There is a problem that the toner concentration in the developer hardly increases in conjunction with the toner supply amount, and it is extremely difficult to control the toner concentration. In addition, since an annular flow of the developer is generated in the circumferential direction of the developer conveying member having a feed screw shape, there is a problem that the circulating conveyance ability is reduced.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. Hei 7-134499, the replenishment toner is in a state of being individually dispersed, and the replenishment toner is preliminarily charged, so that the image formation with a high area ratio can be performed. However, since the toner replenishing section is complicated and the number of parts is greatly increased, there is a problem that the cost is extremely high. Further, since the thin layer blade is worn over time, the toner amount and the toner charge amount on the toner replenishing roller fluctuate, and there is a problem that image quality is low in stability and maintainability.

Also, in the method disclosed in Japanese Patent Application Laid-Open No. Hei 7-134499, since a feed screw-shaped developer conveying member is used to make the toner concentration uniform, a conventional method for making the toner concentration uniform is used. The problem of has not been avoided.

In order to avoid the above problems, it is necessary to increase the stirring force by increasing the number of rotations of the developer conveying member as in the case described above. However, in this case, there is a problem that the deterioration of the developer is accelerated.

According to the method disclosed in Japanese Utility Model Laid-Open No. Hei 4-20064, the effect of removing foreign matters mixed in the developer can be expected as described above. However, since the developer is configured to pass through the filter when it is scraped off from the developer carrier by the layer thickness regulating member,
In the developer circulation step in the developing device, the number of times the developer passes through the filter is one or less, which is extremely small. Therefore, the effect of assisting the mixing and stirring of the toner and the carrier is extremely small. Japanese Utility Model Application Laid-Open No. 4-200464 does not disclose any auxiliary effect relating to mixing and stirring.

The method disclosed in Japanese Patent Publication No. 61-55110 has the advantage that the toner can be immediately dispersed in the developer. There is no description of a method for making the toner concentration uniform, and the uniformization has the same technical problem as the conventional art. In addition, the toner replenishing section becomes complicated and the number of parts is greatly increased, so that there is a problem that the cost becomes extremely high.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to immediately supply replenished toner into a developer without applying an excessive force to the developer. It is possible to impart an appropriate charge amount by dispersing, and has a high ability to uniform the toner concentration of the developer in the developer accommodating section, and is excellent in image quality stability and maintainability, and is manufactured at low cost. It is to provide a possible developing device.

[0019]

According to a first aspect of the present invention, there is provided a developing device comprising: a developer accommodating section accommodating a two-component developer including a toner and a carrier; A developer carrier that is arranged to face an image carrier on which an electrostatic latent image is formed, carries a thin layer of developer, and transports the developer to a position close to the image carrier; In a developing device that transfers the developer on the developer carrier to the image carrier at a position close to the developer carrier and the image carrier to visualize the electrostatic latent image, the developer is stored in the developer accommodating portion. It is assumed that a developer having a screen member passing therethrough and having passed the screen member a plurality of times in the developer accommodating portion is supplied to the developer carrier.

According to a second aspect of the present invention, in the developing device according to the first aspect, a developer transport path through which the developer is circulated is formed in the developer accommodating portion, and the developer transport path is provided. Further, it is assumed that a developer conveying member provided with a wing body for conveying the developer in the axial direction around the rotation axis is provided, and the screen member is fixed to the developer conveying member.

According to a third aspect of the present invention, in the developing device according to the second aspect, the blade body of the developer conveying member is formed in a feed screw shape around the rotation shaft, and the screw is provided.
It is assumed that a connection member is provided between the feed screw shaped wings.

According to a fourth aspect of the present invention, in the developing device according to the first aspect, a developer transport path through which the developer is circulated is formed in the developer accommodating portion. A developer conveying member provided around the rotation axis with a wing body for conveying the developer in the axial direction;
The developer member is fixedly supported around the rotation axis of the developer transport member in a direction perpendicular to the axis of the rotation axis.

According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, the blade body of the developer conveying member is formed in an intermittent feed screw shape around the rotation axis, and The wing member is supported at a portion where the wing body is cut off.

In the developing device according to the first aspect, the screen member has a large number of small gaps or small holes,
Various forms can be used as long as the developer passes through this gap or small hole.
For example, a member in which thin members are juxtaposed at small intervals or a mesh-like member can be used. Also, this screen member may be provided only one,
A plurality may be provided, the developer that has passed the same screen member a plurality of times may be supplied to the developer carrier, or the developer that has passed a plurality of different screen members may be provided. May be supplied to the developer carrying member.

In the developing device according to the present invention, the screen member may be provided separately from the wing, or a part or all of the wing may be a screen member.

(Operation) In the developing device according to the first aspect of the present invention, the developer conveyed in the developer conveying path passes through the small gap or the small hole of the screen member a plurality of times. At this time, the state of aggregation of the replenishing toner is reduced to the size of the small gap or small hole of the screen member. Also,
Since the developer is slightly displaced in the vicinity of the screen member, the chance of contact between the replenishment toner and the carrier is greatly increased as compared with the case where the screen member is not provided.

Further, since the developer is arranged to pass through the screen member a plurality of times in the developer conveying path,
The replenishment toner can be immediately dispersed in the developer without applying an excessive force to the developer, and an appropriate charge amount can be added. Therefore, even when the amount of toner supplied per unit time is large, ground fog and toner scattering do not occur, and it is possible to cope with image formation with a high area ratio.

Further, since the time required for the developer to pass through the screen member is not uniform, a difference occurs in the moving speed of the developer in the developer conveying path. For this reason, the developer distributed on the upstream side and the downstream side of the developer conveyance path can be efficiently stirred, and the developer in the developer accommodating portion can be efficiently applied without exerting an excessive force on the developer. The ability to make the toner concentration uniform can be enhanced. Therefore, image density unevenness does not occur in the longitudinal direction of the developing device. At the same time, when the developer is stirred and transported, the developer is prevented from deteriorating due to excessive force applied thereto, and the initial performance of the developer is maintained for a long time. It is possible to Further, since only the screen member is additionally provided in the developer conveying path, an increase in the number of parts can be minimized, and therefore, it can be provided at a low cost.

In the developing device according to the second aspect, the screen is
Since the toner member is fixed to the developer conveying member and is rotationally driven together with the developer conveying member, the screen member often comes into contact with the toner, and the toner particles are screened many times.
As a result, the developer is stirred and the toner is charged in a shorter time.

In the developing device according to the third aspect, the developer conveying member has a feed screw-shaped wing body around the rotation axis, and the developer is pressed against the surface of the feed screw-shaped wing body. Is transported between the wings. Since the screen member is provided between the spiral wings, most of the conveyed developer comes into contact with the screen member, passes through the screen member, and agitates and charges efficiently. .

In the developing device according to the fourth aspect, the screen is
Since the developer member is supported around the axis of rotation of the developer conveying member and in a direction substantially perpendicular to this axis, most of the developer conveyed by the developer conveying member passes through the screen member, and the efficiency is improved. Stirring and charging are performed.

[0032] In the developing device according to the fifth aspect, a screen is provided.
The screen member is supported by the portion where the feed screw-shaped wing of the developer conveying member is cut off, so that the screen member conveys the developer without being interfered by the rotation of the developer conveying member. Installed across the road. Therefore, the developer conveyed by the developer conveying member is conveyed through the screen member.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of an image recording apparatus to which a developing device according to the present invention is applied.
This image forming apparatus includes a photosensitive drum as an electrostatic latent image carrier, and the photosensitive drum 1 has a photosensitive member layer 1b formed on a surface of a cylindrical member 1a made of a conductive material. . As the photoconductor layer 1b, for example, a negatively charged organic photoconductor (hereinafter, referred to as OPC) is used.
The outer diameter of the photosensitive drum 1 is set to, for example, 100 mm.

A developing device in which a charger 2, an exposing means 3, and a developer carrier 11 formed of a cylindrical member are opposed to the photosensitive drum 1 along the rotation direction around the photosensitive drum 1. 4, transfer corotron 5, and peeling corotron 6
, A cleaner 7 and a light neutralizer 8 are sequentially arranged. In this image recording apparatus, the photosensitive drum 1
It is rotationally driven in the direction of arrow A by driving means (not shown). The surface of the photosensitive drum 1 is uniformly charged to a predetermined voltage by the charger 2. Next, exposure corresponding to the image is performed on the surface of the photosensitive drum 1 by the exposure unit 3 to form an electrostatic latent image. The toner is selectively transferred to the electrostatic latent image formed on the surface of the photosensitive drum 1 by the developing device 4 to be visualized. At this time, a developing bias is applied to the cylindrical sleeve 11 as a developer carrying member by a developing bias power supply (not shown).

The toner image thus formed on the photosensitive drum 1 is transferred onto the recording paper 9 by charging the transfer corotron 5. Subsequently, this recording paper 9
The photosensitive drum 1 is peeled off from the surface of the photosensitive drum 1 by the charging of the peeling corotron 6, and then is conveyed to a fixing device (not shown), where the toner image is fixed on the recording paper 9 and the image recording is completed. The surface of the photosensitive drum 1 after the transfer of the toner image and the step of peeling the recording paper 9 are finished,
After the residual toner has been cleaned, the residual charge is removed by the exposure by the light neutralizer 8 to prepare for the next image recording step.

Next, the formation and development of a latent image in the above-described image forming step will be described in more detail with reference to FIG. In addition,
In this example, the exposure was image portion exposure, and the development was reversal development. The toner is negatively charged and the carrier is positively charged. The surface moving linear velocity of the photosensitive drum 1, that is, the process speed is set to, for example, 160 mm / s. First, the surface of the photosensitive drum 1 is uniformly charged to -450 V by the charger 2.
(FIG. 2A). Subsequently, image portion exposure is performed by laser light to form a negative latent image having an exposed portion potential of -200 V [FIG. 2 (b)]. Then, the negative latent image is developed by the developing device 4 (FIG. 2C). At this time, the developing bias voltage applied to the cylindrical sleeve 11 is an AC voltage on which a DC voltage is superimposed, and the DC component is set to −400 V in order to prevent occurrence of ground fog. Also,
The AC component of the developing bias voltage is a rectangular wave having a frequency of 6 kHz, and is set to a peak-to-peak voltage of 1.5 kV. The surface moving linear velocity of the cylindrical sleeve 11 is, for example, 320 m
m / s.

[First Embodiment] A developing device which performs the above-described developing step and which is an embodiment of the present invention will be described below. FIG. 3 is a schematic configuration diagram of a developing device according to an embodiment of the present invention described in claim 1, claim 2, or claim 3. The developing device 4 is provided with a developing opening 18 at a position facing the photosensitive drum 1, and the developing opening 18 is provided.
The developing roll 10 is disposed facing the surface. The developing roller is a cylindrical sleeve 11 driven to rotate in the circumferential direction.
And a magnet roll fixed and supported inside the developing roller. The outer diameter of the developing roll 10 is 18 mm.
The gap between the cylinder sleeve 11 is set to 500 μm. In addition, the area where the developer can be carried on the cylindrical sleeve 11 is 30 mm in the longitudinal direction of the cylindrical sleeve 11.
0 mm.

The magnet roll is provided with a plurality of magnetic poles in the circumferential direction. A magnetic pole S2 is supplied to a portion where the developing roll 10 and the photosensitive drum 1 are closest, and a developer is supplied to the cylindrical sleeve 11. The magnetic poles N3 are disposed at the respective positions. The developer attached to the cylindrical sleeve 11 by the action of the magnetic pole N3 is regulated by the layer thickness regulating member 13 to a constant layer thickness. The thickness of the developer layer is set to 700 μm on the magnetic pole S2 in a state where the photosensitive drum 1 is not opposed so that the developer layer contacts the photosensitive drum 1. The developer attached to the cylindrical sleeve 11 is transported to a developing area facing the photosensitive drum 1 as the cylindrical sleeve 11 rotates. Also, the developer that has passed through the development area is
Due to the action of the repulsive magnetic field formed by the magnetic poles N2 and N3, the magnetic poles are peeled off from the cylindrical sleeve 11 and fall into the developer accommodating section, and are subjected to the action of the developer carrying member provided in the developer accommodating section. Provided for next use.

A developer accommodating section is provided at the rear of the developing device, and is constituted by a pair of developer conveying paths. The developer is supplied to the developing device 4 in the developer transport path 16.
Is transported from the near side to the far side in the longitudinal direction of FIG. On the other hand, in the developer transport path 17, the developer is transported from the back side to the front side. The length of the developer conveying path was 300 mm in the longitudinal direction of the developing device.
In addition, a partition was not provided between the developer transport paths 16 and 17 at both ends in the longitudinal direction of the developer accommodating section at 15 mm each, and a developer transfer section between the developer transport paths was provided. In this way, the developer is circulated and transported in the longitudinal direction of the developing device 4.

Inside the developer conveying paths 16 and 17,
Developer transport members 14 and 15 are provided, respectively.
Around the rotation shafts of the developer conveying members 14 and 15, a wing body formed in a feed screw shape is provided, and the developer is conveyed by the rotation thereof. In FIG. 3, the winding direction of the screw portion viewed from the near side is the right direction in the developer transport member 14 and the left direction in the developer transport member 15. Further, a screen member having a large number of small holes is fixed to the developer conveying members 14 and 15 so as to cross between the feed screw-shaped wing bodies. After passing
The developer is supplied to the developer carrier.

In this developing device, a mesh member is used as a screen member in the developer conveying path. This mesh member is a SUS304 plain-woven wire mesh having a wire diameter of 0.28 mm, an aperture of 1 mm, and an aperture ratio of 61%. The mesh member is provided on both of the developer conveying members 14 and 15 and is not provided in the developer transfer section. FIG. 4 shows a state in which the mesh member 22 is attached to the developer conveying member 14. Mesh member 2
2 is 18 m so as to be equal to the outer diameter of the screw portion 20.
m. The length of the mesh member 22 was set to 270 mm, excluding the 15 mm at both ends from the length of the developer conveying path of 300 mm. The mesh member 22 having a rectangular shape is inserted into the opening 21 as shown in FIG.

FIG. 5 shows a portion provided for the developer transport, excluding the bearing portions at both ends of the developer transport member 14. In FIG. 5, reference numeral 19 denotes a central axis of the developer conveying member;
Reference numeral 20 denotes a screw portion, and reference numeral 21 denotes an opening for attaching a mesh member. In the present embodiment, the outer diameter of the central shaft 19 is 6 mm. The screw portion 20 is formed of a plate-like member having a thickness of 1 mm, the outer diameter thereof is set to 18 mm, and the winding pitch is set to 15 mm. The openings 21 are formed except for 15 mm at both ends of a portion provided for the developer conveyance. With the above configuration, the developer conveyed in the developer conveyance paths 16 and 17 passes through the mesh member a plurality of times when passing through the conveyance paths.

(Experiment on ground fog, scattering of coagulated toner and uneven image density) In order to evaluate the effect of the present invention on the background fog, scattering of coagulated toner and uneven density in the longitudinal direction of the developing device, the above-mentioned developing device was used. A comparative printing experiment was performed using a developing device having no mesh screen member. The results are described below. The conventional developing device used in this experiment does not include a mesh member in the developer transport member, and includes a developer transport path transfer section, that is, a portion where two developer transport paths communicate at both ends. And those without a mesh member at all were used for experiments.
In the case where the mesh member is provided only in the transfer section of the developer transport path, the developer transported in the developer transport path passes through the mesh member once each time it passes through each transport path. Become. The conventional developing device used in this experiment has the same outer dimensions as the developer conveying member shown in FIG.
The one that does not use the mesh member is used.
In the experiment, images having different area ratios were continuously formed on an A4 sheet by 100 sheets, the toner consumption was changed, and the state of the images was observed. The developer used in this experiment is as follows. As the toner, a polyester magenta toner having a weight average particle diameter of 7 μm and a negative charge property.
It was used. As the carrier, a so-called ferrite carrier in which spherical ferrite particles were coated with a resin, was used. The carrier has a weight average particle size of 50 μm and a density of 4.
5 g / c. The mixing ratio of the toner and the carrier in the developer was 8% by weight in terms of the weight ratio of the toner in the developer. In this case, the charge amount of the toner is -15 mC / kg.
It is. Table 1 shows the experimental conditions. The rotation speeds of the developer conveying members 14 and 15 were set at two levels of 60 rpm and 180 rpm.

[0044]

[Table 1] At the time of the experiment, toner was supplied from a toner supply unit (not shown) so that the amount of toner in the developer became constant in accordance with the amount of consumed toner. The evaluation items were background fog, aggregation toner scattering, and image density unevenness in the longitudinal direction.
Evaluation was performed on the recording paper 9 after continuous printing of 0 sheets. In assessing the results, the local fog used limit samples,
The evaluation was made visually. Grade (hereinafter referred to as G) 1 is a state where no ground fog is visually observed, G2 is a level where there is a small amount of ground fog but there is no practical problem, G3 is an unusable level, G1 and G2 are ○, G3 is X. Further, as for the scattering of the aggregated toner, ○ indicates no occurrence and X indicates occurrence. Further, the image density unevenness in the longitudinal direction is measured by using a reflection densitometer (trade name: X-RITE310) to measure the solid image density in ten places corresponding to the longitudinal direction of the photosensitive drum, and to determine the maximum density and the minimum density. ○ when the difference is less than 0.3
0.3 or more was evaluated as x. Table 2 was obtained as a result. The comprehensive evaluation was evaluated as ○ when there was no x in the above three items, and as x when there was at least one x.

[0045]

[Table 2] From Table 2, it can be seen that ground fogging, scattering of coagulated toner, and image density unevenness in the longitudinal direction do not occur by providing the developer conveying member with the mesh member. This is because the use of the mesh member makes it possible to immediately disperse the replenishment toner in the developer to give an appropriate charge amount, and further enhance the ability to make the toner concentration in the developer uniform. This is because it becomes possible. When a mesh member is provided on the developer conveying member, the stirring performance is improved.
The rotation speed of the developer conveying member can be set lower than that of the conventional type having no mesh member. Further, even when the toner consumption amount is large, that is, when the toner replenishment amount per unit number is large, there is no occurrence of background fogging, scattering of aggregated toner, and image density unevenness in the longitudinal direction. Therefore, it is considered that it is possible to cope with image formation with a high area ratio. On the other hand, without providing the developer conveying member with a mesh member, the developer conveying path 16
In the case where the mesh member is provided only in the transfer portion between the transfer member and the transfer member, the auxiliary effect on the mixing and stirring is extremely small, and the result is almost the same as the case where the mesh member is not provided in both the developer transport member and the transfer portion. Was.

(Examination of the aperture and aperture ratio of the screen member) In the above-mentioned developing device, a mesh member was used as the screen member, and the aperture was set to 1 mm. However, there is a problem that clogging is likely to occur due to coarse powder or strong aggregates of the toner or carrier. Further, as the openings become smaller, the developer becomes more difficult to pass through the mesh member, so that the efficiency of circulating and transporting the developer decreases, and there is a problem that image density unevenness tends to occur. This tendency becomes remarkable especially when image formation is performed by a high-speed process. Therefore, in order to cope with a high-speed process, the aperture is set to 0.1.
It is preferably at least 5 mm. On the other hand, the aperture is 4m
If it is larger than m, the possibility that the agglomerated toner contacts the mesh member is extremely low, and the agglutination reducing effect is reduced. Further, the stirring effect due to the minute displacement of the developer near the mesh member is also reduced. Furthermore, the chance of contact between the replenishment toner and the mesh member is sufficiently increased,
In addition, in order to set the number of rotations of the developer conveying member to be sufficiently low while securing the stirring effect due to the minute displacement of the developer, the opening is preferably 2 mm or less. As described above, the aperture of the mesh member is 0.2 mm
It is preferably at least 4 mm and at most 0.5 mm and at most 2 mm. In this embodiment, the aperture ratio of the mesh member is set to 61%. However, as the aperture ratio decreases, the efficiency of the developer circulation and conveyance decreases. For this reason, it is preferable that the aperture ratio of the mesh member is 30% or more from the viewpoint of circulating transfer efficiency.

(Experiment on Deterioration of Developer by Long-Term Printing) In order to evaluate the effect of developer degradation by long-term printing, a developing device provided with the mesh screen member and a developing device not provided with the mesh screen member were used. , A long-term comparative printing experiment was conducted under the conditions of and in Table 1. At the time of the experiment, the toner-to-weight ratio in the developer was 7.5 to 7.5.
The supply toner was adjusted to 8.5% by weight. FIGS. 6 and 7 show the transition results of the background fog on the background portion and the toner charge amount in the long-term printing experiment, respectively. 6 and 7 that when the mesh member according to the present invention is provided, the toner charge amount is favorably maintained over 100k sheets, and no ground fog occurs. on the other hand,
It can be seen that in the case of the conventional type in which the mesh member according to the comparative example is not provided, the toner charge amount decreases. In this conventional type, due to a decrease in the amount of toner charge, background fog of G3 exceeding the permissible limit occurred at 20k sheets, and the developer reached its end of life. Further, as a result of examining the state of the developer after the long-term printing experiment, it was confirmed that in the case of the conventional type according to the comparative example, significant toner deterioration and carrier deterioration occurred. In the case of the conventional type, which is the comparative example, it is necessary to increase the rotation speed of the developer conveying member in order to increase the stirring force, but at this time, since a strong stress acts on the developer, Toner deterioration and carrier deterioration occur early. Due to this effect, the amount of toner charge is reduced as described above, and ground fog occurs. on the other hand,
When the mesh member according to the present invention is provided, the number of rotations of the developer conveying member can be set low, so that the stress acting on the developer becomes extremely small. Therefore, the deterioration of the developer can be prevented. When the mesh member according to the present invention was provided, the toner and the carrier after the long-term printing experiment were in almost the same state as the initial state, and no deterioration state was observed. Thus, in the developing device of the present invention,
Good image quality can be stably maintained over a long period of time.

[Second Embodiment] In this embodiment,
A comb member 23 is used as the screen member fixed to the developer conveying path instead of the mesh member. The comb member is made of SUS304 and the width of the comb teeth is 0.5 m
m, the gap between the comb teeth is 1 mm. The comb member is provided on each of the two developer conveying members,
Similar to the developing device shown in FIGS. 3 and 4, a slit-shaped opening is provided in the central axis 19 of the developer conveying member, and a comb tooth member 23 is inserted into this opening 21, and the developer conveying member 14 Fixed. The outer shape and dimensions of the developer conveying member 14 and other configurations of the developing device are the same as those shown in FIGS. Further, the width of the comb tooth member 23 was set to 18 mm so as to be equal to the outer diameter of the screw portion 20, and the mounting width of the comb tooth member was set to 270 mm as in the first embodiment.

(Evaluation Regarding Background Fog, Scattering of Aggregated Toner and Image Density Unevenness) When an image was recorded by a developing apparatus using the developer conveying member provided with the comb-shaped member, an image having a high area ratio was formed. Even at the time, no background fogging, scattering of the aggregated toner, and uneven image density in the longitudinal direction did not occur. This is because, similarly to the case where the mesh member is used, the replenishment toner can be immediately dispersed in the developer to give an appropriate charge amount by using the comb member. This is because the ability to make the toner density uniform can be improved. Further, even when a comb-shaped member is used, the number of rotations of the developer conveying member can be set low.

(Evaluation of Developer Deterioration Due to Long-Term Printing) Using the developer conveying member provided with the above-described comb-tooth member, the rotation speed of the developer conveying member was set to 60 rpm, and the same long-term operation of 100 k sheets as in the previous embodiment was performed. As a result of the printing test, 1
The toner charge amount was favorably maintained throughout 00k sheets, and no background fog occurred. Further, no deterioration state was observed in the developer after the experiment. As described above, in the developing device of the present embodiment, even when an image with a high area ratio is formed, ground fog, aggregation toner scattering, and image density unevenness in the longitudinal direction do not occur, and good image quality is stably maintained over a long period of time. It is possible to

(Study on Comb Teeth Gap and Aperture Ratio of Screen Member) In this developing device, a comb tooth member was used as a screen member, and the comb tooth gap was made 1 mm. For the same reason as in the case where is used, the gap between the comb teeth can be 0.2 mm or more and 4 mm or less, and more preferably 0.5 mm or more and 2 mm or less. Further, in the present embodiment, the aperture ratio of the comb tooth member is set to 67%, but for the same reason as when the mesh member described above is used, the aperture ratio of the comb tooth member is preferably 30% or more. .

[Third Embodiment] FIG. 9 is a partially enlarged sectional view showing a developing device according to a third embodiment of the present invention. The developer conveying member used in this developing device has a feed screw-shaped wing, but is provided with a plurality of discontinuous portions and is formed intermittently at every pitch. An interval X of about 2 mm is provided in a portion where the wing is discontinuous, and a mesh screen member is provided in this portion. The mesh screen member is supported by the housing of the developing device, and is arranged in a direction perpendicular to the axis of the developer conveying member. A notch is provided at a portion corresponding to the central axis of the developer conveying member, so that the developer conveyed around the notch passes through the mesh of the mesh screen member.
A plurality of such mesh screen members are provided with a sense of 17 mm in the axial direction of the developer conveying member. The other structure of the developing device is the same as that of the developing device shown in FIG. Further, a comb member may be used instead of the mesh screen member.

(Evaluation Regarding Background Fog, Scattering of Aggregated Toner, and Image Density Unevenness) When the above-described mesh screen member was inserted into the developer conveying path and an image was recorded, the background fog was found even when an image having a high area ratio was formed. No aggregation toner scattering and image density unevenness in the longitudinal direction occurred. Also,
Similarly, when the comb-teeth screen member was inserted into the developer conveying path and image recording was performed, the same result as described above was obtained. This is because, by inserting the mesh screen member and the comb-teeth screen member into the developer transport path, the replenishment toner is supplied to the developer similarly to the case where the mesh member and the comb-teeth member are provided in the developer transport member. Can be immediately dispersed to give an appropriate charge amount.
This is because the ability to make the toner concentration in the developer uniform can be improved. Further, by inserting the mesh screen member and the comb screen member into the developer conveying path, the number of rotations of the developer conveying member can be set low.

(Evaluation on Deterioration of Developer Due to Long-Term Printing) The above mesh screen member and comb screen member were inserted into the developer transporting path, and the rotational speed of the developer transporting member was set to 60 rpm. When a long-term printing test of 100k sheets similar to that performed in
The toner charge amount was favorably maintained throughout 100k sheets, and no ground fog occurred. Further, no deterioration state was observed in the developer after the experiment. As described above, in the developing device of the present embodiment, ground fog, aggregation toner scattering, and image density unevenness in the longitudinal direction do not occur even when an image with a high area ratio is formed.
Good image quality can be stably maintained over a long period of time.

In the above-described embodiment, the developer accommodating portion is constituted by a pair of developer conveying paths, and a feed screw-shaped developer conveying member that conveys the developer by its rotation is used as the developer conveying member. However, the present invention is not limited to these, and can have any configuration according to the purpose and application. Further, in the above-described embodiment, the screen member is provided on the feed screw-shaped developer conveying member, or is configured to be inserted into the developer conveying path. However, the present invention is not limited to these. Instead, an arbitrary configuration according to the purpose and application is possible. For example, as shown in FIG. 10, the feed screw portion of the feed screw-shaped developer conveying member may be constituted by a screen member. Further, for example, in an impeller-shaped developer conveying member, the blade portion may be a screen member. Further, in the above-described embodiment, the mesh member and the comb member are used as the screen member. However, the present invention is not limited to these, and any member that can be used as the screen member can be used. Further, the mesh member and the comb-teeth member as the screen member are not limited to the above-described embodiment, and any material and configuration can be used. For example, as the mesh member, a metal mesh other than SUS304 used in the above embodiment, or a resin mesh such as nylon or polyester may be used. The same applies to the comb teeth member. Further, for example, in a triboelectric series, a material on the carrier side as viewed from the toner may be used as a mesh member, or may be provided on the surface of the mesh member to have a function of assisting charge application to the toner. .

[0056]

As described above, in the developing device of the present invention, the screen member is provided in the developer accommodating portion,
The two-component developer supplied to the developer carrier carries the screen.
Since the toner is supplied to the developer carrier after passing through the developer member a plurality of times, the supply toner can be immediately dispersed in the developer and an appropriate charge amount can be imparted. Therefore, even when the amount of replenished toner per unit time is large, ground fog and toner scattering do not occur, and it is possible to cope with image formation with a high area ratio. Further, according to the present invention, it is possible to efficiently agitate the developer without exerting an excessive force due to the difference in the time for the developer to pass through the screen, and to make the toner concentration in the developer uniform. Therefore, occurrence of image density unevenness in the longitudinal direction of the developing device is suppressed. Also,
As described above, not to apply an excessive force to the developer,
The deterioration of the developer can be prevented, and the initial performance of the developer can be maintained for a long period of time. Therefore, it is possible to simultaneously secure the developer stirring and transporting performance and the developer performance. Furthermore, according to the present invention, since only the screen member is additionally provided in the developer conveying path, the increase in the number of parts is minimized, and therefore, it can be provided at a low cost. Has an effect.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus to which a developing device of the present invention is applied.

FIG. 2 is a diagram illustrating a process of forming and developing a latent image in the image forming apparatus illustrated in FIG. 1 by changing a potential on the surface of an image carrier.

FIG. 3 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 1, 2 or 3;

FIG. 4 is a schematic side view of a developer conveying member used in the developing device shown in FIG.

FIG. 5 is a schematic diagram illustrating a mounting structure of a mesh member in the developer conveying member illustrated in FIG. 4;

FIG. 6 is an explanatory diagram showing transition of ground fog in a long-term printing experiment.

FIG. 7 is an explanatory diagram showing a change in toner charge amount in a long-term printing experiment.

FIG. 8 is a schematic side view of a developer conveying member used in a developing device according to another embodiment of the present invention described in claim 1, 2 or 3.

FIG. 9 is a partially enlarged sectional view showing a developing device according to an embodiment of the invention described in claim 4 or 5;

FIG. 10 is a cross-sectional view of the invention according to claim 1 or 2;
FIG. 9 is a schematic side view of a developer conveying member used in a developing device according to another embodiment.

[Explanation of symbols]

1... Photosensitive drum, 2... Charger, 3.
... Exposure means, 4..., Developing device, 5.
・ Transfer corotron, 6 ・ ・ ・ ・ ・ Exfoliation corotron, 7 ・
························································· •
..Recording paper, 10 ... Developing rolls, 11 ...
..Cylindrical sleeves, 12 ... Magnet rolls, 13
···· Layer thickness regulating member, ··························································· Developer Conveyance path, 18 ...
..Developing opening, 19..., Central axis of developer transport member, 20... Wing, 21... Mesh member mounting opening, 22. Member, 2
... Comb member 40, housing of developing device 41, developer conveying member 42
.Mesh members, 51... Developer transport members

Claims (5)

[Claims] 1. A developer accommodating portion for accommodating a two-component developer containing a toner and a carrier, and a developer accommodating portion arranged to face an image carrier having an electrostatic latent image formed on a surface thereof. A developer carrier that carries a layer and transports the developer carrier to a position close to the image carrier; and a developer on the developer carrier at a position close to the developer carrier and the image carrier. In the developing device for transferring the toner to the image carrier to visualize the electrostatic latent image, the developer accommodating portion includes a screen member through which the developer passes. A developing device, wherein the developer that has passed through the screen member a plurality of times is supplied to the developer carrier. 2. The developer device according to claim 1, wherein a developer transport path through which the developer is circulated is formed in the developer storage section, and the developer is transported in the developer transport path in the axial direction. A developer transport member provided around a rotation axis with a wing body for transporting the screen member, and the screen member is fixed to the developer transport member. 3. The developing device according to claim 2, wherein the wing body of the developer conveying member is formed in a feed screw shape around the rotation axis, and the screen member is formed in a feed screw shape. A developing device provided between the wings. 4. The developing device according to claim 1, wherein a developer conveying path through which the developer is circulated is formed in the developer accommodating portion, and the developer is transported in the axial direction in the developer conveying path. A developer transport member provided around the rotation axis with a wing body for transporting the developer member; the screen member is fixedly supported in a direction perpendicular to the axis of the rotation axis around the rotation axis of the developer transport member. A developing device. 5. The developing device according to claim 4, wherein a wing of the developer conveying member is formed in an intermittent feed screw shape around the rotation axis, and the screen member is formed of a wing body. A developing device, wherein the developing device is supported by a broken portion.