JP3684023B2 - Image forming apparatus with developer supply tank - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a printer, a facsimile, and a copying machine using a two-component developer, and more particularly to a developer supply tank that realizes a large storage developer capacity and a stable toner concentration. The present invention relates to an image forming apparatus provided.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a dry developing device widely used in an image forming apparatus is composed of charged carrier particles and charged toner particles adhering to the carrier particles in a triboelectric manner as being suitable for obtaining a high-quality copy image. Many component developers are used. When such a two-component developer is used, it is necessary to consider not only the problem of replenishment of toner consumed every time development is repeated, but also carrier particles. For example, there is a problem that the coating applied to the surface of the carrier particles is peeled off to reinforce the triboelectric charging characteristics due to repeated use, and deteriorates as a carrier.
[0003]
For this reason, it is necessary to replace the carrier thus deteriorated. At first, the image forming apparatus is temporarily stopped, and the developer is manually replaced. Since this is very troublesome, many proposals have been made in the past to automate the replacement of the developer, but at the initial stage of the proposal, the developer that has reached the end of its life is collected, and a fresh developer is supplied to the developing device instead. In order to replace the entire amount of developer in the developing device every time the developer life is reached, an image when a new developer is supplied immediately before and after collecting the developer. There was a drawback that the quality (printing quality) changed significantly. In addition, the machine operation must be interrupted for every replacement work. Therefore, in order to avoid these drawbacks, proposals have been made to realize partial replacement at regular intervals instead of full replacement for each lifetime. For example, in Japanese Patent Application Laid-Open No. 4-29271, when the amount of developer used in the developing device reaches a preset value, a part of the used developer in the developing device is reduced by a predetermined amount. It is disclosed that the new developer is discharged and supplied to the developing device in the same amount as the discharged amount. As a result, the developer in the developing device can maintain a stable degree of fatigue without reaching the lifetime.
[0004]
[Problems to be solved by the invention]
By automating the partial replacement of the developer as described above, it has become possible to avoid a decrease in image quality due to carrier deterioration without stopping the machine operation. However, the old carrier that can be replaced with a new carrier has a considerable margin in terms of life, resulting in considerable waste in terms of resources. In addition, the developer amount tends to be relatively small due to the size restriction of the entire apparatus, and the carrier frequently receives a stirring and conveying action in the developing apparatus. Since the absolute amount is small, the toner concentration in the developer tends to increase greatly due to toner consumption.
[0005]
To avoid these problems, it is better to increase the absolute amount of the developer and suppress the replacement frequency. However, increasing the size of the developing device that accommodates the developer increases the overall size of the image forming apparatus. Not only does this, but also the design constraints are severe.
[0006]
The present invention has been made in view of the above circumstances, and achieves a large storage developer capacity, suppresses stress applied to the developer, and suppresses variations in toner concentration in the developer, while reducing design restrictions. Another object of the present invention is to propose a configuration of an image forming apparatus in which the developer can be easily replaced.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, an image forming apparatus including a developing device that performs a visualization process with a two-component developer is provided.
- the developer supply tank is disposed in a separate position from the developing device,
- at least a portion with the developer supply tank and a developing device as a developing agent capable circulation is connected via a flexible transfer path, wraps around the rotor and the rotor moves the toner in the axial direction by rotating A screw pump means having a rotating space for the rotor and having a stator in contact with the rotor is attached to the developer supply tank,
The developer supply tank has a plurality of agitation transfer means for agitating the developer by rotating and transferring the developer in the direction of the rotation axis;
-Each of the plurality of agitation transfer means is disposed in the developer supply tank so as to deliver the transferred developer to the vicinity of the upstream end of the rotation shaft of another agitation transfer means in the vicinity of the downstream end of the rotation shaft; Arranged,
-One of the plurality of stirring transfer means is directly connected to the screw pump means;
- Another agitating transporting means located immediately upstream of the agitating transfer means, the agitating means for transferring screw pump means directly coupled to convey the developer in opposite directions away from the screw pump means.
[0008]
It is preferable if air supply means for causing the toner moving by the screw pump means to flow in a diffused state is further provided. It is advantageous if the developer supply tank is detachable from the image forming apparatus main body. It is more effective if a plurality of agitation transfer means arranged in the developer supply tank can be driven independently . It is even better if a plurality of toner concentration detection means are distributed to the developer supply tank. A replenishment toner tank may be attached to the developer supply tank.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail based on the illustrated examples. Of course, the following examples illustrate the present invention and do not limit the technical scope of the present invention.
[0010]
In FIG. 1, a copying machine 102 according to the present invention includes a charging device 104 and an exposure device 105 (in the case of a digital type, an image signal around a photoconductor 103 serving as an image carrier along a rotation direction indicated by an arrow. A corresponding optical writing device), a developing device 106, a transfer belt 107, and a cleaning device 108 are arranged. The exposure apparatus 105 includes an exposure optical mechanism 105B including a light source, a reflecting mirror, and an imaging lens for exposing a document placed on a document placement table 105A installed on the upper surface of the copying machine 102, and according to the document. An electrostatic latent image is formed on the photosensitive member 103.
[0011]
The electrostatic latent image formed on the photoreceptor 103 is subjected to visible image processing by the developing device 106 and electrostatically transferred onto the recording paper fed from the paper feeding device 109 on the transfer belt 107. The transferred recording paper is fixed by the fixing device 110 and discharged. A cleaning device for removing toner remaining on the transfer belt 107 after the transfer and a cleaning device 108 for removing residual toner on the surface of the photoreceptor are further provided. The paper feeding device 109 includes a plurality of paper feeding cassettes that can store recording papers of different sizes so that paper of a selected size is fed.
[0012]
In FIG. 2 showing the developing device 106 in cross-section in detail, a developing roller 2 with a built-in magnet as a developer carrying member is disposed so that a part of the developing device 106 is exposed from the opening of the unit facing the photosensitive member 103. Yes. When the developing roller is regarded as a clock, the magnet conveys the developer in the direction facing the photosensitive member 103 in the direction of about 7 o'clock in FIG. 2 and the developer main pole P ₁ in the direction of about 6 o'clock and 4 o'clock, respectively. Magnetic poles P ₂ , P ₃ , magnetic poles P ₄ , P ₅ for transferring developer to the first conveying roller 21 in the direction of approximately 2 o'clock and 1 o'clock respectively (magnetic pole P ₅ can be omitted), direction of approximately 9 o'clock Magnetic poles P ₆ for restricting the developer are formed in directions facing the developing doctor 8. The magnetism of each magnetic pole is, for example, P ₁ is N, P ₂ is S, P ₃ is N, P ₄ is S, P ₅ is N, and P ₆ is S.
[0013]
A hook-shaped agent receiving case 24 having an upper opening as a bearing member is disposed above the developing roller 2 in a direction range in which the magnet in the developing roller has no magnetic pole and the magnetic force is significantly smaller than the other directions. Has been. The lowermost portion located at the center in the width direction of the agent receiving case 24 is shifted to the 11 o'clock side from the 12 o'clock direction of the developing roller 2. The agent receiving case 24 is provided with a lateral stirring unit as a lateral stirring means described later. On the right side of the agent receiving case 24, first to third transport rollers 21, 22 and 23 are disposed along the right side wall of the case, and the developer is removed from the developing roller 2 and removed by these rollers. A pumping means for pumping up the developer to the right end of the upper opening of the second developer receiving case 50 is configured.
[0014]
The first conveying roller 21 faces the developing roller 2 from the direction of 1 to 2 o'clock in FIG. 2, the second conveying roller 22 faces the first conveying roller 21, and further, the second conveying roller 22 from above. The 3rd conveyance roller 23 opposes. These first to third transport rollers 21, 22, 23 have the same structure and cannot rotate inside so as to transport the developer on the side opposite to the second agent receiving case 50. The magnet is housed.
[0015]
On the left side of the agent receiving case 24, there is a predetermined interval between the inner surface of the case 28 of the developing device unit. With this interval, the developer overflowed beyond the upper end of the left side wall of the agent receiving case 24. A developer conveyance path 40 to the surface of the developing roller 2 is provided. The inner surface of the unit case 28 located in the middle of the passage is an inclined surface, and the toner density sensor 29 is provided so that the detection surface 29a is substantially the same as the inclined surface. The toner concentration sensor 29 detects the toner concentration based on a change in the magnetic permeability of the developer. The toner density value detected by the toner density sensor 29 is compared with a reference value, and when the detected density falls below a predetermined value, it is recognized as a toner shortage state, and a toner replenishment signal having a magnitude corresponding to the shortage is generated. It is output to a toner supply circuit (not shown).
[0016]
Further, the developer is laterally agitated and transported in the developing device unit, for example, the outer stirring plate portion 26a and the spiral screw portion 26b for sending the developer from the back side to the front side of the drawing, and the developer from the front side to the back side. The balance with the inner conveying screw 27 for feeding This lateral stirring unit is a dual mixer, and the outer screw paddle 25 has a hollow cylindrical portion 26, a stirring plate portion 26a parallel to a plurality of axes extending radially from the peripheral surface of the hollow cylindrical portion 26, and a central axial direction. A spiral screw portion 26b that conveys the developer from the side toward the near side, and the inside screw that conveys the developer from the near side to the far side along the central axis direction in the hollow cylindrical portion 26 27 is housed. An unillustrated agent intake port for allowing the developer conveyed by the screw 26b to enter the hollow interior is formed at the side end portion on the front side of the hollow cylindrical portion 26, and the inner screw 27 is provided at the back end portion. An unillustrated agent discharge port for discharging the developer conveyed to the side end portion to the outside is formed.
[0017]
In the configuration as described above, the developer carried on the developing roller 2 and passing through the position facing the photoreceptor 103 is removed from the developing roller 2 by the first conveying roller 21 almost 100%, and then the second conveying roller. 22, and further transferred to the third conveying roller 23, and flows down into the second agent receiving case 50 over the right upper edge of the second agent receiving case 50 by centrifugal force or the like. The developer that has flowed down accumulates in the case 50 and is sent to the front side of the apparatus by the lateral conveying screw 51. As can be recognized in FIG. 3, the developer thus transported falls and accumulates in the agent reservoir 52 through a hole opened on the lower surface of the second agent receiving case 50, and further, its own weight and lateral It is transferred to the first powder pump 55 by the conveying screw 54.
[0018]
As the first powder pump 55, a conventionally known screw pump called “Mono pump” is used. The powder pump has a helical rod-like rotor 58 connected to the lateral conveying screw 54, and is disposed so as to wrap around the rotor 58. The powder pump has a rotation space for the rotor and is in partial contact with the rotor. A stator 59, a holder 60 for holding the stator 59, a drive motor 56 connected to the lateral conveying screw 54 through a gear train, and the like. The stator 59 is made of an elastic body such as rubber.
[0019]
There is a gap of about 1 mm between the inner peripheral wall surface of the holder 60 of the powder pump and the outer peripheral surface of the stator 59, and this gap communicates with the developer passage (discharge unit) 61, and the development is performed via the gap. An air supply port 62 is provided so as to blow into the agent passage 61. As shown in FIG. 4, when the air pump 63 is operated, air is blown into the circulating developer through the tube 65 and the air supply port 62 with a predetermined blowing amount, and thereby the air is discharged from the passage 61 of the powder pump 55. Fluidization of the developer is promoted, and the developer transfer by the powder pump 55 is ensured. Then, the developer that has passed through the powder pump 55 is transferred to the developer supply unit 66 (FIG. 1) through a flexible pipe 67 having excellent toner resistance.
[0020]
In FIG. 5 showing a schematic configuration of a developer supply unit 66 detachably attachable from the copying machine and FIG. 6 showing a cross-sectional view from the front, a developer container 68 is built in the unit. The circulating developer is discharged to the upper portion of the container 68 through the flexible pipe 67. A conveying screw 69 for moving the contained developer to the second powder pump 75 is disposed at the lowermost portion of the container 68 over the entire width thereof. The agent is sent out toward the developing device 106 through the flexible pipe 77 (see FIG. 1). As can be recognized from FIG. 5, the conveying screw 69 is directly connected to the rotor of the second powder pump 75 and has a spiral blade on its shaft. Since the structure of the second powder pump 75 is the same as that of the first powder pump 55, a detailed description thereof will be omitted.
[0021]
Inside the container 68, above the conveying screw 69, at least one, usually a plurality of agitation transfer means 71, 72, 73 (three in the illustrated example) are arranged at intervals in the vertical direction. Has been. These agitation moving means are driven by different drive means, respectively, but it is also possible to drive any agitation transfer means by a single drive means via a gear mechanism with a clutch. The uppermost agitation moving means 73 includes a developer transferred from the developing device via the flexible pipe 67, a developer in the container 68, and a virgin toner replenished as necessary from the attached toner container 74. The toner density of the developer is made uniform. The agitating / transporting means 71, 72, 73 and the conveying screw 69 are driven to rotate the contained developer in opposite directions in the width direction of the container 68 as shown by the arrows in FIG. As a result, it is possible to prevent the developer from being displaced in one direction, avoid toner unevenness, and realize uniformization of the concentration early.
[0022]
As shown in FIG. 6, toner concentration sensors 81, 82, and 83 are installed in the vicinity of the agitation transfer units 71, 72, and 73 to detect the toner concentration in the vicinity of the agitation transfer units 71, 72, and 73. If it is within the predetermined concentration range, the driving of the agitation transfer means at that point is stopped so that the developer is not stressed as much as possible. The toner concentration sensors distributed to the containers may be arranged in an appropriate number, and the installation position may be determined independently of the mounting position of the stirring transfer means. In order to avoid agglomeration of the developer, it is more preferable that the agitation transfer means 71, 72, 73 are appropriately driven as necessary. These sensors have basically the same structure as the toner density sensor 29.
[0023]
By connecting the main body of the image forming device and the developer supply device with a powder pump and a flexible pipe with less stress, there are fewer restrictions on the installation of each device, so that the installation location can be used effectively, and development as a whole It is possible to minimize the increase in the size of the entire device while increasing the amount of stored agent, and to improve workability during maintenance by installing a developer supply device outside the main body of the image forming apparatus. Can do. The advantage of increasing the storage amount of the developer is that the conventional type without the developer supply device has, for example, 1 g of toner by image formation in a state where 5 g of toner is present per 100 g of developer. The toner concentration fluctuated from 5% to 4%. By providing the developer supply device, the developer amount can be 500 g. Even if 1 g of toner is consumed, the toner concentration is 5%. This means that it only needs to change from 4.8% to 4.8%.
[0024]
【The invention's effect】
According to the image forming apparatus of the present invention, the developer supply tank is disposed at a position independent of the developing device, and at least a part thereof is flexible so that the developer can circulate between the developer supply tank and the developing device. Since the so-called MONO pump is attached to the developer supply tank , the storage developer is increased in capacity, the stress applied to the developer is suppressed, and the fluctuation of the toner concentration in the developer is also suppressed. However, there are few restrictions on the design, and the developer can be easily replaced.
[Brief description of the drawings]
FIG. 1 is a schematic conceptual diagram of an image forming apparatus according to the present invention.
FIG. 2 is an enlarged end view of a developing device attached to the image forming apparatus of FIG.
3 is a schematic view showing a connection relationship between a lateral conveying screw and a powder pump of the developing device of FIG. 2;
FIG. 4 is a schematic perspective view showing a relationship among a developing device, a powder pump, and an air pump.
FIG. 5 is a front perspective view of a schematic configuration of a developer supply unit.
6 is a cross-sectional view of the developer supply unit of FIG.
[Explanation of symbols]
66 Developer supply unit 67 Flexible pipe 77 for transferring developer from the developing device to the developer supply unit 77 Flexible pipe 103 for transferring developer from the developer supplying unit to the developing device Photoconductor 106 Developing device

Claims (6)

An image forming apparatus including a developing device that performs a visualization process with a two-component developer,
-Place the developer supply tank in a position independent of the developing device,
-At least a part of the developer supply tank and the developing device are connected via a flexible transfer path so that the developer can circulate, and a rotor that moves toner in the axial direction by rotation and the rotor is wrapped around A screw pump means having a rotating space for the rotor and a stator in contact with the rotor is attached to the developer supply tank,
The developer supply tank has a plurality of agitation transfer means for agitating the developer by rotating and transferring the developer in the direction of the rotation axis;
-Each of the plurality of agitation transfer means is disposed in the developer supply tank so as to deliver the transferred developer to the vicinity of the upstream end of the rotation shaft of another agitation transfer means in the vicinity of the downstream end of the rotation shaft; Arranged,
-One of the plurality of stirring transfer means is directly connected to the screw pump means;
The image is characterized in that the another agitation transfer means located immediately upstream of the agitation transfer means conveys the developer away from the screw pump means in the opposite direction to the agitation transfer means directly connected to the screw pump means. Forming equipment.   2. The image forming apparatus according to claim 1, further comprising an air supply means for causing the toner moving by the screw pump means to flow in a diffused state.   The image forming apparatus according to claim 1, wherein the developer supply tank is detachable from the main body of the image forming apparatus.   The image forming apparatus according to claim 1, wherein the plurality of agitation transfer units can be independently driven.   5. The image forming apparatus according to claim 1, wherein a plurality of toner concentration detection units are distributed to the developer supply tank.   6. The image forming apparatus according to claim 1, wherein a replenishing toner tank is attached to the developer supply tank.

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