JP4349941B2 - Developer supply apparatus and image forming apparatus using the apparatus - Google Patents

Description

The present invention relates to a developer supply device for supplying a developer to a two-component developing device and an image forming apparatus using the device.

  In image forming apparatuses such as printers, copiers, facsimiles, and multifunction machines having at least two of these functions, a developing device that develops an electrostatic latent image using a two-component developer composed of toner and carrier is often used. Yes. Since this type of image forming apparatus consumes toner together with image formation, it normally supplies toner in a container sequentially, and when the toner in the container runs out, it is replaced with a new toner container to replenish the toner. .

  On the other hand, the carrier is not consumed, but its performance deteriorates with the number of image formations. Therefore, it is necessary to replace the carrier every certain number of image formations. As a general method of replacement, in a copying machine, a method in which a dedicated service person replaces a carrier, and in a printer, a method in which a developing unit incorporating a carrier is replaced with a new unit for each unit is generally used. . However, if it continues to be used until the carrier deteriorates, the image quality at the beginning and at the time of deterioration is clearly different, and many recorded materials with poor image quality are provided.

  Therefore, recently, a method has been proposed in which a stable image can be continuously obtained by mixing a carrier with the toner to be replenished in advance, sequentially replenishing the toner and carrier to the developing device, and collecting excess developer. And has been implemented. However, the degree of deterioration of the carrier differs between a case where a large amount of recording such as a solid image occupies a large amount of recording and a case where recording mainly uses a low amount of toner such as a line image. Further, the deterioration of the carrier is not constant due to the difference in environment such as temperature and humidity. For this reason, in the method of always supplying a constant premix developer, it is difficult to adjust the toner density in the developing device because independent carrier supply control cannot be performed even if the carrier deteriorates more than expected. Furthermore, when the device is used at an early stage or when the carrier deterioration is slower than expected, even a developer that has not deteriorated is collected as the toner is replenished, resulting in a waste of resources.

JP 11-212346 A JP 2001-209244 A

  Therefore, as seen in Patent Document 1, a container for storing a replenishment carrier is provided, and the carrier is replenished to the developing unit little by little, and as seen in Patent Document 2, the carrier is joined to the replenishment toner. There has also been proposed a method for supplying the carrier at the same time as the toner supply. Thus, if the carrier is stored for each toner, the toner density can be adjusted.

  However, most of the carrier replenishment device transport methods that have been proposed use screws, so there are restrictions such that the transport route is almost straight and cannot be lifted upward. The part had to be provided near the developing device. For this reason, there are problems that the storage capacity of the toner and carrier cannot be increased, the toner and carrier replenishment device cannot be disposed at a position where the user can easily replace the device, and the machine body cannot be downsized.

  Incidentally, it has already been proposed to transport toner and developer using a screw pump. Therefore, if the carrier is transported using a screw pump, the above-mentioned problems can be improved, the degree of freedom in design is increased, and compactness and operability can be improved. However, as a result of various experiments conducted by the inventor, the uniaxial eccentric screw pump as a screw pump is difficult to control because the carrier amount becomes unstable due to the large mass of the carrier. It has been found that there is a problem that the life of the pump is shortened due to accelerated wear, which is not suitable for carrier conveyance.

In view of the above-described conventional circumstances, the present invention provides a developer replenishing device having a high degree of design freedom by using a single-shaft eccentric screw pump and capable of independent carrier replenishment control, and an image forming apparatus using the device. It is a problem.

In order to achieve the above object, the present invention provides a developing device that develops an electrostatic latent image formed on an image carrier with a two-component developer composed of toner and carrier, and supplies the developer composed of toner and carrier with the developer. In the agent replenishing device, a toner storage portion storing toner to be supplied to the developing device, a carrier storage portion separate from the toner storage portion and storing a carrier, and toner in the toner storage portion to the developing device A suction unit that applies a conveying force by a suction pressure; a toner supply line that communicates from the toner storage unit to the developing device; and the suction unit and the toner storage unit in the middle of the toner supply line. a carrier mixer provided between extends in the vertical direction, the Kya replenishing member carriers from said carrier storage part provided to perform supply of the carrier by quantitative in that way A carrier path for conveying to the A mixing unit, wherein the when the suction means are sucking the toner from said toner accommodating portion, said carrier mixing said carrier by said reinforcing member from said carrier housing part A developer replenishing device is proposed in which the developer is dropped and supplied to the part by its own weight .

The present invention is effective when the suction means is a uniaxial eccentric screw pump.

  Further, according to the present invention, it is effective that at least a part of the toner replenishment conduit is made of a tube.

Furthermore, the present invention is effective when the replenishing member is a rotating body having a size for closing the carrier passage, and a measuring recess is provided on the outer periphery of the rotating body.

Furthermore, the present invention is effective when the mixing amount of the carrier is controlled so that the weight ratio of the carrier to the sum of the toner and the carrier does not exceed 50%.

Furthermore, according to the present invention , a carrier concentration detection unit is provided between the carrier mixing unit and the developing device in the toner supply line , and the carrier mixing amount is controlled based on the carrier concentration detected by the carrier concentration detection unit. It is effective.

In order to achieve the above object, the present invention provides an image provided with a developing device that forms an electrostatic latent image on an image carrier and develops the electrostatic latent image with a two-component developer comprising a toner and a carrier. In the forming apparatus, an image forming apparatus is proposed in which the developing device is replenished with the developer replenishing device according to any one of claims 1 to 6 .

  According to the configuration of the present invention, stable image quality can be obtained without requiring special maintenance over time. Carrier consumption can be minimized. It has a high degree of freedom in layout, is simple and does not require a lot of space, and can achieve cost reduction and downsizing of the main body. This is particularly effective in a color image forming apparatus. By controlling the developer in the transfer path to the most fluid range, the developer transfer stability can be improved. In particular, this is particularly effective for toner whose cohesiveness and fluidity have increased due to the reduction in particle size in recent years, resulting in poor transportability. The durable life of the replenishing device can be improved. It is possible to prevent the carrier from being damaged by the conveying means.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an explanatory view showing an outline of a laser printer as an image forming apparatus according to the present invention. The printer has a drum-shaped photoconductor 1 as an image carrier, and the photoconductor 1 is a timepiece in FIG. In this case, the surface is uniformly charged to a predetermined polarity by the charging roller 2. Next, the charged surface is irradiated with a light-modulated laser beam L emitted from the laser writing device 3. As a result, an electrostatic latent image is formed on the photosensitive member 1, and the electrostatic latent image is visualized as a toner image by the developing device 4.

  On the other hand, a recording material P made of, for example, transfer paper is fed from a paper feeding device 5 provided on the lower side of the apparatus main body, and the recording material P is interposed between the photoreceptor 1 and the transfer roller 7 via a registration roller 6. It is sent. A voltage having a polarity opposite to that of the toner on the photosensitive member 1 is applied to the transfer roller 7, whereby the toner image on the photosensitive member 1 is transferred onto the recording material P. The transfer residual toner that is not transferred to the recording material P and remains on the photosensitive member 1 is removed by the cleaning device 8, and further, the residual charge remaining on the photosensitive member 1 is removed by the charge eliminating device 9.

  The recording material P on which the toner image is formed in this manner is sent to the fixing device 11 via the conveying belt 10, and is fixed on the recording material P at this time. 12 is discharged.

Such a laser printer uses a two-component developing device 4 and includes a toner replenishing device that replenishes the toner when the toner in the developing device 4 is consumed.
As shown in FIG. 2, the toner replenishing device has a toner storage container 20 as a toner storage unit. The toner storage container 20 includes a toner storage bag 21 in which toner is stored and a periphery of the toner storage bag 21. A protective case 22 for wrapping and a base member 23 fixed to the bottom of the toner storage bag 21 are provided. The toner storage bag 21 is formed by folding or adhering or adhering four sheets of single-layer or multi-layer sheets made of resin such as polyethylene and nylon or paper, each having a thickness of about 50 to 250 μm. A filter 24 for preventing the internal pressure of the container from rising excessively is provided at the top of the bag. The protective case 22 is made of a material such as rigid paper, cardboard or plastic, and has a structure in which a part thereof engages with the base member 23.

  A toner discharge port 25 is formed in the cap member 23, and a seal member 26 having a notch (not shown) in which a nozzle described later is inserted and removed is attached to a lower portion of the toner discharge port 25. With this configuration, the toner discharge port 25 formed in the base member 23 is normally closed by the seal member 26. The base member 23 is made of a resin such as polyethylene or nylon. At this time, if the toner storage bag 21 and the base member 23 are made of the same material, it is desirable from the viewpoint of recycling, and the toner storage bag 21 is welded to the base member 23. Will also be easier.

  The toner storage container 20 configured as described above is formed in a shape in which the cross section of the toner storage bag 21 is substantially rectangular and is squeezed from the middle toward the base member 23 at the bottom. By using such a narrowed shape, the stored toner can easily move to the base member 23, which is effective in reducing residual toner. It should be noted that the position where the toner storage bag 21 starts to be narrowed may be any position as long as a certain angle of inclination toward the cap member 23 is provided.

  The toner storage container 20 is detachably attached to a set portion provided at an appropriate location in the image forming apparatus main body, and a resin holder 50 that receives and holds the toner storage container 20 is attached to the set portion. Is provided. At the bottom of the holder 50, a nozzle 51 extending in the vertical direction is inserted and removed from the toner storage container 20. The nozzle 51 has a pointed head 52 formed at its tip so that it can be smoothly inserted into the seal member 26, and is formed in a double pipe having a toner passage 53 inside and an air passage 54 outside. Yes. The toner passage 53 is connected at its lower end to a toner conveyance pipe 15 connected to a uniaxial eccentric screw pump 40 described later as a toner conveyance path. The air passage 54 is bent sideways and connected to an air supply tube 62 from an air supply means described later.

  A uniaxial eccentric screw pump (hereinafter referred to as a screw pump) is disposed at the upper portion of the developing device 4. The screw pump 40 includes a female screw-shaped stator 42 formed with a double-pitch spiral groove made of an elastic member such as rubber supported by a holder 43, and is rotatably fitted in the stator 42. And an externally threaded rotor 41 made of resin or the like. The rotor 41 is connected to the drive shaft 45 by a spring pin or the like, and is driven to rotate when the drive shaft 45 is rotated. Since this motion is an eccentric motion, this pump is a uniaxial eccentric screw pump. Also called. The screw pump 40 has several spaces partitioned between the rotor 41 and the stator 42, and these spaces rotate and move in the same shape as the rotor 41 rotates. Therefore, the pump can control the conveyance amount with high accuracy by the rotation amount of the rotor 41.

  When this screw pump 40 is operated, a suction force is generated at the suction port 44 formed in the holder 43, and from the inside of the toner storage bag 21 storing the powder toner to the screw pump 40 via the nozzle 51 and the toner transport tube 15. Since the toner passage connecting the two is hermetically sealed, the suction force generated by the operation of the screw pump 40 is transmitted to the toner in the vicinity of the nozzles in the toner storage bag 21 via the toner conveying tube 15 and the nozzles 51, so that the toner is conveyed. It becomes possible.

  The toner conveying tube 15 that connects the nozzle 51 and the suction port 44 of the screw pump 40 has an inner diameter of about 3 mm to 7 mm, is flexible and has excellent toner resistance, such as polyurethane, nitrile, EPDM, silicon, and the like. By using a plastic material such as polyethylene or nylon, it is possible to freely arrange the toner replenishment path, which is very effective because the degree of freedom in the layout of the image forming apparatus is increased.

  Furthermore, since the toner replenishing device conveys the toner by the suction force of the screw pump, the toner replenishing device can convey the toner without any trouble even when the position of the toner container 20 is lower than the developing device 4. Therefore, since the arrangement of the toner storage container 20 is not limited, the toner storage container 20 can be disposed at a position where the toner replacement operation is most easily performed.

  In the toner replenishing device, the toner is fluidized by air in order to smoothly convey the toner having poor fluidity. Air is generated by operating the air pump 60, and the air is supplied into the toner in the toner storage bag 21 through the electromagnetic valve 61, the air supply tube 62, and the nozzle 51. In the air supply, after the screw pump 40 sucks the toner in the vicinity of the nozzle, a bridging phenomenon (a void is formed in the lost toner portion) occurs in the toner storage bag 21, and the toner replenishment amount becomes unstable or the toner is supplied. It is also used to prevent an excessive increase in the amount of toner remaining in the storage container. Therefore, supplying air to the inside of the toner storage bag 21 stirs and fluidizes the toner, prevents the above-described toner cross-linking phenomenon, and further collapses due to the air supplied with the cross-linked toner. As a result, the toner supply amount is stabilized and the remaining amount of toner in the toner container 20 is reduced. An air permeable filter 24 is provided on the upper portion of the toner storage bag 21, thereby preventing the pressure in the toner storage bag 21 from increasing due to the air supplied from the air pump 60.

  By the way, in the two-component developing device 4, development is performed with a developer composed of toner and carrier, but since the toner is consumed along with the development, the toner is replenished by the toner replenishing device described above. On the other hand, since the carrier is not consumed, it is not necessary to replenish it, but it deteriorates with use over time, leading to a decrease in image quality. Thus, although the toner mixed with the carrier is replenished in advance, there are various problems as described above because the carrier cannot be independently controlled and replenished.

  To replenish the carrier with independent control, the carrier must be transported from the carrier storage portion to the developing device 4, but when the carrier is transported by a screw as in the conventional case, the carrier storage portion is located near the developing device. There are significant restrictions on the installation location.

  The carrier has a particle size of about 20 to 200 μm, and the surface is made of a conventionally known iron powder, ferrite powder, magnetite powder, magnetic resin or the like with an amino resin, polyvinyl and polyvinylidene resin, polystyrene resin, silicon resin, or the like. A coated one is used. The toner is mixed with a binder resin, a wax component, a colorant, and in some cases a charge control agent, etc., using a mixer, etc., kneaded using a kneader such as a hot roll, an extruder, etc. Conventionally known materials such as a pulverized toner obtained by pulverizing with a jet mill or the like and then classified, or a toner using a polymerization method are used, and the particle size is about 4 to 10 μm.

  Conveyance by the screw pump pressure selectively conveys light objects, so that those having a large specific gravity and those that are light but difficult to contain air are difficult to move (only air moves). Furthermore, since the conveyance pressure is generated in proportion to the rotation amount (space movement amount) of the pump, the generated pressure is small because the rotation amount is small particularly in a very small amount of conveyance such as toner replenishment to the developing device, The tendency becomes remarkable. As described above, the carrier is suitable for drop conveyance using gravity because of its heavy specific gravity and good fluidity, but pressure conveyance by a screw pump or the like is very difficult due to its high specific gravity. On the other hand, although the toner has a low specific gravity, many types of toners having good fluidity and poor fluidity are used, and the toner having good fluidity easily contains air and is easy to convey with pressure. However, toner with poor fluidity does not easily contain air, and it has been difficult to use due to problems such as unstable transport amount or clogging in the transport path when transported by pressure.

  Therefore, the carrier can be conveyed by pressure in the toner having a low specific gravity and easily containing air, and the conveying means and path can be simplified. Moreover, it has been found by the present inventors that even a toner with poor fluidity can be stably conveyed by increasing the fluidity by mixing the carrier. Therefore, when the carrier is transported by the screw pump, it is configured so as to be transported by being mixed with the toner, not alone.

Next, carrier supply will be described with reference to FIG.
Reference numeral 70 in the figure denotes a carrier storage container as a carrier storage portion. The carrier storage container 70 of the present embodiment uses the same material and the same structure as the toner storage container 20 described above. That is, the carrier storage container 70 includes a carrier bag 71, a protective case 72, and a base member 73. The base member 73 is formed with a carrier discharge port 75. A carrier discharge port 75, which will be described later, is formed in a lower portion of the carrier discharge port 75. A seal member 76 having a cut (not shown) through which the nozzle is inserted and removed is attached. However, unlike the toner, the carrier has good fluidity, and therefore it is not necessary to supply air to the carrier bag 32, so the filter 24 for preventing an increase in internal pressure is omitted.

  The carrier storage container 70 configured as described above is detachably attached to a set unit set above the transport tube 15 which is the above-described toner supply path. The set portion is provided with a resin holder 80 for receiving and holding the carrier storage container 70. At the bottom of the holder 80, a vertically extending nozzle 81 is inserted and removed from the carrier storage container 70, and the tip of the nozzle 81 has a pointed head so that the insertion into the seal member 76 can be performed smoothly. 82 is formed. The nozzle 81 is formed with a carrier passage 83 that joins the toner supply path via the joining member 84. In the middle of the carrier passage 83, toner is prevented from entering the carrier storage container 70, and a fixed amount of carrier is provided. A replenishing roller 90 is provided as a replenishing member for replenishing. The replenishing roller 90 has a diameter large enough to completely block the carrier passage 83, is rotationally driven by a driving means (not shown), and a measuring recess 91 for receiving a fixed amount of carrier is formed on the peripheral surface thereof. . A bulge into which the roller is fitted is formed in a portion of the carrier passage 83 where the replenishing roller 90 is provided. In addition, although the four measurement recessed parts 91 are formed for every 90 degrees, the number can be set arbitrarily. Further, the merging member 84 is an inverted T-shaped tube member, but is formed integrally with the nozzle 81 in this example.

  In the printer configured as described above, when a toner replenishment command is issued, the air pump 60 operates and air is supplied to the toner in the toner storage container 20 to fluidize the toner. At the same time, or slightly before and after, the screw pump 40 is rotationally driven, so that the toner is supplied to the developing device 4 by the suction pressure of the pump.

  At this time, if a carrier replenishment command is also issued, the replenishment roller 90 rotates while the toner is transported, whereby the carrier is mixed with the transported toner and replenished to the developing device 4 by the pressure of the screw pump 40. The Therefore, even a heavy carrier can be stably supplied by supplying toner together. Since the amount of carrier replenishment can be controlled by the number of rotations of the replenishing roller 90, it is convenient to drive the replenishing roller 90 with a stepping motor capable of controlling the rotation thereof.

  By replenishing the carrier during toner conveyance in this way, even a carrier having a large mass can be conveyed without any trouble by the screw pump 40, and since the conveyance system is shared with the toner, the cost is not increased and the apparatus is compact. Further, the set portion of the toner storage container 20 and the carrier storage container 70 can be set at an arbitrary position that is not limited by the position of the developing device 4. Furthermore, by adding a new carrier, the charging performance of the carrier that gradually deteriorates is compensated, and the total charging performance of the total carriers in the developing device is maintained above the limit value. With this configuration, stable image formation can be continued without the need for periodic carrier replacement (replacement) as in the prior art. In the developing device 4 to which the developer is supplied, surplus developer is discharged due to overflow or the like, and the developer is replaced little by little. For example, in the developing device 4 of FIG. 1, the side discharge unit 13 is provided, and when the developer is replenished and exceeds a predetermined height level, the excess is discharged through the side discharge unit 13.

The inventor has investigated whether the difference in the ratio of the toner and the carrier in the toner conveyance tube 15 causes a difference in developer conveyance. The experimental data are shown in FIGS.
FIG. 3 is a graph in which the cumulative developer transport amount (g) is plotted on the vertical axis and the cumulative rotational speed (rev) of the screw pump 40 is plotted on the horizontal axis when the carrier weight ratio is 20%, 50%, and 90%. Represents the variation in the developer conveyance amount per one rotation of the screw pump at this time, and is obtained by dividing the standard deviation when the data is measured 30 times by the average value.

  In FIG. 3, when the weight ratio of the carrier in the developer is 20%, 50%, and 90%, the cumulative developer transport amount with respect to the initial screw pump cumulative rotational speed is 20B, 50D, and 90F, respectively. In addition, when the carrier weight ratio in the developer was 20%, 50%, and 90%, the cumulative developer transport amount with respect to the screw pump cumulative rotational speed over time was 20C, 50E, and 90G, respectively. Here, the initial stage is a developer replenishing device having a screw pump suction pressure of 22 KPa (differential pressure), and the time elapsed is that the screw pump is rotated 46,000 from the initial stage and immediately after 10 kg of developer has been transported, the screw pump suction pressure is 5 KPa ( (Differential pressure) developer supply device. Further, the coefficient of variation in FIG. 4 represents a variation in the developer transport amount per one rotation of the screw pump, and is obtained by dividing the standard deviation when the data is measured 30 times by the average value.

  From the experimental results, when the weight ratio of the carrier in the developer is 50% (50D, 50E), the developer carrying amount, the carrier carrying amount, and the toner carrying amount are all the largest, and there is almost no difference between the initial time and the time. It can be seen that the coefficient of variation is small and the best. When the weight ratio of the carrier in the developer is 20% (20B, 20C), the difference between the initial time and the aging and the coefficient of variation are small, but the transport amount is slightly smaller than when the carrier weight ratio is 50%. When the weight ratio of the carrier in the developer is 90% (90F, 90G), the developer transport amount is the smallest, and the difference between the initial value and the average value over time and the coefficient of variation are large. In particular, although the carrier concentration is higher than that in the case of 50%, the carrier transport amount is extremely reduced. In other words, the carrier's weight ratio in the developer is 50% for the best transport efficiency and stability, and even 20% can be used because there is no problem with stability, but 90% is used because the transport efficiency and stability are both very poor. It turns out that it is impossible. As described above, since the carrier efficiency and stability become very poor when the carrier weight ratio is too large, the carrier mixing ratio is used in the range of 50% or less, and more preferably in the range of 20 to 50%. This is very important.

  Furthermore, since the developer conveyance amount increases, the rotation amount of the screw pump can be reduced, and the flowability of the developer in the sense of conveying with the screw pump is improved, which greatly improves the durability of the screw pump. It is an effect. Further, improving the fluidity of the developer also has an effect of reducing damage to the carrier.

  Such appropriate control of the carrier weight ratio can be realized by controlling the rotation amount of the replenishing roller 90 in accordance with the operation time of the screw pump 40 and the detection of the carrier concentration in the toner transport pipe 15 described later. . Further, when the mixing ratio of the carrier is controlled within the range of 20 to 50%, the fluidity is increased by mixing an appropriate amount of the carrier even when the toner having poor fluidity is used, and stable pressure conveyance of the screw pump 40 is possible. I found.

  FIG. 5 is a cross-sectional explanatory view showing still another embodiment of the present invention, and the basic configuration itself is similar to that of the embodiment of FIG. The difference is that air is not supplied to the toner storage container 120 and the filter 24 shown in FIG. 2 is not provided in the toner storage container 120, so that a suction-type screw is supplied from the toner storage container 120 through the toner transport path. The point up to the pump 40 is almost completely sealed. Therefore, this is an automatic volume reduction method in which the toner is sucked and discharged by the screw pump 40, and the volume of the toner storage container 120 is reduced (collapsed) by the volume of the discharged toner.

  The toner storage container 120 includes a bag-like flexible toner storage member 121 that stores toner and a base member 122 connected to the lowermost portion thereof. A suction nozzle 151 is inserted into the base member 122. A shutter 123 stops toner outflow when the nozzle 151 is not inserted. Reference numeral 124 denotes a sealing material that is disposed on both sides of the nozzle or shutter 123 to maintain airtightness. A suction-type screw pump 40 similar to that shown in FIG. 2 is connected to the nozzle 151 via the toner conveyance tube 15.

  The portion from the nozzle 151 to the developing device 4 is fixed to the main unit, and the toner storage container 120 is replaced with a new container each time the toner inside the toner is consumed, and the nozzle 151 is attached and detached each time. In order to prevent contamination and air leakage, the sealing between the base member 122 and the nozzle 151 is very important.

The toner storage member 121 is the same as the toner storage bag 21 constituting the toner storage container 20.
To open and close the shutter 123, after the toner container 120 is set in the holder 150, the nozzle 151 moves in the right direction in the figure, and the shutter 123 is pushed out from the inside of the base (right direction) by the nozzle 151. Further, when the toner storage container 120 is taken out from the holder 150, the nozzle 151 moves to the left, and the shutter 123 is urged to the left by the spring 154 and the shutter push-back spring 125. Thus, the small amount remaining in the toner container 120 due to the close contact between the shutter 123 and the two sealing members 124 provided on the nozzle member 122. Can prevent the toner from leaking out. Here, although the means for moving the nozzle 151 in the left-right direction is not shown, a conventionally known moving means such as a lever (manual), a motor, or a solenoid may be used. The seal 125 is formed of a rubber material or the like that is pressed lightly against the shutter 123. The base member 122 is a hard member such as a resin and is provided with a toner discharge port 126, and is adhered or bonded to the toner storage member 121.

  The carrier storage unit has the same structure as the toner storage container 120 and the nozzle 151 in the carrier storage container 170 and the nozzle 181. When a carrier replenishment command is issued, the replenishment roller 90 rotates, and an amount of carrier corresponding to the amount of rotation falls on the transport tube 15 and is replenished to the developing device 4 by the suction force of the screw pump 40.

  The shutter opening / closing method described above does not interfere with the toner flow path, and it is not necessary to provide a shutter retracting space in the base member 122 in order to retract the shutter outside the base member 122, so that the base member 122 is extremely compact. In addition, since it is arranged orthogonal to the toner flow path (pressure), the shutter 123 is not pushed out when the internal pressure of the container increases (due to the atmospheric pressure or the like), and it is safe. Can be mentioned.

  In this embodiment, a carrier concentration sensor 47 that detects the carrier concentration of the developer sucked into the suction port 44 of the screw pump 40 is provided, and the same carrier concentration sensor 47 as the toner concentration sensor can be used. As a sensor system, there are a conventionally known magnetic permeability detection sensor and an optical sensor. The permeability detection sensor uses a resonance circuit and an oscillator consisting of a coil and a capacitor, and determines the carrier bulk density by setting the transmission frequency so that it resonates when the amount of carrier, which is a magnetic material, is within a predetermined range. is there. The optical sensor obtains the carrier content by detecting the reflected light when the developer emits light by utilizing the difference in light reflectance between the carrier and the toner.

  Using the carrier concentration detection result by the carrier concentration sensor 47, the weight ratio of the carrier contained in the toner in the toner transport tube 15 can be accurately managed within an appropriate range. That is, when the carrier weight ratio exceeds 50% from the carrier concentration detection result, the driving of the carrier replenishing roller 90 is prohibited, and when the carrier concentration detection result decreases again to the carrier weight ratio of about 40% or less, the carrier Control such as releasing the prohibition of driving of the supply roller 90 is performed.

  When the carrier concentration sensor 47 is not used, the toner transport amount and the carrier replenishment amount are estimated by the driving time of the screw pump 40 and the carrier replenishment roller 90, and the expected value of the weight ratio of the carrier is obtained from this. The expected value of the carrier weight ratio may differ from the actual value due to various conditions such as fluctuations, toner and carrier manufacturing variations, and deterioration of the screw pump 40 and the replenishing roller 90. That is, there are cases where the developer is transported at a carrier weight ratio outside the proper range, resulting in a large variation in the transport amount or clogging in the transport tube.

  By providing the carrier concentration sensor 47, the above problems are solved, and the conveyance stability of the toner and the carrier is further improved. Needless to say, the carrier concentration sensor 47 can be used in the developer supply device of FIG. 2 and FIG. 7 described later.

  FIG. 6 is a schematic diagram illustrating a color printer which is an example of an image forming apparatus. The image forming means 201 shown in FIG. 1 has first to fourth image carriers 203Y, 203M, 203C, 203BK configured as drum-shaped photosensitive members, and a yellow toner image is formed on each of the image carriers. A magenta toner image, a cyan toner image, and a black toner image are formed. A transfer belt 204 is disposed opposite to the first to fourth image carriers 203Y to 203BK. The transfer belt 204 is wound around a driving roller 205 and a driven roller 206 and is driven to travel in the direction of arrow A.

  Since the operation of forming the toner image on each of the first to fourth image carriers is substantially the same, only the configuration of forming the toner image on the first image carrier 203Y will be described. . The image carrier 203Y is driven to rotate clockwise in FIG. 6, and at this time, the surface of the image carrier is uniformly charged to a predetermined polarity by the charging roller 207. Then, the charged surface is irradiated with a light-modulated laser beam L emitted from the laser writing unit 208. As a result, an electrostatic latent image is formed on the image carrier 203Y, and the electrostatic latent image is visualized as a yellow toner image by the developing device 209.

  On the other hand, a recording medium P made of, for example, transfer paper is fed from a paper supply unit (not shown), and the recording medium P is fed between the image carrier 203Y and the transfer belt 204 and carried on the transfer belt 204. Are transported. A transfer roller 210 is disposed at a position almost opposite to the image carrier 203Y across the transfer belt 204, and a voltage having a polarity opposite to that of the toner on the image carrier 203Y is applied to the transfer roller 210. The yellow toner image on the image carrier 203Y is transferred onto the recording medium P. The transfer residual toner that is not transferred to the recording medium P and remains on the image carrier 203Y is removed by the cleaning device 202.

  In exactly the same manner, magenta toner images, cyan toner images, and black toner images are respectively formed on the second to fourth image carriers 203M, 203C, and 203BK, and these toner images are transferred with the yellow toner image. The images are sequentially superimposed and transferred onto the recording medium P.

  The recording medium P on which the four-color toner images are formed as described above passes through a fixing device (not shown). At this time, the toner image is fixed on the recording medium P and discharged (not shown). It is discharged onto the tray.

  In the case of a color image forming apparatus, four color (yellow, magenta, cyan, black) toner storage containers 220Y, 220M, 220C, and 220BK are used. The toner storage containers 220Y, 220M, 220C, and 220BK of four colors (yellow, magenta, cyan, and black) are stored in the holder 150, and each toner storage container is provided by the toner conveying unit shown in FIG. 2 or FIG. The toner in 220Y, 220M, 220C, and 220BK is conveyed to each developing device 209. In the drawing, reference numerals 215Y, 215M, 215C, and 215BK denote toner transport tubes for the respective colors.

  On the other hand, the carrier storage container 270 is set in the holder 280 and is arranged in a row along with the toner storage containers 220Y, 220M, 220C, and 220BK. A carrier replenished by a replenishment roller, which will be described later, is a toner transport tube 215Y that transports four colors of toner so that the toner transport tubes 215Y, 215M, 215C, and 215BK are easily replenished at the positions of the joining members 284Y, 284M, 284C, and 284BK. 215M, 215C, and 215BK are arranged so that all pass almost directly under the carrier container 170 as shown in the figure.

  FIG. 8 is a cross-sectional explanatory view showing the carrier supply device of FIG. 7. When the carrier storage container 270 is set on the holder 280, the nozzle 281 is inserted into the base member 273 of the carrier storage container 270. Since the carrier has good fluidity, the carrier in the carrier storage container 270 passes through the nozzle 281 and falls into the carrier storage part 283 due to gravity, and the carrier is stored almost completely as shown in the figure. The Replenishing rollers 290Y, 290M, 290C, and 290BK corresponding to the four color toners are disposed under the carrier storage unit 283, and the rotation driving of each of them is controlled independently. Here, for example, if the supply roller 290M for magenta color development is driven, the carrier in the groove 291M provided in the supply roller 290M is carried to the passage 292M and falls to be supplied to the junction member 284M. The merging member 284M is a member for connecting the storage portion 283 and the toner conveying tube 215M of FIG. The replenished carrier merges with the magenta toner in the toner conveyance tube 215M and is conveyed to the developing device 209, that is, replenished into the developing device 209.

  In the present invention, the layout of the carrier replenishing device is high, and the image forming apparatus main body is not greatly increased in size and cost with a simple configuration, and stable image quality can be obtained without special maintenance even over time. Is possible. This is particularly effective in a color image forming apparatus using a multicolor developing device and a toner replenishing device. Furthermore, the fluidity can be improved by merging the carrier with the toner, and the stability of the toner conveying system using a screw pump can also be improved. This is particularly effective for a toner whose cohesiveness and fluidity have increased recently due to the recent reduction in particle size, resulting in poor transportability.

  In the above-described embodiment of the present invention, the carrier is joined to the toner replenishment path by gravity and replenished to the developing device. However, each of the embodiments shown in FIGS. Including the carrier, the toner is replenished and replenished to the developing device.

  In the embodiment shown in FIG. 9, the arrangement of the toner storage container 20 and the carrier storage container 70 is changed, but the apparatus is substantially the same as in FIG. 2, and the suction type screw pump 40 is used as the toner replenishing device. Therefore, the same members as those in FIG. 2 are denoted by the same reference numerals and detailed description thereof is omitted to avoid duplication. In this embodiment, the form of the air pump 360 that supplies air to the toner container 20 is different from that of FIG.

  The air pump 360 of this example is a diaphragm type air pump, and the diaphragm 361 is a container-like member formed of rubber or flexible plastic, and the lower part in the drawing is in close contact with the partition plate 362 in a state where the air is shut off. Is driven in the vertical direction by an eccentric shaft 364 attached to the rotation shaft of the motor 363. By this operation, air is sucked into or discharged from the inside of the diaphragm. The partition plate 362 has two holes, one is a suction hole 365, and the other is a discharge hole 366, each of which is provided with a flexible valve member, a suction valve 367, and a discharge valve 368. With this configuration, the motor 363 is energized and rotated, so that air is sucked from the suction port 369 and air is discharged from the discharge port 370.

  A suction port 369 of the air pump 360 is connected to a nozzle 81 inserted into the carrier storage container 70 by a tube 371, and the nozzle 81 is supplied with a replenishing roller 90 for sending a fixed amount of carrier and air covered by a filter 372. And an opening for inhalation.

  The toner in the toner container 20 is fluidized when air is supplied from the air pump 360, and the fluidized toner is conveyed to the developing device 4 through the toner conveying tube 15 by the suction pressure of the screw pump 40. Is done.

  Since the carrier has very good fluidity compared to the toner, the carrier in the carrier storage container 70 falls into the passage 83 in the nozzle 81 due to gravity. The carrier in the passage 83 enters the measuring recess 91 provided in the replenishing roller 90, and an amount corresponding to the rotation amount is sent to the downstream side by the rotational driving of the replenishing roller 90.

  The carrier is supplied to the toner in the toner container 20 from the passage 83 through the tube 371, the air pump 360, the tube 62, the electromagnetic valve 61, and the nozzle 51 by the operation of the air pump 360. The carrier mixed with the toner in the toner container 20 is sucked and conveyed in the nozzle 51 and the toner conveying tube 15 together with the toner by the operation of the suction type screw pump 40, and further passes through the screw pump 40 to the developing device 4. To be replenished.

  The carrier replenishing operation is performed immediately before or simultaneously with the operation of the air pump 360. At this time, the opening operation of the electromagnetic valve 61 is performed simultaneously with the operation of the air pump 360, and air and carrier are supplied to the toner in the toner storage container 20.

  In FIG. 9, reference numeral 380 denotes a toner remaining amount detection sensor, and an optical sensor is used in this example. The toner remaining amount detection sensor 380 includes a light emitting element provided on the back side facing the paper surface of the toner storage container 20 and a light receiving element provided on the front side facing the paper surface. Light from the light emitting element passes through the toner storage container 20. The presence or absence of toner near the upper portion of the nozzle in the toner storage container 20 can be detected based on the amount of light received when the light is received by the light receiving element. Even when the toner remaining amount detection sensor 380 of this example is not used, it is possible to predict the toner remaining amount based on the driving rotation amount of the screw pump 40, the number of pixels of the document, and the like. When the transfer amount fluctuates, it may be different from the actual value. By using the toner remaining amount detecting sensor 380, the remaining amount of toner can be detected more accurately.

  The developer replenishing device of FIG. 9 mixes the carrier with the toner in the toner storage container 20 as described above, so the weight ratio of the carrier differs depending on the remaining amount of toner in the toner storage container 20. For example, since the weight ratio of the carrier to the toner may increase as the remaining amount of toner decreases, the amount of carrier replenishment is likely to be limited. Therefore, using the detection result of the above-described toner remaining amount detection sensor 380, when the toner remaining amount is large, the carrier replenishment amount is increased, and when the toner remaining amount is small, the carrier replenishment amount is decreased, or It is possible to prohibit the replenishment of the carrier, which makes it easier to control the ratio of the toner amount and the carrier amount in the toner conveying tube 15 to an appropriate range, and further stabilizes the developer transfer amount.

  FIG. 10 is a perspective view showing still another embodiment of carrier replenishment by air. This embodiment is for color, and toner storage containers 420Y, 420M, 420C for four colors (yellow, magenta, cyan, black), 420BK is stored in the holder 450, and the same toner conveying means as that shown in FIG. 9 is used. Reference numerals 15Y, 15M, 15C, and 15BK denote toner transport tubes for transporting toner in the respective toner storage containers 420Y, 420M, 420C, and 420BK by screw pumps that are provided for the respective colors (not shown).

  The carrier container 470 is set in the holder 480 and arranged in a row alongside the toner storage containers 420Y, 420M, 420C, and 420BK as shown in the figure. The carrier in the carrier container 470 is sent out by the distribution replenishing roller in the same manner as in FIG. 8, and the toner is stored through the tubes 462Y, 462M, 462C, 462BK of the four air pumps 460Y, 160M, 160C, 160BK provided for each color. It can supply to containers 420Y, 420M, 420C, and 420BK, respectively.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus of the present invention. FIG. 3 is a cross-sectional explanatory view of a toner and carrier supply device showing an embodiment of the present invention. It is the glass which shows the relationship between the rotation speed of a screw pump by the weight ratio of the carrier to mix, and a developer replenishment amount. It is a table | surface which shows the data per rotation of the screw pump in FIG. FIG. 6 is a cross-sectional explanatory view of a toner and carrier supply device showing still another embodiment of the present invention. 1 is a schematic view showing a main part of a color image forming apparatus of the present invention. FIG. 3 is a perspective view showing a toner and carrier supply device for a color image forming apparatus according to the present invention. FIG. 8 is a cross-sectional explanatory view showing a carrier supply device for the color image forming apparatus of FIG. 7. FIG. 6 is a cross-sectional explanatory view of a toner and carrier supply device showing still another embodiment of the present invention. FIG. 10 is a perspective view showing a toner and carrier supply device when the carrier supply device of FIG. 9 is employed in a color image forming apparatus.

Explanation of symbols

4 209 Developing device 20, 120, 220, 420 Toner container 40 Uniaxial eccentric screw pump 51, 151 Nozzle (for toner)
60, 360 Air pump 70, 170, 270, 470 Carrier storage container 81, 181 Nozzle (for carrier)

Claims (7)

In a developer replenishing device for replenishing a developer comprising a toner and a carrier to a developing device for developing the electrostatic latent image formed on the image carrier with a two-component developer comprising toner and carrier,
A toner storage unit storing toner to be replenished to the developing device;
A carrier storage unit that is separate from the toner storage unit and stores a carrier;
A suction unit that applies a conveying force by suction pressure to the toner in the toner storage unit to the developing device;
A toner replenishment conduit communicating from the toner storage portion to the developing device;
A carrier mixing section provided in the middle of the toner supply pipe and between the suction means and the toner storage section;
A carrier path for transporting the carrier from the carrier storage part to the carrier mixing part, which extends in the vertical direction and is provided with a replenishment member that replenishes the carrier in a certain amount in the middle ;
Have
When the suction unit is sucking toner from the toner storage unit, the carrier is dropped from the carrier storage unit by the replenishing member to the carrier mixing unit by its own weight and supplied. Developer supply device.   The developer supply device according to claim 1, wherein the suction unit is a uniaxial eccentric screw pump.   The developer replenishing device according to claim 1, wherein at least a part of the toner replenishing conduit is formed of a tube.   The developer replenishing device according to claim 1, wherein the replenishing member is a rotating body having a size that closes the carrier passage, and a measuring recess is provided on an outer periphery of the rotating body.   5. The developer replenishing device according to claim 1, wherein a mixing amount of the carrier is controlled so that a weight ratio of the carrier to a sum of the toner and the carrier does not exceed 50%. . A carrier concentration detection unit is provided between the carrier mixing portion and the developing device in the toner supply line , and the carrier mixing amount is controlled based on the carrier concentration detected by the carrier concentration detection unit. Item 5. The developer supply device according to Item 1 or 4 . In an image forming apparatus comprising a developing device that forms an electrostatic latent image on an image carrier and develops the electrostatic latent image with a two-component developer composed of toner and carrier.
Image forming apparatus characterized by replenishing the developer with a developer replenishing device according to any one of claims 1 to 6 to the developing device.

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