JP5381176B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, and a multi-function machine thereof.

  As a developing device used in an image forming apparatus, an apparatus that develops and visualizes an electrostatic latent image formed on an image carrier using a two-component developer composed of toner and carrier is known. In this developing device, the developer that has undergone development processing in the development area and has consumed the toner is collected, mixed and stirred with the replenished toner, and again used for development. The developer used in such a developing device needs to maintain a constant toner density and charge amount in order to obtain a stable toner image. The toner density is adjusted by the toner consumed in development and the amount of replenished toner, and the charge amount is given by frictional charging during mixing of the carrier and the toner. The developing device sufficiently stirs the two-component developer composed of toner and carrier to equalize the toner concentration and charge the toner to stabilize the toner image.

  In a general developing device, toner is dispersed and charged by utilizing the stirring effect of the rotation of two screws during a short time until the replenished toner is pumped up to the developing roller. In particular, when the toner balance is large, the replenished toner is not sufficiently dispersed. In this state, the toner is pumped up to the developing roller, and quality problems such as background contamination and toner scattering occur.

  In order to solve this problem, a separate stirring unit is provided at a location away from the developing unit, the developing unit and the stirring unit are connected by a circulation means, and the stirring unit performs stirring according to the state of the developer, For example, “Patent Document 1”, “Patent Document 2”, and “Patent Document 3” disclose a developing device that supplies a developer with an appropriately adjusted charge amount to a developing unit.

In the developing device described above, the developer is circulated using the air flow. However, such a developing device has the following problems.
In the case where the developer is continuously conveyed using an air flow in the pipe, main components are a developer storage section, a developer supply section, a transport pipe, and an air supply source. Here, since the developer is transported using the pressure (positive pressure) of air and the flow velocity, a differential pressure is generated between the transport source and the transport destination (atmospheric pressure). As a configuration of the developing device, when the developer that has been sent is collected from the developing unit to the developer storing unit and then transported (circulated) again, the developer storing unit is also at atmospheric pressure. In order to transport the toner to the developing unit, it is necessary to seal the developer supply unit so that air from the air supply source does not leak into the developer storage unit. When air leaks, the pressure for transporting the developer decreases, and a problem arises that the transport amount cannot be secured sufficiently. In addition, when air flows backward to the developer storage section (pressure is applied to the developer storage section), the developer entering the developer supply section from the developer storage section is hindered by the reverse air flow, resulting in a decrease in discharge amount. And variations occur.

  A rotary feeder is generally used as a supply device for supplying a developer. The rotary feeder has a rotor having a plurality of rotating blades and a stator that covers the rotor, and is an apparatus having excellent quantitativeness and controllability, but the above-described backflow of air is generated. Therefore, as a method of ensuring the sealing performance, a method can be considered in which the rotor blades are made of an elastic body and have biting (contact) with the stator. However, since the deterioration over time (the wear of the rotor and the stator) is remarkable, it is practical. Not right. In particular, since the carrier constituting the two-component developer is composed of iron or ferrite, it has high hardness and it is difficult to obtain durability with this method. Further, the developer dropped and discharged from the conventional rotary feeder joins with a horizontal pipe and is then transported to the transport destination. Here, the cross-sectional area of the transport pipe is smaller than the cross-sectional area of the opening provided in the lower part of the rotary feeder, and the developer discharged from the rotary feeder is conveyed by the transport pipe having a smaller cross-sectional area by changing the angle by 90 degrees. As a result, pressure loss occurs.

  The present invention solves the above-mentioned problems, greatly reduces the amount of air entering the rotary feeder, and can reduce pressure loss at the joining portion of the developer and air. An object of the present invention is to provide a developing device capable of efficiently and stably supplying a developer having the above and an image forming apparatus using the same.

First aspect of the present invention, a developing unit configured to accommodate developer therein, the a developer貯容unit for貯容the developer provided outside the developing unit sent to the developing unit, the developer貯容unit A rotary feeder that discharges the developer from the inside, a transfer pipe that connects the developing unit and the rotary feeder, and an air flow is generated in the transfer pipe to transfer the developer discharged from the rotary feeder to the developing unit. A developing device comprising an air flow generating means for causing the flow of the developer discharged from the rotary feeder and the air flow generated from the air flow generating means to merge, wherein as the angle between the flow of the developer and the air flow becomes acute in each upstream side, and so that the air flow becomes linear at the upstream side and the downstream side of the merging portion Niso Each is configured, the developer discharged from the rotary feeder is characterized in that the falling linearly with respect to the merging section.

According to a second aspect of the present invention, in the developing device according to the first aspect, the shape of the discharge port for discharging the developer from the rotary feeder is curved so that the discharged developer smoothly joins the air flow. It is formed in the shape .

According to a third aspect of the invention, in the developing device according to claim 1, further wherein the discharge position of the developer from the rotary feeder is provided at a position deviated from the bottom a lower portion of the rotary feeder It is characterized by.

A fourth aspect of the invention is an image forming apparatus having the developing device according to any one of the first to third aspects .

  According to the present invention, since the developer and the air flow smoothly join at the joining portion, the pressure loss is reduced, so that the differential pressure between the developer storing portion and the joining portion is reduced, thereby reducing air flow leakage. In addition, the air pressure required for the developer conveyance is also reduced, and the developer and the air flow are smoothly mixed and conveyed, so that a stable developer conveyance amount can be obtained and the energy efficiency can be improved.

1 is a schematic diagram of a developing device adopting a first embodiment of the present invention. It is sectional drawing of the image development part used for the 1st Embodiment of this invention. FIG. 2 is a schematic view of a main part of the developing device used in the first embodiment of the present invention. It is the schematic explaining the conventional junction part. It is a schematic side view explaining the joint member used for the 1st Embodiment of the present invention. It is the schematic which shows the joint member used for the 2nd Embodiment of this invention. The line which shows the experimental result which measured the conveyance pressure at the time of conveying a developing agent in each merge part of the conventional merge part, the merge part in the 1st Embodiment of this invention, and the merge part in the 2nd Embodiment of this invention. FIG. It is the schematic which shows the joint member used for the 3rd Embodiment of this invention. It is the schematic which shows the rotary feeder used for the 4th Embodiment of this invention. 1 is a schematic view of an image forming apparatus to which an embodiment of the present invention can be applied.

  FIG. 1 is a schematic view of a developing apparatus employing an embodiment of the present invention. In the figure, reference numeral 10 denotes a casing constituting a developing device as a developing unit, and a two-component developer in which toner and a carrier are mixed is stored in the casing 10. Further, inside the casing 10, as shown in FIG. 2, two conveying screws 11, 12 having spiral fins and a developing roller 13 are rotatably arranged. The transport screw 11 transports the developer from the front to the back in FIG. 2, a part of which is adsorbed on the surface of the developing roller 13 by magnetic force, and the adsorbed developer is uniformly uniformed by the doctor blade 14. By subsequently contacting a photoconductor (not shown), the electrostatic latent image on the photoconductor is developed to form a toner image.

  The developed developer is transported from the back to the front of FIG. 2 by the transport screw 12 and discharged from a discharge hole (not shown) formed at the downstream end of the transport screw 12 in the developer transport direction, and then the circulation path 30. To the developer storage section 40. A toner density detection unit (not shown) is provided at the most downstream position in the developer conveyance direction of the conveyance screw 12, and toner is replenished from the toner cartridge 20 based on a signal generated from the toner concentration detection unit. Toner replenishment is performed by rotating a shaftless screw provided in the toner replenishment path 21 by the motor 28, and the toner replenishment path 21 is disposed immediately before the developer storage section 40.

  In the developer storage section 40, the developer after development and the replenished toner become a developer having an appropriate toner concentration and charge amount. The developer in the developer storage section 40 passes through a discharge port disposed in the lower part thereof and is sent into a rotary feeder 50 disposed below the developer outlet. As shown in FIG. 3, the rotary feeder 50 has a rotatable rotor 51 therein, and the developer flowing in from the upper inflow port 50a is sent downward by the rotation of the rotor 51 and is provided below. It is discharged from the discharge port 50b. The discharged developer is returned to the casing 10 again through the circulation path 33 as the transfer pipe by the air flow sent from the air pump 60 as the air flow generation means via the circulation path 31.

  As shown in FIG. 3, the developer storage section 40 has a space 40a for storing the developer, and a screw 43 and a stirring blade 44 that are rotationally driven by a motor 45 are disposed in the space 40a. Yes. In the space 40a, the collected developer and the newly replenished toner are lifted upward by the screw 43. At this time, the developer about to fall by its own weight and the developer lifted by the screw 43 are rubbed. As a result, the toner is dispersed and a charge amount is imparted to the toner. The agitating blade 44 agitates the developer by its rotation and imparts a charge amount to the developer.

  As shown in FIG. 3, the rotary feeder 50 has a rotor 51 having a plurality of blades rotatably inside the stator 55, and a 0.01 between the tip of the blades of the rotor 51 and the inner surface of the stator 55. It has a clearance of about 0.2 mm. The developer from the developer storage section 40 is sequentially filled into the rotary feeder 50 by the rotation of the rotor 51 and then falls by its own weight, and the developer falls into the joint member 52 provided below the rotary feeder 50. As a result, the air flow from the air pump 60 reaches the merging portion 34.

  Here, a joint portion between the developer and the air flow will be described. FIG. 4 shows a conventional merging portion 32 of the developing device described above. In the configuration shown in FIG. 4, the developer dropped vertically downward from the rotary feeder 50 is conveyed after its direction is changed by 90 degrees by the pressure and velocity energy of the airflow flowing in the horizontal direction. Also, in the configuration shown in FIG. 3, the cross section of the air supply port 56 of the joint member 52 that constitutes the transport path of the air flow generated from the air pump 60 is narrower than the discharge port 50b of the rotary feeder 50, and therefore, shown in FIG. The shape is narrowed down like this. This also applies to the configuration shown in FIG. Due to these two factors, a pressure loss different from the load originally required for transporting the developer occurs in the merging portion 32, and the developer having an appropriate toner concentration and charge amount is efficiently and stably supplied to the developing portion. It becomes impossible to supply.

  Therefore, in the developing device 70 adopting the first embodiment of the present invention, as shown in FIG. 3, the line segment 15 indicating the direction of the air flow from the air pump 60 and the flow direction of the developer discharged from the rotary feeder 50. The shape of the joint member 52 having an air supply port 56 disposed below the rotary feeder 50 is set so that the angle α formed on the upstream side of the merging portion 34 with each of the line segments 16 indicating Yes.

  With the above-described configuration, the developer and the air flow smoothly merge to reduce pressure loss. This is because the efficiency is improved when the air flows merge from substantially the same direction without hindering the speed of the developer falling due to its own weight. As the pressure loss is reduced, the differential pressure with the developer reservoir 40 is reduced, so that airflow leakage is reduced and the air pressure required for developer transport is reduced, so that the developer and airflow are smooth. The developer can be mixed and conveyed to obtain a stable developer conveyance amount, and energy efficiency can be improved. Furthermore, since the direction of the air flow is downward, the air flow is less likely to flow upward and less likely to leak to the developer storage section 40, and waste of the air flow can be prevented.

  FIG. 6 shows a joint member 53 used in the second embodiment of the present invention. The joint member 53 is used in place of the joint member 52 in the first embodiment, and other configurations are the same as those in the first embodiment.

  Similarly to the joint member 52, the joint member 53 has an air supply port 56 for taking in an air flow generated from the air pump 60 via the circulation path 31, and the shape of the air supply port 56 is the same as that of the joint member 52. The angle formed between the flow of the developer discharged from the rotary feeder 50 and the air flow from the air pump 60 on the upstream side of the merging portion 34 is an acute angle. Further, the joint member 53 has a discharge port 57 for discharging the mixture of the developer and the air flow from the junction 34 through the circulation path 33, and the shape of the discharge port 57 is the development discharged from the rotary feeder 50. The flow of the mixture of the agent and the air flow is configured to be linear on the upstream side and the downstream side of the joining portion 34.

  With the above-described configuration, the flow of the mixture of the developer and the air flow does not change at the exit portion from the merging portion 34. Therefore, the mixture flows smoothly, pressure loss is further reduced, and the developer and the air flow are smooth. As a result, the developer transport amount is further stabilized and the energy efficiency can be improved.

  FIG. 7 is a diagram of the conventional merging portion 32 shown in FIG. 4, the merging portion 34 in the first embodiment shown in FIG. 3, and the merging portions 34 in the second embodiment shown in FIG. 6. The experimental result which measured the conveyance pressure at the time of conveying a developing agent is shown. In this experiment, a pressure gauge was installed between the air pump and the air supply port, and the pressure during developer conveyance was measured for each air flow velocity. From FIG. 7, it can be seen that in the first embodiment and the second embodiment of the present invention, the developer transport pressure is lower than in the conventional configuration.

  FIG. 8 shows a joint member 54 used in the third embodiment of the present invention. The joint member 54 is used in place of the joint member 52 in the first embodiment, and other configurations are the same as those in the first embodiment.

  Similarly to the joint member 52, the joint member 54 has an air supply port 56 for taking in an air flow generated from the air pump 60 via the circulation path 31, and the shape of the air supply port 56 is the same as that of the joint member 52. The angle formed between the flow of the developer discharged from the rotary feeder 50 and the air flow from the air pump 60 on the upstream side of the merging portion 34 is an acute angle. Further, the joint member 53 has a discharge port 58 for discharging the mixture of the developer and the air flow from the joining portion 34 via the circulation path 33, and the shape of the discharge port 58 is the development discharged from the rotary feeder 50. The flow of the mixture of the agent and the air flow is configured to be curved so as to smoothly join the air flow sent from the air pump 60.

  With the above-described configuration, since there is no corner in the flow path through which the mixture of developer and air flow discharged from the merging portion 34 circulates, the mixture flows smoothly and pressure loss is further reduced. And the air flow are smoothly mixed and transported, the developer transport amount can be further stabilized, and the energy efficiency can be improved. In the example shown in FIG. 8, the air supply port 56 and the discharge port 58 are arranged on the same straight line, but the air supply port 56 and the discharge port 58 are on the same straight line as in the first embodiment. The structure which is not located may be sufficient.

  FIG. 9 shows a rotary feeder 59 used in the fourth embodiment of the present invention. The rotary feeder 59 is used in place of the rotary feeder 50 and the joint member 52 in the first embodiment, and other configurations are the same as those in the first embodiment.

  Similar to the rotary feeder 50, the rotary feeder 59 has a rotor 51 having a plurality of blades inside the stator 55 so as to be rotatable, and an inlet 59a into which the developer flows is provided at the upper part from the lowermost part. A discharge port 59b for discharging the developer is provided at each shifted position. The rotary feeder 59 has a structure having the same function as the joint members 52, 53, and 54 shown in the above embodiments, and an air supply port 56 and a discharge port 57 are provided below the rotary feeder 59. Are integrally formed.

  With the above-described configuration, the rotary feeder 59 has the discharge port 59b at a position shifted from its lowermost portion, so that the height of the rotary feeder 59 can be made lower than that of the conventional configuration, and development can be achieved by reducing the height. The size of the apparatus can be reduced. In the example shown in FIG. 9, the air supply port 56 and the discharge port 57 are arranged on the same straight line, but the air supply port 56 and the discharge port 57 are on the same straight line as in the first embodiment. The structure which is not located may be sufficient.

  FIG. 10 shows an image forming apparatus that can employ the developing device of the present invention. This image forming apparatus is a multifunction machine having a copying function and other functions such as a printer function and a facsimile function, and the copying function, the printer function, and the facsimile function can be switched by a switching key provided in an operation unit (not shown). It is configured. The image forming apparatus includes a main body 100, a writing unit 118 disposed on the top of the main body 100, an image reading unit 106 disposed on the top of the writing unit 118, and an ADF 101 disposed on the top of the image reading unit 106. Have.

  The operation during the copying function will be described below. When a document bundle is placed on the document table 102 of the ADF 101 with the image surface facing up, and a start key on an operation unit (not shown) is pressed, the lowest document is fed by the feeding roller 103 and the feeding belt 104. It is fed to a predetermined position on the contact glass 105. After the image information is read by the image reading unit 106, the document on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107. When the document detection sensor 109 detects that the next document exists on the document table 102, the document is fed onto the contact glass 105 as described above.

  The image reading unit 106 performs line scanning on the image information of the original in the sub-scanning direction while irradiating the original on the contact glass 105 with the two lamps 128, and uses the reflected light as image data as the first mirror 129 and the second mirror. 130, the light is reflected in a predetermined direction by the third mirror 131, and sent to the CCD 133 via the lens unit 132 for reducing and forming an image. The image data read by the image reading unit 106 is sent to a writing unit 118 having a laser light emitting device 134, an fθ lens 135, a reflecting mirror 136, and the like via an image processing unit (not shown), and the photosensitive drum 117 is read by the writing unit 118. An electrostatic latent image corresponding to the original image is formed on the top.

  Inside the main body 100, a photosensitive drum 117, a developing device having a casing 10, a fixing unit 121, a paper discharge unit 122, first to third paper supply devices 110, 111, and 112, a vertical conveyance unit 116, and the like are disposed. Has been. The photosensitive drum 117 is uniformly charged by a charger (not shown) and then exposed to light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image is developed by a developing device and is toner. An image is formed.

  A conveyor belt 120 is disposed below the photosensitive drum 117. The conveyance belt 120 also serves as conveyance means and transfer means for transfer paper as a recording medium. A transfer bias is applied from a power supply (not shown), and the transfer paper from the vertical conveyance unit 116 is conveyed at a constant speed with the photosensitive drum 117. The toner image on the photosensitive drum 117 is transferred to the transfer paper. The toner image transferred to the transfer paper is fixed on the transfer paper in the fixing unit, and the transfer paper on which the image is fixed is discharged onto the paper discharge tray 123 via the paper discharge unit 122. The photosensitive drum 117 is cleaned by a cleaning unit (not shown) after the toner image is transferred, and is prepared for the next image formation.

  The paper discharge unit 122 includes a reversing unit 125 that feeds the transfer paper from the middle thereof by a pair of transport rollers 124, an image forming side transport path 126 that transports the transfer paper reversed by the reversing unit 125 to the vertical transport unit 116 side, and a reversal. A double-sided conveyance path having a paper discharge conveyance path 127 and the like for returning the transferred transfer paper to the paper discharge unit 122 again is provided. With this double-sided conveyance path, images can be formed on both sides of the transfer paper, or discharged onto the paper discharge tray 123 with the image-formed side down.

  When selected, the first to third paper feeding devices 110, 111, and 112 feed transfer sheets stacked on the first tray 113, the second tray 114, and the third tray 115, respectively. The fed transfer paper is conveyed to a position where it comes into contact with the photosensitive drum 17 by the vertical conveyance unit 116.

  In this image forming apparatus, image data from the outside is input to the writing unit 118 instead of the image data from the image processing means during the printer function, and an image is formed on the transfer paper by the image forming means. During the facsimile function, the image data from the image reading unit 106 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit, and is sent to the writing unit 118 instead of the image data from the image processing means. As a result of the input, the image forming means operates to form an image on the transfer paper.

  In the above-described configuration, an example in which a multifunction peripheral is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited thereto, and other image forming apparatuses such as a copying apparatus, a printer, a facsimile machine, and a plotter. In addition, the present invention is applicable.

10 Development section (casing)
15 Direction of air flow 16 Flow direction of developer 33 Transfer pipe (circulation path)
34 Confluence 40 Developer storage 50, 59 Rotary feeder 58 Discharge port 60 Air flow generating means (air pump)
70 Developer α angle

Japanese Patent No. 3733496 Japanese Patent No. 3349286 JP-A-11-143196

Claims (4)

A developing unit for storing the developer therein; a developer storing unit that is provided outside the developing unit and that stores the developer sent to the developing unit; and a rotary that discharges the developer from the inside of the developer storing unit. A feeder, a transfer pipe connecting the developing section and the rotary feeder, and an air flow generating means for generating an air flow in the transfer pipe to transfer the developer discharged from the rotary feeder to the developing section. In the developing device
A developer unit that merges the developer flow discharged from the rotary feeder and the air flow generated by the air flow generation unit; and the developer flow and the air flow on the upstream side of the merge unit, respectively. The developer is discharged from the rotary feeder to the merge portion so that the air flow is an acute angle and the air flow is linear on the upstream side and the downstream side of the merge portion. A developing device characterized by falling linearly . The developing device according to claim 1,
The developing device is characterized in that the shape of the discharge port for discharging the developer from the rotary feeder is formed in a curved shape so that the discharged developer smoothly joins the air flow . The developing device according to claim 1 ,
The developing device is characterized in that the developer discharging position from the rotary feeder is provided at a position below the rotary feeder and shifted from the lowest position . An image forming apparatus comprising the developing device according to claim 1 .

Images