JP2013054086A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the temperature of a developer low even when a developer containing toner and a carrier is circulated and conveyed.SOLUTION: A developing device comprises: a developing container for accommodating a developer containing toner and a carrier; a developing chamber which comprises a developer carrier for carrying a developer and a first rotatable stirring member for stirring and conveying a developer and is formed in the developing container; a stirring chamber which comprises a second rotatable stirring member for stirring and conveying a developer in which a path for circulating the developer between the developing chamber is approximately horizontally configured and is formed in the developing container; a developer supply port which is formed in the developing container for supplying a developer containing at least toner; and an air duct which is extended in an axial direction of the first stirring member and the second stirring member by installing an intake port and an exhaust port of cooling air and is abutted and arranged on the developing container, in which the intake port and the developer supply port are disposed in opposite sides in an axial direction of the developer carrier.

Description

  The present invention relates to a developing device and an image forming apparatus used in an electrophotographic image forming apparatus such as a laser beam printer and a copying machine.

  In the developing device, when the temperature of the developer rises due to stirring or the like, the chargeability of the developer deteriorates, and image defects such as a reduction in image density occur. In particular, when the temperature of the developer rises above its melting point, the developer melts and fuses to the developing roller or the developing blade, resulting in non-uniform developer coating on the developing roller, such as uneven density and image streaks. There arises a problem that an image defect occurs and a rotational load on the developing roller increases.

  Therefore, conventionally, a method of forming a flow of cooling air in the vicinity of the developing device and cooling the entire developing device with this cooling air has been adopted (Patent Document 1).

  In addition, in a conventional electrophotographic image forming apparatus, especially a multicolor image forming apparatus that forms a chromatic image, a two-component developing system that uses a mixture of nonmagnetic toner and a magnetic carrier as a developer is widely used. It's being used. The two-component development method has advantages such as image quality stability and device durability compared to other currently proposed development methods, while developer deterioration, especially carrier deterioration, due to long-term durability. Was inevitable. For this reason, with the long-term use of the multicolor image forming apparatus, an operation of changing the developer is required, which causes an increase in service cost and running cost.

  Conventionally, a method for solving such a problem has been proposed. For example, there is a method of attaching a replaceable developer supply cartridge to a developing device attached to a developing device, and supplying a developer including toner and a carrier and discharging the developer (Patent Document 2). .

JP2008-129562 JP-A-6-308829

  When the developer including the toner and the carrier is circulated in the developing container of the developing device, the developer self-heats due to friction or the like. For this reason, the conventional cooling method has a problem that the cooling performance is insufficient.

  An object of the present invention is to keep the temperature of a developer low even when the developer containing toner and a carrier is circulated and conveyed.

  A typical feature of the present invention for achieving the above-described object is that a developer container containing a developer containing toner and a carrier, a developer carrier that carries the developer, and a rotatable first carrier that agitates and conveys the developer. A developing chamber formed in the developing container, and a path through which the developer circulates between the developing chamber is configured substantially horizontally, and is a rotatable second that agitates and conveys the developer. An agitating chamber formed in the developing container having an agitating member; a developer replenishing port formed in the developing container for replenishing a developer containing at least toner; an intake port and an exhaust port for cooling air; A developing device comprising: an air passage extending in an axial direction of the first stirring member and the second stirring member and disposed in contact with the developing container; and the developer replenishing port In the axial direction of the developer carrier, Characterized in that it is arranged on the opposite side, respectively Re.

  With the above configuration, even when the developer containing toner and carrier is circulated and conveyed, the temperature of the developer can be kept low.

FIG. 2 is an explanatory diagram of an image forming apparatus. Sectional drawing of a developing device. The horizontal sectional view of a developing device. The perspective view from the upper right front of a developing device. The perspective view from the lower right rear of a developing device.

  FIG. 1 is an explanatory diagram of the image forming apparatus, and is a cross-sectional view along the sheet conveyance direction. The image forming apparatus of this embodiment is a color electrophotographic printer as an example. In this embodiment, the color electrophotographic printer is simply referred to as “printer”.

(Image forming device)
The printer 1 shown in FIG. 1 is provided with four image forming stations 10 (10a, 10b, 10c, 10d) which are image forming stations. Each image station has the same configuration. For this reason, in the following description, the subscripts “a” to “d” will be omitted as appropriate in the drawings or the description.

  The printer 1 includes a feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control unit (not shown). Next, each unit will be described in detail.

  In the image forming unit 10, a photosensitive drum 11 (11a, 11b, 11c, 11d) as an image carrier is pivotally supported at its center and is driven to rotate. In each image forming unit 10, the photosensitive drum 11 is exposed to a light beam modulated in accordance with a recording image signal by the optical system 13 (13 a, 13 b, 13 c, 13 d). For example, a laser beam is used as the light beam. As a result, an electrostatic latent image corresponding to the recorded image signal is formed on the photosensitive drum 11.

  Further, the electrostatic latent image is visualized by the developing devices 14 (14a to 14d) each containing developer of four colors such as yellow, cyan, magenta, and black. The visualized visible image is transferred to the intermediate transfer belt 31 (intermediate transfer member) in the primary transfer region T (Ta, Tb, Tc, Td).

  To supply developer to the developing devices 14a to 14d, toner cartridges 16 (16a, 16b, 16c, 16d) connected to the developing device 14 are disposed. In the figure, the toner cartridge 16 and the developing device 14 are illustrated as being independent of the image forming unit 10, and the toner is transferred from the toner cartridge 16 to the developing device 14 through a conveyance path (not shown). Is supplied.

  On the photosensitive drum 11, a cleaning device 15 (15 a, 15 b, 15 c, 15 d) is disposed on the downstream side of the primary transfer region T of the image forming unit 10. The cleaning device 15 scrapes off the toner that is not transferred to the transfer material but remains on the photosensitive drum 11 to clean the drum surface.

  By the process described above, image formation with each toner is sequentially performed.

  Next, a description will be added in accordance with the image forming operation.

  When the image forming operation start signal is issued, first, the cassette 21 in which the transfer material P suitable for the size of the recorded image is stored is selected. Then, the transfer material P is sent out one by one from the cassette 21 by the pickup roller 22 that contacts the uppermost transfer material P stored in the cassette 21.

  The transfer material P is guided between the feeding guides 24 by the feeding roller pair 23 and conveyed to the registration roller pair 25. At that time, the registration roller pair 25 is stopped, and the leading edge of the paper hits the nip portion N of the registration roller pair 25.

  Thereafter, the registration roller pair 25 starts rotating in accordance with the timing at which the image forming unit 10 starts image formation. The rotation start timing of the registration roller pair 25 is set so that the transfer material P and the toner image primary-transferred from the image forming unit 10 onto the intermediate transfer belt 31 exactly coincide with each other in the secondary transfer region Te. Has been.

  On the other hand, when an image forming operation start signal is issued, the image forming unit 10 forms a toner image formed on the photosensitive drum 11 (11a) that is the most upstream in the rotation direction of the intermediate transfer belt 31 by the process described above. The primary transfer is performed on the intermediate transfer belt 31. This primary transfer position is referred to as a primary transfer region T (Ta).

  The primarily transferred toner image is conveyed to the next primary transfer region T (Tb). In this case, image formation is delayed by a time during which the toner image is conveyed between the image forming portions, and the next toner image is transferred with the resist aligned on the previous image. Thereafter, the same process is repeated, and eventually the four color toner images are primarily transferred onto the intermediate transfer belt 31.

  Thereafter, when the transfer material P enters the secondary transfer region Te and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the transfer material P. Then, the four color toner images formed on the intermediate transfer belt 31 by the above-described process are transferred onto the surface of the transfer material P.

  Thereafter, the transfer material P is accurately guided to the nip portion of the fixing roller pair 41 by the conveyance guide 43. The toner image is fixed on the surface of the transfer material P by the heat of the fixing roller pair 41 and the pressure of the nip. Thereafter, the transfer material P is conveyed by the discharge roller 44 and the discharge roller 45, and the transfer material P is discharged out of the printer 1. Note that the transfer material P can be discharged to the upper discharge tray 47 by switching the discharge conveyance guide 46.

  When a single color image is to be obtained, a single color visible image is primarily transferred from the specific image forming unit 10 (for example, 10d) onto the intermediate transfer belt 31, and thereafter a single color image is processed through a process similar to that for forming a full color image. Get.

(Developer)
Next, the developing device 14 will be described with reference to FIGS. FIG. 2 is a sectional view of the developing device. FIG. 3 is a horizontal sectional view of the developing device. FIG. 4 is a perspective view from the upper right front of the developing device. FIG. 5 is a perspective view from the lower right rear of the developing device.

  As shown in FIG. 2, the developing device 14 includes a developing container 100 that contains a developer therein, and a developer carrier 101 at an opening facing the photosensitive drum 11. As a result, the developer stored in the developing container 100 is supplied to the photosensitive drum 11 by the developer carrier 101.

  The interior of the developing container 100 is separated into a developing chamber 103 and a stirring chamber 105 by a partition wall 106. The developing chamber 103 and the stirring chamber 105 are formed with a path substantially horizontally. Each of the developing chamber 103 and the stirring chamber 105 has a screw for transporting the developer, and they are arranged substantially horizontally. The screw in the developing chamber 103 is called a rotatable developing screw 102 (first stirring member) that stirs and conveys the developer, and the screw in the stirring chamber 105 is called a stirring screw 104 (second stirring member). With this configuration, the developer is circulated in the developing container 100.

  As shown in FIG. 3, the developing chamber 103 and the agitating chamber 105 that are partitioned by the partition wall 106 in the developing container 100 are arranged on the front side of the developing device 14 on the front side of the developing device 14 and on the front side of the developing device. It communicates with a certain second communication part 108B.

  The developing screw 102 conveys the developer in the developing chamber 103 and supplies / recovers the developer to / from the developer carrier 101. The stirring screw 104 conveys the developer supplied from the developer supply port 107 shown in FIG. 4 and the developer collected from the developing chamber 103 while stirring in the stirring chamber 105. By the action of the developing screw 102 and the agitating screw 104, the toner concentration of the developer is made uniform, and the developer is conveyed from the first series passage portion 108A to the developing chamber 103. Further, the developer is supplied to the developer carrier 101 by the developing screw 102.

  As shown in FIG. 4, the developer supply port 107 is arranged on the upstream side of the stirring screw 104. Here, the developer (supplemented developer) to be replenished to the developer replenishing port 107 includes toner and a carrier, and the toner is contained in a 5% weight ratio with respect to the developer. On the other hand, the developer in the developer container 100 is about 92% weight ratio of the carrier to the developer. The weight ratio of the developer is not limited to this.

  When the amount of developer in the developer container 100 increases, a developer discharge port 109 is provided to discharge excess developer little by little to the outside of the developer container 100. The developer discharge port 109 is disposed on the downstream side of the developing screw 102. The developer supply port 107 and the developer discharge port 109 are both disposed on the front side of the developing device as shown in FIG.

  When the developer itself circulates in the developing container 100 with the above-described configuration, the developer self-heats. This is a major factor in the heat generation of the developer.

  In order to prevent this heat generation, as shown in FIG. 5, in this embodiment, an air passage 110 is formed in contact with the developing container 100 and extending in the axial direction of the developing screw 102 and the stirring screw 104. Then, the cooling air W is caused to flow through the air passage 110 as indicated by an arrow. Thereby, the developer is cooled.

  Specifically, an intake port 112 through which the cooling air W is sucked in the air passage 110 is provided on the first series passage portion 108A side. Air outside the machine is sucked from the air inlet 112 by a cooling fan (blower member) (not shown). The intake port 112 for the cooling air W is provided on the rear side of the developing device opposite to the front side of the developing device where the developer supply port 107 and the developer discharge port 109 are provided. On the other hand, the exhaust port 113 of the air passage 110 is provided on the second communication portion 108B side.

  A heat sink 114 shown in FIG. 2 is provided on the cooling air passage surface of the developing container 100 to enhance the cooling effect. The cooling effect of the heat sink 114 increases as the thermal conductivity increases. For this reason, in this embodiment, the aluminum material with high heat conductivity is employ | adopted.

  The effects of the developer configured as described above will be described in detail.

  As described above, the main cause of the heat generation source of the developer is self-heating caused by the circulation of the developer itself. Here, in the developing device 14 of the present embodiment, the developer density in the developing container 100 is substantially constant. For this reason, when cooling with cooling air is not performed, the developer temperature in the developing container 100 is substantially constant at any position in the developing container.

  Generally, the amount of heat transfer increases as the temperature difference between the cooling side and the cooling side increases. In this embodiment, cooling is performed by flowing cooling air W in the developer conveyance direction (the axial direction of the two screws). Here, as described above, the developer is at the same temperature at any position in the developer container 100, but the cooling air W gradually increases in temperature by heat exchange, so the temperature difference between the cooling air W and the developer is Gradually get smaller. Then, the heat exchange amount on the downstream side of the cooling air W becomes smaller than the heat exchange amount on the upstream side. As a result, the developer temperature on the downstream side of the cooling air is higher than that on the upstream side.

  In the case of a developer container configured to replenish and discharge the developer as in this embodiment, in order to keep the temperature of the developer in the developer container 100 as low as possible, the developer discharge is related to the developer discharge. It is preferable that a relatively high temperature developer is discharged from the outlet 109. On the other hand, regarding the replenishment of the developer, it is preferable to replenish the replenishment developer having a relatively low temperature with respect to the developer having a relatively high temperature. This is because the heat exchange amount increases as the temperature difference increases as described above.

  Therefore, in the present embodiment, first, a configuration in which the developer container and the developer are cooled by flowing the cooling air W in the developer transport direction (transport screw axial direction) in the developer container, And a structure for discharging. A developer supply port 107 and a developer discharge port 109 are provided on the downstream side of the cooling air W. Thereby, the heat exchange of the developer is efficiently performed as described above, and the temperature of the developer in the developing container 100 can be kept low.

  In the present embodiment, a developing device having a developer discharge port has been described. However, even in a developing device without a discharge port, the supply temperature can be kept low by providing the replenishment port on the downstream side of the cooling air W. it can. However, in this case, the replenished developer is a 100% toner developer.

DESCRIPTION OF SYMBOLS 1 ... Printer 10 ... Image forming part 14 ... Developing apparatus 100 ... Developing container 101 ... Developer carrier 102 ... Developing screw 103 ... Developing chamber 104 ... Agitation screw 105 ... Agitation chamber 106 ... Septum 107 ... Developer supply port 109 ... Development Agent outlet 110 ... Air passage 112 ... Inlet

Claims (4)

A developer container containing a developer including toner and carrier;
A developing chamber formed in the developing container, comprising: a developer carrying member that carries the developer; and a rotatable first stirring member that stirs and conveys the developer;
A stirring chamber formed in the developing container, comprising a rotatable second stirring member configured so that a path for circulating the developer between the developing chamber and the developer chamber is substantially horizontal, and stirs and conveys the developer;
A developer replenishing port formed in the developer container to replenish the developer containing at least toner;
A cooling air intake port and an exhaust port, and an air path extending in the axial direction of the first stirring member and the second stirring member and disposed in contact with the developing container;
In a developing device having
The developing device, wherein the intake port and the developer supply port are arranged on opposite sides in the axial direction of the developer carrier. The stirring chamber is formed with a developer discharge port for discharging excess developer,
The developing device according to claim 1, wherein the intake port and the developer discharge port are disposed on opposite sides in the axial direction of the developer carrier.   The developing device according to claim 1, wherein a heat sink is disposed in the air path. An image carrier;
An image forming apparatus comprising the developing device according to claim 1, wherein a developer is supplied to the image carrier.

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