JP2008015262A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing a developer from staying partially in a developer storage chamber and forming an image high in quality. <P>SOLUTION: The developing device 8 includes a stirring conveyance means whuich is disposed in the developer storage chamber 8a and conveys the developer containing a toner and a carrier while being stirred. The stirring conveyance means has spiral vanes 81a and 82a formed from a plurality of screws disposed adjacent and parallel to one another so that their conveying directions are opposite to each other. The wall faces of the developer storage chamber 8a have bearing parts 8h for supporting the shafts 81b and 82b of the screws. In each transfer part 8f that transfers developer to the adjacent screw and in each area immediately in front of the bearing part at the downstream end of the corresponding spiral vane in the direction of developer conveyance, a conical rectifying member projecting in opposite conveying direction is disposed concentrically with the corresponding shaft. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device provided in an image forming apparatus such as a facsimile machine, a copying machine, or a printer (including these multifunction machines), and more particularly to a developing device using a two-component developer (toner and carrier). .

  As the image forming apparatus as described above, a pair of conveyance rollers (registration roller pair) arranged in the middle of a sheet conveyance path, feeding out sheets (recording sheets) one by one from a sheet feeding unit provided with a sheet cassette or the like. Then, the toner is fed from the developing device to the photosensitive drum of the electrophotographic recording unit and the transfer roller, and the toner image on the surface of the photosensitive drum is transferred to the recording paper. And an electrophotographic image recording unit which is discharged after being fixed.

  As a developer of the image forming apparatus, a two-component developer (hereinafter referred to as a developer) composed of a toner and a carrier is used, and the toner is charged by rubbing the toner and the carrier, and the charged toner Thus, the toner image is formed.

  In the developing device provided in such an image forming apparatus, when the toner image is formed, only the charged toner is electrostatically adhered and supplied to the photosensitive drum, so that the toner supplied to the photosensitive drum is supplied. And a function to replenish the same amount of toner as needed, and is configured to give a predetermined amount of charge to the toner while stirring and mixing the replenished toner and the remaining developer. . At this time, in order to form a homogeneous and high-quality image, the replenished toner and the remaining developer are well mixed with stirring, and the developer mixed with stirring in the developer storage chamber is made uniform. Need to keep.

  However, in the case of stirring and mixing using a plurality of screws as described above, the developer transport is performed near the downstream side of the developer transport direction of each screw, that is, before the portion where the developer is transferred to the adjacent screw. The developer transported from the upstream side of the direction and the developer pushed back by the reverse spiral blade provided at the screw end are mixed, so that the flow of the developer becomes worse and stays on the other hand. In the portion, the developer is not retained by the screw but is transported toward the downstream side in the developer transport direction, which causes a problem that the amount of the developer is not uniform in the longitudinal direction of the screw.

Such a problem occurs particularly when the amount of the developer is non-uniform in the longitudinal direction of the screw located on the side of the developing roller that supplies toner to the photosensitive drum, and the amount of toner supplied to the developing roller is non-uniform. As a result, there is a problem that a homogeneous and high-quality image is not formed.
That is, as described above, in the process in which the toner is transported from the screw located on the developing roller side to the developing roller, in the portion where the developer is transferred to the adjacent screw, the toner stays and is increased and delivered. Since the toner does not stay in the portion, the toner is transported toward the developing roller with a small amount of toner. Therefore, the toner supplied to the developing roller is not uniform in the longitudinal direction, and a uniform and high-quality image is not formed. .

  In addition, if the developer transported to the downstream end portion in the developer transport direction stays, the developer enters the clearance between the screw bearing portions or adheres to the screw shaft near the bearing portion. When the screw rotates in this state, the developer is rubbed and solidified by the rotation, which affects the rotation of the screw shaft. Further, there is a problem that the staying developer leaks out of the developer storage chamber from the gap of the screw bearing portion.

By the way, the following patent document is mentioned as what devised the shape of the blade | wing of a screw in the developing device in which a some screw is arranged in parallel in this way, and a developer is stirred and mixed and conveyed with a screw.
Patent Document 1 below discloses a developing device in which conical blades are provided at both ends of a screw.
Further, in Patent Document 2 below, a disc-shaped restricting member is provided at the downstream end portion in the developer conveyance direction, and a conical stay prevention is provided to prevent the developer from staying between the restricting member and the bearing. A developing device provided with a member is disclosed.
JP-A-5-197283 Japanese Patent Laid-Open No. 11-109734

However, the developing device described in Patent Document 1 pulverizes the toner lump mixed in the toner replenished in the developer storage chamber from the toner replenishment section by the conical blade, and the toner without the toner lump is uniformly mixed. In the same manner as in Patent Document 1, it does not prevent the developer from staying in the vicinity of the downstream side in the developer transport direction, that is, before the above-described delivery portion. .
Further, the retention preventing member described in Patent Document 2 is provided between the regulating member provided at the end of the spiral shaft and the wall of the developing housing (developer housing chamber), and has been transported. Overcoming the plate-shaped restricting member that stops the developer, the developer staying between the restricting member and the wall surface of the development housing is stirred by the stay preventing member to prevent the developer from coagulating, and the spiral shaft can be rotated at high speed. It is possible. Therefore, it does not prevent the developer from staying in the vicinity of the downstream side in the developer conveyance direction, that is, before the above-described delivery portion.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a developing device that prevents partial stagnation of the developer in the developer accommodating chamber and makes the developer uniform in the developer accommodating chamber. Yes.

  A developing device according to a first aspect of the present invention is a developing device including an agitating and conveying means provided in a developer accommodating chamber and conveying the developer containing toner and a carrier while stirring. Comprises a plurality of screws provided with spiral blades and arranged adjacent to each other so that the conveying directions are opposite to each other, and a bearing portion for supporting the screw shaft is provided on the wall surface of the developer accommodating chamber. A conical shape that is convex in the anti-conveying direction at the transfer part that delivers the developer to the adjacent screw immediately before the bearing part at the downstream end of the spiral blade in the developer conveying direction. The straightening member is provided concentrically with the shaft.

  In the present invention, the maximum diameter of the rectifying member may be the same as that of the spiral blade. Moreover, a partition wall is provided between the plurality of screws, respectively, and the partition wall may be formed low at the transfer portion.

According to the developing device of the present invention, since the conical rectifying member that is convex in the anti-conveying direction is provided at the downstream end of the spiral blade in the developer conveying direction, The action promotes the transfer of the developer to the adjacent screw, and it is possible to smoothly transfer the developer to the adjacent screw without deteriorating and staying in the flow of the developer before the transfer portion.
Further, this makes it possible to make the developer uniform in the developer accommodating chamber, so that the toner adhering to the developing roller does not become non-uniform, and as a result, when the developing device is provided in the image forming apparatus, This can contribute to providing a uniform and high-quality image.

Furthermore, if the maximum diameter of the rectifying member is configured to be the same as that of the spiral blade, the transfer to the adjacent screw is more effectively promoted, and the rectifying member is overcome and the bearing portion and the shaft are moved. It is possible to reduce the amount of the developer that enters the space, and to prevent the developer from leaking out of the developer storage chamber through the gap between the bearing portions. Further, since the rectifying member is concentric with the spiral blade and has the same maximum diameter, it is not necessary to change the shape of the developer accommodating chamber particularly at the location where the rectifying member is disposed.
If partition walls are provided between the plurality of screws, and the partition walls are formed low in the transfer section, the plurality of screws can sufficiently supply the developer at the portion where the partition walls are provided. In addition to being conveyed while being stirred and mixed, since the partition wall is formed low in the transfer section, it becomes possible to smoothly convey the developer to the adjacent screw without deteriorating and staying in the flow of the developer. .

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an example of an image forming apparatus employing the developing device of the present invention, FIG. 2 is a plan view showing an embodiment of an agitating / conveying means provided in the developing device, and FIG. 2 is a longitudinal sectional view taken along line XX in FIG. 2, and FIG. 4 is an enlarged sectional view of a Y portion in FIG.

  The image forming apparatus A shown in FIG. 1 is illustrated by taking a printer including an electrophotographic recording unit as an example. However, the image forming apparatus A is not limited thereto, and is not limited thereto. Needless to say, it may be a so-called multi-function machine or the like having both of the above. In the figure, the apparatus main body 1 of the image forming apparatus A includes a recording paper (paper) feeding unit 2, an electrophotographic image recording unit 3, and a printed recording paper discharging unit 4 in this order. Layered in the height direction. The recording paper feed unit 2 includes a detachable paper feed cassette 2a capable of accumulating and storing a large number of recording papers, and a separation paper feed roller (pickup roller) 2b installed at the front end of the paper feed cassette 2a. , And a separation pad 2c that elastically contacts the peripheral surface of the separation paper feed roller 2b. The paper feed unit 2 is not limited to the single-stage cassette system as shown in the figure, but can be a multi-stage cassette system or an optional cassette system.

  The image recording unit 3 includes a charging unit 6, an exposure unit 7 including an LED, a developing unit 8, a transfer roller 9, and a residual toner removing unit 10 arranged in this order around the photosensitive drum 5, and a process unit It is composed of a fixing device 11 on the downstream side. These process units, except for the exposure device 7 and the transfer roller 9, are a drum unit 50 in which the photosensitive drum 5, the charger 6 and the residual toner removing device 10 are integrated, an agitating / conveying means and feeding paddle 83, and a developing roller 84, which will be described later. The drum unit 50 and the developing unit 80 can be attached to and detached from the apparatus main body 1 individually from the front side or in a state where both are connected by some connecting means. It is attached to. It is also possible to make all the process parts except the exposure device 7 and the transfer roller 9 collectively a process unit. Here, the front side of the apparatus main body 1 refers to the front side of the sheet in FIG. 1, and the back side refers to the back side.

The developing device 8 shown in the figure is a developing device using a two-component developer as described above. The developer containing chamber 8a contains a developer composed of toner and a carrier, and a plurality of screws (augers). Here, the developer is supplied to the developing roller 84 biased by the feeding paddle 83 while being stirred and conveyed by the two first screws 81 and the second screw 82 arranged side by side. (See FIG. 2).
A toner sensor 8b comprising a magnetic sensor is attached to the outer surface of the developer accommodating chamber 8a in which the first screw 81 is disposed, and the toner concentration (mixing ratio of toner and carrier) in the developer accommodating chamber 8a is always detected. The A toner hopper 12 is installed at a position away from the process unit including the developing device 8, and when the toner sensor 8b detects that the toner concentration in the developer storage chamber 8a is reduced, a screw conveyor (pipe) The toner is supplied into the developer storage chamber 8a through the toner supply port 8c through the screw 13). In the toner hopper 12, an agitator 12a and a feeding screw 12b are disposed. Incidentally, the agitation and conveying means constituted by the first screw 81 and the second screw 82 provided in the developing device 8 will be described in detail later.

  On the downstream side of the fixing device 11, a switching gate 4a, a discharge roller pair 4b, and a discharge tray 4c are connected in series, and the discharge unit 4 is configured by these. A registration roller pair 14 is disposed in the vicinity of the upstream side of the process section, and the recording paper (paper) separated and fed out from the paper feed cassette 2a one by one by the action of the separation paper feed roller 2b and the separation pad 2c. Is registered by the registration roller pair 14 and introduced into the mating portion between the photosensitive drum 5 and the transfer roller 9. The surface of the photosensitive drum 5 is uniformly charged by the charger 6 while rotating in the direction of the arrow in FIG. 1, and an optical image based on the image information is irradiated to the surface of the photosensitive drum 5 by the exposure device 7. An electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is formed by changing the potential of the light irradiated portion and maintaining the potential of other portions depending on the characteristics of the photoconductor on the surface of the photosensitive drum 5.

  The electrostatic latent image is sequentially developed by the developing device 8 to which a bias is applied, and reaches a mating portion between the photosensitive drum 5 and the transfer roller 9 as a toner image. During this development, toner is attracted to the photosensitive drum 5 due to a potential difference with the developing unit 8 at a portion where the potential has changed due to light irradiation, so that a black portion is formed. As a result, a black and white toner image based on the image information is formed. The registration roller pair 14 is rotationally driven under registration control so that the recording paper is introduced into the mating portion in synchronization with the toner image on the surface of the photosensitive drum 5.

  A bias is applied to the transfer roller 9, and the recording paper is nip-conveyed while being paired with the photosensitive drum 5 and being rotationally driven in the direction indicated by the arrow (with respect to the photosensitive drum 5). The toner image is transferred onto the recording paper. The toner remaining on the surface of the photosensitive drum 5 is removed and collected by the residual toner removing device 10. The recording paper onto which the toner image has been transferred is introduced into the fixing device 11 and fixed as a permanent image, and then the switching gate 4a is pushed up and discharged onto the discharge tray 4c through the discharge roller pair 4b. This series of recording paper feeds rises substantially vertically (vertically) immediately after feeding from the paper feed cassette 2a, and the discharge roller pair 4b makes a U-turn in a direction of about 180 degrees from the feed direction from the paper feed cassette 2a. This is done along the main feeding path P. With such a layout configuration, the entire apparatus can be made compact.

  The image forming apparatus A shown in the figure has a double-sided recording function, and circulates and joins the main feeding path P upstream of the registration roller pair 14 from the mounting position of the switching gate 4a of the main feeding path P. A reverse feeding path P1 is formed. The discharge roller pair 4b can be rotated forward and backward, and the reverse feed path P1 is provided with a pair of transport rollers 15 and 16, and when performing double-sided recording, single-sided recording was performed as described above. When the recording paper is conveyed along the main feed path P and the trailing edge of the recording paper reaches the discharge roller pair 4b, the discharge roller pair 4b temporarily stops and nips the trailing edge of the recording paper. Next, the discharge roller pair 4b is reversed, and the recording paper is conveyed from the rear end thereof by the conveying roller pairs 15 and 16 through the reverse feeding path P1, and joins the main feeding path P to reach the registration roller pair 14. It is registered by the registration roller pair 14 and is again introduced into the mating portion of the photosensitive drum 5 and the transfer roller 9 to record the back surface thereof. The recording paper recorded on both sides is then discharged onto the discharge tray 4c along the main feeding path P as described above.

  The image forming apparatus A shown in the figure is further provided with a manual sheet feeding function, and a manual tray 17 that can be opened and closed is attached to the side of the apparatus body 1. When not in use, the manual feed tray 17 is closed as shown by a two-dot chain line in FIG. 1, and can be opened and closed by a handle 17a. A separation feed roller 17b and a separation pad 17c are arranged in a resilient contact state at the front end of the manual feed tray 17, and a manual feed path P2 that joins the main feed path P is further downstream. It is connected continuously.

  When image recording is performed using the manual feed tray 17, the handle 17a is opened to open the manual feed tray 17, a recording paper is set thereon, and the manual feed roller 17b is operated by a start operation as appropriate. . The recording paper on the manual feed tray 17 is separated and fed out one by one by the action of the separation paper feed roller 17b and the separation pad 17c, is conveyed through the manual feed path P2, and joins the main feed path P. . Thereafter, the image is registered by the registration roller pair 14 and introduced into the mating portion between the photosensitive drum 5 and the transfer roller 9 to perform recording. When double-sided recording is performed on the manual recording sheet, the recording sheet is conveyed through the reverse feeding path P1 by the reverse rotation of the discharge roller pair 4b, and the back side recording is performed as described above. The recording paper on which recording has been completed is discharged onto the discharge tray 4c by the discharge roller pair 4b.

  Next, the stirring and conveying means will be described in detail with reference to FIGS. 2 is a plan view showing the stirring and conveying means of the developing device 8 of the image forming apparatus A in FIG. 1, FIG. 3 is a longitudinal sectional view taken along the line XX in FIG. 2, and FIG. 4 is an enlarged view of the Y portion in FIG. It is sectional drawing. In the developing device 8 of the present embodiment, as shown in FIG. 2, the first screw 81 and the second screw 82 are arranged side by side so as to be adjacent to each other and the transport direction is opposite. A feeding paddle 83 and a developing roller 84 are further disposed adjacent to the screw 82. Each of the screws 81 and 82 includes spiral blades 81a and 82a formed with a predetermined interval and shape.

  A first screw 81 disposed on the side that receives toner replenishment from the toner replenishing port 8 c, and a second screw 82 disposed on the side that supplies toner to the developing roller 84 via the feeding paddle 83. Thus, the agitating and conveying means is configured, and the downstream ends of the screws 81 and 82 in the developer conveying direction serve as transfer portions 8f that deliver the developer to the adjacent screws 82 and 81, respectively. The upstream end is a transfer portion 8g to which the developer is transferred from the transfer portion 8f.

  As described above, in the developer accommodating chamber 8a, the two first screws 81 and the second screw 82 are provided side by side, and the bearing portions 8h provided on the wall surface of the developer accommodating chamber 8a respectively The shafts 81b and 82b of the screws 81 and 82 are supported, and a conical rectifying member 85 that is convex in the counter-transport direction is provided on the downstream end of the spiral blades 81a and 82a in the developer transport direction. It is provided concentrically with 82b. As shown in FIG. 3, a partition wall 8d is provided between the first screw 81 and the second screw 82, whereby the developer storage chamber 8a is partitioned into two, and the partition The portions corresponding to the transfer portion 8f and the transfer portion 8g at both ends of the wall 8d are separated into two developer storage chambers by a low wall portion 8e formed by cutting lower than the other partition walls 8d. 8a is connected.

  The first screw 81 and the second screw 82 are configured so that the developer is conveyed in opposite directions (in the first screw 81, from left to right in FIG. 2 (in the direction of arrow A in FIG. 2), The screw 82 rotates from right to left (in the direction of arrow C in FIG. 2), and the toner consisting of toner and carrier is sufficiently agitated while being circulated and conveyed to charge the toner by friction.

  The toner sensor 8b detects that the toner concentration in the developer storage chamber 8a has decreased, and the toner replenished from the toner replenishing port 8c is first replenished to the first screw 81 side. It is mixed with the developer accommodated by the rotational drive, and stirred and conveyed (in the direction of arrow A in FIG. 2). The developer conveyed to the transfer part 8f on the first screw 81 side gets over the low wall part 8e and is conveyed to the transfer part 8g on the second screw 82 side (in the direction of arrow B in FIG. 2). The first screw 81 is stirred and transported in the opposite direction (direction of arrow C in FIG. 2). A part of the developer is supplied to the developing roller 84 biased by the feeding paddle 83 as necessary, while the developer conveyed to the transfer unit 8f on the second screw 82 side is here. Is circulated and transferred to the transfer portion 8g on the first screw 81 side (in the direction of arrow D in FIG. 2), and such a flow is repeated.

With reference to FIG. 4, the flow of the developer in the transfer section 8f will be described in detail.
As shown in FIG. 4, since the side surface of the conical rectifying member 85 is formed in a tapered shape, the developer conveyed to the transfer unit 8f by the action of the conical surface accompanying the rotation of the screw 82 is sequentially It is conveyed from the transfer unit 8f to the transfer unit 8g (in the direction of arrow E in FIG. 4). That is, the rectifying member 85 applies a component of the conveying force to the developer that has reached the rectifying member 85, the developer flow is guided in the direction of arrow E, and the conveyance to the transfer unit 8f and the transfer unit 8g is performed. As a result, the developer does not accumulate in front of the transfer unit 8f. Here, the inclination angle of the rectifying member 85 having a conical shape is preferably about 45 ° from the relationship between the inductivity of the developer and the component force of the conveyance force.
Although the developer flow on the first screw 81 side has been described based on the example of FIG. 4, the transfer unit 8 f on the second screw 82 side can also be configured in the same manner and has the same function. An effect can be obtained.

According to this, the developer can be smoothly transferred from the transfer portion 8f of each screw 81, 82 to the transfer portion 8g, and the developer can be made uniform in the developer storage chamber 8a. As a result, the amount of developer becomes uniform in the longitudinal direction of the screw 82 on the developing roller 84 side, and the amount of toner supplied to the developing roller 84 via the feeding paddle 83 is also in the longitudinal direction of the developing roller 84. Uniform and uniform and high-quality images can be formed.
Further, the developer is transported while being sufficiently stirred and mixed by the screws 81 and 82 in the portion where the partition wall 8d is provided, and the transfer portion 8f and the transfer portion 8g are formed lower than the partition wall 8d. Since the low wall portion 8g is used, the developer can be smoothly delivered without deteriorating or staying in the flow of the developer.
Note that the developer stays in the transfer section 8f on the first screw 81 side in the same manner as described above when transported from the transfer section 8f on the first screw 81 side to the transfer section 8g on the second screw 82 side. Of course, it can be conveyed to the transfer part 8g on the second screw 82 side.

  Since the rectifying member 85 facilitates the transfer to the adjacent screws 81 and 82 as described above, the developer that gets over the rectifying member 85 and enters between the bearing portion 8h and the shafts 81b and 82b. It is possible to suppress the amount of the developer from leaking out of the developer storage chamber 8a from the gap of the bearing portion 8h. Further, since the developer does not stay in the bearing portion 8h, the rotation of the shafts 81b and 82b is not affected.

Further, as shown in FIG. 4, if the maximum diameter of the rectifying member 85 is configured to have the same diameter Z as that of the spiral blade 82a, the developer conveyed to the rectifying member 85 has the same diameter as the spiral blade 82a. It is effective to push back to the side, and the rectifying member is concentric with the spiral blade and the maximum diameter is the same diameter, so the shape of the developer containing chamber is changed especially at the place where the rectifying member is arranged There is no need to do.
Here, the size of the diameter of the rectifying member 85 can be appropriately designed. However, as described above, at least the same diameter as that of the spiral blades 81a and 82a or more is desirable.

  The configuration of the developer storage chamber 8a, the first screw 81, the second screw 82, the spiral blades 81a, 81b, etc. is not limited to the illustrated example, and in the illustrated example, two screws are used. Although the disposed configuration is described, it is needless to say that the present invention is not limited to this and can be applied to a configuration in which three or more screws are disposed.

1 is a longitudinal sectional view illustrating an example of an image forming apparatus in which a developing device of the present invention is employed. It is a top view which shows one Embodiment of the stirring conveyance means provided in the developing device. FIG. 3 is a longitudinal sectional view taken along line XX in FIG. 2. It is an expanded sectional view of the Y section in FIG.

Explanation of symbols

80 Developing Unit 8 Developing Device 8a Developer Storage Chamber 81, 82 Screw (Agitating and Conveying Means)
81a, 82a Spiral blades 81b, 82b (screw) shaft 8d Partition wall 8e Low wall portion 8f Transfer portion 8g Transfer portion 8h Bearing portion 85 Rectifying member A Image forming apparatus

Claims (3)

A developing device provided with a stirring and conveying means provided in the developer containing chamber and conveying the developer containing toner and carrier while stirring,
The stirring and conveying means comprises a plurality of screws provided with spiral blades, adjacent to each other, and arranged in parallel so that the conveying direction is opposite,
A bearing portion that supports the shaft of the screw is provided on the wall surface of the developer storage chamber,
A conical rectifying member that is convex in the anti-conveying direction is provided in a transfer portion that is a portion immediately before the bearing portion at the downstream end portion in the developer conveying direction of the spiral blade and delivers the developer to an adjacent screw. A developing device provided concentrically with the shaft. The developing device according to claim 1,
2. A developing device according to claim 1, wherein the rectifying member has a maximum diameter equal to that of the spiral blade. In the developing device according to claim 1 or 2,
A developing device, wherein a partition wall is provided between each of the plurality of screws, and the partition wall is formed low at the transfer portion.

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