JP2019090985A - Developing device and image forming apparatus - Google Patents

Abstract

To provide a developing device that can make uniform the distribution of dropping amount of developer dropping from a conveyance path.SOLUTION: The angle θ1 of a surface 114d3 for pushing out a developer 8 of a spiral blade 114d2 of a conveyance screw 114d is set, such that a force in an upper direction applied to the developer 8 from the surface 114d3 for pushing out the developer 8 of the spiral blade 114d2 of the conveyance screw 114d for conveying the developer 8 inside a conveyance path 114c for conveying the developer 8 along the axial direction of a developing sleeve 114a, becomes less than a force required for the developer 8 to get over a regulation wall 114e for regulating the amount of developer dropping from the conveyance path 114c.SELECTED DRAWING: Figure 7

Description

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

  In an electrophotographic image forming apparatus such as a copying machine and a printer, an electrostatic latent image is formed on the surface of a photosensitive member, and a developing agent supplies a developer to the photosensitive member to develop the electrostatic latent image. Thereafter, the toner image formed on the photosensitive member by development is transferred to a sheet such as paper, and fixed by a fixing device. In such an image forming apparatus, the developer is replenished from the developer supply container to the developing device by the amount of the developer consumed in the image formation.

  With the downsizing of the image forming apparatus, the developing device is also miniaturized, and the storage capacity of the developer tends to be reduced. As a result, the developer storage unit (hereinafter referred to as "the hopper") is often provided separately. In this case, it is ideal that the developer is supplied from the hopper to the developing device uniformly along the axial direction of the developer carrier.

  In the developing container of the developing device, a conveyance path is provided which extends along the axial direction of the developer carrier (developing sleeve). A supply port is provided at the upstream end of the transport path in the developer transport direction. Conveying means (hereinafter referred to as “conveying screw”) is provided for conveying the developer replenished from the supply port from the upstream to the downstream of the conveying path.

  The developer transported by the transport screw falls from the transport path along the developer transport direction of the transport path. A regulating wall having an upper edge surface for regulating the amount of falling of the developer is provided along the transport path. The upper edge surface of the restriction wall is inclined so that the height is lowered from the upstream to the downstream in the developer transport direction of the transport path in order to supply the developer substantially uniformly in the axial direction of the developer carrier. doing.

  A hopper is disposed above the supply port. Then, in order to make the amount of developer in the developing container constant, the developer is replenished in accordance with the signal from the developer remaining amount sensor. By intermittently replenishing the developer, it is possible to prevent uneven developer replenishment in the longitudinal direction inside the developing container due to the image ratio of the document.

  The developer supplied from the hopper to the supply port is transported along the transport path by the transport screw provided in the transport path. The developer transported along the transport path is fed over the upper edge surface of the regulating wall sequentially into the stirring chamber. Then, after the new and old developers are stirred by the stirring member provided in the stirring chamber, the developer is carried on the developer carrier. While being conveyed by the rotation of the developer carrier, the developer layer regulation member makes a thin layer coat and is developed on the photoreceptor by a predetermined development method.

  The conveyance screw is controlled to supply the developer supplied from the hopper substantially uniformly along the conveyance path. The developer supplied from the hopper is dropped little by little from the upstream side of the transport path, and the developer remaining without dropping is transported downstream by the transport screw and dropped at the transport destination. By repeating this, the developer replenished from the hopper is supplied with a specific distribution in the longitudinal direction. This distribution is called "fall amount distribution".

  If the drop amount distribution becomes uneven in the longitudinal direction of the transport path, the toner physical properties in the developing container become uneven. For example, when developer replenishment is positively performed on the upstream side in the transport direction of the transport path, a large amount of old developer is deposited on the downstream side. As a result, the old developer on the downstream side is deteriorated in durability and a desired charge amount can not be obtained, resulting in poor development such as low density.

  Also, in the new developer positively replenished on the upstream side, a large amount of external additives for promoting frictional charging and external additives for improving fluidity are added to the surface, and the external additives are supplied to the developer At the same time, there is a tendency for the amount of free external additives to be released upstream. The free external additive strongly adheres to the developer carrier, causing problems such as that the desired developer can not be carried.

  In order to solve this problem, in Patent Document 1, the upper edge surface of the restriction wall is inclined so that the height decreases from the upstream to the downstream of the transport path. Furthermore, the surface width of the upper edge surface is formed wider as the upper edge surface of the restriction wall becomes lower. For this reason, the height of the developer stacked on the surface width of the upper edge surface of the regulating wall is formed to be higher as the regulating wall becomes lower.

  Since the wall is formed by the developer itself transported in the transport path, the developer is transported downstream while falling over the wall of the developer itself. By adopting such a configuration, even when the transportability of the developer in the rotational direction changes due to the use environment, the height of the wall of the developer itself formed on the upper edge surface changes, and the drop amount distribution is elongated. It becomes possible to control uniformly by direction.

JP, 2011-150318, A

  However, in the cross-sectional shape of the conveyance screw (hereinafter referred to as a comparative example) of Patent Document 1, the force for conveying the developer along the conveyance path when the conveyance screw rotates and the upward force for the developer to get over the regulation wall. Occurs. The upward force applied to the developer by the rotation of the transport screw varies with the degree of cohesion of the developer. For this reason, there has been a problem that the amount by which the developer gets over the regulation wall becomes uneven due to the difference in the degree of aggregation of the developer.

  The present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a developing device capable of making the distribution of the amount of falling developer falling from the conveyance path uniform.

  A representative configuration of a developing device according to the present invention for achieving the above object is a transport path for transporting the developer along the axial direction of the developer carrier, and a transport for transporting the developer in the transport path. And a regulating wall provided along the transport path to regulate the amount of developer falling from the transport path, the upward direction in which the surface of the transport means for pushing out the developer gives to the developer The angle of the surface is set to be less than the force required for the developer to get over the regulation wall.

  According to the present invention, it is possible to make uniform the amount distribution of the developer falling from the transport path.

FIG. 1 is a cross-sectional explanatory view showing the configuration of an image forming apparatus provided with a developing device according to the present invention. FIG. 2 is a block diagram showing a configuration of a control unit of the image forming apparatus provided with the developing device according to the present invention. FIG. 2 is an exploded perspective view showing a configuration of a developing device according to the present invention. FIG. 2 is a cross-sectional explanatory view showing the configuration of a developing device according to the present invention. FIG. 6 is a perspective view showing a configuration of a regulating wall provided in a conveyance path of the developing device. 5 is a flowchart showing developer replenishment control of the image forming apparatus provided with the developing device according to the present invention. (A) is cross-sectional explanatory drawing which shows the structure of the conveyance screw of this embodiment. (B) is plane explanatory drawing which shows the force which the helical blade of the conveyance screw of this embodiment gives to a developing agent. It is a figure which shows the amount distribution of falling of the developing agent along the conveyance path of the image development apparatus concerning this invention. (A) is cross-sectional explanatory drawing which shows the force which the helical blade of the conveyance screw of a comparative example gives to the developer with low aggregation degree. (B) is cross-sectional explanatory drawing which shows the force which the helical blade of the conveyance screw of a comparative example gives to the developer with high aggregation degree. It is a figure which shows the amount fall amount of a developing agent along the conveyance path of the image development apparatus of a comparative example.

  An embodiment of an image forming apparatus provided with a developing device according to the present invention will be specifically described with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described in the following embodiments are appropriately changed according to the apparatus configuration to which the present invention is applied and various conditions. Therefore, the scope of the invention is not intended to be limited thereto.

<Image forming apparatus>
The configuration of an image forming apparatus provided with the developing device according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus 2 provided with a developing device 114 according to the present invention. FIG. 2 is a block diagram showing a configuration of a control unit of the image forming apparatus 2 provided with the developing device 114 according to the present invention. The image forming apparatus 2 shown in FIG. 1 is an example of an electrophotographic image forming type copying machine. The developer 8 (toner) used in the image forming apparatus 2 is a magnetic one-component developer according to a pulverizing method, and the particle diameter of the developer is about 5 μm to 10 μm, and the developer charge amount is -5 μC / g to It is about -20 μC / g.

  An image forming apparatus 2 shown in FIG. 1 includes a scanner unit 9, an image forming unit 10, and a sheet deck 11. The scanner unit 9 provided on the upper portion of the image forming apparatus 2 is configured as an image reading unit that reads image information of a book document or the like. The image forming unit 10 provided at the central portion of the main body of the image forming apparatus 2 is configured as an image forming unit that forms a toner image on the sheet 12 (recording material). A sheet deck 11 provided below the image forming unit 10 accommodates a sheet 12 serving as a recording material.

<Scanner unit>
The scanner unit 9 includes a scanning system light source 201, a platen glass 202, an original pressure plate 203 which can be opened and closed with respect to the main body of the image forming apparatus 2, a mirror 204, a light receiving element 205 having a photoelectric conversion element, and the image processing unit 13 shown in FIG. And so on. A document pressure plate 203 shown in FIG. 1 is pivoted open with respect to the main body of the image forming apparatus 2, and a book document such as a book or a sheet-like document is placed on a platen glass 202 with the document surface facing downward. Thereafter, the original pressure plate 203 is pivoted closed with respect to the main body of the image forming apparatus 2, and the back side of the original is pressed to be set in a stationary state.

  When the reading start key provided on the operation panel 14 shown in FIG. 2 is pressed, the scanning system light source 201 scans the lower part of the platen glass 202 in the direction of arrow A in FIG. 1 to read the image information of the document surface. The image information of the document read by the scanning system light source 201 is processed by the image processing unit 13 shown in FIG. 2, converted into an electric signal, and transmitted to the laser scanner 111 serving as the exposure unit provided in the image forming unit 10. Be done.

  The image forming apparatus 2 functions as a copying machine when the processing signal of the image processing unit 13 is input to the laser scanner 111 of the image forming unit 10, and as the printer when an output signal from an external device such as a personal computer is input. Function. The image forming apparatus 2 also functions as a facsimile machine if it receives signals from other facsimile machines or transmits signals from the image processing unit 13 to other facsimile machines.

<Sheet conveying unit>
Below the image forming unit 10, a feeding unit U1 that constitutes feeding means is provided. The feeding unit U1 is configured to have a lower sheet feeding tray 1a and an upper sheet feeding tray 1b. The sheet deck 11 is also provided with a feeding unit U2. The feeding unit U2 is also configured to have a lower sheet feeding tray 1a and an upper sheet feeding tray 1b. In the present embodiment, a total of four feeding trays including two feeding units U1 and U2 are provided so as to be mountable. The upper feed unit U1 is detachably attached to the main body of the image forming apparatus 2, and the lower feed unit U2 is detachably attached to the sheet deck 11.

  A sheet 12 such as a cut sheet accommodated in the lower sheet feeding tray 1a and the upper sheet feeding tray 1b of each of the sheet feeding units U1 and U2 is fed out by a pickup roller 3 constituting a feeding means. Then, the sheet 12 is separated and fed one by one by the cooperation of the feed roller 4 and the retard roller 5, and then the leading end of the sheet 12 strikes the nip portion of the registration roller 106 which is nipped and conveyed by the conveyance rollers 104 and 105 and stopped. It is applied to correct skew. Thereafter, the sheet is nipped and conveyed by the registration roller 106 and is fed to the image forming unit 10 in synchronization with the image forming operation.

  A manual feed tray 6 is provided on the side surface of the image forming apparatus 2 main body. The sheet 12 placed on the manual feed tray 6 is fed out by the manual feed roller 7 and joined to the conveyance path 15, and is pinched and conveyed by the conveyance roller 105, and the leading end of the sheet 12 is nipped by the registration roller 106. The part is abutted to correct skew. Thereafter, the sheet is nipped and conveyed by the registration roller 106 and is fed to the image forming unit 10 in synchronization with the image forming operation.

<Image Forming Unit>
The image forming unit 10 includes a photosensitive drum 112 serving as an image carrier, an image writing optical unit 113, a charging roller 116 serving as a charging unit, a developing device 114 serving as a developing unit, and a transfer roller 115 serving as a transfer unit. It is done. The surface of the photosensitive drum 112 rotating in the clockwise direction in FIG. 1 is uniformly charged by the charging roller 116. A laser beam 111a corresponding to image information emitted from a laser scanner 111 serving as an exposure unit is scanned and irradiated by the image writing optical unit 113 onto the surface of the uniformly charged photosensitive drum 112, and the surface of the photosensitive drum 112 is irradiated. An electrostatic latent image is formed. The developer 8 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 112 by the developing device 114 to form a toner image.

  The sheet 12 nipped and conveyed by the registration roller 106 in synchronization with the rotation of the photosensitive drum 112 reaches a transfer nip N formed by the photosensitive drum 112 and the transfer roller 115. At this time, a transfer bias is applied to the transfer roller 115 from the transfer bias power supply provided in the high voltage control unit 16 shown in FIG. Thus, the toner image formed on the surface of the photosensitive drum 112 is transferred to the first surface of the sheet 12.

  The sheet 12 on which the toner image is transferred to the first surface is conveyed through the conveyance path 117 and conveyed to the fixing device 118 serving as a fixing unit. While the sheet 12 on which the toner image is transferred is nipped and conveyed by the heating roller and the pressure roller provided in the fixing device 118, the toner image is fixed to the sheet 12 while being heated and pressurized. The sheet 12 on which the toner image is fixed is conveyed by the conveyance roller 17 and then discharged onto the discharge tray 120 by the discharge roller 119.

  When printing on the front and back sides of the sheet 12, the discharge roller 119 reversely rotates when the rear end portion in the traveling direction of the sheet 12 passes the branch point 207. Thus, the sheet 12 is guided to the double-sided tray 121. The sheet 12 nipped and conveyed by the conveyance roller 104 joins the conveyance path 15, is conveyed by the conveyance roller 105, and the front and rear surfaces are reversed.

  Thereafter, the leading end of the sheet 12 in the traveling direction is abutted against the stopped nip portion of the registration roller 106 to correct the skew. Then, the toner image is conveyed to the transfer nip N by the registration roller 106 as described above, and the toner image is transferred to the second surface (rear surface) of the sheet 12. Thereafter, the toner image is fixed by the fixing device 118 and conveyed by the conveyance roller 17, and then the sheet is discharged onto the discharge tray 120 by the discharge roller 119. An image forming apparatus 2 as a copying machine shown in FIG. 1 includes a developing device 114 in an image forming unit 10.

  The image forming unit 10 is controlled by the image forming control unit 18 shown in FIG. The image formation control unit 18 has ROMs (Read Only Memory; read only memory) 301 a to 301 c storing various control programs necessary for the image formation operation. Further, a CPU (Central Processing Unit; central processing unit) 302 serving as a control unit that controls the entire operation of the image forming apparatus 2 is provided. The CPU 302 has non-volatile memory and volatile memory for storing various data relating to the image forming operation, and executes various control programs.

  The CPU 302 is bus-connected to various actuators 303 including an image forming control unit 18 involved in an image forming operation, a fixing temperature control unit 19 and a high voltage control unit 16 via a predetermined interface (I / O).

<Developer>
Next, the configuration of the developing device 114 will be described using FIGS. 3 to 5. FIG. 3 is an exploded perspective view showing the configuration of the developing device 114 according to the present invention. FIG. 4 is a cross-sectional explanatory view showing the configuration of the developing device 114 according to the present invention. FIG. 5 is a perspective view showing the configuration of the restriction wall 114e provided in the conveyance path 114c.

  As shown in FIGS. 3 and 4, the developing sleeve 114a as a developer carrier can be rotated at the front end (the lower side of FIG. 3, the left side of FIG. 4) of the developing container 114h provided in the developing device 114. Provided in At a rear end portion (upper side in FIG. 3, right side in FIG. 4) of the developing container 114h, a conveying path 114c having a substantially arc-like cross shape for conveying the developer 8 along the axial direction of the developing sleeve 114a is provided.

  At the upstream end of the transport path 114c in the longitudinal direction (left and right direction in FIG. 3), a supply port 114b to which the hopper 25 shown in FIG. 4 is connected is provided at the upper side. The developer (toner) 8 is supplied from the hopper 25 shown in FIG. 4 into the transport path 114c through the supply port 114b.

  At the edge of the front end side (the lower side in FIG. 3, the left side in FIG. 4) of the conveyance path 114c provided in the developing container 114h of the developing device 114, the regulating wall 114e rises upward along the conveyance path 114c. It is provided. The upper edge surface 114f of the regulating wall 114e is a drop amount of the developer 8 falling into the stirring chamber 114i along the transport direction T (left direction in FIGS. 3 and 5) of the developer 8 in the transport path 114c. Control the developer amount). The upper edge surface 114f of the regulating wall 114e is, as shown in FIG. 5, from the upstream side (right side in FIGS. 3 and 5) of the transport direction T for transporting the developer 8 along the transport path 114c (FIG. 3). And inclined toward the left in FIG.

  The surface width W of the upper edge surface 114f in the front-rear direction (left and right direction in FIG. 4) orthogonal to the transport direction T of the developer 8 is directed toward the transport direction T of the developer 8 (left direction in FIGS. 3 and 5). It is formed to expand. As shown in FIG. 5, the upper edge surface 114f of the regulating wall 114e is high on the upstream side (right side in FIG. 5) of the transport direction T of the developer 8 in the transport path 114c, and goes toward the downstream side (left side in FIG. 5). And the slope is low. Further, the upper edge surface 114f is formed such that the surface width W becomes wider as the height becomes lower.

  As shown in FIGS. 3 and 4, in the transport path 114c, a transport screw 114d serving as transport means is rotatably provided. The developer 8 in the transport path 114c (in the transport path) goes from the upstream side (right side in FIG. 5) of the developer 8 in the transport path 114c in the transport path 114c to the downstream side (left side in FIG. 5) by the transport screw 114d. It is transported. At this time, the developer 8 falls into the stirring chamber 114i while forming a wall of the developer 8 itself on the upper edge surface 114f of the regulation wall 114e.

  As shown in FIG. 4, in the agitating chamber 114i, an agitating member 114g which can rotate around a rotating shaft 114g1 is provided. The developer 8 falls into the stirring chamber 114i beyond the upper edge surface 114f of the regulation wall 114e by the rotation of the conveyance screw 114d from the conveyance path 114c. The developer 8 dropped into the agitating chamber 114i is stirred and conveyed by the agitating member 114g which rotates in the clockwise direction of FIG. 4 around the rotation shaft 114g1 and supplied into the developing chamber 114j provided with the developing sleeve 114a. .

<Developer supply control>
Next, replenishment control of the developer 8 will be described with reference to FIG. FIG. 6 is a flow chart showing developer replenishment control of the image forming apparatus 2 provided with the developing device 114 according to the present invention. In step S1 of FIG. 6, the power of the main body of the image forming apparatus 2 is turned on, and in step S2, a normal image forming operation is started. Then, in step S3, the developing device 114 is driven, and the developer 8 is consumed according to the image formation.

  Next, in step S4, the CPU 302 serving as control means detects the presence or absence of the developer 8 in the developing device 114 based on the detection result of the sensor 114s provided in the stirring chamber 114i. When the presence of the developer (toner) is detected by the sensor 114s in step S4, the process proceeds to step S5. In step S5, the CPU 302 detects the presence or absence of the developer 8 in the hopper 25 shown in FIG. 4 based on the detection result of the sensor 20 shown in FIG. 2 provided in the hopper 25 shown in FIG.

  In step S4, when the sensor 114s detects the absence of the developer (toner) in the developing device 114, the process proceeds to step S6. In step S6, the CPU 302 drives and controls the hopper motor 21 shown in FIG. 2 to rotationally drive the transport screw 24 provided in the hopper 25 shown in FIG. 4 to feed the hopper 25 shown in FIG. The developer (toner) 8 is supplied into the transport path 114c.

  In step S5, when the sensor 20 detects no developer (toner) in the hopper 25 shown in FIG. 4, the process proceeds to step S7. In step S7, the CPU 302 rotationally drives the toner bottle motor 22 shown in FIG. 2 provided in the toner bottle 26 shown in FIG. 4 to supply the developer 8 from the toner bottle 26 shown in FIG. 4 into the hopper 25.

<Conveying screw>
Inside the transport path 114c, as transport means for transporting the developer 8 from the upstream side (right side in FIG. 3) of the transport direction T of the developer 8 in the transport path 114c to the downstream side (left side in FIG. 3) A conveying screw 114d is provided. The conveying screw 114d is provided with a single spiral blade 114d2 on the outer peripheral surface of the rotation shaft 114d1.

<Helical blade>
Next, the configuration of the spiral blade 114d2 provided on the outer peripheral surface of the rotation shaft 114d1 of the conveying screw 114d will be described with reference to FIG. FIG. 7A is a cross-sectional explanatory view showing the configuration of the conveyance screw 114d of the present embodiment. FIG. 7B is an explanatory plan view showing a force applied to the developer 8 by the spiral blade 114d2 of the conveying screw 114d of the present embodiment.

  The angle θ1 of the surface 114d3 of the developer 8 of the spiral blade 114d2 of the conveyance screw 114d with respect to the direction of the rotation axis 114d1 of the conveyance screw 114d of this embodiment (left and right direction in FIGS. 7A and 7B) is considered. The angle θ1 is set such that the developer 8 does not have a force in the direction in which the developer 8 gets over the upper edge surface 114f of the restriction wall 114e by the rotation of the spiral blade 114d2.

  That is, the upward force applied to the developer 8 by the surface 114 d 3 of the spiral blade 114 d 2, which is the surface of the conveyance screw 114 d (conveying means), which pushes out the developer 8 is taken into consideration. The angle θ1 is set such that the upward force is less than the force necessary for the developer 8 to get over the upper edge surface 114f of the regulating wall 114e. The angle θ1 is an angle θ1 of the surface 114d3 of the developer 8 of the spiral blade 114d2 of the conveyance screw 114d which pushes out the developer 8 with respect to the direction of the rotation axis 114d1 of the conveyance screw 114d (left and right direction in FIGS. 7A and 7B).

  The angle θ1 is such that the angle θ1 on the non-obtuse angle at which the surface 114d3 intersects with the conveyance direction (the left and right direction in FIGS. 7A and 7B) of conveying the developer 8 along the conveyance path 114c is 70 ° or more , 90 ° or less. The angle θ1 in the present embodiment is 90 °. At this time, the upward force applied to the developer 8 by the surface 114 d 3 that pushes out the developer 8 of the rotating spiral blade 114 d 2 is zero. As a result, the falling amount of the developer 8 falling over the upper edge surface 114f of the regulating wall 114e from the transport path 114c and falling into the stirring chamber 114i is dominated by the difference in height due to the inclination of the upper edge surface 114f of the regulating wall 114e. .

  The conveying screw 114d is interlocked with the driving of the developing device 114, and the developer 8 in the conveying path 114c shown in FIG. 3 is moved along the axial direction of the developing sleeve 114a by rotation of the conveying screw 114d. Transport in the direction of arrow T. As shown in FIG. 7B, in the spiral blade 114d2 of the conveyance screw 114d of the present embodiment, the force in the direction in which the developer 8 gets over the upper edge surface 114f of the regulating wall 114e by the rotation of the spiral blade 114d2 is I do not have it.

  Here, the behavior of the developer 8 in the middle of conveyance in the conveyance path 114c is considered. Stirring without breaking the wall by the developer 8 by the force of the developer 8 exceeding the height of the wall by the developer 8 itself formed on the upper edge surface 114f of the regulation wall 114e of the conveyance path 114c falling off by gravity It falls into the chamber 114i.

Comparative Example
Next, the configuration of the conveying screw 114d of the comparative example will be described using FIG. FIG. 9A is a cross-sectional explanatory view showing a force applied by the spiral blade 114d2 of the conveyance screw 114d of the comparative example to the developer 8 having a low degree of cohesion G. FIG. FIG. 9B is a cross-sectional explanatory view showing a force applied by the spiral blade 114d2 of the conveyance screw 114d of the comparative example to the developer 8 having a high degree of cohesion G.

  The angle θ2 on the non-obtuse angle at which the surface 114d3 of the spiral blade 114d2 that pushes out the developer 8 with respect to the direction of the rotation axis 114d1 of the conveyance screw 114d of the comparative example shown in FIGS. It is set. For this reason, when the spiral blade 114d2 of the comparative example rotates, as shown in FIG. 9B, the developer 8 gets over the upper edge surface 114f of the regulation wall 114e by the surface 114d3 of pushing out the developer 8 of the spiral blade 114d2. Receive force F in the direction.

  The developer 8 is replenished from the hopper 25 shown in FIG. 4 through the supply port 114b shown in FIG. 3 into the conveyance path 114c. Here, the state in which the aggregation degree G (flowability) of the developer 8 has a central value is taken into consideration. At this time, the developer 8 in the conveyance path 114c passes over the upper edge surface 114f of the regulating wall 114e provided on the stirring chamber 114i side of the conveyance path 114c by the rotation of the conveyance screw 114d and drops into the stirring chamber 114i. At this time, the developer 8 drops into the agitating chamber 114i so as to exhibit a substantially uniform distribution in the longitudinal direction of the developing sleeve 114a.

<Drop amount distribution of developer of comparative example>
FIG. 10 is a view showing a drop amount distribution of the developer 8 along the conveyance path 114c of the developing device 114 of the comparative example. As shown in FIG. 10, the longitudinal direction of the regulating wall 114e is divided into five regions R1 to R5 from the upstream to the downstream of the transport direction T of the developer 8 transported in the transport path 114c. Then, the amount of developer dropped in the regions R1 to R5 in the stirring chamber 114i by measuring the amount of the developer 8 in the conveyance path 114c over the upper edge surface 114f of the regulation wall 114e by the rotation of the conveyance screw 114d was measured.

<Measurement Condition of Fall Amount Distribution of Developer of Comparative Example>
In the conveying screw 114d of the comparative example shown in FIG. 9A, it was found that the drop amount distribution of the developer 8 changes as shown in FIG. The measurement conditions of the falling amount distribution of the developer 8 shown in FIG. 10 are as follows.

  From the hopper 25 shown in FIG. 4 through the supply port 114b provided on the upstream side of the conveyance path 114c of the developing device 114 shown in FIG. Is replenished. In the method of replenishing the developer 8 from the hopper 25 shown in FIG. 4, the developer 8 is replenished intermittently.

<Conveying screw in hopper>
As for the conveyance screw 24 in the hopper 25 shown in FIG. 4, the outer diameter d2 of the spiral blade 24b is 13 mm. The outer diameter d1 of the rotating shaft 24a is 8 mm. The pitch P of the spiral blade 24b in the direction of the rotation axis 24a is 20 mm. The conveying screw 24 in the hopper 25 shown in FIG. 4 is rotated at 24 rpm (rotation per minute) by the hopper motor 21 as a driving source shown in FIG.

<Conveying screw in conveyance path>
The outer diameter D2 of the spiral blade 114d2 of the conveyance screw 114d in the conveyance path 114c of the developing device 114 is 13 mm. The outer diameter D1 of the rotating shaft 114d1 is 8 mm. The pitch P in the direction of the rotation axis 114d1 of the spiral blade 114d2 is 20 mm. The angle θ2 on the side other than the obtuse angle at which the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 with respect to the direction of the rotation axis 114d1 of the conveying screw 114d is 70 °. The conveying screw 114d in the conveying path 114c is rotated at 96 rpm (rotation per minute) by the motor 23 as a driving source shown in FIG. FIG. 9 (a) is a schematic view and is different from the actual relative dimensions.

  That is, the developer 8 is replenished from the hopper 25 shown in FIG. 4 through the supply port 114b provided at the upstream end of the conveyance path 114c of the developing device 114. Then, the developer 8 is transported to the downstream side of the transport path 114c by the rotation of the transport screw 114d provided in the transport path 114c. At this time, the developer 8 gets over the upper edge surface 114f of the regulating wall 114e provided in the conveyance path 114c and falls into the stirring chamber 114i.

  The developer 8 that has passed over the upper edge surface 114f of the regulating wall 114e substantially uniformly along the longitudinal direction of the developing sleeve 114a from the transport path 114c falls into the stirring chamber 114i. In that case, if the cohesion degree G of the developer 8 is different, the transport ability of the developer 8 in the longitudinal direction of the transport path 114c is different.

<The force applied to the developer>
Next, the force that the spiral blade 114d2 of the conveyance screw 114d of the comparative example gives to the developer 8 will be described with reference to FIG. FIG. 9A is a cross-sectional explanatory view showing a force applied by the spiral blade 114d2 of the conveyance screw 114d of the comparative example to the developer 8 having a low degree of cohesion G. FIG. FIG. 9B is a cross-sectional explanatory view showing a force applied by the spiral blade 114d2 of the conveyance screw 114d of the comparative example to the developer 8 having a high degree of cohesion G.

  As shown in FIG. 9A, when the cohesion degree G of the developer 8 is lower than the center value (the flowability is good), the developer 8 pushes out the developer 8 of the spiral blade 114d2 of the conveying screw 114d. I can not go up 114d3. Therefore, the developer 8 is transported to the downstream side of the transport path 114c shown in the direction of arrow T in FIG. 9A. Therefore, the amount of developer falling over the upper edge surface 114f of the regulating wall 114e on the upstream side (left side in FIG. 9A) of the conveyance path 114c and falling into the stirring chamber 114i is reduced.

  On the contrary, as shown in FIG. 9B, when the cohesion degree G of the developer 8 is higher than the central value (the flowability is bad), the developer 8 is the developer 8 of the spiral blade 114d2 of the conveying screw 114d. Can be raised upward. For this reason, the developer 8 breaks the wall by the developer 8 itself formed on the upper surface of the upper edge surface 114f of the regulating wall 114e on the upstream side (left side of FIG. 9B) of the transport path 114c. It gets over and falls into the stirring chamber 114i.

  In this case, the amount of the developer 8 over the upper edge surface 114f of the regulating wall 114e on the downstream side of the transport path 114c without being sufficiently transported to the downstream side of the transport path 114c and falling into the stirring chamber 114i Decreases. The central value of the aggregation degree G of the developer 8 of the present embodiment is about 40% to 50%. The central value of the aggregation degree G of the developer 8 varies depending on the developer 8 (toner) to be used.

<Cohesiveness of developer>
In the present embodiment, the aggregation degree G of the developer 8 was determined using a powder tester manufactured by Hosokawa Micron. First, three circular sieves with a diameter of 100 mm are stacked, and from the top, 60 mesh, 100 mesh, and 200 mesh are made in accordance with JIS standards. A bundle of sieves (sieve) with an interval of 20 mm above and below the mesh of each sieve (sieve) is placed on a vibration generator and a bundle of sieves in the vertical direction with a frequency of 50 Hz and an amplitude of 0.7 mm. Vibrate.

  Further, 5.0 g of the developer 8 to be examined is placed on the mesh of the first screen of the bundle of sieves, and the bundle of sieves is vibrated for 15 seconds. The weight of the developer 8 remaining on the top of the top screen (sieve) is M1. The weight of the developer 8 remaining on the mesh of the second sieve (sieve) is M2. Further, the weight of the developer 8 remaining on the mesh of the lowermost sieve (sieve) is M3. Then, the value of each of the weights M1 to M3 is substituted into the following equation 1 to express the aggregation degree G of the developer 8 as a percentage (%). The coefficients “20”, “12” and “4” in the following equation 1 are set as weightings for each sieve (sieve) in the case where a calculation formula by a powder tester manufactured by Hosokawa Micron Corporation is used.

[Equation 1]
G = M1 × 20 + M2 × 12 + M3 × 4

  According to the method of measuring the aggregation degree G of the developer 8 described above, in the present embodiment, the aggregation degree G of the developer 8 having a high aggregation degree G is 80% according to the above equation 1, and the development is a low aggregation degree G The degree of aggregation G of the agent 8 is 30%.

<Drop amount distribution of developer of comparative example>
FIG. 10 is a view showing a drop amount distribution of the developer 8 along the conveyance path 114c of the developing device 114 in which the conveyance screw 114d of the comparative example shown in FIGS. 9 (a) and 9 (b) is provided in the conveyance path 114c. is there. The angle θ2 on the side other than the obtuse angle at which the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 with respect to the direction of the rotation axis 114d1 of the conveyance screw 114d of the comparative example shown in FIGS. It is.

  The graph a shown in FIG. 10 is a region R1 to R5 in which the longitudinal direction of the conveyance path 114c is equally divided into five in the case of using the developer 8 having a low degree of cohesion G with a degree of cohesion G of 30%. Rate of falling over the upper edge surface 114f and falling into the stirring chamber 114i. Further, in the graph b shown in FIG. 10, when the developer 8 having a high degree of cohesion G with a degree of cohesion G of 80% is used, regions R1 to R5 in which the longitudinal direction of the conveyance path 114c is equally divided into five are regulated respectively It shows the falling amount rate over the upper edge surface 114f of the wall 114e and falling into the stirring chamber 114i.

  The falling amount ratio indicated by the vertical axis in FIG. 10 is the amount of falling of the developer 8 that has fallen over the upper edge surface 114f of the regulating wall 114e in each of the regions R1 to R5 into the stirring chamber 114i. It is a value obtained by dividing the inside of 114 c by the total amount of the developer 8 conveyed.

<Dropping amount distribution of developer of this embodiment>
FIG. 8 is a view showing a drop amount distribution of the developer 8 along the conveyance path 114c of the developing device 114 in which the conveyance screw 114d of the present embodiment shown in FIGS. 7A and 7B is provided in the conveyance path 114c. It is. The angle θ1 of the non-obtuse angle at which the surface 114d3 of the spiral blade 114d2 that pushes out the developer 8 with respect to the direction of the rotation axis 114d1 of the conveyance screw 114d of the present embodiment shown in FIGS. °

  A graph h shown in FIG. 8 is a region R1 to R5 in which the longitudinal direction of the conveyance path 114c is equally divided into five in the case of using the developer 8 having a low degree of cohesion G with a degree of cohesion G of 30%. Rate of falling over the upper edge surface 114f and falling into the stirring chamber 114i. Further, graph i shown in FIG. 8 is restricted in the regions R1 to R5 in which the longitudinal direction of the transport path 114c is equally divided into five when the developer 8 having a high degree of aggregation G with a degree of aggregation G of 80% is used. It shows the falling amount rate over the upper edge surface 114f of the wall 114e and falling into the stirring chamber 114i.

  The falling amount ratio indicated by the vertical axis in FIG. 8 is the amount of falling of the developer 8 that has fallen over the upper edge surface 114f of the regulating wall 114e in each of the regions R1 to R5 into the stirring chamber 114i. It is a value obtained by dividing the inside of 114 c by the total amount of the developer 8 conveyed.

  As shown in FIG. 8, the graph h using the developer 8 having a low degree of cohesion G with a degree of cohesion G of the developer 8 of 30% is considered. Further, the graph i using the developer 8 having a high degree of cohesion G with a cohesion degree G of the developer 8 of 80% is considered. In any of the graphs h and i, in the developing device 114 provided with the conveying screw 114d of the present embodiment shown in FIGS. 7A and 7B, regardless of the degree of aggregation G of the developer 8, In the longitudinal direction, the drop amount distribution of the developer 8 can be made substantially uniform.

  From the hopper 25 shown in FIG. 4, the developer 8 is supplied into the conveyance path 114c through the supply port 114b provided at the upstream end of the conveyance path 114c. The developer 8 supplied into the conveyance path 114c is pushed by the surface 114d3 of the spiral blade 114d2 of the single spiral blade 114d2 rotated by the rotation of the conveyance screw 114d provided in the conveyance path 114c. It is transported downstream.

  At this time, the developer 8 gets over the upper edge surface 114f of the regulating wall 114e provided in the conveyance path 114c and drops into the stirring chamber 114i. At this time, the case where the conveying screw 114d of the present embodiment shown in FIGS. 7A and 7B is provided is considered. At this time, as shown in FIG. 8, the developer 8 dropped into the stirring chamber 114i is substantially uniformly stirred along the longitudinal direction of the developing sleeve 114a regardless of the degree of aggregation G of the developer 8. Fall inside.

<Transportability of developer>
In the developing device 114 provided with the conveying screw 114d of the present embodiment shown in FIGS. 7A and 7B, the developer 8 in the conveying path 114c is shown in the direction of arrow T in FIGS. 7A and 7B. Transport downstream. At this time, the developer 8 is transported downstream by being pushed by the surface 114 d 3 that pushes out the developer 8 of the spiral blade 114 d 2 of the transport screw 114 d. The transport capacity at that time is substantially constant regardless of the degree of aggregation G of the developer 8 in the longitudinal direction of the transport path 114c.

  In the conveying screw 114d of the present embodiment shown in FIG. 7B, the force f to the developer 8 by the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 is only the force f conveyed in the longitudinal direction of the conveying path 114c. Is working. For this reason, as in the comparative example shown in FIG. 9B, the developer F does not have the force F in the direction to get over the upper edge surface 114f of the regulating wall 114e by the rotation of the spiral blade 114d2.

  When the conveying screw 114d of the comparative example shown in FIG. 9B is used, the case where the cohesion degree G of the developer 8 shown in the graph b of FIG. 10 is high is considered. At this time, on the upstream side of the conveyance path 114c, the developer 8 ascends upward the surface 114d3 of the spiral blade 114d2 of the conveyance screw 114d that pushes out the developer 8 and passes over the upper edge surface 114f of the regulation wall 114e to enter the stirring chamber 114i. Concentrate on falling.

  However, in the case where the cohesion degree G of the developer 8 shown in the graph i of FIG. 8 is high when the conveyance screw 114d of the present embodiment shown in FIG. 7B is used, the spiral blade 114d2 of the conveyance screw 114d is The developer 8 does not rise upward on the surface 114 d 3 for pushing out the developer 8. For this reason, the upper edge surface 114f of the regulating wall 114e is not carried over on the upstream side of the conveying path 114c and the concentrated falling in the stirring chamber 114i does not occur, and the regulating wall 114e is approximately uniformly along the longitudinal direction of the conveying path 114c. The developer 8 gets over the upper edge surface 114f and falls into the stirring chamber 114i.

  Even in the case where the cohesion degree G of the developer 8 shown in the graph h of FIG. 8 is low, the developer 8 gets over the upper edge surface 114f of the regulation wall 114e substantially uniformly along the longitudinal direction of the transport path 114c and the inside of the stirring chamber 114i Fall into

  The developer 8 conveyed along the longitudinal direction in the conveyance path 114c is dropped by gravity due to the developer 8 exceeding the height of the wall formed by the developer 8 itself formed on the upper edge surface 114f of the restriction wall 114e. Drops into the stirring chamber 114i by the By continuously causing such a phenomenon, the drop amount distribution of the developer 8 is kept substantially uniform along the longitudinal direction of the transport path 114c as shown in FIG. 8, and there is no image defect. It becomes possible to provide a good image.

  In the present embodiment shown in FIG. 8, regardless of the degree of aggregation G of the developer 8, the drop amount distribution of the developer 8 along the longitudinal direction of the transport path 114 c is clearly and substantially uniformly controlled. Thereby, the difference in density within one page of the toner image printed on the sheet 12 (recording material) is reduced. Therefore, even when the number of printed sheets 12 (recording material) increases, it is possible to obtain a good image without uneven density regardless of the degree of aggregation G of the developer 8.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. In the embodiment described above, the angle θ1 on the side other than the obtuse angle at which the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 with respect to the direction of the rotation shaft 114d1 of the conveyance screw 114d provided in the conveyance path 114c is set to 90 °. . And it is an example which made conveyance screw 114d rotate at 96 rpm.

  In addition, various angles θ1 are set to such an extent that the developer 8 does not have a force in the direction in which the developer 8 gets over the upper edge surface 114f of the regulation wall 114e by rotation of the surface 114d3 that pushes out the developer 8 of the spiral blade 114d2 of the transport screw 114d. can do. Thereby, the same effect as described above can be obtained.

  Further, in the above embodiment, the conveyance screw 114d is used as the conveyance means provided inside the conveyance path 114c. Besides, the conveyance means is a developer conveyance member that pushes out the developer 8 with the surface from the supply port 114 b provided at the upstream end of the conveyance path 114 c to the downstream side in the conveyance direction T without rotationally driving. You may configure.

  At this time, the angle of the surface of the developer conveyance member from which the developer 8 is pushed out with respect to the conveyance direction T of the developer 8 along the longitudinal direction of the conveyance path 114c is taken into consideration. The same effect as described above can be obtained as long as the angle is such that the developer 8 does not have a force in the direction in which the developer 8 gets over the upper edge surface 114f of the regulating wall 114e.

  In the above embodiment, the angle θ1 on the non-obtuse angle at which the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 crosses the direction of the rotation axis 114d1 of the conveyance screw 114d provided inside the conveyance path 114c. did. The angle θ1 is set to an angle θ1 at which the developer 8 does not rise upward from the surface 114d3 from which the developer 8 of the rotating spiral blade 114d2 is pushed out.

  As a result, when the developer 8 is transported in the longitudinal direction of the transport path 114c, the force in the direction in which the developer 8 passes over the upper edge surface 114f of the regulating wall 114e does not work by the rotation of the spiral blade 114d2. Therefore, the developer 8 can be transported along the transport path 114c without breaking the wall of the developer 8 itself formed on the upper edge surface 114f of the regulation wall 114e, and the developer 8 can be along the longitudinal direction of the transport path 114c. The drop amount distribution of the developer 8 is controlled substantially uniformly.

  In the conveyance screw 114d of the comparative example shown in FIG. 9A, the angle θ2 on the side other than the obtuse angle at which the surface 114d3 of the spiral blade 114d2 pushing out the developer 8 in the direction of the rotation shaft 114d1 intersects. The angle θ2 is set to an angle θ2 at which the force F in the direction in which the developer 8 gets over the upper edge surface 114f of the regulating wall 114e by the rotation of the spiral blade 114d2 acts on the developer 8. The angle θ2 is 70 °. In this case, the rotational speed of the conveying screw 114d is taken into consideration. The CPU 302 (control means) may control the rotational speed of the conveying screw 114d to such an extent that the developer 114 can not move up the surface 114d3 of the spiral blade 114d2 of the conveying screw 114d that pushes the developer 8 upward. it can.

  That is, the CPU 302 (control means) controls driving of the motor 23 as a driving source to control the rotational speed of the conveying screw 114d. At this time, the force in the upward direction applied to the developer 8 by the surface 114 d 3 that pushes out the developer 8 of the spiral blade 114 d 2 of the conveyance screw 114 d (conveying means) is considered. The force is controlled to be less than the force required for the developer 8 to get over the upper edge surface 114f of the regulating wall 114e.

  Here, the rotational speed of the conveying screw 114 d corresponds to the moving speed of the surface 114 d 3 of the spiral blade 114 d 2 that pushes out the developer 8. As a result, since the force in the direction in which the developer 8 gets over the upper edge surface 114f of the regulating wall 114e is weakened by the rotation of the spiral blade 114d2, the same effect as described above can be obtained.

  Further, in the above embodiment, as shown in FIG. 1, the case where the present invention is applied to a one-component developing device of a monochrome copying machine has been described, but it can be applied to a color copying machine and a color printer. Moreover, it is applicable also to a two-component developing device. The developer amount detection in the two-component developing device means the ratio of toner to carrier particles, that is, the toner concentration.

  As described above, the angle at which the side of the transport means pushing out the developer 8 with respect to the transport direction T of the developer 8 crosses the obtuse angle, the surface of the developer 8 pushing up the developer 8 upwards Set the angle at which you can not Thus, the developer 8 can be stably transported along the longitudinal direction of the transport path 114c without breaking the wall of the developer 8 itself formed on the upper edge surface 114f of the regulating wall 114e. The developer 8 transported along the longitudinal direction of the transport path 114 c falls over the upper edge surface 114 f of the regulating wall 114 e by the spilling force due to the gravity acting on the developer 8 and falls. The falling amount of the developer 8 at that time is regulated by the regulating wall 114e.

  As a result, it becomes possible to control the drop amount distribution of the developer 8 along the longitudinal direction of the transport path 114c substantially uniformly. Thus, the developer 8 dropped into the agitating chamber 114i is stirred and conveyed by the agitating member 114g which rotates in the clockwise direction of FIG. 4 around the rotation shaft 114g1 and carried on the surface of the developing sleeve 114a in the developing chamber 114j. Ru. At this time, the developer 8 is supplied substantially uniformly in the longitudinal direction of the developing sleeve 114a. As a result, the occurrence of image deterioration due to the distribution of the amount of drop of the developer 8 along the longitudinal direction of the conveyance path 114c is prevented. Thus, the reliability of the developing device 114 and the image forming apparatus 2 can be enhanced with a simple configuration.

8 ... developer 114a ... developing sleeve (developer carrier)
114c ... conveyance path 114d ... conveyance screw (conveying means)
114 d 2 ··· Spiral blade 114 d 3 ··· Surface of pushing out developer 8 of helical blade 114 d 2 (surface to push out developer)
114e ... regulatory wall

Claims (6)

A transport path for transporting the developer along the axial direction of the developer carrier;
Transport means for transporting the developer in the transport path;
A regulating wall which is provided along the transport path and regulates the amount of developer falling from the transport path;
In the developing device having
The angle of the surface is set such that the upward force applied to the developer by the surface of the transport means for pushing out the developer is less than the force required for the developer to get over the restriction wall. Development device.   The angle of the surface is set such that the angle on the non-obtuse angle at which the surface intersects the transport direction in which the developer is transported along the transport path is 70 ° or more and 90 ° or less. Item 2. A developing device according to item 1.   The conveyance means is constituted by a conveyance screw having a spiral blade, and a surface for pushing out the developer is a surface for pushing out the developer of the spiral blade. Developing device.   Movement of the surface of the transport means that pushes out the developer so that the upward force of the surface of the transport means that pushes out the developer to the developer is less than the force required for the developer to get over the control wall The developing device according to any one of claims 1 to 3, further comprising control means for controlling the speed.   The upper edge surface of the restriction wall is inclined such that the height decreases toward the downstream side from the upstream side in the transport direction in which the developer is transported along the transport path. The developing device according to any one of to 4. The developing device according to any one of claims 1 to 5.
An image forming unit that forms an image on a recording material;
An image forming apparatus comprising:

Images