JP2023007943A - Developing device and image forming apparatus - Google Patents

Abstract

An object of the present invention is to improve agitation and transportability of a developer to suppress the occurrence of printing unevenness. A developing device (10) of an image forming apparatus (1) includes a developing tank (14) containing a developer containing toner and a magnetic carrier, a developing roller (15) that carries and conveys the developer to an image carrier, and a developing tank. A first agitating and conveying paddle 11 and a second agitating and conveying paddle 12 are provided to rotate inside the developing roller 14 to agitate and convey the developer. It is The transport paddle 13 includes a rotating shaft 131 and a plurality of blade plate portions 132 arranged around the rotating shaft 131 . The blade plate portion 132 is arranged so that the base portion 133 side is positioned downstream and the tip 134 side is positioned upstream with respect to the rotation direction R3 of the transport paddle 13 . [Selection drawing] Fig. 2

Description

The present invention relates to a developing device and an image forming apparatus equipped with the developing device.

2. Description of the Related Art As a developing device provided in an image forming apparatus such as a copier or a printer, a two-component developing type developing device that performs a developing process using a two-component developer containing toner and a magnetic carrier is widely known.

For example, the developing device disclosed in Japanese Patent Application Laid-Open No. 2002-200000 includes a developing roller carrying developer on its peripheral surface, a developer stirring member having an elliptical plate, and a developer conveying member for supplying the developer to the developing roller. and a developer stirring auxiliary member for correcting quantitative unevenness of the developer. A developer is accommodated in the accommodating portion in which these members are arranged. Further, the developer stirring auxiliary member is arranged between the developer stirring member and the developer conveying member.

To the developing device, toner stored in a toner hopper is appropriately replenished through a toner replenishing roller. The replenished toner is agitated by a developer agitating member together with the already stored toner, supplied onto the developing roller, and the toner carried on the developing roller is thinned appropriately by the doctor portion. Furthermore, in the area facing the photoreceptor drum, the toner thinned on the developing roller is supplied to the latent image on the photoreceptor drum, forming a toner image on the photoreceptor drum.

JP-A-5-119615

In the conventional developing device, it was difficult to precisely maintain the amount of toner stored in the storage unit at a target value. As a result, the amount of stored toner may be too much or too little as compared to the target value. If the amount of toner is insufficient with respect to the target value, there is a possibility that problems such as a decrease in image density may occur. However, like the conventional developing device, the provision of the developer agitation assisting member is not preferable because it causes an increase in the size of the device.

Further, in recent years, in order to reduce costs, an image forming apparatus has been proposed in which the developing device is unitized so that a common developing unit can be applied to both a high-speed machine and a low-speed machine. In such a case, it becomes difficult to optimize the rotational speed of the developer conveying member and the like. The developer is not sufficiently mixed with the incoming developer, and the phenomenon that new developer is layered on the surface layer of the accommodating portion easily occurs. As a result, there is a problem that the formed image has shading and printing unevenness occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and an object of the present invention is to provide a developing device capable of suppressing the occurrence of printing unevenness by enhancing agitating and conveying properties of a developer. An object of the present invention is to provide an image forming apparatus.

The solution of the present invention for achieving the above object is a storage container that stores developer containing toner and magnetic carrier, a developer carrier that carries the developer and transports it to an image carrier, and a plurality of agitating and conveying members that rotate within the container to agitate and convey the developer; a conveying member that conveys and collects the developer from the developer carrier, and the conveying member includes a rotating shaft and a plurality of blades arranged around the rotating shaft. and a plate portion, and the blade plate portion is disposed so that the base side connected to the rotating shaft is positioned downstream and the tip side is positioned upstream with respect to the rotation direction of the conveying member. It is characterized by

By providing such specific items, the developer conveyed from the agitating and conveying member and the developer from the developer carrier are sufficiently agitated in the developing device, and new developer is laminated. It is possible to prevent the phenomenon from occurring.

Further, in the developing device having the above configuration, more preferably, the conveying member is provided so as to rotate in a direction opposite to the rotation direction of the adjacent agitating conveying member.

Further, in the developing device having the above configuration, it is preferable that each of the vane plate portions is provided in a flat plate shape.

Further, in the developing device having the above configuration, it is preferable that the blade plate portion extends in a tangential direction to the outer peripheral surface of the rotating shaft.

Further, in the developing device having the above configuration, the blade plate portions may be provided continuously along the axial direction of the rotating shaft.

Further, in the developing device having the above configuration, it is preferable that the stirring and conveying member has a rotating shaft and spiral blades spirally provided around the rotating shaft.

Further, an image forming apparatus equipped with the developing device according to each of the above solutions is also within the scope of the technical idea of the present invention. As a result, in the developing device and the image forming apparatus, the conveying member can be operated to sufficiently agitate the developer from the developer carrier and the developer from the agitating and conveying member, thereby improving the image density. It is possible to suppress the decrease in the print density and the occurrence of printing unevenness.

According to the present invention, it is possible to suppress the occurrence of printing unevenness by enhancing the stirring and conveying properties of the developer without increasing the size of the apparatus.

1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the invention; FIG. 1 is a schematic cross-sectional view showing a developing device according to an embodiment of the invention; FIG. FIG. 3 is an explanatory view schematically showing the structure of a transport paddle in the developing device viewed in the axial direction; FIG. 5 is an explanatory diagram showing how the developer is stirred in the developing device; 3 is a plan view schematically showing the configuration inside a developing tank in the developing device; FIG. 5 is a graph showing temporal changes in toner density when the amount of developer is 300 g in the developing device according to the present embodiment. 5 is a graph showing changes in toner density over time when the amount of developer is 400 g in the developing device; 4 is a graph showing evaluation of toner density and printing unevenness with different amounts of developer in the developing device. 10 is a graph showing a change in toner concentration over time when the amount of developer is 300 g in a conventional developing device for comparison; 5 is a graph showing a change in toner density over time when the amount of developer is 400 g in the conventional developing device; 5 is a graph showing evaluation of toner density and printing unevenness with different amounts of developer in the conventional developing device. and FIG. 11 is a schematic cross-sectional view showing the configuration of a conventional developing device.

A developing device and an image forming apparatus according to embodiments of the present invention will be described with reference to the drawings.

(Image forming device)
FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 1 as one embodiment. In the present embodiment, as an image forming apparatus 1, a case where the present invention is applied to a monochrome multifunction machine that forms a single-color image (monochrome image) on a recording medium P will be described as an example. Note that the image forming apparatus 1 is not limited to this, and can be applied to various image forming apparatuses including a color printer, a color multifunction machine, a monochrome printer, and the like. As the recording medium P, a sheet of paper, a sheet for an overhead projector, or the like can be used.

When the image forming apparatus 1 is viewed from the front as shown in the figure, the front side (front side) of the image forming apparatus 1 in the front-rear direction X is defined as the front direction X1, and the back side (rear side) of the image forming apparatus 1 is defined as the front direction X1. In the horizontal direction Y, the left side is the left direction Y1, the right side is the right direction Y2, the upper side is the upward direction Z1, and the lower side is the downward direction. Z2 will be described below.

The image forming apparatus 1 is roughly divided into a document conveying section 201 , an image reading section 202 , an image forming section 203 , a recording medium conveying section 204 and a paper feeding section 205 . This image forming apparatus 1 employs a two-component development method using a two-component developer containing toner and magnetic carrier as a developer.

When at least one document is set on document tray 211 , document conveying section 201 pulls out the document one by one from document tray 211 and conveys the document, and places this document on first platen glass 223 of image reading section 202 . lead and pass.

Image reading section 202 includes an optical unit including first scanning section 221 and second scanning section 222 below first platen glass 223 . The light source of the scanning unit 221 exposes the surface of the document, the mirrors of the first scanning unit 221 and the second scanning unit 222 guide the reflected light from the surface of the document to the imaging lens 224, and the imaging lens 224 forms an image of the surface of the document. is imaged on a CCD (Charge Coupled Device) 225 . The CCD 225 repeatedly reads the image of the surface of the document in the main scanning direction and outputs image data representing the image of the surface of the document.

When the original is placed on the second platen glass 226 on the upper surface of the image reading unit 202, the first scanning unit 221 and the second scanning unit 222 are moved in the sub-scanning direction while maintaining a predetermined speed relationship with each other. Meanwhile, the surface of the document on the second platen glass 226 is exposed by the first scanning section 221 , and the reflected light from the surface of the document is further reflected by the first scanning section 221 and the second scanning section 222 to the imaging lens 224 . An image of the document surface is formed on a CCD 225 by an imaging lens 224 .

The output image data is subjected to various image processing by the control circuit and output to the image forming unit 203 . The image forming section 203 has a photoreceptor drum 20 as an image bearing member at substantially the center thereof. Around the photosensitive drum 20, a developing device 10, a charging device 40, an optical scanning device 50, a transfer device 60, a cleaning device 70, and the like are arranged.

The photoreceptor drum 20 has a drum-shaped base and a photoconductive layer formed in a thin film on the surface of the base. The substrate can be composed of, for example, a metal such as aluminum. The photoconductive layer can be composed of, for example, organic photo-semiconductor (OPC), amorphous silicon (a-Si), or the like.

The developing device 10 visualizes the electrostatic latent image on the photoreceptor drum 20 with a developer (toner) to form a developer image on the photoreceptor drum 20 . A toner cartridge 18 for supplying toner is connected to the developing device 10 . Details of the developing device 10 will be described later.

The charging device 40 uniformly charges the surface of the photosensitive drum 20 before the electrostatic latent image is formed. The charging device 40 can be composed of, for example, a charging wire such as a tungsten wire, a corona charger or charging roller made of a metallic shield plate or a grid plate, or a charging brush.

The optical scanning device 50 scans the uniformly charged photosensitive drum 20 with the light beam while modulating the intensity of the light beam according to image data to write an electrostatic latent image. A laser, an LED, or the like can be used as the optical scanning device 50 .

The transfer device 60 transfers the developer image on the photoreceptor drum 20 to the recording medium P while sandwiching the recording medium P between the transfer belt 61 and the photoreceptor drum 20 and conveying it. As the transfer device 60, other than the transfer belt 61, for example, a transfer roller, a charging brush, a corona charger, or the like can be used.

The cleaning device 70 removes toner remaining on the surface of the photosensitive drum 20 after the toner image has been transferred to the recording medium P. FIG. The cleaning device 70 has, for example, a cleaning blade.

A fixing device 80 is arranged above the image forming section 203 . The fixing device 80 sandwiches the recording medium P with the transferred image between a fixing roller 81 having an internal heat source and a pressure roller 82 to fix the image by heat and pressure. After fixing, the recording medium P is transported by transport rollers, and discharged by paper discharge rollers 241 to a paper discharge tray 244 provided in an internal paper discharge space between the image reading unit 202 and the image forming unit 203 . be.

When images are formed on both sides of the recording medium P, the recording medium P is reversed and conveyed in the opposite direction by the discharge rollers 241, and further conveyed to the reverse conveying path 243, where the front and back are reversed before being sent to the image forming unit. The sheet is conveyed to 203 again, and the developer image is transferred and fixed on the rear surface thereof.

The paper feed unit 205 includes a paper feed cassette 251 , and separates and supplies the recording medium P one by one from a tray in the paper feed cassette 251 . The recording medium P is temporarily stopped by a registration roller 242 provided in front of the photoreceptor drum 20 and the transfer device 60 among the transport rollers, and is moved between the photoreceptor drum 20 and the transfer device 60 in time with the transfer timing. The developer image on the photosensitive drum 20 is transferred.

(developing device)
FIG. 2 is a schematic cross-sectional view showing the developing device 10 according to the embodiment of the invention. In the drawings, hatching indicating a cross section is omitted in order to make each component easy to see.

In this embodiment, the developing device 10 supplies non-magnetic toner contained in the two-component developer onto the surface of the photoreceptor drum 20 by means of a developing electric field formed between the photoreceptor drum 20 and the developing device 10 . do.

The developing device 10 has a developing tank (accommodating container) 14 that accommodates a two-component developer containing toner and magnetic carrier. The developer tank 14 is provided with an opening at a position facing the photosensitive drum 20 . The photoreceptor drum 20 is arranged to face this opening.

The developing roller 15 is a magnet roller that functions as a developer carrier and is arranged at a position facing the photosensitive drum 20 . The developing roller 15 includes a non-magnetic cylindrical sleeve portion (not shown) that is rotatable about a rotating shaft 151 and a cylindrical magnet roll portion disposed inside the sleeve portion. I have. A plurality of magnetic poles each having a single polarity are formed on the peripheral surface of the developing roller 15 due to the magnetism of the magnet roll portion. In the exemplary embodiment, the developing roller 15 is provided so that the sleeve portion rotates in the rotation direction R4 around a rotation shaft 151 arranged along the axial direction X. As shown in FIG. The developing roller 15 carries the developer in the developer tank 14 on its surface and conveys the toner contained in the carried developer to the surface of the photosensitive drum 20 .

The rotation direction R4 of the developing roller 15 is set to be the same as the rotation direction R5 of the photosensitive drum 20 at the position facing the photosensitive drum 20 . In the development area where the photoreceptor drum 20 and the developing roller 15 face each other, an electrostatic latent image formed on the surface of the photoreceptor drum 20 is developed with toner.

The developed toner image is transferred onto the recording medium P by the transfer device 60 and fixed by the fixing device 80 (see FIG. 1). Toner remaining on the surface of the photoreceptor drum 20 is removed by the cleaning device 70, and the surface of the photoreceptor drum 20 is neutralized. In the image forming apparatus 1, such an image forming process is repeated as needed.

As shown in FIG. 2, the developing device 10 is provided with a first agitation-conveyance paddle 11 and a second agitation-conveyance paddle 12 as agitation-conveyance members that rotate in the developer tank 14 to agitate and convey the developer. It is

The first stirring and conveying paddle 11 and the second stirring and conveying paddle 12 are provided with spiral blades 112 and 122, respectively. The spiral blades 112 and 122 are spirally formed on the outer circumferences of the rotating shafts 111 and 121, respectively. In the developing device 10, the first agitation-conveyance paddle 11 and the second agitation-conveyance paddle 12 are arranged so that their rotation shafts 111 and 121 face each other in parallel. The mixture is circulated in the tank 14 while being stirred. Further, this agitation causes friction between the toner contained in the developer and the magnetic carrier, and the friction causes the non-magnetic toner to be charged.

The developer tank 14 is closed at the top by a top cover 141 provided in the upward direction Z1, and the inside thereof is partitioned into a plurality of sections by a partition wall 143 between the first agitating and conveying paddle 11 and the second agitating and conveying paddle 12. It is In the exemplary embodiment, the first agitating and conveying paddle 11 is the farthest from the developing roller 15 in the developer tank 14 and is arranged on the opposite side of the photosensitive drum 20 . The second agitating and conveying paddle 12 is arranged at a position closer to the developing roller 15 than the first agitating and conveying paddle 11 in the developer tank 14 . The partition wall 143 is provided with a communicating portion (not shown) through which the developer is circulated by the first stirring and conveying paddle 11 and the second stirring and conveying paddle 12 .

As illustrated, the first agitating and conveying paddle 11 rotates about a rotating shaft 111 in a rotating direction R1. The first agitating and conveying paddle 11 is rotated on the side facing the partition wall 143 so as to move the developer from above to below. The second agitating/conveying paddle 12, on the side facing the partition wall 143, rotates in the rotational direction R2 about the rotating shaft 121 so as to move the developer from above to below. The rotating shafts 111 and 121 are provided along the front-rear direction X in parallel with each other. Therefore, in this case, the front-rear direction X corresponds to the axial direction of the rotation shafts 111 and 121 of the first stirring and conveying paddle 11 and the second stirring and conveying paddle 12 .

The developing device 10 is provided with a transport paddle 13 as a transport member between the developing roller 15 and the second stirring transport paddle 12 . The transport paddle 13 is provided so as to transport the developer to the developing roller 15 and collect the developer from the developing roller 15 .

In the exemplary embodiment, the transport paddle 13 is configured with a rotating shaft 131 and a plurality of vane plate portions 132 arranged around the rotating shaft 131 . In this case, eight vane plate portions 132 are provided. While the second agitating and conveying paddle 12 rotates in the rotational direction R2, the adjacent conveying paddles 13 rotate in the same rotational direction R3 in the region facing the second agitating and conveying paddle 12. is provided in Further, in order to improve the transportability and agitation of the developer, the rotating shaft 131 of the transport paddle 13 is positioned below the rotating shaft 111 of the first stirring and transporting paddle 11 and the rotating shaft 121 of the second stirring and transporting paddle 12. It is provided in the developing tank 14 so as to do so. It is preferable that the rotary shaft 131 of the conveying paddle 13 is provided at such a height that it can be submerged in the developer contained in the developer tank 14 .

Therefore, as shown in FIG. 2, the conveying paddles 13 are provided so as to rotate in the opposite direction (rotating direction R3) to the rotating direction R2 of the adjacent second stirring conveying paddles 12. As shown in FIG. Thus, the conveying paddle 13 is provided so as to rotate upward together with the second stirring and conveying paddle 12 in the region facing the second stirring and conveying paddle 12 .

The developer on the developing roller 15 is supplied to the photosensitive drum 20 by the image forming operation. The toner constituting the developer is attracted to the photoreceptor drum 20 to develop the electrostatic latent image on the surface of the photoreceptor drum 20 to form a toner image. The developer remaining on the developing roller 15 is conveyed again to the developing tank 14 as the developing roller 15 rotates, but the toner concentration of the developer gradually decreases due to the formation of the toner image.

Therefore, the developing device 10 is provided with a toner supply port (not shown) for supplying toner to the developer tank 14 . The toner supply port is connected to the toner cartridge 18, is provided above the first agitating and conveying paddle 11, and is arranged on one side of the axial direction (the front-rear direction X) (for example, closer to the front direction X1). The replenished toner is stirred while being mixed with the magnetic carrier through the first stirring and conveying paddle 11 and the second stirring and conveying paddle 12, and conveyed.

The conveying paddle 13 that conveys the developer to the developing roller 15 is provided with each blade plate portion 132 in a flat plate shape. The blade plate portion 132 is preferably formed of a flexible plate-like member or sheet-like member (flexible sheet) made of, for example, PET (polyethylene terephthalate). Further, it is preferable that the blade plate portion 132 has enough stiffness to agitate the toner and has flexibility to bend when coming into contact with the second agitating/conveying paddle 12 and the bottom surface 142 of the developer tank 14 . The eight blade plate portions 132 are arranged at regular intervals in the circumferential direction around the rotating shaft 131 .

FIG. 3 is an explanatory view schematically showing the configuration of the transport paddle 13 in the developing device 10 according to the present embodiment, viewed in the axial direction (front-rear direction X), and FIG. It is an explanatory view showing the state of.

As shown in FIG. 3, each vane plate portion 132 of the transfer paddle 13 has a base portion 133 connected to and provided near the rotation shaft 131, and continuously extends outward from the base portion 133. is provided. A distal end 134 of the blade plate portion 132 opposite to the base portion 133 is spaced apart from the rotating shaft 131 and positioned radially outward of the rotating shaft 131 . The conveying paddles 13 are arranged so that the base portion 133 side of each blade plate portion 132 is positioned downstream in the rotational direction R3 and the tip 134 side thereof is positioned upstream in the rotational direction R3.

Further, as shown in FIG. 3 , the vane plate portions 132 of the transport paddle 13 extend in a direction (tangential direction) parallel to the tangential line L on the outer peripheral surface of the rotating shaft 131 . The tip 134 side of the blade plate portion 132 is provided in a tapered shape along the bottom surface 142 of the developer tank 14 . The blade plate portions 132 having such a shape are formed continuously along the axial direction (the front-rear direction X) of the rotating shaft 131 .

Here, for comparison with the developing device 10 according to the present embodiment, the configuration of a conventional developing device 900 will be briefly described with reference to FIG.

As shown in FIG. 12, a conventional developing device 900 is provided with a first agitating and conveying paddle 911 that rotates in a rotational direction R11 and a second agitating and conveying paddle 912 that rotates in a rotational direction R12 in a developer tank 914. The developer is conveyed to the developing roller 915 that rotates in the rotation direction R14 so as to face the photosensitive drum 920 . In addition, a conventional transport paddle 913 that rotates in the rotation direction R13 is provided between the second stirring transport paddle 912 and the developing roller 915 . However, as shown in FIG. 12, the conventional transport paddle 913 differs from that of the present embodiment in the form of the blade plate portion 9132. It had a configuration in which the distal end side away from was positioned downstream in the rotational direction R13.

Therefore, the transport paddle 913 rotates in the rotation direction R13 while holding the developer between the plurality of blade plate portions 9132 . As indicated by the arrow in FIG. 12, the developer returned from the developing roller 915 is held by the transport paddle 913 and transported in the direction of the second agitation transport paddle 912 , but remains between the blade plate portions 9132 . There is a risk that the toner will be held by the second stirring and conveying paddle 912 and will not be sufficiently mixed with the developer from the second agitating and conveying paddle 912 and will be conveyed toward the developing roller 915 again.

Therefore, the developer returned from the developing roller 915 is supplied to the developing roller 915 without being sufficiently agitated with the developer from the second agitating and conveying paddle 912 when the toner is consumed and the toner density is low. become. The developer is insufficiently agitated, and even if the developer is supplied to the photoreceptor drum 20, the density of the formed image is uneven, resulting in uneven printing. Such a phenomenon appears conspicuously in the case of an image that consumes a large amount of toner, and if the stirring of the developer is insufficient, it is likely to occur on the side of the toner supply port in the axial direction (front-to-rear direction X) as well. rice field.

On the other hand, in the developing device 10 according to the present embodiment, as shown in FIG. is positioned upstream in the direction of rotation R3. Since the tip 134 side of the blade plate portion 132 is located upstream in the rotation direction R3 from the base portion 133 side, the rotation about the rotary shaft 131 pushes the developer outward (for example, toward the second agitating and conveying paddle 12). acts on

Therefore, as shown in FIG. 4, the developer returned from the developing roller 15 reaches the transport paddle 13 along the bottom surface 142 of the developer tank 14, and is transported in the rotation direction R3 by each blade plate portion 132. They are pushed out sequentially toward the second agitating and conveying paddle 12 . The pushed-out developer mixes with the developer conveyed by the rotation of the second stirring and conveying paddle 12 in the rotational direction R2, and is conveyed while being stirred. This promotes sufficient agitation of the developer in the developer tank 14 .

FIG. 5 is a plan view schematically showing the configuration inside the developing tank 14 in the developing device 10. As shown in FIG. As shown in the figure, a toner replenishing port 144 is provided above the first agitating and conveying paddle 11 near the end in the forward direction X1, and new toner is supplied from the toner cartridge 18 to the developing tank 14 as the toner is consumed. is configured to be replenished to

In the developer tank 14 , the developer D is conveyed in the backward direction X<b>2 by the rotation of the first stirring and conveying paddle 11 and is sent to the adjacent second stirring and conveying paddle 12 via the partition wall 143 . Due to the rotation of the second agitating and conveying paddle 12, the developer D is conveyed in the forward direction X1 and circulated in the developer tank 14 while being agitated.

Here, in order to confirm the agitation and transportability of the developer in the developing device 10 according to the present embodiment, the toner concentration in the developing tank 14 was measured, and a test was conducted for comparison with the case of the conventional developing device 900. rice field. The toner density was measured at four points, the front end MXF and rear end MXR of the second agitating and conveying paddle 12 and the front end MGF and rear end MGR of the developing roller 15, as shown in FIG. In the conventional developing device 900 as well, the toner density was measured at the same location.

6 to 8 show the measurement results of the developing device 10 according to the present embodiment, FIG. 6 is a graph showing the change in toner density over time when the amount of developer is 300 g, and FIG. 7 is the amount of developer. FIG. 8 is a graph showing the change in toner concentration with time when the developer is 400 g, and FIG. 8 is a graph showing the toner concentration with different amounts of developer. 9 to 11 show the measurement results of the conventional developing device 900 for comparison, FIG. 9 is a graph showing the change in toner concentration with time when the amount of developer is 300 g, and FIG. 10 is the amount of developer. FIG. 11 is a graph showing the change in toner concentration with time when the developer is 400 g, and FIG. 11 is a graph showing the toner concentration with different amounts of developer.

In the figure, the change in toner density over time is shown on the horizontal axis as T1 before image formation (before printing), T2 after 3 black solid prints on A3 paper, and further black solid printing on A3 paper (black all over). Printing) T3 after printing 3 sheets, T4 after stirring rotation for 3 seconds without image formation, and T5 after stirring rotation for 3 seconds without image formation are shown. 8 and 11 show the evaluation of the degree of printing unevenness when black solid printing is performed on A3 paper with each amount of developer. Black ○ marks indicate that printing unevenness was confirmed by image analysis but was not visually confirmed, △ marks indicate that printing unevenness was confirmed by visual inspection, and × marks indicate This indicates that printing unevenness was visually confirmed.

As shown in FIG. 5, the developer D is circulated while being agitated in the developer tank 14. In this case, when the forward direction X1 and the backward direction X2 of the front-rear direction X are compared, normally the second agitation In the transport paddle 12, the toner density tends to be higher at the trailing edge MXR, which is before toner consumption, than at the leading edge MXF. Similarly, in the developing roller 15, the toner density tends to be higher at the trailing edge MGR than at the leading edge MGF. On the other hand, since the developer flows between the second agitating and conveying paddle 12 and the developing roller 15 which are parallel to each other, there is a difference in toner density between the front ends MXF/MGF and the rear ends MXR/MGR. A smaller difference is preferable, and a large difference is considered to lead to the occurrence of printing unevenness.

When the developer amount is 300 g, as shown in FIG. 9, in the developing device 900 having the conventional transport paddle 913, the toner density is 0 between the front end MXF/MGF and the rear end MXR/MGR. A difference of about 0.5 to 1.5% was produced. In particular, the difference in toner density was large between the trailing edge MXR/MGR. On the other hand, in the developing device 10 of the present embodiment, as shown in FIG. bottom.

Further, when the amount of developer is 400 g, as shown in FIG. There was a difference of about 0.5 to 1.0%. On the other hand, in the developing device 10 of the present embodiment, as shown in FIG. bottom. Also, in FIG. 7, the difference in toner concentration between the front end MXF and the rear end MXR of the second agitating and conveying paddle 12 was kept relatively small, and an extremely good result was obtained.

Therefore, according to the developing device 10 of the present embodiment, the action of the transport paddle 13 promotes sufficient agitation of the developer in the developer tank 14, making it possible to form a good image while suppressing uneven printing. .

For example, when the amount of developer is 400 g, the variation in toner density is smaller than when the amount of developer is 300 g, and the greater the amount of developer, the easier it is to maintain a stable toner density. However, in the conventional developing device 900, as shown in FIG. 11, even when the amount of developer is 400 g, the lower the toner density, the more uneven printing occurs. confirmed. Further, even if the toner concentration was 6.5% or more, printing unevenness was observed when the developer amount was less than 340 g.

On the other hand, since the developing device 10 of the present embodiment is provided with the transport paddle 13, as shown in FIG. 8, no printing unevenness was observed. That is, even if the amount of developer is 400 g, 350 g or less, and even if the toner concentration is as low as 5.5%, the occurrence of uneven printing is suppressed. It was confirmed that the agent was sufficiently stirred.

As described above, in the developing device 10 according to the present embodiment, the transport paddle 13 is provided, and the developer from the developing roller 15 and the developer from the second stirring transport paddle 12 can be sufficiently stirred. It can be said that the agitation and transportability of the developer can be remarkably improved, and the occurrence of printing unevenness can be suppressed. It is also possible to unitize the developing device 10 and apply it to various image forming apparatuses 1 in common. image formation can be performed.

In the transport paddle 13 of the developing device 10, the plurality of blade plate portions 132 are not necessarily formed continuously along the axial direction (front-rear direction X) of the rotating shaft 131, but are discontinuously formed. Alternatively, it may be provided intensively at a location corresponding to toner consumption, such as being provided on the most downstream side with respect to the toner supply port 144 . Alternatively, a combination of the blade plate portion 132 formed continuously and the blade plate portion 132 formed discontinuously may be used.

Further, the toner supply port 144 is not limited to be provided closer to the front direction X1 of the developer tank 14, and may be provided closer to the rear direction X2. In this case as well, the developer is preferably circulated in the developer tank 14 in the front-rear direction X from the first agitation-conveyance paddle 11 to the second agitation-conveyance paddle 12 with the toner supply port as a base point. In either case, the developer can be sufficiently agitated and conveyed by the conveying paddle 13 in the developer tank 14, thereby improving agitation and conveyability of the developer and suppressing the occurrence of printing unevenness. It becomes possible to

The invention is not limited to the embodiments described above, but can be implemented in various other forms. Therefore, the above embodiment is merely an example in all respects and should not be construed in a restrictive manner. The scope of the present invention is indicated by the claims and is not restricted by the text of the specification. Furthermore, all modifications and changes within the equivalent scope of claims are within the scope of the present invention.

1 Image forming apparatus 10 Developing device 11 First stirring and conveying paddle (stirring and conveying member)
111 Rotating shaft 112 Spiral blade 12 Second stirring and conveying paddle (stirring and conveying member)
121 Rotating shaft 122 Spiral blade 13 Conveying paddle (conveying member)
131 Rotating shaft 132 Blade plate portion 133 Base portion 134 Tip 14 Developing tank (container)
15 development roller (developer carrier)
18 toner cartridge 20 photosensitive drum (image carrier)
40 charging device 50 optical scanning device 60 transfer device 70 cleaning device 80 fixing device

Claims (7)

a storage container that stores a developer containing toner and a magnetic carrier;
a developer carrier that carries the developer and conveys it to the image carrier;
a plurality of agitating and conveying members that rotate within the storage container to agitate and convey the developer;
A developing device comprising a conveying member disposed between the developer carrier and the stirring and conveying member for conveying the developer to the developer carrier and recovering the developer from the developer carrier There is
The conveying member includes a rotating shaft and a plurality of blade plate portions arranged around the rotating shaft,
The blade plate portion is disposed so that a base portion connected to the rotating shaft is located downstream and a tip end portion is located upstream with respect to the rotation direction of the conveying member. Device. The developing device according to claim 1,
The developing device, wherein the conveying member is provided so as to rotate in a direction opposite to the rotation direction of the adjacent agitation conveying member. 3. The developing device according to claim 1, wherein
The developing device, wherein each of the blade plate portions is provided in a flat plate shape. In the developing device according to claim 3,
The developing device, wherein the blade plate portion extends in a tangential direction to the outer peripheral surface of the rotating shaft. In the developing device according to any one of claims 1 to 4,
The developing device, wherein the blade plate portions are provided continuously along the axial direction of the rotating shaft. In the developing device according to any one of claims 1 to 5,
The developing device, wherein the stirring and conveying member has a rotating shaft and spiral blades spirally provided around the rotating shaft. An image forming apparatus comprising the developing device according to any one of claims 1 to 6.

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