JP2024049033A - Developing device and image forming apparatus equipped with same - Google Patents

Abstract

[Problem] To provide a developing device capable of suppressing retention of developer, and an image forming apparatus including the same. [Solution] A developing device 14 includes a developing tank 40 that contains developer, a partition wall 40a that divides the internal space of the developing tank 40 into a first stirring chamber 401 and a second stirring chamber 402, a first transport screw 41 that transports the developer in a first direction D1 within the first stirring chamber 401, a second transport screw 42 that transports the developer in a second direction D2 within the second stirring chamber 402, communication ports 43, 44 that communicate between the first stirring chamber 401 and the second stirring chamber 402 to enable the developer to circulate in a circulation direction C, and a developing roller 45 (developer carrier) that supplies the developer from the first transport screw 41 to an image carrier, and a guide portion 47 is provided above at least the first transport screw 41 of the first transport screw 41 and the second transport screw 42 on the downstream side in the circulation direction C to guide the developer to the communication port 43 corresponding to the downstream side. [Selected figure] Figure 2

Description

This disclosure relates to a developing device and an image forming device equipped with the same, such as a copier, multifunction device, printer, or facsimile machine.

Conventionally, developing devices that carry developer on the surface of a developer carrier and develop an electrostatic latent image formed on an image carrier have been widely used. For example, one such developing device is known to have a partition wall that divides the internal space of a developer tank into two stirring chambers, a transport screw that is provided in each of the two stirring chambers and transports developer in opposite directions, and communication ports at both ends of the partition wall that connect the two stirring chambers and allow the developer to circulate through these stirring chambers (see, for example, Patent Document 1).

JP 2021-184018 A

However, in the conventional developing device described above, the developer is merely allowed to circulate through the communication port, and is not structured to promote circulation of the developer. This means that there is a risk of the developer becoming stagnant, particularly when the developer deteriorates and its fluidity worsens.

This disclosure has been made to solve the above-mentioned problems in the past, and aims to provide a developing device that can suppress the accumulation of developer and an image forming device equipped with the same.

In order to achieve the above object, the developing device disclosed in this specification includes a developing tank that contains a developer, a partition wall that divides the internal space of the developing tank into a first stirring chamber and a second stirring chamber, a first transport screw that transports the developer in a first direction in the first stirring chamber, a second transport screw that transports the developer in a second direction opposite to the first direction in the second stirring chamber, communication ports that connect the first stirring chamber and the second stirring chamber at both ends of the partition wall to enable the developer to circulate in a circulation direction including the first direction and the second direction, and a developer carrier that supplies the developer from the first transport screw to an image carrier, and is characterized in that a guide portion that guides the developer to the communication port corresponding to the downstream side is provided above at least the first transport screw of the first transport screw and the second transport screw and downstream in the circulation direction.

In addition, in the developing device, the guide portion may be provided above each of the first conveying screw and the second conveying screw and downstream in the circulation direction.

In addition, in the developing device, the guide portion may have a guide wall portion formed along the circulation direction.

In addition, in the developing device, the guide wall may have an inclined portion that is inclined so as to guide the developer downward as it moves downstream in the circulation direction.

In addition, in the developing device, the guide portion provided above the first conveying screw may have a protruding portion that protrudes downward on the opposite side of the communication opening with the first conveying screw in between.

The image forming apparatus disclosed in this specification is characterized by being equipped with the above-mentioned developing device.

According to this disclosure, it is possible to suppress the accumulation of developer.

1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment, as viewed from the front. FIG. 2 is a perspective view showing an internal structure of the developing device according to the first embodiment. FIG. 3 is a plan view showing the internal structure of the developing device shown in FIG. 2 . This is a cross-sectional view taken along line AA in FIG. FIG. 11 is a schematic diagram showing a state in which the developer is raised in volume. 13 is a plan view showing an internal structure of a developing device according to a modified example of the first embodiment. FIG. FIG. 11 is a perspective view showing a part of the internal structure of a developing device according to a second embodiment. 13 is a schematic rear view showing the guide portion and its surroundings in the third embodiment. FIG.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that identical components in the embodiments described below will be given the same reference numerals, and duplicate descriptions of those components will be omitted.

(Embodiment 1)
-Image forming apparatus-
First, the configuration of the image forming apparatus A in the first embodiment will be described.

Figure 1 is a schematic cross-sectional view of an image forming apparatus A in embodiment 1 as viewed from the front. In the figure, the symbol X indicates the front-rear direction (depth direction), the symbol Y indicates the left-right direction Y perpendicular to the width direction X, and the symbol Z indicates the up-down direction. These settings are the same in the following embodiments.

Image forming device A is an image forming device that forms a monochrome image on a sheet using an electrophotographic method in response to image data read by image reading device 27 or image data transmitted from an external source.

Image forming device A includes a document feeder 10 and an image forming device main body 11 (see FIG. 1). The image forming device main body 11 includes an image forming section 12 and a sheet transport system 20.

The image forming unit 12 includes an exposure device 13, a developing device 14, a photoconductor drum 15 (image carrier), a cleaner unit 16, a charger 17, a transfer device 3, a toner cartridge device 18, and a fixing device 19 (see FIG. 1). The transfer device 3 has a transfer roller 30 as a transfer member that transfers the toner image formed on the photoconductor drum 15 to a sheet.

The sheet transport system 20 includes a tray 21, a discharge tray 22, and a number of transport rollers 23 arranged along the sheet transport path S.

At the top of the image forming device main body 11, there is provided an original placement table 26 made of transparent glass on which an original is placed, and below the original placement table 26, there is provided an image reading device 27 for reading the image of the original. Above the original placement table 26, there is provided an original feeding device 10. The image of the original read by the image reading device 27 is sent to the image forming device main body 11 as image data, and an image formed based on the image data in the image forming device main body 11 is recorded on a sheet.

The image forming device A described above is configured to print an image on a sheet as follows. First, a sheet supplied from a tray 21 is transported to the transfer device 3 by the transport rollers 23. Next, the toner image formed by the image forming section 12 is transferred onto the sheet by the transfer device 3. Thereafter, the unfixed toner on the sheet is melted and fixed by heat by the fixing device 19, and the sheet is discharged onto the discharge tray 22 by the transport rollers 23 and discharge rollers (not shown). In this way, a series of printing operations by the image forming device A is completed.

In addition, image forming device A may be a color image forming device capable of forming full-color images.

-Developing device-
Next, the configuration of the developing device 14 in this embodiment will be described.

Figure 2 is a perspective view showing the internal structure of the developing device 14 in embodiment 1. Figure 3 is a plan view showing the internal structure of the developing device 14 in Figure 2. Figure 4 is a cross-sectional view taken along line A-A in Figure 3. Note that in the following figures, the first direction D1 and the second direction D2 are represented by solid thick arrows, and the circulation direction C is represented by a dashed thick arrow.

The developing device 14 includes a developing tank 40, a partition wall 40a, a first conveying screw 41, a second conveying screw 42, communication ports 43 and 44, a developing roller 45 (developer carrier), and a paddle member 46 (see FIG. 2).

The developer tank 40 contains the developer. The developer used is a two-component developer that contains non-magnetic toner and a magnetic carrier.

The partition wall 40a divides the internal space of the developing tank 40 into a first stirring chamber 401 and a second stirring chamber 402, and in this embodiment, has a longitudinal direction in the front-to-rear direction. A toner supply port 403 for supplying toner to the developing tank 40 is provided at the front side of the second stirring chamber 402.

The first conveying screw 41 conveys the developer in the first stirring chamber 401 in a first direction D1. In this embodiment, the first direction D1 is along the forward direction. The first conveying screw 41 includes a rotating shaft 410 and a spiral blade 411 formed on the outer periphery of the rotating shaft 410 (see FIG. 3). The rotating shaft 410 receives a rotational driving force from a rotation drive unit (not shown) via a drive gear 90 and a driven gear 91 and rotates.

The second conveying screw 42 conveys the developer in the second stirring chamber 402 in a second direction D2 opposite to the first direction D1, and includes a rotating shaft 420 and a spiral blade 421 formed on the outer periphery of the rotating shaft 420 (see FIG. 3). The rotating shaft 420 rotates in the opposite direction to the first conveying screw 41, driven by the rotation of the first conveying screw 41 via a driving gear 90 and driven gears 91 and 92.

The communication openings 43 and 44 communicate the first stirring chamber 401 and the second stirring chamber 402 at both ends of the partition wall 40a (see Figures 2 and 3). The communication opening 43 allows the developer transported in the first direction D1 in the first stirring chamber 401 to enter the second stirring chamber 402, and similarly, the communication opening 44 allows the developer transported in the second direction D2 in the second stirring chamber 402 to enter the first stirring chamber 401. That is, the communication openings 43 and 44 allow the developer to circulate in a circulation direction C including the first direction D1 and the second direction D2. By circulating the developer in the circulation direction C, friction occurs between the toner and the magnetic carrier contained in the developer, and the non-magnetic toner is charged by the friction.

The developing roller 45 carries a developer on its surface and supplies the developer from the first stirring chamber 401 side to the photosensitive drum 15, and is configured with a cylindrical magnet roll (not shown) mounted inside a non-magnetic sleeve 450 formed in a cylindrical shape. The sleeve 450 receives a rotational driving force from a drive unit (not shown) and rotates in a rotational direction R.

The developing roller 45 forms a nip FN with the photoconductor drum 15 (see FIG. 1). At the nip FN, a developing bias (e.g., about -450 V) is applied to the developing roller 45 by a bias power supply (not shown). This causes toner to be supplied from the developer carried on the surface of the developing roller 45 to the electrostatic latent image on the surface of the photoconductor drum 15, forming a toner image on the photoconductor drum 15.

A regulating member 45a that regulates the layer thickness of the developer transported to the photosensitive drum 15 on the developing roller 45 is arranged on the outer circumferential side of the developing roller 45 with a gap provided between it and the outer circumferential surface of the sleeve 450 of the developing roller 45.

The paddle member 46 transports the developer transported by the first transport screw 41 toward the developing roller 45, and transports the developer returning from the developing roller 45 toward the first transport screw 41. It includes a rotating shaft (not shown) that rotates by receiving a rotational driving force from a rotation drive unit (not shown) via a drive gear 90.

Figure 5 is a schematic diagram showing the state in which the developer volume has increased. In Figure 5, the two-dot chain line conceptually shows the volume of the developer. In Figure 5, the communication port 44 and its surroundings are shown in the same way as the communication port 43 and its surroundings, so they are not shown.

It is known that the fluidity of the developer deteriorates as the developer deteriorates over time. When the fluidity of the developer deteriorates, the developer has difficulty smoothly entering the communication openings 43 and 44, and as shown in FIG. 5, the developer bulks up and eventually accumulates near the communication openings 43 and 44. This accumulation of developer causes uneven stirring of the developer, which leads to image defects such as blank areas.

The developing device 14 described above is provided with a guide portion 47 to prevent the developer from accumulating (see Figures 2 to 5). In this embodiment, the guide portion 47 is provided above the first conveying screw 41 and downstream of the circulation direction C, and guides the developer to the communication port 43 corresponding to the downstream side.

The guide portion 47 has a guide wall portion 470 formed along the circulation direction C (see Figures 2 to 5). The guide wall portion 470 is curved along the circulation direction C toward the communication port 43. When the developer is raised, it comes into contact with the guide wall portion 470 of the guide portion 47 and flows toward the communication port 43 along the shape of the guide wall portion 470. By providing such a guide portion 47, the developer can easily enter the communication port 43, which promotes the circulation of the developer in the circulation direction C and thus suppresses the accumulation of the developer. This effect is particularly effective when the developer is raised due to deterioration of the fluidity of the developer caused by aging or the like.

In addition, the guide wall portion 470 as described above allows the developer to be guided to the communication port 43 with a simple configuration.

Figure 6 is a plan view showing the internal structure of the developing device 14 in a modified example of embodiment 1.

As shown in FIG. 6, in addition to the guide portion 47, a guide portion 48 having the same shape as the guide portion 47 may be provided above the second conveying screw 42 and downstream in the circulation direction C. In this case, the guide portion 48 guides the developer to the communication port 44. By providing such a guide portion 48, the developer can easily enter the communication port 44, which further promotes the circulation of the developer in the circulation direction C, and thus can more efficiently suppress the accumulation of the developer.

(Embodiment 2)
Hereinafter, the second embodiment will be described only with respect to the points different from the first embodiment.

Figure 7 is a perspective view showing part of the internal structure of the developing device 14 in embodiment 2.

In the second embodiment, the guide wall portion 470 is formed with an inclined portion 471 that is inclined so as to guide the developer downward as it moves toward the downstream side of the circulation direction C (see FIG. 7). When the developer increases in volume, it comes into contact with the inclined portion 471 in the guide wall portion 470 and flows downward along the shape of the inclined portion 471. By forming such an inclined portion 471 in the guide wall portion 470, the developer can easily move to the lower side of the developer tank 40, which promotes a reduction in the volume of the developer and ultimately suppresses the accumulation of the developer.

(Embodiment 3)
Hereinafter, the third embodiment will be described only with respect to the points different from the first embodiment.

Figure 8 is a schematic rear view showing the guide portion 47 and its surroundings in embodiment 3. In Figure 8, the solid arrows conceptually show the flow of developer.

In the third embodiment, the guide portion 47 has a protrusion 472 that protrudes downward on the side opposite the communication opening 43 with the first conveying screw 41 in between (see FIG. 8). In other words, the guide portion 47 has a protrusion 472 that protrudes toward the blade portion of the first conveying screw 41 on the side opposite the communication opening 43. A curved surface 473 that is curved along the outer circumferential direction of the first conveying screw 41 is formed on the side of the protrusion 472 that faces the first conveying screw 41.

The protrusion 472 narrows the flow path P through which the developer returning from the developing roller 45 via the paddle member 46 passes. By providing such a protrusion 472, the developer returning from the developing roller 45 is compressed in the flow path P compared to when the protrusion 472 is not provided, so the developer can be transported more efficiently toward the first transport screw 41.

The above embodiments and examples are illustrative in all respects and are not intended to be a basis for restrictive interpretation. Therefore, the technical scope of the present disclosure is not interpreted solely by the above embodiments and examples, but is defined based on the claims. Furthermore, all modifications within the meaning and scope equivalent to the claims are included.

A Image forming apparatus 14 Developing device 40 Developing tank 40a Partition wall 401 First stirring chamber 402 Second stirring chamber 41 First conveying screw 42 Second conveying screw 43 Communication port 44 Communication port 45 Developing roller (developer carrier)
47, 48 Guide portion 470 Guide wall portion 471 Inclined portion 472 Projection portion C Circulation direction D1 First direction D2 Second direction

Claims (6)

A developer tank that contains a developer;
a partition wall that divides an internal space of the developing tank into a first stirring chamber and a second stirring chamber;
a first conveying screw that conveys the developer in a first direction within the first mixing chamber;
a second conveying screw that conveys the developer in a second direction opposite to the first direction in the second mixing chamber;
a communication port that communicates the first stirring chamber with the second stirring chamber at both side ends of the partition wall, thereby enabling the developer to circulate in a circulation direction that includes the first direction and the second direction;
a developer carrier that supplies the developer from the first conveying screw to an image carrier,
A developing device characterized in that a guide portion is provided above at least the first conveying screw of the first conveying screw and the second conveying screw, downstream in the circulation direction, for guiding the developer to the communication port corresponding to the downstream side. 2. The developing device according to claim 1,
the guide portion is provided above the first conveying screw and the second conveying screw, respectively, on the downstream side in the circulating direction. 3. The developing device according to claim 1,
The developing device, wherein the guide portion has a guide wall portion formed along the circulation direction. 4. The developing device according to claim 3,
the guide wall portion is formed with an inclined portion that is inclined so as to guide the developer downward as it advances downstream in the circulation direction. 2. The developing device according to claim 1,
a guide portion provided above the first transport screw and having a protruding portion protruding downward on the opposite side of the communication port with the first transport screw therebetween, the guide portion comprising: a developing device; An image forming apparatus comprising the developing device according to claim 1 or 2.

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